The Arsenic Rule and its Impact on Water Utilities

1
The Arsenic Rule and its Impact on Water Utilities

• Ron Clemmer, PE
• ARCADIS
• 2002 RMSAWWA/RMWEA JOINT ANNUAL CONFERENCE
• September 17, 2002

2
Presentation Outline

• Background
• Regulations
• Water Management Options
• Treatment Options

3
Background
4
Arsenic Chemistry

• Symbol As
• Atomic Number 33
• Atomic Weight 74.92
• Chemical behavior of a non-metal
• Stable and sparingly soluble
• No taste, odor, or color in water

5
Periodic Table of Elements
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Fr
Ra
Ac
Rf
Ha
Sg
Ns
Hs
Mt
Uun
Uuu
Uub
Uuq
Uuh
Uuo
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
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Oxidation States in Water

• Arsenite (As III) Arsenate (As
  V)

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Oxidation States in Water

• Arsenite - As (III)
• H3AsO3, H2AsO3-
• More prevalent in anaerobic ground waters
• Non-ionic at neutral pH (no charge)
• Arsenate - As (V)
• H2AsO4-, HAsO42-
• More prevalent in aerobic surface waters
• Ionic with a negative charge (anion)

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Redox Chemistry
9
As Geological Information

• Naturally occurring element
• 20th most abundant element in Earths crust
• Approximately 254 arsenic bearing minerals
  identified
• Highest concentrations in areas of geothermal
  activity

10
Natural Sources and Exposure

• Dissolution, erosion, weathering of rocks
• Uptake by plants, animals
• Consumption of food and water major source of
  human exposure in U.S.

11
Industrial Uses

• Production of pesticides/herbicides
• Cotton and wool processing
• Wood preservative
• Feed additive
• Mining and metal alloys

12
Health Concerns

• Known Carcinogen Bladder, Skin Lung, Kidney,
  Liver
• Cardiovascular Disease
• Blackfoot Disease
• Inorganic forms usually considered more toxic
• Arsenite considered more toxic than arsenate
• Health effects depend on quantity and length of
  exposure

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RegulationsThe New Arsenic Rule
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Old Regulations

• Applies only to CWS
• MCL 0.050 mg/L
• MCLG 0 mg/L
• Health effects language required on CCR if gt0.025
  mg/L

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1996 SDWA Amendments

• Requirement for EPA to revise existing arsenic
  MCL taking into account
• Public health
• Available treatment technologies including small
  systems
• Regulatory costs and benefits
• Must conduct reviews of MCL every 6 years

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History of New Arsenic Rule

• June 2000 0.005 mg/L proposed by EPA w/comments
  on 3, 5, 10, 20 ug/L
• January 2001 New standard published with MCL
  0.01 mg/L
• March 2001 Standard withdrawn for review
• October 2001 New standard established with MCL
  0.01 mg/L

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Key Reports Used By EPA

• National Academy of Sciences (NAS)
• Health effects and risks
• National Drinking Water Advisory Council (NDWAC)
• Cost of compliance
• EPA Science Advisory Board
• Benefits analysis

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The New Arsenic Rule

• Applies to CWS and NTNCWS
• MCL 0.01 mg/L
• MCLG 0 mg/L
• New CCR requirements
• New MR requirements
• Best available technologies (BATs) identified,
  but not a requirement to meet MCL

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The New Arsenic Rule (Cont.)

• No small system variances
• Extended date of compliance to 2006
  (typically 3 years from ruling)
• Clarifies procedures for determining compliance
  with MCLs for IOCs, SOCs, and VOCs
• Revision to approved test methods
• Estimated 2,300 CWS and 1,100 NTNCWS affected by
  new MCL

20
CCR Requirements

• ES Educational Statement
• HE Health Effects Language

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CCR Educational Statement

• While your drinking water meets EPAs
  standard for drinking water, it does contain low
  levels of arsenic. EPAs standard balances the
  current understanding of arsenics possible
  health effects against the costs of removing
  arsenic from drinking water. EPA continues to
  research the health effects of low levels of
  arsenic, which is a mineral known to cause cancer
  in humans at high concentrations and is linked to
  other health effects such as skin damage and
  circulatory problems.

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CCR Health Effects Statement

• Some people who drink water containing
  arsenic in excess of the MCL over many years
  could experience skin damage or problems with
  their circulatory system, and may have an
  increased risk of getting cancer.

