Directory UMM :Data Elmu:jurnal:E:Environmental Management and Health:Vol11.Issue4.2000:
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Cost-effective pre-treatment of
agro-industrial wastewater
Agro-industrial
wastewater
Fatma A. El-Gohary, Fayza A. Nasr and Rifaat A.Wahaab
Water Pollution Control Dept, National Research Centre, Cairo, Egypt
and
297
Hamdy I. Aly
Faculty of Engineering, Ain Shams University, Cairo, Egypt
Keywords Water treatment, Water policies
Abstract Pre-treatment of wastewater discharged from a potato-chips factory was the subject
of this study. Wastewater discharged from this factory is characterized by high values of BOD,
TSS and oil and grease (3,685, 4,115 and 169mg/l, respectively). Treatability studies via
continuous aerobic and anaerobic methods treatment have been investigated. The results
obtained showed marked improvement in the quality of the treated effluent using packing
material versus the upflow anaerobic sludge bed reactor (UASB) without packing. An extra
removal in COD (53 per cent), BOD (61 per cent), TSS (52 per cent) and oil and grease (46 per
cent) was obtained. Corresponding residual values were 398mgO2/l, 235mgO2/l, 108mg/l and
38mg/l, respectively. Based on the laboratory results, engineering designs and economic
evaluation of the different treatment systems were developed.
Introduction
Agro-industries are major contributors to the worldwide industrial pollution
problem, Egypt being no exception. With the tremendous pace of technology
development, substantial research is devoted to cope with wastes of ever
increasing complexity generated by agro-industries. Therefore, agro-industries
more than any other industrial sectors in this field require a dynamic and
comprehensive approach for appropriate waste management.
Biological processes have long been used successfully to treat food industrial
effluents (Busten et al., 1990). The only difficulty occurs in the separation of the
sludge from the treated effluent in the settling tank due to sludge bulking (e.g.
Rensink and Donker, 1990). It has been proved that the feed pattern of the plant
plays a predominant role in the occurrence or the absence of bulking sludge
(Rensink, 1974). The traditional activated sludge process, however, is energy
consuming and requires special skills for its operation and maintenance. A
recent survey showed that the anaerobic technology has successfully been
applied for the treatment of a number of organic wastes (Ni and Nyns, 1993).
Among several anaerobic processes, the upflow anaerobic sludge bed reactor
(UASB) is by far the most widely applied for wastewater treatment. It can be
used both for very small scale and for large scale applications (Lettinga et al.,
1991). It is an attractive alternative for the treatment of industrial effluents
discharged from alcoholic and soft drink bottling industries, paper recycle and
paper making mills, fruit and vegetable canneries, dairy industry and malting
and brewing process (Lettinga and Hulshoff Pol, 1986 ).
Environmental Management and
Health, Vol. 11 No. 4, 2000,
pp. 297-306. # MCB University
Press, 0956-6163
EMH
11,4
298
Extensive research has been focused on the methods of retaining a sufficient
quantity of active biomass in the biological system and optimizing the
microbial activity. Many packing materials were investigated. The support
material that studies point out as useful design parameters are: pore size and
shape of support (Dahab and Young, 1982) and distribute the flow (Song and
Young, 1986). A porous ceramic carrier was used by Kawase et al. (1989) for
immobilization of microorganisms inside the reactor. Polyvinyl chloride and
backed clay carriers develop excellent methanogenic fixed films using acetic
acid as substrate (Kawase et al., 1989). The use of polyurethane foam sponges
can be successfully made as a support material in anaerobic reactors fed on
olive mill effluent (Rozzi, 1989). Chin (1989) also used charcoal chip and sand
with a good performance of aerobic reactor treating high strength edible oil
refinery wastewater.
To optimize microbial activity, the use of packing material has been tested
by several investigators. A good biofilm medium must offer a high specific
surface area, a good surface on which the bacteria can grow and can be held
(Schulz, 1993) and it must avoid the clogging by a surplus of biomass. The
permeation of nutrients and oxygen into all parts of the biomass layers must be
assured (Dodwell Company, 1987). The main objective of the present study is to
propose an appropriate low cost treatment technology for wastewater
discharged from a potato chips factory.
