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Rondebosch 7701

Cape Town  South Africa

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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

Abstract
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 software.  

Introduction
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, 1988). 
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 algorithms.


.....more info here (Basic).

.....more info here (Advanced).



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