WATER QUALITY - Equipment--Dissolved oxygen meters


                                      March 11, 1969

QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM N0. 69.04

To      Regional Hydrologists and District Chiefs, WRD

From:   Chief, Quality of Water Branch, WRD

Subject: WATER QUALITY - Equipment--Dissolved oxygen meters

During the past year this office has received numerous 
requests concerning the reliability under field conditions of 
various dissolved oxygen (DO) meters. Several memoranda from 
headquarters, including WRD Memorandum 68.41, September 8, 
1967, and QW Branch Technical Memorandum No. 68.02, 
September 26, 1968, have emphasized the importance of 
increased WRD activity in dissolved oxygen studies as part of 
the regular operational program.

As part of a major effort to maintain and improve quality 
control for data, the Harrisburg office agreed to conduct an 
evaluation of field DO methods using the most recent DO 
meters compared against standard tests. The enclosed progress 
report, "Field Measurement of Dissolved Oxygen," by Kenneth 
F. Williams, WRD, Harrisburg, Pa., evaluates under a wide 
variety of field conditions the Winkler method (azide
modification), membrane method, and dropping-mercury method, 
the three most widely-used methods in WRD programs.

The short-term test was designed to give a working set of 
comparative data under a wide variety of field conditions. 
This was accomplished, although other types and models of 
equipment planned for testing were not available or the 
equipment failed to function properly.

The present study shows the membrane method as giving the 
best overall performance. Results are accurate, calibration 
is required only infrequently, minimum time is needed for 
analysis, sample collection is generally unnecessary, no 
reagents are required, and the meters are relatively 
inexpensive. The Yellow Springs Instrument, Model 54 
Dissolved Oxygen Meter tested in this study was found to be 
compact, rugged and convenient to use. Within the limits of 
the test and subject to endorsement by the Methods 
Development Unit and the QW Advisory Staff this unit is 
recommended for current purchases.

We welcome comments on the progress report.


                                      W. H. Durum

Attachment

WRD Distribution:
A (Regional Hydrologists only)
FO-LS