Materials and methods
Biological treatment of settled end of pipe wastewater from a potato chips
factory was carried out using continuous flow aerobic and anaerobic systems.
Dimensions and operating conditions of the treatment schemes are presented in
Table I.
Aerobic treatment
To develop the design parameters for the continuous system, batch laboratory
experiments were carried out in two-litre plexiglass columns. MLSS volume
was regulated to cover a range from 2.0 to 3.5g/l. Air supply was adjusted to
maintain a minimum dissolved oxygen concentration of 2.0mg/l. Detention
periods ranging from one hour to 24 hours were examined. The characteristics
of the biologically treated effluent as indicated by COD values were determined
Item
Table I.
Dimensions and
operating conditions of
the treatment schemes
Unit
Volume
Litre
Acting volume
Litre
Hydraulic retention time Hours
Organic load
Kg BOD/m3/day
Biomass
g/l
Activated
Unpacked
Packed anaerobic
sludge reactor anaerobic reactor
reactor
5
3
6
0.9
3
5
5
18
2.9
22
5
3.5
13.5
3.9
22
after 60 minutes' settlement. Sludge characteristics were also determined.
Based on the results obtained, a completely mixed activated sludge unit was
designed and manufactured (see Figure 1).
Anaerobic treatment
Two UASB-Reactors (packed and unpacked) were operated in parallel.
Dimensions and operating conditions are shown in Table I. The two systems
were fed continuously with wastewater. A schematic diagram of the UASBreactor is shown in Figure 2. A bionet-structured tubular plastic medium is
used as a packing material.
The performance of the treatment systems was evaluated by monitoring the
quality of the feed and the effluent of each treatment unit. Physico-chemical
analysis was carried out according to APHA (1997).
Agro-industrial
wastewater
299
Results and discussion
Primary sedimentation
The wastewater contains considerable amounts of total suspended solids (4,115
mg/l) that may adversely affect the microbial activity. Therefore, sedimentation
was necessary prior to the biological treatment step. To determine the optimum
detention time, a settlability test, covering a range from 30 minutes to three
Figure 1.
Schematic diagram of
the completely mixed
activated sludge
EMH
11,4
300
Figure 2.
Schematic diagram of
the UASB reactor
hours was carried out. The results indicated that a detention time of one hour is
the optimum selection. COD, BOD and TSS values were reduced by 48 per cent,
40 per cent and 55 per cent respectively (Table II and Figures 3 and 4).
Aerobic treatment
The results of batch-experiments indicated that the highest BOD removal was
achieved at a retention time ranging from five to six hours using a MLSS of 3g/l.
Based on these results continuous treatment using completely mixed activated
sludge system was carried out. The hydraulic detention time was kept constant
at six hours.The average organic load was around 8.6 kg BOD/m3/day. The
results obtained indicated significant reduction of the organic load. Average
residual values of COD, BOD,TSS and Oil and Grease were 639, 316, 169 and
62mg/l, respectively (Table II and Figures 3 and 4). These values are in
agreement with the standards set by Egyptian law for discharge into the
sewerage system.
Anaerobic treatment
In an attempt to reduce energy cost, the use of packed and unpacked UASB
reactors was investigated.
Unpacked UASB reactor
The reactor was operated at a detention time of 18 hours and average organic
load of 2.9kg BOD/m3/day. Analysis of the UASB effluent showed reductions
of 86 per cent and 82 per cent in COD and BOD. The corresponding residual
values were 650 and 342mgO2/l, respectively. TSS ranged between 116 and
410mg/l with an average value of 203mg/l (Table III and Figures 3 and 4).
