Performance evaluation of a field-scale pilot bioreactor for anaerobic treatment of palm oil mill effluent

•Combined system of anaerobic reactors was investigated to treat POME in Indonesia.•Initial start-up of this system failed due to shock loads of SS and OLR.•Around 70% of COD was removed at 6 kg m−3 day−1 of organic loading rate.•Addition of alkalinity was made at the initial start-up.

A combined system of anaerobic reactors was applied in a field-scale pilot bioreactor to treat palm oil mill effluent (POME) from the Amagra palm plantation in Sumatra Island, Indonesia. The initial start-up of this system failed due to shock loads of suspended solids, organics, and flow rates. After adjusting for influent conditions and operation variables, the second start-up successfully proceeded, where 70% of chemical oxygen demand (COD) was removed at 6 kg m−3 day−1 of the organic loading rate. Nutrients such as N or P were not added. An addition of alkalinity was made at the initial start-up and later found to be not necessary because amino and fatty acids were rapidly removed in this high rate system.