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September 20, 2004

Prof tackles toxins in Delta drinking water

Talk about efficient. At the same time Sacramento State chemistry professor Susan Crawford is tracking the cause of a toxin lurking in drinking water from the Sacramento Delta, a second experiment she’s conducting with absorbent materials called zeolites may turn out to be a possible solution.

More than 22 million people depend on Delta water, but before it can be used it goes through the chlorination process. Unfortunately, Crawford says, the good work of chlorination sometimes results in another problem: “When you chlorinate Delta water, dissolved organic or DOC – carbons associated with peat and other remnants of the land around the Delta – form trihaolmethanes or THMs, such as chloroform, which is considered a carcinogen.”

Working with the U.S. Geological Survey, Crawford uses a variety of sophisticated equipment including nuclear magnetic resonance and infrared spectroscopy to test water samples. She looks at the samples before and after chlorination to see what happens when the THMs form, looking for a link. “We’re trying to determine if there’s something similar between the DOC and the amount of THMs formed,” she says. “Can it be traced to a site, such as near a peat island? Does it happen at a certain time of year, such as during tilling, during flooding or when irrigation takes place?

“There’s a tendency to blame agriculture. But it may be something that occurs in the Delta naturally such as plant decomposition,” Crawford says, noting that before taking a radical, disruptive step such as modifying farming practices in the region, scientists need to be pretty sure of the culprit.

If the source turns out to be a naturally occurring process, Crawford thinks she has a possible solution. Zeolites.

Crawford has been studying the filtering qualities of zeolites for years, including the ability of some zeolites to transform harmful materials into less dangerous ones. The porous rock materials are extremely absorbent, grabbing and holding waste products sort of like a molecular sponge.

If it turns out that the carbon in the Delta can’t be controlled at the source, Crawford thinks zeolites might be an effective way to absorb the chloroform from the water.

In yet another project with Sacramento State’s Office of Water Programs, Crawford is also looking at whether zeolites might be able to play a role in removing metals from storm water that runs off area roads.

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