Microplastics as an emerging contaminant in wastewater treatment plants

Plastic pollution is most visible, ubiquitous, and become one of the most pressing environmental issues. The plastics in the environment break down into small debris called microplastics (MPs <5mm) and are categorized as Primary MPs (intentionally produced) and Secondary MPs (break down from larger items) and tackling microplastics pollution involves identifying the sources ( waterways) and finding suitable management options. This thesis reviewed (Chapter 1 and Chapter 2) studies on global wastewater treatment plants (WWTPs) confirming that they serve as pathways or sources for pollution by microplastics (MPs) into terrestrial and aquatic ecosystems. We critically examined the literature to understand the sources, fate and behaviour of MPs in WWTPs, and the implications of treated effluents on soil and aquatic systems. The transport of chemical and biological contaminants is also discussed in detail and knowledge gaps for methodological approaches for determining plastics in wastewater effluents and biosolids were found. There is a need to develop a framework to examine the interactions of complex chemical mixtures and biological contaminants with the plastics at treatment plants. This research further signifies the importance of collecting data on the transmission of MPs through biosolids and the urgent need to develop a risk assessment strategy that will establish levels of contamination.