Chlorinated hydrocarbons can cause serious environmental and human
health problems as a result of their bioaccumulation, persistence and
toxicity. Improper disposal practices or accidental spills of these
compounds have made them common contaminants of soil and groundwater.
Bioremediation is a promising technology for remediation of sites
contaminated with chlorinated hydrocarbons. However, sites
co-contaminated with heavy metal pollutants can be a problem since
heavy metals can adversely affect potentially important biodegradation
processes of the microorganisms. These effects include extended
acclimation periods, reduced biodegradation rates, and failure of
target compound biodegradation. Remediation of sites co-contaminated
with chlorinated organic compounds and toxic metals is challenging, as
the two components often must be treated differently. Recent approaches
to increasing biodegradation of organic compounds in the presence of
heavy metals include the use of dual bioaugmentation; involving the
utilization of heavy metal-resistant bacteria in conjunction with an
organic-degrading bacterium. The use of zero-valent irons as a novel
reductant, cyclodextrin as a complexing agent, renewable agricultural
biosorbents as adsorbents, biosurfactants that act as chelators of the
co-contaminants and phytoremediation approaches that utilize plants for
the remediation of organic and inorganic compounds have also been
reported. This review provides an overview of the problems associated
with co-contamination of sites with chlorinated organics and heavy
metals, the current strategies being employed to remediate such sites
and the challenges involved