Raw wastewater
Parameter
Unit
pH
Chemical oxygen demand
Biochemical oxygen demand
Total kjeldahl nitrogen
Total phosphates
Total solids at 105ëC
Volatile solids at 550ëC
Total dissolved solids at 105ëC
Volatile dissolved solids at 550ëC
Total suspended solids at 105ëC
Volatile suspended solids at 550ëC
Settlable solids 10
Settlable solids 30
Oil and grease
mgO2/l
mgO2/l
mg N/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
ml/l
ml/l
mg/l
Before sedimentation
Min
Max Aver
4.6
5,206
2,040
132
28
5,654
4,038
1,802
1,496
791
321
102
40
102
6.5
13,860
6,000
399
90
12,830
10,560
6,577
4,660
7,100
6,800
200
240
200
±
8,646
3,685
227
78
8,213
5,834
3,848
3,087
4,115
2,047
114
131
169
After sedimentaion
Min
Max Aver
5.6
2,892
1,287
84
18
2,307
1,225
1,207
589
268
169
3
6
46
7
6,560
2,820
227
45
8,584
5,848
5,954
2,562
4,472
4,362
100
90
193
±
4,932
2,196
164
33
5,133
3,816
3,087
2,410
1,848
1,406
20
23
146
Percentage
removal
Aver
±
48
40
40
42
37
48
20
22
55
42
82
82
18
Treated wastewater
Activated sludge
Percentage
effluent
removal
Min
Max Aver
Aver
7.4
7.9
±
534
690
639
250
400
316
22
100
63
3.5
4.8
4.4
1,001 2,002 1,343
170
680
378
885 1,770 1,140
126
490
266
92
368
169
42
190
101
±
±
±
±
±
±
22
82
62
86
84
62
85
69
85
56
79
89
89
100
100
57.5
Agro-industrial
wastewater
301
Table II.
Performance data of
the treatment system
EMH
11,4
302
Figure 3.
Performance data along
the treatment units
The removal value reached 91 per cent. Average residual concentration of oil
and grease was 63mg/l. The biogas production rate was 0.37m3/kg COD
removed (Table III and Figures 3 and 4).
Packed UASB-reactor
The results from the operation of the packed reactor indicated that an
improvement in COD, BOD, TSS and oil and grease of 53 per cent, 61 per cent,
Agro-industrial
wastewater
303
Figure 4.
Performance data along
the treatment units
52 per cent and 46 per cent, compared to the unpacked reactor was achieved
(Table III and Figures 3 and 4). These results were obtained at a lower retention
time (13.5h).
Design and economic study of the treatment systems
Based on the laboratory results a final process design was developed (Figures 5
and 6). Economic evaluation of the two treatment systems was carried out. The
cost of construction of the treatment plant and supply of mechanical and
Unit
pH
Chemical oxygen demand
Biochemical oxygen demand
Total kjeldahl nitrogen
Total phosphates
Total solids at 105ëC
Volatile solid at 550ëC
Total dissolved solids at 105ëC
Volatile dissolved solids at 550ëC
Total suspended solids at 105ëC
Volatile suspended solids at 550ëC
Settlable solids 10
Settlable solids 30
Oil and grease
±
mgO2/l
mgO2/l
mg N/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
ml/l
ml/l
mg/l
5.6
2,892
1,287
84
18
2,307
1,225
1,207
589
268
169
3
6
46
7
6,560
2,820
227
45
8,084
5,848
5,954
2,562
4,472
4,362
100
90
193
Unpacked anae
reactor-effl.
Min
Max Aver
±
7.1
7.6
±
4,932
547
696
650
2,196
250
400
342
164
64
128
95
33
4.4
5
4.9
5,133 1,062 2,450 1,414
3,016
297 1,020
430
3,087
890 2,040 1,212
1,451
172
634
305
1,848
116
410
203
1,406
28
386
126
20
0.1
0.5
0.3
23
0.2
1.0
0.7
146
24
82
63
EMH
11,4
304
Table III.
Performance data of
the treatment system
Parameter
Settled wastewater
Min
Max Aver
Percentage
removal
Aver
Packed anae
reactor-effl.
