Name
: Ng Peng Sang
Student ID
: 003754
Title Subject
: Lab Report : Chemical Engineering Lab.
(H83CEL) Date Supervisor Due date
: 21st December 2009 : Dr. Dominic Foo : 21st December 2009
1
CONTENTS Title page
1
Contents
2
Summary
3
Introduction
4
Literature Review
5-10
Experimental
11-13
Results
14-18
Discussions
19-21
Conclusion
22
Nomenclature
22
References
23
Appendix
24-27
2
SUMMARY Filtration is a widely used unit operation of Chemical Engineering Process which utilizes the separation of solid and liquid. It uses the theory of solid and liquid separation by flowing liquid with solid suspension through porous mediums or screens which retain the solid suspensions and liquid flows out as filtrate. It is generally used in various industry, such as wastewater treatment industry, food and beverages industry, pharmaceutical industry and chemical industry. Plate and frame filter press is one of the most used filtering machines around due to its simplicity in usage and efficiency it produced. Few considerations has to be decided in order to operate this machine. Firstly, is the selection of filter mediums where a filter medium must have pores smaller than the size of solid suspension in liquid flow or else filtration would not be occurring as the pores would not be able to filter solid suspension. Cake compressibility, on whether it produce compressible cake or incompressible cake, is any factor that needs to be considered to operate this machine. Next, filter aids is important as well as it is applied to solve problems arising from slow filtration rate, unsatisfactory filtrate clarity or rapid medium binding. An experiment has been conducted using a small scale filter press with only the selection of filter paper available. Newspaper sludge is chosen as the feed for this experiment as it can be used to represent pulp and paper industry. It is blended together with water before experiment starts. It is found in this experiment that concentration of mixture affects volumetric flux, as increased concentration of mixture will give a reduction in volumetric flux. In addition, increased in concentration of mixture will give a rise in the pressure of the filter pump. The percentage reduction of solid in mixture and the efficiency is found to be reducing as the concentration of mixture is increased. There are difficulties in this experiment whereby viscosity is unable to be measured and parallax errors are involved when readings are taken. Inadequate equipment in laboratory leads to some discrepancies in the graphs.
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INTRODUCT ION Plate and frame filter press is one of the most used filtering machines in the industry and this filter press also has a good reputation in the industry for being the simplest and most efficient machines available in market. It is widely used in industries, namely food and beverage industry, paper and pulp industry, wastewater treatment, pharmaceutical and chemical industries. Prior to the availability of a small scale plate and frame filter press, an experiment is conducted with intentions to achieve few objectives as follow: 1) To determine the relationship between the concentration of mixture and the volumetric flux.
2) To determine the effect of concentration of mixture on pressure of the filter pump.
3) To determine the percentage reduction of solid in mixture and the efficiency of the plate and frame filter press.
Before the experiment is conducted, feed has to selected and prepare beforehand. A variety of choices of feed are available to conduct the experiment for example
4
paper sludge which represents paper and pulp treatment and blended fruits which represents food and beverage industry.
5
LITERATUR E Plate and frame filtration. Filtration is a widely used unit operation of Chemical Engineering Processes which separates solids from fluids. According to Coulson & Richardson Volume 2, “Filtratrion is the separation of solids form a suspension in a liquid by means of a porous medium or screen which retains the solids and allows the liquid to pass in termed filtration”. This means that fluids or slurries are forced through the pores of the medium which causes solid particles larger than the pores of the filter medium to be removed. As time passes, particles deposited will slowly build up over time and this would lead to the formation of layer of solids which is called a filter cake. As a thicker filter cake is formed, flow resistance increases and this causes pressure to increase which greatly affects the rate of filtration. It is applicable in various industries such as wastewater treatment, paper and pulp industry and as well as food and beverages industry. In wastewater treatment industries, it is a must to make sewage harmless before it is disposed to prevent pollution. One of the most important reasons to treat wastewater is to control the Bio-chemical oxygen demand (BOD) of the water, which is the oxygen required for biological decomposition of biodegradable organic matter under aerobic conditions. Filtration is one of the process used in order to treat wastewater. It is stated in Basic Environment Engineering by R.C. Gaur that “Filtration is a physical and chemical process for separating suspended and colloidal impurities from water by passage through a porous bed made up of gravel and sand.”
