LIVING FILTERS

LIVING FILTERS
By Cindy Kerschner
The Times News, © 2003

June 21, 2003

“As the poet said, ‘Only God can make a tree,’ probably because it’s so hard to get the bark on.” Woody Allen.

It is true that we can’t make trees, or plants for that matter. But we can make the environment they live in cleaner and safer.

And the plants are willing to help.

Phytoremediation is the term used to describe clean up of contaminated areas with assistance from plants. Soil, air and water can benefit from this technology, but for our purposes we are going to focus on groundwater.

Imagine all the possible ways groundwater pollution can occur in our area such as leaky underground storage tanks, mine run-off, industrial by-products, landfills, or spills. Each incident can release a different contaminant.

It’s an alphabetical smorgasbord: TCE, MTBE, PAH,and TNT to name a few.

Phytoremediation can treat these chemicals and more. Dr. Lawrence C. Davis of Kansas State University, found that some plants could absorb chemicals with little ill effects. “Plants will grow with 3 percent weathered crude oil, 100 parts per million of MTBE (methyl tert-butyl ether, a gas additive) or TCE (trichloroethylene, a degreaser) in their water.”

There are three possible scenarios for using plants to remediate contaminated groundwater. We can contain it, make it less harmful or remove it.

Treating groundwater in place or “in-situ” through phytoremediation can cost up to 50 percent less than pumping out the water and transporting it to a facility for treatment. This process is also less devastating to the environment.

According to Dr. Paul Schwab, Professor of Agronomy at Purdue University, some species of trees are excellent for phytoremediation.

“Planting trees directly in the groundwater can be quite effective at stopping or even reversing the flow of groundwater offsite,” Dr. Schwab continued, “Phytoremedia-tion of contaminated groundwater is possible if the roots of the plants can extend into the water. Trees with high water demand (poplar, willow) have found great potential in this application.”

One example of using trees was conducted by the United States Air Force.

Cottonwood trees were used to remove TCE from contaminated groundwater at a rate of up to 200 gallons of water per day. Trees and soil microbes broke down the TCE into less harmful elements of carbon dioxide, water and chlorine.

The trees also lowered the groundwater level and increased the distance between the contaminated soil and the aquifer. This stopped further pollution from entering the water supply.

Dr. Davis summed it up best, “When I was asked to help find plants that might speed up cleaning up some gasoline spills and such, I was willing to give it a try. I knew that plants have a lot of unusual abilities and are part of stable long-term ecosystems where they have experienced many strange chemicals already. So I expected that they could deal with the kinds of things that we are likely to make and spill.”

So hug a tree today. It may have saved your groundwater.

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