IMPROVING THE EFFICACY OF MANGANESE PASSIVE BIOREMEDIATION VIA RAPID ABIOTIC ADSORPTION COMBINED WITH LONG TERM SEQUESTRATION BY MICROBIAL OXIDATIVE PRECIPITATION

Coal mine drainage (CMD) presents an ongoing environmental issue throughout much of Appalachia, resulting in acidification and metal pollution of waterways. Aqueous manganese (Mn) can be a particularly persistent issue in CMD, with passive remediation systems commonly implemented to help facilitate Mn remediation by promoting aqueous Mn(II) precipitation to Mn(IV/III) oxide minerals. These passive remediation systems are often lined with limestone in order to increase pH and encourage Mn oxidative precipitation, and may have amendments to support Mn oxidizing microbial populations, with fungi playing a particularly important role. Alternative methods have been employed to assist with Mn contamination in acid mine drainage via adsorption to zeolites. We find that zeolites, while a costly alternative, can rapidly remove Mn from synthetic coal mine drainage, but that the adsorbed Mn is readily released back into solution with perturbations in solution chemistry and that overall Mn oxidative precipitation (facilitated by the fungus Stagonospora sp. SRC1lsM3a) is decreased relative to limestone systems. Thus, our research focuses on mixtures of limestone and zeolites to help decrease costs of zeolite addition and promote more Mn oxidative precipitation while benefiting from the rapid removal of Mn via adsorption to zeolites. Mixtures of limestone with two zeolite types, a natural clinoptilolite washed with a sodium chloride solution, and a synthetic zeolite (13X) are compared. We find that, with 90% limestone and 10% zeolite mixtures, 13X more rapidly removes Mn from solution than washed natural clinoptilolite while the washed natural clinoptilolite is more effective than 13X at overall Mn remediation. The difference in total Mn remediation between washed natural clinoptilolite and 13X may be due to the large negative impact 13X exerts on fungal growth and fungal-promoted Mn oxidation. Additional mixture fractions of 5% zeolite (95% limestone), 1%, and 0.1% will also be explored to determine the most effective remediation zeolite amendment in terms of both economic cost and overall Mn remediation.