Coupling transformation of carbon, nitrogen and sulfur in a long-term operated full-scale constructed wetland

Wenbo Liu; Md Hasibur Rahaman; Jacek Mąkinia; Jun Zhai

doi:10.1016/j.scitotenv.2021.146016

Coupling transformation of carbon, nitrogen and sulfur in a long-term operated full-scale constructed wetland

Sci Total Environ. 2021 Jul 10:777:146016. doi: 10.1016/j.scitotenv.2021.146016. Epub 2021 Feb 23.

Authors

Wenbo Liu¹, Md Hasibur Rahaman², Jacek Mąkinia³, Jun Zhai⁴

Affiliations

¹ School of Environment and Ecology, Chongqing University, 400045 Chongqing, PR China.
² Department of Environmental Science and Technology, Jashore University of Science and Technology, Jashore 7408, Bangladesh.
³ Faculty of Civil and Environmental Engineering, Gdansk University of Technology,80-233Gdańsk, Poland.
⁴ School of Environment and Ecology, Chongqing University, 400045 Chongqing, PR China. Electronic address: zhaijun@cqu.edu.cn.

PMID: 33689895
DOI: 10.1016/j.scitotenv.2021.146016

Abstract

The coupling transformation of carbon, nitrogen and sulfur compounds has been studied in lab-scale and pilot-scale constructed wetlands (CWs), but few studies investigated full-scale CW. In this study, we used batch experiments to investigate the potentials of carbon, nitrogen and sulfur transformation in a long-term operated, full-scale horizontal subsurface flow wetland. The sediments collected from the HSFW were incubated for 48 h in the laboratory with supplying various dosages of carbon, nitrogen and sulfur compounds. The results showed that heterotrophic denitrification was the main pathway. At the same time, the sulfide (S^2-)-based autotrophic denitrification was also present. Increasing TOC concentration or NO₃^- concentration could promote heterotrophic denitrification but did not inhibit the sulfide-based autotrophic denitrification. In our experiment, the highest NO₃^- removal via autotrophic denitrification was 25.23% while that via heterotrophic denitrification was 73.66%, leading to the total NO₃^- removal of 98.89%. The results also demonstrated that NO₃^- rather than NO₂^- was the preferable electron acceptor for both heterotrophic and sulfide-based autotrophic denitrification in the CW. Increasing S^2- concentrations promote NO₃^- removal from 12.99% to 25.23% without organic carbon, but varying NO₃^- or NO₂^- has no effects. These results indicated that concentrations of S^2-, instead of NO₃^- or NO₂^-, was the limiting factor for sulfide-based autotrophic denitrification in the studied CW. The microbial community analysis and correlation analysis between the transformation of carbon, nitrogen and sulfur compounds and relative abundance of bacteria further confirmed that in the CW, the key pathways coupling transformation were heterotrophic denitrification and sulfide-based autotrophic denitrification. Overall, the current study will enhance understanding of carbon, nitrogen, and sulfur transformation in CW and support better design and treatment efficiency.

Keywords: Carbon, nitrogen and sulfur coupling transformation; Constructed wetland; Heterotrophic denitrification; Sulfide-based autotrophic denitrification.