Dissolved Oxygen Measurement Essay

4915 Words Jul 8th, 2014 20 Pages
Chapter 4

Dissolved Oxygen Measurement


Section 1: Dissolved Oxygen (DO) Introduction 2
Section 2: Glossary 2
Section 3: Approved Methods 3
Section 4: Safety and Hygiene 3-4
Section 5: Sampling 4-5
Section 6: Effects of Temperature on DO 5
Section 7: Interpretations 5
Quiz 4.1 6
Section 8: Modified Winkler Method 6-9
Quiz 4.2 9
Section 9: The Electrometric Meter Method 9-11
Quiz 4.3 12
Section 10: QA/QC 12
Answers to Quizzes 13-14
Appendix A: References
Appendix B: Dissolved Oxygen Reagents
Appendix C: Sample Bench Sheets

Chapter 4



The DO determination measures the amount of dissolved (or
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Section 2: GLOSSARY

Aerobic: A condition in which “free” or DO is present in an aquatic environment.

Anaerobic: A condition in which “free” or DO is not present in an aquatic environment.

Indicator solution: A solution used to determine the endpoint (usually a color change) when titrating.

Titrate: To titrate a sample, a chemical solution of known strength is added on a drop by drop basis until a color change, precipitate or pH change in the sample is observed.



Remember, always refer to your NPDES Permit and 40 CFR Part 136 for approved methods.

The 18th Edition of “Standard Methods for the Examination of Water and Wastewater” includes two methods for the determination of DO in wastewater, including the Winkler method (azide modification) and the electrometric method using membrane electrodes and a DO meter.

The Winkler method is based on the ability of the DO in a sample to oxidize chemicals added to the sample. The azide modification of the Winkler method was developed to correct for the presence of nitrites in a sample. These compounds, found in almost all wastewater samples, interfere with the other modifications of the Winkler procedure.

The membrane electrode procedure utilizes a meter and electrode, and is based on the rate at which oxygen molecules diffuse (or pass through) a membrane covering a set of electrodes. The oxygen

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