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Luminescent Dissolved Oxygen LDO Measurements for Wastewater Applications

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Winkler Titration (1888) EPA Method 360.2. Membrane Electrodes (1959) ... Lower Day-to-Day Cost than Winkler Titration. Luminescent Dissolved Oxygen (LDO) Cons ... – PowerPoint PPT presentation

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Title: Luminescent Dissolved Oxygen LDO Measurements for Wastewater Applications


1
Luminescent Dissolved Oxygen (LDO) Measurements
for Wastewater Applications
  • Edward C. Craig, Ph.D.
  • Cary B. Jackson, Ph.D.
  • Christopher P. Fair
  • Hach Company
  • Loveland, CO

2
Purpose of this Talk
  • Discuss our effort to add Luminescence (LDO) to
    the List of EPA Approved Methods for Dissolved
    Oxygen Measurements
  • Proposed EPA Method 360.3

3
Specifically
  • Discuss our In-House Preparation for a External
    Nationwide Validation Study run as Part of a Tier
    3 EPA Approval Process for the Luminescence
    Method
  • Also share some of the results from the External
    Validation Study

4
Current EPA Approved Methods for Measuring
Dissolved Oxygen Conc.
  • Winkler Titration (1888)
  • EPA Method 360.2
  • Membrane Electrodes (1959)
  • EPA Method 360.1

5
Winkler Titration
  • L.W. Winkler, The Determination of Dissolved
    Oxygen in Water, Ber. Deut. Chem. Ges., 21, 2843
    (1888)
  • EPA Reference Method for Dissolved Oxygen
    Measurement

6
Winkler Titration Reactions
7
Winkler Method Floc Formation
8
Winkler Method - Titration
9
Winkler Titration
  • Pros
  • Direct DO Measurement
  • Easy Clean-up
  • Cons
  • Samples must be Analyzed in a Laboratory
  • Subject to Several Chemical Interferences
  • Very Technique Sensitive

10
Membrane Electrode
  • L.C. Clark
  • Clark Cell
  • Patent Nov. 19, 1959

11
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12
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13
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14
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15
Membrane Electrode
  • Pros
  • In-situ Measurements Possible
  • Easy to Make Measurements
  • Cons
  • Frequent Maintenance Required
  • Must be Polarized Before Use
  • Must be Calibrated Before Use
  • Consumes Oxygen
  • Very Sensitive to Sample Flow

16
Luminescent Dissolve Oxygen (LDO)
  • Completely New Technology
  • Measures the Quenching of a Luminescent Reaction
    caused by Oxygen

17
Luminescent Dissolved Oxygen (LDO) - Probe
18
Luminescent Dissolved Oxygen (LDO) Probe
Components
19
Luminescent Dissolved Oxygen (LDO)
Probe
Photo Diode
LED
LED
20
Luminescent Dissolved Oxygen (LDO)
Probe
Sensor
Photo Diode
LED
LED
21
Luminescent Dissolved Oxygen (LDO)
22
Luminescent Dissolved Oxygen (LDO)
  • Pros
  • No Maintenance
  • Field Measurements Possible
  • No Polarization
  • Insensitive to Sample Flow
  • Rugged

23
Luminescent Dissolved Oxygen (LDO)
  • Pros (cont.)
  • Accurate
  • Precise
  • Very Stable Calibrations
  • No Chemical Interferrents
  • Lower Day-to-Day Cost than Winkler Titration

24
Luminescent Dissolved Oxygen (LDO)
  • Cons
  • Higher Initial Cost than Winkler Titration
  • Not Currently EPA Approved

25
Process LDO
  • Cost Savings
  • Electricity, Labor, and Chemicals
  • John Anderson
  • City of Longmont, WWTP Superintendent

26
Process LDO Longmont WWTP
  • Savings Over 3 Month Period
  • Electricity ( 28,000)
  • Labor ( 15,000)
  • Chemicals ( 36,000)
  • Total Savings ( 70,000)

27
External Validation Study
  • 12 Wastewater Laboratories Nationwide
  • Accuracy Precision (IPR)
  • Method Detection Limit (MDL) Determn.
  • 5 Day BOD
  • Side-by-side Comparisons with Other DO Methods

28
In-House Preparation for External Validation
Study
  • Preparation of Replicate DO Standards
  • Shelf-Life Experiment
  • Shipping Experiment
  • Ruggedness Testing
  • Use Model Comparisons
  • Accuracy Precision Determinations
  • MDL Determination
  • BOD5 Demonstration
  • Side-by-side Comparison with Other Methods

29
Accuracy Precision Determinations
30
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31
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32
Percent Recovery at 1.69 mg/L
33
Percent Recovery in Air-saturated Water
34
LDO Histogram Air-saturated Water
35
MDL Determination
36
LDO In-House Method Detection Limit
37
Pooled MDL and ML Results (mg/L)
38
BOD5 Demonstration
39
BOD5 Comparison
40
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41
Method Comparison DO Measurements Influent and
Effluent Samples from 12 Different Wastewater
Facilities
42
Whats Next?
  • Report for External Validation Study has been
    submitted to EPA
  • Next the results are opened to the public for
    Review and Comments ( 3 mo.)
  • Expect Full EPA Approval in 12 to 18 months
  • Currently Partitioning EPA for Provisional
    Approval (6 to 12 mo.)
  • Soliciting/Helping WW Labs seeking Tier 1
    Approvals

43
Contacts
  • Edward C. Craig, Ph.D.
  • Research Development Chemist
  • ecraig_at_hach.com
  • Cary B. Jackson, Ph.D.
  • Regulatory Chemist
  • cjackson_at_hach.com
  • Christopher Fair
  • Wastewater Applications Chemist
  • cfair_at_hach.com
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