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NC Radon Program |
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| Radon in Water | ||||||||||
| Recommendations for Radon in Drinking Water | ||||||||||
| Methods for Removing Radon from Water | ||||||||||
| Other Concerns & More Information | ||||||||||
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Radon in drinking water is a significant health hazard, though a lesser hazard than radon in indoor air. Homes supplied with drinking water from a private well, or community water systems that use wells as water sources have a greater risk of exposure to radon in water. Radon in water is found in nearly all sources of surface water and groundwater. It is created by the radioactive decay of radium, a naturally occurring radioactive element found in underground rock formations, particularly granite and quartz. Water that flows through or over radium rich rock formations accumulate radium and thus radon from the decay process. Typically, groundwater has much higher levels of radon than surface water. This is because radon in groundwater is "trapped" by being submerged underground and cannot easily escape. Because of this fact, water supplies from underground wells have a much higher probability of having significant levels of radon. If you get your drinking water from a surface water source, radon in water probably is not a significant health hazard. Large, pre-treated municipal water supplies typically have negligible levels of radon in water because usually this type of water supply is drawn from surface water sources, and because water treatment tends to reduce radon levels even further. |
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Recommendations for Radon
in Drinking Water
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Methods for Removing Radon from Water
The two primary methods
for removing radon from water are aeration Removing radon from water by aeration takes advantage of the fact that radon is readily given off (volatile) from water to air. Radon in water is removed by passing as much air through water as efficiently as possible. By venting the now radon-rich air to the outdoors, aeration can remove up to 99.9% of radon from water. Aeration is practical for central treatment of radon in water (i.e. at a water treatment plant, etc.) but is expensive for individual households or small public water systems. A household aeration system suitable for high efficiency radon removal typically costs $3000 - $5000. Special maintenance is required to ensure that waterborne minerals like iron and manganese do not accumulate and foul the aeration system. Otherwise, radon removal efficiency may be reduced. |
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Granular Activated Carbon Absorption (GAC)
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A second method for treating radon in water is granular activated carbon, or GAC, absorption. Water is filtered through granulated carbon (usually in the form of activated charcoal) and radon is attracted onto the surface of the carbon. Maximizing the carbon's surface area and the length of filtration time are crucial to peak radon removal efficiency. GAC absorption can remove up to 99.9% of radon from water if large amounts of carbon and long contact times are used. Typical removal efficiencies for GAC vary from 50-99%. GAC can be used for central treatment schemes for small systems (several hundred users or less), but becomes more expensive for larger systems. GAC is also fairly cost effective for individual residential wells. If high levels of radon are present, disposing of spent carbon filters may be difficult due to the significant amount of radioactive material present in the filter. Small carbon filters attached to kitchen faucets or under sinks are inadequate for removing radon from drinking water. | |||||||||
| An alternative to these active mitigation systems is simple storage. Because radon is a radioactive element which decays over time (Radon-222 has a half-life of 3.8 days), radon levels in water storage tanks will decrease over time. This strategy would probably be most effective for small systems with average radon levels just a bit above the EPA's maximum concentration level. | ||||||||||
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Other Concerns & More Information
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For a more in-depth discussion of these technologies and the associated costs of each, you can see the EPA's Health Risk Reduction and Cost Analysis for Radon in Drinking Water. Section 5 of the Federal Register Notice, "Costs of Radon Treatment Measures" is particularly helpful in understanding the different technologies. Another alternative for some private well owners is to connect to an existing community water system with low radon levels. Drinking bottled water alone will not completely eliminate exposure to radon in water, since this strategy does not prevent radon gas from escaping from well water into indoor air. If you are concerned about radon in your private water supply, a certified professional radon testing and measurement service provider may be of assistance. Contact the Dale Dusenbury, North Carolina Radiation Protection, Environmental Radiation Specialist for further information on Radon in Water. For further information on radon surveys of NC public water supplies, contact Radon Coordinator, Radon Specialist. |
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NCDENR
Radiation Protection Section
1645 Mail Service Center. Raleigh, NC 27699-1645 Office (919)571-4141 Fax (919)571-4148 |
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and granular activated
carbon (GAC) absorption.