Anaerobic ammonium oxidation in sediments of surface flow constructed wetlands treating swine wastewater
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Anaerobic ammonium oxidation (anammox) was suggested to be involved in the nitrogen (N) removal process in constructed wetlands (CWs). Nevertheless, its occurrence and role in CWs treating swine wastewater have not been well evaluated yet. In this study, we investigated the diversity, activity, and role of anammox bacteria in sediments of mesoscale surface flow CWs (SFCWs) subjected to different N loads of swine wastewater. We found that anammox bacteria were abundant in SFCW sediments, as indicated by 7.5 × 105 to 3.5 × 106 copies of the marker hzsB gene per gram of dry soil. Based on stable isotope tracing, potential anammox rates ranged from 1.03 to 12.5 nmol N g−1 dry soil h−1, accounting for 8.63–57.1% of total N2 production. We estimated that a total N removal rate of 0.83–2.68 kg N year−1 was linked to the anammox process, representing ca. 10% of the N load. Phylogenetic analyses of 16S ribosomal RNA (rRNA) revealed the presence of multiple co-occurring anammox genera, including “Candidatus Brocadia” as the most common one, “Ca. Kuenenia,” “Ca. Scalindua,” and four novel unidentified clusters. Correlation analyses suggested that the activity and abundance of anammox bacteria were strongly related to sediments pH, NH4 +-N, and NO2 −-N. In conclusion, our results confirmed the presence of diverse anammox bacteria and indicated that the anammox process could serve as a promising N removal pathway in the treatment of swine wastewater by SFCWs.
KeywordsAnammox Constructed wetlands Swine wastewater N removal Phylogenetic analyses
We sincerely thank Hu Li and San’an Nie (Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Science, Xiamen, China) for their skillful assistance of the 15N isotope-pairing experiments. Special thanks to Public Service Technology Center, Institute of Subtropical Agriculture, Chinese Academy of Sciences, for instrument support. This study was funded by the China Postdoctoral Science Foundation Funded Project (2014M560648, 2015T80878), the National Natural Science Foundation of China (41601272), the National Science and Technology Supporting Project (2014BAD14B05), and the key CAS Programs (KZZD-EW-11).
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
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