Min
Max Aver
Percentage
removal
±
86
82
37
83
68
82
53
73
85
86
98.5
97
57
±
±
±
215
410
303
107
150
135
54
78
67
3.0
4.8
4.5
905
1,481 1,281
227
730
429
820
1,380 1,009
193
451
369
85
153
97
34
100
60
Nil
Nil
Nil
Nil
Nil
Nil
27
40
34
±
94
94
77
86
75
85
67
75
94
96
100
100
77
Agro-industrial
wastewater
305
Figure 5.
Schematic diagram of
the anaerobic treatment
process
Figure 6.
Schematic diagram of
the aerobic treatment
process
electrical equipment is estimated as $1.6 million and $0.735 million for
activated sludge and UASB systems, respectively. Therefore, it is clear that the
cost of the anaerobic treatment using UASB reactor is relatively low an
compared to the activated sludge system. Also, the operation and maintenance
cost are lower due to the savings in energy consumption.
References
Busten, B., Eikebrokn and Thorvaldsem, G. (1990), ``Coagulation as pretreatment of food
industry wastewater'', Wat. Sci. Tech., Vol. 22 No. 9, pp. 1-8.
Chin, K.K. (1989), ``Performance of charcoal chip and sand packed anaerobic reactors'', Wat. Sci.
Tech., Vol. 21, pp. 1677-80.
Dahab, M.F. and Young, C.I. (1982), ``Retention and distribution of solids in fixed bed anaerobic
filter'', Proc. 1st Int. Conf. Fixed-film Biological Process, Vol. 3, pp. 1337-51.
EMH
11,4
306
Dodwell Company (1987), ``Ring-lace as fixed biomass reactor'', Report, Tokyo (obtainable at the
company Grunbeck, D-8884 Hochstadt).
Kawase, M. et al. (1989), ``An anaerobic fixed bed reactor with a porous ceramic carrier'', Wat. Sci.
Tech.
Lettinga, G. and Hulshoff Pol, L. (1986), ``Advanced reactor design, operation and economy'', Wat.
Sci. Tech., Vol. 18, pp. 99-108.
Lettinga, G., van Knippenberg, K., Veenstra, S. and Wiegant, W. (1991), ``Upflow anaerobic
sludge blanket (UASB), low cost sanitation research project in Bandung/Indonesia'', Final
Report, Wageningen Agricultural University, February.
Ni, J.-Q. and Nyns, E.J. (1993), Biomethanation: A Developing Technology in Latin America.
Catholic University of Louvain and Bremen Overseas Research and Development
Association, Druckerei Verwoht, Bremen, Germany.
Rensink, J.H. (1974), ``New approach to preventing bulking sludge'', Journal of Water Pollution
Control Federation, Vol. 46, pp. 1888-94.
Rensink, J.R. and Donker, H.J.G.H. (1990), ``Control of bulking sludge in agro-industrial treatment
plant'', Wat. Sci. Tech., Vol. 22 No. 9, pp. 101-11.
Rozzi, R.A., Passino, R. and Limoni, M. (1989), ``Anaerobic treatment of olive mill effluent in
polymethane'', Process Biochemistry, April.
Schulz, J. (1993), ``Der Finfluss des Tragermaterials auf die Leistungsfahigkeit von
Biofilmsystemen zur Abwasserreinigung'', Korrespondenz Abwasser, Vol. 1, pp. 68-73.
Song, K.H. and Young, C.J. (1986), ``Media design factors for fixed-bed filters'', Jour. WPCF, Vol.
58 No. 2.
Standard Methods for the Examination of Water & Wastewater (1997), 19th ed., APHA.
http://www.mcbup.com/research_registers/emh.asp
The current issue and full text archive of this journal is available at
http://www.emerald-library.com
Cost-effective pre-treatment of
agro-industrial wastewater
Agro-industrial
wastewater
Fatma A. El-Gohary, Fayza A. Nasr and Rifaat A.Wahaab
Water Pollution Control Dept, National Research Centre, Cairo, Egypt
and
297
Hamdy I. Aly
Faculty of Engineering, Ain Shams University, Cairo, Egypt
Keywords Water treatment, Water policies
Abstract Pre-treatment of wastewater discharged from a potato-chips factory was the subject
of this study. Wastewater discharged from this factory is characterized by high values of BOD,
TSS and oil and grease (3,685, 4,115 and 169mg/l, respectively). Treatability studies via
continuous aerobic and anaerobic methods treatment have been investigated. The results
obtained showed marked improvement in the quality of the treated effluent using packing
material versus the upflow anaerobic sludge bed reactor (UASB) without packing. An extra
removal in COD (53 per cent), BOD (61 per cent), TSS (52 per cent) and oil and grease (46 per
cent) was obtained. Corresponding residual values were 398mgO2/l, 235mgO2/l, 108mg/l and
38mg/l, respectively. Based on the laboratory results, engineering designs and economic
evaluation of the different treatment systems were developed.
