Environmental Protection Technology Series
RELATIONSHIP BETWEEN DIAMETER AND HEIGHT
FOR THE DESIGN OF A SWIRL CONCENTRATOR AS
A COMBINED SEWER OVERFLOW REGULATOR
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-670/2-74-039
July 1974
RELATIONSHIP BETWEEN DIAMETER AND HEIGHT FOR THE
DESIGN OF A SWIRL CONCENTRATOR AS A
COMBINED SEWER OVERFLOW REGULATOR
A Supplement to the Swirl Concentrator as a
Combined Sewer Overflow Facility
EPA-R2-72-008, September 1972
By
Richard H. Sullivan, American Public Works Association
Morris M. Cohn, Consultant
James E. Ure, Alexander Potter & Associates
F. E. Parkinson, LaSalle Hydraulic Laboratory, Ltd.
George Galiana, LaSalle Hydraulic Laboratory, Ltd.
Contract No. 68-03-0283
Program Element No. 1BB034
PROJECT OFFICER
Richard Field
Storm and Combined Sewer Section (Edison, N.J.)
Advanced Waste Treatment Research Laboratory
National Environmental Research Center
Cincinnati, Ohio 45268
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI. OHIO 45268
For sale by the Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402
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REVIEW NOTICE
National Environmental Research Center — Cincinnati has reviewed
this report and approved it for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
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FOREWORD
Man and his environment must be protected from the
adverse effects of pesticides, radiation, noise and other
forms of pollution, and the unwise management of solid
waste. Efforts to protect the environment require a focus
that recognizes the interplay between the components of
our physical environment - air, water, and land. The
National Environmental Research Centers provide this
multidisciplinary focus through programs engaged in
• studies on the effects of environmental
contaminants on man and the biosphere, and
• search for ways to prevent contamination and to
recycle valuable resources.
The continued investigation of the swirl concentrator
concept represented in the following report reflects the
latter of these roles. It also points up a meaningful research
and development effort around a new technology that may
influence the treatment of water pollution from combined
sewer overflows for years to come.
The swirl concentrator traces its origins to the work
performed by the American Public Works Association
Research Foundation in 1972 sponsored by the City of
Lancaster, Pennsylvania and the U.S. Environmental
Protection Agency, reported in The Swirl Concentrator as
a Combined Sewer Overflow Regulator Facility, EPA
R2-72-008. This effort demonstrated the capacity of this
nonmechanical device to effect excellent removals of
settleable and floatable solids contained in combined sewer
overflow.
This publication reports the results of further research
and development to establish the most efficient and
economical geometry for the swirl device. It also provides
a better method for design based upon the percentage
removal of organic and inorganic solids. As such, it brings
the most up-to-date information available on this new
technology to the wastewater quality manager to assist in
the handling of combined sewer overflows in a more
efficient way. This research effort of an important new
development demonstrates the best use of the technology
transfer process and a way to better assure the quality of
the nation's water resources.
A. W. Breidenbach, Ph.D
Director
National Environmental
Research Center, Cincinnati
ill
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ABSTRACT
This report is a supplement to the report,
The Swirl Concentrator as a Combined Sewer
Overflow Regulator Facility, EPA-R2-72-008,
September, 1972. The work described by this
report allows flexibility for the designer faced
with structural, head or land area constraints
by enabling interchange of basic heights and
diameter dimensions.
Studies of The Swirl Concentrator as a
Combined Sewer Overflow Regulator Facility,
conducted in 1972 by the American Public
Works Association Research Foundation for
the City of Lancaster, Pennsylvania, and the
U.S. Environmental Protection Agency,
demonstrated that this type of dynamic flow,
non-mechanical device could effect excellent
removals of suspended and floatable solids
contained in admixtures of sanitary sewage
and storm water. This improvement in the
quality of storm flow discharges to receiving
waters, or to treatment or storage facilities
could reduce the pollutional impact on the
nation's water resources.
The 1972 studies established a suitable
relationship between swirl chamber depth and
diameter and their effect on the liquid
flowfield and particle removal efficiencies. It
was deemed advisable to augment the 1972
studies by investigating this depth-to-width
ratio and to define the dimensions which will
provide optimum construction economy and
operating efficiency in terms of solids
separation. This report presents an account of
these supplemental studies of a hydraulic
model of the swirl concentrator at the'LaSalle
Hydraulics Laboratory at Montreal.
The report translates the model study
findings into a design basis that can be used
for any rational flow rate in universal service
for the treatment of combined sewer flows. It
establishes the basic principle that variations
in overflow weir height, or chamber depth, do
not materially influence solids particle
removals and that the most definitive design
parameters are size of inlet sewer and swirl
chamber diameter. While the model studies
showed that a ratio of weir height to chamber
diameter of 1 : 4 was the most convenient to
use as a design aid, the data have been
extrapolated to produce geometry
modification curves that cover swirl chamber
diameters and depths. This information will
be of value in the design of facilities which are
the most economical and efficient.
The report provides design curves for
various influent flow rates, covering chamber
diameters and inlet sewer sizes which will
produce settleable solids removal efficiencies
of 70, 80 and 90 percent. It presents design
details for floatable solids traps to retain these
components, and for essential details of swirl
chamber geometries. Procedures are outlined
on how the model study curves can be used in
the design of prototype swirl concentrator
units of various capacities and dimensional
relationships.
The report of the hydraulics laboratory
model studies is included as an appendix to
the project report.
This report was submitted in partial
fulfillment of Contract 68-03-0283
between the U.S. Environmental Protection
Agency and the American Public Works
Association.
IV
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AMERICAN PUBLIC WORKS ASSOCIATION
BOARD OF DIRECTORS
President
Gilbert M. Schuster
Vice President
Herbert A. Goetsch
Jean V. Arpin James J. McDonough Kenneth A. Meng
Walter A. Schaefer Leo L. Johnson John A. Bailey
Donald S. Frady John J. Roark Rear Admiral A.R. Marschall
Ray W. Burgess James E. McCarty Wesley E. Gilbertson
Robert D. Bugher, Executive Director
APWA RESEARCH FOUNDATION
Chairman
Samuel S. Baxter
Vice Chairman
Milton Pikarsky
Fred J. Benson John A. Lambie
Ross L. Clark James E. McCarty
John F. Collins D. Grant Mickle
W. C. Gribble Marc C. Stragier
Robert D. Bugher, Secretary-Treasurer
Richard H. Sullivan, General Manager
APWA WATER RESOURCES COMMITTEE
Chairman
Vint on W. Bacon
Vice Chairman
Stuart H. Brehm, Jr.
Charles V. Gibbs Morris Klegerman Leo Morris
Donald S. Frady J. M. MacBride Ralph Pickard
Harold A. Hagestad Maj. Gen. J.W. Morris Horace Smith
Shelley F. Jones Donald H. Swets
Richard H. Sullivan, Secretary
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CONTENTS
Page No.
Abstract iv
Section I
Conclusions, Recommendations and Overview 1
Section II
The Study 4
Section III
Alternative Design of Swirl Concentration Facilities 11
Design Procedure .... . . -11
Section IV
References . 26
Section V
Glossary of Pertinent Terms ... 27
Section VI
Appendix A - Report by LaSalle Hydraulics Laboratory on
Hydraulic Model Study of the Swirl Concentrator as a Combined Sewer
Overflow Regulator Facility - Depth-Width Tests 28
INDEX TO TABLES
Table No. Page No.
1 Design Procedure for Swirl Concentrator as a
Combined Sewer Overflow Regulator . 23
2 Data from Design by Earlier Experimentation . . . 24
3 Comparison of Variations in Design Elements . .24
4 Comparison of Variations in Area and Volume Between
Standard Design and Design with Minimum Depth 25
INDEX TO PHOTOGRAPHS
Photograph No. Page No.
1 General View of Model . . . . ... 28
2 Interior of Chamber Showing Submerged Inlet Floor Gutters,
Foul and Clear Water Outlets . . . . 29
VI
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INDEX TO FIGURES
Figure No. Page No.
1 Model Layout 5
2 Chamber Internal Details 6
3 Details of Weir, Scum Ring and Spoiler Assembly 7
4 Prototype Gradation for Grit and Organic Material 9
5 Storm Discharge vs Chamber Diameter 12
6 General Design Details, 1972 Report 1.3
7 Chamber Diameter for 90% Recovery 14
8 Chamber Diameter for 80% Recovery 15
9 Chamber Diameter for 70% Recovery . . . . 16
10 Geometry Modification Curves 17
11 General Design Details 18
12 Settleable Solids Recovery for 30.5 cm (1 ft) 19
13 Settleable Solids Recovery for 45.8 cm (1.5 ft) 19
14 Settleable Solids Recovery for 61 cm (2 ft) 20
15 Settleable Solids Recovery for 91.5 cm (3 ft) 20
16 Settleable Solids Recovery for 122 cm (4 ft) 21
17 Settleable Solids Recovery for 152 cm (5ft) 21
18 Settleable Solids Recovery for 183 cm (6 ft) 22
19 Details of Gutter Centerline Layouts 29
20 Details of Open Vortex Foul Outlet . 30
21 Details of Floatables Trap . . 31
22 Particles Settling Velocities for Grit, Organic Material and
Gilsonite in Still Water 33
23 Gradation Curve for Gilsonite Used in Model 34
24 Prototype Grit Sizes Simulated by Gilsonite on Model 35
25 Prototype Organic Material Sizes Simulated by Gilsonite on Model . . . 35
26 Gilsonite Recovery on Model for 15.2 cm (6 in.) 36
27 Gilsonite Recovery on Model for 12.7 cm (5 in.) . 36
28 Gilsonite Recovery on Model for 10.2 cm (4 in.) 37
29 Gilsonite Recovery on Model for 7.6 cm (3 in.) 37
30 Average Gilsonite Recovery Curves Used for Design Curve Analysis . . 38
31 Average Model Results - Polythene Recovery ... 39
32 Polythene (Floatables) Recovery for 30.5 cm (1 ft) . 39
33 Polythene (Floatables) Recovery for 45.7 cm (1.5 ft) . .' 40
34 Polythene (Floatables) Recovery for 61 cm (2 ft) ... . 40
35 Polythene (Floatables) Recovery for 91.5 cm (3 ft) -41
36 Polythene (Floatables) Recovery for 122 cm (4ft) ... . . . 41
37 Polythene (Floatables) Recovery for 152.5 cm (5 ft) .... 42
38 Polythene (Floatables) Recovery for 183 cm (6 ft) 42
Vll
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ACKNOWLEDGEMENTS
The American Public Works Association
is deeply indebted to the following persons
and their organizations for the services they
have rendered to the APWA Research
Foundation in carrying out this study for the
U. S. Environmental Protection Agency.
CONSULTANTS
Dr. Morris M. Cohn
Dr. Paul Zielinski
Bernard S. Smisson
ALEXANDER POTTER ASSOCIATES, CONSULTING ENGINEERS
Morris H. Klegerman
James E. Ure
LA SALLE HYDRAULIC LABORATORY, LTD.
