Biomedical Engineering Reference
In-Depth Information
Coarse
materials
Wa shing and
sieving
Fine
contaminated
particles
Settling
Disposal
or
treatment
Contaminated
soil or sediment
Screening
Cyclone
Wa ste for disposal
or reuse
FIGURE 10.4
Schematic of soil or sediment washing of contaminated material.
be used (Venghuis and Werther, 1998). The disposal of the treated fine particles
varies depending on the type and levels of the contaminants.
Mixtures of metals and organic contaminants may require sequential washing
with different additives to target the various contaminants. Soil-washing processes
generally use hot water to reduce the viscosity of hydrocarbons. The increased
temperature also increases the solubilities of metal salts. The treated soil can then
be washed to remove any residual wash solution prior to disposal. Ideally, the
wash solution should be recycled. Costs of soil washing are usually in the order
of USD $70-$190/m
3
depending on site size and complexity (Racer software,
Remedial action plan 2006). Although extensively used in Europe, full-scale pro-
cesses are less common in the United States. Feasibility tests should be conducted
to determine optimal conditions (chemical type and dosage, contact time, agita-
tion, temperature, and extraction steps to meet regulatory requirements). As spent
washwater can be a mixture of soluble contaminants and fine particles, treatment
is thus required to meet reuse or disposal requirements. Full-scale demonstra-
tions may be required to demonstrate the feasibility of newly developed treat-
ment processes. Presently, wastewater management systems act as a foundation
for modern public health and environment protection. The idea of most suitable
wastewater management systems is to use less energy, allow for elimination, or
beneficial reuse of biosolids, restore natural nutrient cycles, have much smaller
footprints, be more energy-efficient, and design to eliminate exposed wastewater
surfaces, odors, and hazardous by-products (Daigger, 2005). Some of the incen-
tives for the industry to incorporate sustainability into their wastewater solutions
are as follows (Mosley, 2006). In addition to the technical aspects of a wastewater
treatment technology, selection of a particular technology should be based on all
aspects that determine its sustainability such as the human and environmental
activities that surround it.
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