The　partial　denitrification　(nitrate　to　nitrite)　has　been　a　promising　way　for　nitrate　wastewater　treatment　combined　with　ANAMMOX　system　subsequently.　This　work　investigated　the　effect　of　seeding　sludge　on　partial　denitrification　by　using　sludge　fermentation　liquid　as　carbon　source,　with　the　sludge　taken　from:　anoxic/oxic　reactor　(S-A),　anaerobic-anoxic-oxic　reactor　(SA-A-O)　and　alternately　anaerobic　sludge　fermentation　coupling　anoxic　denitrification　reactor　(SA-A).　The　results　showed　that　transient　accumulation　of　nitrite　was　observed　in　S-A　and　SA-A-O.　However,　at　the　initial　nitrate　concentration　of　30　mg/L,　a　high　nitrite　of　20.91　+/-　0.52　mg/L　was　accumulated　under　complete　nitrate　reduction　in　the　SA-A　system,　which　indicated　that　partial　denitrification　could　be　realized.　Furthermore,　as　much　as　80%　nitrate-to-nitrite　transformation　ratio　(NTR)　was　achieved　in　a　108-day　operation　with　inoculating　SA-A,　which　illustrated　the　stability　of　partial　denitrification　under　long-term　operation.　(C)　2013　Elsevier　Ltd.　All　rights　reserved.