INDEX 1. Scope of Application 2. Reference Document 3. General Requirements 4. Sewage standard and hydraulic calculations for drainage system 5. Lay-out and drainage system 6. Drainage networks and facilities in the drainage network 7. Sewage pumping station and air pumping station 8. Sewage treatment facilities 9. Drainage system for small areas 10. Design characteristics of treatment works of combined drainage system and separate drainage system 11. Electric equipment, technology control, automation and control 12. Requirements on construction solutions and building structure 13. Additional requirements for civil drainage system in some special areas Appendix A (Regulations): Sanitary conditions when disposal of sewage into the main stream Appendix B (Reference): Climatic constant indicators of formula on rain density Appendix C (Regulations): The distance from drainage pipeline to technical network and buildings Appendix D (Reference): Subsidiary facilities of the sewage treatment station Appendix E (Reference): Arrangement of biological lakes
ABSTRACT
TCVN 7957:2008 has been reviewed by Viet Nam’s Water and Environment Joint Stock Company (VINAWASE) on the basis of Vietnam’s construction standard “ Drainage and sewerage-External networks and facilities-Design Standard” which has been proposed by Ministry of Construction, inspected by Directorate for Standards, Metrology, and Quality, and made public by Ministry of Science and Technology.
NATIONAL STANDARD TCVN 7957:2008 Drainage and sewerage- External Networks and Facilities- Design Standard
1. Scope of Application This standard stipulates requirements which are compulsory or be encouraged for application for new construction or re-modernization and upgrading of drainage and sewerage (drainage and sewerageexternal networks and facilities) of urban areas, accumulated civilized areas and industrial areas. NOTES: Design of drainage and sewerage networks is required to comply with other related regulations and standards which are already issued by the State.
2. Reference documents TCVN 7222:2002, General requirements on the environment for main sewerage treatment stations TCVN 6772:2000, Water quality-Domestic sewerage- Allowed pollution limit TCXDVN 33:2006, Water supply-External networks and facilities-Design standards TCVN 5942-1995, Water quality- Surface water quality standard TCVN 5945: 2005, Industrial waste water- Disposal standard TCVN 7382-2004, Quality of water- waste water from hospital- Disposal standard
3. General requirements 3.1 In case of design of drainage network, selection of diagrams and basic solutions shall be in accordance with Construction planning of urban areas, civilized areas, and industrial areas. 3.2 In case of selection of drainage and sewerage network and diagram, it is required to make the assessment on finance, engineering and sanitary assurance level of existing drainage and sewerage facilities and their future use possibilities. 3.3 In case of drainage and sewerage design for civilized areas, it is allowed to use the drainage networks including: general type, semi-separated type, totally separated type or combined type depending on topography, climatic conditions, general requirement of existing drainage network, based on the comparison of econo-technical targets.
3.4 For storm water drainage, in case of favorable conditions, it is allowed to use the network of open trenches, channels and ditchers and special attention is required for polluted storm water. 3.5 The drainage and sewerage network of industrial enterprises are normally designed in the completely separated type, but in case of specific cases combination of the entire or partial collection of production waste water with domestic waste water. 3.6 In case of drainage and sewerage design for industrial production units, it is required to consider the following issues: -
The possibility to collect the valuable substances in the production sewage.
-
The possibility to reduce the production sewage into the environment by application of reasonable technology process, employment of entire or partial circulating water supply, or using the sewage of one production line for another one.
NOTES: It is allowed to use the domestic sewage for production only after being treated and sterilized. 3.7 The used water after production is required to be reused if it is not polluted. When the water cannot be used again, it is allowed to be disposed into the receiving resource or into the storm drainage network. 3.8 Disposal of production water into the urban drainage networks and facilities is required to base on the components of the pollutants in production water, econo-technical targets of the drainage network and sanitary requirements in case of discharge of the water into the receiving resources. In this case, waste water after production shall meet the following requirements: -
Not to assert negative impact on the operation of drainage ditches and waste water treatment facilities;
-
Having the suspended and floating substances not over than 500 mg/l;
-
Not having the substances with the capacities of destroying material, adhesion to the surface of the pipeline or making the drainage ditches or other facilities of the drainage network stuck.
-
Not containing the flammable substances (petroleum, oil) and air dissolvent which are likely to make the explosive mixtures in pipelines or drainage facilities.
-
Not containing the toxic substances with the concentration negatively affecting the biological treatment process or the disposal of waste water into the receiving resources.
NOTES: If waste water from production does not ensure the above mentioned requirements, it is required to have the temporary treatment on the spot. The level of temporary treatment shall obtain the approval of the environment management organizations and local drainage organs. 3.9 In case of connecting the drainage ditches of production units into the urban networks, each production unit shall have the separated disposal ditches and check wells, which are placed out of the areas of the production units. NOTES: It is allowed to place shared ditches for production waste water from factories, and enterprises behind the check wells of each unit. 3.10
The waste water containing toxic substances and pathogenic bacteria shall be de-toxified
and sterilized before it is disposed into the drainage network of urban or civilized areas. 3.11
It is not allowed to discharge many kinds of waste water into one drainage network,
when the combination of these kinds of waste water may compose the toxic substances, explosive air or non-solvent material in large quantity. 3.12
It is not allowed to discharge the production waste water with high concentration of
pollutants in accumulated quantity. When the volume and components of water are changed substantially in one day, it is necessary to design the tanks. 3.13
Besides compliance with the requirements stated in this standard, technology diagram
and remedy methods, parameters for calculation of treatment and smudge facilities, waste water after production shall also be required to follow the relevant regulations, and standards on design and construction of industrial units, the documents issued by the science research organs and experience in management of similar facilities. 3.14
The level of sewage treatment before disposal into the receiving resources is determined
based on the guarantee of sanitary conditions in accordance with the regulations of Vietnam’s environment standard and accepted by environment management organs. 3.15
The waste water treatment facilities of industrial units should be arranged within their
land. 3.16
The sanitary distance from treatment facilities and water pumping stations to building
boundary of public house and food production units ( in consideration with the development capacity of these objects) are stipulated as follows: -
For treatment facilities and domestic sewage pumping station, refer to Table 1;
-
For treatment facilities and production sewage out of the land of the enterprise, if it is pumped and treated or pumped and treated in combination with domestic waste water, the
regulated sanitary standards are used in case of design of sanitary facilities as per the design standards for industrial enterprises issued by the State or governing ministries, but not less than the regulations in Table 1. Table 1 Name of facilities
The sanitary isolation distance in meter, as per the calculation capacity of facilities, thousand m3/d Less than 0.2
From 0.2 to 5
From 5 to 50
>50
1.Mechanical and biological 150 treatment facilities with smudge drying yard
200
400
500
2.Mechanical and biological 100 treatment facilities with smudge treatment by mechanical equipment
150
300
400
3.Submerged filtration yard
200
300
-
-
4.Watering field
150
200
400
-
5.Biological lake
200
200
300
-
6. Circulating oxidation ditches
150
200
400
-
7. Pumping station
15
20
20
30
NOTES: 1.When the above mentioned minimum distance is not ensured, it is required to include the suitable technological solutions to guarantee the sanitary conditions and is approved by local environment management organs. 2.When there is submerged filtration yard of less than 0.5 ha within the area of mechanical and biological sewage treatment plants with the capacity less than 50 m3/d, the distance above is selected to be 100m. 3.The sanitary isolation distance for submerged filtration yard with the capacity less than 15 m3/d, 15 m is selected. 4.The sanitary isolation distance of septic tank is 5 m, and of seepage well is 8m. 5.The isolation distance in Table 1 is allowed to increase, but not more than two times when the apartment is built in the end of main wind direction in comparison with treatment plants, decrease is accepted, but not more than 25% if the apartment is built in the favorable wind direction as per sanitary perspective.
6.In case of drying unstable smudge in the smudge drying yard, the sanitary distance shall be calculated in accordance with environment standards and accepted by local environment management organs. 7.For the reformed works, depending on situations, the exceptional cases can be still be used differently with the regulations in the table but it is required the approval of local environment management organs. 3.17
It is not allowed to dispose the storm water in the following cases:
-
Directly into the yards used for bathing;
-
Into the hollow area without self-drainage and easily to make marsh.
-
Into erosion area, if the design does not have the bank consolidation methods.
3.18
It is required to consider the possibility to put the facilities into every stage of
construction and operation of the entire facility in necessary cases, as well as the future development possibility when it exceeds the calculated capacity of the works. NOTES: Putting the works into use in accordance with the stages of full construction or operation shall be generated from sanitary conditions in case of sewage disposal into the receiving resources. 3.19
The basic technical solutions are design based on comparison econo-technical indicators
of proposed methods. The selected solutions shall be economical and ensure the possibility of favorable implementation.
4. Sewage disposal standard and hydraulic calculations for drainage system 4.1 Sewage disposal standard and non- air-condition coefficients 4.1.1
The urban sewage disposal standard includes domestic sewage and determined services
in accordance with relevant water supply standard for every object and every construction stage. 4.1.2
The non-air conditioning coefficient by day of the urban sewage or civilized area Kd is selected
to be 1.15-1.3 depending on the characteristics of each urban area. The shared non-air condition coefficient Ko is referred as Table 2, depending on the average sewage discharge volume per day qtb. Table 2 Zero coefficient for common circulation K0 max
Average sewage volume qtb (l/s) 5
10
20
50
100
300
500
1000
≥5000
2.5
2.1
1.9
1.7
1.6
1.55
1.5
1.47
1.44
K0 min
0.38
0.45
0.5
0.55
0.59
0.62
0.66
0.69
0.71
NOTES: 1.
When the average volume is between the numbers in Table 2, the common zero coefficient is determined by interpolation.
2. The common non-harmonized coefficient K0 is referred to Table 2, which allows to apply when the production wastewater volume does not exceed 45% of the total urban sewage volume. 3. When the average volume of wastewater is less than 5 l/s, K0 is determined to be 5. 4.1.3
Distribution of sewage volume of the urban and civilized areas depends on the day hours based
on the water use diagram. If there is not the water use diagram, the distribution may be based on the management data of the similar sewage objects. 4.1.4
Standard and non-harmonized coefficient of domestic wastewater from industrial enterprises,
from residential houses or separated public works are determined in accordance with the internal drainage standard. 4.1.5
Standards and non-harmonized coefficient of domestic wastewater from industrial units shall be
determined as per production technological document. 4.1.6
The calculation volume of production wastewater from industrial unit can be determined as
follows: -The drainage pipeline from production lines is determined as per the maximum volume per hour; -The main piping of the whole factory is in accordance with hourly water discharge volume diagram; - The main piping of groups of factories is in accordance with the hourly water disposal diagram with consideration of wastewater flowing time in the pipeline.
4.2. Calculation of volume and harmony of storm water volume 4.2.1 Calculation volume of storm water disposal of the ditch network (l/s) is determined as per the following formula: Q= q.C.F q-calculated storm water density (l/s.ha);
(1)
C-Flow coefficient; F-The serving area of the ditch system (ha) The flow coefficient C depends on the kind of top layer and repeated cycles of expected rains P shall be determined as Table 5. 4.2.2 Calculated rain density can be determined by different diagrams or formulas, but it is necessary to include comparison in order to ensure high degree of accuracy.: a. As per relation diagram I-D-F (rain density-time-frequency) is prepared for each territory. b. As per the formula Wenzel i = C/(Td+ f)
(2)
In which: i -Rain density (mm/h): Td- raining time (minute); f- repeated cycle of rain; C- dependant coefficient of repeated cycle of rain c. As per the formula: q= A (1+ C lg P)/(t+b)
(3)
In which: q- rain density (l/s.ha); t-rain flow time (minutes); P-Repeated cycle of rain as per calculation (year); A, C, b, n- the reference is determined as per the raining conditions of the local area, it can refer to Annex B; for the areas which do not have the data refer to the surrounding area. The storm water data which should have the time chain of observation from 20 to 25 years depending on scope and properties of the works, is determined in accordance with Table 3. Table 3
Properties of the
Scope of works
urban area
Channel, trench
Main ditch
Regional branch ditch
Big city, type I
10
5
2-1
Urban area type II, III
5
2
1-0.5
Other urban areas
2
1
0.5-0.33
NOTES: For the urban areas or the urban areas with mountainous terrain, when the area of discharge is more than 150 ha, the slope is more than 0.02 if the main ditch network is situated in the hollow area of the stream, it is no need to discriminate the urban scope, the value P is more than as stipulated in the table, it can select P equal to 10-20 years based on the analysis of combined risk and safety of the facilities. For the accumulated industrial parks, repeated cycle of expected rainstorm P depends on the properties of the urban areas and can be determined as Table 4. Table 4
The properties of the industrial parks
Value P
The industrial park with normal technology
5-10
The industrial park with the production units having special requirements
10-20
Design of drainage networks in the areas of important facilities (like underground trains, railway stations, tunnel across the roads, and so on. or on the important transportation lines in which the flood can bring out serious consequences, the cycle P should be more than as stipulated in Table 3, P can be selected to be 25 years. For the areas with the unfavorable terrains, it can be higher (50 or 100 years) based on the synthetically analysis of risks and safety requirements. 4.2.3 For big cities with many rain measuring stations, it is required to analyze the inter-relation of rainfall of rain measuring station in order to calculate the rainfall distribution coefficient as per points and areas. If there is only one rainfall measuring station, the calculated volume should be multiplied with heavy rain distribution coefficient n. If there is no local reference research documents, it can be accepted to use the diagram compiled by World Meteorological Organization or as stipulated in Annex B. 4.2.4. The flow coefficient C is determined by calculation model of seepage process. When it is not in good condition to calculate in the mathematical mode, C, depending on the characteristics of watershed surface and repeated cycle of expected rain P shall be selected as Table 5. Table 5
Properties of drainage surface
Repeated cycle of expected rain P (year) 2
5
10
25
50
Asphalt road surface
0.73
0.77
0.81
0.86
0.90
Roof, concrete surface
0.75
0.80
0.81
0.88
0.92
Grass, gardens, parks (less than 50% of grass) -
Low slope 1-2%
0.32
0.34
0.37
0.40
0.44
-
Average slope 2-7 %
0.37
0.40
0.43
0.46
0.49
-
High slope
0.40
0.43
0.45
0.49
0.52
NOTES: When the surface area has many different kinds of surfaces, the average coefficient C is determined by the average calculation on area. 4.2.5 The line of rain process for design is selected based on the number of typical rains. The lasting time of rain time depends on the scope of urban area or urban region, and it may take between 3 h and 6h. The designed rain process is based on the characteristics of rain in every region. The diagram I-D-F can be employed to make the designed rain process. 4.2.6. The hydraulic calculation of storm water drainage in general is carried out in two steps as follows: - Step 1: To determine primarily the dimensions of the facilities (by the method of limit strength or Rational method). - Step 2: To check the calculation results in step 1 in the hydraulic method, in necessary cases, the results in step 1 can be adjusted. - To calculate the storm water drainage based on the limit strength is required to comply the regulations from items 4.2.7 to 4.2.12. 4.2.7 The rain flow time until the calculation time t (minute), is determined as the following formula: t = t0+t1+t2
(4)
In which: t0- The time that storm water flows on the surface to the road alley, can be selected from 5 to 10 minutes. In case that in the sub-area there is storm water collection well, it shall be the flowing time to the ditch of the roads (accumulated surface) shall be determined as in item 4.2.8. Particularly for the regions with the unclear urban characteristics, it shall be decided as in item 4.2.10; t1-The time storm water flows along the road trench to the collection well (when there is no rainwater collection well in the sub-area) is determined in item 4.2.8;
t2-The time when storm water flows in the ditch to the calculation area is decided in 4.2.9. 4.2.8 The time storm water flows along the road trench t1 is determined as the above formula: t1= 0.021 L1/V1
(5)
In which: L1- the length of road trench (m); V1- the flow speed in the end of road trench (m/s). 4.2.9 The time when storm water flows in the ditch to the calculation area is determined as the following formula: t2= 0.017∑(L2/V2)
(6)
In which: L2- The length of every calculation ditch (m); V2- the flow speed at the end of road trench (m/s). 4.2.10 For the urban areas with the unclear storm water (no collection well, no road trench), the focused surface storm water (t0+ t1) shall be calculated in the following formula:
t = t0 + t1 =
1.5n 0.6 xL0.6 Z 0.3 xi 0.5 xI 0.3
(minutes)
(7)
In which: n- Maning coefficient of roughness L- the length of flow (m) Z- Surface coefficient, refer to Table 3-5 l- rain density (mm/minutes) i -Surface slope Table 6 Kind of surface
Z coefficient
-Roof, asphalt road surface
0.24
-Stone laid road surface
0.224
-Aggregated road surface
0.145
-Stone mixed road surface
0.125
-Soil road surface
0.084
-Parks, land for planting trees (clay loam)
0.038
-Parks, land for planting trees (sand loam)
0.20
-Pasture
0.015
NOTES: When surface area has many different surfaces, the average coefficient Z is determined in the method of average in areas. 4.2.11 The water collection area for every segment of ditch can be equal to the entire or partial area of water collection so that calculation flow is the maximum volume. 4.2.12 Garden of trees and parks without the storm water drainage do not consider watershed area and flow coefficient. However, when the surface in this area has slope into the roads bigger or equal to 0.008, the land along the roads with the width of 50-100m shall be included in drainage basin. 4.2.13 Harmonization of storm water flow including slowing the flow by the method of seepage and storage, in order to decrease the peak volume, drainage volume, and minimize the passive impacts caused by rainwater, to stabilize the underground water and create the landscape for the environment. The seeping facilities include natural and artificial seeping facilities. The storage facilities include storage tanks, storage lakes, circulating lakes and hollow land in the tree garden, pasture, which can be stored temporarily during rainfall. 4.2.14 In case of design of circulating lake, it is necessary to comply the following requirements: The doors for feeding water into the lakes and disposing water out of shall be arranged reasonably in order to facilitate the control of water level in the lakes, in accordance with the actual happening of rains and landscape of urban lakes. During operation of circulating lake, it is required to replace water in order to ensure the sanitary conditions (2 times per year). The depth of water from minimum level to the bottom of the lake shall be not less than 1m. 4.2.15 Calculation of circulating volume of the lake W (m3) in the diagram of rainstorm in and out of the lakes is based on the average and maximum water levels. For the small facilities, the high degree of accuracy is not required, in case of implementation of limit strength, the circulation volume can be calculated as the following formula:
W=K.Qn.t
(8)
In which: Qn: Calculated volume of inflow storm water (m3/s): t- The calculated time of rain for the whole stream under the ditch network to the discharge gates into the lake (refer to the hydraulic force calculation table for the storm water drainage); K- coefficient, depending on α, refer to the Table 7.
Table 7 α
K
α
K
α
K
0.1
0.5
0.4
0.42
0.15
1.1
0.45
0.36
0.7
0.13
0.20
0.85
0.5
0.3
0.75
0.1
0.25
0.69
0.55
0.25
0.8
0.07
0.30
0.58
0.6
0.21
0.85
0.04
0.35
0.5
0.65
0.16
0.9
0.02
NOTES: α is the rate between rainfall volume which has been regulated flowing into the ditch behind the
lake Qx, and calculated storm water volume into the lake Qn: α =
Qx Qn
4.2 Calculation of hydraulic force for sewage drainage 4.3.1 In case of hydraulic calculation self-flowing drainage or pressed drainage, calculation volume is the maximum sewage volume. In order to make hydraulic calculation, Maning formula is also employed. Q =1 / nxAxR 2 / 3 xI 1 / 2
In which: Q= Calculation volume (m3/s); I-
Hydraulic slope;
R- Hydraulic diameter (m); A- Ditch section (m2);
(9)
n- The roughness coefficient Manning; The coefficient of roughness can be refer to Table 8. Table 8 Kinds of ditch and channel
Coefficient of roughness Manning (n)
Ditch: -
Reinforced concrete
0.013
-
Cast pipe
0.012
-
Steel pipe
0.012
-
Plastic pipe
0.011
Kinds of ditch and channel
Coefficient of roughness Manning (n)
Ditch: -
Grass roof
0.03
-
Stone laid roof
0.025
-
Concrete roof
0.022
-
Concrete roof and bottom
0.015
4.3.2 In case of hydraulic force calculation of smudge pipeline with pressure (feeding fresh smudge, fermented smudge, active slurry) shall consider transmission mechanism, physical properties and characteristics of smudge. 4.4 Calculation of hydraulic force of the shared, semi-separated drainage network and calculation of combined discharge gates with storm water and sewage into the receiving resources. 4.4.1 The shared drainage network shall ensure the drainage of storm water volume in the time of calculated rain density. When the segments of ditch have the total volume of production and domestic wastewater of more than 10 l/s, it is required to check hydraulic conditions in the dry season. The minimum flow speed depends on the level of filling of the ditch or channel, refer to Table 9. Table 9 The density relevant to the volume in the dry season (cm)
The minimum of the sewage (m/s)
10-20
0.75
21-30
0.8
31-40
1.0
41-60
1.1
61-100
1.2
100-150
1.3
>150
1.5
NOTES: If the buildings have already the septic tanks, the allowed minimum will decrease by 30%. 4.4.2. The calculation volume of shared ditch segment in front of discharge gate no. 1 determined by the total volume in the dry season Qkh (domestic and production wastewater) and the storm water volume. The calculation volume Qn of the ditch segment behind the discharge gate shall be determined as the following formula:
Qn = Qkh + no .Q ' kh + Qm
(10)
In which: Qkh - The total average volume of sewage of calculation ditch segment;
Q ' kh - The total average volume of the stream in front of the discharge gate; no - The coefficient of dilution, refer to the item no. 3.27;
Qm -The storm water volume of the direct stream of the ditch segment behind the discharge gates;
4.4.3 When checking the hydraulic force conditions of shared drainage in dry season, the domestic and production wastewater volume shall be determined similarly with completely separate drainage network. 4.4.4 Arrangement of combined discharge gates of storm water and wastewater and determination of the dilution coefficient n0 shall be base on the sanitary conditions, hydrological mechanism, self-cleaning capacity and using properties of the receiving resources. The dilution coefficient n0, normally from 1 to 3, depending on the position of discharge ditches in the drainage network . For the discharge gates in the beginning of the discharge basin, n0 is chosen to be 3; for the discharge gates at the end of the discharge basin n0 shall be 1. When selection of receiving resources in order to arrange combined discharge gates of storm water and wastewater, in addition to compliance with the above mentioned regulations, these following requirements shall be satisfied: -The rivers shall have the continuous flow with minimum speed shall be not lower than 0.3 m/s. The volume of flowing river involving in dilution shall be greater than 5 times compared to sewage volume.
-Natural or artificial lakes shall have the volume and depth, with the continuous flow and ability to replace the lake average water 4-5 times per year. NOTES: At present, in many urban drainage projects, arrangement of sewage discharge gates into the small, shallow lakes and ponds in the city without the ability of replacing water shall be considered the temporary solution; when it is upgraded in the separate ditch network in the discharge points, it is required to arrange sewage separating wells. 4.4.5 Combined volume of storm water and wastewater leading to the treatment stations in rainy seasons, it can be primarily equal to 2-2.5 times compared to the average volume of sewage in dry season. 4.4.6 The combined calculation volume of wastewater qmix (l/s) of the shared ditch network in the semiseparated drainage network determined in the following formula: qmix = qcit + ∑qlim
(11)
In which: qcit -calculation volume of domestic and production sewage with mentioning the non-harmonized
coefficient (l/s).
∑q
lim
- the polluted storm water volume to be treated is equal to the total limit volume of storm water
qlim into the shared ditch network from separation wells to calculated ditch segment (l/s). 4.4.7 The polluted storm water volume qlim (l/s) is determined as per the regulations in item 4.2.1 of this standard with the repeated cycle of calculated rains P = 0,5-1,0 years, which shall ensure the storm water quantity for treatment shall be not lower than 70% of the total polluted storm water. 4.4.8 The sewage and storm water drainage culvert networks in the semi-separated network shall be calculated in the corresponding completely separated networks.
4.5. The minimum diameter of ditch and calculated filling in channels and culverts. 4.5.1 The minimum diameter of discharge culvert is stipulated as follows: Table 10 Type of drainage network
Minimum diameter D (mm) In sub-area
On the road
Domestic drainage network
150
200
Storm water drainage network
200
400
Shared drainage network
300
400
The piping connecting the storm water collection wells to culverts with the diameter D=200mm-300mm. NOTES: 1. The residential areas with the sewage volume of less than 500 m3/d is allowed to use the pipeline D200 mm on the road. 2. In the special cases, production wastewater is permitted to have the diameter of less than 200mm. 3. In the permit table production, the minimum culverts in the domestic sewage network and shared drainage network should apply the oval-shaped section. 4.5.2 The maximum calculated filling of culvert network depends on the diameters of culvert and can be as follows: + For the culverts D = 200-300 mm, filling is not more than 0.6 D; + For the culvert D=350-450 mm, filling is not more than 0.7 D; + For the culverts D= 500-900 mm, filling is not more than 0.75 D. + For the culverts D over 900 mm, filling is not more than 0.8 D. NOTES: 1-For the channels with the height from 0.9 m and the horizontal section have any shapes, the filling is not more than 0.8 H; 2-For the storm water and shared culverts are designed to be filled completely. 3-For the first ditch, it shall be the culvert without calculation and the filling of culvert is not regulated. 4.5.3 The storm water drainage network built in the scope of residential houses, the depth of flow shall be not more than 1m, and the bank of channels shall be higher than the highest water level of 0.2 m above. 4.6 The calculated speed of minimum sewage depends on the components and dimensions of suspended particles in wastewater, hydraulic radius or filling of channel or ditch. For domestic wastewater and storm water, the minimum flowing speed Vmin corresponding to maximum calculated filling of the ditch shall be regulated as follows: -
The ditch with the diameter of 150-200 mm, Vmin = 0.7 m/s;
-
The ditch with the diameter of 300-400 mm, Vmin = 0.8 m/s;
-
The ditch with the diameter of 400-500 mm, Vmin = 0.9 m/s;
-
The ditch with the diameter of 600-800 mm, Vmin = 1 m/s;
-
The ditch with the diameter of 900-1200 mm, Vmin = 1.15m/s;
-
The ditch with the diameter of 1300-1500 mm, Vmin = 1.2 m/s;
-
The ditch with the diameter of >1500 mm, Vmin = 1.3 m/s.
