United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-80-120
August 1980
Research and Development
Converting Rock
Trickling Filters to
Plastic Media
Design and
Performance
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for,the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-80-120
August 1980
CONVERTING ROCK TRICKLING FILTERS
TO PLASTIC MEDIA
Design and Performance
by
Richard J. Stenquist
Kathryn A. Kelly
Brown and Caldwell
Walnut Creek, California 94596
-Contract No. 68-03-2349
Project Officer
Richard C. Brenner
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmen-
tal Research Laboratory, U.S. Environmental Protection Agency,
and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of
the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was created because
of increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony.
to the deterioration of our natural environment. The complexity
of that environment and the interplay between its components
require a concentrated and integrated attack oh the problem.
Research and development is that necessary. first step
in problem solution, and it involves defining the problem,
measuring its impact, and searching for solutions. The
Municipal Environmental Research Laboratory develops new and
improved technology and systems for the prevention, treatment,
and management of wastewater and solid and hazardous waste
pollutant discharges from municipal and community sources
for the preservation and treatment of public drinking water
supplies, and to minimize the adverse economic, social, health,
and aesthetic effects of pollution. This publication is one of
the products of that research; a most vital communications link
between the researcher and the user community.
This report summarizes background considerations, process
and physical design details, secondary system construction and
startup experiences, and 1 yr of operating and performance data
for conversion of three existing rock media trickling filters to
the world's largest plastic media trickling filters. The
information documented herein is recommended reading for design
engineers, facilities planners, and potential municipal users of
attached growth biological wastewater treatment systems.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
111
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ABSTRACT
This investigation was undertaken with the objectives of
reviewing the conversion of trickling filters at the Stockton,
California, Regional Wastewater Control Facility from rock media
to plastic media and to develop general design considerations
for similar conversions which might be carried out elsewhere.
The report reviews the history of wastewater treatment
at Stockton and describes the planning studies which led to
the selection of plastic media trickling filters for use at
Stockton. Information on design of the secondary treatment
modifications is presented, along with a description of plant
construction and startup. Although other portions of the
Stockton plant were upgraded at the time, this investigation
centers on the secondary treatment process and considers other
unit processes only as they relate to the trickling filter
conversion.
The Stockton plastic media trickling filters are designed
to operate in two modes: (1) to oxidize carbonaceous material
during the canning season when plant loadings are high (design
flow = 220,000 m3/day or 58 mgd) and (2) to provide combined
carbon oxidation-nitrification during the noncanning season when
loadings are low (design flow = 87,000 m3/day or 23 mgd).
To evaluate plant performance, a special 1-yr sampling
program was carried out. Analyses are presented for total
and soluble BODs, total and soluble COD, total and volatile
suspended solids, phosphorous, nitrogen forms (organic, ammonia,
nitrate, and nitrite), alkalinity, pH, dissolved oxygen, and
wastewater temperature. Sampling points were raw wastewater,
primary effluent, unsettled trickling filter effluent, and
secondary effluent (not all analyses were made for all sampling
points).
Plant performance for the 1-yr period is presented and
evaluated. Operational changes intended to improve performance
are described, and the results are discussed. Capital and
operating costs for filter conversion are also presented.
Based on information developed from evaluation of the
Stockton plant and from review of other plastic media trickling
filter plants, manufacturers' data, and technical literature,
general design considerations are developed for converting
iv
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rock media trickling filters to plastic media, including both
process design and physical design. Process design includes
such performance parameters as BODs removal, ammonia nitrogen
removal (in combined and separate stage systems), suspended
solids removal, and solids production. Physical design involves
such considerations as wall design, influent and effluent
piping, effluent collection, recirculation, and overall plant
layout.
This report was submitted in fulfillment of Contract
No. 68-03-2349 by Brown and Caldwell under the sponsorship of
the U.S. Environmental Protection Agency. Plant operating and
performance data are included in this report for the 1-yr period
of March 15, 1976, through March 16, 1977.
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CONTENTS
Foreword . iii
Abstract iv
Figures ix
Tables xi
Acknowledgments xiii
1. Introduction 1
Objectives and scope 3
Outline of report 4
2. Conclusions 5
3. Recommendations 8
4. Background 9
History of wastewater treatment
at Stockton 9
Stockton Regional Wastewater
Control Facility 12
Wastewater flows and characteristics 17
5. Design 24
Process design 25
Hydraulic loadings 27
Nitrification 27
Air supply 28
. Specific surface area 28
Pilot study 28
Physical design 32
Filter walls and rotary
distributors 33
Media support system and plastic
media 36
Air flow . ;... 37
Effluent collection system 38
Filter distribution structure
No. 1 and piping 39
Recirculation and trickling filter
supply pumps 46
Miscellaneous aspects unique to Stockton ..... 47
6. Construction and Startup 48
Preconstruction phase 48
Construction phase ... 50
Construction sequence 51
vii
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CONTENTS (continued)
Major construction items 53
Construction progress 60
Startup 62
7. Operation and Performance 64
Special sampling and analytical program 64
Plant operation during sampling
program 67
Performance 70
3005 removal 73
Nitrification 78
Suspended solids 86
Secondary treatment solids
production 90
Design and performance 91
Treatment costs 93
8. General Design Considerations 96
Process design 96
Media selection 97
8005 removal 97
Nitrification * 109
Oxygen transfer 116
Ventilation 117
Clarification 117
Solids production 121
Physical design 121
Walls 122
Influent piping and pumping 124
Center column and distributor
support 125
Effluent collection and return 125
Recirculation structure and
pumping 127
Media support system , 128
Ventilation system 131
Overall plant configuration 131
References 133
Appendices
A. 1969 Discharge Requirements 136
B. 1974 Discharge Requirements 140
C. 1979 Discharge Requirements 149
D. Description of Sampling Program 157
E. Daily Data From Sampling Program 168
viii
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FIGURES
Number
1 Stockton, California, Regional Wastewater
Control Facility
2 Location of Stockton plant
3 Flow diagram of Stockton plant prior to
upgrading
4 Plant layout prior to upgrading
5 Tertiary plant under construction
6 Flow diagram of upgraded plant
7 Plant layout after upgrading
8 Plant flow and 6005 loadings for period of
special sampling program
9 Pilot study nitrification performance
10 Trickling filter sidewall and effluent
collection channel
11 Center columns
12 New distributors for plastic media trickling
filters
13 Media support system
14 Media support system details
15 Plastic media filter fans
16 Plan view of external collection system
17 Section views of effluent collection box
and filter return box
18 Original trickling filter distribution
structure
19 Modified trickling filter distribution
structure
20 Piping diagram for upgraded secondary
treatment facilities
21 Critical path method (CPM) analysis
22 Early phase of filter conversion
23 Operation of distributor prior to media
installation
24 Plastic media installation
25 Plastic media conveyor
26 Trickling filter distribution structure ....
27 Supply and recirculation pumps
28 Secondary sedimentation tank distribution
structure
29 Construction progress
3
10
12
13
16
17
18
22
31
34
35
36
37
38
39
40
41
42
43
44
52
54
55
56
57
58
59
60
61
IX
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FIGURES (continued)
Number Page
30 Plastic media and rock media trickling filters
at Stockton 65
31 Stockton primary clarifiers 68
32 Changes in plant operating parameters during
sampling program 70
33 BOD loadings and removals 74
34 Biofilter effluent dissolved oxygen levels 77
35 Ammonia and nitrate nitrogen levels 80
36 Alkalinity destruction . 85
37 Secondary clarifier 86
38 Secondary effluent suspended solids levels 89
39 B. F. Goodrich's vinly Core II plastic media module 100
40 B. F. Goodrich1s Koro-Z plastic media module 101
41 Effect of specific surface area on BOD
removal 104
42 BODs removal and organic loading at two
biofilter depths 108
43 Effect of BODs/TKN ratio on nitrification rate ... Ill
44 Separate-stage nitrification performance 112
45 Combined carbon oxidation-nitrification
performance 115
46 Effect of overflow rate on trickling filter
secondary clarification performance 119
47 Tube settler schematic 120
48 Effect of tube settlers at Seattle,
Washington 120
49 Corrugated PVC used for trickling filter walls ... 124
50 Biofilter cross section for Simi Valley,
California, plant 126
51 Recirculation structure for Lompoc, California,
plant 128
52 Media support system, with solid walls 130
53 Media support systems using piers 130
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TABLES
Number ,,
1 Design data, Stockton plant prior to upgrading,
1964 .
2 Performance of Stockton plant prior to upgrading,
1972 .
3 Design data for upgraded plant
4 Wastewater flows and characteristics .............
5 Industrial waste loadings for the Stockton
plant
6 Design data summary for secondary treatment
facilities
7 Pilot study results
8 Pilot study nitrification performance .% ...
9 Low bidders for modifications to secondary
treatment facilities
10 Low bidders for filter media supply and
installation
11 Major equipment suppliers submitted by general
contractor
12 Parmeters measured during sampling program
13 Monthly averages for flow, BODs, and soluble
BOD5
14 Monthly averages for suspended solids and volatile
suspended solids
15 Monthly averages for total phosphorus and total
COD .
16 Monthly averages for total Kjeldahl nitrogen,
ammonia nitrogen, and secondary effluent
nitrate nitrogen
17 Monthly averages for alkalinity, wastewater
temperature, pH, and dissolved oxygen
18 BODij removal summary
19 Treatability coefficients for Stockton
20 Nitrification performance study
21 Nitrogen mass balance '.-.
22 Secondary solids production
23 Design and performance comparison
24 Construction cost for trickling filter
convers ion
25 Secondary treatment modifications bid
breakdown
26 Operation and maintenance costs
14
15
19
22
23
26
30
32
49
49
50
66
71
71
72
72
73
75
78
79
84
90
91
93
94
95
XI
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TABLES (continued)
Number
27
28
29
Operation and maintenance labor associated with
major plant components
Examples of available plastic media
Parameters affecting air flow through
biof ilters
Page
95
99
117
xii
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ACKNOWL E DGMENTS
The aid and cooperation of the City of Stockton in
carrying out this investigation is greatly appreciated.
Individuals who deserve recognition include Mr. Robert
Thoreson, Director of Public Works; Mr. Art Vieira, Water
Quality Control Superintendent; Mr. Lynn Norton, Associate
Utilities Superintendent; Mr. Mike Jarvis, Chief Operator;
Mr. Manuel Munoz, Mechanical Maintenance Supervisor; and
Mr. Arnold Hoffman, Chemist.
Analytical work was carried out by Brown and Caldwell's
Environmental Sciences Division in San Francisco, by EPA's
Municipal Environmental Research Laboratory in Cincinnati, and
by the City of Stockton plant laboratory staff.
xiii
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SECTION 1
INTRODUCTION
Their chief
operation, and
contaminants is
(0.8 to 1.6 kg
Rock media trickling filters have traditionally played an
important role in U.S. wastewater treatment and are widely
used in small and moderate-size communities,
attributes are reliability, stability, ease of
low operating costs. Their ability to remove
limited, however; at normal organic loadings
BODs [5-day biochemical oxygen demandl/m^/day or 50 to 100 lb/
1,000 ft3/day), BOD5 and suspended solids removals of 60 to
85 percent are usually attained, with effluent concentrations
generally ranging from 40 to 80 mg/1. At very low loadings
(0.2 to 0.4 kg/m3/day or 10 to 25 lb/1,000 f t3/day) , BODs and
suspended solids removals of over 85 percent can be realized,
but except for all but the smallest plants, an excessive number
of filters* and a very large land area are required.
Nitrification (conversion of ammonia nitrogen to the
nitrate form) can also be attained at very low loadings and, in
the past, has generally occurred incidental to oxidation of
carbonaceous material. Nitrification has, however, become an
important treatment process in recent years, either by itself
for ammonia conversion or as an intermediate process in
nitrogen removal.
An important recent innovation in trickling filtration
technology has been the use of synthetic (plastic) media in
place of rock. Although random-packed synthetic media can be
obtained, the most common configuration involves interlocking
plastic sheets constructed in modules which have a "honeycomb"
appearance. These modules are then stacked to give a highly
porous, clog-resistant trickling filter which can receive high
hydraulic and organic loadings and produce a high quality
effluent.
Recent emphasis on upgrading wastewater effluents
discharged to surface waters has resulted in many trickling
filter plants being unable to meet the more stringent discharge
*In this report, the terms "trickling filter" and "biofilter"
will be used synonymously;, also, where the meaning is clear
from the context, the shorter term "filter" will be used at
times.
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requirements which are now being imposed. Conversion from
rock to plastic media may allow such plants to meet the new
requirements and to receive increased flows and loadings.
Plastic media trickling filters may be used alone in a
conventional secondary treatment mode, or they may be
integrated with other unit processes to provide advanced waste
treatment capability.
In 1969, the City of Stockton, California, was ordered by
the California Regional Water Quality Control Board, Central
Valley Region, to reduce the total nitrogen concentration in
its wastewater effluent discharged to the San Joaquin River.
Stockton is located in an agricultural area in central
California, and its Regional Wastewater Control Facility
(formerly called the Main Water Quality Control Plant) provides
wastewater treatment for over 200,000 area residents and
several industries including six major food processing plants
which, during the canning season (July through October), cause
the plant influent flow to triple and the organic loading to
increase to five times the noncanning season average. In 1969,
the plant flow diagram consisted of primary sedimentation,
trickling filtration, and effluent polishing oxidation ponds.
In order to meet the nitrogen limitation, a waste treatment
scheme was developed which included the conversion of three of
six existing rock media trickling filters to plastic media.
Other plant modifications were undertaken in conjunction
with the trickling filter conversion; the most significant of
these was construction of tertiary algae removal facilities
consisting of dissolved air flotation, dual media filtration,
and chlorination-dechlorination followed by stream discharge.
It was anticipated that the upgraded plant (Figure 1)
would be operated in two modes. During the canning season, the
plastic media trickling filters would remove carbonaceous
oxygen demand from the high-strength wastes, effluent ammonia
nitrogen would be incorporated into algae in the oxidation
ponds, and the algae (and nitrogen) would be removed by
dissolved air flotation-filtration. During the noncanning
season when plant loadings are much lower, the plastic media
filters would provide both the oxidation of carbonaceous
material and nitrification. Nitrified effluent would then
undergo denitrification (conversion of nitrate nitrogen to
nitrogen gas) in the anaerobic bottom layer of the facultative
oxidation ponds. During the transition period between canning
and noncanning seasons, it was anticipated that conversion
of ammonia nitrogen to nitrogen gas through breakpoint
chlorination (followed by dechlorination) would be used to
ensure compliance with the nitrogen limitation provision.
This report has been prepared to describe the conversion
of the rock trickling filters at Stockton to plastic media
filters, designed for removing carbonaceous 8005 during the
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canning season and capable of nitrifying during the noncanning
season when low organic loadings are received at the plant.
Although other plant components were upgraded or expanded during
this same period, this report deals with them only as they
relate to the secondary treatment portion of the facilities.
Figure 1. Stockton, California, Regional Wastewater Control Facility.
Conversion from rock to plastic media trickling filters increased
biological oxidation capacity and provided nitrification during
noncanning season low loading conditions.
OBJECTIVES AND SCOPE
This review of the Stockton plant upgrading has been
undertaken to make available information which may be useful to
communities and engineering consultants who face situations
where existing rock media trickling filters cannot meet new/
more stringent discharge requirements.
Specific objectives were identified as follows:
1. Present information on conversion to the upgraded
facility. This includes preliminary planning,
detailed design, construction, and capital costs for
the secondary treatment modifications.
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2. Review operation and performance of the plastic media
filters. Difficulties encountered in startup and
operation are discussed, along with operational
techniques developed to counter such problems.
Because the rock and plastic media filters are
normally operated in parallel with a common
recirculation sump, a special 1-yr sampling and
analysis program was undertaken to document perfor-
mance. During this 1-yr period, the rock media
filters were shut down to prevent interference with
the plastic media filters. Data developed from the
sampling program are presented, with particular
attention given to comparing performance with design
objectives. Operation and maintenance costs are also
documented.
3. Develop general design considerations for converting
rock trickling filters to plastic media. Experience
gained from the Stockton plant is emphasized, but
information from similar planned or constructed
plants, from plastic media manufacturers, and from
the technical literature is also utilized. Process
design considerations include carbonaceous BODs
removal, nitrification performance, available media
types, hydraulic loading, air requirements, inter-
relationship with secondary clarification, and solids
production. Physical design considerations center
principally on the use of existing structures for
the upgraded plant and cover such items as use of
existing filter structures, possible need for new
influent and effluent lines, construction of new
influent risers and distributors, supply and
recirculation pumping, ventilation systems, and media
installation.
OUTLINE OP REPORT
This report has been organized to present first a
chronological history of the Stockton secondary treatment
modifications and then to discuss specific aspects of plant
operation and performance before setting out general design
considerations. Sections 4 through 6, respectively, review the
background, design, and construction and startup. Operation
of the plastic media filters and the specific task of comparing
performance with design objectives are covered in Section 7.
Also included in Section 7 are capital and operating cost data
for the Stockton secondary treatment facilities. Information
from Sections 4 through 7 is then augmented by data from other
sources for presentation in Section 8, General Design
Considerations.
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SECTION 2
CONCLUSIONS
Use of plastic media in the trickling filtration process
heis .become widespread in the last 10 yr. This investigation
of the Stockton Regional Wastewater Control Facility has
provided valuable information for use in both the planning
and design phases of treatment plant upgrading. Specific
conclusions developed from this study are as follows:
Conversion of.rock media trickling filters to plastic
media can be undertaken if the existing filter
structures are structurally sound and if soil strength
is adequate. Limitations on filter height or on wall
type may result from necessary limits on allowable
structure or soils loads.
In conversion, significant modifications may need
to be made to the following elements of the secondary
treatment system: supply pumping, influent
piping, rotary distribution, effluent collection,
recirculation, and secondary clarification.
Maintaining treatment
design options? for
structure may need
one cannot be shut
modifications.
during construction may limit
example, a new recirculation
to be built if the existing
down for required extensive
The relation between the secondary treatment process
and other plant unit processes, as well as the inter-
relationship among the secondary treatment components,
should be carefully evaluated during design. Using
existing structures usually limits design options, and
considerable ingenuity may be required to provide
overall plant flexibility and reliability.
Module-type plastic media can be used in trickling
filters to provide high 8005 removals. Effluent
total and soluble BODs concentrations measured at
Stockton averaged less than 20 and 10 mg/1, respec-
tively (removals averaged about 90 percent), at
loadings of around 0.32 kg BOD5/m3/day (20 lb/
1,000 ft3/day) during optimal operation of the filters.
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Combined carbon oxidation-nitrification effluent
ammonia nitrogen levels of less than 3.0 mg/1 can be
obtained in plastic media trickling filters (80 to
90 percent nitrification). Organic nitrogen removal
is limited; removals of about 50 percent were measured
at Stockton, with effluent concentrations ranging from
5 to 10 mg/1.
Secondary effluent suspended solids concentrations
at Stockton were above the 30 mg/1 "secondary
treatment" limit during 3 of 10 noncanning season
months. Possible causes include poor hydraulic
distribution among the four secondary clarifiers and
within each clarifier; high secondary clarifier
loading rates; and temperature/density gradients
set up within the clarifiers by the forced draft
ventilation system, which resulted in short-circuiting.
The most commonly used design method for plastic media
trickling filters is the Velz equation which, in one
form, is as follows:
(1)
where: Se
S0
k
effluent BODs, mg/1
influent BODs, mg/1
= treatability coefficient, dependent
upon the wastewater
= media specific surface area, ft2/ft3
= media depth, ft
= hydraulic loadinc
recycle), gpm/ft^
(excluding
While use of
applicability
removal rate
this equation is widespread, its
appears to be limited. Although the
is generally improved by a higher
media specific surface, the direct proportionality
implied by the Velz equation does not appear to exist.
Further, overall total 8005 removal, including
secondary clarification, appears to be independent of
depth for most applications.
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Performance of the Stockton plant was limited during
the first portion of the 1-y.r sampling program by
inadequate total hydraulic loading (influent plus
recycle) capacity and/or inadequate air supply. After
modification of these two operational parameters,
performance (8005 removal and nitrification) improved
significantly.
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SECTION 3
RECOMMENDATIONS
Principal recommendations for future work involve the
effect of secondary clarification on overall biofilter
performance. Further investigation of the use of tube se^J-'e.rs,
and lower clarifier hydraulic loading rates to aid secondary
clarification should be undertaken. Even though lower prganie
loadings (in terms of kg BOD5/m3/day or lb/1,000 ft3/day)
are being used to obtain higher BODs removals, trj.e.k|rifr$
filter clarifier overflow rates are still generally 'being
designed near traditional values of around 40 m^^day/ftj*
(1,000 gpd/ft2). ' , !' '
The possibility that temperature/density gradients can
result from cooling of wastewater passing through ' fetje ฃo\*er
should be investigated. Particularly when combine^ pardon
oxidation-nitrification is being practiced, high a|r flows
and low influent hydraulic loading rates can result in a
significant wastewater temperature drop through the b^ojilfcer.
This in turn may result in density gradients within the
secondary clarifier and consequent short-circuiting arid
deterioration in performance.
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SECTION 4
BACKGROUND
Situated along the San Joaquin River in California's
Central Valley, the City of Stockton is located 80 km (50 mi)
east of San Francisco (Figure 2). Stockton is the county seat
of San Joaquin County and its largest city. With a present
population of approximately 200,000, Stockton is a major
commercial center in the region. Because California's Central
Valley is a rich agricultural area, principal industries in
Stockton have long been those concerned with seasonal fruit and
vegetable processing. Presently, there are six major food
processing plants tributary to the Stockton plant. During the
late summer months of August through October, these plants
operate on an around-the-clock basis, discharging large
quantities of wastewater to the Stockton sewerage system.
Because the canning season coincides with the period of low
flow in the San Joaquin River, the body of water to which
Stockton's wastewater effluent is discharged, the canning season
has always been a critical period for wastewater treatment at
Stockton.
Topographically, the land surface in the Stockton area
is a relatively flat plain which slopes in an east to west
direction about 1 m/km (5 ft/mi). Principal geographical
features of the area include the San Joaquin River, the
Calavaras River, and various sloughs and channels which make up
the eastern part of California's Sacramento-San Joaquin Delta
area. River flow in Stockton is influenced by tidal action and
by upstream diversions of water to state and federal water
projects. These diversions may at times cause a net upstream
water movement in the San Joaquin River at Stockton. Waste
discharge requirements at Stockton have historically been
developed to ensure adequate dissolved oxygen concentrations in
the San Joaquin River and, more recently, to reduce algae
growths in the river.
HISTORY OF WASTEWATER TREATMENT AT STOCKTON
Public sewerage in Stockton began prior to 1893 when
existing sewers in the downtown area were connected to a large
holding tank or cesspool located on the bank of Mormon Channel.
Sewage was pumped from the tank through an outfall line to the
San Joaquin River. Later, after failure of the line/ raw
sewage was discharged directly into Mormon Channel (1).
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REGIONAL WASTEWATER
SCALE IN MILES
1/4 I/E 3/4 i n/2
CONTROL FCILITY
Figure 2. Location of Stockton plant.
Offensive odors and generally foul conditions resulting
from this discharge led, in 1918, to the construction of a
treatment plant on the north bank of Smith's Canal in what is
now the downtown area. In 1922, following delay due to World
War I, the south plant (now the Regional plant) was constructed
adjacent to the San Joaquin River to serve that portion of the
city located south of the Stockton ship channel. These plants
provided only fine screening to accomplish the minimum amount
of treatment.
10
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By 1936, growth of the city had produced overloads on
both plants, and had led to both unsightly and undesirable
conditions in the receiving waters. At this time, primary
sedimentation was provided at both locations.
Increased population and industrial growth brought about
by World War II imposed excessive loadings on existing
collection and treatment facilities. These conditions
threatened to curtail sewer system expansion and industrial
growth. The dissolved oxygen content of adjacent waters of the
San Joaquin River and the Stockton ship channel was seasonally
depressed below levels necessary to support fish life. In
addition, the use of these waters for recreational purposes,
including swimming and boating, presented a serious health
menace. An engineering study undertaken in 1945 recommended
provision of secondary treatment at both plants by construction
of trickling filters and secondary sedimentation tanks.
Secondary treatment was not provided at the Smith's Canal
plant, however, and some of the wastewater previously flowing
to that plant was, therefore, diverted to the Regional plant
where basic structures for primary and secondary treatment
were constructed.
Rapid development of the northern part of the city
occurred after World War II, and in 1964, a new treatment
plant, now identified as the north plant, was constructed to
serve that area north of the Calaveras River. Meanwhile, it
was found more economical to discontinue treatment at the
Smith's Canal plant and to pump sewage from it to the Regional
plant. Despite several increases in secondary treatment
capacity, organic loadings from the Regional plant to the river
exceeded its assimilative capacity during peak periods of
food processing.
The Regional plant, as constituted up to the present
expansion, had its inception from 1946 to 1948. Approximately
$3.0 million were spent for major reconstruction as part of a
plan to divert all industrial wastes south, and to relieve the
heavily overloaded treatment plant located on Smith's Canal.
Units were constructed then to provide primary treatment and a
portion of the recommended secondary treatment facilities
comprising high-rate filters plus additional digester capacity
to handle sludge from the Smith's Canal plant. Peak hydraulic
capacity was 129,000 m3/day (34 mgd). Between 1948 and 1961,
construction projects involving nearly $1.4 million were
undertaken for additions, including primary and secondary
sedimentation tanks, trickling filters, a sludge thickening
unit, a chlorination facilities effluent pumping station, 81 ha
(200 ac) of oxidation ponds, and an oxidation pond circulation
and effluent pumping station. In 1963, work was authorized
to increase hydraulic capacity throughout the plant and to
provide an additional 55 ha (135 ac) of oxidation ponds and
various other improvements necessary for efficient operation.
11
-------
Hydraulic capacity, after
193,000 m3/day (51 mgd). In
oxidation ponds were added.
completion of that
1968 another 121 ha
work, was
(300 ac) of
A flow diagram and the layout of the plant prior to the
1973-78 upgrading are shown in Figures 3 and 4, respectively.
Design data for that plant are shown in Table 1. Performance
of the plant for 1972 is summarized in Table 2.
BYPASSING
DISCHARGE TO
SAN JOAQUIN RIVER
Figure 3. Flow diagram of Stockton plant prior to upgrading.
STOCKTON REGIONAL WASTEWATER CONTROL FACILITY
Groundwork for construction of the present facility was
begun in February 1969 with the imposition of new discharge
requirements by the Regional Water Quality Control Board
(Appendix A). The most important provision of the previous
requirements, issued in 1951, was that the dissolved oxygen
concentration of the receiving water not fall below 3.0 mg/1.
The new requirements raised the minimum allowable concentration
to 5.0 mg/1. In addition, a receiving water total nitrogen
limitation of 3.0 mg/1 was imposed to reduce excessive algae
growth as indicated in Section 1. A treatment scheme to meet
the new regulatory requirements was developed by the city's
consultants, Brown and Caldwell, and involved the use of
12
-------
plastic media trickling filters and a tertiary algae removal
facility. The plant was designed to operate in two modes:
during the canning season (approximately July through October)
when the organic loading is high, the filters were to oxidize
carbonaceous matter only with an expected BOD5 removal of
70 percent. The various forms of nitrogen, primarily ammonia,
were to be substantially removed by the oxidation pond through
conversion to algae cells with subsequent algae removal in the
tertiary facility (Figure 5). During the noncanning season when
the organic loading is low, approximately 90 percent of the
carbonaceous 8005 was to be removed in the trickling -filters
and ammonia nitrogen was to be converted to the nitrate form.
The nitrate nitrogen formed in the filters was to be converted
to nitrogen gas through microbial denitrification in the
anerobic layer of the ponds. Based upon these requirements,
design and construction of the facilities were undertaken.
LEGEND
FILTER DISTRIBUTION
STRUCTURE NO. 1
FILTER
DISTRIBUTION
STRUCTURE
NO. 2
OXIDATION
PONDS
100 200
SCALE IN FEET
300
figure 4. Plant layout prior to upgrading.
13
-------
TABLE 1. DESIGN DATA, STOCKTON PLANT, PRIOR TO UPGRADING, 1964
Parameter
Incoming sewers
Diameter, in.
Number 1
Number 2
Number 3
Capacity without surcharge, mgd
Preliminary treatment
Bar screens
Number
Width, ftc
Water depth, ftc
Grit removal channels
Number
Width, ftc
Maximum depth, ft
Metering flumes
Number c
i Throat width, ft
Capacity each, mgd c
Head at capacity, ft
Comminuting units
Number
Channel width, ft
Two channels
One channel
Raw sewage pumping units
Number .
Total capacity, mgd
Capacity, largest pump not op-
erating, mgdb
Primary treatment
Rectangular tanks
Number
Width, ft0
Length, ftc . c
Average water depth, ft
Square tanks
Number _
Width, ft c
Average water depth, ft
Secondary treatment
Trickling filters
Number
Value
30
48
48
43
3
4.0
2.6
3
4.0
5.2
3
2.0
17
2.2
3
4.0
5.0
4
93
59
4
37
141
15
2
70
14
6
Parameter
Diameter, ft
Rock media depth, ft ,
3
Total media volume, 1,000 ft
Filter recirculation pumping units
Number ,
Total capacity, mgd
Secondary sedimentation tanks
Number
Diameter, ft
Side water depth, ft
Solids treatment
Gravity thickener
Number c
Diameter, ft c
Side water depth, ft
Anaerobic digesters
Number
Primary, heated
Secondary, unheated
Diameter, ft c
Side water d.epth, ft
Plant effluent pumping units
Old station
Number .
Total capacity, mgd
New station
Number ,
Total capacity, mgd
Oxidation ponds
Number e
Surface area/ AC'
Depth, ftP f
Volume, mil gal
Oxidation pond circulation pumping
units
Number ^
Total capacity, mgd
Oxidation pond effluent pumping units
Number .
Total capacity, mgd
Value
166
4.2
540
4
30
4
100
12
1
70
10
2
1
100
30
2
32
2
68
2
325
4.5
476
2
136
4
56
ain. x 0.0254 - m.
mgd x 3,785 = m /day.
ฐft x 0.305 = m.
dl,000 ft3 x 28.3 = m3.
eac x 0.405 = ha.
fwil gal x 3,785 ซ m3.
14
-------
TABLE 2. PERFORMANCE OF STOCKTON
PLANT PRIOR TO UPGRADING,
1972
Value
Parameter
Carmine
season
Noncanning
seasonb
Flow, mgd
mg/1
Raw wastewater
Primary effluent
Secondary effluent
Pond effluent
Trickling filter organic
loading, Ib BOD5/1,000
ft3/dayd
Secondary treatment BODs
removal, percent
Suspended solids, mg/1
Raw wastewater
Primary effluent
Secondary effluent
Pond effluent
Pond effluent total
nitrogen, mg/1
32.2
380
280
160
33
140
43
340
77
49
190
12.5
240
160
40
15
40
75
210
61
48
38
In September 1974, before
these facilities were
completed, the Regional Water
Quality Control Board again
issued new requirements for the
Stockton plant (Appendix B).
Included in these requirements
were monthly average effluent
BODs and suspended solids
concentrations of 10 mg/1, and
a monthly median total coliform
organism concentration of
23 MPN/100 ml. In addition,
a 3.0 mg/1 limit on effluent
total nitrogen was imposed,
although this limitation only
applied from the period of
July 15 through November 15.
The receiving water standards
of 3.0 mg/1 for total nitrogen
and 5.0 mg/1 for dissolved
oxygen remained in effect.
If operated in two modes
as planned, the plant could not
have met these new discharge
requirements. In January 1975,
Brown and Caldwell analyzed
the alternatives available
for meeting the new require-
ments (2). It was concluded
that the proposed facilities could produce effluent of the
required quality through a change in operating modes. During
the July 15 through November 15 period (which includes the
canning season) when the 3.0-mg/l effluent nitrogen limitation
is in effect, wastewater would be directed through all the unit
processes: primary treatment, secondary treatment by trickling
filtration, oxidation ponds, dissolved air flotation, dual media
filtration, and chlorination-dechlorination. Outside the
July 15 through November 15 period, during those periods when
the river flow is high, the oxidation ponds and dissolved air
flotation processes would be bypassed. Nitrified secondary
effluent would be diverted to the dual media filtration and
chlorination-dechlorination facilities prior to discharge. The
3.0-mg/l receiving water total nitrogen limitation would be met
by dilution in the river.
In late 1979, the Regional Water Quality Control Board
again modified the discharge requirements for Stockton
(Appendix C). During the noncanning period from November 1
through July 31, 30-mg/l limits on monthly average BODs and
suspended solids concentrations apply; from August 1 through
October 31, the limits for these two constituents are 10 mg/1 as
Canning season; July - September.
Noncanning season; October - June.
c 3
mgd x 3,785 = m /day.
dlb/l,000 ft3/day x 0.016 = kg/m3/day.
15
-------
a monthly average. The monthly median coliform limitation is
23 MPN/100 md year-round, and the nitrogen limitation has been
eliminated from the requirements.
The city is planning to operate the tertiary facility
during the canning season when the more stringent requirements
are in effect. During the noncanning season when the 30-mg/l
BODs and suspended solids limits apply, the city will operate
the lightly loaded oxidation ponds in a series mode and bypass
the tertiary facility.
Figure 5. Tertiary plant under construction. Dissolved air flotation will
remove algae from oxidation pond effluent.
It is believed that the 30-mg/l requirements can be met
with oxidation pond effluent for a significant portion of the
year, but all or a portion of the tertiary facility may be
needed at times to meet these limits.
The flow diagram for the upgraded Stockton plant is shown
in Figure 6. The layout (excluding the tertiary facilities) is
shown in Figure 7. Plant design data are presented in Table 3.
16
-------
r
T
BYPASSING
SLUDGE CAKE
DISPOSAL
J
DISCHARGE TO
SAN JOAQUIN RIVER
Figure 6. Flow diagram of upgraded plant.
WASTEWATER FLOWS AND CHARACTERISTICS
As previously mentioned, the occurrence of the fruit and
vegetable canning season during the period of low river flow
has historically been the critical period for wastewater
treatment and discharge at Stockton. Shown in Figure 8 are
weekly flows and BOD5 loadings received at the plant during
the period from March 15, 1976, through March 16, 1977, when
the special sampling program was undertaken for this study.
The canning season began abruptly on August 1 when a
cannery workers strike ended; normally, the canning season
begins gradually in mid-July. The canning season also ended
earlier than normal because of unusual late summer rains
in September which resulted in considerable crop damage.
Therefore, the canning season for 1976 was several weeks shorter
than usual. Monthly plant influent characteristics are
summarized in Table 4.
17
-------
Shown in Table 5 are industrial loadings from eight major
industries in Stockton, the six canneries plus a meat packer
and a cardboard box manufacturer. The last two have a combined
flow of approximately 15,000 m3/day (4.0 mgd) and contributed
most of the industrial loadings outside the months of August
and September 1976.
LEGEND
SEWER MAINTENANCE
INFLUENT BUILDING
DISTRIBUTION
STRUCTURE
100 200
SCALE IN FEET
Figure 7. Plant layout after upgrading.
18
-------
TABLE 3. DESIGN DATA FOR UPGRADED PLANT
Parameter
Value
Parameter
Value
Basic loading data
Flow, mgda
Noncanning season
Average dry weather (ADWF)
Peak storm rate
Canning season
Maximum month
Peak rate
BOD5/ 1,000 lb/dayb
Noncanning season
Canning season, maximum month
Suspended solids, 1,000 Ib/day
Noncanning season
Canning season, maximum month
Preliminary treatment
Bar screens
Number
Width, ftc
Water depth, ft
Grit channels
Number
Width, ftc c
Maximum depth, ft
Metering flumes
Number c
Throat width, ft
Hydraulic capacity, each, mgd
Raw sewage pumping units
Number a
Capacity, each, mgd
Primary treatment
Sedimentation tanks
Rectangular tanks
Number
Width, ftc
Length, ft c
Average water depth, ft
Weir length, each, ftc
Square tanks
Number
Width, length, ft c
Average water depth, f.t
Weir length, each, ft
Detention time, hours
ADWF noncanning season
Maximum day canning season
2"
Overflow rate, gpd/ft
ADWF noncanning season
Maximum day canning season
Performance during noncanning
season
BODs removal, percent
Suspended solids removal,
percent
Performance during canning
season
BODs removal, percent
Suspended solids removal,
percent
23
60
58
75
54
236
31
167
3
4.0
2.9
6
4.0
5.4
2.0
20
4
34(3)
14.5(1)
4
37
141
15
224
2
70
14
260
3.4
1.2
800
2,200
40
65
20
55
Secondary treatment
Trickling filters
Trickling filters (rock)
Number c
Diameter, ft c
Average depth of media, ft
Volume of media, each,
1,000 ft3
Total volume of media, rock
filters, 1,000 ft36
Hydraulic capacity, each, mgd
Trickling filters (plastic)
Number , c
Diameter, ft c
Average depth of media, ft
Volume of media, each filter,
1,000 ft3e
Total volume of media, plas-
tic filters, 1,000 ft3
Hydraulic capacity, each
filter, mgda
Total volume of media, rock
and plastic filters, 1,000
ft3
Loading, noncanning season
BOD5, lb/1,000 ft3/dayt
BODj removal, percent
Recalculation ratio
Loading, canning season^
BOD5, Ib/l,000ft3/day
BOD5 removal, percent
Recirculation ratio
Sedimentation tanks
Number c
Diameter, ft Q
Side water depth, ft d
Overflow rate, gpd/ft
ADWF noncanning season
Peak storm rate
Maximum month canning season
Peak rate canning season
Suspended solids in effluent,
mg/1
Noncanning.. season
Canning season
Secondary effluent pumping
units
Number
Capacity, all pumps oper-
ating, mgda
Capacity, largest unit out
of service, mgd
Solids treatment
Gravity thickener
Number c
Diameter, ft c
Side water depth, ft
Primary digestion tanks
Number c
Inside diameter, ft c
Side water depth, ft
3
166
4.2
90
270
10
3
166
22
476
1,430
24
1,700
19
90
3.4
110
70
0.76
4
100
12
730
1,910
1,850
2,390
35
165
3
120
90
1
70
10
3
100
30
(continued on next page)
19
-------
TABLES. (continued)
Parameter
Value
Parameter
Value
Solids treatment (con't)
Primary digestion tanks (con't)
Loading, Ib/ft3/dayg
Noncanning season 0.04
Canning season 0.25
Performance, noncanning season
Suspended solids reduction,
percent , 55
Digested sludge,,1,000 Ib/day 12
Gas produced, ft /lb suspended
solids/dayh 6.0
Performance, canning season
Suspended solids reduction,
percent . 45
Digested sludge,,1,000 Ib/day 95
Gas produced, ft /lb suspended
solids/day11 5.5
Secondary sludge lagoons
Number ^ 2
Total area, ac c 3.8
Average liquid depth, ft 6
Digested sludge solids content
from digester, percent 3
Detention time in lagoon, days 59
Solids reduction in lagoon,
percent 20
Vacuum filters
Number 2
Capacity, each, lb suspended
solids/hrJ 1,200
Moisture content of wet cake,
percent 60
Oxidation ponds
net water.surface, ac
Number
Area,
Volume, mil gal"
Loading, noncanning season
8005 Ib/surface ac/dayl
BOD5 in effluent, mg/1
Suspended solids in effluent,
mg/1
Loading, canning season ,
BOD- Ib/surface ac/day
BODg in effluent, mg/1
Suspended solids in effluent,
mg/1
Circulation pumping units
Number
Capacity, each, mgd
Circulation ratio
Tertiary treatment
Loadings
Plow, mgd
Suspended solids
Concentration, mg/1 b
Loading, 1,000 Ib/day
Ammonia nitrogen, peak
Concentration, mg/1
Loading, Ib/day3
4
630
1,320
5
15
35
90
35
170
3
65
3.4
55
170
78
6.5
3,000
Tertiary treatment (con't)
Chemical treatment
Alum, peak rates
Dry dosage, mg/1 (17 percent
. A120)
Volume, 1,000 gal/day1 (8.3
percent A12C>3)
Sulfuric acid, peak rate,
(93 percent H2S04)
Dosage, meq/1 m
Volume, gal/day
Polyelectrolyte, peak rate,
(0.5 percent solution)
Dosage, mg/1
Volume, gpmn
Chlorine, peak capacities
Prechlorination,
mg/1 b
1,000 Ib/day
Filter influent,
mg/1 b
1,000 Ib/day
Disinfection,
mg/1 b
1,000 Ib/day
Ammonia nitrogen removal,
mg/1
1,000 lb/dayb
Dechlorination
Sulfuric dioxide, peak rate,
. mq/1 .
