The Hydraulic Performance
of Chlorine Contact Tanks
CALMET M. SAWYER, Assistant Professor
Department of Civil Engineering
Virginia Military Institute
Lexington, Virginia
PAUL H. KING, Associate Professor
Department of Civil Engineering
Virginia Polytechnic Institute
Blacksburg, Virginia
INTRODUCTION
In future years conventional waste treatment units will have to perform with a
high degree of efficiency in relation to design objectives in order to prevent increased
waste loads from depleting the available waste assimilative capability of receiving
waters. For maximum efficiency, the future performance of such waste treatment
units should be evaluated before the units are actually constructed and put into
operation. A simple and inexpensive means of investigating the operational performance of many types of proposed units involves the use of tracer studies on hydraulic
models.
Chlorine is applied to domestic and industrial waste water to accomplish a wide
variety of treatment objectives. Chlorination of industrial wastes has been used in the
past to accomplish the two major purposes of biological control and chemical oxidation (1). Previous studies of chlorination techniques and facilities have indicated the
pressing need for a more rational approach to chlorine contact tank design. Chlorine
contact tanks are the continuous flow treatment units used to uniformly distribute
chlorine throughout a waste fluid. In addition, contact tanks must provide a design
contact time between the fluid and a particular concentration of dissolved chlorine.
The efficiency of a chlorine contact unit with regard to its performance level will
depend largely on the hydraulic characteristics of the contact basin.
The purpose of the reported research was to study and relate the hydraulic
properties of model and prototype chlorine contact units in order to analyze the
performance efficiency of particular designs. The hydraulic characteristics of the
units were related to the output response curves which were obtained from tracer
tests. The output response curve refers to the non-dimensionalized curve of tracer
concentration versus time monitored in the outlet of each unit (2,3).
Various methods have been employed to analyze the response characteristics of
model treatment units in an attempt to obtain parameters that could then be used to
indicate the type of flow regime within the basin (1,2,3,4,5,6,7,8). Performance
parameters can be obtained from the output response curve that results from a tracer
test. In this type of study, a tracer (dye, electrolyte, radioisotope, or other material)
is injected into the influent to a basin and the tracer concentration in the outlet is
monitored over a period of time. The plot, outlet tracer concentration versus time,
has been referred to by several terms such as the flow-through curve, the dispersion
curve, the flow curve or wave, and the detention time distribution. A much more
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