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Water Supply & Treatment
Miami-Dade County's sole source for drinking water is ground water from wells. The wells feeding the Hialeah and John E. Preston water treatment plants serve most Miami-Dade residents living between the Miami-Dade-Broward County line and SW 8th Street. These treatment plants draw water only from the Biscayne Aquifer. This is also true of the wells feeding the South Dade Water Supply System, which is comprised of five smaller water treatment plants that serve residents south of SW 264th Street in the unincorporated areas of the County.
First, natural dilution (the "thinning out" of contaminants caused by dispersal into a large body of water) can reduce minor contaminant concentrations to levels that are no longer considered harmful.
Today we are faced with a dilemma that has been brewing for some time – a limit to our water supply. The very nature of our water supply requires that each of us become diligent in the protection and conservation of this most important resource.
It may seem odd that South Florida would have to worry about "not enough" water. After all, we get about five feet of rain during any given year! Some places in the country would take a decade to see that much water. Summertime in South Florida means rain – lots of it. So how is it possible that we could run out of water?
We live in a land of extremes – flash floods can dump over a foot of rain in a single day while droughts can last for years. The first step in understanding our water supply to learn about the water cycle.
Water managers keep a close eye on canal levels and the flow of fresh water through South Florida. The South Florida Water Management District is responsible for making sure there’s enough water to feed the needs of a repidly growing urban community, agricultural needs, and the water needs of the Everglades. They are also responsible for making sure there isn’t too much water. Too much storm water in South Florida can cause floods, drown crops, and even damage the health of our environment.
- Water Supply & Treatment
- Biscayne Aquifer
- The Water Cycle
- Water Flouridation
- Water Treatment
- Alternative Water Supply
The Biscayne Aquifer is located just below the surface of the land in South Florida. It is made out of porous rock with tiny cracks and holes. Water then seeps in and fills these tiny cracks and holes.
This water is often referred to as groundwater or the water table, and provides virtually all of the water that is used by South Florida residents, visitors and businesses. This water is generally clean due to the effects of natural filtration.
The water is actually flowing like an underground river at a very slow rate. It travels in an east-southeasterly direction at a rate of only about two feet per day. However, where there are very large openings or man-made canals the flow rate can increase substantially. Because this drinking water supply is so close to the surface (barely a few feet down in most places), it is especially prone to contamination. Typically, an underground water system can cleanse itself of low levels of contaminants in at least two ways.
Water suppliers use a variety of treatment processes to remove contaminants from drinking water. The most commonly used processes include filtration, flocculation and sedimentation, softening, and disinfection. Additional treatments include ion exchange and adsorption. A typical water treatment plant would have only the combination of processes needed to treat the contaminants in the source water used by the facility. If you want to know what types of treatments are used for your water supply, contact your local water supplier or public works department.
The second is the ability of a water system to clean itself through the natural filtration described earlier and through the breakdown of trapped contaminants by soil bacteria.
However, the Biscayne Aquifer has unique physical characteristics that make neither of these systems entirely reliable. This, compounded by the fact that millions of gallons of water are pumped out of the ground each day, contributes to the vulnerability of the region's groundwater supply.
This is why efforts are made to protect the groundwater. Miami-Dade County, in cooperation with other local, state and federal agencies, works to safeguard the supply source for drinking water. This may result in environmental regulations for businesses in the South Florida area being more stringent than other areas of the country, but it is necessary to protect the health of everyone dependent on clean water.
Being proactive can also prevent expensive water treatment processes at our water treatment plants.Back to Top
The Water Cycle
The water on Earth is continuously circulating between the air or atmosphere, the land and the sea. The ways in which water moves around, above, on and within the Earth is the hydrologic or water cycle.
The sun is the energy source for the water cycle, causing water to evaporate from lakes, rivers and oceans, as well as from land surfaces and vegetation. When water evaporates, it changes to a gas (water vapor) and rises in the air. When the water vapor rises and meets cold air, it condenses, forming water droplets, or what we see as clouds or fog. This process is called condensation. Water droplets combine into water drops and return to the Earth as precipitation in the form of rain, sleet, hail or snow.
Exactly how clouds produce rain has eluded meteorologists until recently. In 1999, Dutch scientists using a supercomputer to model cloud behavior announced that rain is produced when whirling masses of water, a few centimeters in diameter, force water droplets outward by centrifugal force. These droplets then collide and grow. To fall to the ground as precipitation, they need to reach a diameter greater than 20 micrometers (Environmental News Network online, November 16, 1999).
Some rain is absorbed by vegetation or evaporates before it reaches the ground. Some evaporates after it reaches the surface. Some soaks into the ground and the Biscayne Aquifer and is taken up by the roots of plants and then released back into the air through the leaves of the plants in a process called transpiration. The combination of evaporation and transpiration is referred to as evapotranspiration. Some rain soaks beneath the water table into underground units of water-bearing rock called aquifers. The remainder becomes surface or stormwater runoff that flows over the ground to wetlands, lakes, ponds, rivers and oceans.
A water molecule's trip from the atmosphere and back may be very long or very short. It may stay in the atmosphere for only a few days or it may remain deeply buried in cavities in the earth or frozen in polar ice caps for thousands of years.Back to Top
The Miami-Dade Water and Sewer Department's three regional water plants fluoridate the water during the treatment process. Fluoride is a compound that contains fluorine, one of the most plentiful elements on earth. It occurs naturally in water supplies.
According to the American Association of Pediatric Dentistry, "using small amounts of fluoride on a routine basis can help prevent tooth decay." Both the American Dental Association and the American Association of Pediatric Dentistry recommend that fluoride be added to community water supplies in areas where fluoride does not occur naturally. Fluoridation is also endorsed by the Centers for Disease Control and Prevention, which considers "community water fluoridation as one of 10 great public health achievements of the 20th century."