1,000 Ib/day
Raw water pumps
Number a
Capacity, each, mgd o
Total head, each,.ft
Flotation tanks
Number _
250
21.2
3.0
4,700
2.0
15.0
17.5
8
17.5
8
5
2.3
105
48
8.3
3.8
4
13.75
11.0
Diameter, each, ft
.ft"
4
85
7
5.1
3
600
Side water depth, i.<- - o
Solids loading rate, Ib/ft /day
Assumed float concentration,
percent n
Peak float discharge rate, gpm
Surface loading rate, includ- ,P
ing pressurized flow, gpm/ft 2.4
Pressurized flow, gpm 4,500
Pressure, maximum psigq 80
Air flow, maximum scfmr 80
Air to solids ratio, minimum, kg
air/kg solids 0.179
Dual medial filters
Number (bifurcated)
Width, ftcc
Length, ft p
Filtration rate, gpm/ft
All filters in service
One in backwash
4
34
50
5.7
7.5
(continued on next page)
20
-------
TABLE 3. (continued)
Parameter
Value
Parameter
Tertiary treatment (con't)
Dual medial filters (con't)
Media
Anthracite coal
Depth, ftc
Effective size/ mm
Sand
Depth, ft
Effective size/ nun
Gravel c
Depth, ft
Backwash
Air _s
Rate, cfm/ft
Volume, cfmr
Water _P
Rate, gpm/ft
Minimum
Maximum
Volume, mgd
Minimum
Maximum
1.0-
1.1
1.5
0.65-
0.75
0.67
4
3,400
13
26
16.0
32.0
Value
Tertiary treatment (cont'd)
Filtered water pumping station
Number of pumps a 3
Capacity, each, mgd 21.5
Total head, ftc 15.7
Chlorine contact canal
Length, ftc 1,030
Average width, ft 19.26
Depth, ftc 7.63
Detention time, min 30
Reaeration blowers
Number 2
Capacity, each, cfmr 1,500
mgd x 3,785 = m /day.
bl,000 Ib/day x 0.454 = 1,000 kg/day.
Cft x 0.305 = m.
dgpd/ft2 x 0.0407 = m3/day/m2.
el,000 ft3 x 0.0283 = 1,000 m3.
flb/l,000 ft3/day x 0.016 = kg/m3/day.
glb/ft3/day x 16 = kg/m3/day.
hft3/lb/day x 0.062 = m3/kg/day.
ac x 0.405 = ha.
3lb x 0.454 = kg.
k 3
mil gal x 3,785 = m .
"Ib/ac/day x 1.12 = kg/ha/day.
mgal/day x 3.78 = I/day.
gpm x 0.063 = I/sec.
ฐlb/ft2/day x 4.88 = kg/m2/day.
pgpm/ft2 x 0.0407 = m3/min/m2.
qpsig x 6.89 = kK/m .
rscfm x 0.0283 = std. m /min.
Scfm/ft2 x 0.305 = m3/min/m2.
21
-------
240
I
NOTES: (1) mgd x 3,785 = m3/day
(2) Ib/day x 0.454 - kg/day
I I I I I 1 1 1
MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC JAN FEB MAR
I
- 160 g
- 120
cc
UJ
5
Figure 8. Plant flow and BOD loadings for period of special sampling program.
TABLE 4. WASTEWATER FLOWS AND
CHARACTERISTICS
Value
Parameter
Canning Noncanning
season3 season"
Flow, mgd
37
17
BOD,, mg/1 d
BODI, 1,000 Ib/day
Suspended solids, mg/1
Suspended solids, 1,000
lb/dayd
COD, mg/1 ,
COD, 1,000 lb/daya
Ammonia nitrogen, mg/1
Organic nitrogen, mg/1
Total phosphorus, mg/1
530
160
660
200
970
300
12
17
6.1
320
45
380
54
670
95
20
15
8.6
aAugust 1 - September 30, 1976.
bMarch 15 - July 31, 1976; November 1, 1976
March 16, 1977.
ฐmgd x 3,785 = m3/day.
dl,000 Ib/day x 0.454 = 1,000 kg/day.
22
-------
TABLES. INDUSTRIAL WASTE
LOADINGS FOR THE
STOCKTON PLANT
Valuec
FlOW,
BOD5,
BOD5,
mgd
mg/1
1,000 lb/daye
Canning
season"-*
22
670
120
Noncanning
season0
3.8
580
18
Suspended solids,
mg/1
Suspended solids,,
1,000 Ib/day?
550
100
450
14
Represents six canneries, one meat packer,
and one cardboard box manufacturer.
August - September 1976.
ฐMarch - July 1976; November 1976 -
February 1977.
mgd x 3,785 = m /day.
el,000 Ib/day x 0.454 = 1,000 kg/day.
23
-------
SECTION 5
DESIGN
Imposition of the February 1969 Regional Water Quality
Control Board requirement calling for a reduction of
nitrogen in the Stockton plant effluent necessitated
development of a scheme for removal of nitrogen during both the
canning and honcanning seasons. This previously described
scheme involved algae removal during the canning season and
nitrification-denitrification during the noncanning season.
Initially, the city's consultants recommended in a 1969
report that the activated sludge process be added to the plant
flow diagram and that it be operated in parallel with the
existing rock trickling filters (3). The algae removal process
recommended for use was coagulation-flocculatipn-sedimentation
to be followed by filtration and disinfection prior to stream
discharge.
Investigation into alternative processes following the
1969 recommendations eventually resulted in two major changes
in the recommended plan. Plastic media trickling filtration,
then coming into widespread use, was substituted for the
parallel activated sludge/rock trickling filter processes.
Dissolved air flotation was substituted for coagulation-
flocculation-sedimentation as the algae removal process.
Use of plastic media trickling filtration had two major
advantages over the dual process plan previously considered.
First, conversion of the existing rock media biofilters to
plastic media was significantly less costly than addition
of separate aeration tanks and activated sludge secondary
clarifiers. Second, operating the two processes in parallel
would have resulted in needless operational complexities; the
situation would have been equivalent to operating two separate
plants with twice the probability for upsets and problems.
Since plastic media trickling filtration was a relatively new
process, however, there was some doubt concerning the expected
performance of the filters, particularly with regard to
nitrification. To ensure that the recommended biofilters could
perform as planned, a 5-mo pilot study was carried out during
the summer of 1972. Results of that study will be described
briefly below.
24
-------
Design of the secondary treatment modifications at
Stockton can be conveniently divided into two aspects: process
design and physical design. While these aspects cannot be
totally divorced from each other, the differentiation is useful
in presenting an organized discussion of the Stockton
upgrading. Process design includes the interrelationships
among projected influent loadings, required effluent
characteristics, anticipated removals in each unit process,
and sizing of added unit processes. Physical design includes
such factors as general site layout, structural design of the
biofilters and associated structures, mechanical equipment
specifications, site piping, and operational flexibility.
A description of the entire plant, including primary-,
secondary, and tertiary treatment facilities and solids
handling and treatment processes, was presented in Section 4.
Information in this section will concern the secondary
treatment portion of the plant. A summary of design data for
the secondary treatment facilities is presented in Table 6.
PROCESS DESIGN
In contrast to the relatively sophisticated design
approaches which have been developed for the activated sludge
process, trickling filtration design has remained essentially
empirical in nature. A method often used for design of plastic
media biofilters involves use of the Velz equation:
=
0.5
(la)
where:
Se = effluent 6005, mg/1
So = influent 6005, mg/1
kj = treatability coefficient
D = media depth, ft
q = hydraulic loading, (excluding recycle)
gpm/ft2.
The treatability coefficient, k, depends on the type of
waste being treated. For domestic wastewater, values of
0.07 to 0.08 are usually cited. For industrial wastes, lower
values of k are often found. Industrial waste treatability
varies more than domestic waste, but typically cited values of
k range from 0.04 to 0.055. (Equation la differs slightly from
Equation 1 in that the media specific surface is hidden in the
treatability coefficient, k.)
25
-------
TABLE 6. DESIGN DATA SUMMARY FOR SECONDARY TREATMENT FACILITIES
Parameter
Value
Parameter
Value
Flow, mgda
Noncanning season
Average dry weather 23
Peak storm rate 60
Canning season, peak month 58
Loadings
BOD5, mg/1
Noncanning season 170
Canning season, peak month 390
BOD5, 1,000 Ib/day
Noncanning season 32
Canning season, maximum month 189
Suspended solids, mg/1
Noncanning season 60
Canning season, peak month 155
t>
Suspended solids, 1,000 Ib/day
Noncanning season 11
Canning season, peak month 75
Trickling filters
Rock media trickling filters
Number c 3
Diameter, ft c 166
Media depth, ft 3d 4.2
Total volume, 1,000 ft 270
Total hydraulic capacity (includ-
ing recirculation), mgda 30
Plastic media trickling filters
Number 3
Diameter, ft 166
Media depth,ft 22
Total volume, 1,000 ft3 1,430
Total hydraulic capacity (includ-
ing recirculation), mgda 72
Unit loading, Ib BODg/1,000 ft3/daye
Noncanning season 19
Canning season, peak month 110
Recirculation
Recirculation pump capacity, mgd 76
Recirculation ratio (recycle/in-
fluent)
Noncanning season
Canning season, peak month
Secondary sedimentation tanks
Number
Diameter, ft
Side water depth, ft
Detention time, hr
Noncanning season
Canning season, maximum month
Overflow rate, gpd/ft
Noncanning-season, ADWF
Peak storm rate
Canning season, maximum month
Secondary treatment performance
Noncanning season
BOD5 removal, percent
Effluent BODs, mg/1
Effluent suspended solids, mg/1
Canning season, maximum month
BOD5 removal, percent
Effluent BOD5, mg/1
Effluent suspended solids, mg/1
3.4
0.76
4
100
12
2.9
1.2
700
1,900
1,800
90
17
35
70
120
165
mgd x 3,785 = m /day.
bl,000 Ib/day x 0.454 = 1,000 kg/day.
1,000 ft3 x 28.3 = m3.
lb/1,000 ft3/day x 0.016
fgpd/ft2 x 0.0407
kg/m /day.
m /day/m .
Modifications to the Stockton trickling filters involved
conversion of three of the existing rock media biofilters to
plastic media and retaining the three remaining rock media
biofilters. Loadings and recirculation rates given in Tables 3
and 6 are based upon this configuration. This was a slight
modification to an earlier plan involving two plastic media
filters (6.7 m or 22 ft deep) and four redwood media filters
(1.3 m or 4.25 ft deep). Canning season organic loadings,
normally critical for design, were 2.2 kg BOD5/m3/day
(135 lb/1,000 ft3/day) for two plastic and four redwood media
filters and 1.8 kg/m3/day (110 lb/1,000 ft3/day) for three
plastic and three rock biofilters. Noncanning season loadings
26
-------
were 0.37 kg BOD5/m3/day (23 lb/1,000 ft3/ day) for two plastic
and four redwood filters and 0.30 kg/m3/day (19 lb/1,000 ft3/
day) for three rock and three plastic media filters. Estimated
removals were 70 percent for the canning season and 90 percent
for the noncanning season. Although cross-connections between
the rock and plastic filters makes it difficult to relate these
removals to their respective loadings using the Velz equation,
evaluations of k for plastic media alone will be presented in
Section 7 for the pilot study and for the Stockton plant during
the special 1-yr sampling program undertaken in conjunction
with this study.
Hydraulic Loadings
The maximum hydraulic loading for the plastic media
filters is 0.031 m3/min/m2 (0.77 gpm/ft2) at the design
application rate of 91,000 m3/day (24 mgd) per filter. At this
loading, the recirculation ratio during the canning season
maximum month is 0.76:1; during the noncanning season, it is
3.4:1.
Because the speed of the trickling filter supply pumps can
be varied, the hydraulic loading can be decreased below the
maximum value cited above. A lower hydraulics loading,
approximately 0.024 m3/min/m2 (0.6 gpm/ft2), was being applied
to the plastic media biofilters during the first portion of
the sampling program carried out for this study. Because this
loading was lower than that recommended by the media manufac-
turer for complete "wetting" of the media surface, the pump
speed was increased during the last portion of the sampling
program in an attempt to improve performance. The results of
that operational change are presented in Section 7.
Nitrification
There was little information available at the time
concerning nitrification (conversion of ammonia nitrogen to the
nitrate form) in trickling filters, particularly with plastic
media. The most extensive study had been done by the National
Research Council during World War II (4). That study indicated
that a high degree of nitrification could be obtained in rock
media trickling filters at organic loadings below approximately
0.19 kg BOD5/m3/day (12 lb/1,000 ft3/day). The specific
surface of plastic media is much greater than for rock media,
82 to 132 m2/m3 (25 to 40 ft2/ft3) for plastic compared with
39 to 59 m2/m3 (12 to 18 ft2/ft3) for 8-cm (3-in.) rock. It
is, therefore, reasonable to expect that nitrification can be
obtained with higher loadings when using plastic media. The
combined noncanning-season, design average loading of 0.30 kg
BOD5/m3/day (19 lb/1,000 ft3/day) for the plastic plus rock
filters was judged to be sufficiently low to expect a high
degree of nitrification.
27
-------
Air Supply
Air containing oxygen to allow bacterial growth is
supplied to each plastic media biofilter by eight fans. The
design air flow with all fans operating is 1.8 m3/min/m^
(6.0 cfm/ft2), which is equivalent to an oxygen supply of
approximately 1,270,000 kg oxygen/day (2,800,000 Ib/day) to
each of the three filters.
Generally, it is estimated that 2 to 5 percent of the
oxygen that passes through a biofilter is available for use by
microorganisms. The maximum-day design BOD5 loading to the
filters is 111,000 kg/day (245,000 Ib/day). Assuming that the
oxygen required is equal to the BODs loading, the peak rate
of oxygen required is approximately 3 percent of the maximum
supply rate.
Forced draft ventilation was chosen for use because of the
high canning season loads received at Stockton. The question
of whether natural ventilation is adequate or whether forced
draft ventilation is necessary will be discussed in Section 8.
Specific Surface Area
Contract documents prepared for the Stockton project did
not specify a minimum specific surface area. The two plastic
media manufacturers represented in the bidding (see Section 6)
were Dow Chemical Co. and B. F. Goodrich; both offered media
with a specific surface area of 89 m2/m3 (27 ft2/ft3). The
contractor representing B. F. Goodrich was the low bidder and
was selected for the job (see Section 6).
Pilot Study
Because the design loadings for the Stockton plant were
unique and because of the relative absence of data regarding
nitrification performance of plastic media biofilters, a 5-mo
pilot study was conducted from mid-July through mid-December,
1972 (5,6). A further purpose of the study was to determine
whether odors might be produced by the tower during high
loading periods. Previous odor problems from plastic media
biofilters used for combined domestic and cannery wastes in a
nearby city were the principal cause for this concern. A brief
description of the pilot study and its results is presented
below. A more complete discussion has been published
elsewhere (6).
Description of Pilot Plant and Procedures
The pilot plant used for the study consisted of a steel
shell 0.9 m (3 ft) in diameter and approximately 9.1 m (30 ft)
high which contained a total of 4.2 m3 (150 ft3) of Surfpac
plastic media (6.55 m or 21.5 ft high and 0.65 m2 or 7 ft2
.cross-sectional area). The specific surface for Surfpac
28
-------
(manufactured at that time by Dow Chemical Co. and now
manufactured by- Envirotech) is 89 m2/m3 (27 ft2/ft3). Loadings
applied to the pilot plant (with the exception of two particular
periods) were varied to simulate loadings which would have been
received by the full-scale plant had it been in operation in
1972. The study was timed to obtain data from the canning
season, a portion of the noncanning season, and the transition
period from canning to noncanning loadings when nitrification
would be initiated within the biofilter.
During two portions of the study, once in the canning
season and once in the noncanning season, the loadings were
increased. This allowed performance of the filter to be
evaluated under design loading conditions.
Forced ,air flow through the tower at the design rate
of 1.8 m^/min/m2 (6 cfm/ft2) was provided by a small fan.
Supplemental nitrogen was added to the nutrient-deficient
cannery waste during the canning season; diammonium phosphate
was added to the influent at a sufficient rate to provide 1 kg
nitrogen/20 kg 6005 removed.
Twenty-four-hr composite samples of influent (Stockton
plant primary effluent) and effluent streams were taken three
times per week from July 17, 1972, through December 13, 1972.
Pilot plant effluent samples were settled 60 min in an Imhoff
cone prior to analysis to simulate secondary clarification.
Analyses were made for 6005, soluble 8005, COD, suspended
solids, nitrogen forms, alkalinity, and pH.
During the latter part of the study, high effluent BODs
values led to the belief that nitrification was occurring in
the BOD5 bottle. Normally, nitrification in the BOD test takes
15 to 20 days to occur; values obtained in the standard 5-day
test period then represent carbonaceous BOD only. However,
when BOD5 analyses are undertaken on well-stabilized effluents
containing high populations of nitrifying organisms and ammonia
nitrogen for substrate, it is possible for nitrification to
occur within the 5-day incubation period.
In order to prevent this from occurring, 6005 tests for
the last portion of the study were run using a 0.1-M ammonium
chloride solution to suppress nitrification (7). Ammonia
nitrogen in such excessively high concentration is toxic to the
nitrifying organisms.
At the time the pilot study was undertaken, it was
believed that while the 0.1-M ammonium chloride solution would
preclude nitrification in the BODs test, carbonaceous 6005
would not be affected. Information developed since that time,
however, now indictes that carbonaceous BOD may in fact be
reduced by the addition of ammonium chloride. This question is
discussed further in Appendix D.
29
-------
Pilot Study Results
Results of the 1972 pilot study are summarized in Table 7
for two periods: the canning season (July 17 through Septem-
ber 15, 1972) and the noncanning season (October 16 through
December 13, 1972). The transition period from September 16
through October 15 was omitted from the table. For the
noncanning season, effluent BODs values are shown with and
without suppression of nitrification.
TABLET. PILOT STUDY RESULTS
Canning season
Noncanning season
parameter
Main plant flow, mgde
Temperature, C
BODj, mg/1
With nitrogen suppres-
sion f
Without nitrogen sup-
pression
Soluble BODs, mg/1
With nitrogen suppres-
sionf
Without nitrogen sup-
pression
COD, mg/1
Total suspended solids,
mg/1
Organic nitrogen, mg/1
Ammonia nitrogen, mg/1
Alkalinity, mg/1 as CaC03
pH
Influent0 Effluentd
36
29
_ _
310 71
_ _
280 37
550 220
110 42
15 11
3 . 5g 18^
240 310
6.9 7.7
Removal,
percent
-
-
_
77
_
87
60
62
27
-
-
~
Influent0
15
26
140
150
120
120
340
70
12
16
170
7.0
Effluent*3
-
-
10
21
16
18
97
27
8.9
1.4
110
7.7
Removal,
percent
-
-
93
86
86
84
72
61
26
91
-
"
July 17, 1972 to September 15, 1972.
bOctober 16, 1972 to December 13, 1972.
cStoekton plant primary effluent.
Settled 1 hr in an Imhoff cone.
emgd x 3,785 - m3/day.
November 1 to December 13, 1972; 0.1-M ammonia nitrogen used.
^Ammonia added to nutrient-deficient cannery waste.
Nitrification performance during the pilot study is
summarized in Figure 9 and Table 8. Figure 9 depicts time
histories of effluent concentrations for total Kjeldahl nitrogen
(TKN), ammonia nitrogen, nitrite nitrogen, and. nitrate nitrogen
from the canning season through the transition period into the
noncanning season. Nitrification began in mid-September when
30
-------
E
z"
o
cc
I-
(-
01
36
32
28
24
20
16
12
8
4
0
5.
O
IT
I-
01
AUG
SEPT
NOV
OCT
DATE, 1972
(a) AMMONIA NITROGEN AND TOTAL KJELDAHL NITROGEN
DEC
oooooo-looo
AUG
SEPT OCT
DATE, 1972
(b) NITRITE NITROGEN
NOV
DEC
AUG
SEPT OCT
DATE, 1972
(c) NITRATE NITROGEN
NOV
DEC
Figure 9. Pilot study nitrification performance.
31
-------
the organic loadings decreased and was initially manifested by
an increase in the nitrite nitrogen levels. Steady state
nitrification was occurring by the latter part of October.
TABLE 8. PILOT STUDY NITRIFICATION PERFORMANCE
Concentration, mg/1
Period Ib BOD-/l?OOOgft3/daya
Influent
Effluent
Removal, percent
10/23/72
to
11/21/72
11/27/72
to
12/13/72
Ammonia
nitrogen
14 17
22 18
TKV Ammonia
nitrogen
28 1.0
29 2.0
Ammonia
nitrogen
9.9 94
11 89
TKN
65
62
*lb/l,000 ft3/day x 0.016 = kg/m3/day.
Shown in Table 8 are steady state nitrification results
for two periods during the noncanning season. At an organic
loading of 0.22 kg BOD5/m3/day (14 lb/1,000 ft3/day), an
ammonia nitrogen removal of 94 percent was obtained with an
effluent ammonia nitrogen concentration of 1.0 mg/1. During
the final weeks of the study, the organic loading was increased
to 0.35 kg BOD5/m3/day (22 lb/1,000 ft3/ day), close to
the design value. The ammonia nitrogen removal during this
period was 89 percent with an effluent concentration of
2.0 mg/1.
Although the ammonia nitrogen removals obtained were quite
high, organic nitrogen removals were low, averaging 19 percent
for the periods covered by Table 8. It was concluded that the
contact time of the waste in the biofilter was insufficient to
allow conversion of organic nitrogen to ammonia which would
then undergo nitrification.
The conclusions drawn from the pilot study were that the
plastic media trickling filters could perform as planned,
removing carbonaceous BOD$ during the canning season without
producing odors and reducing ammonia nitrogen concentrations
to low levels during the noncanning season. Design and
constuction of the upgraded facilities then proceeded as
originally devised.
PHYSICAL DESIGN
Conversion of the existing trickling filters from rock
media to plastic media required, in addition to modifications
to the filters themselves, substantial modifications to the
32
-------
filter distribution and collection systems. Provision had to be
made in the filters for taller, heavier center columns and
rotary distributors, for air inlet ducts and fans, and for a
plastic media support system. Other changes included addition
of pumps and major distribution lines, routing of foul air from
the plant headworks through two of the plastic-media filters for
odor control, and addition of electrical controls.
Filter Walls and Rotary Distributors
In order to retain the existing filter foundations, a
light-weight wall was used to contain the plastic media. The
original filter walls were solid concrete 2.0 m (6.5 ft) high;
the new walls are 8.8 m (29 ft) high. A concrete-block wall
was built on top of the existing wall as shown in Figure 10.
Three layers of concrete blocks are separated by 20-cm (8-in.)
high sections of solid concrete; the walls are capped by a
reinforced concrete tension ring.
Three characteristics of the concrete-block construction
make the selection of a sealer for the filter walls critical:
(1) the blocks are porous and thus absorb the sealer as it is
applied, (-2) expansion and contraction of the wall can cause
cracking in the sealer, and (3) the concrete blocks tend to
transmit fluids by capillary action. A coal-tar epoxy was
used to seal one of the filters but leaks developed soon after
startup (see Section 6). A thin film of polyurethane was used
on the other two filters; polyurethane was selected because i,t
does not contain volatile solvents, which would produce bubbles
in the film, and it stays soft and elastic. This reduced
leakage drastically but did not completely eliminate it.
The new taller center column required a new foundation.
An 1.7-m2 (18-ft2) slab was removed from the center of the
existing foundation to allow excavation and construction of the
new foundation. Filters No. 5 and 6 incorporate a foul-air
distribution chamber in the center column foundation; a
1.22-m (48-in.) diameter foul-air duct under the,filter floor
terminates at the distribution chamber. Section views of the
center columns are shown in Figure 11. The existing 0.91-m
(36-in.) diameter filter supply line was determined to be
sufficiently large to handle the increased flows and was
retained. The center column has an inner diameter of 1.2-m
(4.0 ft) and an outer diameter of 2.0 m (6.5 ft). It has an
overall height of approximately 7.6 m (25 ft), 1.8 m (6 ft) of
which is below the filter foundation.
New Walker Process rotary distributors were installed on
the center columns (Figure 12). At the center, the four arms
are connected to a center column assembly composed of the
support column for the truss guide-wires, an outer cylinder,
two inner weirs, and a waterproof thrust-bearing assembly. The
33
-------
EL. 123.00-
GRATING-
EL. 121.1'
PVC
FILTER
MEDIA
ORIGINAL
FILTER
WALL-
EL. 97.17
MEDIA SUPPORT SYSTEM
~\
-EL. 04.18
UPPER
RING
BEAM
CONCRETE
BLOCKS
REINFORCING STEEL
AND PEA GRAVEL
" GROUT PLACED IN
BLOCK WALL
LOWER
RING
BEAM
EFFLUENT
CHANNEL COVER
EFFLUENT
CHANNEL
^*wf!ffef
Figure 10. Trickling filter sidewall and effluent collection channel. Photographs
show collection channels before and after conversion.
34
-------
6'-6" DIA.
-
FOUL AIR
DISTRIBUTION
CHAMBER \
\\\\\\\\\\N
^
j
"DIA. '
DUCT
EL. 82.00 -y
o
\
\
' o
f.
0;
0.
0
'0
0
1
^
t*f
a-
r
O
4'-0"
DIA.
-^T
ซ .
.<
$
0
,-.
z*~-
0'
<
b-
.'ซ
0*
.1
V
'd
/
T?
L^?
1
0.
' ''''."'. o '
-
0
t
0
0 ' . 0
.' . o ''.--.
18'-0" SQUARE
o '
-MEDIA SUPPORT
SYSTEM EX.STING
HLItH I-LOUH
P*
^ .
-ป.
y EL. 94.19
>. XX \\\\\ XXX
(
^ 36" DIA.
INFLUENT PIPE
EXISTING
FILTER FLOOR
EL. 94.19 v
EXISTING i.
EL. 82.00
_j
o .
\ 36" DIA.
INFLUENT PIPE
EXISTING
FILTER 4 ONLY
Figure 11. Center columns.
35
-------
four opposing arms penetrate and are joined to the outer
cylinder. Two of the opposing pipes have weirs welded to the
outer cylinder such that water entering the outer cylinder must
flow over the weir in order to flow into the arms. The upper
rim of the inner weirs is above the level of the pipes but
below the level of the outer cylinder. At low flows, this
allows water to flow in only two of the arms ensuring an even
distribution of flow to the media surface. Each arm has a
series of holes drilled in its counterclockwise side at
centerline. Into these holes are inserted spray nozzles.
The nozzle openings are rectangular in shape, and their size is
adjustable. Water flows out the holes in a flat spray pattern.
Portions of the original distributors from the converted filters
were salvaged and used in the other three rock media filters.
Figure 12. New distributors for plastic media trickling filters.
Media Support System and Plastic Media
The new media support system provides greater air space
below the media for increased ventilation. The plastic media
is supported by U-shaped concrete channels 0.46 m (1.5 ft) wide.
Holes in the channels 20 cm (8 in.) in diameter at 0.60-m (2-ft)
spacing aid ventilation. The channels are placed in parallel
rows along the filter foundation supported by piers of concrete
36
-------
blocks which are keyed into the foundation with dowels
(Figure 13). Concrete blocks were used for economy since large
quantities of concrete blocks were used for the filter walls.
Details of the media support system are shown in Figure 14.
Clearance between the
bottom of the plastic media
and the filter floor is 0.91 m
(3 ft) except over the air
inlet ducts and fan-housing
enclosures. Media support
channels were placed on 10-cm
(4-in.) high supports over the
ducts, as shown in Figure 14.
The increase in elevation of
the bottom of the plastic
media over the ducts is 0.30 m
(1 ft).
The plastic media used in
the filters was Vinyl Core,
manufactured by B. F. Goodrich.
The polyvinyl chloride (PVC)
media comes in modules (0.61 m
x 0.61 m x 1.22 m, or 2 ft
x 2 ft x 4 f t); the blocks are
cut to fit around the center
column and the filter walls.
The lower modules were made
from PVC sheets of greater
thickness to provide higher
strength. The modules were
installed in alternating
layers, with each layer
composed entirely of one
type of module. The pattern
of the media modules differed
for odd and even layers to
prevent short-circuiting of the wastewater. A plastic grating
was placed over the top of the last layer. The overall depth of
the media is 6.7 m (22 ft).
Air Flow
A forced-air ventilation system was provided in the
plastic media filters to maintain aerobic conditions. Four
air inlet ducts were constructed on each filter foundation at
90-degree spacings. The ducts extend from the outer walls of
the filter inward toward the center column. Each duct is 2.1 m
(7 ft) wide by 0.91 m (3 ft) high. A piece of the original
filter wall was removed opposite each duct to allow for the
installation of fans. Two fans supply each duct as shown in
Figure 13. Media support system.
37
-------
Figure 15. The fans are axial-flow, constant-speed types and
were manufactured by the Pennsylvania Ventilator Company. They
are driven by Westinghouse 3.7-kW (5-hp) motors. Manual
controls are provided for each fan. Holes in the air inlet
ducts allow the air from outside to reach the filters; air is
forced by the fans up through the plastic media from below.
Upward air flow is approximately 1.8 m3/min/m2 (6 cfm/ft2)
with all fans operating.
NOTE: ft x 0.305 = m
PRECAST
CHANNELS
PVC FILTER MEDIA
X
CONCRETE
BLOCKS
Figure 14. Media support system details.
In addition to the fresh-air ventilation, filters
No. 5 and 6 receive foul air from the headworks of the plant.
Foul air flows through 1.2-m (48-in.) ducts beneath the
foundation to the foul-air distribution chamber in the center
column foundation. The foul air is deodorized by biological
oxidation as it rises through the plastic media.
Effluent Collection System
In order to provide increased effluent collection
capacity, an external collection pipe system was added to each
plastic media filter. The external collection system consists
of two effluent collection boxes at opposite sides of the
filter and 0.91-m (36-in.) diameter effluent collection pipes
leading to a filter return box at the original filter return
pipe connection (Figures 16 and 17). The original collection
system consisted of an open channel 0.60 m (2 ft) deep
surrounding the filter wall and sloping toward the filter
return pipe. The channel width varies from its maximum width
near the filter return pipe, to accommodate the accumulated
flow, to a minimum on the opposite side of the filter,
coinciding with the high point of the channel bottom. This
existing channel was covered during conversion to ensure that
ventilation air would be forced up through the media and not
out into the collection channel (see Figure 10).
38
-------
Figure 15. Plastic media filter fans.
At two separate locations,
each 90 degrees from the filter
return pipe, a portion of the
bottom of the original effluent
channel was removed and an
effluent collection box
constructed. The bottom
elevation of the box, which is
the same as the 0.91-m (36-in.)
collection pipe invert eleva-
tion, is over 1.22 m (4 ft)
below the original channel
bottom.
Effluent from the side
opposite the filter return box
flows along the channel to the
collection boxes; it then drops
down into the boxes and flows
through the effluent collection
pipes to the filter return box.
Effluent entering the channel
between the collection boxes
and the return box continues in
the original channel and enters
the filter return box through a
portion of the original filter
return pipe. Effluent then
flows from the return box
to the filter distribution
structure through new 1.22-m
(48-in.) diameter pipes.
Filter Distribution Structure No. 1 and Piping
The existing filter distribution structure was enlarged
and modified extensively to provide for increased capacity and
better control. An isometric view of the original structure
is shown in Figure 18 and the modified structure is shown in
Figure 19.
Distribution Structure Functions
The four major functions of the distribution structure are:
(1) To combine primary effluent with recycled trickling
filter effluent and distribute it to the individual
filters,
(2) To control filter effluent recirculation to maintain a
constant flow to the filter,
(3) To discharge effluent to the secondary sedimentation
tanks, and
39
-------
NOTE: in. x 2.54 = cm
EFFLUENT
COLLECTION
BOX
36"INFLUENT
PIPE
CENTER COLUMN
EFFLUENT
COLLECTION
BOX
{ FOR SECTION
VIEWSEE FIG. 17 )
48" PIPE
FILTER
RETURN
BOX
( FOR SECTION
VIEW, SEE
FIG. 17)
36" PIPE
ORIGINAL EFFLUENT
COLLECTION CHANNNEL
Figure 16. Plan view of external collection system.
40
-------
5'-4"
FILTER FAN
HOUSING
BOLT-ON
COVER r
/
ORIGINAL
EFFLUENT
COLLECTION
CHANNEL
'36" RCP^
ITO FILTER}
.RETURN,
.^
/
.. 89.00
EFFLUENT COLLECTION BOX
NOTES: \n. x 2.54 = cm
ft x 0.305 = m
2'-0" DIA. MANHOLE
8"
5'-0"
TO CIRCULATION
STRUCTURE
8'
EL. 95.00 9 {+)
FROM EFFLUENT
COLLECTION BOX
INV. 88.42
FILTER RETURN BOX
Figure 17. Section views of effluent collection box and filter return box.
41
-------
(4) To provide sufficient head to supply effluent to the
rock media filters by gravity.
FROM
FILTER N0.5
FROM PRIMARY
SEDIMENTATION
TO SECONDARY
SEDIMENTATION
FROM NO.3
TO NO.4
FROM NO.1&2
FROM NO.4
Figure 18. Original trickling filter distribution structure.
The structure is composed of two main chambers: an outer
effluent chamber and a higher, inner influent chamber. In the
original structure, a 1.52-m (60-in.) diameter line from the
primary sedimentation tanks supplied primary effluent to the
influent box of the distribution structure. Effluent from the
six rock media filters entered the outer box through five
separate filter return lines. Recirculation pumps lifted the
filter effluent into the higher influent box to mix with
the primary effluent. The mixture of primary and secondary
effluent flowed by gravity through five filter supply lines.
Filters No. 3, 4, 5, and 6 each have separate supply lines. A
smaller distribution structure located between filters No. 1 and
2 distributes the flow from one line between the two filters
and combines the effluent from the two filters to return it to
the larger structure. This smaller distribution structure was
not modified. A plan view of the area and major pipelines is
shown in Figure "20.
42
-------
NEW REC1RCULATION PUMPS
TO SECONDARY
SEDIMENTATION
TO N0.3
TO NO'S.1&2
FROM NO'S.1&2
Figure 19. Modified trickling filter distribution structure.
43
-------
FILTER NO. 6
SUPPLY PUMPS
NO. 5 & 6
PRIMARY
SEDIMENTATION
TANKS
DISTRIBUTION
STRUCTURE NO. 1
FROM PRIMARY
SEDIMENTATION
TANKS NO. 5 & 6
SECONDARY
SEDIMENTATION
TANKS
EXISTING
36" HOP'S
AND
SUBSTATION
SUPPLY PUMP
NO. 4
FILTER NO. 3
NOT CONVERTED
TO PLASTIC MEDIA)
SECONDARY
CLARIFIER
DISTRIBUTION
STRUCTURE
LEGEND
NEW
EXISTING
DISTRIBUTION I
STRUCTURE NO. 2
-EXISTING
42" PIPES
(ONE ACOVE
THE OTHER)
NOTE: in. x 2.54 - cm
RCP - REINFORCED CONCRETE PIPE
MCC - MOTOR CONTROL CENTER
Figure 20. Piping diagram for upgraded secondary treatment facilities.
Modifications to the Structure
The modified structure retains the basic inner and outer
boxes, although both are enlarged. A new 1.52-m (60-in.)
diameter pipe was added to supply trickling filter effluent to
the secondary sedimentation tanks. The two 1.52-m (60-in.)
diameter pipes provide capacity to ultimately supply five
secondary sedimentation tanks, four of which presently exist.
Larger filter return lines from the filter return boxes to the
effluent chamber were provided. Two additional recirculation
pumps were installed, making a total of six, to accommodate
higher flow rates through the structure. An emergency overflow
line was constructed between the influent and effluent chambers.
Supply Piping to Filters
From the influent chamber of the structure, five pipes run
to various locations as follows (Figure 19):
(1) A 0.91-m (36-in.) line to trickling filter No. 3
(2) A 1.07-m (42-in.) line to trickling filter distribu-
tion structure No. 2
44
-------
(3) A 0.91-m (36-in.) line to trickling filter No. 4
supply pump
(4) .A 0.91-m (36-in.) line to trickling filter No. 5
supply pump
(5) A 0.91-m (36-in.) line to trickling filter No. 6
supply pump
These five pipes have manually-operated, isolating sluice gates
located inside the influent chamber.
Return Piping from Filters
There are five pipes that enter the effluent chamber from
various locations as follows:
(1) A 0.91-m (36-in.) line from trickling filter No. 3
(2) A 1.07-m (42-in.) line from trickling filter distribu-
tion structure No. 2
(3) A 1.22-m (48-in.) line from trickling filter No. 4
(4) A 1.22-m (48-in.) line from trickling filter No. 5
(5) A 1.22-m (48-in.) line from trickling filter No. 6
These lines have no isolating sluice gates.
Emergency Overflow Line
A 0.76-m (30-in.) diameter pipe from the influent chamber
to the effluent chamber of the structure provides for emergency
overflow. The influent end of the pipe terminates at a vertical
0.91-m (36-in.) diameter pipe section, the upper end of which
is at elevation 102.00. Mounted inside the vertical section is
a 1.07-m (42-in.) long telescoping weir pipe section. It is
attached to a pedestal-mounted operator by means of a threaded
valve stem. The operator is a manually operated handwheel
located on the center walkway atop the structure. The weir
elevation is adjustable between elevation 102.00 and 105.25.
Trickling Filter Supply
The rock media filters are gravity fed. The water level in
the influent chamber determines the head on the rock media
filter distribution system; a higher water level results in a
higher flow to the filters. The water level is adjusted by
varying the set point for operation of the recirculation pumps.
Since the plastic media filters are over 6.1 m (20 ft)
taller than the original filters, each must be supplied by an
influent supply pump. The change in water surface elevation in
the influent chamber is small relative to the operation head of
the supply pumps (on the order of 0.6m/6.7m or 2 ft/22 ft);
thus, the fluctuations which control the rock media supply rates
have little effect on supply to the plastic media filters.
45
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Chlorine Solution Supply
A chlorine solution supply line terminates at a hose
bib at the southwest corner of the structure. By employing
hoses, chlorine may be added to either the influent or effluent
chambers. When added to the influent chamber, chlorine is used
for filter fly control; when added to the effluent chamber, it
is used for foam control.
Recirculation and Trickling Filter Supply Pumps
Conversion to the plastic medic filters required the addi-
tion of five pumps: three pumps to supply the converted filters
and two additional recirculation pumps for increased flows.
Recirculation Pumps
Recirculation of trickling filter effluent is accomplished
by pumping wastewater which enters the distribution structure
effluent box into the influent box to mix with incoming primary
effluent. Six vertical, motor-driven, fixed-speed, axial-flow
pumps are located around the periphery of the upper structure
(influent chamber) atop the effluent chamber. The four small
pumps at the east end of the structure were part of the original
equipment. These four pumps discharge directly into the
influent chamber above the maximum water level. At the west end
of the structure are two new one-stage Johnston vertical pumps,
Model 24PO (see Figure 19 for pump locations). The new pumps
have a rated design capacity of 1,060 I/sec (16,800 gpm) against
a total dynamic head of 3.4 m (11 ft) at 700 rpm. They
discharge into the effluent chamber below the minimum water
level. Local manual controls for each pump are located on the
structure wall adjacent to the pump. The feeders and the remote
controls for the pumps are located in cubicles in the main motor
control center (MCC) in the operations building.
A conductance-type level probe is mounted on the east
inside wall of the influent chamber which measures the water
level in the influent chamber and transmits a signal to the
level controller located at the main MCC. When the individual
pump selector switches are set for automatic operation, the
level controller will start and stop the recirculation pumps
remotely. Since the recirculation pumps are a fixed-speed type,
recirculation flow rate is controlled by varying the number of
pumps in operation.
Trickling Filter Supply Pumps
Each variable-speed trickling filter supply pump is located
between the distribution structure and the plastic media filter
which it supplies (see Figure 20 for pump locations). Each is
a Johnston vertical pump, Model 24PS, with a rated capacity of
1,060 I/sec (16,800 gpm) against a total dynamic head of 7.3 m
(24 ft) at 700 rpm. The drive unit is a 1750-rpm, 112 kW
(150-hp), Reliance electric motor, integral with a variable-
speed hydraulic drive directly coupled through an in-line gear
46
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reducer. The gear reducer employs helical gears to give a
reduction ratio of 2.5 to 1. The pumping rate is controlled by
manual adjustment of the variable-speed hydraulic unit.
Secondary Sedimentation Tank Distribution Structure
The original secondary sedimentation tank distribution
structure was replaced by an entirely new structure. The new
structure was designed to accommodate a second 1.52-m (60-in.
diameter influent line from the filter distribution structure
and a future fifth secondary sedimentation tank; the fifth
effluent line will remain capped until the fifth tank is
constructed. New 1.07-m (42-in.) square sluice gates were
installed at each sedimentation tank supply line. The sluice
gates are manually controlled from the top of the structure.
Motor Control'Center (MCC) and Electrical System
A new MCC and trickling filter substation were installed
next to the filter distribution structure for the blowers and
supply pumps. Modifications to the existing electrical system
had to be made to provide for the new controls and to provide
power to the new pumps.
