Field demonstration of permeable wall flushing for biostimulation of a Shallow Sandy Aquifer

A pilot-scale nutrient injection wall (NIW) (4 m by 4 m by 1 m) was installed in the Borden Aquifer to serve as a pulsed injection source of a potassium acetate solution for:the stimulation of anaerobic microbial activity. The success of the flushing procedure was evaluated by monitoring the breakthrough of the acetate solution at several multilevel piezometers installed in the wall. Although some variation in the ground water velocity was observed with depth, the wall was flushed with reasonable uniformity after about six hours of injection and withdrawal, representing about one pore volume. Calculations based on head level data collected during the flush, and on the solute breakthrough curves, indicated that about 90% of the flow induced by the pumping and injecting was confined to the permeable wall. These results show that a permeable wall injection system is a viable method of introducing solutes uniformly to a cross section of aquifer, with minimal perturbation of the natural now system. In addition to its importance for the biostimulation system tested in this project, the flushing of permeable walls may have applications in other semi-passive remedial systems, such as the rejuvenation of reactive barriers.