Enhanced nitrogen removal from sludge dewatering liquor by simultaneous primary sludge fermentation and nitrate reduction in batch and continuous reactors

► We use primary sludge as the carbon source to enhance nitrogen removal of reject water in a novel system. ► Good nitrogen removal could be accomplished with the co-occurrence of sludge fermentation and denitrification. ► The degradation of primary sludge was accelerated by the existence of nitrate. ► The decrease of ammonia is observed in sludge fermentation process when nitrate is added. ► Integration of fermentation and denitrification are more attractive than conventional fermentation-elutriation.