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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 measurement 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
x
Θ
(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 (see Method Configuration in SOUR Setup).
Before starting a SOUR measurement remember to set the SOUR configuration from the setup menu
and make sure the has been calibrated in DO mode.
To measure the
SOUR
of a sample:
• Press
and then
to select SOUR
measure mode.
• Place calibrated probe into sample.
• Press
to start taking the measurement.
• At the end of the measurement the meter will display
the computed SOUR value, the duration of the mea-
surement and the pressure and temperature values.
SOUR MEASUREMENT
