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Radioactivity is energy given off during the spontaneous decay of unstable atoms called radionuclides. Due to our geological conditions, New Hampshire has a strong presence of radionuclides that show up in water from drilled bedrock wells.
Uranium is naturally occurring as a mineral deposit in bedrock, which can become dissolved into water supplies that travel through the fractures of our bedrock, coming in contact with the mineral. It has a half-life of 4.5 billion years. The half life is the length of time it takes a certain amount of uranium to decay into half the original amount. Ingestion of uranium through water can lead to kidney damage and is believed to be carcinogenic. The EPA standard for uranium in drinking water is 30 ug/L (micro-grams or parts per billion) or 20 pCi/L (picoCuries per liter).
When uranium decays it becomes radium which has a half life of 1620 years. Ingestion of radium through water can lead to bone cancer. Radium accumulates in the bones. The EPA standard for radium in drinking water is 5 pCi/L for the sum of radium 226 and 228.
Radium decays into radon, which is a gas. Radon has a half life of 3.8 days, which is enough time for it to travel through soil, and become dissolved into water. Breathing in radon gas increases the risk of lung cancer. The decay products of radon (polonium, lead, bismuth) have very short lives and are the primary source of radon induced lung cancer. These decay products are solid particles rather than gases, and act like invisible aerosols in the air. They easily attach themselves to solid objects such as dust and smoke and are carried into the lungs. Because of this, radon gas is much more dangerous for smokers, wood workers, miners and anyone living in a dusty environment. There is no EPA standard for radon in water as of now. States set their own guidelines, NH uses 2,000 pCi/L and MA uses 10,000 pCi/L as a guideline.
These radionuclides destabilize nearby atoms as they travel through a cell. This can damage chromosomes, leading to either death of the cell, or to unnatural reproduction of the cell, possibly becoming cancer.
The basic unit of radioactivity is the Curie, which is the amount of radioactivity produced by one gram of radium 226. For the low levels of radioactivity found in drinking water the picoCurie is used, with pico meaning one trillionth.
For treatment of dissolved uranium or radium the choice must be made whether treatment is desired for drinking water only or for the whole house stream. When drinking water treatment is desired it is done with a reverse osmosis system in the kitchen or in the kitchen and bathrooms. When whole house treatment is desired, a custom configuration is designed including ion exchange with special resins.
Radon treatment must be done for the whole house water stream because the health risk centers around the breathing of the gas as it escapes the water, rather than drinking the water. For levels up to 5,000 pCi/L, the installation of a large sized carbon filter is appropriate. To avoid the build up of radioactive decay products in the carbon, the carbon must be rebedded every 2-3 years. For levels over 5,000 pCi/L, an “air stripper” or aeration system is used. These systems remove the radon gas by blowing air through the water, which breaks up the surface tension, allowing the gas to escape. These systems are able to remove 99% of the radon gas which is vented outside where it rapidly becomes dilute. |
