EPA-600/2-75-033
September 1975
This document has not been
submitted to NTIS, therefore it
should be retained.
Environmental Protection Technology Series
TREATMENT OF
COMBINED SEWER OVERFLOWS BY
DISSOLVED AIR FLOTATION
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
point sources of pollution. This work provides the new or improved
technology required for the control and treatment of pollution
sources to meet environmental quality standards.
This document is available to the public through the National
Technical Information Service, Springfield, Virginia 22161.
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EPA-600/2-75-033
September 1975
TREATMENT OF COMBINED SEWER OVERFLOWS
BY DISSOLVED AIR FLOTATION
by
Taras A. Bursztynsky, Donald L. Feuerstein,
William 0. Maddaus, and Ching H. Huang
Engineering-Science, Inc.
Berkeley, California 94710
Project No. 11023DXL(S-802781-01)
Program Element No. 1BB034
Project Officer
Robert M. Rock
U.S. Environmental Protection Agency
Region IX
San Francisco, California 94111
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Environmental
Region Ve N
9-40
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publi-
cation. 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.
ii
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K
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 Municipal Environ-
mental Research Laboratory contributes to this multidisciplinary focus
through programs engaged in
• studies on the effects of environmental contaminants on the
biosphere, and
• a search for ways to prevent contamination and to recycle
valuable resources.
Essentially every metropolitan area of the United States has a
stormwater pollution problem. This report presents an evaluation of
the use of dissolved air flotation for the treatment of combined sewer
overflows.
iii
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ABSTRACT
This program investigated the use of dissolved air flotation for
the treatment of combined sewer overflows. As a result of this program
a 24-mgd prototype facility was constructed and evaluated.
The most recent study phase demonstrated the performance character-
istics of the prototype Baker Street dissolved air flotation facility
for the treatment of combined sewer overflows under a broad range of
operating conditions. Summary data from initial studies in this program
using a pilot plant and the prototype facility with dry-weather flow are
compared with the recent results. Improvements are suggested in the
design and operation of dissolved air flotation facilities.
Under several specific test conditions the Baker Street facility
effected reductions in combined sewage constituents which resulted in
an effluent quality meeting some local discharge requirements. Diffi-
culties were encountered with alum floe carry-over into the effluent.
Wastewater pollutant removals were highest—51 percent suspended solids
from an influent of 99.5 mg/1 and 82 percent BOD from an influent of
32.1 mg/1, measured in Test No. 8—at surface loading rates of 145 m3/
(m)2(day) [3,580 gal/(ft)2(day)], an alum dosage of 75 mg/1, and a
minimum air to solids ratio of 0.05 kg air/kg solids.
Specific design modifications are recommended for investigation to
determine their effect on system performance of the Baker Street
facility.
The construction cost for the 24-mgd Baker Street facility with
architectural treatment was $2,518,000, adjusted to an ENR index of
2240. Annual 0 & M costs are calculated to be $17,200.
This report was submitted in fulfillment of Project Number 11023
DIG (S 802281-01), by the City and County of San Francisco, under
partial sponsorship of the U.S. Environmental Protection Agency. Work
was completed as of April, 1974.
iv
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CONTENTS
Page
Abstract iv
List of Figures viii
List of Tables xi
Acknowledgments xiii
Section
I CONCLUSIONS 1
II RECOMMENDATIONS 5
III INTRODUCTION 8
Introduction 8
Project Objectives 9
Project Conduct 10
The Dissolved Air Flotation Process 11
The Baker Street Dissolved Air Flotation Facility 17
IV DISSOLVED AIR FLOTATION FACILITIES AND TESTING PROGRAM 18
Laboratory Program 18
Pilot-Plant Facilities 19
Baker Street Facility 22
Analytical Methods 36
V CHARACTERIZATION OF STUDY AREA 38
Drainage Basins 38
Hydrology 40
Sewerage and Diversion Systems 40
v
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CONTENTS (Continued)
Section Page
Dry-Weather Wastewater Characteristics 41
Combined Sewage Characteristics 42
VI PRESENTATION OF TEST DATA 44
Wet-Weather Data • 44
VII SYSTEM PERFORMANCE EVALUATION 71
Wet-Weather Wastewater Characteristics 71
Dry-Weather Wastewater Characteristics 75
Laboratory Test Studies 76
Pilot-Plant Test Studies 78
Dry-Weather Test Program 90
Wet-Weather Test Program 97
Optimization of Baker Street Facility Performance 126
Effluent Quality Requirements 131
Sludge Production 133
VIII ANALYSIS OF THE BAKER STREET FACILITY 135
Principal Combined Sewage Flow Path 135
Solids Removal System 138
Pressurization System 140
Chemical Feed System 142
Facility Operation 145
Facility Utilization 146
IX ECONOMIC ANALYSIS 150
Construction Cost Estimate 150
Operating and Maintenance Costs 151
X REFERENCES 156
XI APPENDICES 158
A. Description of Pre-Modification Standard Plant 159
Instrumentation and Control Systems
B. Nonstandard Analytical Methods 173
C. Tabulation of Operating Conditions and Process 177
Performance During Pilot-Plant Studies
VI
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CONTENTS (Continued)
Section Page
D. Tabulation of Operating Conditions and Process 184
Performance During Dry-Weather Testing of
the Baker Street DAF Facility
E. Results of Baker Street Dissolved Air Flotation 192
Treatment of Combined Sewage
F. Waste Discharge Requirements for City and County 208
of San Francisco Baker Street Flotation Facility
vii
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FIGURES
Figure Page
1 Flow sheet for dissolved air flotation process 12
2 Flow sheet of pilot-scale dissolved air flotation process 20
3 Baker Street dissolved air flotation facility and outfall 23
4 The Baker Street dissolved air flotation facility 24
5 Simplified process flow sheet of Baker Street dissolved 26
air flotation facility
6 The pressurization system 29
7 Control console at the Baker Street dissolved air 30
flotation facility
8 Effluent sampling station at the Baker Street dissolved 34
air flotation facility
9 Baker Street DAF facility performance at 0 mg/1 alum and 48
103 m3/(m)2(day); Test No. 1 (unmodified west-side
facility)
10 Baker Street DAF facility performance at 0 mg/1 of alum 50
and 145 m3/(m)2(day); Test No. 2
11 Baker Street DAF acility performance at 0 mg/1 alum and 51
182 m3/(m)2(day); Test No. 3
12 Baker Street DAF facility performance at 0 mg/1 alum and 52
232 m3/(m)2(day); Test No. 4
13 Baker Street DAF facility performance at 150 mg/1 alum 54
and 232 m3/(m)2(day); Test No. 5
14 Baker Street DAF facility performance at 300 mg/1 alum 55
and 232 m3/(m)2(day); Test No. 6
15 Baker Street DAF facility performance at 150 mg/1 alum 57
and 182 m3/(m)2(day); Test No. 7
16 Baker Street DAF facility performance at 75 mg/1 alum 59
and 145 m3/(m)2(day); Test No. 8
viii
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FIGURES (continued)
Page
17 Baker Street DAF facility performance at 0 mg/1 alum and 60
145 m3/(m)2(day); Test No. 9
18 Baker Street DAF facility performance at 150 mg/1 alum 61
and 145 m3/(m)2(day); Test No. 10
1*9 Baker Street DAF facility performance at 75 mg/1 alum 63
and 103 m3/(m)2(day); Test No. 11
20 Baker Street DAF facility performance at 0 mg/1 alum 64
and 103 m3/(m)2(day); Test No. 12
21 Baker Street DAF facility performance at 75 mg/1 alum 65
and 182 m3/(m)2(day); Test No. 13
22 Baker Street DAF facility performance at 300 mg/1 alum 66
and 182 m3/(m)2(day); Test No. 14
23 Baker Street DAF facility performance at 75 mg/1 alum 67
and 232 m3/(m)2(day); Test No. 15
24 Maximum removal of solids in pilot plant batch tests 79
25 Effect of specific alum dose on pilot-plant performance 81
26 Effect of specific polymer dose on pilot plant performance 83
27 Effect of surface loading rate on pilot plant performance 85
28 Effect of recycle ratio on pilot plant performance 87
29 Effect of air to solids ratio on pilot plant performance 89
30 Effect of specific alum dose on prototype dry-weather 93
performance
31 Effect of specific polymer dose on prototype dry-weather 94
performance
32 Effect of surface loading rate on prototype dry-weather 96
performance
33 Effect of air to solids ratio on prototype dry-weather 98
performance
34 Suspended solids removal with varying surface loading 101
IX
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FIGURES (continued)
Page
35 Suspended solids removal with varying alum dose 102
36 Floatables removal with varying surface loading 1Q5
37 Floatables removal with varying alum dose 1Q6
38 BOD removal with varying surface loading 107
39 BOD removal with varying alum dose 108
40 COD removal with varying surface loading 111
41 COD removal with varying alum dose 112
42 Oil and grease removal with varying surface loading 114
43 Oil and grease removal with varying alum dose 115
44 Settleable solids removal with varying surface loading 117
45 Settleable solids removal with varying alum dose 118
46 Turbidity removal with varying surface loading 119
47 Turbidity removal with varying alum dose 120
48 Ammonia removal with varying surface loading 122
49 Ammonia removal with varying alum dose 123
50 Organic nitrogen removal with varying surface loading 124
51 Organic nitrogen removal with varying alum dose 125
52 Frequency of treatment at specified flow rates at the 147
Baker Street dissolved air flotation facility
53 Comparison of treatment rate and untreated bypass with 148
the frequency of bypass at the Baker Street dissolved
air flotation facility
54 Construction costs of dissolved air flotaiton facilities 154
for combined sewer overflows
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TABLES
Table
1 Components and Characteristics of Pilot Plant 21
2 Ranges of Process Variables During Pilot-Plant Tests 22
3 Principal Characteristics and Components of Baker Street 27
Dissolved Air Flotation Facility
4 Summary of Prototype Dry-Weather Testing Program 33
5 Wet-Weather Testing Schedule 35
6 Average Dry-Weather Domestic Sewage Constituent Concen- 42
trations and Discharge Factors for Baker Street
Drainage Basin
7 Average Combined Sewage Constituent Concentrations and 43
Rainfall at the Baker Street Drainage Basin During
Pre-Construction Studies
8 Average Adjusted Constituent Analyses of Baker Street 69
DAF Facility Wet-Weather Program
9 Comparison of San Francisco Combined Sewage Wet-Weather 72
Program Wastewater
10 Influent Quality During Prototype Dry-Weather Testing 75
11 Diluted Sewage Concentrations for Pilot-Plant Testing 76
12 Effect of Alum and Alum-Polymer on Average Turbidity 91
Removal Efficiency
13 Baker Street DAF Facility Wet-Weather Performance Summary 99
14 Analysis of Performance Data for the Optimization of 130
Constituent Removal
15 Comparison of Baker Street DAF Facility Effluent with 132
Various Discharge Criteria
16 Current Construction Cost of the Baker Street Dissolved 152
Air Flotation Facility
17 Estimated Construction Costs for Dissolved Air Flotation 153
Facilities
18 Estimated Annual Operating and Maintenance Costs for 155
Dissolved Air Flotation Facilities
xi
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TABLES (Continued)
Table
Page
19 Summary of Pilot-Plant Operating Conditions 178
20 Summary of Influent and Effluent Characteristics of the 180
Pilot-Plant Tests
21 Summary of Influent and Effluent Characteristics for 181
Selected Pilot-Plant Tests
22 Summary of Pilot-Plant Performance 182
23 Summary of Float and Sludge Characteristics, Pilot- 183
Plant Continuous Runs
24 Baker Street Dry-Weather Testing Conditions 185
25 Summary of Influent and Effluent Characteristics, 186
Baker Street Dry-Weather Tests
26 Summary of Baker Street DAF Facility Performance During 189
Dry-Weather Testing
27 Summary of Float and Settled Solids Characteristics of 191
the Baker Street Dry-Weather Tests
28-42 First through Fifteenth Series Test Runs, Baker Street 193
Wastewater Analyses
xii
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ACKNOWLEDGMENTS
This project, conducted by Engineering Science, Inc., was supported
by the City and County of San Francisco, Department of Public Works,
under DPW Order No. 95,611, and the U.S. Environmental Protection Agency,
Office of Research and Development.
Specific mention must be made of the help received from the City
and County of San Francisco, notably Mr. S. Myron Tatarian, Director
of Public Works; Mr. Robert Levy, City Engineer; Mr. Alan 0. Friedland,
Chief of the Division of Sanitary Engineering, Bureau of Engineering,
and members of his staff, Mr. L. Vagadori and Mr. R. T. Cockburn. Much
of the project could not have been completed without the aid of Mr.
Daniel McNulty, Superintendent of the North Point Sewage Treatment Plant,
and Mr. William Hockenberry, Chief Operator of the Baker Street
Dissolved Air Flotation facility.
The assistance of Mr. Robert Rock, Project Officer for the U.S.
Environmental Protection Agency, who with his patience and helpful
suggestions saw this program through to a successful conclusion, is
gratefully acknowledged.
Many personnel from Engineering-Science, Inc. were involved in the
extended program of the Baker Street Dissolved Air Flotation facility
pre-construction studies, design and post-construction evaluation. This
report, which terminates the Phase III effort and summarizes the results
of the entire program, was prepared by Dr. D. L. Feuerstein, Program
Director; T. A. Bursztynsky, Project Manager; W. 0. Maddaus, Project
Engineer; and Dr. C. H. Huang, Project Engineer. The manuscript was
prepared by Ms. Mary Stauduhar.
xiii
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SECTION I
CONCLUSIONS
The conclusions based on the results of this study may have
wide application to the design of future dissolved air flotation
facilities and to the improvement of operations in the Baker Street
facility. Although some data were developed through extensive use
of laboratory, pilot-scale and prototype facilities, the data base
supporting the conclusions, particularly those obtained during the
wet-weather testing programs, is limited. Because of the normally
high variations occurring in the quality and quantity of combined
sewage overflows, the general applicability of findings and con-
clusions based upon a limited number of observations should be
carefully considered. Also, the unique influent conditions extant
at the Baker Street facility, namely a high capacity diversion sewer
with normally concomitant low flow velocities which provide for
sedimentation of settleable material immediately upstream of the
Baker Street processing facility, limit the indiscriminate appli-
cation of the conclusions presented herein.
On the basis of the results obtained during this study, the
following conclusions are presented.
(1) The dissolved air flotation process, in conjunction with
conventional wastewater facilities for treatment of re-
covered solids streams, has the capability to substantially
improve the quality of combined sewage overflows.
(2) Results of the wet-weather testing conducted over a wide
3 2
range of surface loading rates from 103 to 232 m /(m) (day)
2
[2,530 to 5,690 gal/(ft) (day)] and a range of alum dosages
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from 0 to 300 mg/1 indicated that the most desirable perfor-
mance of the Baker Street dissolved air flotation facility
was obtained at a surface loading rate of 145 m3/(m)2(day)
2
[3,580 gal/(ft) (day)] and an alum dosage of 75 mg/1 (Test
Run 8). At this operating condition, the following pollutant
removals were effected:
Concentration
Parameter
Total suspended solids,
mg/1
Settleable solids, ml/1
Floatable solids, mg/1
Turbidity, JTU
BOD, mg/1
COD, mg/1
Oil and grease, mg/1
Kjeldahl nitrogen, mg/1
Influent
99.5
1.8
1.6
53.2
32.1
97.3
1.8
5.9
Effluent
48.6
0.1
0.5
17.9
5.9
58.4
2.8
3.1
Percentage
temoval
51
94
68
66
82
40
0
47
(3) The Baker Street dissolved air flotation facility would
intercept approximately 113 combined sewage discharges
o
annually, providing treatment or storage for 337,000 m
[89 million gallons] of wastewater. It is calculated
3
that less than 1320 m [350,000 gallons] annually of com-
bined sewage would exceed the capacity of the Baker Street
facility.
(4) Chlorination of the influent to the Baker Street dissolved
air flotation facility effected large and almost total reduc-
tions of fecal coliforms.
(5) Chemical conditioning, with alum, of the influent to the dis-
solved air flotation process was essential to achieve accept-
able performance. On the basis of pilot-plant studies, alum
used singly was found to be more effective than polymer (DOW
Purifloc C-31) used singly.
(6) Control of pH during wet-weather testing was extremely diffi-
cult using a flow-proportioned feed of caustic soda, due to
a highly varying influent water quality. These normal varia-
tions in influent water quality can be expected to make precise
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chemical conditioning of the influent also quite difficult .
(7) The results of the prototype dry-weather tests were comparable
to the wet-weather test results, in spite of significant dif-
ferences in operating procedures. This implies that sanitary
sewages can be used to establish, on a preliminary basis, the
general performance of a specific dissolved air flotation fa-
cility design. The pilot-plant test results with diluted
sanitary sewages were generally superior to the prototype dry-
weather and wet-weather test results. This is believed to be
a result of significant differences in mechanical and struc-
tural features between pilot-plant and prototype facilities.
Therefore, if a pilot plant is to be used to verify the effec-
tiveness of a dissolved air flotation facility design, it
should have features identical with those of the full-scale,
or prototype, facility.
(8) The generally superior performance of the pilot plant over
that of the prototype and the alum carry-over into the effluent
experienced with the prototype appear to indicate that a
good flocculation system, available in the pilot plant and
not the prototype, is essential in treating combined sewages.
(9) Wet-weather testing experience demonstrated that operator
presence was not necessary for the Baker Street dissolved air
flotation facility to commence operation and treat combined
sewer overflow at present operating conditions. Operator
presence is necessary, however, to perform routine maintenance,
calibrate instruments, collect automatically composited samples
for delivery to an analytical laboratory, and alter maximum
surface loadings and chemical dosages, if desired.
(10) The capital cost for the 1 m3/sec [24 mgd] Baker Street
facility with architectural treatment and extended operational
flexibility was $2,518,000, adjusted to an ENR construction
cost index of 2240. Reduction of the design surface loading
rate from 214 m3/(m)2(day) [5260 gal/(ft)2(day)] to 127 m3/
(m)2(day) 3120 gal/Cft)2(day) is calculated to raise construe-
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tion costs to $3,200,000. This would represent an increase in
construction costs by $56,000 from $216,000 on an annual basis.
Annual operating and maintenance costs are calculated to be
$17,200.
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SECTION II
RECOMMENDATIONS
The recommendations derived from this study are intended to aid
designers and operators of dissolved air flotation facilities used for
the treatment of combined sewer overflows. Recommendations specifically
applicable to the Baker Street dissolved air flotation facility will be
so noted.
The following actions are recommended.
(1) The City of San Francisco should take full advantage of the
Baker Street dissolved air flotation test facility as presently
configured. During the next wet-weather season, the data base
acquired during this study should be expanded by conducting
further tests, particularly to verify performance character-
istics near the observed best operating point, while simultan-
eously operating the facility for its primary function, which
is treatment of combined sewer overflows. These tests should
include studies of the Baker Street facility hydraulics and
the use of other chemicals for aiding flocculation and
achieving pH control. Particular emphasis should be placed
upon sodium carbonate for pH control with alum and various
polymers as replacements for alum.
(2) Until further data are developed to indicate otherwise, the
Baker Street dissolved air flotation facility, or that portion
of the facility (i.e. the west flotation tank) not being used
for further testing, should be operated at an alum dosage of
75 mg/1 and a minimum air-to-solids ratio of 0.06 kg/kg
(equivalent to 21 ml of air dissolved in each liter of
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pressurized liquid). The pH should be adjusted with sodium
carbonate. Chemicals should continue to be injected into
the pressurized system. These recommendations are based
upon the combined wastewater characteristics specific to the
Baker Street drainage area.
(3) The Baker Street dissolved air flotation facility should with-
draw feed to the pressurization system from the untreated
influent stream and not from the facility effluent stream.
During the testing program, chemicals were added to the re-
cycled pressurization stream and the initial wastewater flow
into the system prior to recycle did not receive adequate
chemical dosage.
(4) Large instructional signs clearly explaining functions and
procedures should be located in the facility. This will
greatly aid personnel who, because of other full-time duties
and the intermittent operation of the facility, might not be
continuously practiced in the operation of the facility.
(5) If further testing of the Baker Street dissolved air flota-
tion facility is to be performed, the City of San Francisco
should consider alleviating the undesirable hydraulic con-
ditions, i.e. low velocities and high residence times, created
in the trunk sewer leading from the diversion structure to the
Baker Street facility during low and moderate runoff periods.
(6) A sharp-crested weir, or some other device or means which can
minimize water surface level variations, should be used to
collect treated flotator effluent.
(7) Although an airlift pump is adequate for settled solids removal,
the air supply to the pump at the Baker Street facility should
be equipped with a flow meter to aid in proper adjustment.
(8) The pressurization wastewater flow system at the Baker Street
facility should be equipped with a flow meter. This is
essential in determining the volume of air delivered to the
flotation system.
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(9) Automatic pH control systems should be incorporated into the
design of dissolved air flotation facilities which employ
chemicals for the enhanced removals of pollutants from com-
bined sewer overflows.
(10) A flocculator should be incorporated into the design of
dissolved air flotation facilities treating combined sewer
overflows. The flocculator would serve the dual purpose of
achieving better chemical floe formation and providing a sens-
ing point for the automatic control of pH.
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SECTION III
INTRODUCTION
INTRODUCTION
Combined sewage is a mixture of various types of discharges to a
sewer system designed for conveyance of both domestic and industrial
wastewaters and storm water runoff in a single conduit. During periods
of excess storm water runoff, combined sewage flow rates frequently
exceed the capacity of existing dry-weather sewage treatment facilities.
Traditionally, for those time intervals during which the capacity of
treatment facilities is exceeded, the excess flow has been bypassed
directly to receiving waters without the benefit of treatment. These
combined sewer overflows have been identified as a major short-term
source of pollution contributing to the degradation of the aquatic envi-
ronment adjacent to many urban areas.
Urban demands for a high quality land and water environment have
generated a need for treatment of combined sewer overflows to improve
water quality but have also reduced land availability in the urban envi-
ronment for construction of appropriate treatment facilities. In addi-
tion, the need for treatment of combined sewer overflows has placed
demands on available technology for wastewater management systems which
can remove pollutant materials deleterious to the quality of receiving
waters and which require a minimum of land space, maintenance, and
operating staff.
Recognizing the need to upgrade quality levels of wet-weather dis-
charges from their combined sewer system, the City and County of San
Francisco has developed a comprehensive program for wet-weather control.
As part of this program, a U.S. Environmental Protection Agency
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Facilities Demonstration Grant Project was undertaken. The project
consisted of the design, construction, operation, and evaluation of a
demonstration dissolved air flotation facility for the treatment of
combined sewer overflows. This was the first municipal facility in the
United States constructed for the treatment of combined sewer overflows.
The demonstration facility is located adjacent to the principal municipal
marina on the shoreline of San Francisco Bay. The treatment site was
selected because of the size of the contributing drainage basin for
demonstration purposes and because of the need for improvement of the
quality of receiving water contiguous to Outer Marina Beach during wet
weather.
The overall Facilities Demonstration Grant Project was divided into
three phases extending over a six-year period from 1968 to 1971 and from
1973 to 1974:
Phase I Preconstruction studies on quality and quantity relation-
ships of combined sewage flows and receiving water
studies at Outer Marina Beach.
Phase II Design and construction of Baker Street stormwater
pollution control treatment facility.
Phase III Post-construction studies on operation and evaluation of
Baker Street stormwater pollution control facility.
This report emphasizes the findings and conclusions of the Phase III
study and gives a summary of the overall project. Results of the Phase I
studies have been presented to the City and County of San Francisco in an
earlier report (Reference 1).
PROJECT OBJECTIVES
The general objective of Phase I of this project was to provide
background data for the determination of the efficacy of the dissolved
air flotation process in treating combined sewer overflows for the abate-
ment of receiving water pollution.
The objective of Phase II was to design and construct the Baker
Street storm water pollution control treatment facility.
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The general objective of Phase III was to demonstrate the efficacy
of the dissolved air flotation process in treating combined sewer over-
flows for the abatement of receiving water pollution. Specific objec-
tives were:
(1) to operate the Baker Street dissolved air flotation facility
during the occurrence of combined sewer overflows;
(2) to evaluate the results from the operation of the Baker Street
facility in terms of the relationships between process control
variables and performance characteristics for the development
of design criteria;
(3) to translate operating data and design experience gained from
this prototype facility into useful information for future
installations; and
(4) to determine total costs of dissolved air flotation facilities
in these applications.
PROJECT CONDUCT
Phase I included a characterization of six drainage basins in San
Francisco, five of which are served by combined sewers. A total of 20
storms were monitored on selected basins during the period November 1968
to April 1970, and quantity and quality relationships were developed for
each of the drainage basins. Data from the Baker Street basin were used
to design the prototype dissolved air flotation facility. Background
receiving water studies (Reference 2) were also done in the vicinity of
the proposed treatment facility outfall location.
Phase II included development of laboratory- and pilot plant-scale
data to establish process behavior prior to operation of the full-scale
Baker Street facility. The actual evaluation of the Baker Street faci-
lity was done in Phase III. Laboratory jar tests and flotation cell
studies, pilot-plant tests, and an evaluation of the Baker Street faci-
lity with dry-weather domestic sewage were undertaken from the period
October 1970 to July 1971. Evaluation of the Baker Street facility during
wet-weather combined sewage flows was conducted during the period Septem-
ber 1973 to April 1974. This report attempts to bring together all data
10
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collected in the dissolved air flotation studies, to compare them on a
common basis, and to evaluate the efficacy and economics of the Baker
Street dissolved air flotation facility for the treatment of combined
sewer overflows.
THE DISSOLVED AIR FLOTATION PROCESS
Air flotation is a unit operation for the separation of a solid
phase from a liquid phase. Essential elements of the flotation process
are introduction of air into the liquid stream, formation of minute
bubbles, formation of air-discrete solid aggregates, and separation of
the aggregates from the liquid.
An initial distinction between types of air flotation processes can
be made on the basis of the method of introducing air to the liquid
stream and the method of bubble formation. In dispersed air flotation,
which has been applied extensively in the metallurgical industry, gas
bubbles are generated by mechanical shear of propellers, diffusion of gas
through porous media, or homogenization of the gas and liquid streams.
In dissolved air flotation, gas bubbles are generated by the precipita-
tion of air from a supersaturated solution. Dissolved air flotation can
be further classified into either pressure or vacuum flotation, depending
on the pressure used to cause gas precipitation. Solution of gas under
elevated pressure and its subsequent precipitation from solution at
atmospheric conditions constitutes pressure flotation. Vacuum flotation
involves gas solution under atmospheric pressure and gas dissolution
under vacuum. Subsequent discussion refers only to the pressure flota-
tion aspects of the dissolved air flotation process. A flow sheet for
the dissolved air flotation process is shown in Figure 1.
The basic objective for the sanitary engineering application of the
dissolved air flotation process has been to maximize the removal of
influent solids as floated or settled solids. A corollary objective in
the application of the dissolved air flotation process for treatment of
raw sewage, primary sewage effluents, and combined sewage flows has been
to maximize the selective recovery of other floatable, or potentially
floatable, constituents. The fundamental dissolved air flotation process
11
-------
UJ
RAW WASTE
N
cr
13
CO
CO
UJ
cc
a.
INFLUENT
RECYCLE FOR
PRESSURIZATION
•AIR
I PUMP
PRESSURIZED
AIR SOLUTION TANK
FLOTATION
CHAMBER
TREATED
FLOW ^
AFLOAT AND
"^SETTLED SOLIDS
Figure I . Flow sheet for dissolved air flotation process
-------
parameters -which can be manipulated to attain these objectives are the
independent process variables associated with the input and precipitation
of air, chemical addition, and solids and surface loading rates. The
fundamental subprocess interactions and mechanisms operative in the dis-
solved air flotation process have been described in detail (Reference 3).
The following discussion is presented for the purpose of illuminating the
relationships which define the subprocess interactions and of providing a
basis for evaluation of the performance of the dissolved air flotation
facility at Baker Street.
Introduction of Air
The pressure dissolved air flotation process is dependent upon gas
dissolution into the liquid phase at elevated pressure. It has been
reported (Reference 3) that a 60- to 80-percent saturation of the liquid
with air can be accomplished by air injection to the suction side of a
centrifugal pressurization pump. Up to 110 percent of the air required
for saturation can be added to the suction side of a centrifugal pump
without air binding the pump. An air solution tank with 30- to 60-sec
hydraulic residence, times is generally provided to assure maximum satura-
tion of liquid with air.
The pilot-plant and prototype facilities in this project were
2
operated at 42,200 to 45,700 kgf/m [60 to 65 psig] in the pressurization
system.
Formation of Air Bubble-Particle Aggregates
The formation of air bubble-particle aggregates can be viewed as a
sequence of events including gas precipitation, chemical conditioning of
solids, and aggregate formation. Gas precipitated as fine bubbles is
the driving force for the flotation of particles whose density is greater
than that of the suspending liquid. The bulk density of the air-discrete
solid aggregates must be less than the bulk density of the liquid for
flotation of the aggregate to occur . Application of chemical flocculat-
ing agents to promote formation of floes and air bubble-particle aggre-
gates in flotation has been cited frequently in the sanitary engineering.
literature as a fundamental requirement for improved process performance.
13
-------
Chemicals such as alum, ferric chloride, and polyelectrolytes, either
singly or in combination, have been used (References 4, 5, 6, and 7).
The quantification of the size, number, and character of air bubble-
particle aggregates formed in a dissolved air flotation process applica-
tion cannot be readily accomplished at the present time. In the absence
of an explicit parameter, the air to solids ratio, or ratio of mass of
air provided per mass of solids loaded, has been used as an implicit
parameter to define a relative driving force to float the aggregate.
Loading Rates
Depending upon the application, either the solids loading rate,
2 2
expressed as kg/(m) (day) [lb/(ft) (day)], or the liquid surface loading
32 2
rate, expressed as m /(m) (day) [gal/(ft) (day)], is the primary inde-
pendent variable in the dissolved air flotation process and governs the
surface area required for the flotation tank.
Solids Loading Rate—
The solids loading rate is the measure of the burden placed on the
flotator and is a basic factor in determining the air input and chemical
addition requirements for successful flotation. Solids loading rates
reported (References 5, 8, 9, 10, and 11) for dissolved air flotation
applications with combined sewage, primary sewage effluents, primary
sewage sludges, and mixtures of primary and waste activated sludges vary
within the range of 20 to 156 kg/(m)2(day) [4 to 32 lb/(ft)2(day)] for
dilute streams with less than 500 mg/1 feed solids concentration and
between 20 to 244 kg/(m)2(day) [4 to 50 lb/(ft)2(day)] for sludge
thickening applications.
The solids removal levels for these applications reflect the
effects of the diverse types of inlet structures, recycle schemes, and
flotation tank designs used in the various plants, as well as actual
process performance. In general, solids removal efficiency in the
dilute-stream dissolved air flotation applications was found to vary
inversely with the solids loading rate.
14
-------
Liquid Surface Loading Rate—
The liquid surface loading rate takes precedence over the solids
loading rate when, for a given solids loading rate and influent solids
concentration in a wastewater, the required liquid throughput rate is at
such a level that flow velocities and turbulence adversely affect the
recovery of floated and settled solids in the process. The surface
loading rate can also affect the height of flow over fixed effluent
launders in the tank and the tank level at which the skimming system must
be functional. With increasing liquid surface loading rates, one or more
of the following factors can be expected to limit process performance:
(1) aggregate destruction in the flotation chamber;
(2) hydraulic overloading of the effluent launders or the skimming
system;
(3) agitation of the liquid surface in the flotator and break-up
of the float; and
(4) short-circuiting of influent feed through the flotator.
Recycle Ratio
Two modes of introducing pressurized flow are currently in use.
Because it is unnecessary, and due to substantially greater equipment and
operating costs, the entire influent stream is not pressurized for solu-
tion of air. It is common practice to saturate a smaller stream of
liquid with the necessary air to effect flotation. One mode of operation
pressurizes a portion of the influent stream, which is subsequently mixed
with the balance of the flow in the flotator. Another mode of operation
recirculates a portion of the facility's treated effluent through the
pressurization system to the flotator. Since the quantity of water re-
circulated through the system can effect the hydraulics of the system,
the recycle ratio of return flow to untreated influent flow is used as a
control parameter by the system operator. The pilot-plant and prototype
facilities tested in this program employed the recycle pressurization
mode of operation.
15
-------
Float Development and Removal
The float (or froth) in the dissolved air flotation process builds
up in the flotation tank and is comprised of floated solid particles and
collapsing air bubbles. The float is formed by the introduction of the
pressurized waste stream into the flotation tank. Upon formation of air
bubble-particle aggregates, the aggregates rise toward the liquid surface
and form a scum layer. The final volume of the float is a function of
the input solids loading, the degree of thickening in the float, and the
efficiency of scum removal from the flotator. The solids in the float
can be skimmed off the liquid surface by mechanical or hydraulic means.
The concentration of solids in the float is a function of float skimmer
depth and the rate of float removal. It has been noted that at slow
skimming speeds the float tends to deteriorate and lose solids; experi-
ence suggests that there is an optimum skimming speed dependent on the
individual system characteristics.
Summary of Control and Performance Variables
From the foregoing information, the key variables which define the
performance of a given dissolved air flotation treatment facility are:
3 2
(1) surface loading rate to the flotation tank, m /(m) (day) [gal/
2
(ft) (day)], defined as influent plus recycle flows divided by
the effective cross-sectional area of the flotation tank;
(2) chemical dose, mg/1, and type;
(3) influent suspended solids concentration to the flotation tank,
mg/1;
(4) recycle ratio, percentage of recycle flow rate to influent
flow rate;
(5) air to solids ratio, kg air/kg solids; and
(6) float skimming height, cm [in.], and skimmer speed, cm/sec
[fpm].
Because of the presently limited availability of operating data for
sanitary engineering applications of the dissolved air flotation process,
establishment of the effect of the above variables upon performance and
calibration for best performance is a necessity for all new installations,
16
-------
THE BAKER STREET DISSOLVED AIR FLOTATION FACILITY
The Baker Street dissolved air flotation facility was designed for
the treatment of combined sewer overflows and, as such, was intended to
be operated as a support facility to the North Point wastewater treatment
facility. Thus, the Baker Street facility is used to reduce the pollu-
tional effects of combined sewer overflows to San Francisco Bay and to
reduce the hydraulic loading upon the North Point facility during periods
of storm water runoff. The sludges created at Baker Street, containing
the floated and settled solids and other pollutants separated from the
bulk of the treated combined sewage, are pumped to the Beach Street sewer
leading to the North Point facility where they are removed and treated as
primary sludge.
In those instances where the dissolved air flotation process repre-
sents a terminal treatment facility, appropriate works for treating and
disposing of floated and settled solids removed by the dissolved air
flotation process would be required.