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Monitoring Requirements

• Must monitor at each entry point in the
  distribution system (State has discretion)
• Monitoring requirements vary for groundwater and
  surface water systems
• States can issue monitoring waivers under the new
  rule

24
Groundwater Monitoring Requirements

• Initial monitoring - One sample between 2005 and
  2007
• Reduced monitoring - If initial monitoring below
  MCL, must collect one sample every three years
• Increased monitoring If initial monitoring
  exceeds MCL, must collect quarterly samples at
  that sampling point until consistently below MCL
• Waiver Must conduct a minimum of 3 rounds of
  monitoring with levels below 10 µg/L

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Surface Water Monitoring Requirements

• Initial monitoring - One sample in 2006
• Reduced monitoring - If initial monitoring below
  MCL, must collect annual samples
• Increased monitoring If initial monitoring
  exceeds MCL, must collect quarterly samples at
  that sampling point until consistently below MCL
• Waiver Must conduct a minimum of 3 rounds of
  monitoring with levels below 10 µg/L

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Approved Test Methods

• EPA 200.7 and SM 3120B (ICP-AES) have been
  withdrawn due to high detection limits

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Best Available Technologies
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Critical Deadlines
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Water Management Options
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Management Options

• Consider water management options before assuming
  treatment is necessary!!
• Options include
• Identify new water sources
• Well modification
• Operational strategy changes
• Blending of existing source waters

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Well Modification

• Aquifer formation
• Well construction
• Varying As concentrations

• Apache Junction, AZ Arsenic was
  concentrated at the bottom of the wells

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Spinner Logging
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Apache Junction Options

• Arsenic treatment
• New wells
• Alternate water source

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Aquifer Evaluation

• Wells into deeper confined aquifer and shallow
  unconfined aquifer
• Test well constructed to determine arsenic
  concentrations in different aquifers
• New wells in shallow aquifer

• Vale, OR Arsenic was 50 ppb in the lower
  confined aquifer and below the 10 ppb limit in
  shallow aquifer

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Operational Strategies

• Use impacted wells for non-potable uses
• Reduce potable water demands

36
Blending of Source Water

• Blending is an acceptable option assuming the
  customer has no possible chance of receiving
  unblended water
• Consider other water quality issues

• Edwards AFB Modifications to distribution
  system and controlled blending of source water
  avoided over 8 million in As treatment costs

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Treatment
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Factors in Selecting Treatment

• Existing treatment processes
• Water quality and chemistry
• Type of arsenic
• Bench/pilot testing results
• Capital and OM costs

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Pre-Oxidation

• Convert As3 to As5 for more effective treatment
• Oxidizers
• Cl2 (must consider DBP formation)
• KMnO4
• O3
• H2O2

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Treatment Options

• Activated Alumina (AA)
• Coagulation/Microfiltration (C/MF)
• Electrodialysis Reversal (EDR)
• Ion Exchange (IX)
• Reverse Osmosis (RO)
• Granular Ferric Hydroxide (GFH)

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Activated Alumina
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Activated Alumina (AA)
AA is an extremely porous media that removes
arsenic and other contaminants through adsorption
HAsO42-
AA
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• Activated Alumina

• Activated by passing oxidizing gases through
  aluminum ore at extremely high temperatures
• Forms
• Granule
• Powder
• Pellet
• Selection based on contaminants and
  manufacturers recommendations

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Factors Affecting Adsorption

• Physical properties of the media
• Raw material used
• Method of activation
• Pore size distribution
• Surface area
• Chemical/electrical nature of the media
• Exposure time

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Factors Affecting Adsorption (Cont.)

• Flowrate
• Chemical composition of the water
• Concentration of competing ions
• Size/similarity of compounds
• Temperature/pH
• Adsorption usually increases as temperature and
  pH decrease

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Selectivity sequence for the removal of arsenic
with AA at a neutral pH
Arsenic Removal with AA
OH- gt H2AsO4- , H2PO4- gt H3SiO4- gt F- gt gt SO42-
gt gt HCO3-, Cl- gt NO3-
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Advantages

• Well established technology
• Improves taste and odor

Disadvantages

• Requires pH adjustment and post-treatment
  corrosion control for effective arsenic removal
  (pHlt6)
• Bacteria may grow on alumina surface
• Requires careful monitoring

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Regeneration of Media

• Disposable AA
• Non-hazardous waste landfill
• Regenerated AA
• Acid addition for precipitation of
  aluminum-arsenic solids, dewatering, disposal by
  non-hazardous landfill
• Disposal of regenerant may be difficult
• Regenerant handled by evaporation ponds or sewer
• May be considered a hazardous waste
• Regeneration is incomplete (50 - 70)
• Usually cheaper to replace the media than
  regenerate

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Coagulation/Microfiltration(C/MF)
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Process Description

• Chemical/physical process consisting of
  chemical addition, rapid mix, coagulation,
  flocculation, and microfiltration

Coagulant
Product
Feed
Rapid Mix/Clarifier
Microfilter
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Process Description

• Not listed as an EPA BAT for arsenic removal due
  to limited full-scale operation history
• Clarification requirements vary significantly
• Bench/pilot testing highly recommended

