Treatment and Reuse of Effluents from Palm Oil, Pulp, and Paper Mills as a Combined Substrate by Using Purple Nonsulfur Bacteria

The growth of Rhodobacter sphaeroides NCIMB8253 was investigated under photoanaerobic conditions with different concentrations of palm oil mill effluent in a dual effluent growth medium. The influence of pulp and paper mill effluent as an alternative diluting agent on the bacterial growth was also investigated. During this study, it was determined that the use of pulp and paper mill effluent as a diluting agent promoted bacterial growth compared with the use of raw palm oil mill effluent medium alone. The cell growth data for all experimental sets were well-fitted to the logistic and modified Gompertz models. The results revealed that 25% (v/v) palm oil mill effluent medium with pulp and paper mill effluent as a diluting agent, namely G5 medium, can be applied as a suitable growth medium. A maximum colony-forming-units (CFU) number of 360 × 10 8 CFU/mL was achieved in G5, which was higher than that for raw palm oil mill effluent and comparable with that for water-diluted palm oil mill effluent medium. Furthermore, chemical oxygen demand level (COD total and COD soluble ) reductions were observed in all treatments.