Field Testing for Chlorine Dioxide Application Note

Document ID

Document ID CO347

Published Date

Published Date 01/16/2019
Field Testing for Chlorine Dioxide Application Note
Chlorine dioxide (ClO2) may be used as either an oxidant or disinfectant in drinking water production. It is most frequently used as a pre-oxidant in conjunction with another disinfectant such as chlorine. Pre-oxidation with chlorine dioxide serves several treatment goals. Chlorine dioxide assists in the coagulation and removal of iron and manganese, oxidizes organic compounds without forming halogenated by-products, and is a potent disinfectant across a broad pH range.
When chlorine dioxide is used, it is essential that disinfectant and disinfectant by-product residual limits are not exceeded. The primary disinfection by-product of chlorine dioxide is chlorite (ClO2-). The US EPA maximum residual disinfectant level (MRDL) for chlorine dioxide is 0.8 mg/L at the entry point to the distribution system. Chlorite residuals most not exceed the maximum contaminant level (MCL) of 1.0 mg/L. The MRDL and MCL can be met through accurate dosing of chlorine dioxide as a pre oxidant. In addition, accurate dosing can ensure a small residual of disinfectant is maintained throughout the treatment process prior to primary disinfection.

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