For production wastewater, the minimum flow speed should be got as per the functional departments or study documents. NOTES: 1. For production wastewater, the characteristics are similar to those of domestic wastewater, the minimum flow speed is based on the production wastewater. 2. For the storm water with the repeated cycle of calculated rain P smaller than or equal to 0.5 years, the minimum speed shall be 0.7 m/s. 3. The culverts in the beginning of the network which do not guarantee the minimum speed as stipulated or the calculated filling is less than 0.2 D, the detergent well should be built. 4.6.2 The minimum flow speed in the culverts of sewage after sediment or biological treatment, it is allowed to be equal to 0.4 m/s. 4.6.3 The maximum flow speed of sewage in the metallic culvert shall not be more than 8 m/s, in the nonmetallic culvert shall not be more than 4 m/s. For the storm water, it shall be 10 and 7 m/s, respectively. 4.6.4 The calculated flow speed of wastewater in the sipping pipeline shall be not more than 1 m/s; the flow speed of sewage in the culvert connected with siphon piping shall not be more than flow speed in siphon piping. 4.6.5 The minimum flow speed in the smudge pressure piping (raw slurry, decayed smudge, active smudge) has been pressed as Table 11. Table 11 The humidity of smudge %
Calculated flow speed in the pressure piping for smudge transmission (m/s) depending on the diameter of the smudge transmission piping D (mm) D= 150-200
92
1.4
D= 250-400 1.5
93
1.3
1.4
94
1.2
1.3
95
1.1
1.2
96
1.0
1.1
97
0.9
1.0
98
0.8
0.9
4.6.6 The maximum flow speed in the storm water and production sewage transporting channel which is permitted to dispose into the receiving resources, refer to Table 12.
Table 12 Name of soil type and type of consolidation
Maximum flow speed (m/s) with the depth of water flow H = 0.4-1m
-Consolidation with the concrete slab
4
-Limestone, sandstone
4
-Stone with cement mixture
3-3.5
-Fine sand, average sand, clay sand
0.4
-Raw sand, inclusion with weak clay
0.8
-Clay inclusion
1.0
-Clay
1.2
-Grass in the bottom of the channel
1.0
-Grass on the sides of the channel
1.6
NOTES: When the depth of the flow H lies outside the value range 0.4-1 m, the speeds in the table shall be multiplied with the adjustment coefficient K. + If H is less than 0.4 m, the coefficient K= 0.85. + If H is more than 1 m, the coefficient K =1,25. 4.7 The slope of drainage culverts, channels and canals
4.7.1 The minimum slope of the culvert imim shall be selected on the base of ensuring the minimum flow speed which has been stipulated for each kind of culvert and dimension of culverts. The slope of culverts from the storm water collection wells to drainage culvert is chosen to be 0.02. 4.7.2 The slope of the road trench, drainage channel shall be taken as Table 13. Table 13 Items
The minimum slope of road trench, channel
-Road trench covered with asphalt surface
0.003
-Road trench covered with chippings or rock
0.004
-Road trench covered with gravel stone or pebble stone,
0.005
4.7.3 The minimum dimensions of channels with trapezoid-shaped cross-section shall be taken as follows: The width of the bottom is 0.3 m, the depth is 0.4 m. Talley refers to Table 14. Table 14 Kind of soil in the canal + Fine sand
Talley rate 1:3
+ Small-sized sand, mortar and raw a)Separated type with the average compact
1:2
b) Compact
1:15
+ Inclusion with sand
1:1.5
+ Clay inclusion and clay
1:1.25
+ Gravel mixed soil and pebble mixed soil
1:1.125
+ Stone soil and water-proof soil
1:0.5
+ Weathered rock
1:0.25
+ Rock
1:0.1
5. Lay-out and drainage network 5.1 Lay-out and drainage network for residential area
5.1.1
For the residential points, it can select the basic types of drainage pipeline as stipulate in item 3.3 of this standard. In reality, depending on the natural conditions, the existing condition of drainage and the urban properties, the following types can be applied flexibly:
-
The shared drainage network: it is implemented for the old urban area only having the existing shared type or for the urban area having the favorable natural conditions.
-
When making the drainage planning, it is necessary to consider the capacity of reforming the shared culvert into the totally separated one in the future.
-
The separate drainage network: to apply for the new urban areas, expanded urban area, accumulated residential area with high population density (over 200 people/ha).
-
The combined drainage network: to apply for the big cities.
In the old urban areas, the storm water on the roof, in the garden, and so on. is normally discharged with domestic sewage. The upgrading to separate the two individual network has many difficulties. In this case, we have the incompletely separated network. The semi-separate network can be applied for the new urban areas with high environment standards in order to guarantee the sanitary conditions for the water reservoir, storage lakes or bathing yard. 5.1.2. For the small areas with the population of less than 5000 people, depending on the annual rainfall and other conditions, it can be applied the incompletely separate type or simply shared culverts. NOTES: The simple shared culvert is the tube culvert with the reinforced strings is mainly served for surface drainage. The domestic wastewater is primarily treated by septic tanks within each house. 5.1.3. For the mountainous area, the incompletely separate network in which the storm water is directly disposed into the receiving resources, the wastewater can be transported by self-flowing or by pressure. 5.1.4. It can employ the central management method for one or some residential points or groups of isolated buildings or in combination with sewage in production area. 5.1.5. It can organize distributed drainage in case of low population density (less than 200 people/ha) and permitted sanitary conditions, particularly there is no risk of pollution of soil , and water resources. In case the distributed drainage organization can be applied for the wastewater treatment facilities as follows: -
Septic tanks of many kinds;
-
Septic tanks with the treatment facilities under the soil;
-
Aeroten air blowing lasting;
-
Biological lakes and filtration yard to plant trees.
5.1. The characteristics of drainage network design of industrial units 5.2.1 The number of production sewage drainage network within the area of the industrial units is decided based on the components, volumes, temperature, ability to re-use wastewater and the necessity to treat primarily the kinds of wastewater. 5.2.2 Within the area of industrial units, depending on the components of the wastewater allowed to put in the drainage piping in the closed trench, opened channel, tunnels or guide bridge. 5.2.3 The distance from the walls of the tunnel to the sewage ditch storing the corrosive , high volatile, or high flammable substances (with the air and moist weight is less than 0.8 compared the atmosphere) shall be less than 3m. The distances among the pipeline to the underground layers shall be not less than 6m. 5.2.4 The locking, blocking, checking and connecting devices on the sewage drainage pipeline containing toxic, high volatile, high flammable substances shall be sealed completely. 5.2.5 Depending on the components, concentration and temperature of production wastewater having the corrosive properties, the following types (faience, pottery, glass, PVC, composite, steel with rubber bottom, cast iron with bitumen) will be used reasonably. NOTES: The pipelines made of polytelen, cast iron pipe dipped with bitumen, piping layered with rubber are used when the temperature of wastewater less than 60oC. The other flexible pipelines shall follow the instructions of the manufacturers. 5.2.6 Caulking of sewage ditches with acid properties is done with asbestos fiber dipped with bitumen and covered by acid-resistant concrete mortar. 5.2.7 It is required to have the protection methods for the facilities on the sewage drainage network with corrosive properties caused by moisture and water; and shall be ensured to prevent the leakage into the soil. 5.2.8. The inner of the manhole on the sewage drainage ditch with the corrosity shall be made of corrosion-resistant material. Ladders in the manholes shall not be made of material of high corrosity. NOTES: If the diameter of sewage diameter piping is below 600mm, it should layer the distribution channel with the plastic pipe segment divided into two or suitable corrosion-resistant material.
5.2.9. The sewage discharge wells containing the flammable, explosive substances of the production lines shall have the hydraulic screen while on the external network shall comply the industrial enterprise design standard or regulations of the functional authorities. 5.2.10. In the areas of warehouses, fuel tank, high flammable, toxic, acid and alkaline substances without stain sewage, the storm water should be transferred through distribution wells with valves. In the normal cases, it can be discharged into the storm water drainage network, in case of accidents, it can be disposed into emergency tanks.
5.3 The drainage diagram of polluted water surface of the residential points and industrial parks. 5.3.1 For the residential areas with separate drainage network not mentioning the treatment requirement for polluted surface water (rainwater of early season, road washing water, yards, and so on), when making the drainage master plan, it is required to consider the requirement to make the capacity of implementation in the future. However, in the near future, in the favorable conditions, it is encouraged to apply simple solutions (seepage, storage) in order to decrease the level of pollution due to surface water. 5.3.2 When discharge of storm water into the bathing yard and the aquarium planting area, it is required to have the minimization solutions of pollution, meeting the request of water use of each object. 5.3.3 For industrial parks, it is necessary to control strictly kinds of other storm waters and surface waters. The stagnant surface water shall be treated in order to ensure the sanitary standard. The surface water is expected not to be polluted shall also be collected into the storage tanks in order to control before discharge into the receiving resources.
6. The sewage drainage network and facilities on the network 6.1 The principles of lining and installation of ditch 6.1.1 During the classification of streams and lining sewage drainage network, it is required to pay attention to natural conditions and master plan of the urban area, it is necessary to make use of topographic conditions to build self-flowing ditch network. For the urban areas to be renovated, it is required to re-use the existing sewage drainage network. 6.1.2 The arrangement of sewage drainage on the master plan as well as the minimum distance from the outside of the ditch to the facilities and the other technical networks shall comply with Construction standard of technical infrastructure, in accordance with the master plan of the urban area, at the same time considering the detailed conditions of each road line.
Arrangement of drainage culvert shall study the use ability of vehicles for construction. 6.1.3 Arrangement of some pressure pipeline in parallel, the distance between external faces of the piping shall ensure the construction and maintenance capacity in need. The distances between the culverts B shall not be less than the following values, depending on the production material, internal pressure and geological conditions. -
When the diameter of the culverts up to 300 mm: B = 0.7 m
-
When the diameter of the culverts from 400 to 1000 mm; B – 1.0 m
-
When the diameter of the culverts over 1000mm: B= 1.5m
NOTES: In case it is required to decrease the distance B as per the regulation, the culverts must be placed on the concrete floor. 6.1.4 Arrangement of culverts on the streets shall at the same time arrange subsidiary culverts (culvert level 3 or level 4) in order to connecting to indoors network. Connecting to internal culverts for urban culverts shall be included manholes. Manholes are the landmarks stipulating the responsibility limit of maintenance of the urban drainage units and drainage households. 6.1.5 In the sewage drainage network, it is required to build emergency discharge gates for discharging wastewater into the storm water drainage or receiving resources in case of accidents. Construction and determination of position for discharge gates shall have the agreement of drainage units and local environment management organs. 6.1.6. Within the residential area, drainage pressure pipeline shall not to be put afloat or hanged over the ground. NOTES: For the drainage culverts going by deep holes, rivers, lakes or when placing the external drainage piping out of residential area shall be allowed to be put on the surface or hanged on the bridge.
6.2. Bending corner or piping. Connecting pipe and depth of placing pipes 6.2.1 Connecting corners between two sewage ditch networks shall not be less than 90o. NOTES: It is allowed to randomly take connecting corners when connecting the culverts through the step wells of straightly vertical type or connecting the storm water collection wells with the step wells. 6.2.2 In the bending position, it is necessary to build manholes with the internal curve trench of the radius not less than the radius of the manholes. When the culvert radius is equal or more than 1200 mm, it is
allowed to build curve culverts with the radius not less than 5 times of the culvert radius and shall have manholes in two ends of curved culverts. 6.2.3 Connecting the culverts with different diameters in manholes as peak culvert level, or as per the calculated water level. 6.2.4 Connecting the trench with closed culverts shall be across the manholes with sedimentary pits and trash rack. 6.2.5 The depth for placing the smallest culvert hmin for culvert peak is regulated as follows: -For the culverts having the diameters less than 300mm placed in the area without travelling of vehicles
hmin = 0.3 m. - For the area with travelling of vehicles, hmin = 0.7 m. In the special cases, when the depth is less than 0.7 m, there shall have protection measures for culverts. NOTES: The biggest depth to place culverts is determined as per calculation, depending on piping material, technical and meteorological geological conditions, construction method and other technical factors.
6.3 Piping, pipe supports, accessories and piping foundation 6.3.1 The following ditches can be used for drainage: a)Self-flowing ditches: reinforced concrete ditches without pressure, concrete ditches, asbestos cement ditches in the centrifugal method, pottery ditches and kinds of reinforced concrete structures for assembly. b) Pressure ditches: using the reinforced concrete pipes with pressure, asbestos cement pipe, cast iron pipe, stainless pipe and plastic pipes. NOTES: -All the kinds of ditches, besides to ensuring the mechanical strength, waterproof, it is required to guarantee the smoothness of the internal surface as international standards. - When selection of drainage ditches, it is required to consider use of local material to pipe fabrication and on the condition of spot fabrication (geographic-technical conditions, underground level). -It is permitted to use cast iron pipes to discharge self-flowing water and steel pipe to discharge pressure water in the following cases:
- When placing ditches in the areas of difficult construction, subsiding soil, expanded soil and smarsh, the area under mineral exploitation, caster phenomenon, the areas across the rivers, railways or motorbike road, when intersection with domestic water supply piping, when placing the ditches on the guide bridges or the places with mechanical turbulence. - When placing in the erosive environment, the anti-erosive types of ditches or protection methods shall be available. - The steel pipes shall have corrosion-resistant layer on the surface. In the places with the phenomenon of electrochemical corrosion, there shall have the special protection methods. 6.3.2 When using the hard plastic pipes is required to take consideration on protection methods for piping with external cover. 6.3.3 The types of foundation for piping depend on the strength bearing capacity of soil and mechanical loads on ditches. The sewage ditches may be placed directly on the natural soil foundation after carefully compacted. In case of weak soil, it is required to make artificial foundation before placing ditches. It is necessary to be based on natural conditions, construction capacity and capacity to use local material to select the suitable type of foundation for placing ditches. 6.3.4 On the pressure drainage ditches, it is required to put valves, discharge valves, expansion joints, in the manholes. 6.3.5 The slope of pressure ditches against the discharge valves shall not be less than 0.001. The diameter of discharge valves shall ensure full drainage of ditches for not more than 3 hours. It is required to dispose water into the storm water drainage network or into the surface water resources provided that the sanitary conditions are guaranteed. In case the discharge cannot be carried out, building local pumping stations or transporting the wastewater by xitec cars. 6.3.6 At the positions of change of flow directions, in case tensile cannot be transferred to connection point of ditch, the pipe support must be used. NOTES: -In the following cases the pipe supports are allowed not to use pipe support: -Pressure pipes with bowl type have working pressure up to 100 N/cm2 and bending corner up tp 10o. -Pressure pipes made from welded steel is placed with bending corner up to 30o in the vertical surface.
6.4 Connection joints of pipes
6.4.1 Sewer connection of bowl type connected with rubber gasket and the smooth ditches at two ends connected by concrete belt used only for small-diameter culverts. 6.4.2 Requirements for joints of pressure sewer lines are based on design criteria for water supply.
6.5 Manholes 6.5.1 In the sewerage network, manholes need to be put in the following positions: - Place of connecting the culvert lines. - Redirecting culverts, slope changes or changes in diameter. - On the straightly placed culvert segments, according to a certain distance, depending on the size of culverts shall be taken from Table 15. Table 15 Pipe diameter D (mm) (m)
The distance between manholes
150-300 20-30 400-600 40 700-1000 60 Over 1000 100 Notes: For pipes with diameter D400-600 mm, if the thickness is less than 0.5 D and the calculated velocity calculated is equal to the minimum velocity, the distance between the manholes shall be 30 m. 6.5.2 In manholes, the edge of trenches must be placed horizontally to the level of peak culverts having the largest diameter. Manholes have the culverts with diameters of 700 mm or more, it is allowed to make working platforms on one side of the trench. The platforms is far from the facing walls not less than 100 mm. In the manholes with the culverts of 2,000 mm or more in diameter, it is allowed to place on the working platform on cantilever beams; then, the size of drain openings must not be smaller than 2000x2000 mm. 6.5.3 The size of manholes shall be regulated as follows: a) The culverts with the diameter less than or equal to 800 mm , the internal size of manholes shall be: D = 1000 mm or axb = 1000 x 1000 mm). b) Drain culverts with the diameter D of 800 mm or more , the internal size of manholes is 1200 mm in length and D +500 mm in width). c) The gates of manholes has the smallest size of 600x700 mm or 700 mm in diameter.
NOTES: - The small manholes have the width of not more than 700 mm, the depth of not exceeding 1.20 m. - The manholes are made of concrete or reinforced concrete. The manholes are made of bricks just for drainage works in the small residential or urban areas. 6.5.4 Dimensions of manhole foundation in the turning points shall be determined by arrangement conditions of curved trenches in manholes. 6.5.5 The height of the working platforms in manholes (from working platforms to the supporting frame for the neck of the manholes) is usually taken at 1.8 m. The manholes are more than 1.8 m deep, there will not have the neck of the manholes. 5.5.6 There shall have ladders in manholes for maintenance work. Ladders can be fixed up on the body of the manholes or portable ladders. The distance between the ladder steps is 300 mm. The first ladder step is 0.5 m far from the manhole's mouth. 6.5.7 In areas of complete construction, the cover of the manholes is placed at the same level with the road surface. In the areas of planting trees, manhole covers must be 50-70 mm higher than the ground , while in the areas without building the distance is 200 mm. In case of special requirements (avoiding flooding by rainwater), the manhole covers may be set higher. 6.5.8 The manholes in storm water drainage network have the similar construction as those of wastewater network, but only the manhole bottoms shall be required to have sediment pits. Depending on the completion level of the drainage areas, the depth of sediment pits can be taken from 0.3 to 0.5 m. 6.5.9 There must be the solutions of waterproof for the walls and bottom of the manholes. If the manholes are made of brick, waterproofing must be 0.5 m higher than groundwater levels. 6.5.10 The manhole covers and the step turning manholes may be made of cast iron or reinforced concrete, bearing the load in accordance with H30 standard. If using a reinforced concrete caps, the manhole mouths must have the appropriate structure to avoid chipping, or breakage due to impact of vehicles as well as opening and closing the caps. The size of reinforced concrete caps must ensure the convenient covering and opening. NOTES: - If manhole caps are placed on roads with heavy trucks, individual design calculation must be required. - In a municipality or an urban area, the manhole caps must be made in the same type.
5.6.11 When the sewer line is located in the high speed roadways with large traffic density, it is allowed to construct the manholes on pavements and connect with the drains by tunnels. The height of the tunnels is equal to the height of the largest drains, the tunnel basement is 0.3 m higher than the bottom of drains.
6.6 Manholes and connection wells to the urban sewage 6.6.1 Manholes (see clause 6.1.4) have the horizontal view of round or square shape with the size 400x400 mm or 600x600 mm. The manholes are usually arranged on pavements, and rarely opened, so the manhole caps can be made of reinforced concrete. The wells connected to the urban sewage can have simple structure. In the case of the street lines built in the type of separate houses, there will have more connections wells close together.
6.7 Well for washing drains 6.7.1 The first culvert segments of the totally separated sewer drainage network often fail to completely ensure self- cleaning speed, so there should arrange semi automatic or manual drain washing wells.
6.8 Wells in transition 6.8.1 Wells in transition are built for the following reasons: - Transfer of wastewater, storm water down to the drains with greater depth. - Ensuring the flow rate of water in the pipe does not exceed the allowable values or to avoid sudden changes of the flow rate. - In case of avoiding the underground facilities. - When discharging water in the flood discharge method . NOTES: For the pipes with the diameter smaller than 600mm, if the step switching height is less than 0.3 m, it is allowed to replace step switching wells with manhole with overflow dam smooth flow. 6.8.2 For step switching wells with the height less than 3m, on the sewer lines with the diameter of 600 mm or more, the type of spillway dam should be built. 6.8.3 For step switching wells with the height less than 3m, on the sewer lines with the diameter of 500 mm or more, the type having one vertical pipe inside and the cross section area not less than the input pipes should be built.
Above the standing pipe, there must have water collection funnels, under the standing pipe there is energy consuming holes with the metal plates placed at the bottom. NOTES: For the vertical pipes with the diameters under 300mm diameter, it is allowed to use flow orienting conduits the flow of energy to replace energy dissipaters. 6.8.4 When the height of switch level is greater than that specified in items 6.8.2 and 6.8.3, it is allowed to construct the wells according to their own design. These usually applied types of wells in this case include: ladder step-typed wells, eddy overflow dams, or so on.
6.9 Rainwater collecting wells 6.9.1 Storm water wells are located in the trench lines of roads have distances determined by calculation, in addition, there should arrange collecting wells in hollows, the crossroads and in front of walkway across the roads. When the streets are less than 30 m wide and have no collection wells within sub-areas, the distance between the wells may take according to Table 16 . Table 16 Slope along the streets
Distance between collection wells (m)
Less than or equal to 0.004
50
From 0.004 to 0.006
60
From 0.006 to 0.01
70
From 0.01 to 0.03
80
NOTES: 1. The regulation does not apply for collection wells of curb pit type (collection wells with vaulted entrance). 2. When the street width is greater than 30 meter or when the slope is greater than 0.03, the distance between the collecting wells shall not be more than 60m. 3. Regarding to the urban areas with high rainfall intensity, more plant leaves or garbage on the streets, it should be applied the type of the combined wells ( types of both pavement and curb collection) or increase the length of the collecting wells twice compared with conventional wells. 4. Regarding to the lower areas (often at crossroads) where there are multiple water flows to converge, the number of water collection wells must be increased double.
5. For mountainous areas, the streets often are steep at the points of collection wells, so it shall lower the surface of roads about 0.1 m or create turning angles to improve collection capacity of collection wells. 6.9.2 The length of the pipe sections connected from the collection wells to manholes of the culvert network shall not more than 40m. 6.9.3 It is permitted to connect storm water drain culverts of houses into the storm water collection wells. 6.9.4 The bottom of the rainwater collection wells is required to include sediment reservoir with the depth from 0.3 to 0.5 m and collection gates must have trash rack. Trash rack must be placed about 20-30 mm lower than the road trench. 6.9.5 For common drainage network in residential areas, the collection wells must be included hydraulic locks to prevent odors; water layer height shall not be less than 0.1 m . For urban areas with large annual evaporation quantity, it is necessary to apply combined hydraulic lock type in manholes (the wells connected with the collection wells). Despite hydraulic locks, by all cases it is still required to pay attention to ventilation for sewer drainage culverts. 6.9.6 Connecting to the sewer drain openings with closed culverts with the manholes having sediment pits, the craters of the pits must be placed with trash rack with the openings not exceeding 50mm; the diameter of connected pipe segment is determined by calculation but not less than 300 mm. 6.9.7 For the rainwater drainage network, when the level difference among the culvert bottom is less than or equal to 0.5 m, a diameter of the culvert is less than 1,500 mm and the speed does not exceed 4 m/s, the sewer connection with manholes is allowed. When the level difference is greater, the step switch wells are required.
6.10 Conduit through rivers, streams, or canals 6.10.1 The diameter of conduit through rivers and streams shall not be not less than 150 mm. The number of normal operating conduit shall be at least two, steel pipes coated with corrosion resistant layer and guaranteed from mechanical impacts. Each pipe must be tested the capacity of guiding calculated water flow with the consideration into the allowed rise level. If wastewater flow does not guarantee the minimum calculated speed, only use a pipe for operation and another pipe for emergency case. In addition two operating pipelines, it is required to build one standby pipe network for discharge in case of accidents.
When designing the conduit through rivers for water supply sources, it is required to acquire the local organs for natural resource and environmental management or local organs of stand-by sanitation for permission. When designing the conduit through rivers with the travel of ships and boats, it must comply with the river way safety regulations and must be approved by waterways management agencies. NOTES: When passing through the slit, dry valleys, it is allowed to put a threaded pipe. 6.10.2 When designing conduit, it should take: - Peak of the conduit is placed deeply, at least 0.5 m apart from the river bottom. - In the river areas with many vessels travelling through, the depth shall be not less than 1 m. - Inclination of pipe segments against in two riversides shall be not larger than 20o from horizontal line. - The distance between the outer edge of two conduit shall not be less than 0.7 to 1.5 m, depending on the pressure of water in the pipe. 6.10.3 The manholes located at the entrance, exist doors and emergency discharge wells must be installed with stop-logs. Arrangement or emergency discharge wells must be permitted by local management agency of water resources and the environment. 6.10.4 If the manholes are constructed in the riverside battures, it is required to estimate the ability to avoid the flood in water raising seasons. 6.10.5 For general drainage systems, it must be checked one threaded pipe in order to ensure drainage conditions in the dry season as per the specified standards.
6.11 Pipeline across the roads 6.11.1 When running through railways, roads with heavy load trucks or main streets , the sewer drainage lines must be put into the closed pipes or submerged tunnel. 6.11.2 Before and after the sewer lines across the roads there must have manholes and in special cases the lock devices are required. 6.11.3 Design profile of drain lines across the roads must be approved by the relevant authorities.
