BIOMAGIC: summary of progress and recommendations

Abstract

Research at the University of Toronto and Boojum Research has focused on assessing the feasibility of an in situ BIOremediation of Mine Area Groundwater Inorganic Contamination (BIOMAGIC) process for South Bay, and elsewhere. It is a joint project, supported by NRC ( the National Research Council of Canada) and has two components. The theoretical work is carried out at U. of Toronto, under contract from Boojum Research and the company carries out the field work, with field tests and scale up. The concept is based on using urea-degrading bacteria to increase the pH and alkalinity of acidic groundwater containing high concentrations of dissolved metals. This is intended not only to reduce the extent of acidification that normally accompanies the hydrolysis of dissolved metals in mine drainage, particularly ferric iron, but also to initiate the removal of dissolved metals through mineral precipitation and sorption reactions. Anticipated benefits include restoration of normal pH values and substantially reduced metal-loading in water that is apt to move off mine site property. Moreover, urea is produced as a bulk commodity agricultural fertilizer that is readily available. The approach used in this preliminary evaluation of the potential use of ureadegrading bacteria for BIOMAGIC involved both geochemical modeling and 2 microbiological investigations. Flow-through column work has also been undertaken to help in the assessment of South Bay hydrogeology, and to learn about the potential impact of bacteria on groundwater flow in porous geological media. Construction of the geochemical model using the MINEQL+ program was based on South Bay groundwater chemistry provided by Boojum Research. The objective of the modeling exercise was to determine (i) the extent to which groundwater pH would change in response to urea degradation, (ii) the minimum amount of urea that must be degraded to restore nearneutral pH, and (iii) the impact of anticipated pH changes on the aqueous chemistry and solubility of dissolved metals. Microbiological studies initially encompassed a survey of South Bay groundwaters to determine whether any urea-degrading bacteria existed in the mine site aquifer, and to identify specific locations with conditions favorable to their growth. Subsequent work involved single colony isolation of South Bay urea-degrading bacteria to compare their activity with that of a reference bacterial culture (Bacillus pasturii) from the American Type Culture Collection (ATCC). These pure culture studies are being done under anaerobic conditions in South Bay groundwater. All of this microbiological information is needed to determine where to initiate BIOMAGIC, and whether natural populations of bacteria might be used or, alternatively, whether a need exists to add urea-degrading bacteria to the groundwater system.