pH对生物硝化过程动力学抑制及N2O释放影响

The Effect of pH on Inhibitory Kinetics of Nitrification Process and Characteristic of N2O Emission

生物硝化过程是导致生物脱氮过程N2O释放的重要因素。文章利用小试反应器,采用连续进水的方式,考察了不同pH下氨氧化菌(AOB)硝化过程氨氮氧化速率(AOR)和氧化亚氮释放速率(N2OR)之间的关系。pH影响动力学结果表明,pH=6.5和8.5时,AOB的比耗氧速率(SOUR)分别降至其最大值(SOURmax,pH=7.5)的50%。不同氧化还原酶具有不同的最适pH值(pHopt),pH的变化导致硝化过程不同中间产物的积累。其中,一氧化氮还原酶、亚硝态氮还原酶和氧化亚氮还原酶对生物硝化过程中N2O释放起着重要作用。pH=6.0~7.5之间,AOR和N2OR随pH的增加而增加,p H=7.5时,其N2OR和AOR分别达最大值(0.34±0.08)和(16.30±1.25)mgN/(gVSS·h)。此后,随pH的增加而逐渐降低。不同pH下,N2OR和AOR呈线性关系。AOR增加,为AOB好氧反硝化过程提供了更多的电子,导致更多N2O释放。

In wastewater biological nitrogen removal process,nitrifier denitrificaiton by AOB(ammonia oxidising bacteria)was shown to be the major source of N2O production.By continuous feeding mode,the impact of pH on N2O production rate(N2OR)and ammonia oxidation rate(AOR)was investigated in a laboratory batch-scale system with activated sludge for treating domestic wastewater.p H was shown to have a major impact on AOR and N2OR during nitrification process.The specific oxygen uptake rate(SOUR)of AOB was half of SOURmax(pH=7.5)at pH 6.5 and pH 8.5.The pH optima for each reductase was identical,which may result in different intermediates accumulation during nitrification process.Nitric oxide reductase(NOR),nitrite reductase(NIR)and nitrous oxide reductase(NOS)are of great importance to the net N2O production during N-conversions.In the investigated pH range(pH=6.0~7.5),the specific AOR and N2OR increased with the increasing pH to a maximum of(0.34±0.08)and(16.30±1.25)mg N/(gVSS·h)respectively at pH 7.5,and decreased with the increasing pH.Alinear relationship between N2OR and AOR was observed suggesting that increased ammonium oxidation activity may have promoted the N2O production by supplying more electrons to the nitrifier denitrification process.