Radium is a naturally occurring radioactive element that contaminates drinking water, primarily originating from the natural decay of uranium and thorium found in rock and soil deposits. It enters water supplies, particularly groundwater and deep wells, as it leaches from surrounding geological formations. While radium is colorless and odorless, its presence is a concern because long-term consumption may increase the risk of certain health issues. Effective removal relies on specific testing protocols and specialized water treatment technologies.
Understanding Radium Testing
Testing is the first step to confirm the presence of radium and determine if treatment is required. Since radium cannot be detected by taste or smell, the water must be sent to a certified laboratory specializing in radiochemical analysis. The initial screening test measures the total alpha particle activity, which indicates the presence of various radioactive elements.
If the gross alpha activity exceeds a threshold, the lab tests for the specific isotopes: Radium-226 and Radium-228. The U.S. Environmental Protection Agency (EPA) established a Maximum Contaminant Level (MCL) of 5 picocuries per liter (pCi/L) for the combined concentration of these isotopes in public water systems. For private well owners, this 5 pCi/L level serves as the guideline for determining when treatment is appropriate. Interpreting results involves comparing the combined Ra-226 and Ra-228 concentrations against this regulatory standard.
Effective Residential Removal Technologies
Several methods are available to remove radium from residential water supplies, each working on different scientific principles. Ion exchange (IE) is a common whole-house solution for radium removal. This process involves passing water through a resin bed where positively charged radium ions are swapped out for non-radioactive ions, such as sodium, bound to the resin. The system operates similarly to a conventional water softener.
Reverse osmosis (RO) is a physical separation method that uses pressure to force water through a semipermeable membrane. This membrane has pores small enough to block the radium ions. While effective at removal, RO systems process water slowly, which limits their application to treating water at a single tap for drinking and cooking purposes.
Chemical and physical binding uses manganese greensand or similar media. Radium ions adsorb onto the surface of hydrous manganese oxides. The system works by chemically promoting the formation of a manganese floc that captures the radium, which is then filtered out by the greensand media. This method is suitable when the water source also contains high levels of iron or manganese, as the system can treat all three contaminants simultaneously.
System Selection and Ongoing Maintenance
The choice between a whole-house and a single-tap system depends on the user’s goals and budget. Point-of-Entry (POE) systems, such as ion exchange, treat all water entering the home, providing radium-free water for every faucet and appliance. Point-of-Use (POU) systems, like reverse osmosis, only treat water at the specific location where they are installed, such as the kitchen sink. POU systems are less expensive to install but only address water used for ingestion, while POE systems offer comprehensive protection.
A primary consideration for any radium removal system is the management of the radioactive waste it generates. Both ion exchange resins and reverse osmosis membranes concentrate the radium onto the filter media. Over time, this spent media can accumulate enough radioactivity to be classified as low-level radioactive waste.
The disposal of this concentrated waste must adhere to local, state, and federal regulations, requiring disposal at a licensed waste management facility. Homeowners must consult with the system provider and local regulators to understand the proper handling, transportation, and disposal protocols for the exhausted media. This long-term responsibility, including potential costs for specialized waste disposal, is part of the commitment when treating radium contamination.