Effect of NOx--N Accumulation on Endogenous Denitrification of Aerobic Granular Sludge
Aerobic granular sludge(AGS)is capable of endogenous denitrification,and the utilization of its own carbon source for denitrification to potentially reduce the operational cost in the treatment of wastewater from rare earth mine.The effects of nitrite nitrogen(0～100 mg/L)and nitrate nitrogen(0～100 mg/L)accumulation on the endogenous denitrification of AGS were explored by single factor experiment.The seed AGS introduced ammonia nitrogen with concentration of 7～24 mg/L into the reactor.However,the AGS demonstrated good nitrification performance with the removal efficiencies of ammonia nitrogen all close to 100％under different accumulated concentrations of NOx--N.When the initial nitrite nitrogen was no greater than 10 mg/L,the removal efficiencies of total inorganic nitrogen(TIN)were between 44.39％and 77.6％.With the initial nitrite nitrogen further increasing to 100 mg/L,the removal efficiencies of TIN were less than 7.1％at the end of the reaction.When the initial nitrate nitrogen was no greater than 10 mg/L,the removal efficiencies of TIN were between 36.23％and 83.02％at the end of the reaction.As the initial nitrate nitrogen further increasing to 100 mg/L,the removal efficiencies of TIN were less than 4.38％at the end of the reaction.The overall nitrogen removal performance of AGS under nitrite nitrogen accumulation was better than that under nitrate nitrogen accumulation,mainly due to the lower dissolved oxygen under nitrite nitrogen accumulation environment.
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