Environmental Engineering Reference
In-Depth Information
sediments and should prevent them from getting resuspended
by storms. The original sediment bed must be able to support
the cap, suitable capping materials (clean sand) must be avail-
able, and suitable water conditions (including depth) must
exist to permit placement of the cap and to avoid compromis-
ing its integrity. Changes in the local substrate, burrowing
benthic animals, or the depth at a site where new sediments
are naturally deposited may subject the cap to erosion. A bar-
rier to the use of capping is the Superfund legislation, which
prefers more permanent controls, and capping is not consid-
ered to be a permanent control.
What is Confined Aquatic Disposal (CAD)?
Confined aquatic disposal (CAD) involves digging a deep pit
in the bottom and placing the contaminated sediments inside
it, then capping it. This technique is applicable to contami-
nated sites in shallow waters where capping is not possible
and is good for the disposal and containment of slightly con-
taminated material from navigation dredging. Although the
methodology has been developed, CAD has not been widely
used. Among its advantages are that it can be performed
with conventional dredging equipment and that the chemi-
cal environment surrounding the cap remains unchanged.
Disadvantages include the possible loss of contaminated sedi-
ments during movement and placement.
What is bioremediation of metals?
Bioremediation is the process of using naturally occurring
microbes to take up, digest, or convert waste material into
harmless substances. Technologies can be generally classi-
fied as in situ or ex situ . In situ bioremediation involves treat-
ing the contaminated material at the site, while ex situ involves
removing the contaminated material and treating it elsewhere.
Bioremediation can occur naturally with the microorganisms
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