solutions for the end semester examination paper of sewerage and sewage treatment plant - 2014.
sewage treatment plantFull description
jtlkrejfldfjladskffFull description
sewage treatment plant (STP)
STP
Domestic waste water treatment plant (sewage) template for easy plant design.
PLANTA DE TRATAMIENTO DE AGUAS RESIDUALES Peco Facet
codeFull description
sewage treatment plant (STP)
8005Full description
A study on domestic waste water characterization has been performed followed by the design of sewage treatment plant. The present study involves the analysis of pH value, total solids, total suspended solids, hardness, acidity, alkalinity, chloride,
Sewerage Design
Al Ansab MBR Sewage Plant
A study on domestic waste water characterization has been performed followed by the design of sewage treatment plant. The present study involves the analysis of pH value, total solids, total suspended solids, hardness, acidity, alkalinity, chloride,
reservoirFull description
reservoirDescripción completa
Full description
Full description
adsa
Fluid mechanics
Tutorial-1 Theoretical, Chemical and Biochemical Oxygen Demand 1. Wastewater generated from a glucose manufacturing factory is having 275 mg/L of glucose as organic contamination. Find the theoretical oxygen demand of the wastewater? 2. Mixed liquor from the aeration tank of an activated sludge treatment process has 1700 mg/L microbial biomass concentration. If empirical formula of the microbial biomass is C60H87O23N12P find the theoretical oxygen demand of the mixed liquor? Assume nitrogen transforms into ammonical nitrogen and phosphorus demands no oxygen. a b 3c a 3c C n H a Ob N c + n + − − O2 → nCO2 + − H 2 O + cNH 3 4 2 4 2 2
3. Effluent from a stabilization pond system is having 40 mg/L of algal cells. Express the algal cell concentration in terms of theoretical oxygen demand? Take C106 H 180O45 N16 P as the empirical formula for the algal biomass? Assume nitrogen transforms into ammonical nitrogen and phosphorus demands no oxygen. 4. Find Nm3 of methane produced from the anaerobic stabilization of 1 kg of bacterial biomass (C60H87O23N12P)? Assume 15% of the bacterial biomass will be left behind as cell debris and 17% of the biomass utilized is used up in the anaerobic bio-oxidation process including biomass synthesis. If CO2 level is 35% find the Nm3 of biogas generated? Equation of methane production from organic matter is a b 3d n a b 3d n a b 3d Cn H a Ob N d + n − − + H 2O → + − − CH 4 + − + + CO2 + dNH 3 4 2 4 2 8 4 8 2 8 4 8
5. A wastewater treatment plant is treating 250 m3/hour flow of wastewater. The wastewater is having 300 mg/L of BOD5 at 20°C, and the treatment is resulting in 85% removal of the BOD. Each kg of BOD removed is producing 0.64 kg of secondary sludge. Consistency of the sludge is 1% and empirical formula of the sludge is C60H87O23N12P. The secondary sludge is believed to have 15% nonbiodegradable organic matter. The sludge is stabilized in an anaerobic sludge digester. 17% of the biodegradable sludge is not contributing to the biogas production. Methane content of the biogas generated is 65%. Find the daily volume and quantity of sludge generated? Find the biogas generation rate of the sludge digester?
Tutorial -2 (BOD and BOD kinetics) 6. A wastewater sample has been tested to have 107 mg/L of 5 day BOD and 135 mg/L of 8 day BOD at 20°C. Find out the BOD kinetics parameters for the sample? Also find out 3 day BOD of the sample at 27°C? 7. A industrial wastewater sample was tested for 5 day BOD at 20°C after diluting by 45 times. A blank was also run but with 7 times the seed added. Results obtained from the testing are as given below: Sample Blank Initial 8 8.2 Final 1.4 6.5 Using these results find out the sample’s BOD5 at 20°C? 8.
