INVESTIGATION OF THE WEST COLLEGE AVENUE
LACUNA, 5EBASTOPOL AND ROHNERT PARK
SEWAGE TREATMENT PLANTS
Surveillance and Analysis Division
United States Environmental Protection Agency
Region IX
Son Francisco, CA 94111
Report No:
EPA-909/2- 4-001
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INVESTIGATION OF THE WEST COLLEGE AVENUE,
LACUNA, SEBASTOPOL AND ROHNERT PARK
SEWAGE TREATMENT PLANTS
FEBRUARY 1974
SURVEILLANCE & ANALYSIS DIVISION
U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION IX
SAN FRANCISCO, CA 94111
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TABLE OF CONTENTS
Section Page
I. INTRODUCTION
A. Statement of Problem 1
B. Purpose of Investigation 1
C. Scope of Study 2
D. Acknowledgements 2
II. FINDINGS AND DISCUSSION
A. West College Avenue STP
1. Physical Description 3
2. Operation and Maintenance 6
3. Monitoring 7
4. Data Evaluation 7
5. Discussion 11
B. Laguna Wastewater Treatment Plant 12
C. Sebastopol STP 16
D. Rohnert Park STP 19
III. CONCLUSIONS AND RECOMMENDATIONS
A. Conclusions 20
B. Recommendations 22
APPENDICES
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LIST OF FIGURES
Number
1. Ultimate BOD Curve for West College 24
Avenue STP Final Clarifier Effluent
2. Reduction and Transformation of 25
Nitrogen Forms at the West College
Avenue STP
3. Flow Diagram for Santa Rosa-West 26
College S.T.P.
4. Schematic - Santa Rosa WWTP 27
5. Schematic - Sebastopol WWTP 28
6. Schematic - Rohnert Park STP 29
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Investigation of the West College Avenue (Santa Rosa),
Laguna, Sebastopol and Rohnert Park Sewage
Treatment Plants
Introduction.
A. Statement of Problem
In a letter of 22 June, 1973, Bill B. Dendy of the
California State Water Resources Control Board
requested assistance from the Environmental Pro-
tection Agency (EPA) in the form of an engineering
evaluation of four sewage treatment plants in the
Santa Rosa Basin. This evaluation was specifically
requested for the West College Avenue, Laguna,
Sebastopol and Rohnert Park sewage treatment plants.
Special emphasis was requested on the West College
Plant to gather information that might be used in
upcoming enforcement action on the part of the State,
The Program Evaluation Branch, Air and Water Divi-
sion, EPA, is currently reviewing a FY 73-74 grant
in the Santa Rosa Plain project. The project con-
cept calls for the abandonment of the West College
Avenue, Sebastopol and Rohnert Park plants and for
wastewaters presently treated by these facilities
to be conveyed to a regionalized Laguna Wastewater
Treatment Plant. However, the cities of Santa Rosa
and Sebastopol believe they can modify the West Col-
lege Avenue and the Sebastopol Plants so as to meet
all water quality requirements at less cost than the
recommended regionalization concept.
B. Purpose of Investigation
The objectives of this investigation are:
1. To evaluate the existing facilities and
determine overall performance with res-
pect to removal efficiencies of each of
the four wastewater treatment plants.
2. To perform an operation and maintenance
evaluation of the four plants.
3. To characterize the influent waste strengths
to the four plants.
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4. To provide the North Coast Regional Water
Quality Board with effluent data from the
four plants for the purpose of making
stream loading determinations from the
respective plants.
C. Scope of Study
A sampling survey was conducted for 3 consecutive
24-hour periods by the EPA on August 21-24, 1973.
Two 24-hour composite samples (2-hour interval sampling)
were collected at 7 stations at the West College
Avenue plant from 10:00 a.m., August 21 through
8:00 a.m., August 23. One 24-hour composite sample
(3-hour interval sampling) was collected each at the
influent and the final effluent of the Laguna, Sebas-
topol and the Rohnert Park plants from 11:00 a.m.,
August 23 through 8:00 a.m., August 24 (see sample
schedule in the Appendix for parameters tested and
location of sampling stations).
The basic purpose of the survey was to characterize
the influent wastes to the four plants and to deter-
mine the subsequent performance and stream loadings
resulting from the plant effluents. Internal samples
were collected at the West College Avenue plant to
determine loading rates and removal efficiency of
various units within this plant. Major parameters
of concern were solids (settleable and suspended),
oxygen-demanding materials, nutrients (nitrogen and
phosphorus) and effluent fecal coliform.
D. Acknowledgements
The project officer for this investigation was Daryl G.
DeRuiter, Sanitary Engineer, Surveillance and Analysis
Division (S & AD). Assistance in the form of plant
evaluation and sample collection was respectively pro-
vided by James R. Jones, Sanitary Engineer, and Daniel
Yee, Chemical Engineer, both of S & AD.
A special word of appreciation is extended to members
of the North Coastal Regional Water Quality Control
Board for their assistance in sampling the four plants
and to the plant operators for their complete coopera-
tion during the survey.
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II Findings and Discussion.
A. West College Avenue STP
1. Physical Description
The Santa Rosa STP located at West College Avenue
is a secondary treatment facility with a design
flow of 18,925 cu m/day (5 mgd). The treatment
process consists of pre-chlorination, comminution,
preaeration, primary sedimentation, trickling fil-
ters, secondary clarification, oxidation ponds, and
post-chlorination. Primary and secondary sludges
are pumped to one of two primary digesters and
ultimately to a sludge lagoon. See Appendix for a
list of design factors. A piping diagram is also
included in the Appendix.
Raw sewage is collected and transported via a sepa-
rate sewer system and enters the plant through a
152.4-cm (60-inch) and a 91.4-cm (36-inch) gravity
line. A raw sewage by-pass to the first oxidation
pond is provided. Process water flows through the
entire plant by gravity with the exception of the
primary effluent and recirculation from the second-
ary clarifier which are pumped to the trickling fil-
ters and the Pond II water which is recycled to
Pond I. Raw and waste secondary sludges are pumped
to the digesters while digested sludge flows by
gravity to the sludge lagoon.
The two influent lines enter a common channel
where chlorine is added for odor control pur-
poses. At approximately 9:00 a.m. the chlorine
is turned on at a rate of 136 kg/day (300 Ib/day),
increased to 181 kg/day (400 Ib/day) at 10:00 or
10:30 a.m., reduced to 136 kg/day at 8:30 or
9:00 p.m., and turned off at 10:30 or 11:00 p.m.
for the remainder of the day.
The raw sewage then passes through a comminutor
and a Parshall flume with a float recorder prior
to the preaeration tanks. Grit is generally
removed from the preaeration tanks only once per
day by means of two water eductor type grit
ejectors in each tank. These water eductors
feed a grit washer with the overflow recycled
back to the preaeration tanks. Approximately
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0.056-0.084 cu m/day (2-3 cu ft/day) of grit is
removed during the summer and 0.336-0.420 cu m/day
(12-15 cu ft/day) during the winter.
The two primary sedimentation tanks (see Design
Factors in the Appendix for sizes and loading
rates) are equipped with a sludge scraping mech-
anism which returns the raw sludge to the influ-
ent end. Cross collectors deliver the sludge to
a cone at the corner of each primary tank where
air-lift pumps transfer the sludge to the sludge
pit located adjacent to the primary tanks. These
air-lift pumps normally operate 6 to 9 minutes
every half hour. Scum is forced to the influent
end by a series of surface sprays and then drained
into the sludge pit with the raw sludge. Raw
sludge is pumped to the digesters by means of
two Moyno rotor-and-stator variable-speed pumps.
