A Web-Enabled Tool for Predicting Perchlorate, Chlorate, and Bromate in Hypochlorite Solutions

Authors:

  • Catherine Keenan and Benjamin D. Stanford - Hazen and Sawyer
  • Aleks Pisarenko - Southern Nevada Water Authority
  • Gilbert Gordon - Miami University

Our Applied Research staff recently completed work contracted by the American Water Works Association to develop a web-based tool for predicting the decomposition of sodium hypochlorite solutions during transit and storage and the subsequent formation of perchlorate and chlorate in the solution.

Sodium hypochlorite is commonly used in drinking water applications for its ability to disinfect and maintain a residual level of disinfectant throughout the distribution system. However, hypochlorite solutions contain regulated contaminants such as bromate and chlorite in addition to unregulated contaminants such as chlorate and perchlorate, any of which can be formed during the manufacturing process or during storage.

In light of EPA’s recent notice to the Federal Register indicating its decision to regulate perchlorate in drinking waters at levels as low as 2 μg/L, the addition of chlorate to the 3rd Unregulated Contaminant Monitoring Rule (UCMR3) program, and potential federal regulations that could make the continued use of chlorine gas difficult, many utilities are concerned about the selection and use of any disinfectant in their treatment process and how such use may impact contaminant concentrations in finished waters.

The development of the web-enabled model was completed based on a 2008 study funded by AWWA/WITAF and Water Research Foundation to elucidate the kinetics of perchlorate and bromate formation in bulk and on-site generated hypochlorite solutions and to develop a kinetic model that could be used to provide quantitative suggestions to utilities to assist them in minimizing perchlorate formation.

This presentation highlights the study findings but will focus on a rollout of the web-based model and will demonstrate how the model can be used to assist utilities in making management decisions about hypochlorite handling and storage in order to minimize the introduction of perchlorate and chlorate into finished water.

For more information on this presentation, please contact the author at ckeenan@hazenandsawyer.com.

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