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Adsorption PreTreatment Considerations EPA Workshop on the Design and Operation of Adsorption Media

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Title: Adsorption PreTreatment Considerations EPA Workshop on the Design and Operation of Adsorption Media


1
Adsorption Pre-Treatment Considerations EPA
Workshop on the Design and Operation of
Adsorption Media Processes for the Removal of
Arsenic from Drinking WaterAugust 10-11, 2004
  • Greg Gilles
  • Vice President
  • AdEdge Technologies, Inc
  • Atlanta, Georgia
  • 678-835-0052
  • greg_at_adedgetechnologies.com

2
Topics
  • Importance of Pre-Treatment
  • Common Interferents for Adsorption
  • Pre-Treatment Technologies and Project Examples
    for
  • Suspended solids, Sediment
  • Iron, manganese, sulfides
  • High pH
  • Organics, Tannins
  • Bacteria and Biofilms

3
Why Pre-Treatment?
  • Preserves the media for intended purpose
  • Prevents premature exhaustion of media
  • Reduces affects of interferents that can blind
    adsorption sites or foul media
  • Prevents blocking of pore based adsorption sites
    where 90 of adsorption takes place
  • Lowers long-term operation and maintenance costs
  • Improves aesthetics of water (e.g., Secondary
    MCL)
  • Attainment of lower arsenic effluent levels ltlt10
    ppb

4
  • Be aware that some parameters can place too heavy
    a burden on the mediabeyond its intended purpose
  • Dont just consider the obvious
  • Be sure youre awake when designing adsorption
    systems

5
Accessible area of Granular Media
As
Diffusion
200-300 m2/g
gt 99 of surface for removal is internal
Source M. Edwards June, 2003
6
Common Myths
  • I can effectively use my media bed as a filter
    for other contaminants and backwash when needed
  • Specialty adsorption medias can remove multiple
    contaminants in addition to arsenic with equal
    effectiveness without negative consequences
  • Naturally occurring iron is always beneficial in
    arsenic adsorption processes since iron has an
    affinity for arsenic
  • All medias are affected similarly by interferants
  • pH adjustment for high pH waters will always be
    the most economical or preferred approach

7
Pre-Treatment Considerations begin in the design
stage with understanding of the site specific
water chemistry
8
Most Important Water Parameters
9
Parameters for Pre-Treatment
  • Suspended solids / sediment
  • Iron and/or manganese
  • High pH
  • Sulfides
  • Organics, Tannins
  • Bacteria, Biofilms

10
Common Pre-treatment Scenarios
11
Project Examples and Field Applications
12
Well Pump 2
13
Rollinsford, New Hampshire
  • EPA Demo Site
  • 100 gpm system
  • pH 8.4 typical
  • pH adjustment with CO2 gas
  • 58,000 gallons/day
  • Arsenic influent 40-50 ppb
  • Operational Jan, 2004

14
pH Adjustment Using CO2(Rollinsford, NH)
Gas Injection point
  • 100 gpm flow rate, 12 hours/day
  • (3) 50 lb gas cylinders on-line
  • Delivery pressure approx. 100 psi
  • 2-4 scfh injection rate through CO2 membrane
  • pH monitoring probe and control panel
  • CO2 cylinder change-out approx every 3 weeks

15
Membrane based CO2 Injection for pH Adjustment
  • Has some advantages over acid
  • Health and safety
  • Low operating costs
  • Rapid pH adjustment with very short contact time
  • Higher initial capital cost
  • Requires monitoring system for control and
    measurement
  • Natural de-gassing after treatment raises pH
  • Depending on water quality, probes and membrane
    may require periodic cleanings

16
Oxidation of As(III) to As(V)
17
IronFriend or Foe?
  • Arsenic has a natural affinity for iron
  • Naturally occurring iron in water can be
    maximized in design to help reduce arsenic
    efficiencies vary by process and water chemistry
  • Iron can foul / plug adsorption and many
    processes and therefore pretreatment is
    recommended above certain thresholds
  • Combination of iron pretreatment and adsorption
    polishing is ideal for effectively reducing
    arsenic to meet MCL

