EPA released a memorandum via e-mail to its regional drinking water branch chiefs, certification authorities and others about the calibration requirements of online chlorine monitors used to continuously measure disinfectant residuals. The reason for the memorandum was to alert officials of the calibration requirements for these instruments as noted in the Surface Water Treatment Rule [141.74(a)(2)] and Ground Water Rule [141.403(b)(3)(i)], which reference [141.74(a)(2)].
The memo states that utilities using a continuous chlorine disinfectant residual monitor for compliance must calibrate the unit with a grab sample at least every five days or with a protocol approved by the State.
The memo also says that per the regulations, “utilities can operate their continuous chlorine disinfectant residual monitor under the requirements of EPA Method 334.0, approved as an "alternate testing method" on November 10. 2009 (74 FR 57908).”
“Routine re-calibration is not required as long as (1) the weekly calibration check meets the quality control requirements of the method and (2) this calibration verification protocol and frequency are approved by the State (i.e., in lieu of re-calibration every five days).”
Questions about EPA’s memo should be directed to Steve Wendelken of the Technical Support Center at [email protected] or (513) 569-7491.