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According to the US Geological Survey, the average person uses about 80 to 100 gallons of water per day. Most of that water is used to flush the toilet, and after that, to take baths and showers. In 1995, daily household water use in the US totaled about 26.1 billion gallons. About 44 percent of that water came from ground water sources, such as a well.
The other 55 percent came from surface water sources, such as a river, lake, or reservoir. Of the 267 million people living in the US at that time, 42 million supplied their own water (mostly from wells) and the other 225 million had their water delivered from a public supply system. The JWC currently purchases water from the City of Minneapolis. The Minneapolis Water Works (MWW) draws its water supply from the Mississippi River in Fridley. After treatment and purification, the water is pumped to customers in Minneapolis, Columbia Heights, Hilltop, Bloomington, Edina, and the JWC communities of Crystal, Golden Valley, and New Hope. Over the years, the Mississippi River has been a reliable source of water. It carries such a large volume of water through the Twin Cities area that localized drought conditions are seldom a problem. The JWC's suburban neighbors rely on groundwater as their source for water. These communities are typically impacted more by the heavy water use that results from drought than are the communities that use surface water. The Minneapolis Water Works draws about 25 billion gallons from the Mississippi annually, producing an average of 70 million gallons per day (MGD). Peak rates during the summer may be as high as 180 MGD. The largest pump in the Minneapolis system has a 45 MGD capacity and is driven by a 2,200 horsepower electric motor. [top] The quality of the Mississippi River water makes it relatively easy to treat. It is naturally much softer than ground water, but it is further softened during treatment, saving water users the expense of purchasing and maintaining a home softening system. First the water is filtered through large beds of sand, gravel, and carbon, then lime is added to soften the water and alum is used to remove color and turbidity (cloudiness). Both the lime and alum settle out during the softening process. Powdered activated carbon, and occasionally potassium permanganate, are added to remove taste and odor. The water is treated with carbon dioxide to lower the pH and stabilize the remaining hardness before being pumped to one of two filtration plants. At the Fridley Water Filtration Plant, chlorine and ammonia are added to disinfect the water, fluoride is added to prevent tooth decay prevention, and ferric chloride is added to remove remaining color and turbidity. The water then enters a series of basins and is filtered with single, dual, or mixed media filters, and a blended poly/ortho phosphate is added as a corrosion inhibitor. For added safety, the water receives a dose of chloraminate as a final disinfectant before being fed into the reservoirs and pumped into the distribution system. The quality of water is assured and controlled through the various stages of treatment by plant and laboratory tests. An average of 500 chemical, physical, and bacteriological examinations are done each and every day (182,500 tests per year). The City of Minneapolis' treatment systems are based on tried and true technologies. The systems are operated in accordance with standard utility practices, and the treated water quality meets all current state and federal regulations. However, the systems currently do not provide a complete barrier against pathogens and other harmful bacteria. The City of Minneapolis is currently undertaking a large-scale program to install such a barrier using a reverse osmosis technology. This technology squeezes water through manufactured membrane tubes at very high pressure. Pathogens and other harmful bacteria common in river water are left behind since they are too big to squeeze through the tiny openings in the membranes. This is expensive technology, but it is required by new federal regulations. [top] The system that brings water to your house involves miles of piping. Treated water is pumped from the MWW plant through large pipes (the largest of which is 48 inches in diameter) to two JWC water reservoirs in Crystal and Golden Valley. The storage capacity of the two reservoirs is 27 million gallons. The water is pumped from the reservoirs into the water distribution systems separately owned and maintained by each of the three JWC cities. Each city is responsible for installing and operating its own water mains, pumping stations, water towers, and utility billing. The three JWC Cities use about seven million gallons each day. Water demands of JWC customers have been relatively constant over the past 10 years. During the day, the amount of water used by residences and businesses fluctuate hour by hour. The JWC water storage reservoirs are big enough to meet each day's needs, keeping the water flowing through the pipelines at an adequate pressure to meet customer needs. Water demands in the summer increase dramatically (often up to 17 million gallons each day) when residences and businesses sprinkle their lawns. The most customers have used in a single day was 20 million gallons. Adequate supplies must also be available to provide water to hydrants in the event of a fire. The JWC operates and maintains reservoirs capable of storing 28 million gallons. Operators often fill these reservoirs at night to be ready for another day of demands from customers. [top] |
