Assignment 1: Steam Enhanced Extraction
(SEE)
March 1, 2017
Steam Enhanced Extraction (SEE)
Principles and applications
Steam Enhanced Extraction (SEE) is a thermal remediation technique used in
particularly permeable soils to heat the ground in such a way that removes organic contaminants.
The main principle of SEE is to heat the subsoil and groundwater aggressively,
whilst containing and extracting contaminants. SEE involves steam injection
into wells and the extraction of hot fluids from multi phase extraction wells.
Figure 1: SEE General Components
SEE has been utilised for the extractions and contaminant removal of Nonaqueous phase liquid(NAPL). This process involved the displacement of the
NAPL and extraction of the contaminant with the pumped groundwater. The
below image illustrated the general working principle of SEE to remove NAPL.
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Figure 2: Principle of NAPL removal
The SEE remediation method has is also utilised for the removal of contaminants
via vaporisation in the steam zone, accelerated vaporisation and extraction in
the vapour phase through pulsed pressurisation and depressurisation cycle, and
the dissolution, destruction and removal of contaminated with the extracted
groundwater.
The SEE remediation method can be utilised in areas in which have significant permeability and/or groundwater flow. The method allows for a high net
extraction of fluids by displacing large amounts of groundwater towards the
extraction well. As such, the steam technique facilitates NAPL mobility and
as such the associated stem pressure gradient displace the mobile NAPL and
vaporised components which are recovered at the extraction wells.
As the SEE method is based on steam injection, the method can be undertaken
above and below the water table. As such, the SEE method has been routinely used to treat sites contaminated with the following volatile and oils/light
substances:
• trichloroethylene (TCE)
• tetrachloroethene (PCE)
• Non-aqueous phase liquid (LNAPL)
• Chlorinated solvents
• Fossil fuels
• Heavy hydrocarbons
The SEE method ha proved to be particularly efficient in the removal of
hydro carbons from contaminated sites. The SEE method is utilised to reduce
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the viscosity of heavy oils and then displaces the oil toward the extraction wells.
At theses sites complete contaminant remediation is not feasible
In concluding, the decision to utilise the SEE method must be based on both
the soil type and contaminant to be removed and the properties of the porous
media to be remediated. Steam injection is justified when the comtaninant is
volatile or semi volatile and some chlorinated solvents. Soil type also plays a role
in the utilisation of the SEE method, with course soils having greater removal
results when compared to fine sediments.also the homogeneity of the subsurface
may also determine the effectiveness of the SEE method.
Case Study
A case study in which involved the use of the SEE method, was the removal of
Denser than water Non-Aqueous Phase Liquid (DNAPL) from a comtaminated
site in Florida.
In 2003, the US Energy Department completed a full scale DNAPL remediation using the SEE method and electrical heating resistance. The site was
observed to be contaminated with around 2.3 tonnes of NAPL substances such
as TCE, DCE, methylene chloride, toluene, and petroleum hydrocarbons.
The method to remediated this site lasted approximately four and a half months
and involved the heating of the target areas to near boiling point and subsequent pressure cycling to increase the removal of contaminants. This process
was continued until such a time as the vapour phase recovery was minimal..
When sampling was undertaken after the remediation attempts, it was observed
the concentrations of all contaminants were below the remediation goals. It was
also observed the groundwater concentrations were well below the maximum
contaminant level for all contaminants of potential concern.
In finishing, subsequent to the remediation efforts, it was observed that approximately 0.5 kgs of VOC’s remained in the remediated volume, constituting
a a remedial efficiency of 99.85 - 99.99% for the four DNAPL COPC.
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References
1. United States Environmental Protection Agency,. Injection For Soil And
Aquifer Remediation. United States Environmental Protection Agency: Office
of Research and Development:Office of Solid Waste and Emergency Response,
1998. Available: https://www.epa.gov/sites/production/files/2015-06/documents/steaminj.pdf
2. Gavaskar, A.R., Chen, A.S.C (2004) Remediation of Chlorinated and Recalcitrant Compounds, Proceedings of the Fourth International Conference on Remediation of Chlorinated and Recalcitrant Compounds: Battelle Press, Columbus,
OH,. .
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