Whereas fluoridated drinking water provides only about one-third to one-half the amount of fluoride that an individual should be getting on a daily basis, it is a benefit that cuts across socio-economic dividers, offering everyone equal health benefits.
The American Dental Association supports community water fluoridation as the single most effective public health measure to prevent tooth decay: "Water Fluoridation is a powerful strategy to reduce disparities in tooth decay among different populations and is more cost-effective than other forms of fluoride treatments or applications."
Facts about flouridation in tap water:
- Fluoride is a naturally occurring mineral found in both surface water and groundwater.
- Since 1958, the Miami-Dade Water and Sewer Department has adjusted the existing natural fluoride level of 0.2 parts per million in the water to the optimal range for dental health of 0.7 parts per million.
- Fluoride helps teeth resist decay by strengthening the protective layer of tooth enamel and can reverse newly formed cavities.
- Community water fluoridation is supported by most major national and international health service organizations. Supporters include the American Dental Association, American Medical Association, American Academy of Pediatric Dentistry, World Health Organization and the U.S. Centers for Disease Control and Prevention.
- Fluoridation does not change the taste, odor or appearance of your water.
- No evidence exists that fluoridated water at the levels prescribed for human consumption is harmful to animals or pets.
Back to Top
Approximately 330 million gallons per day (mgd) are withdrawn from the Biscayne Aquifer through wells extending an average of 80 feet below the ground surface to meet the needs of the community.
As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and can pick up substances resulting from the presence of animals or from human activity. In order to ensure that tap water is safe to drink, the U.S. Environmental Protection Agency (EPA) regulates the contaminants in water provided by public water systems.
The Hialeah and Preston Plants serve residents who live north of Flagler Street up to the Miami-Dade/Broward line. The Alexander Orr Plant serves residents south of Flagler Street to S.W. 248 Street. These three regional water plants supply treated water to a common distribution system.
Highly trained microbiologists, chemists and water treatment specialists conduct or supervise more than 100,000 analyses of water samples each year. Water quality samples are collected throughout the county and tested regularly. Samples include untreated and treated water taken at our facilities, sample sites throughout the service areas and at customers’ homes. These tests are overseen by various regulatory agencies on a federal, state and local level.
The South Dade Water Supply System is comprised of five smaller water treatment plants that serve residents south of S.W. 248 Street in the unincorporated areas of the County. These five plants pump treated water into a common distribution system, which is separate from the main system.Back to Top
Alternative Water Supply
During the 2005 State Legislative Session a bill creating the Water Protection and Sustainability Program, or SB444, was enacted, providing significant state funding for Alternative Water Supply Projects that are identified in the Water Management Districts' Regional Water Supply Plans.
Alternative Water Supply Projects are defined as:
- saltwater & brackish water
- surface water captured predominately during wet-weather flows
- sources made available through the addition of new storage capacity reclaimed water stormwater (for use by a consumptive use permittee) any other source designated as nontraditional in a regional water supply plan
Water reuse plays an important role in water resource, wastewater, and ecosystem management in Florida. It reduces demands on valuable surface and ground water, sources used for drinking water. Reclaimed water also reduces discharges to surface waters, recharges groundwater, and postpones costly investment for development of new water sources and supplies. Water reuse has allowed some communities to continue to grow where the availability of historically used freshwater sources has become extremely limited.
Water reuse involves taking domestic wastewater, giving it a high degree of treatment, and using the resulting high-quality reclaimed water for a new, beneficial purpose. The resulting water is called reclaimed water. Extensive treatment and disinfection ensure that public health and environmental quality are protected. Reclaimed water can be used for many purposes including:
- Irrigation of golf courses, parks, residential properties, highway medians, and other landscaped areas.
- Urban uses such as toilet flushing, car washing, dust control, and aesthetic purposes (i.e. decorative lakes, ponds, and fountains)
- Agricultural uses such as irrigation of edible food crops such as, citrus, corn, and soybeans; other crops such as, pasture lands, grasslands, and other feed and fodder crops; and irrigation at nurseries
- Wetlands creation, restoration and enhancement
- Recharging ground water with the use of rapid infiltration basins (percolation ponds), absorption fields, and direct injection to ground waters
- Augmentation of surface waters that are used for drinking water supplies
- Industrial uses including plant wash down, processing water, and cooling water purposes
Continuous monitoring of the reclaimed water is required and ensures excellent water quality for protection of the public and the environment. The Florida Department of Health has stated a reuse facility designed, constructed, and operated in accordance with applicable rules poses no threat to public health. The use of reclaimed water has increased significantly throughout the nation, state, and district for all types of uses.
Aquifer Storage Recovery (ASR)
Aquifer Storage Recovery (ASR) is defined as the storage of freshwater in an aquifer by injecting water through the wells during wet periods for subsequent retrieval from these same wells during dry periods. The freshwater forms a bubble of injected water within the aquifer around the ASR well, and it can be retrieved when needed to meet seasonal, long-term, emergency or other demands. During the past ten years, ASR technology has evolved from merely a concept to a proven, cost-effective and environmentally desirable water management tool.
Reverse Osmosis (RO)
Reverse osmosis is a process used to purify concentrated solutions of dissolved minerals and salts. Reverse osmosis involves forcing water through a semipermeable membrane under high pressure, leaving the dissolved salts and other solutes behind on the surface of the membrane.
Wastewater is extracted from sewage and treated to produce high quality reclaimed water for irrigation purposes.Back to Top Page Last Edited: Tue Oct 21, 2014 11:58:41 AM
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