3.2 Measurement Of Oxygen Transfer
Determination of DO concentrations in the different areas of the test tank is accomplished by means of four Yellow Springs Instruments YSI 52 membrane DO probes. Precision, accuracy and response time of such probes is adequate for the application of the testing method used.
Location of DO probes in the test volume is represented in the attached drawing (Figure 3).
Such distribution has been adopted to ensure good sampling of the test contents and representativity of the data collected.
Calibration of probes was done by comparison with an independent DO measurement method (Winkler method).
Winkler tests for probe calibration were conducted in ATC´s facilities just beside the test tank.
At the beginning of each test day, three water samples from the saturated test water were and analysed for Dissolved Oxygen concentration. The average of the three determinations was used to calibrate probes.
Data registration was done automatically connecting all probes to a laptop computer, and readings of the DO v/s time data points were taken at variable time intervals depending on the specific requirements of each test.
The interval between readings was adjusted so that between 50 and 100+ data points were obtained for each test run.
3.3 Data Analysis
The data collected from each test is prepared for analysis following the truncation criteria contained in the applied standard and is analysed for Kla and C* values using the non linear regression method.
Parameter values for each individual probe and test run are obtained and usedfor system performance calculations.
Kla and C* values are corrected tostandard temperature and pressure conditions using the expressions includedin the applied standard and SOTE (Oxygen Transfer Efficiency at 20ºC, 1 atm) values are then calculated
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