Simple Versatile System
Waterloo Emitters are available to fit 2", 4" and 6" (50 mm, 100 mm and 150 mm) wells. They can be installed in open wells, or they can be permanently installed with sand packs in boreholes or trenches. The 51" (130 cm) long Waterloo Emitters can be installed individually or stacked one on top of another, to ensure full coverage of the contaminant plume. They are also effective in horizontal applications.
Because there is no minimum hydraulic head required, the Emitters are effective at any depth below water. When used in conjunction with packers and/or circulating pumps, the radius of influence is increased.
The Waterloo Emitter’s unique diffusive technology allows for the use of almost any chemical as an amendment to treat contaminated groundwater. The PVC frame accommodates the insertion of monitoring or sampling devices for observing groundwater conditions during the remediation process.
The Waterloo Emitter consists of silicone or polyethylene tubing coiled around a PVC frame. When a fluid is introduced into the tubing a concentration gradient is created between the inside of the tubing and the groundwater.
The Emitter works in accordance with Fick’s Law, whereby diffusion will occur until there is equilibration in chemical concentration inside and outside of the tubing. With the Emitter technology, the oxygen (or other amendment) is replenished continuously, and as groundwater continues to flow around the Emitter, equilibration never occurs. This results in continuous diffusion from the Emitter into the groundwater.
When a gas is applied to the Emitter there is a direct correlation between an increase in applied pressure and an increase in the amount of gas that will diffuse into the groundwater, however, diffusion is the only mechanism that allows the amendment to be added to the groundwater.
BTEX TPH Remediation Case Study
In 2007, Emitters were installed to clean up a former gas station site in Guelph, Ontario. The contaminant plume containing gasoline and diesel occurred in unconsolidated silty sand to a depth of approximately 3 m (10 ft). The initial plume stretched 30 m (100 ft) long and 15 m (50 ft) wide.
Migration towards down gradient receptors was a concern; therefore a solution that worked quickly and effectively was required to help eliminate the potential for exposure. A total of 14 Waterloo Emitters using LDPE tubing were installed in 4" wells screened at and below the water table. Emitters were placed to form a “fence” along the down gradient property boundary to cut off the contamination plume. Dried air containing 21% oxygen was released through the tubing.
During the remediation process, Dissolved Oxygen (DO) samples were collected on a monthly basis and groundwater samples for BTEX and TPH were collected quarterly from down gradient wells. Within one month of the installation, DO levels in the monitoring wells increased an average of 880%.
Initial TPH levels were a maximum of 27 mg/L (average 9.6 mg/L) and initial BTEX levels were approximately 11 mg/L. Within six months, results showed that the levels of BTEX and TPH had dropped below the analytical detection limit, meeting the Soil, Ground Water and Sediment Standards of the Ontario Environmental Protection Act, thus enabling the Emitter system to be decommissioned just one year after the installation.
Please see Case Studies for more case studies, papers and resources.