USING AN INDUSTRIAL BYPRODUCT TO TREAT ACID MINE DRAINAGE IMPACTED WATER: PRELIMINARY RESULTS

Surface mining is an important revenue generating industry. During mining, a metal-rich acid solution called acid mine drainage (AMD) is generated, which, if left untreated severely damages the aquatic system. Currently in the US alone, over 19,000 km of rivers and streams, and 730 km² of lakes and reservoirs are adversely impacted by AMD. Existing AMD treatment technologies are mostly expensive and/or time consuming, and not environmentally or ecologically sustainable. This study used the metal binding and acid-neutralizing capacity of an industrial by-product, namely drinking water treatment residuals (WTRs), to treat AMD water collected from the Tab Simco coal mine in Carbondale, Illinois. The ultimate objective of this study is to design a filter media using locally generated aluminum (Al)-based WTRs to remove contaminants (Fe, Ni, Zn, SO₄^2-) from AMD impacted water. As the first step toward fulfilling this objective, WTR-filter bed-columns were prepared using 15 cm x 2.54 cm clear PVC pipes. To increase permeability of the media, Al-WTRs were mixed with sand at 10 different ratios, ranging from 1:1 to 1:10. Threshold pump flow rate (mL/min), time required for 1-bed volume (min), flow rate (mL/min) inside the column, and effect of height of water accumulated over filter bed on outlet flow rate were calculated for each column using DI water. A WTR: sand ratio of 1:6 was selected for further scaled-up studies based on the hydraulic test results. AMD-impacted water was passed through the column at a flow rate of 15 mL/min. The filter bed had a volume of 53 mL, and representative samples were collected from each bed volume up to 2 hr. Preliminary results showed that the WTR filter bed removed 92% of the initial Fe conc. (32.12 mg/L), 44% of the initial Ni conc. (0.63 mg/L), 49% of the initial Zn conc. (22.12 mg/L) and 43% of the initial SO₄^2- conc. (2134 mg/L) from the AMD-impacted water. Scaled-up studies are ongoing. Preliminary results from the reported study demonstrated that this “green” (recycling of a waste product), inexpensive (raw materials obtained free-of-charge), and ecologically sustainable (no adverse effect on ecosystem) method has the potential to effectively treat AMD-impacted water.