SAN FRANCISCO
WASTEWATER TREATMENT PLANTS STUDY
U,S, ENVIRONMENTAL PROTECTION AGENCY
REGION IX
SAN FRANCISCO, CALIFORNIA
SEPTEMBER, 1980
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SAN FRANCISCO
WASTEWATER TREATMENT PLANTS STUDY
U,S, ENVIRONMENTAL PROTECTION AGENCY
REGION IX
SAN FRANCISCO, CALIFORNIA
SEPTEMBER, 1980
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ENVIRONMENTAL PROTECTION AGENCY
REGION IX
SURVEILLANCE & ANALYSIS DIVISION
NPDES Compliance Monitoring Report
Permittee: City of San Francisco, California
Facility: San Francisco Wastewater Treatment Plants
Permit Nos.: CA0037664, CA0037672, and CA0037681
Date of Inspection: February, April, and June, 1980
Report Prepared by: Anthony V. Resnik
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TABLE OF CONTENTS
PART ONE
Section Page
I Executive Summary 1
II Introduction 6
A. Purpose 6
B. Statement of Problem 6
C. Inspection Participants 8
D. Study Methodology 8
E. Acknowledgements 9
-fi-I--~. -Recommendations 10
IV Summary of Findings 13
A. NPDES Permit Compliance 14
B. Operation and- Maintenance 14
C. Industrial/Commercial
Wastes 15
D. Plant Design 16
E. Emergency Bypass 16
F. Impending Changes 16
V Tables and Graphs 20
PART TWO
PRESENT OPERATIONS 46
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I. EXECUTIVE SUMMARY
The present level of San Francisco's Wastewater Program including
facility management and facility operation was determined by a
comprehensive investigation. Issues relating to the current
operation of the plants together with projected transitional
effects emerged during the study. Care was exercised to assure
that the recommendations contained in this report are compatible
with subsequent phases of the City's long-range management plan.
Prudent responsibility was also used to assure that the recommend-
ations are in harmony with the State and Regional Water Quality
Boards' actions. Implementation of the recommendations will be
beneficial not only to the present operation, but will also serve
as a valuable adjunct in the fulfillment of the San Francisco
Wastewater Program.
The City and County of San Francisco is embarked on a compre-
hensive wastewater program going from a simple basic treatment
system to a dry weather/wet weather storage transport system
feeding a high purity oxygen secondary treatment plant for the
east side of the City and a large dry weather/wet weather plant
system on the west side of the City.
San Francisco's three wastewater treatment plants are profession-
ally managed by experienced wastewater engineers and chemists.
Dr. A.E. Bagot and Robert Todd Cockburn, Superintendent, Bureau
of Water Pollution Control and General Superintendent, T & P
Divisions respectively are to be highly commended for optimizing
treatment for primary plants constructed almost 30 years ago.
The City acknowledges, however, by its proposed actions that
major changes in the existing organization, staffing and training
will be necessary to realize the full potential of the capital
investment in the wastewater system with the resultant socio-
economic and environmental benefits.
The City is presently pursuing a functional reorganization along
the line of adding middle management positions and assigning
technical engineering staff to the wastewater plants' organiza-
tion. This process is presently before the various Commissions
and Boards for approval. Not only are additional middle level
management staff and additional engineering personnel necessary,
the present operating staff must be trained in the activated
sludge treatment process.
Plans are underway to provide training for the existing personnel
in the basics of biological treatment at the City's small act-
ivated sludge plant in Golden Gate Park. It is proposed that
this plant serve as a continuing training center for all new
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operators. This is in addition to the start-up training included
in the various construction grants for facilities. This proposal
merits favorable consideration as a cost-effective method of
training. It is also recommended that consideration be given to
sending key operating and management personnel to similar plants
in size and treatment mode for "hands on" experience. For
example, the knowledge and experience gained by the East Bay MUD
personnel in the start-up and operation of their pure oxygen
activated sludge facility would be extremely beneficial to the
San Francisco personnel.
While there is no substitute for hands on experience, this must
be supplemented with formal training courses. It is highly
desirable, if not necessary, that selected key personnel includ-
ing supervisory staff receive formal training at special schools
such as the San Marcos Center. It must be noted that training
does not preclude the need for special consultants. The City
proposes to engage special consultants for assistance in areas of
concern such as start-up and training. Experience has shown that
the use of special consultants has proven valuable to wastewater
program managers.
To minimize start-up problems the City proposes to have key
personnel fuction in the construction inspection team. In this
program the personnel will become thoroughly familiar with the
new facilities minimizing orientation problems. These key people
will participate in the dry-run and wet-run training for the
other personnel.
The City's industrial waste source control program must be
expanded. A more comprehensive quantification and characteriza-
tion of the influent wastewaters will be necessary. Thirty-six
priority pollutants were detected in the influent and effluent
wastewaters of the three treatment plants. All of the metals
included in the priority pollutants were present. The latest
industrial waste report covering the period July 1, 1978 to June
30, 1979, shows that there has been an increase in the influent
mass of arsenic, zinc, copper and cadmium. There is increasing
evidence that many of the priority pollutants are not only
detrimental to the environment but may greatly reduce treatment
efficiency. The activated sludge treatment process used in the
new 85 MGD Southeast secondary treatment plant will be much more
sensitive to industrial wastes than the existing primary system.
The use of ferric chloride, presently used as a flocculant, will
cease when the new plants go on line. Since arsenic and chrome
are both impurities in the ferric chloride it is expected that
the influent mass of arsenic and chromium will be reduced.
However, the degree of reduction should be determined by
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appropriate tests and calculations prior to completion of the
present building program.
San Francisco's wastewater system is unique. Essentially all
municipal and industrial wastewaters are transported with storm
runoff in combined sewers, most of which were constructed in the
early 1900's. During storms, flow in the combined sewers
increases to as much as 14,000 mgd. This is a 140 fold increase
compared to the aproximate 100 mgd dry weather flow. Floatables
and other solids of sewage origin have been noted on the beaches
in San Francisco County for a number of years. Studies have
documented the recreational uses of the beaches and projected the
adverse effects of the pollution resulting from overflows con-
taining sewage.
Both the number and design of the overflow structures which were
based on criteria developed from data obtained from many compre-
hensive studies have been established. The complementary issue
of the number of overflow events deserves additional emphasis.
The lack of incentives in past NPDES permits and the lack of flow
measurement instrumentation in the existing system have mitigated
against minimizing overflow events. While the greatest number of
overflow events will naturally occur during the wettest months of
December and January, the number of overflow events will also be
dependent upon the operational strategy for handling wet weather
flows. This includes optimizing storage capacity, proper
sequencing the start-up and shutdown of treatment modules and
full utilization of all treatment facilities.
The California Regional Water Quality Control Board, San Fran-
cisco Bay Region, has required, in Order No. 80-11, that the City
submit an operational strategy report by October 15, 1980 for
handling wet weather flows. Automated storage level indicators
and flow measurement instrumentation with computer programmed
start-up and shutdown may be necessary to insure full compliance
with the Regional Board Order.
The treatment and disposal of sludges is often the most difficult
and costly portion of a water pollution control system. In San
Francisco, not only will the Quantities of solids greatly
increase but the character of the solids will change with the
activated sludge process. The problems will be compounded in
that not only will the City be increasing sludge Quantities by
improving dry-weather treatment going from primary to secondary
but the capture and treatment of large Quantities of combined
overflows, previously untreated, will add huge volumes of solids
of indeterminate character.
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Many of the present solids treatment units including the anaero-
bic digesters, elutriation tanks and vacuum filters will be used
in the renovated system. Field studies by the author during the
latter half of March, 1980 indicate that the rotating blade type
scum skimmers in the elutriation tanks do not adequately remove
the scum. The sludge digestion which starts in the thickening
tanks continues in the elutriation tanks resulting in large
sludge mats on the surface (photos 1-4). Periodically, the
solids are vacuumed off by suction lines discharging into Public
Works Department tank trucks (photos 5, 6). The operational
efficiency of the elutriation tanks as they relate to existing
and future operation merit additional study. While the overflow
from the elutriation tanks is routinely sampled and analyzed, the
results are not truly representative of the overflow due to the
method of sampling.
Another point of interest is the capacity of the existing four
vacuum filters. Dewatering of the conditioned sludge is
accomplished by four vacuum filters located adjacent to the
elutriation tanks. Present cake production is approximately
15,000 tons per year at an average solids concentration of 20
percent. Studies and operating data indicate that the percent
solids in the sludge cake will decrease substantially with the
treatment of activated sludges. Some municipalities are provid-
ing separate anaerobic digestion facilities for the activated
sludges and the primary sludges to prevent frothing problems in
the digesters. Also, EPA and State engineers have observed
during O&M inspections of other plants many malfunctions in the
sophisticated automatic control and instrumentation systems
relating principally to solids removal and treatment. It is
recommended that the final study of the solids handling for the
Southeast facility be inmplemented as soon as possible..
The number of treatment units and appurtenances will greatly
increase both in number and complexity. This dictates the need
for a modern computerized maintenance program. At the present
time, the records, inventory and ordering systems, together with
the preventive maintenance program are maintained manually. The
City recognizesy- the need for, and plans to computerize*the
maintenance program.
The influent wastewaters have not been adequately characterized
to determine the optimum treatability by the activated sludge
process. Series of grab sample analyses are needed to determine
the fluctuations in both the industrial and domestic waste load-
ings to the plants. Key pollution parameters should be profiled.
It would be desirable to establish a permanent surveillance-
monitoring system for sample collection from distinct interceptor
areas. When the plant(s) experience upsets the previously
collected samples from the network would be analyzed to determine
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the causative factors. The samples from the permanent detection
system would be automatically discarded and the samplers would
automatically reset until plant upsets and/or plant imbalances
occur requiring analysis of the samples.
The degree or extent the permit parameters are exceeded may be
more important than the number of times the NPDES permit limits
have been exceeded. For example, facility data show a high
percent compliance with NPDES permit limits for San Francisco's
wastewater treatment plants. However, the data also indicates
that there have been occasions where the amount of the permit
excess was of critical concern. Facility data show that a 50.0
mg/1 chlorine concentration was detected in the effluent from the
North Point Plant in November, 1979. Records also show that a
18.4 mg/1 chlorine concentration was detected in the effluent
from the Southeast plant in January, 1980. NPDES permit limit-
ations for both facilities stipulate a zero chlorine residual.
Available data show that chlorine at these concentrations pose a
serious hazard to marine and estuarine life and can result in
formation of halogenated compounds toxic to human and aquatic
life. Restoration of bay marine and ocean aquatic biota requires
considerable time.
Records also show that wastewaters with an extremely low pH
values have been discharged. pH values of 3.3 (Southeast plant
November, 1978) and pH values of 4.2 and 4.6 were reported in the
effluent from the North Point plant in February 1979 and February
1980, respectively. Wastewaters with these low pH values not
only inhibit and/or destroy aquatic biota but also upset the
biological treatment processes which may take weeks to completely
recover. The need for a controlled environment and biological
community is essential in the design and operation of a biolog-
ical wastewater treatment plant. The pH of a solution is a key
factor in the growth of organisms. Most organisms cannot tol-
erate pH levels above 9.5 or below 4.0. Generally, the optimum
pH for growth lies between 6.5 and 7.5.
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II INTRODUCTION
A. Purpose
On February 1, 1980, the Surveillance & Analysis
Division, EPA, Region IX, received a request from the
Enforcement Division to evaluate the 3 major Wastewater
Treatment Plants which serve the City of San Francisco,
California. The purposes of the investigation were to:
1. Determine compliance with the NPDES permit
requirements.
2. Evaluate the operation and maintenance of the
three wastewater treatment plants.
3. Recommend interim operational alternatives to
improve effluent quality.
4. Recommend operational alternatives to provide an
orderly transition from primary treatment to
secondary treatment.
B. Statement of Problem
NPDES permits numbers CA0037664, CA0037672, and
CA0037681 for the Southeast plant, North Point Plant
and Richmond-Sunset plant respectively were issued to
the City and County of San Francisco (the permittee) on
December 6, 1974. The California Regional Water Qual-
ity Control Board, San Francisco Bay Region, issued the
permits Under Authority of Section 402(b) of the Clean
Water Act, as amended [33 U.S.C. 1342(b)]. The permits
were modified on June 21, 1977. The permits were
further modified in 1979 by the San Francisco Regional
Water Quality Control Board.
The NPDES permits contain both general and specific
conditions. The permittee has, on occasion, discharged
effluent in violation of the terms and conditions of
the effluent limits. Records also indicate that the
permittee failed to comply with provisions of the
permits which required completion of secondary facili-
ties to treat combined North Point and Southeast flows
by July 1, 1977.
The Environmental Protection Agency, Region IX, on
April 6, 1979, issued Findings of Violation with
respect to violations of provisions of the following
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NPDES permits: Southeast plant (NPDES No. CA0037664),
North Point Plant (NPDES No. CA0037672), Richmond
Sunset Plant (NPDES No. CA0037681), Richmond Sunset
Sewerage Zone (NPDES No. CA00384115), and Southeast
Sewerage Zone (NPDES No. CA0038423). EPA's April 6,
1979 letter to the permittee constituted notice pur-
suant to Section 309(a)(l) of the Clean Water Act.
On April 23, 1979, representatives of the City,
Regional Water Quality Control Board and EPA met in the
offices of the RWQCB to discuss the status of viola-
tions of the NPDES permits for the City's North Point
and Southeast Water Pollution Control Plants.
