Microplastic Pollution in an Urban Wastewater Treatment Plant: Unravelling Problems and Proposing Solutions

Microplastics (MPs) are detected ubiquitously in aquatic environments worldwide, with wastewater treatment plants (WWTPs) serving as significant pathways for their entry. This study investigates MP removal efficiency and suggests improvements in a conventional municipal WWTP in Bangkok, Thailand. Wastewater samples were collected using a volume-reduced method and filtered into three size ranges (0.05-0.5, 0.5-1.0, and 1.0-5.0 mm). Particles bigger than 0.5 mm were assessed for abundance using an optical microscope and identified for polymer types using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, while smaller particles were analyzed using fluorescence microscopy and micro-FTIR. The average concentration of MPs entering the WWTP was 16.55±9.92 MPs/L, whereas the concentration discharged into the environment was 3.52±1.43 MPs/L. The resultant MP removal efficiency of the Bangkok WWTP stands at approximately 78%, a figure lower than that of WWTPs in developed countries. This discrepancy is attributed to the absence of a primary clarifier within the Bangkok WWTP and an under-designed grit channel. Thus, the implementation of a filter system using activated carbon is suggested. Based on the calculations, 21 filter units are required for the Bangkok WWTP to improve MPs’ removal effectiveness. This study provides vital data on the presence of MPs in a Bangkok WWTP, emphasizing challenges that impede effective removal efficiency. Additionally, this study proposes potential solutions to enhance the removal of MPs and address these issues.