DOI: 10.14457/tu.the.2019.59
title: Analysis of micro-plastics (MPs) in bottled water, tap water, and a conventional water treatment plant in Thailand

description: With the extensive plastic pollution occurring in freshwater bodies, it is an hourly need to look into the drinking water sources as well, to ascertain their MP contamination levels. Few studies concentrated to Europe and United States, report on the plastics found in human consumable water. In an era where there are lot of concerns on the potable water quality, and given the size- and shape-dependent toxicity of MPs, more focus is needed on MPs in drinking water, especially in Asian regions.This study focuses on the MP content of three drinking water sources in Thailand: water from Bang Khen water treatment plant, tap water in Thammasat University, and bottled water. The objectives of the study are to enumerate the MPs in above samples based on size fractions and morphology, detect the polymers among the sorted MPs, evaluate the MP removability at each treatment unit of the treatment plant, and suggest possible sources of contamination with respect to the findings. MPs were analyzed down to 6.5 µm, categorizing into size fractions within the 6.5-≥500 µm range. Combined methods of optical microscopic sorting and analysis by fluorescence microscope (Nile Red-tagged particles) were followed to enumerate the MPs. Polymers were identified by the ATR-FT-IR spectroscopy and Confocal Raman microscopy. In the treatment plant, the overall removal efficiency averaged across the two seasons was found to be 63.7%, having 594.5±73.7 p/L escaped with the treated water. Clarification and dual media-filtration collectively make a larger contribution to achieve this removability. Tap water was found to contain 95.4±8.9 p/L in average. With respect to the MP concentration in the treatment plant-effluent, this is a significant reduction due to the effect of the filtration techniques used at the end of the water supply pipe lines. All bottled water samples too showed the signs of MP contamination, irrespective of the packaging type (PET, PC and glass). However, PET-bottled water had the highest MP count (221.7±21.5 p/L), with the PC dispenser bottle having the second highest concentration (125.0±36.9 p/L). The average in glass-bottled water (103.4±5.2 p/L) was significantly less than that of plastic-bottled water, implying the positive effect of plastic packaging on MP contamination in bottled water. In all the samples, the least size fraction dominated (6.5-53 µm in treatment plant-samples and tap water; 6.5-20 µm in bottled water), while fibers and fragments were abundantly found. Polymers like PE, PP, PET, PA and PVC were commonly identified, having special components like PAM been detected in treatment plant-samples indicating the contamination within the plant, and rutile having been found in PET-bottled water showing the plastic additive-leaching.The findings convince that the drinking water quality in Thailand is challenged with plastic contamination, exposing humans to direct plastic intake. Long-term exposure to plastic particles leads to several health implications. MPs of &lt;200 µm have been proven for their potential for cellular uptake which is highly concerned. Given the abundance of &lt;200 µm MPs in these drinking water sources, it is encouraged to extend the studies to monitor the contamination within the treatment plants, water supply system, and bottling plants.