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Investigation of Practical Issues Associated with Dichlor/Trichlor Disinfection.

Over the past six months, the TSC optimization team has collaborated with researchers from ORD to investigate monitoring interferences and implications for water systems that use chlorinated isocyanurates (also known as “dichlor/trichlor”) as a disinfectant; there is currently no approved method for measuring this disinfectant residual. Interferences with various EPA-approved free chlorine methods (DPD, indophenol, amperometric electrode) were evaluated, disinfectant residual stability and regulated DBP formation were compared, and a water chemistry model for dichlor/trichlor was updated to include temperature dependence.  Results from this investigation will be used to support OGWDW technical guidance to SDWA primacy agencies that oversee water systems using dichlor/trichlor as a disinfectant. Preliminary results were presented at the AWWA WQTC and TSC expects to jointly author a peer-reviewed journal article with ORD.  (Matthew Alexander and Alison Dugan, U.S. EPA Technical Support Center).