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Microfiltration

• Hollow-fiber membranes
• Fully automated
• On-line integrity testing
• Backwash (1/hr)
• Chemical cleaning (1/mo)

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Advantages

• Generally low capital and OM costs for large
  systems
• Proven and reliable

Disadvantages

• Produces high sludge volume
• Requires operator care with chemical usage
• High or low pH reduces treatment efficiency

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Coagulants

• Ferric Chloride
• May cause corrosion
• Some As-removal pilot studies show problems with
  clogging of microfiltration membranes
• Ferric Sulfate
• Typically more effective for As removal

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Electrodialysis Reversal (EDR)
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Process Description

• EDR is an electrochemical process in which
  ions migrate through an ion-selective
  semi-permeable membrane as a result of their
  attraction to the electrically charged membrane
  surface

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Review of Water Chemistry
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Electrodialysis (ED)
Feed Water
A
A
C
C
Cathode (-)
Anode ()
Reject
Reject
A Anion Transfer Membrane
Product
C Cation Transfer Membrane
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Electrodialysis Reversal (EDR)
Feed Water
A
A
C
C
After Polarity Reversal
Cathode (-)
Anode ()
Reject
Reject
Feed Water
Product
A
A
C
C
Before Polarity Reversal
Cathode (-)
Anode ()
Reject
Product
Product
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ED/EDR

• Removes ions from water - it does NOT remove
  uncharged molecules (i.e., suspended solids,
  microorganisms, etc.)
• Configuration
• Plate and frame
• Operating pressure 40 psi
• EDR can operate without fouling or scaling
  (self-cleaning, low OM requirements)

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Advantages

• Reduces TDS
• Can operate without fouling or scaling
  (self-cleaning, low OM requirements)
• Low pressure requirements
• Long membrane life

Disadvantages

• Can be energy intensive
• High volume of waste (15-25)
• Does not remove suspended solids

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OM Issues

• Requires occasional chemical cleaning
• Can be taken apart and cleaned
• May require antiscalants or acid addition at
  higher TDS
• Prefilters required for suspended solids (10µm)

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Ion Exchange (IX)
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Process Description

• IX is a reversible process in which ions
  from an insoluble resin bed are exchanged for
  ions in the water

H2AsO4-
IX
Cl-
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Advantages

• Ease of operation, highly reliable
• Resins will not wear out with regular
  regeneration
• Suitable for small and large installations

Disadvantages

• Requires salt storage and regular regeneration
• Strongly basic anion exchange resins susceptible
  to organic fouling
• Waste disposal may be an issue

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Selectivity sequence for the removal of arsenic
with anion exchange at a neutral pH
Arsenic Removal with Anion Exchange
SO42- gt HAsO42- gt NO3- gt Cl- gt HCO3- gt F- ,
H3SiO4-
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Regeneration

• Regenerate with NaCl or KCl solution
• Brine recycle can minimize waste

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Reverse Osmosis(RO)
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Process Description

• Physical process in which contaminants are
  removed by forcing water through a semipermeable
  membrane

Membrane
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Membrane Schematic
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Natural Osmosis
Posm
Osmosis
Salt Water
Pure Water
Salt Water
Pure Water
Semi-PermeableMembrane
Semi-PermeableMembrane
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Reverse Osmosis
Pressure
ReverseOsmosis
Salt Water
Pure Water
Salt Water
Pure Water
Semi-PermeableMembrane
Semi-PermeableMembrane
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Advantages

• Produces highest arsenic removal and highest
  quality water
• Provides a barrier for microorganisms

Disadvantages

• May require significant pretreatment
• Relatively expensive to install and operate
• Requires frequent monitoring and maintenance
• Chemically sensitive
• Pressure, temperature, and pH requirements

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OM Issues

• Biofouling
• Scaling
• Requires chemical cleaning
• Extensive monitoring
• Performance tracking

75
Large-Scale RO
Yuma Desalting Plant 70 MGD RO Plant
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Granular Ferric Hydroxide(GFH)
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Granular Ferric Hydroxide (GFH)

• Promising emerging technology
• 3 to 10 times more efficient than AA
• Good As capacity at neutral pH
• Adsorbs As V and As III
• 20 plants in Europe
• Other granular ferric media being developed

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Alternative Treatment Methods
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Alternatives

• Oxidation/Filtration (Greensand)
• Zeolites
• Iron-doped alumina (Alcan FS50)
• Sulfur modified iron
• Other proprietary media

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Point of Use/Point of Entry (POU/POE)
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POU/POE

• POU
• Treatment at the tap
• AA and RO

• POE
• Whole house treatment
• AA and IX

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Issues to Consider for POU/POE

• Access for routine maintenance
• Requires extensive record keeping
• May require increased monitoring to ensure
  compliance
• Does not reduce need for well-maintained
  distribution system
• Can not delegate responsibility to the customer
• Breakthrough issues

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QuestionsandComments