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 NH₄⁺-N (~ 90.7 mg/) as a sole nitrogen source, the removal efficiency (RE) of NH₄⁺-N in 24 h was 99.35%, and there was no accumulation of NO₃⁻-N or NO₂⁻-N. When NO₃⁻-N (~ 101.79 mg/L) or NO₂⁻-N (~ 106.00 mg/L) was the sole nitrogen source, respectively, it was almost completely removed. Furthermore, when NH₄⁺-N (~ 105.68 mg/L) and NO₃⁻-N (~ 100.40 mg/L) were the composite nitrogen sources, the RE of NH₄⁺-N and NO₃⁻-N were 99.17% and 94.07% in 24 h, respectively. The RE of NH₄⁺-N was up to 99.31% when NH₄⁺-N (~ 102.33 mg/L) and NO₂⁻-N (~ 114.56 mg/L) used as composite nitrogen sources, and NO₂⁻-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 NH₂OH to NO instead of NO₂⁻-N by SND microbes. [ABSTRACT FROM AUTHOR]