On September 18, 1979, the Regional Board conducted a
public hearing in the Assembly Room, State Building,
1111 Jackson Street, Oakland, at which the discharger
appeared and evidence was received concerning the
discharge. All paragraphs of Board Order Nos. 76-4 and
76-3 under item II (Northpoint plant and Southeast
plant respectively) were rescinded. Additional para-
graphs were added to Board Order Nos. 76-3 and 76-4
under Item II.
The Regional Board also ordered the Discharger to
submit a report by November 1, 1979 documenting com-
pletion of all measures (both physical and manpower
related), relative to the North Point plant headworks
that will ensure use of maximum capacity during wet
weather flow periods.
San Francisco presently discharges untreated and par-
tially treated wastewater to the Bay and ocean. During
rainfall periods, untreated wastewater may overflow at,..
any of 39 overflow points discharging up to(2jbillion
gallons of untreated wastes in an average year, result-
ing in the build-up of floatables and other solids of
sewage origin on the beaches.
Studies show that each overflow may contain a variety
of pollutants including heavy metals, suspended solids,
floatables and disease causing bacteria. Data
indicates that, at times, such pollutants can present a
significant public heatlh hazard as well as degrade the
ecological communities and aesthetics of receiving
waters. Studies also show that the Ocean beaches are
used for water-contact recreation and that bacterial
contamination may persist in Bay waters from 5 to 28
days after an overflow event.
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C. Inspection Participants
1. Environmental Protection Agency
Anthony Resnik, Project Officer
Enforcement Investigations Section
Milton Tunzi and Helen Johnson
Sampling and Analysis Section
Water Branch, Surveillance & Analysis Division
2. City of San Francisco
Dr. A.E. Bagot, Superintendant, Bureau of Water
Pollution Control
Robert Todd Cockburn, General Supt., T & P Divisions
Dan L. McNulty, Superintendant, Richmond-Sunset Plant
Roland Chin, Superintendant, North Point Plant
Eugene L. Mooney, Chief Engineer, WW Pump Division
Hyman Gurman, Superintendant, Southeast Plant
Lynwood Messer, Senior Stationary Engineer, SE Plant
Igor Tebneff, Chief Engineer, Southeast Plant
Jack Barro^jy^ Director, Industrial Waste Program
Arvid Ekenberg, Stationary Engineer
3. Consultants for the City of San Francisco
Richard B. Meighan, CH2M Hill
D. Study Methodology
The study consisted of three phases. One part of the study
consisted of the NPDES compliance sampling inspection. The
second phase involved evaluation of the treatment facilities
during wet weather conditions and the final phase of the study
included the evaluation of the treatment facilities during dry
weather conditions. The Project Officer met with operating and
management personnel as well as with representatives of the two
engineering firms retained by the City- Additional information
was obtained through a review of the facility's records dating
back to 1967-68 and information obtained from the Consulting
Engineer's reports.
The findings noted in this report generally relate to conditions
as they existed at the time of the inspections. The City has
initiated several actions to upgrade the facilities. These are
noted where deemed appropriate. However, the complete document-
ation of the ongoing operation and maintenance program must
necessarily be the responsiblity of the permittee.
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E. Acknowledgements
EPA is grateful to the participating facility personnel of the
City of San Francisco for their invaluable services provided
during the study- Appreciation is extended to Dr. Teng-Chung Wu
and Rill Dalke of the Regional Water Quality Control Board for
thefr contribution to the study. Special recognition is extended
to Mr] Cockburn for his cooperation and assistance.
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Ill RECOMMENDATIONS (All Plants)
1. Develop and implement procedures for the characterization of
the influent wastewaters to determine optimum treatability by
the activated sludge process.
2. Determine the fluctuations in both the industrial and
domestic waste loadings to the plants through the analysis of
a series of grab samples.
3. Establish a permanent surveillance-monitoring system for
wastewater characterization from distinct interceptor areas.
4. Profile key pollution parameters.
5. Strengthen the industrial waste program by:
(a) Establish a regular monitoring program for the 36
priority pollutants previously identified in the
influent wastewaters. Make necessary adaptions in
program based on results of analyses.
(b) Determine and abate the source(s) of the priority
pollutants.
6. Characterize and quantify all return waste streams to each of
the plants to determine the possible adverse effects on
facility performance.
7. Carefully re-examine each plant's personnel needs recognizing
that, due to the complexity of the solids handling and large
plant area of the treatment units, existing manpower guide-
lines are not wholly applicable.
8. Consider employing additional middle management personnel.
9. Fill vacancies with permanent employees through timely
completion of the necessary civil service examinations.
10. Establish and provide budgeting support for a formal training-
program for plant personnel including the regular attendance
at EPA, State, and other training courses.
11. Utilize the City's activated sludge plant in Golden Gate Park
as a training center for new operators.
12. Consider an exchange program to train operators at existing
activated sludge wastewater treatment plants.
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13. Develop and implement operational procedures for optimizing
storage capacity, proper sequencing the start-up arid shut-
down of the treatment modules and for full utilization of
all treatment units.
14. Conduct necessary studies to determine the solids processing
capability of the present elutriation tanks and vacuum fil-
ters (Southeast plant).
15. Develop plans for emergency methods of disinfection during
the period of transition to the liquid NAOCL and NaHS03
systems.
16. Determine the causative factors for the occasional high
toxicity levels in the effluent of each plant.
17. Re-evaluate the reasons for the HPDES effluent violations
relating to settleable solids, coliform, chlorine residual
and pH requirements.
IS. Develop written definitive coordination procedures with all
contractors and agents working on site to minimize operating
interruptions.
19. Minimize the number of bypasses and reduce the quantity of
wastewaters bypassed by operating at established treatment
capacity during rainy periods.
RECOMMENDATIONS (tlorth Point Plant)
1. Establish the maximum wet weather treatment rate at 135 MGD.
2. Maintain the 135 MGD rate during wet weather:
(a) Install new coarse racks.
(b) Renovate the air agitation systems and provide
additional air.
(c) Investigate the feasibility of increasing the weight of
the rake assembly for increased gripping capability.
(d) Investigate the feasibility of increasing the "bite" of
the rake teeth through sharpening.
(e) Employ additional personnel for the bar rack operations
during the wet weather months.
(f) Investigate alternate means to keep the bar screen
fully operative during tiie wet weather months.
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Investigate methods for a more rapid closing (less than 6
minutes) of the inlet gate.
Maintain the influent pump sump level at greater than 17
feet.
Conduct necessary studies to evaluate if a higher ferric
chloride feed rate would improve plant efficiency.
Maintain the recently established higher SC>2 dosage for
the alleviation of the chlorine residual violations
(Southeast).
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IV SUMMARY OF FINDINGS (Southeast Plant)
A. NPDES Permit Compliance
The Southeast facility has, on occasion, exceeded the
effluent limits contained in the NPDES permit for chlorine
residual, settleable matter, pH, total coliform and toxicity
The NPDES self-monitoring record for the reporting period
July 1977 through February 1980 is provided in Table I. For
the years 1976 through 1979 the facility reported the fol-
lowing compliance percentages:
The percent compliance for the maximum settleable matter
limit of 1.0 ml/l/hr. has been greater than 99 percent in
each of the last 4 years; 99.79% in 1979, 99.74% in 1978;
and 99.84% in both 1977 and 1976. The percent compliance
for the average settleable matter limit (6 daily grab
samples) of 0.5 ml/l/hr. has also been greater than 99
percent in each of the last 4 years; 100% in 1979, 99.18% in
both 1978 and 1977, and 99.73% in 1976.
There has been an improvement during the past two years in
the percent compliance for the total coliform maximum day
limit of 10,000/100 ml. In 1979 there was a 98.68% com-
pliance with a 100% compliance in 1978 and a 83.60% and
79.30% in 1977 and 1976 respectively. The average coliform
(5 day median) limit of 240/100 ml has been exceeded on
numerous occasions. This is a recurring problem which has
proven difficult to solve. The limit was exceeded on 47 of
the 303 samples in 1979 which resulted in 84.49% compliance.
There was a 90.40% compliance rate in 1978 and a 83.60% and
a 85.11% compliance in 1977 and 1976 respectively.
The pH peak flow limits of 6.0 - 9.0 have generally been met
with a compliance of 99.73% in 1979 and 98.80%, 99.60%, and
99.18% in 1978, 1977, and 1976 respectively.
The percent compliance with the zero chlorine residual limit
in the effluent has shown improvement each succeeding year.
There was a 99.03% compliance in 1979 with a 95.80% and a
91.74% compliance in 1978 and 1977 respectively. There was
no requirement in 1976.
The foregoing data was collected and analyzed by facility
personnel. However, both Regional Board personnel and EPA
personnel have verified facility sampling results through
their own analyses. During the EPA sampling inspection on
March 14-15 and April 4, 1979, the pH, residual chlorine,
settleable solids and total coliform met effluent limits.
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EPA reported a zero percent survival on the analysis of the
toxicity sample collected on March 13, 1979 and a 50 percent
survival in the undiluted waste for the March 14, 1979
sample. EPA personnel conducted an evaluation of the
sampling and analysis techniques employed at the Southeast
plant laboratory on February 19-20, 1980. The evaluation
team found all self-monitoring procedures in accordance with
EPA requirements, EPA recommendations and NPDES permit
specifications. EPA also provided a set of quality control
samples to facility personnel. The unknowns included BOD,
suspended solids, cyanide, and light metals. Except for
cyanide, their results were within one standard deviation of
the true values. No major deficiencies were noted.
B. Operation and Maintenance
The operation and maintenance of the facility is generally
sound. There was a 72 percent removal of suspended solids
during calendar year 1978 and 64.5 percent removal in 1979.
As may be noted from graph No. 1 the average monthly removal
for suspended solids during 1978 ranged from a low of
approximately 62 percent in both March and April to a high
of almost 82 percent in June. The percent removal for
grease ranged from a low of 61 percent to a high of greater
than 76 percent (Graph No. 2). The influent, effluent, and
percent removals of BOD and COD are shown on graphs Nos. 3
and 4 respectively. The mirnimura and maximum influent pH
values are shown on graph No. 5.
The problems of meeting the coliform requirements were due
in part to the turn-over of laboratory staff. This defi-
ciency should be alleviated with the completion of the civil
service examination for the series of chemist postions for
permanent employees in both the Senior Sewage Treatment
Chemist and the Water Quality Chemist positions.
There are insufficient process tests for the characteri-
zation and quantification of the return waste streams to
determine the possible adverse effects on facility perfor-
mance. There is also insufficient data to adequately
determine' the treatability of the influent wastewaters by
both physical-chemical and the planned biological
processes.
C. Industrial/Commercial Wastes
27 of the 129 EPA priority pollutants were detected in the
influent during wet weather conditions at the SE plant. As
may be noted from tables number 2 and 3; heavy metals,
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chlorinated benzenes, chlorinated ethanes, the phthalates,
phenols, cyanide and toluene showed the greatest concentra-
tion. All of the metals included in the priority pollutants
were detected in the influent and effluent wastewaters.
A value of 3,000 ug/1 of chromium was reported in the
Southeast plant effluent during dry-weather flow. The City
reported chromium levels rose dramatically during the
sampling of a storm occurring on Tuesday, February 13, 1979.
Before 8:00 A.M. chromium levels were ranging between 115 to
215 ug/1. Samples taken after 8:00 A.M. showed chromium
levels of between 2750 and 4180 ug/1.
While there are a spectrum of highly effective methods
available for the removal of heavy metals from water, preci-
pitation appears to be capable of bringing the concentration
of metals down to _<_ 0.5 mg/1, provided suspended solids con-
centration content is sufficiently low (£ 10 mg/1
estimated).
D. Plant Design
The Southeast facility is, in effect, two separate treatment
plants. One is a conventional primary treatment plant
serving the SE portion of the City. The other provides
solids treatment both to the sludge and scum pumped from the
North point plant and to the solids removed at the Southeast
primary plant.
The facility at an overflow rate of 2,000 gal/ft^/day
has a sedimentation tank capacity of approximately 70 MGD,
however, the plant is limited to a peak capacity of between
32-38 MGD by the grit tank influent system.
E. Emergency Bypass
The Southeast and North point plants do not bypass in the
conventional sense. Operators throttle to the maximum
hydraulic capacity available resulting in overflows in the
combined system at diversion structures upstream. Bypassing
also occurs as the P-S.'s and interceptors are overloaded.
Bypassing takes place by throttling the inlet gates. The
inlet gates were throttled 375.5 hours or an average of 12.9
hours per each day of the month for February, 1980. Maximum
flow recorded during the month ranged from 31 to 42 MGD.
Throttling causing flow diversion resulted largely from
rainfall, however, evaluation of the operating records show
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malfunction of the bar rakes and also a power failure
necessitated flow diversion.
Records indicate that these overflows occur 82 times a year
(Citywide average). The excess flow is discharged through
39 shoreline overflow structures distributed around the ^__
periphery of the City. Studies note that the composition of
these overflows can range from approximately 2 parts sani-
tary flow to one part runoff to greater than 50 parts runoff
to one part sanitary and the duration of overflows can range I
from a few minutes to a few days.
During high tide, Bay water occasionally infiltrates if the
flap gates of overflow bypass structure gates are not
tightly closed due to debris caught in gates.
