World Journal of Microbiology & Biotechnology 10, 11-13
Anaerobic filter treatment of fishery wastewater P. Prasertsan,* S. Jung and K.A. Buckle Anaerobic treatment of wastewater from a selected seafood processing plant was conducted at organic loading rates (OLR) ranging from 0.3 to 1.8 kg chemical oxygen demand (COD)/m3.day and hydraulic retention times (HRT) ranging from 36 to 6 days. COD reduction decreased with increasing OLR. More than 75% COD reduction could be maintained up to an OLR of about I kg COD/m3.day with an HRT of 11 days. An OLR of 1.3 kg COD/m3.day corresponding to an HRT of 6.6 days gave maximal biogas productivity of 1.5 m3/m3.day or 1.3 m 3 biogas/kg COD with a 65% COD reduction. If the HRT was kept constant at 11 days, an OLR of 1.3 kg COD/m3.day achieved maximal biogas productivity (1.1 m3/m3.day) and yield (0.75 m3/kg COD) and a 60% COD reduction for treatment of tuna condensate. Key words: Anaerobic digestion, biogas, fishery waste, wastewater.
Thailand has earned more than 50,000 million Baht (approx. US $2 billion) annually from exports of seafood and seafood products in the last 5 years and the demand is still increasing. There are more than 40 seafood processing factories in Southern Thailand. In the Songhkla region alone, the amount of wastewater from each factory ranges from 300 to 500 m3/day (Prasertsan et al. 1988). Wastewater treatment systems operating in this region at present are activated sludge, aerated lagoon, oxidation pond and anaerobic lagoon, but no anaerobic reactors. The latter have only been employed in Central Thailand using wastewaters from tapioca starch and distillery factories (Tantichareon eta[. I986).
Materials and Methods Wastewater Characteristics Wastewater samples were collected, from the centre of collecting tanks receiving wastewater from discharge lines of two local canning companies (see Table I), twice daily for 10 working days. Samples were analysed for biological (BOD) and chemical oxygen demand (COD), pH, alkalinity, total solids, total nitrogen, phosphorus, chloride and grease (American Public Health P. Prasertsan and S. Jung are with the Department of Agro-lndustry, Faculty of Natural Resources, Prince of Songkta University, Hatyai 90110, Thailand ; fax: + 66-74-212823. K.A~ Buckle is with the Department of Food Science and Technology, University of New South Wales, Kensington, NSW 2033, Australia. *Corresponding author.
Association 1985). Heavy metals and cations were determined by atomic absorption spectrophotometry. Anaerobic Filter-treatment of Fishery Wastewater Tuna condensate was obtained from another source and also analysed as described above. At start-up of the bioreactor, 500 ml of sludge from an anaerobic lagoon of a seafood processing plant was added to a 2.5-1 glass bottle and 200 ml wastewater was added every 3 days for at least 6 weeks. The acclimatized wastewater was then transferred to a 5-1 acrylic reactor (12.8 cm diam. x 37.5 cm high) with a working volume of 3.2 1 filled with PVC rings (1.63 cm diam. x 1.80 cm long). The digester was operated at ambient temperature (30 to 35°C). Wastewater (200 ml) was fed every 3 days until all PVC rings were submerged, which took 6 weeks. The anaerobic digestion in the reactor was initiated at an organic loading rate (OLR) of 0.30 kg COD/m3.day and hydraulic retention time (HRT) of 36 days for the wastewater, while the values of OLR and HRT for tuna condensate were 0.99 kg COD/m3.day and 11 days, respectively. Prior to each feeding, the digester was thoroughly mixed via the loop at the reactor side for about i0 min and a fixed volume of effluent was withdrawn and replaced with an equal amount of the influent.
Results and Discussion The chemical composition of wastewater from the two seafood processing factories is presented in Table I. Organic loading rates (OLR) had a great influence on the biodegradation of organic matter in the wastewater,
© 1994 Rapid Communications of Oxford Ltd World Journal of Microbiology & Biotechnology, Vo] lO, 2994
11
P. Prasertsan, S. ]ung and K.A. Buckle Table 1. Characteristics of the wastewaters from two seafood processing factories. Wastewater characteristic
Tropical Canning Cod
Royal Canning Co.* Tuna pre-cooking
pH Alkalinity (mg CaCOdl) Total solids (mg/I) Volatile solids (mg/I) Settleable solids (ml/I) Grease (mg/I) BOD (mg/I) COD (mg/I) Total nitrogen (mg/I) Phosphorus (mg/I) Chloride (mg NaCI/I)
5.8 319 6259 4445 48 2822 11874 46955 456 43 493
Canning process
64 630 12375 6711 19 2834 7460 10582 703 44 4103
Freezing process
64 200 5985 1959 9 1002 1733 3320 207 41 3977
69 90 4998 1464 3 662 814 1472 126 32 3319
* Mean values of 30 samples t Mean values of 20 samples.