F. E. Parkinson
G. Galiana
T. W. BEAK, CONSULTANTS, LTD.
Stephen L. Hodd
David C. Morin
Robert J. Dalrymple
APWA STAFF
Lois Borton Cecelia Smith
Shirley Olinger Oleta Ward
U. S. ENVIRONMENTAL PROTECTION AGENCY
Richard Field, Project Officer
Chief, Storm and Combined Sewer Section (Edison, N.J.)
Advanced Waste Treatment Research Laboratory
Cincinnati, Ohio 45268
Vlll
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PREAMBLE
The study was performed with synthetic
solid particles. Designers should carefully
evaluate the size and density distribution of
sewage in their areas before setting individual
criteria.
IX
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SECTION I
CONCLUSIONS, RECOMMENDATIONS AND OVERVIEW
This study of the relationship between
the diameter of a swirl concentrator and the
height of the overflow weir, in terms of size
of inlet conduit and efficiency of removal of
settleable and floatable solids contained in
combined sewer flows, is an extension of
original studies in 1972 on the application of
the swirl flow principle as a combined sewer
overflow regulator facility. The study
provides design parameters which will give the
greatest solids removal efficiencies under
specific conditions in full-scale prototype
installations.
The need for reduction in the amount of
hydraulic head loss needed to achieve the
desired chamber depth can make it necessary
to determine if increasing the diameter of the
chamber could reduce the height, thus making
it possible to use the swirl separation principle
in a greater number of locations. Similarly,
vertical or horizontal limitations at the
construction site would be made relatively
flexible, again expanding the potential use of
the swirl concentrator regulator. The
hydraulic model studies undertaken at the
LaSalle Hydraulics Laboratory, and as
reported here, make it possible to draw the
following conclusions:
1. Design parameters can be definitively
established, covering swirl concentrator
chamber diameter, inlet pipe dimensions, and
internal chamber facilities, to provide specific
solids removal efficiencies for prototype
combined sewer overflow systems.
2. For chambers having a ratio of
chamber diameter to chamber depth of 4 : 1
it was found that the depth had little effect
on recovery rate. The same condition was
found when the ratio of chamber diameter to
inlet dimension was in the range of 6 : 1 or
7.2 : 1. When the ratio of chamber diameter
to inlet dimension was increased to 9 : 1 or
12: 1 the depth or weir height had more
influence on recovery rates.
For any given discharge the use of a
smaller ratio of chamber diameter to inlet
dimension results in lower inlet velocity and
lower chamber area and volume. Hence for
economy reasons the designer should attempt
to reduce this ratio as close to six as is
possible with the use of the design curves
given in this report.
3. Where circumstances are not favorable
for the standard design with a ratio of
chamber diameter to depth of 4 : 1 it is
possible to decrease the chamber depth to a
value equal to the inlet dimension. This also
results in an increase in the chamber diameter
and chamber area. The chamber volume may
also be somewhat affected either up or down
by this change.
These conclusions are translatable into
the following recommendations:
• It is recommended that the swirl
concentrator principle be utilized more
extensively for the removal of solids
pollutants of both inorganic and organic
nature which are contained in combined
sewer overflow wastes. These concentrators
offer a rapid and relatively economical means
for the improvement of the quality of such
overflows and a reduction in the pollutional
impact on receiving waters, or on overflow
holding and treatment facilities.
• The use of such quality control
facilities, over and above the prototype
installation at Onondaga County, New York,
will demonstrate in full-scale operation the
validity and applicability of the model studies
which have been conducted in the APWA
report The Swirl Concentrator as a Combined
Sewer Overflow Regulator Facility (EPA R2 —
72-008, Sept., 1972), and as presented in this
report on supplementary investigations of the
relationship between diameter and height in
terms of design parameters.
OVERVIEW OF STUDY
A study of Combined Sewer Regulator
Overflow Facilities, 11022 DMU 07/70
carried out by the APWA Research
Foundation for the U. S. Environmental
Protection Agency, disclosed the need for more
effective design, installation, operation and
maintenance of regulator devices. Too many
installations failed to regulate the flows of
stormwater-sanitary sewage admixtures
intercepted for transmission to treatment
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works and the volumes discharged
"overboard" to receiving streams, lakes and
coastal waters.
Of significance to the water pollution
problem in areas served by combined sewers
in this country was the finding that overflow
regulators were not designed to entrain the
most concentrated and polluted increments of
flow during storm flow periods in order to
discharge such concentrations to interceptors
leading to treatment works, and thereby
reduce the pollutional impacts of overflow
volumes on receiving waters. Greater emphasis
on improvement in overflow wastewater
quality in overflow regulator facilities was
found in European practice.
The report on the study of regulator
facilities, issued in 1970 as a result of the
studies, emphasized the fact that a regulator
must be charged with two responsible
functions: effective reduction in the volume,
time, frequency and duration of overflows;
and effective control of the quality of the
overflow wastewaters. This dual function of
regulator devices was referred to as the "2 Q"
principle of regulation of quantity and
quality. The use of vortex-type chambers as
regulator devices in Bristol, England, led to
the proposal that such facilities could serve
the "2 Q" purposes in American practice and
that further study of the applicability of this
principle to combined sewer regulator service
should be undertaken.
Subsequently, a study of The Swirl
Concentrator as a Combined Sewer Overflow
Regulator Facility (EPA-R2-72-008, Sept.
1972) was undertaken by the APWA Research
Foundation in 1971 for the U.S. EPA and the
City of Lancaster, Pennsylvania, where a
prototype installation of such a device is
proposed. The report on this project was
completed in July 1972. This investigation
involved the development and study of a
hydraulic model at the LaSalle Hydraulic
Laboratory, LaSalle, Quebec, and an
evaluation of a mathematical model of such a
system and its flow patterns and
performances by the General Electric
Company, Philadelphia, Pennsylvania.
The studies established the dimensions
and configurations of a swirl regulator that
would perform the quality improvement
function proposed in the earlier combined
sewer regulator investigation. The scale
model, based on a proposed 1:12 (based on
Froude number) enlargement for the
Lancaster installation, provided an efficient
structure that clarified the synthesized
solids-liquids admixture injected into the swirl
flow pattern, the device produced relatively
clear overflow for discharge to receiving
waters or holding-treatment facilities; and a
concentrated portion of the flow that
contained the major amount of settleable
contaminant solids which could be collected
in the bottom of the swirl concentrator and
discharged through a so-called foul sewer line
for transmission via the interceptor to a
wastewater works. Thus, in addition to serving
as a quantity regulator, the swirl concentrator
performed the quality control function
envisioned in the "2 Q" principle.
The hydraulic model used in the original
swirl concentrator to handle combined sewer
wastewaters provided a fixed set of geometric
proportions to achieve these results for given
flow conditions. Further analysis of the data
developed with the combined sewer swirl
concentrator-regulator indicated the
desirability of extending the hydraulic
investigations to obtain information on how
such a facility would perform with different
depth-to-width ratios.
The e'ffect of swirl concentrator
depth-to-width ratio, in the initial study, on
the liquid flow field and solids particle
removal efficiency was determined by
operating the mathematical model for two
different chamber depths, with all other
parameters held constant. This mathematical
model study of depth-to-width ratios served
to augment and validate the hydraulic studies
carried out by the LaSalle Laboratory. The
mathematical model investigation
demonstrated little change in liquid flow
characteristics resulting from changes in
chamber depth but the model predicted a
marginal improvement in solid particle
removals for greater depths - 67.1 percent
from 63.4 percent with particle settling
velocity of 2.2 cm/sec (0.0717 fps); and 96.0
percent from 93.2 percent with settling
velocities of 6.4 cm/sec (0.212 fps): this was
not verified by testing with hydraulics
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laboratory configurations. However,
laboratory tests utilizing earlier concentrator
configurations indicated that "marginal, even
questionable" increases in performance were
observed at a depth of up to 4.56 m (15 ft).
The economic feasibility of providing
increased depth of swirl concentrator
construction to achieve such minimal, and
even questionable, improvements in solids
separation performance remains doubtful. In
the case of so-called conventional gravity
solids separation settling chambers, the depth
factor is empirically chosen. The design
criteria for such basins are "locked in" in
many cases by the specific flow rate to be
handled and by regulatory agency standards
which establish surface settling rate
parameters.
The swirl concentrator principle, on the
other hand, is not based on velocity of flows
or any surface area parameter, but, rather, on
long-path geometric liquid flow patterns
which create the dynamic solids-liquid
separation with minimal turbulence. Thus, the
optimum depth of a swirl concentrator is that
depth that will give effective solids deposition
in the proper place in the chamber floor and
removal of concentrated solids via a foul
sewer bottom outlet (orifice) properly
located. Any depth that will provide the flow
patterns to separate solids and not permit
turbulences of flow to cause an upsweep of
solids out over the clear liquor outlet weir will
assure the desired chamber efficiency.
The diameter of the wier was not varied
due to the" conclusion after the first
laboratory and mathematical modeling that
an optimum relationship had been
established.
Further analysis of the data obtained in
the swirl hydraulic studies indicated the
desirability of extending studies to provide
information on its performance capabilities
with different width-depth ratios in order to
reduce the hydraulic head requirements. The
current series of tests were carried out to
augment earlier findings, and to determine the
solids recovery rates when the chamber'
diameter (width) and weir height (depth), are
varied and the inlet pipe size held constant
relative to each other.
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SECTION II
THE STUDY
The supplemental studies of the
relationship between swirl chamber width, or
diameter, inlet size, and height of clear liquid
weir, or depth of the chamber, were based on
the concentrator configurations utilized in the
original 1972 investigation of the solids-liquid
separation performance. The principle of
chamber design to provide a controlled
combination of solids settling and rotational
flow to concentrate the deposited solids at
the center of the chamber floor (and to
provide a surface trap facility to entrain and
retain floatable solids) was the basic guideline
for the supplemental laboratory studies
reported herein.
It was deemed impracticable to vary the
swirl chamber diameter from the hydraulic
investigative device used in the earlier
configuration and performance studies. The
model diameter, thus, remained at 91.4 cm
(36 in.), with a 50.8 cm (20 in.) diameter
clear liquid overflow weir and the 61 cm (24
in.) diameter scum ring.
