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Friday, May 26, 2006

Environmentally friendy water storage

West central Florida is experimenting with a new fresh water storage system called "aquifer storage," literally storing a bubble of fresh water beneath ground with out tanks or other artificial containers.

The fresh water, runoff from overburden during heavy, seasonal rains, is pump injected into the center of deep, natural underground water wells. These wells are produced by erosion from natural seepage through the permeable limestone coral that forms the foundation of the Florida peninsula. The water in these natural wells is extremely brackish and not at all suited for human consumption nor even landscaping.

Fresh rainfall runoff, which occurs annually during Florida's summer season, is typically stored in surface retention ponds. When the rains are too monsoon-like, the excess is diverted over spillways into the Gulf of Mexico and lost.

Because fresh water is less dense than brackish, the fresh rainwater forms a bubble within the surrounding salt laden underground well. The bubble of fresh water mixes only slightly, at its interface, with the surrounding brackish water.

Later, when dryer months come, the fresh water bubble, which had been treated by ultraviolet light to kill bacteria and any pathogens, can be pumped back to the surface and used for irrigation. Project engineers plan to build a full-scale demonstration system this summer, capable of storing 60 to 120-million gallons of fresh water. If all goes well, they expect to begin pumping as much as a million barrels a day from the well.

by Harlan Weikle
Greener Magazine

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