Green Remediation Technology on the Rise

There is a new awareness in the selection of remediation technologies at brownfield sites which considers the impact of remediation on the environment. This approach, which considers sustainability issues, has been dubbed "green remediation" and seems to be growing throughout the brownfield industry.

Green remediation considers whether the process of getting to the end point overshadows the end result and takes a more holistic assessment of the way in which the process will be achieved. For example, a site in Kentucky has an obvious dig-and-haul remedial solution, but the soil needs to be transported to a hazardous waste landfill in Canada. The resulting carbon footprint for transportation, the potential for roadway accidents and the resulting concentration of waste in one location suggest that a local solution might be more environmentally acceptable and sustainable. An in-situ destruction process would limit the carbon footprint, eliminate the potential for roadway accidents and totally alter the hazardous nature of the soil, even though it might entail a higher initial capital cost.

In the article "Integrating Sustainability into Remediation of Brownfield Sites," (Brownfield News, December 2007) author Dave Ellis, Ph.D., provided a good introduction to the DuPont approach to thinking on a holistic and sustainable basis. The focus of the approach, wrote Ellis, is to "lead to innovative brownfield cleanups, a smaller environmental footprint and better protection of human health and the environment."

Similarly, the California Department of Toxic Substances Control (DTSC) has the Green Remediation Initiative. Started in February 2007, it is in the process of defining green remediation, developing an evaluation tool, developing training for staff, and publicizing the initiative. The evaluation tool is focused on development of a rating matrix for selection of remediation technology and considers a wide variety of factors, including energy consumption, liquid and waste production, air quality, product recycling, community benefits, duration, treatment effectiveness, life-cycle cost and worker safety.

In-situ technology selection is prominent in a green remediation approach. Using natural allies and resources to conduct remediation makes sustainable sense and there have been a number of exciting advancements in the field. Naturally occurring bacteria have been used for years to break down hydrocarbons; now the science is well developed and focuses on differences between bio-stimulation and bio-augmentation of the bacteria to do the work.  

Micro- and nanotechnology are entering the remediation field. Nano-scale zero-valent iron has been an effective in-situ tool in reactive barrier walls for treatment of solvent-containing groundwater. New advances include the use of a slow release micro-scale zero-valent iron for treatment. Tools for investigating sites, like membrane interface probes (MIPs), are allowing technology specialists to more effectively home-in on viable solutions.

Designed wetlands for surface water and sewage treatment, and the use of carefully selected plants (i.e., phytotechnology) for groundwater remediation are excellent uses of natural resources to achieve in-situ remediation goals.

The underlying ideas of green remediation are not new, but are being packaged in a new way. Civil engineers have for some years been considering "context sensitive design" as a means to more holistically look at the way site improvements impact each other. Green remediation is an evolution of common sense efficiency. All in all, the emerging focus of green in remediation technology is a real boost to sustainable end points on brownfield sites.

Ken Kastman, P.E., is a vice president and senior principal engineer with URS Corp. in Chicago.

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