EPA sampled the discharge from the overflow structures in
the SE tributary area during three storm periods on 2/28,
3/1, 3/26, and 3/28, 1979. Analyses were performed for the
heavy metals, total and fecal coliform, oil & grease, TICH,
pH and settleable solids. Fecal coliform counts up to
2,400,000/100 ml were recorded. The highest values reported
for chromium, lead, zinc, nickel, and copper were 0.42 mg/1,
0.47 mg/1, 1.2 mg/1, 0.33 mg/1, and 0.27 mg/1 respectively-
Settleable solids up to 8.5 ml/1 and pH values as low as 6.0
were reported.
m
F. Impending Changes
The chlorination-dechlorination system is being replaced by
liquid NAOCL and NaHSC>2 systems.
G. System Failures Due to Construction
Liaison procedures with the construction management
personnel and the City are being revised and strenghened to
minimize treatment process disruption during the new
construction period.
SUMMARY OF FINDINGS - North Point Plant
A. NPDES Permit Compliance
The NPDES self-monitoring record for the reporting period
July 1977 through February 1980 is provided in Table IV.
The following permit compliance percentages for the North
Point facility were achieved for the year 1978 through the
first quarter (March 1979):
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Max. settleable solids = 99.41 percent compliance (2724)
Ave. settleable solids = 99.12 percent compliance (j^j)
Total coliform 5 day Medium = 94.06 (yjjj)
Total coliform (Max. day) = 100.00
pH peak flow = 97.80 (~)
C12 residual = 99.93 (^ J9? )
Toxicity (1978) = 83.3 (~)
The pH, residual chlorine, and settleable solids met
effluent limits during the time of the EPA sampling inspect-
ion on 3/13/79. EPA representatives collected composite
samples of the effluent beginning at 9:00 A.M. on 3/13 and
3/14/79 for fish toxicity tests. There was no (zero) survi-
val in undiluted wastes from both of the composite samples.
A toxicity value of _< 1.2 was reported for the 3/13 test
with a 1.3 toxicity value for the test conducted on the
3/14/79 sample.
Ten samples collected on 5/7/79 and analyzed for total
coliform met permit limits.
B. Operation and Maintenance
There was a greater than 70 percent removal of suspended
solids during calendar year 1978. The monthly average
suspended solids removal ranged from a low of 60.1 percent
in December to a high of 73.7 percent in September (graph
No. 6). The grease removal ranged from a low of 54 percent
to a high of 76;5 percent (graph No. 7). The influent,
effluent, and percent removals of BOD and COD are shown on
graph Nos. 8 and 9 respectively. The minimum and maximum
influent pH values are shown on graph No. 10.
The two principal reasons for exceeding the settleable
solids limit were (1) hydraulic overloading of the sed-
imentation tanks during wet weather and (2) the forced
shutdowns of the NPWPCP during construction of the Southeast
17.
-------
facility. The original design for the North Point WWTP is
for a peak flow of 150 MGD.
Additional studies should be conducted to optimize the
ferric chloride feed rate. The North Point plant does not
have the waste streams associated with solids disposal.
Furthermore, the treatability of the influent wastewaters
are less adversely affected by industrial wastes than the
Southeast facility. The ferric chloride feed rate is in the
range of 12 to 16 mg/1 while the ferric chloride feed rate
at the Southeast plant is 28-32 mg/1. During calendar year
1978, the average percent removal of suspended solids from
the Southeast plant was 72.0 percent removal and the percent
removal at the North Point facility was 70.3 percent.
Inadequate chlorination facilities including mixing and feed
controls together with improper sampling techniques have
resulted in exceeding the coliform requirement at the
NPWPCP.
C. Industrial/Commercial Wastes
26 of the designated priority pollutants were detected in
the influent during wet weather conditions at the North
Point plant.
D. Plant Design
The original design for the North Point WWTP, which was
completed in 1951, is for a peak flow of 150 MGD with an
overflow rate of 2200 gal/ft2/day. Records indicate,
however, that the NPDES permit limits for settleable solids
are exceeded when the flow is greater than 135 MGD. This
results in an overflow rate of 2,000 gal/ft2/day with
all the sedimentation tanks in service. The mean forward
velocity at this rate is 4.8 fpm which is in the upper
limits of design for compliance with settleable solids
requirements.
The chlorination facilities are inadequate. No mixing is
provided. Chlorine application is limited to approximately
150 Ibs/day feed rate ahead of the sumps and 170 Ib/day
ahead of the sedimentation tanks.
Emergency Bypass
Bypassing is accomplished by throttling a 72 by 72-inch
inlet gate to the plant.
18.
-------
Evaluation of plant records indicate that there have been
periods when the peak flows have reached 185 MGD. This
excessive flow rate resulted in solids washout over the
weirs of the sedimentation tanks.
Plant records also show that during storm weather throttling
and subsequent bypassing has occurred with flow rates less
than 100 MGD being recorded. This is due to the clogging of
the mechanical bar screens with rags and debris.
19.
-------
PHOTOGRAPHS
TABLES
GRAPHS
20
-------
No. 1 Subject: Scum and solids on surface of
elutriation tanks
Photographer:
A.V. Resnik
Witness :
3-26-80
Time: 9:30 AM
Direction: N
Facility; Southeast Plant, San Francisco, CA
Photographer:
A.V. Resnik
Witness :
Date: 3-26-80
•
Time: 9:35 AM
Direction: N
No. 2 Subject;__ Similar to photo #1
Solids on surface of elutriation tanks
Facility: ""Southeast plant, San Francisco, CA
EPA-IX-FORM 753 21.
-------
-,. - -
Photographer:
A.V. Resnik _
Witness:
Date: 3-26-80
Time: 10 :00 AM
Direction: NW
No. 3 Subject; Department of Public Works
Employees skimming off solids from eiutriation
tanks
Facility; Southeast Plant, San Francisco, CA
Photographer:
A.V. Resnik
Witness:
Date: 3-26-80
Time: 10:05 AM
Direction: NW
No. 4 Subject; Solids on eiutriation tanks
Facility; Southeast Plant, San Francisco, CA
22.
-------
Photographer:
A.V. Resnik
Witness:
No. 5 Subject; Department of Public Works
Truck used in skimming elutriation tanks
Date: 3-26-80
Time: 10:1°
Direction: NW
Facility: Southeast Plant. San Francisco. CA
Pfiotographer
A.V. Resnik
Witness:
No. 6 Subject: 8 inch1suction line-skimming
solids from elutriation tanks
Facility: Southeast Plant, San Francisco, CA
23.
Date: 3-26-80
Time: 10:15 AM
Direction: NW
-------
Name of Discharger: City and County of San Francisco
Location: Southeast Plant
Reporting Period: July 1977 through February 1980
NPDES Permit No.: CA0037664
Permit Effluent Effluent
Condition Constituent Limitation Month
A.l.e Chlorine 0.0 . Jul. 77
Residual Instantaneous Aug. 77
1 ', Maximum Sep. 77
Oct. 77
Nov. 77
Dec. 77
Jan. 78
Feb. 78
Mar. 78
Apr. 78
May 78
June 78
July 78
Aug. 78
Sep. 78
Oct. 78
Nov. 78
Jan. 79
Feb. 79
Mar. 79
Apr. 79
June 79
July' 79
Aug.i 79
Sep. 79
Nov., 79
Dec.1 79
1 Jan. 80
Value(s)
Reported
22.6
20.6
17.9
20.0
5.3
9.5'
9.0
6.8
6.0
4.8
'0.8
4.4
4.1 •
5.0
2.5
1.1
17.0
11.9
6.0
0.7
6.8
2.0
0.1
0.6
0.5
, 0.8
4.8
18.4
# of Exceptions/
# of Samples
741/741
744/744
1 **
71/387
5/379
15/366
**
**
8/231
**
**
13/213
4/224
9/224
! 5/228
3/233
', 5/223 :
2/206
2/190
3/215
1/199
2/178
1/207
4/207
2/205
1/204
5/208
1/206 '
tr«
Ijd
** No data
-------
Name of Discharger: -City and County of San Francisco
Location: Southeast Plant
Reporting Period: July 1977 through February 1980
NPDES Permit No.: CA0037664
o
o
U1
Permit Effluent Effluent
Condition Constituent Limitation Month
A. 2 ' Settleable 1.0 ml/l/hr Aug.
i \ Matter maximum Oct.
any sample De'c.
Jan.
Apr.
June
Aug.
' Nov.
Dec.
.; Jan.
\ ' Feb .
June
Aug.
Jan.
i
A. 5 Total ; 240 MPN/100 ml Aug.
Coliform median of Sep.
five samples Oct.
Nov.
* Jan.
( May
Sep.
Nov.
Dec.
77
77
77
78
78
78
78
78
78
79
79
79
79
80
77
77
77
77
78
78
78
76
78
Value(s) # of Exceptions/
Reported # of Samples
(Maximum)
10.0
5.5
2.0
2.0
1.3
1.5
3.5
15.0
3,.0
9.0
1.5
3.0
1.5 ;
2.0 ;
i
3300 '
24000
1100
430
330
790
340
790
1700
| 1/372
1/368
2/372
A*
**
1/358
**
5/353
**
3/367^
**
2/354
2/364
1/367
i
i
I
6/23
19/20
3/20
5/20
1/21
4/21
4/20
2/21
13/24
B"
Ir1
W
H
** No data
-------
Name of Discharger: City and County of San Francisco
Location: Southeast Plant
Reporting Period: July 1977 through February 1980
NPDES Permit No.: CA0037664
O
O
3
rt
to
Permit Effluent Effluent
Condition Constituent Limitation Month
,
A. 5 (cont.,) Total 240 MPN/100 ml Mar.
• Coliform median of Apr,
five samples June
Aug.
Sep.
"1 Oct.
Nov.
Dec.
1 . Jan.
:: •: Feb.
V
1
A. 5 Total 10000 MPN/100 ml Sep.
Coliform any single sample Nov.
Sep.
Nov.
K Dec.
Aug.
Oct.
Nov.
Feb.
A. 6 pH 6.0 to 9.0 Sep.
Jan.
Feb.
| NOV.
. Jan.
79
79
79
79
79
79
79
79
80
80
77
77
78
78
78
79
79
79
80
i
77
78
78
78
79
Value(s) # of Exceptions/
Reported # of Samples
(Maximum)
2600
2400
1700
330
220
24000
490
24000
1300
330
92000
11000 ;
24000 i
24000
16000 '
24000
24000
24000
16000
*
(Min./Max. )
5.8 to 6.7
5.9 to 6.9
'5.7 to 6.8
3.3 to 7.0
5.2 to 6.8
' 4/29
2/28
3/20
5/29
8/24
11/23
3/21
13/20
5/22
3/17! ;
1/20
1/20
**
** i
**
1/29
6/23
2/20
1/17
1/20
1/4
**
1/21 r
1/30
** No data
-------
Parameter
antimony
arsenic
beryllium
cadmium
chromium
copper
lead
mercury
nickel
selenium
silver
thallium
zinc
manganese
cyanide
benzene
1,2 , 4-trichlorobenzene
1, 1,1-trichloroe thane
1,1,2, 2-tetrachloroethane
chloroform
1 , 2-dichlorobenzene
1 , 4-dichlorobenzene
1 , 1-dichloroethylene
1 , 2-trans-dichloroethylene
ethylbenzene
bis (2-chloroethoxy) methane
methylene chloride
trichlorof lourome thane
naphthalene
phenol
bis (2-ethylhexyl) phthalate
butyl benzyl phthalate
dl-n-butyl phthalate
diethyl phthalate
tetrachloroethylene
toluene
t rich loroe thy lene
NORTHPOINT WPCP
Influent Effluent
Wet-Weather
li.xed
< -L
<5
<5
3
20
'170
220
5.1
10
< 5
20
10
1900
120
.01
nd
nd
10
nd
nd
6
7
nd
nd
7
i nd
| 45
j nd
nd
]. nd
95
j 95
1 14
19
6
, 35
•'I 45
Sett.
J
< 5
< 5
1
10
100
56
«: 1
35
<: 5
<: 10
6
1700
95
4.004
nd
nd
12
, nd
nd
nd
nd,
nd
nd
14
nd
nd
nd
nd
nd
40
50
10
50
16
95
110
Dry-Weather
Mixed
< 33
15
< 15
< 2
<- 50
135
23
<. 2
<- 50
4 5
30
21
201
140
10
5
nd
nd
nd
45
nd
nd
14
30
12
nd
18
nd
nd
52
10
nd
nd
nd
7
45
395
Sett.
< 33
< 30
<15
< 2
< 50
50
56
<- 2
<: 50
< 5
17
* 1
61
100
16
nd
nd
320
nd
25
nd
nd
6
15
10
nd
10
nd
nd
58
nd
nd
nd
nd
5
30
245
SOUTHEAST WPCP
Influent Kf fluent-
Wet-Weather
Mixed
2
< 5
< 5
5
180
170
180
^ 1
80
< 5
15
5
520
220
^.004
85
nd
12
nd
nd
nd
nd
nd
nd
10
nd
25
nd
9
nd
90
25
14
16
13
110
nd
Sett.
