L uminescent D issolved O xygen ( 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

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. Probe Sensor Photo Diode LED LED Clear, Gas Impermeable Substrate Luminescent Indicator Molecules Gas Permeable Polymer Matrix Oxygen 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. 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

26. 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

27. Accuracy & Precision Determinations

30. Percent Recovery at 1.69 mg/L

31. Percent Recovery in Air-saturated Water

32. MDL Determination

33. LDO – In-House Method Detection Limit

34. Pooled MDL and ML Results (mg/L)

35. BOD5 Demonstration

36. BOD5 Comparison

38. Method Comparison – DO Measurements Influent and Effluent Samples from 12 Different Wastewater Facilities

39. What’s 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

40. Contacts… • Edward C. Craig, Ph.D. • Research & Development Chemist • ecraig@hach.com • Cary B. Jackson, Ph.D. • Regulatory Chemist • cjackson@hach.com • Christopher Fair • Wastewater Applications Chemist • cfair@hach.com