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January 9. 1996 -5- 933 271 3 005 <br /> from two separate continuous flow systems (Dvorak and McIntire, 1992). The lower <br /> percent reductions in sulfate were related partially to the exhaustion of organic matter and <br /> short-circuiting through the wetland. However, in a system designed specially to maximize <br /> sulfate reduction, removal efficiencies as high as 70 plus percent have been reported using <br /> sludge from a domestic wastewater treatment plant as the organic carbon source (Maree and <br /> Strydom, 1985). The untreated sulfate levels employed in the various studies ranged from <br /> about 1,000-3,000 mg/l. <br /> An initial growth and acclimation period of 10 to 15 days is usually needed, along with a <br /> degradation period ranging from 10 to 15 days. For design purposes, a conservative total <br /> retention time for growth, acclimation, and degradation on the order of 5 to 20 days would <br /> be recommended for the configuration of the biological passive treatment system. <br /> Site Specific Design Criteria and Issues <br /> The site specific design criteria are summarized below. <br /> ► Reclamation and closure activities at the Longfellow Koehler Mine <br /> complex would likely consist of: <br /> 1. upgradient lined surface water diversions; and, <br /> 2. regrading of waste rock dumps and covering with a low permeability <br /> barrier layer. <br /> ► Residual seepage (assumed to be 50 gpm maximum) would be collected <br /> and routed to the three stage passive treatment system. <br /> ► The first stage of the passive treatment cell would consist of a aeration <br /> pond to promote oxidation and removal of iron and aluminum. <br /> ► The second stage of the system includes the anaerobic treatment cell. <br /> The conceptual sizing is a 100,000 cubic ft. pond which will allow a <br /> residence time for treatment of 10 days at a flow rate of 50 gpm. <br /> ► The final stage of the system includes an anaerobic leach field for <br /> infiltration of the treated water. <br /> Design issues which have not been resolved include the following. <br /> ► Due to the high iron and aluminum concentrations an effective <br /> pretreatment step is necessary to ensure permeability and longevity of <br /> the anaerobic cell. If aeration is not effective in reducing these metal <br /> concentrations an active treatment option (i.e., pH adjustment) would <br /> be required. <br /> Golder Associates <br />