2
< 5
< 5
2
75
55
42
<- 1
65
5
20
5
200
180
<1.004
nd
140
20
nd
nd
nd
nd
nd
nd
nd
nd
25
nd
nd
nd
45
9
12
14
18
nd
nd
nry-Wf^
Mixed
<20
15
<15
4
3,000
80
300 ^
«£ 2
<50
-------
KJ
oo
Parameter
antimony
arsenic
beryllium
cadmium
chromium
copper
lead
mercury
nickel
selenium
silver
thallium
zinc
manganese
cyanide
benzene
1,2, 4-trichlorobenzene
1,1, 1-trichloroe thane
1,1,2 ,2-tetrachloroe thane
chloroform
1 , 2-dichlorobenzene
1 , 4-dichlorobenzene
1 , 1-dichl oroethy lene
1 , 2-trans-dichloroethylene
ethylbenzene
bis (2-chloroethoxy) methane
me thy lene chloride
trichlorof lourome thane
naphthalene
phenol
bis (2-ethylhexyl) phthalate
butyl benzyl phthalate
di-n-butyl phthalate
diethyl phthalate
tetrachloroe thy lene
toluene
trichloroethylene _
" Al
RICHMOND-SUNSET WPCP
Influent
Wet-Weather
Mixed
•
Sett.
,
Dry-Weather
Mixed
< 20
16
< 15
2
< 50
120
/ISO)
^•-^
< 50
<: 5
45O^
<: 2
< 50
< 5
<15
< 1
178
50
23
nd
nd
nd
nd
nd
nd
nd
nd
nd
9
nd
270.
nd
•5
61
50
10
30
nd
nd
10
nd
concentrations expressed in /a.g/liter~ •
ther
Sett.
-------
N)
VO
Name of Discharger: City and County of San Francisco
Location: North Point Plant
Reporting Period: July 1977 through February 1980
NPDES Permit No.: CA0037672
Permit
Condition
A.l.e
,;
i ).
Effluent
Constituent
Chlorine
Residual
Effluent
Limitation
0.0 mg/1
Instantaneous
Maximum
Month
Oct.
Dec.
Mar.
Nov.
Dec.
Mar.
77
77
78
79
79
80
Value(s)
Reported
6.6
7.2
5.0
,50.0
5.4
1.7
# of Exceptions/
# of Samples
5/31*
> 3/31*
1/31*
2/240
5/248
1/248
A.2
pH
6.0 to 9.0
Dec
Jan
Feb
77
78
78
A.4
Settleable
Matter
1.0 ml/l/hr
any sample
Maximum
Apr. 78
Nov. 78
Jan. 79
Feb. 79
Nov. 79
Dec. 79
Feb. 80
Oct. 77
Jan. 78
Feb. ,78
July 78
Feb. '79
Oct. 79
Nov. ,79
Dec. 79
(Min./Max.)
4.2 to 6.7
5.4 ,to 6.9
5.0 to 6.8
5.8 to 7.0.
5.8 to 6.8'-
5.5 to 6.8
4.2 to 6.9
5.2 to 6.9
5.8 to 7.5
4.6 to 6.9
1.5
2.6
1.2
1.9
3.0
1.5
' 3.5
2.0
1/31
1/31
2/28!
1/30
1/30
1/31
2/28
1/30'
1/31
1/29
1/185
1/184
1/167
3/186
9/168
1/186
1/186
1/186
*
* A
No. of days exceeded limit/No, of sample days
No data.
-------
Name of Discharger: City and County of San Francisco
Location: North Point Plant
Reporting Period: July 1977 through February 1980
NPDES Permit No.: CA0037672
o
o
Permit
Condition
A. 7
i'
1 ',
1 1
Effluent
Constituent
Total
Coliform
Effluent
Limitation
240 MPN/
100 ml
Median of
five samples
Month
July 78
Aug. 78
Sep. 78
Jan. 79
Nov. 79
Jan. 80
Value(s)
Reported
350
540
920
350
540
1400
# of Exceptions/
# of Samples
2/20*
i 6/23*
7/21*
3/23*
3/22
5/23
*
**
No. of days exceeded limit/No, of sample, days
No data.
-------
(jj
CO
o
a
COj
H3
O
co
a1
co,
^
Ml
2>
O:
M>
O,
CO
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tr^i
H1
a
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300
270
240
210
180
150
120
90
60
30
0
s
-•-" \
J
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**>*^
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00
00
] Effluent "
V
g I
CO
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M
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100
90
80
70
60
50
40
30
20
10
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§
i 00
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-------
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to
it
, tn
'.' hi?
o
I;
100
90
80
70
60
50
40
30
20
10
0
i Effluent
4 1 L
100
90
80
70
60
50
40
30
20
10
0
CO
O
CO
CO
CO
en
M
CO
CO
-------
U)
to
en
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03!
100
90
80
70
60
50
40.
30
20
10
0
ft
oo
-------
U)
en
O
a
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ffl
cn
n
o,
a
1000
900
800
700
600
500
400
300
200
100
Influent':
;Effluent
% Removal
0 JL
oo
00
00
en
M
oo
00
2!
O
CO
(
100
90
80
70
60 f
so
40
30
20
10
,o
-------
10.0
to
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9.0
8.0
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6. 0
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%
00
t .minimum
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2!
O
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^
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2!
1-3:
en
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M
2!
a
M
O
O
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H
a
en
300
270
240
210
180
150
120
90
60
30
% Removal
Effluent •
I
CO
n
S3
00
00
00
en
H
00
2!
O
CO
100
90
80
70
60
50 ig
40
30
20
10
0
oY
-------
co
tu
O
Q
cn
100
90
80
70
60
50
40
30
20
10
0
Removal!
; Effluent
,» — • — .
00
8
CXD
K
CO
00
CO
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00
2!
§
CO
100
90
80
70
60
50
40
30
20
TO
0
o\o
IS
-------
;' O
u> ,
oo ( Oi
"i H
O,
'@
tr*
O
D
300
270
240
210
180
150
12Q
90
60
30
0
/
CO
CO
cx>
K
CO
CO
§
CO
J.OO
90
80
70
60
50
40
30
20
10
0
en
MD
-------
iff i
o
o
o
>3
1000
900
800
700
600
500
400
300
200
100
% Removal;
Effluent-
_i I
oo
00
-4
00
CO
M
00
§
00
100
90
80
70
60
50
40
30
20
10
io
$
tr1
"$'
00
-------
a
o
i§
0
O
H
•a
C!
td
a
10.0
9. 0>
8. 0
7.0
6.0
maximum '{
{minimum 'i
00
O
w
00
~ 1
CD
i-Jj
I"!
tn
M
!co
CD
-------
O
il
'( ' ''
en
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O
.cn!
Gi
Cfl
^:
w
2!
Ol
M
CO
O
tr1
H
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CO
300
270
240
210
180
150
120
90
60
30
0
Influent
Effluent
oo
tu
00
00
00
en
M
oo .
a
o
00
100
90
80
70
60
50
40
30
20
10
0
CD
s
f
-------
H
OS
as
jo
O
I
en
en
O
fj
••»
3
\i
I-1,
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
9
|S,
tr*
-j
00
00
00
00
en
M
oo
O
-------
bJ
50
H
n
a1
21
o
I
en
en
fed
O
CO
§
300
270
240
210
180
150
120
90
60
30
-4
00
00
2!
O
-J
00
00
•s
-J
vo
100
90
80
70
60
50 i s:
40
30
20
10
0
; oj
00
CO
-------
O
a
g
2
a
i
en
en
o
o
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3!
\
H
1000
900
800
700
600
500
400
300
200
100
100
90
80
70
60 :
50 !§'
is
40 i
30
20
10
0
a
-------
10.0
9.0
I
SI
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cn
c!
!3
cn
8.0
O
m
M
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maximum
7.0
f minimum
6.0
a
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00
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a
00
.
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CO
G
tr1
oo
w
H3
CO
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00
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Z
-------
PART TWO
EXISTING OPERATIONS
46.
-------
The City of San Francisco is divided into three sewerage service
areas, each of which is served by a primary treatment plant. The
three plants are the North Point, Richmond-Sunset and Southeast
Water Pollution Control Plants.
NORTH POINT WATER POLLUTION CONTROL PLANT
The North Point Water Pollution Control Plant, completed in 1951,
serves a dry weather flow area of approximately 9,300 acres. The
tributary area is mostly residential in character but also in-
cludes commercial and industrial developments along the Port of
San Francisco.
The treatment units are arranged in two groups of buildings with
the pretreatment building (screens and grit tanks) and the
influent pumping station and administration building located on
the south side of Bay Street and the preaeration and sedimenta-
tion buildings, postchlorination building and maintenance
building on the north side.
Sewage Treatment
The plant provides conventional primary treatment consisting of
prechlorination, screening, grit removal, preaeration, primary
sedimentation, postchlorination, and dechlorination. Due to the
residential nature of the area where the plant is situated, all
treatment units are housed for odor control.
Emergency Bypass
The original design for the North Point WWTP is for a peak flow
of 150 MG which has an overflow rate of 2200 gal/ft2/day. To
consistently meet NPDES permit limits for settleable solids the
treatment capacity must be lowered to a peak flow of approxi-
mately 135-140 MGD with an overflow rate of 2,000 gal/ftVday
with all the sedimentation tanks in service. The "AC" for the NP
district is about 5,700. Thus at 150 MG peak WWF and 60 MG ADWF,
the remaining 90 MGD is equal to 0.02 inches per hour (iph).
Initially all plants, conveyances and appurtenances were designed
to handle the larger of either ADWF + 0.02 iph rainfall, or PDWF
+0.01 iph rainfall.
Bypassing is accomplished by throttling a 72 by 72-inch inlet
gate to the plant. It has been the practice to throttle depend-
ing upon the number of sedimentation or grit channels in service,
i.e., 27 MG for each grit channel in operation. Efforts are made
to keep all facilities in operation during the rainy winter
months.
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Evaluation of plant records indicate that there have been periods
when the peak flows have reached 185 MGD. This excessive flow
rate resulted in solids washout over the weirs of the sedimenta-
tion tanks.
Plant records also show that during storm weather throttling has
occurred with flow rates in the 80-100 MGD range. This is due to
the clogging of the mechanical bar screens with rags and debris.
The mechanical bar screens are of the straight-line front-clean
front-return type provided with one cleaning rake. To prevent
grit from settling in the screen channels, compressed air ijh
injected through diffuser plates both in front and behind the bar
screens. These screens require constant attention during storm
weather due to the large amount of screenings retained. The
cleaning rake tends to ride over the screenings thereby failing
to engage the bar screen. To prevent this, operators have to use
wooden poles to force the cleaning rake in position as it reaches
the channel bottom.
Recently, operating personnel have attempted to run the pumps at
the 17' level instead of the usual 19'-21' level during storms to
reduce an upstream flooding problem. Because of the loss of
pumping efficiency, pumping is limited to a maximum of 135 MGD
at which rate throttling occurs. This practice is being
re-evaluated.
In case of a power failure a separate 72 by 72-inch inlet gate
closes automatically and all the flow is bypassed to the bay.
The hydraulic system for the inlet and throttling gates operates
from the plant high pressure water system. It takes approxi-
mately 6 minutes for the gates to close fully under emergency
conditions.
•
Screenings
After passing through the throttling sluice gate the flow is
divided into four channels each provided with a 60 by 60-inch
hydraulically operated inlet sluice gate, a 5-foot wide manually
cleaned coarse bar rack and a 10-foot wide mechanically cleaned
bar screen.
The inlet gates are used to select the in-service channel. The
coarse bar racks extend only about two feet below the sewage
surface at design flow. Their purpose is to protect the mech-
anical bar screens from damage caused by large floating debris
which often finds its way into the incoming sewer. The mechani-
cal bar screens run continuously when they are in service.
Screenings are brought up from the bar screen by the cleaning
48.
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rake and deposited into 20 cubic foot capacity storage ducts.
Truck loads of grit and screenings are hauled to the city dump
daily.
Grit Removal
Immediately after passing through the fine screens, the incoming
sewage flows into the grit chambers. Each grit chamber is
directly connected to a screen channel thereby requiring these
two process elements to operate as a single unit.
Each of the four grit chambers is 96 feet long and 10 feet wide.
Chamber depth varies in direct relationship to flow and is
controlled by a 4-foot Parshall flume at the downstream outlet
from the chamber. Each flume measures the flow through the
chamber and operates with free discharge under all hydraulic flow
conditions. A hydraulically operated sluice gate downstream of
each Parshall flume provides a means of isolating each chamber
from the system.
Settled grit is moved to the inlet end of each chamber by con-
tinuous chain flights which operate along the entire bottom of
the chamber. At the inlet end of the chamber a screw conveyer
picks up the grit and raises it to the operation floor level and
dumps it into a sluice trough from where it is flushed to one of
two grit collection sumps. Flights and screw conveyers operate
continuously whenever the grit chamber is in service. Each grit
collection sump serves two grit chambers and is located next to
the outside chamber of each pair.
Normally at least two grit chambers are in service. When the
flow entering the treatment plant reaches approximately 60 mgd a
third unit is manually started by opening its inlet gate. If
flow continues to increase, the fourth unit is placed in service
when the flow reaches approximately 82 mgd. Equal flow distrib-
ution is attempted by throttling the inlet gate to each
combination bar screen-grit chamber unit.
To prevent development of septic conditions in a grit chamber
when it is out of service, compressed air is injected along its
entire length through a system of 3/8-inch diffusers. Compressed
air is supplied by five blowers with a total capacity of 2,500
cfm. In addition to supplying the air required for the grit
chambers, these blowers also supply the air required by the
diffuser plates located on either side of the mechanical bar
screens.
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Grit Disposal
Grit disposal is achieved by pumping the grit from the collection
sumps to grit washers that in turn deposit it into storage bins
from which it is hauled to the city dump.
Adjacent to each grit collection sump is a dry well where two
grit pumps are located. The grit pumps are constant speed units.
