Section Sixteen
AEROBIC PROCESSES
55 CHEMICAL ENHANCEMENT AND DEPRESSION
OF OXYGEN TRANSFER IN INDUSTRIAL
WASTEWATERS
Robert C. Backman, Doctoral Candidate
Frederic C. Blanc, Professor Department of Civil Engineering
Northeastern University
Boston, Massachusetts 02115
Frederick J. Siino, Marketing Manager
Mass Transfer Systems, Inc.
Fall River, Massachusetts 02722
James C. O'Shaughnessy, Chairman Department of Civil Engineering
Worcester Polytechnic Institute
Worcester, Massachusetts 01609
INTRODUCTION
The effect of organic and inorganic chemical compounds on oxygen transfer rates has received
considerable attention over the past thirty years. Many of the early studies arose due to the widespread
use of household detergents and their relation to the deterioration of oxygen transfer rates in aeration
systems used in sewage treatment plants. Later studies performed on industrial wastewaters and
synthetic wastewaters showed that, in the presence of certain chemical compounds and hydrodynamic
conditions, the rate of oxygen transfer into bulk solution could either be depressed or enhanced.'-2'3
The on-going research at Northeastern University is being carried out to further define the effect of
various chemical substances on oxygen transfer. Early testing was performed on actual industrial
wastewaters.3 It is the purpose of this paper to present the results of testing oxygen transfer capabilities in the presence of specific organic compounds.
In designing the experiment, the results of past research were carefully considered. Particular
attention was given to scale. The majority of past studies were performed at the laboratory scale, and
it was the intent of this study to perform past experiments at a similar scale and compare results. The
second consideration was to take the study one step further by performing parallel testing at the pilot
scale. Pilot scale testing was performed at power densities (HP/volume) similar to full scale industrial
aeration systems because past research indicates this is the single most important parameter in applying pilot scale data to full scale design.
A third consideration was to evaluate two different aeration devices at both the laboratory and pilot
scale. The purpose for doing so was to compare the effects of chemical substances on hydrodynamic
properties. This phase of the experiment was carried out due to the number of past articles which
indicated that the type of aeration device plays an important role in oxygen transfer. Also, others have
speculated that there is a relationship between the hydrodynamic conditions and chemical composition of the bulk solution on the overall oxygen transfer rate. For this study, jet aerators and fine
bubble dome aerators were used.
OXYGEN TRANSFER THEORY
Among the theories describing gas transfer through the gas/liquid interface, the most widely
accepted theory is "the two film theory", which was postulated by Lewis and Whitman.4 The basic
concept of this theory is the existence of a thin film on each side of the gas/liquid interface and the
resistances to transfer of solutes across the gas and liquid films are considered in series.
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