Impacts of lipids on the performance of anaerobic membrane bioreactors for food wastewater treatment

Abstract

This study investigated the resistance of anaerobic membrane bioreactor (AnMBR) to lipid gradients during food wastewater treatment. Sodium oleate (oleate-Na) was added to synthetic food wastewater to simulate lipids. Results show that AnMBR could adapt to a certain content of lipids by stimulate biomass growth and activity. As the dosage of oleate-Na increased from 0 to 2 g/L, the removal of total organic carbon (TOC) decreased for several days and then recovered back to above 90%. Such a decrease and increase profile was also observed for biogas production and methane yield, which stabilized at 0.61 and 0.41 L/gCOD, respectively, after oleate-Na addition was maintained at 2 g/L for 13 days. Nevertheless, further addition of 4 g/L oleate-Na led to system failure with a reduction of TOC removal and biogas production from 92% to 62% and from 0.61 L/gCOD to 0.083 L/gCOD, respectively, given a significant accumulation of volatile fatty acids to 2940 mg/L. Further microbial analysis showed that the genus Methanosaeta enriched to 50% with 2 g/L oleate-Na addition and thus contributed to the recovery of methane production. By contrast, adding 4 g/L oleate-Na inhibited the proliferation of the genus Methanosarcina to reduce organic biodegradation and then methane production.