The PRO-BES project (Pioneering Real-time Observations with BioElectrochemical Systems) will undertake simultaneous field trials of real-time water quality biosensors in wastewater treatment works spread across the UK. The biosensors incorporate Microbial Fuel Cells (MFCs), a type of BES technology, which feature an electrode on which bacteria generate small amounts of electricity relative to their consumption of organic pollution in the wastewater. The project progresses an innovative collaboration between Newcastle University and University of South Wales, and is supported by end-users Welsh Water, Northumbrian Water and Chivas Brothers where the field trials will take place. Building upon prior BBSRC funding, the biosensor will advance from a laboratory proof-of-concept beyond prototype stage towards a fully realised commercial device ready for deployment and scaled-up manufacture. An understanding will be gained of how biofilm microbial communities respond to key operational factors (temperature, flow rate, external resistance) and how changes in biofilm dynamics/activity affect response of the sensor. BES biofilms will be grown using diverse wastewaters from water companies in Wales and North-East England and whisky distilling wastewater in Scotland. Analyses of the biosensors across these trials will enable fundamental understanding of the microbiology and bioelectrochemistry of these devices in addition to providing valuable insights for future research, development and optimisation.