EPA-R2-73-236
im* Environmental Protection Technology Series
MAY 19/3
Tertiary Treatment of Combined
Domestic and Industrial Wastes
Office of Research and Monitoring
U.S. Environmental Protection Agency
Washington. D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environmental quality
standards.
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EPA-R2-73-236
May 1973
TERTIARY TREATMENT
OF
COMBINED DOMESTIC AND INDUSTRIAL WASTES
by
John W. Lee, Jr.
Grant No. 11060 DLF
Program Element 1B2037
(Project 12130 DLF)
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
Price $2.60 domestic postpaid or $2.25 GPO Bookstore
Dennis W. Taylor, Project Officer
Pacific N.W. Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330
Prepared for
OFFICE OF RESEARCH AND MONITORJNG
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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EPA REVIEW NOTICE
This report has been reviewed by the Environmental Protection Agency and approved for
publication. Approval does not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention of trade names of
commercial products constitute endorsement or recommendation for use.
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ABSTRACT
Operation of a secondary-tertiary treatment facility for combined domestic and pet food
manufacturing industrial wastewaters at the City of Tualatin, Oregon, was studied for 16
months. The study demonstrated the feasibility of automated tertiary treatment for small
communities treating a combined domestic and industrial wastewater at a reasonable cost.
The system was designed for an average daily flow of 280,000 gpd and a BODs load of
630 pounds per day. The extended aeration activated sludge process with a design
detention time of 24 hours was employed for secondary treatment. An experimental 60
degree inclined tube settler located in the aeration-surge basin provided secondary
effluent clarification.
The tertiary system consisted of a four step process: 1) alum and polyelectrolyte
coagulation, 2) flocculation, 3) inclined tube sedimentation, and 4) mixed media
filtration. The tertiary system demonstrated the capability to produce an effluent quality
of less than 10 mg/1 BOD5 and 5 mg/1 suspended solids with a total phosphate residual
of 0.1 to 1.0 mg/1 (as P).
The total capital cost of the facility was $245,800. Based on total annual cost, the cost
of treatment at the design conditions was $0.42 per 1000 gallons processed and $0.19
per pound of BOD5 removed.
This report was submitted in fulfillment of Grant No. 11060 DLF under the partial
sponsorship of the Environmental Protection Agency.
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CONTENTS
SECTION PAGE
I CONCLUSIONS 1
II RECOMMENDATIONS 5
Design Modifications 5
Additional Equipment 6
Areas for Further Study 7
III INTRODUCTION 9
Scope 9
Background 10
Theoretical Considerations 11
Extended Aeration Activated Sludge Process 11
Tube Clarification 16
Tertiary Treatment 19
IV TREATMENT FACILITIES 33
General Description 33
Design Concept 37
Design Criteria 39
Design Factors 40
V DEMONSTRATION PROCEDURES 45
Plant Startup 45
Operation 45
Sampling Schedule and Procedures 47
Plant Influent 47
Aeration-Surge Basin 47
Secondary Effluent 47
Waste Activated Sludge 47
Tertiary (Plant) Effluent 47
Sludge Pond Supernatant 49
Analytical Methods 49
Nitrogen and Phosphorus 49
VI WASTEWATER CHARACTERISTICS 51
General 51
Influent Characteristics 51
Flow 53
Biochemical Oxygen Demand 53
Total Suspended Solids 57
Nitrogen 57
Phosphorus 57
Nutrient Ratio 57
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CONTENTS - CONTINUED
SECTION PAGE
VI WASTEWATER CHARACTERISTICS (continued)
Total Alkalinity and pH 58
Temperature 58
Loading 58
Flow 58
BOD 58
TSS 60
Total Nitrogen 60
Total Phosphorus 60
Industrial Wastewater 60
Domestic Per Capita Loadings 63
Infiltration 63
VII TREATMENT PLANT PERFORMANCE 65
General Plant Performance 65
Secondary Treatment System 66
General 66
