Ethanolamine is commonly used in gas sweetening operations and in some cases, has been found in the soil and groundwater at gas plants. Ethanolamine is reported to be amenable to biodegradation. At certain sites, however, low permeability soils hamper the ability to provide microbial consortia with the necessary nutrients for metabolism. A research program was initiated at a former Edmonton area gas plant site to demonstrate in-situ site remediation techniques.
A shallow horizontal well was used to hydraulically induce twelve sand-filled fractures in the subsurface to increase the overall permeability of the porous media. The fractures were successfully introduced into the subsurface and were demonstrated to increase the overall permeability of the fractured region by at least one order of magnitude. Tensile failure of the PVC casing in the initial horizontal well was avoided in a subsequent well by using a pre-tensioned steel cable to reduce tension on the PVC during completion. The second well was not fractured and had relatively poor connectivity to the fracture network. While horizontal wells may provide an efficient means of installing a fracture network, fractured vertical wells may carry less risk of losing access to the whole network during well completion. Bioventing at the site was hindered by unexpectedly high water levels, but a subsequent dewatering bioventing program demonstrated a reduction in MEA concentration. Oxygen depletion, carbon dioxide production, and ammonia accumulation provide evidence of MEA biodegradation. Microbial activity in water samples is moderately high and indicates that despite the high levels of ammonia and MEA, the water is not toxic to all organisms. Bacterial testing provides preliminary evidence that nitrification is not occurring in the groundwater. This may prevent the assimilation of ammonia at the site and must be considered for the bioremediation of this site and others impacted with alkanolamines.