Mine Environment Neutral Drainage Program, 71 pp, 2019

Lab and field studies were conducted to demonstrate in-pit batch treatment of arsenic-contaminated water in mine pits using ferric sulfate. The overall objective of the investigation was to demonstrate that in-pit batch treatment of arsenic represents a viable and economical alternative to traditional water treatment applications. Phase 1 included a bench-scale study that was used to define the design criteria, including the attainable treatment efficiencies, the required reagent dosages, and the sludge production rates. Phase 2 of this study included a field-scale treatment trial that evaluated the practicality and efficacy of in-pit batch treatment of arsenic within the Night Hawk Lake Mine open pit, as informed by the results in Phase 1. Total and dissolved arsenic concentrations at 3 depths were compared pre- and post-treatment in 3 sampling events at two stations (NHP 1 and NHP2). Immediately post-treatment, total arsenic concentration at the surface at NHP1 decreased from 0.6 mg/L to 0.01 mg/L total arsenic with a dissolved concentration <0.002 mg/L for a treatment efficiency of ~98% within the surface depths. The mid-depth samples for the same sampling event were ~0.03 and 0.01 mg/L for the total and dissolved arsenic concentrations, respectively. The arsenic concentrations at depth remained close to the initial concentrations before treatment. http://mend-nedem.org/wp-content/uploads/3.60.1.pdf