Aeration-Surge Basin Performance 67
Secondary Effluent 73
Velocity Profiles 79
Solids Accumulation 83
Tertiary Treatment System 83
General 83
Jar Tests 85
Chemical Feed Rates 85
Filtration Rate 87
Filter Cycle 90
Effluent Quality 90
Chlorination 96
Waste Solids Storage 99
Waste Activated Sludge Storage 99
Chemical Sludge Storage 102
Combined Return Sludge Lagoon Supernatant 105
Operational Considerations 105
Operator Accident 106
PVC Liner Failure 106
Influent Pumps 106
Aeration Equipment 106
Soda Ash Feed 107
Secondary Tube Clarifier Modifications 107
Flocculator Modifications 107
Tertiary Tube Settler/Filter Modifications 108
Chemical Sludge Decant Pump 108
Surface Wash Diaphragm Valve 108
Other Mechanical Problems 108
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CONTENTS - CONTINUED
SECTION PAGE
VIII DISCUSSION 109
Secondary Treatment System 109
Microbiology 109
Sludge Yield 109
Substrate Removal 1 ] 6
Sludge Volume Index 119
Secondary Clarifier Performance 119
Nitrification 125
Phosphate Removal 132
Aerator Oxygen Transfer Rate 132
Tertiary Treatment System 135
Tertiary System Performance 135
Phosphate Removal 144
Waste Solids Storage and Disposal 148
Design Modification and Equipment Recommendations 149
General 149
Flow Measurement 149
Sampling 149
Instrumentation 150
Influent Pump Station 150
Aeration-Surge Basin 150
Secondary Tube Clarifier 151
Tertiary System 151
Laboratory Equipment 152
Operational Recommendations 152
General 152
Secondary System 153
Tertiary System 153
Sampling and Testing 154
Future Research and Demonstration Project
Recommendations 155
IX FINANCIAL CONSIDERATIONS 157
Operation and Maintenance Costs 157
Research and Demonstration Costs 157
Total Annual Costs 157
Treatment Costs 158
X ACKNOWLEDGMENTS 161
XI REFERENCES 163
XII PUBLICATIONS 167
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CONTENTS - CONTINUED
SECTION PAGE
XIII ABBREVIATIONS 169
XIV APPENDIXES 171
Appendix A - Design Factors 173
Appendix B - Photographs 183
Appendix C - Process and Laboratory Equipment 193
Appendix D - Costs 197
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FIGURES
NO. PAGE
1 Idealized Settling of Discrete Particles in a Horizontal
Flow Basin 18
2 Idealized Settling of a Discrete Particle in an Inclined Tube 18
3 Basic Tube Settler Configurations 20
4 Alkalimetric and Acidimetric Titration of A1(OH>3 in Solution 24
5 Effect of pH on Various Forms of Orthophosphate 27
6 Solubility of Aluminum(III) Phosphate 27
7 Cross-Section Through Single-Media Bed Such as Conventional
Rapid Sand Filter 31
8 Cross-Section Through Ideal Filter Uniformly Graded From Coarse
to Fine From Top to Bottom 31
9 Distribution of Media in a Properly Designed Mixed-Media Filter 32
10 Treatment Facilities 34
11 Schematic Plan Tualatin Tertiary Treatment System 38
12 Aeration-Surge Basin Typical Section 41
13 Tube Clarifier Typical Section 42
14 60 Degree Inclined Tube Module 42
15 Tertiary Settler/Filter Unit 43
16 Population, Rainfall and Flow Versus Time 55
17 Influent BOD and TSS Concentration Versus Time 56
18 Influent BOD and TSS Loadings Versus Time 61
19 Influent Nitrogen and Phosphorous Loadings Versus Time 62
20 Effect of Infiltration on Total Plant Flow 64
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FIGURES - CONTINUED
NO PAGE
21 Aeration-Surge Basin Temperature, pH and Total Alkalinity
Versus Time 69
22 Aeration-Surge Basin Dissolved Oxygen and SVI Versus Time 71
23 MLSS. Sludge Age and F/M Versus Time 72
24 Secondary Effluent BOD and TSS Concentration Versus Time 75
25 Secondary Effluent Total BOD Versus Suspended Solids 76
26 Secondary Effluent Nitrogen and Phosphorous Concentrations
Versus Time ^8
27 Aeration-Surge Basin Velocity Profile at 1 Foot Depth 80
28 Aeration-Surge Basin Velocity Profile at 6 Foot Depth 81
29 Aeration-Surge Basin Velocity Profile at 9 Foot Depth 82
30 Aeration-Surge Basin Solids Accumulation 84
31 Tertiary Chemical Dosages Versus Time 88
32 Tertiary Flow Rate and Filter Run Time Versus Time 89
