低DO对活性污泥系统碳和氮去除影响的研究

考察了长期低溶解氧（DO）条件下推流式活性污泥系统碳和氮去除的效果，并从微生物群落结构及动力学特征方面进行了机理分析. 结果表明， 将DO浓度从2.0mg/L降低至0.3mg/L，系统仍可有效地去除污水中的碳和氮，但当DO降低至0.3mg/L时， 系统的脱氮性能波动较大. 随着DO浓度的降低， 系统中细菌的总体群落结构发生改变， 但功能菌群仍为Proteobacteria，约占65%.Nitrosomonas oligotropha、Nitrobacter winogradskyi spp.和Group1Nitrospira等是低溶解氧条件下的主要硝化细菌. qPCR结果显示DO从2.0mg/L降至0.5mg/L时硝化细菌（主要是Nitrospira）得到富集， 保证了低DO条件下的完全硝化. 硝化反应动力学分析也表明， 在一定范围内降低DO可以延迟细菌衰亡以维持活性污泥系统中硝化细菌的生物量. 本研究可为污水处理厂降低DO实现节能运行提供理论支持.

Effects of low dissolved oxygen on carbon and nitrogen removal in activated sludge process

Impact of dissolved oxygen (DO) on pollutant removal and bacterial community structure was evaluated in a plug-flow activated sludge system. Results show that the bioprocess could still maintain high removal efficiencies of chemical oxygen demand and nitrogen from sewage when DO concentration decreased from 2.0 to 0.3mg/L, however, the nitrogen removal efficiency fluctuated greatly. The functional bacteria Proteobacteria remained dominant (~ 65%) under lower DO conditions, yet the total bacterial community structure changed in the aeration tank. The Nitrosomonas oligotropha-like ammonia-oxidizing bacteria, Nitrobacter winogradskyi spp., and Group1Nitrospira were identified as the major contributor of nitrification under low DO conditions. The quantitative PCR analysis showed that reducing DO concentration from 2.0 to 0.5mg/L enriched the nitrifiers (mainly Nitrospira), thereby ensuring complete nitrification under low DO conditions. The kinetics coefficient analysis also indicated that reducing DO concentration did not significantly affect the nitrifying bacterial growth, but retarded their decay to ensure biomass in the activated sludge system. These results provide positive support for wastewater treatment plants for saving energy by reducing DO concentration in the aeration tank.