Beneficiation is the initial processing and concentration of the 
phosphate ores near the mine site. After the overburden is removed,the 
ore is scooped from the ground and transported as a slurry to a nearby 
processing plant. The ore is crushed, washed, separated from the clay 
and sand, sized through a series of screens, and dried. This process 
creates a slime of water and finely ground clay and sand which has no 
economic use and must be stored and dewatered. Dewatering requires a 
period of several years due to the small size of the clay particles, and 
the slimes are stored in large, diked impoundments. Retaining dikes have 
broken a number of times over the years, releasing large quantities of 
slime into both the Peace and Alafia River. These breaks have resulted 
in vegetation being covered by thick layers of slime for miles downstream 
and have caused massive fish kills. 
Chemical plants which process the raw phosphate ore into enriched 
phosphate compounds used in fertilizer present a different set of 
potential problems. Phosphate rock, as mined, is chemically bound to 
fluoride, which makes it practically insoluble in water. The fluoride 
must be removed before the ore can be processed further. Fluoride 
removal is accomplished by the addition of heat or acid, which releases 
free fluoride. Gaseous fluoride is highly toxic to plants, animals, and 
humans. In the past, fluoride was released to the atmosphere, but 
following a public outcry in the 1950’s after agricultural crops and 
cattle began dying, the industry undertook measures to recover the 
fluorides. Fluoride is produced in almost every stage of chemical 
manufacture (Blakely 1973), and one chemical plant located on Tampa Bay 
near the mouth of the Alafia River discharged fluorides directly into 
Tampa Bay for many years. In seawater, fluoride reacts with calcium 
carbonate to form fluorite. Fluorite forms a hard crust on the bay 
bottom and destroys benthic infauna. These deposits can extend hundreds 
of meters from the discharge. At this plant, areas of continous fluorite 
crust and fluorite chips cover nearly 100 acres of bay bottom. 
Gypsum is another byproduct of the enrichment process. Like the 
slimes generated at the mine site, gypsum must be dewatered and is stored 
at the chemical plants in large impoundments called gypsum stacks. 
Gypsum stack wastewaters are treated by liming and settling before they 
are released into Tampa Bay. Frequent spills have occurred from the 
gypsum stacks at the two chemical plants located on Tampa Bay causing 
adverse environmental effects. 
Many environmental problems associated with the phosphate industry 
have been eliminated by measures to control discharges, but potential 
problems of spills from mine slime ponds and chemical plant gypsum stacks 
remain. The slowdown of the phosphate industry has raised the 
possibility of the closure of mines and chemical plants. Bay management 
plans must include provisions to ensure that, following closure, slime 
ponds and gypsum stacks are sealed and properly maintained to prevent 
future catastrophic spills of toxic substances into the environment. 
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