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Remediating Manufactured Gas Plant Sites: Emerging Remediation Technologies
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Quick Look |
| Although MGPs have closed
and most have been demolished, such facilities have left a legacy
of environmental contamination. |
| Releases of coal tars, oils,
and condensates produced in MGP plants contributed to a wide range
of contamination with PAHs, phenols, benzene, and cyanide. |
| As utilities discover more
MGP sites, they are faced with the need to identify cost-effective,
environmentally safe, and innovative approaches for the characterization
and remediation of those sites. |
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From the early 1800s through the mid-1900s, manufactured gas plant (MGP)
sites were operated nationwide to produce gas from coal or oil for lighting,
heating, and cooking. The gas manufacturing and purification processes
conducted at the plants yielded gas plant residues that included tars,
sludges, lampblack, light oils, spent oxide wastes, and other hydrocarbon
products. Although many of the by-products were recycled, excess residues
remained at MGP sites. The residues contain polycyclic aromatic hydrocarbons
(PAH), petroleum hydrocarbons, benzene, cyanide, metals, and phenols.
The base contaminant, coal tar, is composed of a complex mixture of PAHs
that generally exhibit low volatility, low solubility, and low biodegradability.
Consequently, those components are difficult to treat.
There are an estimated 3,000 to 5,000 former MGP sites across the country;
some of those sites still are owned by the successors to the utilities
that founded them. MGPs typically were built on the outskirts of cities
that since have grown. Today, therefore, the under-used sites often are
located in inner city areas, many of which are being considered for redevelopment
under the Brownfields Program. The redevelopment of MGP sites for reuse
can help the utility industry turn potential liabilities into assets.
For example, in the city of Fort Myers, Florida, a former MGP site was
redeveloped into a private, nonprofit museum and aquarium called the Imaginarium.
As the business environment has spurred companies to reassess land holdings
and better manage environmental concerns, the MGP sites have become a
central focus. Many companies are investigating and remediating such sites.
The similarities in the configuration of the sites and in the contaminants
found at them provide opportunities to apply innovative approaches that
benefit from economies of scale. Former MGP sites offer an ideal opportunity
to apply tools and technologies that expedite site characterization and
source remediation.
Thermal desorption has been used successfully to remediate soils that
contain MGP wastes (for example, lampblack and coal tar), achieving reductions
of more than 98 percent in concentrations of PAHs; total petroleum hydrocarbons
(TPH); benzene, toluene, ethylbenzene, and xylene (BTEX) compounds; and
cyanide. Performance data have demonstrated that less than 10 parts per
billion (ppb) of residual PAHs and cyanides can be achieved through the
application of thermal desorption. Other technologies that have proven
successful in remediating MGP wastes include co-burning in utility boilers,
recycling in road beds, in situ bioremediation, landfarming, and soil
washing.
Because former MGP sites are prevalent and represent a large area of
unused land with complex remedy needs, new technologies are being encouraged
and field-tested to demonstrate their technical feasibility. Opportunities
exist to demonstrate and refine new assessment and remediation technologies
that can assist in expediting cleanup processes that can place these contaminated
sites back into productive use.
For more information see the following resources:
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