POU Arsenic Treatment

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POU Arsenic Treatment
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Aqueous Chemistry of Arsenic

• Found primarily in the inorganic form
• Two different oxidation states
• arsenate (As5 or AS V)
• arsenite (As3 or As III)
• As V exists as negatively charged ions (HAsO42-
  H2AsO41-) in the normal pH range of drinking
  water
• As III is a neutral species (H3AsO3) below pH
  9.2
• )

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Arsenic Chemistry

• As III H3AsO30, H2AsO3-1, HAsO3-2
• As V H3AsO40, HAsO4-1, AsO4-2

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ANSI/NSF Standard Arsenic Test Water - background
parameters

• Magnesium (Mg)
• Sulfate (SO42-)
• Nitrate (NO3-) as nitrogen (N)
• Fluoride (F-)
• Silicates(SiO2)
• Phosphates (PO4) as phosphorous (P)
• Calcium (Ca2)
• pH

• 12 milligrams per liter (mg/L)
• 50 mg/L
• 2 mg/L
• 1 mg/L
• 20 mg/L
• 0.04 mg/L
• 40 mg/L
• 6.5 and 8.5

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ANSI/NSF Standard Arsenic Test - feed conditions

• Claim for arsenic V
• AsO43-
• Claim for arsenic III AsO33-

• 50 or 300 parts per billion (ppb) As V
• 0.5 mg/L free chlorine
• pH 6.5 and 8.5
• 50 or 300 ppb As III
• _at_pH 6.5
• 0.3 mg/L Fe2
• 0.05 mg/L Mn2
• lt1 mg/L dissolved oxygen
• _at_pH 8.5
• no Fe2 and no Mn2
• lt1 mg/L dissolved oxygen

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Adsorptive Mediafor removal of arsenic from
drinking water

• Base Material
• Activated Alumina AA, Modified AA
• Iron Oxide, Hydroxide, Iron Coated
• Other Lanthanum Oxide, Zeolites, and others

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Arsenic Removal Adsorptive MediaListed in
NSF/ANSI 61
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Arsenic Adsorption Processes

• Process Removal
• Activated Alumina 90
• Iron Media 90

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Adsorption Media Kineticsfor Arsenic
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Arsenic Adsorptive Mediawater quality factors
that impact arsenic removal capacity

• pH of source water
• Competitive ligands such as SiO2, PO4, etc.
• Concentration of As and other ligands

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Activated Alumina SelectivitypH 5.5 8.5From
Clifford. AWWA, WQT 5th ed

• OH-1 gt H2AsO4-1 gt Si(OH)3O-1 gt F-1 gt HSeO3-1 gt gt
  HCO3-1 gt Cl-1 gt NO3-1
• Iron based media and other materials (?)
• (silica and phosphate)

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Arsenic Adsorption Capacity
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Adsorption Media Cost
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Point-of-Use (POU) Cartridge Configuration with
Granular Ferric Hydroxide (GFH) Adsorption Media

• Bed Dimensions
• - Length
• - Diameter
• Bed Volume
• Flow Rate
• EBCT (empty bed contact time)

• 7 inches (18 cm)
• 2.1 inches (5.3 cm)
• 24 cubic inches (400 ml)
• 0.6 gallons per minute (2.3 L/min)
• 10.6 seconds

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POU Cartridge Arsenic V Reduction at pH 8.5
Courtesy of Gary L. Hatch, Ph.D., Plymouth
Products and U.S. Filter Corporation
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POU Cartridge Arsenic V Reduction at pH 6.5
Courtesy of Gary L. Hatch, Ph.D., Plymouth
Products and U. S. Filter Corporation
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POU Cartridge Arsenic III Reduction at pH 8.5
Total Arsenic Concentration vs. Gallons of
Water GFH, EBCT 10.6 sec., 6-8 mg/L DO,
50/50 cycle _at_ 0.6 gpm
Courtesy of Gary L. Hatch, Ph.D., Plymouth
Products and U. S. Filter Corporation
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POU Cartridge Arsenic III Reduction _at_ pH 6.5
Total Arsenic Concentration vs. Gallons of
Water GFH, EBCT 10.6 sec., no Fe2 or Mn2,
6-8 mg/L DO, 50/50 cycle _at_ 0.6 gpm
Courtesy of Gary l. Hatch, Ph.D., Plymouth
Products and U. S. Filter Corporation