Introduction
Agro-industries are major contributors to the worldwide industrial pollution
problem, Egypt being no exception. With the tremendous pace of technology
development, substantial research is devoted to cope with wastes of ever
increasing complexity generated by agro-industries. Therefore, agro-industries
more than any other industrial sectors in this field require a dynamic and
comprehensive approach for appropriate waste management.
Biological processes have long been used successfully to treat food industrial
effluents (Busten et al., 1990). The only difficulty occurs in the separation of the
sludge from the treated effluent in the settling tank due to sludge bulking (e.g.
Rensink and Donker, 1990). It has been proved that the feed pattern of the plant
plays a predominant role in the occurrence or the absence of bulking sludge
(Rensink, 1974). The traditional activated sludge process, however, is energy
consuming and requires special skills for its operation and maintenance. A
recent survey showed that the anaerobic technology has successfully been
applied for the treatment of a number of organic wastes (Ni and Nyns, 1993).
Among several anaerobic processes, the upflow anaerobic sludge bed reactor
(UASB) is by far the most widely applied for wastewater treatment. It can be
used both for very small scale and for large scale applications (Lettinga et al.,
1991). It is an attractive alternative for the treatment of industrial effluents
discharged from alcoholic and soft drink bottling industries, paper recycle and
paper making mills, fruit and vegetable canneries, dairy industry and malting
and brewing process (Lettinga and Hulshoff Pol, 1986 ).
Environmental Management and
Health, Vol. 11 No. 4, 2000,
pp. 297-306. # MCB University
Press, 0956-6163
EMH
11,4
298
Extensive research has been focused on the methods of retaining a sufficient
quantity of active biomass in the biological system and optimizing the
microbial activity. Many packing materials were investigated. The support
material that studies point out as useful design parameters are: pore size and
shape of support (Dahab and Young, 1982) and distribute the flow (Song and
Young, 1986). A porous ceramic carrier was used by Kawase et al. (1989) for
immobilization of microorganisms inside the reactor. Polyvinyl chloride and
backed clay carriers develop excellent methanogenic fixed films using acetic
acid as substrate (Kawase et al., 1989). The use of polyurethane foam sponges
can be successfully made as a support material in anaerobic reactors fed on
olive mill effluent (Rozzi, 1989). Chin (1989) also used charcoal chip and sand
with a good performance of aerobic reactor treating high strength edible oil
refinery wastewater.
To optimize microbial activity, the use of packing material has been tested
by several investigators. A good biofilm medium must offer a high specific
surface area, a good surface on which the bacteria can grow and can be held
(Schulz, 1993) and it must avoid the clogging by a surplus of biomass. The
permeation of nutrients and oxygen into all parts of the biomass layers must be
assured (Dodwell Company, 1987). The main objective of the present study is to
propose an appropriate low cost treatment technology for wastewater
discharged from a potato chips factory.
Materials and methods
Biological treatment of settled end of pipe wastewater from a potato chips
factory was carried out using continuous flow aerobic and anaerobic systems.
Dimensions and operating conditions of the treatment schemes are presented in
Table I.
Aerobic treatment
To develop the design parameters for the continuous system, batch laboratory
experiments were carried out in two-litre plexiglass columns. MLSS volume
was regulated to cover a range from 2.0 to 3.5g/l. Air supply was adjusted to
maintain a minimum dissolved oxygen concentration of 2.0mg/l. Detention
periods ranging from one hour to 24 hours were examined. The characteristics
of the biologically treated effluent as indicated by COD values were determined
Item
Table I.
