Determining an optimized laboratory procedure to extract microplastics from wastewater treatment plant effluents using the acid-washing process

Nowadays, due to population growth and changing consumption patterns, environmental damage has considerably increased. One of these problems is the microplastics present in aqueous media. The important point is that wastewater treatment plants cannot completely remove microplastics and they end up entering aquatic and terrestrial receiving environments, which in turn can endanger living organisms. In the present study, an optimized method is introduced to efficiently detect and extract microplastics from the input effluent and output waste streams of the wastewater treatment plants. First, the seasonal sampling was performed in three seasons: spring, summer, and autumn, to determine the season with the most microplastic production. Then, the acid washing using 30% hydrogen peroxide (H 2 O 2 ) and 0.05 M divalent iron was performed on the prepared samples. Also, since this method is based on creating density differences, sodium chloride (NaCl) salt was used. As a result of this procedure, the number of microparticles and microfibers along with their size (up to lower than 10 m) and morphology were detected in the domestic effluents with an efficiency of more than 98%. Notably, the performance of the studied wastewater treatment plant in terms of microplastic removal efficiency was also evaluated using this method.