technologies for radon & radionuclide removal tom sorg u. s. environmental protection agency
TRANSCRIPT
Technologies for
Radon &
Radionuclide RemovalTom Sorg
U. S. Environmental Protection Agency
Radon Rn
Radium Ra
Uranium U
Radionuclides
Radioactive Element in the Uranium 238 decay series
Decay product of Ra 226
Alpha emitter
Half life of 3.8 days
Radon - 222
Rn 222 3.8 days
Po 218 3 minPb 214 27 min
Bi 214 20 minPo 214 1.6x10-6 sec
Pb 210 20 years
Radon - 222
Gas
Naturally occurring ground water contaminant
Proposed MCL - 300 pCi/L
MMM Program - 4000pCi/L (AMCL)
Radon - 222
Aeration (BAT) 70 - 99 %
GAC 80 - 99 %
Radon Removal Technology
Packed tower 90 -99 %High performance PP 90 - 99%Diffused bubble 70 - 99 %Tray 80 - 90 %Spray 80 - 90 %Mechanical surface >90 %
Aeration Technology
GAC 80 - 99 %
High EBCT requirementsPotential radiation exposure problemsPotential waste disposal problems
GAC TechnologyVery Small Systems/ POU/POE
Ra 224Thorium seriesAlpha emitterHalf life of 3.6 days
Ra 226Uranium seriesAlpha emitterHalf life of 1620 years
Radium
Ra 228Thorium seriesBeta emitterHalf life of 6.7 years
Radium
Cation Ra+2
Naturally occurring ground water contaminant
Current MCL - 5 pCi/L (Ra 226 + Ra 228)
Radium
Chemistry is similar to calcium and magnesium
(hardness elements)
Radium
Cation Exchange 65 - 95 %
Lime Softening 80 - 95 %
Membrane Processes 90 - 99 %
Selective Complexers 97+ %
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
Radium Removal Technology
U 238Uranium seriesAlpha emitterHalf life of 4.5x109 years
U 234Uranium seriesAlpha emitterHalf life of 2.5x105 years
Uranium
U 235Actinium seriesAlpha emitterHalf life of 7.1x106 years
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
Uranium
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
Coagulation/Filtration 80 - 95 %Lime softening 85 - 99 %Anion Exchange 90 - 99 % Activated Alumina 90 - 99 %Membrane processes 90 - 99 %
Uranium Removal Technology
Anion Exchange - High U capacity
Treat 10k -100k bed volumes
Capacity sulfate dependent
Uranium Removal Technology
Cation /Anion Exchange System
Ra 100 -1500 BVsU 10k -100k BVs
Adjust amount of cation / anion resinOptimum mixture - 10 % anion
90 % cation
Uranium + RadiumRemoval Technology
Gross Alpha, Beta Particle & Photon Emiters
MCLs
Gross alpha - 15 pCi/L (including Ra 226)
Beta particle &photon emitters - 4 mrem/year
Gross alpha Reverse osmosis
Beta particle & Ion Exchangephoton emitters Reverse Osmosis
Gross Alpha, Beta Particle & Photon Emiters
BAT
SUMMARY
•Radon, radium & uranium are naturally occurring contaminants usually occurring in ground water.
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.
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.
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.
