生活污水不同生物脱氮过程中N_2O产量及控制

利用好氧-缺氧SBR反应器和全程曝气SBBR反应器处理生活污水,分别实现了全程、短程和同步硝化反硝化脱氮过程,研究了不同脱氮过程中N2O的产生及释放情况,同时考察了不同DO条件下同步脱氮效率及N2O产生量。结果表明,全程、短程生物脱氮过程中N2O主要产生于硝化过程,反硝化过程有利于降低系统N2O产量。全程、短程、同步硝化反硝化脱氮过程中N2O产量分别为4.67、6.48和0.35mg.L-1。硝化过程中NO2-N的积累是导致系统N2O产生的主要原因。部分AOB在限氧条件下以NH4+-N作为电子供体,NO2-N作为电子受体进行反硝化,最终产物是N2O。不同DO条件下同步硝化反硝化过程中N2O的产生表明:控制SBBR系统中DO浓度达到稳定的同步脱氮效率可使系统N2O产量最低。

Formation of N2O in various biological nitrogen removal processes for treatment of domestic sewage

The formation and emission of N₂O in various nitrogen removal processes for treatment of domestic sewage were investigated using oxic-anoxic SBR systems and a continuum aerobic submerged biofilm reactor system SBBR, from which complete, shortcut and simultaneous nitrification and denitrification(SND) processes were realized, respectively.Meanwhile, the effect of DO on the SND efficiency and N₂O yield in SBBR was also studied.The results showed that for both complete and shortcut N removal processes the formation of N₂O was in nitrification process, while denitrification one was favorable for decrease of N₂O emission.N₂O yield was 4.67 mg·L^-1，6.48 mg·L^-1 and 0.35 mg·L^-1 for complete, shortcut and simultaneous nitrification-denitrification processes, respectively.The main reason for the formation of N₂O was the accumulation of NO₂^--N during N removal process.A part of AOB could be denitrified between NH₄⁺-N as electron donor and NO₂^--N as electron acceptor under low DO level,which led to the formation of N₂O finally.The formation of N₂O in simultaneous nitrification and denitrification process at various DO conditions showed that in SBBR system, the minimun N₂O yield could be achieved by the control of DO concentration and the efficiency balance of nitrogen removal in both nitrification and denitrification processes.