The Science of the Total Environment, 66 (1987) Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

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1 The Science of the Total Environment, 66 (987) Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands MANAGEMENT OF WASTEWATER FROM SOAP AND FOOD INDUSTRIES: A CASE STUDY FATMA A. EL-GOHARY and SOHAIR I. ABO-ELELA Water Pollution Control Laboratory, National Research Centre, Dokki, Cairo (Egypt) HAMDY I. ALI Department of Sanitary Engineering, Faculty of Engineering, Ain-Shams University (Egypt) (Received November 24th, 986; accepted February 9th, 987) ABSTRACT This paper presents the wastewater management of an industrial complex which produces different products, i.e. soap, perfume extract, macaroni, jam and juices. A continuous monitoring programme for departmental as well as final effluents was carried out for almost 3 months. Characterization of the composite wastewater from both soap and food processing plants indicated that the waste was highly contaminated with organic compounds as indicated by COD and BOD values. Moreover, effluent from the soap manufacturing plant contains significant concentrations of oil and grease amounting to 563 mg Soap manufacturing effluent and the combined wastes discharged from the whole industrial complex were subjected to different treatment processes, namely dissolved air flotation, chemical coagulation-sedimentation, and biological treatment via a completely mixed activated sludge process. Although coagulation using alum followed by sedimentation removed 52% of COD, residual values did not comply with the regulatory standards. Biological treatment of the composite combined wastewater significantly removed the organic contaminants in wastewater. Average residual BOD, COD, oil and grease values were 30, 92 and 8.3 mg - respectively. Based on the laboratory results a final process design was developed. INTRODUCTION Rapid industrialization in Egypt has created pollution problems hitherto not encountered. As industrialization is followed by population growth, increase in traffic and other pollution generating activities, their cumulative effect is causing mounting public and Government concern. Therefore, in an attempt to tackle these problems new pollution control legislation has been enacted. To meet the required standards, an ambitious water pollution abatement programme has been adopted by the industrial sector. Priority has been given to the most polluting industries. This paper presents the wastewater management of an industrial complex which produces different products, i.e. soap, perfume extract, macaroni, jam and juices /87/$ Elsevier Science Publishers B.V.

2 Oil I 204 Perfume E~traction 0 m3/day I. Kato Aromatic Factory Jam and Syrup ii0 m3/day Agricultural Drain Macaroni and Noodles 30 m3/day f L Soap 250 m3/day Agricultural Drain Fig.. Flow diagram of production lines and their wastewater. -I Boiler I... ~ (Mazzot) I Storage Tanks For and Grease i - Dissolving Oil Nacl + NaoH _~ Bleaching of Grease Filters Continuous SaDon~flcation I ~ ~lycrine~:~:entra- tion l Distillation of Pure water ~ Giycrine... Industrial wastewater Drying I,Final Product I---~" Fig. 2. Flow diagram of sources of pollution in the soap factory.

3 205 TABLE Characteristics of composite combined industrial wastewater Parameter Combined industrial wastewater Range mean ph Biological oxygen demand (rag O 2 ) Chemical oxygen demand (mg O2-) Total dissolved solids (rag i) Total suspended solids (rag -) Total phosphorous (mg P -) Total Kjeldahl nitrogen (mg N ) Oil and grease (mg ) ~ ~ ~ (~ MATERIAL AND METHODS The various processes occurring in the factory are shown in the form of flow diagrams in Figs and 2. Due to the great variation in the quality and quantity of wastewater produced a continuous monitoring programme was carried out for almost 3 months. The characteristics of wastewater discharged from each of the four production lines, as well as the final effluent, were examined. All analyses were carried out according to Standard Methods for Examination of Water and Wastewater (980). Wastewater discharged from soap manufacturing during the two working shifts is estimated to be ~ 250 m 3 day ~. The other three production lines are operated only during the first shift. Wastewater produced from these plants are equivalent to 250m 3 day -. For treatability studies wastes were mixed according to their actual discharge ratio. Effluents from the soap manufacturing plant and the combined wastes discharged from the whole industrial complex (Table ) were subjected to different treatment processes, namely dissolved air flotation, chemical coagulation-- sedimentation, and biological treatment. Coagulation efficiency was tested by adding appropriate doses of alum using a jar-test procedure. For dissolved air flotation experiments, a laboratory-scale unit similar to that used by E-Gohary and Abo-Elela (980) was designed. Factors affecting the performance of the system such as detention time and air/solids ratio were determined (Eckenfelder, 966). Biological treatment of the combined composite was carried out using both a batch and a continuous activated sludge system (Fig. 3). To compensate for the deficiency in phosphorous content, the wastewater was mixed with an equal volume of domestic sewage.