33 Tertiary Effluent Total and Soluble BOD and TSS Concentrations
Versus Time 9_
34 Tertiary Effluent Nitrogen and Phosphorous Concentrations
Versus Time 93
35 Tertiary Effluent pH, Alkalinity and Turbidity Versus Time 94
36 Tertiary Effluent TSS and Turbidity Versus pH 95
37 Tertiary Effluent Turbidity Versus Nitrate Concentration 97
38 Waste Activated Sludge Storage Lagoon Drying Versus Time 101
39 Waste Activated Sludge Storage Lagoon Profile 101
40 Chemical Sludge Lagoon Drying Versus Time 104
41 Chemical Sludge Aliquot Drying Versus Time 104
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FIGURES - CONTINUED
NO. PAGE
42 Gross Sludge Yield Versus Sludge Age 110
43 Gross Sludge Yield Versus Influent TSS/Total BOD5 Removed 113
44 Influent Total Suspended Solids Degradation Versus Sludge Age 114
45 Net Sludge Yield Versus Sludge Age 115
46 Substrate Removal Rate Versus Tertiary Effluent Soluble BOD5 117
47 Dissolved Oxygen Versus SVI 120
48 Secondary Effluent Suspended Solids Versus MLSS 121
49 Secondary Effluent Suspended Solids Versus pH 124
50 Secondary Effluent Suspended Solids Versus Ammonium Ion
Concentration 126
51 Nitrification Versus Sludge Age 126
52 Nitrification Versus Aeration-Surge Basin Dissolved Oxygen 127
53 NO2/NO3 Versus Aeration-Surge Basin Dissolved Oxygen 128
54 Sequence of Nitrification Reactions 129
55 Nitrogen Removal in Aeration-Surge Basin 131
56 Secondary Treatment System Phosphate Removal Versus pH 133
57 Aeration-Surge Basin D.O. Versus Influent BOD5 134
58 Suspended Solids, Head Loss and Turbidity Versus
Filter Run Time 137
59 Tertiary Throughput Volume Versus Secondary Effluent TSS
Concentration (Without Chemical Feed) 138
60 Tertiary Throughput Volume Versus Secondary Effluent TSS
Concentration (With Chemical Feed) 139
61 Effect of Alum Dosage on Filter Cycle 141
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FIGURES - CONTINUED
NO. PAGE
62 Effect of Pre Filter Polyelectrolyte Addition on Filter
Breakthrough 142
63 Effect of Pre Filter Polyelectrolyte Addition on Filter Run Time 143
64 Effect of Pre Settler Polyelectrolyte Addition on Tertiary
Solids Removal 145
65 Effect of pH, Alum Dosage and Secondary Effluent Orthophosphate
Concentration on Phosphate Removal 146
66 Relationship of Aluminum(III), Initial Orthophosphate Concentration
and pH on Orthophosphate Removal 147
67 Capital Cost, Operating and Maintenance Cost and Debt Service
Versus Design Capacity Adjusted to June 1972 160
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TABLES
NO. PAGE
1 Forms of Phosphorus in Domestic Wastewater 26
2 Design Criteria 39
3 Detailed Operational Schedule 46
4 Routine Sampling and Testing Schedule 48
5 Combined Industrial and Domestic Influent Wastewater
Characteristics 52
6 Domestic Wastewater Influent Characteristics 54
7 Influent Loadings 59
8 Aeration-Surge Basin Data Summary 68
9 Secondary Effluent Characteristics 74
10 Tertiary Performance Summary 86
11 Filtration Rate Comparison 90
12 Plant Effluent Chlorination Data Summary 98
13 Combined Return Sludge Lagoon Supernatant Characteristics 105
14 Total Annual Costs 158
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SECTION I
CONCLUSIONS
The operation of a small (0.28 mgd) secondary-tertiary facility, providing treatment of
combined domestic and pet food manufacturing industrial wastewaters for the City of
Tualatin, Oregon, was evaluated from August 1970 through October 1971.
The following conclusions have been reached, based on the results of the study presented
in this report:
1. Application of alum coagulation, sedimentation, and mixed-media
filtration is an effective tertiary treatment process for polishing and
removing phosphate from the effluent of a complete-mix activated
sludge extended aeration system.
2. A final effluent quality of 10 mg/1 BODg, 5 mg/1 total suspended
solids, and 0.1 to 1.0 total phosphate could be maintained, even
under high suspended solids conditions in the secondary effluent.
