Effect of coagulation-sedimentation pretreatment on methane production from Indonesian palm oil mill effluent and kinetics

The current study purposed to investigate the influence of coagulation-sedimentation (CS) pretreatment on methane production from Indonesian palm oil mill effluent (POME). In the CS pretreatment, the coagulation process was conducted for 2 h at various alum doses (2, 4, 6, and 8 g/L), followed by the sedimentation process for 24 h to separate sludges from supernatants. Then, supernatants were used as methane feedstocks. The CS pretreatment with an alum dose of 6 g/L generated the highest reduction in chemical oxygen demand (COD) of 70.02 %. The anaerobic digestion (AD) of supernatant resulting from CS pretreatment with an alum dose of 6 g/L generated 8-fold higher methane production than the AD of raw POME. In kinetic analyses, the modified Gompertz model had a higher accuracy (R2 of 0.9938) in predicting methane yield evolution than the first-order model and the Cone model (R2 of 0.9449 and 0.9923).