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Taking energy conservation and environmental cleanup to the next level

  • Published
  • By Mark Smith
  • 60th Civil Engineering Squadron
TRAVIS AIR FORCE BASE, Calif. --  Over the last 25 years, the Air Force has devoted a lot of effort and resources to clean up soil and groundwater contamination from past industrial activities. Although the Environmental Protection Agency has overseen and supported this cleanup work and other cleanup projects across the country, it has recently become concerned with the amount of energy consumed and pollution created to carry out cleanup work. 

As a response to this concern, the EPA has developed the concept of sustainable remediation. Sustainable remediation means that one part of the environment is cleaned up without dirtying up another part of the environment. An example is a treatment plant that is powered by an energy source that does not create green house gases. Two key objectives of sustainable remediation are to reduce energy consumption and to minimize or eliminate carbon dioxide emissions to the air. 

Travis Air Force Base has been on the forefront of sustainable remediation when it began in 2005 to install solar-powered pumps to parts of the base where electricity was not readily available. Solar power is plentiful, cheap and generates no greenhouse gases. 

Because of past successes in sustainable remediation and a willingness to try innovative cleanup approaches, the base was recently selected by the Air Force Center for Engineering and the Environment to demonstrate a new sustainable solar-powered cleanup technology called a bioreactor. A bioreactor is pit or trench that is filled with mulch, iron filings or vegetable oil and surrounded by a network of extraction and injection wells. Contaminated water runs though the reactive material and is cleaned by biological and chemical processes. The wells recirculate the water through the reactive material to complete the cleanup process, and solar panels provide the power to run the system. 

"We thought we were doing well when we added batteries to the two solar wells so that groundwater extraction and treatment could run at night, but this new bio-reactor is far superior, especially when you consider the energy savings involved," stated Mr. Lonnie Duke of the Environmental Restoration Program staff. 

The test site for the bioreactor is a battery shop that was a source of solvent contamination in the local groundwater. Most of the contamination has been removed from the soil and groundwater in the source area, but the residual contamination is hard to extract.

"Currently, cleanup in the source area takes a lot of vapor extraction as well as water extraction and treatment," said Mr. Duke, "and it takes electricity to run the pumps and treatment plants. In many ways, groundwater cleanup is like squeezing soap out of a sponge; after a while, you are putting in the same effort but getting out less and less contamination."

The use of a bio-reactor to speed up the cleanup of the solvent source area also makes sense from an energy conservation perspective, since it eliminates the need to use the base power grid to run the pumps and treatment plants. Instead, two solar photo-voltaic panels, about the same size as full sheet of plywood, will power an electric submersible groundwater pump installed in the source area.

"Picture a large coffee percolator that pumps water through the mulch, much like a coffee maker does," said Mr. Duke. "Instead of making coffee, the groundwater becomes enriched with nutrients that stimulate bacteria growth. This kind of bacteria also consumes the contaminants."

In early 2008, the AFCEE Technology Division published an offer to Air Force bases to fund the testing of innovative cleanup strategies under real world conditions. Glenn Anderson of the ERP staff submitted a very detailed description of the cleanup challenges and environmental conditions at the former battery shop, and as a result, Travis was one of a few installations to be selected. "We were ecstatic," said Mr. Anderson. "Basically this is free money to promote our cleanup efforts in a truly environmentally-friendly way."

The bio-reactor is expected to be fully operational by the end of 2008.

"We believe that the bioreactor offers the best opportunity to clean up the source area and facilitate the remediation of the remaining dissolved portion of the solvent plume at this site," said Mr. Anderson.

Initial energy savings will be small and consist of the reduction of electricity consumption from the two extraction wells currently in operation. However, this does take Travis one step closer to shutting down its four groundwater treatment plants that currently cost about $7,000 a month in utilities to operate.