reflected in the biogas productivity and the profiles of pH and volatile fatty acids (Figure I). The highest COD reduction (84%) was obtained at the minimum OLR (0.3 kg COD/m3.day) and maximum HRT (36 days). The higher the OLR, the lower the COD reduction efficiency. The highest loading rate in which the system still maintained its high conversion efficiency (over 78% COD reduction) was 0.99kg COD/m3.day at an HRT of 11 days. This corresponded well with the stability of pH and volatile fatty acid levels. At an OLR of 1.2 kg COD/m3.day and an HRT of 9.2 days, COD reduction was only 68%, with the pH decreasing below 7.2. The concentration of volatile fatty acids should be less than 0.5 g/1 at pH 7.0 in order to
i
prevent system failure (Halbert 198I), as too high concentrations are toxic to the microbial population (FoMay & Greenfield I982). The cause of the accumulation is either too high an organic loading rate or insufficient nitrogen concentration, since the COD/N ratio was over I00:2. The changes in mineral concentrations in the influent and effluent during the anaerobic digestion were also studied (data not shown). All values were far below reported toxic levels (Halbert 1981; Anderson et al. I982). The results of the anaerobic treatment of tuna condensate are presented in Figure 2. Feed condensate was taken from large-size tuna and therefore contained a high content of volatile acids (3.34 g/l). The COD reduction was maintained at 60% up to an OLR of 1.67 kg COD/m3.day and sharply decreased thereafter. Biogas productivity was highest at an OLR of 1.3I kg COD/m3.day, with the pH of the effluent
90
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-4
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5.8
Hydraulic retention time (days)
Figure 1. Anaerobic filter treatment of seafood processing wastewater (Royal Canning Co.--see Table 1) at different organic loading rates and hydraulic retention t i m e s O - - C O D reduction; O - - b i o g a s productivity; I-I--volatile acids; /k--pH.
12
World Journal of Microbiology & Biotechnology, Vol I0, 1994
OL
;'0'.8
1'.2
1 ~6
N >
2'.0
Organic loading (kg COD/m~day)
Figure 2. Anaerobic filter treatment of tuna condensate at different organic loading rates and hydraulic retention times. O ~ O D reduction; O - - b i o g a s productivity; 17--volatile acids; A--pH.
Anaerobic filter treatment 7.68. The biogas yield decreased with a further increase in OLR. An OLR of 2.00 kg COD/m3.day initiated system failure as the pH decreased and the volatile fatty acid concentration increased two-fold. Biogas production stopped completely at an OLR of 2.5 kg COD/m3.day.
Acknowledgements The authors wish to thank the Thai-Australia Prince of Songkla University Project and the Faculty of Natural Resources for financial support.
References American Public Health Association 1985 Standard Methods for the Examination of Water and Wastewater, 16th edn. Washington DC: APHA.
Anderson, G.K., Donelly, T. & McKeuwan, K.J. 1982 Identification and control of inhibition in the anaerobic treatment of industrial wastewater. ProcessBiochemistry 4, 28-41. Forday, W. & Greenfield, P.F. 1982 The role of anaerobic digestion in wastewater treatment. In Anaerobic Digestion--Recent Developments in Technology and Control, ed Halbert, E. pp. 1-15. University of Sydney: Department of Chemical Engineering. Halbert, E.J. 1981 Process operation and monitoring: poisons and inhibitors. In Proceedingsof the 1st ASEAN Seminar Workshop on Biogas Technology, pp. 369-385. Manila: ASEAN Committee on Science and Technology. Prasertsan, P., Wuttijumnong, P., Sophanodora, P. & Choorit, W. 1988 Seafood processing industries within Songkhla-Hatyai region: the survey of basic data emphasis on wastes. Songklanakarin Journal of Science and Technology 10, 447-451. Tantichareon, M., Lerttriluck, S., Bhumiratana, S. & Supajanya, N. 1986 Biogas production from tapioca starch wastewater. In
Proceedings of a Regional Training Workshop on Energy from Biomass, Bangkok, Thailand, 3 to 7 March 1986, pp. 523-544. Thonburi, Thailand: Mongkut's Institute of Technology.
