Insights into thiosulfate-driven partial denitrification synergistically mediated by anaerobic ammonium oxidation: Biosynthesized signaling molecules and enzymatic collaboration

Abstract

The integrated thiosulfate-based autotrophic partial denitrification-anaerobic ammonium oxidation (anammox) (TS-AuPD/A) system achieved effective removal of ammonium and nitrate in a continuous reactor. The reactor (R1) containing only activated sludge achieved a total nitrogen removal efficiency (TNRE) of 81.8 ± 1.1 % and a nitrite removal efficiency (NiRE) of 90.2 ± 3.7 % over 96 days, while the reactor (R2) with mixed anammox biomass demonstrated accelerated nitrate removal, reaching 83.0 ± 2.2 % TNRE and 90.8 ± 4.3 % NiRE within just 33 days. These results suggest that anammox activity selectively benefits denitratation in the denitrifying pathway. The next-generation sequencing verified that Candidatus Brocadia sapporoensis and the denitrifying Denitratisoma oestradiolicum have a mutually beneficial relationship in TS-AuPD/A. Batch tests specifically were designed to elucidate the bacterial communication for efficient nitrogen removal in TS-AuPD/A. The quorum sensing in bacterial communities was responsible for this function. N-acyl-homoserine lactones biosynthesized by anammox, C8-HSL, played a significant mediating role in nitrite and nitrate reduction, enhancing the symbiotic interaction within the TS-AuPD/A system. These findings highlight the critical interplay between TS-AuPD and anammox, mediated by AHL signaling molecules in the TS-AuPD/A systems for enhanced and stable nitrogen removal in wastewater treatment.