6.12 Culvert discharge of wastewater, rainwater and storm water overflow wells
6.12.1 Wastewater discharge drain into rivers and lakes must ensure good conditions of dilution of stream water with wastewater and must not affect the aesthetic view and local environmental areas. Sewer discharge culverts into the rivers should be arranged in the areas so that it can enhance the disorder movement
of flow (shrinking space, falls or so on.) Depending on the conditions of the treated
wastewater discharge into rivers discharge types can be applied: coastal discharge or discharge into the center of the riverbed, concentrated or diffused discharge. When the treated wastewater is discharged into reservoirs, discharge doors must be deep under water surface. 6.12.2 The wastewater discharge pipes into the center of riverbed and deeply under water surface must be made of steel with corrosion resistant layer and placed in the trench. Discharge mouth is placed on the center of riverbed, coastal discharge and flood discharge all must be reinforced with concrete . The structure of discharge gates must take into account the following factors: traveling of boats and vessels, river water levels, the effect of waves, geological conditions, changes in the river bed, and so on. 6.12.3 Storm water discharge can apply these following types: 1. When there is no bank reinforcement- the type of open ditches. 2. When there is bank reinforcement- a sealed discharge gate. NOTE: To prevent the backflow of water from the receiver into sewer system (in the case of that water levels in the receiver is higher than the water level in the drain culverts), at the discharge gates backflow blocking valves should be installed. 6.12.4 Storm water overflow wells of common drainage systems shall have a spillway to prevent sewage (CSO). Dimensions and structure of overflow dams are dependent discharge of water flow into the source, the water levels in the receiving resources and sewer culverts. Storm water overflow wells must include deposition of blocking for sand sediment and trash rack. 6.12.5 Location of discharge gates for wastewater or storm water and their composition must be approved by agencies for natural resources and environment management and local agencies for waterways management. When designing the sewer network, the preliminary treatment works (sand or slurry sediment) should be considered to be built at the locations of combined sewer overflow (CSO) to ensure that rainwater or a mixture of rain water and waste water not to cause negative impacts on the sanitary conditions of the receiving water.
6.13 Air release for to the drainage network 6.13.1 The air exhaust for the sewerage network is done through indoor vertical standing pipes or the slots on the manholes. 6.13.2 The special equipment for air release is arranged in the gates into conduit through into the rivers, in the manholes (in the positions of lower flow velocity in the culverts with the diameter greater than 400mm) and in the transfer wells where transfer level is more than 1m and wastewater flow is over 50 l/s. 6.13.3 In the special cases, it is allowed to design forced air exhaust system. 6.13.4 In the case of natural ventilation for external drainage network to guide the wastewaters containing toxic and flammable substances, at each connection point of indoor culverts into the outdoor culverts, it is required to arrange the vertical exhaust pipes with the diameter not less than 200 mm.
7. Sewage pumping stations and air pumping stations 7.1 General Requirements 7.1.1 According to the credibility, sewage pumping stations and air pumping stations are classified into three distinguished categories, shown in Table 17. Table 17 Sort by reliability
Operation features of the pump stations
Type I
Not allowed to stop or reduce the flow
Type II
Permitted to stop sewage pump for not more than 6 hours
Type III
Permitted to stop sewage pump for not more than 1 day
NOTE: The stoppage of pumping sewage specified for pumping stations no. II and III, takes into account the conditions of production technology or the water supply suspension during not more than 1 day for residential areas with less than 5,000 people. 7.1.2 When designing production wastewater pump stations is hot water, the water contains flammable substances, and hazardous substances, in addition to compliance with the provisions of this standard, it shall also follow the standards of the respective industries.
7.2 Wastewater pumping stations
7.2.1 Selection of pumps, equipment and waste water pipelines are selected depending on the flow for calculation, the water column height to pump, physical and chemical properties of waste water and sediment, has taken into account the characteristics of pumps and pipes as well as putting the facilities to use in phases. The number of standby pumps is determined according to Table 18 Domestic waste water or production wastewater with similar characteristics with those of domestic one.
Waste water with corrosive features
Number of pumps Number of working pumps
Number of stand-by pumps as per the reliability of pumping stations
Number of working pumps
Number of stand-by pumps for all kinds of pumping stations
Type I
Type II
Type III
1
2
1
1
1
1
2
2
1
1
2-3
2
3 or more
2
2
1 and 1 in 4 stock
3
-
-
-
-
Not less than 50 %
5 or more
NOTES: 1. During the storm water pumping stations, there are not backup pumps, except for the accidents when rainwater cannot be discharged. 2. Renovation to increase the pumping capacity of the pump stations type III to pump domestic wastewater and production wastewater with the similar characteristics as those of domestic one, it is allowed to have no backup pumps, but they must be available in stock. 7.2.2 Pumping stations of domestic wastewater and contaminated surface water must be built into separate projects. Wastewater pumping station is allowed to be build in the whole block in the production building or in the subsidiary building. In the machinery cabin of pumping stations, it is permitted to place kinds of pump for different sewage types, except for the hot waste water , and the waste water containing combustibles and toxic substances. It is allowed to set out the pumps to pump domestic wastewater in subsidiary houses of the wastewater treatment plant.
7.2.3 On the sewage distribution pipes into pumping stations, block valve must be required and can stand on the ground for closing and opening. 7.2.4 The number of pressure pipelines for pump stations type I is not less than 2 and must be ensured in case of an incident when a pipeline stops working, the remaining conduit shall ensure 100 % load of calculated flow; in this case, it should consider using backup pumps. For pump stations type II and type III, only one pressure pipeline is permitted. 7.2.5 It is recommended to use submersible pumps for sewage pumping, if other types of pump are used, self-priming pumps must be installed. In special cases when the pumps must be placed higher the water level in the collection compartment, it is necessary to take measures for its priming. The axis of sludge pumps are always placed below the mud level in the mud tank. 7.2.6 Each pump should have a separate suction nozzle. 7.2.7 Velocity of wastewater or sludge in suction and discharge pipes shall be ensured not to cause sedimentation. For domestic wastewater, the minimum velocity shall refer to Article 4.6.1. 7.2.8 In some sludge pump stations, the washing measures for suction and discharge pipes are required. In the special cases, it is permitted flushing these pipes by mechanical methods. 7.2.9 To protect the pumps from clogging, in the sewage collection compartment there is a need to install trash racks of manual, mechanical or combined with grinding types. As the volume of the garbage is less than 0.1 m3/d, it is permitted to use but manual trash rack. The width of the gap of trash rack must be 10-20 mm smaller than the diameter of entrance of pumps. When using mechanical trash rack or the combined trash rack with the grinding, the number of backup devices is taken from Table 19. Table 9 Type of trash rack
Quantity Working
Backup
1.Mechanical trash rack with the gap -Over 20 mm
1 to 3
1
-16-20 mm
Over 3
2
2.Trash rack in combination with grinding
1 to 3
1 (mechanical)
-Mounted on the pipelines
1 to 3
1
-Mounted on the channels
Over 3
2
3.Mechanical trash rack
1
-
7.2.10 The sewage velocity corresponding to maximum flow through the gap of mechanical trash rack is 0.8 - 1 m/s, but through combined trash rack with grinding is 1.2 m/s. 7.2.11 If the pump stations use mechanized trash rack, there must be a grinding machine. Debris after being crushed will be discharged in front of trash racks. If the garbage volume is over 1.0 T/day, there should be garbage grinding machine. 7.2.12 Garbage volume is taken from the trash rack can preliminarily be calculated following Table 20. Table 20 The width of the gap of trash rack (mm)
The trash volume from trash rack calculated for one person (l/year)
16-20
8
25-35
3
40-60
2.3
60-80
1.6
90-100
1.2
The individual weight of garbage is about 750 kg/m3, non-regulated time coefficient of garbage is taken to the pump station will be preliminarily 2. 7.2.13 In determining the foundation size of the machine room, a minimum width of aisles between the most convex parts of pumps, pipes and motors can be taken as follows: a) Among the motor units - if the electric motor has the voltage less than 1000 V, the minimum width will be 1 m. If the motors with the voltage more than 1000 V, the width will be 1.2 m. b ) Between the motor unit and wall of pump stations: - In the well-typed pumping station, it will be 0.7 m. - In the pump stations of other types, it will be 1 m. c ) Prior to the electrical panels - 2 m d ) Between the convex parts of fixed equipment: 0.7 m. In the pump stations, there must be machine installation platform, with the size to ensure the width of walkways around equipment not less than 0.7 m, including moving the lifting equipment to mounting position.
NOTES: 1. In pump stations located deeply, it is required to use the motors with the voltage below 1000 V and diameter of suction pipe less than 200mm; it is allowed to place pumps at least 0.25 m apart from the wall of machine room, but the aisle width between the machine nits must comply with the above-mentioned regulations. 2. It is permitted to put 2 pumps with a motor of power up to 125 KW, and voltage below 1000 V on the same footing. In this case, it is no need to leave the aisle between 2 machines but ensuring walkways around the machine with a width of not less than 0.7 m. 7.2.14 Height above the ground of the machine room (from the installation floor to the underside of roof beams) depends on the lifting devices, the height of pumps, the length of cable (0.5-1m), the distance from the installation floor to the pump units (not greater than 0.5 m), and the size of the lifting devices (from the hooks to the underside of the roof beams). 7.2.15 To manage spare parts and equipment, pump stations should be equipped with lifting devices: - If the weight of the device is used less than 1 ton, pulley block of fixed suspension or suspended crane with manual control. - If the equipment weights less than 5 tons, suspended crane girder with manual control will be used. - If the equipment’s weight is over 5 tons, electrically driven cranes will be used. NOTE: When hoisting equipment with a height of 6 meters or more , or machine length more than18m, electricity run lifting devices is needed. 7.2.16 Floors of machine room must contain leaking water collection pits, pumps or measures separately. The slope of the floor against the pits of water leakage shall be 0.01- 0.02. 7.2.17 The collection compartment volume of pumping station is determined wastewater flow, power capacity and the working mode of the pumps but not less than a pump of the maximum capacity working in 5 minutes. The collection compartment of pump station with the capacity larger than 100,000 m3/d should be divided into two compartments, but should not increase the total volume. The receiver compartment volume of pump station of fresh sludge, fermented sludge or activated sludge is determined by the mud discharged amount from the tanks of sediment, methane, circulating activated sludge and activated sludge residue. The smallest volume of the receiver compartment of mud pump stations to remove sediment out of the treatment plants is determined to be equal to the capacity of a pump working for 15 minutes. If sludge
from the treatment works is transmitted to intermittent tanks during pump operation, the volume of container is allowed to decrease. The storage compartment of sludge pump station is allowed to use as quantification equipment or water storage for slurry pipeline flush. 7.2.18 In the mud storage tank, it must be equipped must mud mixture and pool washing. The slope of the tank bottom to the water reservoir pit shall be not less than 0.1. 7.2.19 Collection compartment of sewage pumping stations can be divided into separate sections to classify different types of waste water for individual treatment methods or mixture to form toxic gases or sedimentation. 7.2.20 The distance from the outside of the receiver compartments for production waste water containing combustibles and toxics from other works is specified as follows: - To the pump station, it is less than 10 m. - To the other premises, it is not less than 20 m. - To the public facilities, it is not less than 100 m. 7.2.21 Structure of wastewater collection compartments containing corrosive or toxic substances must ensure prevention these substances from seeping into the soil; for wastewater containing corrosive substances, the measures against corrosion is necessary. 7.2.22 The machine room of the sewage pumping stations containing corrosive substances is required to have anti-corrosion measures for building structures (floor, foundation, etc.). 7.2.23 In the pumping stations of sewage with corrosity, flammable, explosive or volatile substances should place pipes and fittings on the floor and must be convenient for inspection and repair as needed, the number of valves should be used as least as possible. NOTES: Placing pipeline in the trench should require ventilation measures for the trench or filling trench with sand. 7.2.24 In front of the sewage pumping stations in the common or private sewer system, the sand settling tanks is required. 7.2.25 The pumping stations should be included with daily supporting facilities (sanitary ware, bathing or dressing room). Auxiliary area depends on the capacity of pump stations, specified in Table 21. Table 21 Capacity of pumping
Auxiliary area (m2)
station (m3/d)
Catering area
Workshop
Storage
Up to 5000
-
-
-
From 5000 to 15000
8
10
6
From 15000 to 100000
12
15
6
Over 100000
20
25
10
NOTES: 1. The auxiliary area in pump stations located in the factories, enterprises and treatment works may not be necessary if there have been similar projects in nearby houses. When the distance is over 50m, the sanitary equipment should be arranged in pump stations. 2. During the pumping stations without regular servants, auxiliary rooms are not required.
7.3 Air pump stations 7.3.1 The air pump station must be located near end users and electrical distribution equipment within the waste water treatment plant. In air pump stations, it is permitted to place air filter devices, pumps to pump technical water and drain aeroten tanks, activated sludge pumps; central control equipment, distribution equipment, transformers, and living rooms, and other auxiliaries. 7.3.2 Design of air pump stations must consider the possibility of increasing design capacity by placing additional gas supply machines or replacing with the machine with greater capacity. 7.3.3 Air pump stations must be powered continuously. 7.3.4 Capacity, type and quantity of air pumps must be chosen based on the technological calculation of air supply facilities with the attention to the structural characteristics of these buildings. 7.3.5 When the capacity of air pump stations is over 5000 m3/h, at least 2 pumps are required; while in case of smaller capacity, only one pump is allowed. Number of standby generators is regulated as follows: - When 3 generators are under operation - 1 standby generator is required. - When 4 or more generators are under operation - 2 standby generators are required. 7.3.6 In necessary case, it may supply oil for air pumps collectively.
7.3.7 Cooling water should be constantly provided for the drive shafts of the pump cluster and the oil coolers of air pumps. The quality and temperature of cooling water should ensure to comply strictly with the gas pump manufacturer's requirements. 7.3.8 The machine room must be separated from other rooms and include doors directly to the outside. 7.3.9 The equipment layout in the machine room should ensure the following conditions: a) The path between the machine cluster and the building wall: - From the gas pumps, it shall be not less than 1.5 m. - From the electric motors: it shall be large enough to remove rotors. b ) The path between the convex part of the machine cluster shall be not less than 1.5 m. 7.3.10 In order to manage spare parts and equipment, air pump stations must be included lifting equipment as prescribed in Article 2.7.16. 7.3.11 Equipment for air exchange must be designed as the regulations for ventilation, heat supply and air condition, or as directed by a specialized consulting agencies. The air should be cleaned in sealed filters. Arranging the air filters must ensure the ability to remove each unit for replacement or recovery. When there are 3 air filters under operation, a backup filter is needed; if there are more than 3 air filters under operation, two standby filters are required. NOTES: 1. In case of air distribution in aeroten with drilled holes, it is required to use air without filtration. 2. When the capacity of air pump station is over 20 thousand m3/h, each machine cluster must have separate collection chamber and air filter. 7.3.12 Velocity of air movement is regulated as follows: - In the filter chamber: under 4 m/s; - In the conduit: less than 6 m/s; - In the pipeline: from 10 m/s to 40 m/s. 7.3.13 While calculating conduit, it should pay attention to the phenomenon of temperature increase when air is compressed and ensure minimum pressure difference between the chambers of air supply.
NOTE: The calculated value of pressure loss in the gas distribution equipment has considered the resistance increased with duration of use. 7.3.14 In case of using thin-walled steel pipes, electric welding, or production of air conduit with pressure, measures should be taken against noise and heat insulation for piping when placed indoors.
8 . Works for sewage treatment 8.1 General requirements 8.1.1 Method and level of wastewater treatment depend on the flow, composition, and characteristics of wastewater, characteristics of the receiving water and sanitation requirements during sewage discharge into the source and the specific conditions of local areas, and so on. Wastewater during discharge into the sources must meet the provisions of current environmental standards. The effort is required to take advantage of available natural conditions such as ponds, lakes, tree planting area, etc. for wastewater treatment. Only when the treatments by natural conditions are not allowed, or not applicable , shall the new construction of artificial wastewater treatment be carried out. The effort is also required to make use of the treated wastewater for agricultural production or for other economic purposes. Sewage sludge must be treated before use as fertilizers or for other purposes. NOTES: The level of wastewater treatment should be limited to the processing efficiency that the biological treatment facilities in artificial conditions can be guaranteed. 8.1.2 Capacity of wastewater treatment stations is determined to comply with the following rules: - Power capacity: Q = 0.8 a N (m/d)
(12)
In which: a - water supply standards; N - number of people with water supply. Normally the number of people with water supply is less than urban population, depending on the ratio of the population connected to the urban drainage system m. N = m No
( 13 )
In which: m - coefficient of connection; No- population in the area of calculation. - Maximum flow in the dry season: Qmax.kh =1/24.Q.k (m/h)
(14)
- Maximum flow in the rainy season : Qmax.m =1/24.Q . N (m/h)
(15)
In which: k - coefficient of non-regulating hours; n - dilution factor. 8.1.3 The capacity of the wastewater treatment station of industrial concentration is determined based on of each wastewater plant put on station. In the absence of this data, the capacity of the wastewater treatment plant Q (m3/d) was determined according to the following formula: Q = qxF
(16)
In which: q -wastewater standard (m3/ha.d), depending on production types in industrial zones; for this type of production with less wastewater, q is preliminarily selected to be 15-25 m3/ha.d; for this kind of production with average wastewater, q is 30 to 40 m3/ha.d; and for the type of large wastewater, q is 50 to 70 m3/ha.d. F - industrial area where sewerage systems serve, ha. 8.1.4 Mixture of domestic and production wastewater when being put to the biological treatment plant must always ensure the following requirements: - pH shall not be less than 6.5 and not greater than 8.5; - Temperature shall not be less than 100C and not above 40oC; - The total concentration of dissolved salts (TDS) shall not be more than 15g/l; BOD5 while putting in biological or pushing aeroten filtration tanks shall not exceed 500 mg/l; While putting aeroten into dispersed water distribution, the amount shall not exceed 1000mg/l. The concentration of organic matter must not exceed the prescribed regulations in Table 22 and toxic substances shall not exceed the regulations specified in Table 23. Wastewater does not contain insoluble fats, plastics and fuel oil. -
Not containing surface active agents which cannot be oxidized in treatment works.
-
Nutrient content must not be lower than the level specified in Table 23. Table 23
Substances
BOD5
COD
(mg/mg of inspected substance)
(mg/mg of inspected substance)
Allowed concentratio n limit for treated sewage in
Average oxidation speed under treatment in mixed aeroten
Permitted concentration (mg/l), in urban sewer (biologically treated completely
mixed aeroten (mg/l)
(mg BOD5/g activated dry smudge/hour)
in aerotens with 1.8 g/l mud, air blowing time of 7 hour)
Anilin
1.9
2.4
100
9
6
Axetandehyt
1.07
1.88
750
12
20
Axeton
1,68
2.17
600
28
40
Acid benzonic
1,61
1.97
150
14
15
Butanol
1.8
2.58
600
15
10
Glycerin
0.86
1.23
1150
30
90
Caprolactam
1.8
2.12
300
22
25
Andehit crotonic
1.6
2.5
400
3.5
6
Metanol
1.05
1.5
950
23
30
Propanol
1.68
2.4
600
18
12
Toluen
1.1
1.87
200
8
15
Axetic acid
0.86
1.06
200
26
45
Phenol
1.18
2.38
1000
14
15
Etanol
1.45
2.08
700
19
14
Dietyl hecxanol
1.55
2.55
400
100
6
NOTES: 1. The average rate of oxidation of a mixture of many substances shall be determined experimentally. When it cannot be calculated by the experiments, the method of average calculation of oxidation speed for each substance (according to the ratio of the mass and BOD5 of substances) during air blowing is applied. 2. When connecting sewer culverts of industrial enterprises into the urban drainage system, the calculated concentration of substance shall be the concentration in the general flow. Table 23 Name of substance
Oil and petroleum products (1)
Permitted concentration of each substance in sewage while transporting to completely biological treatment facilities (mg/l) 25
Removing level of polluted substances during complete treatment (%) 85-90
Combined surface active substance (2) -Easy anion oxidation substances
20
80
-Non-ion oxidation substances
50
90
-Anion intermediate substances
20
60
-Non-ion intermediate substances
20
75
Formaldehyde
25
80
Sunfit
1
99.5
Copper
0.5
80
Potassium
0.5
50
Cadmi
0.1
60
Crom with valence no. 3
2.5
20
Zinc
1
70
Vulcanized dying agent
25
90
Combined dying agent
25
70
Arsene (3)
0.1
50
Cyan
1.5
-
Mercury
0.005
-
Lead
0.1
50
Cobane
1
20
NOTES: 1. Petroleum products are less or non clogged substances, dissoluted in hecxen solution. 2. If there are not big anion surface active compounds in wastewater, shared concentration of these compounds do not exceed 20 mg/l. 3. Excluding ferrocyanides. Table 24 Combined domestic and production sewage BOD5 for every 100 mg/l (for aerobic biological treatment facilities)
Required minimum quantity of nutrients Total nitrogen
Total phosphate (mg/l)
5
1
COD for every 350 mg/l (for anaerobic biological treatment facilities)
5
1
NOTES: 1. Having considered treatment efficiency and dilution rate in the receiving water, allowed concentration of substances in Table 23 and Table 24 may be reduced to ensure hygiene requirements of the receiving water. 2. When BOD5 of wastewater for biological treatment facilities is required to be cut-down, the cleaned water is used for dilution. 3. When discharging production wastewater in urban drainage network, the ratio COD:BOD5 must not be exceeded than 1.5. 8.1.5 If the provisions stated in Article 8.1.4 are not satisfied, the production waste water before discharging into the of the drainage system of residential areas, must be preliminarily treated. 8.1.6 The requirements for production wastewater to be treated separately in biological treatment facilities of industrial units or the combination of production with domestic sewage are adjusted according to the practical documents or the documents of similar industrial facilities. 8.1.7 When designing cleaning facilities for newly constructed cities, depending on the level of convenience and local conditions, the amount of polluted substance for one person is to determine concentration of contaminants in domestic wastewater can preliminarily determined according to Table 25. The amount and discharge mode, the composition and concentration of contaminants in production waste water is determined by technology material. Table 25 Indicators
Weight (g/person.day)
Suspended solid (SS)
60-65
BOD5 of sediment sewage
30-35
BOD5 of un-sediment sewage
65
Nitrogen of ammoniac salt (N-NH4)
8
Phosphate (P2O5)
3.3
Chloride (Cl-)
10
Surface working substances
2-2.5
NOTES: - If the discharge households in urban area have their own septic tanks, it should be considered to reduce the amount of suspended solids. Based on the experience, the wastewater after being treated through septic tanks has SS concentration decreased by 55% to 65%. - When discharging domestic wastewater of industrial enterprises into the drainage network of residential area, it is not necessary to take into account additional impurities contained in the kinds of water. 8.1.8 Selection of location and area of land for construction of wastewater treatment plants must comply with the design, planning and construction of the object in need of drainage, with paying attention to the solutions for external urban facilities (railways, roadways, water supply, steam, electricity, and so on.) The position of wastewater treatment plant must meet the provisions of article 3:16 in this standard or the related regulations as stipulated in ISO 7222:2002-General requirements for accumulated domestic wastewater treatment plants. 8.1.9 The land for building the treatment plant is usually situated at the end of prevailing wind direction of summers compared with the construction regions of residential houses and below population points in the direction of river flow. The land for construction must have the slope level to ensure wastewater’s self-flowing through facilities and favorable drainage of storm water, the land to build the plant must be located in the places without being flooded and low underground water table. NOTES: It is allowed to arrange the treatment plant in the beginning of the wind direction, but sanitary separation distance must be increased as prescribed in Article 3:16. 8.1.10 Planning sewage treatment plants must ensure the rational use of the land for the expected period, as well as for future development. Arrangement of facilities shall ensure the following conditions: - Capacity to build in different stages. - The capacity to expand the capacity when the wastewater flow increases. - Length of the technical pipe must be the shortest (canals, pipes, etc.) - Convenience for management and repair. 8.1.11 When designing wastewater treatment plants, there is a need to consider the assembly possibility of building blocks and limiting odor to spread around the environment. 8.1.12 The wastewater treatment facilities should be arranged outdoors; only in special cases and with legitimate reasons, construction of roof shall be allowed.
8.1.13 In wastewater treatment plants, the following equipment is required: a) Equipment to distribute evenly wastewater to facilities. b) Equipment to suspend construction activities; remove residue and flush works, pipelines when needed. c) The equipment for drainage in case of incidents before and after the mechanical treatment facilities and walkways with easy access to opening/closing device. d) Instrument to measure wastewater flows, muddy sediment, re-circulated activated sludge and residue activated sludge, air, steam, power, etc. e) Automatic sampling equipment and self-recording instruments for parameters of wastewater quality sediment and sludge. 8.1.14 Gutters in the waste water treatment plants must be calculated on the highest flow in one second multiplied by the factor 1.4. 8.1.15 In addition to main technology facilities, depending on the capacity of stations and local conditions, there is a need to build auxiliary and serving facilities (refer to Appendix D). 8.1.16 Areas of wastewater treatment plants must have protective barriers, be completed and equipped with lighting. Depending on local conditions, it may be taken measures of slope landslide due to rain. in the event. If necessary, depending on the requirements of safety techniques, the barriers for separate projects are arranged.
8.2 Trash rack 8.2.1 In the components of the wastewater treatment stations, trash racks must be included, the width of the trash rack slits is 15 - 20mm. 8.2.2 Number and size of trash rack, water flow rate through the gap, the amount of garbage taken from trash rack, the distance between the devices etc. shall be stipulated in articles no. 7.2.9 and 2.7.13. 8.2.3 When a large volume of trash is over 0.1 m3/d, it should mechanize the process of trash collection and grinding. If the amount of garbage is less than 0.1 m3/d, the mechanical trash rack is used. 8.2.4 Debris after being crushed is allowed to be poured into trash rack or into methane tanks. 8.2.5 Floor level of the buildings to put trash rack must be at least 0.5 m higher than the highest water level in the trench. 8.2.6 Loss of pressure through the trash rack is determined according to the formula for clean trash rack and then increases by a factor of 3.