The pumping frequency and duration is controlled
by a bubbler level sensor in the sludge pit. The
average influent flow rate for the 2-day survey
of this plant was 2422 cu m/day (6.40 mgd). The
corresponding surface overflow rate is 62.5 cu m/
day/sq m (1532 gpd/sq ft), the weir overflow rate
is 241.6 cu m/day/m (19,480 gpd/sq ft), the
hydraulic detention time is 1.17 hours and the
mean horizontal velocity is 0.476 m/sec (1.56 ft/sec)
Primary effluent is pumped to the trickling filters
by means of one of two available Fairbanks-Morse
propeller pumps, each driven by a 110-hp variable
speed engine. Digester gas is generally used as
fuel for these engines with the option of using
propane or a combination of digester gas and pro-
pane. Each pump has a rated capacity of 68,100
cu m/day (18.0 mgd), but are operated at an engine
speed of 1000 rpm which yields approximately 45,400
cu m/day (12.0 mgd) in one pump and 48,400 cu m/day
(12.8 mgd) in the other pump as indicated by the
meters in the trickling filter influent lines.
22,700 cu m/day (6.0 mgd) is the flow rate required
to revolve each trickling filter arm at a velocity
of approximately 1 revolution per minute. Since
the influent flow rate is somewhat less than 45,400
cu m/day (12.0 mgd), sludge flow from the secondary
clarifier is used as inake-up water. The butterfly
valve on this sludge line is set such that a maxi-
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mum of approximately 22,700 cu m/day (6.0 mgd) will
be returned. During the early morning hours, when
plant influent flow drops below 22,700 cu m/day
(6.0 mgd), additional make-up water is required.
The plant operator then opens a gate valve in the
by-pass structure and returns secondary clarifier
effluent. Because of odor problems in the past,
a chlorinator unit has been installed to inject
chlorine to the combined primary effluent and
recirculated flows in the wet well prior to pump-
ing to the trickling filters. The rate of chlor-
ine addition is 113.5 kg/day, or an equivalent
of 2.50 p.p.m.
Each of the two high-rate trickling filters are
33.56 m (110 ft) in diameter, 1.295 m (4.25 ft)
deep and contain 5.08-8.89 cm (2-3.5 in) rock media,
These filters were not designed to allow flooding
of the media. The filters are operated in parallel
and each receives approximately 22,700 cu m/day
(6.0 mgd) which yields a hydraulic loading rate of
25.8 cu m/day/sq m (27.5 mgd/acre).
Trickling filter effluent flows by gravity into
two secondary clarifiers. Settled sludge is
mechanically scraped to the sludge cones at the
influent end and removed from the clarifiers by
gravity through a telescopic valve from which the
sludge is either returned to the trickling fil-
ters or wasted to the digesters. The surface
overflow rate in the final clarifiers is 57.8 cu m/
day/sq m (1416 gpd/sq ft) and the weir overflow
rate is 232 cu m/day/m (18,700 gpd/ft).
Secondary clarifier effluent flov/s to the first
cell of a two-cell oxidation pond system. These
ponds were designed at 21.2 ha (52.4 acres) at a
depth of 1.22 m (4.0 ft). This yields a total
volume of 271,500 cu m (220 acre-ft) and at the
observed flow the detention time would be 11.2
days. Flow is recirculated from Pond II to the
influent end of Pond I to provide a seeding effect
to the clarifier effluent entering Pond I. One of
two pumps rated at 26,500 cu m/day (7 mgd) each
runs continuously. Occasionally when algal concen-
trations reach relatively high levels, the recycle
pumps are shut down for a time. The reasoning for
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this method of operation is not known and is ques-
tionable in terms of optimum treatment efficiency.
Pond II effluent is chlorinated automatically at
the head-end of a chlorine contact channel which
discharges to the Santa Rosa Creek. The rate of
chlorine addition is controlled by a chlorine
residual detector which is located 1.83 m (6 ft)
downstream from the diffuser. At the time of the
survey, the automatic control was set to maintain
approximately 7 p.p.m.
The two digesters (see Design Factors in Appendix
for sizes and design criteria) are operated in
parallel. Each is equipped with sludge heating
and recirculation, floating gas collector covers
(with gas storage in digester No. 2) and gas mixing
by means of 8 gas shear boxes on a 10-foot diameter,
Each digester is fed alternately on 2-day cycles.
Just prior to loading, the gas mixing is terminated
to allow the solids to settle, and the settled
sludge is drained (generally from the center of the
digester) by gravity to the sludge lagoon. Just
enough volume is drained to allow for loading for
the 2-day cycle (approximately 15.14 cu m (40,000
gal)). The hydraulic detention time is thus approx-
mately 43 days. Several loading, heating, recircu-
lating and draw-off options are available to the
operator. The total digester gas accumulation is
metered before separation into use gas and excess
gas. The excess gas is disposed of by means of a
waste gas burner. The use gas passes through
a scrubber and use gas-meter before utilization
by the main pump engines and the heat exchangers.
2. Operation and Maintenance
Personnel associated with the operation and main-
tenance of the West College Avenue sewage treat-
ment facilities are identified as follows:
NUMBER TITLE DUTIES
1 Superintendent Organization and
supervision of all
city sanitation
facilities
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1 Chief Operator Supervision of sew-
age treatment plant
4 Operators Routine operation
1 Relief Operator and maintenance of
sewage treatment plant
1 Maintenance Man Repair equipment
1 Lab Technician Performs lab analyses
for effluent monitor-
ing and process control
24-hour operation is provided with one operator on
duty during each shift. The chief operator, main-
tenance man, and laboratory technician are normally
present during the day shift. The plant grounds and
equipment are generally well-groomed and well main-
tained, and most of the equipment is functioning
reliably. Routine maintenance work is performed
regularly and special maintenance problems are taken
care of as they arise.
3. Monitoring
The monitoring and reporting program and the waste
discharge requirements adopted for the West College
Avenue plant by the North Coast Regional Water Qual-
ity Control Board are attached in the Appendix.
Monthly operating reports are prepared by the plant
personnel. These reports are relatively complete
with respect to plant performance as the monitoring
and reporting program requires and also contains a
sufficient amount of plant operating information.
Noticeably absent, however, are the fish bioassay
data required according to the monitoring and report-
ing program.
4. Data Evaluation
All data collected during this survey are included
in the Appendix to this report. The plant influent
concentrations for the parameters measured are
normal for municipal wastewaters.
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The settleable solids values in the primary clarifier
effluent during the peak-day flows were 0.45 ml/l/hr
with an average value for the two-day survey period
of 0.26 ml/l/hr. The suspended solids removal and
the COD removal efficiencies were 56% and 27% res-
pectively. These performance values are less than
would be expected from a properly loaded and operated
primary system. However, since the primary tanks are
followed by a secondary system, these performance
figures should not be of too much concern.
The organic loading rate to the trickling filters
(not including recirculated flow) was 2.785 kg COD/
day/cu m (172 Ib COD/day/1000 FTs), or an estimated
1.49 kg BOD5/day/cu m (92 Ib BOD5/day/1000 FT3).
Neither the hydraulic loading rate nor the organic
loading was excessive for high rate trickling fil-
ters. The BODs removal efficiency of 73.4% through
the trickling filters and final clarifiers was
slightly better than that expected using the empir-
ical design formula developed by the National
Research Council (see the trickling filter evalua-
tion in the Appendix). The overall removal effi-
ciencies (raw influent through the final clarifiers)
for suspended solids and 3005 were 77.9% and 80.6%
respectively.
