Characteristics and removal efficiency of microplastics in sewage treatment plant of Xi'an City, Northwest China

Wastewater treatment plants (WWTP) are the important source of microplastics (MPs) in the environment, but the distribution and property of MPs in WWTPs are not fully understood. The study systematically investigated the transportation, characteristics and fate of MPs in both sewage and sludge of WWTP in Xi'an, a western region of China to complement the research on the fate of MPs in WWTP in inland China. The consequence was abundance, size, shape, color and type of MPs in sewage and sludge of different treatment processes were analyzed and compared by the metallurgical microscope and Fourier Transform Infrared (FTIR) spectrometer. Results showed that the MP abundance decreased from 288.5 n/L of the influent to 22.9 n/L of the effluent, corresponding to the removal rate of 92.1%. Among them, the secondary treatment has the best removal effect, with a removal rate of 72.1%. With the treatment process, the distribution of MPs with different characteristics is constantly changing, which leads to differences in the distribution of MPs in sludge and sewage. It is speculated from the characteristics of MPs that domestic sewage is still the main source of microplastics in Beishiqiao WWTP. Restricting the use of plastic products in daily life or finding alternatives is of great significance to the construction of MPs pollution.