Systematic analysis of biomass characteristics associated membrane fouling during start-up of a hybrid membrane bioreactor using worm reactor for sludge reduction

► The effect of the worm reactor on microbial community development was investigated. ► The viability of sludge was slightly weakened with the predated sludge recycle. ► The microbial community was shifted with the predated sludge recycle. ► Changed EPS and SMP might be closely associated with microbial community. ► Microbial community shift might be responsible for improved membrane permeability.