4 Outer Cone 3- Inlet Tube 5-Inner Cone 7- Diffuser 2-0utlet Tube 4- Drain Assembly 6- Clorifier Fig. 3. Activated sludge system. RESULTS AND DISCUSSION Wastewater characterization Effluents from soap manufacturing plants are among the main sources of industrial water pollution. These wastewaters are inevitably characterized by high values of BOD, COD and oil and grease. The ph of the wastewater under investigation fluctuates between 6.5 and.8. In terms of COD and BOD, the organic load is estimated to be as high as 357 and 625 kg day - respectively. Oil and grease reach 563 mg. Wastewater constituents from the food processing and perfume extraction factories are mainly organic in nature. Table 2 summarizes the characteristics of wastewater from the two main drainage lines. Treatability studies Treatment of wastewater from soap manufacturing plant Wastewater from the soap manufacturing plant was treated by dissolved air flotation alone or chemical coagulation-sedimentation. Alum at its optimum

5 207 TABLE 2 Characteristics of composite wastewater from different plants Parameter Soap plant Range Mean Food processing + perfume extraction plants Range Mean ph Chemical oxygen demand (rag O 2 l- ) Biological oxygen demand 79~ (mg O2 i) Total dissolved solids (mg ) Total suspended solids (mg - ) Total phosphorous (~ ~) (mg P -) Total kjeldahl nitrogen (mg N ) Oil and grease concentration was used as coagulant. The results obtained are summarized in Table 3. Batch dissolved air flotation experiments indicated that a retention time of 7 min was sufficient for solids separation at a pressure of 4 atm. The average optimum air/solids ratio was calculated to be -~ COD removal varied from 40 to 46%; corresponding oil and grease removals were 40.2 and 49.5% respectively. These results are similar to those obtained by Abo-Elela and Nawar (980) for soap wastewater treatment. The results obtained show that, although oil and grease can be removed by flotation, the emulsified form is not affected, therefore chemical coagulation is required for breaking down emulsions (Patterson, 975). TABLE 3 Efficiency of physical and chemical treatment of soap wastewater Wastewater Raw Effluent Parameter Dissolved air flotation chemical coagulation Turbidity (NTU) ~ Chemical oxygen demand (mg 02 -) % Removal ~.9 Oil and grease % Removal

6 TABLE 4 The overall efficiency of physico-chemical treatment of combined wastewater from soap and food processing plants Parameter Dissolved air flotation followed by chemical Raw wastewater Dissolved air flotation coagulation (00mg - alum) Range Chemical oxygen demand (mg 02 l- ) % Removal Biological oxygen demand ~ 50 (rag 02 -) % Removal 5-53 Oil and grease (mg -) % Removal Chemical coagulation sedimentation (200 mg l- alum) Influent Effluent

7 Chemical coagulation of raw wastewater using alum was carried out. The optimum alum dose varied from 00 to 300 mg - depending on the characteristics of the wastewater under investigation. Available data showed that oil and grease removal were relatively high. Residual values varied from 6.6 to 2.mg -. Although COD removal up to 82% was achieved, residual values are considered to be very high (l62mg ). These results are in agreement with those obtained by Chin and Wong (98). From the results obtained, it is obvious that the use of physico-chemical processes will not produce an effluent which complies with the National Standards regulating wastewater disposal into surface water. Treatment of combined wastewater from soap and food processing plant Physico-chemical treatment.composite samples collected from the two main drainage lines were mixed according to their actual discharge, and subjected to different treatments. Batch laboratory studies showed that dissolved air flotation led to 2-5.6% COD removal. Residual values ranged between 72 and 2754mg. Oil and grease removal ranged from 25 to 54.6%. Chemical coagulation using 200mg - alum gave unsatisfactory results (Table 4). Although the COD value was reduced by 5.6%, the residual values were high. Similar results were obtained by Sengill et al. (982). From these results it is obvious that the characteristics of wastewater treated via physico-chemical or chemical sedimentation processes do not com- 209 o 5OO 400 o / Removal of C0O for non-filter sample * %Removal of COO for fitter sample ~' COO Residuat of non fitter sample COD Residual of filter sample <t< o. 4 S 8O ~o 2O I 24 Time hrs Fig. 4. Determination of optimum retention time of biological treatment.

