Treatment of mine influenced water: Utilization of biogeochemical process in reducing risk from metal contamination to environmental systems
Citation:
Starr, L. AND Souhail R. Al-Abed. Treatment of mine influenced water: Utilization of biogeochemical process in reducing risk from metal contamination to environmental systems. American Chemical Society National Meeting, San Fanscisco, CA, August 13 - 17, 2023.
Impact/Purpose:
Mine influenced water (MIW) is acidic with high concentrations of metals such as Zn, Cd, Mn, Cu, and Pb. These contaminant metals cause degredation to surrounding ecosystems, which rely on clean water. Previous work on MIW used treatments that would increase alkalinity with limestone to raise the pH, which would precipitate sulfide metal complexes. Using limestone can create a sludge that is not easily biodegradable. Other materials have also been used like chitin, which is costly and not native to many mining areas inland. This presentation compares previous results from MIW studies in Formosa, OR to a current study in the same area using different materials. The materials used in the current study are all local and sustainable to the area compared to previous studies, which used outside materials. This work is important to the scientific community as treatment of anthropogenic environmental stressors with biodegradable material is rising. The cost effectiveness of using local and natural materials as well as the potential to use the breakdown of the materials as fertilizer is potentially important to the surrounding local stakeholders.
Description:
Mining influenced water (MIW) emitted from mine sites poses a major environmental concern due to its impact on water contamination. This is caused by low pH and the presence of high concentrations of toxic metals in soluble and bioavailable forms. Biological activity creates reducing conditions where the soluble metals transform into a less soluble sulfide metal. The amount of toxicity from MIW is dependent on minerology of the rock material, surface area, crystallography, temperature, and oxygen concentrations. The exposure of sulfide minerals to water and oxygen causes oxidation, which can be accelerated by microbes, leading to sulfates and metallic hydroxides. Metals most often associated with MIW are iron, copper, nickel, manganese, cadmium, lead, aluminium, and zinc. Treatment of MIW to remove metals has been done with precipitation ponds, wetlands, bioreactors, and vertical flow retention systems. Each environmental system containing MIW is different and designs for treatment vary in their applicability to site contamination. In general, many of these systems are acidic with sulfide minerals, treatment in these systems often contains limestone to add alkalinity and raise pH. We will present sustainable and effective approach using sulfate reducing bacteria (SRB) to reduce sulfate and transform soluble metals such as copper, zinc, cadmium, and lead. We use readily available substrate such as wood chips, biochar, and manure to stimulate sulfate reduction in our bioreactors to form sulfide metals. Metals that are not bound to sulfide in the initial bioreactor step then go through a polishing step, a vertical wetland, to remove those metals such as manganese and iron. Overall, MIW is an environmental concern, and each system needs to be treated differently to account for water chemistry and toxic metals present.