The FKAA delivers approximately 17,000,000 gallons per day of high-quality drinking water to the residents of the Florida Keys. The FKAA’s primary water supply, the Biscayne Aquifer, is a superior source water meeting and exceeding all regulatory drinking water standards prior to treatment.
To supplement this source the FKAA also utilizes the Floridan Aquifer, a deeper, more brackish aquifer. In emergency situations, the FKAA has the capability of utilizes two seawater plants, one in Marathon and one in Stock Island, to supply additional water.
The water treatment plant is an integrated source facility staffed by state-licensed personnel. Water produced from the FKAA’s primary supply, the Biscayne Aquifer is treated through a lime softening process.
Water obtained from the Floridan Aquifer is treated through a low-pressure reverse osmosis treatment system and combined with the treated Biscayne water. A disinfectant and fluoride are added prior to distribution.
- J. Robert Dean Water Treatment FacilityName
- Kermit H. Lewin Reverse Osmosis & Marathon Reverse Osmosis Water Treatment Facilities
J. Robert Dean Water Treatment Facility [Public Water System Identification (PWS ID) Number: FL4134357]
The water treatment plant is an integrated source facility staffed by state-licensed personnel. Groundwater extracted from the Biscayne Aquifer is the primary source water for this facility. A secondary groundwater source, the Floridan Aquifer, is utilized to a much lesser extent.
The Biscayne source water is classified as very hard due to the high concentration of calcium in the water. A process called lime softening is used to reduce calcium hardness.
Lime softening is achieved by the addition of excess calcium under high pH conditions. This allows the water to become supersaturated with calcium, causing the calcium to sink to the bottom of the lime softening treatment unit, leaving less hard (softened) water for use by Florida Keys Aqueduct Authority (FKAA). The FKAA finished product water is considered moderately hard.
The softened water is then piped to dual media filters, which are made up of layers of anthracite and fine sand, for additional removal of particles (calcium) and further purification. Chlorine and ammonia are injected into the water to form chloramines, which provide long-lasting disinfectant protection without the objectionable taste and odor of regular chlorine. Fluoride, which is recommended for drinking water by the American Dental Association to prevent cavities, is also added.
Low-Pressure Reverse Osmosis (LPRO)
In order to comply with Biscayne Aquifer withdrawal limitations, a Floridan wellfield and LPRO water treatment plant were constructed. Operational since the summer of 2009, the LPRO water treatment plant treats the brackish water of the Floridan Aquifer. The Floridan raw water contains approximately 4,000 to 5,000 parts per million (ppm) of salt.
This concentration is significantly lower than the 35,000 ppm typically found in seawater, but higher than the 200 ppm found in the Biscayne Aquifer. This LPRO system utilizes very fine membrane elements. The water is pressurized to approximately 250 pounds per square inch (psi), rejecting the salt while allowing the passage of the pure finished water. The LPRO water is disinfected in the same manner as the Biscayne lime-softened water.
Finished water from the LPRO Water Treatment Plant (WTP) is blended with water treated from the Biscayne Aquifer. The FKAA treated water is pumped 130 miles from Florida City to Key West, supplying water to the entire Florida Keys. The water provided to customers in the Florida Keys is continuously monitored and tested to ensure the water quality is consistent, safe, and meets all federal and state drinking water standards. The FKAA operates two treatment plants.
Kermit H. Lewin Reverse Osmosis & Marathon Reverse Osmosis Water Treatment Facilities (PWS ID Number: FL5444047)
Through a process called Reverse Osmosis (RO), the Kermit H. Lewin and Marathon RO water treatment facilities desalinate saltwater, producing potable water. The saltwater from seawater wells first enters the cartridge filter to remove particulate matter. From the filters, the water is pressurized up to 900 pounds per square inch.
These pressures are significantly higher than those required at the Florida City LPRO due to the significantly higher salt content of the seawater. The high pressure forces some of the water in through the RO membranes and is commonly referred to as permeate; the remainder of water is rejected as brine and disposed in an underground injection well. The permeate flows into a degasifier and clear well, where hydrogen sulfide and carbon dioxide are removed.
Next, sodium hydroxide is added to raise the pH, and a corrosion inhibitor may be added to provide corrosion control. In the final treatment stage, the permeate is disinfected with chloramines, and the finished product is transferred to the storage tank for distribution.
The freshwater Biscayne Aquifer is the primary groundwater supply source for the Florida Keys Aqueduct Authority. Our wellfield is located within an environmentally protected pine rockland forest west of Florida City on the mainland. The location of the wellfield near Everglades National Park, along with restrictions enforced by state and local regulatory agencies, contribute to the unusually high quality of the raw water.
The FKAA wellfield contains some of the highest quality groundwater in the country, meeting and exceeding all regulatory drinking water standards prior to treatment. Strong laws and regulations protect our wellfield from potential contaminating land uses. The J. Robert Dean Water Treatment Plant is staffed by state licensed personnel and it is home to one of our two nationally certified water testing laboratories.
The water taken from the ground at our well field is classified as very hard due to the relatively high concentration of calcium in the water. We use a process called lime softening to reduce the calcium hardness. Lime softening is achieved by the addition of excess calcium.
This allows the water to become supersaturated with calcium, thereby causing the calcium to sink to the bottom of the treatment unit leaving softened water for use by our customers. Softened water does not deposit as much calcium scale on household plumbing fixtures and cooking utensils and allows shampoo, laundry detergent and other soaps to lather better.
The softened water is then piped to "dual media filters": layers of anthracite and fine sand, a copy of the process that Mother Nature uses to filter water. We then add a disinfectant to prevent any bacteria growth the water could pick up on its journey from Florida City to Key West. Chlorine and ammonia are combined in the water to form Chloramines, a long-lasting disinfectant without the objectionable taste and odor of regular chlorine. We then add Fluoride, which is recommended for drinking water by the American Dental Association to prevent cavities and strengthen bones.
Our water is pumped to the Keys through a 130-mile long transmission main at a maximum pressure of 250 pounds per square inch. Our pipe begins with a diameter of 36 inches, narrowing to 24 inches and ending with an 18-inch diameter. We use 800 horsepower electric motors at the water plant to pump water south.
In case of an emergency or power outage, we have two 1,000 horsepower diesel pumps and forty-five thousand gallons of fuel in storage. As an example, the diesel pumps were run for 28 days continuously after Hurricane Andrew. High pressure is required to move the water over long distances. The FKAA has booster pump stations in Key Largo, Long Key, Marathon, Ramrod Key and Stock Island to maintain desired pressures in the water main.