Sustain. Environ. Res., 23(3), 153-170 (2013)
Yi-Jing Chan, Mei-Fong Chong and Chung-Lim Law
Optimization, anaerobic, aerobic, wastewater treatment, palm oil mill effluent (POME)
An optimization study on the simultaneous anaerobic and aerobic processes in an integrated anaerobic-aerobic bioreactor (IAAB) treatment system for palm oil mill effluent was conducted for the first time based on the response surface methodology. Three major constraints of the compliance to the Malaysian discharge standard (Biochemical Oxygen Demand (BOD) < 100 mg L-1), methane gas production (methane content > 60%) and stability of the IAAB (pH and total alkalinity of the anaerobic effluent > 7.0 and > 2,000 mg respectively) were considered in this study. The IAAB's treatment efficiency, methane gas production and process stability were comprehensively examined at different levels of three critical parameters (organic loading rates (OLR), MLVSS (mixed liquor volatile suspended solids) concentration in anaerobic (MLVSSan) and aerobic compartments (MLVSSa)). It is worth noting that the anaerobic Chemical Oxygen Demand (COD) removals affect considerably the overall treatment efficiency of IAAB, unless they are maintained under the appropriate range of 77 to 87%. The IAAB achieved highest overall COD, BOD and total suspended solids removal efficiencies of > 99% at optimum OLR of 12.8 g COD L-1 d-1, MLVSSan of 40,600 mg L-1, and MLVSSa of 18,700 mg L-1. The treated effluents were well below the discharge standard with BOD concentrations of 37 mg L-1. Further pilot scale studies are proposed before implementing into industrial practice.