More improvements to Hanford groundwater treatment plants are in the works, even as they set new records for removing contaminants from the groundwater beneath Hanford.
CH2M Hill Plateau Remediation Co. met the goal set by the Department of Energy to treat 2.1 billion gallons of contaminated groundwater by Wednesday, the end of the fiscal year, six weeks early. More than 75 tons of contaminants were removed from the groundwater.
“We’re treating more groundwater and removing more contamination than any year in the past two decades,” said Michael Cline, director of the DOE soil and groundwater division at Hanford.
Work that started under the American Recovery and Reinvestment Act of 2009 is paying dividends now.
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Since then two more plants have begun treating groundwater to remove hexavalent chromium along the Columbia River and the 200 West Pump and Treat Facility has begun removing multiple contaminants from groundwater in central Hanford.
Those and more efficient operation of treatment plants have contributed to at least the third record-breaking year in a row for groundwater treatment and have dramatically increased the amount of contaminants removed.
Since 2009 CH2M has more than quadrupled the groundwater treatment capacity at Hanford, from 500 million gallons a year to more than 2.1 billion gallons this fiscal year. Last year 1.9 billion gallons of groundwater were treated.
The 75 tons of contaminants removed this year are more than a third of the 200 tons of contaminants removed since work started in the 1990s.
The contaminated water is pumped out of the ground, treated to remove contaminants at one of Hanford’s six “pump and treat” plants, and then released back into the ground.
“Our groundwater treatment programs are designed to protect the river by slowing the spread of contamination near the river and preventing contamination in the center of the Hanford Site from making its way to the river,” said Karen Wiemelt, vice president of soil and groundwater remediation for CH2M, in a statement.
As contaminants are reduced in the groundwater in one area, workers “chase the plume,” Cline said. They realign wells to draw up water from areas with more contamination.
Not only are more treatment plants operating, but they are operating more efficiently.
A new type of resin tried at one of the pump and treat plants along the river is now being used at Hanford’s other Columbia River plants. It strips out the hexavalent chromium, which was added as a corrosion inhibitor to river water used to cool the reactors that produced plutonium for the nation’s nuclear weapons program.
The resin used previously had to be changed out every six weeks, Cline said. The new resin lasts for several years, reducing the time plants have to be taken offline.
With the new resin, the plants have been reconfigured to treat more water, operating at an average of 113 percent of the capacity for which they were designed.
The next major improvements to groundwater cleanup are happening at the 200 West Pump and Treat Facility.
A new system that removes uranium from groundwater has been operating without hands-on tending for a week, Cline said. It should be fully operational by the end of the year.
The plant already was the most sophisticated groundwater treatment plant at Hanford. Microorganisms at the plant consume nitrates. An air stripping system removes tetrachloride. The plant also treats hexavalent chromium and trichloroethene.
The 17,500-square-foot radiological building on one end of the plant was built to remove radioactive contaminants from water.
The ion exchange columns installed there initially treated water to remove technetium 99. But space was saved in the building to expand its capabilities with an additional set of three ion exchange columns using resins that capture uranium.
The ion exchange columns, a well-established technology similar to that used in home water softeners, were manufactured off site and trucked already assembled to the plant for installation.
The uranium contamination to be treated came primarily from Hanford’s U Plant, which was used to recover uranium from waste stored in underground tanks. Liquid waste from the plant was discharged to the soil, where it moves easily through the ground, leaving a plume of contaminated groundwater covering about 102 acres.
The ion exchange system also will be used to treat about 2 million gallons of uranium-contaminated water that has collected, or perched, in the soil above the water table in central Hanford. The goal is to capture and treat as much of it as possible before more of it seeps into the aquifer and contributes to groundwater contamination.
An 8-mile-long pipeline from the perched water area in the Hanford 200 East Area to the 200 West Pump and Treat Facility is nearly complete.
The next upgrade for the plant will be to the 52,000-square-foot biological treatment facility. There bacteria is used to treat waste, generating solids that must be removed. The capacity to remove solids will be increased, Cline said.
Because of the down time for that upgrade, the record set this fiscal year for groundwater treatment might stand for another year.
“We’re doing a lot of good work,” Cline said. “We plan to continue.”