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

Abstract

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.

Scientific Opinion on the risks to public health related to the presence of perchlorate in food, in particular fruits and vegetables

“…In 2005, the Massachusetts Department of Environmental Protection (MDEP) reported significant levels of perchlorate in commercial solutions of sodium hypochlorite used for water disinfection (levels ranging from 260 to 6 750 μg/L were measured, with concentrations of perchlorate increasing with time of product storage) (MDEP, 2005). Stanford et al (2011) confirmed these findings and estimated that the formation of perchlorate is reduced by a factor of 7 or a factor of 36, when a 2 M solution of hypochlorite is diluted to 1 or 0.5 M, respectively. Further studies were performed to confirm these results.…”

“…MDEP concluded that these levels could result in a concentration of 0.2-0.4 g/L in drinking water. In addition, Stanford et al (2011) noted an increased decomposition of hypochlorite to perchlorate at temperatures > 15 °C and a pH < 11. Greiner et al (2008) analysed chemicals used for water disinfection collected from 102 different manufacturing locations.…”

Determination of Perchlorate in Bottled Water from Italy

“…We compared these results with those of tap water from different regions of Italy and we found that in all cases values of these latter were higher than those of bottled water (roughly one order magnitude) probably because of different conditions of the water sources and different biogeochemical processes governing perchlorate behavior in groundwater. Moreover a recent study has found that small amounts of perchlorate and other contaminants may be added during disinfection by municipal water treatment facilities that employ sodium hypochlorite [45]. For the sake of clarity, we note that Italian bottled water is not subjected to pre-treatment procedures, such as disinfection techniques that can result in perchlorate production, or processing steps that include carbon absorption and can remove perchlorate from the water.…”

Chlorate and Other Oxychlorine Contaminants Within the Dairy Supply Chain

“…The perchlorate ion is found in sodium hypochlorite solutions, and similar to the chlorate ion, perchlorate concentration increases over time (Pisarenko et al., ; Snyder, Stanford, Pisarenko, Gilbert & Asami, ; Stanford, Pisarenko, Snyder, & Gordon, ). The rate of perchlorate formation is a second‐order reaction, dependent on hypochlorite and chlorate concentrations (Gordon & Tachiyashiki, ; Snyder et al., ).…”