3. High influent organic loadings exceeded the design aeration capacity
for much of the demonstration period, substantially affecting the
performance of the secondary treatment system.
4. The tertiary effluent quality reported above was maintained while
treating secondary effluent from an extended aeration system having
an average sludge age of 13.3 days (range 4 to 31 days), and an
average aeration-surge basin detention time of 2.6 days (range 1.6 to
7.1 days).
5. The influent suspended solids had a significant effect upon the gross
sludge yield from the secondary treatment system. The influent
suspended solids did not appear to begin biological breakdown until
retained in the secondary system for at least five days. Eighty (80)
percent of the influent suspended solids was determined to be
resistant to biological degradation.
6. The gross sludge yield, nondegraded influent suspended solids plus
biologically synthesized solids in the MLSS. of the secondary system
at a sludge age of 10 to 30 days was determined to be about 1.0
pounds of solids per pound of influent BOD^ removed.
7. The net sludge yield, solids biologically synthesized less endogenous
respiration loss, decreased from 0.4 to 0.17 pounds per pound of
6005 removed between sludge ages of 5 and 30 days.
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8. The net sludge yield and endogenous coefficients were determined to
be 0.60 and 0.15 day"^ respectively.
9. The substrate removal coefficient, k, based on total MLSS was
determined to be 0.0235 Ibs BOD5 removed per day per Ibs of MLSS
per mg/1 soluble effluent BOD5.
10. The substrate removal coefficient, k' , expressed in terms of the
estimated biological mass (Mg), was calculated to be 0.098 Ibs BODj
removed per day per Ibs Mg per mg/1 effluent soluble BOD^.
11. The secondary tube clarifier performance was found to be dependent
upon MLSS concentration, overflow rate, temperature, pH, and the
extent of nitrification.
12. Complete nitrification (98 percent oxidation of soluble nitrogen)
occurred at D.O. levels above 1.0 to 1.5 mg/1 and sludge ages greater
than 10 to 12 days within a temperature range of 8 to 22 degrees C.
13. Sludge ages of less than 5 days or D.O. levels of less than 0.4 to 0.6
mg/1 effectively inhibited nitrification.
14. Optimum phosphate removal (approaching 60 percent) in the
aeration-surge basin occurred at a pH of 7.0 to 7.25.
15. The aerator field oxygen transfer rate was determined to be about
1.4 Ibs O2/hp-hr. The corresponding clean water transfer rate was
calculated to be about 2.1 Ibs of O2/hp/hr.
16. The filter throughput volume per cycle was not affected by filtration
rates ranging from 1.4 to 4.0 gpm/sq ft.
17. Solids carryover from the tertiary tube settler significantly reduced
the tertiary filter cycle time,
18. Filter cycle time was also influenced by the secondary effluent
suspended solids concentration, alum dosage, and excessive prefilter
polyelectrolyte addition.
19. Anionic polyelectrolyte addition of up to 2.0 mg/1 prior to
flocculation did not appear to appreciably aid chemical floe
formation or improve tertiary performance.
20. Anionic polyelectrolyte dosages of 0.03 to 0.06 mg/1 applied prior to
filtration, were effective in controlling turbidity breakthrough.
Prefilter polymer dosages in excess of 0.1 mg/1 produced "filter
binding," reducing the filter cycle time.
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21. Orthophosphate removal in the tertiary system was dependent upon
the alum dosage, pH, and the secondary effluent orthophosphate
concentration.
22. Optimum phosphate removals occurred at a tertiary effluent pH of
5.5 to 6 and at [Al(III)]/[secondary effluent ortho P] molar
concentration ratios of 2 to 3.
23. The lowest levels of residual suspended solids and turbidity in the
tertiary effluent occurred in a pH range of 5.8 to 6.3. Tertiary
effluent turbidity also appeared to correlate with nitrate
concentration.
24. The extent of nitrification and its effect on alkalinity in the
aeration-surge basin had a significant effect on tertiary operation.
25. Lagooning of waste activated and tertiary chemical sludge was an
effective means of storing waste solids. No objectionable odors were
detected from the lagoons. The volatile solids content of the waste
activated and chemical sludges after storage for 6 to 9 months
averaged 52 percent and 48.5 percent, respectively.
26. Separate drying bed experiments indicated the stabilized waste
activated sludge applied at an average depth of 6 inches, would dry
to a cinder-like humus material with a moisture content of 9 to 12
percent after 4 weeks.