17
-------
SECTION IV
DISSOLVED AIR FLOTATION FACILITIES
AND TESTING PROGRAM
Dissolved air flotation facilities used in the conduct of this
program consisted of laboratory jar-test equipment and flotation cells,
a pilot-scale plant, and the Baker Street dissolved air flotation facil-
ity. Detailed descriptions of the laboratory facilities and the pilot-
plant facilities may be found in References 3 and 12, respectively.
LABORATORY PROGRAM
The apparatus used in the laboratory program consisted of a stand-
ard jar-test unit as described in Standard Methods for the Examination
of Water and Wastewater, 13th Edition (Reference 13).
A departure from the methodology of Standard Methods for the jar
tests was used in the program because of the physical characteristics
of the Baker Street facility. Specifically, a rapid mix of two minutes'
duration was used throughout the experiments to simulate mixing time
(under two minutes) in the recycle loop of the prototype facility.
After mixing, the contents of the jars were observed for floe formation
and settleability. The settling time of 20 minutes was used in the jar
tests to simulate the detention time in the flotation tank. Samples
were taken from each jar from the same depths and analyzed for pH and
turbidity. Turbidity readings were converted to suspended solids con-
centrations by means of a correlation curve. Jar-test data were
collected frequently to establish investigative ranges of operating
variables for the pilot-plant and the Baker Street dissolved air
flotation facilities.
18
-------
PILOT-PLANT FACILITIES
Description
The pilot plant was located on the grounds of the North Point water
pollution control plant and consisted of a. 3.2-1/sec [50-gpm] Float-Treat
unit (Rex-Chainbelt, Inc.). A process flow sheet for the pilot-plant
system is presented in Figure 2. The characteristics and components of
the unit are listed in Table 1. The pilot plant contained one signifi-
cant difference from the prototype facility in that only the pilot plant
was equipped with a slow mix or flocculation system. Pilot-scale tests,
conducted during the construction of the prototype facility, indicated
that similar performance could be achieved either with or without a
flocculation system. It should be noted that these tests were conducted
with a wastewater of consistent quality, very unlike the highly variable
combined sewage feed to the prototype.
Test Procedures
Batch-Test Program—
Batch tests were made on the pilot-plant unit in an effort to as-
certain the range of chemical dosages for the continuous-run program and
to establish the maximum amount of suspended solids that could be re-
moved by this process. Batch tests were performed by filling the unit
with chemically treated wastewater and then adding air, recycling the
tank contents, and operating the float and sludge removal systems until
the quality of the samples taken from the effluent clear well showed no
further improvement. Tests were conducted on domestic sewage diluted
with tap water to the level of 100 mg/1 suspended solids at the start of
the test. Test conditions for the four batch tests conducted were:
alum dosages of 52,70, and 370 mg/1 at a surface loading rate (due to
recycle only) of 37.2 m3/(m)2(day) [915 gal/(ft)2(day)]; and an alum
dosage of 105 mg/1 at a surface loading rate (due to recycle only) of
19.8 m /(m) (day) [486 gal/(ft) (day)]. For all tests, pH varied between
6.2 and 6.5.
Continuous-Run Program—
The continuous-run program with the pilot-plant unit was designed
to collect data during steady-state operating conditions. Surface load-
ing rate, recycle flow rate, influent quality, chemical dosage, air to
19
-------
AIR
K3
o
^-PRESSURIZED
/AIR SOLUTION
Jfr y TANK
^"^"**r
ALTERNATE CHEMICAL ADDITION It ^ f \*
(WITH FLOCCULATOR BY-PASS) H
DILUTION
WATER
RAW SEWAGE fc DILUTION
FROM BEACH ST. W SYSTEM
SEWER
1
1
1
1
1
i^J
f !
1 1
1
| ^ FLOCCULATION V 1
V^X
^"•••m»^
o:
o
u.
Ul
o
0
UJ
cc
k
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0
fe
N
CO
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o.
1
h-UJ
r ^ ^.^.^« 5* TREATED ^
^* CHAMBER w '""«'w" 3^ FLOW "
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U._J
ll 1 t \
h»« N.^
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CHEMICAL £ i Q §
ADDITION 3u! 3uj
u. tr to cc
Figure 2 : Flow sheet of pilot-scale dissolved air flotation process
-------
Table 1. COMPONENTS AND CHARACTERISTICS OF PILOT PLANT
Sector
Item
Description
Hydraulic
Flotation chamber
Flocculation chamber
Recycle system
Chemical feed
Treatment capacity
Surface loading rate
Surface area
Volume
Flight speed range
Sludge
Volume
Paddle speed range
Recycle pump
Air requirement
Alum
Polymer
Caustic
Approximately 3.15 I/sec [50 gpm]
maximum
170 m3/(m)2(day) [4,200 gal/(ft)2
(day)]
2.2 m2 [23.7 ft2]
2460 1 [650 gal]
0-5.59 cm/see [0-11 fpm]
1.02 cm/sec [2 fpm]
644 1 [170 gal]
0-0.55 m/sec [0-1.8 ft/sec]
0-1.26 I/sec [0-20 gpm]
0.109 I/sec at 29,500 kgf/m2
[0.23 cfm at 42 psig]
0-500 ml/min
0-500 ml/min
0-500 ml/min
-------
solids ratio, skimmer speed, and flocculator paddle speed (when used)
were preset at desired levels. For the process evaluation, one control
parameter was varied while all others were maintained at the reference
levels. The influent suspended solids concentration was adjusted by
adding tap water to raw sewage and was monitored by frequent checking of
influent turbidity. Influent and effluent sampling was commenced at
10-minute intervals following a 30-minute period of relatively constant
influent and effluent turbidities.
On the basis of the results of the laboratory tests and batch runs,
continuous-run objectives were formulated and the process control vari-
ables were set as shown in Table 2.
Table 2. RANGES OF PROCESS VARIABLES DURING PILOT-PLANT TESTS
Variable3
Specific alum dose
Recycle ratio
Surface loading rate
Air/solids ratio
Influent TSS concentration
Specific polymer dose
Alum/polymer combinations
Range
0
20
39
0.01-
60
0
0/0 -
3.2
130
170
0.21
140
0.65
0.9/0.15
Unit
mg/mg influent TSS
%
3 2
m /(m) (day)
kg air/kg TSS
mg/1
mg/mg influent TSS
mg/mg influent TSS
o
A constant skimmer system flight travel rate of 1 cm/sec [2 fpm]
was used in all runs, and a constant flocculator paddle speed of 0.5
cm/sec [1 fpm] was used in all runs when the flocculator was used.
BAKER STREET FACILITY
Description
The Baker Street facility is located at the northwest corner of the
Marina Green in San Francisco. Figure 3 is a location map showing the
facility, the 2.7-m [108-in.] diameter outfall from the facility and the
sewerage immediately upstream from the plant at the intersection of
Baker Street and Marina Boulevard. Figure 4 shows an external view of
22
-------
\x DISCHARGE AT 9m BELOW
V\\ MEAN TIDE LEVEL
2.7 m 0 OUTFALL
FLOTATION
FACILITY
EXIST. 0.53 m0
SEWER TO
MARINA PUMP
STATION
IDENTICAL
BYPASS WEIR
STRUCTURE
DIVERSION
STRUCTURE
1.5 m 0 SEWER •
Figure 3 • Baker Street dissolved air flotation
facility and outfall
23
-------
-r\
td
c
H
3-
ct>
CD
Q
3T
(0
(0
0>
(0
O)
Q.
O
-+•
Q
O
O
-------
the facility with the public sun deck located directly over the flotation
tanks.
A process flow sheet for the Baker Street facility is presented in
Figure 5, and the principal characteristics and components of the facil-
ity are listed in Table 3. The hydraulic capacity of the entire treat-
ment facility is 1 m^/sec [24 mgd], and the capacity of the influent
structure and outfall is 7 m-Vsec F160 mad], which is sufficient to
accommodate the runoff from a five-year storm. The treatment facility
o
is comprised of two modules, each of 0.5-m [12-mgd] capacity and
each capable of independent operation. Each module has the following
major components.
(1) Flotation tank, designed at a nominal surface loading rate of
255 m3/(m)2(day)[6,310 gal/(ft)2(day)] and equipped with sludge
and scum removal systems.
2
(2) Recycle system, with pumping capacity rated at 0.1 m /sec
[2.4 mgd] (or 20 percent of the maximum influent flow rate)
and piping to permit intake of recycle flow either from the
flotation tank at a point just under the effluent launder or
from the raw influent stream. Recycle system includes a two-
stage centrifugal pump, retention tank, and four pressure-reduc-
ing valves (one for each of the four flotation cells) for each
tank.
(3) Air pressurization systems for addition of air between stages
of the recycle centrifugal pumps, as shown in Figure 6;
(4) Chemical feed systems for handling alum, caustic, polyelectro-
lyte, and sodium hypochlorite solutions, which can be introduced
separately or in any combination to either flotation tank.
Three different introduction points are available; namely, into
the main influent line, into the inlet manifold or into the
recycle piping.
(5) Solids handling system, providing for the air-lifting of
settled solids and gravity flow of floated solids to a common
solids sump for both flotation tanks and for the ultimate trans-
fer of material from the solids sump to the Marina pumping station.
25
-------
LEGEND
A AIR
P PRESSURIZED FLOW
R RECYCLE
S SOLIDS TO WASTE
FS FLOATABLE SOLIDS
SS SETTLEABLE SOLIDS
TO TREATMENT
I m^/sec
AIR SOLUTION ( ) — P
TANK \J
COMPRESSOR
AUTOMATIC
BUTTERFLY
VALVE
PRESSURE
REDUCING
VALVES
STORM FLOW /
7 m3/sec
BAR
,— .
MAGNET
t y 4
i-i, i (* i
1X1 S
c 1
SCREEN FLOW METER R
TO BYPASS
MAGNETIC -\
FLOW >
METER
FORCE MAIN TO o J
MARINA PUMPING w
AIR LIFT
PUMP
SOLIDS
HANDLING
PUMP
J~\3 s —
} j
_iJl
^
1 ,
1
COVERED FLOTATION
TANK
(2 UNITS, 0.5 m3/sec
CAPACITY EACH
l
fl FS
v
SS FS
i i
SOLIDS
SUMP
^ PLANT EFFLUENT
/ 1 m3/sec
/
/
i OUTFALL
. STATION
7 rrrVsec
Figure 5 . Simplified process flow sheet of Baker Street
dissolved air flotation facility
-------
Table 3; PRINCIPAL CHARACTERISTICS AND COMPONENTS OF BAKER STREET DISSOLVED AIR FLOTATION FACILITY
Sector
Item
Description
Hydraulic Treatment capacity
Influent/effluent
Flotation cells Surface loading rate
Volume
Detention time
Weir loading rate
Flight speed
Sludge removal
Skimmer system
Recycle system Recycle pumps
Air solution tank
1 m3/sec [24 mgd] total; 0.5 m3/sec [12 mgd] each of
2 flotation tanks of 0.13 m3/sec [3 mgd] each of 8
flotation cells
7 m3/sec [160 mgd]; 1 m3/sec [24 mgd] treated flow
and 6 m3/sec [136 mgd] bypass
255 m3/(m)2(day) [6,310 gal/(ft)2(day)]
197,000 1 [52,000 gall/cell or 795,000 1 [210,000 gal]/
tank
25 min
817 m3/(m)(day) [65,800 gal/(ft)(day)]
1 cm/sec [fpm]
Screw conveyor: 5, 10, 15 rpm variable; 0.3 I/sec
[100 gpm] maximum
Front skimming depth, 0-5 cm [0-2 in.]; back skimming
depth, 0-2.5 cm [0-1 in.]; 3/4-min skimming cycle per
0 to 30-min interval
One 2-stage centrifugal pump per tank, each
o
0.1 m /sec [2.4 mgd] capacity
3 3
One per tank at 4.25 m [150 ft ] each, or 74-sec
hydraulic residence time
-------
Table 3 (Continued). PRINCIPAL CHARACTERISTICS AND COMPONENTS OF
BAKER STREET DISSOLVED AIR FLOTATION FACILITY
Sector
Item
Description
Recycle
system
Chemical feed
system
fo
oo
Solids
handling
system
Air supply
Alum solution
Alum storage
Alum feed rate
Caustic solution
Caustic storage
Caustic feed rate
Polyelectrolyte solution
Polyelectrolyte storage
Polyelectrolyte feed rate
Hypochlorite solution
Hypochlorite storage
Hypochlorite feed rate
Air lift pump
Solids sump pump
One compressor per tank rated at 12.3 I/sec [26 cfm] each
2
at 45,700 kgf/m [65 psig]; actual available supply
4.7 to 6.1 I/sec [10 to 13 cfm] per tank
36° Bes-A12(SO ) = 28% as Al^SO^
One 10,200 1 [2,700-gal] tank
One pump variable to 0.33 I/sec [310 gph] maximum
30% caustic, 39.9% NaOH
One 2,630-1 [700-gal] tank
One pump variable to 0.1 I/sec [100 gph] maximum
Dow Purifloc C-31, 50,800 mg/1
One 4,920 1 [1,300-gal] tank
One pump per tank, each variable to 0.1 I/sec
[110 gph] maximum
14% available C12
One 13,600 1 [3,600-gal] tank
One pump per tank, each variable to 0.08 I/sec
[75 gph] maximum
One pump per tank for transfer of settled solids to
solids sump; air consumption to est. 0.085 m /sec
[3 cfs] maximum
One pump variable to 34.7 I/sec [550 gpm] maximum
-------
PRESSURIZED AIR
SOLUTION TANK
CHEMICAL INJECTION
AIR INJECTION AND
ROTAMETER
SECOND STAGE
CENTRIFUGAL PUMP
FIRST STAGE
CENTRIFUGAL PUMP
Figure 6. The pressurization system
-------
u>
o
Figure 7. Control console at the Baker Street
dissolved air flotation facility
-------
The control system of the facility provides for the fully automatic
start-up of the module selected for initial filling and for sequential
automatic start-up of the other module after a re-set flow rate is attained
in the first module. The master control panel is shown in Figure 7. The
description of existing plant instrumentation and control work is presented
in Appendix A.
Major differences between the Baker Street and pilot-plant systems
were as follows.
(1) In the Baker Street facility, the recycle stream was withdrawn
from the flotator at a point just under the effluent
launder; in the pilot plant the recycle stream was withdrawn
from the effluent clear well.
(2) An inlet manifold was used to distribute the combined influent-
pressurized recycle stream into the Baker Street flotator; in
the pilot plant, the pressurized flow was pumped through a
distributor header into the flotator, where mixing with the
influent stream was accomplished.
(3) The pilot plant used a flocculation chamber to accomplish
chemical mixing and promote floe formation. The Baker Street
facility could accomplish mixing of chemical additives with the
wastewater only by the addition of chemicals to the pressuriz-
ation system; no separate compartment was used to promote floe
formation.
(4) An oscillating pipe trough and flight system was used to remove
float in the Baker Street facility, whereas a beach and flight
system was used in the pilot plant.
Test Procedures
Dry-Weather Testing Plant Modifications—
To divert dry-weather sewage flow from the Baker Street drainage basin
to the Baker Street dissolved air flotation facility, a metal shear gate
was installed at the manhole located on Marina Boulevard about 61 m [200 ft]
east of the diversions structure at Baker Street and Marina Boulevard.
Essentially all of the flow from the Baker Street drainage basin could
31
-------
thus be diverted to the Baker Street facility for processing.
3
To augment the dry-weather flow, which was on the order of 0.044 m /
sec [1.0 mgd], a variable-speed pump, rated at 95 I/sec [1,500 gpm], was
installed to pump from the westerly flotation tank, which was used as a
storage reservoir, into the plant influent works. Thus, with sufficient
storage of wastewater at the facility in addition to the normal dry-
weather flow, influent to the plant could be maintained fairly constant
3
at a rate of up to 0.11 m /sec [2.5 mgd] for a period sufficient for
testing.
To enable the achievement of surface loading rates up to design
rates, tests were made on a single flotation cell by diverting all influ-
ent into one cell in the east flotation tank. Although the single cell
was somewhat isolated by design, it was necessary to perform tests using
the entire east flotation tank recycle flow and the entire east flotation
tank air supply. The net effect of these conditions was to produce in-
creased turbulence in the inlet section of the flotation cell.
Dry-Weather Testing Program—
The facility was evaluated by conducting a series of continuous runs
and determining the effectiveness of the process in removing specified
pollutants from the influent stream. For the dry-weather tests the in-
fluent stream consisted of raw sewage augmented with settled sewage from
the west flotation tank. A continuous run consisted of maintaining all
process control variables—influent flow rate, specific chemical dosage,
air to solids ratio, and skimmer operation—at the desired levels for a
period of time sufficient to establish a steady-state condition. A con-
tinuous run was completed when a stable effluent quality, as measured by
effluent turbidity, was achieved for a period not less than one-half
hour in duration. At the time when this criterion was met, influent and
effluent grab samples and samples of the float and settled sludge compos-
ited over the run during steady-state operation were collected and
analyzed for specific quality constituents. For the process evaluation,
one control parameter was varied while all others were maintained constant
at reference values. Table 4 presents the range of parameters investi-
gated during the dry-weather tests.
32
-------
Wet-Weather Testing Plant Modifications—
In order to correct some of the deficiencies in the dry-weather test
conditions, the dissolved air flotation facility was modified for the wet-
weather tests. Modifications to the flotation tank involved physically
and hydraulically isolating the test cell from the remainder of the east
flotation tank. The recycle system capacity was scaled down to the single-
cell design level. An influent feed pump was installed for better flow
control,and float and settled sludge collection were routed through elect-
rically metered, positive-displacement pumps. Automatic discrete samplers
on the influent and effluent lines, automatic composite samplers on the
float and sludge lines, and a recording effluent turbidimeter were in-
stalled, as shown in Figure 8, to facilitate data collection during the
randomly occurring storm events. The automatic samplers on the influent
and effluent wastewater lines were equipped with 1/8-inch mesh screens to
protect the electrically operated valves. Particulates of larger size
were thereby excluded from the sampling equipment and the wastewater char-
acterization. This method of sampling differs substantially from the
two-inch diameter suction centrifugal pumps used to collect samples during
the drainage basin characterization studies and the simple buckets used
in pilot-plant and dry-weather prototype studies. One half of the Baker
3
Street facility was thus converted to a 0.13-m /sec [3-mgd] plant with
the same operational characteristics as the full-capacity facility.
Table 4. SUMMARY OF PROTOTYPE DRY-WEATHER TESTING PROGRAM
Variable
Range
Specific alum dose
Surface loading rate
Air/solids ratio
Specific polymer dose
Alum/polymer combinations
mg/mg influent TSS
m /(m) (day)
kg air/kg TSS
mg/mg influent TSS
0/0 - 1.5/0.1 mg/mg influent TSS
0-15
196 - 2109
0.02 - 0.50
0 - 0.15
aA constant skimmer system flight travel rate of 1 cm/sec [2 fpm] was
used in all runs. The scum pipe was set for continuous operation with
the front skimming depth at 5 cm [2 in.] and the back skimming depth
at 2.5 cm [1 in.].
33
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•RESIDUAL CHLORINE
ANALYZER
TURBIDIMETER
DISCRETE EFFLUENT
SAMPLER
COMPOSITING EFFLUENT
SAMPLER
_\
Figure 8. Effluent sampling station at the
Baker Street dissolved air flotation facility
-------
Wet-Weather Testing Program—
The wet-weather testing program used several predetermined operat-
ing parameter and efficiency relationships such as air to solids and
recycle to influent flow ratios which had been established in the pilot-
plant and dry-weather testing programs. On the basis of the data from
previous studies, a nominal air to solids ratio of 0.06 kg/kg was
selected for the wet-weather program. A recycle to influent flow ratio
of one to five at the maximum modified cell capacity of 0.12 m /sec
[2.7 mgd] resulted in a recycle flow of 23.7 I/sec [375 gpm], which was
maintained with other influent loading rates.
The variable parameters of the wet-weather evaluation program were
surface loading rate and alum dosage. The alum feed was varied from
zero to 300 mg/1, as shown in Table 5. The surface loading rates used
3 2
in the evaluation were 103, 145, 183, and 232 m /(m) (day) [2,530,
3,580, 4,460, and 5,690 gal/(ft)2(day)], inclusive of recycle flow.
Table 5. WET-WEATHER TESTING SCHEDULE
Alum dosage,
mg/1 A12(S04)3
0
75
150
300
Test numbers
Surface
103
1,12
11
-
-
loading
145
2,9
8
10
-
3
rate, m /(m)
182
3
13
7
14
2 (day)
232
4
15
5
6
The basic procedures followed during wet-weather testing were as
follows: City of San Francisco personnel at the Richmond-Sunset waste-
water treatment facility observed storms sweeping in from the Pacific
Ocean and, after judging their intensity, notified personnel at the
North Point wastewater treatment facility. Roving pump station crew-
men based at North Point were dispatched to the Baker Street dissolved
air flotation facility during evening, night, and weekend shifts.
Weekday shifts were manned regularly by City of San Francisco personnel
during the entire rainy season.
35
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When rainfall occurred at the Baker Street facility, the Marina
Boulevard shear gate was closed and all storm water runoff and domestic
sewage in the tributary area was diverted to the facility. Facility
operation was semi-automatic, with all equipment energized by the level
of combined sewage in the influent structure. The facility personnel
adjusted various flow and feed rates and activated special sampling and
testing equipment.
During storms of long duration, two testing events, each lasting a
minimum of 2.5 hours, were conducted. ••
ANALYTICAL METHODS
Samples obtained from the automatic discrete and compositing
samplers during the wet-weather testing were collected immediately at
the end of each storm and delivered to storage refrigerators at the
Berkeley laboratory of Engineering-Science, Inc. Procedures outlined in
Standard Methods (Reference 13) were followed for the analysis of settle-
able solids, temperature, pH, biochemical oxygen demand (BOD), chemical
oxygen demand (COD), ammonia nitrogen, organic nitrogen, fecal coliform,
and toxicity for all tests. Total suspended solids (TSS) from samples
collected during the wet-weather and dry-weather prototype studies were
evaluated in accordance with Standard Methods. Suspended solids of
samples collected from pilot-scale studies were calculated from a re-
lationship between turbidity and total suspended solids developed from
comparisons of blenderized wastewater samples.
The floatable solids in a wastewater sample were separated from the
water in a three-liter funnel provided with a steep, conical bottom
(Imhoff cone), and a bottom stopcock. Mixing was done by means of a
paddle with an adjustable-speed drive. Funnel, mixer, and all surfaces
which came into contact with samples were precoated with Teflon to pre-
vent grease from sticking to the surfaces. The procedures of the float-
able material determination are described in Appendix B,
Turbidity measurements were performed in the field, using a HACK
Model 1860 turbidimeter.
36
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The hexane extractable materials were first hydrolyzed by acidifi-
cation and heating for approximately one hour. Grease and oil was then
extracted in a continuous Pearson-Thomas extraction apparatus (Reference
14) for four hours. The residue remaining after evaporation of the hex-
ane solvent was weighed. Detailed procedures are described in Appendix B.
Toxicity of composited effluent samples was measured according to
the static fish bioassay method presented in Standard Methods (Reference
13). Sticklebacks (Gasterosteus aculeatus) were used as the test fish.
The bioassay results were expressed as 96-hr percent survival in undi-
luted wastBwater, or as 96-hr TL (median tolerance limit).
m
The Baker Street facility practiced excess chlorination during the
wet-weather testing program, and in order to evaluate the dissolved air
flotation system performance, it was necessary to eliminate the extraneous
interference of excess chlorine by dechlorinating the wastewater samples
prior to toxicity and BOD analyses. As a result, the toxicities reported
herein for the Baker Street facility effluent are probably less than they
would have been had the samples not been dechlorinated.
37
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SECTION V
CHARACTERIZATION OF STUDY AREA
The City and County of San Francisco is divided into three main
drainage districts for purposes of sewerage and sewage treatment.
Because essentially the entire system is sewered with combined sewers,
these districts also define the main watershed areas for storm water
runoff. The Richmond-Sunset District lies on the west side of San
Francisco and comprises a largely residential area of 3,800 ha [9,500
acres]. The North Point District encompasses 3,600 ha [9,000 acres] in
northeastern corner of San Francisco and includes the entire downtown
section as well as much of the industrial park located south of the Bay
Bridge Skyway. The Southeast District covers approximately 2,900 ha
[7,100 acres] of residential and industrial land.
DRAINAGE BASINS
Combined sewer overflows were characterized by a study of dry- and
wet-weather wastewater discharges from six drainage basins in San Fran-
cisco. Five of the six drainage basins (Baker Street, Mariposa Street,
Brotherhood Way, Selby Street, and Laguna Street) have combined sewage
systems in which the wet-weather discharges consist of sanitary waste-
waters, industrial discharges, where applicable, and surface water
runoff. The sixth basin is located at the foot of the Vicente Street
and contains separate storm and sanitary sewer systems.
Dry- and wet-weather monitoring in two of the six basins (Selby and
Laguna) was conducted during an earlier (1966-1967) study (Reference 1);
the Baker, Mariposa, Brotherhood, and Vicente basins were monitored in
the present study. The focus of this report is on the dissolved air
38
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flotation facility for treatment of combined sewage from the Baker
Street drainage basin, and this section therefore emphasizes that
drainage basin. Data from other basins are provided in Reference 2.
The Baker Street urban drainage basin borders the southeastern
corner of the Presidio Military Reservation, with the easterly boundary
running along Broderick and Divisadero s'treets and the southerly
boundary along Clay Street. This area is the only source of wastewaters
to the combined sewer system except for sanitary wastes from the
Presidio. The Presidio has a separate storm water system which does not
connect with the Baker Street combined sewer system. The basin encloses
an area of 68 ha [168 acres], with an estimated population of 13,000,
including 5,800 persons in the Presidio. The population density in the
area which has combined sewerage (outside the Presidio) is 18 persons/ha
[44 persons/acre]. Over 80 percent of the land is used for residential
purposes. Commercial use of land is estimated to be eight percent, with
the remaining land being vacant or belonging to governmental agencies.
The basin is divided topographically into two different sections
with different land-use characteristics. The southerly section between
Pacific and Clay Streets is totally residential, with a significant
amount of grass and trees; the housing is mostly middle- to high-income,
single-family dwellings. The streets are well maintained, with almost
every block having one or more litter boxes. The streets and gutters
contain a minimum amount of litter, mostly grass, deciduous tree leaves,
pine needles, and little or no paper or garbage-type material. The
northeasterly section below Pacific Street has some commercial activity
centered on and below Lombard Street. The streets surrounding the
commercial area are generally more littered with paper than are other
sections of the basin. This area has several centrally located dumpster-
type litter containers which are emptied regularly.
The Baker Street drainage basin contains approximately 140 catch
basins distributed over 14 km [8.8 miles] of street. Generally the
basin is characterized by steep slopes, with over 38 percent of the land
having slopes in excess of 10 percent.
39
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HYDROLOGY
The long-term mean rainfall in San Francisco is 52.8 cm [20.8 in.].
Nearly all of the rainfall occurs in the period from September to May.
The San Francisco Bureau of Engineering has analyzed the historical
rainfall patterns and runoff characteristics of each of the drainage
basins mentioned previously, using precipitation data reported for the
Federal Office Building, which is located downtown. Estimated peak
discharges for storms of five-year recurrence at the points of diversion
3
range from 1.2 m /sec [27 mgd] for the Vicente Street drainage basin to
3
76.5 m /sec [1,740 mgd] for the Selby Street drainage basin. The peak
five-year discharge from the Baker Street drainage basin is estimated to
3
be 6 m /sec [137 mgd].
It is calculated that prior to the construction of the diversion
structure at Marina Boulevard the annual total of combined sewage
3
discharges to the Bay was 167,000 m [44 million gallons] from approxi-
mately 113 discharges. Construction of the diversion structure in
conjunction with the Baker Street facility increased the total combined
3
sewage flow diverted to the facility and then to the Bay to 337,000 m
3
[89 million gallons] annually, of which 265,000 m [70 million gallons]
is rainfall runoff. An analysis of the frequency of operation and rate
of combined sewage treatment will be presented in Section VIII.
SEWERAGE AND DIVERSION SYSTEMS
The combined sewer systems of the Baker, Mariposa, Brotherhood,
Selby, and Laguna basins are intercepted at or before the points of
discharge to the receiving waters, and all of the dry-weather flow
converges to three sewage treatment plants, which have a total design
3
hydraulic flow capacity of 14.9 m /sec [340 mgd].
Dry-weather and combined sewage flows from the Baker Street drain-
age basin are collected and transported to a diversion structure located
at Marina Boulevard and Baker Street, at which point flow is intercepted
and transported to the Marina pumping station, where it is pumped to the
North Point sewage treatment plant. The diversion structure was con-
structed in a 1.5-m [5-ft] diameter sewer and consists of a side-flow
40
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weir designed to prevent the incursion of Bay water into the dry-weather
system and to direct dry-weather flows into the 53.3-cm [21-in.] diameter
sewer in Marina Boulevard. During wet-weather conditions (varying rain-
fall intensities), flows from the Baker and adjacent drainage basins
exceed the capacity of the Marina pumping station, resulting in the over-
flow of a major portion of combined sewage flow from the Baker drainage
basin.
The interceptor systems and sewage treatment plants are designed to
handle the dry-weather flow plus the runoff from 0.025 to 0.05 cm/hr
[0.01 to 0.02 in./hr] of rainfall, which is equivalent to about twice
the normal dry-weather flow but amounts to approximately two percent of
the design hydraulic capacity of the storm drain system.
DRY-WEATHER WASTEWATER CHARACTERISTICS
Dry-weather monitoring of combined sewer systems was conducted in
the Baker, Mariposa, and Brotherhood basins during this study, and in
the Selby and Laguna basins in 1966-1967 (Reference 1), to provide data
for estimation of the dry-weather sewage component of combined sewage
flows. Hourly samples were taken and flow measurements made over one or
more 24-hour periods in each of the five basins with combined sewer
systems.
The average per capita flow and mass emission factors for dry-
weather flows from the Baker Street drainage basin are presented in
Table 6. These average discharge factors are not representative for all
the drainage basins of San Francisco. The flow observations made for
all systems showed variations typical of urban areas. Flow maxima
occurred during morning and evening periods, and a principal minimum
occurred between 5:00 and 7:00 a.m. for the basins monitored. The
diurnal sewage quality variations were also characteristic of urban
areas, and no unusual patterns were observed.
The median value of coliform MPN concentrations in dry-weather raw
sewages (all samples) was 14 x 10 MPN/100 ml.
41
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Table 6. AVERAGE DRY-WEATHER'DOMESTIC SEWAGE CONSTITUENT
CONCENTRATIONS AND DISCHARGE FACTORS FOR BAKER STREET DRAINAGE BASIN
Flow-weighted Discharge factor,
mean concentration, g/(cap)(day)
Constituent mg/1 [lb/(cap) (day)]
Flow, I/ (cap) (day) [gal/ (cap)
(day) ]
Chemical oxygen demand
Total suspended solids
Volatile suspended solids
Floatable materials
Hexane extractable materials
Total nitrogen
Ammonia nitrogen
Orthophosphate phosphorus
-
294
130
112
1.8
56.8
18.3
6.4
5.9
496 [131]
146 [0.321]
64 [0.142]
55 [0.122]
1 [0.002]
28 [0.062]
9 [0.02]
3 [0.007]
3 [0.0064]
COMBINED SEWAGE CHARACTERISTICS
Wet-weather monitoring of combined sewer flows in the Baker,
Mariposa, and Brotherhood basins was conducted during the early phases
of this study in 1969. The methods of sample collection and analysis
and all available data have been reported earlier (Reference 2) . The
analyses of combined wastewater from the Baker Street drainage area are
presented in this section for a later comparison with the wastewater
quality observed at the Baker Street dissolved air flotation facility
during wet-weather testing.
Table 7 is a compilation of the flow-weighted average concentra-
tions of wastewater constituents and the rainfall data collected during
rainfall events on 4 and 5 April 1969, 15 October 1969, and 5 November
1969.
42
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Table 7. AVERAGE COMBINED SEWAGE CONSTITUENT CONCENTRATIONS AND
RAINFALL AT THE BAKER STREET DRAINAGE BASIN
DURING PRE-CONSTRUCTION STUDIES
Characteristic
Total suspended
solids, mg/1
Settleable solids,
ml/1
Floatables, mg/1
Biochemical oxygen
demand, mg/1
Chemical oxygen
demand, mg/1
Grease and oils,
mg/1
Organic nitrogen,
mg/1
Ammonium nitrogen,
mg/1
Rainfall intensity,
mm/hr
Rainfall,0 mm
Wastewater flow,
I/sec
4-5 April 1969
102a
1.1
2.5
I4b
117
4.9
3.9
1.1
1.4
6.35
206
15 October 1969
57.6
1.1
0.7
25
75
3.2
2.8
1.9
0.64
5.84
257
5 November 1969
99
2.3
•1.7
28.6
288
42 .1
7.7
1.2
1.98
16.3
700
bafter first two hours, TSS ranged from 20 to 50 mg/1
cbased upon single measurement
immediately preceding and during sampling only
43
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SECTION VI
PRESENTATION OF TEST DATA
A total of 54 tests on the dissolved air flotation process was
conducted during the pilot-plant and prototype testing programs. A
number of other tests, with laboratory jar-test apparatus, was also
performed to establish guidelines for the selection of operating ranges
of the process variables. The operating and performance data collected
during the pilot-plant and dry-weather prototype testing were presented
in earlier reports to the City of San Francisco (References 3, 12, and
15) and are summarized in Appendices C and D. The data collected during
the wet-weather testing on the modified east flotation tank, along with
notable occurrences during each test, are presented in the following
pages. Comparison of test results from pilot-plant, dry-weather and
wet-weather programs will be made in Section VII.
WET-WEATHER DATA
Fifteen wet-weather test runs were conducted on the modified Baker
Street dissolved air flotation facility during the last half of the 1973-
74 rainy season. The lateness of the testing program was caused primar-
ily by unforeseeable delays in obtaining manufactured equipment for the
modification of the facility to the single flotation cell testing config-
uration. Therefore, it became necessary to conduct the evaluation program
before a thorough shake-down of the facility could be completed and even
before several items of equipment had been delivered. Consequently,
there were difficulties in obtaining trouble-free, automatic operation
44
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of the Baker Street facility, and data collection was hampered by these
difficulties. Approximately two-thirds of the wet-weather testing
program had passed before the test facility was operating completely
satisfactorily.
Along the main wastewater flow path, several corrections to equip-
ment or operating procedures were necessary during the testing program.
Intermittent fluctuations in flow meter readings were traced to a faulty
ground connection and the presence of air in the magnetic flow meter.
