Answer to Question #12705 Submitted to "Ask the Experts"
Category: Environmental and Background Radiation — Water
The following question was answered by an expert in the appropriate field:
Can radiation be removed from water? If radioactive contamination is filtered from water, would the filter become radioactive? Would the water be safe?
The short answer is that in general, radioactive chemicals (radionuclides) can be removed from water if they are particles, and then the filtered water is safe to use. Let me explain further.
We usually filter water to remove natural radionuclides, like uranium and thorium, that are found naturally in the soil and rocks of our environment. These radionuclides are in the form of particles, and they are captured by the filter medium.
However, some natural radionuclides, like radon, are not particles but are gases. Radon gas dissolves in water, then after a few weeks at most, essentially all the radon gas decays to other radionuclides that are atomic-sized particles. These particulate radon decay products can then be filtered out of the water.
The filter used to remove radionuclides from water is radioactive because it holds the uranium or thorium or other radioactive particles. For most residential water filtration systems where the radionuclide levels in water are relatively low, the radioactivity of each filter is also quite low and is not a hazard. Still, it would be prudent to handle the used filter carefully and place it in a plastic bag for disposal.
No matter what radionuclide particle is in the water, filtration will remove it, and the water will be safe to use. It is important, however, to be sure that the filter is changed as often as recommended by the manufacturer of the filtration system. If the filter becomes overloaded or is damaged, it will be less effective at trapping particles and some may pass through into the water.
I hope this answers your questions.
Linnea Wahl, CHP
HPS Ask the Experts Topic Editor