A 24-hour composite sample of the secondary sludge
yielded a suspended solids concentration of only
123 mg/1. This is a very low value for settled
sludge from a trickling filter system. It was
observed that sloughing from the trickling filters
was minimal and the solid material in the filter
effluent was largely comprised of fly larvae. It is
suspected that either the chlorine addition to the
trickling filter influent is hindering the growth
of bacterial organisms or the grazing organisms are
ingesting the biomass almost as rapidly as it is
produced or a combination of these two phenomena.
Whatever the cause, the sludge production in the
secondary treatment system is significantly below
normal.
Pond I and Pond II are approximately 81,400 sq m
(20.1 acres) and 130,700 cu m (32.3 acres) respec-
tively. The surface organic loading rate based on
the composite samples to Pond I was 11.06 gm/day/
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sq ra (98.7 Ib/day/acre). This loading rate seems
quite high for a facultative pond and it is felt
that recirculation from Pond II to the influent of
Pond I is beneficial to the condition of Pond I.
The BODe increased from 37 mg/1 at the influent of
Pond I to 75 mg/1 (unfiltered sample) at the efflu-
ent of Pond II. The dissolved 8005 at the Pond II
effluent was 46.5 mg/1 (filtered sample).
A portion of this increase in dissolved BOD5 may
be attributed to conversion of solid material to
dissolved organic material at the bottom of the
ponds. But probably more significant is the BOD5
introduced to Pond II from the sludge lagoon super-
natant. Chlorine is added to the Pond II effluent
at such a rate that it reduced the BODs from 75 mg/1
to 21 mg/1 in the unfiltered sample and from 46.5 mg/1
to 8.5 mg/1 in the filtered sample.
An ultimate BOD analysis was performed on an unfil-
tered final effluent sample (after chlorination).
The results of this test can be seen in Figure 1.
The second stage demand may be due strictly to the
nitrogenous demand or a combination of the nitro-
genous demand and the demand attributed to the
decomposition of algae.
The levels of inorganic and organic phosphorus are
relatively unchanged throughout the treatment proc-
ess. The reduction and conversion of nitrogen can be
observed from Figure II. The decrease in total
nitrogen observed between the influent and final
clarifier effluent was probably due to removal of
sludges. Essentially no nitrification occurs
through these stages. The most significant de-
crease in nitrogen expectedly occurred in the sta-
bilization ponds. It is hypothesized that ammonia
nitrogen was utilized in the synthesis of algal cells
and subsequently lost to the atmosphere in the form
of nitrogen gas. Some nitrification of ammonia to
nitrite occurred in this phase of the treatment proc-
ess, but very little nitrification to the nitrate
level. The most surprising aspect of the nitrogen
transformations was the decrease in organic nitrogen
in the ponds. It is suspected that this decrease
occurred because the recirculation from Pond II to
Pond I was shut off during the survey, thus reducing
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the rate of algae production. This reduction in algal
concentration when recirculation was terminated was
significant enough to be detected visually. The oxi-
dation pond effluent was quite high in nitrogen, espe-
cially ammonia and total nitrogen. Little change in
nitrogen form or concentration resulted from chlori-
nation except that some of the nitrite was oxidized to
nitrate nitrogen.
The effects of filtering on nutrient concentrations
in the final effluent can be seen in the following
table:
FINAL EFFLUENT, mg/1
Parameter Unfiltered Filtered
NH3-N 6.0 5.5
N02-N 1.2 1.1
N03-N 2.2 1.85
Organic N 5.5 1.6
Total N 14.9 10.05
Ortho-P 10.45 8.95
Total P 15 14
Filtering the oxidation pond effluent reduced the
organic nitrogen by 51% and the total nitrogen by
20%. The total nitrogen concentration in the Pond II
effluent was 14.7 mg/1 before filtering and 11.8 mg/1
after filtering. Filtering the final effluent reduced
the organic nitrogran by 71% and the total nitrogen
by 31.5%. The total nitrogen concentration in the
final effluent was 14.9 mg/1 before filtering and
10.05 mg/1 after filtering.
The fecal coliform concentrations of less than
67/100 ml were well under the level of not more
than 200 per 100 ml (geometric mean of 30 consecu-
tive days) specified under the newly accepted defi-
nition of secondary treatment.
The overall plant performance is summarized in the
following table:
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INFLUENT EFFLUENT
PARAMETER CONCENTRATION CONCENTRATION
(mg/1) (mg/1) % REMOVAL
Suspended Solids 196.5 35.582.0
B.O.D.5 190 21 88.9
COD 355 96 73.0
NH3-N 21.5 6.0 72.1
N02-N 0.045 1.2
NOa-N 0.11 2.2
Organic N 7.5 5.5 26TT
Total N 29.1 14.9 48.7
Ortho P 7.25 10.45
Total P 14 15
5. Discussion
Infiltration in the sewer system is a significant
problem of this facility. The highest average daily
plant flow for a given month reported during the
1972-73 fiscal year was 44,300 cu m/day (11.72 mgd)
and occurred during February, 1973 as compared to
25,500 cu m/day (6.73 mgd) during July, 1972. It
is likely that actual wastewater flows exceed the
metered flows due to a by-pass to Pond II which is
located in the influent line. However, if flow
exceeds the capacity of the main pumps, or if a
breakdown occurs, two options are available: All
or part of the raw influent can be by-passed to
Pond I, or the flow can be sent through the pri-
mary sedimentation tanks and then by-passed to
Pond I. Thus the raw sewage receives treatment
from the stabilization ponds before reaching Santa
Rosa Creek.
Home development in the near proximity of the plant
site has imposed significant problems associated
with odors in the past. The practice of chlori-
nating the influent flow to the trickling filters
for odor control purposes could prove to be quite
hazardous if not monitored frequently. Malfunction
of the chlorination equipment or over-chlorination
due to a significant period decrease in chlorine
demand could cause a severe kill of the trickling
filter bacteria which are essential to reduction of
BODs through this process. Chlorination of this
type can also prove to be quite costly.
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More effective treatment would probably be achieved
by recirculating clarified effluent to the filters
rather than settled sludge. The principle of the
trickling filter process is to convert soluble BOD
to solid material which can be settled out and removed
in the final clarifiers. Returning the solids serves
no real purpose and often results in excessive load-
ings to the filters. Returning the clarified effluent
would result in greater contact time of the dissolved
organic material with the active organisms in the
filter and would result in higher organic removal
efficiencies. This in turn would reduce the loading
rate to the oxidation ponds.
The effluent launders in the final clarifiers extend
very close to the turbulent zone at the influent end
of the clarifiers. The solids carry-over was signi-
ficantly higher at the influent end of the launders
than at the effluent end. Surface skimmers were
noticeably absent from the final clarifiers.
Operation of the digesters in series might prove to
be more effective than parallel operation. Allowing
the secondary digester to operate without mixing
should result in better solids separation which
means less draw-off volume to the sludge lagoon.
Supernatant could be returned to the plant head-
works .
It is suspected that the return of sludge lagoon
supernatant to Pond II has a severe effect on the
lagoon performance and"thus final effluent quality.
This supernatant contains a high amount of organic
material which will not be completely oxidized or
converted to algal cells in the relatively short
retention period of Pond II.
B. Laguna Wastewater Treatment Plant
The Laguna Wastewater Treatment Plant was constructed
in 1967 by the City of Santa Rosa in cooperation with
the County of Sonoma. The facility, an activated sludge
treatment plant, was designed and built with an initial
capacity of 9460 cu m/day (2.5 mgd) and provisions for
an ultimate capacity of 75,700 cu m/day (20mgd). During
the survey, wastewater flow averaged about 7,600 cu m/day
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(2.0 mgd) which was indicative of current weather flow.
