Remediation and Management of Contaminated Soil - Sustainable Practices in Geoenvironmental Engineering - page 403

11
Remediati on and Management of Contaminated Soil
11.1 Introduction
The dumping of materials, bankrupt and abandoned manufacturing plants, insuficient
methods for waste storage, treatment, and disposal facilities have contributed to the con-
tamination of many sites as indicated in previous chapters. Chemical waste categories
include organic liquids such as solvents from dry cleaning, oils including lubricating oils,
automotive oils, hydraulic oils, fuel oils, and organic sludges/solids and organic aque-
ous wastes and wastewaters. Most soil contamination is the result of accidental spills and
leaks, generation of chemical waste leachates and sludges from cleaning of equipment, res-
idues left in used containers and outdated materials and indiscriminant dumping. Smaller
generators of chemical contaminants include improperly managed landills, automobile
service establishments, maintenance shops, and photographic ilm processors. Household
wastes including pesticides, paints, cleaning, and automotive products may also contrib-
ute signiicantly as sources of organic chemicals (LaGrega et al., 2010). The more common
heavy metals include lead (Pb), cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni),
iron (Fe), mercury (Hg), and zinc (Zn).
A variety of in situ and ex situ remediation techniques exists to manage the contami-
nated sites. For evaluation of the most appropriate technique, the procedure in Figure 11.1
should be followed. Ex situ techniques include excavation, contaminant ixation or isola-
tion, incineration or vitriication, washing, and biological treatment processes. In situ pro-
cesses include (a) bioremediation, air or steam stripping, or thermal treatment for volatile
compounds, (b) extraction methods for soluble components, (c) chemical treatments for
oxidation or detoxiication, and (d) stabilization/solidiication with cements, limes, and
resins for heavy metal contaminants. Phytoremediation, although less developed, has also
been used. The most suitable types of plants must be selected based on pollutant type and
recovery techniques for disposal of the contaminated plants. Other technologies related to
nanotechnologies are also being developed.
Most in situ remediation techniques are potentially less expensive and disruptive than
ex situ ones, particularly for large contaminated areas. Natural or synthetic additives can
be utilized to enhance precipitation, ion exchange, sorption, and redox reactions (Mench
et al., 2000). The sustainability of reducing and maintaining reduced solubility conditions
is key to the long-term success of the treatment. Ex situ techniques are expensive and can
disrupt the ecosystem and the landscape. For shallow-ground contamination, remedia-
tion costs, worker exposure, and environmental disruption can be reduced using in situ
remediation techniques.
In this chapter, various soil remediation technologies will be described. Groundwater
remediation techniques and monitored natural attenuation techniques have been described
403