Specific Conductance Reduction in Valley Fill Runoff Using the Cost-Effective Sulfate Removal Process

Abstract

Abstract:In recent years, the specific conductance (SC) of Appalachian coal mining runoff waters has become a parameter of concern with the EPA due to its negative effect on aquatic life and water quality. In order to comply with the EPA guidance suggesting an effluent SC of 500 µS/cm, the Appalachian Research Initiative for Environmental Science (ARIES) Center at Virginia Tech requested that testing be conducted to determine the most effective technologies for reduction of SC. Runoff water was collected from two sites in southwestern Virginia and characterized to determine the source of SC. The primary contributing ions were determined to be Na + , Mg 2+ , Ca 2+ , and SO4 2-. Once characterized, the sample water was treated using a two-step precipitation method called the Cost-Effective Sulfate Removal (CESR) process. Study results indicate that source water with an SC of 1,500-2,500 µS/cm could be successfully reduced below the proposed EPA limit of 500 µS/cm when the second step of the CESR process lasted 18 hours and the reagent dose was 1.25x the source water sulfate concentration. The success of this process was due to its ability to remove more than 85% of the Ca, Mg, and SO4 2-from the water, which together accounted for more than 90% of ions in the source water.