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DocuSign Envelope ID: D07924E6-3D94-4398-A066-B683COBAB33E February 24,2021 Angela Aalbers,Chantell Johnson Page 9 of 12 Reference: Biological Sulfate Reduction Bench-Scale Test Results-Revision 1 Table 9 - Laboratory Analytical Summary from November 17 and 18, 2020 Effluent P,73 Effluent Effluent Ca(mg/L) 76.3 50.2 - - Mg(mg/L) 113 112 - - Mn (mg/L) 0.0939 <0.0080 - - I Na(mg/L) 765 756 - - Fe(mg/L) <0.020 <0.020 - - Ammonia as N (mg/L) <0.150 <0.030 <0.060 <0.150 Total Alkalinity(mg/L 1,080 1,070 1,140 1,130 as CaCO3) Bicarbonate(mg/L as 1,030 999 1,140 1,130 CaCCt3) Carbonate(mg/L as 465 69 4.0 <1.0 CaCCt3) P(mg/L) 0.051 0.063 0.064 0.117 Dissolved Carbon (mg/L) 119 13.6 112 84.1 Chloride(mg/L) 30.7 30.6 - - Nitrate as N (mg/L) <0.050 <0.050 <0.050 <0.050 Sulfate as SO4(mg/L) 1,310 1,380 1,400 1,400 SUPPLEMENTAL TESTING As expected, the BSR treatment method was able to reduce the overall level of sulfate in the water, particularly for the 4X and 8X test conditions. However, preliminary review of WET tests showed only minor changes in toxicity, indicating that modifications to the test were required. Two additional parameters were identified as potential toxicants aside from the TDS issue that was previously identified. Elevated calcium carbonate levels were observed as precipitate in samples of the BSR tests, suggesting supersaturation. Carbonate ions are added to the water by the BSR process as the organic carbon is oxidized. Supersaturated calcium carbonate to have effects on lethal toxicity where calcite would precipitate on the gills of the fish. Fish reproduction is also known to be affected above a pH of 8.5. The field results showed pH levels up to 8.86. A decrease in pH would improve fish reproduction and has the added benefit of decreasing the saturation level of the calcium carbonate. Two additional tests were proposed for investigation based on the 4X BSR test condition (0.5 g carbon per gram of sulfate)which provided optimal results for reduction of sulfate concentrations. The first of these two additional tests are a control test employing a BSR approach followed by pH adjustment to 7.5. The second Desi� h community in mii dpg llus0321-ppfss01lshared_projects\233001407\reports\6_bench_scale_report\rpLbench_scale_report_24feb2O20_final_rl.docx