MISCELLANEOUS ASPECTS UNIQUE TO STOCKTON
* Several aspects of the Stockton design were unique to that
situation and may not be applicable in other instances. These
are mostly due to the existence of the oxidation ponds following
secondary treatment. A temporary deterioration in secondary
effluent quality does not cause a dropoff in overall plant
performance. This allowed the trickling filter distribution
structure No. 1 to be shut down for 3 mo while construction was
taking place; primary effluent was bypassed to the oxidation
ponds during that period. In other situations, secondary treat-
ment might need to be continued during the construction period.
Another unique aspect of the Stockton design is that each
plastic media biofilter is fed by a single supply pump. If a
pump is shut down for repairs, the associated biofilter must
also be shut down. A more conventional design (and one which
might be difficult to implement in an upgrading situation) would
be to provide a common supply header between the supply pumps
and the biofilter. In that situation, shutdown of one pump
would not reduce the number of operating filters. The buffering
effect of the Stockton oxidation ponds allowed a simpler, less
costly design to be used.
A final point (not related to the oxidation ponds) concerns
the retention of the original 0.91-m (36-in.) influent feed
lines under the biofilters. Although these had deteriorated
and required repair, they were sufficiently large to permit
their use with the higher flows. At other plants, excessive
deterioration or insufficient size might necessitate their
replacement.
47
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SECTION 6
CONSTRUCTION AND STARTUP
Modifications to an existing wastewater treatment plant
impose added constraints compared with construction of a new
facility. An acceptable level of treatment performance must be
maintained even when structures which require modification are
bypassed. At Stockton, the availability of oxidation ponds made
bypassing of the entire secondary treatment facilities possible
during the noncanning season without violation of discharge
requirements. The heavy seasonal loading on the Stockton plant
by local canneries created a time constraint; with construction
starting in January, four filters, including one plastic media
filter, had to be back in service prior to July.
Maximum utilization of existing structures required unique
designs as discussed in the previous section. Using existing
structures also created construction problems; portions of the
original structures had to be demolished and parts had to be
salvaged, and some parts which were initially thought to be
reusable had to be replaced. Unforeseen deterioration to some
facilities also necessitated repairs.
PRECONSTRUCTION PHASE
The construction contract for the trickling filter
conversion was advertised for bidding twice. The first bids,
opened on November 28, 1972, were more than 20 percent over the
engineer's estimate. Reasons for the high bids were probably:
(1) extra labor costs to meet the tight time schedule, (2) the
possibility of penalties for failure to meet the time schedule,
and (3) possible penalties for treatment interruption related
to bypassing of secondary facilities. The City of Stockton
rejected the first bids.
The second set of bids was opened on December 15, 1972.
Table 9 shows the three low bidders and the amounts of the
bids. The low bid of $1,722,000 by the joint venture, company
Caputo-COAC was found to be in order, and Caputo-COAC was
awarded the contract.
The successful contract bid included furnishing all labor,
materials (excluding the media itself), and equipment for the
conversion of three filters to plastic media; repairs to the
48
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other three filters; modifications to the filter distribution
structure; and the secondary sedimentation tank distribution
structure; electrical modifications; and pump installations;.
The bid also included $50,000 for contingencies.
TABLE 9.
LOW BIDDERS FOR MODIFI-
CATIONS TO SECONDARY
TREATMENT FACILITIES
Order
Bidder
Bid
amount,
dollars
1,722,000
1,793,000
1,819,000
The contract for supplying
and installing the plastic
media was also bid twice. The
first bids were nullified
because the affadavit of
noncollusion was inadvertently
left out of thes e t p f
documents given to the bidders.
The second set of bids was
opened on December 15, 1972.
Table 10 summarizes the three
low bids, the bid amounts, and
the media manufacturers. The
bid by the Linford Mechanical
Company was for a single
filter, using redwood rather than plastic media. The contract
was awarded to the Lomar Corporation, which, possessing a
California contractor's license, represented B. F. Goodrich, a
plastic media manufacturer. A representative of the Ethyl
Corporation protested the bid award, claiming that the B. F.
Goodrich media did not meet specifications, specifically that-, it
had not been used in a comparable operation for 2 yr., -The
city's consulting engineer decided that the Ethyl Corporation
misinterpreted the specifications, and the bid award was upheld.
Caputo-COAC, San Jose
Homer J. Olsen, Inc.,
Union City
DeNarde Construction Co.,
San Francisco
TABLE 10. LOW BIDDERS FOR FILTER MEDIA SUPPLY AND INSTALLATION
Order
Bidder
Bid
amount,
dollars
Media
type
Media' '
manufacturer
Lomar Corporation,
Santa Ana
Linford Mechanical Co.,
Oakland
COAC, Inc., Milbrae
1,839,930
Plastic
713,789a Redwood
2,316,000 Plastic
B. F. Gopdrictv ';-
Del Pak " -: -c;-*
Ethyl Corporation
For filter No. 6 only.
Major equipment items were selected and ordered immediately
after .bid awards. These items included the trickling filter
supply pumps, the recirculation pumps, the rotary distributors,
and the new MCC. The major equipment list submitted';by
49
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Caputo-COAC is presented in Table 11. The manufacturers
selected by the city were: (1) Johnston Pump, (2) Johnston
Pump, (3) Walker Process, and (4) Westinghouse.
TABLE 11. MAJOR EQUIPMENT SUPPLIERS SUBMITTED BY GENERAL
CONTRACTOR
Description
Manufacturer
Installed
price, dollars
Guaranteed delivery
time, days
1.
2.
3.
4.
Trickling filter
supply pumps
Trickling filter
recirculation pumps
Rotary distributors
Motor control center
Johnston Pump
Fairbanks Morse
Johnston Pump
Fairbanks Morse
Walker Process
Pacific Flush Tank
Enviro Tech
Cutler-Hammer
General Electric
Delta Switchboard
Westinghouse
Sierra Switchboard
65,000
Not available
25,000
Not available
125,000-
Not available
125,000
25,000
Not available
22,250
22,000
21,750
150
150
140
150
175
150
150
150
The first preconstruction conference was held on
January 10, 1973. A change order was agreed upon allowing
the contractor to substitute filter No. 4 for No. 5 in the
construction schedule; this filter was to be converted first,
before the start of the canning season. Brown and Caldwell was
retained to inspect construction and review shop drawings.
The contractor submitted a detailed cost breakdown which was
subsequently revised. The revised cost breakdown, is presented
in Section 7.
CONSTRUCTION PHASE
The construction schedule for the Stockton plant was
determined by the need to have four trickling filters on line
by the start of the canning season to avoid overloading the
oxidation ponds. One plastic media filter (No. 4) and the
remaining three rock media filters were scheduled to be in
service by the end of June 1973. The three filters which were
to be converted to plastic media were shut down in January 1973,
the beginning of the construction phase.
Modifications to the distribution structures required that
all the secondary facilities be bypassed. Primary effluent was
bypassed to existing oxidation ponds for secondary treatment;
a bypass period of 90 days was allowed in the construction
specifications. Repairs to the rock media filters were also
made during the bypass period.
50
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Construction Sequence
A Critical Path Method (CPM) analysis of the construction
activities required to put the four trickling filters on line
before the canning season is shown in Figure 21. The CPM chart
is usually made to determine the shortest length of time in
which construction can be completed. Major time constraints are
blocked in, and then other activities are added in the logical
construction sequence, allowing a certain number of days to
complete each item. Solid lines on the chart indicate fixed
times between events. Dotted lines indicate "float" times
for particular activities; e.g., the electrical modifications
could have been done anytime from the start of the contract to
the time that the pumps arrived. In fact, the electrical
modifications were spaced out to cover almost the entire float
time, although they could have been done in less time.
project
to show
The CPM chart in Figure 21 was constructed after
completion to illustrate the construction sequence and
the interrelationships between construction elements. The
length of each box represents the approximate amount of time
that the activity required. Some events shown in the boxes
overlapped slightly; they have been separated for clarity
in presentation.
The vertical dotted lines indicate major milestones in
progress toward putting the four filters back on line. These
milestones are: (1) shutdown of the filters to be converted
to plastic media, (2) the beginning of the scheduled 90-day
bypassing of secondary facilities, (3) completion of major
structural modifications to filter No. 4, which allowed the
plastic media installation contractor to begin work, and (4) the
end of bypassing when the four filters were back on line.
Modification of filters No. 5 and 6 was initiated during
and extended beyond the time period covered by the chart.
Construction activities for these two filters are, for clarity
of presentation, not shown on the chart.
The critical path is the sequence of events which
determines the minimum time required for construction. The
heavy dark line in Figure 21 shows the critical path for this
project. A procurement time of 160 days for the pumps was
the major contribution to the critical path time period. Once
the pumps arrived, the time required for their installation
determined the length of the critical path; all major structural
work on the filter distribution structure was completed before
the pumps arrived. Long procurement times for mechanical
equipment was a chronic problem around 1973. If more normal
delivery times had been experienced, the modification to
trickling filter No. 4 would have been on the critical path.
51
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(A
-------
Also, the modifications to filter distribution structure No. 1
required essentially the whole 90-day bypass period to complete
and thus represents the critical path for this period.
The 90-day bypass period determined scheduling of
modifications to the two distribution structures and the
repairs to the rock media filters. All major modifications to
filter distribution structure No. 1 were completed within the
bypass period and prior to the arrival of the pumps. Repairs
to the rock media filters and modifications to the secondary
clarifier distribution structure had to be completed within the
bypass period and prior to startup.
Temporary chlorine piping had to be installed before
bypassing to allow disinfection of primary effluent prior to
discharge to the ponds. This procedure required only a few days
and was most conveniently accomplished just before bypassing
began. The temporary piping had to be removed and the original
system reconnected just prior to startup.
Major Construction Items
Construction activities for each major construction item
are discussed briefly in this subsection, along with problems
encountered and adjustments made. The timing of the activities
which were required to put the four filters back into operation,
has been previously itemized in Figure 21. Most of the
additional work involved the conversion of filters No. 5 and
6 to plastic media. The construction sequence for these filters
was nearly the same as that shown for filter No. 4 in Figure 21.
Plastic Media Filter Conversion
Filters No. 4, 5, and 6 were shut down in January 1973 for
modifications. Removal of the rock media and dismantling of the
rotary distributors were begun immediately on all three filters.
Modifications were made first to filter No. 4, since it had to
be in operation first. Structural work on filter No. 4 was
approximately halfway complete before construction was begun on
filters No. 5 and 6.
Some demolition of the existing filter walls and floors was
necessary to allow for new structures. Holes were broken in the
bottom of the effluent collection channels for the new effluent
collection boxes. A portion of the filter wall was removed in
four places on each filter for the air inlet ducts. On filters
No. 5 and 6, a portion of the floor was removed in order to put
in the foul air ducts leading from the headworks. A 4.6-m
(15-ft) square area was broken out of each filter floor to allow
excavation for the new center column foundations. Excavation of
a vertical wall is normally difficult because of the possibility
of a cave-in; the ground under the filters was unexpectedly
stable. The excavation pit was shored for safety and compliance
with safety codes. Excavation was also required for the new
effluent collection boxes.
53
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The first concrete pour was for the effluent channel cover
and was followed by those for the lower ring beam on the filter
wall and the air ducts. The lower ring beam was poured in two
sections. Filter No. 6 is shown at this stage of construction
in Figure 22. The center column support, the lower ring beam,
the effluent channel cover, and three of the air ducts are
complete.
Figure 22. Early phase of filter conversion. Shown are the center column,
influent distributor column, air ducts, lower ring beam, and fan
housing for filter No. 4.
The piers for the media support system were installed by
quadrant; variations in the floor elevation of up to 8 cm
(3 in.) made modifications in pier heights necessary. The
piers were designed to be a nominal 3-1/2 concrete blocks high;
this design po's'ed a problem in that concrete blocks had to be
cut to allow for floor elevation variations. Piers of equal
height were installed and then cut to compensate for the
variations. This proved to be a time-consuming procedure.
Media support channels were measured and precut, then set on
the piers with a crane. The quality of the precast channels
was poor; depth variations were excessive, and many had not
been cut to the right lengths.
54
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During construction, it was found that hydrogen sulfide
had caused deterioration of existing filter influent lines on
filters No. 5 and 6 and portions of these lines had to be
repaired. Flexible joints were installed between the influent
lines and the new center column foundation to allow for
differential settling.
After the filter walls were constructed, a sealer was
applied to the inside of the walls. The coal .tar epoxy sealer
used on filter No. 4 did not seal properly. A polyurethane
sealer was used instead on filters No. 5 and 6. The center
columns and the rotary distributor were installed in filters
No. 5 and 6 before the plastic media; the filters were then
operated without the media to test the sealer (Figure 23). The
polyurethane sealed the walls satisfactorily.
Figure 23. Operation of distributor prior to media installation. After leakage
occurred through walls of filter No. 4, a different sealer was used for
the inside walls of filters No. 5 and 6. These filters were then tested
for leaks prior to media installation.
55
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Excavation for the 0.91-m (36-in.) effluent collection
pipes and the filter return box was begun, but not completed,
prior to media installation at each filter.
was then turned over to the Lomar Corporation for
The filter
installation
of the plastic media.
is shown in Figure
media blocks to the
Media installation
No. 4. When media
resumed on the effluent
collection pipes were
The first layer of media in filter No. 5
24. The conveyor belt which lifted the
top of the filter is shown in Figure 25.
required approximately 6 wk for filter
installation was nearly complete, work
collection system. After the effluent
laid and the trenches backfilled,
the housings for the filter fans were formed
The rotary distributors were leveled after the
place.
and poured.
media was in
Figure 24. Plastic media installation.
filter No. 5.
First layer of media being installed for
Filter No. 4 was started up before it was entirely
complete to receive canning season loadings. A portion of the
effluent collection system and the electrical connections to
the fans were completed after startup.
56
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Figure 25. Plastic media conveyor.
Media modules were fabri-
cated near the site, deliv-
ered by truck, and con-
veyed to the top of the
filter wall.
Filter Distribution Structure
No. 1 and Piping
Excavation around the
trickling filter distribution
structure and for the new
1.52-m (60-in.) effluent pipe
began in April 1973. Secondary
facilities were bypassed (the
beginning of the 90-day pe'riod)
to allow demolition of one wall
of the structure and replace-
ment of piping. A leaky valve
on one pipe from the primary
sedimentation tank delayed
demolition several days.
Laying of the, 1.52-m
(60-in.) reinforced concrete
pipe to the secondary sedi-
mentation tank distribution
structure was the first major
task, followed by demolition
of the western wall of the
structure. The original 0.91-m
(36-in.) effluent pipes from
filters No. 4, 5, and 6 were
removed and replaced with
1.22-m (48-in.) pipes. The
existing 0.91-m (36-in.) filter
supply pipes were partially
removed and replaced with new
0.91-m (36-in.) pipes which
routed influent through the
supply pumps.
Forming and pouring' the new chamber walls and the collars
for pipe connections constituted most of the work on the filter
distribution structure. The south wall of the structure with
the concrete forms in place is shown in Figure 26. The concrete
work for the complicated structure (Figure. 19, Section 5) was
completed in a single pour. For the most part, work proceeded
steadily and without problems or adjustments. Backfilling of
excavated areas and painting of the structure was begun in
early July.
The supply pump for filter No. 4 was installed first,
during the second week in July. This was followed by
reinstallation of the four original recirculation pumps which
were removed before modifications were begun. The electrical
connections to the original recirculation pumps were completed
while filters No. 1, 2, and 3 were started up. The two new
recirculation pumps were electrically connected after the
57
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rock media filters were put on line and just prior to startup of
filter No. 4. Supply pumps No. 5 and 6 were installed in
August; they are shown in the foreground in Figure 27. Supply
pump No. 4 is to the left of the distribution structure; one of
the new recirculation pumps can be seen on the far right end
of the structure.
Figure 26. Trickling filter distribution structure. New portion of structure is to
the left.
A leak was discovered in an original line between trickling
filter distribution stuctures No. 1 and 2 after startup. The
area around the pipe was excavated and a collar was formed
around the leaky pipe.
Secondary Sedimentation Tank Distribution Structure
Excavation for the secondary sedimentation tank distribu-
tion structure began in early May. The original structure was
entirely demolished, and a small, submersible electric pump was
installed in the excavated area to pump out groundwater. The
entire structure was located 53 cm (1 ft-9 in.) east of the plan
location to avoid an existing bypass line. New collars were
formed on existing pipes for connection to the new structure. A
portion of the pipe to a planned-for fifth sedimentation tank
was laid and capped. The east side of the structure is shown in
Figure 28. In the center foreground is a section of the new
1.52-m (60-in.) influent pipe; to the right of the new pipe is
the old 1.52-m (60-in.) pipe.
The structure was essentially complete by the end of June.
Installation of the sluic.e gates and backfilling around the
structure were done the first week in July. Painting was
completed just before the end of bypassing.
58
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Figure 27. Supply and recirculation pumps. Supply pumps for filters No. 5 and 6
are in foreground; supply pump for filter No. 4 is beyond distribution
structure to the left. One of the new recirculation pumps is near the
right side of the distribution structure.
Repairs to Rock Media Filters
During the bypass period required for modifications to the
distribution structures, repairs were made on the three rock
media filters (filters No. 1, 2, and 3). The major repair
was to the rotary distributors. Portions of the original
distributors from filters No. 4, 5, and 6 were salvaged and
combined to make two good ones for filters No. 1 and 2.
The distributor for filter No. 3 was left in place; it was
sandblasted and repainted. Distributor columns from filters
No. 5 and 6 were installed in filters No. 1 and 2; repair of
the center piers which support the distributor columns was
necessary.
The salvaged distributors were sandblasted, and corroded
parts were replaced. An organic zinc primer coat was applied
prior to four coats of paint. Center column bearings were
59
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repaired or replaced. The distributors for filters No. 1 and 2
were then installed and leveled. The CPM chart (Figure 21)
shows the timing of the repair operations relative to work on
the other structures. Flow was readmitted to the filters as
soon as the distributors were operating. Minor repairs and
adjustments were made after bypassing was discontinued.
Electrical Modifications
Electrical work began
in mid-March and continued
steadily throughout the
contract. Some difficulty was
experienced in delivery of
equipment. Delivery of 'a
critical high-voltage cable was
delayed; however, the local
electric utility company,
Pacific Gas and Electric,
released a similar cable it
had ordered to help avoid
construction delays.
Figure 28.
Secondary sedimentation
tank distribution struc-
ture. New filter effluent
line is at center; old
line is at right.
The ducts and conduits
were laid while electricians
worked on operations building
modifications. A new main
switch station was installed
in June. Electrical activities intensified as the filter
distribution structure neared completion. Electrical hookups to
pumps and the trickling filter substation were part of the
critical path just prior to startup (see Figure 21).
Construction Progress
An unusual amount of rain during the months of January,
February, and March 1973 caused construction delays. Regular
overtime hours were authorized in February to compensate for
time lost in January. Exceptionally heavy rains in February
and March resulted in a 10-working-day extension of the required
completion time for filter No. 4. Operations continued at a
slower-than-normal pace. For example, masonry for the filter
walls could not be placed during rain. The contractor ordered
extra material for concrete forms in order to pour several
structures concurrently rather than consecutively as planned.
Construction progress is illustrated in Figure 29.
Construction progress payments were used as an indicator of the
percent of project completion. When filter No. 4 went into
operation in July, approximately 70 percent of constuction was
complete; by November 1973, 99.7 percent of construction was
complete. Correction of deficiency items continued through 1974
and into 1975.
60
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100 -
ti 80 -
I
CO
CO
LU
oc
C3
o
cc
a.
60 -
40 -
20 -
MODIFICATIONS TO
SECONDARY FACILITIES
I I I " I I I I I I I I I I I T
.J FMAM J J AS ONDJ F MA
1973 1974
MONTH
Figure 29. Construction progress.
Filter No. 4 had been scheduled to be structurally
complete by April 15, 1973; plastic media was to be installed
between April 15 and June 15. Filter No. 4 was to be on line by
June 30 and filters No. 5 and 6 on line by September 15.
Filter No. 4 was structurally complete except for the
effluent collection pipes on April 27, 12 days after the
scheduled date. The filter-media contractor moved in on May 2.
There were some delays in plastic media installation due to slow
material deliveries, but filter-media installation was completed
by June 15, the original scheduled date.
Unexpected deterioration (wall leaks) of portions of the
filter distribution structure required extra work for the
contractor as did deterioration of the 0.91-m (36-in.) influent
61
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pipes to filters No. 5 and 6. Other problems included a
breakdown stoppage of the plant effluent pump which caused
flooding of both distribution structures.
The rock filters were put into operation on July 17;
filter No. 4 began operation July 24. Delays in starting
up filter No. 4 after media installation was complete were
attributed to: (1) problems with the rock media filters which
required additional crew labor time, (2) miscalculation of
electrician, pipe fitter, and millwright crews' production
time, and (3) the last-minute cancellation of an electrical
test equipment order and subsequent time needed to locate an
alternate equipment source. One effluent return line and the
air inlet fans were installed with filter No. 4 in service.
The two new recirculation pumps were installed after all four
filters were operating.
Media installation for filters No. 5 and 6 commenced on
October 3, 1973; the start date was originally scheduled for
August 15. Rain began in September 1973, again slowing
constuction progress. Fifteen working days were lost in
December 1973 due to a strike by the carpenters' union.
Installation of the media for filters No. 5 and 6 proceeded at
a much slower pace than for No. 4. Delays in delivery of the
plastic grating for the top of the media were attributed to the
oil shortage. Media installation was complete, except for the
grating, in January 1974.
Filters No. 5 and 6 were put into operation while awaiting
the arrival of the grating. In early April, the filters were
shut down and the new plastic grating material was installed
The contract was essentially completed in July 1974, 6 mo after
the scheduled completion of January 1974, although the trickling
filters were all operable during this period.
STARTUP
The three rock media filters and one plastic media
filter were operational in time for the 1973 canning season
as required. Filters No. 5 and 6 were completed and were
operational by January 1974. Operational problems encountered
during startup were leakage through the walls of filter No. 4,
overheating of one of the new recirculation pumps, and slamming
of the check valves in the new recirculation pumps.
Leakage through the walls on filter No. 4 was noticed
immediately after startup. As indicated above, a coal tar
epoxy had been used as a sealer on the inside walls and, for
the reasons discussed previously, allowed wastewater to leak
through the filter walls.. While resulting in an unsightly
appearance and causing aquatic growths on the outside walls, it
was determined that no structural damage would result.
62
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Because filters No. 5 and 6 had not been completed at this
time, it was possible to use another method of sealing their
walls. The polyurethane sealer used for these two filters
provided a significant improvement, although a few minor leaks
did occur.
The occurrence of the leaks points out the necessity
of taking adequate precautions against such problems when
open-block construction is used. Suggested techniques for
accomplishing this are presented in Section 8.
Overheating of the new filter recirculation pump was
traced to an unexpectedly high pumping head, coupled with
marginally sized electric wires leading from the control
building. During subsequent plant modification (undertaken in
1977), the pumping head was reduced by installing new secondary
clarifier effluent troughs at a higher elevation than the old
ones. This caused the water level in the outer box of the
filter recirculation sump to be raised and reduced the head on
the pumps.
The new filter recirculation pumps were installed to
provide discharge below the water line in the inner chamber of
the distribution structure. This necessitated installation of
check valves to prevent backflow into the outer chamber when
the pumps are not operating. Severe slamming resulted when the
pumps were shut off, however.
63
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SECTION 7
OPERATION AND PERFORMANCE
With completion of the secondary treatment modifications in
December 1973, the city began full-time operation of the plastic
media biofilters. Normally, the plastic media filters and
the three remaining rock filters (Figure 30) are operated in
parallel from the common distribution structure as described in
Section 5. A disadvantage to this method of operation is that
it is impossible to evaluate the performance of the plastic
media alone because of the mixing of the effluent from each type
prior to recirculation.
Because the plant's capacity had not been reached and
because the treatment contribution of the rock filters was
minimal, the city agreed to shut down the three rock filters for
a 1-yr period while a special sampling program was undertaken
in conjunction with this study. The purpose of the sampling
program was to document the performance of the plastic media
filters over the entire range of conditions encountered at
Stockton, including the canning and noncanning seasons and the
transition periods between them.
SPECIAL SAMPLING AND ANALYTICAL PROGRAM
A complete description of the sampling program and the
sampling and analytical techniques employed is presented in
Appendix D. Briefly, sampling was begun on March 15, 1976,
and completed on March 16, 1977. Four sampling points were
used: raw wastewater (primary influent), primary effluent,
trickling filter effluent (unsettled), and secondary effluent.
Four portable, refrigerated, automatic composite samplers
were used. Sampling was triggered by a 24-hr timer which
had been calibrated to provide a simulated diurnal flow
variation by sampling at varying frequencies throughout the
day. This provided samples which were reasonably close to being
flow-proportioned.
Samples were taken 3 days per week, beginning each Monday,
Tuesday, and Wednesday morning at approximately 9:00 a.m. and
collected on the following day. The samples were packed in ice
and shipped to Brown and Caldwell's laboratory facilities in
San Francisco. The samples were then split, and portions
of them were preserved and shipped via air freight to EPA's
64
-------
Figure 30. Plastic media and rock media trickling filters at Stockton. The three
original rock filters are normally operated in parallel with the three
new plastic media filters, but they were shut down during the special
1-year sampling program for this study.
65
-------
Municipal Environmental Research Laboratory in Cincinnati.
Analysis of certain constituents was undertaken at Cincinnati to
reduce the overall costs of the study.
Analyses performed included BODs , soluble BODs , suspended
solids, volatile suspended solids, and alkalinity at
San Francisco and COD, soluble COD, ammonia nitrogen, total
Kjeldahl nitrogen, nitrite nitrogen, nitrate nitrogen, and total
phosphorus at Cincinnati. City laboratory and operation records
were used to obtain values of wastewater flow, temperature,
dissolved oxygen level, and pH. A complete listing of analyses
is presented in Table 12. Data obtained during the study
are presented on a daily basis in Tables E-l through E-3 in
Appendix E. Selected data are presented below as necessary to
illustrate specific aspects of plant operation and performance.
TABLE 12. PARAMETERS MEASURED DURING SAMPLING PROGRAM
Sampling location
Parameter
Raw
influent
Primary
effluent
Biofliter
effluent
Secondary
effluent
Flow
Trickling filter recircula-
tion flow3
BODs b
Soluble BODs
CODd ,
Soluble CODa b
Suspended solids ,
Volatile suspended solids
Total phosphorus d
Total Kjeldahl nitrogen
Ammonia nitrogen?
Nitrite nitrogen"
Nitrate nitrogen
Alkalinityba
Temperature
Dissolved oxygena
X
X
X
X
X
X
X
X
X
X
xc
X
X
X
X
X
X
X
X
xc
X
X
x
X
X
X
X
X
X
Xc
x
X
X
X
X
X
X
X
aMeasured or analyzed by plant staff.
bAnalyzed by Brown and Caldwell.
ฐMeasured once per week.
^Analyzed by EPA, Cincinnati.
At the time the sampling program was undertaken, several
elements of the upgraded plant had not been completed. The most
significant of these was the tertiary algae removal facility,
consisting of dissolved air flotation, dual-media filtration,
and chlorination-dechlorination. During the sampling program,
secondary effluent was treated in the oxidation ponds and then
discharged to the San Joaquin River.
66
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Other portions of the upgraded plant described in Section 4
which had not been completed at the time the sampling program
was initiated included construction of a new river crossing,
provision of vacuum filtration for sludge dewatering, and
installation of new secondary clarifier effluent collection
troughs. The last item is of interest because of the poor
hydraulic distribution among the four secondary clarifiers and
within each clarifier. Poor hydraulic distribution in the
secondary clarifiers had been a problem for several years. The
existence of the large oxidation ponds eliminated concern over
this poor distribution because of the ponds' large treatment
capacity. Secondary effluent data presented in this report,
however, might have exhibited lower contaminant levels if the
new facilities had been completed at the time of the sampling
program.
An important construction item affecting data evaluation
during the sampling program involved the expansion and
modification of the headworks area. This included addition
of three new grit removal channels and Parshall flumes and
rehabilitation of the three existing channels and flumes. As a
result of this construction, adequate plant flow data are not
available for the first 2 mo of the study. Based on available
data from prior and subsequent periods, the flow during this
time has been estimated at 61,000 m3/day (16.0 mgd). This
value is used throughout this report for the period from
March 15 through May 19, 1976.
PLANT OPERATION DURING SAMPLING PROGRAM
Several operational changes occurred during the sampling
program which affected data collection. Various units were
out of service for a portion of the sampling period; one of
the plastic media biofilters was shut down for 2 mo at the
beginning of the program, and one or more of the primary and
secondary clarifiers were kept out of service during the
noncanning season.
Some changes were initiated by the plant staff in response
to problems which occurred. Shortly after the beginning of the
canning season, it was determined that the primary clarifier
sludge removal equipment was unable to handle the large
quantity of solids entering the plant and that significant
carryover of settleable solids to the secondary treatment
system was occurring (Figure 31). Solids removed from the
secondary clarifier are normally recycled back to the head-
works, and the result was a gradual buildup of solids in the
primary and secondary treatment systems. The plant staff
solved the problem by constructing a temporary pipeline and
pumping secondary sludge from the secondary clarifiers directly
to the sludge lagoons. This was continued until the end of the
canning season.
67
-------
-,.*;*
Figure 31. Stockton primary clarifiers. Heavy solids loading during the 1976
canning season overloaded sludge removal system.
Several operational changes were implemented in response to
data developed during the sampling program. These relate to the
total hydraulic loading (influent plus recycle) on the filters
and to the air flow provided by the forced draft ventilation
system. As discussed below, ammonia nitrogen removal during the
first portion of the sampling program prior to the start of the
canning season (March 15 to July 31, 1976) was inconsistent.
Among the possible explanations were inadequate total hydraulic
loading to achieve effective media wetting and inadequate air
supply; therefore, these operating parameters were modified
during the latter portion of the sampling program in an attempt
to obtain improved performance.
Most manufacturers of synthetic trickling filter media
recommend a minimum total hydraulic loading to ensure complete
wetting of the media surface, which allows the media to be
fully effective in biological treatment. B. F. Goodrich
recommends a minimum value of 0.031 m^/min/m2 (0.75 gpm/ft2)
for Vinyl Core (8). Plant records indicated that the total
hydraulic loading being applied at Stockton was approximately
0.024 m3/min/m2 (0.6 gpm/ft2); the variable-speed supply pumps
were being operated at a motor speed of about 1,500 rpm. It
was, therefore, requested that the city increase the trickling
filter supply flow (and thus the recirculation flow) to the
68
-------
recommended minimum wetting rate. The city readily agreed, and
in mid-October the change was made; the total hydraulic loading
was increased to approximately 0.031 m3/min/m2 (0.75 gpm/ft2).
At the same time that the hydraulic loading was increased,
the air supply to the biofilters was also increased. Grab
sample dissolved oxygen concentrations of unsettled biofilter
effluent are measured each day by the laboratory staff. Review
of plant records for the period in question showed the
concentrations measured to be high, usually above 5 mg/1, even
though very few fans, two or fewer (of eight per filter) were
being operated. It was hypothesized that the wastewater
dissolved oxygen concentration was being raised when the water
drops fell from the media to the floor and were transported to
the effluent collection boxes where the grab samples were taken.
Therefore, the number of operating fans was increased to four
per filter.
As will be discussed in the subsection on nitrification
performance, nitrification efficiency increased significantly
subsequent to these changes, although it cannot be certain
which (if either) of the operational changes influenced
performance. This question will be discussed again below.
Another change in fan operation was made in January 1977
just prior to the end of the study. The change was made in an
attempt to reduce suspended solids levels in the secondary
effluent during the noncanning season. Shortly after the
plastic media biofilters had been put into operation, the plant
staff began to notice that during portions of the day, high
concentrations of finely dispersed solids were noticeable near
the surface of the secondary clarifiers. Qualitative dye
tracer tests undertaken by the staff showed dye breaking
through and appearing in the secondary clarifier effluent in
less than 5 min. This condition was indicative of severe
short-circuiting.
Observations made during the course of this study, and
which are described below under the subsection on performance,
led to the tentative conclusion that the problem resulted
from temperature/density gradients being set up in the
secondary clarifiers by the diurnal fluctuations in ambient air
temperature and wastewater flow. During the night, low air
temperatures and low wastewater flows result in a large waste-
water temperature drop through the biofilter, and relatively
cold water would thus enter the clarifiers. In the morning,
the air temperature and wastewater flow would increase, causing
the temperature of the biofilter effluent to increase. This
warmer, less dense water would then rise to the surface and
move over the cold, more dense water present in the clarifiers.
The low hydraulic loadings and high air flows required for
nitrification would magnify the problem. It was expected that
the layering phenomenon would be quite unstable and could be
eliminated by turbulence within several hours.
69
-------
Thermodynamics calculations indicated that daytime and
nighttime temperature drops through the biofilters could be
made nearly equal by operating six fans during the day (from
8:00 a.m. to 8:00 p.m.) and two fans at night. The fans were
operated in this manner for the last several weeks of the
program, and a significant (though short-term) reduction in
secondary effluent suspended solids concentrations resulted.
Summarized in Figure 32 are the major changes in plant
operating parameters discussed above. Shown on the figure are
primary and secondary clarifier operations, secondary sludge
pumping, hydraulic loading, and fan operation.
NUMBER OF PLASTIC MEDIA
BIOFILTERS OPERATING
NUMBER OF PRIMARY
CLARIFIERS OPERATING
NUMBER OF SECONDARY
CLARIFIERS OPERATING
FLOWMETER OPERATING
NUMBER OF FORCED DRAFT
VENTILATION FANS OPERATING
SECONDARY SLUDGE PUMPED
DIRECTLY TO LAGOONS
BIOFILTER HYDRAULIC LOADING,
INCLUDING RECYCLE (APPROXIMATE)
SEASON
NO
YES
NO
YES
NO
0.6 GPM/FT "
0.75 GPM/FT
NONCANNING
CANNING__
NONCANNING
_L
_L
_L
TRANSITION
_L
J_
NOTE: gpm/ft2 x 0.041
m3/min/m2
MAR APR MAY JUN
JUL AUG
1976
SEP OCT NOV DEC
JAN FEB MAR
1977
Figure 32. Changes in plant operating parameters during sampling program.
PERFORMANCE
Prior to discussing specific aspects of secondary
treatment performance, a summary of plant performance is
presented here to give an overview of the Stockton plant
operations during 1976-1977. Monthly averages of major
constituent concentrations are presented in Tables 13 through
17. Included are total and soluble BODs, total COD, total
70
-------
and volatile suspended solids, total phosphorus, total Kjeldahl
nitrogen, ammonia nitrogen, secondary effluent nitrate nitrogen,
alkalinity, wastewater temperature, dissolved oxygen, and pH.
Daily values for these and other data are listed in Appendix E.
TABLE 13. MONTHLY AVERAGES FOR FLOW, BODC/ AND SOLUBLE BOD,
5 5
BOD,-, mg/1
Soluble BODg, mg/1
Month,
1976-77
March
April
May
June
July
August
September
October
November .
December
January
February
March
Flow,
mgda
16b
16ฃ
19b
18
18
39
35
19
17
17
18
18
17
Raw
Influent
290
250
260
270
300
630
420
380
330
430
370
380
360
Primary
Effluent
170
150
130
140
150
320
240
210
220
230
220
180
190
Secondary
Effluent
28
16
21
27
29
130
59
33
24
19
15
15
14
Primary
Effluent
75
52
48
66
60
210
180
110
120
97
130
85
Secondary
Effluent
18
6
10
12
16
93
26
15
13
10
7
6
7
amgd x 3,785 = m3/day.
Flow meter not working.
from 3/15/76 to 5/19/76.
Flow estimated at 60,000 m /day (16.0 mgd)
TABLE IH. MONTHLY AVERAGES FOR SUSPENDED SOLIDS AND VOLATILE
SUSPENDED SOLIDS
Month ,
1976-7'7
March
April
May
June
July
August
September
October
November
December .
January
February
March
Suspended solids, mg/1
Raw
Infl.
360
280
320
320
450
740
' 580
520
390
400
470
410
410
Prim.
Effl.
230
140
140
120
140
220
140
150
130
140
120
170
240
Filter
Effl.
140
140
160
140
150
220
150
160
140
140
140
160
150
Sec.
Effl.
37
27
25
42
23
51 .
44
47
36
25
30
19
26
Volatile suspended solids
Raw
Infl.
280
230
230
230
290
480
370
370
310
320
370
320
310
Prim.
Effl.
150
130
110
91
120
190
120
120
120
120
96
140
180
Filter
Effl.
90
110
110
90
120
190
120
130
12.0
110
100
120
120
, mg/1
Sec.
Effl.
28
22
19
31
19
47
38
43
32
23
24
17
18
71
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TABLE 15. MONTHLY AVERAGES FOR TOTAL PHOSPHORUS AND TOTAL COD
1976-77
March
April
May
June
July
August
September
October
November
December
January
February
March
Total phosphorus, mg/1 as P
Raw
Infl.
7.5
7.2
7.3
6.7
7.7
6.0
6.1
8.2
11
11
9.9
9.3
8.6
Prim.
Effl.
6.6
6.6
6.3
6.8
6.0
3.3
3.3
6.1
9.4
8.4
6.7
7.7
7.4a
Sec. ,
Effl.
5.8
6.1
5.5
6.3
5.6
2.1
2.7
5.1
6.5
7.5
6.3
6.6
6.8
Raw
Infl.
650
590
570
540
610
1,040
900
820
690
810
810
780
690
Total COD, mg/1
Prim.
Effl.
380
360
320
260
270
530
450
390
350
390
350
310
370a
Filter
Effl.
220
220
210
160 .
180
360
260
220
190
190
200
230
290
Sec.
Effl.
110
110
120
90
100
260
200
150
110
100
100
110
90
Data available for 1 day only.
TABLE 16. MONTHLY AVERAGES FOR TOTAL KJELDAHL NITROGEN, AMMONIA
NITROGEN, AND SECONDARY EFFLUENT NITRATE NITROGEN
Month ,
1976-77
March
April
May
June
July
August
September
October
November
December
January
February
March
Total Kjeldahl nitrogen, mg/1
Raw
Influent
30
24
28
23
29
34
29
40
36
46
55
40
39
Primary
Effluent
27
24
25
21
24
41
27
31
32
38
38
34
21
Secondary
Effluent
16
9.2
10
9.0
11
31
19
16
10
14
16
7.6
5.4
Ammonia nitrogen
Raw
Influent
17
16
13
15
18
11
12
16
20
25
26
23
24
Primary
Effluent
14
15
15
16
15
22
14
17
20
23
23
19
20
, mg/1
Secondary
Effluent
9.4
4.7
5.8
4.0
5.0
16
8.4
8.0
4.2
4,6
2.0
1.5
1.4
Nitrate
nitrogen,
mg/1
Secondary ,
Effluent
0.3
2.7
5.0
1.8
0.8
<0.1
<0.1
0.4
1.1
0.8
2.2
2.9
2.5
Several aspects of plant operation are apparent from these
tables. The abrupt start of the canning season at the beginning
of August is indicated by a significant increase in several raw
wastewater parameters, including flow, BODs, suspended solidsf
and alkalinity. A decrease in filter effluent dissolved oxygen
also reflects the increased loadings. August was the peak
loading month; concentrations and flows were slightly lower in
September and decreased significantly in early October as unsea-
sonal late summer storms cut off the end of the growing season.
72
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TABLE 17. MONTHLY AVERAGES FOR ALKALINITY, WASTEWATER TEMPERATURE,
pH, AND DISSOLVED OXYGEN
Month
1976-77
March
April
May
June
July
August
September
October
November
December
January
February
March
Alkalinity, mg/1
as CaCOj
Prim.
Effl.
200
. 200
190
190
220
400
370
260
210
240
210
170
210
Sec.
Effl.
130
100
120
110
140
370
320
210
92
100
63
59
53
Wastewater
temperature, C
Prim.
Effl.
26
26
28
29
30
, 30
30
28
26
23.
22
24
24
Filter
Effl.
24
24
27
28
29
30
29
28
24
21
19
22
22
pH
Prim.
Effl.
6.8
7.0
7.1
7.2
7.1
8.4
8.9
7.2
6.9
7.0
6.7
6.9
6.6
Filter
Effl.
7.6
7.5 .
7.6
7.7 '
7.8 '
8.3
.8.3 .
7.5
7.2
7.5
7.1
7.2
7.2
Dissolved
oxygen,
mg/1
Filter
Effl.
6.3
7.1
5.6
6.2
5.0
1.7
4.1
6.3
6.5
6.4
7.2
8.2
7.3
Also associated with the canning season is an increase in
ammonia nitrogen level between the raw wastewater and primary
effluent (Table 16). The cannery waste, principally tomatoes
and peaches, is nutrient deficient, and ammonia gas is added
to the waste stream to ensure that an adequate bacterial
population will develop. Consequences of an insufficient supply
of nutrients include growth of fungi in the biological treatment
system, deterioration in performance, and odors.
Improvement in performance when the noncanning season
resumed in November 1976 can be seen in the reduced concentra-
tions of several secondary effluent constituents: BODs,
suspended solids, and ammonia nitrogen. It is assumed that
this improvement (over that experienced before the start of the
canning season) is due to the operating changes discussed above.
