Palm Oil Fuel Ash-Enhanced Biofilm Reactor: Performance and Microbial Dynamics in POME Treatment

The rapid growth of the palm oil industry produces large amounts of palm oil mill effluent (POME), which contains high organic content and is challenging to treat using conventional ponding systems. These traditional systems often fail to meet discharge standards for biochemical oxygen demand (BOD) and chemical oxygen demand (COD). This study tested anaerobic biofilm reactors enhanced with biochips and chemically treated palm oil fuel ash (TPOFA) to improve POME degradation and biogas production. Two 3 L reactors were operated at the same feed-to-microorganism (F/M) ratio: a control (C) and a combination of both (P + B). Biochips helped microbes attach and form biofilms, while TPOFA acted as an adsorbent, creating better conditions for anaerobic breakdown. The P + B reactor outperformed others, achieving over 95% COD removal, high microbial biomass (MLVSS: 24,500 mg/L), and the highest biogas yield at 917 mL per day. Microbial analysis showed dominant groups, including phyla groups of Halobacterota, Bacteroidota, and Firmicutes. Class Methanosarcina in archaeal phylum of Halobaterota was key in converting acetate to methane. Bacteroidota primarily aided organic matter breakdown and nutrient removal, while Firmicutes supported hydrolysis and electron transfer. Less abundant Desulfobacterota also helped by interacting with methanogenic archaea. Overall, combining biochips with TPOFA in anaerobic biofilm reactors offers an effective, sustainable method for treating POME and recovering renewable energy through biogas.