Treatment of Synthetic Palm Oil Mill Effluent (POME) Using AnMBR: Biological and Filtration Performance

Abstract

Palm oil mill effluent (POME) is a high organic pollution produced during the palm oil mill process, with a brownish color and stingy odor at high temperatures. Given the popularity in palm oil output over the years, the massive amount of POME causes growing concern. The enforcement of wastewater discharge standards and laws, as well as energy recycling of sustainability goals have facilitated the development of POME treatment processes. Several lab-scale studies have looked into the treatment of industrial wastewater using anaerobic membrane bioreactor (AnMBR) which has received considerable research interest due to its demonstrated potential for POME treatment. In this study, the synthetic POME was treated by a lab-scale crossflow anaerobic membrane bioreactor system. This study tested the feasibility of thermophilic PVDF-AnMBR systems for synthetic POME treatment, and meanwhile evaluated the biological and filtration performance of AnMBR treating lipid-rich wastewater at different sludge retention times (SRTs = 60 days, 90 days, and 140 days). AnMBR showed an adequate biological performance during the stabilizing state. The synthetic POME could be treated with over 98% of COD removal efficiency in all operational conditions. Plus, better digestion efficiency could be achieved at higher SRT (140 days). However, this study stresses that even though the membrane ensures biomass retention, the AnMBR process is still dodged by long-chain fatty acid (LCFA) accumulation and inhibition problems, especially at short SRT (60 days). The continuous reduction of biomass concentration during the stabilizing process of SRT at 60 days eventually resulted in the decreased methane production and system instability. Under all operational conditions, sufficient filtration performance and net permeate fluxes between 8 and 11 LMH were achieved. The trans-membrane pressure (TMP) was under 200 mbar throughout operating process. No membrane cleaning was needed. The results showed that better sludge filterability could be achieved at SRT of 90 days. The sludge filterability was compared as per the standard methods, including specific resistance to filtration and capillary suction time, which did not show a linear relationship with SRTs. Meanwhile, the physical-chemical characteristics of the sludge during the operational phases, including TSS concentrations and SMP, have a close correlation with sludge filterability parameters, such as capillary suction time and supernatant filterability.