Behavior of nitrogen, phosphorus and antibiotic resistance genes under polyvinyl chloride microplastics pressures in an aerobic granular sludge system

Polyvinyl chloride (PVC) is the common microplastics (MPs) detected in wastewater treatment plants causing harmful effects on organisms. However, the effects of PVC MPs on an aerobic granular sludge (AGS) system is not clear. In present study, the behavior of nitrogen, phosphorus and antibiotic resistance genes (ARGs) under PVC MPs pressure in an AGS system was investigated. Results showed PVC MPs promoted the phosphorus release and uptake of polyphosphate accumulating organisms (PAOs) and reduced total inorganic nitrogen removal efficiency. Extracellular polymeric substances were positively linked to PVC MPs. Moreover, PVC MPs increased the abundance of PAOs and Nitrospira, but decreased the abundance of denitrifying bacteria. The propagation of intI1 and tetE could be facilitated by PVC MPs, and the main antibiotic resistance mechanism of AGS system was the efflux pump. Chloroffexi, Actinobacteria, Bacteroidetes and Nitrospirae hold higher tolerance to PVC MPs than Proteobacteria. Network analysis showed PVC MPs positively correlated with some Accumulibacter clades and ARGs. This study indicated PVC MPs inhibited nitrogen removal and benefited ARGs propagation, which need to cause great concern.