A serial BOD test conducted on a sample for 6 days gave the following results: Time (days) 1 2 3 4 5 6
BODt 40 70 88 110 119 123
Using the results of the serial BOD find out the BOD kinetics parameters by each of the following methods: • • • • • • •
Method of least squares Method of moments Log difference method Fugimoto method Daily difference method Rapid ratio method Thomas method
Method of Least squares
Method of moments
Thomas Method
Method of Moments for BOD kinetic parameters
Tutorial-3 (Bar Screens) 1. What is peaking factor? If the present peaking factor and the design peaking factor are 3.0 and 2.8 respectively, and if the present average flow and the design average flows are 1000 m3/day and 1500 m3/day respectively, find the present peak flow and the design peak flow? 2. Find width and slope of a rectangular channel carrying 1000 m3/hour flow at 0.4 m/sec. velocity? Find what will be the flow velocity and depth of flow when the flow rates are 300 m3/hour and 3000 m3/hour respectively? 3. Design a bar screen for the design peak flow of 125 m3/hour while assuming the following: a. Thickness and depth of bars: 6 mm and 50 mm respectively b. Inclination angle of the screen: 65° from the horizontal c. Spacing between bars: 12 mm d. Flow velocity in the approach channel: 0.6 m/sec e. Average flow: 40 m3/hour Find the flow velocity in the approach channel for average flow conditions (assume average flow as 40 m3/hour)? Find the flow rate through the screen when the flow velocity in the approach channel is 0.4 m/sec.? Find flow velocity through the screen and head loss across the screen under the clean screen and the clogged screen conditions while assuming discharge coefficient as 0.7 for clean screen and 0.6 for clogged screen? Indicate the drop you will provide at the bar screen?
Tutorial-4 (Flow and/or Strength Equalization) Sewage from a township is showing the following flow and BOD5 at 20°C over 24 hours of a day: Time of the day 01-00 hr 02-00 hr 03-00 hr 04-00 hr 05-00 hr 06-00 hr 07-00 hr 08-00 hr 09-00 hr 10-00 hr 11-00 hr 12-00 hr 13-00 hr 14-00 hr 15-00 hr 16-00 hr 17-00 hr 18-00 hr 19-00 hr 20-00 hr 21-00 hr 22-00 hr 23-00 hr 24-00 hr
Find the theoretical flow equalization volume? by the method of net cumulative flow by the method of cumulative inflow and cumulative outflow Find hourly BOD loads, and, when the residual volume of the equalization tank is 20% of the theoretical equalization volume, find the hourly BOD loads in the equalized flow? If the same size equalization tank is used for only the strength equalization (but not for the flow equalization), find the hourly BOD loads in the outflow from the equalization tank?
Tutorial-5-Grit chambers 1. Find terminal settling velocity of two particles, one of 0.21 mm size and the other of 1.00 mm size, for 2.65 and 1.05 specific gravities? Take kinematic viscosity as 1.003x10-6 m2/sec. (dynamic viscosity corresponding to this is 1.003x10-3 N-s/m2). What will be the terminal settling velocities of the particles when laminar flow conditions and turbulent flow conditions are assumed? 2. River water with grit is being treated in a grit channel designed for 100% removal of grit particles of size 0.21 mm. If size distribution of the grit in the water is as given below, find out overall grit removal efficiency? Size (mm)
<0.04
0.04 to <0.08
0.08 to <0.12
0.12 to <0.16
0.16 to 0.21
>0.21
percentage
5%
9%
16%
20%
30%
20%
3. Design a horizontal flow grit channel (for the removal of 0.15 mm size grit particles of 2.60 specific gravity) for the handling of 400 m3/hour average flow and 100 m3/hr peak flow? Design proportional weir at the control section? Find head loss occurring across the grit channel? Assume depth of flow as half the width of the channel under average flow conditions. Take desired horizontal flow velocity as 0.3 m/sec. for average flow and 0.4 m/sec. for peak flow. Take head loss at the control section as 30-40% of the depth of the flow.
Stoke’s Law and terminal settling velocity of particle Net force of the particle (ma) makes the particle to accelerate When drag force becomes equal to the net of gravity force and buoyant force, acceleration of the particle becomes zero and the particle settles at constant
velocity (terminal settling velocity)
Where
Where
For laminar flow
For turbulent flow ν is 1.003 x 10-6
Cd value is 0.6 to 0.65 b is taken as ‘channel width – 150 mm’!