The electrical connection was repaired, automatic air bleed valves were
installed upon all magnetic flow meters and flow constrictions for speci-
fic test conditions were performed, whenever possible, down-stream of the
magnetic meters. The influent pump used an inordinate quantity of a
special gear oil. This oil was difficult to obtain, and when the supply
ran short the lack of oil precluded several days of facility shake-down
with dry-weather flow. Level sensing electronic trips in the influent
structure were mis-adjusted, and automatic equipment was not properly
sequenced until the trips were readjusted. The distribution manifold in
the flotation tank was so oriented as to cause boils at the water surface
and hydraulic short-circuiting, and required redirection to achieve a
better flow distribution. The standard practice of leaving approximately
two feet of water in the flotation tank at the end of a test in order to
protect the gears of the scraper-flight mechanism and the sludge transport
screw was found to result in the accumulation of solids, which may have
interfered with subsequent tests. During the testing program it became
necessary to completely pump out this flotation tank between rainfall
events.
Several difficulties were encountered with the pressurization
system. The air compressors for operation of automatic flow controlling
valves were started before the recycle system was operational. On
several occasions, this resulted in compressed air filling and air-binding
the recycle pressurization pumps until automatic air-bleed lines were
installed. The practice of using recycled effluent in the pressurization
system was felt to be of detriment throughout the testing program.
Effluent could not be recycled until the flotation tank was two-thirds
45
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full of wastewater. This meant that pressurized air and chemicals,
which were injected into the recycle stream, could not be added to the
first two-thirds of the tank volume. The injection of proper quantities
of pressurized air into the recycle stream was difficult to control be-
cause of the presence of water in the air flow meter. This was traced
to both a failure in a downstream check valve and very heavy condensa-
tion of water in the air compressor.
Chemical feed systems failed on several occasions during treatment
tests and required several days for repairs. Varying influent caustic
demand required an operator's presence to control pH. The occasional
presence of operators unfamiliar with the details of the Baker Street
facility operations resulted, at times, in improper settings for chem-
ical feed pumps, requiring a re-initiation of these tests upon the
arrival of Engineering-Science, Inc. technicians.
Inadequate float removal caused substantial difficulties during
testing at the Baker Street facility. Due to a need to measure float
collection, a flow restricting positive-displacement pump was placed
downstream of the float-collecting tilt pipe. Varying water surface
levels in the flotation tank resulted in collection of float in excess
of pump capacity at a specific tilt-pipe submergence. It was necessary
to substantially modify the tilt-pipe driving mechanism before necessary
adjustments in submergence depth could be made. The automatic selector
switch for the float-collecting pump failed on several occasions before
it was corrected by the supplier.
The automatically compositing influent and effluent samplers could
not be adjusted to operate for a period longer than one to one-and-one-
half hours. Also, it was necessary to operate the compositing sludge
samplers manually until the delayed arrival of automatic valves.
All of these typical start-up problems made the collection of data
very difficult and limited the results that could be obtained during
the facility evaluation.
The system was operated over a range of alum dosages from 0 to 300
mg/1 alum and at various surface loading rates ranging from 103 to 232
m3/(m)2(day) [.2,530 to 5,690 gal/(ft)2(day) 1. The detailed testing
46
-------
program is presented in Table 5. The following is a presentation of the
test results for each rainfall event.
Test Run 1
The first rainfall of the 1973-74 rainy season occurred in San
Francisco in the early morning of 20 September 1973. This storm event
produced 0.5 cm [0.2 in.] of rainfall. The combined storm water over-
flow was routed to and treated at the unmodified west flotation tank of
the Baker Street dissolved air flotation facility.
Eighteen samples of wastewater were collected for analysis. The
analytical results are presented in Appendix E (Table 28). Figure 9
presents graphically the facility performance during this test. The
facility was operated in the simplest, fully automatic mode, with no
chemical treatment other than chlorination. A flow of 0.36 m3/sec [0.9
mgd] through the flotation tank was recorded. This flow corresponds to
a surface loading rate of 103 m3/(m)2(day)[2,530 gal/(ft)2(day)] and a
residence time of 83 min.
The unmodified west flotation tank was operated in an uncalibrated
and untested condition shortly after it had undergone construction
modifications. Various mechanical items had not worked properly, and
performance data collected during the test are considered valueless.
The influent flow characterization of samples collected from the influ-
ent structure upstream of the malfunctioning facility did provide, however,
a characterization of the first seasonal rainfall.
Test Run 2
The second wet-weather testing event occurred during a light rain
of 0.6 cm [0.22 in.] extending over 24 hours on 11 January 1974. The
test was conducted at a surface loading rate of 145 m3/(m)2(day) [3,580
gal/(ft) (day)] with no chemical addition other than sodium hypochlorite.
Although a thin, but very dark, float was produced in the flotation tank,
the tilt pipe, which had operated with an adequate submergence of one-
half inch during calibration, did not submerge sufficiently at lower
flow rates to collect float. It was impossible to reset the tilt pipe
linkage arms without binding the drive motor. The difficulty was later
47
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FIGURE 9. Baker Street DAF facility performance
at 0 mg/£ alum and 103 m3/(m)2(day); Test No. 1
only test conducted on unmodified west - side facili
ty)
48
-------
rectified by bolting a longer connecting arm to the tilt pipe. The .waste-
water stream analyses presented in Appendix E (Table 29) are of samples
collected during a period when no float was removed from the top of the
flotation tank. Figure 10 shows the time-adjusted relationships between:
influent and effluent constituents. The time-adjustments are explained
later in this Section.
Test Run 3
the third wet-weather test, which took place on 16 January 1974,
occurred in moderate to heavy rain of 1.3 cm[0.5 in.J total accumulation,'
with plant effluent discharge commencing at approximately 9:00 a.m.
During the first hour of testing, an electronics technician, from an
equipment-supplier, was intermittently interrupting operations while
correcting some electrical malfunctions. The float produced during this
*3 O n
test at a surface loading rate of 182 m /(m) (day) [4,460 gal/(ft) (day)]
and with no chemical addition was very heavy and thick. A tilt-pipe weir
submergence of one-half inch was insufficient to pass the thick float.
Adjustment of the linkage arms led to a binding of the tilt-pipe drive
motor in the flooding position for over 15 minutes, starting at 11:30 a.m.
This was reflected in the increased effluent floatables concentrations
shown in Figure 11, although other effluent constituents did not demon-
strate a corresponding increase. Appendix E (Table 30) contains the
laboratory analytical data from this test.
Test Run 4
The fourth wet-weather test occurred on 16 January 1974 and took
place in moderate rain during the late afternoon between 3:00 and 7:00 1
p.m. The influent flow rate was set at 0.1 m3/sec [2.7 mgd], or a
surface loading rate of 232 m3/(m)2(day) [5,690 gal/(ft)2(day)], with
no chemical addition. The float formed during this test was light
colored, sparse and less than 2.5 cm '[1.0 in.] in thickness. The test
results are summarized in Appendix E (Table 31) and presented graphic-
ally in Figure 12.
After these tests had been completed, the tilt-pipe linkage arm was
bent 15 degrees to allow greater submergence of the tilt-pipe weir.
49
-------
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°0 * 1 ' 2 3 "0 23 -0 123
THE, hr THE, hr THE, hr
FIGURE 10. Baker Street DAF facility performance
at 0 mg/4 of alum and 145 m3/(m)2(day); Test No. 2
50
-------
220
200
* 180
V)
S 140
° 120
i 100
LU
I 80
~ 60
| 40
20
0
14
0
— W-INFLUENT —
— -EFFLUENT —
S
E
12
10
8
6
l
2
0
100
90
80
70
60
50
40
30
20
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TIME, hr
3
10
9
i
5
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0
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180
160
140
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ea
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60
40
20
0
0
1 2
TIHE, hr
22
20
18
16
14
12
10
8
6
4
2
0
35
30
25
20
FIGURE 11. Baker Street DAF facility performance
at 0 mg/€ alum and 182 m3/(m)2(day.); Test No. 3
51
-------
220
200
^ 18°
" 160
C4
= 140
-*J
°'120
ea
i 100
LU
% 80
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~ 60
| 40
20
0
14
12
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i 40
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id
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1123
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12
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200
180
180
140
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•'
- — •• . - '. — —
1 12 3
TIME, hr TIME, hr TIME, hr
FIGURE 12. Baker Street DAF facility performance
at 0 mg// alum and 232 m3/(m)2(day); Test No. 4
52
-------
This could have resulted in the collection of larger quantities of water
than could be handled by the floatables measuring pump. In compensation,
the frequency of the tilt-pipe weir submergence was reduced from approx-
imately three per minute to two every three minutes. In this way, effec-
tive float removal could be accomplished without the withdrawal of exces-
sive amounts of water.
Test Run 5
The fifth test occurred on 31 January 1974 between 2:20 and 5:00 p.m.
in a light rain of 0.8 cm [0.33 in.] accumulation. At a combined sewage
32 2
surface overflow rate of 232 m /(m) (day) [5,690 gal/(ft) (day)], alum
was added at a concentration of 150 mg/1.
No mechanical difficulties were encountered during this test, al-
though it was found that caustic chemical dosages determined during dry-
weather flow calibration were inadequate with combined sewage overflows ,
as the effluent pH value fell below 5 during the second and third sampling
periods. This occurred because the chemical characteristics of the com-
bined sewage influent to the facility varied with time and it was neces-
sary to manually readjust the caustic chemical dosage to maintain an
effluent pH between 6 and 7. Figure 13 presents a comparison of influent
and effluent water quality for this test run; Appendix E (Table 30) con-
tains a summary of the analytical data.
Test Run 6
The sixth test of the program occurred on 1 February 1974 in a very
light rain totalling 0.3 cm [0.13 in.] at an influent flow rate of 0.12
3
m /sec [2.7 mgd], which is equivalent to a surface loading rate of 232
32 2
m /(m) (day) [5,690 gal/(ft) (day)], and an alum feed concentration of
300 mg/1. The operational difficulties of selecting a caustic chemical
feed rate were similar to those of the previous test. However, the
effluent pH values ranged from 6.7 to 8.5, which were on the high side
for optimum coagulation and flocculation, which is between 5.0 and 7.0
pH units. The relationship of effluent to influent water qualities is
shown in Figure 14 and specific analytical results are summarized in
Appendix E (Table 33). The increase in effluent pH during the fifth
53
-------
Li\>
200
^180
" 180
00
5 140
O
•» 120
a
£ 100
£
S; 80
™*
" 60
^c
5 40
^™
20
12
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^ „
E 8
T 6
§T 4
2
inn
lUU
90
80
= 70
^ 60
s 50
£ 40
^ 30
20
10
J 2 3
— —
— —
— —
— —
— —
— — _
— —
— —
— —
— —
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— / /-INFLUENT —
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i
i
— —
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i i
1123
TIME, hr
FIGURE 13.
at 150 mg./4
1 '
1
10
j= 9
' 8
^-
^ 7
S 6
_
= 5
CO
iXj t
_i 4
^~
S i
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1
n
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12
^ 10
E
8
6
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/uu
180
180
140
^120
* 100
i BO
60
40
20
I
Baker
alum i
I 2 3
i
•
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— —
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— —
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— X —
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H ^^.
\
* r*
) 2 3
TIME, hr
Street DAF fac
jnd 232 m3/(m)2(
22c
LL
20
18
16
^
2 14
E
M 12
UJ
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S 8
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1123
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1123
TIME, hr
Derformance
Test No. 5
54
-------
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i 140
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7 v
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400
380
320
280
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80
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I
°0 2 3 "0 1 2 3 "0 1 2 3
TIME, hr TIME, hr TIME, hr
FIGURE 14. Baker Street DAF fac ity performance
at 300 mg/tf alum and 232 m3/(m)2(day); Test No. 6
55
-------
sampling period is reflected in Figure 14 by an increase in effluent
floatables, turbidity, ammonia and grease and a decrease in settleable
solids due to the lack of alum coagulation and flocculation at that pH.
Also, alum floe was first noticed in effluent samples collected during
this test.
Test Run 7
The seventh test run occurred in a moderate rainfall of 1.1 cm
[0.42 in.] daily accumulation on 19 February 1974 at a surface loading
32 2
rate of 182 m /(m) (day) [4,460 gal/(ft) (day)]. Alum was fed at a
concentration of 150 mg/1 and no mechanical difficulties were encountered
during facility operation. Graphic and tabulated presentations of analy-
tical results are shown in Figure 15 and Appendix E (Table 34), respect-
ively.
Carry-over of alum floes into the effluent stream was observed as
high settleable solids in the effluent samples during the fifth through
the seventh tests. Effluent samples from these three tests appeared to
contain substantial quantities of alum floe that interfered with the
determinations of total suspended solids, turbidity and settleable solids.
The influent distribution header in the flotation tank was examined
for the possibility of short-circuiting in the flotation tank. The dis-
charge ports in the header were found to be pointing in a vertical direc-
tion toward the water surface and the floatables collecting tilt pipe
located immediately above the header. Reasoning that this configuration
could induce short-circuiting and hinder floatables collection at the
tilt pipe, the adjustable discharge headers were rotated until the ports
faced downward at a 45° angle toward the edge between the tank floor and
wall immediately behind the header. This new configuration directed the
initial influent flow away from the effluent weirs and the tilt pipe and
used the divergence of flow from the recoil with the tank wall to effect
an improved influent distribution. All tests subsequent to the seventh
were conducted with the new inlet flow direction.
56
-------
i.i\l
200
^180
" 160
i MO
_1
s 120
*™*
c=» 100
3K
lAJ
I 60
ftO
•^c
i 40
20
14
12
~ 10
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i* 4
2
0
100
90
80
= 70
~~. 60
1 50
i 40
"" 30
20
10
n
— ;
•'••__
C EFFLUENT
'''' \ ~~
— —
— —
— - — _
/V£ INFLUENT
/ \
/ \
/ \
_/ \ _
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it
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35
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0
400
360
320
280
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120
80
40
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1 T™~"T~1^J
0 123 "0 23 "023
TIME, hr TIKE, hr TIME, hr
F GURE 15. Baker Street DAF fac I i ty performance
at 150 mg/£ alum and 182 m3/(m)2(day) ; Test No. 7
57
-------
Test Run 8
The eighth test run occurred on 28 February 1974 in a light rain
totalling 0.6 cm 10.22 in.] over 24 hours. The facility was operated
at a surface loading rate of 145 m3/(m)2(day) {3,580 gal/(ft)2(day)] with
an alum dosage of 75 mg/1. Figure 16 presents the comparison of influent
and effluent water quality and the analytical data are summarized in
Appendix E (Table 35). No alum floe carry-over was observed during this
test. The pre-selected caustic chemical feed rate was too low as indi-
cated during the third effluent sampling period when the pH value fell
below 5.0. Individual samples collected during pH control difficulties
were excluded from calculations of process performance.
Test Run 9
The ninth test run took place on 28 February 1974 during a light
rain totalling 0.6 cm [0.22 in.]. The facility was operated in the same
mode as the eighth test run except no alum was fed to the system. The
facility performed well mechanically and no operational difficulties were
encountered. This test was a retrial of the Test Run 2 during which no
float had been collected. Graphic presentation of facility performance
is shown in Figure 17 and summarized analytical data are provided in
Appendix E (Table 36).
Test Run 10
The tenth test run occurred in a very heavy rain totalling 2.3 cm
[0.89 in.] on 1 March 1974. The facility was operated at a flow rate of
32 2
1.5 mgd, or a surface loading rate of 145 m /(m) (day) [3,580 gal/(ft)
(day)], with an alum dosage of 150 mg/1. The effluent pH values were
low due to the difficulty of controlling the caustic chemical feed rate
as may be seen in Appendix E (Table 37). Chlorination of the effluent
appeared to be effective as the coliform levels in the effluent sample
were less than 3 MPN/100 ml compared to approximately 24 x 10 MPN/100
ml in the influent samples. Figure 18 is a comparison between influent
and effluent samples collected during this test.
58
-------
1 2
TIME, hr
3
22°
20
18
16
•i 14
s 12
| 10
«K Q
<= 0
^ 6
4
2
0
35
^ 30
e*
". 25
LU
1 2°
S 15
* 10
— 5
0
400
360
320
280
I-200
° 160
120
80
40
°
1 2 3
_ 1 _
— —
— —
— —
— —
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( .J |-^.
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*f- t^yi-N-H
- ' -
— —
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— —
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\ ^^^
""""""""^x
i 7 r
] 1 2 3
FIGURE 16. Baker Street DAF facility perfo
at 75 mg/£ alum and 145 m3/(m)2(day); Test
TIME, hr
rmance
No. 8
59
-------
220
200
5s! 180
t_0
E_ 160
Vi
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O
*• 120
i 100
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5 80
* 6°
£ 40
20
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= 70
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n
I i i | 3 ' ° 2 3 0-0 23
— —
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— I (/ —
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__-__ris:----__i>-*--.,
1
10
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180
160
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400
360
320
260
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T
0 1 2 3 "0 1 2 3 "0 23
TIKE, hr TIUE, hr TIME, hr
FIGURE 17. Baker Street DAF faci 1 i ty performance
at 0 mg/t? alum and 145 m3/(m)2(day) ; Test No. 9
60
-------
zzu
200
^ 180
00
* 160
i 140
5 120
i 100
LU
5; 80
C*9
MK
o 40
20
12
~ 10
1 ,
* 6
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100
90
60
= 70
"". 60
± 50
ca
S 40
" 30
20
10
n
0
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— —
— yINFLUENT —
— \ —
— \ —
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EFFLUENT;^
— —
— —
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0 2 2
TIME, hr
1 1
10
£ 9
i 8
"^ 7
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12
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180
160
140
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TIME, hr
LL
20
18
16
^ 14
23 '2
£ 10
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^j
"• 6
4
2
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oc
03
|30
25
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1 2°
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360
320
280
^24|J
^200
•S 160
120
80
40
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1 I
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1 1 1 1
3123
TIME, hr
FIGURE 18. Baker Street DAF facility performance
at 150 mg/£ alum and 145 m3/(m)2(day); Test No. 10
61
-------
Test Run 11
The eleventh test run occurred in a light to moderate rain total-
ling 1.0 cm (0.40 in.] on 7 March 1974. The facility was operated at a
surface loading rate of 103 m /(m)2(day) 12,530 gal/(ft)2(day)J with an
alum dosage of 75 mg/1. The test results are summarized in Appendix E
(Table 38) and presented graphically in Figure 19. No substantial mech-
anical operating difficulties were noted.
Test Run 12
The twelfth test run occurred on 25 March 1974 in a relatively heavy
rain of 1.9 cm [0.74 in.] over 24 hours. A surface loading rate of 107
32 2
m /(m) (day) [2,530 gal/(ft) (day)] was employed with no alum addition.
The pil ranged between 6.1 and 6.8. The analytical data are shown in
Figure 20 and Appendix E (Table 39).
Test Run 13
The thirteenth test run occurred on 27 March 1974 in a moderate
rain totalling 1.1 cm [0.45 in.]. The facility was operated at a surface
loading rate of 182 m /(m)2(day) [4,460 gal/(ft)2(day)] and an alum
dosage of 75 mg/1. Facility operation was satisfactory and almost no
alum carry-over was observed in the effluent samples as is shown in Figure
21 and Appendix E (Table 40). The higher suspended solids in the effluent
were not identified or analyzed for alum content but the low settleable
solids level in the effluent indicates the presence of some non-settling
colloids.
Test Run 14
On 28 March 1974, the fourteenth test run was conducted in a light
rain of 0.4 cm [0.17 in.] over 24 hours. The system was operated at a
surface loading rate of 182 m3/(m)2(day) [4,460 gal/(ft)2(day)] with an
alum dosage of 300 mg/1. The total suspended solids concentrations and
turbidity readings in the effluent samples were higher than thbesn in the
influent. It was suspected that some colloidal alum floe was carried
through the system because the settleable solids, BOD and COD were low
in the effluent, as may be seen in Figure 22 and Appendix E (Table 41).
62
-------
LLU
200
^180
E 160
i 140
S 120
1 100
LU
5 80
5 60
| 40
20
0
14
12
^ 10
^ 8
z 6
i
1* 4
2
0
100
90
80
= 70
"". 60
i 50
£ 40
" 30
20
10
°
__ —
, — —
— —
— . —
"V-EFFLUENT ~~
~T x-INFLUENT
\ \ ~
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) 1 2 3
THE, hr TIME, hr TIME, hr
F GURE 19. Baker Street OAF fac lity performance
at 75 mg/£ alum and 103 m3//m)2(day) ; Test No. 11
63
-------
220
200
^ 180
DO
E 160
-- 1 -*^~~"
— A —
~~ ''1 \ ~
/' / \
— / / V—
s*x
-------
LL\)
200
^180
* 160
V*
S 140
— 1
~ 120
C3
LU
fe 80
=3
~ 60
o 40
20
0
14
12
s? 10
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> 4
2
0
100
90
80
=» 70
H—
i 50
i 40
r 30
20
10
0
_ 1 _
— • . —
1 • i^— —
— —
x-INFLUENT
— ( x-EFFLUENT~
— \( —
— -iyN/,—
~l~j~~j2
•
— ' —
— . —
I /^I
xf^fXfj" ]~
1 _
— • -i —
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— . ' . —
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— - f — '
— ^^-~/*~-^
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] 23
i i
10
^ 9
3!
£ 6
g 5
1 a 1 J
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12
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ac
6
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200
180
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ca
s 80
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— — .
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— . — .
— • —
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— - • ; • — -
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~~/\^*^~
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) 123
THE, hr TIKE, hr TIME, hr
FIGURE 21. Baker Street DAF facility performance
at 75 mg/tf alum and 182 m3/(m)2(day); Test No. 13
65
-------
220
200
^180
" 180
v>
2 140
S 120
ca
<=> 100
S; 80
5 BO
1 40
20
0
14
12
-y 10
e 8
i 8
= 4
2
0
100
90
80
= 70
^_
I 50
£ 40
^ 30
20
10
•<
0 2 I
— —
— —
— —
— —
— — '
— INFLUENT-~v —
_ EFFLUENT-A
~/~ \ • / —
~r^4-/~
— —
— —
— —
— —
/*VA
~JrT\~
— —
— —
— —
-
1 **-^*.,
1 '
1
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i
) 1 2 3
1
10
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1 8
^£
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S 6
S 5
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t 2
1
0
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^ 10
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6
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0
200
180
160
140
^120
I- 10°
8 80
80
40
20
•i
9 2 3
_' _
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— —
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— —
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1 2 3
22
20
18
16
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gc
a 12
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35
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1 2°
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o 5
0
400
360
320
2N
^240
I-280
S 160
120
80
40
°0
1 1 23
_ I _
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— —
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".j^rM"
— —
— —
— —
— —
— —
— __
— —
— —
•y--^>^-
2 3
TIRE, hr TIME, hr TIME, hr
FIGURE 22. Baker Street DAF facility performance
at 300 mg/tf alum and 182 m3/(m)2(day); Test No. 14
66
-------
0
s
220
200
180
160
140
120
100
80
80
40
20
0
14
12
10
4
2
0
100
90
80
70
60
50
40
30
20
10
0
"r-h-rr
1 2
TIME, hr
1 1
10
Z 9
5* 8
^ 7
S 6
g 5
iti 4
fiD
i 3
uj 2
CO
1
0
14
12
^ 10
E 8
* 8
1 2
0
200
180
180
140
^120
•g—
. 100
ca
80
SO
40
20
0
_ 1 _
— —
— —
i — —
— —
__ —
— —
— —
— —
~k i J~~
1 1 _
— —
~~ A ~~
/ \
~{ v— -I
i V Nil
_ 1
— — .
— __.
— —
— —
— \ —
\
\
~^r\
3 2 3
22D
20
18
16
|, 14
Co" n
LLj
S I0
i—
S 8
"~ 6
4
2
0
35
^ 30
* 25
LkJ
I 2°
S 15
ca
" 10
5 5
0
400
360
320
280
^240
' 200
s 160
120
80
40
0
1 2 3
__ 1 1 _
— —
— —
— — •
— —
— —
— — .
• — ' —
— —
~KU-f
-------
Test Run 15
The fifteenth test run was conducted in a light rain totalling 0.8
cm [0.31 in.] during the night of 9 March 1974. The system was operated
32 9
at a surface loading rate of 232 m /(m) (day) [5,690 gal/(ft) (day)]
with an alum dosage of.75 mg/1. Alum dosage and caustic feed were
easily controlled, and no alum floe carry-over was observed as shown in
Figure 23. Summarized analytical data are presented in Appendix E
(Table 42).
Average Concentration of Wastewater Parameters
The average concentrations of each wastewater parameter for in-
fluent and effluent samples were calculated according to the data pro-
cessing procedure outlined in this section, and are presented in Table 8.
Serious consideration was given to the retention time, physical config-
uration of flotator and the physico-chemical reaction in the flotator.
In the absence of hydraulic tracer studies, and for the purposes of data
processing, the mean residence time in the system was assumed to be
equal to the theoretical hydraulic residence time.
Based on the foregoing assumption, in constructing Figures 9 through
23, the effluent sample was assumed to have a lag period of one mean
hydraulic residence time after the influent sample entering the flotation
tank. Hence, the corresponding influent and effluent concentrations of
each parameter during a test run were plotted on the same figure with a
lag response time of one hydraulic residence time for influent parameters.
The average influent and effluent concentrations shown in Table 8 were
calculated on the basis of the total mass entering and leaving the system
during a time when adjusted influent and effluent sampling periods over-
lapped.
Included in Table 8 are the averaged wastewater parameter concen-
trations for turbidity, BOD, COD, oil and grease, organic nitrogen,
ammonium, total suspended solids, settleable solids and floatable solids.
Data collected during pH control difficulties, i.e., when the pH fell
below 5.0, were excluded from data processing. Table 8 also includes
the total suspended solids, settleable solids and floatable solids concen-
trations in the float arid settled matter.
68
-------
Table 8. AVERAGE ADJUSTED CONSTITUENT ANALYSES OF
BAKER STREET DAF FACILITY WET-WEATHER PROGRAM
Constituent Concentration, tng/1
Teat
run
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Total Suspended solids
Influent
31,3
72.7
86.3
69.5
-
-
45.8
99.5
23.8
98.7
31.2
41.4
22.0
10.2
34.2
Effluent Float
42.5
68.9
94.7
66.0
-
-
139
48.6
26.8
55.6
34.1
34.6
43.1
43.3
31.4
-
70.
508
116
-
-
4,400
1,130
1,130
12,500
740
277
1,590
355
1,850
Settleable solids3
Settled Influent
103
7 162
98
73
..-
-
539
134
58.5
2,770
86
78
50
271
30
13.4
0.11
1.12
0.17
0.20
0.1
0.35
1.77
0.11
1.2
0.19
0.27
<0.1
0.12
0.13
Floatable
Effluent Float Settled Influent
18.6
0.02
0.49
0.12
15.3
28.9
53.4
0.1
0.1
2.5
<0.1
0.1
<0. 1
<0. 1
<0.1
-
0.03
19
0.75
283
204
710
510
100
990
70
18
230
980
470
78.6
0.8
0.6
0.05
70
4
180
15.2
0
19.5
0.9
0.15
0.23
0.35
0.4
0.26
0.71
4.26
0.66
0.79
1.37
1.85
1.55
0.33
0.57
0.83
0.54
0.50
1.05
1.07
solids
Effluent Float Settled
0.16
0.43
12.9
0.67
6.29
3.82
0.83
0.50
0.77
1.10
0.74
0.78
0.62
1.42
0.51
-
0.6
4.9
0.7
2.1
1.4
8.7
8.0
7.8
84.3
<0.1
3.1
1.93
1.93
0.36
0.07
1.93
8.8
1.4
7
0.2
1.4
0.6
3.1
4.5
2.2
2.1
0.9V
0.9
0.46
aml/(l)(hr)
-------
Table 8 (continued). AVERAGE ADJUSTED CONSTITUENT ANALYSES OF
BAKER STREET DAF FACILITY WET-WEATHER
Constituent Concentration, me/1
Test
run
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Turbiditv a
Influent
45.3
20.5
12.9
22.9
35
14.2
-
53.2
14
32.1
24.2
25.2
24.8
22
22.5
Effluent
56.4
29.9
13.5
29
46
43.7
25.8
17.9
17.2
13.7
28
25
30.2
49.4
18.7
BOD
Influent
13.1
84.3
46.4
62.9
38.1
27.2
17.5
32.1
19.5
28.3
28.9
52.7
46.5
40.3
22.2
Effluent
15.5
96.8
53
61.6
10.5
12
3.58
5.87
9.70
1.68
3.09
4.1
22.8
7.06
15
COD
Influent
107
189
96.3
135
-
-
42.6
97.3
54.3
57.5
111
117
71
42.9
62.7
Effluent
132
231
104
149
-
-
37.6
58.4
48
32.2
99.3
128
55.4
32.8
28.3
Oil & grease
Influent
8.62
10.2
6.52
2.73
1.71
5.49
7.11
1.78
2.58
2.61
1.69
3.24
5.19
5
3.33
Effluent
7.06
12
1.58
2.85
<0.1
3.48
10.5
2.75
7.52
2.31
3.74
4.05
2.57
2.89
3.11
Organic nitrogen
Influent
1.41
5.04
0.70
1.65
<0.1
0.29
<0.1
4.27
1.05
<0.1
1.09
3.64
1.62
1.84
1.38
Effluent
1.37
5.28
0.80
1.54
<0.1
<0.1
<0.1
0.5
0.1
<0.1
2.07
5.62
2.52
1.19
4.07
Ammonium
Influent
2.41
3.3
2.06
0.86
1.08
1.06
<0.1
1.6
3.48
2.99
10.9
6.49
4.43
2.58
3.35
nitrogen
Effluent
2.62
1.04
1.3
0.95
1.05
0.85
<0.1
2.56
1.38
0.95
3.77
3.8
1.65
2.62
1.29
3JTO
-------
SECTION VII
SYSTEM PERFORMANCE EVALUATION
The Baker Street dissolved air flotation facility and a pilot-scale
dissolved air flotation plant were operated during 1970-1971 with raw
and diluted sanitary sewages to simulate the behavior and performance
characteristics of the dissolved air flotation process in the treatment
of combined sewer overflows. The results obtained during both programs
served as a guide to the wet-weather full-scale operation, which was
conducted during the 1973-1974 rainy season. The system performance
under each testing program was evaluated in terms of removals of pollu-
tants; namely, the various forms of solids, turbidity, BOD, COD, oil and
grease, ammonium, and organic nitrogen. The relationships between
process control variables and suspended solids removal efficiencies over
a -wide range of surface loading rates were the principal determinants in
characterizing system performance from the dry-weather flow studies.
WET-WEATHER WASTEWATER CHARACTERISTICS
A large variation in combined sewage quality can normally be
expected, and the results of the drainage basin studies and the wet-
weather testing program confirmed these expectations. The averaged
constituent concentrations of combined sewage flow in the Baker Street
drainage basin during the three storms monitored during 1969 and pre-
sented in Table 7 showed large variations between storms. Similarly,
the averaged constituent concentrations of the influent to the Baker
Street facility during the 15 testing events of the wet-weather
evaluation program also showed great variations. Table 9 presents a
direct comparison of the combined sewage qualities measured during the
71
-------
Table 9. COMPARISON OF SAN FRANCISCO COMBINED SEWAGE AND WET-WEATHER PROGRAM WASTEWATER
Constituent concentrations,
ma/1
Drainage basin studies
Constituent
Total suspended
solids
Settleable solids*
Floatable solids
BOD
COD
Grease and oil
Organic nitrogen
Ammonium nl trogen
Fecal colifom
Total coliform
Wet-weather
program
Average
(Ranged)
51
(10.2-99.5)
1.3
(0.1-13.4)
1.1
(0.2-4.3)
37.3
(13.1-84.3)
91
(42.6-189)
4.5
(1.7-10.2)
1.6
3.1
(0.9-460)
A
Baker Street
Average0
(Ranged)
86.2
(57.6-102)
1.5
(1.1-2.3)
1.6
(0.7-2.5)
22.5
(14-28.6)
160
(75-288)
16.7
(3.2-42.1)
4.8
(2.8-7.7)
1.4
(1.1-1.9)
30
(0.8-40)
A
Harlposa Street
Average
(Ranged)
277
(4.4-478)
M
2.5
a. 1-4. 3)
110
(24.5-232)
521
(299-647)
49.9
(35.9-58.9)
8.6
(4-11.9)
4.2
(0.6-6.1)
3.2
(1.9-12.4)
<:,
Brotherhood
Way
Average
(Ranged)
407
(94.3-735)
2.2
(1-3.6)
67.8
(10.2-183)
50.1
(18.8-83.2)
142.8
(69.4-263)
31.8
(10.9-60.1)
17.2
(11.8-26)
1.1
(0.8-1.5)
1.9
(0.5-4.7)
<:,
Vicente
Area 1
Aver-
age
59.6
1.1
2.9
23.1
111
9
1.9
0.4
0.36
~
Street
Area 2
Aver-
age
68.4
1.3
4.1
8.6
87.3
12.9
1.2
1.3
0.16
—
Sewage treatment plant combined Influent
Northpolnt
Average
(Range)
161
(62-386)
2.5
(0.1-35)
(I)
194
(48-324)
304
(126-615)
57.8
(23.2-127)
(I)
(:)
A
28.3
(0.001-240)
Richmond-
Sunset
Average
(Range)
155
(40-404)
2.6
(0-42)
(I)
193
(77-279)
(I)
46.8
(10-167)
("-)
^
(I)
6.4
(0.000045-24)
Southeast
Average
(Range)
211
(38-787)
1.6
(0-14.4)
^
197
(44-415)
553
(274-860)
67.9
(18-247)
(I)
A
M
10.6
(0.012-240)
^Reference 2
"n*»t-« f~T\ar.t-mA *l.ii-4ni» amtm^t-Ait r*-lfif»11 Avont* frnn Tehruarv 1971 thrmifth Mjiv 1974
'average of storm averages
range of averages
*ml/l/hr
106 MPN/100 ml
-------
separate phases of this program.
The average total suspended solids, chemical oxygen demand, grease
and oil, and organic nitrogen concentrations measured during the Baker
Street drainage basin characterization were somewhat higher than those
of the wet-weather program although there was considerable overlap in
the ranges of averaged values between the two programs. The measured
concentrations of settleable solids, floatable solids, and fecal coli-
forms were comparable for the two phases, and the average biochemical
oxygen demand and ammonium nitrogen concentrations were noticeably
higher in the wet-weather program although, again, the ranges of test
averages were considerably overlapped.
The substantially higher COD and grease content of the Baker Street
drainage basin study flows are due in great measure to an unusually high
average level of grease and oil at 42.1 mg/1 (single storm range of 6 to
110 mg/1) for the storm samples on 5 November 1969. If it can be
assumed that a single large discharge of grease and oil, caused perhaps
by the dumping of crank case oil into a catchbasin, had occurred during
that storm, it would explain the measurement of high chemical oxygen
demand, grease and oil content, and typical biochemical oxygen demand.
Without these rather high values, the average measurements for these
constituents obtained during the other two storms in the Phase I study
are much more comparable to the wet-weather program averages.
