Tracing and Quantifying Microplastics in Bristol’s Urban Water System

<title>Abstract</title> The extent of microplastic pollution is widespread, including aquatic ecosystems in urban environments. The aim here was to build a quantified mass balance model, exploring and tracing the microplastics within Bristol’s urban water system, filling a knowledge gap, specific to this geographical region but developing a model that can be applied more generally for urban water systems. A multitude of secondary data were compiled, reviewed, analysed and quantified to inform a mass balance model. The model represents the number of microplastics passing through each section of Bristol’s water system where one of the main findings indicates domestic households as a major source of microplastics to the urban water system, while wastewater treatment plants capture ~99.8% of microplastics. Our second finding implies the transfer of microplastics from wastewater to sludge is a sink, but if the sludge is turned into fertilizer, this is to be considered as an important microplastic source for the wider environment. A source of uncertainty stems from the range of quantification methods used in the reviewed data and points out the necessity of further research regarding standardised sampling techniques and approaches to feed into sophisticated detection, quantification, and modelling systems.