The variable factors chosen to provide the
chamber depth-to-width relationships were:
weir height, and the inlet pipe diameter.
Figure 1, Model Layout, portrays the facilities
utilized in the study. Details are shown in
Figure 2, Chamber Internal Details. Figure 3,
Details of Weir, Scum Ring and Spoiler
Assembly, shows the details of the other
major components.
The study covered five rates of discharge,
including the rational ranges that would be
imposed on a full-scale unit. This enabled the
study to encompass operational capacities
that would result in findings that would make
possible the "universalization of the swirl
concentrator as a combined sewer regulator
facility." These flow rates, on a 1 : 12 scale of
laboratory model to prototype, were: 1.42;
2.83; 4.25; 5.66; and 8.49 cm/sec (50; 100;
150; 200; and 300 cfs). Four inlet pipe
diameters were studied: 0.91; 1.22; 1.52; and
1.83 meters (3; 4; 5; and 6 ft).
At least three weir heights, or chamber
depths, were tested for each inlet pipe
diameter. The range selected for the hydraulic
study was: 1.83; 2.14; 2.74; 3.36; and 3.97
meters (6; 7; 9; 11; and 13 ft). Some of the
lower weir heights could not be tested
because they would interfere, or be interfered
with, by the weir and the scum ring assembly.
The dimensions listed, and the test operations
with these configurations, were deemed to
cover all of the parameters required for the
depth-width relationships to be studied. The
full details of the model portrayed in Figure 2
are described in the LaSalle Hydraulic
Laboratory, report contained in Appendix A.
The model used for the supplemental
studies was the same unit utilized in the first
studies in 1972. The separation chamber was
a vertical cylinder made of 13 mm (1/2 in.)
Plexiglas®, 91.4 cm (36 in.) in diameter and
102 cm (40 in.) high. The inlet synthetic
wastewater line was made of polyvinyl
chloride pipe, varying in size of 7.6; 10.2;
12.7; or 15.2 cm (3; 4; 5; or 6 in.), set at a
slope of 1 : 1,000 to provide tangential flow
of the incoming liquid in the swirl
concentrator chamber. The incoming flow
was composed of water supply from a
constant level tank in the laboratory, and
solids of proper composition injected into the
inflow stream by a vibrating feed unit.
The clear water outlet from the swirl
concentrator was through a polyvinyl chloride
pipe 15.2 cm (6 in.) in diameter which was
installed upward through the bottom of the
model centerline. The height could be varied
at will by adding or removing segments to or
from the top of the pipe. The foul flow
(concentrate) was discharged from the
bottom of the chamber through a flexible 5.1
cm (2 in.) tube, leading to a solids settling
tower fitted with an adjustable level outlet
pipe which could be raised or lowered to
regulate the rate of discharge of the foul flow
(concentrate).
The solids introduced into the inlet flow
were synthesized to simulate the physical
character of combined sewer flows which
would be handled in actual practice by a
prototype swirl concentrator. This involved
synthesizing grit material, organic material
and floatable materials of representative sizes,
specific gravities and quantities. Appendix A
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Foul outflow Foul solids
settling tower recovery screen
Chamber cylinder - l/2"(l3mm)
plexiglass- 36" dig. (914mm.)
Clear outflow settling basin
Calibrated V- notch weir
c
1 T /
1
\—T—\
/ '
Clear water overflow
outlet pipe - 4"plexiglass (102mm)
PLAN
Foul outlet
D discharge
control
Small water supply'
for solids injection
Water supply from
pumping station
Foul Outlet
discharge control
Chamber cylinder - l/2"(l3mn.
plexiglass- 36" dia. (914mm)
Vibrator
Discharge returned
to pumping station
Foul outflow
settling tower
Butterfly
'TOI valve
Clear water overflow pipe-
4" plexiglass (102mm)
Clear outflow settling basin
Foul solids
recovery screen
ELEVATION
Section A-A
FIGURE 1
MODEL LAYOUT
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D3= 61cm (24")
D4 = SOBcm (20")
B-B(From FIG. I)
VFOU!
Outlet
Square
Inlets
-Open Vortex Foul Outlet
See details on FIG. 5
6lcm(24")0 Scum Ring
50.8 cm (20" )0 Weir
5.1 cm
y
T
7.6cm 1.27cm
(3") (1/2")
C -C(From FIG. I)
•rrr—'
Square
Inlets
V777////////////.
FIGURE 2
CHAMBER INTERNAL DETAILS
(Sections are from Figure 1)
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61cm (24")
Scum Ring
50.8 cm (20")
Weir
180
Four flow spoilers
used on model
Floatdbles
Trap
15.2cm (6")0
Clearwater
Downshoft
5.1cm
30.5cm (12")
2. 54cm
7.6cm
(3")
, 25.4cm
(10")
„ .,
Spoiler
/ 1.27cm
r c/2 ")
15.2 en (6")
^-7.6 cm.
(3")
A-A
3.8cm ( l-l/a")
FIGURE 3
DETAILS OF WEIR, SCUM RING AND SPOILER ASSEMBLY
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describes in detail the materials utilized for
these purposes.
The grit increment of the solids injected
into the stream flow to the swirl, to stimulate
combined se'wage flows, was assumed to have
a specific gravity of 2.65 and a straight line
grain size distribution was selected as a
representative average of samples taken from
existing combined sewer systems — from 0.2
to 2.0 mm (No. 70 to 10 sieve sizes). The
concentration range was 20 to 360 mg/1.
Figure 4, Prototype Gradation for Grit and
Organic Material, represents the prototype
gradations for grit and organic material that
the synthetic solids scale up to.
Particle sizes greater than 1 mm move
along in a flowing liquid stream according to
equations deduced by Meyer-Peter and
Muller1 or Einstein2. Particles between 1 mm
and 0.2 mm are considered to be in a
transition zone between the Meyer-Peter,
Muller or Einstein equation and the Stokes
relation. It was necessary to deduce curves of
particle settling velocities for grit, organics
and Gilsonite material, as shown in Appendix
A, utilizing the Froude law of similitude.
Gilsonite components of the simulated
combined sewage solids material were
deduced as described in Appendix A. While
the Gilsonite did not adequately cover the
larger prototype particle sizes, it was assumed
that the larger size particles not represented
by the Gilsonite material used in the studies
would have settled at least as effectively as
the recovery rates shown for the other
material. Thus, the estimates of removal
efficiencies through the swirl concentrator
would be on the conservative side. Even if all
the lighter materials not covered by the
Gilsonite were assumed to be lost over the
clear outlet weir, they would represent only
10 percent of the prototype grit, at most.
The organic material contained in
combined sewage to be removed from the
flow in a prototype swirl concentrator, was
defined as having a specific gravity of 1.2 and
a grain size distribution from less than 0.1 to
5 mm. The Gilsonite utilized in the laboratory
studies adequately simulated the upper limits
of the range but the lower range left a
significant zone of finer solids or particles not
simulated across the scales considered in the
studies. However, the Gilsonite represented
the major portion of the prototype organics
and its use was deemed suitable for the
investigations.
The floatable increment injected in the
flow had a specific gravity of 0.9 to 0.998 and
a size range from 5 to 25 mm. The
concentration range was 10 to 80 mg/1. The
simulated floatables material used was
polythene particles 4 mm in diameter having a
specific gravity of 0.92.
It is obvious that the hydraulic model
studies could not duplicate the variations in
inflow rates and in combined wastewater
solids concentration, which normally occur in
sewer system operations. Steady-state flows
were investigated in the swirl chamber
rotational flow pattern and steady-state
discharges were established. Similarly, a
specific grit-organics-floatables solids
concentration was utilized in the studies, by
means of injecting one liter of Gilsonite and
polythene into the steady-state flow rates.
Removal efficiency was based on the
amounts of synthesized solids introduced into
the swirl concentrator, the amount discharged
through the foul sewer (concentrate line), the
amount spilled over the clear overflow weir
with the supernatant liquor, the amount
retained on the floor of the chamber after
each flow pattern had been studied, and the
lighter-than-water materials entrained in the
floatables trap. The Gilsonite material used
was considered to represent both the grit and
organic components of the simulated
combined wastewater.
As stated, solids recovery, or removal,
was evaluated for four sizes of pipe inlets and
various weir heights. For an inlet size of 15.2
•em (6 in.), increasing or reducing the weir
height produced little impact on recovery
rates. Likewise, the 12.7 cm (5 in.) inlet
demonstrated similar recovery rates for the
weir heights (or chamber depths) tested; the
depth range investigated varied from 22.8 cm
to 33 cm (9 to 13 in.). However, a smaller
inlet size than 12.7 cm (5 in.) produced
differences in recovery rates when the weir
height was varied.
The basic finding that weir height has
minimal effect on solids recovery made it
possible to develop fundamental design curves
which relate recovery rates to inlet size (as it
relates to chamber diameter) and discharge
-------
U.S. STANDARD SIEVE NUMBERS
3 4 6 8 10 16 20 30 40 50 70 100 140
\
\
\
ORGANICS
^
GRIT
\
\
S
\
100
90
80
O>
a>
50
20
10
0.6 0.4
0.2
FINE
GRAVEL
Gram size
COARSE
in mm
MEDIUM
FINE
SAND
U.S. SIEVE SIZE
4
10
20
40
50
70
SIZE mm
5.0
2.0
0.84
0.42
0.30
0.20
% FINER BY WEIGHT
GRIT
100
100
63
31
18
0
ORGANICS
100
53
31
17
14
10
FIGURE 4
PROTOTYPE GRADATION FOR GRIT AND ORGANIC MATERIAL
-------
rates. This eliminates the weir height
parameter, within a broad range, as a factor in
design decisions, making it possible for the
designer to choose the solids recovery
efficiency he hopes to achieve and, thus,
determine the ratio between the chamber
diameter and inlet dimension for the
discharge rate upon which his design will be
based.
The practical value of the scale-up curves
developed from the hydraulic laboratory
studies will be obvious to designers. They
translate discharge rates and theoretical
settleable solids recovery efficiencies to
various inlet dimensions and chambers of
different sizes.
Of even greater value to the designer are
extrapolated curves which relate discharge
flows to swirl chamber diameters for desired
settleable solids removal efficiencies ranging
from 90 percent to 70 percent.
Section III provides a step-by-step
explanation of how these hydraulic data can
be utilized in design procedures. Based on the
known criteria of design flow rates to be
handled and the solids removals, the inlet
dimension, the chamber diameter and other
general design details can be determined. This
information is invaluable; it converts the
model studies to the realities of utilizing the
swirl principle for the improvement of
combined sewer overflow quality by
concentrating solids pollutants for discharge
to municipal treatment facilities and by
discharging clarified supernatant liquors to
receiving streams, retention facilities or storm-
water treatment systems.
