Contamination by ≥ 6.5 μm-sized microplastics and their removability in a conventional water treatment plant (WTP) in Thailand

Plastic-contaminated drinking water is currently a global concern. This study focused on the microplastics (MPs) contamination in a conventional water treatment plant (WTP) in Thailand. MPs were enumerated based on size fractions (6.5?>500 ?m) and morphology, and the polymer types of the sorted MPs were detected. Also, the MPs removability in the different treatment units was evaluated. Grab samples were collected in the dry and rainy seasons from five sampling points (9 L from each). These samples were raw water, effluents of the screen, clarifier, and filter, and treated drinking water. Optical microscopy, ATR-FTIR spectroscopy (300?>500 ?m), Nile Red-tagging (6.5-300 ?m), and Confocal Raman spectroscopy (1-300 ?m) were used as the analytical techniques. The overall removal efficiency of the WTP was found to be 67.6 % and 57.2 % in the dry and rainy seasons, respectively, with an average of 609.1 ? 84.7 p/L still present in the treated water. Clarification and dual media-filtration contributed toward the removal of MPs. The smallest-size fraction (6.5-53 ?m) dominated the samples, while fibers and fragments were abundantly found. PE, PP, PET, PA, and PVC were commonly identified. Possible sources of MPs contamination can be from raw water and contamination from within the WTP. A substantial number of MPs escape with treated effluent, imposing a challenge on the drinking water quality in Thailand. The current study found a high abundance of MPs within the 6.5-300 ?m range, largely representing fibers. Given the evidence of their cytotoxicity by the latest researches, the contamination within WTPs should be monitored.

Automated summary

Plastic-contaminated drinking water is a global concern, with a focus on microplastics contamination in a conventional water treatment plant in Thailand. The study found that the water treatment plant had an overall removal efficiency of 67.6% to 57.2%, with a substantial number of microplastics still present in the treated water. The dominant sources of microplastics contamination were identified as raw water and internal contamination within the plant, posing a challenge to drinking water quality in Thailand.