Sustainable Water Management - Sustainable Practices in Geoenvironmental Engineering - page 91

Vitriication, a high-temperature solidiication process, leads to the formation of a glassy
solid, and is especially applicable for treatment of arsenic-contaminated soils since arsenic
possesses low volatility. The melting ability of the contaminated soil depends on the soil's
silica content. The maximum allowable oxide content in a soil containing arsenic as a con-
taminant is 5% (Smith et al., 1995). It is the best demonstrated available technology (BDATs)
for Resource Conservation and Recovery Act (RCRA) wastes. Off-gas collection and treat-
ment may be required. Melting of the soil leads to volume reduction upon elimination of
void spaces and this backill is required to replace subsidence.
As an example, information regarding the sustainability of arsenic immobilization could
be obtained for sequential extraction techniques to evaluate the adsorption, sequestration,
and bioavailability of arsenic in soils (Yong and Mulligan, 2004) before and after treatment
with additives such as iron, aluminum, calcium, and manganese, cement, lime, and poz-
zolanic materials as was previously shown for phosphate treatment.

3.4.1.2 Extraction Treatment Techniques

To remove NAPLs from the groundwater, extraction of the groundwater can be performed
by extraction pumping of the contaminated dissolved phase and/or free phase NAPL
zone. Drinking water standards can be achieved with the method of treatment. However,
substantial periods can be required before this occurs. To enhance the removal rates of
the contaminants, extraction solutions can be iniltrated into the soil using surface lood-
ing, sprinklers, leach ields, horizontal, or vertical drains. Water with or without additives
is employed to solubilize and extract the contaminants as shown in Figure 3.9. Chemical

Buried leaking storage drums

Extraction wells for
water treatment

Injection wells

Groundwater
flow direction

Monitoring
wells

Contaminant plume

FIGURE 3.9
Schematic diagram of a soil lushing process for removal of contaminants.