Abstract: Using domestic sewage with low C/N as treatment objective,the performance of modified A²/O process for denitrification and phosphorus removal was investigated.In order to suitable allocation of carbon sources required by anaerobic phosphorus release and anoxic denitrification,raw water was distributed into anaerobic tank and anoxic tank according to different proportion.To stabilize nitrification and denitrification processes and improve their efficiency some packing was filled in aerobic and anoxic tanks whose effluent flowed into aerobic tank to reduce the sludge flow path.Under the optimal conditions:average influent COD/TN ratio 5.54,HRT 11 h,SRT 15 d,MLSS 3000—4000 mg·L^-1,sludge reflux ratio 50%,the effect of inflow distribution ratio and internal reflux ratio on denitrification and phosphorus removal was investigated.The results showed that the optimal inflow distribution ratio was 5:5,at which iallocation of carbon source was reasonable for denitrification and phosphorous removal.And the optimal reflux ratio was 200%,if it is too high DO environment in anaerobic tank could be damaged and if it is too low the efficiency of denitrification in anoxic tank could not be full played.Under these optimal operating conditions,COD,NH₃-N,TN and TP in effluent were 29.7 mg·L^-1,0.1 mg·L^-1,11.8 mg·L^-1 and 0.42 mg·L^-1 respectively,the average removal efficiency reached 87.8%,99.7%,72.4% and 91.3% respectively.The effluent could be better than the first level A of the discharging standard of pollutants for municipal wastewater treatment plant(WWTP)(GB 18918—2002).At the same time,in anoxic tank noteworthy denitrification and phosphorus removal were observed.

Key words: modified A²/O process, low C/N ratio, nitrogen and phosphorus removal, inflow distribution ratio, denitrifying phosphorus removal

摘要： 以低C/N比城市生活污水为研究对象,重点考查了改良A²/O工艺的脱氮除磷性能。原水按一定比例分配给厌氧池和缺氧池,以合理分配厌氧释磷和缺氧反硝化所需的碳源;在好氧池和缺氧池中分别投加填料,以稳定系统的硝化和反硝化效果,提高系统的脱氮性能;厌氧池和缺氧池出水都直接进入好氧池。在进水COD/TN平均为5.54,HRT为11 h,SRT为15 d,MLSS为3000～4000 mg·L^-1,污泥回流比为50%条件下,通过三种不同进水分配比以及三种混合液回流比的对比试验研究,得到系统最佳进水分配比5:5,对分配脱氮和除磷所需碳源更加合理;而混合液回流比为200%,过高会破坏缺氧池的溶解氧环境,过低又会导致缺氧池反硝化作用不能充分发挥。在最优工况下COD、NH₃-N、TN和TP出水水质分别为29.7、0.1、11.8和0.42 mg·L^-1,平均去除率分别达到87.8%、99.7%、72.4%和91.3%,出水优于国家GB 18918—2002一级A排放标准,并且在缺氧池中发生了明显的反硝化除磷现象。

关键词: 改良A²/O工艺, 低C/N比, 脱氮除磷, 进水分配比, 反硝化除磷