Potable Water Storage Tanks Need Active Mixing
There are more than 50,000 municipal water systems in the United States and most of these systems rely on water towers, above-ground, and below-ground tanks to store their treated potable water. Many operators rely on mixing via normal cycling of water in and out of the tank to limit water age and deterioration of disinfectant chemicals.
This reliance on “passive mixing” is not enough in most cases to prevent thermal stratification, which can lead to a drop in residual chlorine and a resultant growth of bacteria.
When bacteria contamination occurs in a tank, a common response is to set the tank for deep draw down and in extreme cases, completely drain- flush- and re-fill the tank. Not only is this strategy a big waste of water resources, it also raises cost for labor and chemicals.
When continuous mechanical mixing is combined with frequent sampling & periodic chlorine boosting (when needed), water quality is maintained and less disinfectant is required. This paper will address Medora Corporation active mixing technologies developed to completely mix potable water storage tanks up to 100 million gallons or more. Complete and thorough mixing can virtually eliminate thermal stratification, sampling inconsistencies and other tank water quality issues. These technologies have the additional benefits of reduced labor and chemical expenditures as well as providing a means for EPA regulatory compliance.