The presence of cationic polyacrylamide attenuated the toxicity of polyvinyl chloride microplastics to anaerobic digestion of waste activated sludge

[Display omitted] •Cationic polyacrylamide (cPAM) at 3.0 mg/g TS recovered the methane production.•cPAM inhibited solubilization but facilitated hydrolysis and acidification.•The addition of cPAM effectively restored the performance of anaerobic sludge.•The presence of cPAM increased the abundances of dominant acidogens and methanogens.•cPAM reduced the bisphenol-A leaching and the reactive oxygen species in cell. The broad sources of microplastics rendered their inevitable transportation from raw wastewater to wastewater treatment plants. Most of the microplastics are found to be accumulated in waste activated sludge (WAS) and the retention of microplastics is now threatening the subsequent anaerobic digestion of WAS. Therefore, it is urgent to develop viable methods to mitigate the adverse impacts of microplastics on methane production. Here, the feasibility of adding cationic polyacrylamide (cPAM) to alleviate the toxicity of polyvinyl chloride (PVC) microplastics (i.e., 30 mg/g TS) to WAS anaerobic digestion was investigated. As a result, the moderate addition of cPAM (i.e., 3.0 mg/g TS) significantly recovered the methane production from 15.6 ± 1.7% inhibition to 5.8 ± 0.6% inhibition compared with the control reactor containing PVC microplastics (P