CHARACTERIZING REMEDIATION OF TRICHLOROETHYLENE PLUME USING SLOW-RELEASE PERMANGANATE GEL IN FLOW-TANK

Trichloroethylene (TCE) is an organic compound used as an industrial solvent. Historically, TCE has frequently escaped confinement and contaminated groundwater, where it belongs to a class of chemicals known as DNAPLs (dense nonaqueous phase liquids). TCE sinks below the water table until it encounters a confining unit, where it pools and creates a dilute dissolved contaminant plume as groundwater flows by. It is a known carcinogen which poses a threat to human health when it contaminates drinking water, and the EPA has established a maximum contaminant level (MCL) of 5 ppb.

Because TCE sinks below the surface, it is difficult to treat. Accessing the source is often impossible, and thus efforts are focused on remediating the plume. Current techniques, such as pump and treat or flushing, have proven inefficient and expensive to run. We propose an in-situ chemical oxidation (ISCO) technique which remediates contaminated groundwater at a low cost and over an extended period by using a slow-release permanganate gel (SRP-G). This gel is injected as a liquid which forms an inverse cone-of-depression in the subsurface and steadily releases dilute concentrations of the remedial agent (MnO₄^-) across a wide lateral area and for an extended timeframe.

In preparation for a future field demonstration, we will test the SRP-G treatment scheme using a flow-tank. The flow tank is filled with silica sand and contains twelve wells for gel injection and contaminant monitoring across three dimensions as the experiment progresses. The tank’s inflow will be replaced by dilute dissolved TCE in DI water and allowed to completely flush through before the SRP-G is injected. We will then monitor and collect samples from downstream wells which will be sent to a lab for TCE concentration data. Samples will also be analyzed with a UV spectrophotometer to measure MnO₄^- release and spread.

We anticipate a high chance of success in this experiment, as previous work developing the SRP-G in column and batch tests has shown great promise, and flow-tank tests so far injecting the gel without TCE have demonstrated an extended dilute release with lateral spreading.