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There are a lot of different types of filter equipments. Filter equipments consists of bed filters, bag filters, filter press, pressure leaf filters, cartridge filters, vacuum filters, band filters, rotary drum filters and rotary disc filters. The experiment that is about to be conducted is based on a plate and frame filter press which is one type of filter press. The other type of filter press is called recessed plate or chamber press.
Figure 1: The plate and frame filter press available in laboratory.
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Figure 2: An example of industrial-scale plate and frame filter press. (Coulson & Richardson Volume 2)
In general, plate and frame filter press functions as solids removal from slurries or fluid. It has a series of plates and frames in alternating arrangements which are covered with fiber cloths or filter papers. In order to remove solids from slurries or fluids, selection of a filter paper or fiber cloths are of high importance. According to Tarleton and Wakeman (2007), they state that, “The term filter medium can be defined as ‘any material that, under the operating conditions of the filter, is permeable to one or more components of a mixture, solution or suspension, and is impermeable to the remaining components’ (Purchas and Sutherland, 2002)”. Tarleton and Wakeman (2007) also claimed that, “Selection of the filter medium must take account into many factors; criteria by which a medium is assessed include the permeability of clean medium, its particle retention capability and the permeability”. So, if selection of filter medium is not critically considered before operation filter presses, there might be occurrence of using filter mediums with too big pores which will eventually end up to a very small cake formed, or no cake formed at all. Main Type
Subdivisions
Smallest particle retained (µm) (approximate)
8
Solid fabrications
Metal sheets
Rigid porous media
Cartridges
Plastic sheets
Flat wedge-wire screens
100
Wire-wound tubes
100
Stacks of rings
5
Perforated
100
Woven Wire
5
Ceramics and stoneware
1
Carbon
<1
Sintered metals
3
Plastics
10
Sheet fabrications
3
Bonded beds
2
Yarn wound
2
Woven monofilaments Fibrillated film Porous sheets
Membranes
Polymeric
<0.1
Ceramic
<0.1
Metal
0.2
Woven fabrics
Staple fibre yarns
5
Non-woven media
Filter sheets
0.5
Felts and needlefelts
10
Paper (cellulose and glass)
5 and 2
Polymeric (melt blown, spun bonded, etc.)
10
Fibres
1
Powders
<1
Loose media
Table 1: Shows the filter media based on rigidity (Purchas, 1981) 9
Table 1 (taken from Tarleton and Wakeman, 2007) shows the general guideline for classifications of different filter mediums. In another source, McCabe et. al, 2005, it states that. “The septum in any filter must meet the following requirements: 1) It must retain the solids to be filtered, giving a reasonable clear filtrate. 2) It must not plug or blind. 3) It must be resistant chemically and strong enough physically to withstand the process conditions. 4) It must permit the cake formed to discharge cleanly and completely 5) It must not be prohibitively expensive. Canvas cloths are common filter mediums but when corrosive liquids are used, it requires the use of other filter media, such as woolen cloth, metal cloth of monel or stainless steel, glass cloth, or paper”. Cake compressibility is another essential property which has to be considered in this operation. Generally, there will only be 2 types of cakes which would be formed, namely: 1) Compressible filter cakes; 2) Incompressible filter cakes. For both different type of cakes, McCabe et. al, 2005, states that “Compressible cakes are cakes where the flocs are deposited from the slurry on the upstream face of the cake and form a complicated network of channels. The resistance of such a cake is sensitive to the method used in preparing the slurry and to the age and temperature of the material. In addition, the flocs are distorted and broken down by the forces existing in the cake and vary from layer to layer. In another case, where incompressible cakes are concerned, specific cake resistance, α, varies with distance from the septum because the cake nearest to the septum is subject to the greatest compressive force and has the lowest void fraction. This makes the pressure gradient nonlinear and specific cake resistance may also vary with time” A good example of a compressible filter cake is the sludge of pulp and paper wastewater treatment where when it is filtered, a cake with a considerably thick layer is formed. If an incompressible filter cake is formed, for example using charcoal as impurities within the solution, a cake will be formed and it barely retain its shape giving difficulties in measuring cake thickness. In order to do calculations for filtration experiments, a few important equations have to be used in order to plot curve or measure a certain variable. According to Tarleton and Wakeman, 2007, “The general filtration equation, where 10
