Diffused Air in Deep Tank Aeration
FRANK L. SCHMIT, Executive Vice President
PAUL M. THAYER, Vice President of Engineering
SANITAIRE — Water Pollution Control Corporation
Milwaukee, Wisconsin 53201
DAVID T. REDMON, Engineer
Ewing Engineering Company
Milwaukee, Wisconsin 53209
INTRODUCTION
Present day requirements for higher degrees of treatment, coupled with high land,
construction, and power costs, have stimulated interest in the possible economies of deeper
aeration tanks and higher loadings.
The purpose of this study was to determine the relationship between water depth, tank
width, and oxygen transfer rates to oxygen transfer efficiencies and power requirements.
An earlier study by Schmit and Redmon (1) considered the effect of water depth. The
objective of this investigation is to provide useful information for treatment plant design.
DESCRIPTION OF FACILITY
The testing facility is a steel tank 34'-4" wide by 6'-0" long by 24'-0" deep. Temporary
baffles as shown in Figure 1 permit evaluation of two tank widths. SANITAIRE Model D-
24 diffusers were placed to extend 2'-0" on both sides of a header at mid-width of the tank,
2'-0" from the bottom. The tank is located adjacent to the SANITAIRE-Water Pollution
Control Corp. office in Glendale, Wisconsin. Water is taken from the Glendale Water
System, the source of which is Lake Michigan.
Air is supplied by a rotary-positive blower driven with a 20 HP 1,750 rpm motor by
means of v-belts. Air volume is controlled by changing motor or blower sheaves, with fine
adjustment through a bleed valve. Air pressure is measured by a mercury column. Air
volume is measured by an orifice type flow meter. Temperature is measured by a
thermometer in a well located just ahead of the orifice plate. Sampling points are shown in
Figure 1. Each sampling point consisted of an anti-air entrainment collector connected to a
rotameter by means of equal length tubing. Laboratory tests indicated agreement with
Miller (2) that the anti-entrainment device was necessary. For some tests, four samples were
taken; for others, sample points were manifolded and one composite sample was taken.
Sample points used for various tank widths and depths are indicated in Table I.
LABORATORY PROCEDURES
These tests utilized the non-steady state procedure generally described by Eckenfelder
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