![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Integrated Passive Biological Treatment Process Demonstration
Figure 7. Block flow diagram.
Primary Issue Addressed: Acid Drainage/Water Treatment
Secondary Issues Addressed: Biological Treatment, including manganese removal
Project Site: Surething Mine in the Elliston Mining District of Montana
Collaborating Entities: MSE
Cost Share: None
Project Description
The Integrated Passive Biological Treatment Process demonstrates that a technology consisting of a series of biological processes can be employed to completely mitigate acid drainage. The first part of this project proved that the technology could be successful at bench-scale. The field demonstration is being attempted at the Surething Mine, a remote abandoned mine near Elliston, Montana.
A series of four, lined, subsurface bioreactors were constructed downgradient of the mine (see Figure 7). The integrated process uses both anaerobic and aerobic bacteria to treat dissolved metallic and anionic constituents. The majority of the treatment is conducted in anaerobic sulfate-reducing bacteria (SRB) bioreactors consisting of 50% cow manure and 50% walnut shell substrate mixture. Additional treatment is conducted in an aerobic, manganese-oxidizing bacteria (MOB) bioreactor that was designed to have an indigenous bacteria population self-establish as a biofilm on the limestone cobble. The pH of the final process effluent is near neutral.
Status
The field demonstration has been monitored since September 2001. The data generally demonstrates a significant decrease in metals concentrations, with the exception of manganese.
Figure 8. Aerobic bioreactor with manganese deposits.
Shortly after the system started operation (see Figure 8), over 95% of the influent manganese was removed. Removal was less over the winter months and rose again in the spring. Thereafter, the manganese removals indicated that a population of manganese-oxidizing bacteria was having problems developing. It was determined that the original passive aeration configuration was not sufficient to treat the amount of sulfide being carried over from the upstream SRB Reactors. Over the past two summers, additional aeration capacity was added and the MOB reactor was modified to increase aerobic conditions. Late in the summer of 2004, measurable amounts of manganese oxidizing bacteria were detected with a corresponding removal of manganese. The process will be monitored into early FY06, and the final project report will be completed by the end of FY06.