Presented below are discussions of several specific
performance parameters for the Stockton secondary treatment
process: BOD5 removal, ammonia nitrogen removal, suspended
solids removal, and solids production. Following this discus-
sion is a performance summary comparing experienced performance
with design.
BOD5 Removal
The occurrence of a 2- to 3-mo canning season at Stockton
provides a wide range of organic loadings on the biofilters.
Weekly loadings during the sampling program ranged from 0.16 to
1.3 kg/m3/day (10 to 80 lb/1,000 ftVday). A graph of weekly
average removals vs loadings is shown in Figure 33, and a
summary of average seasonal parameters is presented in Table 18.
73
-------
100
90
S 80
1 70
uj
DC
in
Q
O
ffl
60
50
40
i
O*ซซM
ฐป.
O .
OO+
oซ
o
oo o
O BEFORE OPERATING CHANGES
AFTER OPERATING CHANGES
o o
o
0ฐ0
NONCANNING
SEASON DESIGN
VALUE
o o
CANNING SEASON
DESIGN VALUE
NOTE: lb/1,000 ft3/day x 0.016 = kg/m3/day
J_
20 40 60 80 100
ORGANIC LOADING, Ib BOD5 / 1,000 ft3/ day
Figure 33. BOD_ loadings and removals.
120
140
Removals were much lower than expected prior to the
operational changes discussed above, averaging 84 and 80 per-
cent for total and soluble BOD5, respectively, in the
March-July 1976 noncanning period. During the peak canning
month of August, total BODs removal averaged 59 percent at a
loading of 0.7'8 kg/m3/day (49 Ib BOD5/1,000 ft3/day). Design
removal for the canning season is, by contrast, 70 percent at a
loading of 2.16 kg/m3/<3ay (135 Ib/ 1,000 ft3/day).
The operational changes which were instituted to improve
nitrification apparently also had significant impact on
BODc reduction. Total BODs removal increased from the
previous 84 percent (March-July 1976) to 92 percent in the
74
-------
November 1976-March 1977 period. The secondary effluent total
BODs concentration dropped from 24 to 17 mg/1. Soluble BODs
removal increased from 80 to 91 percent, with effluent
concentrations decreasing from 12 to 9 mg/1. This improvement
was obtained in conjunction with a slight increase in loading
from 0.30 to 0.34 kg/m3/day (19 to 21 lb/1,000 ft3/day).
TABLETS. BOD 5 REMOVAL SUMMARY
Parameter
Canning season
August,
September
1977
Noncanning season
March
through
July 1976
November 1977
through
March 1978
Flow, mgd
Biofliter loading, lb/1,000 ft3/dayb
BODs, mg/1
Raw influent
Primary effluent
Secondary effluent
removal, percent
Primary treatment
Secondary treatment
Total
37
60
530
280
95
47
66
82
17
19
270
150
24
44
84
91
17
21
370
210
17
43
92
95
Soluble 8005
Primary effluent
Secondary effluent
Soluble BOD_ removal, percent
200
60
70
60
12
80
97.
9'
.91'
amgd x 3,785 = m3/day.
blb/l,000 ft3/day x 0.016
kg/m3/day.
In the following subsection on nitrification, the possible
impact of the operational modifications is discussed; no
definite conclusion can be drawn. For example, plant records
show that the biofilter dissolved oxygen level was high even
before the number of operating fans was increased; weekly
average dissolved oxygen levels are shown in Figure 34. These
analyses are made daily by the plant laboratory staff on grab
samples taken at approximately 1:00 p.m. from the effluent
collection channels. Figure 34 also indicates that dissolved
oxygen (in addition to low hydraulic loadings) may have been
limiting 8005 removal during the canning season, as measured
values fell to less than 1.0 mg/1 at times during August and
September when removals were very low.
The most widely used design equation for plastic media
trickling filtration is one which is usually termed the
Velz equation, after the developer of the original version.
75
-------
Several variations have been proposed over the years, and the
most general form of the equation is as follows:
= e
(2)
where :
So
Se
k
Av
D
q
= influent 8005, mg/1
= effluent BODs, mg/1
treatability coefficient, dependent upon the
wastewater
= media specific surface area,
s media depth, ft
= hydraulic loading (excluding recycle), gpm/ft2
m,n = exponents
The values most commonly used for m and n are 1.0 and 0.5,
respectively, yielding the simplified form of the Velz equation
cited earlier in Section 2:
ฃe_ _ -kAvD/qฐ'5
(1)
Although Equation 1 is, strictly speaking, limited in its
application to soluble BODs, it has been used, particularly by
media manufacturers, with So and Se representing secondary
influent and secondary effluent total BOD$ , respectively.
To take into account the effect of secondary clarification
on performance, it is possible to use Equation 1 with So
representing secondary influent total BOD5 and Se representing
secondary effluent soluble BODs. This approach is based upon
the assumption that all of the suspended BOD5 leaving the
secondary clarifier represents solids sloughed from the media
surface rather than waste material which has passed through
the biofilter unoxidized. This is probably a reasonable
assumption, particularly when organic loadings on the biofilter
are low, as is the case for Stockton during the noncanning
season. Although the assumption of influent soluble BOD5
is inherent in the development of Equation 1, it is not
76
-------
inappropriate to use influent total BODs in its application,
particularly in view of all the other assumptions required for
its development.
11
10
9
8
7
6
S
4
3
2
1
0
FORCED DRAFT VENTILATION
2 FANS PER TOWER
POINTS REPRESENT WEEKLY
AVERAGES OF GRAB SAMPLES
TAKEN ONCE PER DAY AT
APPROXIMATELY 1:00 P.M.
MAR APR MAY JUN JUL AUG SEPT OCT
MONTH, 1976-1977
NOV
DEC
JAN
FEB
MAR
Figure 34. Biofilter effluent dissolved oxygen levels.
The treatability coefficient, k, is included in the
equation to account for differences in wastewater characteris-
tics. Shown in Table 19 are treatability coefficients for
Equation 1 for the period of October 25, 1976, through March 16,
1977. This period has been chosen as representing optimal
performance of the plant following the increases in hydraulic
loading and air flow. The value of k in Table 19 has been
adjusted to 20 C using the relation k^ = k2Q (1.035)T~2^.
Also shown in Table 19 are treatability coefficients
computed from data obtained in the 1972 pilot study (5).
Comparison of the two sets shows good agreement, although values
from the present study are slightly higher, meaning slightly
better performance for the full-scale facility.
A common representation of the treatability coefficient
is the combined parameter of ki = kAv. For a specific surface
of 89 m2/m3 (27 ft2/ft3), a value of ki = 0.040 is obtained
for Stockton, using influent and effluent total 8005. It was
noted previously in the pilot study report (5,6) that, the
values obtained at Stockton are somewhat lower, than those
normally cited for treatment of domestic waste. For example,
77
-------
a comprehensive review of trickling filter performance by
Benjes (9) shows an average of ki = 0.06 (total BODs basis) for
15 redwood and plastic media biofilter plants; values ranged
from 0.03 to 0.11.
TABLE 19. TREATABILITY COEFFICIENTS FOR STOCKTON
Method of computation
Treatability coefficient
Special sampling program,
1976 - 1977
Influent soluble BODc n nfn,
Effluent soluble BOD5 u.uuj.^
Influent total BOD, n nniir
Effluent total BODJ: u.uuj.3
Influent total BODs n nnls
Effluent soluble BOD5 U.UUJ.D
Pilot stud^ ,
1972b
0.0013
0.0013
0.0015
,Se,
a, m (so}
(1.035)
D/q
0.3
Period of October through December 1972. Nitrification not suppressed in
effluent BODg samples. Effluent settled one hour in Imhoff Cone.
The probable cause for the slightly lower coefficients
experienced at Stockton is the combination of operating the
secondary system to obtain low effluent residuals under
conditions of lower-than-normal organic loadings. Equations 1
and 2 are essentially empirical in nature, and extrapolation to
loadings and removals outside the normal ranges is risky. In
particular, very low effluent BOD5 values are difficult to
attain, as the remaining BODs becomes increasingly difficult to
remove. Care must be taken in applying "average" treatability
coefficients, or coefficients obtained with a particular
wastewater at higher loadings, when high BODs removals are
required. Equations 1 and 2 and their applicability to BOD5
removal will be discussed further in Section 8.
Nitrification
Conversion of ammonia nitrogen to the nitrate form is an
important function of the Stockton biofilters during the
noncanning sea'son. Presented in the following subsections
are discussions on ammonia nitrogen removal, organic nitrogen
removal, possible denitrification in the biofilters, and the
effect of nitrification on wastewater alkalinity.
Ammonia Nitrogen Removal
As discussed previously, poor ammonia nitrogen removal
during the first portion of the study was cause for concern
78
-------
and led to a search for possible reasons and for measures to
improve performance. Increasing the forced draft ventilation
air flow and the hydraulic loading on the plastic media
biofilters appear to have resulted in greater ammonia nitrogen
removals during the latter portion of the study.
A summary of nitrification performance is shown in
Table 20. For the period of March through July 1976, ammonia
nitrogen removal averaged only 61 percent with an effluent
ammonia nitrogen concentration of 5.8 mg/1. During the
4 1/2-mo period from November 1976 through March 16, 1977,
removal averaged 87 percent, and the effluent ammonia nitrogen
concentration averaged 2.7 mg/1. During the last 2 1/2 mo of
the sampling program, removal was over 90 percent and effluent
concentrations were below 2.0 mg/1. An upset from unknown
causes occurred in mid-November and produced increases in both
effluent BODs and ammonia nitrogen levels. Without this upset,
average performance results for the full 4 1/2-mo period would
have been even better. Weekly primary and secondary effluent
concentrations for the noncanning season are summarized in
Figure 35. The improvement during the latter portion of the
program is readily apparent.
TABLE 20. NITRIFICATION PERFORMANCE STUDY
March
Parameter through
July 1976
Flow, mgda 17
November 1976
through
March 1977
17
Biof liter loading, BOD,-/1,000 ft /
dayb 3
Biof liter recirculation ratio, total
applied flow/plant flow
Ammonia nitrogen
Primary effluent, mg/1
Secondary effluent, mg/1
Removal, percent
19
2.7
15
5.8
61
21
3.8
21
2.7
87
Organic nitrogen
Primary effluent, mg/1
Secondary effluent, mg/1
Removal, percent
Nitrate nitrogen, secondary effluent,
mg/1
10
5.3
47
2.1
17
8.6
49
1..9
mgd x 3,785 = m /day.
blb/l,000 ft3/day x 0.016 = kg/m3/day.
The reason for the improvement is still uncertain.
No attempt was made to segregate the period of increased
air flow from the period of increased hydraulic loading,
79
-------
and neither the total hydraulic loading nor the dissolved
oxygen (DO) levels were increased significantly by these
actions.
cc
111
o
I I I I I I
AFTER \ OPERATING CHANGES
BEFORE OPERATING CHANGES
PRIMARY EFFLUENT
AMMONIA NITROGEN
SECONDARY EFFLUENT
AMMONIA NITROGEN
SECONDARY EFFLUENT
NITRATE NITROGEN
10 20 30 10 20 30 10 20 30 10 20 30 10 20 30 20 30 10 20 30 10 20 30 10 20 30
MAR APR MAY JUN JUL OCT NOV DEC JAN
1976
Figure 35. Ammonia and nitrate nitrogen levels.
10 20
FEB
1977
30 10 20
MAR
Plotted against time in Figure 34 are the weekly average
DO concentrations for biofilter effluent. For noncanning
season conditions, DO levels were high, averaging 6.0 mg/1
during the March-July 1976 period and 7.1 mg/1 during the
November 1976-March 1977 period when higher air flows were
used. By contrast, the average DO level for August, the peak
canning season month, was only 1.7 mg/1; the plant staff
operated two to four fans per biofilter during the canning
season. These figures, in themselves, do not indicate
80
-------
that inadequate oxygen supply was the cause of the poor
nitrification performance during the first part of the program.
A DO concentration of 6.0 mg/1 is sufficiently high to preclude
inhibition of nitrification.
With the high recirculation rate employed, the DO level
hear the top of the tower was kept high by dilution of the
incoming waste with high-DO recycled effluent. It is possible,
however, that in the middle portion of the biofilter, the DO
level is significantly below the concentration at the upper and
lower levels. This could result in reduced nitrification.
.The total hydraulic loading (including recycle) during the
first part oฃ the study was approximately 0.024 m3/min/m2
(0*6 gpm/ft2 ); in October 1976 it was increased to approx-
imately the minimum value recommended by the manufacturer for
complete wetting of the media surface 0.031 m3/min/m2
(0.75 gpm/ft2). This increase is only 25 percent and would
not seem significant except for the improvement in performance
obtained.
An alternative explanation for the effect of increased
hydraulic loading on performance is related to the contact time
of the wastewater passing through the biofilters. In contrast
to carbonaceous BODs removal, where the waste material can be
sorbed onto the biomass and oxidized later, the conversion of
ammonia nitrogen to nitrate nitrogen must occur during the time
that the wastewater is in the biofilter. Thus, reduced contact
times may result in poorer performance.
Contact time is related to flow by the following relation-
ship:
t - K
"
(3)
where:
t = once-through contact time, min
K = coefficient
q = hydraulic loading, gpm/ft2
n = exponent
With recirculation flow, r(gpm/ft2):
t =
t'q
(q+r)
K
(q+r)n
81
-------
where:
t1 = total contact time (min), which reduces to:
q (q+r)" q
..(
(5)
K has been cited as varying between 0.5 and 1. If n = 0.5:
t1 =
= K(q+r)
q
ฐ'5
(6)
and increasing the recirculation flow, r, will increase
the contact time in the biofilter. (If n = I, increasing
recirculation flow will not cause an increase in contact time.)
Thus, increasing the hydraulic loading (q+r) by 25 percent
(as at Stockton) would increase the total contact time, t1, by
about 12 percent. This is, as with the other parameters, a
fairly small increase and does not seem significant. Further,
if contact time were limiting, nitrite nitrogen bleedthrough
might be expected in the effluent. Although measurable
concentrations of nitrite nitrogen (0.2 to 0.4 mg/1) were
detected during the March-July 1976 portion of the sampling
program, these values are not sufficiently high to suggest
that contact time was limiting. Nonetheless; the calculations
shown above do indicate that contact time may be an important
parameter in nitrification performance.
Williamson and McCarty have developed a rational theory of
biofilter performance which can be applied to attached growth
reactors such as trickling filters (10). One of the conclusions
drawn from the theory is that oxygen transfer, rather than
substrate utilization, will limit nitrification when the
dissolved oxygen level is less than 2.7 times the ammonia
nitrogen concentration. The two operational changes which can
be undertaken to increase the DO/ammonia nitrogen ratio are to
increase the DO level (by increased air flow or use of high
purity oxygen) or to increase recirculation, thereby diluting
the ammonia nitrogen in the influent. These steps are in fact
the ones which were taken at Stockton and which were followed
by a significant improvement in nitrification performance.
In summary, no definite conclusion can be drawn regarding
the cause of poor nitrification during the first part of the
Stockton sampling program or regarding the reason for increased
nitrification during the latter portion. It is highly likely
that one or both of the operational changes which were
82
-------
instituted were effective in aiding performance. In designing
trickling filter nitrification systems, provision of adequate
air supply and recirculation appear to be very important.
Organic Nitrogen Removal
Poor organic nitrogen removals, approximately 25 percent,
were obtained during the 1972 pilot study (5,6). It was noted
that the reactions involving conversion of organic nitrogen to
ammonia nitrogen (which can then be converted to the nitrate
form) are slow and usually quite incomplete in biological
treatment processes. Clarification is often the principal
removal mechanism since much of the organic nitrogen is in the
insoluble form.
Organic nitrogen removals obtained during the present
sampling program were also low, averaging about 48 percent for
the noncanning season and 24 percent for August and September
1976, the peak months of the canning season.
Nitrogen Mass Balance
Nitrification in biological treatment processes is
normally manifested by high secondary effluent nitrate nitrogen
concentrations (10 to 25 mg/1). The data gathered for this
study showed an overall average of 2.0 mg/1 (noncanning season)
with a maximum monthly value of 5.0 mg/1 in May 1976. Even
when effluent ammonia nitrogen concentrations were less than
2.0 mg/1 in January-March 1977, nitrate nitrogen concentrations
ranged only from 2.2 to 2.9 mg/1.
To provide insight into this phenomenon, a nitrogen mass
balance for the secondary treatment process is given in
Table 21. Primary and secondary effluent concentrations are
given for ammonia, organic, nitrite, and nitrate nitrogen.
Also shown is the estimated quantity of nitrogen assimilated
into the biomass. This value was computed by assuming that the
biofilter effluent volatile suspended solids contain 5 percent
nitrogen. Nitrogen concentrations normally cited for activated
sludge or trickling filter humus range from about 3 to
7 percent (11,12).
For the canning season months of August and September, the
biofilter influent nitrogen concentration equals the computed
biofilter effluent concentration, 34 mg/1. This indicates that
the assumption of 5 percent nitrogen in the biofilter effluent
volatile suspended solids is reasonable. For the noncanning
season portion of the sampling program, the influent nitrogen
concentration exceeds the effluent concentration by 8 mg/1
(28 mg/1 for influent; 20 mg/1 for effluent).
The cause of the apparent nitrogen loss through the
biofilters is uncertain. Denitrification (conversion of
nitrate to nitrogen gas) within the anaerobic portion of the
83
-------
biomass is a plausible reason. A second possible explanation
is that the biofilter effluent suspended solids contain a
higher concentration of nitrogen than assumed above. If the
effluent volatile suspended solids are assumed to consist
solely of biological cells sloughed from the media surface
(most applicable to the noncanning season), then nitrogen
concentration may be estimated. The formula CsHyNC^ is often
cited as being representative of cell material (13). The
nitrogen fraction then would be 12 percent of the effluent
volatile suspended solids concentration. Using this assumption,
the assimilated nitrogen concentration for the noncanning
season increases to 13 mg/1, which would give a biofilter
effluent nitrogen concentration of 26 mg/1 in Table 21, very
close to the influent concentration of 28 mg/1. Although the
nitrogen concentration of the biofilter effluent solids at
Stockton was not measured, all the values reported in the
literature are significantly lower than 12 percent.
TABLE 21. NITROGEN MASS BALANCE
Parameter
Concentration, mg/1
Noncanning Canning
Primary effluent
Ammonia nitrogen
Organic nitrogen
Nitrite nitrogen
Nitrate nitrogen
18
10
18
16
<0. 1
34
12
13
9.3
34
Total 28
Secondary or biofilter
effluent0
Ammonia nitrogen 4.3
Organic nitrogen 6.5
Nitrite nitrogen 0.2
Nitrate nitrogen 2.0
Assimilated nit-
rogen 7.3
Total 20
Difference, primary
effluent minus bio-
filter effluent 8
aMarch - July 1976; November 1976 - March 1977.
August - September 1976.
Secondary effluent concentrations used for
ammonia, organic, nitrite, and nitrate nit-
rogen; biorilter effluent used for assimilated
nitrogen.
Assimilated nitrogen = 0.05 x biofilter
effluent VSS.
associated with the higher 6005
achieved at that time.
Alkalinity and pH
Conversion of ammonia
nitrogen to nitrate nitrogen
in biological treatment is
accompanied by the destruction
of alkalinity. A potential
problem results from the
possible subsequent depression
of pH and associated inhibition
of nitrification rates. The
effect is mediated by the
stripping of carbon dioxide
from the liquid by the process
of aeration, which tends to
elevate the pH level. In
enclosed systems such as the
high purity oxygen activated
sludge process, the carbon
dioxide is less efficiently
stripped from the liquid and pH
depression can be severe.
Monthly primary and
secondary effluent alkalinity
concentrations from Stockton
are shown in Figure 36.
Greater drops in alkalinity,
and lower total concentrations,
occurred in the noncanning
season. A greater alkalinity
drop occurred during the last
portion of the study and is
and ammonia nitrogen removals
84
-------
400
to
O
o
as
O
CO
en
ฃ
z
_1
<
_l
<
300
200
100
NONCANNING
CANNING
I I I T
NONCANNING
PRIMARY
EFFLUENT
SECONDARY
EFFLUENT
I
I
I
M
M
A
1976
N
F M
1977
Figure 36. Alkalinity destruction.
It can be calculated that 7.1 mg of alkalinity as CaCO3 is
destroyed per mg of ammonia nitrogen oxidized. Measured values
range from about 6.0 to 7.4 mg/mg (14). Attempts to calculate
alkalinity destruction ratios for the Stockton data result in a
value of 10 mg alkalinity as CaC03 destroyed per mg ammonia
nitrogen oxidized. The higher value probably results from
other reactions occurring in the secondary treatment process
and indicates that in combined carbon/nitrogen oxidation
systems, alkalinity destruction cannot be predicted on the
basis of ammonia nitrogen oxidation alone.
Carbon dioxide stripping due to the high air flow through
the Stockton biofilters apparently offset the effect of
alkalinity destruction during the noncanning season months as
the pH level rose in passing through the secondary system from
6.9 to 7.4. During the canning season months of August and
September, pH levels dropped from 8.7 to 8.3 in the secondary
treatment process.
85
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Suspended Solids
Questions regarding the ability of plastic media trickling
filters to produce an effluent with a low suspended solids
concentration have been voiced increasingly during the past
few years. The principal reason is the federal guidelines
which specify a monthly average effluent suspended solids
concentration of. 30 mg/1 or less to provide secondary treatment
as mandated by the 1972 Federal Water Pollution Control Act
Amendments.
Data collected during the 1-yr sampling program at Stockton
(Table 14) showed that the 30 mg/1 requirement was not met
during three of the ten noncanning season months. There appear
to be three principal reasons for this: (1) high clarifier
overflow rates, (2) poor clarifier hydraulic characteristics,
and (3) possible short circuiting caused by temperature/density
gradients set up in the secondary clarifiers. The last item,
possible temperature density gradients, as described below, is
still a nebulous concept at this time but is an intriguing
possibility which should be explored further.
Figure 37. Secondary clarifier. Poor hydraulic distribution and short circuiting
may have hindered overall secondary treatment performance.
The four existing secondary clarifiers (Figure 37) at
Stockton have been in use for many years, and their number has
not been increased even though the overall capacity of the plant
86
-------
has been increased several times. At a design noncanning season
flow of 87,000 m3/day (23 mgd), use of all four clarifiers
would result in an overflow rate of approximately 30 m3/day/m2
(730 gpd/ft2). As noted above, practice has been to use only
three of the four clarifiers during the noncanning season,
resulting in experienced overflow rates of about 40 mS/day/m2^
(970 gpd/ft2). Such values are close to traditional design
loadings for secondary clarifiers following biofiltration.
Historically, however, such systems have not been designed to
meet the lower effluent suspended solids and BODs concentrations
now required. Even though performance requirements have become
more stringent, there has been a tendency to continue sizing
secondary clarifiers as in the past, which may, in some cases,
be responsible for difficulties in attaining low suspended
solids levels.
The second possible cause of the high measured secondary
effluent suspended solids levels is poor hydraulic characteris-
tics in the clarifiers. Poor flow distribution among the
clarifiers has been a chronic problem, and within each
clarifier, uneven effluent weirs have resulted in a large
fraction of the flow passing over a small percentage of the
weir length. Although the plant staff has undertaken minor
maintenance to improve the flow characteristics, major repairs
had not been made up to the time of the present study because
the buffering effect of the tertiary oxidation ponds made less
than optimum performance of the secondary clarifiers tolerable.
Modifications to the effluent troughs were implemented subse-
quent to completion of this study, and these should result in
improved performance in the future.
The third possible reason for high effluent suspended
solids concentrations is related to the wastewater temperature
drop caused by the forced draft ventilation system. The low
hydraulic loadings (excluding recycle) and high air flows which
must be used for nitrification mean that the biofilters act
like cooling towers. Wastewater temperature drops of 5 C
through the biofilters were measured at mid-day (on a cold day
with air temperature approximately 8 C) during the study.
A phenomenon to which these high temperature drops can be
hypothetically related had been occurring at the plant.
Observation of the secondary clarifiers during the middle of
the day showed an increase in turbidity and apparent short
circuiting of influent which rose to the surface near the
feedwell and moved rapidly across the clarifier to the effluent
troughs. This phenomenon had been observed for some time by
the plant staff, but no explanation had been found for its
occurrence. On one occasion, a dye tracer was added to the
clarifier at the influent while the phenomenon was occurring,
and in approximately 5 min, the dye was observed passing over
the effluent weir. This indicates that the short circuiting
was severe.
87
-------
After observing the phenomenon for several months
during the sampling program, it was theorized that the short
circuiting may have been due to temperature/density gradients
set up within the clarifier. With low hydraulic loadings and
high air flows to promote nitrification in the towers, colder
air temperatures and lower flows at night resulted in a greater
cooling of the wastewater as it passed through the towers. As
the wastewater flow and temperature increased in the morning
hours, the drop in wastewater temperature through the towers
would decrease and the water entering the clarifiers would
be warmer and lighter. If the difference in density was
sufficiently great and if the change from cold to warm water
occurred sufficiently rapidly, short circuiting of the type
observed might be expected to occur.
On several occasions, a dissolved oxygen/temperature probe
was used to measure temperature in the secondary clarifiers to
determine whether density gradients of the type described above
might exist. Measurements did show that temperature gradients
occurred within the clarifiers, but correlation of these
gradients with the observed short circuiting was difficult.
Nonetheless, after consultation with the plant staff, it was
decided to operate the fans in such a way as to counter the
phenomenon. Two fans were operated at night between the hours
of 8 p.m. and 8 a.m. when air temperatures and wastewater flows
were low. Six fans were operated between the hours of 8 a.m.
and 8 p.m. With fewer fans operating at night, the temperature
drop through the towers would be decreased. Thus, the 24-hr
variation in tower effluent temperature should be decreased,
and problems resulting from short circuiting should be
diminished.
The results of this operational modification were
inconclusive. The short circuiting phenomenon continued to
occur, but the occurrences appeared (from visual observation)
to be less frequent and less severe than they had been
previously. Twenty-four-hr average suspended solids concentra-
tions decreased dramatically during the initial period
following the change in procedure, indicating that the change
had an important beneficial effect on performance. During the
last 2 wk of the program, however, effluent concentrations
again rose, leaving doubt concerning the proposed explanation
for the observed phenomenon and the methods used to eliminate
it.
Weekly average secondary effluent suspended solid^
concentrations for the last 5 mo of the study are shown in
Figure 38. Large variations are seen to occur through the
period. The very high levels in late November occurred at
the same time that effluent ammonia nitrogen and BODs levels
increased, indicating an overall upset in the secondary
treatment process. The period of February 2 through March 2
88
-------
produced consistently low suspended solids concentrations,
averaging 18 mg/l , with a high daily value of 25 mg/1
(13 measurements). The overall February 2-March 16, 1977,
average was 21 mg/1, compared to an average of 30 mg/1 for the
period from October 25, 1976, through February 1, 1977, when
four fans were operated continuously.
CO
o
Q
z
UJ
I
co
H
OC
O
a
CO
I I I I
AVERAGES:
10/25/76 - 2/1/77 : 30 mg/l
2/2/77 - 3/16/77 : 21 mg/l
1976
1977
Figure 38. Secondary effluent suspended solids levels.
There is no apparent cause for the increase during the
final 2 wk. Inspection of unsettled biofilter effluent data
shows no increase in suspended solids levels which would be
associated with periodic sloughing of the media surface.
In summary, the cause of the short circuiting is still
not known. Temperature/density gradients may be the cause,
although the density gradients which would occur are small.
Temperature gradients were observed within the clarifiers,
but they could not be correlated with the presence of short
circuiting. Attempting to reduce or eliminate the density
gradients by varying the number of forced draft ventilation
fans seemed, from visual observation, to reduce the severity
of short circuiting. Daily averages of secondary effluent
suspended solids concentrations dropped markedly for a 1-mo
89
-------
period following the change in fan operation but increased
again during the final 2 wk of the sampling program without
explanation.
Secondary Treatment Solids Production
Total and waste secondary (or biological) solids produc-
tion, is summarized in Table 22 on both BOD5 and COD bases.
Waste secondary solids production is computed by subtracting
the solids in the secondary effluent; it represents the
quantity of secondary sludge to be processed by the plant's
solids handling system. Total secondary volatile solids
production averaged 0.43 kg/COD removed and 0.67 kg/kg 6005
removed. Total secondary influent and soluble secondary
effluent COD or BODs values were used in the computations.
TABLE 22. SECONDARY SOLIDS PRODUCTION
Average
BOD5 basis
COD basis
Month
1976-77
March
April
May
, June
July
August
September
October
November
December
January
February
March
Total solids
production3
kg TSS/
kg BOD5
removed
0.93
1.0
1.3
1.1
1.2
1.0
0.71
0.80
0.67
0.64
0.67
0.94
0.83
kgVSS/
kgBOD5
removed
0.60
0.79
0.92
0.69
0.92
0.83
0.57
0.65
0.57
0.50
0.48
0.71
0.67
Waste solids
production'3
kg TSS/
kg BODg
removed
0.69
0.81
1.1
0.75
0.98
0.73
0.50
0.57
0.50
0.52
0.52
0.83
0.69
kg VSS/
kg BODs
removed
0.41
0.63
0.76
0.45
0.78
0.62
0.39
0.44
0.42
0.40
0.36
0.61
0.57
Total solids
production3
kg TSS/
kg COD
removed
0.47
0.50
0.70
0.70
0.75
0.59
0.44
0.32
0.50
0.44
0.50
0.67
0.50
kg VSS/
kg COD
removed
0.30
0.39
0.48
0.45
0.60
0.51
0.35
0.42
0.43
0.34
0.36
0.50
0.40
Waste solids
production^
kg TSS/
kg COD
removed
0.34
0.40
0.59
0.49
0.64
0.46
0.31
0.36
0.37
0.36
0.39
0.59
0.41
kg VSS/
kg COD
removed
0.21
0.31
0.40
0.30
0.51
0.39
0.24
0.28
0.31
0.27
0.27
0.43
0.34
0.83
0.67
0.65
0.51
0.54
0.43
0.43
0.33
Total solids production = secondary system waste
sludge solids + secondary effluent solids.
Waste solids production = secondary system waste
sludge only.
Comparison of solids production during the noncanning
season before and after the operational modifications shows a
substantial decrease for the latter period. For example, total
volatile solids production averaged 0.78 kg/kg 6005 removed
for the March-July 1976 period. For the November 1976-March
1977 period with higher hydraulic loadings and air flows,
production averaged 0.59 kg/kg BODs removed.
90
-------
The lower production during the latter portion of the
study may be due to higher DO levels resulting from increased
air supply. It is a well-known fact that in the activated
sludge process, adequate DO levels are necessary to minimize
sludge production. The same phenomenon may be applicable to
trickling filtration.
DESIGN AND PERFORMANCE
Shown in Table 23 is a comparison between performance
predicted for the Stockton biofilters and that obtained during
the 1976-77 sampling program.
23. DESIGN AND PERFORMANCE COMPARISON
Parameter
Flow, mgd
Trickling filter loading
BOD5, mg/1 , e
BODs, lb/1,000 ftVday
Suspended solids, mg/1
Secondary effluent
BOD-, mg/1
BODง removal, percent
Suspended solids, mg/1
Ammonia nitrogen, mg/1
Canning
a
Design
58
390
110
155
120
70
165
season
Actual
39
320
73
220
130
59
51
Noncanning
Design
23 '
170
19
60
17
90
35
season
Actual0
17 ,
210
21
160
17
92
27
7 "7
aMaximum month.
bAugust 1976.
CNovember 1976 - March 1977.
dmgd x 3,785 = m3/day.
elb/l,000 ft3/day x 0.016
kg/m /day.
The peak month of August 1976 was used to represent the
canning season in comparison with the maximum month projected
values. The period of November 1976 through March 1977 was
used to represent the noncanning season; this followed the
operational changes which were made in an attempt to improve
nitrification performance. Performance during this period was
better than that obtained during the first part of the sampling
program, from March through July 1976, and represents what is
believed to be optimal plant performance.
Flows for both the canning and noncanning seasons were
below design capacity. The biofilter organic loading is well
below design for the canning season but slightly above the
design loading for the noncanning season due to higher than
expected primary effluent BODs concentrations.
91
-------
Maximum month canning season BOD5 removal averaged
59 percent, below the projected value of 70 percent even
though the loading was relatively low, 1. 17 kg/m3/day
(73 lb/1,000 ft3/day). It is likely that if the operational
changes discussed previously had been in effect during the
canning season, greater BOD5 removal would have resulted.
Biofilter effluent DO levels, in particular, were very low
during the canning season and would have benefitted from
a greater number of fans being operated.
Noncanning season BOD5 removal for
Lod essentially met ,. - -.,
average effluent concentration
Noncanning season BOD5 remov
March 1977 period essentially met
levels, with an average effluent
and an average removal of 92 percent.
the November 1976-
the projected performance
of 17 mg/1
The canning season effluent suspended solid concentration
was 51 mg/1, far better than the predicted value of 165 mg/1,
which seems high, even when the higher clarifier loading
rates which would occur at design flow are considered. The
non-canning season average of 27 mg/1 is below the projected
level of 35 mg/1. Possible methods of ensuring the "secondary
treatment" level of 30 mg/1 suspended solids are discussed
in Section 8.
Although no secondary effluent ammonia nitrogen level was
specified in the design data, the average over the last portion
of the sampling program was 2.7 mg/1. At a comparable loading
during the 1972 pilot study, an effluent concentration of
2.0 mg/1 was obtained.
In summary, after making operational changes, specifically
increasing the forced draft ventilation air flow and increasing
recirculation, performance improved to the level anticipated.
It is not certain if these changes actually caused the
improvement in performance, but the correlation between the
changes and improved performance is definite.
Besides the question of which operational change,
increased air flow or increased recirculation, improved
performance (or whether both or neither helped), the major
remaining question regarding performance involves the cause of
the short circuiting (with consequent high effluent suspended
solids levels) which occurred in the secondary clarifiers. It
has been hypothesized that temperature/density gradients set up
in the clarifiers caused the short circuiting. Attempts to
measure temperature gradients were inconclusive, and it remains
for future investigations to determine the cause of the observed
phenomenon.
92
-------
TREATMENT COSTS
Total construction cost for an engineering project such as
conversion of the Stockton trickling filters includes not only
the contract cost, but expenses for design and construction
inspection. Presented in Table 24 are total construction
costs for modification of the Stockton secondary treatment
facilities. The total cost of $3,953,000 is associated with an
ENR Construction Cost Index of 2200 for the San Francisco area
in July 1973, the approximate midpoint of the construction
period.
TABLE 24. CONSTRUCTION COST FOR
TRICKLING FILTER
CONVERSION
Component
Cost, thousand
dollars
A breakdown
successful secondary
modification bid is
in Table 25. This
was prepared by the
of the
treatment
presented
breakdown
contractor
Secondary treatment modifi-
cations
Filter media supply and
1,820
installation
Engineering design
Resident engineering3
Total construction cost
1,840
234
59
3,953
Does not include construction inspection
services provided by city staff.
prior to beginning of construc-
tion and was used as the basis
for construction progress
payments. The total cost shown
in Table 25, $1,722,000, is
lower than the total shown
for secondary treatment
modifications in Table 24,
$1,820,000, because of change
orders during construction.
Annual operation and
maintenance (O&M) cost for the
Stockton Regional plant are presented in Table 26 for fiscal
years 1975 and 1976. Principal cost increases between these
2 yr are in the categories of utilities (principally gas and
electricity), chemicals (chlorine for disinfection and ammonia
gas for use as a nutrient supplement, in the ponds and biofilters
during the canning season), and motor pool expenses (which may
be principally due to gasoline costs). The overall increase
from fiscal year 75 to fiscal year 76 was 41 percent. Chemical
costs accounted for the biggest increase, 106 percent.
Presented in Table 27 is an estimate of the percentage
of operation and maintenance labor hours associated with
each major unit process in the plant. The highest, by far,
52 percent, is for preliminary and primary treatment which
includes grit removal, bar screening, flow measurement,
raw sewage pumping, and primary sedimentation. Secondary
treatment, including the rock and plastic media trickling
filters, filter recirculation, and secondary clarification,
accounts for 17 percent of the total.
93
-------
TABLE 25. SECONDARY TREATMENT MODIFICATIONS BID BREAKDOWN
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
ain. x
byd3x
clineal
ft2 x
elb x 0
ฃ
ton x
Description
Demolition
Removal and disposal of
existing media
Structural excavation
Structural backfill
In-place concrete
In-place precast concrete
In-place masonry
Miscellaneous metal
60 in.a distribution pipe
48 in .3 filter return pipe
48 in. foul air duct
36 in. effluent supply and
pipe collection
Filter distributors
Filter supply pumps
Filter circulation pumps
42 in.* by 42 in.a sluice
gates
Furnish and install fans
Painting
12/20.8 SV switch station
Modify existing MCC
New MCC
1000 KVA substation
750 KVA substation
Buried 4 in .a conduit in duct
Buried 3 in.a conduit in duct
Buried 1 in.a conduit iii duct
Buried 23 KV conduit in duct
Paving
Other work
Subtotal
Contingency
Total
2.54 = cm.
0.765 = m3.
ft x 0.305 = lineal m.
0.929 = m2.
.454 = kg.
0.907 = metric ton.
Quantity
Lump sum
9,700
1,840
910
1,570
24,000
29,550
34,000
360
80
172
924
3
3
2
5
24
Lump sum
Lump sum
Lump sum
Lump sum
Lump sum
Lump sum
2,600
8,100
10,400
8,300
2,000
Lump sum
Unit
b
ydf b
yd
lineal ft
lbe
lineal ftฐ
lineal ft
lineal ftc
lineal ftฐ
Each
Each
Each
Each
Each
.
~
-
-
lineal ftฐ
lineal ft
lineal ft
lineal ft
Tonf
Unit price,
dollars/unit
-
10
25
15
225
7.50
4.00
1.50
110
150
125
70
41,600
22,000
12,500
5,000
800
-
-
14
3
2.50
5.00
14.50
Cost,
dollars
50,000
97,000
46,000
13 ,650
353,250"
180,000
118,200
51,000
39,600
12,000
21,500
64,600
124,800
66,000
25,000
25,000
19,200
60 , 000
34,900
TO o A n
J.O , j U U
26,000
22, 000
18, 250
36,400
24, 300
26,000
41,500
29,000
28,470
1,672,000
50,000
1,722,000
94
-------
TABLE 26.
OPERATION AND
MAINTENANCE COSTS
Category
Annual operation
and maintenance
cost, thousand
dollars/yeara
Salaries, fringe bene-
fits, and overhead
Utilities
Chemicals
Materials and supplies
Professional services
Motor pool
Other
Total
1974-75
556
103
156
47
33
36
4
935
1975-76ฐ
651
152
322
92
45
57
4
1,323
aEstimated from records which include cost
of a second, smaller plant operated by the
City.
bFY 1975.
CFY 1976.
TABLE 27. OPERATION AND
MAINTENANCE LABOR
ASSOCIATED WITH MAJOR
PLANT COMPONENTS
Process
Estimated amount df
operation and
maintenance labor
associated with
process, percent
Preliminary and pri-
mary treatment
Secondary treatment
(trickling filters)
Oxidation ponds
Chlorination
Solids handling
52
17
12
4
15
95
-------
SECTION 8
GENERAL DESIGN CONSIDERATIONS
Upgrading a conventional rock media trickling filter plant
through conversion to plastic media may be an economical,
efficient way for many communities to obtain improved
wastewater treatment through maximum use of existing
facilities. In determining whether plastic media trickling
filtration should be selected for use at a particular plant,
questions must be asked concerning the ability of the process
to meet effluent quality requirements, the physical condition
of existing structures, the ability of existing pipes and
pumping facilities (with necessary modifications) to receive
increased flows, and the ability to maintain adequate treatment
capability during construction. Working with an existing plant
configuration may impose particular design constraints; for
example, inability to bypass during construction may affect
design, or the plant configuration may make future expansion
difficult. Comparison of plastic media trickling filtration
with alternative treatment processes such as the activated
sludge process must be made with full knowledge of all these
factors. If plastic media trickling filtration is selected for
use, anticipation of design and construction problems will be
very important as the detailed design and construction phases
follow.
It is the purpose of this section to present information
on design considerations for conversion of rock media trickling
filters to plastic media. Material presented here is based on
the information from Sections 4 through 7, data from conver-
sions at other wastewater treatment plants, manufacturers'
information, and the technical literature. As in Section 5,
the subject of design has been divided into two categories,
process design and physical design. The information presented
under each category is intended to be useful in both the
planning and detailed design engineering phases of treatment
plant upgrading.
PROCESS DESIGN
Difficulty in describing the trickling filtration process
mathematically has resulted in most designs being based on
empiricism, experience, standard practices, and, occasionally,
pilot investigations. Increased use of plastic media has
96
-------
resulted in an increased use of equations which, although
developed on a semirational basis, remain essentially empirical
in nature. Coefficients determined from experience or from
pilot studies are inserted into the equation, and the required
media volume and loading parameters can be determined.