10
-------
SECTION III
ALTERNATIVE DESIGN OF SWIRL CONCENTRATION FACILITIES
The initial report, The Swirl Concentrator
as a Combined Sewer Overflow Regulator
Facility, recommended specific dimensional
relationships.
DX - inlet dimension.
D2 = diameter of chamber = 6Dj.
di = height of weir = 1 l/2Di
Therefore D2 = 4dj
(Note: dj is designated as H! in this
supplemental study of alternative design
factors.)
The purpose of this supplemental study
was to determine the effect of varying ratios
of swirl chamber diameter to height, or D2 to
Hj. The results indicated that the optimum
weir height had the same relationship as in the
original study, i.e., Hj/D2 = 0.25. This study
indicated that the ratio of the diameter of the
chamber to the dimension of the inlet has
considerable effect on the recovery of
settleable solids. The resultant design
dimensions indicate a range of the ratio of D2
to D! of from 6-12. In the original study the
ratio of D2 to DI was reported as six.
In the original report, Figure 5, Storm
Discharge vs. Chamber Diameter, and Figure
6, General Design Details, were to be used in
determining the chamber diameter. At the
design discharge it was found that the design
configuration would result in removal of 90
percent of grit larger than 0.35 mm, and of
settleable organics larger than 1.0 mm.
The supplemental study reported herein
used Gilsonite in a range of sizes which
simulated grit over 0.2 mm size and organics
over 0.4 mm size with model scale of 1 : 4
and grit over 0.25 mm size and organics over
0.7 mm size in the model with model scale of
1 : 24. Hence the supplemental design charts
are based on removing particles of smaller size
than in the original study report. This report
presents design figures for removing either 90,
80 or 70 percent of the grit and organics.
These design figures should be used in
preference to Figures 5 and 6.
Three sets of curves for sizing the swirl
concentrator were developed from the
hydraulic model studies, based upon the
desired degree of efficiency of settleable
solids removal at the design discharge. Figures
7, 8 and 9, Chamber Diameters for 90%, 80%
and 70% Recovery, respectively, are used to
determine the chamber diameter for various
inlet dimensions.
Where it is desired to modify the chamber
dimensions to minimize the weir height,
Figure 10, Geometry Modification Curves,
may be used. Use of these curves presumes
that the inlet dimension will be retained and
that the weir height and chamber diameter
will be modified.
In order to determine the percent
recovery of settleable solids for various inlet
diameters, Figures 12, 13, 14, 15, 16, 17, and
18, Settleable Solids Recovery for 30.5 cm (1
ft); 45.8 cm (1.5 ft); 61 cm (2 ft); 91.5 cm (3
ft); 122 cm (4 ft); 152.5 cm (5 ft); and 183
cm (6 ft). Inlet and Different Sized Chambers,
respectively, should be used. Use of these
figures allows a rapid check of anticipated
efficiency of settleable solids removal.
Design Procedure
The design procedure, utilizing Figures
7-10:
1. Select Design Discharge
The design engineer must select the
design discharge appropriate to each project,
based on the design criteria for the project.
2. Select the Recovery Efficiency Desired
One of three performance efficiencies can
be chosen — either 90, 80 or 70 percent
recovery of settleable solids. It is suggested
that 90 percent settleable solids recovery be
taken for peak storm discharges. Only in cases
where low probability peak flows are being
considered would it be reasonable to design
on the basis of 80 percent or 70 percent
recovery.
3. Find the Inlet Dimension — Dj
Having selected the desired recovery rate
and the design discharge, use the
corresponding chart in the series of Figures 7,
8 and 9 for determining Dj. Using the proper
chart with the design discharge, follow this
vertically upward to the broken D! line which
most nearly corresponds to the inlet sewer
diameter. (Note: It might be advantageous to
select a larger or smaller Dt to coincide
exactly with the inlet sewer size.) In the
11
-------
60 —i
50 —
40 —
I30
fa
I
1*
OJ
-------
Inlet. Chamber Diameters
Weir. Scum Ring Diameters
D! = unit D2 = 6D!
hi = Dj/2 h2 = Di/3
d2 = 5/6 D! RI = 2 1/3 Dj
R4 = 1 1/8 DI Rs = 32/3Dt
£
f_
Weir. Scum Ring Petals
R2
= 4D,
= DJ3
= 11/2:
= D!/6
I
D4
R3
Inlet Detail
3 1/3D,
1 1/2 D,
5/8 D,
u
Centerline Secondkry Guner
Centeriine Primary Gutter
FIGURE 6
GENERAL DESIGN DETAILS
Note: From original APWA study, do not use
13
-------
IB 20 28 90 3640 48 ef>
ft.
100-
90-
80-
TO-
SO -
50-
0.05 0.07 O.I O.IS 0.2 0.3 0.4 0.5 0.6 0.* 1.0 1.3 •/*
Discharge.
m
-28
-20
h 18
40-
O
I
« 20-
jQ
E
18 -
10-
I III
l I I l
7
-10
- 8
I
48 SO 60 70 80 90 100
i . i i i I I I
ISO 200 250 300
I I I I I I I
400 SOO 600 cfl
. . . . ! I
1.5
25 3 3.5 4 S 6
Discharge,
8 9 10
FIGURE 7
H! : D2 =0.25
CHAMBER DIAMETERS FOR 90% RECOVERY
14
-------
0.05 0.07 O.I
O.IS 0.2 0.3 0.4 0.5 0.6 0.8 1.0 1.3 mV»
Discharge,
45 60 60 70 80 90 100
ISO ZOO 260 300
Discharge,
400 600 600 cfl
FIGURE 8
H! : D2 = 0.25
CHAMBER DIAMETER FOR 80% RECOVERY
15
-------
10
46 50 60 TO 80 90 100
I I i i i i I I I
ISO 200 290 300 400 SOO «OO cfl
I I | l I I I I .... I I
I.S
2.9 3 3.5 4 9 6 7 8 9 10
Discharge,
19 m'A
FIGURE 9
H! : D2 =0.25
CHAMBER DIAMETER FOR 70% RECOVERY
16
-------
3.0 -
• z.o
1.0
V Model Study limits -
\ Values outside are
\ extrapolated.
Standard
Design line
\ for H,/D2=0.25
10 II
D2/D,
12 13 14 15 16 17
FIGURE 10
GEOMETRY MODIFICATION CURVES
model tests, the square inlet dimension was
the same as the inlet sewer diameter, an ideal
condition for this unit.
In cases where the square inlet dimension
cannot conveniently be made the same as the
inlet sewer, a reducing or expanding adapter
or conversion section would be necessary to
ensure obtaining the efficiencies given in the
curves. If the inlet sewer is concentrically
aligned with the swirl chamber inlet, the
transition section should have a length of at
least three times Dt (i.e. 3D!). Another
possibility would be to provide for the inlet
sewer to discharge into an inspection
manhole. From the manhole, a conduit with
a square cross section would be provided to the
swirl chamber. The distance from this
conversion manhole to the square inlet
discharge into the chamber should also be a
minimum of three times (Dj (i.e. 3D,). This
manhole arrangement could be used to
provide for change in the alignment, elevation
or size between the inlet sewer and the square
inlet into the swirl chamber.
4. Find Chamber Diameter — D2
The intersection point found in 3, above,
defines the chamber diameter, D2, on the
ordinate scale of the chart. In choosing D! , it
might be a valuable aid to check the D2 size,
as well. Using a smaller Dt will make a larger
D2 necessary; the designer can determine the
optimum relation between the two
dimensions.
5. Check Discharge Range Covered
The anticipated efficiency at various flow
rates can be determined for different sized
inlets and chambers by using Figures 12-18. If
the selected D2 curve is not shown in the
figure, its recovery line can be interpolated
and drawn between the given curves.
The recovery rates over the range of
discharges represented by the sewer
hydrograph should be checked, including the
design discharge. The designing engineer must
17
-------
INLET. CHAMBER DIAMETERS
WEIR. SCUM RING DIAMETERS
INLET DETAIL
CENTERLINE PRIMARY GUTTER
D| » FROM FIGURE 7, 8, 9, OR 10 Q^ > 5/9 0-
Dj • FROM FIGURE 7, 8, 9, OR 10 h| D. /2
H| • 02/4 ORFROMFIGURE10 hj. • D| / 3
D3 « 2/3
,
D2/I8
WEIR. SCUM RING DETAILS
CENTERLINE SECONDARY PUTTER
R, • 7/18 Dj R5. Il/ie02
R2 • D2/4 R6. Curvi smoothed
R3 • 5/48 D2 in to m««t
R4 • 3/16 D2 inltt ctnttrlint
FIGURE 11
GENERAL DESIGN DETAILS
18
-------
Hj:D2=0.25
.02 .03 .04 .05
.10 .15 .2 .3 .4 .5.6m3/s
2 345
Discharge,
10
20 cfs
FIGURE 12
SETTLEABLE SOLIDS RECOVERY FOR 30.5 cm (1 ft)
100
06 .08 .1 .15 .2 3 A 5 6 .6 1.0 mVs
3 4567810 15 20 35 30 40 cfs
H,:Da=0.25
FIGURE 13
SETTLEABLE SOLIDS RECOVERY FOR 45'.8 cm (1.5 ft)
19
-------
O.I 0.15 0.2 0.3 0.4 0.5
I i i i i 1 i I I
1.0 1.5 2.0 m
I I
345 10 20 30 40 50 lOOcfs
Discharge,
FIGURE 14
SETTLEABLE SOLIDS RECOVERY FOR 61 cm (2 ft)
100
90
80
f 70
>*
I 60
O
V
QL
« 50
'o
CO
« 40
.o
o
«
1 30
en
20
10
H,:D2=0.25
.3 .4 .5 .6 .7 .8 1.0 1.5 2.0 3.0
I i III I
m'/t
J I
10
20 30 40 50 100
Discharge,
200 cfs
FIGURE 15
SETTLEABLE SOLIDS RECOVER FOR 91.5 cm (3 ft)
20
-------
100
90
80
70
60
50
40
30
20
10
0
1^:02=0.25
20
1.0 1.5 2.0 3.0 4.0 5.0 7.0 10.0 15.0 m*/«
I i i i ill |
50 100 150 200 300 400 500 cfi
Dischorge,
FIGURE 16
SETTLEABLE SOLIDS RECOVERY FOR 122 cm (4 ft)
'i ' i 'i1 'i—i1 i 'i i i1' i 'i 'i ' \ '
3 4 5 6 7 8 10 12 15 20 m'/s
50 60 80 100 150 200 300 400 500 800 1000 cf«
Discharge,
FIGURE 17
SETTLEABLE SOLIDS RECOVERY FOR 152.5 cm (5 ft)
21
-------
100
200 300 4OO 500
Discharge,
800 1000 cfs
FIGURE 18
SETTLEABLE SOLIDS RECOVERY FOR 183 cm (6 ft)
determine at this stage that the discharge
range and recovery rates are. adequate, 'or
carry out further adjustments in DL and D2
dimensions through steps 3, 4 and 5 until
they are adequate.
