Urine source separation-based pretreatment: A sustainable strategy for improving methane production from anaerobic digestion of waste activated sludge

Urine wastewater derived from source separation technology was employed to pretreat waste activated sludge (WAS) for anaerobic digestion in this study. In comparison to the control group, cumulative methane production was identified to be improved by 23% after pretreated by urine wastewater with its volumetric proportion of 1:8. Urea and hydrolyzed free ammonia (FA) in urine wastewater were observed to pose a synergistic effect on sludge disintegration, benefiting the reduction of sludge volume and enrichment of available substrates for bio-processes. Analysis of microbial community further revealed that acid-producing microbes were enriched in the experimental digesters. Although FA was found to be the major inhibitor to several microbial stages, metal ions supplemented by urine pretreatment might have alleviated such suppression. The proposed strategy would pave a more sustainable way for sludge pretreatment with waste materials. © 2022 The Author(s)