A FIELD-SCALE FILTER DEVELOPMENT FOR “GREEN” REMEDIATION OF AMD-IMPACTED WATER

One of the major environmental problems associated with surface mining is production of a highly acidic and metal-rich solution called Acid Mine Drainage (AMD). In absence of proper management practices, AMD severely impacts surrounding ecosystems. Search for newer AMD management technology is ongoing, as current techniques are expensive, ineffective, and/or environmentally unsustainable. This study developed a green remediation technology using a by-product of drinking water treatment process, namely Water Treatment Residuals (WTR) to remediate AMD-impacted water. The main objective of this study was to design a filter media using metal binding and acid-neutralizing capacity of locally generated aluminum (Al) and calcium (Ca)-based WTRs to treat AMD-impacted water collected from the Tab Simco surface coal mine in Carbondale, IL. Initially, WTR-filter bed-columns were prepared using 15 cm x 2.54 cm clear PVC pipes. As WTRs are relatively impermeable, a series of hydraulic tests were performed with sand as substrate, and based on these test results, a 1:6 WTR to sand ratio was used to optimize permeability of the filter media. Al- and Ca-WTRs were mixed at 1:1 ratio. A 53mL filter bed volume and 15 mL/min flow rate were used during the study, and representative samples were collected from various bed volumes up to 24 hr. Results showed that the WTR filter bed removed 99.7% of the initial Fe concentration (137 mg/L), 94% of the initial Ni concentration. (4 mg/L), 96% of the initial Zn concentration (11 mg/L), 98% of the initial Pb concentration (10 mg/L), 100% initial As concentration (5 mg/L), 99% of the initial Cu concentration (4 mg/L), and 43% of SO₄^2- concentration (2134 mg/L) from the AMD-impacted water. Also, pH of AMD-impacted water increased from 2.07 to 6.15. A scaled-up 55 gallon drum filter was prepared as the final phase of the study for field implementation. Experiments with the drum filter is ongoing. Results showed that this “green” (recycling of a waste product), environment-friendly remediation technology can efficiently and cost-effectively treat AMD-impacted water.