Anaerobic treatment of palm oil mill effluent using combined high-rate anaerobic reactors

Combined system of high-rate anaerobic reactors for treating palm oil mill effluent (POME) was developed and investigated in this study. The system composed of one common primary hybrid reactor which was shared by two different secondary filter reactors. An overall COD removal efficiency of 93.5% was achieved in both systems. The secondary reactors contributed not only in enhancing the COD removal efficiency, but also ensured the performance stability of the entire system. Biomass remained intact in the secondary reactor in contrast to the primary reactor in which occasional washout of biomass was observed. The pH of POME was adjusted at the beginning of the operation, as the process continued POME did not require the external pH adjustment as the pH was maintained in desired range. The biogas was produced up to 110 l/d with the yield of 0.171–0.269 l [CH4]/g [COD removed] and 59.5–78.2% content of methane.

► The combined sequential anaerobic reactors were developed for POME treatment. ► Average COD removal of 93.5% was obtained with the OLR of 8.5–23 kg [COD]/m3/d. ► Maximum COD removal of 95.6% was achieved at 13 kg [COD]/m3/d OLR in primary AHR. ► The secondary reactors helped to improve the safety and performance of the system. ► Average methane yield of 0.171–0.269 l [CH4]/g [COD removed] was obtained.