Investigation of microplastic removal in wastewater treatment plants

In addition to the rapidly increasing production of plastics in recent years and the use of these materials in every field, inadequate management of plastic wastes has caused plastic pollution to be seen intensively all over the world. Microplastic (MP) particles, which are formed as a result of the physical, biological and chemical breakdown of macroplastics and also originate from cleaning products, cosmetics and personal care products, have been detected in different environmental environments such as sea, lake, river, atmosphere and soil. Wastewater Treatment Plants (WWTPs) are known to be important point sources of MP for aquatic and terrestrial environments. Although MP removal efficiencies are high in WWTPs, there is a significant amount of MP release considering the daily amount of effluent discharged to receiving environments. In this study, the properties of MPs in wastewater and sludge samples taken from different units of WWTP in Gemlik district of Bursa during 12 months were investigated. Wastewater and sludge samples collected from 7 different points of the plant were subjected to different treatments with organic and inorganic removal methods and MPs were separated from the samples. MPs were first classified in terms of size, shape, color and counted using a stereo microscope. Then, plastic types were determined using ATR-FTIR spectroscopy. The MP concentration in the influent and effluent of the WWTP was 107.1±40.2 MP/L and 4.1±1.1 MP/L, respectively. Although the MP removal efficiency of the plant is 96.17%, approximately 74 825 000 MP is discharged into the Marmara Sea every day. The amount of MP in the effluent sludge is 14.3±7.1 MP/g. The daily amount of sludge generated in the WWTP is 22 tons/day and the amount of MP accumulated in the waste sludge is 314 600 000 MP/day and the annual accumulated amount is calculated as approximately 1.15 × 10 11 MP. In the wastewater and sludge samples, the predominant MPs in terms of shape, size, color and type were determined as fiber shaped, 1 mm - 0.5 mm in size, black and transparent colored and PE, PP, PET types, respectively.