Grit pump operation is controlled by a timer. A flow controlled
valve admits water into the sump when the level drops below a
preset elevation.
Grit pumps discharge grit slurry from the sumps into two grit
washers of the reciprocating rake type. Washed and dewatered
grit is dumped into two 300 cubic foot storage bins from which it
is loaded in trucks and hauled away for disposal. Overflow from
the grit washers is returned to the plant influent upstream of
the coarse racks.
Influent Pumping
Sewage leaving the grit chamber Parshall flumes flows via a
10-foot wide concrete channel to the receiving well of the
influent pumping station located in the basement of the admini-
stration building. The structure is of the "wet-well" design
generally associated with the use of constant speed pumps.
The receiving well is divided into two 111 by 43.5-foot sumps,
east and west, with a combined storage volume of about 900,000
gallons. Originally, both sumps were equipped with scum skimming
and grit removal systems. Scum and grit pumps are still used,
but the continuous chain grit scrapers were removed in 1965.
Design modifications for the grit scrapers have been tried but
have not proved successful. The sumps are skimmed daily and the
scum is pumped to the Southeast plant via the cross-town sludge
main. Periodically, the sumps are drained and washed down. The
sand is pumped back to the headworks.
The five raw sewage pumping units are of the mixed flow type and
are located in a 6,000 square foot room approximately 36 feet
below ground level. Four of the units are dual speed with two
having a capacity of 15/30 mgd and two having a capacity of 20/40
mgd. The fifth unit is constant speed having a capacity of 50
mgd. The pumps are arranged so that one 15/30 mgd and one 20/40
mgd pump are connected to each sump while the 50 mgd unit can
pump from either sump through a double gate arrangement. Grit,
scum and sump drain pumps are located in a separate room at a
lower elevation. Each influent pump discharges independently to
a receiving structure on the north side of Bay Street through a
48-inch reinforced concrete pipe provided with a flap gate for
backflow prevention. The scum and drainage pumps discharge into
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the channel that connects the receiving structure with the
primary sedimentation tanks.
Under normal operating conditions both sumps are in service. At
present, raw sewage pumping is controlled manually from the main
control room situated in the administration building. The
automatic control system originally provided was discontinued
shortly after the plant was put in operation apparently due to
surges caused by the starting and stopping of the pumps. Pumps
are started and stopped according to flow variations trying to
maintain sump level variations within a 2 to-3 foot range. Until
recently the sump levels were held within the 19 to 21 foot
range. The sumps will flood at 21.9 feet. To avoid large
changes in output, the scum and sump drainage pumps are also used
for raw sewage pumping.
Preaeration and Primary Sedimentation
Primary settling takes place in six combination preaeration-
sedimentation tanks. Tanks are divided into two groups of three
and housed in separate buildings. Each tank is 233 feet long, 38
feet wide with an average depth of 10.7 feet at the design flow
of 65 mgd. Detention time at design flow is 2 hours.
The first 74 feet of each tank is provided with four longitudinal
rows of air diffusion plates for preaeration of the incoming
sewage prior to sedimentation. At design flow conditions the
detention in this section of the tank is approximately 30
minutes. Compressed air is supplied by five positive displace-
ment blowers rated at 870 cfm each.
Effluent sewage is collected from each primary sedimentation tank
through four metal troughs provided with 90 degree V-notch weirs
on both sides. Each trough has a weir length of approximately
138 feet and extends approximately 86 feet toward the influent
end of the tank.
Each tank is equipped with two longitudinal sludge collectors and
a cross collector for sludge removal. All are of the continuous
chain and flight type. Longitudinal collectors run the entire
length of the preaeration-sedimentation tanks. The longitudinal
collectors transport settled sludge to the effluent end of the
tank where a cross collector moves it to a 5-foot square collect-
ion hopper. The raw sludge pump takes its suction from the
hopper. Both longitudinal and cross collectors run continuously
when a preaeration-sedimentation tank is in service. Surface
scum which accumulates on the surface of the sedimentation tanks
is forced by water sprays into the skimming troughs located 100'
from the influent end of the tanks. This scum is pumped to the
51.
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Southeast plant. The scum from the main sumps is no longer
pumped to the sedimentation tanks. Skimming troughs are of the
tipping trough types and are manually operated. Under normal
conditions, all six tanks are in operation. Each sedimentation
tank is taken out of service every year for inspection and minor
repairs; each tank requires about one week. Every year two
sedimentation tanks are completely overhauled. Over a three year
period all tanks will have been rechained, etc. The average
chain life at the North Point WPCP is about 4 years. It requires
approximately 25 working days to overhaul each tank.
Chlorination
Prechlorination is provided before the flow enters the plant.
This is primarily for odor control. Since the dechlorination
facilities were installed in 1975, the North Point Plant has been
forced to rely on the Chlorination of raw sewage in order to
achieve disinfection of the effluent. The effluent disinfection
system had to be abandoned because the contact time between the
point of chlorine application to that at dechlorination was about
4 minutes.
Chlorine for disinfection is now applied at two points: (1) ahead
of the main raw sewage pump sumps, and (2) ahead of the sediment-
ation tanks.
Chlorine is received in 55 ton tank cars. A 55 ton storage tank
is also provided. Chlorine is fed by 5-8000 Ib/day chlorinators
and evaporators. Chlorine is injected into the sewage by PVC
diffusers. No mixing is provided. Chlorine application is
limited to approximately 150 Ib/day feed rate ahead of the sumps
and 170 Ib/day ahead of the sedimentation tanks. Feed rates
higher than these result in "gassing off" and releasing eye
irritating substances into the administration building or into
the sedimentation tank buildings. The San Francisco Health
Department, the State Health Department, and CAL/OSHA have con-
ducted investigations of this problem.
Contact time through the sedimentation tanks varies from 0.5
hours (allowing for short circuiting) to 4 hours (at low a.m.
flows) .
Chlorination is flow paced controlled. Residuals are run hourly
and the chlorine feed rates manual set. Residuals are very
difficult to control due to the long contact time in the sedi-
mentation tanks.
The bacteriological samples are taken from a channel just down-
stream from the combined flow of the sedimentation tanks.
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Dechlorination
Sulfur dioxide is delivered in 20 ton tank trucks and transferred
into one of two 45 ton storage tanks. Sulfur dioxide is fed by
three 6,000-lb/day sulfonators and evaporators. The sulfur
dioxide is injected into the effluent by PVC diffusers in the
post chlorination building. Control is feed forward residual
flow placed. Chlorine residual tests are performed hourly and
the chlorine feed is adjusted as necessary.
At the present time, liquid chlorine and liquid sulfur dioxide
are being phased out. Sodium hypochlorite for disinfection and
sodium bisulfite for dechlorination will be used. The hypo-
chlorite facilities will consist of five 18,000 gallon storage
tanks, 2 prechlorination feed pumps with a range of 9.6 to 96
gph. Feed rates will be set manually and flow paced controlled.
Two 30-hp flash mixers will be provided at the presedimentation
injection point. No chlorination will be provided before the
main pump sumps.
The dechlorination system consists of three 4042-gallon storage
tanks and 2 feed pumps with a range of 30.6 - 306 gph. Control
will be feed forward/residual/flow paced. Sodium bisulfite will
be injected at the same point as sulfur dioxide.
Effluent Disposal
Plant effluent is measured in a 6-foot throat Palmer Bowlus flume
located in the effluent channel just upstream of the chlorine
contact tank. Turbulence through the flume mixes the chlorine
with the effluent. From the chlorine contact tank the plant
effluent flows over a 14-foot wide weir into an 8-foot reinforced
concrete pipes. Each 6-foot line in turn branches into two'
48-inch cast iron outfalls. These four lines discharge the
effluent into San Francisco Bay approximately 10 feet below mean
lower low water. Two outfalls are suspended under Pier 33 and
two under Pier 35. All outfalls end in a 45 degree elbow about
800 feet offshore.
Solids Treatment
The North Point plant does not include facilities for the treat-
ment and disposal of any of the solids removed during the sewage
treatment process. Sludge and scum removed in the primary sedi-
mentation tanks are pumped six miles through a 10-inch diameter
force main to the Southeast plant. At the present time the
average flow of sludge pumped from the North Point plant to
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the Southeast plant is approximately 850,000 gpd at a solids
concentration of about one percent.
Sludge and Scum Removal
Raw sludge is removed from the sedimentation tanks by six centri-
fugal pumps. Each raw sludge pump transfers the sludge from the
sedimentation tank collection hopper to one of two sumps located
at the effluent end of the preaeration and sedimentation
buildings.
Each raw sludge pump was originally rated at 300 gpm and driven
by a variable speed driver. At present, each pump is run only at
constant speed. Pumps have their own independent discharge pipe-
line to the sumps and each pipeline is provided with a Venturi
flow meter.
Raw sludge pump operation is sequential and is manually control-
led from the sludge control center. During normal operation, two
raw sludge pumping units run simultaneously. When the operator
observes that the sludge is thinning out, he switches to the next
two units.
Occasionally, depending on raw sludge concentrations, a third
unit is put on line. When this occurs, the output of the three
units exceeds the capacity of the disposal pump and sludge
overflows from the transfer sumps to the influent sewer through a
16-inch overflow pipe.
Scum skimming troughs in the three sedimentation tanks in each
sedimentation building are interconnected. Scum collected in the
troughs is flushed to a sump located between the sedimentation
buildings. The skimming troughs can be isolated by closing a
slide gate at the sumps. A scum pumping unit, rated at 300 gpm,
is provided at each sump. Scum from the sumps is pumped directly
to the suction line of the sludge disposal pump which is in
service. The scum removal operation is performed manually and
independently of raw sludge pumping operation. When the scum
pumps are discharging into the sludge disposal pump, its sludge
pumping capacity decreases and the sludge sump level raises.
Solids Disposal
Sludge and scum are pumped to the Southeast plant by two dual
speed sludge disposal pumps having capacities of 1050/600 gpm.
The pumps are interconnected so each can pump from either sump.
A venturi type flow meter is provided in the common discharge
line from the pumps.
Under normal operation, one disposal pump runs continuously at
low speed unless there is an obstruction in the 10-inch force
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main. The pump is speeded up when it is necessary to clear the
line. Once a week, usually on Monday morning, a cleaning tool is
inserted in the force main and the pump is run at high speed
until the tool is recovered at the Southeast plant end of the
line.
Power and Control
Power is supplied by Pacific Gas and Electric Company. There is
no source of emergency power and, as a consequence, the treatment
plant has to be shut down in the event of a power failure.
Control of the treatment process is performed from control
centers located in the pretreatment building, administration
building and sludge control area. Station No. 1 in the pretreat-
ment structure controls the operation of the main and throttling
gates, fine screens, and grit tanks. Raw sewage, grit, scum and
drainage pumps in the influent pumping station are all controlled
from Station No. 2 in the administration building. Preaeration
blowers, sludge collectors and raw sludge and sludge disposal
pumps are controlled from Station No. 3 located in the sludge
control center.
Indicators and recorders for the monitored processes are housed
in the control centers. All treatment process operation, with
the exception of chlorination, is manually initiated from these
stations.
Treatment Plant Personnel
The North Point plant has an operation and maintenance staff of
42. The plant is attended 24 hours a day. The following table
lists the classes and numbers of personnel employed at the North
Point plant during the 1978-1979 fiscal year.
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Class and Number of Operating Personnel
North Point Plant
Class Title Number
Sewage treatment plant superintendent 1
Chief stationary engineer 1
Senior sewage treatment chemist 1
Sewage treatment chemist 3
Senior clerk typist 1
Senior stationary engineer 6
^sia/tion.ary engineer "^ ,:;/,.\ ;r '? 22
<• «
Truck driver 1
Janitor 1
GET A 1
General laborer 4
Total42
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SOUTHEAST WATER POLLUTION CONTROL PLANT
The Southeast Water Pollution Control Plant completed in 1951
serves a dry weather flow area of approximately 10,200 acres.
The plant serves the heavy industrialized area situated in the
southeast corner of the City of San Francisco. The tributary
area also includes some residential developments.
The Southeast plant can be more accurately described as two
separate treatment plants at a single site divided by a public
artery, Jerrold Avenue. One is a conventional primary treatment
plant serving the southeast tributary area. The other provides
solids treatment both to the sludge and scum pumped from the
North Point plant and to the raw sludge and scum removed at the
Southeast primary plant.
Sewage Treatment
The Southeast primary treatment plant consists of prechlorina-
tion, screening, influent pumping, grit removal, preaeration and
primary sedimentation, postchlorination, dechlorination and
effluent disposal. Sewage solids, removed both at the Southeast
and North Point plants, are subjected to gravity thickening,
digestion, elutriation, chemical conditioning, and vacuum
filtration prior to disposal. All the treatment units, with the
exception of the grit tanks, are housed for improved appearance
and odor control. The main plant structures include a headworks
building, two sedimentation buildings, a sludge control building,
administration and maintenance buildings, and a chlorination
building. An effluent pumping station is located at a separate
site between Third Street and Arthur Avenue.
Emergency Bypass
Initially all STP's, PS's and interceptors were sized to handle
the larger of either:
ADWF + 0.02 iph rainfall, or
PDWF + 0.01 iph rainfall
»
whichever was larger.
This rule, however, was not consistently applied and thus each of
the three plants have factors which determine the plant capacity.
