Fixed nitrogen removal mechanisms associated with sulfur cycling in tropical wetlands

• Published in: Water research (Oxford) Vol. 189; p. 116619
• Main Authors: Wang, Qingkun, Rogers, Matthew James, Ng, Sir Sing, He, Jianzhong
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2021
• Subjects: Ammonium Compounds; Anaerobiosis; Anammox; Denitrification; DNRA; Nitrogen; Nitrogen removal; Oxidation-Reduction; Sulfate reduction; Sulfur; Tropical wetlands; Wetlands; Sulfate reduction; Nitrogen removal; Anammox; DNRA; Tropical wetlands
• DOI: 10.1016/j.watres.2020.116619
• ISSN: 0043-1354

•Novel and diverse anammox genera were found in tropical wetland ecosystems.•Anammox accounted for up to 57.4% of nitrogen loss in ex situ batch experiments.•Sulfide-driven DNRA supports anammox by supplying nitrite and/or ammonium.•Anammox activity was inferred from sulfate concentrations and dsr and nrf abundance.•Combining sulfide-driven DNRA and anammox could reduce N2O emissions from WWTPs. Wetland ecosystems play an important role in nitrogen cycling, yet the role of anaerobic ammonium oxidation (anammox) in tropical wetlands remains unclear. In the current study the anammox process accounted for 29.8 ~ 57.3% of nitrogen loss in ex situ activity batch tests of microcosms established from anoxic sediments of different tropical wetlands, with the highest activity being 17.95±0.51 nmol-N/g dry sediment/h. This activity was most likely driven by sulfide oxidation with dissimilatory nitrate reduction to ammonium (sulfide-driven DNRA). Microbial community analyses revealed a variety of anammox bacteria related to several known lineages, including Candidatus Anammoximicrobium, Candidatus Brocadia and Candidatus Kuenenia, at different wetlands. Metagenome predictions, batch tests, and isotope-tracing suggested that the high level of anammox activity was due to sulfide-driven DNRA. This was corroborated by a strong correlation (through Pearson's analysis) between the abundance of anammox bacteria and the nrfA (a dissimilatory nitrate reduction to ammonium gene) and dsrA (a sulfate reductase gene) genes, as well as sulfate, ammonium and nitrate concentrations. These correlations suggest syntrophic interactions among sulfate-reducing, sulfide-driven DNRA, and anammox bacterial populations. A better understanding of the role of sulfur in nitrogen loss via the anammox reaction in natural systems could inform development of a viable wastewater treatment strategy that utilizes sulfate to minimize the activity of denitrifying bacteria and thus to reduce nitrous oxide emissions from wastewater treatment plants. [Display omitted]