Radionuclides: Uranium and Radium

Sources of Uranium and Radium

So you've just had your water tested and the lab results are telling you that you've got radionuclides.

Radionuclides are radioactive isotopes or unstable forms of elements.  Radioactivity is the release of energy, radiation, that occurs when these unstable elements decay or breakdown into more stable elements.  This process is known as radioactive decay and is measured by the half-life of the element.  The half-life is the time required for half of the original element to decay.  The half-life for radionuclides can range from a few thousands of a second to a few billion years. The two most common radionuclides found in groundwater supplies are Uranium and Radium.  Uranium and Radium are naturally occurring elements that are found throughout the Mid-Atlantic and Northeastern United States in bedrock deposits like shale or granite deep below the surface.  Rather than the glowing green rocks often portrayed in cinema or television, uranium and radium are found in ores mixed with other minerals and metals.  Uranium is the largest naturally occurring element on earth, nearly 70% denser than lead, and exists naturally as three different isotopes: U-234, U-235, and U-238, with U-238 and U-235 being the most common.  U-235 is the preferred isotope for nuclear power generation.  All three forms of uranium have the same chemical and physical properties, but have different radioactive properties.  In very low pH conditions, uranium exists in a cation oxidized form UO2, but it is most commonly present as anionic compounds UO2(CO3)2 and UO2(CO3)3.  As uranium decays naturally over time, it releases radiation and forms new elements like radium, lead, and radon gas.

Radium occurs naturally from the radioactive decay of uranium over time.  The most common forms of radium are Ra-226 and Ra-228, but all isotopic forms are radioactive.  Over time, Radium will decay to form other elements like Radon, a dangerous and potentially lethal gas that tends to collect in the basements of homes.  Radium was used to make luminous paints for watch dials and military instruments, but was discontinued due to health hazards from constant exposure.  Radium is now used in some medical equipment and cancer treatment drugs.

Potential Health Effects

Exposure to Uranium and Radium over time can result in dangerous and harmful health effects.   Over enough time and exposure, Uranium and Radium can lead to increased risk of cancer and organ failure.  Also, the natural decay of both elements into other radioactive substances further increases health concerns. Uranium can naturally decay to form radium, which naturally decays to from deadly radon gas.  According to the National Academy of Sciences, exposure to radon gas is the second leading cause of lung cancer in the United States.  Radium also presents a unique threat due to its position in the periodic table.  Radium is an alkaline earth metal and therefore shares many of the same physical and chemical properties as magnesium and calcium, elements the body uses for bone development.  If ingested, radium can be readily absorbed into the skeletal system and potentially cause bone cancer.

It is assumed and expected that any exposure to radiation carries some degree of risk.  Therefore, both are listed under the National Primary Drinking Water Regulations as set by the Environmental Protection Agency.  The goal is always to have zero measurable levels of contaminants like uranium or radium in your drinking water, this goal is referred to as the Maximum Contaminant Level Goal (MCLG). The Maximum Contaminant Level (MCL) is the maximum permissible level of a contaminant in water which is delivered to any user of a public system.  The MCL for Uranium is 30 ug/L, which is equivalent to 20.27 pCi/L.  The MCL for Radium is 5 pCi/L.

Treatment Methods

As always, the most important step in water treatment is to have a water analysis performed on your water by an EPA Certified Laboratory capable of performing radiochemistry analysis, in order to determine the proper course of action when considering treatment options.  Master Water has provided a list of certified analytical laboratories for state in the Mid-Atlantic and Northeastern  US found here.

Radium reduction can be achieved through the use of a Strong Acid Cation exchange resin in the sodium form that is regenerated with sodium chloride (NaCl).  Cation exchange resin has a greater affinity for radium than calcium or magnesium, so considerable radium reduction can be expected.  Radium selective strong acid cation exchange resins are also an option depending on the application.  It is important to have the proper brining and regeneration procedures in place so that the resin is properly cleaned and that breakthrough does not occur.  With proper brining and regeneration, cation exchange resins can last up to 10 or more years of service.  Point of Entry and Point of Use (POE/POU) Reverse Osmosis systems are both effective as well.

Uranium reduction can be achieved through the use of a Strong Base Type II Anion Exchange Resin in the Chloride form.  Strong Base Type II Anion Exchange Resin has a greater regeneration efficiency, and is more resistant to organic fouling than Strong Base Type I Anion Exchange Resin.  Sodium chloride is used to regenerate the resin and chloride becomes the ion that the resin will exchange for anions like Uranium.  Strong Base Type II Anion Resin has an affinity for Uranium that is up to 100 times greater than other common anions like sulfate or carbonate.  Due to the nature of the resin, carbonate ions, a major component of alkalinity, will be still be exchanged after the resin is regenerated.  Therefore, pH correction is often needed after a chloride form anion exchange system.  With proper brining and regeneration, anion exchange resins can last up to 5 or more years of service.  Point of Entry and Point of Use (POE/POU) Reverse Osmosis systems are both effective as well.

Due to the health risks associated with Uranium and Radium, a number of concerns should be properly addressed before any system is installed.  First it is important to evaluate the efficacy of any system being installed. Second, it is important to properly maintain the system (regeneration settings, salt in the brine tank, etc.). Finally, the treated water from the system should be monitored through proper water analysis over time.  Master Water Conditioning has multiple options for treating radionuclides, including our Satin Series MP-MCA water softeners and MP-MCAU uranium ion exchange systems, as well as POE and POU R.O. systems.