8.2.7 To replace when needed, before and after trash rack, there must have stop-log gate and the discharge door for water canals. NOTES: - If the manual, trash rack is used, prepare stop-log slots available for use when needed. - Debris picked up is put into container with a lid and is carried to solid waste handling places. - Crushed organic debris is also put into treatment with organic sludge of wastewater treatment plants. 8.2.8 To assemble and repair trash rack, the trash grinding and other equipment are required to include lifting equipment as stipulated in article 2.7.15. 8.2.9 In the trash rack buildings, it should be placed sand pump sand of sand settling basin.
8.3 Sand sediment tanks 8.3.1 For the wastewater treatment plants with the capacity of over 100 m3/d needed, sand settling basins are required. Choosing the types of sand settling basins should be based on the capacity of stations, maps of wastewater treatment technology and sludge. 8.3.2 Number of pools and sections working at the same time of sand settling tanks shall not be less than 2, while raking sand by the machine, standby tanks are required. 8.3.3 Calculation of horizontal sedimentation tanks and sand settling tanks with air blowing must follow the below formula: 1 . Area of wet area W (m2): W =
Q Vxn
(17)
In which: Q - the largest flow of wastewater (m3/s); n - Number of tanks or sections; V - Velocity of water in tanks (m/s). 2 . Working length of tanks L (m):
L=
Kx1000 H n V U0
(18)
In which: U0 and U- The hydraulic magnitude of particles (mm/s), determined by the free settling rate of sand particles in static and dynamic conditions in tanks shall be indicated in Table 26. K - Ratio factor U0:U chosen according to Table 27. Hn- Calculated height of sand settling tanks. For sand settling tanks with air blowing, it shall be selected to be half of the total height of tanks. V- Velocity of the wastewater in tanks, mm/s, is selected by Table 28. Table 26 Diameter of sand particle (mm)
0.1
0.1 2
0.15
0.2
0.25
0.3
0.35
0.4
0.50
Hydraulic magnitude U0(mm/s)
5.1 2
7.2 7
11.2
17.1
24.2
29.7
35.1
40.7
51.6
Table 27 Minimum diameter of kept sand particle (mm)
Hydraulic magnitude particle, (mm/s)
Value K depends on type of sand settling tanks and the rate of B:H of the sand settling tanks with air blowing U0 Horizontal settling tank
sand Sand settling tanks with air blowing B:H=1
B:H=1.25
B:H=1.5
0.15
13.2
-
2.62
2.5
2.39
0.20
18.7
1.7
2.43
2.25
2.08
0.25
24.2
1.3
-
-
-
Depth H (m)
Kept amount of sand (l/personday-night)
Moisture of sand (%)
Sand percentag e in smudge (%)
Table 28 Type of sand settling tank
Hydraulic magnitude of sand particle U0 (mm/s)
Water velocity (mm/s) when the flow reaches Min
Max
Horizontal
18.7-24.2
0.15
0.3
0.5-2
0.02
60
55-60
Air-blowing
13.2-18.7
-
0.080.12
0.7-3.5
0.03
-
90-95
Tangential
18.7-24.2
-
-
0.5
0.02
60
70-75
Selecting the minimum size of retained particles in tanks depends on the type of following treatment facilities. For settlement tanks where smudge should be handled in methane tanks or settling tanks with shells, the minimum size of retained sand grain shall be 0.2 to 0.25 mm. To create a constant speed in tanks, the entrance into the tanks must be built in the type for channel expansion, and the exit of narrow style and relevant length. 8.3.4 Designing sand settling tanks should follow the following rules: a) Horizontal sediment sand tanks: - Flow velocity in tanks at the maximum flow is0.3 m/s; at the lowest flow it is 0.15 m/s. - The hydraulic magnitude of retained sand grains in tanks U0 will be 18 to 24 mm/s. - Sand settling time shall not be less than 30 s at maximum flow. - Calculated depth Hn is from 0.25 to 1m. b ) Sediment sand tank with air blowing: - The hydraulic magnitude of sand grains U0 will be taken at 18mm/s. - The strength of air blowing is 3-5 m3/m2 h. - The transverse slope of tank bottoms (towards receiver trench) shall be from 0.2 to 04. - Doors to guide water into tanks shall coincide with the rotating direction of water in tanks and water discharge gates shall be submersed. - Total depth of tanks H shall be 0.2 to 3.5 m. - Gas distribution frame is made of copper tube with drilled holes of 3.5 mm diameter is located at a depth of 0.7 H. - Flow rate at maximum flow V is from 0.08 to 0.12 m/s. - The ratio between the width and depth of tanks B: H will be 1:1.5. c. For sand settling tanks of tangential type: - Selecting a surface load q 110 m3/m2.h with the largest flow of sewage, - Leading water into in the tangential manner,
- Depth is equal to half of diameter, - Diameter of tanks shall not exceed 6 m. Table 29 is the data on formed sizes of settling tanks with water level and rotary moving. Table 29 Calculated flow of one tank (l/s)
Diameter (m)
Settling trench width (m)
Total height of settling trench (m)
Total length of settling trench (m)
25-200
4
0.6-0.9
0.44-0.78
9
300
6
1.6
1.75
13.8
8.3.5 The amount of retained sand
in sand settling tanks depends urban environment sanitation
conditions, the working status of the sewer network and the performance of sand settling tanks. In the absence of empirical data, it is allowed to calculate preliminarily the amount of retained sand according to the following criteria: - For completely private drainage system, retain sand amount is 0.02 l/person/d. - For common drainage system, retained sand amount is 0.04 l/person/d. - Humidity of sand is 60 %, the individual weight is about 1.5 t/m3. The sand discharged out of settling tank can be made by the following methods: - Manual method when sand amount is up to 0.1 m3/d. - Mechanical method, hydraulic method or pumping, and then transportation is made by pan conveyor when sand amount is over 0.1 m3/d. Technical water flow qh (l/s) during sand discharge by hydraulic lifting equipment is determined by the formula: qh = vh lsc bsc
( 19 )
In which: vh - Upward velocity of the flushing water flow in trench, is chosen to be 0.0065 m/s.
l sc - Length of bottom of sand settling tanks, excluding sand collected pits. bsc - The width of the lower bottom of sand settling tank, is selected to be 0.5 m.
Primarily, it can be set the technical water amount 20 times higher than removed sand amount of from tanks. 8.3.6 The volume of sand collecting pits shall be not larger than volumes of sand deposited in two days, inclination angle of the bottom shall be not less than 60o compared to the horizontal direction. 8.3.7 In order to stabilize the flow velocity in horizontal sand settling tanks, at the bottom of the tanks there should be spillway dam. Calculation of spillway dams uses the following formula: - The level difference between the tank bottom and overflow threshold (m):
P=
hmax − K q2 / 3hmin K q2 / 3 −1
(20)
In which: Kq - ratio of maximum and minimum flow (K = Qmax:q min). hmax, and hmin-The depth of water in tanks corresponds with qmax and q min, flow velocity V = 0.3 m/s. -
Width of overflow dam b0 (m):
b0 =
qmax m
2 g ( p + hmax ) 3 / 2
(21)
In which: m–flow coefficient of spillway dam depends on the shrinking condition of flow, will be taken 0.35 to 0.8. 8.3.8 To dry sand from sand settling tanks, there should be sand drying yards or sand pits. Around sand drying yards, high embankment is required to be 1-2m. Dimensions of sand drying yards are determined with the conditions: total height h of sand layer is selected to be 3-5 m3/m2.year. Dry sand is often transferred to other places. Water is separated from sand, then is transmitted to the first processes of wastewater treatment plants.
8.4 Regulating tanks 8.4.1 Regulating tanks are to regulate the flow and concentration of contaminants in wastewater and sewage produced in urban areas. Tank volume is determined by the flow chart and the graph of concentration fluctuations of contaminants in wastewater.
NOTES: If there are no diagrams of water discharge, tank volume can be determined according to wastewater in a production shift. 8.4.2 When an water regulating tank is placed in front of settling tank, there must have sedimentation proof equipment in the tank. Choosing regulating tanks (mixing with compressed air, with mechanical agitators, or tanks with many corridors) based on the oscillation characteristics of contaminant concentration (cycles, chaos or concentrated water discharge), as well as the characteristics and concentrations of suspended solids. 8.4.3 In the tanks with mixing agitators by compressed air or mechanical one, if wastewater contains volatile toxic substances, the covering and ventilation measures must be required. 8.4.4 Using stirred regulating tanks with compressed air to regulate the concentration of wastewater when suspended solids concentration is less than 500 mg/l with hydraulic magnitude of 10 mm/s. - Tank volume during accumulated wastewater discharge is calculated according to the following formula:
Wdh =
1.3qW t z K yc when K yc is less than 5 ln K yc −1
(22)
Wdh =1.3q w .ttt when K yc is equal to or more than 5
(23)
In which: qw - Wastewater flow, m3/h;
t tt - discharge time of collected wastewater volume, h; K yc - Regulating coefficient required and equal to:
K yc =
C max −CTB Ccp − Cmax
(24)
In which: C max - the largest concentration of contaminants during being discharged collectively, mg/l;
CTB - The average concentration of contaminants in wastewater, mg/l; Ccp - Allowed concentrations of contaminants after regulation depends on the work conditions of the
backyard facilities, mg/l.
8.4.5 Regulating tank volume (m3), when the concentration fluctuates periodically, is determined by the formula as follows: Wdh =0.21qt .t ck
K yc −1
when K yc < 5
(25)
Wdh =1.3qt .t ck K yc , when K yc > = 5
(26)
In which: t ck - fluctuation cycle of concentration, h; K yc - Required regulating coefficient, is determined by the formula (24).
With any fluctuating concentration, tank volume will be calculated based on the method of asymptotic approximation. 8.4.6 The distribution of the wastewater as per air-mixed regulating tank surface must ensure uniformity. Perforated distribution pipe or overflow gutter of section V, or U is used for distribution. Water flow velocity in the gutter will not be less than 0.4 m/s. 8.4.7 Aeration system of regulating tank is as follows: - Aeration equipment: the pipes of bored holes with diameter d = 5mm spaced 3-6 cm, located in lower side of the pipe. The pipe must be put absolutely horizontal, along vertical wall of the tank on racks at a height of 6-10 cm compared to the bottom. - If aerators are placed on only one side and close to the walls of the tank, the distance from the device to the opposite walls will be taken to be 1 to 1.5 H. - Diameter of aerators is taken at 50 mm if aeration intensity is less than 8m3/h for 1m in length and at 75mm in case of greater aeration intensity. 8.4.8 Regulating tanks with mechanical agitation is used to regulate the concentration of suspended solids over 500 mg/ l with any mode of input water in tanks. Tank volume with mechanical agitation is also similarly calculated to air aeration tanks. 8.4.9 Regulating tank volume with many corridors during concentrated wastewater discharge is determined by the formula:
Wdh = In which: qt - wastewater flow (m3/h);
qt ttt K yc 2
(27)
t tt - a period of concentrated wastewater discharge, (h); K yc - Required regulating coefficient.
8.4.10 Structure of volume regulating tanks is similar to that of stage 1 sedimentation tanks or normal tanks and must have holes to collect residue and residue discharge device. Pumps can be used to pump sewage
to next wastewater treatment facilities in the time of smallest flow. Calculation of
flow
regulating tank volume is similar to that of tanks or water towers in water supply systems. 4.8.11 Choosing the value of the non-regulating coefficients after regulation K dh , regulating tank volume Wdh is determined by the following relationships: y dh = K dh / K dho
(28)
t dh =Wdh / qTB
(29)
In which: K dhyo - no-regulating factor of wastewater flowing into tanks;
qTB - hour average flow of wastewater. The dependence between y dh and t dh is defined according to Table 30. Table 30 y dh t dh
1 0
0.95
0.9
0.85
0.8
0.75
0.67
0.65
0.24
0.5
0.9
1.5
2.15
3.3
4.4
8.4.12 In case of regulating both flow and concentration of wastewater, tank volume, flow and concentration of impurities are calculated step by step. Increments of water volume ΔW, m3 and concentration ΔC, g/m3, after a computation step are defined by the formula: ∆W = ( qinput − qoutput ) ∆t
(30)
∆C =[(Cinput −Coutput )∆t ] / Wdh
(31)
In which: qinput , Cinput , Coutput - flow, concentration of pollutants in waste water at a time after a calculation
step.
Wdh - water volume in corresponding regulating tanks at the time of calculation.
8.5 Sedimentation tank 8.5.1 Choosing types of sedimentation tanks must be based on wastewater capacity, and characteristics, natural conditions and specific conditions of local areas. Generally, it can be chosen preliminarily the type of sedimentation tanks as per capacity of wastewater treatment plants as follows: Standing sediment tanks: Less than 20,000 m3/d. Horizontal sediment tanks: more than 15,000 m3/d. Centrifugal sediment tank: more than 20,000 m3/d. Settling tanks with two shells and settling tank combined with sludge fermentation are usually applied for wastewater treatment plants with small or medium capacity, less than 10,000 m3/d. 8.5.2 Number of sediment tanks shall be not less than two and all tanks must operate together. 8.5.3 Calculation of sedimentation tanks (except for 2 nd phase settling tanks after biological treatment facilities) is based on the study of deposition kinetics of suspended particles in consideration with necessary sediment efficiency. When wastewater is discharged after sedimentation tanks into the receiving water, the concentration of remaining suspended solids in wastewater must be ensured hygienic conditions according to environmental standards. 8.5.4 Calculation of sedimentation tanks according to the following formula: a) Sediment tank size: Length of horizontal settling tanks l (m): l=
V .H K .U 0
(32)
Radius of vertical, centrifugal sedimentation tank R (m): R=
In which:
Q 3.6πK .U 0
(33)
Q- calculated flow of wastewater (m3/h); H–calculated depth of sedimentation region (from top of neutral layer to surface of the tank, m), following with the instructions in this 8.6.2; V-calculated average velocity in the sedimentation area, in centrifugal sedimentation tanks is the speed at the section at the point between the radius from the center to radius boundary (mm/s). For horizontal and centrifugal sedimentation tanks ,V will be 5-10 mm/s; K–dependent coefficient of sedimentation tank type, and structure of water distribution and collection equipment, is stipulated as follows: - 0.5 for horizontal sedimentation tanks. - 0.45 for centrifugal sedimentation tanks. - 0.35 for standing sedimentation tanks. U 0 - The hydraulic magnitude of residue grains (mm/s).
b) The hydraulic magnitude of U 0 (mm/s) is determined by the deposition kinetics curves or by the following formula:
U0 =
1000.K .H −ω KH n α.t ( ) h
(34)
In which:
α
- the factor to mention the influence of water temperature on viscosity is taken from Table 31;
ω - vertical component of the wastewater speed in tanks is taken from Table 32; t -Time of deposition (s) of wastewater in cylindrical experimental flasks with water depth h, achieving deposition efficiency equal to calculated settlement efficiency; in case of the lack of experimental data, t can be taken from Table 33 (for a certain number of grains); n - convergence coefficient, depending on the suspension nature of the main grains is determined by experiments depending on the nature of sewage sludge. In the absence of experimental data, it can be obtained preliminarily as follows: - n shall be 0.25 for suspended grains with capability of convergence in domestic sewage; - n shall be 0.4 for solid mineral grains with specific mass of 2-3 g/cm3; - n shall be 0.5 for heavy smudge grains with specific mass of 5-6 g/cm3.
The value (
KH n ) during calculating 1st phase sedimentation tanks for domestic wastewater can be h
taken from Table 34. Table 31 Average temperature as per the lowest month in degree Celsius Factor
α
60
50
40
30
25
20
15
10
0.45
0.55
0.66
0.8
0.9
1
1.44
1.3
Table 32 V (mm/s)
5
10
15
20
ω (mm/s)
0
0.05
0.1
0.5
Table 33 Sediment efficiency E(%)
Sediment time in cylinders with the depth h= 500 mm (s) n=0.25
n=0.4
N=0.6
Concentration (mg/l) 100
200
300
500
500
1000
2000
3000
200
300
400
20
600
300
-
-
150
140
100
40
-
-
-
30
900
540
300
180
180
1200
120
50
-
-
-
40
1320
650
450
390
200
180
150
60
75
60
45
50
1900
900
640
450
240
200
180
80
120
90
80
60
3800
1200
970
680
280
240
200
100
180
120
75
70
-
3600
2600
1830
360
280
230
130
390
180
130
80
-
-
-
5260
1920
690
570
370
3000
580
380
90
-
-
-
-
-
2230
1470
1080
-
-
-
100
-
-
-
-
-
-
3600
1850
-
-
-
NOTES: 1. Deposition time corresponding to temperature 20oC. 2. For intermediate values of sediment components and deposition efficiency compared with the values in the table, deposition time is determined by interpolation method.
3. Deposition kinetics of the suspended solids in wastewater and convergence factor shall be determined the conditions of static deposition in cylindrical flasks with a diameter of not less than 120 mm. Table 34 Working height of sediment tank H
Value (
KH n ) for sedimentation tanks of many types h
Standing type
Centrifugal type
Horizontal type
1.0
-
-
-
1.5
-
1.08
1.1
2.0
1.11
1.16
1.19
3.0
1.21
1.29
1.32
4.0
1.29
1.35
1.41
5.0
-
1.46
1.5
- After determining L and R, then check actual speed Vth (mm/s) in the deposition part. - For horizontal sedimentation tanks: Vth =
Q 3.6 HB
(35 )
In which: B - Width of sedimentation tanks during 2-5 H. - For the centrifugal sedimentation tanks (in the section in the middle of radius): Vth =
Q 3.6πHB
(36)
When Vth and V values are different, different values of L and R should be adjusted. 8.5.5 Volume of sediment discharged from tanks depends on calculated sedimentation efficiency. Sediment humidity of domestic wastewater is about 95 % for all types of 1 st phase settling tanks during sludge discharge by self-flowing; about 93.5 to 94 % at sludge discharge by piston pumps, sludge moisture of production sewage shall follow with experimental documents. 8.5.6 2nd phase sediment tanks after biological filtration tanks are calculated based on surface hydraulic load q0 (m3/m2/h) as follows: q0 = 3.6 K s u0
In which:
(37)
u0 - The hydraulic magnitude of bio-films during complete biological treatment u0 = 1.4 mm/s;
K s - capacity utilization coefficient is selected according to article 8.5.7.
When determining the volume of settling tanks, it is required to calculate circulatory smudge flow. 8.5.7 2nd phase sedimentation tanks after aeroten which is calculated based on material balance of the hydraulic load system qo (m/m.h) depends on the concentration of activated sludge a (g/l), the mud indicator I (cm/g) and allowed sludge concentration after sedimentation at (mg/l). Hydraulic load can be calculated by the formula:
q0 =
4.5 K s H 0.8 (0.1Ia) 0.5−0.01at
(38)
In which: Ks – capacity use ratio of the deposition area is chosen to be 0.4 for centrifugal sedimentation tanks, 0.35 for standing sedimentation tanks, and 0.45 for standing settling tanks with water discharge from the perimeter, 0.4 for horizontal sedimentation tanks; a- Concentration of activated sludge in the aeroten tank is selected to be not more than 15 g/l; at - Activated sludge concentration of water after sedimentation is not less than 10 mg/l. 8.5.8 Sedimentation time and greatest velocity of flow to calculate 2 nd phase settling tanks will be taken from Table 35 .
Table 35 The data to calculate the 2nd sedimentation tanks
Use of tanks
Deposition time (h) the at the largest maximum flow
Maximum flow velocity (mm/s)
Types of sedimentation tank Horizontal, centrifugal, standing
horizontal, centrifugal
vertical
2nd phase sedimentation tanks a) After trickling filter
0.73
5
0.5
b) After high-load biological tanks
1.5
5
0.5
c) After not entirely cleaning Aeroten - When the BOD reduction to 20 %
0.75
7
0.7
- When the BOD reduction to 80 %
1
5
0.5
d) After completely cleaned Aeroten
2
5
0.5
NOTES: In general, the data to calculate 2 nd sedimentation tanks after Aeroten must be based on the experimental ground, depending on the working mode of Aeroten. 8.5.9 Content of suspended solids in the wastewater after 2 nd phase settling tanks for domestic wastewater will be taken from Table 36, for the wastewater production, it must be obtained from experimental data. Table 36 Deposition time (h)
Concentration of suspended solids in domestic wastewater 2 nd after settling tanks (mg/l). When BOD of wastewater is cleaned (mg/l) by 15
20
25
50
75
100
0.75
21
27
33
66
86
100
1
18
24
29
58
80
93
1.5
15
20
25
51
70
83
2
12
16
21
45
63
75
8.5.10 To discharge domestic sewage sludge from 1st settling tanks, piston pumps or hydrostatic pressure of not less than 1.5m water column can be used. For 2nd phase settling tanks, hydrostatic pressure shall be not less than 1.2m for settling tanks after trickling or high load filter biological tanks; it shall not be less than 0.9 m for sedimentation tanks after Aeroten. For 1st and 2nd phase settling tanks after biological filters, sludge tank volume should be taken to be equal to sediment sludge volume within no more than a day, for 2nd phase sedimentation tanks after Aeroten shall not be more than 2 hours. When sludge is discharged mechanically, the sludge compartment volume of 1 st sedimentation tanks should take sediment weight in 8 hours. Diameter of pipes discharging smudge from the 1 st and 2nd sedimentation tanks is determined by calculation but not less than 200 mm. The height of sedimentation tank walls from the water level upwards shall be 0.3 m. The structure of 1st phase sedimentation tanks must have collectors and separators of floating substances. Overflow gutters to collect sediment water in settling tanks can be made in the flat or jigsaw form; hydraulic load of the gutters should not exceed 10 l/sm
8.5.11 Designing settling tanks should comply with the following provisions: a) Horizontal sedimentation tanks: + Depth calculation of the H deposition area will be taken 1.5-3m, depending on the capacity of the wastewater treatment facilities, in some cases it can be taken up to 4m . + The ratio between the length and depth of the tanks is 8-12, in some cases it can be chosen to be 8 20 (for production wastewater). + Wastewater into and out of the tanks must be distributed along the width of the tanks. + Inclination angle of the sludge pit edge shall not be less than 50o. + The draining devices are required. + The slope of the tank bottom shall be not less than 0.005. + Height of neutral water layer shall be 0.3 m higher than the bottom of the tanks (at the end of the tanks). + Height of the sludge layers of 2nd phase settling tanks will be selected to be 0.2 to 0.5 m. b) Centrifugal sedimentation tanks The depth of the deposition area H is taken 1.5-5m. The ratio between tank diameter and sedimentation zone depth will be selected to be 6-12, in some cases it can take from 6-30 (for production wastewater). + Tank diameter shall not be less than 1 m. + Height of neutral water layer shall be 0.3 m. + Mud depth in 2nd phase settling tanks will be 0.3 to 0.5 m . For 2nd settling tanks with smudge suction machines, tank bottom slope shall be from 0.01 to 0.03, but in case of scraping mud devices, pit bottom slope must be 0.01. c) Standing sedimentation tanks: + Tank diameter D = 4 - 9m + Depth calculation of the H deposition area will be taken from 2.7 to 3.8 m; for 2 nd phase settling tanks, H shall not be less than 1.5 m. + Central pipe has the calculation length equal to the calculation height of the deposition zone with the funnel month and fixe overhead plate at the bottom. + Diameter and height of funnels shall be 1.5 times with in diameter of central pipe.
+ Diameter of overhead plate shall be 1.3 diameter of funnel. The tilt angle between the surface of overhead plate with the horizontal plane: 17o. The height from the underside of the overhead plate to the surface of residue must be 0.3 m. + Water velocity in the central pipe is not greater than 30 mm/s; water velocity through the gap between lower edge of central pipe and overhead plate surface in 1st sedimentation tanks must not be larger than 20 mm/s, in the 2nd phase sedimentation tanks, 15 mm/s will be chosen. + Gutters to collect settled water are placed in the inner sides of the sedimentation tanks. + Tilting angle of 1st and 2nd sedimentation tanks against with horizontal direction not be less than 50o.
8.6 Sedimentation with two shells 8.6.1 Sediment tanks with two shells can be single or double types. For dual tanks, it must be ensured the frequent changes in flow direction in sediment gutters. 8.6.2 Sediment tanks with two shells are designed in compliance with the provisions referred to in articles 8.5.1; 8.5.2; and 8.5.3, and in accordance with the following provisions: - The free surface of tanks to afloat the residue must not be less than 20% of the tank surface area. - The distance between the outer wall of sedimentation gutters shall not be less than 0.5 m. - Tilting angle of sedimentation gutter walls shall not be less than 50o, two tilting walls of sedimentation gutters must be inter-layered at least 0.15 m, depth of sedimentation gutters depends on the length and will be taken from 1.2 to 2.5m. Slit width of sedimentation gutters shall be 0.15 m. - The height of the neutral water layer obtained from sedimentation gutter openings to surface of residue layer in septic compartments is 0.5 m. - tilting angle of the conic bottom of septic compartments should not be less than 30o. - Humidity of sludge removed from tanks is 90%. - The sedimentation effect of suspended solids from tanks is 45-50%. - Decomposition efficiency of organic matter is 40 %. 8.6.3 The volume of the septic compartment of sedimentation tanks with two shells can be defined as in Table 37. Table 37
Average temperature of wastewater in winter
Volume of septic compartment in tanks of two is calculated by liter for 1 person
10
65
12
50
15
30
20
15
25
10
NOTES: 1. Septic compartment volume of sedimentation tanks of two shells must be increased additional 75% in case of inputting completely treated mud from Aeroten tanks or quite high load biological tanks, or must be increased by 30% in case of sludge discharge out of sedimentation tanks after trickling bio-filtration tanks, or inputting not completely treated Aeroten. 2. Absence of experimental data on wastewater temperature, it is allowed to get average annual temperature of the air for calculation. 3. Septic compartment volume of sedimentation tanks of 2 shells for wastewater treatment, before being put into filtration yard, shall be allowed to decrease by not more than 20%. 8.7 Equipment to receive oil 8.7.1 Oil collection tanks are used to retain crude oil particles when oil concentration is greater than 100 mg/l. Calculation of oil receiver tanks is completely the same as that of horizontal sedimentation tanks, with more attention on the floating kinetics of oil particles. If there is no data on the kinetics of the oil, it is allowed to be as follows: - Hydraulic magnitude (floating speed of oil particles) is from 0.4 to 0.6 mm/s. - Average calculated velocity of flowing water in the tank V is 4-6mm/s. - The weight of trapped oil particles in this case is about: - 70% when the oil particles have hydraulic magnitude of 0.4 mm/s. - 60% when the oil particles have hydraulic magnitude of 0.6 mm/s. 8.7.2 When designing an oil collecting tank, it should be taken as follows: - The depth of flowing water in tanks H will be 2m.
