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Studies tap into drinking water quality

CHICAGO -- Two studies under way at Purdue University are tapping into new information on potentially hazardous byproducts that can form in water during the treatment process.

In one study, researchers from Purdue's School of Civil Engineering and Department of Chemistry have determined a chemical pathway by which cyanogen chloride, a toxic disinfection byproduct, can be formed.

In the other study, researchers are looking at the role copper plays in forming dangerous byproducts known as trihalomethanes, or THMs. The studies were presented Thursday (8/24) in Chicago at the annual meeting of the American Chemical Society.

Public water systems use disinfection processes to kill bacteria, viruses and other microorganisms that can cause illness or disease. However, the chemicals and substances used for disinfection also can react with other agents typically present in raw waters to form byproducts, some of which, at relatively high levels, pose health risks of their own.

Chlorine, for example, has been found to react with natural organic matter to produce THMs, some of which are thought to be carcinogenic. Though the Environmental Protection Agency currently regulates chlorine water treatment processes to keep THMs within certain limits, some water treatment facilities have begun using agents other than chlorine to disinfect water.

One of the most popular alternative methods uses ozone as a primary or initial disinfecting agent. This method has been used by water treatment facilities in California and a few other states.

"One problem with this method is that ozone doesn't stay in the water very long, so there's no residual ozone left to act as a disinfectant until the water gets to your tap," says Erik J. Pedersen, a doctoral student in environmental engineering and author of the first study. "For this reason, chloramines, chlorine substitutes that do not produce THMs, are added in the final stage of ozone treatment."

Though this water treatment process eliminates the production of THMs, routine quality control tests done for the utilities using the system have detected the presence of another hazardous byproduct, called cyanogen chloride. In its gaseous form, cyanogen chloride is highly toxic. Though the toxicity of dissolved cyanogen chloride at levels present in drinking water is not known, it is thought by scientists to be potentially harmful.

"Though cyanogen chloride is currently not regulated by the EPA, it is listed on the agency's priority list and is being looked at very closely to determine what levels, if any, are safe for consumption," Pedersen says.

Up to this point, scientists didn't know how the agent formed. Working under the direction of Purdue Professors Benito Mariñas and Dale Margerum, Pedersen found that cyanogen chloride forms through the interaction of monochloramine, the form of chloramine most frequently used in such treatments, and formaldehyde.

"Though low levels of formaldehyde are sometimes present in water, the process of treating water with ozone appears to enhance this interaction, or perhaps increase the amount of formaldehyde present," Pedersen says.

Using a stopped-flow spectrophotometer, an instrument designed to measure very rapid reactions, he monitored the reaction between monochloramine and formaldehyde over a wide range of concentrations and time intervals.

"The results show that the combination of formaldehyde with monochloramine result in a rapidly forming intermediate, which slowly decomposes over a period of hours to form cyanogen chloride," Pedersen says. "The initial reaction is very fast -- on the order of seconds."

He notes that the cyanogen chloride probably forms in drinking water through other pathways as well. "It's highly probable that the chloramines used in treatment will react with other organic molecules to produce cyanogen chloride," he says.

In an unrelated study, civil engineering Professor Ernest Blatchley and doctoral student Ravi Duggirala designed experiments to see how copper contributes to the formation of THMs -- especially chloroform -- during water treatment processes using chlorine. Chloroform causes cancer in animals.

Copper, which occurs naturally in water, also is used sometimes in water treatment in the form of copper sulfate to control algae. In addition, drinking water may interact with copper as the water travels through copper pipes or fixtures.

The results of the study show that the presence of copper increases the formation of chloroform in water when chlorine is present, says Duggirala.

"This suggests that copper may play a role in the formation of some THMs," Duggirala says. "It also might imply that, by minimizing water's exposure to copper, we could reduce the production of disinfection byproducts in water."

Both studies were funded by Purdue University.

Sources: Erik J. Pedersen, (765) 494-9645, Internet,
Ravi Duggirala, (765) 494-2192, Internet,
Ernest Blatchley, (765) 494-0316, Internet,
Dale Margerum, (765) 494-5268, Internet,

Writer: Susan Gaidos, (765) 494-2081; Internet,

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