Occurrence of microplastics in influent, sewage sludge and effluent of municipal wastewater treatment plant, A case study center of Iran, Qom city

Articles in Press

Document Type : Original Research Paper

Authors

1 Student Research Committee, Qom University of Medical Sciences, Qom, Iran

2 Research Center for Environmental Pollutants, Qom University of Medical Sciences, Qom, Iran

3 Department of Epidemiology and Biostatistics, Faculty of Health, Qom University of Medical Sciences, Qom, Iran

4 Faculty of Health, Qom University of Medical Sciences, Qom, Iran

5 Monitoring and monitoring center for water and sewage quality, department of Qom province water and wastewater, Qom, Iran

6 Environmental Technologies Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, B15 2TT Birmingham, United Kingdom

10.22059/poll.2025.398193.3013

Abstract

The presence of Microplastics (MPs) in the environment poses a significant threat to both humans and ecosystems health. One common source of environmental MPs pollution is the sludge and effluent discharged by wastewater treatment facilities. The purpose of this study is to investigate the MPs removal capacity under different conditions by analysis of MPs in the inlet wastewater, outlet effluent, and sludge of one of the wastewater treatment plants (WWTPs) in Qom city, Iran. Monthly sampling was conducted in spring and summer of 2022, resulting in analysis of a total of 18 samples from wastewater, effluent, and sludge. MPs were identified and separated according to established guidelines followed by further analysis using scanning electron microscopy (SEM) and µ-Raman spectroscopy. The average MPs concentration in wastewater and effluent were 710± 34.67 MP/L and 51± 4.42 MP/L, respectively, while it was 30.76±7.19MP/g in sludge. The treatment plant demonstrated an average MPs removal efficiency of 92.81%. Overall, polyethylene terephthalate (PET) and fibers were the most frequent type and shape of MPs identified across all samples. The dominant sizes of MPs in wastewater and sludge ranged between 250-500 µm, while in the effluent, the MPs were primarily within the 250-100 µm. Based on the findings, approximately 2652×106 MPs are released daily into the environment via effluent, contributing to air, soil, and water pollution. Sludge and effluent used as fertilizer or irrigation can lead to significant MP accumulation in soil, threatening ecosystems and organisms.

Keywords

Main Subjects

Pollution

Articles in Press, Accepted Manuscript
Available Online from 21 December 2025

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