The Southeast plant is limited to a peak capacity of between
32-38 MGD by the grit tank-influent system. The facility at an
overflow rate of 2,000 gal/ft2/day has a sedimentation tank
capacity of approximately 70 MGD. During normal operation only
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two sedimentation tanks are in service. The "AC" for the
district is 4,700. Thus at ADWF of 18 MGD and 36 MGD peak, the
18 MGD is equal to 0.006 inches per hour.
The treatment plant capacity during wet weather is based on a
rainfall intensity of 0.02 inches per hour. This provides
sufficient capacity to treat all dry weather flows. Storm flows
in excess of plant capacity are bypassed directly to San
Francisco Bay. Bypassing takes place by throttling the inlet
gates. In case of a power failure these gates close automatic-
ally and all the incoming flow is bypassed to the Bay. Other
conditions that may cause emergency flow diversion are breakdowns
in the bar screens, influent pumps, grit removal tanks or sedi-
mentation tanks.
The last month of record (February, 1980) the inlet gates were
throttled 375.5 hours or an average of 12.9 hours per each day of
the month. Maximum flow recorded during the month ranged from 31
to 42 MGD. Throttling causing flow diversion resulted largely
from rainfall, however, evaluation of the operating records show
malfunction of the bar rakes and also a power failure necessi-
tated flow diversion.
It must be noted that under wet weather conditions the Northpoint
and Southeast plants do not bypass in the conventional sense.
They throttle to the maximum hydraulic capacity available and
thus the combined system overflows at diversion structures
upstream. Bypassing also occurs as the P-S.'s and interceptor
systems are overloaded.
The number of hours and the number of days the influent flow was
limited by throttling the inlet gates increased during each of
the last three years of record. From March 1, 1977 through
February, 1978 the inlet gates were throttled 1087 hours on 81
days. The inlet gates were throttled 1433 hours on 98 days from
March 1, 1978 through February, 1979. For the latest 12 month
period of record from March 1, 1979 through February 1980 the
inlet gates were thro.ttled 1495 hours on 105 days.
The periods of time for limiting the flow to the plant by throt-
tling the inlet gates generally corresponded with the amount of
rainfall, i.e., the greater the amount of rainfall received the
more hours throttling occurred. For example, the inlet gates
were throttled more hours (400) during the month of the heaviest
rainfall (6.2 inches) in January, 1978.
The number of hours and the number of days the head gates were
completely closed preventing any flow to the Southeast plant
ranged from 30.95 hours for the period from March 1, 1977 through
February, 1978 to 95.6 hours for the 12 month period from
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March 1, 1978 through February, 1979. The plant was shut down
for 67.4 hours for the 12 month period from March 1, 1979 through
February, 1980. The days the head gates were completely closed
for varying periods of time ranged from 18 days for the 1977-1978
period to 26 days for 1978-1979 to 25 days during the 1979-1980
period. The complete closing of the inlet gates resulted prin-
cipally from interruptions of utility lines and/or damage to
major treatment units.
Screenings
After passing through an influent chamber where chlorine is
applied, the flow is divided into two channels located approxi-
mately 23 feet below ground level. Each channel is provided with
a 5-foot diameter hydraulically operated sluice gate, a 6-foot
wide manually cleaned coarse bar rack and an 8.5 foot wide mech-
anically cleaned bar screen.
Normally, only one inlet channel is kept in service. The large
floating debris which is retained in the coarse rack is removed
manually by lifting the rack assembly to an operation platform
approximately 3.5 feet below ground level. After passing through
the coarse screens, the incoming sewage flows through the orig-
inal grit chamber and measuring flumes, now abandoned, and the
mechanical bar screens. The mechanical bar screens are of the
front-cleaned, back-return type provided with 18 cleaning rakes.
The screens can be either operated on time control or run con-
tinuously. Continuous is the normal mode of operation during dry
weather, while manual control is the normal wet weather operation
mode. Screenings retained on the bar racks of the mechanical bar
screens are lifted 57 feet to the headworks building roof by the
cleaning rakes and dumped onto a covered belt conveyor. The belt
conveyor carries the screenings to a storage bin from where it is
hauled by truck periodically to the City dump.
Influent Pumping
Sewage leaving each mechanical bar screen flows into a small
separate sump. A constant speed 11,700 gpm pump and a variable
speed 18,500 gpm pump are connected to each sump through a common
33-inch suction line. The raw sewage pumps are located in a 1300
square foot room 36.5 feet below ground level.
The two sumps are interconnected with a sluice gate to provide
standby for each other. Each influent pump discharges indepen-
dently to the pump discharge chamber ahead of the grit removal
tanks. The discharge lines from the constant speed units are 24
inches in diameter while the discharge lines from the variable
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speed units are 30 inches in diameter. Each discharge line is
provided with a flap gate for backflow prevention.
Normally, the variable speed pumps run continuously with speed
changing according to water surface variations in its related
sump. With increasing water level, the constant speed pump
starts and runs until the water surface drops to about 6 feet
above the lower level in the screen channel.
Overflow from sludge thickening and elutriation tanks is returned
to the pump discharge chamber.
Grit Removal
Grit is removed in two rectangular tanks, 40.5 feet long and 10
feet wide with a depth of about 13 feet at the present average
dry weather flow of approximately 19 mgd. These units replaced
the original grit chambers and were designed to operate as
aerated grit chambers. The aeration system has been abandoned,
however, and the tanks now operate as straight-through flow
units.
Sewage from the pump discharge chamber flows through a connecting
channel and enters each grit tank separately through two isolat-
ing cutoff gates. Effluent from the tanks passes over a full
width transverse rectangular weir, free falling into a common
collection channel and then to the sedimentation tanks.
Settled grit is moved to a collection hopper located at the inlet
end of each tank by continuous chain flights which operate in a
trough running along the entire bottom of the tank. Normally,
both grit removal basins are in operation and collectors run
continuously.
Grit Disposal
Grit disposal is accomplished by pumping from the collection
hopper to a separator-dewatering unit. Three grit pumps and two
detritor-dewatering units are included in the system.
The three grit pumps are located directly beneath the grit tank
influent channels. The pumps are motor driven, constant speed
units. Suction lines are manifolded to allow the middle pump to
act as a standby for the other two units.
The dewatering units are mounted on the roof of the headworks
building. Dewaterers are of the detritor type. Overflow from
the dewatering units is returned to the headworks through the
plant drainage system. Washed grit is dumped directly into the
-------
same hoppers used to store screenings and is hauled to the City
dump each day.
Primary Sedimentation
Discharge from the grit tanks normally flows to four combination
preaeration-sedimentation tanks. These units are arranged in
pairs in two separate buildings.
Chemicals are used to improve primary sedimentation efficiency.
Ferric chloride is added in the influent channel upstream of the
bar racks prior to grit removal and the polymer is introduced
ahead of the Parshall flumes, downstream from grit removal.
Records show the ferric chloride dosage range from 25 to 35 mg/1
(as FeCl3) and the feed range for the polymer is from 0.2
mg/1 to 0.6 mg/1.
Originally each preaeration-sedimentation tank was 262 feet long,
37 feet wide and had an average depth of 11 feet at present ADWF.
After modification, the tanks are only 247 feet long, with the
last 15 feet being abandoned.
The first 79 feet of each tank is provided with four longitudinal
rows of air diffusion plates for preaeration of the incoming
sewage prior to sedimentation. In the modified tanks, the
diffuser plates were replaced by spargers. Compressed air for
diffusers is supplied by four centrifugal blowers, each rated at
1520 cfm. Blowers are located on the ground floor of the
headworks building.
Effluent is collected from each primary sedimentation tank
through four metal launders provided with baffles on both sides.
Effluent is collected through a system of vertical pipes located
along the launder bottoms. Each launder has a weir length of
approximately 73 feet, extends aproximately 92 feet toward the
influent end of the tank and discharges through a 30-inch dia-
meter submerged pipe into a common collection channel. Each
discharge pipe is equipped with a backflow preventing flap gate
at its point of discharge. Effluent is collected through a
system of 56, 3-inch vertical pipes spaced at 16 inches and
located along the bottom of the launders. Prior to the modifi-
cation, all preaeration-sedimentation tanks were equipped with
two full length longitudinal collectors and a cross collector for
sludge collection. The cross collector was located at the
effluent end of each tank. Modifications relocated the cross
collector to the approximate middle of the tanks with the result
that each tank has two sets of much shorter longitudinal collect-
ors and the effluent end collector moves the sludge away from
instead of towards the effluent end of the tanks. All sludge
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collectors are driven by a single common motor for each tank.
Drives in the modified tanks are provided with individual speed
adjustable hydraulic motors for each collector.
Scum collected on the water surface of the existing sedimentation
tanks, upstream of the effluent launders, is moved by water
sprays to a tipping trough located just downstream from the
preaeration segment of each tank. Scum rising to the surface in
the vicinity of the effluent launders is isolated from the weirs
by redwood outboard baffles and collected near the tank end wall
by manually adjustable skimming troughs provided for each tank.
Modifications eliminated all existing skimming facilities and
replaced them with two full width scum skimmers located at both
ends of the effluent launders.
The unit at the upstream end of the launders is an electrically
driven, double rubber blade rotating skimmer. The one at the
downstream end is the manually operated tipping trough type.
Under normal conditions, two tanks are in operation. Tanks are
taken out of service at annual intervals for maintenance and
repair.
Chlorination
Chlorination facilities provide for prechlorination of influent
sewage for odor control and hydrogen sulfide suppression and for
post-chlorination of plant effluent for disinfection.
These facilities include 5 hot water type evaporators and 5
V-notch chlorinators each with a capacity of 8,000 Ib per day.
Evaporators and chlorinators are piped to operate as intergral
units. One chlorinator is used for prechlorination and the
others for postchlorination. All facilities are housed in a
separate Chlorination building. Chlorine storage is provided by
55-ton capacity tank cars located adjacent to the Chlorination
building. Liquid chlorine is delivered by these railroad tank
cars to a spur track within the plant site.
Chlorine solution for prechlorination is applied through diffusers
in the effluent channel just outside the sedimentation buildings.
Dosage is set between 250 and 350 Ib. per million gallons.
Dechlorination
Dechlorination of the SE effluent is continuous to provide an
effluent residual of 0.0. SC-2 is delivered to the plant via
20 ton truck loads and stored in a 40 ton steel tank.
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Liquid SO2 is passed through one of three 6,000 Ib/day evap-
orators and one of three 6,000 Ib/day V-notch sulfonators. Gas
then goes by 4" PVC line to the influent channel at the effluent
Booster Pump Station. No mechanical mixing is provided and only
the channel turbulence coupled with the diffuser system is
available for mixing.
Detention time from point of Cl2 application to SC>2 appli-
cation is about 20 minutes at 30 MGD flow. The bacteriological
sample (Coliform MPN) is manually grabbed from the entrance to
the Booster Pump Station just downstream of dechlorination.
The chlorination-dechlorination system is being replaced by
liquid NaOCl and NaHSC>3 systems. The NaOCl system will be
much the same as the existing Cl2 system except the liquid
will be directly added to the diffusers under the effluent weir.
The NaHSC>3 will be added about two blocks upstream of the Bay
Pumping Station and all mixing will by in-channel turbulence.
Effluent Pumping
After passing over a lateral measuring weir, plant effluent is
chlorinated and flows into a 6-foot diameter reinforced concrete
sewer. The effluent sewer is approximately 2,900 feet long and
terminates in the outfall booster pumping station built in 1968.
Effluent flows into two 29.5 by 10-foot sumps, each provided with
a 48 by 48-inch hydraulically operated inlet sluice gate. The
sumps are separated by an overflow chamber that allows effluent
to flow directly by means of a 6-foot pipeline into Islais Creek
when the pumps are inoperative and the effluent cannot flow
through the outfall by gravity. Two effluent pumps are housed in
a 1,050 square foot room located directly above the receiving
sumps, one pump for each sump. This room also houses the station
control panel and the master hydraulic power unit. Pumping units
are motor driven, variable speed mixed flow pumps. Each pump is
capable of delivering approximately 32,000 gpm when operating at
a maximum speed of 555 rpm against a head of approximately 32
feet. Each pump discharges into a 42-inch steel pipe to a
54-inch manifold. Two 30-inch gravity lines also interconnect
the sumps to the 54-inch manifold. The manifold in turn divides
into separate 42-inch and 36-inch lines which cross Islais Creek
as a two-barrel inverted siphon. Pump discharge and gravity
interconnecting lines are provided with hydraulically operated
control valves. One pump is operated as a standby for the other
pump.
When plant effluent can no longer discharge by gravity through
the outfall to San Francisco Bay, the level in the pumping
station sumps rises until a preset elevation is reached at which
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time one pump starts at low speed, the pump's discharge line
control valve opens and the 30-inch gravity interconnecting line
control valves close. Pump speed changes with flow variation to
maintain a constant sump level. When the level drops below the
minimum set elevation, the pump discharge line control valve
closes, the pump stops, the 30-inch gravity interconnecting line
control valves open and the plant effluent again flows by gravity
through the outfall to the bay.
Effluent Disposal
From the outfall booster pumping station, the effluent flows
through the Islais Creek inverted siphon and into a special man-
hole where the plant outfall begins. The outfall consists of
approximately 4,250 feet of 54-inch diameter pipe and a 300-foot
submarine diffuser section. The diffuser section reduces in size
from 54 inches to 16 inches and is provided with 18 T-shaped
diffusers, each with two lateral ports. The vertical section of
each diffuser is about 8.5 feet long and 10 inches in diameter.
The laterals are each 4 feet long and 6 inches in diameter.
