Hydrogen generated by electrochemical water splitting as electron donor for nitrate removal from micro-polluted reservoir water

• Published in: Journal of hazardous materials 2024-12, Vol.480, p.135964, Article 135964
• Main Authors: Shi, Xinxin, Ma, Zhuolin, Evlashin, Stanislav A., Fedorov, Fedor S., Shi, Julian, Liu, Yang, Zhu, Weihuang, Guo, Pengfei, Huang, Tinglin, Wen, Gang
• Format: Article
• Language: English
• Subjects: Denitrifying bacterial communities; Hydrogen evolution; Hydrogenotrophic denitrification; Micro-polluted reservoir water
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.135964

Extremely limited organic carbon sources and aerobic environment in micro-polluted reservoir water make conventional denitrification exceptionally challenging. As a result, total nitrogen (TN) concentration in most reservoir waters exceeds standard value year-round. In this study, for the first time, we constructed a mini water-lifting and aeration system (mini-WLAS) to remove nitrate in actual reservoir water. In the mini-WLAS, H2 was produced through electrolysis of reservoir water without adding any electrolyte, and the ascending water flow carried the generated H2 from lower layer to upper bacteria layer. The maximum denitrification rate reached 0.29 mg (L·d)−1 under dissolved oxygen (DO) concentration of 6–8 mg L−1, 6.04 times higher than that of the control group. There is almost no accumulation of NH4+-N, NO2--N, and N2O, and the concentration of CODMn decreased by 55.2 %. More importantly, the pH stayed near-neutral steadily throughout the whole process. Microbial community analysis showed that the abundances of hydrogenotrophic denitrifying bacteria (HDB) were 2 orders higher than those in the control system. Some HDB could work under aerobic conditions, providing an explanation for the excellent denitrification performance under high DO. This study provides a novel perspective for TN removal from reservoir water. [Display omitted] •In-situ system coupling H2 evolution with hydrogenotrophic denitrification is built.•H2-bubbles (HBs) are electrically produced in primitive reservoir water.•The denitrification rate of HE-8V system exceeds the control by 6.04 times.•Aerobic hydrogenotrophic denitrifying bacteria are enriched from reservoir water.