The utilization of 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 alleviating the demand on groundwater. A laboratory column leaching study was performed to quantify the filtration capacity of tailing sands with respect to bacteriological/virological parameters. Low and high permeability tailing sands were placed in columns with unsaturated depths of 1, 2, and 3 feet. The columns were seeded with a solution containing E. coli bacteria, coliphage MS2 bacterial virus, human poliovirus, and fluorescent microspheres as tracers and sampled over a 38 day period. After each sample event, an equal volume of deionized water was added to the top of each column to simulate recharge. The results indicate that the tailing sand filtration is capable of removing more that 98% of the applied virus. The lower permeability sand was better able to remove microorganisms than the higher permeability tailing sand. Removal of microorganisms was greater with increasing unsaturated depth. The use of tailing sands with low permeability in conjunction with a deep (>5 feet) unsaturated zone is effective in removing microorganisms from stormwater and treated wastewater.
Peter J. Schreuder and John Dumeyer, Schreuder, Inc.; Lillian M. Stark, Florida Department of Health, Tampa Branch Laboratory, Tampa, Florida. August 2001.