梯度曝气A2O2-MBR工艺强化同步硝化反硝化效能OA北大核心CSTPCD

Aiming at poor denitrification effect and high energy consumption when treating the wastewater with the low C/N ratio in wastewater treatment plant(WWTPs),a step-wise aeration A2O2-MBR process was developed.The separated low-oxic zone(O1)and oxic zone(O2)were design with the DO concentrations decreased gradually to 0.6 mg·L-1 and 1.7 mg·L-1,respectively.When the influent C/N ratio decreased from 6.0 to 5.0 and 4.0,the total nitrogen(TN)removal efficiency maintained at around 85％.The simultaneous nitrification and denitrification(SND)efficiency of the O1 and O2 zones kept at around 90％.Both O zones(O1+O2)and membrane zones contributed to above 82.5％of TN removal,and 64.9％～83.2％of COD removal.High-throughput gene sequencing showed that,under low DO and low C/N ratio conditions,the abundance of nitrite-oxidizing bacteria(NOB)decreased,while the abundance of denitrifying glycogen accumulating organisms(DGAOs)increased.Rich denitrifiers occurrred,of which the abundance of Pseudomonas was highest.Besides,the abundance of Thauera and Zoogloea increased under low C/N ratio condition.Most of TN was removed by ordinary denitrifying bacteria(DNB),rather than DGAOs.Compared with the startup stage,the total aeration rate of the O1 and O2 zones decreased by 44.2％.The results showed that the step-wise aeration mode could gradually lower the DO concentrations,enrich the functional bacteria,then enhance the SND effect,increase TN removal,save the energy consumption.