Membrane bioreactor for the tertiary treatment of palm oil mill effluent

Abstract

A ponding system comprising of anaerobic and aerobic ponds is currently used to treat palm oil mill effluent (POME). However, the effluents are still coloured and do not comply with the limits set by the Department of Environment (DOE), Malaysia. This study investigates the feasibility of using a Membrane Bioreactor (MBR) as the tertiary treatment. The study was conducted by using wastewater from the Facultative Pond 1 (FP1) and the Facultative Pond 3 (FP3) of PPNJ Palm Oil Mill in Kahang. Initially, the effluents from the ponding system were characterized and an in-depth Chemical Oxygen Demand (COD) fractionation study was conducted on the effluents of FP1 and FP3. The effluents were then treated using a lab-scale MBR system and the effect of powder activated carbon (PAC) on the system performance was evaluated. The characterization of the effluent showed the reduction of the pollutants concentration as the wastewater passed through the ponds arranged in series. From COD fractionation analysis, the biodegradable:non-biodegradable fractions (in %) of FP1 and FP3 were 29:71 and 26:74, respectively. The readily biodegradable fraction in the FP1 was much higher than the FP3, which was 17% and 3.2%, respectively. The average COD removal during the MBR treatment was 87% and 68% for the FP1 and the FP3, respectively. However, the observation on the transmembrane pressure (TMP) behaviour showed that membrane fouling tend to occur quickly during MBR treatment of the FP1 as compared to the FP3 POME. The addition of PAC as the biofouling reducer (BFR) into the MBR improved its performance. The removal of organics with the addition of PAC was 92% and 86% for FP1 and FP3, respectively. The colour residual in the permeate for the FP1 and the FP3 were significantly reduced after the addition of PAC and the time for a membrane before it started to foul was also increased. The study showed the possibility of using an MBR as the tertiary treatment of POME for a better effluent quality.