Response of wastewater treatment performance and bacterial community to original and aged polyvinyl chloride microplastics in sequencing batch reactors

Microplastics (MPs) are prevalent in wastewater treatment systems, and their behavior is further complicated after undergoing aging processes. This study explored the impact of original and aged polyvinyl chloride (PVC) MPs on wastewater treatment performance and bacterial communities. Results revealed that Fenton-aging treatment induced surface roughening of the MPs and altered their chemical properties. Prolonged exposure to original and aged PVC MPs severely inhibited the removal of chemical oxygen demand and NH₄⁺-N, along with lower sludge concentrations. Additionally, PVC MPs increased the production of loosely-bound extracellular polymeric substances (EPS) and decreased protein levels in tightly-bound fractions. The presence of PVC MPs also shifted the bacterial community, reducing nitrogen removal bacteria while enriching EPS-forming bacteria. Furthermore, exposure to PVC MPs led to a decrease in the abundance of key genes involved in nitrogen metabolism. These findings offer insights into the effects of MPs, especially aged variants, on wastewater treatment processes.