The average total suspended solids concentration of 86.2 mg/1 for
the Baker Street drainage basin studies is 35 mg/1 higher than the
average for the wet-weather tests although there were many individual
tests with comparable averages. Two factors could account for this
variation in measured values. First, the comparatively small mesh size
(1/8 inch) of the screens protecting the automatic samplers of the wet-
weather program and their orientation parallel to the main flow streams
caused particles to be rejected that would have been included by the
sampling techniques of the drainage basin studies.
Secondly, the large diameter diversion sewer supplying the Baker
q
Street facility, designed for peak storm flows of 7 m /sec [160 mgd],
provided some storage capacity and low flow velocities at wastewater
73
-------
3
flows below the Baker Street facility treatment capacity of 1 m /sec
[24 mgd]. It is surmised that some sedimentation of suspended particu-
lates occurred in this sewer, resulting in the lower concentrations
measured at the Baker Street influent structure.
Total nitrogen content of the wastewaters from the two programs was
very similar. During pre-construction studies, organic nitrogen concen-
trations were higher than those of ammonium nitrogen. Presumably due to
bacterial action in the sewerage system, much of the organic nitrogen
was converted to ammonium nitrogen by the time the combined sewage
reached the Baker Street facility during wet-weather testing.
It may be seen from this comparison that except for total suspended
solids concentrations the combined wastewater influent to the Baker
Street facility was very comparable to combined sewages measured during
pre-construction studies in the Baker Street drainage area. The
apparent 41 percent reduction in influent suspended solids, possibly due
to the size of the diversion sewer, represents a loss of readily sepa-
rable material that should have been amenable to separation by dissolved
air flotation. The effects of this variation in wastewater quality upon
the evaluation of the Baker Street facility performance are estimated to
be: (1) possible lower apparent suspended solids removal efficiencies
than eould be achieved with a different influent condition; (2) temper-
ing of combined sewage quality variations due to the storage capacity of
the diversion sewer; and (3) a need to exercise caution in the evalua-
tion of the Baker Street facility and in the application of the resulting
conclusions to other facilities.
Table 9 also contains combined sewage characteristics from the
Mariposa Street, Brotherhood Way, and Vicente Street drainage basins and
the three City wastewater treatment facilities. There is similarity in
constituent concentrations among wastewaters from Baker Street, Vicente
Street, and the wet-weather program, but other drainage basins have
substantially different combined sewage characteristics. This fact
emphasizes the need to characterize the combined sewage in a specific
drainage basin before a specific course of treatment is adopted.
74
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DRY-WEATHER WASTEWATER CHARACTERISTICS
Prototype Testing
Capacities of inlet facilities between the diversion structure and
the Baker Street dissolved air flotation plant were sufficiently large
to provide a detention time of over six hours in these facilities when
the influent flow was 1 mgd. This retention would effect the removal
of settleable solids and would tend to "dilute" the raw sewage to a
quality more nearly representative of the average quality of combined
sewage. Indeed, measurements of influent solids concentrations during
the dry-weather testing at Baker Street, presented in Table 10, indi-
cated values that, with the exception of higher biochemical oxygen
demand and total nitrogen, approximated the wet-weather wastewater con-
centrations found in Table 9.
Table 10. INFLUENT QUALITY DURING PROTOTYPE DRY-WEATHER TESTING
Constituent
Total suspended solids
Settleable solids3
Floatable solids
BOD
COD
Grease and oil
Organic nitrogen
Ammonium nitrogen
Concentration ,
Average
96
0.3
0.1
122
211
22.7
5.3
16.2
mg/1
Range
67.5 - 145
<0.1 - 1.5
0 - 0.34
84 - 174
138 - 294
5.7 - 113
2.9 - 6.7
13.3 - 21.4
aml/l
Pilot-Plant Testing
The pilot-plant tests were conducted on an influent wastewater
consisting of raw sewage from the Beach Street sewer of the North Point
sewage treatment plant, diluted with fresh water to a suspended solids
concentration level approximating that of combined sewage. Table 11
summarizes the resulting wastewater characteristics. Although the
75
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influent suspended solids content approximated that of combined sewage,
the other constituent concentrations were higher than encountered during
wet-weather testing.
Table 11. DILUTED SEWAGE CONCENTRATIONS FOR PILOT-PLANT TESTING
Constituent
Total suspended solids
Settleable solids
Floatable solids
BOD
COD
Grease and oil
Total nitrogen
Concentration ,
Average
99.4
12.4
1.6
152
282
25.7
10.3
mg/1
Range
45.9 -
2.6 -
0.3 -
77.9 -
184
6.1 -
3.8 -
159
38
5.7
200
434
55
22.7
ml/1
LABORATORY TEST STUDIES
Jar Tests
Over 75 individual jar and laboratory flotation cell tests were
conducted using dilute raw sewages containing 40 to 100 mg/1 total
suspended solids (TSS) . The dosage ranges selected for evaluation in
the test program varied from 0 to 3 mg alum/mg TSS and 0 to 1 mg polymer/
mg TSS. The ranges of chemical dosages were selected in conjunction with
the pilot-plant test programs but also presented an opportunity for
evaluating the relative merits of the different chemical treatment
systems and provided a base of information for comparing optimal jar-test
results with the corresponding optimal results obtained in the pilot-
plant test runs.
An evaluation of the results of tests done with polymer alone indi-
cated that an optimal turbidity removal of about 60 percent in flotation
cell tests was obtained at a specific dosage of 0.035 mg/mg TSS (equiva-
lent to a dosage of 3.5 mg/1 at a TSS concentration of 100 mg/1), as
76
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compared with less than 30 percent removal in the control tests where
no chemicals were used. At specific polymer dosages in excess of 0.035
mg/mg TSS, turbidity removal decreased rapidly to 30 percent at 0.08 mg/
mg TSS. Jar tests conducted with polymer produced a turbidity removal
of 90 percent with a much higher specific dosage of polymer at 0.35 mg/
mg TSS.
An analysis of the results of jar tests conducted with alum alone
indicated that more than 90 percent turbidity removal could be achieved
with alum dosages greater than 1 mg/mg TSS. A turbidity removal plateau
of about 95 percent was obtained for specific alum dosages between 1.5
and 2.5 mg/mg TSS. Turbidity removal in excess of 95 percent was
obtained at an alum dosage of 3 mg/mg TSS, and an alum blanketing effect
was observed in jar tests conducted with alum dosages in excess of 2.5
mg/mg TSS. The turbidity removal results obtained with alum alone did
not appear to be pH sensitive in that similar removal levels were
obtained in the dosage ranges tested over a final test liquid pH range
of 6.5 to 7.4.
Jar and flotation cell tests conducted with alum-polymer dosage
combinations were performed to ascertain whether economies could be
achieved or turbidity reductions increased using alum and polymer in
combination rather than individually. It was found in the jar tests
that over 80 percent, and up to 90 percent, turbidity removal could be
achieved over a wide range of polymer dosages at alum dosages of about
1.8 mg/mg TSS. In the flotation -cell tests, about 70 percent turbidity
removal was observed with an alum dosage of 1.8 mg/mg TSS, polymer
dosages of 0.015 to 0.018 mg/mg TSS, and a test liquid final pH of 6.2
to 6.5. The results indicated that the use of a high level of alum
additive could effect a 50-percent reduction in the dosage of polymer
necessary to achieve a turbidity removal equivalent to that obtained
when the chemicals were used individually. On the basis of the above
results, it did not appear that the use of alum and polymer in combina-
tion offered any significant advantage over the use of either chemical
individually, in terms of either enhanced turbidity removal or reduced
chemical dosage requirements.
77
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It appeared from the jar test results that (1) alum alone is effec-
tive for removing turbidity in excess of 90 percent over a broad dosage
range, with a minimal dosage of 1 rag/nig TSS for 90 percent turbidity
removal; (2) optimal turbidity removal of 60 percent was achieved with
polymer alone in a narrow dosage range at about 0.035 mg/mg TSS; (3)
alum at 1.8 mg/mg TSS and polymer at 0.015 mg/mg TSS produced a 70 per-
cent solids removal in flotation cell tests; and (4) flotation cell and
jar tests do not produce identical results.
PILOT-PLANT TEST STUDIES
Batch Tests
A total of four batch tests were conducted with the pilot plant
using a range of specific chemical dosages from 1.5 to 3.4 mg/mg TSS
and two liquid loading rates of 20 and 37 m3/(m)2(day) [486 and 915
gal/(ft)2(day)] from recycle flow only. It was ascertained after
initial experimentation that the pH level associated with optimal
solids removal was 6.2 to 6.5; thus, the pH was controlled within this
range during all four batch tests and the subsequent continuous-run
tests.
The results of the batch tests are shown in Figure 24. The initial
TSS concentration in the influent stream used to fill the flotator
varied from 84 to 100 mg/1, and the Initial TSS concentrations observed
in the flotator varied from 30 to 110 mg/1. The initial TSS concentra-
tions observed in the flotator reflected both the impact of the specific
chemical dosages and the sedimentation of solids that occurred inadver-
tently prior to the initial sampling. The nonremovable solids fraction
was defined as the asymptotic value of the solids concentration in the
flotator and was found to vary from 7 to 20 mg/1, with the higher non-
removable solids levels being associated with lower specific chemical
dosages. The optimal solids removal of 93 percent was obtained at the
specific alum dosage of 3.35 mg/mg TSS, and it appeared from the re-
sults that chemical dosage rather than surface loading rate had a
greater effect on the efficiency of solids removal for the range of
78
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SUSPENDED SOLIDS CONCENTRATION IN FLOTATOR, mg//
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-------
chemical dosages and surface loading rates evaluated. The solids re-
moval efficiency of all the batch runs varied from 76 to 93 percent,
and averaged 87 percent.
It is concluded from the results of the batch runs that:
1) Under optimal conditions of pilot-plant batch operation, the
dissolved air flotation process was capable, as an upper performance
boundary, of removing 93 percent of the influent total suspended solids
concentration; and
2) Under batch operating conditions, process efficiency increased
with increasing alum dosage and with decreasing surface loading rate
for the ranges of these individual parameters tested.
Continuous Feed Tests
The data obtained in the 23 pilot-plant continuous run tests were
evaluated to document the response surfaces for each process variable
in terms of TSS removal efficiency and to ascertain the efficiency of
dissolved air flotation for removal of other wastewater constituents.
Alum—
The relationship between specific alum dosage and process
efficiency is illustrated by the data shown in Figure 25. The values
of recycle ratio, surface loading rate, and influent total suspended
solids for the runs included in the analysis were within ranges in
which process efficiency did not vary as a function of the individual
parameters.
Process efficiency, as measured by TSS removal, was found to vary
from a reference efficiency (no chemical) of 62 percent to a peak re-
moval efficiency of 85 percent at the maximum tested alum dosage of
3.1 mg/mg TSS. In all cases the effluent pH range at which optimal
performance was observed was between 6.2 and 6.4, or about one pH unit
less than the pH level at which optimal removals were obtained in the
jar tests. The alum dosage at which optimal solids removals were
observed in the pilot plant was at 0.9 mg/mg TSS, about 10 to 15 per-
cent less than that observed in the jar tests.
It is apparent from the relationship shown on Figure 25 that with
80
-------
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60
40
20
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P-l
P-IO
1
1
1
JL__L
0-8 12 1.6 2.0 2.4 2.8
SPECIFIC ALUM DOSE, mg a!um/mg influent suspended solids
3.2
Figure 25. Effect of specific alum dose on pilot -plant performance
-------
increasing alum dosage the process efficiency of the pilot plant
increased to a saturation level at an alum dosage of about 0.8 mg/mg TSS,
and remained essentially stable thereafter with increasing alum dosages
for the four comparable tests. The stability of process efficiency over
a wide range of alum dosages would be a desirable characteristic of
dissolved air flotation treatment using alum for two reasons:
1) Less operator judgment and control capacity would be required
to maintain the specific alum dosage (and pH) in the desired range; and
2) It might be possible to achieve a stability of process per-
formance under a wide range of influent solids loadings such as typically
is experienced in treatment of combined sewage.
Polymer (Dow Purifloc C-31)—•
The relationship between process efficiency and specific polymer
dosage is illustrated by the data presented in Figure 26. Essentially
constant levels of recycle ratio, surface loading rate, and influent
suspended solids were used in eight test runs with polymer. In two
of the eight runs (P-21 and P-23), the flocculator was bypassed; and
in those runs for which the specific polymer dosage exceeded 0.1 mg/mg
TSS, the polymer concentrations were sufficient to buffer the pH of the
liquid in the range of 7.3 to 7.6.
The response surface of Figure 26 assumes the shape that would be
predicted from the jar test results, i.e., a narrow range of variation
of process efficiency from 60 to 80 percent was observed over the same
range of polymer dosages as tested in the jar-test program, and peak
process efficiency was observed at a specific polymer dosage of 0.3 to
0.45 mg/mg TSS. The total polymer dosage required to achieve a
solids removal efficiency of 80 percent was in the order of 30 mg/1, or
nearly one order of magnitude greater than that typically used in waste
treatment applications and observed in the laboratory flotation cell
tests. The optimal polymer dosage in the dissolved air flotation pro-
cess was about 20 percent greater than the optimal dosage observed in
the jar tests.
The results shown in Figure 26 do not indicate that the bypassing
82
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INFLUENT SUSPENDED SOLIDS REMOVAL EFFICIENCY, %
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of the flocuulator had an adverse effect on the performance of the
dissolved air flotation process. In the case of Test Run P-21, the
process efficiency was less than indicated by the general relationship,
and in the other case of Test Run P-23, the opposite situation occurred.
It is evident from these data that polymer was approximately 10
percent less efficient than alum in affecting chemical conversion in the
dissolved air flotation process, and that significantly higher dosages
of polymer were required to effect optimum process efficiency than have
been required in wastewater treatment applications elsewhere. For this
reason alum was used in the pilot-plant continuous runs to determine
response surface relationships for the process variables. Tests with
alum and polymer combinations were not conducted on the pilot plant.
Surface Loading Rate—:
The relationship between process efficiency and surface loading
rate in the dissolved air flotation process is illustrated by the data
shown in Figure 27. The values of air to solids and recycle ratios,
surface loading rate, and influent suspended solids concentrations for
the runs included in the analysis were within ranges in which process
efficiency did not vary significantly as a function of the individual
parameters. The flocculator of the pilot plant was used in seven of
the eight runs and was bypassed in Test Run P-9.
The response surface shown in Figure 27 defines a relationship in
which process efficiency decreases with increasing surface loading rates
from an efficiency of 90 percent at 39 m3/(m)2(day) [970 gal/(ft)2(day)]
to about 60 percent at 162 m3/(m)2(day) [4,000 gal/(ft)2(day)]. The
surface loading rate of 162 m3/(m)2(day) [4,000 gal/(ft)2(day)] was near
the maximum hydraulic capacity of the pilot plant. In comparison, the
maximum process efficiency observed in the batch tests was 93 percent,
indicating that less than a four percent difference was observed between
optimal performance levels in either test mode. The performance
efficiency observed in Test Run P-9, in which the flocculator was by-
passed, exceeded that observed in Test Run P-8, in which the flocculator
was used.
Several deductions might be made from the results presented in
84
-------
INFLUENT SUSPENDED SOLIDS REMOVAL EFFICIENCY,0/*
31
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Figure 27. In the treatment of raw and dilute raw sewages with dissolved
air flotation, the pilot plant surface loading rate could be increased
four fold from 40 m3/(m)2(day) [1,000 gal/(ft)2(day)] with a 30 percent
reduction in process efficiency; for this reason the dissolved air
flotation process can offer an apparent degree of treatment stability
that is highly advantageous for its use in the treatment of combined
sewage overflows under conditions of rapidly varying hydraulic loading.
At a surface loading rate of 162 m3/(m)2(day) [4,000 gal/(ft)2(day)] in
the pilot plant, the estimated process efficiency was 60 percent, or
equivalent to the typical performance level of a primary sedimentation
facility.
The decrease in process efficiency as surface loading increased
may be associated with one or more of the following factors:
1) Destruction of air bubble-particle aggregates in the inlet
structure with increasing hydraulic loading to the flotation chamber;
2) Hydraulic overloading of the effluent launders;
3) Breakup of float by agitation of the liquid surface in the
flotator; or
4) Hydraulic short-circuiting in the flotator.
Effect of Recycle Ratio—
The relationship between process efficiency and recycle ratio in
the dissolved air flotation process is illustrated by the data pre-
sented in Figure 28. The values of air to solids ratio, surface loading
rate, and influent suspended solids concentration in the test runs
included in the analysis were within ranges of the individual parameters
for which process efficiency was essentially constant. The pilot-plant
flocculator was not used in one of the four runs.
The reference point on the response surface was the minimum
recycle ratio of 20 percent, which corresponded to the recycle ratio
incorporated in the design capacity of the prototype facility. The
response surface defines a relationship of increasing process efficiency
at a decreasing rate with increasing recycle ratio at fixed surface
loading rates, such that process efficiency increased by about 10
86
-------
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SUSPENDED SOLIDS REMOVAL EFFICIENCY, %
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percent as the recycle ratio increased from 20 to 120 percent. The hy-
draulic capacity of the pilot-plant recycle system precluded the inves-
tigation of process performance at recycle ratios greater than 120 per-
cent. However, on the basis of information presented in the state-of-
the-art evaluation (Reference 1), it is anticipated that process
efficiency will gradually peak, and then decrease, with increasing re-
cycle ratios in relation to increasing levels of surface loading rate.
Effect of Air to Solids Ratio—
The relationship between process efficiency and air to solids ratio
in the dissolved air flotation process is shown by the data presented in
Figure 29. The values of process variables other than air to solids
ratio used in the runs selected for the analysis were within ranges of
the individual parameters in which process efficiency varied by less
than 10 percent. The flocculator was used in all runs for which data
are presented in Figure 29.
The response surface for the air to solids ratio was characterized
by a rapid increase in process efficiency from zero at a ratio of 0.01
kg air/kg TSS to an excess of 80 percent at a ratio of 0.05, followed
by a gradual decrease in process efficiency to 70 percent at a ratio
of 0.20. The response surfaces indicate that the efficiency of the
process was unstable until a saturation value of process efficiency was
attained at a ratio of 0.03. The saturation and decay characteristics
of the air to solids ratio response surface have been observed in prior
investigations (Reference 1) and have been attributed to the following:
(1) The saturation relationship was attributed to the increase
in the terminal rise velocity of air bubble-particle aggregates with
increasing air to solids ratios.
(2) The decay relationship occurring with increasing ratios
beyond the saturation value was associated with the destruction of air
bubble-particle aggregates and float due to the shearing effects of
turbulence caused by the release of excessive air.
88
-------
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0.025 0.050
0.075
0.100
0125
O.I5O
0.175
0.200
AIR TO SOLIDS RATIO, kg dissolved air released/kg solids entering flotator
Figure 29 • Effect of air to solids ratio on pi!6t plant performance
-------
DRY-WEATHER.TEST PROGRAM
Jar Tests
Over 30 individual jar tests were run using raw sewages containing
70 to 110 mg/1 TSS as measured by turbidity. These jar tests were con-
ducted prior to and during the dry-weather testing program and are
independently evaluated from those conducted during pilot-plant studies.
The dosage ranges selected for evaluation in the test program
varied from 0 to 3 mg alum/mg TSS and 0 to 0.6 mg polymer/mg TSS. The
ranges of chemical dosages presented an opportunity for evaluating the
relative merits of the different chemical treatment systems, and pro-
vided a base of information for comparing optimal jar-test results with
the corresponding optimal results obtained in dry-weather test runs.
An evaluation of the results of the jar tests done with polymer
alone has indicated that a maximum turbidity removal of about 60 per-
cent was obtained at a specific dosage of 0.5 mg/mg TSS, as compared with
about 15 percent removal in the control test where no chemicals were
used. The optimal specific dosage of 0.5 mg/mg TSS, equivalent to a
dosage of 50 mg/1 at a TSS concentration of 100 mg/1, was about the same
as the 0.35 mg/mg TSS observed during the pilot-plant studies.
Turbidity removals observed at alum dosages ranging from 0 to 3.0
mg/mg TSS and polymer (DOW Purifloc C-31) dosages between 0 and 0.13
mg/mg TSS were averaged for fixed alum dose levels and are presented in
Table 12.
For jar tests conducted with alum alone, average turbidity removal
efficiencies increased rapidly from 15 percent with no alum to an ob-
served removal of 95 percent at an alum dosage of 0.5 mg/mg TSS. As
alum dosage levels were increased further, a gradual decrease in re-
moval efficiency to an intermediate minimum of 80 percent at 1.5 mg/mg
TSS was observed, followed by an increase to 89 percent at 3.0 mg/mg TSS.
When alum and polymer were used in combination, increasing average
turbidity removal efficiencies were noted with increasing alum dosage
levels, reaching a maximum of 96 percent at the highest alum dosage
employed (3.0 mg/mg TSS).
90
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Table 12. EFFECT OF ALUM AND ALUM-POLYMER ON AVERAGE
TURBIDITY REMOVAL EFFICIENCY
Alum dosage,
mg/mg TSS
0
0.5
1.0
1.5
2.0
2.5
3.0
Average
Alum
15
95
86
80
81
82
89
turbidity removal^ %
Alum-P o lyme r *
-
68
86
86
92
93
96
*Polymer dosages less than 0.15 mg/mg TSS
When alum and polymer were used in combination, increasing average
turbidity removal efficiencies were noted with increasing alum dosage
levels, reaching a maximum of 96 percent at the highest alum dosage
employed (3.0 mg/mg TSS).
It appears that the combined use of alum and polymer in the range
of alum dosages between 1.0 and 3.0 mg/mg TSS and polymer dosages less
than 0.13 mg/mg TSS offers an advantage over the use of alum alone, in
terms of enhanced turbidity removal.
It is evident from the jar-test results that: (1) alum alone was
effective for removing turbidity in excess of 80 percent over a broad
dosage range; (2) maximum turbidity removal of 60 percent was achieved
with polymer in a narrow dosage range at about 0.5 mg/mg TSS; and (3)
improved turbidity removals at the larger alum dosages were obtained in
combination with small dosages of polymer. This result reverses the
findings of the laboratory air flotation cell tests where alum used
singly was found to be more effective.
Baker Street DAF Facility Dry-Weather Tests
The basic data obtained in. the 24 dry-weather test runs, with the
exception of data from Test Runs D-2 and D-4 through D-9, which were
91
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obtained when the chemical feed pumps were malfunctioning, were evaluated
to document the response surfaces for each process variable in terms of
TSS removal efficiency and to ascertain the efficiency of dissolved air
flotation for removal of other wastewater constituents.
Alum—
The relationship between specific alum dose and process efficiency
is illustrated by the data in Figure 30. The values of recycle ratio,
surface loading rate, air to solids ratio and influent suspended solids
concentration for the runs included in the analysis were maintained
within a range calculated not to affect process performance.
Process efficiency, as measured by turbidity removal, was found to
increase from 14 percent at no alum addition to a peak removal effi-
ciency of near 65 percent at an alum dosage of 6 mg/mg TSS.
It is apparent from the relationship shown in Figure 30 that with
increasing alum dosage, process efficiency increased to a saturation
level at an alum dosage of about 6.0 mg/mg TSS, and remained essentially
stable thereafter ,with increasing alum dosages.
Polymer (DOW Purifloc C-31)— ;n;
The relationship between process efficiency and specific polymer.
dosage is illustrated in Figure 31. The polymer dosages selected for
dry-weather test runs (0.04 to 0.15 mg/mg TSS) were comparable to levels
at which maximum solids removals were obtained in the jar tests.
The response surface of Figure 31 is difficult to evaluate but
shows an optimal turbidity removal at a polymer dosage of 0.06 mg/mg
TSS. This optimal removal of 15 percent is only slightly higher than 12
percent achieved by the dry-weather test without polymer addit-ion. Also,
suspended solids removal efficiencies decreased to near zero as polymer
dosages were increased above 0.15 mg/mg TSS. Thus for the"polymer dos-
ages tested under dry-weather test conditions in this study, no improve-
ment in suspended solids removal efficiency was observed by the use of
polymer alone.
92
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1
INITIAL SUSPENDED SOLIDS REMOVAL EFFICIENCY, %
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D-17
0.05
0.10
0.15
SPECIFIC POLYMER DOSE, mg/mg suspended solids
Figure 31 - Effect of specific polymer dose on prototype dry-weather performance
-------
Surface Loading Rate—
The relationship between process efficiency and the surface loading
rate in the dissolved air flotation process is illustrated by the data
shown in Figure 32. Four runs were conducted at an alum dosage very
near 2.5 mg/mg TSS and were used to establish the shape of the response
surface. However, since suspended solids removal efficiencies were
relatively low at these dosages, single data points and the derived re-
lationship values at higher alum dosages are included on Figure 32 to
indicate expected removals as a function of alum dose level.
The response surface shown on Figure 32 at an average alum dosage
of 2.5 mg/mg TSS defines a relationship in which process efficiency
decreased at a gradually decreasing rate with increasing surface loading
rate from an efficiency of 34 percent at 171 m3/(m)2(day) [4,230 gal/
(ft)2(day)] to about 16 percent at 247 m3/(m)2(day) [6,110 gal/(ft)2
(day)]. At 257 m3/(m)2(day) [6,340 gal/(ft)2(day)] with an alum dosage
of 5.2 mg/mg TSS, the relationship presented in Figure 32 indicated a
suspended solids removal of 76 percent. A decrease in process effi-
ciency was observed at a higher alum dosage of 13.8 mg/mg TSS. This is
believed to be a consequence of the carry-over of alum floes into the
effluent at such high alum dosage and a possible encroachment into the
region of peptization.
Pressurization Mode—
The relationship between process efficiency and recycle ratio was
not investigated in this study because flow control in the two-stage
constant-rate recycle pump was not feasible at the time. Two test runs
(D-16 and D-21) were conducted to assess the impact of pressurization
mode on process efficiency. The process variables for these two runs
did not vary by more than 10 percent except that in Test Run D-16, flo-
tator recycle was used and in Test Run D-21, a portion of the influent
flow was pressurized. The turbidity and suspended solids removal
efficiencies were higher by only four percentage points for Test Run
D-21 while the BOD and COD removals were, respectively, three and two
percentage points higher for Test Run D-16.
95
-------
96
SUSPENDED SOLIDS REMOVAL EFFICIENCY, %
i
OJ
N)
m
—H
s*
o
CO
I
s
o"
Q
Q.
3"
(0
3
«0
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ca
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O
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8
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K
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10
ex ro
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«< o
01
ro
o
-------
Air to Solids Ratio—
The relationship between prototype process efficiency with dry-
weather flow,and air to solids ratio in the dissolved air flotation
process is shown by the data presented in Figure 33. The values of
other process variables used in the runs selected for the analysis were
within ranges of the individual parameters in which process efficiency
was not affected significantly. '< ;
The response surface for air to solids ratio was characterized by ;
a rapid increase in process efficiency from zero at a ratio Of 0.02 kg
air/kg TSS to an excess of 30 percent at an air to solids'ratio of 0.5.
The saturation characteristics of the air to solids response surface
also were observed in the pilot-plant investigation and provided the
general shape for their relationship.
WET-WEATHER TEST PROGRAM
The results obtained from 15 wet-weather test runs were evaluated
in terms of pollutant removal efficiencies with respect to alum dosage, ';
and surface loading rate. Pilot-plant and dry-weather simulation stud-
ies yielded some optimal operational information on process variables
of recycle ratio and air to solids ratio. A minimum recycle ratio of 20
percent and an air to solids ratio of 0.06 at maximum plant flow were
employed during the wet-weather testing program. Table 13 presents the
removal efficiencies of total suspended solids, settleable solids, float-
able solids, turbidity, BOD, COD, oil and grease, organic nitrogen,
ammonium, and fecal coliform counts. The corresponding alum dose and
surface loading rate are also included in Table 13.
In addition to presenting the system performance of the Baker Street
dissolved air flotation facility under the wet-weather testing program,
performance data obtained during pilot-plant and dry-weather testing
programs are also included for comparison to determine if the wet-
weather dissolved air flotation operation can be simulated by using
dilute raw sewage instead of combined sewage and storm water overflow.
The relationships between operating variables of surface loading ,
rate and alum dosage and process efficiency are characterized by
97
-------
86
SUSPENDED SOLIDS REMOVAL EFFICIENCY, %
(Q
CD
OJ
04
m
-+i
-*»
CD
O
O
-+»
Q
in
g_
OL
W
Q
5"
o
13
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6
30
CD
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CD
a
CD
-1
CD
3
a
is
o
CD
to
(fl
(D
Q.
(D
O
V>
> O O
**vH L
V^
o a
i 5
o
m
z i
H >
35
si
9 co
2 m
U] o
w <
~~ co m
—
1 1
UJ -C»
O 0
1 1
"\
I
1
1
1
1
1
1
1
1
1
1
1
1
1
i
a
i
(jt
1 1
01
0
— —
—
—
-------
Table 13. BAKER STREET DAF FACILITY WET-WEATHER PERFORMANCE SUMMARY
Constituent removals, %
Test
run
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Surface
3 2
m /(m) (day
103
145
182
232
232
232
182
145
145
145
103
103
182
182
232
loading
[gal/(ft)2(day)]
[2,530]
[3,580]
[4,460]
[5,690]
[5,690]
[5,690]
{4,460]
[3,580]
[3,580]
[3,580]
[2,5.10]
[2,530]
[4,460]
[4,460]
[5,690]
Alum
dosage,
mg/1
0
0
0
0
150
300
150
75
0
150
75
0
75
300
75
TSS
-35.8
5.2
- 9.7
5.0
-
-
-209
51.2
-12.6
43.7
-9.3
15.8
-95.9
-325
8.2
Settle-
able
solids
-38.8
79
56.2
30.2
-7,750
-28,800
-15,400
94.4
9.1
-87.5
46.5
62.3
0
15.3
23.7
Flotable
solids
37.1
38.6
-203
-2.75
-697
-179
55.4
67.7
-130
-94.7
11.3
-43
23.2
-35.2
52
Turbidity
-24.5
-45.9
-4.7
-26.6
-31.4
-208
-
66.4
-22.9
57.3
-15.7
0.8
-21.8
-125
16.9
BOD
-18.3
-14.8
-14.2
2.1
72.4
55.9
79.5
81.7
50.3
94.1
89.3
92.2
51.0
82.5
32.4
COD
-23.4
-22.2
-8.0
-10.4
-
-
11.7
40.0
11.6
44.0
10.5
-9.4
22.0
23.5
54.9
Oil
and
grease
18.1
-17.7
75.8
-4.4
94.2
36.6
-47.7
-54.5
-191
11.5
-121
-25
50.5
42.2
6.6
Organic
N
2.8
-4.8
-14.8
6.7
0
65.6
0
88.3
90.5
0
-89.9
-54.4
-55.6
35.3
-195
NH4-N
-8.7
68.5
36.9
-10.6
2.8
20.1
0
-60
60.3
68.2
65.4
41.4
62.8
-1.6
61.5
Fecal
coli-
form
-
-
-
-
-
-
99.9
-
-
99.9
99.9
99.9
99.9
99.9
99.9
-------
removal efficiencies of the following pollutant parameters: total sus-
pended solids, settleable solids, floatable solids, turbidity, BOD, COD,
oil and grease, ammonium, and organic nitrogen.
A departure from the preceding air flotation studies was made in
the measurement of alum dosage in terms of mg/1 rather than mg alum/mg
TSS. It was felt that the Baker Street dissolved air flotation facility
operator had no practical means of instantantously adjusting alum doaage
to reflect influent suspended solids concentrations. Since most influent
suspended solids concentrations had varied in a range between 40 and 100
mg/1 and because the chemical feed pumps had been designed to.be paced
from an 'influent magnetic flow meter, it was'decided that information on
the total alum dosage rate would Be of more value to the facility opera-
tor and other persons faced with the realities of purchasing instrumen-
tation and equipment currently on the market.
The following removal efficiencies might have been substantially
improved if a portion of the raw influent had been used for pressuriza-
tion rather than the recycle of', effluent. At the Baker Street facility,
recycle of effluent could not occur tint 11 ""the flotation tank was approx-
imately two-thirds full. Since alum and caustic .were added to the pres-
surized stream, this meant that two-thirds of the initial flotation tank
volume did not receive chemical treatment or pressurized air in the same
proportion as subsequent flows." It is felt that this condition could
not have helped improve process performance and that it could be readily
alleviated by pressurizing a portion of the combined sewage influent.
Total Suspended Solids Removal Efficiency
Figures 34 and 35 illustrate the Baker Street dissolved air flota-
tion facility performance measured by the removal of total suspended
solids as a function of surface loading rate and alum dosage. During
ail of the 15, wet-weather test runs, the total suspended solids removal
reached a peak of 51 percent at an alum dosage of 75 mg/1 (or 0.75 mg
09
alum/mg TSS) and at a surface loading rate of 145 nr/(m)^(day) [3,580
• " r\ •_ ,•-.•• ..,•_• _,.-.- i . ._ .
gal/(ft) (day)]. Suspended solids removals at higher surface loading
rates decreased rapidly and contrary to results obtained during pilot-
100
-------
TOT
SUSPENDED SOLIDS REMOVAL , %
to
c
CD
01
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tn
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CD
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LOADING RATE
3
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0
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3
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to
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ro
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-------
ZOT
SUSPENDED SOLIDS REMOVAL , %
m
3
«o
*>»
<»*
a
ro
C/J
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-------
plant studies and dry-weather testing of the Baker Street dissolved air
flotation facility, suspended solids removals were also low at surface
loading rates below 120 m3/(m)2(day) [2,950 gal/(ft)2(day)].
Removals of influent suspended solids ranged from zero to 15 percent
with no alum to the peak removal of 51 percent at 75 mg/1 alum and a
surface loading rate of 145 m3/(m)2(day) [3,580 gal/(ft)2(day)]. Sus-
pended solids removal at other surface loading rates either dropped sig-
nificantly or were maintained at a nearly constant level. A comparison
of wet-weather data with those of previous tests in the prototype
facility indicates that solids removals could not be significantly in-
creased with a one- to four-fold increase in alum dosage.
It was noted during the tests with alum feed to the recycle stream
that some samples, when brought to the laboratory and left standing in
settleable solids measuring cones, either just became or were cloudy and
exhibited a flocculation and settling of particulates. These particu-
lates were chemically identified as alum floe which had not been
removed during the dissolved air flotation process either because of
post-precipitation of the alum after treatment or because of physical or
hydraulic features of the Baker Street facility. Such conditions, which
resulted in greater suspended solids concentrations in the effluent
than in the untreated influent, produced some tests with net negative
removals. These tests have been treated as producing zero removals of
influent suspended solids. The value of replacing polluting wastewater
solids with a nonbiodegradable aluminum floe has not been studied, but
within the strictest definition of a suspended solids analysis, the
Baker Street dissolved air flotation facility exhibited a low removal
of suspended solids from combined wastewaters.
