Columbia's water is tested more frequently and more thoroughly than is required by law. The well water is monitored for any possibility of contamination and over 4,000 tests are run each year on samples at the Water Treatment Plant and from 41 locations throughout Columbia.
Columbia's drinking water meets or exceeds all quality standards set by the Federal Environmental Protection Agency and the Missouri Department of Natural Resources (see letter for more information). For detailed information, please see the complete list of testing results, the Water Quality Report or the Source Water Protection Plan.
Columbia's water is pumped from wells that tap into a water-filled bed of sand and gravel beneath the bottom land bordering the Missouri River just southwest of the city. Long ago, melting glaciers washed sand, gravel and boulders downstream and left thick deposits along the course of the river. This geological formation is an alluvium and when saturated with water becomes an alluvial aquifer. Water slowly moves through the aquifer, which acts as a natural filtration system. Forty-four billion gallons of water fill the area which is constantly replenished by groundwater sources. The wells average 110 feet deep, penetrating the aquifer near its bottom.
Aeration: At the treatment plant, the water first flows through aerators and is exposed to air that is drawn through the aerators by fans. This oxidation of the well water reduces levels of iron, carbon dioxide and hydrogen sulfide that are naturally found in the water.
Softening: Lime is then added to the aerated water, and a chemical reaction occurs between the lime and the calcium and magnesium dissolved in the well water. Heavy, insoluble particles of calcium and magnesium form and settle to the bottom of the softening basins, and as it accumulates, it is piped to storage lagoons. This process physically removes fifty percent of the hardness causing minerals from the water. Softened water enables you to use less laundry detergent and reduces scale formed in water heaters and pipes.
Filtration: Any particles remaining in the water after the softening process are filtered through layers of anthracite coal and sand. Chlorine may be added before or after filtration to prevent bacterial growth. Fluoride is added to meet Environmental Protection Agency recommendations and helps improve dental health.
Disinfection: Water must be disinfected to prevent bacterial growth and prevent disease causing illnesses like typhoid, hepatitis and cholera. The disinfection method used in Columbia allows for disinfection of the water through the distribution system all the way to the faucet. The Columbia Water Treatment Plant first disinfects the water with chlorine, than adds ammonia, forming chloramine. Chloramine is a common disinfectant that has been used for the last 90 years. There are 0.6 milligrams of ammonia added per liter of water. For comparison, this would be similar to adding six grains of table salt to a one gallon container of water. For more information on disinfection methods, please see a 2009 report from the University of Missouri's Department of Civil and Environmental Engineering and the Missouri Water Resource Research Center.
Note: During the summer months, the Department of Natural Resources recommends that Columbia Water & Light switch from the chloramine disinfection method to the chlorine disinfection process to reduce nitrification. Usually this is done during the summer. During the time that chlorine is being used to disinfect the water, consumers might notice more of a taste and smell of chlorine than during times when chloramines are used. Customers who are sensitive to the chlorine taste can fill a pitcher with water and wait for several hours to drink it. Activated carbon filters will also reduce the chlorine taste. Customers using filters are urged to replace filters as recommended by the manufacturer to reduce the risk of harmful microorganisms forming.
Softened, filtered water is pumped from the water treatment plant to reservoirs at the West Ash, South Pump and Hillsdale pumping stations. The water is then pumped throughout the city to consumers. Water is stored in three water towers that provide capacity for peak water use and fire fighting.