Effects of Sand Filters in Wastewater Treatment Plants on Microplastic Output

Microplastics have been found in the oceans and in freshwater systems and can carry bacteria that the usual suspended solids do not. They also have a high potential for bioaccumulation, as tiny organisms at the bottom of the food chain can ingest them because of their small size. Because the research on microplastics in freshwater is limited, I wanted to know if microplastics could be detected in freshwater streams, if they would be found in higher concentrations downstream from wastewater treatment plants, and if having sand filters on wastewater treatment plants would decrease their output of microplastics. In this study, microplastics were pieces of plastic smaller than 5mm but greater than 0.3mm, and a 0.064 mm plankton net was used to collect samples at eight sites in and around four wastewater treatment plants, two with sand filters and two without. Microplastics were found in all of the samples collected, both upstream and downstream of wastewater treatment plants. The effect of having sand filters in wastewater treatment plants on the amount of microplastics downstream was that although the total weight of the microplastics per liter did not increase, the number of pieces of microplastic did. These pieces were much smaller than those found downstream of wastewater treatment plants that did not have sand filters.