Simultaneous　sludge　fermentation　and　nitrite　removal　(SFNR)　was　investigated　as　a　novel　sludge/wastewater　treatment　process　with　high　nitrogen　concentrations.　The　results　showed　that　introducing　nitrite　improved　the　primary　sludge　(PS)　fermentation　system　by　improving　the　chemical　oxygen　demand　(COD)　yields　and　the　volatile　suspend　solid　(VSS)　reduction.　At　a　nitrite　dosage　of　0.2　g　g　SS-1,　the　COD　production　was　1.02　g　g　VSS-1　and　the　VSS　reduction　was　63.4%　within　7-day　fermentation,　while　the　COD　production　was　only　0.17　g　g　VSS-1　and　the　VSS　reduction　was　only　4.9%　in　the　blank　test.　Nitrite　contained　in　wastewater　was　removed　through　denitrification　process　in　the　SFNR　system.　The　solubility　of　carbohydrate　and　protein　was　substantially　enhanced,　and　their　contents　reached　the　peak　once　nitrite　was　consumed.　In　addition,　the　nutrient　release　and　methane　generation　were　inhibited　in　the　SFNR　system,　which　alleviated　the　environmental　pollution.　Unlike　traditional　fermentation　systems,　neither　alkaline　condition　nor　high　free　nitrite　acid　(FNA)　concentration　affected　the　PS　fermentation　in　the　SFNR　system.　Molecular　weight　distribution　(MWD)　and　Live/Dead　cell　analysis　indicated　that　the　sludge　disruption　by　nitrite　and　the　consumption　of　soluble　organic　substances　in　sludge　might　play　important　roles　in　SFNR.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.