Dimensions and
operating conditions of
the treatment schemes
Unit
Volume
Litre
Acting volume
Litre
Hydraulic retention time Hours
Organic load
Kg BOD/m3/day
Biomass
g/l
Activated
Unpacked
Packed anaerobic
sludge reactor anaerobic reactor
reactor
5
3
6
0.9
3
5
5
18
2.9
22
5
3.5
13.5
3.9
22
after 60 minutes' settlement. Sludge characteristics were also determined.
Based on the results obtained, a completely mixed activated sludge unit was
designed and manufactured (see Figure 1).
Anaerobic treatment
Two UASB-Reactors (packed and unpacked) were operated in parallel.
Dimensions and operating conditions are shown in Table I. The two systems
were fed continuously with wastewater. A schematic diagram of the UASBreactor is shown in Figure 2. A bionet-structured tubular plastic medium is
used as a packing material.
The performance of the treatment systems was evaluated by monitoring the
quality of the feed and the effluent of each treatment unit. Physico-chemical
analysis was carried out according to APHA (1997).
Agro-industrial
wastewater
299
Results and discussion
Primary sedimentation
The wastewater contains considerable amounts of total suspended solids (4,115
mg/l) that may adversely affect the microbial activity. Therefore, sedimentation
was necessary prior to the biological treatment step. To determine the optimum
detention time, a settlability test, covering a range from 30 minutes to three
Figure 1.
Schematic diagram of
the completely mixed
activated sludge
EMH
11,4
300
Figure 2.
Schematic diagram of
the UASB reactor
hours was carried out. The results indicated that a detention time of one hour is
the optimum selection. COD, BOD and TSS values were reduced by 48 per cent,
40 per cent and 55 per cent respectively (Table II and Figures 3 and 4).
Aerobic treatment
The results of batch-experiments indicated that the highest BOD removal was
achieved at a retention time ranging from five to six hours using a MLSS of 3g/l.
Based on these results continuous treatment using completely mixed activated
sludge system was carried out. The hydraulic detention time was kept constant
at six hours.The average organic load was around 8.6 kg BOD/m3/day. The
results obtained indicated significant reduction of the organic load. Average
residual values of COD, BOD,TSS and Oil and Grease were 639, 316, 169 and
62mg/l, respectively (Table II and Figures 3 and 4). These values are in
agreement with the standards set by Egyptian law for discharge into the
sewerage system.
Anaerobic treatment
In an attempt to reduce energy cost, the use of packed and unpacked UASB
reactors was investigated.
Unpacked UASB reactor
The reactor was operated at a detention time of 18 hours and average organic
load of 2.9kg BOD/m3/day. Analysis of the UASB effluent showed reductions
of 86 per cent and 82 per cent in COD and BOD. The corresponding residual
values were 650 and 342mgO2/l, respectively. TSS ranged between 116 and
410mg/l with an average value of 203mg/l (Table III and Figures 3 and 4).
Raw wastewater
Parameter
Unit
pH
Chemical oxygen demand
Biochemical oxygen demand
Total kjeldahl nitrogen
Total phosphates
Total solids at 105ëC
Volatile solids at 550ëC
Total dissolved solids at 105ëC
Volatile dissolved solids at 550ëC
Total suspended solids at 105ëC
Volatile suspended solids at 550ëC
Settlable solids 10
Settlable solids 30
Oil and grease
mgO2/l
mgO2/l
mg N/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
ml/l
ml/l
mg/l
Before sedimentation
Min
Max Aver
4.6
5,206
2,040
132
28
5,654
4,038
1,802
1,496
791
321
102
40
102
6.5
13,860
6,000
399
90
12,830
10,560
6,577
4,660
7,100
6,800
200
240
200
±
8,646
3,685
227
78
8,213
5,834
3,848
3,087
4,115
2,047
114
131
169
After sedimentaion
Min
Max Aver
5.6
2,892
1,287
84
18
2,307
1,225
1,207
589
268
169
3
6
46
7
6,560
2,820
227
45
8,584
5,848
5,954
2,562
4,472
4,362
100
90
193
±
4,932
2,196
164
33
5,133
3,816
3,087
2,410
1,848
1,406
20
23
146
Percentage
removal
Aver
±
48
40
40
42
37
48
20
22
55
42
82
82
18
Treated wastewater
Activated sludge
Percentage
effluent
removal
Min
Max Aver
Aver
7.4
7.9
±
534
690
639
250
400
316
22
100
63
3.5
4.8
4.4
1,001 2,002 1,343
170
680
378
885 1,770 1,140
126
490
266
92
368
169
42
190
101
±
±
±
±
±
±
22
82
62
86
84
62
85
69
85
56
79
89
89
100
100
57.5
Agro-industrial
wastewater
301
Table II.