The comparison of pilot-plant and prototype facility performances
with dry-weather flow against the prototype operation during wet-
weather flow is presented in Figures 34 and 35. It appears that in
terms of suspended solids removal, dry-weather testing of the. prototype
facility produced results similar to that of wet-weather testing. Pilot-
plant performance data are substantially better than that from either
prototype program.
103
-------
Floatable Solids Removal Efficiency
Floatable solids removal efficiencies during wet-weather testing
periods varied widely under the tested surface loading rates ranging
from 103 to 232 m3/(m)2(day) [2,530 to 5,690 gal/(ft)2(day)]. This
variation was probably due to the operational difficulties encountered
in adjusting tilt-pipe submergence depth and the low concentrations of
floatable solids in the effluent and influent samples. Figures 36 and
37 show that a reasonably effective range of surface loading rates was
between 141 and 182 m3/(m)2(day) [3,500 and 4,500 gal/(ft)2(day)] and
the most desirable alum dosage was 75 mg/1.
Dry-weather and pilot-plant study results of floatable solids
removal efficiencies showed completely different trends from those of
wet-weather results. No apparent conclusion could be drawn from the
plot of floatable solids removal versus surface loading rate in the
dry-weather studies. Increased alum dosages above 150 mg/1 generally
improved floatables removal in the pilot-plant and dry-weather programs.
BOD Removal Efficiency
Biochemical oxygen demand, a conventional wastewater parameter
directly indicative of the biologically degradable organic content of
wastewater, was employed in evaluating the wet-weather system perfor-
mance. Figures 38 and 39 show the BOD removal efficiency as a function
of surface loading rate and alum dose.
Process efficiency, measured as BOD removal obtained during wet-
weather test runs, decreased from 90 percent to a surface loading rate
of 103 m3/(m)2(day) [2,530 gal/(ft)2(day)]at 0 and 75 mg/1 of alum to
about 50 to 80 percent at 145 m3/(m)2(day) [-3,580 gal/(ft)2(day)] with
an alum dosage range of 0 to 150 mg/1. BOD removal efficiency
decreased rapidly when the surface loading rate was greater than
145 m3/(m)2(day). The optional range of surface loading rate with
3 ?
maximum BOD removal was between 100 and 145 m / (my-(day) [2,500 and
3,600 gal/(ft)2(day)].
BOD removal efficiency generally increased with increasing alum
dosage from 0 to 150 mg/1. It also appeared that above an alum dosage
104
-------
o
Lfl
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cr
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100
80
60
40
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4. WET-WEATHER
ALL DOSAGES AS
ng/-r\ . •• /
JSukA^MiS
4,5,6
1000 2000 3000 4000 5000 6000 7000 8000
gal/(ft)2(day)
I
I
I
I
I
50 100 150 200 250
SURFACE LOADING RATE, m3/(m)2(day)
300
Figure 36 • Floatables removal with varying surface loading
-------
IOO
o
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a:
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PI LOT-PL ANT
• DRY-WEATHER
A WET-WEATHER
232 m3/(m)2(doy)
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ALUM DOSE, mg/4 as AI2(S04)3
400
Figure 37 . Floatables removal with varying alum dose
-------
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7000 800
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SURFACE LOADING RATE, m/(m)(doy)
Figure 38 . BOD removal with varying surface loading
-------
80T
BOD REMOVAL, %
(O
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CD
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-------
of 150 mg/1 there was a decline in BOD removal efficiency at a surface
loading of 232 m3/(m)2(day) [5,690 gal/(ft)2(day)], while a very slight
30 ?
increase in removals was obtained at 182 m /(m) (day) [4,460 gal/(ft)
(day)]. It was evident from the results that the optimal range of alum
dosage for BOD removal was between lOO and 200 mg/1 with a peak a.t
150 mg/1. Higher dosages did not produce substantial improvements in
BOD removal. The relationships between BOD removal efficiency and
surface loading rate as well as alum dose for dry-weather test runs are
also presented in Figures 38 and 39, respectively. Both relationships
parallel the family of curves obtained from wet-weather test runs.
Dry-weather studies indicate also that BOD removal decreased sharply
as surface loading rate increased and the desirable upper limit of
32 2
surface loading rate was approximately 120 m /(m) (day) [3,000 gal/(ft)
(day)]. On the other hand, BOD removal increased to a constant maximum
removal level when alum dosage was greater than 180 mg/1.
It thus appears that although suspended solids removals were
dubious and low due to alum floe carry-over difficulties BOD, which is
traditionally representative of pollutant levels in a wastewater, was
removed at very substantial rates at 145 m3/(m)2(day) [3,580 gal/(ft)2
(day)], approaching treatment levels achieved by many secondary waste-
water treatment facilities. This substantiates the idea that influent
pollutant solids were replaced by alum floe during several of the wet-
weather tests.
A comparison of the plotted data in Figures 38 and 39 reveals
that there is a good correlation between pilot-plant dry-weather proto-
type and wet-weather prototype BOD removals.
The correlation is particularly significant due to the relatively
low combined sewage BOD levels encountered in drainage basin characteri-
zation and wet-weather testing programs in comparison to the much
higher BOD levels found in the dry-weather and pilot-plant testing
programs. This correlation is better than that achieved with suspended
solids or floatables, and it suggests that an alum floe carry-over or
post-precipitation problem experienced with the Baker Street facility
was the principal factor distinguishing its performance from that of
109
-------
the pilot plant.
COD Removal Efficiency
COD removal efficiencies as a function of surface loading rate and
alum dosage under wet-weather testing conditions followed similar
patterns to those of BOD removal efficiencies, as shown in Figures 40
and 41. However, the COD removals were lower than for BOD. This
suggests that a high content of soluble, nonbiogradable organic matter
existed in the combined sewage.
During the wet-weather testing program, COD removal efficiencies
increased and peaked between 40 and 65 percent as surface loading rate
increased from 103 to 145 m3/(m)2(day) [2,530 to 3,580 gal/(ft)2(day)].
3 2
Removals decreased sharply at surface loading rates above 145 m /(m)
day). The optimal surface loading rate for COD removal was between
120 and 160 m3/(m)2(day) [3,000 and 4,000 gal/(ft)2(day)]. On the
other hand, the COD removal efficiency increased with alum dosage and
reached a miximum efficiency at 75 mg/1 and then remained relatively
level at alum dosages greater than 75 mg/1. The optimal range of alum
dosage appeared to be between 75 and 150 mg/1.
Several COD measurements were made on the influent and effluent
samples during the dry-weather test runs. Figures 40 and 41 show the
COD removal efficiency versus surface loading rate and alum dosage for
dry-weather as well as wet-weather test studies. Similar trends were
observed for both testing programs, with COD removal efficiencies
3
dropping sharply as surface loading rates increased to above 143 m /
(m)2(day) [3,500 gal/(ft)2(day)] and with inexplicable increases in
3 2
removals at surface loading rates above 182 m /(m) (day) [4,500 gal/
i-\
(ft) (day)]. Alum dosage levels seemed to have less effect on COD
removal during dry-weather test runs, with COD removal remaining
between 10 and 60 percent throughout the alum testing range. There was
insufficient data from pilot-plant operations to make a comparison on
this parameter.
Oil and Grease Removal Efficiency
The oil and grease removal efficiency obtained during wet-weather
110
-------
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80
*
REMOVAL,
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1000 2000 3000 4000 5000 6000 7000 800(
gal/(ft)2(day)
1 I 1 1 If
0 50 100 150 200 PRO ™n
SURFACE LOADING RATE, m3/(m)2(day)
Figure 40- COD removal with varying surface loading
-------
100
80
g2
REMOVAL,
Ji Cn
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20
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^/:^.-^_^,03m3/(m)2(day) } {
o\ 100
^-1,2,3,4,12
200 300
ALUM DOSE , mg/^ as AI2(S04)3
400
Figure 41 • COD removal with varying alum dose
-------
testing periods varied widely and inconsistently with the alum dosages
and surface loading rates employed. Two principal reasons for such
wide variations were the small magnitude of oil and grease content in
the samples, ranging from 0.1 to 12 mg/1, and handling losses in
sampling, transferring, and preparing samples for analysis. However,
on the basis of the results it appears that the optimal surface loading
and optimal alum dosage for maximum oil and grease removal were between
182 a"nd 232 m /(m) (day) [4,460 and 5,690 gal/(ft)2(day)] and^above
150 mg/1, respectively. ; c'..
Contrary to the wet-weather results, some apparent trend of oil
and grease removal relating to surface loading rate and alum dosage can
be summarized from the dry-weather and pilot-plant studies... The oil
and grease removal efficiency decreased sharply as surface loading ,
increased from 41 to 163 m3/(m)2(day [1,000 to 4,000 gal/(ft)2(day)].
However, the oil and grease removal efficiency with respect to alum
dosage decreased gradually from 76 to about 35 percent as alum dosage
increased from 0 to 400 ing/1. The oil and grease removal efficiencies
are plotted in Figures 42 and 43.
lettleable Solids Removal Efficiency
Process efficiency as measured"by settleable solids removal was
inappropriate for process performance .evaluation during the wet-weather
testing program because most settleable;solids concentration measure-
ments were very close to the detection limit [0.1 ml/(l)(hr)] of the
standard laboratory method, and precipitation of alum floe occurred
during several of the laboratory analyses. Therefore, few definitive
conclusions can be drawn from the resulting widely scattered data. •
No correlation between alum dosage or surface loading rate and
settleable solids removal could be obtained from the pilot-plant and
dry-weather prototype tests. Settleable solids removals were far .-•>
higher during pilot-plant tests than with the prototype and again
reflect unique alum carry-over problems in the prototype unit.
During Test Runs 3, 8, 11, and 12, however, the Baker Street
dissolved air flotation facility did remove more than 45 percent of
113
-------
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80
60
40
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SURFACE LOADING RATE, m3/(m)2(day)
Figure 42. Oil and grease removal with varying surface loading
-------
100
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400
ALUM DOSE, mg/4 as AI2(S04)3
Figure 43. Oil and grease removal with varying alum dose
-------
the settleable solids. From this, it appears that the optimal surface
loading rate was between 100 and 170 m3/(m)2(day) [2,500 and 4,200 gal/
2
(ft) (day)], as shown in Figures 44 and 45.
At alum dosage rates of 150 mg/1 and higher, sufficient alum floe
appeared in the effluent to produce zero or negative settleable solids
removals. In order to minimize this effect, a maximum alum dosage of
75 mg/1 is recommended. If effective flocculation had been achieved,
a higher alum dosage, as recommended from pilot-scale and jar tests,
might have produced better results.
Turbidity Removal Efficiency
Turbidity measurements during the wet-weather program were
affected by the alum floe carry-over and precipitation problems in a
manner similar to that of the effect on total suspended solids measure-
ments. Additionally, laboratory turbidity measurements were misleading
because of settling and agglomeration of particulates during sample
transport and storage. Only field measurements could capture a "true"
turbidity. During the wet-weather program, field measurements were
made but were somewhat inaccurate due to minute air bubbles condensing
in the effluent samples.
Only three test runs (8, 10, and 15) indicated turbidity removals
and Test Runs 8 and 10 did exhibit a removal of more than 50 percent
of the influent turbidity. This leads to an optimal surface loading
rate for turbidity removal of 145 m /(m)2(day) [3,580 gal/(ft)2(day)].
Similarly, optimal alum dosages were found to be 75 mg/1 during the
wet-weather studies as shown in Figures 46 and 47. The dry-weather
studies produced results similar to the wet-weather program.
Ammonium and Organic Nitrogen Removal Efficiencies
Ammonium and organic nitrogen concentrations in the influent and
effluent samples of wet-weather runs were relatively low in magnitude,
ranging from 0.10 to 10.9 mg/1 as N. Approximately 15 percent of the
measurements were below the analytical detection limit, which is 0.1
mg/1 as N. Therefore, using ammonium or organic nitrogen removal
efficiency as a measure of process performance can be misleading.
116
-------
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However, substantial removals of ammonium were observed during Test
Runs 6, 8, and 9 and of organic nitrogen during Test Runs 9, 10, 11,
13, and 15. It appears that for maximum ammonium removal the alum
dosage range was between 0 and 150 mg/1 and the surface loading rate
was between 100 and 182 m3/(m)2(day) [2,500 and 4,500 gal/(ft)2(day)].
On the other hand, for maximum organic nitrogen removal the optimal
alum dosage was between 0 and 75 mg/1 and the surface loading rate was
145 m3/(m)2(day) [3,580 gal/(ft)2(day)].
Results of ammonium and organic nitrogen removals are presented
with wet-weather data in Figures 48, 49, 50, and 51. It appears that
surface loading had little effect on ammonium and organic nitrogen
removal from raw sewage. The maximum ammonium and organic nitrogen
removal efficiencies decreased from 80 and 90 percent, respectively,
as alum dosage increased from 0 to 150 mg/1. Above 150 mg/1 of alum
applied, the maximum nitrogen removal efficiencies increased from 19
percent organic nitrogen removal and 14 percent ammonium removal to
24 and 29 percent, respectively, at 400 mg/1 of alum.
Fecal Coliforms
With influent fecal coliform concentrations ranging anywhere from
9 x 105 MPN/100 ml to 46 x 10 MPN/100 ml, the combined treatment of
chlorination and dissolved air flotation was sufficient to reduce the
fecal coliforms in all samples analyzed to less than 3 MPN/100 ml.
Chlorine demand arid effluent residual chlorine were not monitored on a
consistent basis due to difficulties with the residual chlorine
analyzer. However, intermittent chemical analyses of effluent samples
indicated residual chlorine concentrations ranging from 1 to 12 mg/1.
The bacterial quality of the Baker Street dissolved air flotation
facility effluent makes it highly compatible with nearby water-oriented
recreation facilities.
Toxicity
Effluent samples from three wet-weather tests were analyzed for
toxicity after appropriate de-chlorination. There was a 100-percent
survival of fish after 96 hours in effluent that had been treated with
121
-------
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Figure 50 . Organic nitrogen removal with varying surface loading
-------
ORGANIC NITROGEN REMOVAL, %
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300 mg/1 of alum. On the other two tests, 100- and 80-percent survi-
vals were recorded for effluents that had been treated with 75 tag/1 of
alum. It was deemed appropriate to de-chlorinate samples because the
chlorine is not a typical constituent of combined sewages but was added
at Baker Street in a process incidental to dissolved air flotation.
OPTIMIZATION OF BAKER STREET FACILITY
PERFORMANCE
The pilot-plant and the Baker Street dissolved air flotation
facility dry-weather tests were conducted with raw and diluted raw
sewages. The Baker Street dissolved air flotation facility wet-weather
tests were performed with only combined sewage and storm water runoff.
In addition to determining process control settings for the best
performance of the facility, this section will also explore the use of
pilot-scale and dry-weather testing for prediction of prototype behav-
ior with wet-weather flows.
The operating variables investigated in the current wet-weather
evaluation program and in the preceding studies include surface load-
ing rate, recycle ratio, pressurization mode, air to solids ratio,
alum feed rate, and polymer feed rate. Of these six major process
variables, only surface loading rate and alum dosage were explored in
the Baker Street facility wet-weather evaluation and all of the pre-
vious testing programs. The other process variables for any storm
test would include only the parameters under evaluation.
Air to Solids Ratio
The effects of air to solids ratio on solids removal efficiency
were defined in the pilot-plant and prototype dry-weather flow tests.
Figure 29 demonstrated the general shape of the air to solids response
surface indicating a peak in solids removal efficiency at an air to
solids ratio of 0.05. At higher air to solids ratios there was a
rapid decline in process efficiency. In the prototype dry-weather
testing program, few comparable data points were collected for an
investigation of the effects of air to solids ratio on performance.
126
-------
The shape of the curve presented in Figure 33 was taken directly from
the preceding pilot-plant studies. Therefore, principally on the basis
of the results of the pilot-plant studies, a minimum design air to
solids ratio of 0.06 kg/kg was selected for all further testing. The
setting of this design ratio at the maximum expected facility flow
will result in higher ratios at lower facility loading rates. As may
be seen in Figure 29, this should produce only a slight decrease in
process performance.
Pressurization Mode
Two test runs were conducted during the dry-weather program to
study the effects of using effluent recycle versus a portion of the
influent flow for pressurization. The effluent recycle mode produced
slightly higher turbidity and suspended solids removals in Test Run
D-21, and the influent pressurization mode resulted in slightly higher
BOD and COD removals in Test Run D-16. Since no substantial benefit
was demonstrated for either system, and since the influent pressuriza-
tion mode could result in increased fouling of gauges and valves, the
effluent recirculation mode was selected for wet-weather testing. It
must be noted that the current piping configuration at the Baker
Street facility permits either mode of operation. Actual experience
with wet-weather operation indicated that influent pressurization would
be a preferred mode of operation. A detailed explanation may be found
in Section VIII, Pre^s^urization System.
Recycle Ratio
Recycle was employed when a portion of the treated effluent from
the dissolved air flotation process was returned through the pressuri-
zation system into the flotation tank. The minimum recycle ratio
incorporated into the Baker Street dissolved air flotation facilit. is
20 percent. Pilot-plant studies indicated a 22-percent increase in
suspended solids removal with an increase in recycle ratio from 20 to
120 percent. With a constant recycle flow, influent loadings lower
than the facility's design capacity will result in increased recycle
ratios and improved solids removal.
127
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Polymer Feed Rate
The use of polymer to improve solids and air bubble aggregation
was not investigated during the wet-weather program. Pilot-plant
performance exhibited a convex response surface with respect to polymer
dosage. Maximum suspended solids removals of 80 percent were observed
at specific polymer dosages of 0.3 to 0.45 mg/mg TSS and minimum
removal occurred at zero polymer dosage and above 0.7 mg/mg TSS.
The relationship between polymer and performance found during the
prototype dry-weather studies was substantially different. A maximum
suspended solids removal efficiency of 15 percent occurred at a specific
polymer dosage of 0.06 mg/mg TSS; this effectiveness dropped rapidly to
zero at a polymer dosage of 0.16 mg/mg TSS. From this relationship and
in comparison with alum effectiveness to be discussed in the following
section, polymer (Dow Purifloc C-31) alone cannot be recommended for use
as a coagulant or flocculant aid in the dissolved air flotation treat-
ment of combined sewer overflows at the Baker Street facility.
Alum Feed Rate
The alum feed rate was investigated in preceding studies on the
basis of specific dosage of alum as mg alum/rag suspended solids. On
the basis of laboratory jar-test studies, a range of 0 to 3 mg alum/mg
TSS was chosen for pilot-plant investigation. Jar-test studies indi-
cated a maximum turbidity removal of 95 percent between alum dosages
of 1.5 and 2.5 mg/mg TSS. Lower and higher alum dosages resulted in
lesser process performance. Pilot-plant experience indicated an
optimum specific alum dosage of 1.6 mg/mg TSS, achieving 90-percent
suspended solids removal. Again, lower and higher specific alum
dosages produced a lesser quality effluent.
Dry-weather flow studies at the Baker Street dissolved air flota-
tion facility indicated that a much higher alum dosage of 5.5 mg/mg
TSS was necessary for maximum removal of suspended solids at 75-percent
efficiency. The equivalent optimum total alum dosages for jar-test,
pilot-plant, and dry-weather programs were 112, 120, and 413 mg/1,
respectively, assuming an influent suspended solids concentration of
128
-------
75 mg/1.
Prior to the wet-weather program it was decided, for reasons pre-
sented earlier, to evaluate all future data with respect to total alum
dosage expressed in mg/1. A summary of the effects of varying alum
dosage on storm water constituent removals, both for the wet-weather
evaluation program and for comparable earlier tests, is presented in
Table 14. It may be seen, evaluated from the viewpoint of maximizing
constituent removals, that the Baker Street dissolved air flotation
facility alum feed rates should be maintained in the range of 75 to 100
mg/1. This should result in an optimized alum dosage for removal of
suspended solids, turbidity, floatables, COD, oil and grease, and
ammonium.
Recent studies conducted at the City of San Francisco's Richmond-
Sunset wastewater treatment facility indicate that a substantial prob-
lem may exist in maintaining a proper coagulant dosage for combined
sewage overflow (Reference 16). In testing coagulation and floccula-
tion of raw sewage with the aid of alum, sodium hydroxide, and polymer,
the required alum dosages were found to vary from 200 to 375 mg/1 and
caustic dosages from 20 to 35 mg/1 during dry-weather flow in a consis-
tent diurnal pattern. Combined sewage posed substantial control prob-
lems because required alum dosages would vary from 25 to 150 mg/1 and
caustic dosages from 10 to 25 mg/1. While the results of gravity
sedimentation tests are not strictly transferrable to a dissolved air
flotation facility, there is at least strong indication that the com-
bined sewage requirement for optimum coagulation and precipitation
with alum can vary during a storm. However, a comparison of figure
pairs 34 and 35, 36 and 37, 38 and 39, and 40 and 41 indicates that
there appears to be a range of acceptable alum dosages for dissolved
air flotation treatment and that alum dosage is not as sensitive a
controlling parameter as is the surface loading rate at the Baker
Street facility.
Surface Loading Rate
The pilot-plant program resulted in predictable performance for
129
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the dissolved air flotation process. High suspended solids removals
of 80 to 90 percent were observed at low surface loading rates between
40 and 60 m3/(m)2(day) [1,000 and 1,400 gal/(ft)2(day)], with declining
removals occurring at higher surface loading rates. Prototype dry-
weather performance, on the contrary, indicated no removal of suspended
32 ?
solids at a surface loading rate of 100 m /(m) (day) [2,500 gal/(ft)
(day], increasing to maxim'ums from 35 to 75 percent, depending on alum
32 2
dosage, at 163 m /(m) (day) [4,000 gal/(ft) (day)] and generally
declining in performance at higher loading rates.
The prototype facility exhibited similar wet-weather and dry-
weather performance for suspended solids removals. Low suspended
solids removals obtained at low surface loading rates, improving to
32 2
good removals at approximately 145 m /(m) (day) [2,580 gal/(ft) (day)]
and thereafter declining at higher loading rates. This basic perfor-
mance pattern occurred for suspended solids, oil and grease, turbidity,
floatables, settleables, organic nitrogen, and COD removals. BOD
removals were high at low loading rates and declined with increasing
surface loads. Table 14 summarizes the most desirable surface loading
rates for the removal of various combined flow constituents at the
Baker Street facility.
Table 14 . ANALYSIS OF PERFORMANCE DATA FOR THE
OPTIMIZATION OF CONSTITUENT REMOVAL
Storm water
constituent
Total suspended solids
Turbidity
Floatables
Settleable solids
BOD
COD
Oil and grease
Organic nitrogen
Ammonium
Alum dosage,
ng/1
75-150
75
75-100
50
150
75-150
<100-150
indeterminable
0-75
Surface
m3/(m)2(day)
145
145
145-182
145
103-145
145
160-200
145
160
loading rate,
[gal/ (ft)2 (day)]
[3,580]
[3,580]
[3,580 to 4,460]
[3,580]
[2,530 to 3,580]
[3,580]
[4,000 to 5,000]
[3,580]
[4,000]
130
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EFFLUENT QUALITY REQUIREMENTS
The San Francisco Bay Regional Water Quality Control Board, which
has regulatory jurisdiction, has established temporary waste discharge
requirements pursuant to the granting of an operating permit for the
Baker Street facility. These waste discharge requirements are pre-
sented in Appendix F.
The effluent quality from Test Run 8, which was conducted at the
recommended facility operating mode using 75 mg/1 of alum and a sur-
face loading rate of 145 m3/(m)2(day) [3,580 gal/(ft) (day)], is com-
pared in Table 15 with these requirements. In addition, the require-
ments of the U.S. Environmental Protection Agency and the California
Water Resources Control Board for discharge of treated wastewater to
the ocean have been included for comparison and as a guide to possible
future discharge requirements for dissolved air flotation facilities
on the San Francisco peninsula.
It appears that under test conditions representing best perfor-
mance the Baker Street dissolved air flotation facility effluent can
meet all of the Regional Board permit requirements. An effective bar
screen on the influent structure of the facility removed all of the
large trash and materials carried in the combined wastewater, and the
effluent stream was never seen to contain discrete visible suspended
matter. At the desirable operating conditions, the effluent easily met
discharge requirements for suspended solids, settleable solids, float-
able solids, turbidity, oil and grease, fecal coliforms, and toxicity.
With the exception of the settleable solids content of Tests 1, 5, 6,
7, and 10, the effluent from the Baker Street facility also met the
permit requirements during the other wet-weather tests, although it
must be recognized that the permit requirements were aimed at large
solids and bacterial pollutants and not at the relatively low levels
of other pollutants in the untreated combined sewage flow. The efflu-
ent pH generally did not fall in the acceptable range of the permit
requirement because the optimum pH for alum coagulation at 5.5 to 7 is
lower than the 7 to 8.5 required by the Board.
The California State Water Resources Control Board Ocean Plan has
131
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Table 15. COMPARISON OF BAKER STREET DAF FACILITY EFFLUENT WITH VARIOUS DISCHARGE CRITERIA5
NJ
Combined overflow
constituent
Suspended solids
Settleable solids
Floatable solids
Turbidity
BOD
COD
Oil and grease
Organic nitrogen
Ammonium
pH
Fecal coliform
Toxicity
Units
mg/1
ml/(l)(hr)
mg/1
JTU
mg/1
mg/1
mg/1
mg/1 as N
mg/1 as N
MPN/100 ml
96-hr %
Survival
Baker Street
influent
99. 5C
1.8
1.6C
53.2
32.1
97.3
1.8
4.3
1.6
7.2
>24 x 107
-
Baker Street
effluent
48.6
0.1
0.5
17.9
5.9
58.4
2.75
0.5
2.56
-
<3
90d
California Regional State Water Resources
Water Quality Control Board U.S. EPA
Control Board Ocean Plan CPL92-5001b
macroscopic solids
prohibited
1
visible solids
prohibited
no change in receiving
water
-
_
25
-
-
7 to 8.5
240 in receiving water
90
50 30
0.1
1
50
30
— mm
10
_. _ -
40
6 to 9
200
1.5 TU
jAt optimum test conditions of 145 m3/(m)2(day) [3,580 gal/(ft)2(day)] and 75 mg/1 alum (Test Run 8).
cFor discharges of treated municipal wastewaters.
dSubstantial quantities of floating large solids removed by influent structure bar screen.
Average from other tests.
-------
more restrictive prohibitions on wastewater discharges than does the
California Regional Water Quality Control Board permit for the Baker
Street facility and includes many micro-pollutants such as metals and
pesticides. Micro-pollutant removals were not measured during this
testing program. Of the tested parameters, grease and oil, ammonium
and turbidity levels in the Baker Street influent generally fell below
the Ocean Plan requirements. With the exception of the early wet-
weather program tests, the suspended, settleable, and floatable solids
in the effluent met the Ocean Plan requirements, and, of these, several
influent suspended and floatable solids concentrations also met the
requirements.
The U.S. Environmental Protection Agency has established discharge
requirements in connection with its intent to implement secondary
treatment of all municipal wastewaters. The Baker Street dissolved air
flotation facility is not intended to provide secondary treatment for
municipal wastewaters, and its effluent during most of the tests did
not meet the requirement for 30 mg/1 of suspended solids although it
did meet all of the remaining requirements.
SLUDGE PRODUCTION
The sludge production rate of the Baker Street facility during
the eighth test in the wet-weather program was 190 kg [418 Ib] of dry
solids per 3,800 m3 [one million gallons] of wastewater treated. It
O
has been estimated that of the 337,000 m [9 million gallons] treated
at Baker Street in one year 265,000 m3 [70 million gallons] were due
to rainfall runoff and 72,000 m3 [19 million gallons] were due to
domestic flow. If the suspended solids removal rate of 50 percent, as
demonstrated in the eighth test, were maintained at every storm event,
the Baker Street facility would produce approximately 13.2 metric tons
[14.6 short tons] of dry sewage solids annually due to rainfall runoff.
This compares to 33,000 metric tons [36,500 short tons] of combined
primary sewage sludge production for the Northpcint and South East
wastewater treatment plants. The sludge solids produced at Baker
Street therefore could be readily accommodated at the primary sewage
133
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treatment plants.
At a sludge solids concentration of 1,100 mg/1, the sludge volume
pumped from Baker Street to the Northpoint plant during Test 8 was
4.6 m /100 m [46 thousand gallons/million gallons] treated, or a 95.4-
percent reduction of total combined sewage flow from the Baker Street
drainage area.
134
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SECTION VIII
ANALYSIS OF THE BAKER STREET FACILITY
One of the original objectives of the Baker Street dissolved air
flotation facility studies was to obtain information that would be useful
in the design of other air flotation facilities for storm water treatment.
The Baker Street installation was a prototype model for municipal combined
sewage overflow treatment facilities and as such was designed with oper-
ating and testing flexibility within the resources available. Various
components within the facility were to receive their initial field testing
with actual combined sewage overflow. This section of the report eval-
uates the component systems of the Baker Street dissolved air flotation
facility, and, where a specific application or configuration was found
to be lacking in performance, alternative suggestions are presented for
the Baker Street facility. In some cases, these suggestions can no longer
be practically implemented at Baker Street, but it is intended that the
knowledge gained from this program should aid in the design of future
installations. Some observations may be limited in scope and applicabil-
ity, but it should be remembered that the Baker Street dissolved air
flotation facility has had less than 100 hours of test operation with
combined sewer overflows under widely varying conditions.
PRINCIPAL COMBINED SEWAGE FLOW PATH
The components of the main flow path of the Baker Street dissolved
air flotation facility include the diversion sewer, the influent struc-
ture and bar screen, magnetic flow meter, butterfly throttling valve,
distribution header in the flotation tank, the flotation tank and the
V-notch effluent launder.
135
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Diversion Sewer
The Marina Boulevard diversion sewer originates at the Marina
Boulevard and Baker Street diversion structure. This gravity sewer of
2.44-m [96-in.] diameter is approximately 914 m [3,000 ft.] long, lies
on a shallow grade, and leads directly to the Baker Street facility
influent structure. This sewer was designed to accommodate the runoff
o
from a five-year storm of approximately 7 m /sec [160 mgd]. At the much
more common lower flow rates normally encountered at the facility, flow
velocities drop below 0.61 m/sec [2 ft/sec.] and sedimentation of some
suspended material occurs in the sewer. This is substantiated by the
apparent reduction in suspended solids presented earlier in Table 9.
Whether this material is gradually building up in the bottom of the
sewer or is being flushed into the Baker Street dissolved air flotation
facility at the beginning of every storm has not been determined. The
possibilities of pumping combined sewage into the facility have not been
investigated, but possible advantages are a steeper permissible hydraulic
gradeline for the diversion sewer and reduced hydraulic fluctuation
through the facility. Depending upon the nature of the upstream drainage
area, local characteristics, and storage capacity in the sewerage system,
a pumped flow operation may require upstream storage facilities. Unfor-
tunately any storage facilities, unless equipped with a mixing apparatus,
would also suffer from premature solids sedimentation.
Influent Structure and Bar Screen
No difficulties were encountered with the present influent structure
and the bar screen successfully collected large suspended objects from
the combined wastewater flow.
Magnetic Influent Flow Meter
The magnetic influent flow meter operated satisfactorily during the
testing program. The output signal from this meter was used to control
operation of chemical feed systems and the influent butterfly throttling
valve. Two minor difficulties encountered with the magnetic flowmeter
were the need to provide additional electrical grounding for the flow
136
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sensing unit and the erratic readings received when air was present in
the sensing unit. The addition of automatic air-bleed valves eliminated
the latter problem during facility operation, although the flow totalizer
would continue to record flow from the meter when the influent pipe was
empty between storms. A smaller magnetic flow meter was used during
the wet-weather evaluation program with the modified east side of the
facility.
Butterfly Throttling Valve
The butterfly throttling valve on the 91-cm [36-in.] diameter in-
fluent line to the east side of the facility operated well within certain
limits. The valve could not be set to control flow to less than 40
percent of maximum and was replaced during the wet-weather program with
an air-operated diaphragm valve of smaller size. Exact flow control was
not possible with an automatic butterfly valve and for this reason a
diaphragm valve was chosen for the wet-weather evaluation program.
Distribution Header
Influent flow to the flotation tank was distributed through a
perforated pipe placed horizontally across one end of a flotation tank.
At the start of the wet-weather evaluation program the perforations
were aligned so that flow was directed vertically upward. Subsequently
it was thought that this configuration was conducive to short circuiting
in the flotation tank. Furthermores the float collecting tilt pipe was
located directly above the influent distribution header, and surface
boils were seen to interfere with float collection. Even though calcu-
lations indicated a very low exit velocity from the distribution header,
the header was rotated to face the lower back wall of the flotation tank.
The divergence of flow due to recoil from the tank wall was believed to
have resulted in an improved flow distribution in the flotation tank and
surface boils did not recur.
Careful consideration should be given in future designs to a low
velocity, even-flow distribution in the flotation tank.
137
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Flotation Tank
The rectangular design of the flotation tank was not evaluated for
its hydraulic characteristics or effects upon float separation efficiency.
It should be noted that the pilot-scale unit which employed a rectangular
flotation tank achieved very good wastewater constituent removals.
Effluent Weir
Treated effluent passed over a V-notch weir into the effluent
channel. The characteristics of a V-notch weir are such that wide
variations in liquid flow produce substantial variations in the flota-
tion tank liquid surface level. This situation made adjustment of the
float removal systems difficult during the testing program, and it
would not be possible to make any adjustments during the course of a
rainstorm with typical combined sewer overflow variations. The varia-
tions in flotation tank surface level could be attenuated by using a
sharp-crested overflow weir instead of the V-notch type.
The variations in flotation tank surface elevation resulting in
widely varying quantities of float removal were a problem only during the
the testing program as is explained in the following section. This would
not be as severe a problem during actual full scale operation where the
float would not normally be passed through a restriction such as a fixed
capacity pump. In such cases, the sharp-crested overflow weir, set to
produce the minimum allowable tilt-pipe submergence during low flow
operation, would be an adequate solution to this problem. If, as is
the case at Baker Street, the ultimate float removal pumps in the solids
sump were adequately sized, the increased float flows resulting from
higher surface loading operations would be readily accomodated by the
equipment.
SOLIDS REMOVAL SYSTEM
The solids removal system consisted of float and settled solids
collection and the transport of these solids from the dissolved air
flotation facility.
138
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Float Collection
Float collection frequently presented a problem during the wet-
weather testing of the Baker Street facility. The basic cause of the
difficulties was the variation in liquid surface level with changes in
surface loading rate. For each surface loading rate, it was necessary
to readjust the tilt-pipe connecting arm linkages. It was soon found
that only a limited range of tilt could be accommodated with the standard
arms. Through the course of the program, it became necessary to drill
holes and change the location of the lever arm on the tilt-pipe, to
install a new, longer lever arm, and to bend the lever arm to a new shape.
At no time was it possible to collect float from both sides of the tilt
pipe, resulting in a two-foot wide strip, running the width of the
flotation tank next to the tilt pipe, that accumulated float which was
never properly removed.