The plant as shown in Figure No. 4 consists primarily of
a comminutor, aerated grit removal tanks, primary sedi-
mentation tank, activate sludge unit, secondary sedimen-
tation tanks, aerobic digester and chlorination unit.
The headworks, consisting of the comminutor, raw sludge
pumps and sewage flow meter, is located in the bottom
of an 11 meter (35 ft) deep influent structure. The
comminutor may be by-passed by using one of two manually
cleaned bar screens. Raw sludge is pumped to the grit
chamber through the influent flow meters by two variable
pumps each with a rated capacity 56,800 cu m/day (15 mgd)
at a static head of 11 meters (35 ft). An aerated grit
chamber, which is also refered to and acts much like a
preaeration tank, has a detention time of 1.1 hours at
design flow.
Three standard design rectangular primary clarifiers were
built with the initial construction. In the initial stage
only one of the clarifiers is being used as a primary clar-
ifier while the other two are being used as final clari-
fiers. Each clarifier has a surface area of 256 sq m
(2755 sq ft) and a volume of 694 cu m (24,800 cu ft). At
design flow, the overflow rate for the single primary
clarifier is 37.1 cu m/day/sq m (910 gal/day/sq ft) and
the detention time is 1.8 hours. These loading rates
seem adequate. At the time of the inspection the unit
appeared to be operating in a satisfactory manner.
As with the clarifiers, the aeration tanks are of a
conventional design but are being used in a modified
nature in the initial phase of plant growth. Of the
two existing, parallel aeration tanks, one unit is
being used for activated sludge while the other is
used for aerobic digestion. In future stages of
plant growth, anaerobic digestion will be used,
releasing the present aerobic digester for use as
an activated sludge unit. The activated sludge
unit has a volume of 3060 cu m (108,000 cu ft) with
a design organic loading of 0.368 Kg BOD/cu m/day
23 Ibs BOD/1000 cu ft/day). The units are quite
flexible and may be operated in any one of several
modes. Currently the unit is being operated in a
modified contact stabilization regime. The return
sludge is introduced at the south or head end of the
unit with the raw sewage introduced about one-quarter
of the way through the unit. Mixed liquor suspended
solids is maintained at approximately 1000 mg/1 with
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a solids retention time of about 5 days.
As stated earlier, final clarification is performed
in two of the initially constructed primary clari-
fiers. The two clarifiers with a total area of
512 sq m (5510 sq ft) give an overflow rate of 18.5
cu m/day/sq m (453 gal/day/sq ft) and a detention
time of 3.6 hours at design flow, both well within
accepted design standards. At the time of the inspec-
tion, clarification was quite satisfactory with very
little carry over of suspended solids.
Primary and final clarifier sludges are stabilized in
an aerobic digestion tank. As the plant is enlarged,
the aerobic digester will be converted to an activated
sludge unit and anaerobic digestion will be employed.
Digested sludge is spread on drying beds at the site
and plowed into the ground after drying. Because of
limited area of drying beds, the operator feels that
he could not handle more sludge than is currently gene-
rated without incurring odor problems.
Final clarifier effluent is chlorinated at the
effluent junction structure. Two chlorinators,
one used as standby, are each capable of deli-
vering 910 kg/day (2000 Ibs/day). As no chlorine
contact chamber was built in the initial phase of
construction, chlorine contact time was obtained
by backing up the effluent in the effluent outfall.
At design flow the theoretical chlorine contact time
is 41 minutes. The plant effluent is discharged to
the Laguna de Santa Rosa.
Dry weather"flow through the plant is averaging about
7570 cu m/day (2.0 mgd). At these flows, the Laguna
plant has had little problems meeting most discharge
requirements established by the Regional Board. A
review of plant records for the past year indicates
they are consistently discharging treated effluent
with BODs averaging about 5 mg/1 and suspended solids
averaging about 15 mg/1. Each is below the median of
30 mg/1 required for both parameters. Settleable
solids are normally no more than trace. However,
total coliform counts average about 20 MPN/100 ml,
greater than the required median of 2.2 MPN/100 ml.
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Additionally, chlorine residuals, which average about
8 mg/1, exceed the required maximum of 0.1 mg/1. This
is undoubtedly a result of poor mixing and will be
remedied by installation of a chlorine contact basin.
Results of E.P.A. 24-hour, flow weighted composite
sample are comparable t.o Laguna STP data indicating
BODs of 2 mg/1, suspended solids of 7 mg/1 and coli-
form count of 6.0 MPN/100 ml (See Table 2).
With the current overloading problem at the West Col-
lege Plant, one proposal to solve the problem is to
divert a portion of the flow for treatment to the
Laguna Plant. Even though the Laguna Plant is designed
for 9460 cu m/day (2.5 mgd), it is possible that
with tight controls it could be pushed to treat a
greater flow and still meet discharge requirements.
Due to the nature of the process, precise predictions
are difficult to make. However, using upper limits of
accepted operational parameters and loading rates, a
reasonable approximation can be established.
By increasing overflow rate in the primary clarifier
from 37.1 cu m/day/sq m {910 gal/day/sq ft) for design
to 61.2 cu m/day/sq m (1500 gal/day/sq ft) a flow
of 15,600 cu m/day (4.1 mgd) might be handled.
Assuming 63 per cent removal of BOD^ in the primary
clarifier and 1,200 kg/day/cu m (75 lbs/day/1000 cu ft)
for a contact-stabilization regime, a flow of 26,500
cu m/day (7.0 mgd) might be treated in the one aeration
tank. As a check, a minimum detention time of 3 hours
would give a slightly higher flow of 27,200 cu m/day
(7.2 mgd). For final clarification, if the overflow
rate was raised from 18.6 cu m/day/sq m (455 gal/day/
sq ft), to 40.8 cu m/day/sq m (1000 gal/day/sq/ft),
the flow through the unit could be raised to 20,800
cu/m/day (5.5 mgd). It therefore appears, that of
the major units, the primary clarifier would be the
controlling unit with a flow of 15,600 cu m/day. Other
minor units, pumps and piping appear to be adequate to
accept that flow. It is possible that an interim solu-
tion to increase clarifier capacity might be the instal-
lation of settling tubes or modules in the clarifiers
to increase their capacity. The only readily apparent
limitation might be the lack of drying beds to adequately
handle sludge from the aerobic digester.
-15-
-------
In conclusion, the Laguna Wastewater Treatment Plant is
operated and maintained in a satisfactory manner. Plant
personnel are adequately trained and capable of operating
this plant. The plant is relatively new and the equipment
is in excellent shape so there is no apparent reason why
they should not be able to adequately treat to design flows
and possibly up to 60 per cent greater than design flows.
C. Sebastopol STP
The Sebastopol Sewage Treatment Plant was last modified
in 1949. The plant is located east of the City of
Sebastopol on the west bank of the Laguna de Santa Rosa
River. The plant consists of a bar screen, two primary
clarifiers, trickling filter, digesters, sludge drying
beds, oxidation ponds and a chlorine contact basin.
(See Figure 5). The treatment plant was designed theo-
retically to provide secondary treatment at a flow of
2650 cu m/day (0.7 mgd).
The treatment facility serves approximately 1800 sewer
hook-ups with a total population of approximately 4000.
No influent flow rate data are available; however, a
meter at the chlorine contact basin measures the efflu-
ent flow. Dry weather effluent flows normally range
from 1320 cu m/day (.35 mgd) to 1510 cu m/day (.40 mgd).
Assuming an evaporation rats of 1.2 m (4 ft) per year,
evaporation in the oxidation ponds would account for
another 190 cu m/day (0.05 mgd) to the influent flow.
The wastewater is principally of domestic origin.
The headworks, contained in a small three-story building,
consist of a bar screen and raw sewage pumps. Located in
the basement, the bar screen must be manually cleaned.
