Microplastics in Wastewater

Microplastics are ubiquitous across ecosystems. Commonly found in aquatic and terrestrial environments, and classified as small particles and fibers less than 5 mm in size, microplastics can be incorporated into a wide range of organisms across the food web. So far, the majority of microplastic research has occurred in marine and estuarine ecosystems. Freshwater microplastic research is slowly increasing, with majority of the efforts being focused on quantifying concentrations in streams and developing analytical methods. More recently, researchers have turned towards identifying the sources of microplastics. One source with the potential to introduce large quantities of microplastics into the environment are wastewater treatment plants. Most cities and towns in a developed nation have centralized wastewater treatment plants that receive sewage reflecting human activities within the service area. Therefore, treatment plants can serve a model system to understand microplastics used and disposed by humans, the effectiveness of treatment processes in removing microplastics, and the concentration and characteristics of microplastics being discharged into receiving streams via wastewater effluent. Inflow and infiltration to treatment plants can also reflect the presence of microplastics in stormwater runoff. Wastewater treatment plants have already been identified as an important pathway by which microplastics enter the environment, but it is unclear how great a role they play compared to other pathways. Moreover, a lack of standardized sampling, quantification and characterization techniques for microplastics in aqueous samples makes it challenging to compare results between different studies, and evaluate the sources effectively.

To address some of the abovementioned knowledge gaps in freshwater and wastewater microplastic research, we are conducting a study to assess microplastics in three wastewater treatment plants and their respective receiving streams around middle Tennessee. We are focusing focus on treatment plants that differ in service area population density, impact of urbanization, hydraulic capacity, treatment processes, and receiving streams where wastewater effluent is discharged, to understand if and how these factors may regulate microplastics entering Tennessee’s aquatic environment. We will also develop and optimize laboratory techniques for sampling, sample processing, quantifying and characterizing microplastics in wastewater and stream samples.

Findings from this preliminary study will be used to develop standardized sampling and analysis methodologies for microplastics in wastewater treatment plants and streams in Tennessee. Such methodologies can be used by state, federal and other entities interested in monitoring microplastics in Tennessee’s waterbodies. The study will also, for the first time, provide a preliminary understanding of the fate and contributions of microplastics from Tennessee’s wastewater treatment plants. The findings may help inform future management strategies to reduce the burden of microplastics in Tennessee’s diverse aquatic ecosystem.

Collaborator: Dr. Tania Datta at Tennessee Tech