27. Stabilized chemical sludge applied to a small-scale drying bed at a
depth of 9 inches and 3.3 percent solids content dewatered to a
solids content of 68 percent after 27 days.
28. A combined secondary-tertiary treatment system of this type can be
constructed and operated at a substantial savings in cost compared to
a conventional activated sludge system with tertiary treatment. The
total capital cost was about 71 percent of the cost for a comparable
size conventional activated sludge plant with tertiary treatment.
29. The total annual cost, based on design conditions, was calculated to
be S0.421 per 1,000 gallons treated. The individual cost allocations
for the secondary and tertiary systems were estimated to be $0.287
and SO. 134 per 1,000 gallons treated respectively. (These costs do
not include waste solids disposal).
30. In terms of organic loading, the total annual treatment cost based on
design conditions averaged SO. 187 per pound of BOD5 removed for
the first year of operation. (This cost does not include waste solids
disposal).
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SECTION II
RECOMMENDATIONS
The demonstration program identified several design modifications and items of
additional equipment, which can improve plant performance and operation. Additional
operational research studies to further explore various aspects of the secondary and
tertiary treatment processes would also be desirable.
DESIGN MODIFICATIONS
1. Gas accumulation under the aeration-surge basin PVC liner caused the membrane to
tear away from the ringwall footing and float. The liner was repaired and a venting
system installed under the liner to provide gas relief. It is recommended that a gas
venting system be included in the design of aeration-surge basins using membrane
liners.
2. Where wide fluctuations in organic loading are expected in extended aeration
systems treating combined industrial and domestic wastewater, it is recommended
that two speed, as opposed to single speed, mechanical surface aerators be
considered. In addition it is suggested that more units of lower horsepower be used
than a lesser number of higher aeration capacity. This concept allows flexibility in
adjusting the air supply to satisfy the incoming oxygen demand. Increased
equipment costs can be offset by the savings in power realized.
3. Satisfactory secondary tube clarifier performance was restricted to MLSS levels
below 2,200 mg/1. Additional study of tube module design to extend the allowable
MLSS range of effective clarification is warranted. Provisions were not included to
thicken waste activated sludge. A means of concentrating waste activated sludge
should be incorporated in the secondary tube clarifier design. An air sparging
system, installed midway through the demonstration project, proved to be an
effective method of cleaning and preventing solids buildup in the tubes. It is
recommended that air sparging also be included in the clarifier design.
4. Considerable short circuiting occurred in the flocculator tank. Modifications were
made to minimize this condition. It is recommended that in future designs of the
flocculation system, careful consideration be given to preventing short circuiting. For
small tertiary systems it may be convenient to include the flocculator as part of the
tertiary tube settler/filter unit.
5. High velocity constrictions in the tertiary tube settler inlet system were suspected to
cause a breakup of the fragile chemical floe. The results of modifications to correct
this condition were inconclusive. It is recommended that the inlet system be
redesigned to prevent turbulence from damaging the chemical floe.
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6. The tertiary tube settler modules did not have adequate storage volume for the
solids loadings encountered. The effective surface overflow rate should be reduced to
about 35 gallons per day per square foot.
7. Pumping the chemical sludge holding tank supernatant, after settling, to the
aeration-surge basin resulted in severe pH depression when the secondary system was
highly nitrified. It is recommended that the supernatant be combined with
secondary effluent for return to the tertiary system.
8. Low secondary effluent alkalinity conditions, produced by nitrification in the
aeration-surge basin, required the addition of soda ash to the tertiary influent to
maintain pH control in the tertiary process. It is recommended that soda ash mixing,
storage and metering equipment be included as part of the chemical feed facilities in
secondary-tertiary treatment systems of this type treating relatively soft waters.
ADDITIONAL EQUIPMENT
1. The plant effluent was the only wastewater flow accurately measured and recorded.
Because of low influent flow conditions and the surge capacity of the aeration-surge
basin, the plant influent and effluent flow rates were not necessarily equivalent.
Measurement and recording of the plant influent, as well as waste activated sludge
and sludge storage lagoon supernatant return flows, are recommended.
2. For treatment systems receiving combined domestic and industrial wastewaters with
large fluctuations in both organic and hydraulic loadings, flow proportioned
automatic sampling of the plant influent, secondary effluent and tertiary effluent is
recommended. Flow proportioned automatic sampling of significant industrial waste
flows is also suggested.
