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Looking Ahead to 2006
During fiscal 2006, the following new projects will be funded under the Mine Waste Technology Program (MWTP).
RESOURCE RECOVERY FROM FLOODED UNDERGROUND MINE WORKINGS--BUTTE, MONTANA (MSE)
Beneficial recovery of auxiliary resources from flooded underground mine workings in mine waste impacted areas will be investigated. Specifically, the feasibilities of recovering irrigation water and geothermal heat from the Belmont mine will be determined. A century of historic mining practices in the highly mineralized Butte, Montana, district resulted in many hundreds of miles of flooded underground mine workings. For almost three decades, land developers disregarded this area. However, in the past few years, the area has become home to several public facilities. Continued redevelopment of the area could benefit significantly from a low cost supply of irrigation water and a low cost heat supply. This MWTP project will determine the cost-effectiveness of utilizing underground water for nonagricultural irrigation and employing closed loop heat exchanges for supplementary building heat.
TECHNOLOGY TRANSFER – SELENIUM (MSE)
The Selenium Removal Treatment Alternatives project conducted a demonstration of several technologies for removing selenium to drinking water standards from selenium-bearing groundwater. The technologies evaluated included a catalyzed cementation process developed by Dr. Larry Twidwell at Montana Tech in Butte, Montana; a biological process developed by Applied Biosciences, Inc. of Park City, Utah; and ferrihydrite adsorption, the U.S. Environmental Protection Agency’s (EPA) designated Best Demonstrated Available Technology (BDAT) for selenium removal from water. Both the cementation and biological processes showed better performance than ferrihydrite adsorption, and both processes have been improved upon since the Selenium Removal Treatment Alternatives project was completed in 2000. The purpose of this project is to investigate the applicability of, and hopefully implement, these technologies to remove selenium from leachate from coal mining-related valley fills in West Virginia.
INFLUENCE OF ANIONS ON THE REMOVAL OF ARSENIC BY COPRECIPITATION AND LONG-TERM STABILITY OF FERRIHYDRITE AND MODIFIED FERRIHYDRITE (MONTANA TECH)
The main objective of this proposed project is to examine change as a function of depth in the geochemistry and stable isotope composition of mine shaft water in Butte, Montana. This project is a continuation/outgrowth of two previous MWTP projects, which focused on the geochemistry and stable isotope composition of mine water in the Berkeley Pit lake and the Kelley Mine shaft, Anselmo Mine shaft, and Steward Mine shaft of the East Camp flooded mine workings, and the West Camp Extraction Well that drains the West Camp flooded mine workings. These previous projects, in conjunction with ongoing monitoring by the Montana Bureau of Mines and Geology (MBMG), have documented the incredible diversity in the chemistry of mine waters in the Butte district, as well as the various processes, both biological and geological, that have influenced these waters. However, a good understanding exists of vertical changes in chemistry of the Berkeley Pit lake, very little information exists on similar changes in chemistry or microbiology of the flooded mine shafts. Typically in the past, MBMG has collected samples of mine shaft water from a depth of 100 feet below static water level. Although some field parameter profiles for the top 300 feet of several shafts were obtained in 2000, no water quality samples were collected. Thus, no information is available for field parameters or water samples at depths greater than 300 feet, despite the fact that the vast majority of the underground mine workings are at depths between 1,000 and 5,000 feet. Monitoring to date has only characterized a two-dimensional slice of the very top of the mine water complex—more than 90% of the accessible water in the flooded complex has never been sampled.
VERTICAL GRADIENTS IN BIOGEOCHEMISTRY OF FLOODED MINE SHAFTS IN THE BUTTE, MONTANA FLOODED MINE COMPLEX (MONTANA TECH)
Arsenic removal by adsorption on a ferri-oxyhydroxide (ferrihydrite) surface is EPA’s BDAT. This technology is used throughout the industry for removing arsenic from wastewaters; however, long-term stability of ferrihydrite is questionable. During the MWTP project, Modified Ferrihydrite for Enhanced Removal of Arsenic from Mine Wastewater, it was observed that the removal of arsenate from solution appeared to be greatly influenced by the choice of the ferric salt compound chosen as the iron reagent. This was unexpected and has not been observed or evaluated by other investigators and could be a significant development in the understanding of the EPA BDAT ferrihydrite coprecipitation and adsorption technologies. This project will have two major components: 1) evaluating the influence of the anions on the removal of arsenic from wastewater and drinking water; and 2) evaluating the long-term stability of ferrihydrite and aluminum modified ferrihydrite.