Study of occurrence, abundance, and characterization of microplastics in wastewater treatment plant in New Delhi, India

Wastewater treatment plants (WWTPs) are considered the most significant contributors to microplastic (MP) pollution in aquatic ecosystems. MPs are defined as plastic particles less than 5 mm in size that are difficult to remove by WWTPs, posing risks to aquatic life, human health, and the overall ecosystem. This study investigates the prevalence of MPs in influent wastewater, treated effluent water, and sludge from WWTP. The samples were collected from Keshopur WWTP in New Delhi, whose effluents flows into the Yamuna River via Najafgarh drain. The collected samples were filtered through various sieves, digested with wet peroxide oxidation, sorted, and assessed. Visual inspection and microscopic analysis showed that the majority of MPs in the samples were blue, red, golden, white, and green in color, appearing as fibers, films, fragments, pellets, and beads. The abundance of MPs has been estimated to be 7 MPs/L in influent, 4 MPs/L in treated effluent, and 993 MPs/kg in sludge. The chemical composition of MPs was determined using Raman spectroscopy and was identified as polyethylene terephthalate, polystyrene, polyethylene, polypropylene, polyester, and polyvinyl alcohol. Notably, polypropylene was most prevalent in sludge (40.27%), while polyester dominated in influent wastewater (63.93%) and treated effluent water (61.76%). The average removal effectiveness of MPs in WWTP was discovered to be only 42.86%. The polymer hazard index employed MP risk assessment, whereby indicated a high to danger category of pollution. Therefore, understanding the behavior of MPs within WWTPs is crucial for developing more effective treatment strategies and mitigating their impact on the environment.