3. Tertiary filter head loss was indicated, but not recorded. A recording turbidimeter
was borrowed during the demonstration program to monitor tertiary effluent
quality. It is recommended that both filter head loss and tertiary effluent turbidity
be recorded, as well as indicated, to effectively regulate chemical feed, assess tertiary
system performance and control plant effluent quality.
4. The most important control parameter for the tertiary process was pH. It is
recommended that the pH of the flocculator effluent be continuously indicated and
recorded.
5. The extent of nitrification in the secondary system substantially influenced tertiary
treatment performance. Where size of the treatment facility can justify the expense,
it is suggested that the D.O. and ammonium ion concentration of the aeration-surge
basin be measured and recorded.
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AREAS FOR FURTHER STUDY
1. The effect of polymer addition on flocculation was not adequately demonstrated
and should be further investigated.
2. Alkalinity is suspected to influence alum-phosphate coagulation and warrants further
research.
3. Tertiary effluent quality depended primarily on the characteristics of the secondary
effluent and chemical dosages applied, and did not appear to be affected by
filtration rate. Additional study is needed to verify these observations, where the
tertiary influent characteristics can be more closely controlled.
5. Ammonium ion, pH and the oxidative condition in the aeration-surge basin appeared
to affect secondary clarifier performance. Further research is needed to more fully
explore the effect of these variables on coagulation of colloidal participate.
6. Optimum orthophosphate removals in the secondary system were observed to occur
in a narrow pH range. Further research is needed to determine the influence of pH
and the mechanism(s) of phosphate removal in activated sludge systems.
7. Nitrate ion and pH appeared to affect the turbidity level and suspended solids
concentration of the tertiary effluent. This is another area deserving additional
study.
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SECTION III
INTRODUCTION
SCOPE
A secondary-tertiary system, designed to treat combined domestic and industrial wastes,
was constructed at the City of Tualatin. Oregon, and studied during the period from
August 1970 through October 1971. This project was financed with the aid of a research,
development, and demonstration grant provided by the Environmental Protection Agency
(EPA), under grant project No. 1 1060 DLF.
The basic purpose of this program was to develop design criteria, evaluate operating
characteristics, and determine the effectiveness of a small, low cost, municipal tertiary
treatment plant treating combined domestic and industrial wastes. At the time this
project was initiated, no plant scale installations of this type of secondary-tertiary
treatment, providing nutrient removal, existed.
The primary objectives of this program were to:
1. Demonstrate in full scale plant operation, the BOD, suspended solids, and the
phosphate removal capabilities of a completely automated high-rate tertiary
filtration system treating combined domestic and industrial waste flows.
2. Determine the economics of the system providing an effluent quality of 10
mg/1 total BOD and 10 mg/1 suspended solids or less and a total phosphate
residual of 0.1 to 1.0 mg/1 (as P).
3. Demonstrate the applicability of the tertiary treatment process as
supplementary treatment for the extended aeration modification of the
activated sludge process. Extended aeration is becoming prevalent throughout
the country as a secondary treatment process for small municipalities.
4. Demonstrate the application of tube type clarifiers for use in extended aeration
activated sludge systems as a substitute for conventional clarifier tanks and
mechanisms.
5. Study the operating techniques required and the problems associated with
disposal of tertiary treatment chemical sludge, including the degree of sludge
dewatering and compaction in storage ponds, and the most desirable means of
off-site disposal.
6. Provide detailed design criteria and operations recommendations for use in
adapting the secondary-tertiary treatment system to other locations.
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Secondary objectives of the project were to:
1. Determine an aeration-surge basin velocity profile.
2. Determine the dewatering and drying characteristics of the waste activated
sludge.
3. Determine the solids accumulation in the bottom of the aeration-surge basin at
the end of the program.
4. Determine the volume and density of both the chemical and activated sludge
deposits in the holding ponds at the end of the program.
5. Identify potential problems associated with chemical and activated sludge
disposal.
BACKGROUND
National awareness of the deteriorating quality of many of our receiving waters has
prompted governmental agencies to place increasingly stringent effluent quality discharge
requirements on wastewater treatment plants. Secondary treatment alone is rapidly
becoming inadequate in many locations of the country and must be supplemented by
tertiary treatment.
