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Sewage treatment plant (STP) acts as a potential source of microplastic contamination in the environment. The presence of microplastics in the sewage treatment plant is reported over the globe in varying concentrations. Hence, the current study is intended to evaluate the presence and abundance of microplastics occurring in sewage treatment plants in India. The samples were processed through digestion and density separation, followed by microscopic and polymer identification through Fourier transform infrared spectroscopy. Also, different wastewater parameters were studied to analyze their influence. High microplastic concentrations were detected in the influent (1860 ± 265 MPs/L), which reduced by > 90%, to around 148 ± 51 MPs/L in the effluent. The concentration of microplastics in sewage sludge was 830 MPs/kg. The prominent plastic types identified include low-density polyethylene, polypropylene, polyurethane, polyvinyl chloride, and rayon. The smaller particles prevail in the effluent, releasing around 30 billion particles per day to the environment. This suggests that the current STP is efficient in removing the majority of the particles, but considerations are needed to avoid the ecological risks associated. [ABSTRACT FROM AUTHOR]

This study investigates the occurrence and characterization of microplastic (MP) in sewage sludge from 3 different cities along the Ganga River, India and their toxic impact while applying sludge for crop production. MP occurred in the ranges of 29.2–60.8 × 103 particles kg−1 with an abundance of 1–5 mm (11.12%), <1 mm–100 μm (32.65%), and 20–100 μm (56.23%) size particles. ATR-FTIR analysis suggested polypropylene, polyethylene, nylon, and polycarbonate as sludge's most common MP polymer. In lab scale trials, sludge MP showed significant toxicity in Vigna radiata and reduced vegetative growth and plant weight was recorded with sludge-inoculated setups. Seedlings with sludge exhibited higher activities of catalase, superoxide dismutase, hydrogen peroxide (H 2 O 2), and malondialdehyde than the control setups. Furthermore, fluorescence microscopy confirmed the MP bioaccumulation in tested seedlings. In summary, our results suggested that wastewater treatment plants (WWTPs) sink large volumes of MP in sewage sludge, which could be hazardous while applying such biosolids for crop production. MP seasonal dynamics in local WWTPs and their role in the mobilization of other toxicant chemicals could be investigated in future studies in this series. [Display omitted] • MP load in sewage sludge ranged between 29.2 and 60.8 × 103 particles/kg. • MP-sized 20–100 μm were higher in sludge. • The plant grown in sludge showed low growth but high oxidative stress. • Fluorescence microscopy confirms the MP accumulation in seedling roots. [ABSTRACT FROM AUTHOR]

Sewage treatment plants (STPs) as a carrier of microplastics (MPs) have received considerable attention worldwide recently. In India, the majority of studies on MPs have been conducted in sediments, riverine, and marine systems, while knowledge on MPs occurrence in STPs is scarce. Henceforth, this work evaluated the presence of MPs in sewage and sludge in a hybrid growth, secondary treatment-based STP system. Optical microscopy, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy methods were used to examine the abundance of MPs in raw sewage, effluent from different treatment units of the STP, and sludge samples. A total number of MPs of 201 ± 19 (2021) and 197 ± 22 (2022) were detected in the studied STP system. Results showed that MPs ranged between 64.3 ± 4.89–47.66 ± 4.71 n/L (sewage) and 1.14 ± 0.30–1.38 ± 0.65 n/g (sludge) with the overall removal efficacy of the studied STP estimated to be around 80%. Fragments and fibers were predominant among all shapes and particles mostly belonged to sizes <50 μm and <50 μm–250 μm in sewage and sludge, respectively. In total, seven polymers were identified of which low-density polyethylene (LDPE) constituted the highest proportion in sewage (26%–31%) and polyvinyl chloride (PVC) contributed the highest in the sludge (22%–27%). Moreover, MPs control measures have been discussed based on the findings of this study to restrict MPs re-entry into the environment via treated effluent and sludge. [Display omitted] • First study on MPs occurrence and removal in a hybrid growth MBBR-based STP. • Around 80% MPs were removed via the primary and secondary treatment stages in the STP. • LDPE (in sewage) and PVC (in sludge) were the most prevalent polymers. • Small-sized MPs (<250 μm) like fragments and fibers were predominant shapes. • Advanced treatment options for MPs removal from secondary-treated effluent discussed. [ABSTRACT FROM AUTHOR]