Oguz Merve T, Robinson Kevin G, Layton Alice C, Sayler Gary S
Department of Civil and Environmental Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA.
Biotechnol Bioeng. 2007 Aug 15;97(6):1562-72. doi: 10.1002/bit.21379.
The goal of this research was to investigate the simultaneous occurrence of nitrification and denitrification by activated sludge exposed to volatile fatty acids (VFAs) during aerobic wastewater treatment using a single-stage reactor. A mixture of VFAs was spiked directly into a continuous-stirred tank reactor (CSTR) to assess subsequent impacts on nitrite removal, nitrate formation, CO(2) fixation, total bacterial density, and dominant nitrite oxidizing bacteria (NOB) concentration (i.e., Nitrospira). The activity of the periplasmic nitrate reductase (NAP) enzyme and the presence of nap gene were also measured. A rapid decrease in the nitrate formation rate (>70% reduction) was measured for activated sludge exposed to VFAs; however, the nitrite removal rate was not reduced. The total bacterial density and Nitrospira concentration remained essentially constant; therefore, the reduction in nitrate formation rate was likely not due to heterotrophic uptake of nitrogen or to a decrease in the dominant NOB population. Additionally, VFA exposure did not impact microbial CO(2) fixation efficiency. The activity of NAP enzyme increased in the presence of VFAs suggesting that nitrate produced as a consequence of nitrite oxidation was likely further reduced to gaseous denitrification products via catalysis by NAP. Little, if any, nitrogen was discharged in the aqueous effluent of the CSTR after exposure to VFAs demonstrating that activated sludge treatment yielded compounds other than those typically produced solely by nitrification.
本研究的目标是调查在单级反应器好氧废水处理过程中，暴露于挥发性脂肪酸（VFA）的活性污泥同时发生硝化和反硝化的情况。将VFA混合物直接加入连续搅拌槽式反应器（CSTR）中，以评估其对亚硝酸盐去除、硝酸盐形成、CO₂固定、总细菌密度和优势亚硝酸盐氧化细菌（NOB）浓度（即硝化螺菌属）的后续影响。还测定了周质硝酸还原酶（NAP）的活性以及nap基因的存在情况。对于暴露于VFA的活性污泥，硝酸盐形成速率迅速下降（降低>70%）；然而，亚硝酸盐去除率并未降低。总细菌密度和硝化螺菌属浓度基本保持恒定；因此，硝酸盐形成速率的降低可能不是由于氮的异养吸收或优势NOB种群的减少。此外，VFA暴露并未影响微生物CO₂固定效率。在VFA存在的情况下，NAP酶的活性增加，这表明由亚硝酸盐氧化产生的硝酸盐可能通过NAP催化进一步还原为气态反硝化产物。暴露于VFA后，CSTR的出水几乎没有氮排放，这表明活性污泥处理产生的化合物并非仅由硝化作用通常产生的那些化合物。
