Chemical contaminants such as nitrogenous wastes found in aquacultures or groundwater may contaminate nearby areas and drinking water supplies. Groundwater pollution may be caused by activities such as industrial waste disposal accidental spills fuel tank leakage or application of fertilizers herbicides or pesticides to crops. Natural causes such as arsenic also may result in groundwater contamination. Organisms are a major cause of water and aqueous environment contamination and are one of the world’s largest health concerns. Insects nematodes bacteria protists viruses and other organisms may contaminate water and produce cysts that can survive for weeks or months in water systems. Various methods exist for removing contamination from aqueous solutions. Methods for removal of fuel and organic contaminants may be costly and can result in the formation of other contaminants in concentrations above recommended limits. Chemical treatment with chlorine is the most common method to disinfect aqueous solutions but chlorine content must be monitored formation of carcinogenic byproducts is possible chlorine has an unpleasant smell and taste and the water must be held in a tank for a specific time period. Alternative approaches for treating aqueous solutions to reduce contaminants are needed that do not require long-term storage or result in the addition of chemical constituents or production of hazardous byproducts. UW-Madison researchers have developed a method to treat aqueous solutions to reduce amounts of contaminants and pollutants. The technology is an expansion of the inventors’ previous discovery which uses photoelectrocatalytic oxidation (PECO) to eliminate ammonia from aquacultures by converting it to nitrogen gas for removal (see WARF reference number P06336US). The researchers have now discovered that PECO technology can be useful for decontamination applications involving a variety of contaminants and pollutants in aqueous solutions. The method uses a photoelectrocatalytic composite photoanode that is constructed from a conducting metal such as titanium as the support electrode. Alternatively the photoanode can be composite electrodes comprising a conducting metal such as titanium with a support electrode coated with a thin film of sintered nanoporous titanium dioxide. The device utilizes PECO to oxidize contaminants and pollutants in an aqueous solution effectively reducing or eliminating the contaminants and pollutants. Technology Applications: Decontamination and purification of aqueous solutions such as groundwater wastewater drinking water ballast water aquarium water and aquaculture water.