- The ratio of between the length and the depth is 15-20. - The width of a compartment is 3-6m. - Number of compartments to get air must be less than 2. - Thickness of floating oil layer is 0.1 m. - Sediment layer is up to 0.1 m thick. - Humidity of new sediment is 95 %, specific gravity of 1.1 T/m3. - Humidity of composed sediment is 70%, specific gravity is 1.5 T/m3. - Weight of trapped sediment is calculated in dry matters 80-120 g/m3 of wastewater. Equipment to collect and discharge floating oils is needed.
8.8 Hydraulic Siclon 8.8.1 Open hydraulic siclon is applied to separate sediments and floating impurities with the structure belonging to rough diffusing system. Sealed hydraulic Siclon (pressure) is used to separate the compounds with stabilized grain structure diffuses under rough diffusing system. 8.8.2 Three following hydraulic siclon categories can be applied: a) Hydraulic Siclon with no equipment, used to remove impurities under small and rough distributed system has hydraulic magnitude of 5 mm/s or more. b) Hydraulic siclon has dividing membrane and cylindrical walls are used when the flow of each tank is up to 200m3/h, to handle the substances under raw and small distributed systems with hydraulic magnitude from 0.2 mm/s or more, as well as precipitated suspended solids and petroleum products. c) Multi-layer hydraulic siclon is employed when the volume of each tank is larger than 300m3/h, to remove caking impurities of coarse and small distributed system with hydraulic magnitude of 0.2 mm/s or higher as well as the petroleum products. 8.8.3 When designing the hydraulic siclon, the following notes are required: - Removing sludge with buckets, hydraulic lifting device or by hydrostatic pressure. - Using the semi-submersible semi-floating annular shield is placed in front of overflow dams with the gap of not more than 50mm to retain afloat impurities. - Separation of afloat substances by the funnel reversely placed in water.
When designing the hydraulic siclon, the following should be taken: a) For all open hydraulic siclons with hydraulic load q (m3/m2.hour) shall be defined by the formula: q = 3.6 K.U0
(39)
In which: K – dependent coefficient of siclon type; U0 - hydraulic crudeness of trapped sediment particles (mm/s). The loss of pressure in hydraulic siclon will be 0.5 m. b) For hydraulic siclons with no equipment inside - Coefficient K is 0.61. The height of the cylindrical portion H is equal to siclon diameter. - Diameter of discharge hose is 0.10 m. - The tilting angle of the conic walls is equal 60o. c ) For hydraulic siclon with diaphragm and separation cylinder - Coefficient K is 1.98. - The diameter of the cylindrical part of the tank H is equal to D. - The diameter of holes in diaphragms is 0,5 D. - The cone-shaped angle of the diaphragm is 45o. - Diameter of the diaphragm is 0.85 D. - The height of the diaphragm is taken equal to 0.8 D. - The number of input nozzles on the line with the lower part of baffles is between 3 and 5. - The input nozzle diameter is from 0.05 to 0.07 D. - Inclination angle of conical components is taken equal to the natural sliding angle of sediment in water, but not less than 60o. d ) Multi-layer hydraulic Siclon: - Coefficient: - Number of floors: 4-20.
K=
D2 − d 2 D2
(40)
- Hydraulic Siclon’s diameter: 2 - 6m. - Diameter of the central hole of the diaphragm d = 0.5 to 1.4 m. - The distance among floors in vertical direction is from 200 to 300mm. - Number of sprinklers on each floor is 3, and placed tangentially (distance among sprinklers is 1200 mm). - Speed of drainage water from each tap is taken from 0.3 to 0.5 m/s. - Tilting angle of diaphragm is equal to the natural slide angle of sediment in water but must not be less than 45o. NOTES: The general hydraulic load of multi-layer hydraulic siclon is proportional to the number of layers. 8.8.4 The selection of size and the structure of hydraulic siclon with pressure depending on the number, concentration, and nature of sewage sludge. Application of hydraulic siclon for wastewater having suspended solids of 0.2 to 0.4g/l with a specific gravity of 2.5 g/cm3 is allowed. Design and specifications of hydraulic siclon is taken from Table 38. Table 38 The magnitude of the hydraulic
Structure and specifications of hydraulic pressure siclon
sediment particles trapped in hydraulic siclon (mm/s) Loss of pressure in hydraulic siclon by m water column
Capacity of a equipment (m3/h)
Loss of water and mud in % as per productivity.
1.7-1 1
0.25-0.2
50
0.28
0.4
0.12
1
10-15
3-4
2-3
2.1-1.3
0.4-0.3
15
0.24
0.27
0.12
1
15-20
5-6
3-5
3.7-2.7
0.5-0.4
250
0.2
0.23
0.1
0.7
15-25
46-53
5-7
4.6-3.6
1.1-0.8
350
0.18
0.22
0.07
0.88
20-30
75-85
2-3
4.8-4.3
2-1.8
500
0.13
0.22
0.05
0.8
25-35
85-90
1.5-2
8.9 Flotation Devices 8.9.1 Flotation Device (mechanical) is used to remove grease, mineral wool fibers, asbestos, wool, surface working, insoluble substances in water has large surface and the substances with the mass approximately equal to that of water, contained in sewage. Mechanical flotation device is used to separate from water the impurities of raw distributed system. Pressure flotation device is used to separate from water impurities of fine distribution system. In necessary cases, it is required to thoroughly treat the aforementioned contaminants by using all kinds of alum to coagulate impurities. 8.9.2 When designing flotation devices, the following should be taken: a) Mechanical flotation device - Flotation time: 20 -30 minutes; - The rotational speed of agitator: 12-15 m/s; - Agitator’s diameter D: 200-750mm; - The amount of air per area unit in the flotation compartment of 40-50m3/m2.h; - The depth of water in the flotation: from 1.5 to 3m. If tank is square, each side is equal to 6D. The area for each agitator is not more than 35D2. Flotation compartment volume W (m3) is calculated according to the following formula: Q.t W = 0.85
(41)
In which: Q - Wastewater flow (m3/h); t - flotation time (minutes). b) Pressure flotation device: The amount of air is taken 3-5 % volume of water to be treated. Air intake is done with ejector into the suction pipe of pumps. Residual pressure in pressure tank: 30-50N/cm2 Air saturation time: 1-3 minutes
Settling tanks combined with rectangular flotation compartment having the depth 1-1.5m, flotation time of 20 minutes are used for wastewater treatment facilities with the capacity of less than 100 m3/h. Settling tanks combined with centrifugal flotation compartment having the depth not be less than 3m (flotation and sedimentation for each zone is not less than 1.5 m) when the capacity is larger than 100 m3/h. NOTES: When designing flotation devices, it must be considered the increased of 10 % in emulsion concentration in wastewater.
8.10 Biological Lakes 8.10.1 Biological lakes can be applied to be completely biologically treated or not completely wastewaters. Biological lakes can also be applied to thoroughly treat wastewater as high wastewater treatment level is required. 8.10.2 Biological lakes have the following forms: - Anaerobic lakes; - Optional lakes; - Aerobic lakes NOTES: It is possible to apply biological lakes for wastewater treatment after mechanical treatment in sedimentation tanks or lakes can be applied as a biological treatment works complete. 8.10.3 Designing biological lakes should study to incorporate wastewater treatment functions for other purposes, such as storm water regulation, aquaculture, water storage for agricultural irrigation, etc. 8.10.4 Bio-lakes can be one or many working in serial. Selection and arrangement of the lakes depend on wastewater treatment requirements, local natural conditions and ability to use the lakes for different economic and technical purposes. The layout of the lakes can be referred in Appendix E. 8.10.5 Anaerobic lakes are aimed to treat domestic sewage or production sewage with the components and properties similar to those of domestic wastewater. The lakes are used for sludge and wastewater treatment. The lakes are the most suitable for the areas with average temperatures in winter above 15oC. Time of water kept in anaerobic lakes is from 2 to 5 days.
Minimum separation distance of anaerobic lakes to residential areas is 1000m; when arranged in favorable wind direction and permitted sanitary conditions or closed lakes, the distance may be allowed to cut down but shall not be less than 500m. 8.10.6 The calculation formula of anaerobic lakes: F=
Lα.Q λv.H
(42)
W = F.H
(43)
In which: F- average surface area of the lakes (m2); W-operating volume of the lakes (m3); La - BOD5 of wastewater flow into the lakes (mg/l); Q - Wastewater flow (m3/d); H - depth of the lakes;
λv - organic load of the lake surface (gBOD5/m3.d), depending on temperature and determined by Table 39. Table 39
λv (gBOD5/m3.d )
The average temperature of air in winter T (0C)
Treatment performance of BOD5 (%)
10-20
20T - 100
2T +20
20-25
10T +100
2T +20
> 25
350
70
8.10.7 Depth of anaerobic lakes should be taken 3-5 meters, in case of favorable conditions, it may create deep lakes to reduce unpleasant odor. There must be at least 2 compartment to work in parallel. The amount of mud in the lakes, can preliminarily be taken from 0.03 to 0.05 m3/person/year. Sludge must be dredged periodically to ensure regular working mode. 8.10.8 Structure of input and discharge gates water is as follows: - The input can be designed in the flooded or not flooded forms. For flooded type, it should be placed in the center of the lakes, and must not be placed close to the bottom.
- The arrangement of input gates must ensure even distribution of sediments over the entire area of the lakes. When the area of the lakes is less than 0.5 ha, it is allowed to arrange input gates in the middle of the lakes. - The discharge gates can be designed in the non-flooded type and must be equipped with the equipment to prevent foam and floating membrane on the lake surfaces from draining together with the flow. 8.10.9 Optional lakes can be applied for preliminarily treated wastewater in settling tanks, septic tanks, anaerobic lakes or untreated wastewater. Treatment level based on BOD5 shall usually be not more than 70-85 %. 8.10.10 The surface area of the lake work haphazardly defined as follows: F=
Q Lα ( −1) H .K Lt
(44)
La - BOD5 of wastewater put into the lakes (g/m3); Lt - BOD5 of wastewater after being cleaned in the lakes (g/m3); Q -Wastewater flow (m3/d); H - Depth of lake (m), from 1.5 to 2.5 m, is selected according to Table 40. K – Decomposition coefficient of organic matter in the arbitrary lakes (day -1). At 20oC temperature, K is chosen to be 0.25 d-1. At temperature T, K coefficient shall be determined by the formula:
K = 0.25 x1.06T −20
(45) Table 40
Depth ( m )
Temperature conditions and wastewater characteristics
1.5 to 2.0
Evenly warm temperatures, sewage is cleaned preliminarily.
2,0 - 2,5
The temperature changes in seasons, sewage contains the sludge particles with capacity of deposition
8.10.11 For arbitrary lakes, when the volume is more than 500 m3/d, the lakes should be divided into many compartments working in parallel (at least 2 compartments). If using existing natural lakes or on the annually windy areas with wind speeds of above 3 m/s, it is not required to divide the lakes into multiple compartments. 8.10.12 Thoroughly treated lakes (maturation lakes) are mainly used for wastewater disinfection and thorough handling of organic material to ensure hygienic safety for receiving water. The lakes operate in
natural aerobic conditions (with the depth from 1.0 to 1.5 m) or forced aerobic (with depth of from 1.5 to 2.5 m). Residence time of water in the lakes is from 7-10 days or longer. To determine preliminarily processing efficiency, the formula (46) can be applied:
Nt =
Na (1 + K b .t1 )(1 + K b t 2 )...(1 + K b t n )
(46)
In which: Na and Nt - number of pathogens in sewage into and out of lakes (coli form bacteria /100 ml ); t1 , t2 , ... , tn – Staying time of water in the levels of lakes, day; n - Number of lake levels; Kb - Killing bactericidal of fecal coli form: at 20oC Kb is 2.6 days-1 ; at temperature T, Kb is determined as follows:
K b = 2.6 x1.19T −20 , (day −1 )
(47)
8.10.13 In artificial lakes, oxygen is supplied mainly by the forced method by surface agitation or aeration. The lakes have a depth H of from 2 to 6 m and retention time t is from 3 to 10 days; and activated sludge concentration of x is from 200 to 400 mg/l. 8.10.14 The volume of fresh artificial lakes is determined on the basis of retention time in the lake t according to the following formula:
Lt 1 = La 1 + K T t
(48)
In which: Lt and La - BOD5 concentrations of wastewater into and out of the lakes (mg/l). Kt - transformation ratio of BOD in lakes (day -1): at 20°C, KT is obtained to be 2.5 days- 1. At different temperatures, KT can be defined as follows:
K T = 2.5θ T −20
(49)
In which: θ - Temperature coefficient , taken to be 1.056 at 20 < T ≤ 30°C and 1.135 at T ≤ 20°C. 8.10.15 The amount of oxygen required for artificial transient lakes GO2 (gO2/day) is defined as follows: GO 2 = a ( La − Lt )Q
(50)
In which: a- coefficient of oxygen consumed in waste water, shall be taken from 0.9 to 1.5; Q - flow of wastewater into the lakes (m3/d).
8.11 Wastewater treatment works in wet soil 8.11.1 Irrigated agriculture fields can be applied for permeable soil types in different climates. When using wastewater for irrigation should be included the plan for continuous irrigation throughout the year. Without the capacity of to continuous irrigation, it is recommend to use thoroughly these hollow areas, ponds or lakes for storage, only just in necessary cases, it is required to consider new construction of additional treatment facilities (working in time of no irrigation). 8.11.2 Standards and quality of irrigation depend on climatic conditions, crops, soil characteristics, groundwater depth, ... and determined by the direction of the local agricultural and environment management agencies. 8.11.3 Flooded filtration tanks for wastewater treatment consist of two types: surface flooded and bottom flooded (underground filtration yard), usually applied to sand mixed soil and light clay for completely biological treatment after preliminary sedimentation. To construct filtration yards, it should be required to select flat smooth ground with the slope not exceeding 0.02. On the surface of flooded filtration types, trees of layered or foam trunks should be planted. 8.11.4 Flooded filtration yards shall not be built on the land with groundwater, and the areas with submerged caves (Caster region). 8.11.5 Flooded filtration yards must be placed under the flow of groundwater collection works, its distance is determined by the affecting radius of the collection wells, but not less than the following limits: For small clay, it is 200m, for mixed sand, is 300m and for sand it is 500m. When placed flooded filtration yards on groundwater flow, the distance of the filtration yards to water collection works should take into geological and hydrological conditions, sanitary protection requirements of water resources. 8.11.6 Wastewater before treatment in flooded filtration yards must be treated preliminarily in septic tanks damage or other 1st phase settling tanks. Hydraulic load to calculate the flooded filtration area is base on empirical research data. In the absence of research data, present the area of flooded filtration yard types shall be calculated according to the formula specified in clauses 8.12.3 and 8.13.1. 8.11.7 Useful area of flooded filtration yards F (m2) is defined as follows:
F=
Q.(ln La − ln Lt + ln ∫) ( Av )1.75 .K T .(d m .n + d w )
(51)
In which: Q - average flow of wastewater treated on filtration yard (m3/d); dm - Depth of filtration soil (m); dw -surface soil height (m); n - coefficient of filtering soil mechanical components. n is taken at 0.75; Av – helpful unit surface area for microbial activities (m2/m3). Av is often chosen to be 15.0 m2/m3; f - The part of BOD is not metabolized in sediment sludge in the first areas of filtration yards, for domestic wastewater, f is sleeted to be from 0.52 to 0.62 KT - coefficient depending on the temperature of wastewater and determined by the formula:
K T = K 20 .θ T −20 , day −1
(52)
conditions at 20oC K 20 is 0.0057 day −1 , θ is taken by 1.1. 8.11.8 Useful area of lower submerged filtration yards F (m2) is defined as follows:
F=
Q L − L* ln( t ) K La − L*
(53)
In which: Q - Average flow of treated wastewater on filtration yards (m3/d); K - factor of organic matter decomposition, usually taken at 0.095 m/d; L* - BOD concentration of substrate inside the submerged filter material (mg/l) depending on the initial BOD values La and determined by the following formula: L* = 3.5 + 0.053La
(54)
8.11.9 Irrigation pipe connected to submerged filtration yards must be set higher than groundwater levels of at least 1m. Depth of pipe truss must not be larger than 1.8 m and not less than 0.5 m above the ground. Irrigation pipe is coated by one layer of gravel, blast furnace slag, crushed stone or coarse sand with thickness of 20-250 cm. Total length of irrigation pipe depends the unit load of irrigation pipe. Each irrigation pipe length shall not be greater than 20m.
8.11.10 Unit load of irrigation pipe shall be taken from Table 41: Table 41 Soil
Sand
Sandy loam
Average annual air temperature, oC
Irrigation load l/s over 1 meter of irrigation pipe length, depending average depth of the groundwater level, taking into account of the sprinkler bottom, m 1
2
3
Below 11
20
24
27
Above 11
22
26
30
Below 11
10
12
14
Above 11
11
13
16
Note: For areas with heavy rainfall over 1.500 mm/year, the value must be reduced to 15 -20 %.
8.11.11 Irrigation pipe network can be made of plastic pipe or trench made of bricks, re-imforced concrete, with a diameter or width of 75-100mm. Irrigation pipe is placed in sandy soil with the slope from 0.001 to 0.003, in sandy soil, it can be set horizontal. The distance between irrigation pipes is placed in parallel 1.5-2m deep in sandy soil, in sand mixed soil is 2.5 m. At the end of irrigation pipes, there must be ventilation pipes with 100 mm in diameter, and the pipe peak placed 0.5 m above the ground.
8.12 Preliminary clearing works done and biological coagulation 8.12.1 Preliminarily clearing or biological coagulation tanks are used to: - Increase efficiency of deposition in 1 st phase sedimentation tanks, ensuring that levels of suspended solids in wastewater not exceed the permissible limits (usually 150 mg/l) prior to putting into biological treatment facilities. - Recovery of heavy metal salts (due to adsorption) and other contaminants can affect adversely biological treatment process. 8.12.2 Preliminarily clearing and biological coagulation tanks which are placed in front of 1 st phase sedimentation tanks may be independent or in blocks with 1 st phase sedimentation tanks. For biological coagulation tanks, sludge from 2nd phase sedimentation tanks is required. The amount of sludge back to biological coagulation tanks is 50-100% for activated sludge residue or 100% for the amount of bio-film. NOTES:
1. It is required to guide sludge from regeneration tanks to biological coagulation tanks. When there is regeneration tanks for mud blocks with biological coagulation tanks. Capacity of regeneration compartment is from 0.25 to 0.3 of the total tank capacity. 2. Regard to biological membranes back to biological coagulation tanks, regeneration perform is done within 24-h. 8.12.3 When designing preliminary clearing tanks and biological coagulation tanks, it is required: - To select the tank number of no less than 2 and they all work. - Time of preliminary clearing is selected as 20 minutes. - The amount of air for tanks is 0.5 m3 for 1 m3 of wastewater. - Efficiency of removing contaminants in 1 st phase settling tanks (as BOD5 and suspended solids) is increased up to 10-15 % for preliminarily clearing tanks and 20-25 % for biological coagulation tanks. - Hydraulic load in the sedimentation area of tanks is taken to be 3m3/m2.h.
8.13 Biological filtration tanks - General requirements 8.13.1 Bio-filters (trickling type and high load type) for wastewater treatment by completely or incompletely biological methods. Trickling filter allows user to treat wastewater fully biological at the stations with not large capacity (usually not exceeding 1,000 m3/d). High load biological filter can be applied to large power stations (up to 30,000 m3 /d or more). For production wastewater bio- filters of 2 levels can be designed. 8.13.2 biological filter tank designed as a tank round or rectangular tank with a tank, and scavenge the tank floor. Floor openings to fill filter filtering material. Regulation size structure as follows: - The height of the space between filter floor and floor of tanks is less than 0.6 m. - The slope of tank floor towards the water collection gutters shall be no less than 0.01. - The vertical slope along the water collection gutters must be retrieved with maximum capacity, which the tank structure allows but not less than 0.005. - The tank walls is 0.5 m above the filter material layer.
8.13.3 Trickling filter tanks are designed with natural ventilation, high load biological filters-natural or artificial ventilation. Natural ventilation is done through the air vents arranged around the walls of the tank surface (mainly in screening floor, tank floor). The total area of ventilation within the tank and filtering floor will be taken at 1-5% of filter tank area. In case of artificial ventilation, the tanks must be closed, fans are use to blow air into the space between the filtering floor and bottom floor with pressure 100 mm water column (at the entrance door). In pipes out of the tanks there is hydraulic lockers with depth of 200mm. 8.13.4 Filter materials can be used: crushed stone, gravel, slag, KERAMZIT stone, plastics(capable of withstanding temperatures of 6 – 30oC without loss of endurance). The filter material of natural and man-made types must (except plastic): - Withstand the loads not less than 10 N/cm2, in bulks up to 10.000N/m3 in its natural state. - Be resistant to Sodium Sulfate saturated solution, soaked at least 5 times. - Be resistant to boiling for 1 hour in solution of hydrochloric acid 5%; weight 3 times greater than the weight of the test materials. - After all the testing, filtration material may not be apparently damaged and weight must not be reduced 10% compared the original. 8.13.5 Filter materials should have the same height, uniform particle size along tank height. Particularly, filter material supports at the bottom, thickness of 0.2 m larger particle size should be required (70100mm). 8.13.6 The particle size of filter material used in trickling filters should be taken according to Table 42 . Table 42 Type of filters and Conventional % by weight of filter material retained on the frame with filter material diameter of hole diameter d (mm) filter 70 55 40 30 25 20 material D(mm) High load bio-filter 40-70 tank with stone, pebble
0-5
40-70
95-100
-
Dripping bio-filter 25-40 tank with pebble stone, and gravel
-
-
0-5
40-7095100
Trickling
-
-
0-8
Not
bio-filter 20-40
-
-
Not
98-100
tank with KERAMZIT material
specified
specified
NOTES: 1. Flattened and long particle number in filter material may not be less than 5% . 2. For filter material for support at the bottom in all cases it must be used the kind of particle sizes from 70-100mm. 8.13.7 The sewage distribution on the surface of the filter material is done in many different ways. When water distribution by nozzles the following must be designed: - Free initial pressure in the last nozzle must not be less than 0.5 m. - Diameter of the hose shall be 18 - 40 mm. - Height of the nozzles protruding above the surface of filter material must be about 0.15 to 0.2 m . - For drip filter tanks at the peak volume of water, irrigation time is 5-6 minutes. - When using a jet irrigation equipment, it is required to choose: - Number and diameter of distribution irrigation pipe are determined by calculating with the velocity of wastewater at the beginning of pipe is 0.5-1m/s. - The number and diameter of holes on sprinklers are determined by calculating the velocity through the holes must not be less than 0.5 m/s, hole diameter must not be less than 10mm. - Pressure at the nozzles must be determined by calculation but not less than 0.5 m. - Position to place sprinklers must be 0.2 m higher than surface of filtration layer. 8.13.8 Number of filter compartments must not be less than 2 and not more than 8, all must work. Calculation of distribution and drain gutters of bio-filters at the maximum flow. Equipment is needed to discharge sludge and wash tank bottoms of bio-filter as needed.
8.14 Trickling bio-filter tank 8.14.1 BOD5 concentrations of wastewater put into trickling bio-filter tanks is not greater than 200 mg/l. If wastewater has BOD5 of more than 200 mg/l, it must be circulated. Calculation method is determined by calculations.
8.14.2 Design trickling bio-filter should be taken: Working height H is 1.5-2m. Hydraulic load q is 1-3 m3/m3 materials/d. 8.14.3 When calculating the trickling bio-filter tanks, it is necessary to determine the activity coefficient of tanks K: K =La/Lt
(55)
In which: La - BOD5 of initial wastewater; Lt - BOD5 of normally processed wastewater (15mg/l). The parameters of trickling bio-filters as height of filter material layer H (m) and volume hydraulic load q (m3 water water/m3 filter material/d) shall be taken from Table 43 corresponding determined value K.
The total area of trickling bio-filters is determined by the volume of wastewater (including dilution water) through the bio-filter in a day and volume hydraulic load q. Table 43 Hydraulic load q (m3/m3/d)
K value correspond with height of filter material H (m) and average temperature of sewage in winter T 14- 20oC H = 1.5
H=2
1
11.4
15.1
1.5
10
12.8
2
8
11.5
2.5
6.7
10.7
3
5.9
10.2
NOTES: When the calculated temperature T is greater than 20oC, the value K is necessary to be determined experimentally. In the absence of real data, it can be calculated by using T of 20oC. Where the calculated value K exceeds the values in Table 43, circulation must be required. In this case the calculation is prescribed in Article 8.15.7.
8.14.4 The amount of residual bio-film in treatment plants using trickling bio-filter tanks is about 8 g of dry matter for one person in a day, humidity= 96 %.
