1. U. S. Environmental Protection Agency
Technologies
for
Arsenic Removal
Tom Sorg
U. S. Environmental Protection Agency

2. Arsenic Chemistry
Two primary valence states
As (III)
As (V)

3. Arsenic III
H3AsO30
H2AsO3-1
HAsO3-2

4. Arsenic V
H3AsO40
H2AsO4-1
HAsO4-2
AsO4-3

5. As V more effectively removed
Why is arsenic form important?
Final Answer!
As V more effectively removed by
ALL technologies

6. Example! Treatment Process Percent Removal As III As V
Iron Coag/Filt - pH
Alum Coag/Filt - pH

7. Example! Ion exchange treatment As III - 0 percent removal
As V percent removal

8. Arsenic Occurrence Surface waters predominantly As(V)
Ground waters generally As(III), but not always

9. Arsenic Speciation Method
On site anion exchange separation
As III, As V As V
As V retained on resin column
As III passes through column
As III

10. Arsenic Speciation - Anion separation of AsIII/AsV

11. As III easily oxidized to As V
Good News!
As III easily oxidized to As V by
several oxidants

12. As III Oxidation Study Dr. Dennis Clifford Univ. of Houston
Oxidants Studied Free Chlorine Chloramine Ozone Chlorine Dioxide UV Radiation Potassium Permanganate Oxidizing Media

13. Arsenic Removal Processes
Precipitative processes
Adsorption processes
Ion Exchange process
Iron Removal processes
Membrane processes
POU/POE devices

14. Arsenic Removal Processes
Emerging processes
Iron coagulation with microfiltration
Iron based adsorption media

15. Precipitative Processes
Process Removal
Coagulation/ %
Filtration
Lime softening %

16. Adsorption Processes Processes Removal Activated Alumina 90+ %
Iron Media %

17. Ion Exchange
95 + % removal

18. Iron Removal Processes
Process Removal
Oxidation/filtration 80+ %
Manganese greensand %
(Dependent on amount of Fe)

19. Membrane Processes Process Removal Reverse osmosis (RO) 90+ %
Nanofiltration (NF) %
Ultrafiltration (UF) %

20. Arsenic Removal Processes
Large Systems Using Surface Waters
Coagulation/filtration
Direct filtration
Lime softening

21. Arsenic Removal Processes
Large Systems Using Ground Waters
Lime softening
Membrane Separation Processes
-reverse osmosis (RO)
-ultrafiltration (UF
-electrodialysis reversal (EDR)
Iron Removal processes - oxidation/filtration

22. Arsenic Removal Processes
Small Systems Using Surface Waters
Coagulation/filtration package plants
Iron Removal processes oxidation/filtration
Lime softening package plants

23. Arsenic Removal Processes
Small Systems Using Ground Waters
Anion Exchange
Activated Alumina adsorption
Iron Removal processes - oxid/filt.
Membrane Separation Processes
-reverse osmosis (RO)
-ultrafiltration (UF)
-electrodialysis reversal (EDR)

24. Arsenic Removal Processes
Very Small Community Option
Point-of-use systems
-RO, AA
Point-of-entry systems
-RO, Ion Exchange

25. Evaluation of Treatment Plant Performance
Investigator - Battelle, Columbus, OH
Processes - 5
Conventional Coag Systems
Lime Softening System
Iron Removal Systems
Anion Exchange Systems
Activated Alumina Systems

26. AA System - Source Water Quality (Avg)
Analysis - ug/L CS (30)
Total As
Particulate As
Soluble As
As III <1
As V (100%)
pH - Units
Hardness – mg/L
Sulfate – mg/L
Alkalinity - mg/L

27. Activated Alumina System - New Hampshire
Non regeneration
system A A
Roughing filter
Polishing filter B B

28. Activated Alumina System, 20 gpm - NH

29. Activated Alumina System, NH

30. IE System - Source Water Quality (Avg)
Analysis - ug/L MMA (45)
Total As
Particulate As <1
Soluble As
As III <1
As V (100%)
pH - Units
Hardness – mg/L
Sulfate – mg/L
Alkalinity - mg/L

31. Ion Exchange System, ME A B Mixed bed resin Oxidizing filter media
KMnO4
regeneration A B
Mixed bed resin

32. Ion Exchange System with Oxidizing Filter, ME
2 gpm

33. Ion Exchange System, ME

34. Iron Media System, MI Source Water Quality
Parameter Concentration - mg/L
Arsenic
As III %
As V %
Calcium
Magnesium
Iron
Manganese
Sulfate
Silica pH

35. Iron Media System, MI Distribution system Well Tank 1A Tank 2A Tank 3A
Cl2
Acid
Tank 1B
Tank 2B
Tank 3B
Softener
Distribution system

36. Iron Media System, MI

37. Iron Media System, MI

38. As V is dominant in oxygenated waters
SUMMARY
Soluble arsenic occurs in natural water in the As III and As V oxidation states.
As V is dominant in oxygenated waters
As III is dominant in anoxic water

39. Treatment processes remove As V more effectively than As III
SUMMARY
Treatment processes remove As V more effectively than As III
As III can be converted to As V with strong oxidants

40. SUMMARY
Most conventional treatment processes have capability to reduce arsenic to less than 10 ug/L, many to to 5 ug/L or less.

41. Tom Sorg
USEPA
Cincinnati, OH 45268