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Insight

Combining Remedies for Complex Superfund Sites

by Tamzen Macbeth, Ph.D. Vice President, environmental engineer
To achieve the remedial goals at complex Superfund sites, a multi-component treatment strategy that includes a combination of tech­nolo­gies may be required.

Remediation approaches at Superfund sites come in many configurations, each designed to meet site-specific cleanup complexities and goals. Now that many of the smaller and simpler hazardous waste Superfund cleanups have achieved their objectives, what remain are often very large or complex cleanups, where a single remedial technology alone cannot achieve restoration. 

The traditional path of applying different tech­nolo­gies until one works is actually inefficient and expensive; it's more cost-effective to research and implement the right combination of tech­nolo­gies.
Tamzen MacBeth, PhD, vice president, envi­ron­men­tal engineer
Combined remedies leverage multiple technologies to achieve a common remedial goal, and innovations in combined remedies are currently being used to optimize existing remedies and develop successful clean up strategies. Combinations can take three forms:

 

  1. Spatial: Multiple technologies are “mapped” to different areas within a contaminated site, based on site characteristics or contamination nature and extent. For instance, a site’s remedial footprint might include in situ thermal remediation (ISTR) to address concentrated sources, but the volume treated with this energy-intensive and expensive technology could be reduced by using in situ bioremediation (ISB) in parallel to treat lower concentration fringe areas.

  2. Temporal: Multiple technologies are applied in a sequence, often referred to as a treatment train approach. Remediation usually begins with an aggressive technology and then transitions to more passive, cost-effective technology. This stepwise approach allows the aggressive and expensive technology to be applied until it reaches a “point of diminishing return” in contaminant removal rates, which is often still above remedial goals. Subsequently, the polishing technology(ies) is used to reduce contaminants further until remedial goals are achieved.

  3. Integrated: Different technological approaches are integrated to take advantage of synergy and make the overall treatment more effective. For example, integrating ISTR with in situ chemical oxidation (ISCO) or ISB can reduce the above ground infrastructure required to extract and treat contaminants during ISTR, and increased temperatures can improve contaminant mass treatment rates by accelerating chemical or biological reactions in situ. These synergies can be used to develop an integrated strategy that is often more efficient than implementing either technology alone
A combined remedy should be considered as part of any remedial strategy for today’s complex cont­a­m­i­nated sites.
Tamzen MacBeth, PhD, vice president, environmental engineer

Dismissing Miscon­cep­tions

With the growing number of successful combined remedy imple­men­ta­tions, many miscon­cep­tions are being dismissed. One belief was that by combining tech­nolo­gies you increase treatment costs. From a life-cycle perspective, the traditional path of applying different tech­nolo­gies until one works is actually inefficient and expensive; it's more cost-effective to research and implement the right combination of tech­nolo­gies. Another is that certain tech­nolo­gies cannot be combined. For example, it was believed that more aggressive tech­nolo­gies, such as ISTR or ISCO, would have a negative effect on more passive tech­nolo­gies, like ISB. However, research has proven these synergistic tech­nolo­gies can effectively be integrated with careful design consid­er­a­tions.
 
How tech­nolo­gies are deployed is as important as which tools are used, and a combined remedy should be considered as part of any remedial strategy for today’s complex cont­a­m­i­nated sites. Combined remedies should be applied in a flexible, adaptive and attentive manner. Incor­po­rat­ing multiple tech­nolo­gies and strategies can maximise the net envi­ron­men­tal benefits of cleanup actions.
How technologies are deployed is as important as which tools are used for today's more and more complex remediation projects.

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