In this study

a sequencing batch reactor (SBR) was used to treat domestic wastewater

and the optimal aeration rate and time to realize partial nitritation (PN

NH4+-N was partially converted to NO2--N) were obtained through three preliminary tests. A long-term PNSBR was operated more than 110 d (450 cycles) with an optimal aeration rate [7.2-12 L·(h·L)-1] and time (2-3 h) during aeration. The results showed that the nitrite accumulation rate in the effluent maintained 94%-100%

indicating the stable partial nitrification. The ratios between NO2--N and NH4+-N were in the range of 2-4. Further analysis demonstrated that in the long-term operation of PNSBR

the low dissolved oxygen (DO) by controlling aeration benefited the ammonia oxidizing bacteria (AOB) activity but inhibited the nitrite oxidizing bacteria (NOB) one. On the other hand

the residual nitrite after decanting in a cycle was removed via denitrification (endogenous in this cycle and exogenous in next cycle) by using organics in raw wastewater

through which substrates for NOB were prohibited

and thus stable PN was realized. The process of simultaneous anammox and denitrification (SAD) was widespread

and PNSBR

as a pre-treatment reactor

can provide substrates for SAD

and thus PN was a potential technology in future.