Collaborative Research: Optimization of metal attenuation in biologically-active remediation systems

CBET 1336496/1336247

Colleen Hansel/Cara Santelli

Woods Hole Ocean Inst. /Smithsonian Instutution

Coal-mining activities have resulted in worldwide environmental pollution due to the production of acidic, metal-rich waters that damage entire ecosystems and contaminate water supplies compromising public health. Coal mine drainage (CMD) throughout the Appalachian region contains particularly elevated concentrations of dissolved manganese (Mn), that at such high levels may lead to neurological disorders. One of the most promising and economically feasible approaches to treat metal-laden CMD containing elevated Mn are biologically active limestone treatment beds. Limestone is used to raise the pH of the contaminated waters to promote growth of microorganisms that can transform (via oxidation reactions) soluble Mn to solid Mn oxide minerals that are subsequently retained within the treatment beds. Formation of these minerals effectively removes Mn from the water and also produces a substrate that serves as a water treatment filter, effectively removing additional contaminants, such as cobalt, zinc, and nickel, from CMD. At this time, the successful removal of Mn and other metal contaminants from mine waters is highly variable and as low as 20% removal of Mn in some systems in Pennsylvania. Success of these treatment systems is currently limited by an insufficient knowledge of the individual and collective activities of microbial populations and the optimal conditions for biologically mediated Mn oxide formation. This research will address these knowledge gaps by simulating limestone treatment systems under controlled laboratory conditions to better establish the most effective biogeochemical conditions for stimulating both microbial growth and subsequent metal attenuation in CMD treatment systems. Specifically, the project will first identify the most effective microbial species and nutrient conditions (e.g., organic carbon and nitrogen composition) stimulating optimal Mn oxide formation by pure and mixed laboratory cultures of bacteria, fungi, and algae previously isolated from CMD treatment systems. These vital nutrient and microbiological conditions will then be employed and tested in laboratory-simulated treatment systems to further optimize Mn removal and precipitation efficiencies by complex microbial assemblages and the activity of key microbial species. Throughout the experiments, the microbial population structure and community interactions that impact Mn removal and Mn oxide formation will be identified. The composition and stability of the biologically precipitated Mn oxide minerals and their efficacy in removing metal contaminants will also be assessed.

The development of successful and cost-effective approaches for cleaning contaminated environments and water supplies is an immediate priority. This project will answer key scientific questions limiting the success of biologically stimulated treatment processes and optimize low-cost, green technologies currently employed throughout the world in an attempt to clean environments devastated by mine drainage. Essential knowledge gained by this project will be conveyed to scientists, engineers, educators, and government regulators for direct application to limestone treatment systems currently being used at hundreds of sites in Appalachia to treat coal mine drainage. An equally important goal of this project is to educate future generations and the general public on the causes, effects, and solutions to mine drainage. The PIs will integrate this research into two outreach activities, including (1) high school science teacher internships to aid in the development of new curricula that will engage underrepresented students in STEM fields and introduce them to green technologies used to treat environmental pollution and (2) informal presentations and inquiry-based learning exercises at the National Museum of Natural History, Smithsonian Institution, to communicate science activities and products to the general public and provide opportunities for visitors to ask questions and personally interact with the scientists.