BEHAVIOR OF MICROPLASTICS IN WASTEWATER TREATMENT PROCESSES AND ESTIMATION OF ITS LOADING TO LAKE BIWA

Abstract

 Main objectives of this study are to know the behavior of microplastics in wastewater treatment processes and to estimate the loading to Lake Biwa. Four wastewater treatment plants which are separate sewer system were investigated. Microplastics bigger than 100 micrometer were sampled in wastewater treatment processes, and influent and effluent were sampled in order to know the behavior of microplastics which size were 10 to 100 micrometer. As the results of this study, 30 components were identified from wastewater, treated water, sludge, and scum. Concentration of MPs in influent was 158 to 5,000 pieces/m³. Concentration of MPs in effluent was 0.3 to 2.2 pieces/m³, and it was similar to the concentration of MPs in surface water of Lake Biwa. On the other hand, removal efficiency of MPs which size was 10 to 100 micrometer was 76.3%. It was not enough to remove the MPs smaller than 100 micrometer by the rapid sand filtration. The sum of MPs loading from four wastewater treatment plants was estimated to be 501,630 pieces/day, it was close to the total MPs loading from rivers around Lake Biwa in a fine day.