A tilt-pipe float collection system of improved design combined with
the sharp-crested weir recommended in the preceeding discussion would be
an adequate system for normal operating conditions where free flow of
the float to the solids sump is permitted. A ramp or beach and flight
system for float collection had been considered as one alternative to the
float collection system. The nature of the float created with chemical
conditioning is such that when scraped into the trough of a beach collec-
tor, it would sit there as a foamy mass and require the addition of water
to make the float transportable and capable of being pumped. For this
reason, the beach and flight collection system offers no substantial
advantages over a tilt-pipe.
Settled Solids Collection
The flights that drove float towards the tilt pipe would on their
return journey travel along the bottom of the flotation tank and drive
settled solids toward a trough at the discharge end of the flotation
tank. In this trough, an Archimedes screw would collect the solids to
one side of the group of four cells in a flotation tank. From there an
air-lift pump would transport solids to the common solids sump. This
139
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system always worked satisfactorily and never suffered mechanical
failures.
It would be desirable, however, to have a flowmeter placed on the
air line leading directly to the air-lift pump so that an adjustment of
its capacity could be made accurately. Additionally, the air-lift pump
and the settled solids transport line are completely enclosed from view
and it would be desirable if the facility operator could have a ready
means of verifying pump operation.
Solids Transport
Float and settled solids were collected in a common sump where a
bubbler-type level sensor would periodically activate pumps to remove
the sludges to a sewer tributary to the North Point sewage treatment
plant. The volume of sludge production was measured by a magnetic flow-
meter. The sludge transport system was adequately sized and performed
with no difficulties.
A unique and frequently used feature of the Baker Street dissolved
air flotation facility was the ability to use the sludge transport
centrifugal pumps to dewater the flotation tanks at the end of a test
or storm event.
PRESSURIZATION SYSTEM
The pressurization system in the Baker Street dissolved air flota-
tion facility consisted of recycle flow collection, pressurization of
flow, compressed air supply, air-solution tank, and pressurized liquid
injection.
Recycle Flow
An effluent recycle flow of 24 I/sec [375 gpm] was used during the
entire wet-weather evaluation program. Earlier studies with the pilot
plant had indicated that pressurization of a recycled portion of the
treated effluent produced treatment levels equivalent to pressurization
of a portion of the raw influent. In fact, the pilot-plant studies had
indicated an improvement in solids removal with increased recycle from
20 to 120 percent.
140
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In the Baker Street facility, the conditioning chemicals and the
pressurized air were added to the pressurization pumps, where a high
turbulence evenly distributed the additives in the pressurized flow.
A short retention period in the air-solution tank further ensured
solution of air and distribution of chemicals.
The chemical feed system would only work when the pressurization
pumps were operating and these pumps would operate only when the liquid
level in the flotator reached a minimum level of 1.8 m [6 ft]. This
meant that the initial flush of combined wastewater into the flotation
tank would not receive the correct proportions of conditioning chemicals
and air. If, alternately, the recycle return were collected at a lower
level in the flotation tank, settled solids might be swept up in the
flow and degrade performance.
The alternative to this system would be to pressurize a portion of
the raw influent and not use recycle. It would thus be possible to
chemically condition the entire flow into the flotation tanks, which
should substantially improve performance with intermittent flows.
Pressurization Pumps
The two-stage centrifugal pressurization pumps were very satisfactory
for pressurizing the flow and as injection points for chemicals and air.
During the automatic start-ups of the facility, the air compressor would
start operating at the first energization of the facility so that air-
controlled valves and systems could be used while the flotation tank was
being filled. On occasion, this early discharge of air into the pres-
surization pumps would air-bind them and create the risk of serious
damage to the bearings when the pumps were activated. An air bleed was
installed on the pump casings to prevent this occurrence. It was also
found very advantageous during the testing program to be able to check
on pump operation by referring to a flow meter installed on the pres-
surized flow line.
Compressor
No difficulties were encountered with the operation of the air
compressors. It should be noted that in the high ambient humidity of a
141
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dissolved air flotation facility, there is considerable condensation of
water in the air compressor and the compressed air lines. If left un-
attended, this water could be detrimental to instrumentation and flow
controllers dependent on compressed air.
Air-Solution Tank
The air-solution tank installed to aid the solution of air into the
pressurized flow was a proprietary item with an undetermined internal
baffle arrangement. No difficulties were encountered with this equipment.
Pressurized Liquid Injection
Pressurized liquid was distributed through a header to each cell in
a flotation tank. A pressure gauge was installed at each pressure-
reducing valve just prior to the mixing point of the air-saturated liquid
with the raw influent in the flotation tank distribution header. With
the aid of the gauges, an evenly balanced distribution of flow could be
achieved among the four cells in a flotation tank. The pressure gauges
were subject to severe operating conditions of long idle periods alter-
nating with pressurized wastewater flow, which required the cleaning of
the gauges at regular intervals.
CHEMICAL FEED SYSTEM
The chemical feed system at the Baker Street facility consisted of
storage and metered injection of alum, caustic, sodium hypochlorite, and
polymer. The polymer feed system was not used during the wet-weather
evaluation program.
Alum
Alum was purchased as a bulk liquid of 36° Be or 28% as A1?(SO,)_.
The alum was injected into the second-stage pressurization pump at a
rate determined by the raw influent magnetic flow meter. The feed-pump
response was reasonably linear with the meter signal and did not cause
any difficulties during the program.
One difficulty was experienced directly as a result of using alum
to improve coagulation and flocculation. In several wet-weather tests,
142
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primarily at the higher alum dosages and surface loading rates, effluent
samples were collected with excessive alum floe or produced alum floe
during laboratory testing for settleable solids. It appears that there
was an incomplete or delayed alum flocculation and precipitation in the
flotation chamber. This phenomenon had not been observed during pilot-
plant studies. It may be the result of short-circuiting in the flotation
tank, the lack of a flocculation chamber preceding the flotation tank as
was available in the pilot plant or due to trying to match a varying water
quality with a flow-paced chemical dosing. In the absence of hydraulic
tracer studies of the Baker Street flotation tank, and in view of the
commonly accepted need to flocculate alum solutions prior to gravity
sedimentation, it can be assumed that a flocculation tank for an alum
and wastewater mixture prior to the addition of the pressurized liquid
stream might provide for improved performance. With such an arrange-
ment, it would in all likelihood be possible to use greater alum dosages
and a wider range of surface loading rates with the dissolved air flota-
tion system, as shown in pilot-scale tests, than those conditions recom-
mended in the preceding section.
Caustic Soda
The pH control of the combined wastewater was done using sodium
hydroxide to counteract the acidic effects of alum and to maintain pH
at the proper level for aluminum hydroxide precipitation. Although the
caustic feed pump could be preset to respond to the magnetic flow-meter
signal, it was found that this was a very unsatisfactory mode of opera-
tion. The quality of the combined wastewater flow to the facility
changed during the course of a storm, and different amounts of caustic
were needed to maintain pH at a constant alum feed rate. The Baker
Street dissolved air flotation facility was not equipped with automatic
pH monitoring and control, and except for manual pH measurements and
pump adjustments, the effluent pH would have varied widely during the
tests.
The physical characteristics of the facility are such that there is
no good place to measure pH for automatic control except in the
143
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flotation tank. With theoretical detention times ranging from 27 to 83
minutes, there would be too long a response time to pH changes.
An alternative investigated for application at the Baker Street
dissolved air flotation facility is the use of a chemical other than
sodium hydroxide for pH adjustment. The titration curve of sodium
hydroxide in an alum solution is very steep and the slightest changes in
caustic dosage or combined wastewater alkalinity can result in large
changes in the pH. A commonly available chemical that shows promise for
pH adjustment, replacing sodium hydroxide, is sodium carbonate. The
titration curve for sodium carbonate has inflection points of stability
in the pH range which is optimum for alum precipitation. The use of
sodium carbonate should result in larger tolerances for pH and alka-
linity variations in the combined wastewater. The difficulties exper-
ienced with pH control during the wet-weather testing program might have
been substantially alleviated by the use of sodium carbonate and this
chemical has been included in the economic analysis presented subse-
quently. The use of lime for pH control was not considered because of
the unsuitability of the installed equipment for lime slurry feeding and
lime sludge handling.
Hypochlorite
No difficulties were encountered with the sodium hypochlorite in-
jection system. There was a problem in obtaining consistent readings
from the chlorine residual continuous analyzer and recorder. Without an
accurate guide to dosage, the facility staff was not able to prevent
frequent occurrences of excess chlorine addition.
Polymer
No studies were conducted during the wet-weather program with the
polymer feed system. Furthermore, the use of polymer (DOW C-31) produced
very poor results in the dry-weather flow studies with the prototype unit.
In conjunction with alum in laboratory flotation cell and jar-tests,
polymer did not produce significant improvements over alum alone.
However, polymer alone produced as high as 80 percent suspended solids
removals in the pilot-plant tests and 60 percent removals in the
144
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flotation cell tests.
It is known that polymers can be used to increase the speed of
flocculation and have an added advantage in that no pH adjustment would
be needed due to the use of polymer alone and there would be no post-
precipitation problem as encountered with alum. Only one type of cationic
polymer (DOW C-31) was evaluated in this program and many different
cationic and anionic polymers are available on the market. For these
reasons, further investigations in the use of other types of polymers
should be conducted.
Although the success of polymer application to raw wastewaters has
varied considerably, an example of beneficial results can be found in
the recent studies conducted by the City of San Francisco (Reference 16).
3 2
Using gravity sedimentation and surface loading rates of 82 m /(m) (day)
2
[2000 gal/(ft) (day)], suspended solids removals of approximately 70 per-
cent were achieved through the addition of American Cyanamid's Magnifloc
509-C.
FACILITY OPERATION
The unique nature of the Baker Street dissolved air flotation
facility is principally in the sporadic and intermittent periods of
operation separated by extensive periods of idleness. This creates a
difficulty in providing personnel with sufficient knowledge and ex-
perience to operate a somewhat unconventional and complex facility on a
part-time basis. It is unreasonable to provide personnel during the
summer period when there is little, if any rainfall in San Francisco.
During the winter wet-weather season, the facility may be in operation
at any time of the day or night. In the absence of a full-time attend-
ing staff, the Baker Street dissolved air flotation facility has been
automated to the greatest extent practicable to minimize work for the
operators during storm events.
Because the effectiveness of the automatic control systems is
entirely dependent upon the remote sensors and condition of the
mechanical and electrical equipment, it is essential that a rigorous
145
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program of preventive maintenance be carried out on a frequent basis
by personnel intimately familiar with the facility operation. This
program of preventive maintenance will be dependent on manufacturers'
recommendations for equipment servicing and a gradually increasing
fund of operator experience with the need for and frequency of clean-
ing and renovating sensing and control equipment.
To aid personnel who come to operate the facility at odd hours and
who may not, because of the course of their regular duties, have had
recent practice in the operation of the Baker Street facility, it would
be extremely beneficial to have a set of visual aids and operating
instructions printed in large type and located throughout the facility.
FACILITY UTILIZATION
The City of San Francisco provided an analysis of the frequency of
operation at the Baker Street facility as influenced by the predetermined
hydraulic surface loading rate. Using the TREAT computer program de-
veloped by the City staff for evaluating Master Plan alternatives, the
variable factor of rainfall frequency, duration and intensity for the
City of San Francisco and facility mode of operation were combined to
provide a picture of facility utilization. It was assumed for purposes
of this analysis that the modified test cell would be disassembled and
the entire facility operated as an integrated unit.
Figure 52 shows the calculated frequency of treatment at specified
flow rates at the Baker Street facility. Only one or two rainfall events
per year would result in sufficient runoff to operate the facility at its
maximum hydraulic capacity of 1 m^/sec [24 mgd] and surface loading
rate of 214 m3/(m)2(sec) [5,260 gal/(ft)2(day)]. From Figure 53 it may
be seen that the Baker Street facility would be forced to bypass excess,
untreated combined sewage approximately once every two years for an
3
annual average of less than 1300 m [350,000 gallons]. This compares to
a total of 337,000 m3 [89 million gallons] annually of combined sewage
flow being treated or stored at the Baker Street facility.
3 2
At the recommended surface loading rate of 145 m /(m) (day) [3,580
gal/(ft)2(day) ], the Baker Street facility would be treating combined
146
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0 O.I 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 I.I
TREATMENT RATE, m3/sec
Figure 52 • Frequency of treatment at specified
flow rates at the Baker Street
dissolved air flotation facility
147
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0.8
0.7
0.6
0.5
0.4
0.3
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OVERFLOW FOR TOTAL PLANT
ONE-HALF PLANT USED FOR STORAGE
TREATMENT RATE FOR TOTAL PLANT
ONE-HALF PLANT USED FOR STORAGE
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15
30
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FREQUENCY OF FACILITY BYPASS, number /year
Figure 53 • Comparison of treatment rate and untreated bypass with the
frequency of bypass at the Baker Street dissolved air flotation facility
-------
sewage at the rate of 0.7 m /sec [16 mgd] approximately 6.5 times
annually. Combined sewage from storms of lesser intensity would be
treated more frequently while higher flow rates of combined sewage would
o
be accomodated up to the facility's capacity of 1 m /sec [24 mgd].
o
Limiting the influent rate to 0.7 m /sec [16 mgd] would result in a
discharge of untreated combined sewage to Fan Francisco Bay on the order
of 2,500 m3 [0.7 million gallons] per year.
It is preferable that standard procedure involve, operating only one
o
side of the facility up to a flow rate of 0.35 m /sec [8 mgd] while
using the other half for storage and activating the storage side only if
flows exceeded 0.35 m3/sec [8 mpd]. The Baker Street facility would be
operated approximatelv 22 times annually at this flow rate, and more
frequently at lesser flows.
The rainfall events that would fill the storage capacity of one
half of the facility and produce sufficient runoff to operate the other
half at a low flow rate of 0.14 m3/sec [3.25 mgd] number from 40 to 50
annually.
149
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SECTION IX
ECONOMIC ANALYSIS
This section presents cost information for the construction,
operation, and maintenance of dissolved air flotation facilities for
the treatment of combined sewer overflows. Cost estimates were made
for plants ranging in size from 1 to 8.8 m /sec [24 to 200 mgd] using
surface loading rates of 64, 127, and 214 m /(m)2(day) [1,560, 3,120,
2
and 5,260 gal/(ft) (day)] with the assumption of no treated effluent
recycle. By utilizing these costs in conjunction with the performance
data presented in Section VII, economics of dissolved air flotation
facilities for a wide range of flow capacities and desired pollutant
removal efficiencies can be estimated.
Estimates for the dissolved air flotation plants do not include
the cost of the float or sludge disposal. It has been assumed that the
material removed from the flotation units will be pumped back to the
interceptor sewer for final treatment at an existing wastewater treat-
ment plant.
CONSTRUCTION COST ESTIMATE
In the preparation of all of the estimates, no allowance was made
for the cost of land or right-of-ways. All estimates include an
allowance for engineering, overhead, inspection, and contract adminis-
tration. Special foundation work, such as piles, special foundations,
or site dewatering, were not included in the estimates as these items
would be peculiar to the specific site selected for construction. An
Analysis of the cost items included in the construction of the Baker
150
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Street dissolved air flotation facility is given in Table 16.
Estimated construction costs for dissolved air flotation facilities
of varying design capacity and surface loading rates are shown in Table
17 and displayed graphically in Figure 54. Annual capital costs were
computed by using an interest rate of seven percent and an amortization
period of 15 years for controls and equipment and 40 years for structures.
OPERATING AND MAINTENANCE COSTS
Estimates of annual costs for operating and maintaining plants are
shown in Table 18. The major cost items were categorized as electrical
energy, labor, chemicals, miscellaneous expenses, and contingencies.
The cost estimates were assumed to be independent of surface loading
rate.
The cost of electrical energy wss based on the total electrical
demand at a 1 m3/sec [24 mgd] plant and a cost of $0.02/kwhr. The period
of combined sewer overflow for the Baker Street drainage basin has been
estimated as occurring three percent of the time, or 300 hours annually.
The electrical energy cost for a 1 m3/sec [24 mgd] plant was based upon
300 hours of operation annually. Energy costs for plants of larger size
were scaled up in proportion to design capacity and assumed the same
period of operation.
Labor costs were estimated on the basis of attendance at the facili-
ty for 10 percent of the time or 880 hours of operator attendance
annually and supervision and administration for 3 percent of the time, or
300 man-hours annually.
Chemical costs were based upon the following chemical dosages:
alum, 75 mg/1; sodium carbonate, 160 mg/1; sodium hypochlorite, 15 mg/1.
Miscellaneous expenses were assigned on the basis of plant size. A
ten-percent contingency was added to the subtotal of operating and
maintenance costs.
151
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Table 16. CURRENT CONSTRUCTION COST OF
THE BAKER STREET DISSOLVED AIR FLOTATION FACILITY3
Item Cost
Mechanical Equipment
Bar screens $ 21,000
Flotation tank mechanism 87,000
Prescmrization system 62,000
Settleables pumps 5 QOO
Floatables pumps 6 000
Screening conveyor 25 000
Chemical feed 47*000
Regulating gates 3l]oOQ
Total mechanical
equipment $ 284,000
Erection mechanical
equipment $ 98,000
Instrumentation and
controls $ 73,000
Control building $ 156,000
Pipe valves and fittings $ 98,000
Earthwork $ 59,000
Concrete $ 798,000
Electrical $ 118,000
$1,684,000
Miscellaneous (15%) 253,000
$1,937,000
Engineering, inspection,
contingencies, and
administration 581,000
Total facility $2,518,000
Engineering News Record construction cost index of 2240
152
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Table 17. ESTIMATED CONSTRUCTION COSTS FOR
rED AIR FLOTATION FACIL!
(thousands of dollars)
DISSOLVED AIR FLOTATION FACILITIES3
Design flow capacity, m /sec [mgd]
Item 1 [24] 2.2 150] 4.4 [100] 8.8 [200]
Surface loading rate, 214 m3/(m)2(day) [5,260 gal/(ft)2(day)]
Mechanical equipment
and controls
Capital cost
Annual cost*5
Structure and engineering
Capital cost
Annual costc
Total costs
Capital cost
Annual cos t
800
88
1,700
128
2,500
216
3 2
Surface loading rate, 127 m /(m) (day)
Mechanical equipment
and controls
Capital cost
Annual cost*1
Structure and engineering
Capital cost
Annual costc
Total costs
Capital cost
Annual cost
900
99
2,300
173
3,200
272
Surface loading rate, 64 m-V(m)Z(day)
Mechanical equipment
and controls
Capital cost
Annual cost*3
Structure and engineering
Capital cost
Annual costc
Total costs
Capital cost
Annual cost
1,100
121
3,100
233
4,200
354
1,400
154
2,500
188
3,900
342
[3,120
1,700
187
3,500
263
5,200
450
[1,560
2,000
220
4,900
368
6,900
588
2,000
220
3,600
270
5,600
490
2,900
318
5,700
428
8,600
746
gal/(ft)2(day)]
2,400
263
5,800
435
8,200
698
Kal/(ft)2(day)
2,900
319
9,300
699
12,200
1,018
4,300
472
9,500
713
13,800
1,185
1
6,400
704
15,800
1,187
22,200
1,891
Engineering News Record construction cost index of 2240.
''Interest at seven .percent for 15 years.
clnterest at seven percent for 40 years.
153
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W
C
o
I-
OT
O
O
h-
O
Z>
o:
I-
c/>
z
o
o
50
40
30
20
10
9
8
7
6
5
4
10
0.5
SURFACE LOADING RATE
64m3/(m)2(day)
1560 gal/(ft)2(day)
SURFACE LOADING RATE
I27m3/(m)2(day)
3120 gal /(ftftday)
SURFACE LOADING RATE
214 m3/(m)2(day)
5260 gal/(ftftday)
20
30 40 50
mgd
J L
100
200
300 400
I 2345
DESIGN CAPACITY, m3/sec
10
Costs are based on an ENR construction cost index of 2240
and include engineering, inspection and architectural
treatment but do not include influent or effluent pumping
stations, land or right-of-way, special foundation work, or
sludge processing or disposal.
Figure 54. Construction costs of dissolved air flotation
facilities for combined sewer overflows
154
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Table 18. ESTIMATED ANNUAL OPERATING AND MAINTENANCE COSTS FOR
DISSOLVED AIR FLOTATION FACILITIES
(1974 dollars)
Item
Design flow capacity, m^/sec [mgd]
1 [24] 2.2 [50] 4.4 [100] 8.8 [200]
Electrical energy
Labor
Chemicals
Alum
Sodium carbonate
Hypochlorite
Miscellaneous supplies
Contingencies (10%)
Total
2,000 4,000 8,000 16,000
9,800 9,800 17,600 27,400
900
1,700
300
1,000
1,500
17,200
1,900
3,500
600
1,500
2.100
23,400
3,800
7,000
1,200
2,500
4,000
44,100
7,600
14,000
2,400
4,000
7,100
78,500
155
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SECTION X
REFERENCES
1. "Characterization and Treatment of Combined Sewer Overflows", report
to City and County of San Francisco, by Engineering-Science, Inc.,
Berkeley, Ca. (November 1967).
2. "Dissolved Air Flotation - Appendix A, Phase I - Preconstruction
Studies on Quality and Quantity Relationships of Combined Sewage
Flows and Receiving Water Studies at Outer Marina Beach", report to
City and County of San Francisco, by Engineering-Science, Inc.,
Berkeley, Ca. (July 1971).
3. "Dissolved Air Flotation - Appendix B, Technical Objectives for
Field Demonstration of Baker Street Dissolved Air Flotation Facility,"
report to City and County of San Francisco by Engineering-Science,
Inc., Berkeley, Ca. (July 1971).
4. Vrablik, E.R., "Fundamental Principles of Dissolved-Air Flotation of
Industrial Wastes", Proceedings 14th Purdue Industrial Waste
Conference. 743-779 (1959).
5. Ettelt, G.A., "Activated Sludge Thickening by Dissolved Air Flotation",
Proceedings 19th Purdue Industrial Waste Conference. 210-244 (1964).
6. Hansen, C.A. and Gotaas, H.B., "Sewage Treatment'by Flotation",
Siewage Works Journal, Vol. 15 (2) 242-254 (March 1943).
7. "Dissolved Air Flotation Treatment of Combined Sewer Overflows",
FWPCA Report WP-20-17 (January 1970).
156
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8. Mason, Donald G., "The Use of Screening/Dissolved Air Flotation
for Treating Combined Sewer Overflows", presented at symposium on
Storm and Combined Overflows, Chicago, Illinois (22-23 June 1970).
9. "Engineering Report on Preliminary Design-Marine Sewage Disposal
System for Rio de Janiero", prepared by Engineering-Science, Inc.,
for SURSAN, Rio de Janiero, GB, Brazil (June 1969).
10. Mulbarger, M.C. and Huffman, D.D., "Mixed Liquor Solids Separation
by Flotation", Journal SEP, ASCE , 96 (SA4), 861-871 (August 1970).
11. Katz, W.J. and Geinopolos, A., "Sludge Thickening by Dissolved-
Air Flotation", JWPCF .39 (6), 946-957 (June 1967).
12. "Dissolved Air Flotation - Appendix C, Treatment of Raw and Dilute
Raw Sewage with the Dissolved Air Flotation Process—A Pilot Plant
Study," report to the City and County of San Francisco by Engineering-
Science, Inc., Berkeley, Ca. (July 1971).
13. Standard Methods for the Examination of Water and Wastewater, 13th
Edition, by the American Public Health Association, New York, 1971.
14. Pearson, E.A. and J.F. Thomas, "Liquid-Liquid Extraction for Sewage
Sludges and Industrial Wastes," Sanitary Engineering Research
Laboratory, University of California, Berkeley (1956).
15. "Dissolved Air Flotation - Appendix G, Performance Evaluation of
Baker Street Facility with Raw Sewage," report to the City and
County of San Francisco by Engineering-Science, Inc., Berkeley,
Ca. (July 1971).
16 Personal communication Mr. R. T. Cockburn, Bureau of Engineering,
Division of Sanitary Engineering, City of San Francisco, 11 November
1974.
157
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SECTION XI
APPENDICES
Page
A. Description of Pre-Modification Standard Plant Instrumenta- 159
tion and Control System
B. Nonstandard Analytical Methods ^73
C. Tabulation of Operating Conditions and Process Performance 177
During Pilot-Plant Studies
D. Tabulation of Operating Conditions and Process Performance 184
During Dry-Weather Testing of the Baker Street DAF Facility
E. Results of Baker Street Dissolved Air Flotation Treatment of 192
Combined Sewage
F. Waste Discharge Requirements for City and County of San 208
Francisco Baker Street Flotation Facility
158
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APPENDIX A
DESCRIPTION OF PRE-MODIFICATION STANDARD
PLANT INSTRUMENTATION AND CONTROL SYSTEM
159
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DESCRIPTION OF EXISTING PLANT SYSTEMS
Plant Start-UP Operation
Prior to the occurrence of a combined sewer overflow over the weir
at the intersection of Baker Street and Marina Boulevard, either the
east or the west flotation system shall be set to operate first. This
is accomplished by means of the two-way selector switch mounted on the
control console. By placing the switch in the east (west) position the
east (west) plant inlet gate will be set to open first and all the equip-
ment for the east (west) flotation system will commence operation when
actuated as described below.
As flow enters the plant and the rate of flow increases, the east
(west) magnetic flow meter senses the flow and sends a signal to the
east (west) rate of flow recorder. This recorder sends a signal to the
flow adder which sends its output signal to an electronic trip (ET-218)
which has an adjustable set point from 0 to 100 percent. At its set
value the trip will energize a 0-to 60-minute adjustable time delay re-
lay. Upon completion of the time delay, the west (east) gate will open
and west (east) flotation system will commence operation as described
below. Should the flow drop below 4 mgd before the time delay runs out,
then the time delay relay will be de-energized and the west (east) gate
will not open. The flow must increase again up to 8 mgd to re-energize
the time clock.
All electrically operated equipment in both the east and west plant
except motor operated skim pipes have hand-off-automatic switches. All
hand-off-automatic switches except for bypass and plant inlet gates are
console mounted.
When an overflow does occur, the plant start-up probe mounted
immediately downstream of the overflow weir at Baker and Marina and pres-
ently set at Elevation -6.25 will send a signal to the console mounted
level relay (Kl). This relay actuates multiple contacts (K2) which di-
rect power to the influent recorders and to the ventilation system.
160
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As the water level in the inlet structure rises, the new influent
level sensing system with a bubbler-type, pneumatic, back-pressure sensing
device shall sense the level in the plant influent structure and transmit
an electronic signal, linearly proportional to depth, to a level indica-
tor mounted in the control panel. Integrally wired with this circuit and
recorder are two adjustable electronic trips. One trip, when energized,
energizes and de-energizes the existing console mounted level relay (K8).
The other trip, when energized, energizes an elapsed time meter (0 to 24
hr) mounted in the control panel. This elapsed time meter totalizes the
time that the level in the plant inlet structure was at an elevation
sufficiently high to allow bypassing of plant influent over the inlet
structure overflow weir. The elapsed time meter is manually reset.
Console mounted level relay (K8) actuates one of two pairs of con-
tacts (as chosen by the east-west selector switch) which signals one of
the plant inlet gates to open. Flow increases to the preset control
point, the time clock is energized, and after the time delay (described
above) the other plant inlet gate will open.
As soon as the east (west) magnetic influent flow meter senses flow,
both the east (west) mechanically cleaned bar screen and screenings con-
veyor commence operation due to the energizing of contacts K19. The bar
screens and the conveyor have hand-off-automatic switches mounted on the
control console.
The influent to each flotation system passes through a 30-inch di-
ameter butterfly valve with electronic operator and thence through a 30-
inch diameter magnetic flow meter. This signal converter takes an ac
signal and converts it to a linear output signal, and sends this signal
to each of four console-mounted instruments as follows: (1) flow indica-
tor-recorder, (2) current converter, (3) flow controller, and (4) flow
adder. The signal converter also sends a pulse signal to a panel-mounted
flow integrator which sums the total volume of influent to the plant for
any given treatment cycle.
161
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The current converters amplify the linear signal for input to the
chemical feeding system. The flow adder sums the flows from both flota-
tion systems and this total flow signal is input to the bypass control
gates system and to the circuitry which energizes the second flotation
system. Each flow controller can be manually set between 0 to 12 mgd.
The flotation tank equipment for each flotation unit (consisting of
sludge collectors, screw conveyors, recycle pumps, air compressors, and
air-lift solenoid valves) is activated when the level in the flotation
tank reaches a prescribed level. The level transmitter mounted on each
flotation unit sends a signal, linear with depth, to the console-mounted
level indicator which indicates the depth of water in the tank. The
signal from the level transmitter also passes through an electronic trip,
(K63 East; K52 West) mounted in the control console. This trip has
0-to 100-percent range (equivalent to water surface elevations in the
flotation tanks between-9.08 and -0.58). When the water level in the
tanks reaches a preset adjustable elevation, then another relay with
multiple contacts (K64 East; K53 West) energizes the flotation tank
equipment.
In addition, another electronic trip (one each for both the east and
the west flotation unit) is installed in the flotation tank level cir-
cuitry. The trips have 0- to 100-percent range. The new trips are set
for elevation -3.00 (the bottom of the V-notches in effluent launder).
These trips energize elapsed time meters (0 to 24 hr) and event recorders
(one for each east and west flotation units) mounted in the control panel.
These elapsed time meters sum the total time that the level in each flo-
tation unit was at an elevation sufficiently high to allow a plant efflu-
ent discharge over the effluent weir. The elapsed time meters are man-
ually reset. The trips also activate the effluent samplers and the chlo-
rine residual analysis system to be described below.
Plant Bypass Gate Detection System
Two electronic trips exist in parallel to the circuitry of the limit
switches for the lowered position on both the plant bypass gates. If
162
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either of the gates is not fully lowered, then the associated trip will
energize an elapsed time meter which will sum the total ttoe that com-
bined sewer overflow could be bypassing the plant through one of the
plant bypass gates. This same trip also energizes an event recorder to
record the actual time period during which either bypass gate was in the
open position.
Plant Shut-Down Sequence
As rainfall abates and runoff subsides, the combined sewage flow to
the plant will decrease. Eventually the water surface in the plant inlet
structure will drop below the required operating level. This will be
due to the sewage flowing into the dry-weather system consisting of the
21-inch diameter sewer upstream of the overflow weir at Baker and Marina
which flows easterly to the Marina pump station. If no more storm water
enters the collection system, the water in the flotation tanks and in
the inlet system will drain to a final elevation of -6.60 (the elevation
of the overflow weir at Baker and Marina) through this 21-inch sewer.
When the level in the flotation tanks falls below approximately
elevation -6.25 (this elevation is determined by the normal built-in
dead band-approximately 9 inches-in the electronic trip K63 and K52,
mentioned above), the following items of equipment will be shut down:
(1) Recycle pumps;
(2) Air compressors;
(3) Sludge collectors;
(4) Solenoid valves for air pumps; and
(5) Screw conveyors.
When the water level in the plant inlet structure falls below ele-
vation -6.50, the inlet gates closure probe will signal both plant inlet
gates to close by de-energizing relay K8. After the gates are closed
there will be no flow through the magnetic flow meters. Therefore, the
chemical feed pumps will shut off.
When the level of water, upstream of the overflow weir at Baker and
Marina, falls below elevation -6.80, the plant shutdown probe, located
163
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upstream of the weir and immediately ahead of the entrance to the 20-
inch diameter (dry-weather system) sewer, will deenergize relay K2 and
cause the following items of equipment to shut down:
(1) Bar Screens;
(2) Screenings conveyor;
(3) Ventilation system; and
(4) Flow recorder chart drives.
Chemical Feeding System
The console-mounted current-to-current converter sends a dc signal,
linear with flow to four chemical feeding systems.
Sodium Hypochlorination System—
The 4-to 20-ma dc linear electronic output signal from the current-
to current converter (I/I) is used by the automatic electric input con-
troller mounted on each of the two existing sodium hypochlorite feed
pumps (one pump for each flotation unit).
Polyelectrolyte Feeding System—
The 4-to 20-ma dc linear electronic output signal from the I/I is
used by the automatic electric input controller mounted on each of the
two existing polyelectrolyte feed pumps (one pump for each flotation
unit).
Alum Feeding System—
The 4-to 20-ma dc linear electronic output signal from the I/I is
used by the automatic electronic input controller mounted on the two
alum feed pumps (one pump for each flotation unit).
Caustic Feeding System—
The 4-to 20-ma dc linear electronic output signal from the I/I is
used by the automatic electronic input controller, mounted on the two
caustic feed pumps (one for each flotation unit).
164
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Chemical Storage Indicating System
Sodium Hypochlorite System—
The electronic differential pressure sensing device mounted on the
storage tank sends a 4-to 20-ma dc linear electronic signal to a level
indicator, calibrated in 100fs of gallons of sodium hypochlorite and
mounted on the control panel. The electronic trip (K74) is used in
activating the low level alarm for telemetering.
Polyelectrolyte System—
The polyelectrolyte storage tank includes an exterior sight gage.
Alum System—
The underground alum storage tank level is sensed by an electronic,
differential-pressure sensing device which transmits a 4-to 20-ma dc
electronic signal, linear with depth, to a level indicator, calibrated
in 100's of gallons of liquid alum and mounted in the control panel.
Caustic System;—
The caustic tank has an exterior sight gage.
The chemicals to be used in the process are stored in fiberglass
storage tanks. The capacities of these tanks are as follows:
(1) Alum 2,700 gal (underground);
(2) Sodium hypochlorite 3,600 gal (control building);
(3) Caustic soda 800 gal (control building);and
(4) Polyelectrolyte 1,300 gal (control building).
The commercial chemicals used in the process have the following
concentrations:
(1) Alum 36 Be' - 28% Al^SO^;
(2) Sodium hypochlorite 14% = 1.17 Ib Cl2/gal;
(3) Caustic soda 50% = 6.38 Ib NaOH/gal; and
(4) Polyelectrolyte 100%
By adjusting the 0-to 100-percent adjustable manual override panel
(mounted on the wall next to each pump), the dosage rate for each pump
can be adjusted according to the chemical concentration.
165
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Feed Pump Capacities—
The chemical feed pumps have the following capacities:
(1) Alum 10 to 310;
(2) Caustic soda 1 to 100;
(3) Sodium hypochlorite 3 to 75;'and
(4) Polyelectrolyte 2 to 110.
All chemical feed pumps have console mounted hand-off-automatic
switches.
Solids Collection and Disposal Systems
The sludge collectors move the flotable materials across the water
surface to the skim pipes.
Each double section of skim pipe is rotated through a suitable
linkage by one constant-speed drive unit which allows a skimming cycle
to be completed in 3/4 minute. The linkage is adjustable to provide
a means of varying the depth of submergence of the pipe lip.