Solids Treatment
As stated previously, the Southeast plant is provided with facil-
ities to treat not only the sewage solids removed during the
primary treatment process at the plant site but also the sludge
that originates at the North Point plant. The processes include
gravity thickening, sludge digestion, elutriation, digested
sludge chemical conditioning and sludge dewatering.
Sludge and Scum Removal
Modifications made to the sedimentation tanks completely revised
sludge and scum removal facilities. The modifications included
construction of two sludge and scum removal facilities for these
tanks. The modifications include construction of two sludge
pumping stations and new scum collection system at each of the
tanks. Each pumping station contains two sludge removal pumps
with short suction pipes connecting to each tank's sludge hopper.
The sludge removal pumps discharge into the new scum collection
system troughs and the sludge and scum combination flow by
gravity to two transfer sumps in the new sludge pumping station
located between the two sedimentation buildings. Each transfer
sump is equipped with a multi-bladed turbo-mixer. Two sludge
transfer pumps are provided at each sump and pump the sludge and
scum to the sludge thickeners through a new 6-inch force main.
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Sludge Thickening
Sludge from the North Point plant is discharged directly to the
sludge thickening facilities. The flow is measured through
6-inch Parshall flumes prior to being discharged to the thicken-
ing tanks. The Southeast sludge is discharged directly to #10
digester.
Sludge thickening facilities consist of two gravity separation
type thickening tanks and a thickened sludge pumping station.
Each sludge thickener is 91 feet long by 18 feet wide and has an
average water depth of approximately 12 feet. Tanks are provided
with longitudinal sludge collectors of the continuous chain and
flight type. Collectors run the entire length of each tank. The
longitudinal collectors move the thickened sludge to two separ-
ate scum skimmers. One is a transverse continuous chain and
flight type skimmer located at the inlet end of the tank while
the other is the manually operated tipping trough type located
near the effluent end of the tank. The transverse inlet skimmer
operates intermittently and discharges directly into a large scum
collection sump. Scum at the outlet end of the tank is removed
manually once a day and flows by gravity to the same sump.
Thickening tank overflow is collected in a full width transverse
trough near the outlet end of the thickeners. The overflow flows
through a 22-inch return line to the raw sewage pump discharge
chamber.
A sludge transfer pumping station is located at the inlet end of
the thickeners. The station contains a pump room and a control
room. The control room houses the process control and instrument
panel and has direct access to the thickening tanks walkways.
Two centrifugal pumps are provided in the pump room to pump
thickened sludge to digester No. 10. The pumps are interconnect-
ed to be able to pump from either tank. Pump operation is timer
controlled. Normally, only one pump is used to transfer sludge
to the digester.
Scum from the collection sump is pumped manually at least once a
day to the digesters using the sludge pumps. If either sludge or
scum density is such that it is difficult to pump, the two pumps
are connected in series. This operation is also manually per-
formed. Total solids content of the thickened sludge and scum
averages approximately 4-5 percent.
Sludge Digestion
The Southeast treatment plant is provided with ten digesters
divided in two groups of five tanks, each arranged around a cen-
tral control building. Each tank is 100 feet in diameter with a
side water depth of 20.5 feet and is provided with a floating
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cover. Digesters were originally designed as standard rate
tanks, but four of them, tanks Nos. 6, 8, 9, and 10 have been
converted to high rate operation by the installation of internal
gas mixing systems. Each control building houses sludge circu-
lation and transfer pumps, heat exchangers and control panels.
Present operation involves the normal use of only the four high-
rate digesters with the remaining digesters in the group not
available for standby service. Sludge can also be fed to the
other group of five tanks but this is done only on an emergency
basis. All sludge is pumped to #10.
Sludge from digester No. 10 is pumped to digesters Nos. 6,8, and
9 every day in sequence, approximately three hours to each tank.
Digested sludge overflows 6, 8, and 9 and goes by gravity to the
digested sludge thickening tanks. Thickened digested sludge is
pumped to digesters 4 and 5.
Solids Mixing
Mixing of the digester contents is accomplished by injecting
compressed sludge gas through diffusers located at the tank
bottom. Gas is compressed by three rotary type gas compressors,
to 15 psi for injection into the digesters. Digester contents
are also mixed by the sludge recirculation pumps operating in
conjunction with the heat exchangers and the discharge piping
ring around each high-rate digester.
Gas System
Sludge gas produced in the digestion process is metered and then
goes to the gas compressor building where it is compressed to a
pressure of 28 pounds per square inch. Gas is used for digester
contents mixing and as fuel for two steam boilers. Excess gas is
burned in four waste gas burners. A gas holder provided in the
original installation is no longer used.
Heating System
The temperature of the digestion tanks contents is maintained at
approximately 95°F. Digesting sludge is circulated continuously
through spiral heat exhangers using vertical centrifugal pumps.
Hot water provided by steam-to-water heat exchangers is used to
heat the spiral heat exchangers. Heated sludge may be returned
to any of 20 different points of digesters 6, 8, 9, and 10.
Return points in digesters 6, 8, 9, and 10 are changed in
sequence every hour.
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Solids Conditioning and Disposal
The final phase in the solids stabilization process involves the
preparation of the digested sludge for its ultimate removal from
the treatment plant.
Elutriation
Digested sludge is thickened prior to vacuum filtration in tanks. ,
The tanks are divided into two batteries of four each and are
housed in the filtration building. Each tank is 60 feet long by
16 feet wide with an average water depth of approximately 12.5
feet. Each tank is preceeded by a 4 by 4-foot mixing box. Bpxes
are arranged in pairs and each is equipped with a mechanical
mixer. Each tank is provided with a longitudinal sludge collect-
or of the continuous chain and flight type. Four tanks, the two
intermediate ones in each battery, are also provided with scum
skimmers of the rotating blade type. Sludge transfer and scum
pumps are located in an equipment gallery located underneath the
filter room next to the inlet end of each tank.
Under normal operation, the thickening system is operated on a
two-stage mode. Generally, only one group of tanks is used.
Thickened sludge is pumped to digesters 4 and 5 for holding prior
to vacuum filtration.
Filtration
Dewatering of the conditioned sludge is accomplished by four
vacuum filters located in a large room adjacent to the elutria-
tion tanks. The filters are 11.5 feet in diameter and 16 feet
long. The coil-type units are capable of dewatering 150 tons of
solids per day. Each filter is provided with a small sludge
flocculation tank adjacent to it where coagulants are added prior
to filtration. Filter auxiliary equipment includes three vacuum
pumps, four filtrate pumps, two air blowers and three polymer
mixing and storage tanks. The vacuum filter operation is cont-
inuous except for a washdown and start-up period of two to three
hours every morning. Normally, two of the larger filters are
used.
Digested sludge is fed to the filter from digesters 4 or 5.
Filter cake is carried in belt conveyors and stored in two bins
from which it is trucked away to a land fill. All trucking is
done in the morning hours. Bins have the capacity of storing 100
tons. Present cake production is approximately 15,000 tons per
year at an average solids concentration of 20 percent.
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Power and Control;
Plant power is supplied by Pacific Gas and Electric Company.
There is no source of emergency power, consequently the treatment
plant has to be shut down in the event of a power failure.
Control of each phase of the treatment process is performed at
separate control centers located throughout the plant. There are
control panels in the headworks building, sedimentation build-
ings, chlorination building, sludge control building, thickening
building, digester control buildings, and filtration building.
All treatment process operation is initiated from these control
stations.
Treatment Plant Personnel
The Southeast plant has an operation and maintenance staff of 72.
The plant is attended 24 hours a day- The following table lists
the classes and number of personnel employed at the Southeast
plant during the 1978-1979 fiscal year.
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Class and Number of Operating Personnel
Southeast Plant
Class Title
Number
Sewage treatment plant superintendent
Chief stationary engineer
Senior sewage treatment chemist
Sewage treatment chemist
Senior clerk typist
Senior stationary engineer
Stationary engineer
Apprentice stationary engineer
Truck Driver
Janitor
GET A
General laborer
1
1
1
9
1
6
40
2
1
1
3
6
Total
72
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RICHMOND-SUNSET WATER POLLLUTION
CONTROL PLANT
The Richmond-Sunset Plant was completed in 1939 with a design
peak wet weather flow (PWWF) capacity of 45 mgd. It was enlarged
and modified in 1965 and 1971 to its present design PWWF capacity
of 70 mgd. The plant is located,in the southwest corner of the
Golden Gate Park and serves a tributary area of about 10,600
acres, the development of which is almost entirely residential.
About 60 percent of the total flow to the plant arrives by grav-
ity through two main interceptors. The remainder is pumped from
the Mile Rock interceptor sewer by the Sunset pumping station to
a receiving structure upstream of the plant overflow weir.
Sewage Treatment
The plant provides conventional primary treatment consisting of
screening, grit removal, primary sedimentation, effluent disin-
fection and dechlorination prior to its discharge to the ocean.
Solids separated during settling are subjected to two-staj^l
digestion, sludge conditioning and dewatering before disposal as
a soil filler within the park. All the treatment units are
housed in four buildings: pretreatment, sedimentation, adminis-
tration and digester buildings.
Sunset Pumping Station
The Sunset pumping station is incorporated into the treatment
plant administration building. Incoming flow to the station is
diverted from the 9 by 11-foot Mile Rock sewer through a 3.5-foot
wide channel fitted with coarse bar racks. After passing through
the bar racks, the flow enters a minimum sized receiving well.
Modified and enlarged in 1964, the station contains three ident-
ical motor-driven variable speed centrifugal pumps and has a
maximum capacity of 33 mgd. Each pump discharge is carried
through a separate 20-inch force main to the plant headworks and
each line is provided with a 14-inch magnetic flow meter. The
three pumps are situated in the motor and pump control room
approximately 17 feet below ground level. Access to the receiv-
ing well operating level, where the influent sluice gate and
coarse bar racks are located, is through a sluice gate and coarse
bar racks are located, is through a watertight door from this
room. The hydraulic power unit for controlling the sluice gate
is located in the receiving well.
Pump operation is automatically controlled by variations of sew-
age level in the sump as sensed and transmitted by means of a
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bubbler system. Pumps are programmed to start in sequence. The
lead pump starts at minimum speed and increases its speed as the
sump level rises until it reaches its maximum speed. If the sump
depth continues to increase, a second pump starts and the two
pumps operate at approximately the same pumping speed. In the
event of a continuously rising water surface elevation, the third
unit starts and the operation sequence repeats itself. Provis-
ions are incorporated in the controls to throttle and finally
close the influent sluice gate when the incoming flow exceeds the
combined pumping capacity of the three units. The gate also
shuts down during power failure. Pumps shut down with decreasing
levels in the sump in reverse order to start-up.
Emergency Bypass
Bypassing in the Richmond-Sunset plant occurs at two locations:
The overflow weir of the Sunset pumping station diversion struct-
ure in the Mile Rock sewer (weir crest elevation 0.0 feet City of
San Francisco datum) when the flow exceeds the station capacity
or upon power failure and (2) the overflow weir in the plant
headworks bypass structure (weir crest elevation 21.3 feet) when
the flow exceeds plant capacity. The influent sluice gate
to the Sunset pumping station is throttled during periods of
bypass at the Mile Rock sewer overflow weir. Throttling of the
gate starts when the water surface elevation reaches the level of
the overflow weir. Flows in excess of 33 MGD are bypassed to the
Mile Rock outfall.
Without throttling, bypassing at the headworks overflow weir
takes place when the total flow through the plant reaches
approximately 70 MGD. At this time raw sewage overflows into a
6.5-foot wide channel, passes through a 4-foot throat Parshall
flume and enters a 54-inch diameter bypass line that connects to
the Mile Rock outfall. However, the maximum wet weather flows
are throttled to 47 MGD.
The Richmond-Sunset plant at an overflow rate of 2,000 gal/ft2
with all sedimentation tanks in service has a capacity of approx-
imately 50 MGD. Using 20 MGD ADWF leaves 30 MGD for rainfall.
With an "AC" of 5,000 the equivalent rainfall is 0.009 iph.
Provisions are available to chlorinate the headworks bypassed
sewage. The point of application of the chlorine solution is
immediately downstream from the measuring flume and the dosage
will be varied in proportion to the flow. There are no facil-
ities to chlorinate raw sewage bypassed at the pumping station
diversion structure. Facility personnel state the reason the
bypassed sewage is not chlorinated at this point is that 1300
feet downstream from the plant on the Mile Rock Outfall, the
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', i •
Fulton Street Pump Station diversion structure will also overflow
into the outfall line and no provisions are available to chlor-
inate at this point either.
Screenings __
The incoming sewage flows through a 6 by 5-foot influent channel
past the overflow weir in the plant headworks bypass and is
divided into three 36-inch diameter influent pipes each terminat-
ing in a 5-foot wide mechanically cleaned bar screen channel.
Grit Removal
After passing through the bar screens, sewage flows into a common
channel from which it enters four grit tanks through inlet ports
provided with butterfly gates. The grit tanks were originally
designed as grit and scum removal units, but the scum system was
eliminated when the treatment plant was expanded in 1968. Each
tank is 48 feet long and 10 feet wide at the top, with one wall
sloping at a 45 degree angle to form a V-shaped cross section.
Tanks are divided into four compartments by transverse baffles
that extend approximately two-thirds the depth of the grit
chamber.
Settled grit is moved to a hopper located at the end of the cham-
ber by continuous chain flights which travel along the entire
length of the tank.
