生活污水生物脱氮反硝化过程中电子竞争对N2O产生的影响

Effect of Electron Competition on N_2O Production During Domestic Sewage Biological Denitrification Process

目前,已有研究主要认为较小的COD/N是导致污水反硝化过程中N2O产生的关键因素,但有少部分研究发现即使在较小的COD/N下也没有发生N2O的累积.本研究利用SBR反应器,以实际生活污水为研究对象,考察了不同COD/N下各类电子受体类型(NO-3、NO-2、N2O及其组合)中氮氧化物的还原情况,进而探索反硝化过程中N2O产生的机理.结果表明:(1)在反硝化过程中,NO-3还原酶(Nar)、NO-2还原酶(Nir)、NO还原酶(Nor)以及N2O还原酶(Nos)均会发生对电子的竞争;(2)4种氮素还原酶对电子的竞争既会出现在碳源充足时,也会出现在碳源受限时;(3)COD/N的增加能够提高电子受体的还原速率和电子消耗速率,但在电子竞争环境下,N2O是否会发生积累取决于电子在Nos上分布的多少而不是COD/N的高低.

Currently,most studies showed that low COD / N ratio was a key factor leading to N2O production during sewage denitrification process,however,a few studies found that no N2O accumulation at low COD / N. In this study,sequencing bath reactors（ SBRs） were operated by feeding with real domestic sewage to investigate the reduction of different electronic receptors（ NO3-,NO2-,N2O and their combinations） under various COD / N ratios and to explore the mechanism of N2O production during denitrification process. The experimental results show that：（ 1） Electron competition occurs among nitrate reductase,nitrite reductase,NO reductase,and N2O reductase in biological denitrication process;（ 2） Electron competition among the 4nitrogen reductases could occur under both carbon limiting and carbon abundant conditions;（ 3） Increasing COD/N ratio can improve the reduction and consumption rate of the electron acceptors,however,accumulation levels of N2O depends on the electron distribution in the N2O reductase rather than the level of COD / N.