6. Find Dimensions for the Whole Structure
Having made decisions on acceptable DI
and D2 values, these can be applied to Figure
11, General Design Details, to determine the
necessary dimensions for all the features of
the entire swirl chamber.
7. Geometry Modifications
The above steps have provided the
structural configurations to meet the design
hydraulic conditions. However, at this stage
other considerations such as available space,
depth or head, or economic factors, might
make it desirable to modify the general
proportions of the chamber. The same
operating conditions can be obtained if the
gepmetry is modified according to Figure 10.
This procedure .assumes that the inlet
dimension, Dj, is retained from the above
procedures, and that the chamber diameter
and weir height would be modified.
Using the D2 : D! abscissa chosen for the
standard design above, move vertically to the
intersection with the bold standard design line
to locate the working point. Constant
operating conditions for the specific design
then lie on the geometry modification curve
passing through the working point. Moving
down to the right corresponds to increasing
the chamber diameter or width and lowering
the weir height or chamber depth. Moving up
to the left reduces the chamber diameter and
increases the weir height.
Any choice of D2 : Dj or Ht : D!
relationship can then be made, and the
corresponding values found. It will then be
necessary to re-dimension the other elements
of the structure, based on the general design
details in Figure 11.
Table 1, Design Procedure for Swirl
Concentrator as a Combined Sewer Overflow
Regulator, illustrates the design procedure.
Item 1 is the design discharge. Item 2 is the
design settleable solids recovery efficiency.
Item 3 is the possible inlet diameters selected
from Figure 7. Item 4 is the chamber
22
-------
TABLE 1
DESIGN PROCEDURE FOR SWIRL CONCENTRATOR
AS A COMBINED SEWER OVERFLOW REGULATOR
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Design Discharge
Operating Efficiency
Inlet D! (Fig. 7)
Diameter D2 (Fig. 7)
Recovery (Fig. 12)
(Fig. 13)
(Fig. 14)
(Fig. 15)
Revised D2 (Fig. 12)
Design Diameter D2
Depth Hj
Inlet Velocity
Da/Dj (Line 7 / Line 3)
Design Modifications
(Min. Hi) Dj
Revised HJ/D! (Fig. 10)
Revised DJ/D! (Fig. 10)
Hj
D2
m3/s
cfs
%
m
ft
m
ft
%
%
%
%
m
ft
m
ft
m
ft
cm/s
fps
m
ft
m
ft
m
ft
1.416
50
90
0.9
3
7.9
26
75
28
8.5
28
2.1
7
170
5.6
9.35
0.9
3
1.0
11.5
0.9
3.0
10.5
34.5
90
1.5
5
9.8
32
90
9.8
32
2.4
8
122
4.0
6.4
1.5
5
1.0
7.5
1.5
5.0
11.4
37.5
2.832
100
90
1.2
4
11.3
37
92
11.3
37
2.8
9.25
189
6.2
9.25
1.2
4
1.0
11.4
1.2
4.0
13.9
45.5
90
0.9
3
11.9
39
90
11.9
39
3.0
9.75
338
11.1
13
0.9
3
1.1
17
1.0
3.3
17.1
56.0
90
1.8
6
12.1
40
90
12.1
40
3.0
10
140
4.6
6.7
1.8
6
1.0
7.9
1.8
6.0
14.5
47.5
4.673
165
90
1.5
5
13.7
45
90
13.7
45
3.4
11.25
201
6.6
9.0
1.5
5
1.0
11.2
1.5
5.0
16.8
55.0
90
1.2
4
14.6
48
90
14.6
48
3.6
12
314
10.3
12.0
1.2
4
1.0
16.0
1.2
4.0
19.5
64.0
diameters selected from Figure 7. Item 5
indicates the actual recovery rates selected
from Figures 12-15. One recovery rate is
below 90 percent, therefore a greater
diameter (D2) must be selected from Figure
15 to conform with 90 percent recovery
(Items 6 and 7). The final diameters (D2) are
shown in Item 7. The chamber depth or
height of weir (Hi) in Item 8 is equal to 0.25
D2.
The inlet velocity is shown in Item 9. It
is obvious that, where there is a choice of
inlet sizes, the largest inlet size will result in
the lowest inlet velocity, and the smallest and
most economical structure. Hence, the
designer should select the largest inlet size
shown on the design figures as being suitable
for the design discharge with the hydraulic
head available and the hydraulic constraint of
the inlet sewer.
The resultant depth (Ht) is equal to the
inlet dimension (Di) and the chamber-
diameter (D2) is larger than the diameter
selected in Item 7 of the standard design.
The foregoing design is based on a ratio
of chamber diameter to depth of 4 : 1.
This ratio can be modified by use of the
geometry modification curves in Figure 10.
Assume it is desirable to reduce the depth to
its minimum value. Determine the ratio of
D2 /D! as shown in Item 10 of Table 1. Then,
with the use of Figure 10, proceed as shown
in Item 11. Enter Figure 10 with D2/Dlg,
extend line vertically to standard design line,
to working point. Move down parallel to
modification curves to horizontal line where
ratio of H[/D, is 1.0. Then proceed down
vertically to obtain revised ratio of D2 /Dl.
diameter (D2) is larger than the diameter
selected in Item 7 of the standard design.
23
-------
For informational purpose, Table 2, Data
from Design by Earlier Experimentation,
reviews the major design elements for the
flows investigated in Table 1 as obtained from
the original experimentation.
Table 3, Comparison of Variations in
Design Elements, indicates the difference in
the major factors of inlet diameter, diameter
and height, comparing the results of the 1972
study (original) which did not consider
percent of settleable solids removed, the
present study (revised), based upon 90
percent settleable solids removal, and
dimensions with minimum Hj (min H! ). The
table indicates that a change from the
standard design to one with a minimum depth
for a discharge of 4.673 m3/s (165 cfs) results
in a decrease of the depth from 3.0 to 1.8
meters or a decrease of 1.2 meters and an
increase in the chamber diameter from 12.1
to 14.5 meters or an increase of 2.4 meters.
Table 4, Comparison of Variations in
Area and Volume between Standard Design
and Design with Minimum Depth, lists the
areas and volumes for the structures shown in
Table 1 for 2.832 m3/s (100 cfs) and 4.673
m3/s (165 cfs). For the standard design it is
obvious that the largest inlet size results in the
minimum area and volume. The areas and
volumes of the modified design with
minimum depth are compared with the areas
and volumes of the smallest chamber in
standard design. For the two sizes shown the
design with minimum depth compared to the
smallest standard design show an increase in
area of 38 to 42 percent and a decrease in
volume of 14 to 15 percent. This table
indicates that for any given situation the
designer has several choices and must weigh
the advantages of each before reaching a final
decision.
TABLE 2
DATA FROM DESIGN BY EARLIER EXPERIMENTATION
Design Discharge
Diameter D2
Inlet D!
Depth H!
m3/s
cfs
m
ft
m
ft
m
ft
1.416
50
6.8
11.5
1.1
3.75
1.7
5.62
2.832
100
9.0
19.5
1.5
4.92
2.2
7.38
4.673
165
11.0
36
1.8
6
2.7
9
TABLE 3
COMPARISON OF VARIATIONS IN DESIGN ELEMENTS
50 cfs- 1.416m3/s
Original (1972)
Standard Design
Min. H!
100cfs-2.832m3/s
Original (1972)
Standard Design
Min. H,
165 cfs-4.673 m3/s
Original (1972
Standard Design
Min. H!
Depth
H,
(m)
1.7
2.1
0.9
2.2
2.4
1.5
2.7
3.0
1.8
Inlet
Dt
(m)
1.1
0.9
0.9
1.5
1.5
1.5
Diameter (width)
D2
(m)
6.8
8.5
10.5
9.0
9.8
11.4
11.0
12.1
14.5
24
-------
TABLE 4
COMPARISON OF VARIATIONS IN AREA AND VOLUME
BETWEEN STANDARD DESIGN AND DESIGN WITH MINIMUM DEPTH
1.
2.
Design Discharge
Inlet DI
m3/s
cfs
m
ft
1.5
5
2.832
100
1.2
4
0.9
3
1.8
6
4.673
165
1.5
5
1.2
4
Standard Design
3.
4.
5.
6.
Area
Volume
Area change
from smallest
Volume change
from smallest
m2
sf
m3
cf
%
%
74
800
181
6400
0
0
97
1040
280
9900
+30
+55
111
1200
328
11600
+50
+82
116
1250
354
12500
0
0
148
1590
504
17800
+27
+43
168
1810
617
21800
+45
+66
Modified Design — Min. Ht
7.
8.
9.
10.
Area
Volume
Area change from
smallest standard
Volume change from
m2
sf
m3
cf
%
102
1100
156
5500
+38
150
1620
184
6500
+102
228
2450
229
8100
+206
164
1770
300
10600
+42
220
2370
337
11900
+90
299
3220
365
12900
+158
smallest standard
-14 +2
Note: Area and volume are based on dimensions given in Table 1
-------
SECTION IV
REFERENCES
1. Formulas for Bed-Load Transport. E. Technical Bulletin No. 1026, September
Meyer-Peter and R. Muller, Proceedings 1950.
I.A.H.R., Second Meeting, Stockholm, 3. Swirl Concentrator as a Combined
Sweden, 1948. Sewer Overflow Regulator Facility; EPA -
2. The Bed Load Function for Sediment R2-72-008, September, 1972. PB-214 687.
Transportation in Open Channel Flows. H.A. 4. Combined Sewer Regulator Overflow
Einstein, U.S. Department of Agriculture, Facilities. 11022DMU 07/70. PB-215 902.
26
-------
SECTION V
GLOSSARY OF PERTINENT TERMS
Combined Sewer — A pipe or conduit
which collects and transports sanitary sewage,
with its component commercial and industrial
wastes and infiltration and inflow during
dry-weather conditions, and which, in
addition, serves as the collector and conveyor
of stormwater runoff flows from streets and
other sources during precipitation and thaw
periods, thus handling all of these types of
wastewaters in a "combined" facility.
