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

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

Arsenic III H3AsO30 H2AsO3-1 HAsO3-2

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

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

Example! Treatment Process Percent Removal As III As V Iron Coag/Filt - pH 7 55 97 Alum Coag/Filt - pH 7 18 95

Example! Ion exchange treatment As III - 0 percent removal As V - 98+ percent removal

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

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

Arsenic Speciation - Anion separation of AsIII/AsV

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

As III Oxidation Study Dr. Dennis Clifford Univ. of Houston Oxidants Studied 1. Free Chlorine 2. Chloramine 3. Ozone 4. Chlorine Dioxide 5. UV Radiation 6. Potassium Permanganate 7. Oxidizing Media

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

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

Precipitative Processes Process Removal Coagulation/ 95 % Filtration Lime softening 85+ %

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

Ion Exchange 95 + % removal

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

Membrane Processes Process Removal Reverse osmosis (RO) 90+ % Nanofiltration (NF) 65-90 % Ultrafiltration (UF) 35-75 %

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

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

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

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)

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

Evaluation of Treatment Plant Performance Investigator - Battelle, Columbus, OH Processes - 5 Conventional Coag. -- 2 Systems Lime Softening ------- 1 System Iron Removal ----------2 Systems Anion Exchange -------2 Systems Activated Alumina ----2 Systems

AA System - Source Water Quality (Avg) Analysis - ug/L CS (30) Total As 63 Particulate As 2 Soluble As 66 As III <1 As V 66 (100%) pH - Units 8.4 Hardness – mg/L 37 Sulfate – mg/L 14 Alkalinity - mg/L 57

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

Activated Alumina System, 20 gpm - NH

Activated Alumina System, NH

IE System - Source Water Quality (Avg) Analysis - ug/L MMA (45) Total As 57 Particulate As <1 Soluble As 57 As III <1 As V 57 (100%) pH - Units 8.3 Hardness – mg/L 38 Sulfate – mg/L 45 Alkalinity - mg/L 64

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

Ion Exchange System with Oxidizing Filter, ME 2 gpm

Ion Exchange System, ME

Iron Media System, MI Source Water Quality Parameter Concentration - mg/L Arsenic 0.025 - 0.041 As III 85 % As V 15 % Calcium 80 - 90 Magnesium 34 - 35 Iron 1.06 - 1.35 Manganese 0.02 - 0.03 Sulfate 21 - 30 Silica 19 - 20 pH 7.1 - 7.2

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

Iron Media System, MI

Iron Media System, MI

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

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

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

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