In addition to the domestic load, many small communities are faced with the problem of
providing wastewater treatment services to local industry. The waste loads from such
industries as food processors can constitute the major organic load on the treatment
plant, adding to the difficulty of providing the degree of treatment required to comply
with governmental discharge standards. These small cities therefore require an economical
treatment system that will provide the level of treatment necessary, without placing a
financial burden on the community.
Severe pollution problems encountered during periods of low stream flow prompted the
Oregon State Sanitary Authority (OSSA), presently the Oregon State Department of
Environmental Quality (OSDEQ), to issue a directive in September 1966 prohibiting
construction of additional secondary treatment plants along the Tualatin River, unless
discharge to the river was eliminated during the summer months or tertiary treatment
provided. Tertiary treatment was defined as an effluent containing not more than 10 mg/1
BOD and 10 mg/1 suspended solids. As a result of this action by the OSSA, all new
construction activity was halted in the Tualatin River Basin.
The City of Tualatin, Oregon, having convenient highway and rail access as well as
available land, had actively encouraged industrial and residential development. Since
adequate sewerage service was a major factor in attracting new growth, a method of
sewage treatment approved by the OSSA was necessary for development to continue. No
installations of small municipal tertiary plants existed at that time. A critical need existed
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for the development of plant design criteria and operating characteristics, demonstration
of advanced waste treatment equipment, and economic evaluation of such installations.
In December 1966, the City of Tualatin submitted an application to the Federal
Government for a Municipal Research and Demonstration Grant to assist in financing the
design, construction, and operation of a demonstration tertiary treatment plant for
combined domestic and industrial wastes.
Tentative approval of the grant project was given in November 1968, by the then Federal
Water Pollution Control Administration (FWPCA), presently the EPA. The original grant
project No. WPRD 27-01-68 was changed by the FWPCA to No. 11060 DLF.
The City of Tualatin retained the engineering firm of Cornell, Howland, Hayes &
Merryfield to design the treatment facility and to exercise technical supervision over the
research and development program. Construction was completed, and the facility started
up in April 1970. Several problems delayed the beginning of the research and
demonstration program until August 1970.
The treatment system received a combination of domestic and commercial wastewaters as
well as an industrial effluent from a pet food manufacturer.
The secondary-tertiary treatment system was designed to be able to produce an effluent
containing not more than 10 mg/1 BOD and 10 mg/1 suspended solids and a total
phosphate content of 0.1 to 1.0 mg/1 (as P). The secondary treatment process used was a
completely mixed extended aeration activated sludge system without primary treatment.
A tube settler located in the aeration-surge basin provided secondary clarification. The
tertiary treatment system was a chemical (alum-polyelectrolyte) coagulation,
sedimentation, and filtration process developed by Neptune MicroFLOC, Inc.
The treatment plant was designed and constructed as a temporary facility for research
and development in conjunction with treatment of combined industrial and domestic
wastes. The plant was to operate for approximately 5 years, at which time connection
would be made to a regional sewerage system. Research and demonstration activities were
carried out during the first 15 months of operation.
A complete list of definitions of the technical terms used in this report may be found in
the WPCF Glossary [1], and a list of abbreviations and symbols used is contained in
Section XIII.
THEORETICAL CONSIDERATIONS
EXTENDED AERATION ACTIVATED
SLUDGE PROCESS
GENERAL-The complete mix extended aeration activated sludge process differs from
more conventional activated sludge systems in several respects. Primary treatment is not
usually provided. Incoming raw waste is instantaneously and completely mixed with the
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aeration basin contents. Larger aeration basins are used to increase the aeration detention
time to between 12 and 24 noun, or longer.
The effect of the larger aeration volume is to provide a greater total mass of organisms
(M) and a longer activated sludge retention time than conventional systems at the same
microorganism (mixed liquor) concentrations to metabolize the incoming organic wastes
or "food" (F). The longer sludge retention time and lower ratio of F to M result in an
overall increase in waste metabolism, reducing the amount of biological solids that must
be disposed of.
The larger mass of active microorganisms, as well as the concept of complete mixing,
provides inherently greater process stability than conventional activated sludge systems,
minimizing the potential for sudden variations in organic and hydraulic loading or
introduction of toxic materials to upset the biological treatment process.
A brief discussion of the theory of the basic activated sludge process follows:
MICROBIOLOGY—The living organisms found in activated sludge are classified as either
plants or animals. The plants consist of bacteria and fungi. The animals are primarily
protozoa, rotifers, and nematodes.