Generally, however, such design parameters as media depth,
hydraulic loading, and specific surface area are constrained
within certain ranges by various factors, and the design
parameter which can be varied over the greatest range is
organic loading in kg BODs/m3/day (lb/1,000 ft3/day) or, in the
case of separate-stage nitrification, ammonia nitrogen loading
in kg NHt-N/m2 media surface area/day (lb/1,000 ft2/day).
Items covered below under process design include media
selection, BODs removal, nitrification, oxygen transfer,
ventilation, secondary clarification, and solids production.
Media Selection
Plastic trickling filter media falls into two main types:
corrugated sheet modules (e.g., B. F. Goodrich's Vinyl Core)
and dumped media. Shown in Table 28 are representative
examples of each type along with the specific surface area for
each (other values may be available). Lower specific surface
areas are used for BODs removal or combined carbon oxidation-
nitrification. Higher values are used for separate-stage
nitrification.
Shown on Figure 39 is a module of B. F. Goodrich's Vinyl
Core II synthetic media with specific surface areas which can
range from 72 to 121 m2/m3 (22 to 37 ft2/ft3). In Figure 40 is
a high-specific-surface-area media, Koro-Z, manufactured by
B. F. Goodrich for separate-stage nitrification. Available
specific surface areas range from 138 to 217 m2/m3 (42 to
66 ft2/ft3).
BOD5 Removal
Removal of oxygen demanding substances from the waste
stream has historically been the most important performance
parameter for trickling filters. Rock trickling filter 8005
removal efficiencies generally range from 60 to 85 percent with
effluent concentrations between 35 and 75 mg/1. Many inves-
tigators have proposed equations to predict trickling filter
BOD5 removal, including the National Research Council (NCR),4
Caller and Gotaas,15 Fairall,16 and Rankin.17 The concept on
which most present-day plastic media design relationships are
based was first proposed by Velz^-S in 1948:
(7)
97
-------
where:
Se - effluent BOD5
S0 = influent BODs
D = media depth
k2 = rate coefficient
It is based on the principal that the rate of extraction of
organic matter is proportional to the amount remaining, or:
dt
In integrated form, the equation is:
(8)
(9)
where:
Se = effluent
So = influent
k3 = rate coefficient
Equation 9 is equivalent to Equation 7 if the contact time, t,
is assumed to be proportional to depth and if base 10 logarithms
are converted to natural logarithms.
Variations of Equation 9 usually include some or all of the
following additional parameters:
ฃฃ = e-kAvDm/qn
S0
(2)
where:
q
k,mfn
media specific surface area,
hydraulic loading (excluding recycle), gpm/ft2
coefficients
98
-------
TABLE 28. EXAMPLES OF AVAILABLE PLASTIC MEDIA
Manufacturer
Trade name
Type
Specific surface
area available,*3
ft2/ft3d
Envirotech Corp., Californiac
Surfpac Corrugated sheet
modules
B.F. Goodrich, Marietta,- Ohio Vinyl Core Corrugated sheet
modules
Enviro Development Co.,, Inc.
Palo Alto, California Flocor Corrugated sheet
modules
Mass Transfer, Ltd., Houston, Filterpack Dumped rings
Texas
Norton Co., Akron, Ohio
Actifil Dumped rings
27
30.5
45
27
40
36
57
27
42
Munters Corp., Ft. Meyers,
Florida
PLASdek Corrugated sheet
modules
42
68
Formerly available from the Dow Chemical Co., Midland, Michigan.
Under license from ICI, Great Britain; formerly available from the Ethyl
Corp., Baton Rouge, Louisiana.
ฐRepresentative values only; other specific surfaces may be available.
dft2/ft3 x 3.28 = m2/m3.
The inclusion of Av in the relation is intended to reflect
the better treatment provided by more slime surface area per
unit volume as provided by a higher specific surface area.
The term q is included to show that the contact time may be
decreased by an increase in the hydraulic loading on the filter
and, thus, is affected by q as well as D.
The exponents m and n have generally been cited as ranging
from 0.5 to 1.0, with 1.0 the most commonly mentioned value for
m and 0.5 or 0.67 the most common value for n. The coefficients
k, k2 , or k3 (or ki where ki = kAv) are termed treatability
coefficients and are considered to be determined by characteris-
tics of the wastewater. Treatability coefficients for domestic
wastewaters are fairly predictable, but those for industrial
wastes are more variable. Often, pilot tests are run to
determine the treatability of specific industrial wastes.
The most commonly used form of Equation 2 appears to be:
ฃe _ -k,D/q
So
0.5
(10)
99
-------
This form of the equation is used by several plastic media
manufacturers for design purposes.
Figure 39. B. F. Goodrich's Vinyl Core II plastic media module
(photograph courtesy B. F. Goodrich).
While these equations can be useful in predicting
performance, they are limited in important respects. The
treatability coefficient is often determined by more than merely
the character of the waste, and certain factors limit the usable
ranges of specific surface area, depth, and hydraulic loading.
The various parameters of Equation 2 are discussed briefly
below.
Influent and Effluent BODs Values
Equation 2 is employed almost universally for situations
where primary effluent is treated by the trickling filter.
Usually, total (soluble plus suspended) 8005 values are used
100
-------
for influent and secondary clarifier effluent concentrations,
since they are the values most often measured and because
discharge requirements are written in terms of total 8005.
Figure 40. B. F. Goodrich's Koro-Z plastic media module. This is a high-specific
surface-area plastic media option which can be used for separate-stage
nitrification applications (photograph courtesy B. F. Goodrich).
Much of the published theory on biological treatment
kinetics uses influent and effluent soluble BOD$ concentrations.
While this may allow more rational development of kinetic
models, application to specific design situations becomes
difficult. .
Utilization of influent total 3005 and effluent soluble
BODs offers specific advantages in applying the basic design
equation. Although Equation 2 may not be strictly applicable to
101
-------
the removal of suspended biodegradable material, values of total
influent BODs are nearly always available for planning or
design purposes.
It is, therefore, convenient to use influent total BODs
values in design. Inaccuracies will be minimal where domestic
wastewater is being treated and the fraction of soluble BODs
is fairly consistent. In dealing with industrial wastes, pilot
studies may need to be undertaken with loading parameters near
those anticipated for des,ign. This will reduce the necessity of
extrapolating results, which can result in inaccuracies.
Suspended BODs in the trickling filter (and secondary
clarifier) effluent consists principally of particles sloughed
from the media surface and do not represent material which has
passed through the filter unoxidized. This is particularly
true when loadings are low and treatment efficiency is high.
(It is less true when the trickling filter is used in a
roughing mode under high loadings.)
The ability of a secondary treatment system to produce
effluents with low suspended BODs concentrations is primarily
dependent upon solids separation efficiency. It is therefore
reasonable to use effluent soluble BODs when discussing
performance of the trickling filter alone, i.e., in applying
Equations 2 or 10.
The Stockton data provides evidence that it is possible to
produce secondary effluents containing soluble BODs concentra-
tions of less than 10 mg/1 with plastic media trickling filters.
Tertiary, multi-media filtration can then be expected to produce
an effluent with a total BODs concentration near this value.
Other methods of improving solids separation will be discussed
below under the subsection on suspended solids removal.
Specific Surface Area
The derivative form of Equation 2 indicates that the rate
of removal of organic material is directly proportional to the
specific surface area of the media used.
f
(11)
This equation predicts that the specific surface area will have
a strong effect on performance and suggests that the designer
should attempt to use a media with as high a specific surface
area as possible. There appear, however, to be two limitations
to this concept.
102
-------
The first concerns possible plugging of the media when a
high specific surface area is used. Specific surface areas
for plastic media generally range from 82 to 246 m2/m3 (25 to
75 ft2/ft3), although some companies manufacture media with even
higher values. Associated with higher specific surface areas
are smaller voids in the media which can become more easily
plugged by developing biomass. Generally, for secondary
treatment applications, the specific surface area should be less
than 131 m2/m3 (40 ft2/ft3) unless prior pilot testing is under-
taken to ensure that plugging will not occur. For applications
such as separate-stage nitrification of secondary effluent,
which involves very thin slime layers, higher specific surface
areas can be used.
The second limitation also involves growth of the biomass
within the filter and is, in fact, a phenomenon which has
plugging as its extreme manifestation. As the slime layer in
the media increases in thickness, the effective surface area may
be decreased as small voids become filled with biomass. This
effect will be more pronounced, of course, at high specific
surface areas, and doubling the specific surface areas,
therefore, may not double the removal rate. One of the most
comprehensive studies involving trickling filtration with media
of varying specific surface areas was described in two papers by
Bruce and Merkens (19,20). They reported on 3-1/2 yr of pilot
studies in Great Britain which evaluated six media ranging in
specific surface from 39 to 220 m2/m3 (12 to 67 ft2/ft3). Four
of the media were plastic module types; the other two were rock
and blast furnace slag (both 39 m2/m3 or 12 ft2/ft3). Total
BOD5 was measured on both the influent and effluent from the
pilot clarifiers. All of the pilot biofilters were 2.1 m
(7.0 ft) deep, and organic loadings over the period of study
ranged from 0.64 to 4.5 kg BOD5/m3/day (40 to 280 lb/1,000 ft3/
day). The range for any particular media type may have been
less.
The effect of specific surface area on performance can be
evaluated by rewriting Equation 2 as follows:
(12)
The exponent p can be evaluated to determine the effect of A
on performance. Assuming n = 0.67 and given that D = 2.1 m
(7.0 ft) for all the data:
= e
(15)
103
-------
Then:
In
0.67
(14)
,<>ซ mis..,
(15)
Plotting qO.67 in(Se/So) vs. Av on log-log coordinates will
allow the exponent p to be evaluated. Shown on Figure 41 is
such a plot for the data obtained by Bruce and Merkens (20).
The slope of the line drawn through the plotted points
represents the exponent p. From Figure 41, a value of
approximately 0.7 is obtained. Figure 41 indicates that while
increased specific surface area may be expected to lead to
improved performance, the dependency is not as strong as
Equation 11 suggests.
6.0
5.0
4.0
3.0
CD I Q
S 2.0
r-
to
d
T
1.0
0.9
0.8
0.7
0.6
0.5
T
SOURCE: REF.20
T
20 30 40 60 80 100 200 300
Av/ m2/m3
Figure 41. Effect of specific surface area on BOD removal.
400
104
-------
Data from the medium with the highest specific surface
area of those tested (Cloisonyle at 220 m2/m3 or 67 ft2/ft3) w
ere not used in determining the slope. The data developed by
Bruce and Merkens and by Hutchison (discussed below) showed that
for Cloisonyle, which consists of vertical tubes extending the
entire depth of the filter, performance fell far below that
which would be expected from a medium with such a high specific
surface area. Measurement of contact times for the various
media showed that Cloisonyle produced contact times which
were much lower than expected for its high specific surface
area (19). A strong correlation between specific surface area
and contact time was shown for the other media tested.
Hutchison, in pilot studies at Auckland, New Zealand,
tested four types of synthetic media, with specific surface
areas of 89, 89, 118, and 220 m2/m3 (27, 27,36, and 67 ft2/
ftj) (21). While improved soluble BOD5 removal resulted from
increasing the specific surface area from 89 to 118 m2/m3 (27 to
36 ft2/ft2, increasing the specific surface area to 220 m2/m3
(67 ft2/ft3) (Cloisonyle) resulted in deteriorating performance.
These results are similar to these reported by Bruce and
Merkens.
In pilot studies on secondary treatment processes for
the Municipality of Metropolitan Seattle (22), high-specific-
surface-area media (138 mVm3 and 223 m2/m3 or 42 ft2/ft3 and
68 ft2/ft3, both manufactured by Munters) of the modular type
was employed in the belief that high BOD5 removals would be
obtained. The clearances between the 223 m2/m3 (68 ft2/ft3)
media sheets were too small, however, and the pilot tower failed
due to plugging. The tower with the 138 m2/m3 (42 ft2/ft3)
media did not fail, but removal and inspection of the media
showed a buildup of slime which might have eventually led to
plugging.
A random-packed media with a specific surface area of
95 mVm3 (29 ft2/ft3) was also employed at Seattle, and it also
failed due to plugging. The reason for the plugging was that
the small void spaces did not allow sloughing of the biomass.
During the second phase of the Seattle study, two modular
media designs were evaluated in parallel tests (22). The first
design was a medium with a constant specific surface area of
89 mVm3 (27 ft2/ft3) with a total media depth of 6.7 m (22 ft).
The second design used a 89 m2/m3 (27 ft2/ft3) medium at the top
of the tower, increasing to 138 m2/m3 (42 ft2/ft3) at the bottom
of the tower. It was believed that plugging could be avoided by
using a medium with larger void spaces at the top of the tower
where biomass growth is greatest. In the lower part of the
tower, where the slime thickness is less and plugging would not
be expected to occur, a higher specific surface area should aid
performance. Preliminary analysis shows little difference
105
-------
in performance between the two designs. In the loading range of
0.4 to 0.8 kg soluble BOD5/m3/day (25 to 50 lb/1,000 ft-Vday),
effluent soluble BODs concentrations ranged from about 7 to
15 mg/1. The only apparent advantage of the graded media was a
more consistent performance with less scatter to the data,
but there are signs that the graded media also suffers from
occasional temporary plugging problems.
Also during the second phase of the Seattle pilot study,
an evaluation was made of a random media with a specific
surface area of 98 m2/3 (30 ft2/ft3), which is claimed by the
manufacturer to possess a geometry for which plugging is not a
problem. During the first 3 mo- of operation, this media was
used without apparent problems.
The plugging which has occurred at Seattle may be peculiar
to that set of circumstances; much of the BOD5 removal and
consequent biomass growth has occurred in the top portion of the
towers. Thus, plugging might be more likely to occur.
In summary, attempting to obtain improved secondary
treatment performance by using a media with a very high
specific surface area (greater than approximately 115 mVmJ to
164 m2/m3 or 35 to 50 ft2/ft3) may prove futile. The expected
performance may not be achieved, and a total breakdown due to
plugging may occur.
High-specific-surface-area media (greater than 131 m2/m3
or 40 ft2/ft3) do have an important role to play in wastewater
treatment, particularly in separate-stage nitrification applica-
tions and in two-stage secondary treatment processes, but they
should probably not be used in single-stage secondary treatment
applications without pilot testing to predict performance.
Media Depth .
Economic considerations usually result in plastic media
biofliters being constructed at depths (6.1 to 9.1 m or 20 to
30 ft) much greater than rock media filters (1.2 to 2.4 m
or 4 to 8 ft) . The appearance of D in Equation 2 may be
misleading, however, in regard to the importance of depth as a
design parameter for obtaining a specified level of performance.
Consider the basic design equation as written below:
(16)
Substituting Q/A for q yields
(17)
o
106
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where:
Q = influent flow (excluding recycle), gpm
A = biofilter cross-sectional area, ft2
If ra = n:
Se m -k,(DA)n/Qn = e-kl(V/Q)
n
(18)
where:
V = media volume,
Equation 18 is closely related to the traditional loading
parameter of kg/m3/day (Ib BOD5/1,000 ft3/day). The media
volume thus becomes the chief design parameter once the media
specific surface area, influent flow, influent BODs level, and
required effluent quality are known.
Even when m^n, available experimental evidence indicates
that volumetric organic loading is a better indicator of 8005
removal than tower depth (19,22,23). Shown in Figure 42 is a
plot of BOD5 removal and organic loading for two plastic media
trickling filters with media depths of 7.4 m (24.3 ft) and
2.1 m (6.9 ft) (19). Removal is based on total influent BOD5
and total effluent BOD5 after settling. Over a wide range of
loadings, there is no discernible difference in performance
between the two filters.
This point is stressed because normally cited values for
m in Equation 16 are greater than those normally given for
n. With such values, Equation 16 predicts that deep towers
will perform better than shallow towers at the same media
volumes. Most of the available evidence does not support this
conclusion, however. The normal range of depths usually found
is about 4.6 to 9.1 m (15 to 30 ft), with 6.1 to 7.6 m (20 to
25 ft) most common.
Hydraulic Loading and Recirculation
Hydraulic loading is also a parameter whose importance can
be overestimated from inspection of the Velz equation, where it
appears as an independent variable.
Once the design organic loading is established, the
resultant total hydraulic loading (including recycle) should be
inspected to determine whether it falls between recommended
minimum and maximum values and to ensure that recirculation is
adequate.
107
-------
100
Q
UJ
O
s.
Ul
oc
in
O
O
m
9 24.3 ft DEEP
O 6.9ft DEEP
NOTES:
(1) ftx 0.305 = m
(2) Ib/1,000ft3/day x 0.016= kg/m3/day
SOURCE: REF. 19
20 -
100 150 200
BOD5 LOADING, Ib/1,000ft3/day
250
300
350
Figure 42. BODg removal and organic loading at two biofilter depths.
A minimum total hydraulic loading is recommended by each
media manufacturer to ensure complete wetting of the media
surface which, in turn, assures that the entire media surface
contributes to biological treatment. A minimum application
rate also helps prevent freezing in cold climates. The
nrule-of-thumb" recommended minimum for B. P. Goodrich's Vinyl
Core and Envirotech's Surface, for example, is 0.031 m3/min/m2
(0.75 gpm/ft2).
Section 7 described how performance at Stockton was
improved by increasing the total hydraulic loading (by
increasing recirculation) from about 0.024 to 0.031 m3/min/m3
(0.6 to 0.75 gpm/ft2) in conjunction with increasing the forced
draft ventilation. It is uncertain which of these actions had
a beneficial effect, but both nitrification and 6005 removal
improved substantially after the operational modifications
were made.
Exceeding recommended maximum hydraulic loadings will not
normally occur in applications where a moderate or high degree
108
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of treatment is provided. Exceptions may occur in roughing
applications, such as where a trickling filter precedes an
activated sludge unit. Total hydraulic loadings of 0.16 to
0.24 m-Vmin/m^ (4.0 to 6.0 gpm/ft^) have been used with good
results, but the upper limit on allowable hydraulic loading
is uncertain.
Benefits to be attained from recirculation with plastic
media are intangible, but experience has indicated that,
particularly where nitrification is desired, provision of
recirculation can result in more stable and improved perfor-
mance. The Velz equation (Equation 2) can be modified to
incorporate the effect of recirculation on predicted 8005
removal. This calculated difference is in most cases
negligible, and the .Velz equation should not be used to attempt
to predict the effect of recirculation.
In Section 7, it was indicated that recirculation can
increase the contact time of the wastewater in the filter. For
example, the "fall velocity" of wastewater through the media
double its original value if the total
is doubled through an increase in the
As contact time may affect nitrification,
be an important factor in attaining the
will be less than
hydraulic loading
recirculation rate.
recirculation may
desired nitrification performance.
Normally, meeting the recommended minimum total hydraulic
loading will require high recirculation ratios where nitrifica-
tion (either combined or separate-stage) is practiced. For
carbonaceous oxidation alone, a recirculation ratio of 1:1 is
probably a good "rule-of-thumb."
Summary
The widespread use of the Velz equation and similar
relationships make it almost mandatory to rely on them for
design purposes. More rational design procedures such as
that developed by Williamson and McCarty (10) are difficult to
utilize, and the semi-empirical methods will continue to be
relied upon for the foreseeable future.
The key to using empirical design methods sensibly is to
avoid extrapolation of variables (e.g., BODs removal, media
depth, specific surface area) beyond values for which reliable
operational and performance data are available. If unusual
circumstances are envisioned, pilot studies may be used to
develop reliable information on expected performance.
Nitrification
While a great deal of effort has been expended toward
defining the carbonaceous 6005 removal characteristics
of plastic media biofiltration, much less information is
109
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available on the ability of this process to nitrify. A few
studies (24,25,26,27,) have been carried out on separate-stage
nitrification of secondary effluent, but this report and
the 1972 Stockton pilot study (5,6) appear to be the most
substantive investigations undertaken on combined carbon
oxidation- nitrification in plastic media biofilters. Neverthe-
less, available information on nitrification kinetics, coupled
with data obtained from the activated sludge process, rotating
biological discs, and rock trickling filters, allows presenta-
tion of an empirical basis for design and provides insight
into the design and operational parameters which apply to
nitrification in plastic media trickling filtration. For an
in-depth review of nitrification process kinetics and the
factors which can affect nitrification performance, the reader
is referred to the U.S. Environmental Protection Agency
Technology Transfer publication, Process Design Manual for
Nitrogen Control (14).
This subsection is divided into two parts. In the
first part, a review of available information on design of
separate-stage nitrification is discussed. Secondly, design and
operating criteria for combined carbon oxidation-nitrification
are presented.
Separate Stage Nitrification
Nitrification in the trickling filter process (or any
other biological treatment process) can be classified as
either separate-stage nitrification or combined carbon
oxidation-nitrification, which is used at Stockton. Combined
carbon oxidation-nitrification processes have a low population
of nitrifiers due to a high ratio of BODs to total Kjeldahl
nitrogen (TKN) in the influent (14). Separate-stage nitrifica-
tion has a lower BODs load relative to the influent ammonia
nitrogen load. As a result, a higher fraction of nitrifiers
is obtained, resulting in higher rates of nitrification. To
achieve separate-stage nitrification, pretreatment (chemical
primary or biological secondary treatment) is required to lower
the organic load or the BOD5/TKN ratio.
An illustration of the effect of the BOD5/TKN ratio
on nitrification rates in an attached growth reactor is
presented in Figure 43 (28). Interestingly, a small amount of
BODs (about 10 mg/1) was found to enhance the nitrification
rate.
In general, combined carbon oxidation-systems have
BOD5/TKN ratios greater than 5.0, and separate-stage systems
have BODs/TKN ratios less than 3.0. In combined systems, the
nitrogenous oxygen demand (NOD) generally accounts for less
than 40 percent of the total oxygen demand. In separate-stage
systems, NOD normally accounts for 60 to 70 percent or more of
the total demand.
110
-------
en
E
LO
Q
O
DO
HI
LL
O
HI
O
DC
LJJ
Q_
100
80
60
40
20
SOURCE: REF. 28
INITIAL NHj-Nw 20 mg/l;
CONTACT TIME,94 SEC;
pH,7.4; TEMPERATURE, 23 C
0
1.0
2.0
3.0
4.0
5.0
BOD5 /TKN RATIO
Figure 43. Effect of BODs/TKN ratio on nitrification rate.
In separate-stage nitrification applications, the
nitrification rate is proportional to the surface area exposed
to the liquid (10,30). In other words, when all other
parameters are held constant, the loading/performance relation-
ship can be expected to be related to the media surface area
rather than volume.
Very little biological film development occurs in
separate-stage applications (24,27). Consequently, plugging of
voids and ponding is less of a concern than in cases where
carbonaceous BODs is being removed. One advantage is that
a medium of high specific surface area can be used, up to
230 m2/ra3 (70 ft2/ft3) or higher. Another result of the small
amount of biological growth is the reduced effluent suspended
solids level. In some cases, subsequent solids separation steps
may not be needed.
Loading CriteriaData from two pilot studies, at Midland,
Michigan (24,25), and at Lima, Ohio (26), were used to develop
the loading/performance curves shown in Figure 44. The surface
111
-------
area required, in terms of ft2/lb ammonia nitrogen oxidized/day,
is plotted against desired ammonia nitrogen effluent concentra-
tion. Data are plotted for three temperature ranges, exhibiting
the strong dependence of nitrification rate on wastewater
temperature.
12:000
s 10,000
z
z
.Q
8,000
2" 6,000
EC
a
LU
EC
55 4,000
cc
LU
O
Sj 2,000
) ammonia nitrogen oxidized is indicated
in Figure 44. To reduce the effluent concentration to
1.0 mg/l, a surface area of 2,050 m2/kg (10,000 ft2/lb) ammonia
nitrogen/day, a 250 percent increase, is required. Thus,
3.0 mg/l effluent ammonia nitrogen can be considered the
practical limit for separate-stage nitrification in plastic
media trickling filters.
low,
The BODs/TKN ratios for
1.1 for Midland, Michigan,
these two
and 0.36
studies were very
for Lima, Ohio.
112
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Pilot studies involving nitrificatipn of stabilization pond
effluent (27) at Sunnyvale, California, revealed that about
40 percent more surface area was required than at Midland,
Michigan, to achieve the same effluent ammonia nitrogen levels
at similar operating temperatures. It was hypothesized that
algae trapped in the biofilter were eventually oxidized, which
increased the fraction of heterotrophic organisms in the
bacterial film. This indicates that where BOD5/TKN ratios
are higher, i.e., nearer 3.0, greater surface areas may be
needed to achieve the required degree of nitrification.
Because trickling filters, like any other process used for
nitrification, are affected by diurnal variations in nitrogen
load, this variation should be accounted for in applying
Figure 44. The amount of surface area determined from Figure 44
for average loading conditions can be multiplied by the ammonia
nitrogen peaking factor to establish a design surface area. An
alternative approach would be provision of flow equalization.
Organic Nitrogen RemovalWhile very high ammonia nitrogen
removals can be attained with plastic media biofilters, organic
nitrogen removals are usually quite low. It was noted in
Section 7 that for the combined carbon oxidation-nitrification
system at Stockton, organic nitrogen removals were less than
50 percent. At Midland, Michigan, influent organic nitrogen
concentrations were low, ranging from about 1 to 4 mg/1.
Removals were also low, generally 40 percent or less.
Effect .of Recirculation--An analysis of the Midland,
Michigan and Lima, Ohio data has led to the conclusion
that while recirculation improved nitrification efficiency
only marginally, the periods with recirculation demonstrated
greater consistency than those with
This conclusion, together with
no recirculation (24,25).
improvement seen with
filter combined carbon
recirculation in rock trickling
oxidation-nitrification (14), leads to a general recommendation
for provision of recirculation. A 1:1 recirculation ratio at
average dry weather flow is considered adequate for most
applications.
Effluent ClarificationBecause the organisms are attached
to the media and because the net organism growth is small,
effluent clarification steps are not required in all cases.
In the Midland, Michigan study, it was found that effluent
suspended solids levels were approximately equal to influent
concentrations (10-30 mg/1) (25) when influent 6005 levels were
in the 15-20 mg/1 range. When influent BOD5 concentrations
were increased, effluent solids rose to about 60 mg/1. The use
of a gravity clarifier reduced this to about 20 mg/1, and
subsequent multi-media filtration further reduced suspended
solids to about 5 mg/1. In some cases, filtration alone may be
substituted for gravity clarification.
113
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Combined Carbon Oxidation-Nitrification
Presentation of design concepts for combined carbon
oxidation-nitrification in plastic media biofilters suffers
from both a lack of operating data and from the absence of
any developed kinetic theory comparable to that which has been
developed for the activated sludge process. As previously
noted, the 1972 Stockton pilot study plus the sampling program
undertaken for the present investigation appear to be the only
studies conducted specifically on combined carbon oxidation-
nitrification plastic media trickling filters. The biofilter
theory of Williamson and McCarty may provide insight into design
concepts but is difficult to apply to design situations (10).
Performance-Loading RelationshipsMuch work, at least in
terms of data collection, has been done on nitrification
in rock media, dating back to the NRC studies during World
War II (4), which found that rock media trickling filters used
for secondary treatment were capable of producing nitrified
effluents when organic loadings were low. They stated that
nitrification occurred only when organic loadings were less
than 0.40 kg BOD5/m3/day (25 lb/1,000 ft3/day); the lowest
loadings produced the highest effluent nitrate nitrogen
concentrations. To obtain a highly nitrified effluent
with rock media filters, the loading should be kept below
0.2 kg/m3/day (12 lb/1,000 ft3/day).
If it is assumed that nitrification efficiency is a
function of media specific surface area, data from rock media
and plastic media plants can be compared on that basis. To that
end, Figure 45 was prepared which shows nitrification efficiency
(ammonia nitrogen removal) plotted against organic loading.
Data for rock media biofilters with recirculation were taken
from the U.S. Environmental Protection Agency Technology
Transfer publication, Process Design Manual for Nitrogen
Control (14). An assumed specific surface area
(15 ft2/ft3) was used for the rock media. Data
media are taken from two loading conditions of the 1972 Stockton
pilot study and from the latter portion of the 1976-77 sampling
program at Stockton, after the operational modifications to
improve performance were made.
Figure 45 has been developed for illustration purposes only
and should not be used for design. A serious drawback, for
example, is the exclusion of temperature effect from the plot.
Nevertheless, several conclusions can be drawn. First, although
the loading range for plastic media is limited, there is good
agreement between data for the two media types. Second, the
maximum allowable loading cited by the NRC appears to be
correct. The measured nitrification efficiencies at loadings
greater than 8.3 kg BOD5/1,000 m2/day (1.7 lb/ 1,000 ft2/day)
are probably due not to the conversion of ammonia nitrogen to
the nitrate from but to the assimilation of ammonia nitrogen
of 49 m2/m3
for plastic
114
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bacterial cells produced in the course of carbonaceous
removal. Nitrification efficiency is normally expressed as
percentage ammonia reduction, even though nitrification may not
be the sole mechanism responsible for the measured removal.
100
-------
than 90 percent. At loadings above 4.9 kg/1,000 m2/day
(1.0 lb/ 1,000 ft2/day), performance drops off rapidly as the
fraction of nitrifying organisms decreases.
Organic Nitrogen RemovalEven with high ammonia nitrogen
reductions, organic nitrogen removals will be low. The contact
time is apparently not sufficiently long to allow completion of
the reactions converting organic nitrogen to ammonia nitrogen.
Organic nitrogen removal during the 1972 Stockton pilot study
was about 25 percent; during the sampling program at the
full-scale plant, it was less than 50 percent.
Hydraulic Loading and RecirculationIn order to achieve
low organic loadings and maintain the minimum hydraulic loading
for "wetting" of the media surface, a high recirculation ratio
is required. Minimum hydraulic loadings recommended by
media manufacturers are generally in the range of 0.031 to
0.041 m3/min/m2 (0.75 to 1.0 gpm/ft2). To maintain a hydraulic
loading of 0.031 m3/min/m2 (0.75 gpm/ft2) with an organic
loading of 0.32 kg BOD5/m3/day (20 lb/1,000 ft3/day), an
influent BODs concentration of 150 mg/1, and a media depth of
6.1 m (20 ft), a recirculation ratio of 2.4:1 will be required.
Poor performance at Stockton during the period when hydraulic
loadings were below the recommended minimum wetting rate lends
strong support for providing adequate recirculation capacity in
the design of plastic media facilities.
Oxygen Transfer
Most substrate removal models for biofliters and other
attached-film reactors have assumed that the removal process
is limited by bacterial growth rate. Recent papers by Mehta,
Kingsbury and Davis (29). Schroeder and Tchobanoglous (30), and
Williamson and McCarty (10) have attempted to demonstrate,
however, that under certain conditions, oxygen transfer can
limit BODs removal and nitrification.
The Williamson and McCarty model predicts that, for
attached growth systems, substrate removal becomes limited by
dissolved oxygen (DO) concentrations when the soluble BODs
exposed to the film exceeds about 40 mg/1. This condition can
occur with strong municipal or industrial wastewaters. For
weak wastes, the untreated soluble 6005 may be lower than the
40 mg/1 limit or the soluble 6005 may be reduced to 40 mg/1
in the top few feet of the filter. In either case, oxygen
transfer would not then be limiting.
Williamson and McCarty also developed a theory concerning
nitrification and oxygen transfer. They predicted that the DO
concentration to avoid oxygen flux limitations would have to be
2.7 times the ammonia nitrogen concentration. They noted that
the two operational ways to overcome this limitation are to
116
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dilute the ammonia nitrogen by repirculation or to increase the
DO level. The latter can be done by increasing the forced
draft ventilation rate. It was noted in Section 7 that
increasing the forced draft ventilation rate (which increased
measured DO levels only marginally) and increased recirculatiori
at Stockton resulted in significant improvement in nitrifica-
tion performance.
Ventilation
Most media manufacturers indicate that as long as there
is sufficient freedom for air to flow through the biofilter,
forced draft ventilation is not normally required. Possible
exceptions are where strong industrial or combined wastes are
being treated, as at Stockton. Also, in very cold climates,
a means of restricting air flow may be desirable to prevent
excessive cooling of the wastewater.
TABLE 29. PARAMETERS AFFECTING
AIR FLOW THROUGH
BIOFILTERS
Number Driving fcorce
Resulting air
flow direction
conditions,
desirable to
Clarification
Natural forces cannot be
counted upon, however, to
provide air flow through
the filters under all circum-
stances. Shown in Table 29 are
five factors which can affect
air flow through a biofilter,
along with the direction of
flow which normally results.
Although unlikely, situations
can occur where the net force
directing air flow through the
tower is zero and no movement
occurs. In pilot biofilter
studies at Seattle, Washington
(22), both upward and downward
air flows were observed. The
Seattle climate exhibits
moderate temperatures and high
humidities, meaning that there
is little change in air
temperatures or humidity
__^^_______^_^__ through the tower (items 1 and
2 in Table 29). Under such
provision of forced draft ventilation might be
ensure adequate air flow.
Heat transfer:
water warms or
cools air
Increased relative
humidity of air
in tower
Wind blowing across
top of tower
(whistle effect)
O_ partial pressure
decrease; C02
partial pressure
increase
Downward movement
of water "pul-
ling" air
up or down
up
Up (usually)
down
down
down
A commonly voiced criticism of the trickling filtration
process is that it cannot be counted upon to produce effluents
with low suspended solids concentrations. A specific concern
is the 30-mg/l monthly average suspended solids concentration
as mandated by federal secondary treatment guidelines. In this
117
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subsection, four possible methods of improving clarification
are discussed: (1) reduced secondary clarifier loadings,
(2) tube settlers, (3) chemical addition, and (4) rapid sand
filtration. The first two methods can be expected to produce
effluent suspended solids concentrations in the 20- to 30-mg/l
range. The second two methods are required to reduce effluent
suspended solids concentrations below 15 mg/1.
Reduced Secondary Clarifier Loadings
Historically, trickling filter secondary clarifiers have
been designed with overflow rates of 33 to 49 m^/day/m2
(800 to 1,200 gpd/ft2) (similar to those for primary clari-
fiers), but performance objectives in the past have been much
different from those of today. Design effluent concentrations
were usually around 40 to 80 mg/1 BOD5 and suspended solids;
loadings to both the biofilters and secondary clarifiers were
set to meet these objectives. Recently, although much
effort has been directed to determining the loading-removal
relationships for plastic media biofilters (with the purpose of
providing improved performance), much less work has been done
on the contribution of secondary clarification to overall
performance.
Some evidence exists, however, to indicate that lower
hydraulic loadings can result in sufficiently improved perfor-
mance to meet the 30-30 mg/1 secondary treatment requirements
for BODs and suspended solids (31,32). Shown in Figure 46 is a
graph of secondary clarifier performance vs. overflow rate
for a trickling filter plant (31). This study, undertaken by
Brown et al. to determine methods of improving trickling filter
performance, showed that percentage suspended solids removal
increased from about 30 percent at 57 m^/day/m2 (1,400 gpd/ft2)
to over 60 percent at 16 m^/day/m2 (400 gpd/ft2). Figure 46
clearly illustrates the relationship between loading and
performance. As a result of the study, the authors recommended
that trickling filter secondary clarifiers be designed
with average dry weather overflow rates of around 20 m^/day/m2
(500 gpd/ft2) (32). The data developed in that study are strong
evidence that continued use of traditional design parameters
for biofilter secondary clarifiers may be improper when low
effluent BOD5 and suspended solids concentrations are sought.
Tube Settlers
Pilot studies on plastic media trickling filters at the
Municipality of Metropolitan Seattle have provided evidence
that tube settlers can greatly aid secondary clarifier
performance (22). Tube settlers are groups of 5 cm (2 in.)
square channels or tubes constructed in module form to promote
improved settling by creating laminar flow and reducing
particle settling distance. A schematic diagram of tube
settler operation is shown in Figure 47. The steep slope of
118
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the tube settlers (60 degrees) promotes gravity drainage of the
settled solids countercurrent to the flow. Normally, only a
portion of the clarifier surface is covered.
100
80
c
0>
O
s
LU
QC
vt
Q
0
Z
LLJ
O.
to
(A
60
40
20
T
SOURCE: REF. 33 -
NOTES:
(1) gpd/ft2 x 0.041= m3/day/m2
(2) BASED ON INFLUENT SUSPENDED SOLIDS CONCENTRATION = 110 mg/l
200
400
600
800
1000
1200
1400
OVERFLOW RATE, gpd/ft'
Figure 46.
Effect of overflow rate on trickling filter secondary clarification
performance.
The effect of tube settlers on performance in the Seattle
pilot studies is depicted in Figure 48, which compares the
improvement achieved by the use of tube settlers at increasing
amount of surface coverage. It was concluded that there was
almost no effect on performance at the two lowest coverages,
10 and 15 percent. At 40 percent coverage, effluent suspended
solids concentrations averaged less than 30 mg/l at all solids
loadings.
It was concluded that for the conditions encountered at
Seattle, the maximum removal limits for secondary clarifiers
equipped with tube settlers are 10-15 mg/l suspended solids and
that practical concentration limits will be somewhat higher
than this.
119
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lttjBS'1
.CLARIFIED
' EFFLUENT
ฉ J!!L
-------
addition will be a cost-effective method of reducing suspended
solids levels unless other objectives such as phosphorus
removal also exist.
Information on design considerations for chemical
addition is available in the U.S. Environmental Protection
Agency Technology Transfer publication, Process Design Manual
for Phosphorus Removal (33). :
Filtration-- , . '
Dual-media or rapid sand filtration can also be utilized
to reduce suspended solids levels from biofiltration secondary
clarifiers. Granular media filtration is particularly
applicable when discharge requirements specify very low
effluent suspended solids concentrations, 5 to 15 mg/1.
Dual-media filtration of secondary effluent will be used at
Stockton during the November -15-July 15 period (noncanaing
season) to meet 10 mg/1 BOD5 and suspended solids effluent
limitations.
Design information on wastewater filtration can be
obtained from two U.S. Environmental Protection Agency
Technology Transfer publications: the Process Design Manual
for Suspended Solids Removal (34) and the seminar publication,
"Wastewater Filtration; -----
Design Considerations" (35).
Solids Production
Information presented in Section 7 (Table 22) showed
a total secondary system solids production of 0.83 kg TSS
produced/kg BODs removed over the course of the sampling
program at Stockton. Production decreased during the last
portion of the sampling program, perhaps due to the increased
air supply. For the last 5 mo of the study, production
averaged 0.75 kg TSS produced/kg BOD5 removed. Benjes (9) cites
a typical total solids trickling filter system production as
0.67 kg TSS/kg BODs removed.
Waste solids production, which excludes suspended solids
lost in the effluent, averaged 0.65 kg TSS/kg BODs removed
for the entire Stockton sampling program. For the last 5 mo,
the average was 0.61 kg TSS/kg BOD5 removed. A value cited
by Benjes as typical is 0.45 kg TSS/kg BOD5 removed.
PHYSICAL DESIGN
Physical design considerations include both general design
principles for any filter design and specific problems which
must be resolved in converting an existing filter. A careful
analysis of the existing secondary treatment facilities for
capacity, efficiency, and structural integrity will help the
designer to select appropriate materials, to determine which
121
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structures can be reused, and to determine what additional
facilities are needed. In most situations, the designer must
ensure that the modifications can be constructed with a minimal
interruption of the treatment processes. The modified system
should have operational reliability and flexibility for future
expansions or process additions. Operational ease and
efficiency should be considered, particularly in the location
of controls and parts which require periodic maintenance
and repair.
In most upgrading situations, physical constraints will
exist which limit the options available to the designer and
which will result in a less optimal design than would result
if an entirely new plant were being built. In many cases,
overcoming these constraints will require considerable
ingenuity on the part of the engineer. In extreme cases, the
constraints may be so severe as to make filter conversion
unwarranted; it may be more cost-effective to construct
completely new biofilters.
Biofilters can be either circular or rectangular in shape.
Since the rock media filters which would be considered for
conversion to plastic media are normally circular, those design
aspects peculiar to rectangular filters will not be discussed
here. Further, most of the information presented will concern
module-type media rather than the dumped type.
Conversion of a rock media filter to plastic media should
be viewed in its relation to the rest of the secondary
treatment facilities and to the other unit processes at the
treatment plant. For example, modifications to the electrical
system will probably be required for ventilation fans and
additional pumps, the ventilation system may need to be modi-
fied substantially, and additional secondary clarification may
be necessary. Additional solids handling facilities may be
required by an increase in flow and the increase in solids
production associated with greater BODs removal.
Physical design considerations are discussed below for
the major components of a trickling filter media conversion,
including walls, influent piping and pumping, center column
and distributor support, effluent collection and return,
recirculation structure and pumping, media support system,
ventilation, and overall plant configuration.
Walls
The primary functions of the walls in all biofilters are
to contain the media, biomass, wastewater, and air; to protect
the media from the wind; to insulate the wastewater and biomass
from cold temperatures; and to provide an aesthetic covering.
122
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In rectangular biofilters, the walls must support the wastewater
distribution system. In some designs, the walls must also
support a cover which functions as an air collection system.