Each drive unit is designed to rotate each double section of skim
pipe so that the lip of the pipe is submerged to a maximum depth of two
inches below average liquid level on the upstream side and to a maximum
depth of one inch on the downstream side on each revolution. At the
end of each skimming cycle a single-pole contact limit switch, furnish-
ed with the drive, opens to stop the drive motor. The interval between
skimming cycles of each drive unit is variable by means of a 0- to 30-
minute adjustable time clock, mounted in the motor control center. The
linkage between the drive units and the skim pipes are so designed that
by relocating the connecting points of the linkage, the following can
be accomplished:
(1) Back skimming eliminated without increasing from
skimming to more than maximum submergence; and
(2) Front skimming varied from 1/2-inch depth to the
maximum two inches.
To flush the flotable material collected in the skim pipe down the
pipe to the sludge sump, flushing water is added at the north end of
the skim pipe at the end of each skimming cycle. The flushing water is
166
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supplied through a normally closed solenoid valve. At the end of each
skimming cycle a limit switch, mounted on each south skimmer drive will
energize the solenoid valve. After a 0- to 60-second adjustable time
delay, the solenoid valve will close. The sludge collectors move the
settleable materials across the bottom of the tanks to the trough con-
taining the screw conveyors which move the sludge southerly to the air-
lift pumps which raise the sludge into the solids sump for removal
with the flotables.
The solids pumping system consists of two solids handling pumps.
In the automatic mode of operation one solids handling pump is controlled
by an electronic differential pressure sensing device mounted in the
solids sump. As the level increases, the electronic, differential-pres-
sure sensor sends a linear, de-signal, proportional to level between
Elevation -6.79 and -3.46, to the variable-speed control panel, mounted
in the motor control center, which controls the speed of the solids
handling pump through the electromagnetic clutch-drive unit, according
to the following conditions:
Condition 1 Condition 2
Capacity 550 gpm 260 gpm
Total dynamic head 120 ft 35 ft
Horsepower 40 40
Speed 1,517 794
Maximum shut-off head 140 ft
The second variable-speed solids handling pump is similar to the
first one and performs the following functions:
(1) Acts as a stand-by unit for the existing unit. Should the
existing unit fail, automatic transfer devices bring the
stand-by unit on-line under the same control system. When
operating under these conditions, this second pump has the
same operating characteristics as the first pump.
(2) Acts as a booster pump for the existing unit when dewater-
ing the plant influent system. Under this mode of opera-
tion, each pump is activated manually.
167
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Capacity 790 gpm (both pumps combined)
Total dynamic head 225 ft (both pumps combined)
Horsepower 40 hp each pump
S?eed 1,517 rpm each pump
all solids removed by the treatment process are pumped by this
System through approximately 2,700 feet of 6-inch diameter ductile iron
force main along the north side of Marina Boulevard to the. wet well of
the Marina Street pumping station. The output from this pumping system
is metered by means of a magnetic flow meter on the discharge side of
the pump system. An electronic signal is sent from the magnetic flow
meter to a locally mounted flow indicator and integrator. Both the
flow indicator and the flow integrator are field mounted locally in one
common panel adjacent to the meter. The solids handling system operates
completely independent of other plant systems and equipment.
Chlorine Residual Analysis System
The chlorine residual analysis system consists of a sample pump and
a motorized strainer for each flotation system (east and west) and one
common residual analyzer-recorder. By placing the existing east-west
selector switch in the east (west) position the pump and strainer for
the east (west) side are interlocked to start-up with the east (west)
flotation tank equipment and the west (east) pump and strainer are locked
out from starting. The three-way solenoid valve which directs the sample
to analyzer is set in the appropriate position by the east-west selector
switch. The east (west) pump and strainer and the residual analyzer are
activated when the water level in the east (west) flotation unit reaches
the elevation of the effluent weir. Thus, the electronic trip for the
plant effluent detection system activates the chlorine residual analysis
system. When overflow ceases the chlorine residual analysis system is
de-activated by another electronic trip and the three-way solenoid valve
between the pump and the strainer reverses position to allow flushing
water to be directed to the strainer. After a 0- to 10-minute time de-
lay, the strainer and the residual analyzer are shut down and the three-
way solenoid valve returns to its original, normal position.
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Sampling System
An automatic sampling system consists of one influent sampler and
two effluent samplers, one for each flotation unit (east and west).
The samplers are activated by the instrumentation and control sys-
tem. The influent sampler is controlled by the plant inlet gate circuit
and receives its start signal from the same electronic trip that controls
the plant gate opening. Influent sampling starts at the start of flow
into the plant. An adjustable time delay has been installed to avoid
initial surges. The plant selector switch controls the solenoid valves
on the sampler suction lines. When the gate closes, the sampler is de-
activated. The sampler control circuit is integrated to activate with
the first gate opening and de-activate with the last gate closure.
The east (west) effluent sampler is activated when the water level
in the east (west) flotation unit reaches the elevation of the effluent
weir. Thus, the electronic trips for the plant effluent detection
system (described above) activate the effluent samplers. When overflow
ceases, samplers are de-activated by another electronic trip.
Annunciator Sysjtem
When any of the following equipment is selected to start and fails
to start within a preset time delay, an alarm will be initiated. The
respective time delays are shown in the following annunciator system
delay relay schedule:
Annunciator System Delay Relay Schedule
Time Delay West East
System ___Hi2__—
Bypass control gates 7 TD7
Plant inlet gates 10 TD4 TD3
Bar screens 3 TD10 TD12
Screenings conveyor 3 TD11
Sodium hypochlorite feed pumps 3 TD5 TD6
Recycle pumps 3 TD8 TD9
169
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Annunciator System Delay Relay Schedule (continued)
Time Delay West East
System min
Air compressors (pressure drop) 3 TD8 TD9
Screw conveyors 3 ^DS TD9
Sludge collectors (two-drive
units for both east and west) 3 TD8 TD9
Solids handling pump 3
Ventilation system 3 ID 2
Hydraulic oil power unit 1 TD1
The annunciator consists of a set of light modules and a horn
mounted on the control console. During normal operation the light
modules glow dimly and the horn remains silent. When a failure occurs
for one of the above mentioned items of equipment, the corresponding
light module will flash brightly and the horn will sound. The horn can
be silenced by pressing the "reset" button on the console, and the light
will remain constantly bright. When the malfunction has been corrected,
the light will return to its normal dim light.
Telemetering System
Several functions of the treatment facility are telemetered by
means of AM transistorized tone transmitters and receivers, over a
leased telephone line to a remote receiver panel mounted at the Army
Street pump station.
The following plant functions are presently telemetered. When a
high level is reached in the overflow structure at Baker Street and
Marina Boulevard and the bypass gates are activated, an alarm will be
telemetered to the remote station. If either of the bypass gates fails
to open fully, a failure annunciator signal will also be telemetered
after time delay (TD7), adjustable from 10 minutes. The plant influent
is recorded by means of time-pulse transmitter, receivers, and two-pen
recorder. Operating lights have been provided in the remote panel in
order to indicate plant operation. A common failure annunciator signal
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for recycle pumps, air compressors, screw conveyors, and sludge collect-
ors is telemetered to the remote panel with specific annunciator points
located on the plant control console. An alarm is also telemetered when
the level in the sodium hypochlorite tank falls below a preset level.
In addition, signals are telemetered with the energizing of the
four new elapsed time meters which define the time durations of by-
passing untreated combined sewer overflow and of treatment plant effluent
production, and with the signal energizing the loss of air alarm of the
bubbler air supply system. These five signals are as follows:
(1) Overflow level in influent structure;
(2) Bypass gates not fully closed;
(3) Effluent level in east flotation unit;
(4) Effluent level in west flotation unit; or
(5) Bubbler air supply system loss of air alarm.
Occurrence of any of these conditions lights a separate red light
on the remote panel at the Army Street maintenance yard.
High Level Control Operation
The console-mounted flow adder sends a dc signal to the console-
mounted dual-alarm relay-type electronic trip ET218. When the signal
to the trip exceeds the pre-set level, this same signal will be sent to
the console-mounted gate flow controller, which will then send a dc
signal to the console-mounted control valve positioners. These posi-
tioners are used to position the gates by comparing gate position from
a 4-to 20-ma dc output signal from the gate opening feedback indicator-
transmitter which senses mechanical gate motion. Operating relays in
the positioner will direct operation of the hydraulic oil system sole-
noid operated, direction control valves. When the total plant flow, as
measured by the flow adder, equals or exceeds the preset point on the
gate flow controller presently set at 24 mgd, the gates will open in
parallel to bypass excess flow. When the total plant flow is less than
the preset point, the gates will either move toward the closed position
or remain closed, if already closed.
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Emergency Level Control Operation
When the total influent storm-flow exceeds the hydraulic constraints
of the facility, the bypass gates will be actuated by an emergency actu-
ating system. Emergency high-level and emergency low-level cut-out
probes will sense the water level in the overflow structure at Baker
and Marina. When the water level reaches a pre-set and adjustable level,
presently set at elevation -0.75, a signal is sent to a console-mounted
level relay which will again allow the gate flow control signal to oper-
ate the bypass gates.
Electrical Power Failure Operation
In the event of an electrical power failure, the 15 kw-diesel engine-
driven standby electric plant will automatically come on line. This
standby generator will supply power to the following:
(1) Emergency lighting panel;
(2) Ventilation system;
(3) Emergency 115-v outlets; and
(4) Sump pump.
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APPENDIX B
NONSTANDARD ANALYTICAL METHODS
173
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Appendix B
LABORATORY DETERMINATION OF FLOATABLE MATERIAL
General Discussion
The floatable material in a sample is concentrated on the surface
of the sample in a special Teflon-coated flotation funnel. The remain-
der of the sample is drained off and the floatable material collected,
washed, and weighed on a glass filter paper.
Apparatus
(1) Flotation funnel: A Teflon-coated 3-liter flotation
funnel provided with a 7-mm bore Teflon stopcock. The
flotation funnel should be provided with a 10-, 40T,
200-, and 3,000-ml mark.
(2) Mixer: Variable speed paddle mixer adjustable from
40 to 100 rpm.
(3) Paddle: Teflon-coated brass paddle 75 x 25 mm.
(4) Filter holder: Teflon-coated Millipore filter holders.
(5) Filter papers: Whatman GF/C 5.5cm.
(6) Suction flask
(7) Vacuum pump
(8) Oven: Adjusted to between 35 °C and 40° C.
(9) Cleaning rod: A 3-mm diameter Teflon-coated brass rod
85 cm long.
Procedure
Sample Collection and Preparation—
Collect an 8-liter sample in a bucket provided with a bottom out-
let. Great care must be taken to sample at points where the waste
stream is completely mixed. Best results are obtained when the bucket
is dipped directly into the waste stream. Transport the 8-liter sample
to the laboratory, place a propeller stirrer in the bucket and stir until
floatables are thoroughly mixed throughout the whole 8-liter volume.
While stirring, transfer three liters through the bottom outlet into the
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flotation funnel. The sample shall be transferred to the flotation
funnel within two hours after collection to insure that no significant
change in the amount of floatable material takes place.
Place the flotation funnel in a rack and fastern securely to pre-
vent even slight movements.
Mixing and Flotation—
Place the paddle mixer in the flotation funnel, mix, settle, and
discharge according to the following schedule:
(1) Mix at 40 rpm for 15 minutes;
(2) Let settle 5 minutes;
(3) Mix at 100 rpm for 1 minute;
(4) Let settle 30 minutes;
(5) Discharge 2.8 liters at a rate of 500 ml/min (use
cleaning rod if settled material clogs the stop-
cock.) ;
(6) Wash mixing paddle and sides of the flotation funnel
with distilled water from a wash bottle until all
particulate matter has moved to the bottom of the
funnel;
(7) Let settle 15 minutes;
(8) Discharge down to the 40-ml mark;
(9) Let settle 10 minutes;
(10) Discharge drop-wise to the 10-ml mark; and
(11) Add 500 ml distilled water of same temperature as
the sample, and repeat steps seven through ten.
It is important that the surface of the sample in the flotation
funnel remains undisturbed during the discharge to prevent loss of
floatables. The discharge rate shall be 500 ml per minute except for
the last 30 ml which shall be discharged drop-wise.
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Filtration and Weighing
Place a washed, dried, and weighed glass filter paper in the Tef-
lon-coated filter holder and filter the last 10-ml with the floatable
material. Wash with distilled water. An additional piece of preweighed
filter paper may be used to wipe the bottom of the filter holder if
necessary.
Dry the filter (and the additional piece if used) at 35° C or
40° C for 1-1/2 hours, place in a desiccator for 15 minutes and weigh.
Redry to constant weight.
CALCULATIONS
mg/1 Floatable Material = mS increase in weight of filter
volume of sample in liters
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APPENDIX C
TABULATION OF OPERATING CONDITIONS AND
PROCESS PERFORMANCE DURING PILOT-PLANT STUDIES
177
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Table 19. SUMMARY OF PILOT-PLANT OPERATING CONDITIONS
Test
run Run
P-l Vary
P-2 Vary
P-3 Vary
P-4 Vary
P-5 Vary
P-6 Vary
P-7 Omit
P-8 Vary
Influent
flow,
objective gpm
alum dose
alum dose
alum dose
recycle ratio
recycle ratio
recycle ratio
f locculation
liquid loading
10.9
10.4
10.3
11.6
14.8
21.4
20.8
50.5
Surface
Influent loading Air to
suspended rate, Recycle solids
solids, gal/ ratio, ratio,
mg/1 (ft)2(day) % Ib/lb
106
135
103
128
111
81.5
89.4
46.1
973
943
923
1,409
1,490
1,605
1,566
3,988
48
50
48
131
68
23
24
30
0.273
0.072
0.13
0.198
0.165
0.084
0.079
0.126
Floc-
culator
paddle Alum
speed, dose,
rps mg/1
1
1
1
1
1
1
0
1
165
202
280
166
162
127
130
125
a Specific
Polymer chemical
dose, dose,
mg/1 me /me SS
0
0
0
0
0
0
0
0
1
1
2
1
1
1
1
2
.55
.5
.73
.29
.45
.56
.46
.72
rate
P-9 Omit
f locculation
P-10 No chemicals
P-ll Vary
P-12 Vary
P-13 Vary
P-14 Vary
P-15 Vary
P-16 Vary
air to solids
air to solids
polymer dose
polymer dose
polymer dose
alum + polymer
55.3
15.5
15.8
15.1
14.9
14
15.5
15.4
66.8
117
106
111
103
118
113
112
4,266
1,550
1,570
1,520
1,515
1,455
1,542
1,553
27
65
63
66
67
72
68
66
0.16
0.104
0.033
0.009
0.113
0.071
0.046
0.084
0
1
1
1
1
1
1
1
123
0
156
109
0
0
0
76
dose
0
0
0
0
3.1
37.8
20.3
8.9
1
0
1
0
0
0
0
.84
.47
.98
.03
.32
.18
Based on correlation with turbidity measurenents.
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Table 19 (continued). SUMMARY OF PILOT-PLANT OPERATING CONDITIONS
Surface Floe-
Influent loading Air to culator & Specific
Influent suspended rate, Recycle solids paddle Alum Polymer chemical
Test flow, solids, gal/ ratio, ratio, speed, dose, dose, dose,
7, Ib/lb rps mg/1 mg/1 mg/mg SS
run turn opjeccxve
P-17 Vary alum + polymer
dose
P-18 Vary alum + polymer
dose
P-19 Undiluted raw
sewage
P-20 Vary polymer dose
with floe.
P-21 Vary polymer dose
without floe.
P-22 Vary polymer dose
with floe.
P-23 Vary polymer dose
16.8
15.2
15.5
15.7
16.2
15.8
16
IU&/ J-
112
108
162
125
109
107
112
1,632
1,532
1,550
1,556
1,590
1,570
1,580
60
66
65
64
62
63
63
0.14
0.154
0.053
0.067
0.054
0.062
0.091
1
1
1
1
0
1
0
90 4.5
62 14.1
183 0
0 56.4
0 52.5
0 71.4
0 71.6
-
—
1.13
0.45
0.48
0.67
0.64
without floe.
aDOW Purifloc C-31
-------
Table 20. SUMMARY OF INFLUENT AND EFFLUENT CHARACTERISTICS OF THE PILOT-PLANT TESTS
00
o
Test
run
P-l
P-2
x - j
P-4
P-5
P-6
P-7
-8
P-9
P-10
P-ll
P-12
P-13
P-14
P-15
P-16
P-17
P-18
P-19
P-20
P-21
P-22
P-23
a
1
=
Settleable solids,
Influent
8
7
12
13.2
10
15
13
4
6
38
16
20
21
8
8
15
10
20
10
2.6
5
6
Effluent
<0.1
0.6
2
1.2
<0.1
< 0.1
0.4
3.8
16
0.2
0.2
0.4
1.6
0.2
< 0.1
< 0.1
Constituenf
Oil and grease,
rng/1
Influent
48.1
10.6
9.6
29.7
36.7
34.4
5.2
8
11.7
23.8
12.6
23.8
37
36.9
22.4
46.4
42.9
33.8
31.3
13.7
55
ID. 9
6.1
Effluent
7.6
4.8
5.3
7.9
12.1
12.1
3.1
4.5
3.9
6.7
8.2
20.8
9.8
16.4
16.7
25.4
15.2
13
15.7
13.7
13.2
7.3
5.5
Floatables ,
mg/1
Influent
0.3
-
3
0.9
1.2
1.5
0.5
2
0.4
1
0.5
1.7
1
4.7
5.7
1.1
1
1.3
1.1
2.2
2.2
0.4
1
Effluent
0.3
0.2
0.3
0.5
0
0.2
1.7
0.3
0.5
0.1
1.7
0.5
4.7
5.7
0.3
0.1
0.1
0.3
0.5
0.7
0.3
0.3
Suspended solids,3
mg/1
Influent Efflupnt-
85.5
132
99.4
122
111
81.2
87.7
45.9
66.4
114
102
103
100
116
104
108
108
106
159
125
106
102
110
6 5
16.3
17.8
27.4
27.7
26.4
31.4
21
21.3
42.2
24.1
103
37.8
22.1
27.2
39.1
34.3
28.2
18.4
22
31.6
34.3
28.3
Based on standard laboratory analysis.
-------
Table 21. SUMMARY OF INFLUENT AND EFFLUENT CHARACTERISTICS FOR SELECTED PILOT-PLANT TESTS
Constituent
Test
run
P-l
P-2
P-3
P-ll
P-17
P-19
P-20
Total nitrogen,
mg/1 as N
Influent
7.1
5.3
3.8
14.2
11.8
22.7
7.3
Effluent
7.1
4.9
0.8
10.3
9.76
11.1
6.2
Orthophosphate,
mg/1 as P
Influent
5
2.3
2
5
8
21
11.1
Effluent
0.05
0.07
<0.02
0.15
0.32
0.21
10
Effluent
toxicity
Color, BOD, CUL), yo-nr
nnif mg/1 mg/1 survival,
Influent
35.1
20
33.3
38.6
29.9
30
25
Effluent Influent Effluent Inrluent firriuenc -/„
13
13
7
17 77.9 12.3 189
20 150 62.2 297
10 200 47.2 434
17 180 45 208
-
-
-
87.8 100
140
120 100
100 75
-------
Table 22. SUMMARY OF PILOT-PLANT PERFORMANCE
(% removal)
00
Test
run
P-l
P-2
P-3
P-4
P-5
P-6
P-7
P-8
P-9
P-10
P-ll
P-12
P-13
P-14
P-15
P-16
P-17
P-13
P-19
P-20
P-21
P-22
P-23
Settleable
solids
100
91.4
100
83.3
90.9
100
100
100
90
100
90
0
100
100
100
95
100
100
92
100
94.2
100
100
Oil and
grease
84.2
54.8
45.3
73.4
67.2
64.8
40.4
43.6
66.6
71.8
35
12.6
73.5
55.6
26.4
45.2
64.6
61.5
49.9
0
76
33
9.8
Floatables
0
-
93.3
66.7
58.3
100
71.3
14.9
18.2
45.4
80
0
50
0
0
72.8
90.
92.4
72.1
78.2
68.3
25
70
Suspended
solids
92.4
87.6
82.1
77.5
75
67.5
64.2
54.2
67.9
63.1
76.4
0
62.3
81
73.9
63.7
68.2
73.3
88.4
82.4
70.2
66.2
74.2
Constituent
Total
nitrogen
0
7.4
79
„
-
B-
—
—
B-
<-.
27.5
„
_
—
_
mm
17.2
—
51.3
15.3
_
_
-
Ortho-
phosphate Color BOD
99 63
97 35
99 79
_
97 56 84.2
_
_
96 33 58.6
99.9 66.7 76.3
9.9 32 75
_
— — _
COD
53.6
52.5
72.3
51.7
-------
Table 23. SUMMARY OF FLOAT AND SLUDGE CHARACTERISTICS, PILOT PLANT CONTINUOUS RUNS
00
Test
run
P-l
P-2
P-3
P-4
P-5
P-6
P-7
P-8
P-9
P-10
P-ll
P-12
P-13
P-14
P-15
P-16
P-17
P-18
P-19
P-20
P-21
P-22
P-23
Oil and grease
61.5
286
767
207
1,740
1,390
2,270
180
432
1,330
1,040
121
356
229
870
228
208
261
785
145
213
51
JFioat, mg/i
Total suspended
solids
4,280
21,600
19,100
26,100
18,700
17,100
9,760
4,510
12,500
3,300
376
2,970
4,850
20,800
4,660
6,810
3,530
13,600
3,560
5,040
1,430
1,130
Volatile sus-
pended solids
2,580
14,600
11,600
17,300
11,600
10,700
6,160
2,720
7,880
2,950
254
2,670
4,330
3,730
4,950
2,760
10,800
3,050
4,100
1,150
924
Oil and grease
12.3
56.7
12.8
6
9.4
4.8
6.1
4
23.7
14
93.5
10.8
11.4
14
14.6
25.9
20.9
27.2
26
8.9
7.8
5.9
Total suspended
solids
100
286
232
71.5
14.7
89.3
17.2
25
34.5
83
620
52
19
28
106
62
65
68
46
12
40
22
Volatile sus-
pended solids
56
180
152
44
45.4
6.6
17
18.5
22.5
416
34
17
22
76
42
52
56
31
q
29
13
-------
APPENDIX D
TABULATION OF OPERATING CONDITIONS AND
PROCESS PERFORMANCE DURING DRY-WEATHER
TESTING OF THE BAKER STREET DAF FACILITY
184
-------
Table 24. BAKER STREET DRY-WEATHER TESTING CONDITIONS
00
Influent
Test flow,
run Run objective mpd
D-l Vary alum dose
D-3 No chemicals
D-10 Vary alum dose
D-ll Vary alum dose
D-12 Vary alum dose
D-13 Vary alum dose
D-14 Vary air to solids
D-15 Vary air to solids
D-16 Vary surface loading
D-17 Vary polymer dose
D-18 Vary alum + polymer
dose
D-19 Vary alum + polymer
dose
D-20 Vary polymer dose
D-21 Vary surface loading
D-22 Vary polymer dose
D-23 Vary surface loading
D-24 Vary surface loading
aDOW Purifloc C-31
1,9
1.4
1.0
1.4
1.4
1.4
1.45
1.45
2.5
1.5
1.5
1.5
1.5
2.5
1.5
2.0
0.6
Influent
suspended
solids ,
mg/ 1
145
67.5
95.5
97.3
93.7
92.0
97.2
81.5
86.8
93.8
101
110
97.3
86.8
90.3
101
95.5
Surface
loading rate, Recycle
gal/ ratio,
(ft) (dav) %
6,340
5,460
3,520
4,630
4,180
4,230
4,260
4,160
6,110
3,970
4,020
3,970
4,000
5,730
3,970
4,880
2,420
90.1
122
101
88.4
69.9
71.9
67.5
63.5
39.1
50.8
52.8
50.8
51.8
30.5
50.8
38.8
130
Air to
solids
ratio,
Ib/lb
0.56
0.56
0.90
0.39
0.63
0.50
0.022
0.014
0.21
0.21
0.32
0.24
0.19
0.07
0.22
0.18
0.42
r\
Alum Polymer
dose, dose,
mg / 1 mg / 1
570
0
534
1,010
112
188
176
177
155
0
88
101
0
157
0
171
137
0
0
0
0
0
0
0
0
0
5.7
6.9
5.8
15.5
0
3.7
0
0
Specific
chemical
dose,
mg/mg TSS
5.3
0
7.5
13.8
1.6
2.7
2.4
2.9
2.4
0.06
"
0.16
2.4
0.04
2.3
1.9
-------
Table 25
SUMMARY OF INFLUENT AND EFFLUENT CHARACTERISTICS,BAKER STREET DRY-WEATHER TESTS
00
" " ' • - __'• — — __^__
Test
run
D-l
D-3
D-10
D-ll
D-12
D-13
D-14
D-15
D-16
D-17
D-18
D-19
D-20
D-21
D-22
D-23
D-24
Settleable solids,
Influent Effluent
1.5 <0.1
0.2 <0 1
<0.1 <0.1
<0.1 15
-
0.2 0.1
0.2 0.1
-
1.0 0.1
-
0.1 0.1
<0.1 0.1
-
<0.1 01
<0.1 0.1
0.1 0.1
-
Oil and grease,
mg/1
Influent Effluent
18.4 12.7
25.4
5.7
7.5
12.5
28.8
22.2
13.1
14.8
16.4
15
14.5
14.2
18.4
113
6.9
3.8
3.3
4.6
17.5
21.3
11.6
23.9
13.1
5.7
26.3
10.4
12.7
58.2
Constituent
Floatables,
mg/1
inr JLuenc £r r luent
0.34 0.03
*~
-
0
0.13
0.17
0.28
0.07
0
-
-
-
-
™
-
-
-
-
_
0
0
0
0
0
0
0
0
-
-
-
-
-
-
Suspended
mg./
Influent
145
67.5
95.5
97.3
93.7
92
97.2
81.5
86.8
93.8
101
110
97.3
86.8
90.3
101
95.5
solids ,
1
Effluent
34.3
58.8
65.8
44.8
71
60.5
113
79.8
72.8
79.8
62.5
97.3
99
69.3
86.8
83.3
95.5
Volatile
solids
Influent
128
_
12
18
28
32
12
12
28
14
24
suspended
, ms/1
Effluent
18
_
12
32
16
68
30
24
36
28
26
-------
Table 25 (continued). SUMMARY OF INFLUENT AND EFFLUENT CHARACTERISTICS,
x v ,-,™vr,T-iT,m Tvr>V-.T.TT7ATin7B TVSTS
00
Test
run
D-l
D-3
D-10
D-ll
D-12
D-13
D-14
D-15
D-16
D-17
D-18
D-19
D-20
D-21
D-22
D-23
D-24
Turbidity
JTU
.
Influent Effluent
80
36
52
53
51
50
53
44
47
51
55
60
53
47
49
55
52
17
31
35
23
38
32
62
43
39
43
32
53
54
37
47
45
52
Color,
unit
~ Alkalinity,
me/1 as CaC03
Influent Effluent
50
42
46
40
38
39
35
32
27
36
38
30
19
27
29
-
18
12
2
2
16
12
17
17
9
4
19
16
22
15
—
' -:.f luent
180
138
172
178
180
173
164
218
214
212
194
174
-
196
185
™
Effluent
182
113
86
86
79
60
130
145
141
104
148
125
""
172
106
pH,
unit
Influent
• — - —
7.05
6.70
7.05
6.73
6.70
7.10
7.05
7.15
6.95
6.99
7.05
7.05
6.75
"
7.05
6.75
fill iUtHlL.
7.15
6.45
6.85
6.33
6.30
6.32
6.10
6.75
6.60
7.27
6.85
6.95
6.75
7.10
6.40
-------
Table 25 (continued). SUMMARY OF INFLUENT AND EFFLUENT CHARACTERISTICS
oo
00
— . ... j-m.imv o iimjL. l l>S\j — WCiAlHnK TcSTS
Test
run
D-l
D-3
D-10
D-ll
D-12
D-I3
D-14
D-15
D-16
D-17
D-18
D-19
D-20
D-21
D-22
D-23
D-24
Total nitrogen,
mg/1 as N
Influent Effluent
23
22.6
21.9
_
20.8
22.1
20.5
18.5
21.7
21.8
23.8
19.9
_
18.2
24.4
-
-
19.9
10.6
12.9
16.4
18.6
19.5
18.5
17
18.3
17
19.9
16.2
20.1
-
-
Ammonia
mg/1
Influent
18.6
15.9
17.6
16.8
16.6
15.1
13.3
18.5
17.5
20.1
16.3
15.3
21.4
16.8
19.2
nitrogen,
as N
Effluent
15
3.4
6.9
™"
16.4
14.3
13.8
12.9
13.7
9.6
9.6
11.6
12.1
15.6
14.6
15.5
^unscicuenc
Or thophosphate ,
mg/1 as P
Tn i~ 1 man f- P-F-P 1 11 Q*-» *-
8.9 4.45
6
7.8
"•
9.1
6.3
7.1
5.8
5.2
7.6
6.8
7
~
4.4
5.6
7.1
-
2.44
<0.2
-
0.47
<0.2
<0.2
<0.07
0.19
4.19
0.9
0.78
—
0.07
3.14
0.24
-
BOD,
mg/1
Influent
132
174
136
138
91
156
120
100
108
H
118
124
110
107
84
109
138
trr iuent
114
114
62
58
34
46
71
54
53
58
62
51
66
57
60
61
COD,
me/1
Influent Effluent
174 139
289
294
_
173
190
147
138
252
264
230
_
186
188
234
200
205
130
_
164
69.1
60.5
69.1
95
205
53
•H
74
66
200
130
-------
Table 26. SUMMARY OF BAKER STREET DAF FACILITY PERFORMANCE DURING DRY-WEATHER TESTING
(% removal)
00
Test
irun
D-l
D-3
D-10
D-ll
D-12
D-13
D-14
D-15
D-16 ,-
D-17
D-18
D-19
D-20
D-21
D-22
D-23
D-24
Settleable
solids
93.5
50
0
0
•.
50
50
_
0
_
0
0
_
0
0
0
0
Oil and
grease
31
_
73
33.4
56
63.2
39.3
4.1
11.4
0
20.3
62
0
-
26.7
31
47.8
Floatables
90
-
-
-
100
100
100
100
100
100
100
97
-
100
-
60
-
Constituent
Volatile
Suspended suspended
solids solids
76 85.9
13
31
54
24
34.2
-16.2
2
16.1 0
14 . 9 -43.8
40 42.9
11.2 -113
-1.8 -150
20.2 -100
3.9 -28.6
17.4 -100
0 -8.3
Total
nitrogen
13.5
53
21.2
43
13.8
15.8
4.8
0
21.6
16
28.6
0
-
11.2
17.6
-
-
Ammonia
nitrogen
19.4
78.6
80.7
"*
38.1
13.9
8.6
3
26
45.1
52.2
28.8
—
22.4
27
13.1
19.3
-------
Table 26 (continued). SUMMARY OF BAKER STREET DAF FACILITY PERFORMANCE
DURING DRY-WEATHER TESTING
Test
run Ortno-pnosphate
D-l 49.9
D-3
D-10
D-ll
D-12
D-13
D-14
D-15
D-16
D-17
D-18
D-19
D-20
D-21
D-22
D-23
D-24
59.3
-
-
94.5
97
97
99
96
45
86.6
88.5
-
98.5
43.4
96.5
-
V/o J-emuva.0.^
Consti f-upnt- ~
BOD
13.5
34.5
54.4
58
60.4
70.5
40.8
46
51
50.9
50
53.6
38.3
32.2
45
55.8
COD
20
29
56
-
10.8
63.7
58.8
50
62
™
22.4
77
60
64.4
14.5
35
Turbidity
78.8
13.9
32
56.6
25.5
36
-17
2.3
17
16
41.8
11.7
- 1 Q
21.3
4.1
18.2
0
Color
64
71.5
96
95
79
59
66
47
37
75
89.5
36.6
•-
15.8
18.8
48.
Alkalinity
-1.1
18.1
50
51.7
56.1
65.3
20.7
33.5
34.1
50.9
23.7
28.2
12.2
42.7
-------
Table 27 SUMMARY OF FLOAT AND SETTLED SOLIDS CHARACTERISTICS OF THE BAKER STREET DRY-
WEATHER TESTS
Test
run
D-l
D-3
D-10
D-ll
D-12
D-13
D-14
D-15
D-16
D-17
D-18
D-19
D-20
D-21
D-22
D-23
D-24
Oil and grease,
mg/1
22.4
24.6
44.6
54.2
43
66.9
19.1
18.9
200
89.3
_
21.8
33.8
_
15.4
25
170
..
nno f-
.Ud L
Total
nitrogen,
mg/1 as N
19.7
12.9
-
31.5
20
29
23.1
18.9
56.3
31.9
28.7
22.2
-
21.7
20.4
—
-
_ :
Ammonia
nitrogen,
mg/1 as N
14.9
4.99
""
8.02
12.3
12.4
14.5
13.1
16.5
15.6
13.1
15.9
*"*
14.7
16.2
1 7 5
J. / « J
16.1
-
Ortho-phosphate
mg/1 as P
5
2.21
< 0.2
0.34
< 0.2
< 0.2
< 0.2
< 0.2
0.55
0.29
0.78
0.36
1.78
< 0.2
Settled solids
Nitrate
, nitrogen,
mg/1 as N
0.42
-
_
0.48
0.03
0.37
0.1
0.04
< 0.02
0.03
< 0.02
< 0.02
M
< 0.02
< 0.02
< 0.02
— ^~ j n j
Total suspended
solids ,
ma/1
50
92
1,380
1,080
220
232
88
40
38
190
152
136
36
94
68
176
284
-------
APPENDIX E
RESULTS OF BAKER STREET
DISSOLVED AIR FLOTATION TREATMENT OF
COMBINED SEWAGE
192
-------
Table 28. FIRST SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
20 September 1973
Sampling
Influent
0350
0420
0450
0520
0550
0620
0650
0720
Effluent
0450
0520
0550
0620
0650
0720
a
Solids sump
0350
0420
0520b
8620b
TEST CONDITIONS:
Total suspended
DOlids,
42
37
20
33
30
17
27
33
43
60
45
41
34
33
345
107
68
47
Flow - 0.039
Alum dosaee »
Settleable
•ollds.
24
18
1.5
14
16
3.5
14
10.5
24
34
28
22
2
4.5
308
87
49
10.5
m3/sec [0.9 mgd]
0
Floatables,
BIR/1
0.60
0.33
0.03
0.07
0.50
0.03
0.73
0.37
0.33
0.23
0.03
0.40
0.03
0.10
0.07
0.10
0.07
0.03
Tempera-
Turbidity, ture.
