Deciphering the coupling of partial nitrification/anammox and sulfur autotrophic denitrification: Microbial metabolism and antibiotic resistance genes propagation.

[Display omitted] • PN/A-SAD coupling system was successfully achieved within only four days at 25 °C. • TNRE increased from 66% in PN/A phase to more than 90% in PN/A-SAD coupling phase. • AOB, AnAOB and SOB were enriched with the inhibition of NOB during SAD coupling. • SAD eliminated heterotrophic denitrifiers that might be potential hosts of ARGs. • PN/A-SAD coupling system reduced the risks of the ARGs and MGEs dissemination. Partial nitrification/anaerobic ammonium oxidation (anammox) (PN/A) was considered as an economically beneficial and environmentally friendly biological nitrogen removal process. The elimination of nitrate produced by PN/A system was the key to improving the total nitrogen removal efficiency (TNRE) of the system under mainstream conditions. In this study, the feasibility of the coupling S(0)-driven autotrophic denitrification (SAD) with PN/A in a single sequencing moving bed biofilm reactor (SMBBR) at room temperature was explored. Additionally, biological treatment process is ideal environments for the emerge and spread of emerging pollutants antibiotic resistance genes (ARGs), therefore, the shifts of ARGs in the system were investigated. After the coupling of PN/A and SAD, SMBBR was steadily operated with high TNRE. Nitrite-oxidizing bacteria (Nitrospira and Candidatus Nitrotoga) and nitrite oxidoreductase enzyme were inhibited by SAD process. And anammox bacteria were enriched, especially oligotype GAGTTTAAT of Ca. Brocadia. Sulfurimonas became the predominant autotrophic denitrifier. Heterotrophic denitrifiers Thauera and Dechloromonas were elutriated out from the system during the coupling of PN/A and SAD process, and they might be potential hosts for ARGs, leading to the decrease of ARGs. Overall, this study proposed a new strategy that SAD could promote the TNRE of PN/A and cut the risks of ARGs propagation, and PN/A-SAD coupling system was a biological nitrogen removal technology with promising applications under mainstream conditions. [ABSTRACT FROM AUTHOR]