YAKIMA — Who knew the answers to ridding the Hanford nuclear reservation of wastewater might be in the kitchen?
Researchers at the nation’s most contaminated nuclear site last year injected 5,000 gallons of molasses into the soil to try to clean up toxic groundwater near the Pacific Northwest’s largest waterway. This week, they’re trying their hands at vegetable oil.
State officials who have long pressured the federal government to clean up Hanford call the cooking oil a good idea.
“We support these tests. They’re actually pretty inexpensive,” said John Price, project manager of environmental restoration for the state Department of Ecology. “We’d like to see them scale up to a full system, beyond just tests, sooner rather than later.”
Federal officials announced earlier this year they would step up efforts to clean up groundwater, particularly for a plume of hexavalent chromium that stretches for 11/4 miles along the river shore. The contaminant moves easily with water and is particularly dangerous to salmon in the Columbia River.
Workers installed new wells and additional equipment to triple the amount of groundwater that can be treated. An iron barrier installed in the soil about five years ago breaks down the chromium to a nontoxic form, where it is less mobile and less likely to travel in groundwater to the river.
But scientists also have been researching ways to supplement those methods.
In what was believed to be the first such effort at a nuclear site, they injected 5,000 gallons of molasses mixed with 200,000 gallons of water into a test well last September. The goal was to increase the food supply for natural microbes and remove oxygen from the groundwater, thereby enabling the chromium to convert to the nontoxic form.
So far, the results have been good. After 10 months, levels of toxic chromium in the area of the test well have declined, said Mike Truex, senior program manager for Pacific Northwest National Laboratory.
However, the molasses might have to be injected every couple of years, he said, whereas vegetable oil could provide the same results over a longer period.
Researchers believe an injection of 1,500 gallons of vegetable oil, mixed with 50,000 gallons of water, could work for up to seven years.
It’s not the first time vegetable oil has been tried. For instance, near Barstow, Calif., workers injected a number of organic materials, including lactate, ethanol and vegetable oil, into the soil at a Pacific Gas and Electric Co. site contaminated with hexavalent chromium.
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