Environmental Engineering Reference
In-Depth Information
(a)
(b)
(c)
Nutrient solution
Pump
Groundwater
monitoring well
Tiller
Berm
Contaminated soil
Sand cushion
Aquifer
FIGURE 11.10
Schematic of a land-farming process. (a) Removal of large debris, (b) equipment for soil mixing with cover, and
(c) land farming process itself.
Moisture must be monitored and nutrients can be added to enhance biodegradation.
Occasional turning of the soil increases the oxygen content and permeability of the sedi-
ment/surface soil mixture. Bulking materials and nutrients may also be added. The process
is simple but could lead to contaminant volatilization and leaching. Therefore, monitoring is
required. Land requirements can be extensive. In the United Stated and Belgium, bioremedi-
ated dredged materials have been mixed with compost and/or municipal sewage sludge to
produce soil for landscaping projects and in Germany, it has been used in orchards.
An additive that has been used with land farming is DARAMEND™ (A+Environmental
Solutions, 2014). It is a solid phase amendment (Figure 11.11) to promote anoxic conditions
to enhance the bioremediation of pesticides such as toxaphene, DDT, dieldrin, TNT, RDX,
PCE, TCE, DDD, and DDE. The reduction in the redox potential enhances the dechlorina-
tion of organochlorine compounds. With tilling equipment, the material can be mixed in
to a depth of 0.6 m. Hydrated lime is used to maintain the pH between 6.6 and 8.5. Redox
potential and moisture were monitored at an evaluated at a Superfund Site (Montgomery,
Alabama) of a soil/sediment contaminated with pesticides (USEPA, 2004). Approximately
4500 tonnes were treated, and all contaminated reached speciied levels. Santiago et al.
(2003) evaluated DARAMEND for PAH contaminated sediment. However, PAH concentra-
tions were higher than expected (average of 900 ppm) and thus could be reduced by bio-
remediation to CCME criteria (260 ppm) in bench-scale experiments. Thermal treatment
was successful, however.
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