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Potential Use of Phosphate Mining Tailing Sand for Water Filtration: Leaching Tests


Using waste clay settling areas and tailing sand deposits remaining after phosphate mining to improve the quality of treated wastewater and stormwater in central Florida would aid in minimizing the demand on groundwater. The study was performed to investigate the water quality of tailing sand leachate from three mines with respect to total uranium, radium 226, lead-210, polonium-210, gross alpha, sulfate, and total phosphorus. Low (hydraulic conductivity = 16 ft/day), medium (hydraulic conductivity = 49 ft/day) and highly (hydraulic conductivity = 73 ft/day) permeable tailing sands were placed in 60 gallon barrels. The study tested the tailing sand leachate from the barrels under low, neutral, and high pH conditions sampled periodically over 225 days. The analytical results indicated the leachate from the tailing sands would generally meet the drinking water standards for radioactive elements under the worst-case conditions of a long contact period in a static environment. The highly permeable sand leachate exceeded the drinking water standard for sulfate, but was lower in a subsequent test in which two pore volumes were flushed through the tailing sand. Based upon the results of the investigation of the tailing sand leachate quality, the water filtered by the sand can meet drinking water standards.