Optimization on thermophilic aerobic treatment of anaerobically digested palm oil mill effluent (POME)

This research is aimed at improving the thermophilic aerobic treatment system of anaerobically digested palm oil mill effluent (POME) through optimization of mixed liquor suspended solids (MISS) at high concentration range for the first time besides other parameters of organic loading rate (OLR), dissolved oxygen (DO) concentrations and settling time. Chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total suspended solids (TSS) removal ratios were measured as indicators of the system performance. Experimental results clearly indicate that MLSS and OLR are the crucial parameters in thermophilic aerobic treatment. Optimal COD, BOD and TSS removals up to 86%, 87% and 89%, respectively, were achieved with MLSS concentration and OLR of 27,000 mg/L and 2.5 gCOD/(L day), respectively. More significantly, high MLSS concentration range which is yet to be reported was successfully applied and this has resulted in superior performance as compared to other thermophilic treatment studies. No significant improvement of the treatment efficiency was attained with DO concentration exceeding 5 mg/L and settling time up to 24 h. Hence, operation at DO concentration of 2 mg/L and settling time of 2 h gives a good compromise between effluent quality and system operating costs. (C) 2011 Elsevier B.V. All rights reserved.