A section of carbonate rocks that includes several highly permeable cavernous zones filled with saline water underlies the south part of peninsular Florida at depths from 1,500 to 4,500 ft. Because these cavernous zones are capable of yielding or accepting large quantities of fluids, they are used for storage of industrial and municipal liquid waste at several places. One such place is at the south end of Lake Okeechobee near Belle Glade, Florida, where the effluent from a sugar mill and liquid waste from the production of furfural processed from sugar cane bagasse have been injected at depths between 1,500 and 2,200 ft. The waste ranges in temperature from 71 to 103°C, in pH from 2.6 to 4.5, and is highly organic (COD 6,000-26,000 mg/l). Since 1966 more than 800 mil ion gal of this waste have been injected. Injection rates range from 400 to 800 gal/minute at pressures of 30-60 psi at the well-head. The waste is partly neutralized almost immediately to a pH of 5.5 by dissolution of limestone. Caliper logs show localized patterns of dissolution of the carbonate aquifer. Anaerobic degradation of the organic waste begins near the injection well, as indicated by the presence of hydrogen sulfide, methane, carbon dioxide, and nitrogen.

The waste has moved both upward and laterally in the aquifer system, as detected by water quality changes in monitor wells. Upward movement of altered waste into an overlying brackish-water zone was detected by a 1,400-ft monitor well 75 ft away from the injection well. Lateral movement was detected by a monitor well in the injection zone 1,000 ft away. When upward movement of waste was detected, injection was discontinued and the well was drilled and cased several hundred feet deeper. Data collected since the well was deepened are inconclusive regarding the effectiveness of the increased well depth in restricting the waste to the injection zone. Investigations to date at Belle Glade clearly point up the value of a sound monitoring program.

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