Simultaneous nitrification and denitrification by EPSs in aerobic granular sludge enhanced nitrogen removal of ammonium-nitrogen-rich wastewater

•Nitrification and denitrification take place simultaneously.•Nitrogen in different forms was present in EPSs and underwent dynamic changes.•Biosorption affected the results of batch experiments.•Nitrosomonas eutropha and heterotrophic denitrifiers were identified of the AGS.

In this study, role of extracellular polymeric substances (EPSs) in enhancing nitrogen-removal from ammonium-nitrogen-rich wastewater using aerobic granular sludge (AGS) technology were analyzed. AGS enabled ammonium oxidation and denitrification to occur simultaneously. Air stripping and simultaneous nitrification–denitrification contributed to total-nitrogen removal. Clone-library analysis revealed that close relatives of Nitrosomonas eutropha and heterotrophic denitrifiers were dominant in the AGS, whereas anammox bacteria were not detected. EPSs adsorption of ammonium, nitrite, and nitrate nitrogen results in improved removal of nitrogen in batch experiments.