"Most biofilter designs provide wind protection for the top of
the media by allowing some freeboard between the top of the
media and the top of the walls.
In converting an existing rock media filter to plastic
media, maximizing use of the existing structure will influence
wall design. The wall addition must blend architecturally with
the existing wall, or it may be desirable to demolish the old
wall and construct an entirely new wall. The foundation will
have to support a much greater load; therefore, the adequacy of
the existing foundation should be carefully checked. The
designer should examine the soils report for the original
structure if possible. The nature of the underlying soils and
the condition and thickness of the existing foundation will
determine what additional weight can be supported. The
foundation will have to support the walls, the media,
the biomass, the media support system, and the wastewater
being treated. A design loading of approximately 400 kg/m-*
(25 lb/ft3) plastic media can be used; this figure includes
additional weight for a clogged filter.
A waterproof seal is necessary to prevent the wastewater
from leaking through the walls. The concrete block walls of
the Stockton filters are both lightweight and strong; the
concrete blocks create a sealing problem, however. The porous
blocks absorb the wastewater and transmit it through the
wall. Expansion and contraction of the blocks may crack a
sealer which is painted on the walls. The polyurethane sealer
ultimately used at Stockton has proved sufficiently elastic to
withstand the expansions and contractions. In a new plastic
media filter for separate stage nitrification at Sunnyvale,
California, a sheet liner of Hypalon (chlorosulfonated
polyethylene) was placed inside the walls, held in place with a
redwood framework. This was done to provide further assurances
that leakage would not occur. The redwood frame also acted to
prevent the liner from being cut by the sharp edges of the
plastic media.
Other lightweight wall materials which have been used
successfully in biofilters include corrugated PVC and polyester
fiberglas, held in place with metal supports and wood. The
wood, such as redwood, must be resistant to biological attack.
The fiberglass should be opaque with a resin-rich surface.
Corrugated panels must be overlapped, fitted with a gasket, and
caulked at the seams. The fiberglas panels are probably more
expensive than concrete block; however, they are waterproof and
are easily installed and repaired. A filter with a corrugated
PVC wall is shown in Figure 49.
123
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,11
Figure 49. Corrugated PVC used
for trickling filter walls.
Shown here is a rectan-
gular filter with media
being installed (photograph
courtesy B. F. Goodrich).
between the original piping and
column foundation in the Stockton
tial settling between old and new
A heavier, but very
inexpensive, wall can be made
of precast concrete tip-up
panels. The precast panel
design could be used with walls
which are either polygonal or
circular; a polygonal design
would require removing the
original low wall.
Influent Piping and Pumping
The influent piping
system must be converted to
accommodate the greater flow
associated with plastic media
filters. Many rock media
systems are gravity fed;
influent to the taller plastic
media filters must be pumped.
The original influent lines may
be reusable; they should be
carefully inspected, however,
as the increased pressures of
the pumping system may create
leaks. Although the Stockton
plans called for reusing the
existing influent lines,
much of the piping had to be
repaired; inspection of the
lines during construction
revealed substantial hydrogen
sulfide corrosion. Flexible
connections were installed
the piping in the new center
filters to allow for differen-
structures.
The influent piping system should be designed or modified
to give the system operational flexibility. Sufficient
duplicate equipment should be supplied to continue treatment
during maintenance or repair operations. Sluice gates or valves
should be incorporated in the piping system to isolate parts
which may require repairs. At the Lompoc, California, Regional
Wastewater Reclamation Plant, supply pumps were sized to pump
the peak wet weather flow to the filters with one pump out of
service so that a nonfunctioning pump will shut down the filter.
At the Stockton plant, where the downstream oxidation ponds
provide a treatment buffer, each filter is served by a single
influent line and supply pump. Regular maintenance work on the
pump puts the corresponding filter out of operation. Also, each
pump must be operated continuously, resulting in a shorter
service life.
124
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Piping should be designed to facilitate future expansions.
If, for example, more biofilters will be added in the future,
the piping system can be designed for the ultimate treatment
configuration. That portion of the future piping system which
connects to the present system can be constructed; the end of
the pipe can be capped and a valve installed to prevent future
treatment interruption while the pipe is connected to the future
filter. Similarly, if new pumps are to be added, space for them
should be provided and portions of the connecting pipes should
be constructed.
The necessity for minimizing treatment interruptions during
conversion must also be considered. Unless the entire secondary
treatment facilities can be bypassed, as at Stockton, a portion
of the original system will have to be functional during
construction of the new facilities. This constraint may limit
the amount of the existing facilities which can be reused.
Center Column and Distributor Support
A taller, heavier distributor is required to accommodate
the greater height and heavier hydraulic loadings of the
plastic media filters. A new center column is required to
support the distributor, and a new foundation may be required
to support the heavier structures. At Stockton, the original
center column foundation was demolished and a larger foundation
constructed.
The soil conditions beneath the filter floor should be
investigated before excavation to determine what precautions
will be needed to protect against a cave-in. Normally, sheet
pilings will be needed. At Stockton, the soil was unusually
stable, although shoring was used to comply with OSHA regula-
tions.
A foul-air distribution chamber was incorporated in the
foundation design at Stockton (Figure 11, Section 5) and at the
Goleta, California, plant. Foul air from the headworks enters
the chamber through a duct below the filter floor. Odorous
gases are oxidized in passing through the filter.
Effluent Collection and Return
The effluent collection and return system collects the
wastewater and sloughed biomass from the bottom of the filter.
An efficient collection system performs its functions without
allowing the solids to settle out or the wastewater to become
septic and without providing a breeding place for the psycoda
fly. Circular rock media filters have a sloping floor to direct
effluent either to the center of the filter or to the outside
edge of the filter. Generally, steeper slopes are provided for
wastes with heavier suspended solids loadings. In converting a
rock media filter, the existing filter floor would probably be
reused so that a change in floor slope would be impractical.
125
-------
In order to accommodate the increased loadings of the
plastic media filters, the collection system may need to be
enlarged. An external pipe collection system was added to the
Stockton filters to supplement the existing collection channel.
The additions were illustrated previously in Figure 16,
Section 5. Effluent from the side of the filter opposite the
return line flows in the original channel until it reaches the
effluent collection boxes. The wastewater drops down into
the boxes and flows through the new pipes into the return box.
Effluent from the side of the filter near the return line flows
entirely in the original channel. The collection channel in
the Stockton filters was covered in the conversion in order to
prevent the escape of air from the forced-air ventilation
system.
A section view of a biofilter at the Simi Valley,
California, Water Quality Control Plant is shown in Figure 50.
The effluent collection channel in this design is within the
filter walls; the media support system and the plastic media
extend out over the channel. Although the Simi Valley design
was for a new filter, it might be applicable in a filter
conversion where a larger diameter filter is needed. If the
existing rock media filter has an external collection channel,
as at Stockton, the original wall could be demolished and a new
wall constructed outside of the channel. The converted filter
would then contain additional media volume over the collection
channel.
FILTER
WALL
MEDIA-
SUPPORT
SYSTEM
CENTER
COLUMN
SUPPORT
KN"
EFFLUENT
COLLECTION
CHANNEL
/////
Figure 50. Biofilter cross section for Simi Valley, California, plant.
126
-------
The effluent return lines to the distribution structure
may also need to be enlarged since it is not desirable for them
to operate under pressure. The pressure required to increase
their capacity would have to come from wastewater backing up
inside the filter collection channels.
Recirculation Structure and Pumping
The recirculation structure distributes the flow to the
filters, controls the amount of filter effluent recirculation,
and routes effluent to the secondary sedimentation tanks.
Recycling of. secondary effluent and sludge improves treatment
efficiency. The amount of flow recycled increases with
decreasing flows from the primary treatment processes to
maintain a relatively high and uniform hydraulic application
rate to the plastic media filters. The recycled secondary
effluent-and the primary effluent are mixed in the recircula-
tion structure before being pumped to the filters.
The Stockton recirculation structure (Figure 19,
Section 5) has a center chamber which receives primary effluent;
an outer chamber receives filter effluent and supplies the
secondary sedimentation tanks. Separate chambers are provided
to prevent short-circuiting of primary effluent to the secondary
sedimentation tanks. Secondary effluent is pumped into the
center chamber to maintain a constant liquid level. Each
filter is supplied by a variable-speed pump with manual
controls.
The Lompoc, California recirculation structure uses a
single chamber with weirs to direct the flows. A section view
is shown in Figure 51. Primary effluent enters the .chamber
near the bottom where it mixes with the biofilter effluent in
the main part of the structure. The biofilter supply pump
intake is located on the opposite side of the structure
separated from the inlets by baffles for mixing. Biofilter
effluent enters a small compartment in the structure and
overflows into the main chamber and into the chamber which
supplies the secondary sedimentation tanks. Flow to the
sedimentation tanks is by gravity. The magnitude of the
biofilter effluent flow (approximately three times the average
dry weather flow) assures that the flows will be in the
directions shown and that short-circuiting of primary effluent
to the secondary sedimentation tanks will not occur unless the
biofilter supply pumps have shut down. The biofilter supply
pumps are constant-speed types. A second pump is provided in
case the first fails. Constant-speed pumps are used to ensure
a constant feed rate to the filter. The recirculation ratio
decreases with increasing plant flows.
Because the distribution structure is central to the
secondary treatment process, upgrading an existing plant may
require constructing an entirely new recirculation structure.
127
-------
The capability of bypassing wastewater to the oxidation ponds
at the Stockton plant made possible the modification of the
existing recirculation structure. The original Lompoc biofilter
and recirculation structure were not in service when plant
modifications were begun. Thus, the existing recirculation
structure could have been reused. Necessary modifications were
so extensive, however, that it was easier to build an entirely
new structure.
BIOFILTER
SUPPLY PUMP
BIOFILTER
EFFLUENT
SECONDARY
CLARIFIER
SUPPLY
PRIMARY
EFFLUENT
Figure 51. Recirculation structure for Lompoc, California, plant.
The recirculation structure should be designed to
accommodate future expansions with a minimum of treatment
interruption. The recirculation structure at Goleta was sized
for peak wet weather flow (with no recycle) for an anticipated
doubling of plant capacity.
Media Support System
The media support system physically supports the media and
biomass, allowing solids a.nd liquids to pass down and air to
circulate freely through the filter. Early plastic media
filters required intermediate support systems at several
elevations in the tower. Plastic media is currently designed
to be self-supporting to depths of 7.3 to 9.1 m (24 to 30 ft),
with variations in wall thickness to accommodate varying
weights to be supported. The wall thickness of the media
blocks decreases from the bottom layer to the top layer of the
filter.
128
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The media support system should be designed for the
particular type of media to be used. Media manufacturers
usually recommend a support system which provides the best
support for the media and which can be easily constructed. In
preparing plans and specifications, the designer may want to
provide alternative support system designs for each possible
choice of media.
The media blocks are weakest near the edges; therefore,
the support system should be designed to contact the media
blocks at least 2.5 cm (1 in.) from the edge. The spacing
of the support beams will be determined by the size of the
media blocks. The media support system for the Stockton
plant represented a compromise design to accommodate several
different media types with different block sizes. This
compromise resulted in a system which contacted the selected
media at the edges. In order to maximize the contact area
between the media and the support system, pier elevations were
kept within close tolerances and support channels which were
chipped or improperly formed were rejected.
The support system should be inexpensive to buy,
inexpensive to construct, and corrosion resistant. Hydrogen
sulfide may be present in the wastewater or may arise from
improper operation of the filter. Concrete beams and piers are
particularly suited for the support system. Concrete blocks
are less satisfactory than solid concrete because they are
porous and may support anaerobic growths. Redwood beams have
been used in several filter designs. Redwood is satisfactory
as long as it is wet; however, if the filter must be out of
service for any length of time, the drying redwood may check.
Aluminum gratings have also been used to support the media;
these gratings tend to clog and may be quite expensive.
Plastic media filters require increased air circulation
due to the larger media and biomass volumes and the increased
loading rates. The old drain blocks should be discarded in
favor of a taller support system. A minimum distance of 0.76 m
(2.5 ft) between the floor and the support channels - will
provide room for maintenance. A commonly used system consists
of solid walls running the length of the filter topped by beams
at right angles to the walls as shown in Figure 52 (36). Solid
walls will, however, decrease air circulation. Individual
piers at spacings of several feet will provide a larger space
for ventilation air (Figure 53) (36). The support system must
also be designed to minimize the accumulation of biomass which
hinders air and liquid flow and to prevent wastewater from
collecting and causing corrosion.
The Stockton filter design contained isolated piers of
concrete blocks supporting a precast concrete channel with
large holes for increased air and liquid flow. Construction
129
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REINFORCED
CONCRETE
BEAM
2'-4"
MASONRY
OR CONCRETE
BEAM
Figure 52. Media support system, with solid walls.
(source: reference 36)
"- FILL VOIDS IN CONCRETE BLOCKS
WITH GROUT OR MORTAR
Figure 53. Media support systems using piers.
(source: reference 36)
130
-------
difficulties with the Stockton pier design resulted in an
improved design for the Sunnyvale biofilters. The Stockton
piers were constructed of concrete blocks; height adjustments
had to be made by cutting blocks and varying the amount of
mortar between the piers and the channels. To assure the
proper elevations for the tops of the piers at Sunnyvale,
despite variations in the filter floor elevations, the piers
were poured in place to the desired elevation.
Ventilation System
Constant, even air flow is essential to maintain aerobic
conditions; otherwise, the filters may produce objectionable
odors. A tortuous path for air flow from the inlet to a
portion of the media will cause that portion to be starved for
air. The bottom or plenum chamber of the tower should be
designed so that the pressure drop from the air inlet to any
part of the bottom layer of media is very small compared to the
pressure drop through the media. A relatively small pressure
drop through the plenum chamber will insure an even air flow
through the filter.
For colder climates, a method of restricting air flow may
be desirable. Air flow is most easily restricted by doors or
louvers at the entrance to the plenum chamber. Covering the
filter will allow restriction of the flow at the air outlet.
/
In warmer, humid climates particularly, a forced-draft
ventilation system may be necessary to insure continuous and
adequate air flow, especially when organic loadings are high.
The Stockton filter design included four large air ducts, each
supplied by two rotary fans. The Lompoc design included a
forced-draft ventilation system with round fiberglas air ducts
rather than concrete ducts as in the Stockton design. Both of
these systems use an upward air flow. A downdraft system could
also be used with possibly better control of aerosols. Air
containing odorous and corrosive substances would be exiting
through the fans, however, producing a greater odor impact
(because the fans are closer to the ground) and decreasing the
operating life of the fans.
Overall Plant Configuration
The layout of the existing plant may greatly affect the
feasibility of converting existing rock trickling filters to
plastic media. Cost, flexibility and reliability in operation,
and flexibility for future expansion and upgrading all need to
be considered when evaluating conversion. For example, the
cost of a long pipeline to connect the biofilters with another
unit process may be greater than the cost savings resulting
from use of the existing biofilter structure. As another
example, it was pointed out previously that a new recirculation
131
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structure may need to be built if the old structure must be
kept operating during construction. It may be difficult to
construct a new one in a desirable location.
These are only two of the many problems which may result
when attempts are made to utilize existing structures in such a
conversion. They point out that early in the design phase, and
even in the planning phase if possible, overall plant layout
should be carefully inspected to determine whether conversion
of existing rock media filters to plastic media is feasible and
desirable.
132
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REFERENCES
8
10,
11
Brown and Caldwell, Stockton Sewerage Survey, Prepared for
the City of Stockton, February 1965.
Brown and Caldwell, Cost-Effectiveness Analysis of Tertiary
Alternatives at the Main Water Quality Control Plant,
Prepared for the City of Stockton, January 1975.
Brown and Caldwell, Main Water Quality Control Plant 1969
Enlargement and Modification Study, Prepared for the
City of Stockton, May 1969.
National Research Council, Subcommittee on Sewage Treat-
ment, Sewage Treatment at Military Installations, Sewage
Works Journal, Vol. 18, p. 794, 1946.
Brown and Caldwell, Report on Pilot Trickling Filter
Studies at the Main Water Quality Control Plant, Prepared
for the City of Stockton, March 1973.
Stenquist, R.J. et al., Carbon Oxidation-Nitrification in
Synthetic Media Trickling Filters, JWPCF, Vol. 46, p. 2327,
October 1974.
Siddiqi, R.H. et al., Elimination of Nitrification in the
BOD Determination with 0.10 M Ammonia Nitrogen, JWPCF,
Vol. 39, p. 579, April 1967.
B.F. Goodrich, Vinyl Core Biological Oxidation Media,
Project Catalog, 1975.
Benjes, H.H., Jr., Attached Growth Biological Treatment:
Estimating Performance and Construction Costs and Operating
and Maintenance Requirements, Preliminary draft report
prepared for U.S. Environmental Protection Agency.
Cincinnati, Ohio, January 1977.
Williamson, K., and P.L. McCarty, A Model of Substrate
Utilization by Bacterial Films, JWPCF, Vol. 48, p. 9,
January 1976.
Vesilind, P.A. , Treatment and Disposal of Wastewater
Sludges, Ann Arbor Science, 1974.
133
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12. Sacramento Area Consultants, Study of Wastewater Solids
Processing and Disposal, Prepared for the Sacramento
Regional County Sanitation District, June 1975.
13. Eckenfelder, W.W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York City, 1966.
14. U.S. Environmental Protection Agency, Office of Technology
Transfer, Process Design Manual for Nitrogen Control,
Cincinnati, Ohio, October 1975.
15. Caller, W.S. and Gotaas, H.B., Analysis of Biological
Filter Variables, ASCE, Journal Sanitary Engineering
Division, Vol. 90, p. 59, December 1964.
16. Fairall, J.M., Correlation of Trickling Filter Data, Sewage
and Industral Wastes, Vol. 28, p. 1069, 1956.
17. Rankin, R.S., Evaluation of the Performance of Biofiltra-
tion Plants, Transactions: ASCE, Vol. 120, p. 823, 1955.
18. Velz, C.J., A Basic Law for the Performance of Biological
Filters, Sewage Works Journal, Vol. 20, p. 607, 1948.
19. Bruce, A.M. and J.C. Merkens, Recent Studies of High-Rate
Biological Filtration, Water Pollution Control, Vol. 69,
p. 113, 1970.
20. Bruce, A.M. and J.C. Merkens, Further Studies -.of Partial
Treatment of Sewage by High-Rate Biological Filtration,
Water Pollution Control, Vol. 72, p. 499, 1973.
21. Hutchison, E.G., A Comparative Study of Biological Filter
Media, Presented at Biotechnology Conference, Massey
Unive'rsity, Palmerston North, May 1975.
22. Brown and Caldwell, Unpublished data from pilot studies
carried out for the Municipality of Metropolitan Seattle,
1976-1977.
23. Chipperfield, P.N.J., The Development, Use, and Future
of Plastics in Biological Treatment, Effluent and Water
Treatment Manual, Vinall, H.E. (Ed.), Thunderbird
Enterprises, Ltd., 1978.
24. Duddles, 'G.A. and S.E. Richardson, Application of Plastic
Media Trickling Filters for Biological Nitrification,
U.S. Environmental Protection Agency, Report No. EPA-R2-
73-199, Cincinnati, Ohio, June 1973.
25. Duddles, G.A., Richardson, S.E., and E.F. Earth, Plastic
Medium Trickling Filters for Biological Nitrogen Control,
JWPCF, Vol. 46, p. 937, May 1974.
134
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26
21,
29
30
of Nitrification Towers at Lima,
Second Annual Conference, Water
of Ohio, Columbus, Ohio, October
Sampayo, F.F., The Use of Nitrification Towers .
Ohio, Presented at the Second Annual Conference
Management Association of Ohio, Columbus, Ohio,
1973.
Brown and Caldwell, Report on Tertiary Treatment Pilot
Plant Studies, Prepared for the City of Sunnyvale,
California, February 1975.
28. Huang
W 1. JL1 X Cl f J.'^kJ.I_U.ClJ.^ J. -/ / -*
, C.A., Kinetics and Process Factors of Nitrification
Biological Film Reactor, Ph.D. Thesis, University of
ork at Buffalo, 1973.
11V-J , V_ . i"i . , I\ J.H
-------
APPENDIX A
1969 DISCHARGE REQUIREMENTS
CENTRAL VALLEY REGIONAL WATER QUALITY CONTROL BOARD
WASTE DISCHARGE REQUIREMENTS
FOR THE
CITY OF STOCKTON
MAIN WATER QUALITY CONTROL PLANT
SAN JOAQUIN COUNTY
Resolution No. 69-200
Adopted: 2/14/69
WHEREAS, the City of Stockton
industrial wastes in a treatment
San Joaquin River; and
treats municipal and
works located on the
WHEREAS, the nature of discharges
has been governed by Resolution No. ".
the Central Valley Regional Water Quality
7 November 1951; and
from these facilities
106 (51-85) adopted by
Control Board on
WHEREAS, treated wastes from the Stockton Main Plant are
discharged to the San Joaquin River, or to Burns Cut-Off which
is tributary to the San Joaquin River on either end; and
WHEREAS, the San Joaquin River and tributary channels in
this area are a part of the Delta waters as defined in the
"Water Quality Control Policy for the Sacramento-San Joaquin
Delta" (Delta Water Quality Control Policy) as adopted by the
State Water Quality Control Board (now State Water Resources
Control Board); and
WHEREAS, beneficial uses of these waters, as identified in
the aforesaid Policy are: domestic and municipal supply;
agricultural and industrial supply; propagation, migration,
sustenance, and harvest of fish, aquatic life and wildlife;
recreation, esthetic enjoyment; navigation; and waste disposal,
assimilation, and transport. ' In the Stockton area, recreation
uses include boating, yachting, skiing, and swimming; and
WHEREAS, the aforementioned Policy prescribes a set of
water quality objectives for these waters; arid
WHEREAS, it is the intent of the Central Valley Regional
Water Quality Control Board to preserve the quality of the
136
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San Joaquin River and other Delta waters within the limits
prescribed by the Delta Water Quality Control Policy; and
WHEREAS, it is further the intent of the Central Valley
Regional Water Quality Control Board to so regulate waste
discharges into these waters including the discharge from the
City of Stockton Main Water Quality Control Plant so as to
conform to the Delta Water Quality Control Policy; therefore
be it
RESOLVED, that the following requirements shall govern the
nature of any waste discharge from the Stockton Main Water
Quality Control Plant:
1. Any of the plant effluent, reaching surface waters of
the area, by any means whatsoever, shall:
A. Be adequately disinfected and in no case shall
cause the receiving waters to exceed a median
fecal coliform level of 200/100 ml.
B. Not cause the dissolved oxygen content of the
receiving waters to fall below 5.0 mg/1 at any
time.
C. Not cause the total nitrogen content of receiving
waters to exceed 3.0 mg/1.
D. Not cause concentrations of materials in the
receiving waters which are deleterious to human,
plant, or aquatic life.
E. Not contain recognizable solids of sewage or
waste origin.
F. Not cause fungus growths in the receiving waters
or on stream banks.
G. Not cause objectionable concentrations of
floating or emulsified grease or oil in Delta
waters.
H. Not cause detectable taste or odor in any public
water supply.
I. Not cause sludge deposits in the receiving
waters.
J. Not cause objectionable color in the receiving
waters.
K. Not cause the mean monthly Total Dissolved
Solids (TDS) of receiving waters to increase
137
-------
L.
above 500 mg/1, as measured on the basis of the
average mean daily values for any calendar
month.
Not cause the biocide content, as determined by
the summation of individual concentrations, to
increase above 0.6 ug/1; nor shall the concen-
trations of individual or combinations of
pesticides in the Delta waters, as a result of
this discharge, reach those levels found to be
detrimental to fish or wildlife.
M.
Not cause
below 6.5,
the pH of receiving
nor to exceed 8.5.
waters to fall
2. Neither the waste discharge nor the method of
disposal shall cause a public nuisance by reason of
odors or unsightliness.
3. Waste discharge shall not cause a pollution of usable
ground or surface waters.
RESOLVED, further, that because of the time-lag inherent
in public works construction, the City of Stockton is hereby
to ฃ
ittach
directed
facilities on or before the dates shown
on the
Control
to provide
a"tt ached"""City of"Stockton - Main Water
Quality
Schedule of
23 November
Plant - Modification and Expansion
T970"* to bring its waste dischage into full
compliance with the requirements specified herein, except
that the City of Stockton will be held fully accountable for
complying with the requirements of Resolution No. 51-85 which
shall also remain in effect to govern the waste discharges from
the City of Stockton; and be it
RESOLVED, further, that the City of Stockton shall submit
quarterly progress reports demonstrating that activities and
construction for achieving compliance with these requirements
is under way and on schedule; and be it
RESOLVED, further,
promptly to the Central
Board any future changes
conditions associated with
that the discharger shall report
Valley Regional Water Quality Control
in the discharge or changes in the
its disposal; and be it
RESOLVED, further, that the discharger may be required to
submit technical reports relative to the waste discharge as
provided under Section 13055 of Division 7, California Water
Code.
*Amended by the California
Board, Central Valley Region,
Regional Water Quality Control
on 23 November 1970.
138
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If, in the future, there is a change in the conditions of
the discharge, or use of the disposal area, it may be necessary
for the Central Valley Regional Water Quality Control Board to
revise these requirements.
These requirements do not constitute a license or permit;
neither do they authorize the commission of any act resulting
in injury to the property of another, nor do they protect the
discharger from his liabilities under federal, state, or local
laws.
/s/ John Van Assen
Chairman
ATTEST:
/s/ Charles T. Carnahan
Executive Officer
139
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APPENDIX B
1974 DISCHARGE REQUIREMENTS
CENTRAL REGIONAL WATER QUALITY CONTROL BOARD
CENTRAL VALLEY REGION
ORDER NO. 74-453
NPDES NO. CA0079138
WASTE DISCHARGE REQUIREMENTS
FOR
CITY OF STOCKTON MAIN WATER QUALITY CONTROL PLANT
SAN JOAQUIN COUNTY
The California Regional Water Quality Control
Central Valley Region, (hereinafter Board), finds that:
Board
1.
The City of
s ubmi 11ed
No. CA0079138
Stockton Main Water Quality Control Plant
a report of waste discharge NPDES
dated 9 November 1973
4.
The City of Stockton Main Water Quality Control Plant
discharges an average of 0.84 m3/sec (19.2 mgd) and
a maximum of 2.23 m3/sec (51 mgd) of treated
domestic and industrial waste from secondary
treatment facilities into the San Joaquin River, a
water of the United States, at a point 1.61 km(l mi)
downstream from the Highway 4 bridge, in the NW-1/4 of
Section 17, TIN, R6E, MDB&M.
The report of waste discharge describes the existing
discharge as follows:
Average flow: 72,672 cubic meters per operating
day (19.2 million gallons per operating
day)
Average temperature: 80F Summer; 54F Winter
Average 6005: 14 mg/1
Average total suspended solids: 35 mg/1
Average settleable matter: 0.1 ml/1
pH: 7.2 lowest monthly average; 8.8 highest
monthly average
Maximum flows occur during the summer and fall
months, with the major volume contributed by the
140
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canneries connected to the city sewerage system.
Liquid cannery wastes also provide the major organic
loading to the plant during this period.
5. The City of Stockton proposes to consolidate waste-
water treatment in the Stockton area by accepting all
wastes presently going to the Stockton Northwest and
Lincoln Village treatment plants. This consolidation
will most likely occur within the next 5 yr.
6. The City of Stockton Main Water Quality Control Plant
is presently in the middle of an expansion program
which will result in continuing upgrading of plant
effluent to meet more stringent requirements effective
1 July 1977. The plant capacity will be expanded to a
maximum daily flow of 2.96 m3/sec (67 mgd), a 7-day
average maximum flow of 2.67M3/sec (61 mgd), and a
30-day average maximum flow of 2.54 m3/sec(58 mgd).
7. The Board on 15 June 1971 adopted an Interim Water
Quality Control Plan for the Sacramento-San Joaquin
Delta. The Interim Basin Plan contains water quality
objectives for the San Joaquin River.
8. The beneficial uses of the San Joaquin River and Delta
waters are: municipal, agricultural, and industrial
supply; recreation; esthetic enjoyment; navigation;
and preservation and enhancement of fish, wildlife,
and other aquatic resources.
9. Effluent limitation and toxic and pretreatment
effluent standards established pursuant to
Sections 208b, 301, 302, 303(d), 304, and 307 of the
Federal Water Pollution Control Act and amendments
thereto are applicable to the discharge.
10. The discharge from the City of Stockton Main Water
Quality Control Plant is presently governed by waste
discharge requirements adopted by the Board on
7 November 1951 and 14 February 1969 in Resolution
No. 51-85 and Resolution No. 69-200, respectively.
11. The Board has notified the discharger and interested
agencies and persons of its intent to prescribe waste
discharge requirements for this discharge and has
provided them with an opportunity for a public hearing
and an opportunity to submit their written views and
recommendations.
12. The Board in a public meeting heard and considered
all comments pertaining to the discharge.
141
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13. This Order shall serve as a National Pollutant
Discharge Elimination System permit pursuant to
Section 402 of the Federal Water Pollution Control
Act, or amendments thereto, and shall take effect
10 days from the date of hearing provided the Regional
Administrator has no objections.
IT IS HEREBY ORDERED, the City of Stockton Main Water
Quality Control Plant, in order to meet the provisions contained
in Division 7 of the California Water Code and regulations
adopted thereunder and the provisions of the Federal Water
Pollution Control Act and regulations and guidelines adopted
thereunder, shall comply with the following:
A. Effluent Limitations:
1. Prior to 1 July 1977, the discharge of an
effluent in excess of the following limits is
prohibited:
30-day 7-day 30-day Daily
Units Average Average Median Maximum
Constituent
(1)
BOD
Settleable
Matter
Chlorine
Residual
Total Coliform
Organisms
Grease and
Oil
mg/1
Ib/day
kg/day
ml/1
30
12,750
5,783
45
19,100
8,644
mg/1
(2)
MPN/100
ml
mg/1
Ib/day
kg/day
23
10
4,255
1,930
50
21,250
9,639
0.1
0.1
500
15
6,380
2,894
5-day, 20C Biochemical Oxygen Demand.
can be met at any point in the treatment system.
2.
The arithmetic mean biochemical oxygen demand
(5-day) and suspended solids in effluent samples
collected in a period of 30 consecutive days
shall not exceed 15 percent of the arithmetic
mean of the values for influent samples
collected at approximately the same times during
the same period (85 percent removal).
142
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3. The discharge shall not have a pH less than 6.5
nor greater than 8.5, nor shall it cause a change
greater than 0.5 in the pH of the receiving
waters.
4. Prior to 1 July 1977, the average daily dry
weather discharge shall not exceed 193,035 cubic
meters (51 million gallons).
5. Bypass or overflow of untreated or partially
treated waste is prohibited.
6. The discharger shall use the best practicable
cost effective control technique currently
available to limit mineralization to no more than
a reasonable increment.
7. Survival of test fishes in 96-hr bioassays of
undiluted waste shall be no less than:
Minimum, any one bioassay ...70 percent
Median, any three or more
consecutive bioassays. 90 percent
8. The maximum temperature of the discharge shall
not exceed the natural receiving water tempera-
ture by more than 20 Fahrenheit degrees.
9. The discharge shall not cause degradation of any
water supply.
10. Effective 1 July 1977, the discharge of an
effluent in excess of the following limits is
prohibited:
Constituent
(1)
BOD
Total Suspended
Solids
Settleable
Matter
30-day
Units Average
rag/1
Ib/day
kg/day
mg/1
Ib/day
kg/day
10
4,835
2,193
10
4,835
2,193
7-day 30-day Daily
Average Median Maximum
20
10,175
4,615
20
10,175
4,615
30
16,765
7,605
30
16,765
7,605
ml/1
0.1
(1)
5-day, 20C Biochemical Oxygen Demand,
143
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Constituent
Chlorine
Residual
Total Coliform
Organisms
Grease and
Oil
Total ,? v
Nitrogen^ '
Flow
30-day 7-day 30-day Daily
Units Average Average Median Maximum
mg/1
MEN/100
ml
23
mg/1
Ib/day
kg/day
rag/1
Ib/day
10
4,835
2,193
3.0
1,450
5.0
2,545
mgd m^/sec 58
61
0.1
500
15
8,380
3,801
15.0
8,380
67
^'Compliance with these limitations shall apply fron
15 July to 15 November.
B. Receiving Water Limitations:
1.
2.
Prior to 1 July 1977, the discharge shall not
cause the dissolved oxygen concentration in the
San Joaquin River to fall below 3.0 mg/1.
Effective 1 July 1977, the discharge shall not
cause the dissolved oxygen concentration in the
San Joaquin River to fall below the following
levels:
Units
Minimum Median
5.0
Percent of Saturation
85
95th
Percentile
75
3.
When circumstances cause lesser levels upstream
of the discharge, then the discharge shall cause
no reduction. This requirement is subject to any
modifications to the dissolved oxygen objectives
as stated in the fully-developed Water Quality
Control Plan for the Sacramento- San Joaquin
Delta Basin, when the Plan becomes effective.
The discharge shall not cause visible oil,
grease, scum, or foam in the receiving waters or
watercourses.
144
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4. The discharge shall not cause concentrations of
any materials in the receiving waters which are
deleterious to human, animal, aquatic, or plant
life.
5. The discharge shall not cause esthetically
undesirable discoloration of the receiving
waters.
6. The .discharge shall not cause fungus, slimes, or
other objectionable growths in the receiving
waters.
7. The discharge shall not cause bottom deposits in
the receiving waters.
8. The discharge shall not cause floating or
suspended materials of recognizable sewage origin
in the receiving waters.
9. The discharge shall not increase the turbidity
of the receiving waters by more than 10 percent
over background levels.
10. The discharge either individually or in
combination with other discharges shall not
create a zone, defined by water temperatures
of more than 1 Fahrenheit degree above natural
receiving water temperatiure, which exceeds
25 percent of the cross-sectional area of the
main river channel at any point.
11. The discharge shall not cause a surface water
temperature rise greater than 4 Fahrenheit
degrees above the natural temperature of the
receiving waters at any time or place.
12. The discharge shall not cause the total nitrogen
content of the receiving waters to exceed
3.0 mg/1.
13. The discharge shall not cause the mean monthly
Total Dissolved Solids (TDS) in the receiving
waters to exceed 500 mg/1.
14. The discharge shall not cause a violation of any
applicable water quality standard for receiving
waters adopted by the Board or the State Water
Resources Control Board as required by the
Federal Water Pollution Control Act and regula-
tions adopted thereunder. If more stringent
applicable water quality standards are approved
145
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pursuant to Section 303 of the Federal Water
Pollution Control Act, or amendments thereto,
the Board will revise and modify this Order in
accordance with such more stringent standards.
C. Provisions
1. Neither the discharge nor its treatment shall
create a nuisance as defined in the California
Water Code.
2. The City of Stockton Main Water Quality Control
Plant shall comply with the following time
schedule to assure compliance with Limita-
tions A.2, A.10, B.2, and B.12 of this Order:
Completion
Task Date
Progress Report for Ongoing
Project 10-1-74
Progress Report 4-1-75
Building Additions and
Modifications 9-1-75
Preliminary Treatment
Additions 11-1-75
Sludge Digestion Improvements 1-1-76
Progress Report 5-1-76
Solids Treatment and General
Additions & Modifications 9-1-76
River Crossing 1-1-77
Advanced Wastewater Treatment
Facilities 5-1-77
Full Compliance 7-1-77
Report of
Compliance Due
10-15-74
4-15-75
9-15-75
11-15-75
1-15-76
5-15-76
9-15-76
1-15-77
5-15-77
7-15-77
The City of Stockton Main Water Quality Control
Plant shall submit to the board on or before
each compliance report date, a report detailing
his compliance or noncompliance with the
specific schedule date and task.
If noncompliance is being reported, the reasons
for such noncompliance shall be stated, plus an
estimate of the date when the discharger will be
in compliance. The discharger shall notify
the Board by letter when he has returned to
compliance with the time schedule.
146
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3. The City of Stockton Main Water Quality Control
Plant shall comply with Limitation B.13 no later
than 15 February 1979, and shall furnish the
Board with quarterly progress reports beginning
no later than 1 October 1974.
4. The requirements prescribed by this Order
supersede the requirements prescribed by
Resolution No. 51-85, adopted by the Board on
7 November 1951, which are hereby rescinded.
The requirements prescribed by this Order amend
the requirements prescribed by Resolution
No. 69-200, adopted by the Board on 14 February
1969, which is hereby revised to include the
time schedule in Provision C2 of this Order.
5. This Order includes items 1, 2, 4, and 5 of the
attached "Reporting Requirements".
6. This Order includes items 1 through 11 inclusive
of the attached "Standard Provisions".
7. This Order includes the attached "Industrial
Wastewater Pretreatment Requirements".
8. The discharger shall comply with the Monitoring
and Reporting Program No. 74-453 and the General
Provisions for Monitoring and Reporting as
specified by the Executive Officer.
9. This Order expires on 1 September 1979 and the
City of Stockton Main Water Quality Control
Plant must file a Report of Waste Discharge in
accordance with Title 23, California Administra-
tive Code, not later than 180 days in advance of
such date as application for issuance of new
waste discharge requirements.
10. In the event of any change in control or
ownership of land or waste discharge facilities
presently owned or controlled by the discharger,
the discharger shall notify the succeeding owner
or operator of the existence of this Order by
letter, a copy of which shall be forwarded to
this office.
11. The daily discharge rate is obtained from the
following calculation for any calendar day:
Daily discharge rate =
8.34
N
N
147
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in which N is the number of samples analyzed in
any calendar day. Q^ and Ci are the flow
rate (mgd) and the constituent concentration
(mg/1) respectively, which are associated with
each of the N grab samples which may be taken,
in any calendar day. If a composite sample is
taken, C^ is the concentration measured in the
composite sample, and Qi is the average flow
rate occurring during the period over which
samples are composited.
The 7-day and 30-day average discharge rates
shall be the arithmetic average of all the
values of the daily discharge rate calculated
using the results of analyses of all samples
collected during any 7 and 30 consecutive
calendar day period, respectively. If fewer
than four samples are collected and analyzed
during any 30 consecutive calendar day period,
compliance with the 30-day average discharge
rate limitation shall not be determined. If
fewer than three samples are collected and
analyzed during any 7 consecutive calendar day
period, compliance with the 7-day average rate
limitation shall not be determined.
The daily maximum concentration shall be
determined from the analytical results of any
sample, whether discrete or composite.
I, JAMES A. ROBERTSON, Executive Officer, do hereby certify the
foregoing is a full, true, and correct copy of an order adopted
by the California Regional Water Quality Control Board, Central
Valley Region, on 9/27/74.
JAMES A. ROBERTSON, Executive Officer
Revised 9/4/74 scm/ca
148
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APPENDIX C
CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD
CENTRAL VALLEY REGION
ORDER NO. 74-152
NPDES NO. CA0079138
WASTE DISCHARGE REQUIREMENTS
FOR
CITY OF STOCKTON MAIN WATER QUALITY CONTROL PLANT
SAN JOAQUIN COUNTY
The California Regional Water Quality Control
Central Valley Region, (hereinafter Board), finds that:
Board
1. The City of Stockton Main Water Quality Control Plant
submitted a report of waste discharge NPDES
No. CA0079138 dated 9 November 1973.
2.
3.
4.
The City of Stockton Main Water Quality Control Plant
discharges an average of 0.84 m3/sec (19.2 mgd) and
a maximum of 2.23 m3/sec (51 mgd) of treated
domestic and industrial waste from secondary
treatment facilities into the San Joaquin River, a
water of the United States, at a point one mile ( 1 mi )
downstream from the Highway 4 bridge, in the NW-1/4 of
Section 17, TIN, R6E, MDB&M.]
The report of waste discharge describes the existing
discharge as follows:
Average flow: 72,672 cubic meters per operating
day (19.2 million gallons per operating
day)
Average temperature: 80F Summer; 54F Winter
Average 6005: 14 mg/1
Average total suspended solids: 35 mg/1
Average settleable matter: 0.1 ml/1
pH: 7.2 lowest monthly average; 8.8 highest
monthly average
Maximum waste flows occur during the summer and fall
months, with the major volume contributed by the
149
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canneries connected to the city sewerage system.
Liquid cannery wastes also provide the major organic
loading to the plant during this period.
5. The City of Stockton has consolidated wastewater
treatment in the Stockton area by accepting all wastes
from the Stockton Northwest, Stockton Airport, and
Lincoln Village treatment plants.
6. The City of Stockton Main Water Quality Control Plant
has completed an expansion program, including tertiary
facilities, which will result in upgrading of plant
effluent to meet more stringent requirements. The
plant capacity will be expanded to a maximum daily
flow of 67 mgd, a 7-day average maximum flow of
61 mgd, and a 30-day average maximum flow of 58 mgd.
7. The Board on 25 July 1975 adopted a Water Quality
Control Plan for the Sacramento-San Joaquin Delta.
The Basin Plan contains water quality objectives for
the San Joaquin River and Delta waters.