(Received in revised form 10 May 1993; accepted I7 May I993)
World Journal of Microbiology & Biotechnology, Vot 10, I994
13
Anaerobic filter treatment of fishery wastewater P. Prasertsan,* S. Jung and K.A. Buckle Anaerobic treatment of wastewater from a selected seafood processing plant was conducted at organic loading rates (OLR) ranging from 0.3 to 1.8 kg chemical oxygen demand (COD)/m3.day and hydraulic retention times (HRT) ranging from 36 to 6 days. COD reduction decreased with increasing OLR. More than 75% COD reduction could be maintained up to an OLR of about I kg COD/m3.day with an HRT of 11 days. An OLR of 1.3 kg COD/m3.day corresponding to an HRT of 6.6 days gave maximal biogas productivity of 1.5 m3/m3.day or 1.3 m 3 biogas/kg COD with a 65% COD reduction. If the HRT was kept constant at 11 days, an OLR of 1.3 kg COD/m3.day achieved maximal biogas productivity (1.1 m3/m3.day) and yield (0.75 m3/kg COD) and a 60% COD reduction for treatment of tuna condensate. Key words: Anaerobic digestion, biogas, fishery waste, wastewater.
Thailand has earned more than 50,000 million Baht (approx. US $2 billion) annually from exports of seafood and seafood products in the last 5 years and the demand is still increasing. There are more than 40 seafood processing factories in Southern Thailand. In the Songhkla region alone, the amount of wastewater from each factory ranges from 300 to 500 m3/day (Prasertsan et al. 1988). Wastewater treatment systems operating in this region at present are activated sludge, aerated lagoon, oxidation pond and anaerobic lagoon, but no anaerobic reactors. The latter have only been employed in Central Thailand using wastewaters from tapioca starch and distillery factories (Tantichareon eta[. I986).
Materials and Methods Wastewater Characteristics Wastewater samples were collected, from the centre of collecting tanks receiving wastewater from discharge lines of two local canning companies (see Table I), twice daily for 10 working days. Samples were analysed for biological (BOD) and chemical oxygen demand (COD), pH, alkalinity, total solids, total nitrogen, phosphorus, chloride and grease (American Public Health P. Prasertsan and S. Jung are with the Department of Agro-lndustry, Faculty of Natural Resources, Prince of Songkta University, Hatyai 90110, Thailand ; fax: + 66-74-212823. K.A~ Buckle is with the Department of Food Science and Technology, University of New South Wales, Kensington, NSW 2033, Australia. *Corresponding author.
Association 1985). Heavy metals and cations were determined by atomic absorption spectrophotometry. Anaerobic Filter-treatment of Fishery Wastewater Tuna condensate was obtained from another source and also analysed as described above. At start-up of the bioreactor, 500 ml of sludge from an anaerobic lagoon of a seafood processing plant was added to a 2.5-1 glass bottle and 200 ml wastewater was added every 3 days for at least 6 weeks. The acclimatized wastewater was then transferred to a 5-1 acrylic reactor (12.8 cm diam. x 37.5 cm high) with a working volume of 3.2 1 filled with PVC rings (1.63 cm diam. x 1.80 cm long). The digester was operated at ambient temperature (30 to 35°C). Wastewater (200 ml) was fed every 3 days until all PVC rings were submerged, which took 6 weeks. The anaerobic digestion in the reactor was initiated at an organic loading rate (OLR) of 0.30 kg COD/m3.day and hydraulic retention time (HRT) of 36 days for the wastewater, while the values of OLR and HRT for tuna condensate were 0.99 kg COD/m3.day and 11 days, respectively. Prior to each feeding, the digester was thoroughly mixed via the loop at the reactor side for about i0 min and a fixed volume of effluent was withdrawn and replaced with an equal amount of the influent.
Results and Discussion The chemical composition of wastewater from the two seafood processing factories is presented in Table I. Organic loading rates (OLR) had a great influence on the biodegradation of organic matter in the wastewater,
© 1994 Rapid Communications of Oxford Ltd World Journal of Microbiology & Biotechnology, Vo] lO, 2994
11
P. Prasertsan, S. ]ung and K.A. Buckle Table 1. Characteristics of the wastewaters from two seafood processing factories. Wastewater characteristic
Tropical Canning Cod
Royal Canning Co.* Tuna pre-cooking
pH Alkalinity (mg CaCOdl) Total solids (mg/I) Volatile solids (mg/I) Settleable solids (ml/I) Grease (mg/I) BOD (mg/I) COD (mg/I) Total nitrogen (mg/I) Phosphorus (mg/I) Chloride (mg NaCI/I)
5.8 319 6259 4445 48 2822 11874 46955 456 43 493
Canning process
64 630 12375 6711 19 2834 7460 10582 703 44 4103
Freezing process
64 200 5985 1959 9 1002 1733 3320 207 41 3977
69 90 4998 1464 3 662 814 1472 126 32 3319
* Mean values of 30 samples t Mean values of 20 samples.