8.15 High load bio-filters with artificial ventilation 8.15.1 BOD5 concentrations of wastewater being put in high load bio-filters may not exceed 250 mg/l. In case of larger concentration of BOD5, circulation is required. In the other cases, it should be identified by calculation. 8.15.2 Designing high load bio-filters, the following should be taken: - Height of filter material layer H should be taken 2-4 m. - Hydraulic load q is 10 -30 m3/m2/d. - Unit Air flow B is taken at 8-12 m3/m3 water, including circulating water flow. 8.15.3 When calculating high load bio-filters, it is determined the operating coefficient of tanks K: K = La/Lt
(56)
In which: La - BOD5 of wastewater put into the tanks (mg/l); Lt - BOD5 of treated wastewater (mg/l) The filter parameters of high load filters as H, q and B taken from Table 44 correspond to the average temperature of sewage in winter T and K calculated values. Where no value of K in table is equal to the calculated values, it is allowed to get approximate values. Without diluted circulatory sewage, higher values will be obtained. With diluted circulation, lower values shall be obtained. Area of high load bio-filters without circulation is determined by the hydraulic load q (m3/m2/d) and the volume of wastewater per day Q(m3/d). In case of circulation, the BOD5 of a mixture of untreated sewage and circulation water Lh (mg/l), and circulatory coefficient n and area F (m2) shall be determined by the following formula: Lh = KLt
n=
(57)
La − Lh Lh − Lt
(58)
Q ( n +1) q
(59)
F=
NOTES: Where calculations of bio-filters to treat wastewater with BOD5 concentrations greater than 250 mg/l, K must be is obtained as follows: K = 250 : Lt if the values in Table K ≥ 44; 250 : Lt , then take Lh of 250mg/l and determined under the value Lh, if K = 250: Lt is not included in this table, approximate values should be taken smaller K and then calculate Lh and n respectively. Table 44 B
H
K value depends on the hydraulic load q(m3/m2/d), air quality level B (m3/m3 sewage), filter material layer height H(m) and average temperature of sewage in winter T (oC) T = 14oC
8
10
12
T = 20oC
T = 25oC
q=10
q = 20
q = 30
q = 10
q = 20
q = 30
q = 10
q = 20
q= 30
2
4.3
3.02
2.56
6.85
4.31
3.50
10.36
6.18
4.709
3
8.95
5.25
4.09
12.02
8.93
6.53
14.45
11.48
10.10
4
12.1
9.05
6.95
16.26
12.16
10.67
21.0
15.2
12.86
2
5.09
3.67
3.16
7.76
5.08
4.168
12.03
7.08
5.52
3
9.9
6.04
4.84
16.22
9.86
7.31
19.95
15.49
11.22
4
16.4
10
7.42
21.03
16.37
12.85
28.84
20.41
17.31
2
5.97
4.31
3.7
9.33
6.02
4.89
14.53
8.472
6.546
3
11.7
7.2
5.72
23.01
11.7
8.73
26.01
19.72
13.40
4
23.1
12
8.83
27.10
23.12
15.56
31.88
30.20
23.83
8.15.4 Bio-film volume in 2nd phase sedimentation tanks after high load bio-filters is about 28 grams for a person in a day with humidity 96%. 8.15.5 BOD5 of wastewater poured into bio-filters with plastic filter material shall not be more than 250 mg/l. 8.15.6 For the bio-filters with filter material of plastics, it is allowed to select as follows: - Height of filtration material: H = 3-4 m;
- Class of filtration materials is block of pipes or sheets of PVC, Polystyrol, PE, PP, PA with smooth or perforated surface, pipe diameter is 50-100 mm or bulk materials with the shapes of long, thin tubes 50 150mm long, 30-75 mm in diameter, smooth or checked surface; - If the porosity of filter material layer is 90-96%, the surface area is 90-110 m2/m3 filtration material natural ventilation for tanks is selected; - In the case of stopping to supply wastewater into bio-filters, it is required to arrange the return sewage circulating pump system layout in order to avoid damaging bio-films on the surface of filter material. 8.15.7 When calculating bio-filters with plastic filter material, it is required to determine hydraulic load qm3/m2.day corresponds to the needed level to handle E with known temperature and height H selected according to Table 45. Filter material volume and surface area of the bio-filters shall be determined by hydraulic load and wastewater flow.
Table 45 Processing efficiency(% )
Hydraulic load q (m3/m2/day) and height of filter material layer H (m) H = 3m
H=4m
Average annual temperature of wastewater , ToC 10
12
14
10
12
14
90
6.8
7.5
8.2
9.1
10
10.3
85
9.2
10
11
12.3
13.5
14,
80
11.2
12.3
13.3
15
16.4
17,
8.16 Aeroten tanks 8.16.1 Aeroten for completely or incompletely biological treatment of urban and industrial wastewater. According hydrodynamic regime in aeroten tanks, it can be divided into 2 categories: aeroten mixing and aeroten pushing. Aeroten pushing is employed for wastewater treatment plants with a capacity greater than 10,000 m3/d. Aeroten mixing can be in blocks with settling tanks of many kinds, pure settling tanks and applications in case of the capacity of wastewater treatment plants under 20,000 m3/d. 8.16.2 The wastewater cleaning efficiency of aeroten tanks are shown in two aspects: processing efficiency by biological activities in aeroten tanks and sedimentation efficiency in 2 nd phase settling
tanks. Provided that proper design aeroten tanks, 2nd phase sedimentation tanks could work with the loads as follows: - Aeroten for low-load mud (< 0.2 kg BOD/kg mud.d), 2 nd phase settling tanks can work with the load q= 0.9 m3/m2.h. - Aeroten for medium load mud (0.2 to 1.0 kg BOD/kg mud.d), 2 nd phase settling tanks can work with the load q = 2.0-2.5 m3/m2.h. - Aeroten for high load mud (>1.0 kg BOD/kg bun.d), 2 nd phase settling tanks can work with the low load, likely at only m3/m2.h q = 0.4. - When calculating for design of aeroten tanks, it can be used a number of different formulas, but there should be testing calculations to confirm that the material balance in the whole system and working load of aeroten and 2nd phase settling tanks lie within the allowable range. 8.16.3 Activated sludge should be recycled for aeroten pushing in the following cases: - When BOD5 of sewage put into aeroten La is larger than 150 mg/l. - Production sewage contain substances to present biochemical oxygen. - Wastewater is treated incompletely biological (BOD5 after treatment is greater than 20 mg/l). 8.16.4 The volume of aeroten W (m3) is calculated according to the following formula:
W = Qtt (1 + R ).t , m 3
(60)
In which: t – gas blowing time (h). This time should not be less than 2h; Qtt - Calculated flow (m3/h), is determined as follows:
- When ir-regulating coefficient K ch ≤ 1.25 , Qtt = Qtb ; - Coefficient K ch > 1.25, Qtt is taken to be equal to Qtb , max in t hour has the largest wastewater flow. R - sludge circulation ratio, is determined by the following formula: In which:
R=
a 100 −a I
I - The mud indicator, typically from 100 to 200 ml/g;
(61)
a- Dose of activated sludge as per dry matter (g/l), is selected as follows: o 2-3 g/l for aeroten with high sludge load; o 2.5-3.5 g/l for aeroten with average sludge load; o 3-4 g/l for aeroten with low sludge load; o 3-5 g/l for aeroten with extended air-blower; o 5 g/l for completely mineralized aeroten. 8.16.5 Gas blowing time (processing time) wastewater t (h) of mixed aeroten is determined by the following formula:
t=
La − Lt 15 a (1 − Tr ) ρ T
(62)
In which: T - average temperature of the mixture of wastewater in winter (oC); La and Lt - BOD5 of wastewater before and after treatment (mg/l); Tr – Ash level of activated sludge, depending on types of sewage, and is selected according to Table 46;
ρ - private oxidation rate of organic matter (mgBOD5/g non-ash dry matter of sludge in 1h), is determined by the following formula:
ρ = ρmax
Lt C0 1 x Lt C0 + K1C0 + K 0 Lt 1 + ϕa
(63)
ρmax - largest private oxidation speed (BOD5 mg/g non-ash dry matter of sludge ) in 1 h ; C0 - dissolved oxygen concentrations necessary to maintain in aeroten (mg/l);
K1 - typical constants for the nature of organic contaminants in wastewater (BOD mg/l); K 0 - constant considering the impacts of dissolved oxygen (mg O2/l);
φ - coefficient considering restriction of biological processes by degradation products of activated sludge (l/h). The values of ρmax , K1 , K 0 , φ and Tr of different types of sewage and are determined by empirical studies, or as indicated in Table 46 .
Table 46 Type of sewage
ρmax
φ
K0
K1
Tr
Urban Wastewater
85
33
0.625
0.07
0.3
Refinery waste water system
1 33
3
1.81
0.17
-
Refinery Wastewater System 2
59
24
1.66
0.158
-
Wastewater urea production
140
6
2.4
1.11
-
production of artificial rubber
80
30
0.6
0.06
0.15
production license
650
100
1.5
2
0.16
Wastewater brewing
232
90
1.66
0.16
0.35
Slaughter house wastewater
454
55
1.65
0.176
0.25
production of viscose
90
35
0.7
0.27
-
8.16.6 The time for gas supply (processing time) wastewater t (h) in pushing aeroten without regeneration compartment is determined by the following formula:
t=
L 1 + ϕa [(C0 + K 0 )( L hh −Lt ) + K t C0 ln hh ]K p ρmax C0 a (1 − Tr ) Lt
(64)
In which: K
p
-coefficient taking into account the effects of mixing process along the tanks, taking in 1.5 during
fully biological treatment (Lt<20 mg/l) and equal to 1.25 during incompletely biological treatment (Lt > 20 mg/ l ); Lhh - BOD of the mixture of wastewater and circulated activated sludge into aeroten (mg/l), is
determined by the following formula:
Lhh =
La + Lt R 1+ R
(65)
8.16.7 Pushing aeroten with regeneration of activated sludge consists of two parts: aeroten and recycled activated sludge. Calculation of pushing aeroten with regeneration compartment follows the following steps: 1 . Identifying the working time of aeroten compartments. - Oxidation time of organic matter t0 (h):
t0 =
La − Lt Rar (1 − Tr ) ρ
(66)
In which: ar - activated sludge dose in regeneration compartment, g/l, is calculated as follows: ar = a (
1 +1) 2R
(67)
Private rate of oxidation of organic matter ρ (mg BOD5/g dry matter of non-ash sludge in 1 hour), is determined by the formula (63) with values of activated sludge doses a t . - Time of gas supply in aeroten t a :
ta =
2.5 La lg a 0.5 Lt
(68)
- The time required to regenerate the activated sludge t ts : tts = t 0 −t a
(69)
2 . Aeroten volume - The volume of aeroten compartment Wa (m3): Wa = t a (1 + R )Qtt
(70)
- The volume of recycled aeroten compartment Wts (m3): Wts = tts RQtt
(71)
- Total aeroten volume W (m3): W =Wa +Wts
(72)
8.16.8 Pushing aeroten is usually divided into corridors. Activated sludge is put into the beginning of tanks, wastewater is distributed along the length and width of tanks. The mixture of mud and wastewater is collected at the end of tanks. To ensure hydrodynamic regime of the tank on the pushing principle, the size of aeroten corridor is as follows: - Working height H = 3-6 m;
- Width of each corridor B ≤ 2H; - Length L ≥ 10H corridor. For pushing aeroten with regeneration compartment, based on the ratio Wts/W can be selected the number of aeroten corridors. When this ratio is 25%, choose aeroten with 4 corridors; while the rate is 30 % , then select aeroten with 3 corridors; and the percentage is 50% , choose two corridors. 8.16.9 It is required to consider that aeroten tanks can work with fluctuated volume of regeneration compartment. 8.16.10 circulating activated sludge in the sludge regeneration Aeroten not determined by the concentration of sludge in tanks and the concentration of circulating activated sludge, shall be obtained under the provisions of 8.16.4 and 8.16.7. 8.16.11 When calculating aeroten for production wastewater treatment, sludge concentration, average rate of oxidation, unit air flow and sludge biomass increase obtained from the practical research results. 8.16.12 Increased biomass sludge Pr (mg/l) in aeroten compartments during domestic wastewater treatment will be identified according to the formula: Pr = 0.8C1 + 0.3La
(73)
Where: C1 - The amount of suspended solids in sewage being put into aeroten (mg/l). NOTES: When calculating the compressed mud tanks, diameter of mud distribution pipe and venting pipe, mud biomass growth value determined by the formula (73) should be increased by a factor of 1.3 to mention ir-regulation in seasons. 8.16.13 Unit air flow D (m3 air /m3 wastewater) during wastewater treatment in aerotens of compressed air supply from air blowers, and is determined by the formula:
D=
z ( La − Lt ) K1 K 2 n1n2 (C p − C )
(74)
In which: Z – Unit oxygen flow in mg to treat 1 mg BOD5 is determined as follows: - During fully biological treatment- 1.1 mg oxygen/mg BOD ; - When incompletely biological treatment- 0.9 mg oxygen/mg BOD5; K1 – The coefficient mentioning air supply equipment is obtained as follows:
- Air input equipment with making air bubbles of small size is taken from the ratio of the air intake area and area aeroten (f/F), according to Table 47. Table 47 f/F
0.05
0.1
0.2
0.3
0.4
0.5
0.75
1
K1
1.34
1.47
1.68
1.89
1.94
2
2.13
2.3
Jmaxm3/m2-h
5
10
20
30
40
50
75
100
- Gas distribution foaming equipment of medium size and pressure gas distribution is obtained at 0.75.
K 2 - coefficient depending on depth of placing gas distribution equipment h (m), refer to Table 48. Table 48 h (m)
0.5
0.6
0.7
0.8
0.9
1
3
4
5
6
K2
0.4
0.46
0.6
0.8
0.9
1
2.08
2.52
2.92
3.3
42
38
82
28
24
4
3.5
3
2.5
Jmaxm3/m2-h 43
n1 - coefficient taking into account of sewage temperature impacts is determined by the formula: n1 =1 + 0.02(Ttb − 20)
(75)
In which : Ttb - The average temperature of wastewater in the summer months (oC); n2 - coefficient taking into account the relationship between the rate of oxygen dissolved in a mixture of water and mud at a rate of oxygen dissolved in water obtained as follows: + For domestic wastewater, n2 is 0.85. When there is surface-active substances in domestic wastewater, depending on the value of /F, n2 will be taken according to Table 49 .
Table 49 f/F
0.05
0.1
0.2
0.2
0.4
0.5
0.75
1
n2
0.50
0.59
0.04
0.66
0.72
0.77
0.88
0.99
+ For wastewater production obtained from experimental data. Without this data, it is allowed to get n2 at 0.7. Cp - Solubility of oxygen gas in water ( mg/l) determined by the formula: Among them:
h CT x (10.3 + ) 2 Cρ = 10.3
(76)
CT - Solubility in water of oxygen in the atmosphere depends on temperature and pressure, follow with the table of the oxygen solubility in water; C - average concentration of oxygen in aero ten (mg/l) is 2 mg/l. The area of gas supply is taken from the layout of the gas distribution equipment. For small gas foam distribution equipment, if the distance between the two devices is up to 0.3 m, the surface area of the devices is taken in the area of blown air. According to the values of D and t found, determine aeration intensity J (m3/m2.h ) by the formula: J =
DH t
(77)
Where: H-working depth of aeroten. If aeration intensity is greater than Jmax values , determined by the value of K1, the area of the air blower will be increased, when the value is smaller than the value of Jmax; while it is determined in accordance the value K2, the air flow must be increased to achieve value Jmin. 8.16.14 The aeroten and sludge regeneration compartments are usually designed in a rectangular shape. 8.16.15 For aeroten with recycled sludge, it is stipulated as follows: - The number of compartments is not less than 2. Regard to the station with a capacity of less than 50,000 m3/d, the number of compartments will be 4-6. For the stations with a capacity greater than 50,000 m3/d, take the values of 8-10 provided that all the compartments are working. - Working depth must be taken from 3-6 m. - The ratio of the working width and depth of each corridor is from 1:1 to 1:2. 8.16.16 For air supply system with air blowers, it is allowed to use materials in gas distribution equipment as follows:
- For small gas foam distribution equipment, foam material is used (including foam sheets, discs and sleeves of diffusion membrane) and the synthetic fabrics. - For medium foam gas equipment distribution, pipe with drilled holes or slits used is used. - For large bubbles equipment- pipe has an open end. - If conditions are favorable, it is allowed to use mechanical air supply machine level in the form of agitator. 8.16.17 The types of gas supply equipment under Pneumatic systems are often arranged into strips, each separate air diffuser throat or each frame. The number of air distribution equipment in the mud regeneration compartments and in the first half of the aeroten corridor- push ( along the length of the tank ) should get double the other half. 8.16.18 Depth to set out air distribution equipment in aeroten should take: 0.5-1m in case of using low pressure air supply. 3 - 6m when using different gas supply, depending on tank depth. 8.16.19 The value of calculated pressure loss in the compressed gas supply equipment with taking into account the coefficient of increasing pushing force with time, should take: - For small bubble gas supply equipment, it does not exceed 0.7 m above water column. - For average gas bubbles supply equipment, set 0.3 m deep in the water, take 0.15 m water column. - In the air supply system of low pressure, when gas velocity out of the hole is from 5 to 10 m/s, take at 0.015 to 0.05 m of water column. 8.16.20 In the aerotens, it is required to dry draining equipment network and water draining parts from the aeration equipment. In necessary cases, it is required the foam breaking equipment by water or chemical spraying, water spray intensity will be determined by experiment.
8.17 Aeroten tanks with extended air blowing 8.17.1 Use a stretched blower aeroten to completely oxidize the organic matter in wastewater by aerobic biological methods. The time of air blowing in an entirely oxidized aeroten tank t (h) is defined by the formula:
t=
La − Lt a (1 −Tr ) ρ
(78)
here select average oxidation rate ρ as per BOD5 at 6 mg/gh, mud dose is selected to be 3-4 g/l, sludge ash level Tr is 0.35. Air individual flow is chosen according to the formula (74), in which the separate flow of oxygen per mg/mg of BOD5 for treatment z is 1.25. 8.17.2 The works behind stretched air blowing aeroten for completely biochemical oxidization of organic material is designed according to the following parameters: - Time of water kept the deposition area of 2 nd phase sedimentation tanks with the largest volume not less than 1.5 h. - The mud amount of residual activation is taken by 0.35 kg on 1 kg BOD5. The discharge of surplus activated sludge allows to perform similarly to for settling tanks and aeroten tanks when mud amount reaches 5-6 g/l. - Humidity of discharge sludge from sedimentation tanks is 98% and 99.4% from aeroten. - Load of mud in mud drying yard is selected as for fermented smudge.
8.18 Ditch of oxidization 8.18.1 Ditch of oxidation operates as per the principle of activated sludge, will be used to process quadratic or cubic sewage. The time of air blowing in the ditch is also calculated using the formula (78) with an average speed of oxidation ρ according to BOD5 is 6mg/gh 8.18.2 Select the shape on the surface of circulating oxidized trench as oval style, 1-1.5 m deep, residual activated smudge is 0.4-0.5 kg/kg BOD5, unit gas amount z is 1.25 to 1.45 mg/1 mg BOD5 to be processed. 8.18.3 Carrying out the clearance in circulating oxidized channels by mechanical equipment such as vertical axis or horizontal axis agitators, treadmill, ... put in straight channel segments. Depending on the capacity with oxygen and water speed in channel, dimensions and working parameters of the clearance equipment is selected in compliance with cataloges. 8.18.4 Flow velocity in the circulating oxidation channel V, (m/s) generated by transient equipment is determined by the formula:
J a la
V=
ω(
2
n L + 0.05∑ ξ ) R3/ 4
(79)
Among them: Ja - Pulse pressure of stirrer/paddle, select as in the catalogs; la - Length of stirrer/paddle (m);
ω - Cross section area of the channel (m2); n - roughness coefficient of channel surface. For the concrete walls, n1 = 0.014; R - hydraulic radius of the channel (m); L - Length of channel, m;
∑ ξ - Total local losses (m). For the oval channel, ∑ξ = 0.5 m. The length of the stirrer/paddle la, is chosen not less than the width of the channel bottom. 8.18.5 Oxidation ditch length should be taken: - Oval shaped ditch style; - The depth of trench is approximately 1.0 to 2.0 m; - Amount of active mud residue is 0.5 kg to 1 kg BOD5. 8.18.6 Time of water kept in 2 nd phase settling tanks is selected to be 1.5 h under maximum flow. Circulating mud from 2nd phase sedimentation tanks is continuously led to the channels. Surplus activated sludge is transferred to mud drying yard periodically. Sludge drying yard is calculated base on weight of fermented mud.
8.19 Mud compressing tanks 8.19.1 Mud compressing tanks should be use the vertically standing and centrifugal types; at least there are two tanks to work simultaneously.
NOTES: Mud compressing tanks are often used to compress the activated sludge in 2 nd phase settling tanks as well as sludge mixture from Aeroten tanks. 8.19.2 For centrifugal mud compressor tank. it should be taken as follows: - The ratio of the depth and diameter should be 6-7. - Including mud scraping and pumping machines to discharge sludge from the tanks. - Continuously discharging compressed mud by hydrostatic pressure should not be less than 1m. - Discharging the separated water during compression into Aeroten or regulating tanks. 8.19.3 The data to calculate the sludge compressing tanks is taken from Table 50. Table 50 The nature of activated sludge residue
Data to calculate the sludge compressing tank Humidity of compressed activated smudge (%)
Compressing time (h)
Flow velocity in the sedimentation area in the vertical standing mud compressing tanks (mm/s)
Type of mud compression Vertical
Centrifugal
Vertical
Centrifugal
- Mixture of mud from Aerotens with concentration of 1.5-3 g/l.
97.3
-
5-8
-Activated sludge from the 98 2nd phase deposition tanks with concentration at 4 g/l
97.3
10-12
9-11
Not more than 0.1
-Activated sludge from the 98 sedimentation area in settling Aerotens with concentration of 4.5 - 6.5 g/l
97
16
12-15
-
Activated sludge from completely biological cleaned aerotens
- Mud mixture of from incompletely biological cleaning Aerotens at concentrations of 1.5 -2.5 g/l NOTES:
Not more than 0.2
1 – Compression Time of surplus activated sludge is allowed to vary depending on the nature of the sludge . 2 - Calculation of pipes and pumps to pump compressed mud in need of inspection for mud pump and discharge in case of the mud moisture of to 98.5%. 8.19.4 Hydraulic load in sludge compression tanks qo (m3/m2.h) for excess sludge from the oxygen or aeroten tanks combined with 2 nd phase deposition to work in the mode of sedimentation tanks in which the layer of suspended solids depending mud index l under article 8.5.7 and must be chosen according to Table 51. Table 51 Mud indicator I
100
200
300
400
500
600
qo (m3/m2.h)
5.6
3.3
1.8
1.2
0.8
0.7
8.19.5 Calculation of the flotation tanks for sludge concentration depends on the purification level and amount of suspended solids in mud mixture in Table 52. Table 52 Indicator
Amount of suspended solids (mg/l) 15
10
5
Flotation time (min)
40
50
60
Individual flow of air (l/kg suspended solids)
4
6
9
Pressure in the pressure vessels must be selected by from 0.6 to 0.9 MPa (6-9 kg/cm2), and saturation time is 3-4 minutes.
8.20 Neutralization of sewage 8.20.1 Sewage required for biological treatment must have a pH from 6.5 to 8.5 and during discharge into the receiving water, it must have a pH between 6 and 9. If the pH is out of this value range, it is required to neutralize sewage. a) To neutralize sewage, firstly consider the self-neutralizing ability among types of acid and alkaline containing sewage. Only when it is impossible to take advantage of the mentioned possibilities, then it is allowed to use chemicals to neutralize sewage.
b) Amount of chemicals to neutralize sewage is determined from neutral conditions and the composition of acid or alkaline content such as heavy metals in sewage. The surplus of chemicals must be 10% compared to the calculated amount. NOTES: When determining the amount of chemicals, it is required to take into account the interaction between acid and alkaline reserves, as well as acid and alkaline contained in domestic sewage and lakes, and ponds. c) The most suitable chemical to neutralize acid containing sewage is limestone in the form of activated calcium oxide 5%. It is possible to make use of waste alkali (caustic soda or potassium hydroxide). In addition, it may put sulfuric acid containing sewage to be filtered through layers of limestone or dolomite rock. d) To create acidity for sewage and to neutralize alkaline sewage, technical sulfuric acid should be used. e) To remove residue, it is required to use a sedimentation tank with deposition time of 2h. f) Separated sediment can be dried in drying yard or separating water by conveyor type pressing filters or vacuum filtration.
8.21 The sewage treatment works by means of flocculation 8.21.1 Solution by chemical flocculation is applied to increase the separation of the coarse dispersions, colloidal substances or the solute precipitates capable of processing as well as for chemical decontamination sewage contain chromium or cyanide. In case of additional nutrients during dealing with biological methods, the corresponding devices must also be included. 8.21.2 Chemical coagulants often used are aluminum salts, iron salts and lime. The flocculation adjutants are soluble organic polymers (anions, cations). 8.21.3 Type of flocculation chemicals and their amount are selected on the basis of experimental studies, depending on the nature of the contaminants, the level of required treatment and other local conditions. 8.21.4 During sewage treatment by the flocculation chemicals, it is required to pay attention to ensure optimal value of pH. With urban sewage, and pH of below 7, alum alkaline is selected; in case of pH of above 7, iron alkaline is used. The preparation of flocculation chemicals and mixture of alum solution with treating water can be made in supply water treatment. 8.21.5 Allow mixed with chemical flocculation sewage stirrer or pump on sewage thruster.
