Finished Potable Water Storage Facilities
Finished water storage facilities are used to equalize water demands, reduce fluctuations in pressure, and make available a reserve for firefighting, power outages, and other emergencies. The nature of the holding facilities is such that old water may be in the tanks and under certain conditions enter the distribution system and thereby cause problems. There are both ground storage facilities and elevated storage facilities. The ground facilities can be either covered or uncovered. There are numerous potential water quality problems in the storage facilities which may be microbiological, chemical, or physical in nature. Long detention times or old water can be a greater problem for microbial growth and chemical changes than freshwater moving in and out of the storage facility. Stratification in reservoirs can create zones where the water will age more rapidly than in other zones. This can result in disinfectant decay, regrowth of microorganisms, and nitrification. Sediment can accumulate in the storage facility and affect the water quality. Birds or insects create a major water quality problem in storage tanks. Storage facilities have been shown to be the source of several waterborne outbreaks of disease. Coating materials used in steel storage tanks and in concrete tanks may leach into the water and contaminate it. Metal tanks may become corroded. Disinfectant byproducts are more prominent because of the higher water temperatures in steel tanks during the summer.