The aim of this study is to demonstrate the denitrification potential enhancement determined by the addition of the anaerobic fermentation products from the organic fraction of municipal solid waste in BNR wastewater treatment plants. The denitrification potential rose from 6 to 17 mgNO3-N/l thanks to the good performances showed by the fermentation products in the denitrification step: a typical maximum denitrification rate of about 5 mgN/gVSS d was observed. This value is similar to those obtained by using pure organic substrates. The denitrification capacity increase is determined by a significant increase of S8 and Xs availability in the influent due to the anaerobic fermentation products addition which leads to an influent COD increase equal to 68% of the total load: this value is significantly higher than the one obtained by fermentation of primary and/or waste activated sludge (3-5%).