Concentrate — The portion of the inflow
directed to the interseptor sewer which carries
the bulk of the settleable solids.
Concentrate Outlet — The outlet in the
floor of the chamber in which the
concentrates enter the foul sewer.
Depth of Chamber — The vertical
distance between the floor level of the swirl
concentrator and the crest of the overflow
weir at the central downdraft structure, or at
any other location.
Diameter of Swirl Chamber — The
internal diameter of the concentrator
chamber, a circular device which induces the
swirl flow pattern.
Floatable Solids — Lighter-than-water
solids and congealed floating materials which
rise to the surface of the liquid in the swirl
concentrator and must be intercepted to
prevent discharge with the liquid passing over
the overflow weir crest with the clarified
effluent.
Floatable Trap — A structural
configuration or device in a swirl concentrator
which intercepts or entrains floatable solids
and prevents them from being discharged over
the weir crest with the overflow clarified
liquid by retaining this material until it is
removed and disposed of by predetermined
means.
Foul Sewer — The sewer which carries a
predetermined portion of swirl chamber
liquid and the concentrated settleable solids
deposited in the bottom of the chamber,
discharged from the bottom gutter through an
outlet located at a predetermined location.
Grit — Solids, predominantly mineral in
character, in the combined sewer flow which
are heavier and larger in weight and size and,
thereby, settle readily to the floor of the swirl
chamber by gravimetric classification.
Gutter — A structural configuration in
the floor of the swirl concentrator, which
provides a channel for the desired flow of
sanitary waste water during dry-weather
conditions from the chamber inlet to the foul
sewer (concentrate) outlet, and for
conducting the foul slurry (concentrate) to
the bottom outlet when the chamber is
serving as a solids concentrator.
Inlet Size — The diameter or square
dimensions of the sewer which enters the
swirl concentrator at its floor level and,
thereby, serves to create the flow pattern
which produces the solids-liquid separation
which the chamber is intended to induce.
Long-Flow Flow Pattern — The path of
the swirl flow pattern through the swirl
concentrator, induced by proper baffling
which causes the liquid to traverse the circular
chamber more than once, and prevents the
incoming flow from being diverted or
short-circuited directly to the overflow weir,
thereby inducing the solids to discharge into
the foul sewer channel and outlet.
Organic Solids — Solids of a non-grit, or
lighter weight, contained in the combined
sewer flow, which can decompose and
become oxygen-demanding in receiving
waters, which therefore, must be removed
from the overflow liquid to prevent
pollutional impacts on water sources into
which these overflows are discharged, or on
holding and treatment devices in which
overflows are handled.
Overflow Weir - The structural member
of the swirl concentrator which is intended to
serve as the circular overflow crest for the
clarified or supernatant liquid in the chamber,
thus serving to establish the effective
operating depth of the chamber.
Scum Ring — A circular plate of baffle
encircling the overflow weir, located at a
predetermined distance from the weir and at a
depth that will cause it to retain floatables
and scum and prevent them from passing over
the weir crest with the clarified liquid.
27
-------
SECTION VI
APPENDIX A
REPORT BY LA SALLE HYDRAULICS LABORATORY ON
HYDRAULIC MODEL STUDY OF THE SWIRL CONCENTRATOR AS A COMBINED
SEWER OVERFLOW REGULATOR FACILITY - DEPTH-WIDTH TESTS
The studies described in this report of
hydraulic laboratory studies were undertaken
as an extension of the work covered in the
American Public Works Association Research
Foundation Report, The Swirl Concentrator
as a Combined Sewer Overflow Regulator
Facility, EPA-R2-72-008 September, 1972.
The hydraulic model studies carried out
in the earlier work were performed to the
point where they had developed an efficient
swirl chamber structure with a fixed set of
geometric proportions for given flow
conditions. Further analysis of these data
showed the desirability of extending the
study to provide information on the
performance of the swirl chamber with
different depth-width ratios.
The present series of tests was undertaken
to define the recovery rates when the
chamber diameter, weir height and inlet pipe
size were varied relative to each other.
As described in the earlier study, the
principle involved in these structures is a
controlled combination of solids settling and
rotational flow which tends to concentrate
the heavier particles at the inner part on the
chamber floor. Furthermore, the structure
which had been developed also included a
floatables trap set into the overflow weir.
It was decided to retain the basic
structural configuration that had been
developed for the 1972 studies, and to vary
the weir height and the pipe diameter with
respect to the fixed chamber diameter. The
model layout was shown in Figure 1.
Photograph 1, General View of Model, shows
the laboratory test structure.
Figure 2 gave the chamber internal
details, and Photograph 2, Interior of
Chamber Showing Submerged Inlet Floor
Gutters, Foul and Clear Water Outlets,
portrays the basic model chamber geometry.
Figure 19, Details of Gutter Centerline
Layouts, shows the locations of the gutters in
the chamber floor. It will be noted here that
the main gutter position was varied in the 0°
to 45° section. These minor modifications
PHOTOGRAPH 1
GENERAL VIEW OF MODEL
were required so the gutter centerlines would
coincide with those of the successively smaller
inlet pipes which were installed in the model.
Figure 20, Details of the Open Vortex
Foul Outlet, shows the opening through
which the heavier pollutants were drawn off
from the floor of the chamber. Figure 21,
Details of Floatables Trap, presents the
arrangement which had been developed on
the overflow weir to trap the floatables and
retain them under the weir.
In order to establish practical prototype
values for the study, the model was
considered first at 1/12 scale. On this basis,
the prototype chamber diameter, D2, would
be 10.96 m (36 ft). Five discharges were
selected which would cover any likely limits:
1.42, 2.83, 4.25, 5.66 and 8.49 m3/s (50,
100, 250, 200 and 300 cfs). Four inlet pipe
dimensions, DI , were chosen as being
practical with such a chamber: 0.91, 1.22,
2H
-------
PHOTOGRAPH 2
INTERIOR OF CHAMBER SHOWING SUBMERGED INLET FLOOR
GUTTERS, FOUL AND CLEAR WATER OUTLETS
NOTE-. Both gutters
3.8cm (l-i/t") wide
by 1.9cm (I/O deep
55.9 cm
'(22")
Secondary gutter
goes down on 1:4 slope
to 1.9 cm (3/4 ") depth
below chamber floor.
Position in this section
modified as required to
accommodate smaller
inlets.
35.6cm
(14")
17.1cm (6 s/4M)
22.9cm
(9")
FIGURE 19
DETAILS OF GUTTER CENTERLINE LAYOUTS
29
-------
3.8 cm
(I-1/2")
Gutter and
Outlet 1.9 cm
( 3/«") deep
2.54cm
(!")*
7.6 cm
(3") i
FIGURE 20
DETAILS OF OPEN VORTEX FOUL OUTLET
1.52 and 1.83 m (3 ft, 4 ft, 5 ft and 6 ft).
Photographs showing all four of these inlets
installed on the model appear on Photographs
2, ,3 and 4. These could be adapted directly
onto the model chamber. At least three weir
heights were tested for each inlet pipe
diameter. The total range selected for the
inlet pipe series was: 1.83, 2.14, 2.74, 3.36,
and 3.97 m (6, 7, 9, 11, and 13 ft). On the
model, some of the lower weir heights could
not be installed due to interference of the
weir and scum ring assembly with the inlet.
The structure configuration and range of
operations, as set out above, defined all the
parameters necessary to cover practical
depth-width ratios.
Model Description
The central feature of the swirl model
was the separation chamber itself, which took
the form of a vertical cylinder 91.5 cm (36
in.) diameter and 102 cm (40 in.) high, made
of 13 mm (1/2 in. Plexiglas®. The inflow line
to the chamber was a polyvinyl chloride
(PVC) pipe which could be 7.6, 10.2, 12.7, or
15.2 cm (3, 4, 5, or 6 in.) diameter, set at a
slope of 1 : 1000. A vibrating solids injection
device was installed on this supply pipe, 2.14
m (9 ft) upstream of the chamber. Water
supply to the model through the inlet pipe
was taken directly from the constant level
tank in one of the laboratory permanent
pumping stations.
A flexible 5.1 cm (2 in.) diameter tube
was connected to the swirl cylinder, beneath
the floor of the test chamber to collect the
foul flow. The tube from the bottom of the
cylinder, led to a solids settling tower fitted
with an adjustable level outlet pipe which
could be raised or lowered as required to
control the discharge through the foul outlet.
The clear water outlet was a cylinder,
rising from the chamber on the centerline of
the swirl basin in the form of a 15.2 cm (6
in.) diameter PVC pipe. Its crest level could
be changed easily either by adding or
removing sections of the same diameter pipe.
Outflow from this pipe, representing the
major portion of the total discharge through
the structure, was discharged into a large
30
-------
R= 2.54cm
(I")
5.16cm
(2")0
Flootobles Deflector
1.27cm
(1/2-) -~
SECTION A-A
\
6.3cm
(2-1/2")
FIGURE 21
DETAILS OF FLOATABLES TRAP
31
-------
settling basin equipped with a calibrated
V-notch weir. The basin provided sufficient
time for most of the solids contained in the
clarified swirl chamber overflow to settle out.
A point gauge on a manometer pot read the
level within the basin which determined the
discharge going over the V-notch weir, or the
clear discharge over the circular weir in the
swirl chamber.
In the model at the outset of this study,
the circular inlet pipe entered an enlarged
rectangular Plexiglas® enclosure fixed to the
cylindrical chamber wall. The different sized
square entrance forms could be fitted into
this enclosure to correspond to the inlet
pipes, as shown in Figure 16.
The floor of the chamber was constructed
with a thin cement mortar crust, supported
on a gravel base which filled the lower portion
of the chamber. The features shaped into the
floor included the slope, gutters and foul
outlet shown in Figures 2, 19 and 20.
Solids Simulation
Grit
The prototype gradation of the grit
material in sewage which is to be removed in
the swirl structure was chosen as shown in
Figure 4. The outside grain size limits of 0.2
and 2.0 mm (No. 70 and No. 10 sieve)
represent the standard soil mechanics
definition of medium and fine sand. The
specific gravity of the grit was assumed as
2.65, and the straight-line grain size
distribution was selected as a representative
average of grit size data reported for existing
sewage and treatment plants. Concentration
was considered as being from 20 to 360 mg/1.
Particle sizes larger than about 1 mm (No.
18 sieve) are known to remain suspended and
be transported in flowing water according to
equations of the type reported bv
Meyer-Peter and Muller1 , or H.A. Einstein2.
