USING 3D PRINTING TO IMPROVE FLOW AND CONTAMINANT CHARACTERIZATION IN KARST AQUIFERS (Invited Presentation)

Generalizing flow and contaminant behavior in karst aquifers remains one of the most difficult research problems in karst hydrology. While progress has been made on understanding specific contaminated sites, and modeling flow in karst aquifers has improved greatly in the past decades, our general predictive capabilities regarding contaminants remain very limited, particularly for non-aqueous phase liquids (NAPLs).

To gain a fundamental understanding of NAPL flow in karst conduits, we print rock columns containing conduits with a minimum aperture of one centimeter and investigate two-phase fluid flow under turbulent conditions using a variety of imaging techniques. One of the most promising approaches involves flow imaged with a modified x-ray computed tomography (CT) scanner. The CT images accentuate materials with differing atomic mass, and by doping of water, NAPL, and alginate hydrogel beads (AHBs), we can image some aspects of NAPL and water flow through printed conduits. These images and other data from column experiments using the AHBs allow us to characterize features like NAPL trapping and storage we expect at contaminated field sites.

The extraordinary advantage of using 3D printing is the flexibility for hypothesis testing regarding NAPL behavior in a variety of settings. Ultimately, this deeper understanding of NAPL behavior will allow for the creation of field-safe proxies for contaminants. AHBs can be easily altered to control the density, adhesion, and other physical properties to mimic NAPL. If beads can accurately mimic NAPL flow and trapping in constructed caves, they would represent a significant breakthrough for flow path tracking at contaminated sites and for risk assessment at uncontaminated sites.