U researchers discover water-purifying enzyme

Emily Dalnodar

Through ongoing studies, two University researchers found a way to cleanse a potentially harmful herbicide from water supplies.
Banned in seven European countries, atrazine is the number-one herbicide in the United States and is common in the Midwest. Used to kill broad-leaved weeds in Christmas tree lots and corn and soybean fields, atrazine regularly finds its way into drinking water.
Unless digested in large amounts, atrazine poses little threat to humans, but two soil researchers say enzymes in the soil may be the best defense against it.
An enzyme found in a soil bacteria, called Pseudomonas ADP, eats the atrazine and digests it much like the acids in a stomach, said Lawrence Wackett, soil microbiologist and part of the Center for Biodegradation.
The enzyme can also treat a few other herbicides with some of the same chemical properties, Wackett said.
The Environmental Protection Agency permits certain amounts of atrazine in the drinking water, but far from levels that would be considered dangerous. But according to Health Effects Research Laboratory, an arm of the protection agency, atrazine “is a possible human carcinogen and has been found to cause cancer of the mammary gland in animal studies.”
The limit set by the agency — three parts atrazine per billion parts water — has occasionally been exceeded in Minnesota, said Dick Clark, supervisor of the community water supply program in the health department. The health department did not start monitoring atrazine until the late 1980s, however.
Currently, the water treatment facilities use a power-activated carbon filter, said Frank De Steno, the manager of the field services division at Montgomery Watson — a world-wide environmental consulting firm in Minneapolis.
“(The filter) absorbs organic compounds. It also absorbs man-made chemicals. It works like the filter you see in most fish tanks,” De Steno said. After the chemicals are absorbed, the carbon is either burned or buried.
According to the U.S. Geological Study, however, this method is not sufficient in removing the atrazine. “Several studies have shown that atrazine can be hazardous because of its extensive use, persistence in water, and water solubility and because conventional water treatment does not effectively remove atrazine from the finished water,” the report stated.
A now-closed agricultural chemical dealership in Little Falls, Minn., used to sell the herbicide. This is where the University research began.
The soil near the loading docks of the building — where numerous bags of atrazine would break open and spill onto the ground — had a high concentration of atrazine in the soil.
The researchers, including Michael Sadowsky, a University professor of soil, water, and climate, found in this affected area a bacteria that could digest the herbicide. The bacteria and the enzyme extracted from it was taken back to the University and reproduced in the labs by a team of students working with Wackett and Sadowsky, who is also a member of the Center for Biodegradation.
The studies, funded by the Novartis Corporation and the U.S. Department of Agriculture-BARD program, found that the enzyme is successful at changing the atrazine in water supplies into a more environmentally-friendly carbon dioxide. Novartis markets and manufactures atrazine.
The Pseudomonas ADP enzyme, when used in the purification of drinking water, has not been found to cause side effects.
There have been tests to detect the enzyme further down in the treatment process, Wackett said. By the end of the process, the enzyme is no longer there — all that is left in the water is carbon dioxide.
There is no immediate move to use this enzyme in the water purification process, however, as the research is still in its early stages.
De Steno said although the basic research has been done it will take some time to get it into use at the water facilities treatment centers.
“It moves at a glacial pace,” De Steno said of the research process.
If the enzyme is implemented in the cleansing of drinking water, both Wackett and Sadowsky said they believe it would be a relatively low-cost method.
“The enzyme could just be added to the treatment of water,” Wackett said. “It gets mixed in with whatever else is used.” This, he suggests, makes it economically feasible as no new equipment would be needed to add the enzyme.