Proportional weir (Sutro weir)
Tutorial-6 (primary sedimentation tank) Sewage with 210 mg/L BOD5 at 20C A and 300 mg/L TSS is clarified in a primary sedimentation tank. the sewage flow rate is 425 m3/hr and the primary sedimentation tank is designed for 65% TSS removal. Clarified sewage from the primary sedimentation tank is reported to have 135 mg/L of BOD5 at 20C. Estimate the primary sludge generation rate (both as kg/day and as m3/day)? Assume 4% consistency for the primary sludge. Estimate the biodegradable fraction in the primary sludge generated? Take BOD reaction rate constant as 0.2/day for the raw sewage, and as 0.18/day for the clarified sewage. If the primary sludge is stabilized in an anaerobic sludge digester and 85% of the biodegradable sludge is lost in the stabilization process, estimate the biogas generation rate of the anaerobic digester (in Nm3/day)? The stabilization process leading to biogas generation is shown by the following expression:
a b 3d n a b 3d n a b 3d Cn H a Ob N d + n − − + H 2O → + − − CH 4 + − + + CO2 + dNH 3 4 2 4 2 8 4 8 2 8 4 8
Tutorial -7 (Anaerobic Pond) An anaerobic pond has been planned for the treatment of sewage from a municipal town. Sewage generation rate of the town is 125 m3/hour and composition of the wastewater is as given below: S.N o. 1 2. 3. 4. 5. 6. 7.
1. Design the anaerobic pond and find the dimensions of the pond (top, bottom, mid water level and water surface level dimensions)? Take side slope of the pond as 1 in 1.5. Take average ambient air temperature for the coldest month as 17C.
2. Find the BOD, Coliform count, and TKN content of the treated effluent of the anaerobic pond? Assume TSS in the treated effluent as 60 mg/L.
3. Design the inlet and outlet for the pond? Assume depth of flow over the overflow weir of the out should be < 40 mm. Assume flow velocity in the inlet should be <0.2 m/sec.
4. Estimate biogas generation rate of the anaerobic pond?
5. Estimate the sludge accumulation rate and find the frequency of cleaning required? Assume bottom sludge consistency as 9%.
Temp. T ( oC)
Volumetric Loading (g/m3 d)
BOD removal (%)
<10
100
40
10-20
20T – 100
2T + 20
20-25
10T + 100
2T + 20
>25
350
70
θ is HRT of anaerobic pond
q is weir loading rate in L/m.sec. h is depth of flow in mm
Tutorial -8 (UASB Reactor, UASB pond and Anaerobic Baffled Reactor) Sewage generation rate of the town is 125 m3/hour and composition of the wastewater is as given below: S.N o. 1 2. 3. 4. 5. 6. 7.
1. Design a UASB reactor? Assume the following for the design: Area of influence of a distribution tube: 3 m2 Upflow velocity in the reactor: 0.7 m/hr. Reactor width: 7 m Depth of the reactor portion: 3.5 m 2. If BOD removal efficiency is 70%, find the sludge accumulation rate? Assume TSS in the treated effluent as 20 mg/L. If every time of desludging involves removal of 25% of the sludge accumulated in the reactor find the frequency is desludging required? Maximum depth of the sludge allowed in the reactor is 1/3rd of the reactor depth. Assume sludge concentration in the sludge blanket and sludge bed are 20,000 mg/L and 60,000 mg/L. assume active biosolids in the sludge blanket and the rest in the sludge bed. Also estimate relative quantities of the sludge bed and sludge blanket to be wasted every time.
3. Estimate biogas generation rate?
4. Design a UASB Pond for the wastewater to be treated? Assume TSS in the treated effluent as 30 mg/L. Provide for one day storage of the biogas.
5. Design an Anaerobic Baffled Reactor? Take depth reactor as 4 m and area of influence of a distribution pipe is 16 m2. Assume TSS in the effluent as 40 mg/L and 15 mg/L for the first and second chambers of the reactor. Provide for one day storage of the biogas generated. Find the frequency of desludging for the first chamber and the second chamber of the reactor.
