Abstract
Full-scale anaerobic, anoxic and aerobic (A2O) process is used worldwide for biological nutrient removal (BNR). However, operation parameters for nitrogen removals and information of microbial communities related to nitrogen removal in full-scale A2O wastewater treatment plants (WWTPs) having low and high COD/TN ratios are not available. Based on the analysis of four full-scale A2O WWTPs, it is suggested that maintaining longer SRT of ≥ 30 day and DO of ≥ 0.9±0.2 mg-O2 L-1 is needed to improve nitrogen removal efficiency under low COD/TN ratio (≤ 3.7). On other hand, at high COD/TN ratio (≥ 4.2), DO level of ≥ 2.6 mg-O2 /L and typical SRT of 19‒ 25 days would be suggested. It was confirmed that phosphorus removal efficiency significantly improved under BOD/TP ratio of > 20 for A2O process in these full-scale WWTP. Microbial distribution analysis showed that ammonia-oxidizing archaea (AOA) was abundant under conditions of low DO level, longer SRT, high temperature and low COD/TN ratio (≤ 3.7). Nitrosomonas sp. are mostly found in aerobic tank of full-scale A2O WWTPs. However, abundances of Nitrosomonas sp. are proportional to DO and NH4+ concentrations for WWTPs with high COD/TN ratio. Nitrosospira sp. are only found under operating condition of longer SRT for WWTPs with low COD/TN ratio. Abundances of Nitrobacter sp. are proportional to DO concentration and temperature rather than abundance of Nitrospira sp. Predominance of nosZ-type denitrifiers were found at low COD/TN ratio. Abundance of denitrifiers by using nirS genes was over abundance of denitrifiers by using nirK genes at high COD/TN ratios WWTPs.
Performance Assessment of Full-Scale Wastewater Treatment Plants Based on Seasonal Variability of Microbial Communities via High-Throughput Sequencing
