As part of an ongoing study to evaluate water service lining and coating technologies as alternatives to full or partial lead service line replacement, our research group has investigated the use of epoxy coating materials in drinking water applications. Previous literature has suggested that epoxy based coatings may be particularly reactive with chlorine disinfectants commonly used in drinking water systems for biological control. In this study, fill and dump experiments were conducted on lead and copper pipe sections coated with a commercially available epoxy product. Pipe sections were filled with an extraction water at pH 8 containing free chlorine at an initial concentration of 2 mg/l Cl2 and a hardness of 100 mg/L as CaCO3. The extraction water was allowed to sit in the pipe for 6 - 72 hours prior to removal and analysis. Pipe specimens freshly coated with epoxy exerted a strong demand for free chlorine, consuming a residual of 2 mg/L as Cl2 in 24 hours or less. In follow-up tests, epoxy-coated pipe specimens were found to exert a significant demand for both free and combined chlorine, initially and over an extended period of time (more than 6 months), whether stored wet or dry, even after exposure to a free chlorine concentration of 100 mg/L as Cl2. Similar experiments indicated that the epoxy was also reactive with chloramine disinfectants. The chlorine demand of the epoxy coating could significantly reduce residual disinfectant concentrations in the distribution system, thereby enhancing the potential for biological growths; and the reactions of chlorine with epoxy may form disinfection byproducts that could potentially leach into the water.

Reactivity of an epoxy coating with free and combined chlorine in drinking water service lines

249th National Meeting (2015)

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