reflected in the biogas productivity and the profiles of pH and volatile fatty acids (Figure I). The highest COD reduction (84%) was obtained at the minimum OLR (0.3 kg COD/m3.day) and maximum HRT (36 days). The higher the OLR, the lower the COD reduction efficiency. The highest loading rate in which the system still maintained its high conversion efficiency (over 78% COD reduction) was 0.99kg COD/m3.day at an HRT of 11 days. This corresponded well with the stability of pH and volatile fatty acid levels. At an OLR of 1.2 kg COD/m3.day and an HRT of 9.2 days, COD reduction was only 68%, with the pH decreasing below 7.2. The concentration of volatile fatty acids should be less than 0.5 g/1 at pH 7.0 in order to
i
prevent system failure (Halbert 198I), as too high concentrations are toxic to the microbial population (FoMay & Greenfield I982). The cause of the accumulation is either too high an organic loading rate or insufficient nitrogen concentration, since the COD/N ratio was over I00:2. The changes in mineral concentrations in the influent and effluent during the anaerobic digestion were also studied (data not shown). All values were far below reported toxic levels (Halbert 1981; Anderson et al. I982). The results of the anaerobic treatment of tuna condensate are presented in Figure 2. Feed condensate was taken from large-size tuna and therefore contained a high content of volatile acids (3.34 g/l). The COD reduction was maintained at 60% up to an OLR of 1.67 kg COD/m3.day and sharply decreased thereafter. Biogas productivity was highest at an OLR of 1.3I kg COD/m3.day, with the pH of the effluent
90
7.4
80
7.0
70:
1.6
2.0
100r
7.8
1.2
1.6
80!-
7.4
2.0 ~ ~
1.6 1.2
g 60
~£ 0.8
0.8 so
E E v
{ 7.0 12
1.2
>,
._~ m
0.4
0.4
_>
40 0 0
0.8
40
0.4
20[
cD.
2.0 0.4 0.8 1.2 1.6 Organic loading rate (kg COD/m3.day)
-4
rn
36
17 21
11
9.2 6.6
5.8
Hydraulic retention time (days)
Figure 1. Anaerobic filter treatment of seafood processing wastewater (Royal Canning Co.--see Table 1) at different organic loading rates and hydraulic retention t i m e s O - - C O D reduction; O - - b i o g a s productivity; I-I--volatile acids; /k--pH.
12
World Journal of Microbiology & Biotechnology, Vol I0, 1994
OL
;'0'.8
1'.2
1 ~6
N >
2'.0
Organic loading (kg COD/m~day)
Figure 2. Anaerobic filter treatment of tuna condensate at different organic loading rates and hydraulic retention times. O ~ O D reduction; O - - b i o g a s productivity; 17--volatile acids; A--pH.
Anaerobic filter treatment 7.68. The biogas yield decreased with a further increase in OLR. An OLR of 2.00 kg COD/m3.day initiated system failure as the pH decreased and the volatile fatty acid concentration increased two-fold. Biogas production stopped completely at an OLR of 2.5 kg COD/m3.day.
Acknowledgements The authors wish to thank the Thai-Australia Prince of Songkla University Project and the Faculty of Natural Resources for financial support.
References American Public Health Association 1985 Standard Methods for the Examination of Water and Wastewater, 16th edn. Washington DC: APHA.
Anderson, G.K., Donelly, T. & McKeuwan, K.J. 1982 Identification and control of inhibition in the anaerobic treatment of industrial wastewater. ProcessBiochemistry 4, 28-41. Forday, W. & Greenfield, P.F. 1982 The role of anaerobic digestion in wastewater treatment. In Anaerobic Digestion--Recent Developments in Technology and Control, ed Halbert, E. pp. 1-15. University of Sydney: Department of Chemical Engineering. Halbert, E.J. 1981 Process operation and monitoring: poisons and inhibitors. In Proceedingsof the 1st ASEAN Seminar Workshop on Biogas Technology, pp. 369-385. Manila: ASEAN Committee on Science and Technology. Prasertsan, P., Wuttijumnong, P., Sophanodora, P. & Choorit, W. 1988 Seafood processing industries within Songkhla-Hatyai region: the survey of basic data emphasis on wastes. Songklanakarin Journal of Science and Technology 10, 447-451. Tantichareon, M., Lerttriluck, S., Bhumiratana, S. & Supajanya, N. 1986 Biogas production from tapioca starch wastewater. In
Proceedings of a Regional Training Workshop on Energy from Biomass, Bangkok, Thailand, 3 to 7 March 1986, pp. 523-544. Thonburi, Thailand: Mongkut's Institute of Technology.
(Received in revised form 10 May 1993; accepted I7 May I993)
World Journal of Microbiology & Biotechnology, Vot 10, I994
13
