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Fuels:
Petrol, Diesel etc
Fuels in Ground Water
Common treatment technologies include: |
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| With the exception of Airsparging these
are all ex situ treatment technologies requiring ground
water extraction. |
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Air Stripping
Air stripping involves the mass
transfer of volatile contaminants from water to air. For
ground water remediation, this process is typically conducted
in a packed tower or an aeration tank.
The generic packed tower air stripper
includes a spray nozzle at the top of the tower to distribute
contaminated water over the packing in the column, a fan
to force air counter-current to the water flow, and a
sump at the bottom of the tower to collect decontaminated
water. Auxiliary equipment that can be added to the basic
air stripper includes automated control systems with sump
level switches and safety features such as differential
pressure monitors, high sump level switches and explosion
proof components. The discharged air is treated using
systems such as activated carbon units, catalytic oxidisers,
or thermal oxidisers. Packed tower air strippers are installed
either as permanent installations on concrete pads, on
a skid, or on a trailer.
Carbon Adsorption
Liquid phase carbon adsorption
is a proven technology in which ground water is pumped
through a series of vessels containing activated carbon
to which dissolved contaminants are adsorbed. The carbon
medium can be changed to suit specific contamination within
the ground water.
It is also possible to regenerate the
carbon where high concentrations would reduce the effective
life of the carbon. This can be done by using steam to
effectively strip the contamination from the activated
carbon allowing further use.
Dual Phase Extraction
For dual phase extraction, undissolved
liquid-phase organics are removed from subsurface formations,
either by active methods (e.g., pumping) or a passive
collection system. This process is used primarily in cases
where a fuel hydrocarbon is floating on the water table.
The free product is generally drawn
up to the surface by a pumping system. Systems may be
designed to recover only product, mixed product and water,
or separate streams of product and water (i.e., dual pump
or dual well systems). Dual phase extraction is a proven
widely used technology.
Multi Phase Extraction MEL-MultiVacEx®
In multi phase extraction MEL-MultiVacEx®,
a high vacuum system is applied to simultaneously remove
liquid and gas from low permeability or heterogeneous
formations.
The vacuum extraction well includes
a screened section in the zone of contaminated soils and
ground water. It removes contaminants from above and below
the water table. The system lowers the water table around
the well, exposing more of the formation. Contaminants
in the newly exposed vadose zone are then accessible to
vapour extraction, which can remove contaminants more
efficiently than pump-and-treat.
Bio slurping
Bio slurping is the adaptation
and application of vacuum-enhanced dewatering technologies
to remediate hydrocarbon-contaminated sites. Bio slurping
combines vacuum-assisted free-product recovery with bio
venting to simultaneously recover free product and bioremediate
soils.
Bio slurping can improve free-product
recovery efficiency without extracting large quantities
of ground water. Bio venting of soils is achieved by drawing
air through the soil via the recovery well. The system
is designed to minimise environmental discharge of ground
water and soil gas. When free-product removal activities
are completed, the bio slurping system is easily converted
to a conventional bio venting system to complete the remediation.
Air sparging
Air sparging is an in situ technology
in which air is injected through a contaminated aquifer.
Injected air traverses horizontally
and vertically in channels through the soil column, creating
an underground stripper that removes contaminants by volatilisation.
This injected air helps to flush (bubble) the contaminants
up into the unsaturated zone where a vapour extraction
system is usually implemented in conjunction with air
sparging to remove the generated vapour phase contamination.
This technology is designed to operate at high flow rates
to maintain increased contact between ground water and
soil and strip more ground water by sparging.
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