Biopretreatment of palm oil mill effluent using thermotolerant micro organisms

Poonsuk Prasertsan, Assoc. Prof., D. of Industrial Biotech., F. of Agro-Industry, PSU.
Monticha Petsuit, M. Phil. Student in Environment, King Mongkut U. of Tech. Thonburi, Bangkok
Saithong Kaewchai, M. Phil. Student in Environment, King Mongkut U. of Tech. Thonburi, Bangkok
Siribhorn Madla, M.Sc. Student in Biotech., PSU.
Masao Ukita, Prof., D. of Civil Eng., Yamaguchi U., Yamaguchi, Japan
Tsuyoshi Imai, Assoc. Prof., D. of Civil Eng., Yamaguchi U., Yamaguchi, Japan
Corresponding e-mail : ppoonsuk@ratree.psu.ac.th

Grant : Joint Graduate School of Energy and Environment (JGSEE), KMUTT
Presented : The 2nd Joint Seminar on Development of Thermotolerant Microbial Resources and their Applications, 21-25 November 2000, Yamaguchi, Japan
Key words : biopretreatment, effluent, palm oil mill, thermotolerant

Thermotolerant microorganism is defined as those that can grow both at 30oC as well as 45oC or up to 60oC. A total of fifty-four thermotolerant polymer-producing bacteria were isolated from fifty-one samples taken from wastewater of six seafood processing plants and Hat Yai Manicipal wastewater treatement plant as well as a hot spring (54oC). The culture broth of these strains were tested for flocculating property. Three isolates, strain KF 4.1, WD 90 and SK 4.1 were found to possess very high flocculating activities of 24.8, 14.6 and 10.8 with the flocculating rate of 94.3%, 90.7% and 87.4%, respectively.
Palm oil industry is one of the major agro-industry in Southern Thailand. There are about 45 palm oil mills where about 80% of oil palm fruit brunches are extracted by standard (or wet) process. The quantity of palm oil mill effluent (POME) is enormous and generated from two major sources; sterilizer and decanter (or separator) with the volume of about 0.9 and 1.5 m3/t oil extracted, respectively. The characteristics of POME were analysed and the average volume were as followed : pH 4.5, BOD 46,542 mg/l, COD 95,000 mg/l, total solids 60,115 mg/l, suspended solids 39,145 mg/l, oil&grease 16,970 mg/l, total alkalinity 12.4 mg/l, and total acidity 612 mg/l. The data illustrated that the POME contained very high unsettleable solids due to the emulsion property. The effect of pre-treatment using the polymer-producing bacteria and fungi to separate the solids from the POME was investigated. The isolates KF 4.1, WD 90 and SK 4.1 cultivating in POME were able to flocculate the solids as well as decolorize the POME from dark brown to very light yellow. The POME was also pretreated using two fungal isolates, ST 4 and ST 29, cultivated both at 45-55oC and room temperature under septic and aseptic conditions. The isolate ST 4 gave higher COD removal (63.6%) under septic condition at 45oC. The highest removal of oil&grease by ST 4 and ST 29 were achieved from cultivation under aseptic condition at 45oC. The supernatant from these cultures would be further treated by anaerobic digestion process.
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