Raw sewage pumps #1, #2 and #3 pump from a sump, which
also receives recycled trickling filter effluent.
Pump #1, rated at 2180 cu m/day (0.576 mgd), pumps to
the No. 1 Clarifier. Pumps #3 (rated at 2180 cu m/day
(0.576 mgd)) and #2 (rated at 1635 cu m/day (0.432 mgd))
pump to the No. 2 primary clarifier. The #4 pump, which
by-passes the bar screen to pump directly to No. 1 clar-
ifier , is not now being used because of constant plug-
ging problems. Screening this flow of wastewater to
pump #4 is difficult because it is pumped directly from
a manhole upstream from the headworks building. Thus,
the total pumping capacity of the headworks .is 5450
-16-
-------
cu in/day (1.44 mgd). With the varying flows, the pumps
phase on in the following order: (1) No. 3, (2) No. 1
and (3) No. 2. When there is only enough flow to keep
No. 3 pump operating, there is no flow to Clarifier No. 1.
The primary clarifiers, both Dorrco Squarex Clarifiers
Type AZ, are of a square design with spring-loaded bot-
tom scrapers. The No. 1 Clarifier is 7.9 m (26 ft)
square and 2.1 m (7 ft) deep with a total volume of
134 cu m (4740 cu ft). The No. 2 Clarifier is 9.1 m
(30 ft) square and 2.4m (8 ft) deep with a total vol-
ume of 204 cu m (7200 cu ft). As noted above, the
flow to the clarifiers is not equal or consistent. All
flows up to 2180 cu m/day go to No. 2 Clarifier, with a
maximum load of 26.3 cu m/sq m/day (640 gal/sq ft/day)
which is within a range of reasonable loadings. However,
under dry weather conditions, the No. 1 Clarifier is
normally quite under-loaded with periods of 12 hours or
more at night with no flow at all. During the inspection
period, neither unit appeared to be working satisfacto-
rily. Floating material was present with bubbles rising
to the surface indicating anaerobic conditions and
poor sludge removal. Both units had been drained and
cleaned in the past year but the operator had no know-
ledge of the present condition of the sludge scrapers.
The trickling filter is 20.7m (68 ft) in diameter and 1 m
(3 ft) deep. Hydraulic loading without recycle to the
filter is about 4.5 cu m/day/sq m (110 gal/sq ft/day)
while the organic loading is about 360 g BOD/day/sq m
(74 Ibs BOD/day/sq ft). These rates are high for a con-
ventional trickling filter which should be in the range
of 1.0 to 4.0 cu m/day/sq m for hydraulic loading and
80 to 400 g/day/cu m for organic loading. A variable
portion of the flow, perhaps up to one-half of the influ-
ent, is recycled at different times during the day. Dur-
ing the night-time hours, usually from about 11:00 p.m. to
8:00 a.m., the total flow is recycled. The recycle, all
manually controlled, is for the most part to maintain
enough water in the system to power the filter distribu-
tion arm. The distributor arm has, due to many years of
use, become quite deteriorated and will need to be
replaced soon. The unit still has the original mercury
seal, which as a result of state regulations, will have
to be replaced. At the time of the inspection, there
-17-
-------
appeared to be a viable bacterial growth on the media.
The trickling filter effluent flows .to four unmixed oxida-
tion ponds. The ponds, all approximately 1.5 m (5 ft)
deep, cover a total of approximately 2.0 ha (5 acres).
They are operated in series with a theoretical detention
time of approximately 20 days. However, to reach a com-
monly accepted organic loading of 220 kg/day/ha (20 Ibs/
day/acre), approximately 87 percent of the 360 kg
(800 Ibs) of influent BODg, would need to be removed
through the primary clarifiers and trickling filters.
This seems unlikely considering the condition of the
plant and in light of the lack of final clarifier.
Built into the final oxidation pond, using baffles, is
the chlorine contact basin. At average flow the theo-
retical contact time would be about one hour. The only
measurement of plant flow is at the influent to the
contact basin. The effluent goes directly to the Laguna
de Santa Rosa.
Treatment of sludge from the primary clarifiers is accom-
plished with a set of two-stage digesters. The primary
digester is heated and mixed with a capacity of 174 cu m
(6280 cu ft). At time of the inspection, the unit had
just been cleaned and was ready to be put back into oper-
ation. The secondary digester is an unmixed, unheated
unit of 222 cu m (8000 cu ft). Digested sludge is dried
in sludge drying beds on the site. No data is available
to evaluate operations but the units appear operable and
in satisfactory condition. Assuming 50 percent removal
in the clarifier, the organic loading to the digesters
would be around 0.45 kg/day/cu m (0.028 Ibs/day/cu ft)
which is well below accepted loading factors of 1.6 to
6.4 kg/day/cu m (0.1 to 0.4 Ibs/day/cu ft).
The plant is operated and maintained by one primary oper-
ator with an addition maintenance man to cover on days
off and assist when needed. The operator, who lives in
a house adjacent to the site, has been at the plant quite
a few years. Considering the poor condition of the plant,
he is able to keep the plant operating in an acceptable
manner, but has little formal training or knowledge of
treatment plant processes. Because of their age, the
condition of most of the plant units is quite poor and
requires more time than would normally be needed for main-
-18-
-------
tenance. Several operational procedures, the recycle of
trickling filter effluent for one, are not automated and
require manual operation. This requires the operator to
be available to make plant adjustments as flows fluctuate,
particularly as the flow drops significantly during late
evening hours.
The treatment facilities and oxidation ponds are located
on the flood plain of the Laguna de Santa Rosa. Flooding
which occurs almost annually with big storms causes oper-
ational problems as well as limits access to the plant.
During the big floods of 1955 and 1964, the plant was
almost completely inundated. A high water mark on one
of the doors indicates the water level as about 2 meters
(6 ft) above the pond embankments and about 1 meter (3 ft)
above the trickling filter media, obviously making both
useless.
D. Rohnert Park STP
The Rohnert Park wastewater treatment facility serves
the cities of Rohnert Park, Cotati and the Sonoma State
College with a total population of approximately 11,000.
The treatment of wastes at the present site will be dis-
continued in the next several years with the completion
of an interceptor line to transport the waste to the
Laguna Sewage Treatment Plant. Existing facilities will
then be used as an equilization or flow surge facility.
These existing surge facilities were designed and built
as a demonstration project by Yoder-Trotter-Orlob and
Associates under a grant from EPA in 1972.
Major treatment units in the plant are a comminutor, flow
metering device, primary sedimentation tank, digester,
sludge drying beds, equilization pond, oxidation pond
and chlorination facilities. The plant is capable of
giving primary treatment to approximately 1890 cu m/day
(0.5 mgd). Dry weather flow averages about 3780 cu m/day
(1.0 mgd) with a daily range from 1890 cu m/day (0.5 mgd)
to 6050 cu m/day (1.6 mgd). The maximum hydraulic capa-
city is 22,700 cu m/day (6 mgd). Treated wastewater is
discharged to Hinebaugh Creek which flows to the Laguna
de Santa Rosa.
The headworks facilities, which include the comminutor
-19-
-------
and the flow meter are capable of up to 22,700 cu m/day
(6 mgd). However, the rectangular clarifier with a
capacity of approximately 188 cu m (6700 cu ft) is
capable of treating only 1890 cu m/day (0.5 mgd) which
is almost always exceeded. The anaerobic digester is
an unmixed, unheated unit operated at about 20°C (68°F)
and 20-day retention. Because of the heavy overloading
and short retention time at the existing temperature,
operational problems have been present since initial
start-up of the unit in 1971.
