Scientists develop screening process to remove toxins from tap water

 by Claudia Koerner
 published on Thursday, March 20, 2008

Barb Backes / THE STATE PRESS

WHAT’S IN THE WATER?: ASU assistant professor Rosa Krajmalnik-Brown and graduate research assistant Michal Ziv-El of ASU’s Biodesign Institute use microorganisms to remove a potentially dangerous contaminant from water.

ASU scientists have found a new way to remove a common toxin — proven to be a carcinogen in animal studies — from water.

In their recently published paper in "Environmental Science and Technology," three ASU scientists wrote about how they were able to transform toxic trichloroethane, called TCE, into ethane, a harmless substance.

"We were able to change the TCE completely," said Rosa Krajmalnik-Brown, an assistant professor of civil and environmental engineering.

In addition to being linked to cancer, TCE can cause liver damage when it is in a water supply, according to the U.S. Department of Health and Human Services' Web site. Currently, the Environmental Protection Agency permits only 0.005 milligrams of TCE per liter of water as a safe amount.

Krajmalnik-Brown began working with Director Bruce Rittmann of the Biodesign Institue and another researcher, Jinwook Chung, in 2005. To change the TCE in water samples, the group used the membrane biofilm reactor, a treatment system Rittmann developed several years ago.

In Rittmann's process, microorganisms grow as a biofilm on a membrane that is pumped through with hydrogen, Krajmalnik-Brown said. In a chemical reaction, the microorganisms reduce contaminants, such as TCE, into de-chlorinated structures that aren't harmful to humans.

"One of the good things about this reaction is it encourages growth of those [detoxifying] microorganisms," said Krajmalnik-Brown, who has been working with the microorganisms for the last seven years. "They're capable of growing very well and happy in these biofilms because they're getting what they need."

Because the microorganisms in the biofilm feed on TCE, the treatment process is highly effective. Krajmalnik-Brown said the way microorganisms grow in biofilm is a new area of study.

More basic research is needed to understand how they work because the microorganisms in the biofilm have not been studied before, Krajmalnik-Brown said. However, applications for water-treatment plants may be on the horizon.

"Eventually we can take this to a full-scale," Krajmalnik-Brown said. "That's something we would like to do in the future."

TCE, which used to be a common degreasing agent in cleaning products, has been a problem for the Valley and made headlines earlier this year. In January, a treatment plant that serves Scottsdale and Paradise Valley found the toxin in its water and encouraged residents to drink bottled water instead.

"TCE is one of the most common contaminants in the groundwater in the U.S.," Krajmalnik-Brown said.

Business junior Andrew Bifulco said he is concerned with the quality of water in Arizona.

"I don't drink any of the tap here," the Maine native said. "It's disgusting down here."

But one ASU student and Scottsdale resident said she is more confident about water quality and has never had any problems with tap water.

"I know they do a lot of testing," said Carly Gietler, a microbiology junior. "I just kind of trust that."

Though Gietler said she doesn't worry about contaminated water in her home, she said toxins are a serious matter.

"A lot of cancer and other diseases are caused by environmental factors," Gietler said.

Reach the reporter at: claudia.koerner@asu.edu.