Between 1 mm and 0.2 mm (No. 1 8 and No.
70 sieve) the particles are in the transition
zone between the above equations and the
Stokes relation. Since the particles involved in
both prototype and model extended into
both ranges, across the transition zone, the
above equations could not adequately
describe the scale relations.
It was necessary, therefore, to use curves
of particle settling velocities as shown in
Figure 22, Particle Settling Velocities for Grit,
Organic Material and Gilsonite in Still Water.
For a given grit size with S.G. 2.65 in
prototype, the settling velocity was
determined from Figure 22. Based on
Froude's law of similitude, this was divided
by the square root of the scale being
considered to find the required model settling
velocity. By referring to Figure 22 with this
model settling velocity, the model particle
sizes were found for the simulating material,
Gilsonite.
The physical relations used here can be
expressed as follows:
Model scale = \ = Lp/Lm
where Lp and Lm are corresponding
lengths in the prototype and the model
respectively.
From Froudes Law, the velocity
simulation is expressed by the equation:
'm
and
V
m =
X
For example, if the scale ratio of
prototype to model is 4 : 1, the settling
velocity in the prototype should be divided
by the square root of 4 or 2. From Figure 22,
the settling velocity of prototype grit of 0.2
mm size is 2.6 cm/sec. The model settling
velocity is then 1.3 cm/sec. Thus, in the
model the grit of 0.2 mm size can be
simulated by 0.80 mm Gilsonite.
The Gilsonite available for test work in
the laboratory had the grain size distribution
shown in Figure 23, Gradation Curve for
Gilsonite Used in Model. Practical limits
represented on this curve were chosen
between 0.5 and 3.0 mm (No. 35 and No. 6
sieves), and the corresponding prototype grit
sizes simulated were calculated. The results
are shown in Figure 24, Prototype Grit Sizes
Simulated by Gilsonite on Model.
This figure shows that for smaller scales,
up to about 1/16, the Gilsonite did not cover
the larger prototype particle sizes. However, it
was reasoned that if the structure under study
showed a particular recovery rate for these
scales, the larger particles not simulated
would have settled equally as well. Therefore,
32
-------
Source:
Measurements by
L. H.L.
Source: 6.E. Contribution
to Report A.P.W.A. 70-7
.10 .20 .40
2.0 4.0 6.0
0.01
,03
10.0
.04 .08 .60 1.0
Particle diameter, mm.
FIGURE 22
PARTICLE SETTLING VELOCITIES FOR GRIT, ORGANIC
MATERIAL AND GILSONITE IN STILL WATER
33
-------
3 4
U.S. Standard sieve numbers
8 10 16 20 30 40 50 70 100 140
r i i i i i i 11 i
2 ! 0.6 0.4 0.2
Grain size in mm
0.
FINE
GRAVEL
COARSE
MEDIUM
FINE
SAND
100
FIGURE 23
GRADATION CURVE FOR GILSONITE USED IN MODEL
the recovery rate quoted would be
conservative.
Conversely, for scales larger than 1/16,
the lower model limit left a small zone of fine
grit not simulated. This portion might be
considered as lost, but at most, it actually
represents only 10 percent of the prototype
grit.
Organics
The organic material that it was desired
to remove from the flow in the prototype was
assumed to have a specific gravity of 1.2, and
a grain size distribution as shown in Figure 4.
The same Froude model scale-up procedure
was followed, and the limits simulated by the
Gilsonite were calculated as shown in Figure
34
-------
10.0
8.0
6.0
5.0
4.0
3.0
£ 2.0
E
1
S ..0
N
OT 0.8
~ 0.6
0 0.5
1 °'4
0 0.3
O
ot 0.2
O.I
Upptr 1
V
r
Lowtr
^
Up
'rototyp
S
/
f
'
Prototy
^
per M
• Limit
/
odel I
X
)t Limit v.
l— Lower
.imit
X^
dm
~~~r?.
^odel
dm =
= 0.5
^
Limit
^*-
3mm
mm
•— ••
3 1/4 1/8 1/12 '/I6 "/20 '/24
Model Scale - ^
FIGURE 24
PROTOTYPE GRIT SIZES SIMULATED BY
GILSONITE ON MODEL
25, Prototype Organic Material Sizes
Simulated by Gilsonite on Model.
The upper limits offer no difficulty; all
the larger sizes were very easily covered by
the Gilsonite. However, the lower model limit
left a significant zone of finer particles not
simulated throughout the scales being
considered. At 1/4 scale, particle sizes below
0.35 mm were not covered. Figure 4 shows
that this represents 15 percent of the total
sample. At 1/24 scale, particles smaller than
0.7 mm would not be included; Figure 4
shows that this represents 27 percent of the
sample. Although it would have been
preferable to provide model particles which
more adequately covered these smaller sizes,
the Gilsonite was retained due to its ease of
use in the laboratory, and on the basis that it
would at least give a consistent evaluation for
the major part of the prototype organics.
Floatables
Floating particles were assumed to have a
specific gravity between 0.9 and 0.998, and a
size range between 5 and 25 mm.
Concentrations of 10 to 80 mg/1 were
assumed. In the model studies, uniformly
sized polythene particles 4 mm in diameter
and a specific gravity of 0.92 were used.
Testing Procedure
Although use of the swirl concentrator as
a stormwater regulator would normally
involve a continuously varying discharge over
a storm hydrograph, for testing purposes in
the current depth-to-width investigation,
steady state discharges were used. For each
individual test run, the steady state discharge
was instituted in the model, and equilibrium
conditions were established. A mixture
containing one litre each of Gilsonite and
polythene was injected into the water supply
line entering the swirl chamber, using the
same vibrating rate for all tests; the full two
litres were added over a period of five
minutes.
As soon as all the Gilsonite and polythene
had entered the chamber and their flow
10.0
V
CL
o
o
w
0.
0.
1/8 1/12 1/16 '/20
Model Scale A
1/24
FIGURE 25
PROTOTYPE ORGANIC MATERIAL SIZES
SIMULATED BY GILSONITE ON MODEL
35
-------
pattern was firmly established, the influent
flow was stopped. The amounts of Gilsonite
that was entrained on the bottom of the
chamber or had passed out the foul outlet and
had gone over the weir were measured.
Similarly for the polythene, the amount
retained as floatables under the weir was
measured as well as that which had gone over
the weir.
The recovery, or removal, rate for the
Gilsonite was expressed as the percentage
represented by the amount measured on the
floor and which had gone out the foul outlet
as compared to the original full litre injected.
For the polythene, the percentage recovery
was expressed in terms of the amount
retained under the weir, with respect to the
full litre injected.
Settleable Solids Recovery Results
In discussing settleable solids for the
purpose of this report, reference is made to
the recovery rates for the Gilsonite only. As
described in the section on solids simulation,
the Gilsonite was assumed to represent grit
and organic materials over the ranges as
defined.
The recovery rates for the four sizes of
pipe inlets are shown in Figures 26, 27, 28
and 29, Gilsonite Recovery on Model for
15.2, 12.7, 10.2 and 7.6 cm (6, 5, 4 and 3 in.)
Inlets and Various Weir Heights.
Figure 26 shows that for the 15.2 cm (6
in.) inlet pipe, changes in the weir height had
very little effect on the Gilsonite recovery
rate. The same was true for the 12.7 cm (5
in.) inlet, although there appeared to be a
tendency for the curves to spread, as seen on
Figure 28. This spread, or variation, was more
distinct for the 10.2 cm (4 in.) pipe; Figure
29 and Figure 30 indicate that the different
weir heights did start showing significantly
different recovery rates for a given discharge.
In order to be able to convert the model
data into a useful design procedure, a mean
curve for anticipated settleable solids
(Gilsonite) recovery was selected for each of
the inlet sizes, covering a range of discharge
rates. These curves are portrayed in Figure 30,
Average Gilsonite Recovery Curves Used for
Design Curve Analysis. In fact, these average
curves result in the elimination of the effects
of the weir height changes, as the mean curves
all corresponded to a standard weir height of
O.I 0.2 03 0.4 0.5 0.7 cfs
Discharge,
FIGURE 26
GILSONITE RECOVERY ON
MODEL FOR 15.2 cm (6 in.)
100 -
90
80
70
58 60
•»
8 50
I 40
O
5 30
20
10
_L.—.—' —I L.—L_
H, =27.9 cm ( 11 in.)
H, * 22.8cm
(9 in.)
J L
4 5
10 15
-I 1 I 1_L
O.I
0.2 0.3 0.4 0.5 0.7 cfs
Discharge,
FIGURE 27
GILSONITE RECOVERY
ON MODEL FOR 12.7 cm (5 in.)
36
-------
100
90
80
70
8S
^ 60
01
>
o
£ 50
o»
o 40
_w
O
30
20
10
_j i i
H, - 33cm (13 in.)
HI - 27.9cm (II in.)
4 5
10
15 20
j
O.I 0.2 0.3 0.4 0.5
Discharge,
0.7 cfs
FIGURE 28
GILSONITE RECOVERY
ON MODEL FOR 10.2 cm (4 in.)
22.9 cm (9 in.), or a HI /D2 ratio of 0.25. The
rationale in support of this approach is that
the ratio of inlet dimension to chamber width
produces a far greater effect on the recovery
rates than weir height and therefore, should
be retained as the variable parameter.
Performance and Design Curve Development
Working from the average recovery values
established in Figure 23, these data were
scaled up to prototype structures having inlet
sewer sizes between 30.5 cm (1 ft) and 1.83
m (6 ft). The resulting performance curves
were presented as Figures 12 through 18.
The data presented in Figures 12 through
18 cover the complete range of performance
included in the model study, as applicable to
full-scale prototype installations. It would be
possible to use these curves to select pertinent
dimensions for swirl chamber structures, but
this is not a straightforward procedure.
Therefore, a set of design curves was prepared
for three recovery rates: 90, 80, and 70
percent.
By selecting particular recovery rates as
stated above, it was possible to choose from
100
90 -
80
70
60
o 50
* 40
30
20
10
HI = 33cm (I3in.)
H, = 27.9 cm (11 in.)
HI =22.8 cm (9in.)
HI = 17.8 cm ( 7 in.)
l5.2 cm (6 in.)
4 5
10
15 20 £/s
. i i I
O.I
0.2 0.3 0.4 0.5 0.7 cfs
Discharge,
FIGURE 29
GILSONITE RECOVERY
ON MODEL FOR 7.6 cm (3 in.)
Figures 12 through 18 the. corresponding
values for the discharge, inlet dimension and
chamber diameter over the complete range of
performance. The data resulting from this
analysis were plotted in Figures 7 through \ 0.
