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Effects of polyvinyl chloride microplastics and benzylalkyldimethylethyl compounds on system performance, microbial community and resistance genes in sulfur autotrophic denitrification system
Summary
Researchers found that PVC microplastics and a common disinfectant chemical in wastewater treatment systems promoted the spread of antibiotic resistance genes, with the disinfectant having an even stronger effect than the microplastics. The microplastic surfaces harbored disease-causing bacteria that carried these resistance genes. This is concerning because wastewater treatment plants could be releasing both microplastics and antibiotic-resistant pathogens into waterways, potentially threatening human health.
Benzylalkyldimethylethyl ammonium compounds (BAC) and polyvinyl chloride microplastics (PVC MPs), as the frequently detected pollutants in wastewater treatment plants (WWTPs), have attracted more concerns on their ecosystem risks. Therefore, this study investigated how the sulfur autotrophic denitrification (SAD) system responded to the single and joint stress of PVC MPs (1, 10 and 100 mg/L) and BAC (0.5, 5 and 10 mg/L). After 100 days of operation, the presence of 10 mg/L BAC led to obviously inhibitory effects on system performance and microbial metabolic activity. And the additions of PVC MPs or/and BAC stimulated the proliferation of intracellular resistance genes (RGs), whereas exposure to BAC increased the abundances of extracellular RGs and free RGs in water more significantly. Compared to the joint stress, BAC single stress resulted in higher abundances of free RGs in water, which further increased the risk of RGs propagation. Moreover, the interaction between mobile genetic elements and extracellular polymeric substances further increased the spread of RGs. Pathogens might be the potential hosts of RGs and enriched in SAD system and plastisphere, thereby leading to more serious ecological risks. This study will broaden the understanding of the environmental hazards posed by PVC MPs and BAC in WWTPs.