Assessing the Sources of Microplastic Pollution in The Maumee Watershed: A Geospatial Approach

Abstract:

Microplastics (<5mm) are transported to freshwater by wind, stormwater runoff, rainwater drainage, flooding, wastewater treatment plant (WWTP) discharge, and landfill leachate. Due to the high disposability and low recovery rate of plastic materials associated with its slow degradability, microplastics are accumulating in nature. This study aimed to estimate the annual microplastic discharge in waterbodies from WWTP effluent and biosolids land application for the Maumee River Watershed located in Northwest Ohio, which drains to Western Lake Erie Basin. The results estimated that 3.75 billion microplastic particles are released in the Maumee Watershed annually from 72 WWTPs. In the case of the annual release of microplastics from land applied biosolids - assuming  1%, 5%, 10% and 25% release of microplastic from biosolids applied in all permitted land (only in Ohio) – biosolid sources in the Maumee Watershed are approximately 83.26, 426.29, 832.58 million and 2.08 billion particles respectively. The most WWTP based annual microplastic discharge are found in the Upper Maumee (1.38 billion), Lower Maumee (800.62 million), and Auglaize subwatershed (556.73 million), and county wise- Allen County of Indiana (1.35 billion), Lucas (463.74 million) and Allen (368.6 million) Counties of Ohio. In the case of biosolid-based microplastic release from all biosolid permitted land in the Ohio section of the Maumee Watershed, the estimation of source subwatersheds indicates Auglaize, Lower Maumee and Tiffin subwatersheds altogether releasing approximately 77.58 million (1%) to 1.94 billion (25%) microplastic particles per year into the waterbodies.

Keywords: Microplastic, Wastewater Treatment Plant, Biosolid, Maumee Watershed

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