The University of Colorado at Boulder and the town of Wiggins, Colo., are wrapping up a pilot project which shows a novel drinking-water treatment process that removes nitrates from groundwater is both efficient and cost effective.
|University of Colorado at Boulder engineering Professor JoAnn Silverstein
and postdoctoral researcher Gary Carlson have developed a pilot
drinking-water treatment plant in Wiggins,Colo. that uses natural bacteria
to remove nitrates from groundwater. The pilot plant has proven both cost
effective and efficient. |
Photos by Ken Abbott. CU-Boulder.
Directed by Professor JoAnn Silverstein of the civil, environmental and architectural engineering department, the pilot facility is the first to use natural bacteria to remove nitrates from drinking water. Results of the effort, which are being monitored by the Colorado Department of Public Health and Environment, should pave the way for such facilities in a growing number of towns and cities faced with rising groundwater nitrate levels and limited budgets to deal with them.
Although Wiggins' drinking water easily meets federal and state nitrate drinking water standards, nitrate levels in nearby groundwater supplies have been rising in recent years, said Silverstein. The CU demonstration project was approved in 1995 by the Wiggins Town Council, whose members recognized that a readily available denitrification process might be of use for the town in the future.
"Biological processes have been used to treat wastewater for a long time," she said. "What's new here is that we are using it to treat drinking water." Data from the Wiggins project will be collected by the state health department through October.
Nitrate contamination of drinking water caused by agriculture, industry and commercial and residential development is a growing problem for many rural communities in the United States, Europe and Asia. Although about 80 percent of people living in the rural United States use groundwater for drinking, up to 25 percent of the wells in heavily farmed areas of the Midwest and West exceed nitrate standards for drinking water, according to the Environmental Protection Agency.
Nitrates in drinking water are known to cause infant methemoglobinemia, also known as "blue baby" disease, said Silverstein. The EPA estimates 4.5 million people, including 66,000 infants in the United States, are at risk for drinking well water that exceeds federal nitrate standards of 10 milligrams per liter.
The Wiggins plant includes two 10-foot-high towers containing layers of non-pathogenic microorganisms commonly found in soil and aquatic environments, she said. Groundwater is pumped through the towers, where the microorganisms gobble up nitrates and expel harmless nitrogen and carbon dioxide into the air.
The few bacterial cells that enter the water are easily removed using a conventional slow sand-filter "polishing" process, and excess bacteria from the towers are periodically removed from the system by scouring the towers with air.
Because of the low nitrate levels now in Wiggins groundwater, the CU team has been adding nitrates to the water before treating it to demonstrate the effectiveness of the pilot facility. The bacteria are fed with high fructose corn syrup.
"This is a very simple, low-maintenance system to operate," said Gary Carlson, a CU-Boulder postdoctoral researcher working with Silverstein on the project. "This plant can treat up to 60,000 gallons of water per day, but the process could easily be scaled up to treat much larger quantities of drinking water."
Although water treated at the pilot facility is used only for irrigation and to recharge groundwater supplies, intensive water quality measurements indicate the final product meets all federal and state drinking water standards. "We believe the data generated by this plant justifies building one anywhere in the world," she said.
The two most common methods of removing nitrates from groundwater -- ion exchange and reverse osmosis -- are expensive and labor intensive. Silverstein's method was patented by the University of Colorado and the technology has been licensed to Nitrate Removal Technologies of Denver for commercialization.
The $200,000 pilot project is funded by the Electric Power Research Institute and the National Rural Electric Cooperative Association with additional assistance from Wiggins, the Morgan County Rural Electric Corp., the Tri-State Generating and Transmission Association and the Colorado Department of Local Affairs.
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