Sludge anoxic dermentation and denitrification（SAFD)system was established by adding NO-3-N into the typical sludge anaerobic fermentation system.In SAFD

denitrifiers can utilize the carbon source generated in waste activated sludge（WAS)fermentation for denitrification.This system was aimed at dealing with the carbon source shortage and WAS treatment difficulties in waste water treating plants（WWTPs).The results indicated that suspended solid（SS)and volatile suspended solid（VSS)decreased by 63.8% and 74.7%

respectively

presenting a remarkable effect in sludge reduction when SRT=60d.At the meantime

it showed a good denitrifying performance with complete removal of NO-3-N in the early period of the cycle.SAFD could achieve simultaneous fermentation and denitrification

indicating a better performance than typical anaerobic fermentation.Investigations into the denitrification rate during the cycle demonstrated that denitrification rate was higher in the early period（the 5th day）

while decreased gradually and denitrification was accompanied with the accumulation of volatile fatty acids（VFAs).Besides

pH and oxidation reduction potential（ORP)curves reflected the process capability level of fermentation and denitrification in SAFD system.Conclusions of this study could provide reference for technological upgrading of WWTPs.