Occurrence, identification, and discharge of microplastics from effluent and sludge of the largest WWTP in Iran—South of Tehran

Abstract

Microplastic pollution is a serious threat to the biota and humans, and wastewater treatment plants act as a pathway for entering microplastics into the environment. This study discusses the identification and quantification of microplastics in the south of Tehran municipal WWTP. The sampling was repeated three times in a month, overall, nine times for water samples and once a month in total, three times for digested sludge samples by steel bucket with the WPO method. The microplastics from water and digested sludge samples were identified using the micro‐Raman microscope. According to this study, 98.9% of microplastic particles in effluent and 99.2% of microplastics particles in the sludge were fibers. The influent contained an average of 180 ± 4.3 MP/L and was reduced to 5.3 ± 0.31 MP/L in the final effluent. Despite this significant reduction, we calculate that this WWTP releases 2.3 × 109 microplastics per day through final effluent and 1.61 × 1010 particles per day through dried sludge into the environment. We performed micro‐Raman analyses and ICP mass to measure the amount of heavy metal absorption of MPs. In addition, SEM analyses were used to study the surface morphology of microplastic particles. Practitioner Points Fourteen different polymers were identified in the influent, effluent, and digested sludge. The main collected shapes obtained were fiber, film, and fragment, which fiber was the predominant polymer in this WWTP. The plant releases 2.3 * 109 MPs per day to its downstream environment. This WWTP has average removal with an efficiency of 99.06%.

The effects of land use types on microplastics in river water: A case study on the mainstream of the Wei River, China

“…Previous studies have demonstrated that environmental factors, such as temperature, biochemical oxygen demand (BOD), total suspended substance (TSS) and turbidity, had the greatest influence on microplastics abundance in the Brantas River (Buwono et al, 2021). Various pathways contribute to the transport of microplastics from land to rivers, including runoff, rainstorms, atmospheric deposition, and sewage discharge from wastewater treatment plants, all of which are susceptible to human activities (Hurley et al, 2018;Oveisy et al, 2022;Trainic et al, 2020). Moreover, anthropogenic factors such as land use, urbanization have been reported to correlate strongly with microplastics abundance (Dai et al, 2022).…”