Helm, Paul

This thesis determined the temporal dynamics of microplastics in the biosolid and final effluent of a WWTP for one year (October 2020–September 2021). The WWTP exported 354.1 ± 24.7 billion microplastic particles, or 296.7 ± 39.4 kg of microplastics; of this, 85.7% of counts and 86.6% of mass was exported via biosolids. As such, microplastic loads in biosolids need to be reduced before they are land applied. This thesis further examined the ability of settling treatments to liberate microplastics from biosolids under the effect of four variables (harvest method, stirring, settling time, and biosolid type). Across all treatments, average microplastic removal was 9.01 ± 5.82% in terms of count, and 6.91 ± 4.98% in terms of mass. Overall, this thesis contributed to our understanding of annual microplastic burden in a WWTP and set the foundation for the development of settling-based biosolids treatments to reduce microplastic emissions to the environment.

Author Keywords: Biosolid, Count Concentration, Final Effluent, Mass Concentration, Polymer, Treatment