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Technologies for Radon & Radionuclide Removal

Technologies for Radon & Radionuclide Removal. Tom Sorg U. S. Environmental Protection Agency. Radionuclides. Radon Rn Radium Ra Uranium U. Radon - 222. Radioactive Element in the Uranium 238 decay series Decay product of Ra 226 Alpha emitter

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Technologies for Radon & Radionuclide Removal

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  1. Technologies for Radon & Radionuclide Removal Tom Sorg U. S. Environmental Protection Agency

  2. Radionuclides Radon Rn Radium Ra Uranium U

  3. Radon - 222 Radioactive Element in the Uranium 238 decay series Decay product of Ra 226 Alpha emitter Half life of 3.8 days

  4. Radon - 222 Rn 222 3.8 days Po 218 3 min Pb 214 27 min Bi 214 20 min Po 214 1.6x10-6 sec Pb 210 20 years

  5. Radon - 222 Gas Naturally occurring ground water contaminant Proposed MCL - 300 pCi/L MMM Program - 4000pCi/L (AMCL)

  6. Radon Removal Technology • Aeration (BAT) 70 - 99 % • GAC 80 - 99 %

  7. Aeration Technology Packed tower 90 -99 % High performance PP 90 - 99% Diffused bubble 70 - 99 % Tray 80 - 90 % Spray 80 - 90 % Mechanical surface >90 %

  8. GAC Technology Very Small Systems/ POU/POE GAC 80 - 99 % High EBCT requirements Potential radiation exposure problems Potential waste disposal problems

  9. Radium Ra 224 Thorium series Alpha emitter Half life of 3.6 days Ra 226 Uranium series Alpha emitter Half life of 1620 years

  10. Radium • Ra 228 • Thorium series • Beta emitter • Half life of 6.7 years

  11. Radium Cation Ra+2 Naturally occurring ground water contaminant Current MCL - 5 pCi/L (Ra 226 + Ra 228)

  12. Radium Chemistry is similar to calcium and magnesium (hardness elements)

  13. Radium Removal Technology • Cation Exchange 65 - 95 % • Lime Softening 80 - 95 % • Membrane Processes 90 - 99 % • Selective Complexers 97+ %

  14. Radium Removal Technology Cation Exchange - Selectivity Sequence Ra+2 > Ba+2 > Ca+2 > Mg+2 > Na+2 > H+2 Hardness can be used as a surrogate measurement of radium breakthrough

  15. Uranium U 238 Uranium series Alpha emitter Half life of 4.5x109 years U 234 Uranium series Alpha emitter Half life of 2.5x105 years

  16. Uranium • U 235 • Actinium series • Alpha emitter • Half life of 7.1x106 years

  17. Uranium Cation/Anion/Neutral depending on pH Naturally occurring ground water contaminant Current MCL - none Proposed MCL in 1991 20 ug/L 30 pCi/L

  18. Uranium in Water Chemical Forms pH < 2.5 Cation - UO2+ pH < 2.5 - 7 Neutral - UO2(CO3)0 pH 7 - 10 Anion - UO2(CO3)-2 - UO2(CO3)-4

  19. Uranium Removal Technology • Coagulation/Filtration 80 - 95 % • Lime softening 85 - 99 % • Anion Exchange 90 - 99 % • Activated Alumina 90 - 99 % • Membrane processes 90 - 99 %

  20. Uranium Removal Technology Anion Exchange - High U capacity Treat 10k -100k bed volumes Capacity sulfate dependent

  21. Uranium + Radium Removal Technology Cation /Anion Exchange System Ra 100 -1500 BVs U 10k -100k BVs Adjust amount of cation / anion resin Optimum mixture - 10 % anion 90 % cation

  22. Gross Alpha, Beta Particle & Photon Emiters MCLs Gross alpha - 15 pCi/L (including Ra 226) Beta particle & photon emitters - 4 mrem/year

  23. Gross Alpha, Beta Particle & Photon Emiters BAT Gross alpha Reverse osmosis Beta particle & Ion Exchange photon emitters Reverse Osmosis

  24. SUMMARY • Radon, radium & uranium are naturally occurring contaminants usually occurring in ground water.

  25. SUMMARY - RADON • Aeration and GAC are effective treatment technologies for radon. • Of the two technologies, only aeration will be listed as a BAT and likely be the technology of choice in almost all cases. • GAC will likely be considered for only very small systems and for POU/POE.

  26. SUMMARY - RADIUM • All technologies effective for hardness removal are generally effective for radium removal. • Cation exchange, lime softening and reverse osmosis are the technologies currently being applied for radium removal.

  27. SUMMARY - URANIUM • Most conventional technologies have some capability for uranium removal. • Anion exchange has been successfully applied for uranium removal from small ground water systems.

  28. Tom Sorg USEPA Cincinnati, OH 45268 513-569-7370 sorg.thomas@epa.gov

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