Start-up and treatment of palm oil mill effluent with upflow anaerobic sludge blanket reactors

Anaerobic treatment of palm oil mill effluent (POME) was carried out in 1 liter and 30 litres upflow anaerobic sludge blanket (UASB) reactors at 30 degrees C. The anaerobic sludge was successfully pre-granulated prior to feeding of POME. In the 1 liter reactor, when 100% POME, corrected to pH 7.0, was fed into the reactor, the organic loading rate (OLR) was increased stepwise from 7-20kgCOD/m(3) day. At an OLR of 13kgCOD/m(3) day, 95% chemical oxygen demand (COD) removal was achieved. When the OLR was raised to 17kgCOD/m(3) day, COD conversion reduced to 80% and at 20kgCOD/m(3) day, there was a sudden decrease in pH to 6.0 accompanied by reduced biogas production and COD removal leading to reactor failure. When the process was scaled-up to a 30 litres UASB reactor, there was 95% COD removal efficiency even at an OLR of 18kg COD/m(3) day. When the OLR was increased to 20kg COD/m(3) day reactor failure eventually occured. From the results of this study, the UASB bioreactor system could effectively treat the COD in POME up to 18kg COD/m(3) day successfully.