Occurrence and characteristics of microplastic in different types of industrial wastewater and sludge: A potential threat of emerging pollutants to the freshwater of Bangladesh

Microplastics (MPs) are emerging contaminants found in large quantities in every compartment of the environment. In Bangladesh, this is the first evidence of MPs pollution in wastewater and sludge whereas industry contributes the highest gross domestic product to the country's economy. This study investigated MP's pollution levels in wastewater and sludge from the five different types of industries i.e., dyeing, washing, pharmaceuticals, battery, and printing. Total MPs abundance in the inlet water, outlet water, and sludge was found to be 2713 & PLUSMN; 566 MPs/L, 293 & PLUSMN; 47 MPs/L, and 115,878 & PLUSMN; 20,453 MPs/kg, respectively. The results indicated that MP contamination was comparatively higher in the sludge compared to inlet and outlet water. The existing wastewater treatment showed a certain removal efficiency but that is not at a satisfactory level. Fibers were the most abundant shape among MPs and black, blue, and red was the abundant color. Fourier Transform Infrared (FTIR) analysis showed that nylon, cellulose acetate, and polystyrene are the predominant polymers in the wastewater treatment plant. A significant amount of MPs pollution was found in wastewater and sludge which was related to the industrial raw materials and final products. However, this study suggests that it is high time to implement strict controls to minimize local MPs pollution and reduce the potential threat of emerging pollutants to freshwater.