Simultaneous nitrification-denitrification and membrane fouling alleviation in a submerged biofilm membrane bioreactor with coupling of sponge and biodegradable PBS carrier.

•SND was achieved in SBF-MBR via coupling of sponge and biodegradable PBS.•NH4+-N and TN removal efficiencies in SBF-MBR were high of 99.1% and 94.3%.•EPS components were evaluated by chemical and fluorescent approaches.•Co-existence of nitrifier, heterotrophic denitrifiers and aerobic denitrifiers in bio-carries of SBF-MBR.