Waste　activated　sludge　(WAS)　fermentation　integrated　with　denitritation　(the　reduction　of　nitrite　to　dinitrogen　gas)　at　different　pHs　was　investigated　in　batch-mode　reactors　over　a　24-day　period.　The　results　showed　that　in　comparison　with　controlled　pHs,　the　volatile　fatty　acid　(VFA)　bioproduction　for　in　situ　denitritation　was　significantly　improved　at　uncontrolled　pH.　VFA　fermented　from　WAS　was　quickly　consumed　by　denitritation　at　uncontrolled　pH,　which　accelerated　sludge　degradation.　On　the　other　hand,　sludge　digestion　was　benefited　from　the　alkalinity　produced　from　denitritation,　while　methanogenesis　was　prohibited　by　alkalinity　and　nitrite.　The　integrated　sludge　fermentation　and　denitritation　can　be　cost-effectively　applied　to　wastewater　treatment　plants,　so　that　organic　substrates　(e.g.,　VFAs)　are　produced　for　denitritation　via　simultaneous　sludge　fermentation,　which　enables　WAS　reutilization　and　enhances　nitrogen　removal　efficiency　without　the　need　of　external　carbon　sources.　(C)　2015,　The　Society　for　Biotechnology,　Japan.　All　rights　reserved.