Remediation technology: Pump and treat
Pump and treat is often used to remediate groundwater affected by:
- Presence of dissolved chemicals such as solvents, light fuels, metals etc.
- Free phase such as Light Non-Aqueous Phase Liquid (LNAPL) such as oils, gasoline, diesel, etc. or Dense Non-Aqueous Phase Liquid (DNAPL) such as creosote, lindane etc.
The area to be treated is installed with pumping wells in which the extraction pumps are installed. The pumps can be installed inside the wells as electric or pneumatic pumps or as a combination where the need to draw down the aquifer is required in order to mobilise free phase. If the aquifer is shallow, pumping can be completed from the surface.
This technique can be complemented by injection of treated water up gradient which may include agents to help mobilise the contaminants towards the points of extraction.
The extracted contaminated water or combination of free-phase and water is treated using physical methods, chemical methods or a combination of both.
This method is used for the following:
- Remediation: reduction of the dissolved phase in the water or extract free-phase.
- Groundwater barrier: interception of a contaminated groundwater plume or to prevent its spreading.
Applicability of Pump and Treat
This technique is adequate for aquifers with a medium o high hydraulic conductivity whereas for low yield aquifers this technique is not effective.
The aspects to consider for using this technique depends on the following variables: characteristics of the ground, type of contamination, levels required to decontaminate, number of wells to be installed for pumping, pumping flowrate, depth to the groundwater level and time of operation.
Among the main advantages of treatment using pump and treat are as follows:
- Can be used over a great area.
- One of the few options available to treat affection at great depth.
- Adequate to remove light free-phase (fuels) and dense (DNAPL) such as creosote, chlorides, etc.
- Large range of contaminants can be treated using this technique.
Some of the limitations of this technique are as follows:
- Not an effective technique of the contaminants are precipitates or adsorbed.
- Not applicable in low permeability material (silty clays or clays).
- Long term process.
- Generation of waste.
- Constant maintenance is required to ensure that the pumps and treatment equipment are clean and operational.
- Depending on the ground conditions and contaminants there is a potential of rebound.
Although the initial installation costs may be elevated, the operational costs are low.
As with all other ground remediation techniques, the effectiveness pump & treat decreases with time. Therefore, once the objectives of remediation are 85-95 % completed, cheaper and less intrusive remediation techniques can be employed.
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Publicado el 01/03/17