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

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 pol-lutants 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 sys-tem 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.