Bioresources are a valuable source of soil health-enhancing organic matter and essential crop nutrients that support a circular economy. However, biosolids often contain harmful unregulated contaminants such as microplastics, persistent organics and pharmaceuticals. Persistent contaminants present significant environmental risks as they bioaccumulate in soil and biota, with potential detrimental impacts on soil health. Biosolids contaminants applied to soils can also be mobilised and impact water quality, spreading beyond agricultural systems to surface and groundwaters and eventually the ocean. Upstream and downstream solutions must be implemented if hidden unregulated contaminant dangers, that aren't routinely monitored, are to be tackled.

This presentation will summarise recent important research on the extent and environmental impact of microplastic and organic contaminants present in biosolids, as well as opportunities to reduce the release of these contaminants into the environment. For example, policy-informing evidence of biosolids as a source of microplastics and research into the impact of PFAS (per- and polyfluoroalkyl substances) on soil health and their potential to flow from agricultural land to UK river systems. The presence of contaminants in biosolids is the inevitable byproduct of upstream sources and widespread continued manufacture, use, and release or disposal of products containing these contaminants. We will present potential viable solutions for reducing environmental harm, including downstream wastewater and sewage sludge treatment and upstream source control (e.g., phasing out the most harmful chemicals from use). Overall, this work seeks to encourage water industries, regulators and policy makers to develop a clear road map for tackling the ongoing challenges associated with the recycling of contaminated bioresources to land, in line with circular economy commitments.