To save energy consumption in domestic wastewater treatment

three-stage autotrophic nitrogen removal process including organics removal SBR

partial nitrification SBR and anammox UASB was proposed.At room temperature of (26±1)℃

short-term effect of aeration rate and MLSS on organic removal process was investigated by seeding activity sludge taken from a pilot-plant reactor of partial nitrification.The results show that both concentrations of NO2--N and NO3--N were lower than 0.1 mg·L-1 at various aeration rates and sludge concentrations before the end of COD biodegradation stage.After that

the wastewater entered a difficult-degradating stage in reactor where COD concentration remained at nearly constant level and NO2--N and NO3--N concentrations accumulated rapidly and nitrifying-bacteria activity increased.Obviously

nitrification did not occur during the process removing organics under different aeration conditions.Therefore

under various conditions of aeration and sludge concentration the first organics was removed and then partial nitrification to remove NO3--N.However

for three-stage autotrophic nitrogen removal process

NO4+-N concentration could decrease from 11.6 mg·L-1 to 3.4 mg·L-1(TN loss)during organics removal process under aeration values of 100 L·h-1

60 L·h-1and 20 L·h-1.The peak point of pH profile and the inflexion of DO curve stayed the same with the end of removing organics throughout

and so they could be used as real-time control signals to indicate the end of organic removal process.