JTU C
55
45
50
40
40
35
30
35
55
50
50
50
60
55
210
80
55
70
Surface loading rate
Total 24-hr rainfall
Grease
and oil,
11.1
8.8
8.5
8.8
6.6
6.7
c A
7.0
7.1
6.7
6.8
6.0
7.1
24.4
10.7
8.6
7.9
" 103 m3
- 0.5 cm
COD, BOD,
n.R/1 n.g/1
124
78
114
114
116
98
80
82 -
120
152
130
122
129
135
252
144
268
135
/(m)2(day) [2,
[0.20 in.]
m+-V, Organic H, coliform, 96-hr Z
oiR/1 .TR/1 _P" MPN/100 ml survival
2.4
2.3
2.4
2.4
2.6
2.6
2.6
2.5
3.1
2.6
2.8
2.8
2.4
2.3
1.5
2.4
2.4
2.3
530 gal/ (ft)
2.0 6.9
1.8 6.8
1.2 6.8
1.3 6.8
0.9 6.8
0.9 7.0
0.8 7.0
8.9 7.2
0.4 7.2
1.3 7.2
1.0 7.1
1.0 7.1
2.2 7.3
1.3 7.4
7.1 7.2
2.5 7.1
1.8 7.1
1.7 7.3
2 (day)]
Plant activated at 0250
*Ho float present In solids sump.
bAir lift pump volume reduced.
-------
Table 29. SECOND SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
11 January 1974
Sampling
time
Influent
1940
2010
2040
2110
2140
Effluent
2015
2045
2115
2145
Settled sludge
composite
Floatables
composite
Total Suspended
solids ,
mg/1
63.7
80
68
84
60
74
72
66
68
162
No float removal
i
Settle able
solidi ,
Floatables ,
mg/1
Tempera-
Turbidity, ture,
JTU °c
0-02 0.30 29.0
0-20 0.93 15.0
°-07 0.70 21.5
0.10 0.56 22.5.
°-03 1.13 16.Q
°-05 1.10 35.5
<0.01 0.53 30.5
0-03 0.20 29.0
0-03 0.56 29.0
0-80 1.93 53.0
due to mechanical difficulties with tilt pipe.
Grease
and oil,
ng/1
8.9
6.0
15.4
12.7
3.6
15.1
9.3
6.9
26.2
21.3
COD,
mg/1
261
174
165
183
125
266
224
239
220
349
BOD,
mg/1
84.0
82.8
87.8
72.8
96.8
113.0
78.9
110.0
97.8
104.0
NH4+-N,
mg/1
3.08
3.78
2.94
2.94
0.42
1.26
0. 70
1.33
0.98
1.33
Organic
ma /I
7.02
4.48
4.62
4.48
4.92
3.78
4.62
6.23
4.90
5.16
N,
pti
7.05
7.15
7.23
7.19
7.10
7.10
7.16
7.20
7.24
7.14
Fecal Toxicity
collform, 96-hr Z
Flow - 0.066 in/sec [1.5 mgd]
Alum doange - 0
Plant activated at 19:15
Surface loading rat« - 145 a3/(m)2(dny) [1,580 Rnl/(ft)2(day)]
Shear gate closed at 1240
Total 24-hr rainfall - 0.56 cm [0.22 in.]
-------
VO
Table 30. THIRD SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
16 January 1974
Total suspended
Sampling solids,
Influent3
950
1010
1050
1110
Effluent
1005
1035
1105
1140
1205
Settled sludge
composite
Floa tables
composite
186
68
67
60
130
119
93
80
83
98
508
Settleable
solids,
5.0
0.5
0.25
0.20
6.0
0.4
0.5
0.4
0.3
0.6
19.0
Floatablea,
mg/1
2.3
1.1
7.6
5.8
9.0
14.4
7.5
10.3
38.9
8.8
4.9
Turbidity,
JTU
9.5
9.5
14.5
20.0
14.0
11.5
15.0
15.0
8.0
34.5
19.5
Tenpera- Grease
ture, and oil, COD,
OG mg/1 mg/1
17.4 5.4
7.2
8.8
1.7
2.6
1.3
1.6
1.9
1.0
7; 6
2.3
211
64
101
37
183
128
92
101
83
14.7
642
•\ •>
BOD,
mg/1
61.5
41.0
51.0
33.0
60.6
69.0
51.0
45.0
45.0
51.0
153.0
NH^-N, Organic N,
mg/1 mg/1
2.94
2.10
2.52
0.15
0.96
0.56
1.96
1.40
0.56
2.24
2.49
0.66
0.84
0.72
0.41
0.72
0.28
0.70
1.40
0.56
0.70
0.96
2 .
Fecal Toxicity
collform. 96-hr TL
pH MPN/100 ml survival
7.35
7.26
7.65
9 . 40
7.01
7.10
7.25
7.27
7.33
7.95
7.13
TEST CONDITIONS: Flow - 0.087 ra3/sec [2.0 mgd] Surface loading rate
Alum do8.iB« - 0 Shear gate closed a I I
Plant activated at 9:45 Total 24-hr rainfall
*First influent sample discarded due to incorrect sample valve setting.
182 »3/(m)(day) [4,460 gnl/(ft)Z(dny)J
>!i
1.27 cm [0.5 in.]
-------
Table 31. FOURTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
16 January 1974 - 2nd run
Sampling solids,
time ng/1
Influent
1515 80
1545 83
1615 59
1645 61
1715 70
Effluent
1540 128
16iO 71
1640 62
1710 43
1740 56
Settled sludge 73
composite
Floatables 116
composite
leaDie Tempera-
solids, Floatables, Turbidity, ture,
ml/(l)(hr) mg/1 JTU °c
0-50 0.16 18.5 17.8
0.30 1.60 33.0
0.01 0.10 17.5
0.10 0.26 19.0
0.01 1.23 26.0
0.50 1.40 28.5
0.15 0.80 43.0
0.08 0.90 27.5
0.01 0.26 22.0
0.01 0.16 18.5
0-05 1.4 28.0
0.75 0.70 52.5
Grease
and oil
mg/1
1.3
5.7
1.8
1.5
2.5
1.1
4.0
2.6
3.1
2.1
8.2
8.0
COD,
jng/l
174
165
110
119
119
165
156
147
138
147
165
248
BOD,
mg/1
50.7
79
50
72
49
55
53
80
57
57
81
127
NH^-N,
mg/1
= '
1.12
0. 70
0.84
0.98
0.70
0.56
1.68
0.42
0.98
0.84
0.42
0.56
Organic
mg/1
t"B/ •*•
1.40
0.98
2.38
1.96
1.12
1.14
1.96
1.54
1.36
1.40
0.70
2.94
Fecal
N, coliform,
oM MPN/inn mi
pn riTH/jLUU Ulj.
7.10
7.05
7.10
7.30
7.20
7.58
7. 35
7. 40
7.46
7.50
7.22
7.56
Toxicity
96-hr %
^survival
_
-
Alum dosage - 0
Surface loading rate - 232 »3/(»)2(day) (5.690 gal/(ft)'(day)J
Shear gate closed at 1105
Total 24-hr rainfall - 1.27 en [0.5 in.]
-------
Table 32. FIFTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
31 January 1974
Total suspended Settleable
Sampling solids, solids,
Hme mg/1 ml/(l)(hr)
t HOC » '
Influent
1457
1527
1557
1627
1657
Effluent
1503
1533
1603
1633
1703
Settled sludga -
composite
Floatables
composite
0.
0.
0.
0.
0.
1.
0.
<0.
7.
23.
70
283
15
50
20
20
18
75
15
1
50
0
Floatables,
mg/1
1.
1.
0.
0.
2.
1.
1.
0.
0.
11.
35
50
27
40
00
67
25
70
97
6
7.0
2.
1
Turbidity,
JTU
68
34
36
36
32
34
63
60
49
43
51
180
Tempera- Grease
ture, and oil, COD, BOD,
°C mg/1 mg/1 mg/1
1.2 - 69
12.5 1.5 - 54
<1 - 54
2.0 - 42
<1 - 24
<1 - 33.8
<1 - 36
2.2 - 40.8
15
<1 - 6.0
6.3 - 39
3.9 - 399
NH +-N, Organic N collform,
mst/1 mg/1 pH MPN/100 ml
1.
0.
1.
57
98
40
0.70
2.
1.
1.
0.
1.
0.
13
12
12
84
12
98
1.12
4.
20
<0 . 1 6 .
3.5 7.
<0 . 1 6 .
<0.1 7.
<0.1 7.
<0.1 5.
2.8 4.
<0.1 4.
<0.1 8.
<0.1 5.
2
0
5
2
5
7
6
4
6
9
96-hr Z
survival
—
—
—
—
"
**
~
"•
~
—
<0.1 6.2
<0.1 5.
7
-
TEST CONDITIONS: Flow- 0.12 m /sec 12.7 mn
-------
oo
Table 33. SIXTH SERIES TEST RUN BAKER STREET WASTEtfATER ANALYSES
1 February 1974
Sampling solids, solids,
time mg/1 miy(l)Oir)
Influent
805 -
-------
Table 34. SEVENTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
19 February 1974
Sampling
time
Influent
315
345
415
445
515
Effluent
330
400
430
500
530
City influent
sampler
City effluent
sampler
Settled sludge
composite
Floatables
Total suspended
solids,
mg/1
38
74.5
30
34
31.5
137.5
128
140
150
131
28.5
136
5W
4400
Settleable
solids,
mi/flWhr)
0.1
0.9
0.1
<0.1
0.1
10
20
70
54
71
<0.1
35
180
710
_
Tempera-
Floatables, Turbidity, ture,
m»/l JTU C
1.5 -
2.9
1.5
1.2
0.9
1.2 41 13
11 28 13
0.5 24 13
0.9 27 13
0.9 23 13
0.8
1.2
1.4
8. 7
Grease
and oil»
mg/1
5.0
6.8
8.5
7.1
7.0
9.9
8.2
8.2
13.4
13
4.4
3.4
5.3
9.5
COD,
»g/l
53.9
92.3
11.5
11.5
3.9
41.3
24.8
45.4
41.3
33.0
26.9
37.2
111.4
825.5
BOD,
mg/1
21.0
32.4
9.0
6.8
6.0
3.0
9.0
3.0
1.5
1.0
8.3
9.0
21
261
..
NH.+-N Organic N, coliform, 96-hr X
mg/1 ' mg/1 pH MPN/100 ml survival
<0.1 <0.1 6.9 11 x 10*
<0.1 <0.1 - I1 x 10
<0.1 <0.1 - 93 x 105
<0.1 <0.1 6-8 46 x 10
<0.1 <0.1 - 15 x 106
<0.1 <0.1 5.0 <3
<0.1 <0.1 5.9 <3
<0.1 <0.1 7.0 <3
<0.1 <0.1 5.6 <3
<0.1 <0.1 6-9 <3
1.12 <0.1
<0.1 <0.1 -
1.12 2.8
1.4 <0.1
-• • — •
•}
TEST CONDITIONS: Flow -0.087 m /sec [2.0 mgdj
Alum dosage - 150 rag/1
Plant activated at 0045
Surface loading rate - 182 m3/(i»>2(day> [4,460 gal/(ft) (day)]
Shear gate closed at 0050
Total 24-hr rainfall = 1.07 cm [0.42 in.]
-------
Table 35. EIGHTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
28 February 1974
Sampling
time
Influent
1018
1048
1118
1148
1218
Effluent
0 1013
° 1043
1113
1143
1213
City Influent
sampler
City effluent
sampler
Settled sludge
composite
Floa tables
composite
Total suspended Ssttleable
solids, solids,
206 2.9
7ft in
52.5 0.60
35.5 0.22
66 0.40
HI 6.0
54 5 <0 1
41 s *t\ i
53 5 <0 1
31.5 0.1
44 0.7
52.5 <0 1
114 |52
1.126 510
floa tab lea, Turbidity,
ng/1 JTU
— — — — — — _ — ,
1-6 160
1.5 24
1.6 17
1-0 15
0.4 12
0.6 4fi
0.7 26
0.7 21
0.6 18
<0.1 12
0.6 47
<0.1 23
8n
Tempera-
ture,
°c
15.4
15.3
15.0
15.0
15.1
16.8
16.6
16.3
15.9
16.1
-
"
—
Grease
and oil
0.3
0.7
4.6
0.6
1.4
4.3
1.7
0.7
3.3
2.0
7.3
3.1
1.1
17.7
, COD,
'• _
90
106
90
73
79
118
73
62
62
39
113
73
06
4,977
*—- — i
BOD,
• "
53
31
18
17
13
34
24
16
2.3
3.0
32
23
1A
490
NH/-N,
mg/1
0.95
2.02
1.46
1.76
1.82
3.64
3.92
2.52
2.38
2.10
5.32
4.48
1. /«
48.7
. —
Fecal
Organic N, colifon,,
mg/1 pH MPN/100 ml
4.06 7.5
6.44 7.2
1.12 7.2
3.22 7.2
3.92 7 2
<0.1 5.6
2.66 5.0
2.80 4.6 - '
<0.1 5.4
<0.1 6,6
<0.1 6.7 >24 x 107
<0.1 7.1 <3
•5.04
<0.1
'•'•' i ... - i.
Toxicity
96-hr Z
survival
-
~
-
.
-
Alum dosuge - 75 mg/1
Plant activated at 2035
Surface loading rate - 145 m3/(»)2
-------
Table 36. NINTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
28 February 1974
Total suspended Settleable
Sampling solids, solids,
. /I It1\n,r\
time
Influent
115
145
215
245
315
Effluent
135
205
235
309
335
City influent
sampler
City effluent
sampler
Settled sludge
composite
Floatables
composite
27 0.1
22 0.1
20.5 ^.1
31 <0.1
68.5 0
34 •'O.I
28.5 <0.1
31 <0-1
23 <0.1
16 <0.1
-
58.5 0
1,126 100
Tempera-
Floatables, Turbidity , ture,
mg/1 JTU C
1.1 16 15
0.2 13 15
<0 1 14 15
03 14 16
3.0 12 16
15 15 15
1.0 16 15
11 I? 15
0.4 19 16
n ft 17 16
1.9
— —
3.1
7.8
— Fecal Toxicity
and""! COD BOD, HH*-H. Organic H, coliform, 96-hr %
and oil, IMU, »"", A . •naj1 pli MPN/100 ml survival
!.9 56 47 2.66 <0.1 7.1
2.9 56 14 2.80 <0.1 7.0
0.8 51 11 3.64 1-82 7.0
6.2 56 20 5.32 2.38 7.1
1<5 51 17 <0.1 <0.1 7.2
6.3 68 15 <0.1 7.56 7.0
5.7 62 2.2 <0.1 <0.1 7.0
13.4 51 10 <0.1 <0.1 7-0
2.0 34 14 2.80 <0.1 7.2
8.6 56 8 2.38 <0.1 7.2
60 62 32 3.64 <0.1 - 46 * 106
_
1.4 68 3.3 1.82 <0.1 -
1.5 1,041 240 3.50 <0.1
TEST CONDITIONS: Flow - 0.066 m /sec [1.5 mgd]
Alum dosage » 0
1 2 2
Surface loading rats - 145 » /(«) (day) [3,580 gal/(ft) (day)]
Shear gate closed at 22QO
Total 24-hr rainfall - 0.56 en [0.22 in.]
-------
Table 37. TENTH SERIES TEST RUN BAKER STREET WASTEVATER ANALYSES
1 March 1974
Sampling
time
Influent
1527
1557
1627
1657
1727
Effluent
g 1552
1-0 1622
1652
1722
1752
City influent
sampler
City effluent
sampler
Settled sludge
composite
Floatables
composite
TEST CONniTTDNS. I
Total suspended
solids,
143
112
78
78
67.5
66
44.5
60
63.5
21
46
_
2 , / /O
12,450
Settleable
solids,
1.2
1.6
1.2
0.6
0.6
1.6
0.5
1.8
4.2
10.1
I'J.J
990
Floatables,
og/l_
0.8
0.4
0.4
0.9
0.1
0.9
1.3
1.8
0.7
0.2
4. 5
84.3
Turbidity,
38
35
29
28
18
30
14
13
13
5.5
-
Tempera-
ture *
15
15
15
15
15
15
15
15
15
15
"
-
Grease
and oil
0.6
0.3
5,6
3.1
2.7
2.0
1.7
2.6
1.9
2.6
0.9
"
4.7
COD,
mg/1
85
28
74
57
23
57
17
28
34
23
142
"
2t>(>
3,620
• • •
BOD, NH^-N,
mg/1 me/I
35 4.48
23 4.06
36 <0 . 1
20 4.62
12 2.66
3.6 1.40
3.6 <0.1
0.6 1.26
3.0 <0.1
0.6 1.54
18 6.58
- -
!>() II. IU
85 8.82
"" ' • ,!••.
."i'-JJ". conS. *&"?
<0.1 7.2 75 x 105
<0.1 7.1 11 x 107
'0.1 7.1 £24 x 107
'O.I 7.1 121, x io7
C0.1 6.9 llxlO7
<0.1 5.0
-------
UJ
Table 38. ELEVENTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
7 March 1974
Total suspended Settleable
Sampling solids, solids,
.. „„/! ni/n wtir)
Influent
1335
1405
1435
1535
1535
Effluent
1420
1450
1520
1550
1620
City influent
sampler
City effluent
sampler
Settled sludge
composite
Floatables
composite
8 0.2
39 0.2
35 0.15
32 0.25
36 0.85
142 14
-
Ho 0.9
740 70
Tempera- Grease
Floatables, Turbidity , ture , and oil,
mg/1 JTt' C mg/1
3 27 16 0.8
0.4 24 16 1.4
<0.1 23 16 1.1
1 24 16 6.5
0.9 29 17 0.7
1 7 16 0.4
0.6 12 16 0.5
<0 1 23 16 0.7
09 31 17 7.1
17 40 17 4-6
1.1 - - 2-11
— ~ ~*
•> •> - - 1.47
<0 1 - ~ *-8
COD,
rag/1
153
109
76
164
131
44
61
98
116
89
161
150
271
__ , : ^ — :
Fecal Toxicity
BOD, NH.^-N Organic N, coliform, 96-hr Z
mg/1 rag/I mE/1 pH MPN/100 ml survival
38 9.66 3.92 6.7 *24 x 10
26 10.2 <0.1 6.7 £24 x 107
36 13.2 <0.1 6.7 11 x 10?
33 7.56 3.08 6.7 43 x 105
32 5.46 <0.1 6.8 i24 x 10
6 4.90 <0.1 5.4 <3
2 2.66 5.74 5.5 <3
3 2.24 <0.1 5.6 4
2 5.74 <0.1 5.8 <3
6 3.36 7.84 5.8 <3
24 2.52 <0.1 -
2 0.70 7.74 -
48 5.18 19.32 -
TEST CONDITIONS: Flow = 0.039 m /see [0.9 mgd]
Alum dosage » 75 mg/1
Plant activated nt 0535
32 2
Surface loading rate - 103 m /(m) (day) [2,530 gnl/(ft) (day)]
Shear gate closed at 1040
Total 24-hr rainfall = 1.02 cm [0.4 in.]
-------
Table 39. TWELFTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
25 March 1974
Sampling
time
Influent
1013
1043
1113
1143
1213
Effluent
1028
1058
1128
1158
1228
City influent
sampler
City effluent
sampler
SuLUuJ MluJgu
compos i Lc
Floatables
compos! te
Total suspended Settleable
solids, solids,
mg/1 ml/(l)(hr)
37.5 0.7
39.5 <0.1
53.5 <0.1
34.5 0.5
45 0.6
32 0.4
48 <0.1
35.5 0.1
37.5 <0.1
28.5 <0.1
-
-
78 0.15
277 18
_ - i
Floatables
mg/1
0.7
0.5
0.4
0.3
1.2
0.7
0.4
0.8
0.6
7.1
_
„
2.1
3.1
Terapera-
, Turbidity, ture,
JTU °C
22
26 16
28
27
26
19
23
23
26
24
_
-
-
Grease
and oil
mg/1
6.1
2.1
2.0
8.9
9.1
5.6
3.4
2.2
3.6
5.9
2.2
8.4
, COD,
mg/1
110
110
154
121
132
60.4
87.9
110
137
121
187
121
BOD,
fflg/1
43
57
55
42
45
6.4
3.4
6.8
5.0
0.8
0.6
2.0
NH+-N,
rag/1
6.16
6.44
7.28
6.86
7.00
2.80
3.50
3.64
3.78
3.92
2.24
4.76
Organic N,
mg/1 pH
<0.1 7.1
4.1 7.4
8.7 7.4
<0.1 7.2
1.7 7.2
1.1 6.1
<0.1 6.3
3.6 6.6
5.6 6.8
6.7 6.8
"
4.4
<0.1 -
Fecal Toxiclty
collform, 96_hr j;
MPN/100 ml survival
i24 x 107
_ _
~ -
- -
-
-
TEST CONDITIONS: Flow - Q.039 mJ/sec [0.9 mgd]
Alum dosage » 0
Plant activated at 0540
Surface loading rate - 103 m3/(m)2(day) [2,530 gal/(ft)2(day)]
Shear gate closed at 0535
Total 24-hr rainfall = 1.88 cm [0.74 in.]
-------
Table 40. THIRTEENTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
27 March 1974
Total suspended Settleable
Sampling solids, solids,
,.,„,. m»/i ml/flWhr)
t Line
Influent
1830
1900
1930
2000
2030
Effluent
1845
g 1915
01 1945
1015
2045
City influent
sampler
City effluent
sampler
Settled sludge
composite
Floatables
composite
22 <0.1
22.5 <0.1
22.5 <0.1
20 <0.1
36.5 <0.1
36.5 <0.1
35.5 <0.1
51.5 <0.1
37 <0.1
50 <0.1
35 15
12.5 0.15
JO 0.25
1.586 230
Floa tables,
1.0
0.37
3.2
1.4
0.7
0.5
0. 6
0.8
1.0
0.5
0.9
1.9
Turbidity,
JTU
23
21
24
32
34
24
27
30
29
38
_
-
-
-
Tempera- Grease
ture, and oil,
°C mg/1
17 4.0
16 5.2
17 7.4
18 3.1
18 2.3
17 6.2
17 0.4
17 3.1
18 3.2
18 3.2
3.1
5.6
1.2
3.2
COD,
mg/1
45.5
96
55.6
75.8
60.6
35.4
45.5
40.4
70.7
70.7
20.2
70.7
111.1
1,232
BOD,
mg/1
46
51
43
43
96
24
28
20
22
22
51
51
22
108
Fecal Toxiclty
NH/. -N, Organic N, colifqrm, 96 hr %
mK/1 mp/1 oH MPN/100 ml survival
1.96
3.22
6.30
5.22
4.76
0.70
1.68
0.7
2.24
2.38
3.08
1.40
1.54
2.66
<0.1 6.9 224 x 10
3.64 6.-9 £24 x 10
1.54 7.1 S24 x 107
<0.1 7.2 J24 x 107
<0.1 7.2 9 x 10
<0.1 5.9 <3
0.98 5.7 <3
100Z
<0-1 5.8 <3 survival
4.48 6.4 <3
5.88 6.4 <3
0.98
3.22 -
•> . fi
<0 1 *™ "~
1
TEST CONDITIONS: Flow - 0.087 m3/sec [2.0 mgdj
Alum dosage » 75 mg/1
Plant Activated at 1545
Surface loading rat« - 182 m3/(m)2(day) [4,460 gal/(ft)"(day)]
Shear gate closed at 1610
Total 24-hr rainfall - 1.14 cm [0.45 in.]
-------
Table 41. FOURTEENTH SERIES TEST RUN BAKER STREET WASTEWAIER ANALYSES
28 March 1974
Sampling
ttrae
Influent
2300
2330
2400
0030
0100
Effluent
2338
0008
0038
0108
0138
City influent
sampler
City effluent
sampler
Settled sludge
composite
Floatables
composite
VPfF
Total suspended Settleable
solids, solids,
mg/1 ml/(l)(hr)
16 <0 1
12 <0 1
55 <0 1
10 0.2
43 0.1
27 <0.1
54 0.1
12.5 <0.1
62 <0.1
56 <0 1
11.5 <0.1
100 11 x 107
30 2.2 2.1 6.9 >24 x 107
42 2.7 2.4 7.0 J24 x 107
64 3-9 <0.1 7.0 i24 x 107
44 1-1 <0.1 7.2 >24 x 107
15 <0.1 2.8 6.2 4
11 1-3 3.4 6.3 <3
13 1.1 <0.1 6.5 <3 100X
Survival
1-8 4.6 <0.1 6.6 <3
1.5 3.1 3.2 6.6 <3
31 2.5 2.7 6.7
6 1.5 5.5 7.1
'''i l.-'ii II. 1 -
70 1.7 17.8 -
0.087 m /sec [2.0 mgd]
Alum dosage - 300 mg/1
Plant activated at 1845
Surface loading r«t« - 182 n,J/(m)2(day) [4,460 gal/(f t)2(day) ]
Shear gate closed at 1900
Total 24-hr rainfall . 0.43 cm [0.17 in.]
-------
Table 42. FIFTEENTH SERIES TEST RUN BAKER STREET WASTEWATER ANALYSES
29 March 1974
Total suspended Settleabla
Sampling solids, solids,
time vK/1 ml/(l)(hr)
Influent
2258
2328
2358
0028
0058
Effluent
KJ 2320
-J 2350
0020
0050
0120
City Influent
Sampler
City Effluent
Sampler
Settled Sludge
Composite
Floa tables
Composite
154 0.2
18 <0.1
11.5 <0.1
10.5 <0.1
40.5 0.3
45 <0.1
28 <0.1
29.5 *0. 1
26.5 <0.1
A 9 <0 1
m ^u. i.
60.5 0.1
56.5 <0.1
30 0.4
1,852 470
Floatables,
mg/1
1.3
0.3
0.7
1.6
2.4
1.1
0.6
0.8
0.2
0.4
0.6
0.5
0.4
Turbidity,
JTU
50
22
20
15
13
16
16
19
17
17
16.5
24
-
-
Tempera-
tg«,
17
16
16
16
17
17
17
17
17
17
-
-
-
-
Grease
and oil
g/1
3.3
3.3
3.0
3.8
3.1
4.8
1
3.7
4.1
3.3
0.5
2.5
3.7
6.6
COD,
mg/1
132
60.9
55.8
40.6
50.8
20.3
10.2
40.6
30.5
40.6
35.5
40.6
60.9
1,300
BOD,
mg/1
30
22
19
20
27
90
10
10
4.5
3.8
13
6.6
1.5
19
Fecal
NH^-N, Organic N, collform,
mg/1 mg/1 pH MPN/100 ml
2.66
2.94
2.94
4.2
4.3
1.4
1.26
0.98
1.54
1.4
2.24
1.58
1.54
1.82
7
Toxic Ity
96-hr Z
survival
3.6 7.0 24 x 10'
<0.1 6.9 93 x 105
1.7 6.9 24 x 10?
1.7 6.9 24 x 107
<0.1 6.9 46 x 10?
<0. 1 6
7.6 6
3.4 6
3.4 6
2.8 6
3.9 6
4.5 7
<0.1
21.3
.4 <3
.3 <3
.3 <3
.2 <3
.1 <3
.4
.0
- "~
— —
BOX
Survival
TEST CONDITIONS: Flow - 0.12 m /sec [2.7 mgd)
Alum dosage » 75 mg/1
Surface loading rate - 232 ra3/(m)2(day) [5,65)0 gal/(ft)2(day)J
Shear gate closed at 2230
Total 24-hr rafnfall •= 0.79 cm [0.31 in.]
-------
APPENDIX F
WASTE DISCHARGE REQUIREMENTS FOR
CITY AND COUNTY OF SAN FRANCISCO
BAKER STREET FLOTATION FACILITY
208
-------
APPENDIX F
WASTE DISCHARGE REQUIREMENTS FOR
CITY AND COUNTY OF SAN FRANCISCO
BAKER STREET FLOTATION FACILITY
CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD
SAN FRANCISCO BAY REGION
ORDER NO. 71-20
The California Regional Water Quality Control Board, San Fran-
cisco Bay R£gion, finds that:
1. The City and County of San Francisco, called the
discharger below, submitted a report of waste dis-
charge dated March 2, 1971.
2. The discharge will be treated sewage only, or sewage
and stormwater through a nine-foot diameter outfall
8.34 feet below mean lower low water to San Francisco
Bay, 135 feet from shore. Flows of up to 2.5 mgd
of domestic sewage may be diverted during the testing
period.
3. The Board adopted a water quality control plan for
tidal waters inland from the Golden Gate and within
the San Francisco Bay Region on March 26, 1970.
4. The beneficial uses of the San Francisco Bay are:
Swimming, wading, pleasure boating, marinas,
fishing and shellfishing.
Firefighting and industrial washdown.
Fish, shellfish and wildlife propagation and sus-
tenance, and waterfowl and migratory bird
209
-------
habitat and resting.
Navigation channels and port facilities.
Esthetic enjoyment.
5. The Board has notified the discharger and interested
agencies and persons of its intent to prescribe waste
discharge requirements for the proposed discharge.
6. The Board, in a public meeting on March 25, 1971,
heard and considered all comments pertaining to
discharge.
IT IS HEREBY ORDERED, the discharger shall comply with the fol-
lowing :
A. Waste Discharge Requirements
1. The treatment or disposal of waste shall not create a
nuisance as defined in Section 13050 Cm) of the Califor-
nia Water Code.
2. The discharge shall not cause:
a. Floating, suspended, or deposited macroscopic
particulate matter of foam in waters of the
State at any place;
b. Bottom deposits or aquatic growths at any place;
c. Alteration of temperature, turbidity or apparent
color beyond present natural background levels
in waters of the State at any place;
d. Visible, floating, suspended or deposited oil or
other products of petroleum origin in waters of
the State at any place;
e. Waters of the State to exceed the following limits
of quality at any place within one foot of the
water surface:
Dissolved oxygen 5.0 mg/1 minimum
Mien natural factors
cause lesser concen-
trations then this
discharge shall not
210
-------
Dissolved sulfide
Nutrients
Other substances
Bacterial concentrations
cause further reduc-
tion in the concentration
of dissolved oxygen.
0.1 mg/1 maximum
to be prescribed at
earliest practicable
date.
Any one or more sub-
stances in concentra-
tions that impair any
of the protected
beneficial water uses
or make acquatic life
or wildlife unfit or
unpalatable for con-
sumption.
in excess of a median
value of 240 MPN coli-
form per 100 ml, as
determined in any five
consecutive samples
collected at any one
station, or any single
sample to exceed an
MPN coliform concen-
tration of 10,000/100
ml at any time,
Whenever either of
these bacterial values
is exceeded in the
receiving water for
any reason they shall
both be met instead
in the waste at some
point in the treatment
process, provided
that at least one sam-
ple is collected from
each initial portion
of waste to be dis-
charged through the
outfall. The discharger
may demonstrate com-
pliance in the waste
211
-------
stream as an optional
alternative.
3. Waste as discharged to waters of the State shall meet
these quality limits at all times:
a. In any grab sample:
PH 7.0 minimum
8.5 maximum
b. In any representative set of samples:
Toxicity: Survival of test fishes in
96-hour bioassays of waste
as discharged
Any determination 70% minimum
Average of any three or more
consecutive determinations
made during any 21 or more
days 90% minimum
c. In any grab sample:
Grease 25 mg/1 maximum
Settleable matter 1.0 ml/l/hr maximum
This Board considers these two limitr, to be
goals rather than requirements and will con-
sider requirements for settleable matter,
grease and/or floatable matter after reviewing
additional information on the costs and other
information relative to the feasibility of
compliance therewith.
4. All dry weather discharge from the sewer system to the
Baker Street Flotation Facility or to its outfall is pro-
hibited except for testing purposes during the period from
March 25, 1971 to May 30, 1971.
B. Provisions
1. This Order includes items number 1, 4, and 7 of the attached
"Reporting Requirements" dated August 28, 1970,
212
-------
2. This Order includes numbered 1, 2, 3, 4, 5, 6, and 7 of the
attached "Notifications" dated January 6, 1970.
3. After the information obtained during the testing period
has been reviewed, this Order will be revised to prescribe
requirements for the discharge under normal operating
conditions.
I, Fred H. Dierker, Executive Officer, do hereby certify the
foregoing is a full, true, and correct copy of an order adopted by
the California Regional Water Quality Control Board, San Francisco
Bay Region, on March 25, 1971.
Executive Officer
213
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA-6QO/2-75-033
4. TITLE AND SUBTITLE
TREATMENT OF COMBINED SEWER OVERFLOWS BY
DISSOLVED AIR FLOTATION
7, AUTHOR(S)
Taras A. Bursztynsky, Donald L. Feuerstein,
William 0. Maddaus, and Ching H. Huang
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Department of Public Works, City and County of San
Francisco, San Francisco, California 94102
Through subcontract with
Engineer ing- Science, Inc., 600 Bancroft Way,
Bai-Vol 017 Pa 1 -i f nrnia Qi.710
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
3. RECIPIENT'S ACCESSIOI*NO.
5. REPORT DATE
September 1975 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1BB034
11. CONTRACT/GRANT NO.
WPRO-258-01-68
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
16. ABSTRACT Tnis program investigated the use of dissolved air flotation for the treat-
ment of combined sewer overflows. As a result of this program a 24-mgd prototype
facility was constructed and evaluated. The most recent study phase demonstrated the
1 acuity was constructed ana eva.j-ua.i_t;u.. j.uc IUUBL. j.ci_ci.ii- ai-^^j ^^.^.^.^ ^.^^**^*.~~
performance characteristics of the prototype Baker Street dissolved air flotation
facility for the treatment of combined sewer overflows under a broad range of oper-
ating conditions. Summary data from initial studies in this program using a pilot
plant and the prototype facility with dry-weather flow are compared with the recent
results. Improvements are suggested in the design and operation of dissolved air
flotation facilities. Under several specific test conditions the Baker Street facil-
ity effected reductions in combined sewage constituents which resulted in an effluent
quality meeting some local discharge requirements. Difficulties were encountered with
alum floe carry-over into the effluent. Wastewater pollutant removals were highest—
51 percent suspended solids from an influent of 99.5 mg/1 and 82 percent BOD from an
influent of 32.1 mg/1, measured in Test No. 8—at surface loading rates of 145 m0/(m)
(day) [3,580 gal/(ft)2(day)], an alum dosage of 75 mg/1, and a minimum air to solids
ratio of 0.05 kg air/kg solids. Specific design modifications are recommended for
investigation to determine their effect on system performance of the Baker Street
facility. The construction cost for the 24-mgd Baker Street facility with architec-
tural treatment was $2,518,000, adjusted to an ENR index of 2240. Annual 0 & M costs
are calculated to be $17,200.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COS AT I Field/Group
^Combined sewers
Overflows
Pilot plants
'''Operating costs
Runoff
*Dissolved air flotation
*Combined sewer overflow
Suspended solids
Stormwater runoff
Plant design
*Baker Street facility
(San Francisco, Calif.
13B
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
Unclassified
228
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
214 •M'O.S. GOVERNMENT PRINTING OFFICE: 1975 - 657-695/5314 Region No. 5-II
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