Environmental Engineering Reference
In-Depth Information
3.4 Alternative physical and chemical technologies
Several alternative remediation technologies, excluding biological processes,
are described below. This section will give background on technologies that
are currently available for site remediation. The advantages and disadvan-
tages of these technologies can be compared with bioremediation to show
that in many cases bioremediation will be the treatment technology of choice.
However, each site has unique characteristics that may favor one treatment
technology over another. The appropriateness of each technology must be
evaluated prior to choosing one and implementing a remediation strategy.
3.4.1 Incineration
Incineration is a technology that results in the complete destruction of
organic compounds using high temperatures. Typical operating tempera-
tures are in excess of 1500˚F. For most site remediation applications, incin-
erators are used for the treatment of contaminated soils and free products.
Although the incineration of liquid is possible, it is typically not used to
remediate groundwater and surface water from contaminated sites. The fact
that incineration is a destructive technology that results in the complete
destruction of organic contaminants is a major advantage. Disadvantages of
this technology involve the high cost of operation, poor public acceptance,
and regulatory constraints.
3.4.2 Air stripping
Air stripping is a physical treatment process that relies on contaminant phase
change. This process removes contaminants through volatilization from the
aqueous phase into the gas phase; consequently, it is not a destructive tech-
nology. The higher the contaminant's Henry's law constant, the easier it is
to desorb or “strip” the compound from the aqueous phase to the air phase.
For air stripping to be cost effective, the contaminant must be significantly
more volatile than water. Air stripping is commonly used to remove volatile
organic compounds from contaminated groundwater. Dissolved cations
such as iron can present problems with stripper operation by oxidizing and
precipitating out in the column, thereby clogging the column. Many states
are now requiring treatment of off-gases from air stripping units, which can
significantly increase the cost of treatment because of disposal problems
associated with spent activated carbon. Also, recent emphasis on destructive
technologies is limiting the acceptance and use of this technology by the
regulatory community (Zappi et al., 1993).
3.4.3 Activated carbon adsorption
Activated carbon adsorption is a treatment process generally used for
the removal of dissolved organics, color, and taste- and odor-causing
