When using the combined available chlorine residual (CACR) method, what should be done if the water temperature decreases?

The combined available chlorine residual (CACR) method is sensitive to water temperature because chlorine’s effectiveness as a disinfectant is influenced by thermal conditions. When water temperature decreases, the rate of chlorine reactions with microorganisms also slows down. This means that in cooler water, a higher concentration of chlorine may be required to achieve the same level of disinfection that would occur at warmer temperatures. Thus, increasing the CACR becomes necessary to compensate for the reduced effectiveness of chlorine due to the lower temperature.

In practice, maintaining an adequate chlorine residual is crucial to ensure that water remains free of harmful pathogens and meets safety standards. The increased CACR in colder water helps to ensure that sufficient disinfection occurs, preventing the risk of waterborne diseases and maintaining the overall safety and hygiene of the water supply.