03 February 2014 | Commentary

Routine monitoring of disinfectant residuals in water samples collected from both on-line (circulating) cooling tower cells and off-line (non-circulating) cells is essential to confirm correct biocide dosing.

It is important to monitor off-line cells as well as on-line cells because many automated building management systems may bring these non-circulating cells into rotation at a moment's notice. If the water contained in off-line cooling tower cells is not properly treated during periods when it is not in use, it can impact overall water quality and provide the potential for biological contamination in the rest of the system.

Monitoring also includes Legionella testing by culture. The use of rapid field tests for Legionella hasn't been shown to provide an accurate indicator of Legionella presence or concentration.  Rapid tests, such as ATP, may help determine if changes in the microbiological community are occurring, but they cannot be relied upon for accurate determination of Legionella positivity.

Laboratory culture for Legionella provides "gold-standard" validation of your water treatment program to demonstrate efficacy. Legionella risk assessments, use of biocides effective against Legionella and periodic cultures comprise a program likely to reduce Legionella positivity that could reduce potential liability associated with operation of cooling towers.