User Instructions

47
OUR MEASUREMENT
The Specific Oxygen Uptake Rate (SOUR), also known as the oxygen consumption or respiration rate,
is defined as the milligram of oxygen consumed per gram of volatile suspended solids (VSS) per hour.
This quick test has many advantages: rapid measure of influent organic load and biodegradability,
indication of the presence of toxic or inhibitory wastes, degree of stability and condition of a sample,
and calculation of oxygen demand rates at various points in the aeration basin.
The following equation is used for SOUR determination:
SOUR = OUR / Solids Weight
where:
OUR is the Oxygen Uptake Rate
Solids Weight is the Total solids or the Volatile suspended solids weight in g/L.
Temperature Correction
The SOUR value is corrected to 20 °C (68 °F) according to the Farrel and Bhide equation:
SOUR
20
=SOUR
T
xΘ
(20-T)
Where T is the measured temperature in °C and Θ is a temperature dependent variable:
Θ= 1.05 for T above 20 °C
Θ= 1.07 for T below 20 °C
This calculation is valid only for temperature values in the range 10 to 30 °C. Temperature correction
is performed only if the option SOUR @ 20 °C is enabled.
Before starting a SOUR test remember to set the SOUR configuration from the Setup menu.
Make sure DO probe has been calibrated before using. Clean off probe between samples.
This is an example of possible setting. Follow your normal SOP.
Make sure the DO probe has been calibrated before using. Clean off probe between samples.
Press MODE to select the SOUR measurement mode. Place the calibrated probe into the airtight
container of sample. Stir the sample. Press Start to begin taking measurements.