pressure is considered to represent either pressure or vacuum, the filtration process is most commonly analysed using the following equation: dtdV=1q=μlαavcV+ARA2∆p=μlαavcA2∆pV+μlRA∆p Where V is the cumulative volume of filtrate, t the filtration time, q the filtrate flow rate, A the filter medium area, ∆p the filtration pressure, μl the viscosity of liquid, αav the average specific cake resistance, R the medium resistance and c the effective feed concentration”. Another equation for filtration, which is the filtration at constant pressure, is stated by McCabe et. al, 2005, as follows: dtdV=1q=μcαA2∆p+1qo Konieczny and Rafa, 2000, provided another equation which is used to determine the volumetric flux of a filtration given by this formula: Js=1Fo∙Voto Where Jsis the average filtration flux with respect to opening surfaces, Fo is the opening surface of the filtration, and lastly Vo is the filtrate volume after time, to. The usage of filter aids is another important technique that is frequently applied to solve problems arising from slow filtration rate, unsatisfactory filtrate clarity or rapid medium binding. According to Perry and Green, 1997, “Filter aids are granular or fibrous solids capable of forming a highly permeable filter cake in which very fine solids or slimy, deformable flocs may be trapped”. A very good way of using this technique is the use of a more permeable filter medium than the clarification would require to create filtrate of the same quality by depth filtration. It is also stated in Perry and Green, 1997, that “filter aids should have low buld density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. In addition to this, they should also be porous and capable of forming a porous cake which is capable to minimize flow resistance and chemically inert to the filtrate is a must”. Two examples of the most used filter aids in the industry are: 1) Diatomaceous silica (prepared from deposits of diatom skeletons). 2) Perlite (principally aluminum alkali silicate).
There are ups and downs using plate and frame filter press as well. The advantages of filter press is clearly stated in the specifications manual provided by Lotus Scientific(M) Sdn. Bhd. A very good point about this filter press is that it is 11
easy to clean and replace filter cloth or membranes. Since it is easy to operate, this leads to low maintenance cost as it does not give a tough time in cleaning nor replacing filter cloths or membranes. Besides the mentioned advantages, it is also capable of operating at high pressure conditions in either a cake-filter or a clarifying-filter application. Aside from that, filter press provides large area for filtration on a small floor space. The capacity can also be adjusted simply by inserting or removing plates and frames. Lastly, internal inspection can easily be conducted as leakage is easily detected. With all the characteristics mentioned and its simplicity in operability, it makes filter press one of the most frequently used filters in the industries. However, there are also disadvantages for a plate and frame filter press. As cake densities are varying, it leads to imperfect washing. According to Perry and Green, 1997, “filter-cloth life is relatively short due to the mechanical wear of emptying and cleaning the press (often involving scraping the cloth). It needs a high labour requirements as well. Presses frequently drip or leak and thereby create housekeeping problems, but the biggest problem arises from the requirement to open the filter for cake discharge. This is due to the fact that operators are thus exposed routinely to the contents of the filter, and this is becoming an increasingly severe disadvantage as more and more materials once believed safe are given restricted exposure limits”. Another disadvantage mentioned in the specifications manual provided by Lotus Scientific(M) Sdn. Bhd. is when larger feed concentration is used, inlet ports of the filter have a tendency to encounter blockage or leakage. This will affect the possibility of improper filtration.”
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EXPERIME NTAL
Figure 3: Plate and frame filter press in laboratory.
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Based on figure 3, the tank is where the feed is put into and the feed is then pumped into the plate and frames filter. Before it is operated, appropriate filter paper or filter cloth is to be placed within the plate and frames. Turn the stem to ensure the plates and frames are fully tighten up so no leakage would occur. This equipment contains 2 valves, 1 controlling pressure and another controlling flow rate. Make sure both valves are appropriately open to ensure the machine is working fine. As the feed passes through the plate and frames, it will then be discharged back as filtrate into the tank through the upper hose and the process is continued until the feed in tank is crystal clear. Tank is stirred throughout the whole experiment to ensure everything gets filtered. This machine has a tray with a hole for water to run off to the pail when leakage occurred or when cleaning is in progress.
Preparation of mixture: Adequate amount of paper is shredded beforehand. 5kg of shredded paper would be more than sufficient for this experiment. Paper sludge: Shredded paper (approx: 250g, 350g, 450g) is then blended together with 20 liter of waters. Filter papers are used in this experiment as this is the only available selection in laboratory.
