IMPROVING A NOVEL “MYCOZEO” PASSIVE MANGANESE BIOREMEDIATION SYSTEM: COMPARATIVE EFFICACY OF COAL MINE DRAINAGE REMEDIATION BY MINED, WASHED, AND SYNTHETIC ZEOLITES

Coal mine drainage (CMD) has long impacted the Appalachians, with various metal contaminants and acidity polluting watersheds and ecosystems. Manganese (Mn) is a particularly persistent contaminant in CMD. Passive Mn bioremediation sites typically involve a series of flow through remediation ponds lined with carbonates (e.g., limestone or dolostone), to raise water pH and promote Mn oxidative precipitation, as well as microbial Mn-oxidizers, particularly Mn-oxidizing fungi. These passive bioremediation systems exhibit varying effectiveness in removing aqueous Mn. Thus, our research focuses on using different liner rocks for Mn bioremediation. While dolostone and limestone are most common, zeolites have potential in removing contaminants from acid mine drainage. However, zeolites can have antimicrobial properties that can potentially affect Mn-oxidizing microbes. Here we investigate Mn remediation from synthetic CMD (SCMD) using natural mined zeolites (clinoptilolite), limestone, and mixtures of limestone and zeolites (mimicking adding zeolites to limestone-lined remediation ponds), in systems with and without Mn-oxidizing fungi (Stagonospora sp. SRC1lsM3a). While limestone systems are most effective over the long term, zeolites are found to substantially accelerate Mn remediation. Fungi increases both the overall Mn remediation extent and the average Mn oxidation state of the resulting solids in all systems, as analyzed by Mn K-edge X-ray absorption near edge structure spectroscopy. The fungal 10% zeolite and 90% limestone system may be the most successful, removing 44% of aqueous Mn within 24 hours and reaching 99% Mn removal by experiment end. However, all zeolite systems still have elevated Mn concentration above World Health Organization provisional guidelines (80 ppb), along with other contaminants not in the SCMD (e.g., arsenic), indicating natural zeolites may be pollutant sources. Washing zeolites hastens the kinetics of Mn removal from SCMD by opening more active sites for Mn sorption. While these ‘MycoZeo’ systems may have potential, combining the abiotic rapid Mn adsorption onto zeolites with slower fungal-promoted Mn oxidation, due care and consideration should be given prior to using zeolites to prevent additional contaminants from disrupting microbial communities important to Mn remediation.