76    APPLICATION OF OXYGEN UPTAKE RATE IN MANAGING
AN ACTIVATED SLUDGE PROCESS FOR TREATING
REFINERY WASTEWATER
Mao-Yuan Tur, Chemical Engineer
Ling-Ling Tseng, Chemical Engineer
Ming-Shean Chou, Group Leader
Hung-Yuan Fang, Department Manager
John Hsia, Center Director
Environmental Engineering Department
Refining & Manufacturing Research Center
Chinese Petroleum Corporation
Chia-Yi, Taiwan
Republic of China
INTRODUCTION
Activated sludge process is widely used for treating industrial organic wastewaters. Adequate
managements in operating the biotreatment system are practically necessary to maintain the desired
performance efficiency. Two measurable parameters, specific sludge activity and food-to-
microorganism ratio (F/M), are currently adopted as important monitoring parameters. These two
parameters are based on microbial activity and closely related. Among the various indications of
sludge activities, the specific oxygen uptake rate (SPOUR) was shown to be more accurate and
sensitive than the specific dehydrogenase activity and the specific adenosine triphosphate content,1
and seemed to be a very promising one.2"7 An important advantage of using SPOUR for process
monitoring is its marked response to any disturbances caused by fluctuating influent organic loading
and the presence of toxic substances. Duggan and Cleasby8 reported that SPOUR increased with
increasing BOD loading in an activated sludge sewage treatment process. Besides, Thibault and
Tracy9 showed that SPOUR reflected immediately upon the presence of various shocked loadings in a
pilot study of a typical refinery wastewater treatment. Thus, SPOUR could be regarded as an early
warning of an abnormal operation. This would give the operator some time to restore the treatment
system by, for example, bypassing the flow to be treated at the side stream, or increasing air flow rate
to the aeration basin, or adjusting the sludge discharge and recycle ratio.
However, the limitation on the instantaneous measurement of mixed liquor volatile suspended solid
(MLVSS) makes it difficult to estimate both SPOUR and F/M in time. Apparently, this limitation
would make both parameters not so promising even in a slow-growing activated sludge system.
Hence, oxygen uptake rate (OUR), rather than SPOUR, is considered as a more practical and suitable
monitoring parameter in management or control sense, despite OUR is not an exact bioactivity
indicator.
Because of the inherent validity of OUR in an activated sludge process, monitoring system including measurements of OUR, flowrate, and influent soluble organic concentrations was investigated to
study the feasibility of its application to process control. Objectives of this research are: 1) to find a
method for rapidly obtaining the proposed management parameter, Fr/Mr (oxygen uptake equivalent
F/M) from the monitoring system; 2) to find the correlations between F/M, influent soluble organics
concentrations (sTOC, sCOD) and Fr/Mr in pseudo-steady states; and 3) to trace responses of OUR/
sTOC (OUR/sCOD) to various shocks.
PROPOSED MONITORING SYSTEM
The proposed monitoring system is shown in Figure 1. The system includes three major parts, i.e.:
1) measurements of influent flowrate (Q), influent soluble chemical oxygen demand (sCOD), and
44th Purdue Industrial Waste Conference Proceedings, C<   1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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