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DocuSign Envelope ID: D07924E6-3D94-4398-AO66-B683COBAB33E <br /> February 24,2021 <br /> Angela Aalbers,Chantell Johnson <br /> Page 2 of 12 <br /> Reference: Biological Sulfate Reduction Bench-Scale Test Results-Revision 1 <br /> BASIS OF APPROACH <br /> As stated above, Outfall 010 shows elevated levels of sodium, sulfate, and TDS which are identified as the <br /> most prevalent constituents in the water. The previous evaluations performed showed consistent WET test <br /> passing for the reverse osmosis effluent at high recovery and improved reductions from lime treatment. <br /> The reverse osmosis treatment was conducted at two percentages resulting in conductivities (indirectly <br /> correlated to TDS) of 547 and 2,200 µS/cm respectively. At the lower conductivity level, all lethal and <br /> sublethal effects were removed. At the higher conductivity level, most lethal and some sublethal toxicity was <br /> removed. This lower percentage water was able to pass the WET test some point between 20 and 40% <br /> dilution <br /> Lime treatment is typically effective in lowering the TDS of a water source due to TDS reduction as a result of <br /> calcite (CaCO3) precipitation. Testing records indicate that roughly 11-15% of the alkalinity and up to 6% of <br /> the sulfate was reduced as part of this treatment approach. This was performed in two variations with lime <br /> addition using 7 grams (g) and 14 g of ground limestone per gallon of water which was then filtered. The <br /> lower treated lime option (7g) showed a decrease from the baseline in lethality but worsened effects on <br /> reproductivity. However, testing using the higher limestone dose was able to provide positive results showing <br /> effective reduction in all but sublethal toxicity beyond a 40% dilution (conductivity below approximately 2,700 <br /> µS/cm; dilution water is moderately hard, reconstituted deionized water). Less dilution showed increases in <br /> effects to reproduction which placed the water out of compliance. <br /> Table 2 -Summary of TIE Test Parameters <br /> R01 KUL1 Dilution Dilution <br /> (547 00Range Treatment Range <br /> Test Method (passing <br /> (passing <br /> Sodium _ 100 360 216-288 730 438-584 <br /> Sulfate 85 700 420-560 1411 846-1129 <br /> Bicarbonate 150 330 198-264 687 412-55 <br /> To prioritize a passive treatment method, a BSR was proposed as a means of reducing sulfate which is <br /> known to effectively reduce toxicity in mine water without requiring additional treatment prior to discharge. <br /> While the approach is specific to the individual mine-influenced water, the reduction in sulfate from the <br /> previous tests does show some correlation to reduction of sulfate and reduced toxicity. <br /> Determination of an effective target range for the BSR testing was derived from the dilution ranges of the <br /> reverse osmosis and limestone treatability testing. Passing the WET for the limestone test suggests an upper <br /> TDS concentration of 846 mg/L to be acceptable, with the lower limit between 420-560 µS/cm from the RO <br /> test. Based on these TIE results, a target reduction in the mine water of 1,000 mg/L sulfate was chosen, <br /> resulting in concentration of approximately 500 mg/L. The limestone treated water is considered to have final <br /> water properties that are more representative of BSR effluent than a reverse osmosis permeate. <br /> TEST DESCRIPTION <br /> For the BSR bench-test, two four-column test apparatus were constructed using 4-inch diameter, clear <br /> polyvinylchloride (PVC) piping to produce the necessary anaerobic conditions for sulfate reduction. The first <br /> Desi� in community in mii <br /> dpg llus0321-ppfss01lshared_projects\233001407\reports\6_bench_scale_report\rpt_bench_scale_report_24feb2O20_final_rl.docx <br />