In the consumer marketplace, the hyper-speed pace of technology sets the trends, and the newest, latest version of everything rules.

In the world of brownfield remediation, however, technological change is an evolutionary process measured in years and decades rather than microseconds. Even though technologies that can enhance “green” remediation are top of mind for many projects, the widespread use of such tools is still a work in progress, say industry observers.

“There’s a continuing trend toward less energy consumption in remediation, and a move to using natural systems to help remediate things, that has emerged over the last eight or 10 years,” says Mike McLaughlin, senior vice president, environmental services for SCS Engineers in Reston, Va. “Twenty years ago, if you were faced with a groundwater contamination problem, you typically would install some kind of collection system to suck water out of the ground and then do something with it before putting it back in the ground or discharging it. [Now] there’s a lot more science applied to figuring out ways to inject substrates, or even to create permeable barriers that let [just] the water through.”

“There’s been a definite trend toward more in situ [on-site] treatment in sediment remediation, away from just dredging it and disposing of it,” explains Chuck Hornaday, group manager, lining and remediation technologies at CETCO in Hoffman Estates, Ill., which specializes in environmental and construction technologies. “That’s truckloads and truckloads you’re hauling away to a landfill, versus treating it in place.”

On the regulatory side, both federal and regional government entities are encouraging more on-site treatment of contaminated materials, which can help cut down on greenhouse gases produced by transporting brownfield waste.

“EPA and the states all seem to be moving toward less energy-intensive, shorter-term treatments,” says Evans Paull, a senior policy analyst with the Northeast Midwest Institute in Washington, D.C., which promotes environmental quality for 18 Northeastern and Midwestern states. “And there’s more remediation in place, whether that be by injection or bioremediation or other ways to neutralize the contaminants, sometimes even leaving them in place if that’s a reasonable thing to do given the levels of risk.”

Sometimes, updating technology to be more environmentally friendly means looking at conventional technology with a fresh eye, perhaps to modify it or make more innovative use of it. “Green remediation is certainly the buzz,” says Keith Henn, Remediation & Carbon Management Services manager at Tetra Tech Inc., Pittsburgh. “But it’s important to clarify that creating a sustainable approach may not require you to significantly change the technology selected. You might just be looking at it from a new perspective, or designing with additional criteria in mind. With many in situ technologies such as bioremediation and natural attenuation, for example, you’re working with Mother Nature to solve some of these challenging problems.”

Vapor Intrusion
Vapor intrusion, or the vapor phase migration of volatile organic and/or inorganic compounds into a building from underlying contaminated groundwater and/or soil, is a relatively recent brownfields concern and one where older technology is generating new interest.

“Years ago, exposure to drinking water was the driver of a lot of groundwater cleanup,” says hydrogeologist Jim Mercer, executive vice president of GeoTrans Inc., a wholly owned subsidiary of Tetra Tech Co. in Sterling, Va. “Now in a lot of [brownfield] sites, vapors are more of a driver than groundwater concentrations [of contaminants].”

“Vapor intrusion into buildings is a big challenge for brownfield development,” agrees McLaughlin. “In the last five or six years it has really emerged on the scene.”

And with that emergence has come a new push for spray-applied membranes above a vent system, such as CETCO’s more than 25-year-old LIQUID BOOT Membrane, according to Hornaday. The cold, water-based, spray-applied membrane provides an impermeable barrier against vapor intrusion into structures and is sprayed directly to penetrations, footings, grade beams and pile caps.

Since most spray-applied membranes don’t contain VOCs (volatile organic compounds), they could be considered green products, says Nathan Shamosh, a vapor intrusion specialist and vice president of business development for Advanced Construction Technologies, Irvine, Calif.

“In the last few years, there have been further advancements in enhancing the spray-applied membrane technology,” says Shamosh. “Many times we will put in a spray-applied membrane and an additional layer of sheet membrane. You’re going to spend a little more money, putting in basically an extra layer of membrane, but it’s a good system as long as you use the right materials.”

In general, “the technology for eliminating the [vapor intrusion] pathway into indoor air is not all that new—it’s not new science,” says Jim Ash, vice president of GEI Consultants, Woburn, Mass. “The process of evaluating and installing these [vapor mitigation] systems at the appropriate time in the process is the place where we’re starting to learn more... In a new development, like a brownfield, it’s getting more common to include vapor mitigation controls even if it’s not necessarily a confirmed pathway, just a possibility, because it’s pretty easy to do when you’re constructing from scratch. The costly part is when there has to be a retrofit for a vapor intrusion problem.”

One relatively new product that has made a big splash is the low-profile venting system, according to Shamosh. The first was CETCO’s LIQUID BOOT GeoVent, a low-profile pressure relief, trenchless collection and venting system that can be used as an active or passive venting system. “Instead of using gravel continuously under a foundation and instead of pipe, you would use this. It has cut down costs on the vent system tremendously over the traditional pipe and gravel system,” says Shamosh.

No matter what products are used to mitigate vapor, it’s more important than ever to understand the technology behind them and their effectiveness, he adds, because “more parties are getting involved in the process of choosing the systems. A lot of the lenders, banks and insurance companies are wanting to know a lot more about what these engineered vapor barriers are. They will want to know that the material is sufficient and [that it] will have a warranty.”

