Hydrochemical evaluation and predictive modeling of sulfate-reducing bioreactor cells

Status Start Date End Date Locations
completed Apr 1, 2008 Mar 31, 2011 Martin, Pike
Director: Tracy Branam
Other Researchers: Greg Olyphant, Greg A. Olyphant, , Matthew Reeder
Funding: Indiana Department of Natural Resources (DNR) - Division of Reclamation (DOR)
Issue: Anaerobic wetlands have proven to be effective at reducing contaminant loads in acidic mine drainage (AMD) through the attenuation mechanisms of precipitation and sorption, but the construction of wetlands is limited by size requirements, flow volume, and contaminant concentrations. Anoxic limestone drains (ALD) have been utilized to generate alkalinity within an AMD stream, but chemical composition and concentrations of AMD limit their use. The sulfate-reducing bioreactor cell (SRBC) combines the treatment features of both wetlands and ALDs with fewer constraints. They can be sized to fit smaller treatment areas and can treat low-flow, highly acidic, and mineralized waters. A combination of organic substrate and agricultural limestone provides a medium in which AMD is neutralized immediately upon entering the cell, followed by oxygen depletion by aerobic bacteria. This allows sulfate-reduction by anaerobic bacteria that fixes metals and generates alkalinity. As the limestone and organic substrate are depleted, the neutralization and oxidation-reduction fronts advance through the cell.
Objective: The goal of the research project is to evaluate and model the performance and longevity of SRBCs for the passive remediation of AMD.
Approach: The hydrochemistry of three SRBCs scheduled to be installed by the IDNR - DOR will be intensively monitored. Two of the bioreactors will be located at the “Lacy” site in Martin County, Indiana, and another bioreactor will be installed at the “Midwestern” site in Pike County, Indiana. The data collected in this study will be used to develop a hydrochemical model for predicting the performance of SRBCs based on the identification of fundamental reactions (and their rates) that most significantly affect the functionality of the SRBCs over time.
Products: 1. Detailed data sets capable of being used to evaluate the long-term performance of SRBCs experiencing different inflow rates and chemistries. 2. A detailed understanding of the mechanisms involved in bioreactor performance, including the partitioning of components between dissolved and solid phases over time, reaction rates and phase stability, and the microbial activity associated with the removal of sulfate from the AMD. 3. A coupled physical-chemical model for predicting the long-term behavior of SRBCs and to anticipate the optimal design of future SRBCs. These deliverables will be presented in reports to appropriate agencies as well as peer reviewed publications, conference presentations, and a dissertation.
Benefits: Numerous state and federal agencies will benefit from the results of the proposed study. The IDNR-DOR will benefit by having guidelines for optimal SRBC design and a model for predicting long-term SRBC performance. The Indiana Geological Survey (IGS) will benefit by extending its already substantial expertise on coal-mine hydrology and AMD into the field of AMD remediation technology.

Hydrology and Water Quality Associated With The Midwestern Reclamation Site (Site No. 1087) Pike County, Indiana