The grit tanks have been slightly modified as part of the pre-
treatment building reconstruction project. These changes
included new grit collectors and drives, new inlet butterfly
gates, removal of a 5 by 3-foot portion in each transverse
baffle, removal of a scum baffle at the tank's outlet end, and
relocation of the aeration blowers. Also included is a 4-foot
bypass line which connects to the Mile Rock outfall.
Degritted sewage leaves each tank by flowing over a full width
weir. After passing over the weir, it is once again collected
into a common channel and moved by gravity towards the sediment-
ation building.
Grit Disposal
Material collected in the grit tank hoppers is pumped by four 200
gpm pumps to two grit concentration tanks. From the concentra-
tion tanks grit is lifted by two 300 gpm pumps to two combination
cylcone/classifiers. Grit removed by these units is discharged
into two storage bins. One of these bins is also used to store
screenings. From the bins grit is hauled by truck to the city
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clumg^for disposal. Overflow from the cyclones and classifiers is
returned to the grit tank pumps to discharge to either concentra-
tion tanks and the cyclone-classifier units to operate in series
or parallel in combination with either grit concentration tank.
Primary Sedimentation
Primary settling takes place in five rectangular tanks housed in
the sedimentation building. The first four tanks are identical
units and were originally built as combination flocculation-
sedimentation basins. A fifth tank was added in 1963 and the
other four converted to conventional sedimentation basins. At
that time, flocculation facilities were removed from the existing
tanks. Each tank is now 135.5 by 33.5 feet with an average depth
of 10 feet. Detention time at ADWF of 19 mgd is 2.1 hours. In
January, 1980, the flocculation system was put back into service
to alleviate settleable solids problems. A polymer (Percol 726)
is used alone since trail tests with ferric chloride and polymer
prove unsuccessful. The Southeast and North Point facilities add
salt water (approximately 250 gpm for the S.E. plant) upstream of
the facilities which enhances flocculation. The chloride level
of the influent wastewaters at the Richmond-Sunset plant is low.
This could be elevated by the addition of sea water, however,
piers and other appurtenances are not available. Thus, ferric
chloride used singularly or used in conjunction with a polymer
does not appear to achieve good results until the ionic strength
of the wastewaters are elevated.
Just prior to entering the sedimentation building an adjustable
splitter gate divides the incoming channel flow into two parts.
The splitter is adjusted so that three-fifths of the flow goes to
the east battery of three tanks and two-fifths goes to the west
battery of two tanks. Supernatant return from raw sludge thick-
ening tanks is discharged upstream of the splitter gate.
Automatic sampling takes place immediately upstream of the super-
natant discharge. Incoming flow enters each sedimentation tank
through one opening which is provided with an isolating gate and
baffle.
Settled sewage is collected from each tank through four metal
troughs provided with 90 degree V-notch weirs on both sides.
Total weir length in each trough is approximately 83 feet and
each trough extends about 43 feet toward the influent end of the
tank.
Each of the four original tanks is equipped with two sets of
double longitudinal sludge collectors and a single cross
collector sludge removal. The fifth tank has only one set of
double longitudinal collectors and cross-collector. The
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difference in arrangement is due to the fact that in the original
four units the sludge hopper is located approximately 34 feet
from the tank inlets between the original flocculation portion of
the tank and the settling portion, while in the newer tank the
hopper is situated directly next to the tank inlets. All sludge
collectors are of the continuous chain and flight type.
Longitudinal collectors run continuously, collecting and trans-
porting settled sludge to the transverse valley where the
cross-collector moves it to a small and deep hopper located at
the side of the tank. From this hopper the sludge flows by
gravity to the concentration tanks.
Sludge Collection and Pumping
The original sludge pumping system was replaced by direct pumping
from the sedimentation tanks hoppers to the digesters. Pumping
is timer controlled and by Dorr-Oliver ODS pumps. The original
gravity flow system to the thickening limits have been retained.
Scum which accumulates on the water surface is collected in scum
troughs located upstream of the effluent launders. Each trough
is equipped with rotating skimmers with two rubber blades. Scum
is skimmed by the returning collector flights except in the first
34 feet of the older tanks, where water sprays are used for
skimming. All rotating skimmers are electrically driven.
Under normal conditions, all five sedimentation tanks are kept in
operation. Tanks are usually taken out of service once a year
for routine inspection and maintenance. Sludge and scum lines
are normally backflushed with No. 2 water once a shift.
Chlorination
Chlorination facilities are provided for disinifection of the
plant effluent and Chlorination of raw sewage bypassed over the
new headworks overflow weir. In March, 1980, sodium hypochlorite
and bisulfite facilities replaced the gas Chlorination and sulfur
dioxide dechlorination facilities. The present hypochlorite
system consists of three 10,000 gallon hypochlorite storage tanks
with 3 positive displacement sumps each with a capacity of 25 to
450 gallons/hour. Flow indicator has a maximum range of 600
gal/hour.
Chlorine solution for effluent disinfection is applied through
diffusers in a mixing chamber immediately upstream of the inlet
to the 60-inch effluent line. The rate of chlorine application
is presently controlled in response to variations in sewage flow.
Chlorine residuals are controlled manually. C12 feed is flow
paced. Chlorine contact time is provided by the 60-inch effluent
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line and Mile Rock outfall sewer. At the present average flow of
19 mgd, the contact period is approximately 20 minutes.
Some problems with meters malfunctioning, adjustment of dosage
rates and logistic ordering of the sodium hypochlorite and
bisulfite have been encountered.
Previous chlorination facilities included three hot water type
evaporators and two V-notch chlorinators. Evaporators and
chlorinators were rated at 8,000 Ib. per day- Chlorinators were
fitted with 4,000 Ib. per day orifices. A chlorine storage area
provided space for 24 one-ton cylinders. Chlorinators and
associated equipment and controls were housed in the chlorine
equipment room located at the outlet end of the sedimentation
building. Evaporators, storage cylinders and related piping
occupied a covered open platform adjacent to the chlorinator
room.
Dechlorination
Dechlorination facilities, adjacent to the chlorination room,
consisting of a 40-ton storage tank for sulfur dioxide, two 6,000
Ib/day evaporators and two 6,000 Ib/day sulfonators and control
panel were replaced in March, 1980 by bisulfide facilities con-
sisting of three 4,000 gallon storage tanks with 2 pumps each
capable of delivering 210 gal/hour. Necessary metering and
appurtenances are provided. The diffuser is located downstream
in the Mile Rock Sewer below 48th Avenue and Cabrillo Street.
This gives a chlorine contact time of over 20 minutes before SC>2
solution is added. The dosages are adjusted hourly after the
chlorine residuals have been determined by the operators.
Effluent Disposal
Plant effluent is measured in a 5-foot, wide critical depth flume
located near the junction of the 60-inch effluent line and the
Mile Rock outfall sewer. After flowing through the flume,
effluent drops into a junction vault and enters the outfall
sewer. The 9 by 11-foot outfall discharges into the Pacific
Ocean at the shore line near the entrance to San Francisco Bay,
approximately 7,000 feet north of the treatment plant. The
discharge is surface-shoreline without a diffuser system.
Solids Treatment
As indicated previously, the Richmond-Sunset plant is provided
with facilities for the treatment and disposal of all the solids
removed during the sewage treatment process. Organic solids are
first stabilized in anaerobic digestion tanks, then the digested
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sludge is conditioned by elutriation and coagulant addition, and
finally it is dewatered by vacuum filtration and disposed of as a
soil conditioner.
Sludge and Scum Removal
A new sludge removal system was recently installed. The concen-
tration tanks (thickeners) are being eliminated and the solids
will be pumped directly to the digesters.
Adjustment of pumping rates has proven difficult. At the time of
the inspection, the old thickeners were still being used to
determine the amount of sludge pumped. At the present time the
average raw sludge flow to the digesters is approximately 100,000
gallons per day at a solids concentration of 2.0 - 2.5 percent.
Solids Digestion
Anaerobic sludge digestion takes place in two digesters with a
combined volume of approximately 3,200,000 gallons. One tank is
100 feet in diameter with a fixed cover and the other is 80 feet
in diameter with a gas holding cover. Both digesters are pro-
vided with external heat exchangers for sludge heating and with
compressed gas diffusers for mixing of their contents. The
digester control building, located between the digestion tanks,
houses three sludge circulating pumps, two digested sludge pumps,
two heat exhangers, two sludge gas compressors with their
accessory equipment and both digester overflow boxes.
Digesters are normally operated as two-stage digesters with the
larger tank acting as the primary digester and the smaller as the
secondary. Raw sludge is pumped intermittently into the primary
tank at two points which are alternated daily. Both tanks are
maintained full, so when sludge is added there is an automatic
transfer of primary sludge into the secondary digester and of
secondary supernatant into the elutriation tanks. Sludge from
the primary digester is continually circulated through the heat
exhangers and the temperature maintained at about 95°F.
Normally, the circulating pump draws sludge from only the inter-
mediate level through sampling lines on the control building side
of the digester and returns the heated sludge at the top. The
tank contents of the primary digester are continuously mixed with
compressed sludge gas fed through diffusers located at the tank
bottom.
In the secondary digestion tank, transferred primary sludge is
allowed to stratify and, with the exception of a periodic stir-up
of the tank contents, the digester is not mixed. Secondary
sludge is pumped to the primary tank periodically for a short
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period of time to maintain the desired level of buffering alka-
linity in the primary digester. Digested sludge is withdrawn
from the bottom of both tanks and pumped to the elutriation
system. Digested sludge withdrawal pump operation is manually
controlled to maintain maximum elutriation tank solids level.
Both digesters are sounded periodically to determine grit build-
up and scum formation.
Routine laboratory analysis are made on the sludge of each
digester for pH, alkalinity, volatile solids, percent solids and
temperature.
Solids Conditioning and Disposal
The final phase in the solids stabilization process involves the
preparation of the digested sludge for its ultimate removal from
the treatment plant.
Elutriation
Digested sludge and digester supernatant are conditioned prior to
vacuum fitration in two elutriation tanks. Each tank is 50.5
feet long by 14.7 feet wide and operates at an average water
depth of 9 feet. Each tank is provided with a longitudinal
sludge collector of the continuous chain and flight type and
40-inch diameter influent mixing chamber. Two centrifugal pumps
and a plunger pump are used to transfer sludge from one tank to
the other and to the vacuum filters.
Under normal operation the tanks are run on a counter-current,
two-stage elutriation basis. Digested sludge and/or supernatant
from the digesters flows into the east mixing chamber where it is
mixed and combined with effluent from the west elutriation basin
before entering the elutriation tank. Settled sludge in the east
tank is moved by the chain collectors to a hopper at the tank
inlet end from where it is transferred continuously to the west
mixing chamber. Effluent of the east tank flows over a full
width sharp crested weir and returns to the Mile Rock sewer
upstream of the Sunset pumping station diversion structure.
Settled sludge from the east tank is mixed and combined with
plant effluent in the west mixing chamber prior to flowing into
the west elutriation basin. Settled sludge in the west tank is
moved by the chain collectors to a hopper at the tank inlet end
from where it is pumped to the vacuum filters when these units
are in operation or stored in the elutriation tanks until the
next fitration period. The operation of the vacuum filters is
coordinated with the operation of the digested sludge pumps to
avoid overloading the elutriation system.
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Filtration
Dewatering of the conditioned sludge is accomplished on two
rotary drum vacuum filters. The filters are 8 feet in diameter
by 8 feet long and are provided with Dacron filter media. One
sludge flocculator is located next to the units. Filter auxili-
ary equipment includes two vacuum pumps, two filtrate pumps, one
air blower and ferric chloride chemical storage tank. Sludge can
be fed to the filters by pumping, using one of the transfer
pumps.
Normally, filters are operated three or four days a week for 8 to
12 hours. Ferric chloride is added in the sludge flocculator
just ahead of the filters. Filter cake is collected on horizon-
tal belt conveyor which carries the cake to four bins or, when
available, directly to a truck. From the bins, sludge cake is
loaded into trucks and hauled away. Cake is used in the Golden
Gate Park for filling and as soil stabilizer. Filtrate is pumped
to the elutriation system or returned by gravity to the receiving
well of the Sunset pumping station. Present cake production is
approximately 1,200 tons of dry solids per year at an average
solids concentration of approximately 25 percent.
Control of each phase of the treatment process^ is performed at
separate contol centers located in the pretreatment building;
sedimentation tank area, sludge control room and chlorination
room in the sedimentation building; digester operating building;
and vacuum filter room, elutration tank area, boiler room and
Sunset pumping station motor and control room in the administra-
tion building. Plant power is supplied by Pacific Gas and
Electric Company. There is no source of emergency power.
Treatment Plant Personnel
The Richmond-Sunset plant has an operation and maintenance staff
of 30. The plant is attended 24 hours a day. The following
table lists the classes and number of personnel employed at the
Richmond-Sunset plant during the 1979 fiscal year.
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Class and Number of Operating Personnel
Richmond-Sunset Plant
Class Title Number
Sewage treatment plant superintendent 1
Chief stationary engineer 1
Senior sewage treatment chemist 1
Sewage treatment chemist 3
Senior clerk typist 1
Senior stationary engineer 6
*Stationary engineer 16
(Includes 4 operators for Golden Gate
Park facility)
Truck driver 1
General laborer 3
Total 33
* Operating personnel of the Richmond-Sunset plant also operate
and maintain a one MGD water reclamation plant in Golden Gate
Park. This is an activated sludge facility without solids
handling. .All screenings, primary sludge and waste activated
sludge iJ^returned to the sewer for conveyance back to the
Richmond-Sunset plant.
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