8.21.6 If coagulation with iron salts, use solid mixing tank with aeration, sedimentation tanks blowing sand, clear tank preliminary. These works will ensure the solution transferred into ferric hydroxide, ferric hydroxide two three. Retained water back in time is 7 minutes mixing tank, the aeration intensity from 0.7 to 0.8 m3/m3 sewage be processed in 1 minute, mixing tank depth Selected 2 - 2,5 m . 8.21.7 In the reactor, it is allowed to stir mechanically or hydraulically. Multi- corridor flocculation tanks with decreasing mixing intensity should be chosen. 8.21.8 Time of water kept in reactors is 10-15 mins for alum and 20-30 minutes for flocculation adjuvants during separation of deposited sediment by flocculation. When using flotation to handle, the time of 3-5 minutes will be selected for alum, 10-20 minutes for the glue fluxes. 8.21.9 Mixing intensity of sewage with flocculation chemicals in mixer and reactor tanks will be chosen, according to the gradient value of the average speed (s-1): - For chemical flocculation mixing tanks, it is 200s-1, for glue flux mixing tanks, it is 300-500s-1. - For alum and glue flux reactors: during deposition, it is 20-50s-1; and during flotation, it is 50-75s-1. 8.21.10 To remove the residue from sewage, sedimentation tanks, flotation tanks, centrifugal rotors or filtration through filter material will be used.
8.22 Sewage oxidation - reduction 8.22.1 To detoxify cyanide containing sewage simple and complex with zinc, copper, nickel, cadmium, and so on., it is required to employ oxidation method using chemicals containing active chlorine as calcium chloride, sodium or sodium hypochlorite, liquid chlorine with pH values of 11-11.5. After treatment with active chlorine, it must be re-neutralized until the pH is 8 - 8.5. 8.22.2 Amount of activated chlorine must be selected by calculation with the rate of 2.73 mg/1mg simple cyanide of zinc, nickel, and cadmium salts with strong acids and 3.18 mg/1mg cyanide complexes with copper with the surplus must not be less than 5mg/l. 8.22.3 Operating fluid concentrations of antioxidants must ensure 5-10 % by active chlorine. 8.22.4 To handle sewage containing cyanide, it is required to build intermittent operation stations with not less than two compartments. Sewage-chemical exposure time is 5 minutes during simple cyanide oxidation, and 15 minutes for oxidization of cyanide complexes. 8.22.5 The volume of residual moisture 98% after 2h deposition will be equal to 5% of processed sewage capacity. When adding poliacrylamid (PAA) at a dose of 20mg/l of solution 0.1%, the deposition time can be shortened to 20 minutes only.
8.22.6 To detoxify sewage containing chromium, it is required to use deodorant of bisulphate sodium or sulphate with pH 2.5-3. The amount of natri bisulphate is 7.5 mg/mg Cr+6 with chromium concentration of 100 mg/l and 5.5 mg/ mg Cr +6 chromium with concentrations of above 100 mg/l. Before leading detoxified sewage through deposition, lime is used to neutralize until the pH of 8.5-9.
8.23 Addition of nutrients for biological treatment process of sewage 8.23.1 The following materials should be chosen to supplement the nutrients containing nitrogen and phosphorus for the biological treatment process of sewage: - Substances containing phosphorus include superphosphates or ortophosphoric acid. - Substances containing nitrogen are ammonium sulphate, amoniac water, and so on. - The salts also containing both nitrogen and phosphorus are technical diamoniphotphate, ammophos, and so on. 8.23.2 Concentration of working solution is selected according 5% of P2O5 and 15% of N.
8.24 Sewage treatment works by adsorbing 8.24.1 In order to thoroughly treat sewage from dissolved organic contaminants by adsorption method, adsorbent used is activated carbon in granular or powder form, large adsorption filters with solid material or boiling layer adsorption towers. The amount of activated carbon to handle sewage is determined experimentally. 8.24.2 Structure of adsorption filters may be exposed, with or without pressure with granular coal layer, in size of 0.8 - 5mm. 8.24.3 The amount of suspended solids in sewage on adsorption filters shall not be more than 5 mg/l. 8.24.4 The surface area of adsorption filters Fads (m2), shall be defined by the formula: Fads = qv / v
(80)
Among them: qv - Average flow of sewage per hour (m3/h);
v – Flow velocity of not more than 12 m/h. When splitting a tank out of work, then the filtration rate in the remaining tanks must not exceed 20%.
8.24.5 Number of working adsorption filters in serial Nads is calculated using the formula: Among them: N ads = H tot / H ads
(81)
H ads - Height of adsorption filter material layer of a tank (m), is selected according to the structure;
H tot - The total height of all the adsorbed layers (m) of the tanks, is determined by the formula: H tot = H1 + H2 + H3
(82)
H1 - The height of the adsorbed layer (m), after adsorption cycle, Tads adsorption capacity of material layer loses the effect to the level K, is determined by the formula: min Dsb qv t ads H1 = Fadsγ sb
(83)
Among them:
γsb - Individual mass of activated carbon (g/m3), selected according to the manufacturer's catalog; Dsbmin – minimum dose of activated carbon (g/l), removed from the filters to effect losing coefficient of capacity Ksb is determined by the formula:
Dsbmin =
C a − Ct K sb asbmax
(84)
In which: Ca , Ct - concentration of impurities before and after treatment (mg/l); max asb - the largest adsorption capacity of the activated carbon ( mg/l), determined by experiment;
K sb - The coefficient is chosen to be 0.6-0.8;
H2 – Height of adsorbent layer must ensure the operation of the station until it reaches a concentration Ct in t ads time period, selected according to operating conditions and determined by the formula:
H2 =
max Dsb qv t ads (85) Fadsγ sb
max Dsb - largest dose of activated carbon (g/l), determined by the formula:
min Dsbmax = (Ca − Ct ) / asb
(86)
min a sb - the smallest adsorption capacity of the activated carbon (mg/l), determined by experiment;
H3 – Emergency adsorbed layer (m), calculated according to the operation time of the processing system in overload period and moving adsorbent layer of height H1 to revert. 8.24.6 Loss of pressure in layers of coal with particle size of 0.8 - 5mm, select no more than 0.5 m/1m of filter material layer . 8.24.7 Activated carbon with relatively high expansion of material layers at 20-25% is removed from adsorption filters by using a suction pump, hydraulic lifting equipment or ejector thanks to upward water flow at speeds of 40 - 45m/h. In the adsorption filter with pressure, it can be applied to remove coal under the pressure of 0.3 MPa (3kG/cm2). 8.24.8 Wastewater flowing into the fluidized bed adsorption towers shall not contain suspended solids concentrations exceeding 1 g/l, with large hydraulic force of sediment particles less than 0.3 mm/s. The suspended solids and small coal grains away from the towers must be removed after adsorption equipment. 8.24.9 The adsorbents during being loaded into the fluidized bed adsorption towers with load of more than 0.7 t/m3, it is allowed to measure the weight in wet or dry state, if the density is less than 0.7 t/m3, it shall be quantified only in wet form. 8.24.10 Along the height of the adsorbing towers, every 0.5-1 m there should be set separating grids with the diameters of holes at 10 - 20mm and the rate is 10-15% cross-sectional area. The optimal number of number is 3-4. 8.24.11 The upward flow velocity is selected to be with 30-40 m/h with particle size of 1-2.5 mm for activated carbon and 10 – 20 m/h for the coal particle of size 0.25- 1mm. 8.24.12 All the structure material of the adsorption towers, pipelines, accessories ... shall be protected from corrosion.
8.25 The sewage treatment works by ion-exchange method 8.25.1 The ion exchange tanks are used to handle thoroughly sewage, remove the minerals and organic compounds dissociated into ions, as well as desalination for reusing wastewater in the network of circulating water supply and recovery of precious substances. 8.25.2 Sewage lead into the tanks must not contain salt content exceeding 3000 mg/l, suspended solids not exceeding 8 mg/l and COD less than 8 mg/l.
If sewage contains suspended solids, COD with the quantity exceeding the above values, pretreatment is required before leading into the tanks. 8.25.3 Design calculation of ion exchange tanks is according to the guidelines outlined in Vietnam construction standard TCXDVN 33:2006-Water supply-external networks and facilities-Design Standards.
8.26 Methane tanks 8.26.1 Methane tanks are applied to stabilize domestic wastewater sludge and production wastewater in anaerobic conditions and to recover of methane. It is allowed to put into the tanks different organic materials such as garbage from trash rack, discarded organic materials derived from industrial enterprises, ... after being crushed. 8.26.2 To decompose methane sludge in the methane tanks, it is possible to apply warm fermentation (temperature for fermentation t=330C) or hot fermentation (t= 53oC). Selection which process must be based on economic and technical comparisons with attention on the next process and hygiene requirements when using mud residue. 8.26.3 Determination of methane tank volume W is based on actual moisture of sludge and load of fresh sludge in the tanks taken into the tanks on the date D (%). For domestic wastewater sludge, D can be obtained from Table 53 . Table 53 Ferment mode
Loads of fresh sludge brought into methane tank on the date D (%) with residual moisture of p (%) 93
94
95
96
97
warm
7
8
9
10
11
hot
14
16
18
20
22
For production wastewater sludge, D is obtained from experimental data. When the waste water containing surfactants, D is calculated under the guidance of research institutions. Working volume of methane tank W (m3) is determined according to the following formula: W = 100 M/D
(87)
Where: M - amount of fresh sludge taken on day into methane tank (m3).
8.26.4 The decomposition of organic matter of sludge of methane tanks depends on the load D and determined by the following formula: Y = a – nD
(88)
In which: Y - The ability to decompose organic matter (%); a-The ability of maximum fermentation of organic matter in sediments brought into the tanks depends chemical composition of organic matter in the sludge fresh and determined by the formula: a = (0.92 m + 0.62C + 0.34 A). 100 %
(89)
In which: m, C, A - corresponding component content of fat, sugar and protein in fresh sludge organic matter (%). If without the data on above ingredients, it may not be taken the value of n as follows: - Residue of 1st phase settling tanks, a = 53 %. - Activated sludge residue, a = 44 %. - The mixture of activated sludge and sediment – is determined by the average ratio of the components of mixed organic compounds. n - coefficient depending on the moisture of fresh sludge, refer to Table 54.
Table 54 Fermentation temperature (oC) 33 53
Value of coefficient n with residue moisture brought into the tanks p (%) 93
94
95
96
97
1.05
0.89
0.72
0.56
0.40
0.455
0.385
0.31
0.24
0.17
8.26.5 The amount of gas produced during the decomposition of organic matters in the methane tanks G (m3 air/kg non-ash dry matter of fresh sludge), determined according to the following formula: G = Y/100
(90)
8.26.6 Designing methane tanks should be required to pay attention to explosion prevention and must follow the guidelines of professional organizations.
8.27 Sludge drying facilities 8.27.1 To dry the sludge, the following types of facilities can be applied. - Mud drying yards on the natural ground in case of groundwater located as deep (more than 1.5 m above background level) and while the mud water is allowed to penetrate into the soil. - Mud drying yards of settling type and - Mud drying yards of compression on artificial ground are applied when there is enough space for the mud drying yards on the natural ground. - Drying with mechanical devices (it is convenient to overcome the effects by natural factors as heavy rain, high air humidity, ...) - Using filtration yards with or without planting trees. NOTES: To overcome the impacts of heavy rains, it is allowed to apply the mud drying yards with covering roof, on the basis of comparison of economic and technical indicators with the alternatives. 8.27.2 The calculation and design of sludge drying yards and other drying equipment is compliance with the guidance of the professional bodies.
8.28 Wastewater Disinfection 8.28.1 Domestic wastewater or mixture of domestic and production wastewater, after processing, must be disinfected before discharge into the receiving water. NOTES: 1. In the case of combined biological treatment of domestic domestic and production wastewater, it allows for sterilization of only domestic wastewater after mechanical treatment. 2. In the case of wastewater treatment by biological methods in natural conditions (biological lakes, flooded filtration yards, ... ), sterilization is not necessary. 8.28.2 Liquid chlorine, calcium chloride, sodium hypochlorite produced by electrolysis or ozone produced on-the-spot can be used to sterilize. 8.28.3 The dosage of active chlorine shall be stipulated as follows: - Wastewater after mechanical treatment is 10g/m3; - Wastewater after completely biological treatment is 3g/m3;
- Wastewater after in completely biological treatment is 5g/m3; NOTES: 1. The active chlorine dosage will be adjusted during the management process to ensure the chlorine dosage in water after an contacting tanks must be not less than 1.5 mg/l. 2. Chlorine equipment of treatment plants must ensure the increase in chlorine dose by 1.5 times. 8.28.4 To mix with disinfection chemicals with wastewater, various types of mixing trench can be applied. 8.28.5 Wastewater disinfection process takes place in contacting tanks, similar the design of 1 st phase sedimentation tanks, but without descaling devices with tanks no smaller than 2. Exposure duration of disinfection chemicals with wastewater in contacting tanks, gutters and drains must be not less than 30 minutes. 8.28.6 The amount of sediment in contacting tanks during liquid chlorine disinfection, is calculated for a person in a day as follows: - For a mechanical treatment plant: 0.02 liters. - For completely biological treatment plant in aeroten: 0.03 liters. - For treatment plants with biological filter: 0.05 liters. When chlorine is used for disinfection, sediment concentration will be doubled. 8.28.7 Design of preparation system and storage of chlorine must be in accordance with the guidelines outlined in Vietnam Construction Standard TCXDVN 33:2006 – Water supply – External Network and Facilities – Design Standard.
9 . Sewer for small areas 9.1 Sewer for small areas includes wastewater treatment network and facilities for individual houses, one hospital, schools, a group of houses or residential areas built in the region without urban drainage systems. Wastewater treatment capacity for small areas does usually not exceed 1500 m3/d. 9.2 Selecting the drainage network diagram, wastewater treatment methods, construction location of pump stations and treatment facilities must facilitate the construction in near future and must consider general planning of urban area so that in the presence of the general urban drainage system, the facilities are still being used or renovated at the least extent.
9.3 Depending on the nature of construction and quantity of wastewater scheme to select the appropriate system. Generally, for low-rise houses or the ratio of low-rise houses accounting for over 70%, the common or simplified drainage system scheme should be applied. 9.4 Simplified sewer scheme is collection diagram with low cost and to use trans-sub area sewer network, going through the back of yard or garden. Depth of burying culverts is less than or equal to 0.5 m. Minimum diameter of culverts is allowed to be 100mm, minimum slope is 1/200. Thickness of flow h/D = 0.2- 0.8 Calculated wastewater flow of simplified sewer network Qmax (l/s), defined as follows:
qmax =1.8 x10 −5 PW
(91)
Among them: P - Number of people that sewer segment serves; W - The average daily consumption amount of water (l /person.d). Minimum flow is approximately equal to maximum flow during flushing the toilets, which can be obtained at 1.5 to 2.2 l/s. Manholes are simple inspections wells or rectangular square or round connected sections. 9.5 It is required to utilize terrain conditions, research on reasonable planning solutions in order to take water to the treatment works by self-flowing pipelines. In case of necessity, requiring the pump stations, pumping stations should be arranged after septic tanks (or after 1 st phase settling tanks). 9.6 In case of the completely separate drainage system diagram, when it is still required to build the common type in the first phase, the drainage branch pipes from houses to the shared pipeline of the housing group must be designed in a completely separate type so that in needed cases, it can be separated smoothly. 9.7 The treatment facilities for small areas (in -situ treatment or local treatment) can be applied: - Septic tanks of many types; - Sediment tanks of two shells; - Absorbing well (in case of the wastewater amount not exceeding 1m3/d); - Underground filtration yards;
- Filter trenches; - Showering yards with planting trees; - Underground yards with trees; - Filter tanks with sand (when capacity does not exceed 15m3/d); - Bio-lakes: aerobic, anaerobic or arbitrary; - Oxidation ditch; - Bio-filter tanks; - Biological filtration tower (when the capacity is over 100m3/d); - Aeroten tanks with activated sludge; - Other works accepted for application. NOTES: 1.When choosing the treatment works, first to consider the application of bio-lakes and other works. 2. Underground filter yards, filter trenches and penetrating wells are only applied to a few individual houses, suburban areas and rural areas with low population density, not applicable popularly in the urban areas. Particular attention is required when application of the areas with groundwater extraction wells. 3. Designing the sewage treatment plants by biological methods (bio-filters, watering yards, bio-lakes) should follow the regulations on wastewater treatment by biological methods. 4. On-site wastewater treatment system is applied for separate houses or facilities, and should not be applicable rampantly in urban areas. Especially for the areas of groundwater wells, it is not allowed to build new facilities, and at the same time to take measures of stopping the use of existing on-site treatment facilities. 9.8 Design calculation of septic tanks follows the instructions of Vietnam Construction Standards- Water supply and sewerage systems in houses and buildings. Design calculation of wastewater treatment facilities for other small areas is under the guidance in section 8 of this standard. 9.9 Treating the wastewater of washing and bathing houses containing a washing soap and alkali should be mixed with wastewater at the rate 1:1. Maintain this necessary ratio may need an regulating tanks with exhaust equipment.
There is a need to handle wastewater containing particular compounds prior to putting into septic tanks or settling tanks with two shells. 9.10 When putting wastewater into the treatment works by pumps, calculation of treatment works is according to working capacity of the pumps. Flow calculation for selecting pumps, or design calculation of wastewater distribution and treatment facilities determined by the following formula:
Qmax −hour =
Qmax −day n
(92)
Among them: Qmax −hour - maximum flow by hour; Qmax −day - maximum flow by day;
n – Coefficient obtained as follows: o When the number of users is more than 3000
n = 14
o When the number of users is 1500 - 3000
n = 12
o When the number of users is less than 1,500
n = 10
NOTES: When the drainage network is built in the land without underground water, water discharge standard should be equal 70-80 % corresponding water supply standard for each object. 9.11 Wastewater disinfection is prescribed in the Section 8 of this Standard. For the sewage of hospitals or other works containing many pathogenic microbes, it is necessary to have complete sterilization equipment. For domestic wastewater, depending on the amount of wastewater and specific conditions, it can be determined appropriately. In case of necessity for sterilization, using quartz high pressure or mercury argon low pressure ultraviolet beam. Energy used to disinfect is between 30-60W.h/m3 low voltage power of 110, 220, or 380 V.
10. The design characteristics of treatment facilities of shared and half separate sewer drainage systems 10.1 The wastewater treatment facilities and methods of shared and half separate drainage systems are the same as those of domestic sewage.
10.2 The concentration of major pollutants in rainwater should be determined on the basis of physical and chemical analysis - or by equivalent calculation. When determining the concentration of pollutants should note the following points: - The average rainfall in all year seasons with monitoring data of many years; - The nature of the top layer of the drainage basin; - Environmental sanitation conditions of the area; - For industrial enterprises, pollutant contamination of rainwater must be supplemented the contaminated level by industrial waste. 10.3 Storm water flow to the treatment facilities of combined and separate half sewer systems is determined based on the dilution factor n in storm water discharge drains built before treatment works or main pumping stations. 10.4 When calculating the separate works of combined and half separate sewer system should note the following characteristics: - Trash racks and sand settling tanks should calculate on the total flow of wastewater and rainwater. - Sand sediment tanks is designed to have the ability to keep sand particles with a diameter equivalent 0.15 to 0.2 mm, the sand volume is taken from 0.03 to 0.04 liters/person/day, humidity 60%. - 1st phase sediment tanks and tanks with two shells are calculated based on the flow in rainy seasons. - The wastewater treatment works by biological methods are calculated based on the flow of wastewater in the dry seasons. In rainy seasons, part of the mixture of wastewater and rainwater is transported directly from 1st phase settling tanks back to the sterilization facilities. - The sewage treatment facilities (sludge compartment of two-shelled settling tanks, methane tanks, sludge drying yards, ... ) are calculated according to the volume of sediment formed in case with the rainwater. For preliminary calculations, the volume of the facilities can be obtained greater than 10-20% compared with calculated values according to the flow in dry seasons. - The pipes, and gutters of water distribution and collection in treatment facilities are calculated based on the total volume and increase in sewage capacity by 20-25%. - When rain water flow brought to the treatment plants with the dilution factor from 1-1.9 should, it is required to build rainwater regulating tank on the basis of comparing the technical and economic criteria.
11. Equipped power, technology control, automation and control
11.1 General Instructions 11.1.1 Reliability of power supply for the power consumption facilities of the drainage system is required to follow the "Rules for locating electrical equipment". Reliability of power supply to water and air pumping station is required to be the same as that of pumps (refer Section 7 of this Standard). 11.1.2 For the machine units with long-term operating cycle (pumps, air blowers) when there is no need to adjust the number of rotating numbers, it should use asynchronous motor, while there is a need to adjust the rotation number so that pumps can work in levels - asynchronous motor with winding rotor will be used. In case of sliding joints –Use asynchronous motor with squirrel cage rotor. 11.1.3 The voltage of motors need to be selected as per power, power supply scheme and prospect to increase the capacity of motor units, the required type of motors should be according to the surroundings and characteristics of the houses of electrical appliances. 11.1.4 For the facilities working in normal environment, power distribution equipment, transformers and control cabinets need to be put in the rooms adjacent to machine room considering the possibility their increased capacity. It is allowed to place power distribution equipment, transformers in separate locations. 11.1.5 The classification of the explosive chamber, as well as types and groups similar to explosive chamber, refer to "Practice for installation of electrical equipment". 11.1.6 Check system of technology should be required as follows: - Vehicles, appliances for checking regularly. - Means for periodic inspection (to calibrate and test the operation of the facility ... ). 11.1.7 An audit of technological parameters on water quality should be checked regularly by measuring instruments, analysis machine and by experimental methods. 11.1.8 The control system of technology process and scale, automation degree of the facilities should be selected according to management conditions, the economic–engineering arguments, as well as taking into account factors of social characteristics before decision-making.
11.2 Automation, regulation and inspection of measuring pump stations 11.2.1 pump stations are designed to work semi-automatically and are managed irregularly by human, so the following control forms are designed:
- Automatic control of pumping unit depends on the wastewater level in the tanks. - Controlling at the distance from the regulation stations. - Control in place - with transmitting necessary signal to regulation stations. 11.2.2 Pump stations are equipped motor units with high-voltage electric motor with regular control by human. Controls need to conduct accumutively from the control panels and should use adjustable driven parts. Electrically adjustable driven parts for adjustments should be equipped for one pumping unit located in groups of 2-3 working units. The control of adjustable drive units needs to be automatic according to the water level in the collection pits. 11.2.3 For automated pumping station, there is need to design automatic opening the emergency unit when the working pump is interrupted by incidents. For pump stations with remote control, opening automatically backup pump units needs to be carried with pumping stations of reliability type 1. 11.2.4 When pumping stations are flooded due to incidents, automatic disconnection should be designed for the main pump unit. 11.2.5 When turn on the pumps, as per regulations, the valves on pressure piping must be open. Opening the pumps when the valves on pressure piping still keep closed must consider the dangers of the phenomenon of water clashes, startup control of synchronous motors and other factors in reality. 11.2.6 In pump stations, it is required to check the following technical parameters: - Water flow requires to pump. - Water level in the reservoirs. - Water levels in the collection pit of water leakage. - Pressure in the thruster pipes. - The pressure in the pipe of each pump is created. - Temperature in the shaft. 11.2.7 The pump station should have incident warning signals on the spot. Without regular operators, there is a need of additional signals to the regulating stations or stations with regular operators. The pump stations should automate the following auxiliaries:
- Washing rotary trash racks under the pre-set programs (controlled by time or according to the water level difference). - Pumping leaking water follows the water level in the collection pits. - Turning on the ventilation fans based on temperature in the room.
11.3 Automation, regulation and inspection, and instrument for treatment works 11.3.1 The automation and test workload is necessary to determine in each particular case depending on the capacity of each facility and economic– technical arguments. 11.3.2 It is required to check flow, temperature, and pH in necessary cases. 11.3.3 In the neutralization tanks, input water flow and pH values or other indicators on technology demand must be checked. 11.3.4 In Aeroten, it is required to adjust input air based on dissolved oxygen in wastewater, to check the mixture flow of
mud, activated sludge, dissolved oxygen, NH4+, NO3-, temperature and pH of
wastewater. 11.3.5 In high load bio-filters, the input water flow and temperature, and circulating water must be checked. In 2nd phase settling tanks, it is required to check the sludge level. 11.3.6 In the methane tanks, it is required to check the temperature, the sludge, input sediment flow, flow and pressure must be checked. 11.3.7 In chlorate, there is need to automate the chlorine flow according to the wastewater flow to be cleaned or as residual chlorine in wastewater, to check chlorine flow, residual chlorine value in wastewater and chlorine gas concentrations in the atmosphere at production chamber. 11.3.8 In the gas supply stations, on-spot control of air blower units (in computer time) and control in the distance should be implemented. For air blower units, it is required to check temperature at the bearing axis, air pressure, and cooling water pressure. For bearing lubrication system, check lubricant temperature and pressure. 11.3.9 Neutralization process for wastewater infected with strong acid and alkali, no salts of heavy metals (or contained but little amount) needs to automate following predetermined pH values. 11.3.10 Neutralization process of wastewater containing strong acids and salts of heavy metals in large amount should automate based on pH of wastewater mixed with conductive properties of the original water.
11.3.11 Management of sewer drainage system should ensure focus and testing the operation of the facilities. 11.3.12 Management of large sewer drainage system with large distance among major facilities, prescribed 2 levels from the central and local regulation stations. Normally just one level from the central station is needed. 11.3.13 Required direct contact between the regulating stations and the works to test, as well as between normally operating stations and workshops. 11.3.14 For the project to be checked, need to transfer data symbols and without station moderation we cannot guarantee the management and inspection of the construction work quickly eliminated and prevention the problem is. 11.3.15 The measurement data and signals need to move about the regulating stations a. Measurement: - Wastewater flow to the treatment works for treatment and discharge into receiving resources; - Wastewater pH; - The amount of dissolved oxygen in wastewater; - Wastewater temperature; - Total air flow for aeroten; - The air temperature into aeroten; - Flow of activated sludge into aeroten; - The amount of surplus activated sludge; - Fresh residue into methane tanks. b. Signal: - To unplug equipment malfunction; - The destruction of technology process; - Limitations sewage and residue in the tanks; - Concentrations limit of explosive vapors in the production chambers; - The concentration limit of chlorine gas in the rooms of chlorate station.