Difficulties of Experiment: The first difficulty of this experiment is the lack of equipment in laboratory. Without the availability of an equipment to melt the feed at its melting point, viscosity is unobtainable which gives problems in using most of the filtration equations as it requires viscosity. The only available filter media available in laboratory is filter paper. Filter cloths and other sorts of filter media are not available and the feed used is something which filter paper will be able to filter. The first group dealt with fly ash in their first attempt and filter paper failed to filter fly ash as size of fly ash is smaller than that of the holes in filter paper. Experiments suggested in the specifications manual is unusable due to the fact that viscosity is obtainable. Procedure:
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1) Fill the tank with paper sludge mixture. 2) Set the valve to fully open and turn on the equipment. 3) Obtain the volume of filtrate at the interval of every 20 seconds. Run this process for a time length of 6 minutes. 4) Obtain the pressure of filter press at the interval of every 2 minutes. Let this process runs until the mixture of paper sludge becomes clear. 5) Repeat steps 1 to 5 by using mixture that contains 350g then 450g of blended paper. Results: 1) Plot graph of pressure vs time for all 3 mixtures with different concentrations. 2) Plot graph of volumetric flux vs time for all three mixtures. 3) Calculate the % reduction of solids in mixture ( for all three concentrations) Weight of cake = initial weight of solids before filtration – dry weight of cake obtain
% reduction = (weight of cake / weigh of solid in mixture) x 100%
Then plot graph of % reduction of solids in mixture vs number of plates.
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RESULTS 12.5g/L
17.5g/L
22.5g/L
Time(s)
Flux (ml/m2.s)
Flux (ml/m2.s)
Flux (ml/m2.s)
20
208.33
188.89
94.44
40
200.00
183.33
91.67
60
197.22
175.00
88.89
80
194.44
166.67
86.11
100
188.89
166.67
83.33
120
177.78
163.89
75.00
140
175.00
155.56
66.67
160
166.67
144.44
58.33
180
158.33
136.11
61.11
200
155.56
130.56
52.78
220
150.00
127.78
52.78
240
147.22
122.22
50.00
260
150.00
122.22
47.22
280
144.44
122.22
44.44
300
141.67
119.44
41.67
320
138.89
116.67
41.67
340
138.89
116.67
41.67
360 138.89 116.67 41.67 Table 2: Shows the variation of flux over time for 12.5g/L, 17.5g/L and 22.5g/L of paper sludge.
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12.5g/L
17.5g/L
22.5g/L
Time(min)
P(MPa)
P(MPa)
P(MPa)
0
0.10
0.10
0.16
2
0.12
0.14
0.168
4
0.13
0.15
0.17
6
0.14
0.158
0.17
8
0.14
0.16
0.17
10
0.14
0.16
0.17
12
0.14
0.16
0.17
14
0.14
0.16
0.17
16
0.14
0.16
0.17
18
0.14
0.16
0.17
20 0.14 0.16 0.17 Table 3: Shows the variation of pressure over time for 12.5g/L, 17.5g/L and 22.5g/L of paper sludge.
Paper Sludge (g/L)
Wi
Wf
% Reduction of solids in mixture
12.5
1454
240
96
17.5
1702
328
93.71428571
22.5 1890 412 91.55555556 Table 4: Shows the variation of % reduction of solids in mixture over 12.5g/L, 17.5g/L and 22.5g/L of paper sludge used.
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Figure 4: Shows the relationship for flux against time for 12.5g/L, 17.5g/L and 22.5g/L of paper sludge.
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Figure 5: Shows the relationship between pressure against time for 12.5g/L, 17.5g/L and 22.5g/L of paper sludge.
19
Figure 6: Shows the relationship between % reductions of solids in mixture versus concentration of mixture.
