Microplastics in wastewater from developing countries: A comprehensive review and methodology suggestions

Wastewater is a significant pathway for microplastics (MPs) to enter the terrestrial ecosystem. Developing countries contribute 60 % to global plastic production and consumption, but knowledge of MPs in their wastewater is inadequate. This review presents the MP abundance and methodologies used to collect, quantify, and characterize their presence in wastewater from 26 wastewater treatment plants (WWTPs) across 9 developing countries. The effectiveness of MP removal by the reviewed WWTPs varied between 22 % and 100 %. Despite the variety of sampling and analysis techniques, most studies have demonstrated completeness in their analysis procedures. However, only 9 % of the studies follow the complete quality assurance and quality control criteria procedures. Thus, a detailed procedure for sampling and analyzing MPs in WWTPs is proposed, considering developing countries' challenges. Adaptation might be needed based on wastewater and treatment plant characteristics. Nevertheless, this framework provides a reliable method for accurately analyzing MPs in WWTP samples.