High-efficient nitrogen and phosphorus removal and its mechanism in a partially unsaturated constructed wetland with Fe-C micro-electrolysis substrate

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-03, Vol.431, p.133252, Article 133252
• Main Authors: Li, Xiangzheng, Zhou, Lulu, Zhuang, Lin-Lan, Zhang, Jian, Li, Mengting, Yang, Yanan
• Format: Article
• Language: English
• Subjects: Constructed wetland; Electron doner for denitrification; Fe-C micro-electrolysis; Nitrogen and phosphorus; Unsaturated zone
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.133252

[Display omitted] •Fe addition in partially unsaturated CW could achieve high TN/TP removal (＞75%).•Extra biochar addition decreased Fe dosage but achieved the equivalent TN/TP removal.•Electron generation and transport by Fe-C enhanced denitrification to above 95%.•Fe-metabolic bacteria and electroactive bacteria were enriched by Fe-C addition.•Metallic bonded P and organic P dominated TP removal in Fe-C added CW. Insufficient dissolved oxygen (DO) for ammonia oxidation and limited electron donor for denitrification inhibit the nitrogen removal performance of constructed wetlands (CWs). To solve the problems, partially unsaturated CWs filled with biochar (C) and/or iron shavings (Fe) as functional substrate were proposed in this study and its mechanism on pollutant removal was thoroughly analyzed from the aspects of micro-environment property surrounding substrate, microbial function, plant toxicity, among others. Results showed that partially unsaturated section significantly improved the removal of NH4+-N from 25.1 ± 0.3 mg/L to