Analysis of the microbial diverisity and the mechanism of simultaneous nitrification and denitrification in high nitrogen environments

Simultaneous nitrification and denitrification (SND) is cost-effective, and therefore it is a promising process for biological nitrogen removal. In this study, SND microbes were obtained through domestication of the sludge from Wuhan municipal wastewater treatment plant to enrich effective nitrogen removal SND microbes, to reveal the microbial structure of SND and the denitrogenation mechanism through the high-throughput sequencing technology and quantitative PCR. When NH 4 + -N (~ 90.7 mg/) as a sole nitrogen source, the removal efficiency (RE) of NH 4 + -N in 24 h was 99.35%, and there was no accumulation of NO 3 − -N or NO 2 − -N. When NO 3 − -N (~ 101.79 mg/L) or NO 2 − -N (~ 106.00 mg/L) was the sole nitrogen source, respectively, it was almost completely removed. Furthermore, when NH 4 + -N (~ 105.68 mg/L) and NO 3 − -N (~ 100.40 mg/L) were the composite nitrogen sources, the RE of NH 4 + -N and NO 3 − -N were 99.17% and 94.07% in 24 h, respectively. The RE of NH 4 + -N was up to 99.31% when NH 4 + -N (~ 102.33 mg/L) and NO 2 − -N (~ 114.56 mg/L) used as composite nitrogen sources, and NO 2 − -N was completely removed. Community composition analysis revealed that the dominant phyla were Proteobacteria and Bacteroidetes; and the dominant genera were Paracoccus , Pannonibacter , Taibaiella , Pelagibacterium and Stappia . Gene functional analysis for the nitrogen cycle showed the presence of amoB , hao , narG , nirS , nirK , and nosZ genes; however, nxrA , hzo , hzs , napA , and nasA were not detected. These findings revealed that a possible novel mechanism of nitrogen removal using hao gene to oxidize NH 2 OH to NO instead of NO 2 − -N by SND microbes.