The surge facility, a sedimentation-equilization basin
with a surface aerator, has a capacity of 2840 cu m
(0.75 MG). This offers a 3-hour retention time at the
maximum design flow of 22,700 cu m/day (6 mgd). Pool
sweeps, used to keep solids suspended with water jets,
were evaluated as part of the demonstration grant
and appear to be infeasible in this situation. The
oxidation pond, as the plant is converted to an equi-
lization facility, will be used only during wet
weather as a storage unit. The pond area is 4.86 ha
(12 acres) with a depth of 1 meter (3 ft). At present,
it is heavily overloaded at about 1750 kg/day/ha (150 Ibs/
day/acre), and flow appears to short circuit through the
pond. Chlorination facilities and a chlorine contact
basin are located in the southeast corner of the pond.
Effluent is discharged directly to the Hinebaugh Creek,
a tributary to the Laguna de Santa Rosa.
Even though the plant is heavily overloaded, the oper-
ator is doing as well as can be expected, and in general,
the facilities are operated and maintained in an accept-
able manner. With the exception of the clarifier and
digester which are heavily overloaded, no significant
operational problems were evident. The single operator
is quite competent and has a good knowledge of treatment
plant processes. The plant is manned 8 hours per day,
5 days per week and has an adequate alarm system to warn
of any operational problems when the operator is not
present.
Ill Conclusions and Recommendations.
A. Conclusions
1. Wastewater flows generated by the City of Santa Rosa
exceeds the available treatment plant capacity. This
-20-
-------
phenomemon is especially severe during the wet weather
months.
2. During the 2-day survey of the West College Avenue STPf
the plant was meeting federal standards for secondary
treatment with respect to BODs and fecal coliform.
However, the effluent suspended solids were not within
the secondary treatment requirements. The relatively
high concentration of suspended solids in the final
effluent can be attributed to the algal content of
Pond II effluent.
3. Filtering the final effluent from the West College
Avenue STP was not highly effective in removing the
nutrient concentrations. The detention time in the
oxidation ponds is not sufficient for complete trans-
formation of nutrients into algal cells which can
readily be filtered from the effluent flow.
4. The Laguna Wastewater Treatment Plant is being oper-
ated and maintained in a satisfactory manner. With
the exception of total coliforms the plant is consist-
ently meeting discharge requirements. With good con-
trol of operational parameters, which can be reasonably
expected considering the caliber of operators and con-
dition of the units, the plant might be able to achieve
discharge requirements at flows up to 15,600 cu m/day
(4.1 mgd).
5. Most of the treatment units at the Sebastopol STP are
in a run-down condition stemming from the age of the
plant. Many of these units do not function reliably
and are overloaded. Effluent suspended solids do not
meet secondary treatment requirements. The effluent
is high in nitrogen and phosphorus. The frequency of
flooding at the plant site creates a hazardous condi-
tion with respect to public health.
6. The Rohnert Park STP is overloaded and incapable of
meeting secondary treatment requirements with res-
pect to suspended solids and BODs. The effluent is
high in nutrients, especially ammonia, organic nitro-
gen and phosphorus.
-21-
-------
B. Recommendations
The following recommendations are interim improvements
that should improve the performance of the West College
Avenue STP:
1. If chlorination of the trickling filter influent is
to be continued as a means of odor control, it is sug-
gested that close monitoring of this flow for chlor-
ine residual be practiced as a preventative measure
against over-chlorination and subsequent kill of
trickling filter organisms essential for optimum
treatment.
2. It is suggested that secondary clarifier effluent be
returned to the trickling filters in lieu of settled
secondary sludge. This practice should improve the
reduction of organic material through the trickling
filter process.
3. It is recommended that the sludge lagoon supernatant
be returned to the headworks of the plant rather than
to Pond II. It is believed that this supernatant flow
imposes an unusually heavy organic load to Pond II and
is inadequately treated by the time it reaches the
final effluent.
4. It is suggested that the recirculation pumps that
return Pond II effluent to the influent end of Pond I
be run continuously rather than intermittantly. This
practice should stabilize the process and improve the
performance of these ponds.
Recognizing that the previous recommendations are only
interim improvements intended to improve the efficiency
of the West College Avenue STP and that these improve-
ments may not be sufficient to produce an effluent of
such quality required to prevent further degradation
of the stream to which this plant discharges, the fol-
lowing recommendations are offered with respect to the
four plants discussed in this report and the proposed
regionalization plan presently under consideration:
1. The Laguna wastewater treatment plant should be
expanded as early as possible to provide the capa-
-22-
-------
bility of treating the wastewaters from Rohnert Park
and excess flows from the City of Santa1Rosa.
2. In view of the fact that the Sebastopol STP is anti-
quated and a potential health hazard, it is recom-
mended that this plant either be replaced in the near
future or wastewaters from Sebastopol be diverted to
the Laguna wastewater treatment plant.
3. Considering the fact that major modifications will be
necessary to upgrade the West College Avenue STP, espe-
cially with respect to nutrient removal, additional
studies should be undertaken immediately to determine
the most feasible solution to the problems that pre-.
sently exist. At the present time, the alternatives
that should receive complete consideration are 1) up-
grading the present facilities, 2) provide some means
of effluent disposal, or 3) diversion of the'waste-
waters from the West College Avenue STP to an expanded
Laguna Wastewater Treatment Plant.
-23-
-------
-------
•FAMt 0X/0A7V0A/
' :..'' I *;'. i'-'.'.' i ;
-------
PIPING
MA/A/
BY- PASS
FIGURE 3
Flow Diagram for Santa Rosa-West College S.T.P.
-------
1
9
D
a
\
AIR
\
TO
--,
^r
./
-—0
Moj
FIGURE
-27-
-------
FIGURE 5
-28-
-------
V T7
Q
FIGURE 6
-29-
-------
APPENDICES
A. Design Factors for the West College Avenue STP
B. Sampling Schedule for the Field Investigation
C. Data Collected from the Field Investigation
D. Monitoring and Reporting Program for the West College
Avenue STP
E. Waste Discharge Requirements for the West College
Avenue STP
F. Trickling Filter Evaluation for the West College
Avenue STP
-------
APPENDIX A
City of Santa Rosa, California
Sewage Treatment Plant
DESIGN FACTORS
ESTIMATED POPULATION
Domestic
Present (1950) 21,000
Design (1970) 36,000
Industrial Equivalent
Present (1950) 11,000
Design (1970) 18, SOO
Total design 54,500
FLOW, Million Gallons Per Day
Minimum ,
Design ,
Peak ,
Peak Storm ,
l.S
5.0
9.0
18.0
DESIGN LOADINGS
Flow, million gallons per day 5.0
B.O.D., ppm 288
B.O.D., l.OOOlbs. perday 12.0
Suspended solids, ppm 216
Suspended solids. l.OOOlbs. perday 9.0
BAR SCREEN
Channel width, feet 4.00
Channel depth, feet 4.83
Channel area, square feet 19.32
Clear opening between bars, inches 3/4
Screen opening area, square feet 12.88
Maximum head loss, feet 0.33
Velocity through screen, feet per second
Minimum flow 0.76
Design flow 1.64
Peak flow 2.20
Peak storm Dow 2.83
F ALL FLUME
Throat *idth. Inches IB
Discharge head, feet
Minimum Dow 0. S3
Design flow 1.15
Peak flow .
