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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 regularly, and the groundwater flow around the Emitter is continuous, hence an equilibration point is never reached. This results in a continuous flow, through diffusion, being maintained from inside the Emitter to 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.
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The 51” (130 cm) long Waterloo Emitters can be installed singly or placed in line one on top of the another. These stacked Emitters can be designed to ensure that the full thickness of the contaminant plume will receive the bioremediation enhancement.
If an enhancement gas is to be used for remediation, a small to medium sized gas cylinder can be used. Emitter tubing is selected and pressure is set according to the amount of enhancement gas required. A single gas cylinder can be used to supply multiple Emitters connected in series.
Replenishment of the gas inside the Emitter tubing can be accommodated by periodic purging (weekly/bi-weekly), or a needle bleed valve can be used at the end of the system to allow slow, constant replenishment to occur.
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BTEX TPH Remediation Case Study
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Waterloo Emitters were installed starting in May 2004, in accordance with Ministry of Environment Certificate of Approval, at a food processing plant in Guelph, Ontario to remediate groundwater contaminated from leaking gasoline and chemical storage tanks. The contaminant plume containing BTEX and TPH occurs within shallow sands and gravels, silty tills, and underlying weathered dolostone to a depth of approximately 13 m. Numerical modeling was used to help determine the best locations for placement of Waterloo Emitters which would be used to diffuse oxygen into the contaminant plume to enhance the natural biodegradation of BTEX and TPH.
A total of 10 Emitters were installed inside 2” diameter overburden wells and 12 were installed inside 2” diameter bedrock wells. Emitters were connected to a bottled oxygen supply, which delivers oxygen at between 15-25 psi. At 20 psi, 1.8” Emitters using silicone tubing will release approximately 4.1 litres of oxygen per day to the aquifer.
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As of November 2004, use of the Emitters had resulted in the following observations:
- Emitter wells averaged 12 mg/L of dissolved oxygen (43.0 mg/L max.), a 900% increase over concentrations prior to Emitter installation.
- The areal extent of the plume has decreased.
- Core plume concentrations of BTEX and TPH have decreased by 20% in the overburden aquifer and 39% in the bedrock aquifer.
The use of the Waterloo Emitter on this project has been determined to be very effective, and will continue toward full site remediation.
Please see Papers & Info for more case studies, papers and resources.
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