WASHINGTON -- Scientists have found harmless bacteria that they say can remove radioactive contaminants from wastewater.
The phenomenon may open the way for biological filtration of water-borne nuclear waste that would be cheaper and more effective than chemical methods now in use, said Dr. Brendlyn D. Faison, one of the researchers at Tennessee's Oak Ridge National Laboratory that made the discovery.
While it does not resolve the crucial problem of nuclear-waste disposal, the microbial "scrubbing" of wastewater offers a natural way to remove harmful metals and radioactive contaminants in water that drains from facilities like radiology rooms, nuclear power plants and nuclear weapons factories, Dr. Faison said in a telephone interview. It may also help to clear up radioactive leaks.
"In the case of widespread contamination of a water supply, as occurred at Chernobyl, biological treatment may be a highly cost-effective, environmentally acceptable approach to site restoration," she said.
The process is quite different from the biological treatment of oil spills, she explained.
Unlike the oil-eating bacteria, the microbes that clear radiation do not convert the pollutants into harmless substances.
Instead they select and bind with the particles, similar to magnets attracting iron fillings.
The bacteria become covered with radioactive particles and are then filtered from the water to form a radioactive sediment that can be more easily disposed of -- whether by incineration, vitrification (being fused into glass containers) or simple storage -- than if it had still been in solution, she said.
So far the Oak Ridge laboratory has completed tests with only one bacterium -- Micrococcus luteus -- that can bind with strontium, a metal commonly found in radioactive form in nuclear industry waste water.
The process is almost instantaneous and can reduce strontium concentrations in water to almost immeasurable part-per-billion levels, Dr. Faison said.
Radioactive strontium -- a product of fission from uranium -- is a cancer-causing substance and, if swallowed or breathed, will tend to displace calcium in bones.
The problem of how to dispose of mounting levels of low-level nuclear waste at facilities around the country is presenting the nuclear industry with such a headache that the Nuclear Regulatory Commission recently relaxed waste-disposal regulations.
The changes allow plants to dump low-level radioactive waste, such as chemical effluents, mops and laboratory clothes, in Dumpsters and drains as if it were regular garbage or sewage.
Environmental groups are suing the commission to reverse the new policy, saying it threatens public health.
Nuclear facilities, meanwhile, have for years been using chemical ionization processes to remove radioactive elements from waste water. Dr. Faison said the chemical process of removing strontium is more costly, less selective, and therefore less efficient than the bacterial method.
Micrococcus occurs freely in soil, fresh water and even human and animal skin.
Another advantage it offers is that it binds with strontium equally well whether live or dead, Dr. Faison said, meaning that it does not have to be nurtured or fed and can be used as a substance.
The Oak Ridge research team, meanwhile, is investigating other biological methods of filtering radioactive metals. Dr. Faison said that one of the more promising findings so far is a common alga that seems able to efficiently remove cesium, another harmful metal, from waste water.
"The advantage of microbial technology is that you are working with a natural approach. These are not genetically engineered organisms," she said.
Diane D'Arrigo, spokesman for an anti-nuclear group, the Nuclear Information and Resource Service, said the Oak Ridge findings were "interesting", but the "question is still: What do you do with the radioactive microbes?"
"I hope this type of technology doesn't lead to the misguided assumption that it's OK to contaminate water simply because it can be cleared up more easily," she said.