Oxygen Utilisation Rate
The University of Cape Town developed a dissolved
oxygen utilisation meter for use in the testing
and monitoring of oxygen levels in water.
Hitech is licenced to manufacture this unit by
the University of Cape Town.
.....more info here.
An instrument for the direct determination of
oxygen utilisation rate
ISSN 0378-4738=Water SA Vol.
17 No.1, January 1991
EW Randall, A Wilkinson, GA Ekama
University of Cape Town
, Rondebosch 7700, South Africa
Dept of Chemical Engineering
Dept of Electrical Engineering
Dept of Civil Engineering
An instrument which completely automates oxygen
utilisation rate (OUR) determination in aerobic
biological reactors is described. It
controls the dissolved oxygen (DO) concentration
between specified upper and lower limits with an
on-off solenoid valve in the air supply line and
computes with a microprocessor the OUR from the
DO versus time curve during the air-off period.
In addition to operating as a standalone DO meter
or DO controller/OUR meter, it can be linked to a
host computer (PC) for transfer of the
accumulated OUR data for further processing or
complete control of the instrument via PC
The oxygen utilisation rate (OUR) is an important
indicator of biological activity in activated
sludge reactors; indeed in research at the
University of Cape Town , the OUR has formed
the primary parameter for delineating the
kinetics of the activated sludge process (Dold et
al, 1980; Dold and Marais, 1986; Ekama,
Johnston and Buhr (1982) developed a simple
electronic DO controller instrument which
simplified OUR measurement in aerobic biological
reactors. The electronic controller unit
coupled to a DO meter with probe controlled the
air supply with an on-off solenoid valve in such
a way that the reactor was aerated intermittently
to control the dissolved oxygen concentration
(DO) between specified upper and lower limits.
A DO versus time trace was made on a strip chart
recorder connected to the DO meter and the rate at
which the DO decreased with time during the
air-off periods gave the biological oxygen
utilisation rate (OUR); this was calculated
manually from the slope of the DO-time trace.
[This method gives accurate estimates of the
biological OUR only for reactors with long actual
hydraulic retention times (> 3 h); for short
actual hydraulic retention time reactors (< I
h) e.g. the contact reactor of the contact
stabilisation system or aerobic selectors, the DO
concentration-time slope needs to be adjusted to
take account of the gains and losses of DO in the
influent and effluent flows to obtain the
biological OUR (Ekama and Marais, 1979)].
This paper describes an instrument that
completely automates OUR measurement. The
calculated OUR values may be viewed on a digital
display and are stored in a memory. The
instrument may be optionally linked to a personal
computer (PC) to transfer the stored data to disk
files. The PC may also control the
instrument's input/output (1/0) functions in
order to implement alternative OUR determination
.....more info here (Basic).
.....more info here (Advanced).