Nitrite improved nitrification efficiency and enriched ammonia-oxidizing archaea and bacteria in the simultaneous nitrification and denitrification process

Yu Xiang; Tengzhi Zhou; Siping Deng; Zhiyu Shao; Yiwen Liu; Qiang He; Hongxiang Chai

doi:10.1016/j.wroa.2023.100204

Nitrite improved nitrification efficiency and enriched ammonia-oxidizing archaea and bacteria in the simultaneous nitrification and denitrification process

Water Res X. 2023 Oct 2:21:100204. doi: 10.1016/j.wroa.2023.100204. eCollection 2023 Dec 1.

Authors

Yu Xiang^{1

2}, Tengzhi Zhou², Siping Deng², Zhiyu Shao², Yiwen Liu³, Qiang He², Hongxiang Chai²

Affiliations

¹ School of Architecture and Civil Engineering, Xihua University, Chengdu 610039, China.
² Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Environment and Ecology, Chongqing University, Chongqing 400045, China.
³ School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China.

Abstract

Simultaneous nitrification and denitrification (SND) is effective and energy-saving for wastewater treatment. As an inevitable intermediate product in the SND process, nitrite affects the efficiency of ammonia oxidation and the composition of nitrifiers. To investigate the impact of nitrite on ammonia oxidation efficiency, two reactors performing SND were respectively operated without nitrite (R1 as control) and with 20 mg N/L nitrite addition (R2 as experimental). The total nitrogen removal efficiency was 74.5% in R1 while 99.0% in R2. With nitrite addition (i.e., 20 mg N/L), the ammonia removal rate in R2 increased to 4.5 times of that in R1. The ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) contributed to respective around 46.9% and 41.8% ammonia removal in R2 based on the results of experiments with specific inhibitors. The number of respective AOA and AOB ammonia monooxygenase gene (amoA) copies increased by 280 and 30 times due to nitrite addition, according to the qPCR results. The high-throughput sequencing results illustrated the increase of dominant AOB species from 0.40% in R1 to 1.59% in R2 and the phylogenetic tree analysis revealed a close link to Nitrosospira multiformis. These results indicated that the ammonia removal efficiency was improved and AOA/AOB were enriched by nitrite addition. The specific nitrite reductases in AOA and AOB boosted the adaptation of nitrite addition. This study demonstrated the positive impacts of nitrite addition on the ammonia removal efficiency and rate in the SND process.

Keywords: AOA; AOB; Ammonia oxidizing microorganisms; Nitrogen removal; Wastewater treatment.