Performance data of
the treatment system
EMH
11,4
302
Figure 3.
Performance data along
the treatment units
The removal value reached 91 per cent. Average residual concentration of oil
and grease was 63mg/l. The biogas production rate was 0.37m3/kg COD
removed (Table III and Figures 3 and 4).
Packed UASB-reactor
The results from the operation of the packed reactor indicated that an
improvement in COD, BOD, TSS and oil and grease of 53 per cent, 61 per cent,
Agro-industrial
wastewater
303
Figure 4.
Performance data along
the treatment units
52 per cent and 46 per cent, compared to the unpacked reactor was achieved
(Table III and Figures 3 and 4). These results were obtained at a lower retention
time (13.5h).
Design and economic study of the treatment systems
Based on the laboratory results a final process design was developed (Figures 5
and 6). Economic evaluation of the two treatment systems was carried out. The
cost of construction of the treatment plant and supply of mechanical and
Unit
pH
Chemical oxygen demand
Biochemical oxygen demand
Total kjeldahl nitrogen
Total phosphates
Total solids at 105ëC
Volatile solid at 550ëC
Total dissolved solids at 105ëC
Volatile dissolved solids at 550ëC
Total suspended solids at 105ëC
Volatile suspended solids at 550ëC
Settlable solids 10
Settlable solids 30
Oil and grease
±
mgO2/l
mgO2/l
mg N/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
ml/l
ml/l
mg/l
5.6
2,892
1,287
84
18
2,307
1,225
1,207
589
268
169
3
6
46
7
6,560
2,820
227
45
8,084
5,848
5,954
2,562
4,472
4,362
100
90
193
Unpacked anae
reactor-effl.
Min
Max Aver
±
7.1
7.6
±
4,932
547
696
650
2,196
250
400
342
164
64
128
95
33
4.4
5
4.9
5,133 1,062 2,450 1,414
3,016
297 1,020
430
3,087
890 2,040 1,212
1,451
172
634
305
1,848
116
410
203
1,406
28
386
126
20
0.1
0.5
0.3
23
0.2
1.0
0.7
146
24
82
63
EMH
11,4
304
Table III.
Performance data of
the treatment system
Parameter
Settled wastewater
Min
Max Aver
Percentage
removal
Aver
Packed anae
reactor-effl.
Min
Max Aver
Percentage
removal
±
86
82
37
83
68
82
53
73
85
86
98.5
97
57
±
±
±
215
410
303
107
150
135
54
78
67
3.0
4.8
4.5
905
1,481 1,281
227
730
429
820
1,380 1,009
193
451
369
85
153
97
34
100
60
Nil
Nil
Nil
Nil
Nil
Nil
27
40
34
±
94
94
77
86
75
85
67
75
94
96
100
100
77
Agro-industrial
wastewater
305
Figure 5.
Schematic diagram of
the anaerobic treatment
process
Figure 6.
Schematic diagram of
the aerobic treatment
process
electrical equipment is estimated as $1.6 million and $0.735 million for
activated sludge and UASB systems, respectively. Therefore, it is clear that the
cost of the anaerobic treatment using UASB reactor is relatively low an
compared to the activated sludge system. Also, the operation and maintenance
cost are lower due to the savings in energy consumption.
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