Environmental Engineering & Science

Description

Wasatch Environmental's patented groundwater Density-Driven Convection (DDC) in-well aeration technology provides an effective in situ remediation solution. DDC systems are used for the remediation of volatile and/or aerobically biodegradable organic contaminants, including chlorinated solvents, MTBE, fuel hydrocarbons, and oil within both confined and unconfined aquifers.

Wasatch provides full system design, construction, and installation services based on 18 years of real-world testing and development experience.


Performance

DDC has been proven to effectively remove a broad range of petroleum products and volatile halogenated compounds in a wide range of soil types. More than 70 DDC systems involving over 1,000 DDC wells have been installed. Of these, half have achieved required cleanup levels for soil and groundwater, and the remainder are attaining cleanup goals. A typical DDC well design is shown above.

A DDC system is simple to install and operate and requires very little maintenance. (Site personnel can be trained in system maintenance in less than one day). The system can be designed as a complete grid of wells to aggressively treat an entire plume area or as a line of wells across a plume to act as a barrier to plume migration by removing contaminants as they pass. The system has been applied to a wide range of subsurface hydrogeological environments.

DDC wells are constructed of 2–12” diameter PVC or stainless steel casings screened near the top and bottom of the aquifer section to be treated. Air is injected into the wellbore via a drop tube installed inside the well casing. The air forms bubbles that flow upwards, displacing water and reducing the density of the water column within the wellbore. The effect of the density reduction is to create an upward vertical gradient within the wellbore, drawing contaminated groundwater in through the lower screen and pushing aerated groundwater out through the upper screen. This process creates a groundwater circulation cell within the aquifer surrounding the DDC well. Contaminant removal is effected by air-stripping the water in the wellbore.

Stripping efficiencies of up to 98 percent have been achieved in full-scale systems. Air emitted from the DDC wells may be exhausted to the atmosphere, collected at the well head for treatment, or, for biodegradable contaminants, exhausted via the upper screened interval to the unsaturated zone above the water table. Aerobic bioremediation is stimulated by supplying oxygen to the groundwater through the circulation cells, and to the unsaturated zone by exhausting to the zone above the water table.