Green on Green
With green technologies seemingly sprouting up everywhere, it is perhaps logical to see them increasing in the field of environmental cleanup. “When your goal is to clean up damage previously done to the environment, it just makes sense to do it in a way that is kindest to the earth,” says Brian Riha of the Savannah River National Laboratory. Riha is the co-inventor of SRNL’s MicroBlower™, which—like many of the lab’s environmental cleanup technologies—makes use of natural phenomena. The result is a technology that requires less power than traditional remediation approaches, and causes minimum disruption in the surrounding environment. “Taking advantage of the tools that nature provides can reduce the costs of environmental cleanup and intrude less on the environment,” he says.
The MicroBlower, a sustainable soil vapor extraction system, removes volatile contaminants from the unsaturated subsurface, targeting an area that traditionally has been considered costly to treat. The system combines the natural cycles of pressure difference between above-ground and the subsurface with a small, low power vacuum blower to extract or inject gases into the subsurface for remediation. While similar in design to an active soil vapor extraction (ASVE) blower, the MicroBlower is a low-cost alternative designed to run on renewable sources of energy such as solar and wind energy.
MicroBlowers offer the advantages of a reduced carbon footprint and very low operating and maintenance expenses.
Like many of the lab’s technologies, the MicroBlower was developed as part of the lab’s support of cleanup initiatives at the Savannah River Site (with more than 50 MicroBlower units currently in operation at 7 locations around the 310-square-mile site), but also showed clear commercial potential, because the issues it addresses are so wide-spread. The technology targets volatile compounds in the “vadose zone,” the area of unsaturated soils between the surface and the groundwater, addressing a contamination issue that affects sites ranging from large industrial facilities to the corner dry cleaner and gas station. Current environmental cleanup regulations are primarily concerned with groundwater contamination, rather than the vadose zone. However, if the vadose zone is not remediated, contamination will migrate downward and contaminate the groundwater, requiring additional cleanup. By installing the MicroBlower, the risk of the groundwater being contaminated from the vadose zone would be alleviated.
The system was conceived, designed, implemented and tested at the Savannah River Site, providing in-field results of the viability of the technology and its potential applications for innovative approaches to soil and groundwater activities. During a 10-month period, a MicroBlower removed 234 pounds of volatile organic compounds from the subsurface at SRS.
Recognizing the usefulness of a low-cost, environmentally friendly approach to treating the vadose zone, Tersus Environmental, LLC, Wake Forest, N. C., obtained an exclusive worldwide license to manufacture, use and sell the technology, in partnership with inVentures Technologies, Inc., New Brunswick, Canada.
“This license agreement enables us to expand our strong foundation of intellectual property,” said Gary Birk, managing partner of Tersus Environmental. “A growing trend in environmental remediation is the use of natural processes. The MicroBlower is an example of such an approach. The license agreement provides our customers access to the latest sustainable technology to manage complex, challenging environmental liabilities and reduce costs for site closure.”
The MicroBlower and embodying parts will be substantially manufactured in North Carolina and Tersus has secured a commitment from an Ohio-based company with extensive experience in designing and building soil and groundwater remediation systems, including systems with solar power, to handle overflow capacity if needed.
The system uses a small, low-power vacuum blower to extract or inject gases into the subsurface for characterization or remediation. The system requires only between 20 and 40 watts of power, which can be easily produced by a small photovoltaic panel, small batteries, or wind generators. Because the components of the system have a long operating life, the system is useful for long-term cleanup operations, particularly where mass transfer limits the rate of remediation. The mean time between failures for the pumps is on the order of 15,000 to 20,000 hours.
Perhaps the greatest potential for the MicroBlower is in treatment polishing of an area treated by an expensive, large blower system that still has residual contamination. Installation of an economical system to finish the cleanup at greatly reduced costs allows the larger systems to be used where they can produce greater returns. The MicroBlower also can remediate sites that are smaller than the capacity of typical, large blower systems.
MicroBlowers are ideal for remote locations with limited or no ancillary infrastructure. By using renewable sources of energy, the MicroBlower eliminates the need for generators and fuel storage at remote locations. The design also eliminates ancillary infrastructure that are generally required to run conventional ASVE systems in remote areas. Other SRNL technologies that make use of natural phenomena in environmentally -friendly, sustainable remediation tools include unique combinations of naturally occurring bacteria for the treatment of contaminants, a product that uses biodegradable oils to sequester contaminants and stimulate microorganisms to degrade contaminants in -situ, and a siphon that accelerates the flow of contaminated groundwater through a treatment cell for in -situ remediation.
Angeline French is a writer at the Savannah River National Laboratory