A Ray of Hope: Gamma Radiation for Microplastic Remediation

Abstract

Urban wastewater treatment plants (WWTPs) generate sewage sludge, which retains ≈95% of the microplastics (MPs) processed in wastewater. The literature describes sewage sludges with MP concentrations ranging between 400 and 170,000 particles kg⁻¹ (dry weight) and when this sludge is applied to land, MPs spread into the environment. As a possible treatment for sewage sludge, this study aims to evaluate the effect of gamma-rays on the degradation of sludge MPs. The MPs utilized in the experiments are obtained from secondary sewage sludge provided by a municipal treatment facility and they are physic-chemically characterized (size, shape, composition). MPs are exposed to gamma radiation (γ-irradiation) at different time intervals and total doses to study the response process in sewage sludge. In particular, they are treated with γ-irradiation using cobalt-60 (⁶⁰Co) at doses ranging from 0 to 116 kGy. In this study, MP degradation can be achieved with a maximum degradation percentage of almost 70%. Concerning the specific degradation, research results show that both MP forms exhibit the same 35% degradation rate. This study not only advances the knowledge of how γ-irradiation affects MPs, but it also opens a new approach to fight against the global problem of environmental MPs.