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
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.
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.