FLUME SIMULATIONS TO ASSESS THE EFFECTS OF STREAMBED CHARACTERISTICS ON COLLOID AND SEDIMENT COMPOSITION IN ABANDONED MINE DRAINAGE

This project investigated the effects of bed type and grain size on colloidal and sediment phase compositions in synthetic abandoned mine drainage (AMD) through mixing studies in an annular flume. Previous research on AMD geochemistry focuses primarily on sediment composition while overlooking the role colloids play in heavy metal and organic contaminant transport, as well as other important environmental problems.

Laboratory mixing in an annular flume, with an 18 cm wide channel and 170 cm diameter, provided insight into the chemical and physical evolution of AMD water as it moves downstream. We synthesized AMD water using ferrous sulfate heptahydrate (FeSO₄^.7H₂O) and sodium sulfate (Na₂SO₄) to match known Fe and SO₄ concentrations in anthracite AMD field sites. We sampled the synthetic waters at specific intervals, centrifuged to remove suspended sediment, and then concentrated the colloids using tangential flow ultrafiltration and micro centrifugation. Drying of both phases was followed by an analysis of their compositions using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and x-ray diffraction (XRD). We also compared the colloidal and sediment compositions to field-sampled AMD to validate using laboratory mixing techniques to simulate natural AMD waters. Initial results indicate a difference in colloidal phase composition between control runs with a smooth bed and trials with a coarse quartz sand bed.