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DISCUSSIO NS Plate and frame filtration is a well-known solid liquid separation equipment within industries which include chemical producers, pharmaceutical and also as well as food and beverages industry. This is mainly due to the easy operability and efficiency of this equipment. An experiment has been conducted using this equipment and preparations are made in order to conduct the experiment. Newspaper sludge has been agreed to be the feed used in this experiment and it can definitely be used to represent pulp and paper wastewater treatment industry. Preparations made were to shred a total of 5kg newspapers. Shredded newspapers are then separated into 250g, 350g and 450g before each of it is individually blended to create newspaper sludge. As stated earlier, the first objective set is to determine the relationship between the concentration of mixture and the volumetric flux. Table 2 shows the volumetric flux as time increases and figure 4 summarizes the relationship. It can be seen that as time increases flux would decrease exponentially for all 3 concentrations until a certain time where the flux will be constant thereafter. By referring to the equation: JO=VOA . to Area, A and time, to are constant values and volume is the is only factor affecting flux. As volume increase, flux tends to increase as well. The factor that affects volume is the concentration of newspaper sludge. A higher concentration of newspaper sludge will tend to increase the cake thickness as it is filtered and this will affect the flow rate as a thicker cake will reduce the flow rate of the outlet. This is the case seen in this experiment as with reference to figure 4, an increased in concentration of newspaper sludge will give a decreasing volumetric flux value 21
which is expected to happen. Thus, a relationship between concentration of mixture and the volumetric flux can be formed whereby a higher concentration of mixture leads to a decreasing volumetric flux. The second objective mentioned in this experiment is to determine the effect of concentration of mixture on pressure of the filter pump. In this experiment, there are 2 valves involved, one controlling pressure and the other controlling flow rate. In order to measure the pressure of the filter pump, the pressure valve is fully opened allowing pump to work effectively and pressure readings can be read at the pressure gauge attached. Results produced in the experiment are summarized in table 3 and the variation of pressure over time is more obvious in figure 5. With reference to figure 5, it is clearly seen that as time passes, pressure increases up to a certain extend where it remained constant thereafter. This phenomenon is due to the increased in filter cake thickness in each plate and frames. As filter cake thickness is increased, pressure gauge gives a higher reading for pressure which indicates pressure is increasing. After a certain period of time, the pressure gauge reading remained constant and this happens because the plate and frame reached the limit of filtration and the cakes formed reached its maximum thickness. By this time, filtration would occur at a very low rate and filtrate discharge is usually crystal clear by this time. One of the factors which play an important role to determine the variation in pressure is the concentration of newspaper sludge. Over time, higher concentration would mean cake gets thicker in a quicker manner thus giving off a higher pressure reading. Referring to figure 5, it can clearly be seen that 12.5g/L of newspaper sludge gives a higher pressure readings compared to 17.5g/L and 22.5g/L which is true in this case. So, the effects of concentration on pressure of pump can be concluded as a higher concentration gives an increasing pressure on pump. The last objective for this experiment is to actually determine the percentage reduction of solid in mixture and the efficiency of the plate and frame filter press. This can be done by removing cake and it is then dried up in an oven. After drying, it is then weighed to get the mass remaining, which is the amount of solids removed from filtrate and this value then leads to the final objective of this experiment. As shown in figure 6, percentage reduction of solid in mixture is decreasing as concentration of newspaper sludge is increased. This is mainly due to the concentration issue. As concentration is increased, more and more solids within the filtrate failed to be filtered out because the plate and frame has reached its maximum capacity which leads to the decreased in the percentage reduction of solid in mixture which is also the efficiency. There are problems and difficulties encountered in this experiment as well. One of the most important issues faced is the inability to measure viscosity of feed 22
which is a very important variable in this experiment. In order to do this, newspaper sludge has to be heated until it is over its melting point in order to measure using a viscometer. Since equipments in laboratory is limited, it is impossible to measure the viscosity since there isn’t any equipment to heat newspaper sludge to its melting point. Without viscosity readings, most of the equations cannot be used as it will leave an unsolved variable in calculations. Another problem faced when conducting this experiment is the inaccuracy of some data shown on figure 4. One of the reasons that lead to this discrepancy is due to the lack of equipments. With inadequate equipments supplied in laboratory, inaccuracy of some readings is totally inevitable. There might be some parallax error while reading the water level as well which might contribute to inaccuracy problems.
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CONCLUSI ON In conclusion, increased in concentration of mixture will lead to a decrease in volumetric flow. In addition, increased in concentration of mixture will also lead to the increase in pressure of the filter pump. Lastly, the percentage reduction of solids in mixture and efficiency decreases as concentration increases.