18
Iron / Arsenic RemovalOne must understand the
water chemistry and limitations of the specific
media to be able to determine or predict
long-term affects on performance
19
Factors to Consider
  • What are the treatment goals?
  • The concentration of iron and manganese
  • Oxidation state
  • pH, Alkalinity, and Hardness
  • Dissolved oxygen for some treatment types
  • Presence of iron and manganese bacteria

20
Fe/Mn Treatment Methods
  • Softening
  • Aeration Filtration
  • Oxidation / Filtration Processes
  • AD26 Catalytic Media
  • Mn Greensand with KMnO4 regeneration
  • Pyrolusite
  • Sequestering for Low Concentrations

21
Iron, Manganese Pre-Treatment
  • Softening
  • Only recommended where both iron/manganese and 
    hardness are high
  • Effective for water containing less than 2-4 mg/L
    of dissolved colorless iron or lt 0.5 mg/L
    manganese
  • Adds sodium to the drinking water and  creates
    brine disposal problems.
  • No arsenic removed
  • Oxidation / Filtration Removal
  • Media and non-media based options
  • pH value is important
  • Best results with chemical oxidants e.g., Cl2 or
    KMnO4
  • Contact time
  • Aeration can be used rather than chemicals
  • Greensand with KMnO4
  • pH should preferably be  over 7.5
  • Requires either intermittent or continuous
    regeneration.

22
Project Profile Michigan
  • Elementary School
  • Location Oakland County, Michigan
  • AdEdge APU-40 Adsorption system w/ GFO media
  • Influent Arsenic 37-50 ppb
  • 40 gpm design flow
  • Installation May, 2003
  • Water Conditioning used for Iron and Hardness
    Removal (0.8 mg/L Fe)
  • Effluent arsenic below detection after treatment

23
Project Profile Kenai, Alaska
  • US Fish and Wildlife Service
  • Design flow 50 gpm
  • Location Kenai, Alaska
  • Influent Arsenic 51 ppb
  • Installation March 21, 2003
  • 26 cubic feet Adsorption Media
  • Iron 2.6 mg/L using softening system
  • pH 7.3 
  • Effluent lt 2 ppb As

24
Pilot Nursery Site, Florida
  • AdEdge AD33 Pilot
  • 2 gpm flow rate
  • EBCT of 7.5 min/vessel
  • (2) 12-in vessels in series
  • Iron 1 1.5 mg/L
  • pH approx 7.1
  • 5-micron prefilter
  • Arsenic influent 1.5 2.2 mg/L
  • Treatment goal 0.250 mg/L
  • Continuous operation 24 hr, 7 day/week

25
Arsenic / Iron Treatment
26
AD26 Pre-Treatment Systems
  • Oxidation / Filtration Process
  • Designed for Iron, Manganese and Sulfide low
    level arsenic removal to meet MCLs
  • Utilizes catalytic MnO2 solid media for efficient
    removal of Fe, Mn and co-precipitation of As
  • Stand alone or used as pre-treatment for E33
    based Systems
  • Used most efficiently with hypochlorite addition
  • Media lasts 5 years or more, no regeneration,
    only backwash (1-3x/week)

27
Treatment Selection Co-occurrence of As and Fe
and removal to meet 10 ug/L MCL
60
  • Selection Criteria
  • As
  • Fe, Mn
  • pH
  • Silica
  • TOC
  • Hardness, Alk
  • Space
  • Operator time
  • Chemicals
  • Backwash options
  • Efficiency

AD26 OXIDATION / FILTRATION SYSTEM
ADSORPTION POLISHING
50
45
40
FeAs ratio 201
35
FeAs ratio 301
30
Arsenic Concentration ug/L
ADSORPTION BAYOXIDE E/AD33
25
20
15
AD26 OXIDATION / FILTRATION SYSTEM (optimized for
arsenic removal)
10
5
2000
1600
1800
800
1200
1400
200
400
600
1000
100
Iron Concentration ug/L
28
World War II Memorial SiteWashington, DC
  • Groundwater Treatment
  • (2) 30 gpm AD26 and (2) Sorb 33 Systems
  • Contaminants Iron, Manganese, and Arsenic
  • 20 below grade in vault beneath monument
  • Arsenic influent 20-60 ppb
  • Iron 0.5 10 ppm
  • Mn 0.05 2 ppm
  • 2 ppb treatment limit
  • Operational June, 2004
  • Operated by National Park Service

