TREATMENT OF PALM OIL MILL EFFLUENT BY UPFLOW ANAEROBIC FILTRATION

An upflow anaerobic filter (23 dm(3) working volume) was used for the treatment of palm oil mill effluent. The filter was continuously opera ted for 215 days with organic loads ranging from 1.2 to 11.4 kg of che mical oxygen demand per cubic metre per day and hydraulic retention ti mes from 15 to 6 days. The overall substrate removal efficiency was ve ry high, up to 90% and the filter effluent contained almost no suspend ed solids. For all runs, the operation of the filter exhibited good st ability for acidity and alkalinity, indicating that the use of buffer solutions would not be required. The methane concentration in the biog as, whose production varied from 20 to 165 dm(3) per day, was about 60 %. Daily gas production varied in the range 0.69-0.79 dm(3) per gram o f chemical oxygen demand removed.