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About Reclaimed Water
Watch how the Water & Sewer Department is working to reclaim some of the water that will help recharge the Biscayne Aquifer.
As Miami-Dade County’s population continues to increase, so does our demand for drinking water. Like all natural resources, the Biscayne Aquifer, Miami-Dade County’s current source of drinking water, is not limitless. The use of reclaimed water in Miami-Dade County helps preserve the Biscayne Aquifer.
Reclaimed water is highly treated, filtered and disinfected wastewater that is beneficially reused. Reclaimed water can replace or supplement groundwater supplies. Common uses for reclaimed water include irrigation, wetlands restoration, aquifer recharge, vehicle washing, air conditioning cooling towers, and other industrial uses. The use of reclaimed water is often referred to as wastewater reuse.
Miami-Dade County is currently expanding its water reclamation program and is currently evaluating several water reclamation projects, including the ambitious High-Level Disinfection project and the South District Wastewater Treatment Plant. For more information, read the Reuse Feasbility Study Update Report.
To assess large scale use of reclaimed water, the Miami-Dade Water & Sewer Department is designing two pilot projects. The Aquifer Recharge Pilot Project will evaluate the treatment techniques necessary for recharging the Biscayne Aquifer through the rapid infiltration of highly treated wastewater. The Coastal Wetlands Rehydration Project will investigate the applicability of using highly treated wastewater effluent to replace the historic freshwater flows that once were discharged into the coastal wetlands of Biscayne Bay.
By using reclaimed water, the Miami-Dade Water & Sewer Department is working to provide a sustainable water resource for our environment and our future.
How water reclamation works
- The first step is microfiltration or ultra-filtration -- a filtration process that removes contaminants from a fluid (liquid and gas) by passage through a micro-porous membrane. A typical microfiltration membrane pore size range is 0.1 to 10 micrometers (µm). (A micrometer is one millionth of a meter. For comparison, a strand of human hair is about 100 µm wide.)
- Next, the water goes through reverse osmosis -- basically, a filtration process. It works by using pressure to force a solution through a membrane, retaining the solute on one side and allowing the pure solvent to pass to the other side. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied.
- Hydrogen peroxide is now added. It is commonly used to remove pollutants from wastewater and from air. It contests bacterial growth through oxygen addition. It can also be used to treat pollutants that can be easily oxidized such as iron and sulphides and pollutants that are difficult to oxidize such as dissolved solids, gasoline and pesticides.
- Ultraviolet disinfection, a common treatment of drinking water that uses ultraviolet radiations to inactivate microorganisms, is then added. Ultraviolet disinfection of water consists of a purely physical, chemical-free process. The radiation initiates a photochemical reaction that destroys the genetic information contained in the DNA.
The bacteria lose their reproductive capability and are destroyed. Even parasites such as Cryptosporidia or Giardia, which are extremely resistant to chemical disinfectants, are efficiently reduced. UV can also be used to remove chlorine and chloramines. This process, called photolysis, requires a higher dose than normal disinfection. The sterilized microorganisms are not removed from the water.
UV disinfection does not remove dissolved organics, inorganic compounds or particles in the water. However, UV-oxidation processes can be used to simultaneously destroy trace chemical contaminants and provide high-level disinfection. It is currently in use at the reuse plant in Orange County.
When the full-scale reclaimed water plant is complete and operational it will pump 21 million gallons a day of this purified, highly treated water to the moat at Zoo Miami, where it will recharge our groundwater. The result will be very pure water whose quality will be near that of distilled water.
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