Perchlorate, bromate, and chlorate in hypochlorite solutions: Guidelines for utilities

Hypochlorite solutions contain oxyhalide species such as perchlorate, chlorate, and bromate that form during and after manufacture. Such oxyhalide species have the potential to contaminate finished drinking water if adequate control measures are not taken to minimize their formation during manufacture, shipment, and storage of hypochlorite solutions. This article describes the rate of formation of perchlorate in hypochlorite solutions and discusses the chemistry behind a series of control strategies that utilities and manufacturers can implement to minimize oxyhalide formation and introduction into drinking water. Factors affecting the formation of perchlorate include temperature, ionic strength, hypochlorite concentration, and the presence of transition metal ions. The authors conclude that with proper manufacture, storage conditions, and handling, formation of perchlorate, chlorate, and bromate can be minimized. If care is not taken during manufacture and storage of hypochlorite solutions, however, perchlorate, chlorate, and bromate levels can exceed health‐based guidelines in drinking water.