Integrating microplastic management into a broader wastewater decision-making framework. Is activated granular sludge (AGS) a game changer?

Wastewater treatment plants (WWTPs) are not specifically designed to tackle microplastics (MPs), leaving them in aquatic ecosystems. The novelty of our study is a critical review of the effectiveness of conventional activated sludge (CAS), membrane bioreactors (MBRs), and activated granular sludge (AGS) in managing MPs within WWTPs. We bridge a gap in scientific literature by assessing MP removal and resilience to MPs. Our scope extends beyond MPs management, evaluating these technologies against environmental, economic, and social criteria. Findings show that MBR outperforms CAS and AGS in MP removal but faces challenges with smaller MPs due to fouling and secondary pollution. AGS shows similar removal rates to CAS but often superior resilience to MPs, given its higher decontamination capabilities. Environmentally, AGS may better reduce indirect greenhouse gas (GHG) emissions due to lower energy and chemical demands. Moreover, AGS exhibits higher resource recovery potential (e.g., biopolymers, phosphates). Socially, MBR excels in pathogen removal, reducing waterborne disease risks. Economically, AGS is the most cost-effective technology regarding both operational and capital expenditures. However, MPs can impact these criteria by reducing nutrient removal efficiency and increasing both direct and indirect GHGs. MPs create “plastisphere” habitats, reducing pathogen removal and compromising water safety. Moreover, MPs increase energy and chemical use, especially in MBR systems due to fouling concerns.