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• <br />• <br />• <br />Table 4-4 Bench-Scale Testing Results for In-situ Biological Treatment <br />Constituent BF-2 <br />(2/5/99) In Situ Column Test <br />(3/8/99) <br />Bicazbonate 217 1,200 <br />TDS 1,260 2,120 <br />Calcium 343 589 <br />Sulfate 706 97.6 <br />Sulfide not determined 12.8 <br />Copper 0.061 <0.004 <br />Iron <0.019 32.8 <br />Manganese 5.31 38.8 <br />pH 7.60 6.60 <br />500 g of sediments collected from the azea of the seep adjacent to the Rito Seco. Air was <br />pumped through a diffuser in the bottom of the column to oxygenate the water in the column. <br />Treated water drained from the bottom of the column. After 3 weeks of operation, an additional <br />manganese oxidation column was added. This column was designed to act as a trickle filter to <br />passively aerate the water. The physical matrix of this column was pebble limestone and quartz. <br />After 5 weeks of operation, a complete water quality profile was performed on effluent from each <br />column. As observed for the column simulating in situ treatment, sulfate concentrations were <br />substantially lowered in the anaerobic cell (Table 4-5). The physical matrix of the anaerobic cell <br />released fluoride, iron, manganese, and silica. Release of constituents from the physical matrix <br />can be explained by reductive dissolution of minerals in the soil matrix. In a full-scale <br />implementation, materials would be screened for these elements, and the final materials would be <br />chosen to minimize the presence of soluble forms of these constituents in the anaerobic cells. <br />Bicazbonate concentrations increased as a result of oxidation of the liquid organic substrate <br />during sulfate reduction. <br />Ballle Mounmirt Buonrcu, lnc. <br />pa/00?671reporrslmarchrpAvl6wmmngfmarch.dac 57 <br />March ll. /999 <br />