The more important role of archaea than bacteria in nitrification of wastewater treatment plants in cold season despite their numerical relationships

• Published in: Water research (Oxford) 2018-11, Vol.145, p.552-561
• Main Authors: Pan, Kai-Ling, Gao, Jing-Feng, Fan, Xiao-Yan, Li, Ding-Chang, Dai, Hui-Hui
• Format: Article
• Language: English
• Subjects: Ammonia-oxidizing archaea; Ammonia-oxidizing bacteria; Complete ammonia-oxidizing nitrospira; DNA-based stable isotope probing; Numerical relationships; Wastewater treatment plants
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2018.08.066

Nitrification failure of wastewater treatment plants (WWTPs) in cold season calls into investigations of the functional ammonia-oxidizing microorganisms (AOMs). In this study, we report the abundance of ammonia-oxidizing archaea (AOA), bacteria (AOB) and complete ammonia-oxidizing (comammox) Nitrospira in 23 municipal WWTPs in cold season, and explore the correlations between AOMs abundance and their relative contribution to nitrification. The copy numbers of AOA and AOB amoA gene ranged from 2.42 × 107 to 2.47 × 109 and 5.54 × 106 to 3.31 × 109 copies/g sludge, respectively. The abundance of amoA gene of Candidatus Nitrospira inopinata, an important strain of comammox Nitrospira, was stable with averaged abundance of 8.47 × 106 copies/g sludge. DNA-based stable isotope probing (DNA-SIP) assays were conducted with three typical WWTPs in which the abundance of AOA was lower than, similar to and higher than that of AOB, respectively. The results showed that considerable 13C-assimilation by AOA was detected during active nitrification in all WWTPs, whereas just a much lesser extent of 13C-incorporation by AOB and comammox Nitrospira was found in one WWTP. High-throughput sequencing with 13C-labeled DNA also showed the higher reads abundance of AOA than AOB and comammox Nitrospira. Nitrososphaera viennensis was the dominant active AOA, while Nitrosomonas oligotropha and Nitrosomonas europaea were identified as active AOB. The results obtained suggest that AOA, rather than AOB and comammox Nitrospira, dominate ammonia oxidation in WWTPs in cold season despite the numerical relationships of AOMs. [Display omitted] •AOA dominated ammonia oxidation of WWTPs in winter revealed by DNA-SIP.•AOMs nitrification activity cannot be determined by their numerical relationships.•AOB and comammox Nitrospira were the minor ammonia oxidizers in WWTPs in winter.•Comammox Nitrospira may be strong competitors of AOA in WWTPs with limited NH4+-N.•Nitrososphaera viennensis was the most dominant active AOA.