Peak storm flow
Submergence, per cent
Minimum flow
Design flow
Peak Dow
Peak storm How
1.73
2.71
53
37
34
PREAERATION TANKS
Number 2
Width, feet 19
Length, feet 35
Average water depth, feet 10.58
Detention time, hours 0.51
Number of air dlffuscr tubes per tank 50
Rated capacity per tube, cu. ft. per mm 6.0
Air supplied per tank, cu. ft. per nun 300
Air supplied, cu. ft. per gpm 0.17
Air supplied, cu. ft. per foot of tank length 8.57
Maximum hydraulic capacity per tank, mgd 9.0
SEDIMENTATION TANKS (primary and secondary similar)
Number 2
Width 19
Length, feet 110
Average water depth, feet 10.00
Effluent weir length per tank, feet 164.33
Detention time, hours 1.5
Mean velocity, ft. per mln 1.22
Overflow rate, gals, per sq. ft. per day 1,200
Overflow rate, gals, per ft. of weir per day 15,200
ximum hjdrauhc capacity per tank, mgd 9.0
.
-------
APPENDIX B
2.1 - Z? Awrj /?7-3
. _ 23-2* AM; ff,
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. Soldi
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COD
,<,el«J.
•SSsSar
C
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,r
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»,
/=^^3/ ei'-if-t-vJ- ia^fsi'V. < .or /'*e Sz&Alt-cfwl <3i
-------
APPENDIX C
Data Collected from Field Investigation
Table 1
Coo-
Av
(oLt-i=c,£ Ave. STP:
. RLTER. /A/FLUENT
TP.ICK-
Cu»,l>i?ieR. EPPL.
,2.28
ISO
(90
350
330
75-
/03
220
44
37
37
34
76
43.5-
40.5"
35T.5-
37
67
75-
46. sr
I&O
I3o
too
97
46
2.0
8
7s-
S7~p:
El ERT PAE.VJ.
l(oQ
2
-73
-------
Table 2
«/*
Avt
VJE5T
r Aj/F. "5TP:
. E>FU-. .
zz
.5T8
o.LL
_ Ox.
5T?
sro
.6.8
6.2
<£./
6.0
o. o&
_3.P_
.3,0.
M
1-2.
0.045"
0.1.05-
3.4-r
_3. 3_
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9-'7.
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3-.0.
0.22
0.13
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1.7
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S:
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STP
0. 04
o.o<.
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Vl
esr
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6
7
7-5-
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4-7
70
7.25-
14
9-9
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is-
0.6
14
IS
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14
7.5-
S"»
$77* Ef
I0.\
12
14
14
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14. s
14.
12..
12
18
-------
Table 3
TESTS-
n
A
lc \/a/
SWua PO.NT
. FW Ei™e*r- 21-2^.73:
SO ml SJnuJe /3OO m/.
. .20.1 s^ple/^W
Ro.t>. - "9 A.
5--W
2.0
25-
/2-DAX
31
3s-
/5--M/
34
2O -£>A/
.4«*
W9 .
25iOA/
III
uC
- 5"
Table 4
DATE
. 73
23 A. 73
Cu
.. O. 28
o. oz
-------
Table 5
Results of Bacteriological Examination of
Effluent Discharges from Sewage Treatment
Plants in Santa Rosa, California Area
Coliform per 100 ml
Sewage Treatment Plant Date Total Fecal
West College Avenue 8/22/73 420 <67
West College Avenue 8/23/73 170 <67
Laguna 8/24/73 110 6
Sebastopol 8/24/73 120* <20
Rohnert Park 8/24/73 3700 50*
*Estimate
Source: Laboratory cupport Branch
EPA, Region IX
9/73
-------
Table 6
£>ATA
sv^t? 5"7~P
77**
2<-22. Au4. 73:
f 2. '. 00 A/CCA/
4: oo PM.
8\Oo PAI.
/2 : 00 /Ju0/vVrfj*-/T
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...«.». A. *._.
1 2.3 Au^. 73:
/iUOrfOOM
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(mad )
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do
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6-9
3.7
4.5"
/V^«^r
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2.5:3
2.5T5-
24,0
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„_ 23-0
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Temp. C'O
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-
24.5"
25T(3 .
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W«c £:,
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23.5-
23. sr
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. n.5-..
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7ft.
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o.io
-------
Table 7
Fieuo
TIME
22-23 /Vic,. 73-
//:4S-AM.
... 2, 53- P.*.
5": 5~0 P/*\.
. Q: 5*2 P.M.
//:4o P.rt\
2:5-5- A./n.
. ^ 40 A-").
J: 4s- /V
-------
Table 9
DATA.
/ t AJ! JUT
2r23A*i.7J:
//:06 A.M.
Z'O^- pK\.
5": 00 P*l.
a- oo PM
. Jhoo p/n.
2 : /(J A.A1.
-4; sy A.M.
7: SB A,/n.
- -W -
. _L 3 7
i f£~(t
t * ^7 (^
I. 2Z
1-37
./-o/
A 5-5
0.56
iMR.ueMT
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.25-. o
2570
. 2-3. sr .
23-0
2.3.0
EFTTUUB^
TertPeaATuae (°C)
-• —
5/- 5"
22. 5*
2.2. f
22,0
Z/^__._
.....2.O.6
•2.0.0
ft* .
Serr. SOLID; (^A/k^
/
-------
Table 10
( 1 Vday)
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APPENDIX D
California Regional Water Quality Control Board
North Coast Region
liOrHTOttKG AKD RZPORTIIJG PROCK/Ji 110. ?2-42
for
CITY CF 5AIITA ROSA
Sono.Tia County
MEST COLLEGE AVSNUE SEMAG3 TEEMifENT PLANT
KOIHTCRIKS
Treatment Plant 1-Ionitorjjig
Samples shall be collected at the point of discharge to the oxidation
ponds. Composite samples may be taken by a proportional sampling device
approved by the Executive Officer or by grab scrples conposited in propor-
tion to flow. In coepositing grab samples, the sampling interval shall
not exceed one hour. The follovdng shall constitute the nonitoring
program:
Constituent Units TVpe of Sample S sapling. Frequency
BOD(20°C, 5-day) r?g/l S-hour conposite weekly
Set^Ieable Hatter ial/1 grab daily
llonfilterable Residue rag/1 S-hour composite vreekly
Hydrogen Ion pK grab daily
H-i>drrjni Flow ngd —- daily
Average Daily Flow mgd — daily
Final Effluent lioritoring
Samples shall be collected in the chlorine nixing channel at the last
practical point before the effluent is discharged to Santa Rosa Creek.
The follovang shall constitute the final effluent monitoring program:
Constituent Units Type of Sar.ple Sampling Frequency
EOD(20°C, 5-day) mg/1 grab weekly
Settleable Hatter ml/1 grab daily
1-Ionfilterable Residue m^/l srab weekly
Hydrogen Ion pi I grab daily
Coliform Organises iiPU/100 nl grab v/eekly
Chlorine Residual ng/1 grab daily
Fish Eioa3Sc.y 96-hr % survival grab monthly
lloxdnun Flow ngd -^- daily
Average Daily Flow ragd — daily
The three-spined stidiLeback, GastorOSLous c.cceleatus, shall be used as
the test organism for the Fish Bioassay analysis.
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Order Mo. 72-42 -2-
REPORTIiS
Monthly monitoring reports shall be submitted to the Regional Board by
the 15th day of the follov/ing month. In reporting the monitoring data,
the discharger shall arrange the data in tabular form so that the date,
the constituents, and the concentrations are readily discernible. The
data ahaU be sunoarized in such a manner to illustrate clearly the
compliance ^dth waste discharge requirements. The monitoring and any
necessary narrative reports Bhp.11 be transmitted in accordance vdth
specifications of Resolution Mo. ?l-5 adopted by this Board on
February 3, 1971.