8. The beneficial uses of the San Joaquin River and Delta
waters are municipal, agricultural, and industrial
supply; recreation; esthetic enjoyment; navigation;
and preservation and enhancement of fish, wildlife,
and other aquatic resources.
9. Effluent limitations and toxic and pretreatment
effluent standards established pursuant to
Sections 208b, 301, 302, 304, and 307 of the Federal
Water Pollution Control Act and amendments thereto are
applicable to the discharge.
10. The discharge from the City of Stockton Main Water
Quality Control Plant is presently governed by
waste discharge requirements adopted by the Board on
28 July 1978 in Order No. 78-105.
11. The Board has notified the discharger and interested
agencies and persons of its intent to prescribe waste
discharge requirements for this discharge and has
provided them with an opportunity for a public hearing
and an opportunity to submit their written views and
recommendations.
12. The Board in a public meeting heard and considered all
comments pertaining to the discharge.
13. The action to adopt an NPDES permit is exempt from the
provisions of the California Environmental Quality Act
in accordance with Section 13389 of the Water Code.
150
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14. This Order shall serve as a National Pollutant
Discharge Elimination System permit pursuant to
Section 402 of the Federal Water Pollution Control
Act, or amendments thereto, and shall take effect
10 days from the data of hearing provided the Regional
Administrator, EPA, has no objections.
IT IS HEREBY ORDERED, the City of Stockton Main Water
Quality Control Plant, in order to meet the provisions contained
in Division 7 of the California Water Code and regulations
adopted thereunder and the provisions of the Federal Water
Pollution Control Act and regulations and guidelines adopted
thereunder, shall comply with the following:
A. Effluent Limitations:
1. The discharge of an effluent in excess of the
following limits is prohibited from 1 November
through 31 July:
Constituent
30-day 7-day 30-day Daily
Units Average Average Median Maximum
(1)
a. BOD
b. Total
Suspended
Solids
c. Settleable
Matter
d. Chlorine
Residual
e. Total .
Colifom^ ;
Organisms
f Grease and
Oil
Flow
mg/1 30
Ib/day 12,750
kg/day 5,800
mg/1 30
Ib/day 12,750
kg/day 5,800-
ml/1
mg/1
MPN/100 ml ~
45
19,100
8,700
45
19,100
8,700
50
21,250
9,600
50
21,250
9,600
0.1
.02
23
mg/1
Ib/day
kg/day
mgd
10
4,835
2,200
58
61
500
15
8,380
3,800
67
5-day, 20C Biochemical Oxygen Demand.
Limits can be at any point in the treatment system.
151
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During the period 1 August through 31 October the
discharge of an effluent .in excess of the limits
contained in A.I. above is prohibited excepting:
Constituent
BOD
b. Total
Suspended
Matter
Units
mg/1
Ib/day
kg/day
Ib/day
kg/day
30-day
Average
10
4,840
2,200
10
4,840
2,200
7-day
Average
20
10,180
4,600
20
10,180
4,600
30-day
Median
30
16,770
7,600
30
16,770
7,600
The arithmetic mean biochemical oxygen demand
(5-day) and suspended solids in efflent samples
collected in a period of 30 consecutive days
shall not exceed 15 percent of the arithmetic
mean of the values for influent samples collected
at approximately the same times during the same
period (85 percent removal).
The discharge shall not have a pH less that 6.0
nor greater than 8.5, nor shall it cause a change
greater than 0.5 in the pH of the receiving
waters.
Bypass or overflow of untreated or partially
treated wastes is prohibited.
The discharger shall use the best practicable
cost effective control technique currently
available to limit mineralization to no more than
a reasonable increment.
Survival of test fishes in 96-hour bioassays of
undiluted waste shall be no less than:
Minimum, any one bioassay
Median, any three or more consecutive
bioassays .'
70%
90%
The maximum temperature of the discharge
shall not exceed the natural receiving water
temperature by more than 20 Fahrenheit degrees.
The discharger shall not cause degradation of any
water supply.
152
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B. Receiving Water Limitiations:
1.
The discharge shall not cause the dissolved
oxygen concentration in the San Joaquin River to
fall below the following levels:
Units
mg/1
Percent of
Saturation
Minimum
5.0
Median
85
95
Percentile
75
2.
When circumstances cause dissolved oxygen levels
less than 5.0 mg/1 downstream or upstream of the
discharge, then the City of Stockton facility
shall be operated to comply as stipulated in
A 2.
3. The discharge shall not cause visible oil,
grease, scum, or foam in the receiving waters or
watercourses.
4. The discharger shall not cause concentrations of
any materials in the receiving waters which are
deleterious to human, animal, aquatic, or plant
life.
5.
6.
7.
8.
9.
10.
The discharger shall not cause esthetically
undesirable discoloration of the receiving
waters.
The discharger shall not cause fungus, slimes, or
other objectionable growths in the
waters.
receiving
The discharge shall not
the receiving waters.
cause bottom deposits in
The discharge shall not cause floating or
suspended materials of recognizable sewage origin
in the receiving waters.
The discharge shall not increase the turbidity of
the receiving waters by more than 10% over
background levels. ;
The discharger either individually or in
combination with other discharges shall not
create a zone, defined by water temperatures of
more than one Fahrenheit degree above natural
153
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11,
12,
receiving water, temperature, which exceeds
25 percent of the cross-sectional area of the
main river channel at any time or place.
The discharge shall not cause a surface water
temperature rise greater than 4 Fahrenheit
degrees above the natural temperature of the
receiving waters at any point.
The discharge shall not cause a violation of any
applicable water quality standard for receiving
waters adopted by the Board or the State Water
Resources Control Board as required by the
Federal Water Pollution Control Act and
regulations adopted thereunder. If more
stringent applicable water quality standards are
approved pursuant to Section 303 of the Federal
Water Pollution Control Act, or amendments
thereto, the Board will revise and modify this
Order in accordance with such more stringent
standards.
C. Provisions
1. Neither the discharge not its treatment shall
create a nuisance as defined in the California
Water Code.
2. If future studies indicate that additional
nitrogen removal is necessary to protect water
quality, the Board may revise and modify
this order to include more stringent nitrogen
limitations.
3. The City of Stockton Main Water Quality Control
Plant shall diligently pursue and enforce source
control of Total Dissolved Solids (TDS) to
minimize the level of TDS discharged and shall
furnish a report no later than 15 February of
each year describing the major sources of TDS and
control measures which were taken during the
previous year.
4. The requirements prescribed by this Order
supercede the requirements prescribed by Order
No. 78-105 which is hereby rescinded.
5. This Order includes the attached "Standard
Provisions and Reporting Requirements" for
Municipal Discharges.
6. This Order includes the attached "Industrial
Wastewater Pretreatment Requirements."
154
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7. This discharger shall comply with the Monitoring
and Reporting Program No. 79-152 and the General
provisions for Monitoring and Reporting as
specified by the Executive Officer.
8. This order expires on 1 April 1980 and the City
of Stockton Main Water Quality Control Plant must
file a Report of Waste Discharge in accordance
with Title 23, California Administrative Code,
not later than 180 days in advance of such
date as application for issuance of new waste
discharge requirements.
9. In the event of any change in control or
ownership of land or waste discharge facilities
presently owned or controlled by the discharger,
the discharger shall notify the succeeding owner
or operator of the existence of this order by
letter, a copy of which shall be forwarded to
this office.
10. The daily discharge rate is obtained from the
following calculation for any calendar day:
Daily discharge rate =
8.34
N
N
Qi
in which N is the number of samples analyzed in
any calendar day. Q^ and C^ are the flow
rate (MGD) and the constituent concentration
(mg/1), respectively, which are associated with
each of the N grab samples which may be taken in
any calendar day. If a composite sample is
taken, C^ is the concentration measured in the
composite sample, and Q-[ is the average flow
rate occurring during the period over which
samples are composited.
The 7-day and 30-day average discharge rates
shall be the arithmetic average of all the values
of daily discharge rate calculated using the
results of analyses of all samples collected
during any 7 and 30 consecutive calendar day
period, respectively. If fewer than four
samples are collected and analyzed during any
30 consecutive calendar day period, compliance
with the 30-day average discharge rate limitation
shall not be determined. If fewer than three
samples are collected and analyzed during any
155
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7 consecutive calendar day period, compliance
with the 7-day average rate limitation shall not
be determined.
The daily maximum concentration shall be
determined from the analytical results of any
sample whether discrete or composite.
I, JAMES A. ROBERTSON, Executive Officer, do hereby certify the
foregoing is a full, true, and correct copy of an order adopted
by the California Regional Water Quality Control Board, Central
Valley Region, on June 22, 1979.
JAMES A. ROBERTSON, Executive Officer
156
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APPENDIX D
DESCRIPTION OF SAMPLING PROGRAM
In order to determine the performance characteristics for
the plastic media trickling filters constructed at Stockton, a
special 1-yr sampling program was undertaken. Because the
three rock media and the three plastic media filters operated
in parallel from the common recirculation sump serving all the
trickling filters, it was impossible to measure the performance
of the plastic units independently of the rock filters. The
city agreed, therefore, to shut down the three rock media
filters during the sampling program. Loadings on the filters
during this time were sufficiently below the design loadings to
allow this operating change to be implemented without an
adverse effect on performance. The sampling program was begun
on March 15, 1976, and completed on March 16, 1977. Results
of the sampling program are presented in Section 7 and in
Appendix E. Discussed below are sampling and analytical
techniques, sampler operation and performance, and the history
of the sampling program, including problems, special tests, and
a description of plant operation during the sampling program.
SAMPLING AND ANALYTICAL TECHNIQUES
The analyses conducted for the sampling program are shown
in Table 12, Section 7. They include total and soluble BODg,
total and volatile suspended solids, alkalinity, total and
soluble COD, nitrogen forms, and total phosphorus. Plant
records were used to obtain data on flow, pH, dissolved oxygen,
and wastewater temperature. Flow was measured by Parshall
flumes in the plant headworks. Grab samples taken at
approximately 1:00 p.m. each day were used to determine the
other three parameters. Except for total and soluble BODs
and primary effluent alkalinity, which were measured once per
week, analyses were performed three times per week. BODs,
total and volatile suspended solids, and alkalinity analyses
were performed at Brown and Caldwell's Environmental Sciences
Division in San Francisco. The remaining analyses were
performed at the Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, Ohio.
Total COD, TKN, and total phosphorus samples were
preserved with sulfuric acid to a pH of 2 or less. Ammonia,
nitrate, and nitrate nitrogen samples were preserved with 5 ml
157
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of chloroform per 250 ml of sample. Soluble COD samples were
filtered through a millipore membrane filter and preserved with
sulfuric acid to a pH of 2 or less. Three 24-hr composite
samples of each of the above-preserved types were collected
each week and shipped to Cincinnati the following Monday
morning by air freight.
COD analyses were conducted in accordance with Standard
Methods (36). TKN samples were analyzed using semi-macro
(100-ml flasks) Kjeldahl digestion followed by distillation
and analysis of the free ammonia nitrogen produced via the
automated colorimetric phenate method (37). Nitrite and nitrate
nitrogen were determined simultaneously by stoichiometric
reduction of nitrate ion to nitrite ion with hydrazine sulfate
and measurement of the resultant nitrite by standard automated
colorimetric procedures (38). Nitrite nitrogen was then
analyzed separately without the hydrazine sulfate reduction
step and nitrate nitrogen calculated by subtraction. Total
phosphorus analyses were performed using the automated
colorimetric ascorbic acid reduction method (37).
For total and soluble secondary effluent BODs, it was
believed that nitrification in the BOD bottle might cause
values to be erroneously high. Therefore, suppression of
nitrification was undertaken initially with 0.1 ammonia
nitrogen, which in such high concentrations is toxic to
nitrifying organisms, and later with allylthiourea (ATU).
On May 3, 1976, parallel tests were begun which ran for
4 wk. In these tests, BODs analyses were performed with ATU
and ammonia nitrogen used for nitrification suppression. A
parallel, control test was run without nitrification suppres-
sion. Results of the tests, discussed in greater detail below
under sampling program history, indicated that ammonia nitrogen
inhibited carbonaceous oxidation as well as nitrification.
Therefore, for the remainder of the study, ATU was used to
suppress nitrification in the BOD bottle.
In Section 7 and in Appendix D, secondary effluent total
and soluble BODs concentrations for the first 8 weeks of
the study have been adjusted upward using the results of the
parallel test involving ammonia nitrogen and ATU.
SAMPLER OPERATIONS
Sampling for the special program was accomplished using
four portable, refrigerated composites samplers manufactured by
Instrumentation Specialties Company (ISCO). These samplers,
shown in Figure D-l, are capable of receiving a flow-
proportional signal from a flow meter or other device. Because
of the location of the samplers, far from the existing plant
flowmeter, it was decided to attempt to simulate the diurnal
158
-------
flow variations through the use of a timer manufactured by
the Tork Company. The timers allowed a contact closure signal
to be sent to the samplers at intervals as frequent as every
5 min.
Figure t>-2 illustrates the
diurnal typical flow variation
curve at the Stockton plant for
the noncanning season. The
curve represents hourly flow
values averaged over a 7-day
period. Also shown in the
figure is the simulated flow
pattern developed using the
Tork timers. This technique
proved to be very effective in
simulating flow fluctuations at
the Stockton plant. This
method was much more economical
than attempting to use the
actual measured flows to
trigger the samplers. As the
diurnal flow variation for the
canning season is significantly
different from that shown
in Figure D-2, a different
simulated flow pattern was
developed for that period of
the study.
The primary influent
sampler was located at the
distribution structure for
primary clarifiers No. 1
through 4. This location had
two disadvantages. First, it
was downstream from the grit
removal channels, and second,
it was downstream from the
were taken 3 days per week point at which secondary sludge
at four sampling locations. was returned to the headworks
to be removed in the primary
clarifiers and delivered to
the digesters. It would have been more desirable to have
located the sampler upstream from these points, but the enclosed
headworks required explosion-proof equipment which was not
available.
The primary effluent sampler was located at the top of the
trickling filter circulation sump. Because the water in the
circulation structure consists of both primary effluent and
unsettled trickling filter effluent, it was necessary to locate
Figure D-l,
Isco Model I580R sampler.
Twenty-four-hr flow, pro-
portional composite samples
159
-------
the end of the sampler suction tube within the 1.5-m (60-in.)
primary effluent line connecting the primary clarifiers to the
distribution structure. The device used to hold the end of the
sampling tube in place is shown in Figure D-3. Installation of
the sampling line is shown in Figure D-4. This was the only
point at which a representative primary effluent sample could
be obtained.
NOTE:
MEASURED DIURNAL FLOW CURVE
TAKEN FROM WEEK OF 1/5/76
SIMULATED FLOW CURVE
MEASURED FLOW CURVE
12
TIME
Figure D-2. Measured and simulated diurnal flow variation curves.
The unsettled trickling filter effluent sampler was
located at the outer box of the filter circulation sump. Its
proximity to the primary effluent sampler allowed a single timer
to be used for both.
160
-------
-*
Figure D-4.
Figure D-3. Sampling tube strainer held in place by clamp.
The secondary effluent
sampler was located on the
levee between the secondary
clarifiers and the river
crossing. This location was
necessary in order to obtain a
representative sample from all
the secondary clarifiers. This
was considered necessary
because of the flow distribu-
tion problems among the
secondary clarifiers. As
chlorination of secondary
clarifier influent was
Installation of primary efflu-practiced for disinfection
ent sampling line. To ob-
tain a representative sam-
ple, the sampling tube had
to be located in the end of
the primary effluent line
approximately 4.6 m (15 ft)
below the water surface
in the recirculation
structure.
purposes, sodium thiosulfite
was added to the collection
bottle in the secondary
effluent sampler to eliminate
any effect of the chlorine on
the measured parameters.
The Isco Model 1580R
sampler is a compositing
sampler which can be operated
either at a specified time interval or as a flow-proportional
sampler if a contact closure is provided. The refrigerator
temperature can be adjusted from 0 to 8 C with a calibrated
control. Suction lines for the sampler are 0.64 cm (1/4-in.) in
diameter, and a 0.64-cm (1/4-in.) strainer is provided at the
161
-------
end of the suction tube. A sample volume of up to 18.9 1
(5 gal) can be taken. An automatic shutoff device prevents the
sample bottle from overflowing.
Operational reliability of the samplers was a serious
problem throughout the project. Initially, the tubing inside
the peristaltic pump unit deteriorated rapidly. Eventually
this was solved by allowing the length of tubing within the
pump unit to reach "natural" length before being clamped at
both ends. A more serious problem, which required a shipment
of several samplers back to the manufacturer for repairs,
resulted from an insufficient volume of wastewater being
pumped at each sampling. This apparently resulted from the
malfunction of a counter within the pump unit, which registered
the number of turns of the pump required for a specified
sample volume. Toward the end of the study, a third problem
developed. This involved deterioration of the gears within
the pump, which also required return of the units to the
manufacturer.
During a significant portion of the study, three or fewer
samplers were being operated at any given time. During periods
of sampler breakdown, sampler mechanisms were switched, if
necessary, to ensure that primary effluent and secondary
effluent was being sampled with the automatic samplers. Those
points in the waste stream not sampled automatically were
hand sampled by the plant staff and composited over a 24-hr
period. These samples were not flow-proportioned, however.
SAMPLING PROGRAM HISTORY
Any long-term sampling program undertaken at an operating
wastewater treatment plant will necessarily encounter opera-
tional changes over the course of the program. Principal
operational changes normally undertaken at Stockton include the
use of fewer primary and secondary clarifiers during the
noncanning season when the hydraulic loading is much lower.
Further, certain plant components may be out of service for a
time. During the first 9 wk of the Stockton sampling program,
only two of the three plastic media towers were operating. The
third tower was shut down to allow experiments with insertion
of a plastic liner between the media and the tower wall to
eliminate the leakage problem described in Section 6. Shown in
Figure 32 in Section 7 is an operational history for the
Stockton plant during the sampling program. Indicated in
the figure is the operation of the towers, primary and
secondary clarifiers, and forced-draft ventilation fans.
During the course of the program, several auxiliary tests
were undertaken in order to develop specific information. One
test mentioned previously was the comparison of ammonia
nitrogen and ATU for nitrification suppression in the BOD test.
162
-------
Shown in Table D-l are the results of parallel tests taken over
a 3-wk period. In the first column are secondary effluent
BODs concentrations measured by the Stockton plant laboratory
staff without nitrification suppression. In the second two
columns are secondary effluent BODs concentrations measured
by Brown and Caldwell using ammonia nitrogen and ATU,
respectively, for nitrification suppression. The average
BODs concentrations over the 3-wk period were approximately
equal for the samples suppressed with ATU and for the samples
for which nitrification was not suppressed. Those samples
to which ammonia nitrogen was added had an average BODs
concentration of approximately 15 mg/1 as compared with
23 mg/1 for those suppressed with ATU and those to which no
suppnessant was added. Conclusions resulting from these tests
are that either ammonia nitrogen suppresses both carbonaceous
BOD and nitrification or that ATU is ineffective in inhibiting
nitrification. Most previous information supports the first
conclusion, however, that ammonia nitrogen, when used to
suppress nitrification, can also suppress carbonaceous BOD.
TABLE D-l.
PARALLEL TESTS ON
NITRIFICATION
SUPPRESSION
Date
Measured BODc concentration,
mg/la
These tests indicated that
nitrification within the BOD
bottle was not a significant
problem during the sampling
program at Stockton. Nonethe-
less, ATU was used for
nitrification suppression
during the remainder of the
program.
Similar tests undertaken
at Seattle, Washington, also
indicate that ATU is an
effective inhibitor of
nitrification in the BOD test
and that ammonia nitrogen
inhibits carbonaceous BOD as
well as nitrification.
Results of one of the tests
carried out at Seattle are
shown in Table D-2. Four sets
of ammonia-free solutions of
glucose and glutamic acid were
set up using diluted water
seeded with settled primary
effluent. Ten replicate
were prepared for each set. The analysis compared
using no inhibitor, ammonium chloride, and ATU. In
any differences occurring could only be due to
of carbonaceous oxidation by the nitrification
While the samples with no inhibitor and with ATU
equal 6005 values, the samples with
No
inhibitor
5/10/76
5/11/76
5/12/76
5/17/76
5/18/76
5/19/76
5/24/76
5/25/76
5/26/76
Average
22
27
27
22
17
20
23
Ammonium
chloride0
8
12
16
17
22
33
12
8
11
15
ATUC
29
29
33
12
19
14
23
Tests conducted on secondary effluent.
Analyzed by Stockton plant staff.
"Analyzed by Brown and Caldwell.
samples
results
this test,
inhibition
suppressants.
added gave approximately
163
-------
ammonium chloride added had significantly lower BODs values.
This again indicates that ATU is a mor.e reliable inhibitor of
nitrification and does not inhibit carbonaceous BOD.
TABLE D-2.
NITRIFICATION SUPPRES-
SION TESTS CONDUCTED
FOR SEATTLE PILOT
PLANT
Measured 8005 concentration,
Test
number
1
2
3
4
5
6
7
8
9
10
No
inhibitor
246
252
246
240
256
246
246
234
228
252
*"^/ *
Ammonium
chloride
180b
234
222
228
234
216
204
216
204
222
ATU
240
252
252
246
252
234b
246
258
252
252
Average
245
220
Tests conducted on ammonia-free,
glutamic acid solutions.
Not included in average.
250
glucose,
As a result of the
parallel tests conducted at
Stockton and discussed above,
all secondary effluent BODs
concentrations measured prior
to May 10 have been increased
by 50 percent to account for
the addition of ammonia
nitrogen during this earlier
period.
Another special test
undertaken during the
sampling program involved the
measurement of heavy metals
concentrations in the sludge
sloughed from the trickling
filters. Poor nitrification
performance during the first
part of the study led to the
suspicion that high heavy
metals concentrations in
the slime developed on the
trickling filter could be toxic
to the nitrifying organisms.
On May 17, 1976, a sample of sludge was collected from the
secondary clarifier underflow, refrigerated, and delivered to
EPA, San Francisco. Analyses were performed for zinc, mercury,
chromium, nickel, arsenic, and copper. Results are summarized
in Table D-3, along with values obtained in tests performed
elsewhere. The table shows that the values obtained at Stockton
are not unusually high and, therefore were probably not the
cause of poor nitrification performance.
Later in the program, two operational changes were
instituted in an attempt to improve performance. The first
involved increasing total hydraulic loading (raw plus recycle)
on the towers, and the second involved increasing the air flow
through the forced draft ventilation system to ensure an
adequate oxygen supply for the nitrifying organisms in the
tower.
Because the Stockton towers are designed for a very low
organic loading during the noncanning season to achieve
nitrification, the total hydraulic loading on the tower is
also quite low. Although the total flow is not measured
at Stockton, hydraulic analysis of the supply pumps and
piping indicated that the total loading being obtained was
164
-------
approximately 0.024 m3/min/m2 (0.6 gpm/ft2) which is lower
than the 0.031 to 0.041 m3/min/m2 (0.75 to 1.0 gpm/ft2) normally
recommended as the minimum loading to ensure wetting of the
entire media surface. Therefore, it was requested that the
city, starting in mid-October 1976, increase the hydraulic
loading to the towers by increasing the speed of the variable
speed supply pumps.
TABLE D-3. HEAVY METALS CONCENTRATIONS IN SLUDGE
Concentration mg/kg dry solids
Constituent
Stockton0
Seattle
Typical range
Zinc
Mercury
Chromium
Nickel
Copper
2,600
3
600
42
750
2,560
4.5
570
110
830
1,000 - 3,000
3-7
100 - 1,000
50 - 500
400 - 2,000
Trickling filter solids.
Digested primary sludge.
c
Source: Environmental Science and Technology,
10/ 683 (July 1976). Measured on
various types of sludges.
Another operational change made at this time was to
increase the number of forced draft ventilation fans operating
at the towers. Although measurements undertaken with two or
fewer (out of eight) fans operating indicated that dissolved
oxygen levels in the tower influent were sufficiently high to
ensure nitrification, it was believed that these values
may have been erroneously high due to dissolved oxygen being
added to the wastewater as it dropped from the bottom of the
media to the floor of the tower. Thus, it was requested that
the city increase the number of fans operating to at least four
of eight at each tower.
Data taken before and after the changes in operating
procedure exhibit improved performance after the changes were
made. A more complete discussion of these differences is
presented in Section 7.
Later in the study, another change was made in the
operation of the forced draft ventilation fans. Observation of
the secondary clarifiers during the middle of the day showed an
increase in turbidity and apparent short-circuiting of influent
which rose to the surface near the feedwell and moved rapidly
across the clarifier to the effluent troughs. This phenomonen
had been observed for some time by the plant staff, but no
explanation has been found for its occurrence. After observing
the phenomonen for several months during the sampling program,
165
-------
it was hypothesized that the short circuiting may have been due
to temperature/density gradients set up within the clarifier.
It was theorized that with low hydraulic loadings and high air
flows to employed promote nitrification in the towers, that
colder air temperatures and lower flows at night resulted in a
greater cooling of the wastewater as it passed through the
towers. As the wastewater flow and temperature increased in
the morning hours, the drop in wastewater temperature through
the towers would decrease and the water entering the clarifiers
would be warmer and lighter. If the difference in density were
sufficiently great, short-circuiting of the type observed might
be expected to occur.
As discussed in Section 7, water temperature profiles were
measured and temperature gradients were found although no
correlation with the occurrence of short-circuiting could be
detected. It is still uncertain whether a causal relation
exists between temperature variations and short-circuiting.
Other plant operational changes, which were incidental to
the sampling program, also occurred during the 1-yr period.
From the beginning of the sampling program until May 12, 1976,
only two of the three plastic media towers were being operated.
The third tower was shut down during this period to allow
experimentation with insertion of a plastic liner between the
media and the tower wall in order to prevent the leakage' which
was occurring through the wall. This change did not have an
adverse effect on the sampling program. In fact, the increased
organic loading through the towers during this period approx-
imated the design loading and, therefore, allowed a valuable
comparison between design and performance.
The other significant event during the sampling program
involved the inability of the primary clarifier solids handling
mechanism to remove large quantities of solids received during
the canning season. Normal procedure at Stockton is for the
secondary sludge to be returned to the headworks. Combined
primary and secondary sludges are then removed from the primary
sedimentation tanks and pumped to the digesters. During
the peak of the canning season, the solids loadings on the
primaries were sufficiently high that solids carryover to the
secondary treatment portion of the plant was occurring. When
these solids entered the secondary clarifiers, they settled out
and were returned to the plant headworks. Thus, a build-up of
solids was occurring within the primary and secondary treatment
portions of the plant. To solve this problem, the plant
staff constructed a temporary sludge conveyance line from the
secondary sludge collection box directly to the sludge lagoons.
Secondary sludge was then pumped to the lagoons at a rate
sufficiently high to eliminate the build-up which had occurred.
In a short period of time, the plant influent solids load
166
-------
decreased and the temporary conveyance line was no longer
needed. Operation of the temporary line began on August 21,
1976. All of the secondary sludge was transferred directly to
the lagoons for the next several weeks of the canning season.
167
-------
APPENDIX E
DAILY DATA FROM SAMPLING PROGRAM
168
-------
TABLE E-1
DAILY VALUES FOR FLOW, BOD_, SOLUBLE BOD_, AND
SOLUBLE COD 5 5
Date
3/15/76
3/16/76
3/17/76
3/22/76
3/23/76
3/24/76
3/29/76
3/30/76
3/31/76
4/5/76
4/6/76
4/7/76
4/12/76
4/13/76
4/14/76
4/19/76
4/20/76
4/21/76
4/26/76
4/27/76
4/28/76
5/3/76
5/4/76
5/5/76
5/10/76
5/11/76
5/12/76
5/17/76
5/1S/76
5/19/76
5/24/76
S/25/76
5/26/76
5/31/76
6/y76
6/2/76
6/7/76
6/8/76
6/9/76
6/14/76
6/15/76
6/16/76
6/21/76
6/22/76
6/23/76
6/28/76
6/29/76
6/3Q/76
7/5/76
7/6/76
7/7/76
7/12/76
7/13/76
7/14/76
7/19/76
7/20/76
7/21/76
7/26/76
7/27/76
7/28/76
8/2/76
8/3/76
8/4/76
Flow,
Infl.
b
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16b
16
19
21
21
15
20
17
21
20
15
19
19
19
24
13
19
21
20
16
12
18
19
-
-
-
23
18
~
20
18
19
44
44
40
a
mgd
Recyc .
20
21
20
24
24
19
21
20
21
21
21
17
19
19
19
15
16
20
20
19
20
20
20
19
18
19
36
39
38
38
35
33
30
37
30
36
30
20
37
34
46
53
.48
48
50
39
42
46
47
43
35
-
-
-
37 '
43
-
51
47
41
26
24
23
Raw
Infl.
270
300
300
300
340
-
250
260
300
270
300
260
210
250
' 260
250
220
220
220
230
300
250
310.
240
280
220
230
220
310
300
300
220
330
150
210
220
230
_
230
270
300
270
380
240
310
300
240
320
170
260
300
290
260
360
356
300
240
320
350
320
570
780
520
BOD5, mg/1
Prim.
Effl.
180
180
150
160
240
200
140
150
160
200
200
ISO
130
140
140
140
140
140
140
130
170
130
120
120
150
140
90
130
160
160
180
110
170
70
170
81
140
130
140
190
180
160
190
120
150
110
110
120
81
100
150
140
140
200
200
190
78
150
150
170
310
390
260
Soluble BOD^,
raq/1
Sec.
Effl.
-
-
8
34
15
23
29
29
57
13
54
-
12
10
9
6
3
29
13
8
-
5
12
10
15
29
25 '
27
33
51
12
19
14
21
21
17
34
21
18
34
22
26
44
23
39
26
-
26
30
32
21
26
28
39
27
26
. 17
24
38
40
100
150
110
Prim.
Effl.
86
-
-
_
96
-
_
_
43
58
-
-
_
44
-
_
_
55
52
-
_
43
-
-
39
66
_
-
61
29
-
-
_
71
-
83
_
75
-
34
_
-
_
_
56
86
_
-
_
54
-
-
46
220
-
Sec.
Effl.
_
_
-
8
-'
_
29
5
_
-
_
4
-
_
_
8
9
-
_
4
-
_
17
12
_
-
-
4
15
_
-
_
12
-
14
_
9
-
12
_
-
_
_
10
17
_
-
_
12
-
23
51
-
Raw
Infl.
750
700
680
650
720
-
560
520
610
530
590
550
490
510
'740
670
490
550
740
510
690
660
670
580
300
590
700
530
610
790
470
420
540
550
450
460
_
_
520
500
490
620
530
530
620
580
620
450
490
620
610
600
680
690
610
830
680
620
480
880
900
930
_COD,
Prim.
Effl.
380
430
338
440
360
330
390
410
340
340
450
350
270
370
530
310
330
370
330
290
430
350
340
340
550
340
360
290
310
390
250
250
290
160
150
160
_
_
310
300
300
350
310
270
230
230
230
190
210
260
290
300,
320
390
290
200
280
290
250
460
560
540
mg/1
Filter
Effl.
210
230
200
220
170
180
290
260
260
240
240
260
210
200
370
250
170
180
190
180
200
260
210
250
240
250'
190
190
200
250
140
150
170
290
190
150
_
190
140
190
180
170
180
120
130
150
160
180
140
190
190
170
250
200
180
160
160
160
410
410
480
Sec.
Effl.
100
130
120
120
120
120
110
110
120
120
130
97
110
110
100
. 95
100
130
140
150
150
150
150
140
160
160
97
110
120
88
77
85
68
55
56
_
100
91
95
130
110
120
91
86
72
81
80
100
110
91
120
120
100
100
110
100
280
340
320
Soluble
mg/1
Prim.
Effl.
200
180
150
75
86
83
91
100
130
100
120
79
82
81
82
88
82
78
160
130
150
'170
130
150
200
150
120
95
150
180
110
92
110
78
70
86
,
160
140
140
170
130
110
82
68
73
62
84
100
140
69
100
160
100
67
120
75
74
310
290
260
COD,
Sec.
Effl.
57
83
74
85
84
77
94
77
77
84
97
69
78
75
73
71
68
100
100
110
120
120
. 120
110
130
130
68
69
79
56
53
51
57
43
45
66
63
62
78
75
68
59
66
47
56
55
72
95
60
87
92
72
73
75
72
200
240
230
(continued on next page)
169
-------
TABLE E-l. (continued)
Flow* ragd
IMta
8/9/76
8/10/76
8/11/76
8/16/76
8/17/76
8/18/76
8/23/76
8/24/76
8/25/76
8/30/76
8/31/76
9/1/76
9/6/76
9/7/76
9/8/76
9/13/76
9/14/76
9/15/7$
9/20/76
9/21/76
9/22/76
9/J7/76
9/28/76
9/29/76
10/4/76
10/5/76
10/6/76
10/11/76
10/12/76
10/13/76
10/18/76
10/19/76
10/20/76
10/25/76
10/26/76
10/27/76
11/1/76
11/2/76
11/3/76
11/8/76
11/9/76
11/10/76
11/15/76
11/16/76
11/17/76
11/22/76
11/23/76
11/24/76
11/29/76
11/30/76
12/1/76
12/6/76
12/7/76
12/8/76
12/13/76
12/14/76
12/15/76
12/20/76
12/2V76
12/22/76
12/27/76
12/28/76
12/29/76
Intl.
29
40
42
40
41
42
40
41
41
40
43
42
24
40
42
37
38
37
36
36
38
31
34
31
29
30
23
23
20
19
23
19
18
15
12
18
17
17
17
18
18
13
18
18
13
IS
19
18
19
19
19
18
18
18
19
19
18
19
19
19
16
15
21
Rccyc.
35
21
19
26
23
23
24
23
24
21
46
30
24
28
31
27
20
20
21
29
24
26
24
24
30
26
31
34
27
34
34
39
45
SO
50
48
46
52
49
55
57
57
54
58
58
59
27
32
32
58
32
32
30
30
31
60
50
50
49
51
44
BOD5, mg/1
Raw
Infl.
470
680
670
620
690
720
620
680
540
530
720
470
160
630
470
460
480
430
410
380
380
370
450
490
710
530
380
390
240
350
380
370
190
280
300
230
300
320
200
330
-
330
380
400
330
-
-
420
410
370
350
510
440
440
480
360
340
450
-
520
510
-
Prim.
Effl.
270
300
350
330
350
330
370
320
260
280
300
240
57
280
270
260
260
250
230
240
270
210
270
250
340
280
230
210
200
160
190
200
140
170
190
200
190
210
170
200
-
210
340
210
210
-
-
220
240
210
240
250
210
220
280
210
210
200
-
240
300
-
Sec.
Effl.
120
170
230
140
160
150
120
140
83
66
114
142
21
68
34
54
56
40
46
43
37
118
53
43
65
63
43
29
33
21
25
26
13
16
18
17
13
13
12
12
-
17
42
31
27
-
-
33
50
29
18
20
19
16
29
18
21
-
19
12
-
Soluble BOD ,
mg/1
Prim.
Effl.
180
250
220
210
_
-
220
150
180
160
120
110
70
140
_
-
100
-
-
~
110
-
79
100
110
-
_
-
Sec.
Effl.
130
130
82
71
_
~
30
24
24
24
16
12 -
6
7
_
~
10
-
~
~
22
;
9
11
9
~
-
~
Raw
Infl.
930
970
1,060
980
1,170
1,150
1,080
1,180
1,140
980
1,270
990
530
850
~
850
930
930
1,060
800
1,030
880
980
1,030
1,340
1,330
1,060
770
710
670
650
710
. 700
610
670
670
630
650
610
430
600
~
670
770
850
650
~
~*
1,000
770
740
850
860
750
830
720
690
760
930
~
1,060
790
~
COD,
Prim.
Effl.
500
480
580
600
650
570
540
480
510
470
500
440
250
420
~
440
420
500
490
430
490
490
430
570
500
610
500
430
380
370
280
340
350
270
330
360
320
320
300
290
360
~
320
380
390
320
~
~
490
430
380
310
380
340
420
450
370
420
400
~
430
370
~
mg/1
Filter
Effl.
280
340
300
390
450
450
340
260
300
300
280
420
110
340
~
220
240
280
230
250
220
230
230
360
240
430
240
250
230
240
160
210
210
140
140
160
140
150
140
140
130
~
210
320"
220
170
~
"
220
200-
160
150
110 ;
140
250
230
210
300
250
~
180
140
~
Soluble COD,
mg/1
Sec.
Effl.
200
270
330
260
290
190
190
320
240
220
270
230
140
200
160
200
210
200
180
190
200
210
250
180
230
220
190
150
170
120
130
140
84
92
96
93
77
78
61
69
110
140
130
120
160
170
120
95
93
100
100
150
110
120
110
80
61
Prim.
Effl.
170
150
300
280
330
350
320
340
340
300
310
. 300
96
280
330
270
320
320
250
280
310
270
290
270
380
310
210
200
190
150
200
190
150
180
200
140
220
150
130
180
150
150
180
160
170
190
210
140
180
160
240
200
160
190
200
190
200
Sec.
Effl.
120
140
160
140
150
160
140
150
120
110
150
130
82
98
97
110
120
120
110
110
110
120
120
98
120
110
81
72
80
63
75
80
58
66
77
54
55
52
56
64
64
88
89
80
90
93
88
61
63
62
63
88
62
70
77
58
53
(continued on next page)
170
-------
TABLE E-1. (continued)
Date
1/3/77
1/4/77
1/5/77
1/10/77
1/11/77
1/12/77
1/17/77
1/18/77
1/19/77
1/24/77
1/25/77
1/26/77
1/31/77
2/1/7.7
2/2/77
2/7/77
2/8/77
2/9/77
2/14/77
2/15/77
2/16/77
2/21/77
2/22/77
2/23/77
2/28/77
3/1/77
3/2/77
3/7/77
3/8/77
3/9/77
3/14/77
3/15/77
3/16/77
Flow, mgd I
Infl.
18
19
19
19
20
20
20
19
17
19
19
19
18
18
18
18
-
18
19
19
18
18
18
18
18
23
18
17
17
18
16
19
19
Re eye.
51
48
52
52
50
51
48
48
52
49
50
52
51
59
57
31
-
32
55
53
53
54
52
47
50
45
49
50
55
50 .
53
55
57
Raw
Infl.
380
350
460
300
410
420
380
410
390
240
250
350
440
300
460
340
280
320
460
470
360
170
570
570
290
340
390
370
380
370
340
370
320
30D5, mg/1
Prim.
Effl.
210
300
240
240
250
140
-
180
-
210
-
220
230
180
200
190
190
160
180
130
-
160
240
-
-
170
41
160
260
190
150
200
190
Sec.
Effl.
14
17
15
12
11
22
13
17
18
12
17
16
14
19
11
29
23
18
11
15
10
11
11
12
12
13
12
15
12
14
15
13
19
Soluble BOD,.,
mg/1
Prim. Sec.
Effl. Effl.
. i.
-
160 a
, 180 6
-
-
_
90 8
-
_
-
130 8
<92 7
-
-
_ _
67 11
-
_
-
5
100 4
-
-
_
38 7
-
_ _
95 6
28 9
-
-
Raw
Infl.
860
700
1,030
720
1,050
780
850
890
950
510
370
750
1,070
710
870
630
580
640
950
940
670
400
1,300
960
650
700
690
860
630
650
1,040
730
680
COD,
Prim.
Effl.
420
400
490
400
420
230
230
340
330
320
150
320
440
360
390
300
320
300
460
200
210
320
220
220
160
370
97
280
460
320
440
500
480
mg/1
Filter
Effl.
190
230
190
110
130
210
210
240
270
160
370
160
160
220
200
140
170
100
210
180
300
320
160
440
330
150
440
230
130
84
240
180
200
Soluble COD,
mg/1
Sec.
Effl.
110
97 ,
98
84
87
120
110
91
150
100
97
110
110
130
110
85
87
89
130
110
100
-130
110
130
86
92
97
92
69
72
100
100
110
Prim.
Effl.
220
' 170
260
280
260
99
89
180
130
210
53
210
190
180
180
130
100
120
120
110
71
200
250
74
49
130
63
97
170
160
94
120
170
Sec.
Effl.
56
67
77
54
58
82
62
, 67
85
. 68
67
77
64
67
69
63
70
65
63
65
64
68
65
76
57
71
70
71
58
63
63
54
67
b,
x 3,785 = m /day.
'Flow meter inoperative; estimated flow.
171
-------
TABLE E-2.
DAILY VALUES FOR SUSPENDED SOLIDS, VOLATILE SUSPENDED
SOLIDS, WATER TEMPERATURE, pH, DISSOLVED OXYGEN, AND
ALKALINITY
IVซCO
3/15/76
3/16/76
3/17/76
3/22/76
3/23/76
3/24/76
3/29/76
3/30/76
3/31/76
4/5/76
4/6/76
4/7/76
4/1J/76
4/13/76
4/14/76
4/19/76
A/20/76
4/21/76
4/26/76
4/27/76
4/28/76
5/3/76
5/4/76
5/5/76
5/10/76
5/11/76
5/12/76
5/17/76
5/18/76
5/19/76
5/24/76
5/25/76
5/26/76
5/31/76
6/1/76
6/2/76
6/7/76
6/8/76
6/9/76
6/14/76
6/15/76
6/16/76
6/21/76
6/22/76
6/23/76
6/28/76
6/29/76
6/30/76
7/5/76
7/6/76
7/7/76
7/12/76
7/13/76
7/14/76
7/19/76
7/20/76
7/21/76
7/26/76
7/27/76
7/28/76
8/2/76
8/3/76
8/4/76
Suspended solids, mg/1
RAW
Infl.
