Prior to initiation of the field trial five groundwater monitoring wells (one upgradient, three plume, and one fringe) were investigated to predict the effect of the sulfate amendment on subsurface microbial ecology by incubating two types of Bio-Sep® traps in each well. In each well one trap contained non-baited Bio-Sep® beads. The second trap contained both non-baited beads and beads in which Na₂SO₄ had been incorporated during fabrication. The baited beads provided a source of slow-release sulfate in the trap to mimic the effect of sulfate amendment of the aquifer. After 30 days of incubation the trap biofilms were analyzed using phospholipid fatty acid (PLFA) analysis and analysis of PCR-amplified 16S rDNA. Biofilms from the sulfate-baited traps and the non-baited traps were shown to have distinctly different community structures. Sulfate-baited traps were more likely to contain lipid anaerobic biomarkers, biomarkers for sulfate-reducing bacteria, and specifically identified anaerobes like Geobacter sp.

The aquifer is currently being monitored using non-baited Bio-Sep® traps to determine whether the predicted shifts in the subsurface microbial ecology are observed as the sulfate amendment is introduced. Initial results have shown that the aquifer has become aerobic due to the inadvertent addition of oxygen during sulfate injection. Anaerobes are still present in the groundwater. However, since the initiation of sulfate injection they are not being found in the Bio-Sep® beads indicating that they are not actively growing under the current aquifer conditions.