Radionuclide Treatment Options for Drinking Water - PUB2755

This publication provides drinking water systems general information on the available treatment technologies for the removal of radium, uranium and gross alpha particle activity, the residuals produced by each technology, disposal options and the regulations governing these options.

Maximum Contaminant Level (MCL)

In accordance with 10 CSR 60-4.060, all community water systems must comply with the following MCLs for radionuclides:

• Gross Alpha; 15 Picocuries per liter (pCi/L).
• Combined Radium 226 & 228; 5 pCi/L.
• Beta Particle and Photon Radioactivity; 4 millirem per year.
• Uranium; 30 micrograms per liter.

Nontreatment Compliance Options

• Drilling a new well at another site – If the water system can obtain property at a location where excessive radionuclides are not likely present at the productive depths, then drilling a new well could be an option. Sampling existing wells (including irrigation wells and monitoring wells) in the nearby area can help when evaluating new well sites for the possibility of excessive radionuclides.
• Interconnection with neighboring system – If there is a nearby drinking water system with sufficient capacity, this is a very good solution by using the interconnection to either purchase water or consolidate into one larger system.
• Geophysical study, packer study or plugging a portion of the well – Performing a geophysical study can determine at what location radionuclides are entering the well. Performing a packer study can then temporarily seal off that portion of the well to determine remaining capacity and radionuclide levels. If results are favorable, placing a permanent grout seal to plug a portion of the well could reduce the radionuclide levels to below the MCL. Please note, pursuing this option will likely reduce the well capacity.
• Blending – This option can dilute the radionuclide levels to below the MCL by blending two different sources (one under the MCL and one above the MCL) together. Alternatively, treating only a portion of the water and blending the treated and untreated water can result in a combined concentration below the MCL.

Treatment Options

Ion exchange water softening

• Benefits
  • Represents a best available technology (BAT) and Small System Compliance Technology (SSCT) for radium, uranium, gross alpha, and beta particle and photon emitters.
  • Can remove up to 99% of contaminant.
  • Can be automated to require minimal operator attention.
• Limitations
  • Reduces gross alpha and combined radium by removing Radium 226 and Uranium. However, many other alpha particles will not be removed.
  • High hardness or sulfate levels can lower radionuclide removal efficiency.
  • Can cause increased corrosivity of the finished water possibly effecting lead rule compliance.
  • Can become loaded for radionuclides and still effectively remove hardness. Using hardness as a test surrogate for operational monitoring should be done cautiously.
  • Oxidants such as chlorine can damage certain types of media.
  • Particulates and metals in the source water can clog the media.
  • Certain types of media can reduce the alkalinity of the water.

Reverse osmosis filters

• Benefits
  • Represents a BAT and SSCT for uranium, radium, gross alpha, and beta particles and photon emitters.
  • Can remove up to 99% of contaminant.
• Limitations
  • Direct and indirect integrity testing is required to verify the treatment is operating properly.
  • Pretreatment to remove other contaminants may be required.
  • Oxidants such as chlorine can damage certain types of filters.
  • Can cause increased corrosivity of the finished water possibly effecting lead rule compliance.
  • Units lose a large amount of the incoming water in the waste stream (between 10 and 70%).

Pre-formed hydrous manganese oxide filtration (HMO)

• Benefits
  • Represents a SSCT for radium.
  • Can remove up to 90% of contaminant.
• Limitations
  • Chemicals must be dosed carefully.
  • Intermediate operator skill is required.
  • High iron levels can lower radium removal efficiency.

Water remediation technology Z-88 radium removal system (WRT) – proprietary filter media

• Benefits
  • Media is certified by NSF, a third party certification organization.
  • Media is specific to the desired level of Radium 226 to be removed.
  • Minimal maintenance and operation required.
  • Spent media is properly disposed of by WRT.
• Limitations
  • Will only remove Radium 226.
  • Difficult to determine when media needs replaced.

This is not a comprehensive list of technologies and assumes facilities are designed, constructed, operated and maintained properly. Water systems should not rely solely on this document when making treatment technology decisions; it is important to consult closely with an experienced Missouri registered professional engineer in selecting a treatment solution.

Residuals Management

Filter backwash water and residuals produced by the above mentioned treatment options can include liquid waste (backwash water, rinse water, etc.) and/or solid waste (spent media, resins, or membranes). Disposal options can include discharge to a sewer system, land application, obtaining a General Operating Permit from the Missouri Department of Natural Resources for direct discharge, and disposal  in a landfill. 

Cost Estimate

The above cost estimates were obtained from Engineering Reports submitted to the department by systems with populations between 25-450 evaluating different treatment options for radionuclides. These cost estimates are only for the initial capital cost of the treatment system and do not include costs for site work, plumbing and electric for the building, engineering, legal, or operation and maintenance costs.

Where to Find Help

The department offers financial assistance for eligible small community water systems serving a population less than or equal to 3,300, or community water systems with larger populations that will provide benefit to these small community water systems, to fund engineering report services. This funding allows public water systems to hire an engineer to study their water system and advise them on how to achieve or maintain compliance with drinking water rules and regulations. The program is not a loan program, but rather provides grants to water systems based on their eligibility and priority. More information

• The Missouri Department of Natural Resources’ Financial Assistance Center in the Water Protection Program provides funding to communities for water infrastructure projects with the Drinking Water State Revolving Fund loans and grants and the Small Borrower Loan program. For more information, contact the Department’s Financial Assistance Center at 573-751-1192.
• U.S. Department of Agriculture Rural Development (USDA – RD) loans and grants help very small, financially distressed rural communities finance drinking water source, treatment, storage and distribution improvements to serve rural areas and towns. For more information, contact the USDA-RD Missouri office at 573-876-0976.
• Missouri Department of Economic Development’s Community Development Block Grant offers grants to small Missouri communities to improve local facilities, address critical health and safety concerns, and develop a greater capacity for growth. For more information, contact the Missouri Department of Economic Development at 573-751-3600.

You may request an appointment for a compliance assistance visit from the department. This visit will assist with understanding regulatory requirements, help with achieving and maintaining compliance, and provide a continuing resource for technical assistance. To request a compliance assistance visit, please contact your local regional office or fill out an online request.

Other Links

• Types of Ionizing Radiation
• EPA - Radionuclides Rule
• EPA – Compliance Help with Radionuclides in Drinking Water