Seasonal Variations in Microplastic Abundance and Removal Efficiency in Wastewater Treatment Plants in Bangkok, Thailand

Wastewater treatment plants (WWTP) are significant contributors to the release of microplastics into aquatic environments. Due to the limited information available in Thailand, examining microplastics from WWTPs could assist the Thai government in establishing guidelines for future microplastic control. This study identified microplastics in various WWTPs across Bangkok, Thailand, during two seasons: the dry period (February to May 2022) and the wet period (June to October 2022). The findings revealed a higher abundance of microplastics during the wet season compared to the dry season. In both influent and effluent, fibers were the predominant shape, making up approximately 86.65% during the dry period and 94.37% during the wet period. Fragments, films, granules, and foam were also detected in all samples. Polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) were the most common polymers present in the microplastic samples. The study also highlighted that the removal efficiency of microplastics from WWTPs ranged from 16.7% to 85.4% during the dry period and from 27.6% to 81.0% during the wet period. These results underscore the importance of long-term monitoring and quantification of microplastics in different WWTP systems in Bangkok. This data can be utilized to estimate microplastic loading in WWTPs and develop effective strategies for microplastic removal from wastewater.