进水碳氮比对中试AAO-BAF系统脱氮除磷性能的影响

Effect of Influent ρ(C)/ρ(N) on the Nitrogen and Phosphorus Removal Performance of Pilot-scale AAO-BAF

为了研究进水碳氮比对AAO-曝气生物滤池(BAF)双污泥脱氮除磷系统的影响,以实际生活污水为处理对象,研究了一个处理量约为50m^3/d的中试规模AAO-BAF系统在碳氮比分别为3.3±0.3、4.5±0.3、6.0±0.3时长期运行的脱氮除磷特性.试验结果表明:在碳氮比约为3.3时,AAO-BAF工艺对COD、TN、PO4^3--P的去除率分别可达到71.4%、67.6%和85.6%.适当提高有机物浓度,当碳氮比约为4.5时,AAO-BAF工艺对COD、TN、PO4^3--P的去除率分别可达到79.7%、70.0%和93.5%,系统的脱氮除磷性能最佳,平均出水TN和PO4^3--P为12.40、0.20mg/L.但当碳氮比继续提高至约为6.0时,过量的有机物会使缺氧区内存在大量可利用有机物,反硝化菌优先利用电子受体NO3--N,削弱了反硝化除磷菌的活性.同时会有剩余的有机物进入BAF,导致异养菌的增殖,氨氮不能完全氧化,使得缺氧区的电子受体进一步减少,影响系统的脱氮除磷功能.此时,AAO-BAF工艺对COD的去除率为81.6%,TN、PO43--P的去除率分别迅速下降至55.1%和63.2%以下,系统接近崩溃.

To study the effects of influentρ(C)/ρ(N)on two-sludge nitrogen and phosphorus removal system,the characteristics of a pilot-scale AAO-biological aerated filter(BAF)treating about 50 m^3 real domestic wastewater per day were investigated underρ(C)/ρ(N)level of 3.3±0.3,4.5±0.3,and 6.0±0.3,respectively.Results show that whenρ(C)/ρ(N)is about 3.3,the removal rates of COD,TN and PO4^3--P reach 71.4%,67.6%and 85.6%,respectively.The nitrogen and phosphorus removal performance of the system reach the best whenρ(C)/ρ(N)is raised to 4.5 by adding organic matter,the removal rates of COD,TN and PO4^3--P reaching 79.7%,70%and 93.5%,respectively.The average effluent TN and PO4^3--P are 12.40,0.20 mg/L,respectively.However,whenρ(C)/ρ(N)is about 6.0,a large amount of available organic compounds in the anoxic area result in the rapid depletion of the electronic receptor NO3^--N by denitrifying bacteria,affecting the removal of the nitrogen and phosphorus by DPAOs.As well,residual organic matter is found in the BAF,which result that NH4^+-N cannot be completely oxidized to NO3^--N because of the proliferation of heterotrophic bacteria.In this situation,the removal rate of COD is 81.6%,removal rates of TN and PO4^3--P by AAO-BAF process drop to 55.1% and 63.2% rapidly,and the system is close to collapse.