29
Process Flow Diagram AdEdge Arsenic Reduction
System System with Iron / Manganese Pretreatment
Feed water
Fe / Mn Module (twin vessel typical)
Adsorption Module
Sample
Strainers
Automated valve Package
Automated valve Package
FQI
FI
PDG
PDG
PDG
Backwash
Backwash
Feed
Feed
Chlorine injection
Treated Water
Well Pump
To Storage or Distribution
A
B
Backwash water
Battery Limits
Battery Limits
Sample /Drain
30
Project Profile Alaska
  • Commercial System
  • Location Yakatat, Alaska
  • Arsenic 80-90 ppb
  • 25 gpm System serving regional airport
  • Installed May, 2002
  • 20 cubic feet AD33 Adsorption Media
  • Pre-Treatment Ozone pretreatment for Fe, Mn, and
    bacteria GAC, Softening
  • Effluent arsenic - Non detect

31
Pre-Treatment Backwashing
  • Removes co-precipitated iron, manganese and
    arsenic particulates that are filtered
  • Often performed at differential pressure set
    points or manually
  • Performed typically 1-3x/week depending on water
    profile
  • Rates from 8-25 gpm/sq foot for various products
  • Non-hazardous water can be discharged to POTW,
    septic in most cases

32
Sequestering Agents
  • Polyphosphate based products or others
  • Complexes / chelates iron
  • Reduces or interferes with adsorption processes
    (phosphate interference)
  • If used, inject after the treatment system to
    avoid negative impact to adsorption media

33
Sulfides
  • Sulfides can bind with media
  • Sulfides act as an interferent and/or competitor
    for adsorption sites on iron-based medias form
    low solubility precipitants as well
  • H2S result often of bacterial reduction of SO4
    detected at levels around 0.05 mg/L
  • Obvious aesthetic issues
  • Co-occurrence with iron, As (III), reducing
    conditions

34
Organics
  • Naturally occurring organics from decay of plant
    material
  • Humic and other types of organic acids
  • Not much study on the affects to adsorption
    medias
  • More often issue in surface water rather than
    groundwater
  • Oxidation using Chlorine, ClO2, Ozone are common
    methods of destruction
  • IX resins are available for Tannin removal

35
Biofilms and Biofouling
  • Heterotrophic plate count bacteria are ubiquitous
    in water systems
  • Mostly non-harmful and non-pathogenic
  • Can cause fouling and performance issues for
    adsorption systems
  • Less likely in systems using disinfectants
  • System and/or media may require periodic shock
    treatments if accumulations observe
  • Bacteria carry through can bring arsenic or
    other contaminants with it

36
Pre-Treatment Monitoring
  • Sample contaminant of concern after pretreatment
    unit to determine effectiveness
  • Frequency of sampling should be at least as
    frequently as arsenic samples are obtained
  • Field test kits offer rapid methods
  • Be aware of laboratory analyte interferences and
    detection limits

37
Other Pre-Treatment Issues
  • Backwashing water quality and quantity
  • Discharge Options
  • POTW or Septic
  • Filter and/or coagulate and discharge or recycle
  • Evaporation pond
  • Presents some challenges for remote / rural
    systems with no POTW or Septic options
  • Residuals Management (if not direct discharged)
  • Pre-treatment capital costs can be 50 or more of
    adsorption system costs depending on method

38
Conclusions
  • Do your homework up front on the water chemistry
    to avoid surprises
  • If in doubt about the affects on performance,
    consider pre-treatment or piloting
  • The role and benefits of naturally occurring iron
    for arsenic removal to meet the MCL must be
    evaluated on a case-by-case basis and designed
    carefully
  • Pre-treatment cost/benefit ratio must factor in
  • prolonged life of adsorption media
  • Lower life-cycle costs
  • Improvement to aesthetics
  • Consider residuals management for pre-treatment
    scenarios

39
Adsorption Pre-Treatment Considerations EPA
Workshop on the Design and Operation of
Adsorption Media Processes for the Removal of
Arsenic from Drinking WaterAugust 10-11, 2004
  • Greg Gilles
  • Vice President
  • AdEdge Technologies, Inc
  • Atlanta, Georgia
  • 678-835-0052
  • greg_at_adedgetechnologies.com
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