A completely mixed aeration system was introduced in domestic sewage treatment, and the simultaneous nitrification and denitrification process and microbial community structure were further investigated. The pilot-scale experimental results showed that the operation of the system was stable and the average chemical oxygen demand (COD), NH4+-N and total nitrogen (TN) removal were 93.2%, 96.9% and 75.2%, respectively. The effluent COD, NH4+-N and TN were better than the standard of level A stipulated by Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002) in the absence of external carbon source. The sludge derived from the system showed a significant denitrification capacity and the denitrification rate was 2.86 times higher than that in the wastewater treatment plant. In addition, the existence of aerobic denitrifying bacteria in the system was confirmed by the PCR amplification of genes encoding perplasmic nitrate reductases. The high-throughput sequencing results revealed that Zoogloea, Thauera and Dechloromonas were dominant in the completely mixed aeration system.
Keywords: aerobic denitrification; completely mixed aeration system; high-throughput sequencing; perplasmic nitrate reductases.