300
500
460
380
380
270
290
270
300
240
320
250
210
350
330
280
270
200
280
290
340
380
72
260
240
300
290
760
420
140
280
330
440
280
340
340
450
250
260
300
280
250
400
320
240
270
500
350
410
410
400
500
440
440
750
480
430
520
520
580
Prim.
Effl
220
170
220
320
150
150
100
230
270
120
190
270
120
160
190
130
110
120
84
130
170
110
160
320
120
140
60
160
180
140
140
140
39
57
60
150
120
130
96
80
94
140
200
110
140
160
200
100
130
120
120
160
180
160
130
96
140
160
160
160
240
260
Filter
Effl.
140
210
120
110
96
120
120
180
140
130
140
220
160
130
150
200
120
100
110
92
92
150
_
140
140
150
84
120
170
220
150
180
190
280
180
160
170
130
140
140
120
160
200
130
130
80
110
80
140
88
110
240
130
220
190
ISO
170
110
120
130
180
190
280
Sec.
Effl.
42
42
31
37
37
28
28
32
52
21
28
-
24
25
26
29
32
22
30
30
25
27
_
26
22
33
16
18
44
25
32
22
25
11
7
20
90
56
32
23
25
26
42
40
140
30
-
17
5
20
17
32
32
33
21
29
8
20
30
29
38
44
36
Volatile suspended
solids, mg/1
Raw
Infl.
210
360
340
320
300
230
220
210
250
200
250
220
no
310
260
210
210
180
260
270
260
_
300
68
200
180
200
240
550
300
96
210
220
320
210
230
240
290
180
190
250
200
210
290
240
180
180
380
260
320
310
290
350
290
310
300
290
260
340
370
390
Prim.
Effl.
160
96
140
260
120
110
72
170
200
110
150
,-, 170
120
130
170
96
90
100
84
130
170
80
_
130
260
96
110
60
100
100
84
100
100
31
46
48
88
88
84
80
72
60
100
160
100
92
110
140
64
96
84
120
160
180
110 '
100
96
96
150
160
160
230
230
Filter
Effl,
84
110
60
96
64
110
96
120
96
110
110
160
140
120
110
140
92
80
52
92
92
100
_
100
92
130
64
100
84
110
88
UP
140
. 170
lip '
92
120
40
96
110
84
96
160
96
110
44
76
44
96
48
72
240
130
210
140
' 100
120
72
120
120
170
180
230
Sec.
Effl.
29
35
27
28,
37
24
23
18
32
17
19
-
23
21
24
20
24
17
30
26
23
17
-
19
16
25
14
17
27
15
21
20 .
23
9
6
11
60
48
24
16
18
21
32
29
120
18
-
11
4
1?
11
29
32
27
18
19
8
14
30
23
36
42
32
Water
temperature,
C
Prim.
Effl.
25
26
26
25
26
26
25
26
25
26
26
-
-
26
27
27
24
27
-
28
27
27
27
2f?
29
29
29
-
28
28
28
28
28
28
29
30
-
28
28
29
_
30
-
-
30
28
30
-
.. 28
30
30
31
31
30
30
~
Filter
Effl.
24
26
26
24
24
24
21
25
24
24
23
_
-
21
25
25
22
25
~
26
27
25
26
27
29
27
27
~
26
27
27
27
27
27
28
28
-
27
27
28
-
30
~
-
29
27
-
28
29
29
29
30
30
28
~
pH
Prim.
Effl.
6.4
6.7
6.7
7.1
6.6
6.8
7.1
7.0
6.8
7.1
6.9
6.9
~
7.0
6.9
7.0
7.2
6.8
~
7.0
8.6
7.3
7.1
6,7
6.9
7.1
6.7
~
7,1
7.0
7.1
9.3
7.2
7.1
6.8
6.9
-
6.9
6.9
6.7
-
6.7
~
-
7.1
8.7
7.0
~
6.8
6.7
6.5
6.6
: -
9.5
~
Filter
Effl.
7.3
7.4
7.3
7.6
7.4
7.7
7.8
7.8
7.8
8.0
7.8
7.9
_
^
6.3
7.3
7.6
7.6
7.4
~ ,
7.4
8.1
7.7
7.5
7.1
7.3
7.6
7.6
"*
7.6
8.1
8.1
8.6
7.7
7.7
7.5
7.8
-
7.6
7.6
7.4
-
7.2
~
-
7.8
8.0
"
8.0
7.7
7.5
7.5
-
8.3
"
Dissolved Alkalinity,
oxygen, mg/1 as
mg/1 CaC03
Filter
Effl.
6.4
7.0
5.6
6.4
6.1
5.2
6.8
6.5
6.6
7.6
6.3
6.4
~"
~
7.0
7.0
6.2
7.7
7.7
7.7
4.2
6.2
6.4
6.3
6.2
4.3
5.2
5.5
6.6
5.4
5.4
6.4
6.3
6.0
6,0
6.0
-
6.7
6.4
6.4
-
5.8
-
-
5.1
~
5.5
5.6
3.8
~
4.2
"
Prim.
Effl.
200
-
200
200
220
"
200
"
190
190
"
-
-
-
180
200
"
190
210
190
-
210
180
190
~
~
-
200
240
"
230
_
200
350
"
Sec.
Effl.
110
130
120
110
140
150
130
140
150
160
130
110
110
110
65
98
110
86
78
81
100
~
94
46
110
120
160
160
160
140
140
140
130
170
130
120
92
110
110
100
95
110
92
110
~
110
92
120
130
150
150
170
230
160
120
120
130
130
300
340
290
(continued on next page)
172
-------
TABLE E-2. (continued)
Date
8/9/76
8/10/76
8/11/76
8/16/76
8/17/76
8/18/76
8/23/76
8/24/76
8/25/76
8/30/76
8/31/76
9/1/76
9/6/76
9/7/76
9/8/76
9/13/76
9/14/76
9/15/76
9/20/76
9/21/76
9/22/76
9/27/76
9/28/76
9/29/76
10/4/76
10/5/76
10/6/76
10/11/76
10/12/76
10/13/76
10/18/76
10/19/76
10/20/76
10/25/76
10/26/76
10/27/77
11/1/76
11/2/76
11/3/76
11/8/76
11/9/76
11/11/76
11/15/76
11/16/76
11/17/76
11/22/76
11/23/76
11/24/76
11/29/76
11/30/76
12/1/76
12/6/76
12/7/76
12/8/76
12/13/76
12/14/76
12/15/76
12/20/76
12/21/76
12/22/76
Suspended solids, mg/1
.Raw
Infl.
500
610
740
720
700
840
1,000
1,010
880
910
900
510
500
-
540
500
640
600
660
510
540
470
670
840
890
800
960
550
380
500
320
360
360
370
320
380
300
300
400
240
320
-
420
520
460
430
-
-
460
420
280
400
370
370
350
330 .
270
370
470
-
Prim.
Effl.
250
190
200
300
310
280
180
200
150
160
170
210
130
-
130
96
110
160
130
160
160
120
110
200
200
230
160 '
190
120
180
130
120
150
110
88
76
160
60
100
84
120
-
130
200
140
140
-
-
200
140
120
170
140
140
92
130
150
170
110
-
Filter
Effl.
140
190
200
270
320
300
270
220
120
180
160
140
92
-
184
120
120
200
200
160
180
96
130
220
230
290
200
200
180
110
140
120
200
92
60
64
110
130
96
96
84
-
160
270
190
140
-
-
160
150
100
170
60
88
100
120
190
230
170
-
Sec.
Effl.
38
23
32
62
58
82
54
68
60
58
58
58
36
-
50
30
24
44
48
56
60
34
38
50
66
64
62
60
44
46
38
56
40
24
22
44
24
20
24
28
20
-
42
38
34
46
-
-
60
58
22
34
28
30
12
14
24
34
28
-
Raw
Infl.
290
360
450
510
500
560
580
590
420
680
640
300
280
-
370
320
410
400
430
300
340
330
410
550
270
530
520
380
290
360
260
290
300
280
240
310
220
240
300
230
290
-
320
420
370
360
- -
-
380
320
240
310
300
280
280
270
230
300
400
-
Volatile suspended
solids, rag/1
Prim.
Effl.
210
160
180
260
270
230
180
180
130
150
130
180
110
-
100
96
110
150
92
130
120
120
100
ISO-
140
170
140
160
120
140
-120
110
150
72
68
56
140
56
68
84
120
-
110
170
130
140
-
-
150
120
110
130
120
120
88
110
120
160
110
-
Filter
Effl.
110
160
180
250
280
270
250
190
100
160
130
120
72
:-
170
84
100
140
150
110
150
96
100
200
180
210
160
170
170
96
120
100
160
68
44
56
88
96
80
96
84
-
140
220
150
130
-
-
110
120
84
120 '
56
68
92
110
160
190
140
-
Sec.
Effl.
30
21
32
62
58
82
54
58
54
54
46
52
31
-
45
20
24
44
32
32
48
34
38
50
54
48
60
50
44
46
38
54
40
22
20
40
24
18
12
28
20
' -
40
36
34
46
-
-
44
46
20
26
28
22
12
14
24
34
28
-
Water
tempera ture ,
C
Prim.
Effl.
29
31
29
29
-
-
_
30
30
30
_
30
_
30
30
30
_
30
29
-
-
29
-
29
_
28
-
28
28
-
28
_
28
_
_
28
_
27
28
_
28
-
27
28
25
25
26
25
25
_
25
23
23
-
23
23
23
23
_
24
Filter
Effl.
29
31
29
29
-
-
_
30
30
30
_
30
_
30
29
29
_
30
29
_
-
28
-
28
_
28
-
28
28
-
28
_
28
_
_
25
_
25
26
_
27
-
25
26
24
22
23
22
23
_
23
20
22
-
21
22
21
21
_
21
pH
Prim.
Effl.
9.0
6.2
9.2
8.9
-
-
_
5.9
9.1
9.5
_
8.6
_'
10.3
6.9
9.8
_
9.3
8.2
_
8.7
9.9
-
8.6
_
8.2
-
7.1
-
6.9
_
6.7
_
_
7.2
7.1
6.9
-
_
_
6.9
7.0
6.6
6.8
6.8
6.9
6.9
7.1
_
6.8
7.0
6.9
-
6.9
7.0
6.9
7.0
6.9
7.2
Filter
Effl.
9.1
8.0
8.3
8.3
-
-
_
7.6
8.3
8.2
_
8.2
_
8.4
7.9
8.5
_
8.5
8.1
_
8.2
8.5
-
8.1
_
8.1
-
7.7
_
-
7.5
_
7.2
_
_
7.0
7.0
.6.7
-
_
_
6.7
6.4
7.2
7.4
7.4
7.7
7.8
7.5
_
7.7
7.4
7.5
-
7.4
7.3
7.6
7.4
7.6
7,1
Dissolved Alkalinity,
oxygen, mg/1 as
mg/1 CaCO3
Filter
Effl.
1.2
-
-
1.2
_
-
_
0
1.2
0.5
_
1.4
_
0
1.0
3.1
_
-
5.2
_
4.4
6.1
-
4.6
_
6.0
-
5.8
-
-
6.2
_
6.5
_
_
7.0
_
6.6
6.4
_
_
-
5.6
6.6
5.6
6.6
_
-
7.8
-
5.6
6.0
5.7
-
6.0
6.1
7.4
6.0
7.0
Prim.
Effl.
_
370
-
_
-
500
370
-
-
_
430
-
_
-
-
340
_
-
_
380
-
_
-
400
380
.
-
_
250
-
_
_
220
190
_
-
_
180
-
_
_
-
220
_
-
_
-
_
230
-
_
-
-
250
_
-
_
240
Sec.
Effl.
300
340
400
390
410
460
370
370
390
370
410
400
260
-
340
280
360
350
290
300
320
340
280
350
320
360
430
300
180
190
140
140
130
80
120
140
66
82
81
76
80
-
55
66
.75
100
-
-
140
190
180
110
_
-
110
130
110
72
88
-
(continued on next page)
173
-------
TABLE E-2. (continued)
0ปtป
U/27/76
12/28/76
IS/29/76
1/3/77
1/4/77
1/5/77
1/10/77
1/11/77
1/12/77
1/17/77
1/18/77
1/19/77
1/24/77
1/25/77
V26/77
1/31/77
2/1/77
2/2/77
2/7/77
2/ป/77
2/9/77
2/14/77
2/15/77
2/16/77
2/21/77
2/22/77
2/23/77
2/28/77
3/V77
3/2/77
3/7/77
3/8/77
3/9/77
3/14/77
3/15/77
3/16/77
Suspended s
Raw
Intl.
580
580
-
330
300
870
470
750
420
500
470
410
260
200
520
680
360
480
330
290
280
440
570
310
170
1,070
380
260
290
230
540
420
410
630
390
370
Prim.
Effl.
180
110
-
110
120
100
130
120
110
130
160
150
84
92
88
180
92
140
130
150
160
240
140
-
420
100
-
_
190
-
240
330
150
230
320
190
tolids, mg/1
Filter
Effl.
160
130
-
160
120
100
140
140
140
170
160
190
150
56
120
110
130
150
140
110
92
130
96
170
150
180
300
230
100
160
180
130
120
250
140
140
Sec.
Effl.
22
-
28
18
13
52
27
26
46
36
40
24
14
36
24
26
12
22
15
14
24
20
19
25
23
18
6
15
18
26
29
17
32
39
30
Volatile suspended
solids, mg/1
Raw
Infl.
470
460
-
260
260
680
340
600
310
330
330
300
220
190
440
520
280
330
250
220
220
370
460
250
120
850
300
220
260
190
400
280
270
470
310
280
Prim.
Effl.
140
96
-
96
96
76
84
92
96
68
120
110
84
92
88
150
76
96
76
92
120
200
100
-
370
88
-
_
170
-
180
250
100
160
270
150
Filter
Effl.
110
100
-
100
100
100
80
96
120
100
120
150
140
56
120
80
96
96
72
64
52
110
72
120
130
130
280
190
92
150
140
68
76
170
110
120
Sec.
Effl.
20
-
26
17
13
30
20
22
30
34
28
24
14
36
18
20
6
10
9
6
24
20
16
24
21
18
6
15
11
20
14
6
21
31
28
Water
temperature ,
C
Prim.
Effl.
21
21
20
22
21
22
22
21
22
-
22
24
23
24
22
-
23
23
22
23
24
25
24
-
24
23
24
24
20
25
25
-
25
-
22
Filter
Effl.
18
19
19
20
19
19 .
19
19
18
-
19
20
21
20
20
-
20
23
21
21
24
24
24
-
21
20
20
20
19
23
24
-
23
-
21
pH
Prim.
Effl.
7.6
7.2
6.9
7.3-
6.7
6.7
6.5
6.5
6.6
6.5
-
6.6
-
6.5
6.5
6.8
-
6.7
6.8
7.3
7.2
6.7
6.9
6.6
6.9
6.9
-
6.7
6.5
6.8
6.6
6.7
-
6.2
-
7.0
Filter
Effl.
7.6
7.7
7.2
7.8
7.0
7.3
6.9
7.1
7.0
6.9
-
6.9
-
7.0
7.0
7.2
-
7.1
7.1
7.9
6.4
7.2
7.2
7.0
7.3
7.3
-
7.0
7.3
6.2
7.4
7.2
-
7.3
-
7.5
Dissolved Alkalinity,
oxygen, mg/1 as
mg/1 CaC03
Filter
Effl.
7.6
7.0
6.9
7.2
7.4
6.8
7.8
7.0
7.8
-
7.4
-
7.0
7.0
7.4
-
7.6
5.6
14.6
7.8
6.7
7.2
7.9
-
8.2
S.9
7.8
7.6
6.8
7.7
8.4
-
7.1
-
6.4
Prim.
Effl.
-
-
-
-
250
220
-
~
-
190
-
-
-
170
230
-
-
-
210
-
-
-
-
200
-
-
-
230
-
-
-
210
210
-
"
Sec.
Effl.
61
78
~
34
80
86
27
78
84
69
70
70
48
65
59
46
62
44
75
100
89
35
69
48
48
42
58
39
64
88
19
65
66
37
45
43
174
-------
TABLE E-3.
DAILY VALUES FOR PHOSPHORUS, TOTAL KJELDAHL NITROGEN,
AMMONIA NITROGEN, AND NITRATE NITROGEN
Date
3/15/76
3/16/76
3/17/76
3/22/76
3/23/76
3/24/76
3/29/76
3/30/76
3/31/76
4/5/76
4/6/76
4/7/76
4/12/76
4/13/76
4/14/76
4/19/76
4/20/76
4/21/76
4/26/76
4/27/76
4/28/76
5/3/76
5/4/76
5/5/76
5/10/76
5/11/76
5/12/76
5/17/76
5/18/76
5/19/76
5/24/76
5/25/76
5/26/76
5/31/76
6/1/76
6/2/76
6/7/76
6/8/76
6/9/76
6/14/76
6/15/76
6/16/76
6/21/76
6/22/76
6/23/76
6/28/76
6/29/76
6/30/76
7/5/76
7/6/76
7/7/76
7/12/76
7/13/76
7/14/76
7/19/76
7/20/76
7/21/76
7/26/76
7/27/76
7/28/76
8/2/76
8/3/76
8/4/76
Total phosphorus,
mg/1
Raw
Infl.
10
8.1
8.0
7.4
7.9
-
5.6
6.0
6.9
7.5
6.6
6.6
5.9
5.6
7.0
8.8
6.0
6.6
7.1
11
8.4
8.5
11
8.6
5.8
6.2
5.7
7.0
6.4
7.2
6.6
7.3
6.7
7.1
6.6
6.2
-
-
-
6.6
6.7
5.5
6.5
6.0
6.2
11
6.1
7.0
8.9 '
7.9
5.8
9.4
7.8
6.7
7.0
7.1
8.7
8.0
6.6
7.9
4.6
4.7
5.3
Prim.
Effl.
7.8
6.9
6.2
6.9
6.0
6.1
6.6
5.9
6.7
8.1
6.8
5\ 5
5.3
-6.0
6.7
6.9
5.5
5.6
6.5
8.4
8.0
7.4
8.9
7.8
5.4
5.7
5.1
6.8
5.6
5.8
5.7
6.0
5.6
6.0
4.4
6.2
_
_
-
7.0
7.5
6.4
7.8
6.0
6.0
12
6.0
6.7
6.9
6.0
5.5
7.4
6.5
5.5
5.4
'5.4
5.8
5.9
5.3
5.8
2.3
2.5
3.2
Sec.
Effl.
6.8
6.2
5.4
4.9
5.2
5.9
5.8
5.8
6.2
6.7
5.6
-
5.3
5.6
5.6
6.7
5.2
5.2
5.9
8.1
7.3
7.0
6.7
8.5
4.5
5.2
5.1
5.5
4.9
4.6
4.8
5.3
4.6
5.3
4.1
5.4
_
_
-
6.3
6.4
6.2
6.6
5.6
5.4
11
-
6.2
7.4
5.9
4.7
6.4
6.3
4.7
3.3
5.4
6.1
5.8
5.2
5.6
1.3
1.7
1.9
Total Kjeldahl
nitrogen,
mg/1
Raw
Infl.
25
31
33
37
36
-
25
25
30
24
29
32
25
25
27
29
22
25
22
22
28
33
34
35
19
23
24
28
29
33
27
26
27
26
29
29
_
_
-
27
23
21
27
24
24
25
24
25
34
27
23
30
25
21
34
36
36
35
30
26
28
29
33
Prim.
Effl.
25
25
22
39
27
27
26
28
26
32
29
30
20
23
28
22
22
20
19
19
22
31
28
34
27
24
21
24
24
25
22
21
22
23
20
21
_
_
-
23
25
24
22
19
20
19
19
23
30
16
18
23
19
20
29
27
25
26
30
22
31
41
38
Sec.
Effl.
17
17
15
13
17
17
15
16
19
20
16
-
11
9.4
9.8
6.9
7.9
8.1
4.9
2.2
5.3
12
10
11
5.5
9.3
10
13
12
12
10
8.9
8.5
12
8.1
8.5
_
_
-
8.5
9.9
7.5
8.6
8.5
8.5
12
_
9.4
9.8
4.9
-
8.4
7.6
7.1
8.2
11
14
11
18
16
21
30
25
Raw
Infl.
16
15
16
16
20
-
16
16
22
17
15
20
20
18
18
16
11
12
14
14
15
26
15
17
12
9.3
9.0
13
12
13
13
12
11
11
12
14
_
_
-
17
16
9.8
17
14
14
15
18
17
23
17
17
17
15
15
15
17
19
19
19
19
9.8
8.3
11
Ammonia
nitrogen
mg/1
Prim.
Effl.
15
J3
12
14
16
15
12
15
14
20
14
16
15
15
17
14
14
11
13
13
13
22
18
17
16
13
10
14
14
15
15
14
13
16
14
16
_
_
-
17
16
17
15
17
12
13
14
15
25
11
9.9
13
12
11
13
' 16
15
15
18
17
17
23
17
Nitrite
, nitrogen
mg/1
Sec. Raw Prim.
Effl. Infl. Effl.
8.6 <0.1 <0.1
10 < 0. 1 < 0. 1
7.6 <0.-1 <0.1
6.1 <0.1 <0.1
9.6 <0.1 <0.1
11 - 0.1
9.7 <0.1 <0.1
10 <0.1 <0.1
12 <0.1 <0. 1
13 <0.1 <0.1
8.1 0.1 <0.1
< 0.1 <0.1
5.7 <0.1 <0.1
4.7 0.1 0.1
5.4 < 0.1 < 0. 1
2.4 0.1 0.1
3.4 0.1 0.1
3.6 0.1 0.1
1.8 <0.1 <0.1
2.3 <0.1 <0.1
1.4 < 0.1 < 0.1
6.7 *C 0. 1 < 0.1
5.4 < 0.1 < 0.1
4.7 <0.1 <0.1
0.7 <0.1 <0.1
3.6 <0.1 <0.1
5.1 <0.1 <0.1
7.7 < 0.1 <0 1
7.8 <0.1 <0.1
7.4 <0.1 <0.1
7.0 < 0.1 < 0.1
5.9 <0.1 <0.1
5.3 <0.1 <0.1
8.2 < 0.1 < 0.1
5.7 <0.1 <0.1
6.4 <0.1 <0.1
_
-
-
3.6 < 0.1 < 0.1
3.1 <0.1 <0.1
2.8 <0.1 <0.1
2.8 <0.1 <0.1
3.3 0.1 <0.1
3.3 0.1 0.1
4.5 < 0.1 < 0.1
- < 0 1 < 0 1
4.2 <0.1 < 0.1-
5.6 < 0.1 < 0.1
1.8 <0.1 <0.1
2.2 <0.1 <0.1
2.9 0.1 0.1
2.8 0.1 0.1
2.0 0.1 0.1
1.6 < 0.1 < 0.1
8.0 <0.1 <0.1
6.7 <0.1 <0.1
6.4 < 0.1 < 0.1
10 <0.1 <0.1
9.7 <0.1 <0.1
8.8 < 0.1 < 0.1
15 < 0.1 < 0.1
10 <0.1 <0.1
Sec.
Effl.
0.2
0.2
0.1
0.1
0.2
0.2
0.2
0.1
0.2
0.2
0.2
-
0.3
0.2
0.3
0.1
0.3
0.4
0.1
^0.1
^0.1
<0.1
< 0 . 1
^0.1
< 0.1
0.1
0.1
0.4
0.5
0.5
0.6
0.6
0.6
0.8
0.7
0.7
_
_
-
0.7
1.0
0.5
0.4
0.5
0.3
0.5
0.4
0.9
0.3
0.2
0.3
0.2
0.2
0.1
0.2
0.2
0.1
0.1
0.1
0.2
0.2
0.2
Nitrate
nitrogen,
mg/1
Raw Prim. Sec.
Infl. Effl. Effl.
< 0.1 < 0.1 0.4
<0.1 <0.1 0.3
<0.1 <0.1 0.3
<0.1 <0.1 0.2
<0.1 <0.1 0.2
<0.1 0.3
< 0.1 < 0.1 0.3
<0.1 <0.1 0.3
<0.1 <0.1 0.2
< 0.1 < 0.1 0.3
0.1 <0.1 0.2
<0.1 <0.1
0.1 0.1 0.5
<0.1 <0.1 0.5
<0.1 < 0 . 1 0.5
0.1 0.1 1.0
0.1 0.1 0.7
0.1 0.1 0.6
< 0 . 1 < 0 . 1 10
<0.1 <0.1 7.2
<0.1 <0.1 7.5
<0.1 <0.1 8.9
<0.1 <0.1 8.1
0.1 <0.1 7.3
<0.1 <0.1 4.3
<0.1 <0.1 3.8
0.1 0.1 2.4
<0.1 <0.1 3.1
<0.1 <0.1 2.2
<0.1 <0.1 1.7
0.1 0.1 5.8
0.1 0.1 5.7
0.2 0.1 5.3
<0.1 <0.1 6.8
0.2 <0.1 . 4.6
0.1 <0.1 5.0
_ , -
_
-
0.2 < 0.1 0.9
< 0.1 <0.1 0.1
< 0. 1 < 0.1 0.7
< 0.1 < 0. 1 1.8
< 0. 1 0.5 0.9
< 0.1 <0.1 0.7
0.1 <0.1 2.1
0.1 XO.l 1.2
0.1 0.1 3.2
0.1 <0.1 1.0
0.1 <0.1 0.5
< 0.1 < 0.1 1.4
< 0.1 < 0.1 0.5
<0.1 <0.1 0.3
0.1 <0.1 0.2
0.1 <0.1 0.5
0.1 0.1 0.8
< 0.1 < 0.1 ; 0.6
< 0:1 < 0.1 0.4
<0.1 <0.1 , 0.3
< 0. 1 < 0.1 < 0. 1
< 0~1 <0.1 <0.1
<0.1 <0.1 <0.1
(continued on next page)
175
-------
TABLE E-3. (continued)
Dซto
8/9/76
8/10/76
/11/76
8/16/76
8/17/76
8/18/76
8/23/76
8/24/76
8/J5/76
a/30/16
8/31/76
9/1/76
9/6/76
9/7/76
9/8/76
9/13/76
9/14/76
9/15/76
9/20/76
9/21/76
t/22/76
9/27/76
9/28/76
9/29/76
10/4/76
10/S/76
10/6/76
10/11/76
10/12/76
10/13/76
10/18/76
10/19/76
10/20/76
10/25/76
10/26/76
10/27/76
11/1/76
11/2/76
11/3/76
11/8/76
11/9/76
11/10/76
11/15/76
11/16/76
11/17/76
11/23/76
11/23/76
11/24/76
11/29/76
11/30/76
13/1/76
13/6/76
12/7/76
12/8/76
12/13/76
12/14/76
12/15/76
12/20/76
1J/21/16
12/22/76
12/27/76
13/28/76
12/29/76
Total
RAW
Infl.
5.3
5.8
5. 8
7.8
6.4
6.9
6.4
5.8
6.7
5.9
6.3
7.5
7.6
-
3.9
7.8
6.2
5.7
5.1
4.9
S.4
5.6
6.3
7.7
11
10
12
6.2
6.9
8.1
8.4
11
7.0
6.3
5.8
5.6
7.4
7.0
6.7
6.3
6.2
8.6
8.6
13
13
33
-
-
9.0
8.7
9.3
9.9
8.6
8.4
8.9
8.7
8.3
29
10
-
16
13
-
phosphorus,
mg/1
Prim.
Effl.
4.0
3.2
3.2
4.2
4.6
4.1
2.6
3.1
3.7
2.2
2.7
3.7
4.0
-
2.1
2.9
3.1
3.1
2.7
3.4
3.3
3.2
3.9
4.0
5.4
6.0
6.3
4.4
5.6
6.4
6.3
6.1
6.1
6.7
7.1
6.9
8.3
5.8
7.3
7.4
6.8
7.3
7.3
9.1
8.7
31
-
-
7.3
7.3
6.9
8.2
7.7
8.3
7.9
7.8
8.1
9.3
7.6
-
11
9.6
-
Sec.
Effl.
2.0
2.4
2.2
3.4
2.8
2.6
1.5
2.2
2.8
1.6
1.9
2.6
4.7
-
1.4
2.3
1.7
2.7
2.2
2.2
2.3
2,9
3.7
3.1
4.5
4.6
3.8
3.2
4.9
5.5
6.1
5.7
4.9
6.1
6.0
6.1
8.2
6.9
6.9
7.2
6.3
5.9
5.9
6.8
7.0
11
-
-
5.8
5.6
6.3
7.7
6.2
7.4
7.4
6.7
7.0
8.7
6.9
-
9.5
8.6
-
Total Kjeldahl
nitrogen,
mg/1
Raw
Infl.
28
32
37
38
49
40
42
37
32
27
30
34
27
-
28
27
24
22
31
24
34
30
36
36
43
67
63
27
33
37
31
54
33
31
29
29
33
37
32
32
33
36
36
43
41
33
-
-
40
43
45
38
40
41
57
53
37
35
47
-
50
65
-
Prim.
Effl.
42
42
50
47
52
55
35
35
40
32
38
40
34
-
31
19
25
29
20
25
23
26
26
31
33
46
42
25
27
32
27
31
27
24
28
27
33
26
33
31.
32
29
29
34
33
31
.-
-
34
36
32
29
31
37
52
47
37
36
29
-
47
40
-
Sec.
Effl.
27
32
38
34
34
41
27
30
34
26
30
32
32
~
22
12
14
21
12
13
16
14
18
18
15
21
25
13
18
18
15
20
16
9.4
11
12
7.4
6.8
9.5
6.1
6.4
8.7
8.7
12
13
11
-
-
14
21
15
40
10
IS
10
30
8.4
6.8
7.2
8.0
5.9
-
Ammonia
nitrogen,
mg/1
Raw
Infl.
9.1
10
12
13
16
19
11
9.1
9.9
9.1
9.7
11
15
~
10
14
12
12
12
10
10
10
12
12
13
16
14
10
16
15
'17
19
17
17
17
19
19
22
20
18
16
-
18
20
20
20
-
-
27
24
25
25
23
24
25
27
24
17
22
-
31
34
-
Prim.
Effl.
22
24
29
21
25
32
19
19
25
17
20
26
23
~
17
9.7
11
11
11
11
11
12
13
14
15
15
21
12
18
19
17
17
16
15
17
18
22
18
23
20
19
-
18
19
21
21
-
-
22
22
21
20
20
26
23
26
21
19
19
-
34
29
-
Sec.
Effl.
16
18
21
19
18
25
14
14
20
14
15
21
21
~
11
3.1
4.9
7.0
3.8
3.7
5.4
6.6
7.3
6.7
6.5
7.7
12
5.6
9.1
11
8.0
8.7
6.9
4.1
5.7
6.1
176
1.8
2.9
2.0
1.1
-
0.5
4.3
5.8
3.8
-
-
8.3
15
11
5.5
5.2
9.6
3.1
7.3
2.1
2.0
1.2
~
2.3
0.7
-
Nitrite
nitrogen,
mg/1
Raw Prim. Sec.
Infl. Effl. Effl.
<0.1 <0.1 0.2
<0.1 <0.1 0.2
<0.1 <0.1 0.2
<0.1 {0.1 {0.1
<0.1 <0.1 <0.1
<0.1 <0.1 <0.1
<0.1 <0.1 0.2
<0.1 <0.1 0.2
<0.1 <0.1 <0.1
<0.1 <0.1 0.3
<0.1 {0.1 {0.1
<0.1 {0.1 {0.1
<0.1 <0.1 0.7
_
{0.1 <0.1 <0.1
<0.1 <0.1 0.3
<0.1 <0.1 0.2
<0.1 <0.1 0.3
<0.1 <0.1 0.3
<0.1 {0.1 0.2
{0.3. {0.1 0.3
<0.1 <0.1 0.4
{0.1 <0.1 0.4
<0.1 <0.1 0.4
<0.1 <0.1 0.6
0.1 <0.1 0.6
<0.1 <0.1 0.5
<0.1. <0.1 0.4
<0.1 <0.1 0.7
<0.1 <0.1 0.8
<0.1 <0.1 0.8
<0.1 <0.1 0.7
<0.1 <0.1 0.6
<0.1 <0.1 0.3
<0.1 <0.1 0.2
<0.1 <0.1 0.4
0.1 <0.1 0.2
<0.1 <0.1 0.1
<0.1 <0.1 0.1
<0.1 {0.1 <0.1
{0.1 <0.1 {0.1
_ - -
<0.1 <0.1 <0.1
<0.1 <0.1 0.1
<0.1 <0.1 0.4
<0.1 <0.1 0.3
<0.1 <0.1 0.6
<0.1 <0.1 0.4
<0.1 <0.1 0.6
<0.1 <0.1 0.4
<0.1 <0.1 0.6
<0 . 1 <0 . 1 0.5
<0.1 {0.1 0.2
<0.1 <0.1 0.4
<0.1 <0.1 0.2
<0.1 <0.1 0.2
0.3 <0.1 0.1
{0.1 {0 . 1 {0 . 1
{0.1 {0.1 {0 . 1
_ _ _
{0 . 1 {0 . 1 {0 . 1
<0.1 <0.1 <0.1
_ _ _
Nitrate
nitrogen,
mg/1
Raw Prim: Sec.
Infl. Effl. Effl.
<0.1 <0.1 0.1
<0.1 <0.1 <0.1
<0.1 0.1 {0.1
0.1 <0.1. { 0.1
{0.1 {0.1 >0.1
{ o . i {Q.I {Q.I
{0.1 {0.1 {0.1
{0.1 {0.1 {0.1
{0.1 {0.1 {0.1
{0.1 {0.1 {0.1
{0.1 {Q.l {0.1
{0.1 {0.1 {0.1
{0.1 {0.1 0.1
~ ~ ~
{0.1 {0.1 0.1
{0.1 {0.1 {0.1
{0.1 {0.1 {Q.l
{0.1 {0.1 {0.1
{0.1 {0.1 0.2
{0.1 {0.1 0.1
{0.1 {0.1 0.1
{0.1 {0.1 0.1
{o.i {o.i {o.i
{o.i {o.i {o.i
{0.1 {0.1 0.1
{0.1 {0.1 {0.1
{0.1 {0.1 {0.1
{0.1 {0.1 0.2
{0.1 {0.1 0.2
{0.1 {0.1 0.1
0.1 0.1 0.7
0.1 0.1 0.3
{071 {0.1 0.2
0.1 0.1 1.1
0.1 0.1 0.6
{0.1 {0.1 0.5
0.1 {0.1 1.9
{Q.l {Q.l 1.2
{0.1 0.1 1.1
0.1 0.1 1.3
0.1 {0.1 0.7
_
{0.1 {0.1 1.5
{0.1 {0.1 1.4
Oil {0.1 0.9
{0.1 {0.1 1.2 '
0.1 0.1
0.1 0.1
0.1 0.1 0.6
0.1 0.1 0.4
0.1 {0.1 0.3
{0.1 <0.1 {Q.l
{0.1 {0.1 {0.1
{Q.l {0.1 {O:i
{0.1 {0.1 {0.1
{0.1 {0.1 {0.1
{0.1 {0.1 {0 J 1
{0.1 {0.1 1.5
{0.1 {0.1 1.2
_
{0.1 {0.1 3.1
{0.1 {0.1 1.8
_ _
(continued on next page)
176
-------
TABLE E-3. (continued)
Date
1/3/77
1/4/77
1/5/77
1/10/77
1/11/77
1/12/77
1/17/77
1/18/77
1/19/77
1/24/77
1/25/77
1/26/77
1/31/77
2/1/77
2/2/77
2/7/77
2/8/77
2/9/77
2/14/77
2/15/77
2/16/77
2/21/77
2/22/77
2/23/77
2/28/77
3/1/77
3/2/77
3/7/77
3/8/77
3/9/77
3/14/77
3/15/77
3/16/77
Total phosphorus,
mg/1
Raw
Infl.
11
9.5
11
10
12
8.4
ll
8,4
11
6.2
6.6
9.7
is
7i3
8.4
7.7
6.9
10
12
15
11
5.7
-11
9.4
8.9
8.0
9.1
15
8.5
8.2
12
8.4
8.6
Prim.
Effl.
9.1
8.5
718
5.8
5.5
-
_
5.6
-
5.7
-
5.6
7.8
6.7
6.6
8.0
7.8
7.5
9.4
8.6
-
5.9
6.2
-
-
7.4
-
9.3
7.6
6.9
7.4
12
6.7
Sec.
Effl.
5.4
7.0
5.6
7.5
. 7.0
5.7
6.8
5.3
5.8
6.8
5.9
6.3
6.2
5.6
5.3
6.8
6.1
5.7
8.2
7.4
3.2
6.4
6.2
6.1
6.6
5.7
7.8
9.1
6.3
5.8
6.8
6.0
5.6
Total Kjeldahl
nitrogen,
mg/1
Raw
Infl.
56
49
81
43
46
45
50
0
56
44
71
50
63
45
40
30
35
32
40
51
37
24
60
52
41
46
32
54
47
36
44
49
39 '
Prim.
Effl.
44
44
48
33
29
-
_
47
-
42
-
39
49
42
40
34
30
40
37
49
-
28
30
-
_
41
-
4o
44
31
30
45
38
Sec.
Effl.
8.9
6:3
6.4
7.8
4.6
7.2
17
27
30
37
20
34
8.9
' 8.9
6i4
7.9
12
8.2
5.3
8.6
5.0
9.1
7.5
6.7
5.7
6.6
4.2
11
5.7
8.7
6.5
7.6
23
Raw
Infl.
33
24
36
20
24
20
23
26
26
16
25
29
40
27
23
17
17
22
26
27
33
14
24
25
22
23
32
24
24
24
23
23
19
Ammonia Nitrite
nitrogen, nitrogen,
mg/1 mg/1
Prim.
Effl.
29
27
29
21
19
-
_
19
-
19
..
17
25
25
21
18
19
20
19
37
-
14
20
-
_
20
-
24
23
20
18
. 20
17
Sec. Raw Prim. Sec.
Effl. Infl. Effl. Effl.
0.2 <0.1 <0.1 <0.1
0.7 <0.1 <0.1 <0.1
0.9 <0.1 <0.1 <0.1
6.6 < 0.1 < 0.1 < 0 1
0^4
-------
TECHNICAL REPORT DATA .
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/2-80-120
3. RECIPIENT'S ACCESSION1
TITLE AND SUBTITLE
CONVERTING ROCK TRICKLING FILTERS TO PLASTIC MEDIA
Design and Performance
5. REPORT DATE . . ,
August 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
Richard J. Stenquist
Kathryn A. Kel1y
8. PERFORMING ORGX
PERFORMING ORGANIZATION NAME AND ADDRESS
Brown and Caldwell
1501 North Broadway
Walnut Creek, California 94596
10. PROGRAM ELEMENT NO.
35B1C,D.U.B-124, Task D-l/29
11. CONTRACT/GRANT NO.
Contract No. 68-03-2349
2. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research LaboratoryCin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final, 3/15/76 - 3/16/77
14. SPONSORING AGENCY CODE
EPA/600/14
5. SUPPLEMENTARY NOTES
Project Officer: Richard C. Brenner (513) 684-7657
6. ABSTRACT
This investigation was undertaken with the objectives of reviewing the conversion
of trickling filters at the Stockton, California, Regional Wastewater Control Facility
from rock media to plastic media and to develop general design considerations for
similar conversions which might be carried out elsewhere. Information on design of th
secondary treatment modifications is presented, along with a description of plant con-
struction and startup. The Stockton plastic media trickling filters are designed to
operate in two modes: (1) to oxidize carbonaceous material during the canning season
when plant loadings are high (design flow = 220,000 m3/day or 58 mgd), and (2) to
provide combined carbon oxidation-nitrification during the noncanning season when
loadings are low (design flow = 87,000 nr/day or 23 mgd). To evaluate plant perform-
ance, a special 1-yr sampling program was carried out. Plant performance for the
1-yr period is presented and evaluated. Operational changes intended to improve per-
formance are described, and the results are discussed. Capital and operating costs
for filter conversion are also presented. Based on information developed from
evaluation of the Stockton plan and from review of other plastic media trickling
filter plants, manufacturers' data, and technical literature, general design con-
siderations are developed for converting rock media trickling filters to plastic
media, including both process design and physical design.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTOR'S
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
*Sewage treatment, *Trickling filtration,
Upgrading, Nitrification
*Synthetic (plastic)
media trickling filters,
*Rock media trickling
filters, Canning wastes,
Seasonal load
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
192
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (9-73)
178
* U.S. GOVERNMENT PRINTING OFFICE: 1980 -657-165/0146
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