Environmental Engineering Reference
In-Depth Information
Monitored Natural Attenuation
Encompass intrinsic bioremediation process.
Reliance on a variety of physical, chemical, or
biological processes (within the context of a
carefully controlled and monitored site cleanup
approach) that, under favorable conditions, act
without human intervention to reduce the mass,
toxicity, mobility, volume, or concentration of
contaminants in soil or groundwater.
activated carbon, peat, bentonite, limestone, saw
dust, or other.
Thermal Enhancements
Use of steam, heated water, or radio frequency
(RF) or electrical resistance (alternating current
or AC) heating to alter temperature-dependent
properties of contaminants In-situ to facilitate
their mobilization, solubilization, and removal.
Volatile and semivolatile organic contaminants
may be vaporized; vaporized components then
rise to the vadose zone where they are removed
by vacuum extraction and treated.
Biocolloid Formation
Solid materials containing the basic elements
produced by bacterial transformation assume a
discrete particle which may be referred as bio-
colloids. Biological colloid is the negative charge
that is usually present on the particle surface and
forms the electric double layer surrounding the
colloid particles. The biocolloid system may be
appropriate in remediation of groundwaters and
flowing surface water. The basic requirements
would be the addition of bacteria and metabolism
in the presence of the metal followed by recov-
ery of the biocolloids. Biocolloid methods can be
used for treatment of contaminated ground water
in-situ in recovery of metals (Lovley
1995
).
Electrokinetics
An in situ process involving application of low
intensity direct electrical current across elec-
trode pairs implanted in the ground on each side
of a contaminated area of soil, causing electro-
osmosis and ion migration. Contaminants mi-
grate toward respective electrodes depending
upon their charge. Process may be enhanced
through use of surfactants or reagents to in-
crease contaminant removal rates at the elec-
trodes. Process separates and extracts heavy
metals, radionuclides, and organic contaminants
from saturated or unsaturated soils, sludges, and
sediments.
1.7
Limiting Factors of Intrinsic
Biodegradation
Biological Treatment
Physical, chemical, and biological factors have
complex effects on hydrocarbon biodegradation
in soil. For this reason, experts frequently rec-
ommend that soil bioremediation projects begin
with treatability studies to empirically test the
biodegradability of the (Spormann and Widdel
2000
) contaminants and to optimize treatment
conditions. On the other hand, it is possible that
the expense of such treatability studies could be
avoided or minimized, if certain soil character-
istics could be measured and used to predict the
potential for bioremediation of a site, the kinet-
ics of hydrocarbon removal or the optimal values
for certain controllable treatment conditions. For
example, certain cocontaminants such as heavy
metals might preclude hydrocarbon bioremedia-
tion. Soil particle size distribution might partly
Bioslurping
Use of vacuum-enhanced pumping to recover
light nonaqueous phase liquid (LNAPL) and ini-
tiate vadose zone remediation through biovent-
ing. In bioventing, air is drawn through the im-
pacted vadose zone via extraction wells equipped
with low vacuums to promote biodegradation of
organic compounds.
Intrinsic Bioremediation
Natural, nonenhanced microbial degradation of
organic constituents by which complex organic
compounds are broken down to simpler, usually
less toxic compounds through aerobic or anaero-
bic processes.
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