The indispensable role of assimilation in methane driven nitrate removal

Yongze Lu; Xin Li; Yue Chen; Yongzhen Wang; Guangcan Zhu; Raymond Jianxiong Zeng

doi:10.1016/j.scitotenv.2020.141089

The indispensable role of assimilation in methane driven nitrate removal

Sci Total Environ. 2020 Dec 1:746:141089. doi: 10.1016/j.scitotenv.2020.141089. Epub 2020 Jul 24.

Authors

Yongze Lu¹, Xin Li², Yue Chen³, Yongzhen Wang⁴, Guangcan Zhu⁵, Raymond Jianxiong Zeng⁶

Affiliations

¹ School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China. Electronic address: yzlu@seu.edu.cn.
² School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China. Electronic address: lix@seu.edu.cn.
³ School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China. Electronic address: 15162169381@163.com.
⁴ School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China. Electronic address: yzwang@seu.edu.cn.
⁵ School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096, China; State Key Laboratory of Environmental Medicine Engineering, Ministry of Education, Southeast University, Nanjing, Jiangsu 210096, China. Electronic address: gc-zhu@seu.edu.cn.
⁶ Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China. Electronic address: rzeng@fafu.edu.cn.

PMID: 32745852
DOI: 10.1016/j.scitotenv.2020.141089

Abstract

Methane is a greenhouse gas that can be released from sludge anaerobic fermentation in wastewater treatment plants. Methane is also an alternative additional carbon source for deep nitrate removal of secondary effluent. A sequencing experiment was conducted to study the efficacy of nitrate removal with methane as the sole carbon source. The maximum nitrate removal rate was 17.2 mg-N·L^-1·d^-1. Nitrate removal was confirmed to arise via two pathways: aerobic methane oxidation coupled to denitrification (AME-D) contributed to 55% of the nitrate removal with the rest stemming from assimilation by methanotrophs. Additional study revealed that nitrate assimilated by methanotrophs was used for the synthesis of proteins, resulting in a protein content of 52.2% dry weight. Metagenomic sequencing revealed a high abundance of nitrate assimilation and glutamine synthetase genes, which were primarily provided by methanotrophs (mainly Methylomonas). Assimilatory nitrate removal by methanotrophs has a high potential for advanced nitrogen removal and for alleviating methane emissions. The nitrogen-rich biomass produced by nitrate absorption could also be used as a biofertilizer for nitrogen recycling.

Keywords: Advanced nitrogen removal; Methanotroph; Nitrate assimilation; Nitrogen recovery.

MeSH terms

Bioreactors
Denitrification*
Methane*
Nitrates
Nitrogen
Oxidation-Reduction

Substances

Nitrates
Nitrogen
Methane