Remediation of nitrate contamination by membrane hydrogenotrophic denitrifying biofilm integrated in microbial electrolysis cell

• Published in: Water research (Oxford) 2021-01, Vol.188, p.116498-116498, Article 116498
• Main Authors: Liang, Dandan, He, Weihua, Li, Chao, Wang, Fei, Crittenden, John C., Feng, Yujie
• Format: Article
• Language: English
• Subjects: Biofilms; Bioreactors; Denitrification; Denitrifying metabolic pathway; Ectopic electron compensation; Electrolysis; Hydrogenotrophic denitrification; Membranes; MMEC; Nitrate contaminated water remediation; Nitrates; Nitrogen; RNA, Ribosomal, 16S
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.116498

•Integrated gas diffusion membrane into MEC (MMEC) achieved high TN removal (>90%)•Applied voltage regulation effectively adjusted the electron utilization efficiency•The gas diffusion membrane enabled ectopic hydrogen autotrophic denitrification•Typical hydrogenotrophic denitrifiers dominated in the membrane biofilm in MMEC•Dissimilatory nitrate reduction to ammonia dominated in denitr-cathode biofilm of MEC Complete biological denitrification is usually restricted in electron donor lacking waters. Hydrogenotrophic denitrification attracts attention for its clean and cost-efficiency advantages. Therein, the hydrogen could be effectively generated by microbial electrolysis cells (MECs) from organic wastes. In this study, a gas diffusion membrane (GDM) integrated MEC (MMEC) was constructed and provided a novel non-polluting approach for nitrate contaminated water remediation, in which the hydrogen was recovered from substrate degradation in anode and diffused across GDM as electron donor for denitrification. The high overall nitrogen removal of 91 ± 0.1%–95 ± 1.9% and 90 ± 1.6%–94 ± 2.2% were respectively achieved in Ti-MMEC and SS-MMEC with titanium and stainless-steel mesh as cathode at all applied voltages (0.4–0.8 V). Decreasing applied voltage from 0.8 to 0.4 V significantly improved the electron utilization efficiency for denitrification from 26 ± 3.6% to 73 ± 0.1% in Ti-MMEC. Integrating MEC with GDM greatly improved TN removal by 40% under applied voltage of 0.8 V. The hydrogenotrophic denitrifiers of Rhodocyclaceae, Paracoccus, and Dethiobacter, dominated in MMECs facilitating TN removal. Functional denitrification related genes including napAB, nirKS, norBC and nosZ predicted by PICRUSt2 based on 16S rRNA gene data demonstrated higher abundance in MMECs. [Display omitted]