Eliminating a Hazard by Adding Chemicals
Not all hazardous waste needs to be broken down. Sometimes the answer is to build up the chemicals. William Frankenberger and Ulrich Karlson, soil scientists at UC Riverside, are doing just that.
They may have found a way to reduce high levels of selenium, an element that can be toxic in high concentrations in water--such as in Kesterson National Wildlife Refuge in Central California.
Particular fungi, already in the soil at Kesterson, can convert selenium to a gas form by tacking on additional molecules to the original chemical. “We’ve found out how to trigger nature’s way of taking care of high selenium concentrations,” Frankenberger said. “What we’re doing is stimulating a natural process.”
All these microbes need is a boost of food and oxygen to get them going. As a gas, the new compounds just blow away with the wind, leaving the waters free of toxicity.
But the UCR researchers are still at the experimental stage. “At this point, we can’t come riding in as a white knight and say, ‘Hold everything, we’ve got the answer,’ ” Frankenberger said. Since they only began field testing last summer, they need more time to collect and analyze data before they put the microorganisms to work.
The state originally planned to excavate the Kesterson site and transfer the contaminated soil to a landfill for disposal--at an estimated cost of $50 million to $150 million. But aside from the expense, scientists had begun to wonder whether the method would even work. Test plots that had been excavated continued to contain high levels of selenium.
For those reasons, the U.S. Department of the Interior deferred awarding an on-site disposal contract.
Now the UCR researchers’ experimental method is being considered as a possible alternative to excavation. Frankenberger estimated that fungi could clean the refuge for $5 million.
Frankenberger and Karlson have to figure out the ideal conditions for keeping the fungi active. By adding selected substances to the soil, such as fruit pectin and nitrogen fertilizer, and by irrigating and rototilling the land, Frankenberger said, the microbes can be stimulated to work at an accelerated pace.
There is an added advantage to a biological approach: The soil does not have to be hauled away. The fungi would work right in the earth and the wildlife refuge would not have to be disturbed as it would with excavation.
