The Chemical Investigations Programme (CIP) brings together water companies in England and Wales with regulators to investigate a range of chemical substances, via the UK Water Industry Research platform (UKWIR). Building on CIP3, the CIP4 Sludge Investigation will assess the fate of chemical substances across 8 sewage sludge treatment trains incorporating different treatment types. In addition to ubiquitous substances found in CIP3 biosolids, microplastics and 54 different per/polyfluoroalkyl substances (PFAS) are also analysed. This project will be pivotal to the future direction of this critical biosolids outlet, and by association, the net resource recovery possible by the UK sector’s current asset base. For example, CIP outcomes will be used to understand and assess risks posed by chemical substances as the Sludge Use in Agriculture Regulations look to be replaced in England & Wales. This project will also inform wider discussion on the use of biosolids in agriculture, which is receiving increased global media and public scrutiny. As project lead, AtkinsRéalis tasks include a global review of the scientific literature and the interpretative reporting of analytical results. Sampling and laboratory analysis tasks are led by Tetratech. The presentation will update the sector with key insights, following the completion of this project.