In the future, expect “better technology to allow you to measure and identify where vapor is coming from,” says Jeffrey Marqusee, executive director of the Dept. of Defense’s SERDP (Strategic Environmental Research and Development Program) and ESTCP (Environmental Security Technology Certification Program). “There are a lot of advances in...understanding the physics and chemistry [of vapor intrusion].”

Bioremediation Basics
Bioremediation, which uses microorganisms to degrade organic contaminants in soil, sludge, solids and groundwater, lends itself well to “green” remediation and the growing emphasis on in situ treatments. The technology can be used on or off site, but bioremediation is one of the more frequently used in situ techniques.

“Overall people are avoiding physical removal systems,” says Bill Newman, president of Remediation and Natural Attenuation Services Inc. in Brooklyn Center, Minn. “They want to be able to just inject something in the ground and walk away without operating and maintenance costs. That’s been a major trend in the last few years.”

The bioremediation process usually involves stimulating and creating a favorable environment in which microorganisms can grow and use contaminants as a food and energy source and reduce them into harmless compounds. Oxygen, nutrients and moisture, along with temperature and pH control, are generally required.

“These technologies have to be very specific to a site,” says Jarda Solc, senior research manager for the Energy & Environmental Research Center at the University of North Dakota. “The concentrations of the primary contaminants cannot be extremely high because then it would be poisonous for the [microorganisms] too.”

Tetra Tech’s Henn says bioremediation technology is still progressing, but perhaps at a slower pace than it did in the early 2000s. Such substances as emulsified food-grade vegetable oil, molasses and cheese whey are being successfully used to stimulate the reduction of chlorinated solvents to innocuous compounds, he says, and researchers continue to expand their understanding of the microbes needed for effective biodegradation of recalcitrant contaminants as perchlorate.

“We do a lot of work on perchlorate, and bioremediation is a pretty significant part of it,” says Andrea Leeson, program manager for the Department of Defense’s SERDP Environmental Restoration, which runs demonstrations of environmental technology. “We’re also doing quite a bit of work on solvents—enhanced technology to speed up microbial processes, as well as understanding the natural processes that might be involved for natural attenuation.”

The use of slow-release electron donors such as emulsified oil has become a big part of the bioremediation industry in the past five years, says Newman. “We’re seeing bioaugmentation cultures [pre-grown microbial cultures designed to promote contaminant degradation] being used more and more. Five years ago an emulsified culture was looked at as something innovative you might pilot test. Now, it’s become routine.”

In the next 10 years, look for a clear emergence of molecular biological tools, predicts SERDP’s Marqusee. “Molecular biological tools allow you to directly measure: Are the organisms present that you think are, to do the bioremediation? Is their activity sufficient? Our hope is that through a few simple samplings, you could directly address bioremediation, or in an ongoing project you could monitor its effectiveness almost in real time. Those types of technologies are certainly on the horizon.”

Nanotechnology
Although using nanotechnology for remediation—applying reactive nanomaterials to transform and detoxify contaminants--offers the potential for cutting cleanup costs, saving time, eliminating the need for treating and disposing of contaminated soil, and reducing some contaminant concentrations to nearly zero, it is still at the pre-commercial stage, says Marqusee. “We are putting some resources [into nanotechnology], but it is not as mature as the biological approach,” he says.

Tetra Tech’s Henn agrees: “We’ve done several projects involving nanotechnology, and we believe this is still an emerging market,” he says. “Further research and development are required to make this a technology that would be selected as commonly as bioremediation. But it has great potential, and interested parties and regulators such as the EPA are very interested in seeing this technology develop as another tool in our toolbox.”

Nanomaterials used for groundwater contamination, for example, offer a specific advantage for in situ applications: “Because of their minute size and innovative surface coatings, nanoparticles may be able to pervade very small spaces in the subsurface and remain suspended in groundwater, allowing the particles to travel farther than larger, macro-sized particles and achieve wider distribution,” according to “Nanotechnology and In situ Remediation” by Barbara Karn, Todd Kuiken, and Martha Otto, a June 2009 EHP-in-Press report posted online by the National Institute of Environmental Health Sciences.

Zero valent iron is the most widely used nanomaterial for remediation, according to the report. It is being employed on at least 45 sites in seven countries, including 12 U.S. states, all with some form of chlorinated compounds like PCE, TCE and PCB. For now, the cost and performance data are limited, but a case study cost comparison was performed for a manufacturing site in New Jersey by PARS Environmental Inc., based in Robbinsville, N.J. PARS estimated that remediating the site, which contained TCE and PCE, would cost approximately $4.16 million using pump and treat technology, $2.2 million using a reactive barrier—and $450,000 using nanoscale zero valent iron.

In addition to the potential cost savings of nanoremediation, the technology could also mean huge time savings: “One study using [nanoscale zero valent iron] observed a 99 percent reduction in TCE levels within days of injection,” according to the EHP report.

But the potential risks to the environment and to human health are still not fully understood, and researchers have suggested further study is needed about what kinds of problems might be caused by the release of nanoparticles into ecosystems during remediation.