Traditionally, standard water treatment consists of a sequence of treatments including coagulation-flocculation, sedimentation, biotreatment and in some cases disinfection (tertiary treatment). Additional water-purification processes have been demonstrated to improve treatment efficiency following traditional methods for the removal of recalcitrant and hazardous pollutants and pathogens. These additional or tertiary treatments include advanced oxidation processes (AOPs), based on the generation of reactive oxidant species that oxidise chemical pollutants and inactivate microorganisms in water. Photo-electro-catalysis is a relatively unexplored AOP for water treatment and this chapter aims to describe the fundamentals of photo-electro-catalysis and discuss the main aspects to consider when designing solutions to face the challenge of CECs present in water, including reactor design concepts, materials selection criteria and the considerations related to the pollutants.