The useful role that electrochemical concepts can play in the analysis of the behavior of semiconductor particles in detoxification and disinfection processes is explored. TiO2 was chosen as a model photocatalyst system, and photodriven events at the TiO2 particle–water interface were examined. The electrochemical aspects of photocatalysis are discussed under the headings of rate limitations on detoxification or disinfection, photoanodic detoxification, and photon-flux effects. Competitive reaction pathways are also discussed.