8 20 ply with the regulatory standards for wastewater disposal into surface water. Therefore, soluble organic compounds have to be removed by biodegradation. Biological treatment. Batch laboratory experiments were carried out to identify the best operating conditions for continuous treatment via the activated sludge process. The results obtained (Fig. 4) show that the waste should be mixed with ~ 50% municipal sewage to compensate for deficiency in nutrients. A retention time of 6 h was chosen. The sludge concentration was kept constant at ~ 3 g l- (MLSS). The results obtained from continuous treatment of wastewater (Table 5) indicated that a significant portion of soluble organic constituents could be removed by biodegradation. Treatment via activated sludge gave better results than physico-chemical treatment. Average residual values of BOD, COD, and oil and grease were 30.6, 92.7 and 8.3 mg - respectively. PROCESS DESIGN Analysis of the composite wastewater samples collected from the soap and food processing plants showed that the BOD of the waste was between 360 and 70 mg. The COD values of the same samples were in the range mg. Oil and grease concentrations ranged between 40 and 288mg -. When regularity criteria were considered to determine the level of treatment required, oil separation via dissolved air flotation can be applied and the TABLE 5 Average results of continuous biological treatment of combined wastewater Parameter Influent Effluent Min Max Ave Min Max Ave ph Turbidity (NTU) Chemical oxygen demand (mg 02 l- ) Biological oxygen demand (mg O 2 l- ) Ammonia (mg N -) Nitrite (mg N -) Nitrate (mg N -) Organic nitrogen (rag N -) Total phosphate (rag P l ) Total solids 05 C (mg -) Total dissolved solids Oil and grease (mg -)

9 pre-treated effluent then be discharged into the municipal sewage system. The area where the plants are located is not yet provided with a municipal sewage system but it is still more economical to transport the pre-treated wastewater 5 km to the nearest main collector. As an alternative, the pre-treated wastewater must be treated to a degree which will allow its final disposal to a nearby agricultural drain. In order to obtain the most economical system to provide a high quality effluent, an intensive treatability study was performed to evaluate effective methods of wastewater treatment. Coagulation using alum followed by sedimentation failed to produce an effluent which complied with the regulatory standards. Biological treatment using the mixed activated sludge process significantly removed the organic contaminants in wastewater. Average residual BOD, COD, oil and grease values were 30, 92 and 8.3 mg l- respectively. Design criteria A schematic flow diagram of the treatment plant is shown in Fig. 5. Q~ = Composite industrial wastewater flow, 46.5 m 3 h ; Q, = domestic sewage inflow to aeration tanks, 46.5 m 3 h-l; Q = combined domestic and industrial wastewater. BOD of composite industrial wastewater = mg ; BOD of domestic sewage = 600 mg l- ; BOD of combined wastewater mg -~. T l = Retention period in oil separation units (not less than 7min) = 2 rain; T2 = Retention period in aeration tanks, not less than 6 h. Sizing of oil and grease separation units 2 V= QI x TI One tank 8.0 x 4.0 x 3.0 m deep is required. Air under a pressure of 4.0 atm is supplied to the inflow at a rate to satisfy an air/solids ratio of Chemicats Waste p.r.v." ~ g Air S u p~. Retention Tank Raw ~ewage R'ecyciing Sludge Excess i Sludge ~. Flotation Unit ;- - Aeration Tank Fig. 5. Schematic flow diagram of treatment plant. - Sed,mentot,on Tank -*

10 22 Sizing of aeration tanks Sizing of the required treatment units by applying extended aeration and conventional system procedures led to the conclusion that the extended aeration system could be the most economical for this particulate waste. V=Q T~ Y = [(Y)(LR) (20000)/(MLVSS) (f) (Kd)] 8.333/000 where V = volume in m3; Y = yield, kg of cells produced per kg BOD removed = 0.50; LR = kg of BOD removed per day; MLVSS = mixed liquor volatile suspended solids (mg l-), common design value ppm, with the lower value being more conservative; f = the fraction of MLVSS that is biodegradable. A value of 0.90 is generally applicable for extended aeration plants; Kd = endogenous respiration coefficient (day -) = The value of MLVSS, in the equation, depends on the fraction of the daily flow that must be recycled (r), where r = Ct/(C, - Ct); Ct = concentration of MLVSS in aeration tank (mg -2); Cs = concentration of MLVSS in sludge from clarifier. Accordingly, two tanks are required each 26 m in length, 6.0 m wide and 3.2 m deep. Also, a clarifier 9.8m in diameter and 2.m in depth is required. REFERENCES Abo-Elela, S.I. and S. Nawar, 980. Treatment of wastewater from oil and soap factory via dissolved air flotation. Environ. Int., 4: Chin, K.K. and K.K. Wong, 98. Palm oil refinery wastes treatment. Water Res., 5: Eckenfelder, W.W., 966. Industrial Water Pollution Control. McGraw-Hill, New York. E-Gohary, F.A. and S.I. Abo El-Ela, 980. The Optimization of wastewater treatment via combined techniques. Part II: Combined biological~iissolved air flotation. Environ. Int., 3: Patterson, J.W., 975. Wastewater Treatment Technology. Ann Arbor Science Publishers, Ann Arbor, Michigan. Sengill, F., A. Muezzinoglu and B. Baysal, 982. Proc. Environmental Technology for Developing Countries, Bogazici University of Environmental Sciences and Technology, Istanbul, Turkey, ~4 July. Standard Methods for The Examination of Water and Wastewater, APHA, AWWA, WPCF, 5th edn. Washington, 980.