11.3.16 Regulating chamber allows being in blocks with technology works (gas pump stations, management room, testing, and so on. ). The regulating chamber should be soundproof. Regulating chambers comprise the following parts: - Regulating chambers include distribution cabinet, control panel and contact media monitored regularly by people. - Auxiliary facilities (warehouse, repair shop, break room, restroom, ... ) . 11.3.17 Automation of industrial wastewater treatment technology processes and test volume should be selected according to the data of scientific research agency.
12 The requirements for construction and structure solutions 12.1 Construction and Structure 12.1.1 Planning and construction of the facilities of drainage system must be compatible with the general technology requirements, the guidelines in design and planning standards of enterprises and the requirements of Chapter 13, Vietnam Construction Standard TCXDVN 33:2006-Water Supply – Piping Network and Works - Design Standards. 12.1.2 The land for construction of cleaning facilities of the drainage system of the residential areas and industrial enterprises located within industrial land must include protective barriers. Particularly, penetration yards may not need fences. 12.1.3 In the construction area with cleaning facilities, the area without facilities to build, needs planting grass for protection. To improve environmental sanitary conditions in land perimeter and isolated areas, it is allowed to plant timber trees and industrial crops. 12.1.4 Structural design for the works of the drainage system must comply with design standards for production facilities, industrial enterprises, the requirements in Chapter 13 of Vietnam Construction Standard TCXDVN 33:2006 (Water Supply - Piping Network and Works-Design Standards) and the requirements of this standard. 12.1.5 When designing the works of the drainage system should pay attention to fire prevention requirements, particularly for the production wastewater containing combustibles. 12.1.6 The drainage tubes of normal reinforced concrete, or pre-stressed reinforced concrete in centrifugal casting or vibration method. It is permitted by manual molding method with concrete pipes with a diameter < 300mm or far, isolated, or mountainous areas without the transit of precast concrete
pipes at the plants. Reinforced concrete drainage pipe in centrifugal casting or vibration method must have mark of 300 or above. 12.1.7 When calculating the structure and foundation for the water distribution systems, and storm water and wastewater treatment facilities, it is required to minimize uneven subsidence phenomenon. For storm water and wastewater treatment facilities, circular culverts, box-shaped culverts including ancillary works on-line (collection pits, manholes, pump stations, separation wells, outlet, etc.), even settlement is allowed to be maximum 8 cm. 12.1.8 The production facilities of different units, will possibly integrated into a single works collectively to meet the technological requirements, sanitation and fire prevention requirements, reasonable in the perspectives of planning, and economic technical facts. 12.1.9 Plastering and paving inside the buildings of manufacturing, administrative, management, laboratory and other rooms of the buildings of drainage system will be taken from Table 10-1, and the building for collective activities follow the requirements of the design standard of accessories building and buildings of industrial enterprises. 12.1.10 Calculating the structure of buildings and works of the drainage system must comply with the regulations, procedures and regulations on the used material, the impact load, bearing properties of works, time use, building location, the climate, and the temperature issued by the State. 12.1.11 Design for erosion control for construction structure of the sewage drainage buildings works should comply with the standards specified in the design of against erosion-proof for buildings and works. Table 55 Type of rooms and buildings
Works content: walls
ceiling
foundation
1. Building or rooms to Cement plastering, coloring place trash rack.
Cement plastering
Paving glazed tiles or mortar finishing
2.Chemicals rooms with Cement plastering, coloring, normal moisture painting
Cement plastering
Paving tiles
glazed
3.Chemicals rooms with Cement plastering, coloring, high humidity, uncovered painting water storage tank
Cement plastering
Paving tiles
glazed
4. Warehouse chemicals
Cement plastering
Paving tiles
Facilities with production nature
of
dry Compo mortar plastering with white lime
5. Bio-filters
Cement plastering, coloring
Cement plastering, coloring
6. Chamber control of methane tanks
Cement plastering
-Distribution compartments
Cement plastering for walls, coloring
-Pumping stations
Cement plastering for walls
Cement plastering
mortar finishing, coloring
7.Clorato
Cement plastering for walls 1m high above the floor, the upper with glass water or color painting
-As above
Acid-proof glazed tile paving or acid-proof mortar finishing
8.Chloride
Cement plastering for walls, carefully at the connection corners between walls and floor, walls with ceiling
Mortar As above plastering, brushing with white lime
9.Ải pumping station
mortar finishing, coloring
Compo mortar Glazed plastering,
tile
paving
brushing with white lime -Machinery room -Subsidiary
room
(or Compo
mortar
plastering,
mortar finishing
management room)
white lime coating
10. Filtration tank
Mortar plastering for walls,
Mortar finishing
coloring
for
floor,
coloring 11.Pumping stations
Brick
laying
-Machinery room
plastering
for
and
mortar
the
above
mortar finishing
surface, mortar on the ground, mortar plastering for the face, bitumen for inside, mortar plastering -Subsidiary storage tanks
room
on Mortar plastering for walls, the submerged parts with concrete, mortar plastering and coloring
12.2 Ventilation
Cement plastering
12.2.1 Design of ventilation for houses and buildings of the drainage system must comply with the provisions of this standard, taking into account the requirements of the design standards of auxiliary houses and buildings of industrial enterprises. 12.2.2 In the buildings or rooms to place trash racks, air ventilation is required to push up to 80% ventilation air from closed channels and 20% from the upper parts of rooms and the trash collection places of trash grinding plants. 12.2.3 In wastewater pump stations, separate wind drain pipe is required for turbine rooms and tank rooms are allowed to arrange combined discharge device in case of one-way valves on wind pipes, tank rooms and trash racks. Air exchange must be ensured continuously so that the air can avoid from being contaminated over permissible limits. 12.2.4 In machine room and storage tanks of sewage pumping stations, when there is toxic air leakage, in addition to ventilation systems in the mode of regularly working, it should be included the devices to transmit signals to the center, to control measurement of poisonous gas level, and emergency ventilation systems. 12.2.5 In the tunnels with drainage systems arranged, there must have natural ventilation system, and mechanical ventilation systems before workers go down into the tunnels. When the wastewater contains toxic substances, explosive or is exothermic, it is required to include mechanical ventilation. The number of air changes is determined by calculation. Control equipment of mechanical ventilation system are arranged at the doors of tunnels.
13 Some additional requirements for construction drainage system in the special areas 13.1 The area of settlement land 13.1.1 Design construction sewer system in settlement lands must comply with the design standards of house and building foundations. When designing the works with pipelines, the ground must be treated appropriate to ensure stability and durability. 13.1.2 The distances between buildings, works and piping will be taken from the requirements of Chapter 14 of the standard design of water supply. 13.1.3 Pipes going through the wall or bridge foundation are placed exposed or put behind cage pipes. The size of holes or caged pipe must be larger than squeezed pipes. Use elastic material for caulking cracks.
13.1.4 Sludge drying yard must set lower than other treatment facilities. It is not allowed to discharge penetrated water of mud drying yards into the land of construction area.
13.2 Earthquake zone 13.2.1 When designing drainage systems for industrial factories and urban areas locating in the zone of earthquakes, preventive measures must be required to avoid wastewater from flooding the construction area, polluting underground water and surface water sources due to the destruction of pipeline cleaning facilities. On the drainage network, the emergency discharge gates should be arranged. 13.2.2 Bio-lakes or penetrating yards should be applied to clean waste water. 13.2.3 The pumping stations of the project are located in the earthquake zone level 7, and level 8, the connecting location of pipes to pump stations, the project must resolve with flexible connection to avoid broken pipes. 13.2.4 For self-running networks in the earthquake zone level 7-8, it is designed to use reinforced concrete pipe, not allowed to use concrete pipe without reinforcement. 13.2.5 For pressure pipelines in earthquake zones of level 6 or higher, design should be applied as follows: - For reinforced concrete pipe, take the pipes number of one level higher than that of the areas without earthquake. - Cast iron pipe with working pressure up to 60 N/cm2, while steel pipe with working pressure of 90 N/cm2 or higher. 13.2.6 Flexible connection for reinforced concrete pipe, cast iron pipe with or without pressure-bearing in an earthquake zone . 13.2.7 Design of drainage houses and works in seismic regions should follow building design standard for the seismic areas and the requirements stated in the standard TCXDVN 33:2006 - Water Supply -Pipeline networks and structures - Design Standards.
Appendix A (Regulations) Sanitary conditions during discharge of wastewater into surface water sources A.1 General Provisions A.1.1 The levels to require treatment of urban wastewater before discharge into surface water sources must be based on the following conditions: - The volume and composition of pollutants and waste water regime. - Flow, water quality, self-cleaning ability and hydrological regime of rivers and lakes. - Status and use of water resources in design time and in the future. A.1.2 Wastewater discharged into surface water sources must take into account the self-cleaning ability of the resources and meet the two following conditions: a. Prerequisites: Waste water must be not polluted, reducing water quality in the downstream of discharge point. At the nearest water taking point of the downstream, the concentration of pollutants in the mixture of source water and wastewater shall not exceed the permissible limit values specified in the environment standard TCVN 5942-1995 for all kinds of water sources under various purposes (Table A.1). Table A.1 – The table on concentration limit of the substances in the mixture flow of urban waste water and river and lake water
in the cross section for calculations of discharge sewer
downstream. Indicators
Source Type 1
Source Type 2
pH
6 to 8.5
5.5 to 9
Allowed concentration of suspended solids not exceeding, mg/l
1.0
2.0
BOD5, not bigger, mg/l
4
25
COD, not bigger, mg/l
10
35
Dissolved Oxygen, not less than, mg/l
6
2 or 6 *
N - NH4, not bigger, mg/l
0.05
1
Coli form, no larger than MPN/100 ml
5000
10000
NOTES:
Source Class 1- rivers, lakes and other surface waters used as raw water supply for urban water supply systems, residential or industrial zones. Source Type 2 - rivers, lakes and surface waters used for other purposes. b. Full conditions: When discharging into the surface water, wastewater is not allowed to contaminate the water at the downstream discharge sewer. The concentration of pollutants in wastewater CXA (mg/l) must be lower than the permitted limit values specified for discharge into the surface water in the standard ISO 5945:2005 industrial waste – discharge standards taking into account the coefficient of flow/capacity of the receiving wastewater Kq and the flow coefficient Kf wastewater comply with the Decision No. 22/2006/QĐ-BTNMT dated 18/12/2006 issued by the Ministry of Natural Resources and Environment, according to the following formula. Cdrain ≤ Ccp = Cb xK q xK f
(A1)
Among them: Ccp - Concentration limits for pollutants allowedly discharged into the surface water (mg/l);
Cb - Allowed maximum concentration to discharge pollutants into surface water in accordance with the
standard ISO 5945:2005 (mg/l), shall be determined in accordance with Table A.2; K q - Flow/capacity factor of the receiving water, shall be determined according to Table A.3 for river
water and Table A.4 for lake water; kf -Coefficient of sewage discharged into the sources, shall be determined in accordance with Table A.5. Table A.2 - Permissible limit concentrations of some pollutants in wastewater when being discharged into the surface water area vary according to TCVN 5945:2005 - Industrial waste water Discharge standards Source Indicator Source
Type 1
Type 2
pH
6-9
5.5 - 9
Concentrations of suspended solids, mg/l
50
100
BOD5, mg/l
30
50
COD, mg/l
50
80
N - NH4, mg/l
5
10
Total nitrogen, mg/l
15
30
Total phosphorus
4
6
Coliform, MPN/100 ml
3000
5000
Table A.3 - Kq coefficient value corresponding to the flow rate of receiving rivers 3 -month average flow of the dry season of river flow QS (m3/s)
Kq value
QS ≤ 50 m3/s
0.9
50 m3/s < QS ≤ 200 m3/s
1
QS > 200 m3/s
1.1
NOTES: In case of canals, small streams without flow data, take Kq at 0.9. Table A.4 - The value of the coefficient Kq with capacity corresponding to receiving waste water reservoirs 3 -month average volume of the dry season of the lake V ( 106m3 )
value Kq
V ≤ 10 . 106m3
0.9
10 . 106m3 < V ≤ 100 . 106m3
1
V > 100 . 106m3
1.1
NOTES: Where the receiving water of waste water is the coastal area, take Kq at 1.2. Coastal sea for the purpose of protecting aquatic being, or underwater sports and recreation, take Kq at 1.0 Table A.5 . Coefficient Kf with an average flow of wastewater Wastewater flow Q (m3/d)
Kf value
Q ≤ 50m3/d
1.2
50 m3/d < Q ≤ 500 m3/d
1.1
500 m3/d < Q ≤ 5000 m3/d
1.0
Q > 5000 m3/d
0.9
A.1.3 At the discharge of wastewater containing toxic substances into rivers, lake levels, the permissible limits of the particular substances are calculated by the following formula: m
Ci
∑C i =1
i , cp
≤1 ( A2 )
Among them: o Ci - concentration of pollutants calculated I in wastewater; o Ci ,cp - permissible limit concentrations of pollutants i in wastewater permitted to discharge into stipulated sources; o m- The number of pollution element in wastewater. A.1.4 For domestic wastewater of service establishments, public establishments, apartments ... in the areas with no drainage system and shared sewage treatment, concentration limits of pollutants in wastewater allowed to be discharged into the external environment may be identified as prescribed in the standard ISO 6772:2000 Water Quality -Wastewater – Allowed pollution limit. This standard is not used for industrial wastewater as prescribed by ISO 5945:2005. A.1.5 For hospital wastewater, concentration limits of pollutants in wastewater allowed to be discharged into the environment may be identified as prescribed in ISO 7382-2004:Water Quality - Hospital Wastewater - Discharge standards. A.1.6 The discharge points must be located in the downstream of the flow from residential areas as well as the lower positions of water input points serving the residential areas in consideration of the possibility of backflow during tides, cumulative wind or flow changes due to the operation of the hydroelectric projects. Points of calculation in sewage receiving rivers, and lakes must be 500 to 1000 m far from the upstream of water use points (water points, collecting gates of water supply facilities, beaches, hotel, feeding fish etc. .. ) nearest to the river flow or 2 side from the water use points in the region of static water. A.1.7 The self-cleaning process of wastewater in rivers and lakes is calculated in the following conditions: a. Wastewater flow discharged into rivers and lakes is average flow. b. The hydrological conditions of rivers and lakes include as follows: - For reregulating flow, it is the smallest monthly average flow per year with the 95% guarantee (according to data provided hydrological agencies). - For regulating flow, the lower dam, removing the possibility of backflow from downstream. - For static reservoir, it is determined in the most unfavorable mode, by a tabulation to calculate the effects of wind on discharge gates, and other natural conditions.
A.2 ISO 6772:2000 -Water Quality - Domestic Wastewater Standards A.2.1 Scope of application Standards applicable to all kinds of domestic wastewater from service facilities, public facilities and condominiums during being discharged into the specified waters where there are no regulations wastewater collection and treatment. A.2.2 Allowed pollution limit Table A.6 - Environmental parameters and permissible limits No
Parameters
Limit Value Level I
Level II
Level III
Level IV
Level V
1
pH
5-9
5-9
5-9
5-9
5-9
2
BOD, mg/l
20
30
40
50
200
3
Suspended solids, mg/l
50
50
60
100
100
4
Settling Solids, mg/l
0.5
0.5
0.5
0.5
KQD
5
Total dissolved solids, mg/l
500
500
500
500
KQD
6
Sun sulfur (as H2S), mg/l
1.0
1.0
3.0
4.0
KQD
7
nitrate (NO3-), mg/l
30
30
40
50
KQD
8
Grease (food), mg/l
20
20
20
20
100
9
phosphate (PO43-), mg/l
6
6
10
10
KQD
10
Coliform, MPN/100ml
1,000
1,000
5,000
5,000
10,000
NOTES: KQD - Not specified value. Levels I, II , III , IV and V: type and scale of service facilities as follows: Table A.7 - The application rate for the service facilities, public facilities and apartment Type 1.Hotels
2.Rented
houses,
Scale
Level application in Table 1
Less than 60 rooms
Level III
From 60 to 200 rooms
Level II
More than 200 rooms
Level I
guest From 10 to 50 rooms
Level IV
Notes
houses
3. Smaller hospitals, clinics
From 50 to 250 rooms
Level III
More than 250 rooms
Level II
from 10 to 30 beds
Level II
More than 30 beds
Level I
4 . General hospital
level I
5.Headquarters administrative agencies, representative offices,…
Type 6. Schools, institutes, or facilities 7.Department supermarkets
Wastewater disinfection required
From 5000 to 10.000m2
Level III
From 10,000 to 50.000m2
level II
Over 50,000 m2
level I
Scale
Level application in Notes Table 1
research from 5.000 to 25.000m2 similar Over 25,000 m2
Level II Level I
stores, From 5,000 to 25,000 m2
Level II
Over 25,000 m2
Level I
From 500 to 1,000 m2
Level IV
From 1,000 to 1,500 m2
Level III
From 1,500 to 25,000 m2
Level II
Over 25,000 m2
Level I
8. Market of fresh food
9.Restaurants, public Under 100 m2 canteens, food shops From 100 to 250 m2
10.Apartment area
Calculated area is working area
level V level IV
Food From 250 to 500 m2
level III
From 500 to 2,500 m2
Level II
Over 2,500 m2
Level I
Under 100 apartments
Level III
From 100 to 500 apartments
Level II
More than 500 apartments
Level I
NOTE: For parameters not to be included in this Appendix, their permitted limit concentrations are determined according to the standard TCVN 5945:2005. A.3 TCVN 7382-2004 : Water Quality - Wastewater hospital - Emission standards No
Parameter
Unit
Limit Value
Method of determining
1
pH
Level I
Level II
6.5 to 8.5
6.5 to 8.5
TCVN 6492 : 1999 (ISO 10523:1994 )
2
Suspended solids
mg / l
50
100
TCVN 6625 : 2000 (ISO 11923: 1997)
3
BOD5 ( 20oC )
mg / l
20
30
TCVN 6001 : 1995 (ISO 5815 : 1989)
4
sulfur ( S2-, by H2S )
mg / l
1.0
1.0
TCVN 4567 : 1988 or SMEWW 4500 - S2 -
5
6
ammonium (NH4+, based on mg/ l N)
10
Nitrate ( NO3-, in N )
30
mg/ l
10
TCVN 5988 : 1995 (ISO 5664 : 1984)
30
TCVN 6180 : 1996 (ISO 7890-3: 1988 ( E ) )
7
Oil and fats
mg / l
5
10
SMEWW 5520 - B
8
Orthophosphate ( PO43 - , in
mg / l
4
6
ISO 6494-2 : 2000
PO43-) 9
Total coliforms
(ISO 10304-2: 1995) MPN/100ml
1000
5000
ISO 6187-1 : 1996 (ISO 9308-1: 1990 ( E ) ) or ISO 6187-2:1996 (ISO 9308-2:1990 ( E ) )
10
11
Intestinal pathogenic bacteria
SMEWW 9260 B
Salmonella
KPHD
KPHD
SMEWW 9260 E
Shigella
KPHD
KPHD
SMEWW 9260 H
Vibrio cholera
KPHD
KPHD
Total activity of radioactive
Bq / l
0.1
0.1
TCVN 6053: 1995 (ISO 9696 : 1992)
12
Total radioactivity õ
Bq / l
1.0
1.0
TCVN 6219: 1995 (ISO 9697 : 1992)
KPHD - not found Level I: Hospital wastewater into waters with different purposes. Level II : Hospital wastewater into designated places, the City sewer system.
APPENDIX B (REFERENCE) Climatic constant of rain intensity formula The rain intensity formula is as follows:
q=
A(1 + C lg P ) (t + b) n
B1)
In which: q: rain intensity (l/s.ha); P: Repeated cycle of rain (year); T: Rain period (minutes); A,C,b,n: Climatic constant depending on rain conditions of the locality. Table B.1- Climatic constants in the rain intensity formula of some cities No.
Name of city
A
C
b
n
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.
Bao Loc Bac Can Bac Giang Bac Quang Ba Xuyen Buon Me Thuot Ca Mau Cua Tung Do Luong Da Nang Ha Giang Ha Nam Ha Noi Hai Duong Hai Phong Ha Chi Minh Hon Gai Hung Yen Hoa Binh Hue Lao Cai Lai Chau Lien Khuong Mong Cai Nam Dinh Nha Trang
11100 8150 7650 8860 9430 8920 9210 2340 3540 2170 4640 4850 5890 4260 5950 11650 4720 760 5500 1610 6210 4200 9230 4860 4320 1810
0,58 0,53 0,55 0,57 0,55 0,58 0,48 0,49 0,55 0,52 0,42 0,51 0,65 0,42 0,55 0,58 0,42 0,59 0,45 0,55 0,58 0,5 0,52 0,46 0,55 0,55
30 27 28 29 30 28 25 14 19 10 22 11 20 18 21 32 20 20 19 12 22 16 29 20 19 12
0,95 0,87 0,85 0,8 0,95 0,93 0,92 0,62 0,7 0,65 0,79 0,8 0,84 0,78 0,82 0,95 0,78 0,83 0,82 0,55 0,84 0,8 0,92 0,79 0,79 0,65
27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48.
Ninh Binh Phan Thiet Play Cu Quang Ngai Quang Tri Quy Nhon Son La Son Tay Sa Pa Tay Hieu Tam Dao Thai Binh Thai Nguyen Thanh Hoa Tra Vinh Tuy Hoa Tuyen Quang Van Ly Vinh Viet Tri Vinh Yen Yen Bai
4930 7070 8820 2590 2230 2610 4120 5210 1720 3360 5460 5220 7710 3640 9150 2820 8670 4560 3430 5830 5670 7500
0,48 0,55 0,49 0,58 0,48 0,55 0,42 0,62 0,5 0,54 0,55 0,45 0,52 0,53 0,53 0,48 0,55 0,52 0,55 0,55 0,53 0,54
19 25 29 16 15 14 20 19 10 19 20 19 28 19 28 15 30 21 20 18 21 29
0,8 0,92 0,92 0,67 0,62 0,68 0,8 0,82 0,56 0,69 0,81 0,81 0,85 0,72 0,97 0,72 0,87 0,79 0,69 0,85 0,8 0,85
Table B.2- Coefficient of heavy rain distribution n
Basin area (ha)
300
500
1000
2000
3000
4000
Coefficient of heavy rain 0.96 distribution
0.94
0.91
0.87
0.83
0.8
APPENDIX C (REGULATIONS) The distance from drainage piping to the technical network and facilities Table C-1- the distance from drainage piping to technical network and facilities Name of facility
Horizontal distance (m)
1 - To the foundations of buildings and facilities, over passing bridge, and tunnels
3
2 - To the barrier for traffic poles, telephone poles
3
3 – To the last rail shaft of railway
4
Distance Notes calculated based on the outer edge of pipes and cable (m)
(but not less than the height of the filled foundation) 4 - Electric train lines
2.8
5 - To street curb
1.5
6 - To the outside of the drainage ditch or embankment foot
1
7 – To the power pole foundation: -1KV and lighting bulbs
1
-1-25KV
2
-110KV and higher
3
8-Water supply pipe with diameter <200
1.5 0. 1
The value in numerator is horizontal distance
=200
3 0. 1
The value in denominator is vertical distance
>200
3 0. 1
9-Domestic sewage ditches
0.4 0
10-Low underground level and sewage drainage culverts
0.4 0
11-Stron power cable-lower than 35KV
0. 5 0
12-Strong power cable 35KV-110KV
1 0. 1
13-Information cable
0. 5 0. 1
Appendix D (for reference) The auxiliary works of wastewater treatment plants D.1 Depending on the capacity and the specific conditions of each position on the treatment plants, the auxiliary works should be built. The area of the auxiliary works can be obtained according to the following Table D.1. Table D.1 - Area of ancillary facilities of the wastewater treatment plants Name of project
Smallest area ( m2 ) dependent power stations Under
25,000-
Over 100.000
25.000m3/d
100.000m3/d
m3/d
Physical and chemical laboratory
15
25
40
Microbiological Laboratory
12
20
30
8
12
20
20
25
40
Regularly standing room
15
15
20
Head of station room
20
20
20
Repair workshop
20
25
40
Standing Room
12
12
15
Storage of materials
25
30
40
Storage
of
chemicals
and
laboratory equipment Office for administrative staff technicians
NOTES: The area of a bath, toilet complies with the standards prescribed in industrial design. D.2 Arrange the auxiliary works on the principle of user convenience, non-interrelation, repair shop, warehouse of material, depending on the conditions can be arranged with production areas (pump stations, gas pump stations). D.3 The width of walkway in the he treatment plant may be taken: - Hiking walkway - 1.5 to 2.0 m - Car roads - 3.0 to 4.0 m
Appendix E ( for reference) Bio-filter layout E.1 Depending on the composition and nature of wastewater and the specific conditions of each locality, bio-filters is applied to build a complete treatment works or is a wastewater treatment works after having been settled preliminarily. E.2 Bio-filters system may include a type or a few types of lakes (anaerobic, arbitrary, aerobic steps 1, aerobic with thorough treatment) working in sequence. Depending on flow, component, and nature of wastewater and conditions of each locality can select one of bio-filer network diagrams as follows:
NOTES: F- arbitrary lake; K-anaerobic lake; H-aerobic lake; H1 - aerobic lake level 1; Aerobic lake level 2- square lake; L-sedimentation lake; La-BOD of untreated wastewater; Lt-BOD of the treated wastewater in the lake system.
