Occerence of microplastic in municipal sewage treatment plant (STPs) in Korea

Municipal sewage treatment plants (STPs) are suspected to be point sources of microplastics in freshwater systems. In order to survey the occurrence of microplastics in Korean STPs, a nationwide reconnaisance monitoring was conducted in influents and effluents of 50 STPs, covering wide range of treatment processes and capacity. Sampling volumes 60 mL and 1000 L for influent and effluent samples, respectively. Influent samples were brought to laboratory where they were pretreated and filtered through 45 μm stainless steel sieve. On the other hand, effluent samples were filtered through cunstom-made sieves at the lowest size of 100 μm. Filtrate microplastic particles were confirmed using their infrared spectrum under dissection microscope. The major shape of microplastics was fragment type and thermoplastics were main materials of microplastics in STPs. Typical levels of microplastics were approximately …