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Common treatment technologies for nonhalogenated SVOCs in
soil, sediment, and sludge include biodegradation, incineration,
and excavation with off-site disposal.
All types of biodegradation, both in situ or ex situ, can be
considered to remediate soils: in situ bioremediation,
bioventing, composting, controlled solid phase, or landfarming.
Slurry phase biological treatment is also applicable but is less
widely used. Treatability studies should be conducted to evaluate
design parameters, such as degradation rates, supplemental
organism addition, cleanup levels achievable, degradation
intermediates, and nutrient/oxygen addition.
Biodegradation uses
a process in which indigenous or inoculated microorganisms (e.g.,
fungi, bacteria, and other microbes) degrade (i.e., metabolize)
organic contaminants found in soil and/or ground water. In the
presence of sufficient oxygen (aerobic conditions),
microorganisms will ultimately convert many organic contaminants
to carbon dioxide, water, and microbial cell mass. In the absence
of oxygen (anaerobic conditions), the contaminants will be
ultimately metabolized to methane and carbon dioxide. Sometimes
contaminants may not be completely degraded, but only transformed
to intermediate products that may be less, equally, or more
hazardous than the original contaminant.
In situ bioremediation of soil typically involves the
percolation or injection of ground water or uncontaminated water
containing dissolved oxygen and nutrients. Ex situ bioremediation
typically uses tilling or continuously mixed slurries to apply
oxygen and nutrients, and is performed in a prepared bed (liners
and aeration) or reactor. Bioventing is also potentially
applicable to some nonhalogenated SVOCs.
Incineration uses
high temperatures, 870o to 1,200o C (1,400o
to 2,200o F), to volatilize and
combust (in the presence of oxygen) organic constituents in
hazardous wastes. The destruction and removal efficiency (DRE)
for properly operated incinerators exceeds the 99.99% requirement
for hazardous waste.
Distinct incinerator designs available for solids are rotary
kiln, fluidized bed, and infrared units. All three types have
been used successfully at full scale.
Excavation, retrieval, and
off-site disposal of contaminated soil (with or
without stabilization) to a landfill have been performed
extensively at many sites. Landfilling of hazardous materials,
especially hazardous wastes, is becoming increasingly difficult
and expensive as a result of growing regulatory control, and may
be cost-prohibitive for sites with large volumes, greater depths,
or complex hydrogeologic environments. Determining the
feasibility of off-site disposal requires knowledge of land
disposal restrictions and other regulations developed by state
governments.
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