Mechanical pretreatment processes for enhancement of biogas production from palm oil mill effluent (POME)

Various pretreatment methods including ultrasonication, coalescer filtration, and dissolved air flotation (DAF) have been investigated for palm oil mill effluent (POME) treatment prior to the biogas system. These methods showed significant improvement in the biodegradability characteristics of POME in comparison with non-pretreatment. Their efficiencies were determined by measuring the biochemical oxygen demand (BOD)/total chemical oxygen demand (TCOD) ratio, soluble chemical oxygen demand (SCOD)/TCOD ratio, and reducing sugar content, as well as TCOD removal, fat, oil and grease removal, and biomethane production. Ultrasonication, coalescer, and DAF increases oil removal efficiencies by 50.30%, 53.13%, and 68.21%, respectively. The results found that the BOD/TCOD and SCOD/TCOD values for POME were increased slightly by pretreatment methods, but remained within the range for biodegradable values. While the coalescer and DAF increased the reducing sugar content in POME from 4.36 to 4.80 g/L and 4.36 to 4.40 g/L, respectively, sonication can increase it by nearly double, from 4.36 to 8.12 g/L. Maximum methane production was 3.05 LCH 4 /L POME and a methane production rate of 88.52 LCH 4 /day was also found with ultrasonication.