Partial　denitrification　(PD)　is　another　important　pathway　producing　nitrite　for　anammox,　however,　whether　its　performance　is　affected　by　overlong　reaction　time,　a　situation　that　often　takes　place　is　still　unknown.　Three　sequencing　batch　reactors　were　operated　for　PD　to　evaluate　this　factor　on　nitrite　production.　Results　indicated　effluent　nitrite　was　very　close　despite　reaction　time　even　extending　to　four　times　longer　than　control　(i.e.,　nitrate　-to-nitrite　transformation　ratio　(NTR)　of　94.4%-89.8%).　Meanwhile,　it　was　found　PD　could　recover　to　the　normal　after　suffering　from　high　organics　shocking.　Cycle　studies　suggested　produced　nitrite　would　not　be　further　reduced　with　prolonged　time,　as　indicated　by　changing　trend　of　pH　and　alkalinity.　Microbial　analysis　revealed　PD　functional　bacteria,　Thauera,　slightly　decreased　with　prolonged　reaction,　while　it　was　always　predominated.　Taken　together,　this　study　indicated　overlong　reaction　time　had　minor　influence　on　PD,　demonstrating　its　robustness　with　great　technological　superiority　in　supplying　nitrite　for　anammox.