低氧条件下生物反硝化过程中N2O的产量

利用SBR反应器，控制曝气量为0.3 L·min-1，通过改变N2∶O2比例，调节反硝化过程中DO浓度，以连续投加乙醇作为反硝化碳源，考察了低氧条件下NO-3N反硝化过程及N2O的产量。结果表明，DO对反硝化菌的活性具有明显的抑制作用。DO由0增至0.7 mg·L-1，NO-3N还原速率由18.12 mg N·(g MLSS)-1·h-1降至11.37 mg N·( gMLSS)-1·h-1，系统N2O产量由0.23 mg·L-1增至1.74 mg·L-1。其原因为：(1)较高的NO-2N浓度导致系统反硝化速率降低，N2O积累并释放；（2）DO对N2O还原酶活性具有明显的抑制作用。降低缺氧-好氧生物脱氮过程中缺氧反应器内部DO含量，是减少生物脱氮过程中N2O产量的关键因素。

Formation of N2O during denitrification process at low oxygen concentration

The effect of dissolved oxygen(DO)and ratio of N2 and O2 on N2O yield during bio denitritation process using nitrate solution as electron acceptor and ethanol as carbon source was investigated in a sequencing batch reactor by controlling gas rate at 0.3 L·min-1 and at low oxygen concentration.The results show that DO could decrease significantly activity of denitritation bacteria.The aeration rate falls off from 18.12 mg N·（g MLSS）-1·h-1to 11.37 mg N·（g MLSS）-1·h-1, while N2O yield increases from 0.23 mg·L-1 to 1.74 mg·L-1.The phenomena can be attributed to:(1)higher concentration of NO-3N leads to decrease of denitritation rate as well as accumulation and emission of N2O;(2)both synthesis and reducing N2O activity of enzymes cause inhibition of DO. A key factor for decreasing N2O emission during bio denitritation process is to lessen the content of DO in bio reactor.