Chloroxylenol was the last straw for mixed disinfectants in inhibiting the activity of the heterotrophic/sulfur autotrophic denitrification systems: Performance, microbial community and different fractions of resistance genes

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-10, Vol.498, p.155518, Article 155518
• Main Authors: Guo, Yi, Gao, Jingfeng, Yuan, Yukun, Wang, Yuxuan, Wang, Hanyi
• Format: Article
• Language: English
• Subjects: Bacterial community structure; Benzethonium chloride; Chloroxylenol; Heterotrophic/sulfur autotrophic denitrification; Resistance genes
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.155518

[Display omitted] •An efficient HNAD was successfully initiated by thiosulfate and sodium acetate.•PCMX improved but BEC and mixed disinfectants inhibited denitrification activity.•PCMX elevated the levels of EPS, which was damaged by BEC and mixed disinfectants.•P-HSAD had the most enriched iRGs, and PB-HSAD led to a more complex spread of RGs.•Reduced Sulfurimonas led to inhibition of denitrification in B-HSAD and PB-HSAD. The effects of typical disinfectants chloroxylenol (PCMX) and benzethonium chloride (BEC) on heterotrophic/sulfur autotrophic denitrification (HSAD) systems under single and mixed stress were studied. PCMX increased the system’s denitrification activity, but BEC and mixed disinfectants, particularly mixed disinfectants, significantly reduced denitrification activity. PCMX elevated the content of extracellular polymeric substances (EPS) in HSAD system, and the structure of EPS was tight and stable. Whereas the other two systems had lower EPS content and looser structure, highlighting the greater damaging effects of BEC and mixed disinfectants. PCMX led to the enrichment of more than half of the resistance genes (RGs), while mixed disinfectants resulted in the fewest RGs enriched and the lowest correlations between bacteria and RGs of three systems. The transformation of extracellular qacE was induced by PCMX. BEC caused RGs to leak out of bacteria, and mixed disinfectants contributed to transformation and efflux of RGs. PCMX increased the abundance of Thiobacillus and Sulfurimonas. Thiobacillus was more abundant in low doses of BEC and mixed disinfectants, but it reduced at high concentrations, while the amount of Sulfurimonas continued to decrease. This study provided an insight into the effects of single and mixed disinfectants on HSAD systems, and guided future efforts to control disinfectants and RGs pollution in wastewater treatment.