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Effects of polyvinylchloride microplastics on the toxicity of nanoparticles and antibiotics to aerobic granular sludge: Nitrogen removal, microbial community and resistance genes
Summary
Researchers examined how PVC microplastics affect wastewater treatment systems that also contain copper oxide nanoparticles and the antibiotic ciprofloxacin. They found that low concentrations of microplastics actually reduced some toxic effects of the other pollutants, but higher concentrations worsened nitrogen removal efficiency and increased antibiotic resistance genes. The study highlights the complex ways microplastics can alter the behavior of other contaminants in water treatment.
Copper oxide nanoparticles (CuO NPs) and ciprofloxacin (CIP) have ecological risk to humans and ecosystems. Polyvinylchloride microplastics (PVC MPs), as a representative of microplastics, may often coexist with CuO NPs and CIP in wastewater treatment systems due to their widespread application. However, the co-impact of PVC MPs in wastewater systems contained with CuO NPs and CIP on nitrogen removal and ecological risk is not clear. In this work, PVC MPs co-impacts on the toxicity of CuO NPs and CIP to aerobic granular sludge (AGS) systems and potential mechanisms were investigated. 10 mg/L PVC MPs co-addition did not significantly affect the nitrogen removal, but it definitely changed the microbial community structure and enhanced the propagation and horizontal transfer of antibiotics resistance genes (ARGs). 100 mg/L PVC MPs co-addition resulted in a raise of CuO NP toxicity to the AGS system, but reduced the co-toxicity of CuO NPs and CIP and ARGs expression. The co-impacts with different PVC MPs concentration influenced Cu concentrations, cell membrane integrity, extracellular polymeric substances (EPS) contents and microbial communities in AGS systems, and lead to a change of nitrogen removal.