As stated earlier, the data application
steps required selection of a fixed weir height
to chamber diameter ratio — i.e., HL : D2 =
0.25. This dimensional relationship will be
retained as the so-called Standard Design.
However, it is obvious that for specific
design case, with a given discharge and inlet
size, if the chamber diameter can be
increased, it will be possible to reduce the
weir height, or depth of the swirl chamber.
Similarly, if the chamber diameter is reduced,
the required weir height or chamber depth
will be increased. The following procedure
was followed to modify the test data to allow
changes in the Standard Design geometry to
fit other depth-width (Hj : D2) ratios.
Based on 90 percent recoveries on the
average Gilsonite curves in Figure 30, the
values were scaled up to provide a nominal
30.5 cm (1 ft) inlet. The ratios of the
chamber volumes to inlet energies were
37
-------
100 -
10.2cm (4 in )
7.6cm (3in )
10 -
.2 .3 .4
Discharge
.6cfs
FIGURE 30
AVERAGE GILSONITE RECOVERY CURVES
USED FOR DESIGN CURVE ANALYSIS
computed as a function of the D2 : DI ratio
and presented graphically. For the four given
cases, with HI : D2 = 0.25, progressively
larger and smaller chamber diameters were
selected, varying the D2 : DX ratio. For each
new D2 : DI , a value for the volume-energy
ratio was found; this value was then divided
by the constant energy for the fixed inlet size
and discharge, to provide a corresponding new
chamber volume. The new weir height or
chamber depth was then computed as a
function of the chamber diameter.
The final results for H, : Dt and D2 :Dj
ratios were expressed in non-dimensional
form, as shown on Figure 11. This provides
information upon which to base design of
optimum swirl chambers to meet individual
project needs.
The design procedure utilizing these
figures is explained in Chapter III.
Floatables Recovery Results
Results of the tests with the polythene,
representing floatable material, were not as
uniform as for Gilsonite. The interpreted
average results for the four sizes of inlets
tested are shown on Figure 31, Average Model
Results — Polythene Recovery.
Following the same procedures as for
Gilsonite, the average curves we're scaled up
over the selected prototype range as shown on
Figures 32 to 38, Polythene (Floatables)
Recovery for 30.5, 45.7, 61, 91.5, 122,
152.5, 183 cm (1, 1.5, 2, 3, 4, 5, 6 ft) Inlet
Sewers and Different Sized Chambers.
Figure 38 portrays the curve for the 15.2
cm (6 in.) inlet, showing a polythene recovery
rate of only 10 percent for 9 1/s (0.33 cfs). In
the 1972 original tests a recovery of 65
percent was obtained. The only difference
between the 1972 tests and the current
studies was the inlet configuration. The
present inlet consisted of a square cross
section which advanced tangentially into the
chamber to the 0° position. In the earlier
work, the square cross section was terminated
at the chamber perimeter, and a baffle then
continued its inside wall to the 0° position.
38
-------
100
90
80
70
5«
^ 60
|
I 50
«
| 40
>.
"o
0- 30
20
10
D. = 12.7cm (5 in)
- D, = 15.2 cm (6 in )
2 3 45678 10 15
.10 .15 .20 , .y> .4 .5 .6 .7cf
Discharge,
FIGURE 31
AVERAGE MODEL RESULTS - POLYTHENE RECOVERY
100 -
03 .04.05.06 I .15 .2 .25.3m'/s
2 3 4 5 6 7 8 910 cfs
FIGURE 32
POLYTHENE (FLOATABLES) RECOVERY FOR 30.5 cm (1 ft)
39
-------
'i ' 'i ' ' '. 1" i ', I i1
3 4 5 6 7 8 10 15 20 25 30 40 cfs
FIGURE 33
POLYTHENE (FLOATABLES) RECOVERY FOR 45.7 cm (1.5 ft)
100
10 20 30 40 50
Discharge,
IOO cfs
FIGURE 34
POLYTHENE (FLOATABLES) RECOVERY FOR 61 cm (2 ft)
40
-------
100
90
80
70
60
50
40
30
20
10
0
20 30 40 50 100
i i i i i I i ill
200 cfs
.3 .4 .5 .6 .7 .8 1.0 1.5 2.0 3.0
Discharge,
mVs
FIGURE 35
POLYTHENE (FLOATABLES) RECOVERY FOR 91.5 cm (3 ft)
40 50 60 80 100 150 200 300 400 cfs
Discharge,
FIGURE 36
POLYTHENE (FLOATABLES) RECOVERY FOR 122 cm (4 ft)
41
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1.5 2 2.5 3 4 5 6 7 8 10 12 15 20
5060 80 100 150 200 300400500 800 1000 cfs
Discharge,
FIGURE 37
POLYTHENE (FLOATABLES) RECOVERY FOR 152.5 cm (5 ft)
100
200 300400500 800 1000 cfs
Discharge,
FIGURE 38
POLYTHENE (FLOATABLES) RECOVERY FOR 183 cm (6 ft)
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This baffle extended up to the same elevation
as the underside of the scum ring.
It appeared that the square inlet, being
lower, allowed a higher velocity to build up in
the top layers of the outside annular ring,
which later were transmitted to the area
under the weir disc. Although all the
polythene was captured by the floatables trap
and forced down under the weir disc, the
higher velocities carried it further and
gradually drew it out under the skirt and over
the weir.
The results of these tests, therefore,
provide a sound argument in favor of
retaining the baffle inlet developed in the
1972 project for DI : D2 ratios of say 1 : 6 to
1 : 9. From D! : D2 = 1.9 to 1 : 12, the
square inlet would give acceptable floatables
recovery.
Conclusions
1. With larger inlet lines entering the
chamber, say with a DI : D2 relationships of
1 : 6 to 1 : 72 variation of the weir height, or
chamber depth, had very little effect on
settleable solids recovery.
2. With smaller inlets, for D! : D2 of
1 : 9 or 1 : 12, the weir heights began to show
varying Gilsonite recoveries as they were
changed. However, a fixed ratio with the weir
height being one quarter the chamber
diameter, H, : D2 = 0.25, was retained for
the data analysis.
3. A set of Standard Design curves and a
design procedure were developed on the basis
of the Gilsonite (settleable solids) recovery
forH, : D2 =0.25.
4. A procedure was developed to modify
the depth-width ratio for any Standard Design
case, making it possible to select weir heights
and chamber diameters which might better
conform with other project requirements.
, 5. Floatables recovery, as represented by
polythene in the model, was less than
satisfactory for the larger square inlets, with
D! : D2 = 1 : 6 to 1 : 9. In this range, the use
of a baffle inlet is recommended.
6. For D! : D2 of 1 : 9 to 1 : 12, the
square inlet concept could provide acceptable
floatables recovery.
43
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-670/2-74-039
2.
3. RECIPIENT'S XCCESSIOWNO.
4. TITLE AND SUBTITLE
RELATIONSHIP BETWEEN DIAMETER AND HEIGHT FOR
THE DESIGN OF A SWIRL CONCENTRATOR AS A COM-
BINED SEWER OVERFLOW REGULATOR
5. REPORT DATE
July 1974;
Issuing Date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Richard H. Sullivan, Morris M. Cohn, James E
Ure, Fred E. Parkinson, and,George Galiana
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
AMERICAN PUBLIC WORKS ASSOCIATION
1313 East 60th Street
Chicago, Illinois 60637
10. PROGRAM ELEMENT NO.
1BB034/ROAP 21ATA/TASK 31
11. CONTRACT/GRANT NO:
68-03-0283
12. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
IB. SUPPLEMENTARY NOTES
Supplement to "The Swirl Concentrator as a Combined Sewer Overflow
Regulator Facility," EPA-R2-72-008, September 1972 (PB-214 687)
16. ABSTRACT
This report is a supplement to the report, The Swirl Concentrator as a Combined Sewer Overflow Regulator Facility,
EPA-R2-72-008, September, 1972. The work described by this report allows flexibility for the designer faced with structural, head or
land area constraints by enabling interchange of basic heights and diameter dimensions.
Studies of The Swirl Concentrator as a Combined Sewer Overflow Regulator Facility, conducted in 1972 by the American Public
Works Association Research Foundation for the City of Lancaster, Pennsylvania, and the U.S. Environmental Protection Agency,
demonstrated that this type of dynamic flow, non-mechanical device could effect excellent removals of suspended and floatable solids
contained in admixtures of sanitary sewage and storm water. This improvement in the quality of storm flow discharges to receiving
waters, or to treatment or storage facilities could reduce the pollutional impact on the nation's water resources.
The 1972 studies established a suitable relationship between swirl chamber depth and diameter and their effect on the liquid
flowfield and particle removal efficiencies. It was deemed advisable to augment the 1972 studies by investigating this depth-to-width
ratio and to define the dimensions which will provide optimum construction economy and operating efficiency in terms of solids
separation. This report presents an account of these supplemental studies of a hydraulic model of the swirl concentrator at.the LaSalle
Hydraulics Laboratory at Montreal.
The report translates the model study findings into a design basis that can be used for any rational flow rate in universal service for
the treatment of combined sewer flows. It establishes the basic principle that variations in overflow weir height, or chamber
depth, do not materially influence solids particle removals and that the most definitive design parameters are size of inlet sewer and swirl
chamber diameter. While the model studies showed that a ratio of weir height to chamber diameter of 1 : 4 was the most convenient to
use as a design aid, the data have been extrapolated to produce geometry modification curves that cover swirl chamber diameters and
depths. This information will be of value in the design of facilities which are the most economical and efficient.
The report provides design curves for various influent flow rates, covering chamber diameters and inlet sewer sizes which will
produce settleable solids removal efficiencies of 70, 80 and 90 percent. It presents design details for floatable solids traps to retain these
components, and for essential details of swirl chamber geometries. Procedures are outlined on how the model study curves can be used in
the design of prototype swirl concentrator units of various capacities and dimensional relationships.
The report was submitted in partial fulfillment of Contract 68-03-0283 between the U.S. Environmental Protection Agency and the
American Public Works Association.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
*0verflows, Design, *Combined
sewers, *Flow .control, *Flow regu-
lators, Flow rate, *Swirling--
separation, *Water treatment,
*Waste treatment
*Solids separation,
*Swirl concentrator,
Overflow quantity,
Overflow quality
13B
r18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)'
UNCLASSIFIED
21. NO. OF PAGES
54
RELEASE TO PUBLIC
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
44
U. S. GOVERNMENT PRINTING OFFICE: !97'i-757-5tiV5331 Region No. 5-11
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