Ordered by
Davad C. Joseph
Executive Officer
25, 19?2
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APPENDIX E
California Regional ' fat or Duality Control Board
i.-orth Coast Region
Order ilo. 72-42
WAST* DISCHARGE
for
r OF SAIITA RCSA
T.EST COUZGE AVZnil] S2/AGJ OSATiSLZT PIA1IT
The California Regional Water Quality Control Board, Ilcrth Coaat Region,
finds that:
1. liuniclpal waste frou riost of the City of Santa Rosa is treated at
the i Jest College Avenue Set/age Trea'«.:3nt Plant prior to discharge
to Santa Rosa Cresl:. During dry wither, waste is treated to
••secondary" level, disi.ifected av.d discharged to the relatively
shiall creel: flow. Decause of infiltration, wat weather flows are
e:Arcjiiely high and treatnent eL'ficicncy is lowered.
2. The design "capacity1 of the Wsst Collsge Avenus Sewase Treatment
Pla-.it is 5 n^d. However, oxidation ponds and diainfectioii facili-
ties have Biiablsd conpliance with conventional affluent parameters at
dry weather flew rates up to 6.5 -T.igd.
3. On Juris ji4, .1971, the Regional Board adopted Interim "J?.ter Quality
Control Flail for the ITorth Coastal Basin v/hich included a "Program
of Ir.rple/.iSiit.atio-.v1 calling for diversion of excess flo-/s fror.i the
•Jest ^ollego Avenue S^ase TrsaUient Plant in 1972; e^ansion of
capacity at the Lacuna Sev-a^e Treatment Plart in 1973; and aanage-
nent of conLiJL^lsd natural and \;aste flows in the laguna de Santa
Rosa by ley 15, 1974.
4. Beneficial usss of Santa Rosa Creel; and laguna de Santa Rosa include:
a. agricultural v:ater supply
b. preservation and eiili-r.pceraent of fish and uildlife
c. recreation
d. aesthetic enjoyiiieiit
Beneficial uses of the P.ussi?^ River include:
a. douestic \;ater supply'
b. industrial './atcr supp3.y
c. a^riculaural vctcr supply
c*. v.'atcr contact recreation
e. preservation ar.d cnhar.censnt of fish and -..-ildlifc
f. aesthetic cnjoyi?.3nt
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Order ilo. 72-42 -2- October 25, 1972
5. On February 23, 1972. the r.egio:ial Board adopted Order ilo. 72-1,
Uaste Discharge acquirements for the Git;- or Santa Hosa ".Jest
College Avenue Sewage Treatment Plant.
6. • The Bureau or Sanitary 3ngineeri:ig, Calirornia State Depertuent of
Public Health, has established "Unifcm Guidelines Tor Se-.reige Disin-
fection" which rsojAiro sewage effluent that is discharged to
ephemeral streams such as Santa Tlosa Creek to be disinfected, to a
nedian colifor_i level or 2.2 LJPil/lOG ulj the corresponding
CO percentile cclifcru level is 4,3 IIPLI/ICO ul.
7. Tiie State of California Departuer.t of Pish and Gai:e has adopted a
policy which calls for the prohibition or zones of acute toxLcity in
receiving waters.
G. The Board lias notified the discharger and the interested agencies and
persons of its intent to prescribe revised waste discharge require-
nsnts for the discharge.
9, The Board in a public i.iscstir^ heard a:id considered all consents
pertaining to the discharge.
:, IT IS K32^E1' 07cD2CD, f,iat order '.:o. 72-1, 'Jaste Discharge Hequire-
r.ents Tor ths Cit;' of Santa Rosa -.,:cst Collese Avenue Sewage Treatv.i.3r.t Plant,
adopt 3d on February 23, 19?2, bo rescinded and the Cit;T of Santa Rosa shall
coup?.;- idth the A
A. DISCI'-AIKa SFJGIFICATI013
lt" The discharge shall not co:itai:i constituents iii excess of the
Tcllowing Units;
Constituent Units l.'edLzui SO Percer.tile jjas
a; KJD(20°c,J-day) i.!g/'l 30 50
b. Settleable litter Ld/1 0.2 — 1.0
c. ITonfiloerable Residue .ng/l 20 50
d.' Colifom Org-o:ils.-js IJil/lOO ..a 2.2 4.0
e. Total Chlorine Residual 2.13/1 — — 0.1
2.- The discharge shall not have a pH less than 6.5 nor greater than
G.5 scalar units.
3« "he neon daily dr;r weather flov shall not exceed 6.5 "-igd.
4. Tho discharge shall not cav.se a pollution.
5. Neither the tredO:.;cnt nor the discharge of waste shall cause a
nuisance.
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Order lio. 72-42 -3- October 25, 1972
6. The discharge shall not cause the dissolved o^-gen at an;- point in
Santa Rosa Creelc to be less than 7.0 s.ig/1.
?t The discharge shall not cause visible evidence of any floatable
uaterial or oil and srease ir. the waters of Santa Rosa Creel:.
C. The discharge shall not cause bottom deposits at anj- point in
Santa 2osa Cree!:.
9. The discharge shall not significantly alter the color of the waters
of Santa Rosa Creek.
10. The discharge shall not increase the turbidity of the waters of
Santa Rosa Creeic nore than 20f> above naturally occurring backgrour-d
levels ,
11. The survival o£ test fishes in 9$ hour static bioassays in undiluted
effluent shall for any one deterrination equal or e::ceed 70 percent
of the test fish. The average survival for any three or i.iore con-
secutive determinations over a 21-day period shall equal or exceed
90 percent of the test fish.
12. Jo toxic or other deleterious substances shall be present in con-
centrations or quantities i.'hicli tiill cause deleterious effects on
aquatic biota, \dldlife or water foul or render any of these unfit
for huLian consumption either at levels created in receiving \ra.ters
or as a result of biological concentrations.
B.
1. The discharger shall coiv.ply -t/itii the "ilonitoring and Reporting
Prograu lib. rf2-^2:< ar.d the -General frovisions for Monitoring and
Reporting'1 as spocified by ths ".2::3cutive officer.
2. Compliance \,ltli o.cdian and psrcentile values vri.ll bs established by
analysis of representative sa:.iplin£ results over the nost recent
30-day period.
3. On or before i.ay 15, 1974, the City of Scnta Rosa shall
its discharge of vaste to tho Russian River or any tributary
flcr.ting to tha Russian -liver during tne period of I jay 15 through
Septenbsr 30 and all oihsr periods v.'I-ien the flow of the Russian
Pdver as i.-.ciasiared at Ilealdsjurg (U5G5 Ga{-e ilo. 11-4640.00) is less
tiian 10CO cfs,
4.' Tha City of Santa Rosa shall comply \/itli Discl:arse Specifications
l(a, b, c, d), and 2 through 10 of this order fort'.v.dth.
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Order I.o. 72-42 -4- October 25, 1972
5. The City of Santa Rosa shall comply tath tho follo'.jins tine schedule
to assure coj-ipliaiics t/ith discharge specifications, l(e), 11 and 12
of this Order.
Report of
gas!: Cprjtgletipri _ Dato C oj.iuLLancg__ pat e
I, 'David C. Joseph, li:ecutive officer, do
here'c^- certify tliat the foregoiiis is a full,
true and correct cop3r of an order adopted 07
ths Califor.Tia ?iC3io:ial './ater i}uality Control
Soard, liortli Coastal Hegion, on October 25,
1972.
Original "signed by
'ld C« slossph
3:;ecutive Officca;
Conduct studies to detcry.dne iJay 1, 1973 *ay 15, 1973
facilities required to co.-ipl-r
with requirements
Design and construct facilities \&j 15, 197^ '^~J 15, 1974
and ccnpl" -i/ith rscui regents
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APPENDIX F
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