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NOMENCLAT URE Symbol
Unit
Definition
t
s
Time
V
mL
Volume
P
MPa
Pressure
JO
ml/m2s
Volumetric flux
Wi
g
Initial weight of cake before drying
Wf
g
Final weight of cake after drying
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REFERENCE S 1) Gaur, R.C. 2008, Basic Environmental Engineering, New Age International (P) Limited, Publishers, New Delhi. 2) Richardson, J. F., Harker,J. H. 2002, Coulson and Richardson’s Chemical Engineering Volume 2: Particle Technology and Separation Processes, Fifth Edition, Butterworth Heinemann, Oxford. 3) Tarleton, S., Wakeman, R. 2003, Solid/Liquid Separation: Equipment Selection and Process Design, First Edition, Butterworth Heinemann, Oxford. 4) McCabe, W. L. et al. 2005, Unit Operations of Chemical Engineering, Seventh Edition, McGraw-Hill, New York. 5) Perry, R. H. 1999, Perry’s Chemical Engineers’ Handbook, Seventh Edition, McGraw-Hill, New York. 6) Konieczny, K, Rafa J. 2000, Modeling of the Membrane Filtration Process of Natural Waters, Polsh Journal of Environmental Studies Vol. 9, No. 1 (2000), 57-63.
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APPENDIX Raw Data T(s) V(ml) P(MPa) 20 750 1.7 40 720 1.7 60 710 1.7 80 700 1.7 100 680 1.7 120 640 1.7 140 630 1.7 160 600 1.7 180 570 1.7 200 560 1.7 220 540 1.7 240 530 1.7 260 540 1.7 280 520 1.7 300 510 1.7 320 500 1.7 340 500 1.7 360 500 1.7 Table 5: Shows the Volume collected and pressure change for 12.5g/L of paper sludge. T(min) P(MPa) 0 0.10 2 0.12 4 0.13 6 0.14 8 0.14 10 0.14 12 0.14 14 0.14 16 0.14 18 0.14 20 0.14 Table 6: Shows the Pressure change for 12.5g/L of paper sludge. 27
T(s) V(ml) (MPa) 20 680 0.160 40 660 0.160 60 630 0.160 80 600 0.155 100 600 0.140 120 590 0.150 140 560 0.160 160 520 0.160 180 490 0.160 200 470 0.160 220 460 0.160 240 440 0.160 260 440 0.160 280 440 0.160 300 430 0.160 320 420 0.160 340 420 0.160 360 420 0.160 Table 7: Shows the Volume collected and pressure change for 17.5g/L of paper sludge.
T(min) P(MPa) 0 0.10 2 0.14 4 0.15 6 0.158 8 0.16 10 0.16 12 0.16 14 0.16 16 0.16 18 0.16 20 0.16 Table 8: Shows the Pressure change for 12.5g/L of paper sludge.
Time, T(s)
Volume,V(ml)
Pressure, P(MPa) 28
20 340 0.165 40 330 0.165 60 320 0.160 80 310 0.160 100 300 0.155 120 270 0.155 140 240 0.155 160 210 0.155 180 220 0.160 200 190 0.155 220 190 0.150 240 180 0.150 260 170 0.150 280 160 0.160 300 150 0.168 320 150 0.160 340 150 0.140 360 150 0.160 Table 9: Shows the Volume collected and pressure change for 22.5g/L of paper sludge.
T(min) P(MPa) 0 0.16 2 0.168 4 0.17 6 0.17 8 0.17 10 0.17 12 0.17 14 0.17 16 0.17 18 0.17 20 0.17 Table 10: Shows the Pressure change for 22.5g/L of paper sludge.
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Calculations 1) Conversion of paper sludge mass to concentration of paper sludge in water Example: 250g of paper sludge mixed with 20L of water Concentration, CO=250g20L=12.5gL
2) Area of plate and frame filter press. Area for 1 filter cake is given as 0.03m2 Since there are 6 cakes involved, area of 6 filter cakes is 0.03 X 6 = 0.18m2
3) Volumetric flux Example: 12.5g/L at 20s; V = 750mL, Using the formula: JO=VOA . to JO=7500.18×20 JO=208.33mlm2.s
4) % Reduction of solids in mixture Example: 12.5g/L of paper sludge; Final weight of paper sludge is 240g Using the formula: % Reduction=Final weight of cake after dryin Initial weight of paper sludge before filtration×100 % Reduction=24012.5×20×100=96%
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