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8.6 Contaminated Site Remediation
Environmental remediation is reversing or stopping environmental damage caused
to soil/groundwater/sediment/surface water. It is a costly option as society or community pays when it makes a series of wrong decisions or due to disaster or due to
environmental crime. Some of the methods used in environmental remediation are
given below.
Thermal Desorption
In this process, a desorber volatilizes the pollutants to separate them from sludge/
soil. The contaminants can be destroyed/collected in at site or offsite.
Excavation or Dredging
This process involves excavation and transportation of contaminated soil to a regulated landfill. The process may involve aeration/bio-augmentation/bio-stimulation
of contaminated material to remove contaminants.
Pump and Treat
Pump and treat involves pumping out polluted groundwater and treatment.
Surfactant-Enhanced Aquifer Remediation (SEAR)
Remediation with pump-and-treat methods may require years to decades to reach
treatment goals with respect to non-aqueous-phase liquid (NAPLs), which are
trapped in the subsurface due to capillary forces. Since many NAPLs have low
aqueous solubility and are biologically unmanageable, mass removal from the dissolved phase is slow (Battelle and Duke Engineering and Services 2002).
In this method, surfactant solution is pumped through a contaminated zone by
introducing an injection point and removing from an extraction point.
Surfactants are surface-active agents that exhibit solubility in both water and oil
and help to improve NAPL recovery. SEAR has been used to remove contaminants
such as creosote, gasoline, jet fuels, besides polychlorinated biphenyls (PCBs)
(Lowe et al. 1999).
Solidification and Stabilization
In this method, stabilization is done by addition of reagents to a contaminated material to get more chemically stable constituents. Solidification is done by the addition
of reagents to a contaminated substance to impart physical/dimensional stability.
In Situ Oxidation
This method involves the injection of strong oxidants (like hydrogen peroxide,
potassium permanganate, ozone gas or persulfates) or oxygen gas or ambient air.
Soil Vapour Extraction
In this method, contaminant from the solid (sorbed) and liquid (aqueous or nonaqueous) phases is converted into a gas phase and collected in extraction wells.
Contaminant thus extracted in the gas phase is treated in treatment systems
above ground.
8.5 Disposal
8.6 Contaminated Site Remediation
Environmental remediation is reversing or stopping environmental damage caused
to soil/groundwater/sediment/surface water. It is a costly option as society or community pays when it makes a series of wrong decisions or due to disaster or due to
environmental crime. Some of the methods used in environmental remediation are
given below.
Thermal Desorption
In this process, a desorber volatilizes the pollutants to separate them from sludge/
soil. The contaminants can be destroyed/collected in at site or offsite.
Excavation or Dredging
This process involves excavation and transportation of contaminated soil to a regulated landfill. The process may involve aeration/bio-augmentation/bio-stimulation
of contaminated material to remove contaminants.
Pump and Treat
Pump and treat involves pumping out polluted groundwater and treatment.
Surfactant-Enhanced Aquifer Remediation (SEAR)
Remediation with pump-and-treat methods may require years to decades to reach
treatment goals with respect to non-aqueous-phase liquid (NAPLs), which are
trapped in the subsurface due to capillary forces. Since many NAPLs have low
aqueous solubility and are biologically unmanageable, mass removal from the dissolved phase is slow (Battelle and Duke Engineering and Services 2002).
In this method, surfactant solution is pumped through a contaminated zone by
introducing an injection point and removing from an extraction point.
Surfactants are surface-active agents that exhibit solubility in both water and oil
and help to improve NAPL recovery. SEAR has been used to remove contaminants
such as creosote, gasoline, jet fuels, besides polychlorinated biphenyls (PCBs)
(Lowe et al. 1999).
Solidification and Stabilization
In this method, stabilization is done by addition of reagents to a contaminated material to get more chemically stable constituents. Solidification is done by the addition
of reagents to a contaminated substance to impart physical/dimensional stability.
In Situ Oxidation
This method involves the injection of strong oxidants (like hydrogen peroxide,
potassium permanganate, ozone gas or persulfates) or oxygen gas or ambient air.
Soil Vapour Extraction
In this method, contaminant from the solid (sorbed) and liquid (aqueous or nonaqueous) phases is converted into a gas phase and collected in extraction wells.
Contaminant thus extracted in the gas phase is treated in treatment systems
above ground.
8.5 Disposal