Hawkes [2] states that bacteria are normally the dominant primary feeders on organic
wastes. Various holozoic protozoa are secondary feeders. Rotifers and nematodes occupy
higher levels in the food chain. Fungi normally cannot compete witli bacteria, but they
may predominate as primary feeders if certain conditions exist, such as low pH, nitrogen
deficiency, or low dissolved oxygen [3]. High-carbohydrate wastes are also reported to
stimulate fungi growth.
The composition of the organic wastes determines to a large extent which bacterial
genera will predominate [2,3]- Protein wastes favor Alcaligenes, Flavobacterium, and
Bacillus, while carbohydrate wastes favor Pseudomonas. A large population of free
swimming bacteria will sustain free swimming ciliata as the predominate protozoa:
however, if the food level is lowered by a reduction in the free swimming bacterial
population, the free swimming ciliates will yield to stalked ciliates which require less
energy.
Rotifers thrive in very stable systems and are better indicators of stable conditions than
are the nematode worms.
METABOLISM—The metabolic reactions that occur within activated sludge can be
divided into three phases: (1) oxidation, (2) synthesis, and (3) endogenous respiration.
The reactions in each phase are described by the following general equations, formulated
by Weston and Eckenfelder [4]:
-12-
-------
where:
(1) Organic Matter Oxidation
CxHyOz + aO2 -» xCO2 + bH2O + Energy
(2) Cell Material Synthesis
CXH Oz + NH3 + dO2 + Energy — C5H?NO2 + eCO2 + fH2O
where: d = x+^-^-5
e = x - 5
f = y - 2
(3) Cell Material Endogenous Respiration
C5H7NO7 + 5O2 — 5CO2 + 2H2O + NH3 + Energy
Microorganisms oxidize about one-third of the organic matter removed from wastewater
directly to carbon dioxide and water. This oxidation process provides the energy
necessary to convert the remaining two-thirds of the organic material removed from
solution to cell tissue [5]. A portion of the synthesized cell tissue is subsequently
oxidized to carbon dioxide, water and other metabolic end products by endogenous
respiration.
SUBSTRATE REMOVAL KINETICS-Several authors [6,7,8,9] have developed equations
to describe the BOD, or substrate, removal kinetics of the complete-mix activated sludge
process. The Michaelis-Menton relationship is the fundamental principle underlying most
of these equations and is the basis on which substrate removal kinetics have been
evaluated in this study.
The rate of BOD removal, mass of organisms present and soluble effluent BOD
concentration in a completely mixed system are related by the Michaelis-Menton equation
as follows:
R =
where:
Fs
S + s
R =
F =
s =
S =
BOD removal rate (Ibs per day/lb MLSS)
Maximum BOD removal rate (Ibs per day/lb MLSS)
Soluble effluent BOD (mg/1)
BOD concentration at R = 1/2 F, Michaelis Constant (mg/1)
-13-
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In an extended aeration complete - mix system the BOD concentration in the
aeration-surge basin is normally very low compared to the influent BOD concentration.
Thus, S is usually large as compared to s. Under these conditions, the Michaelis-Menton
rate can be approximated as:
R = |^ = ks
p
where: k = -~- is the BOD removal coefficient expressed as Ibs BOD removed
per day per Ib MLSS per mg/1 soluble effluent BOD.
This simplification takes the form of the straight line equation with a slope k. The BOD
removal per unit of MLSS is proportional to the BOD remaining in solution.
SLUDGE YIELD-Excess solids in the activated sludge system will result from the
suspended solids in the influent which are not biodegraded and synthesized cell tissue
which is not metabolized by endogenous respiration.
McCarty and Brodersen [10] have developed the following equation to estimate the net
sludge accumulation in terms of pounds of volatile biological solids produced per pound
of BOD removed:
A- 06s °-53
r* — U.OJ - r
where: A = net accumulation of volatile biological solids
F = BOD removed
E = suspended solids lost from system per day
M = total suspended solids in system
b = endogenous respiration constant
This equation assumes the net accumulation of solids to be dependent on the rate of
synthesis of biological solids, and the rate of solids degradation by endogenous
respiration. The endogenous respiration constant, b, is in turn dependent on the average
M
retention time, TS = -=r, of the biological solids (sludge age) and the temperature of the
system.
NITRIFICATION-Under favorable operating conditions, oxidation of ammonia nitrogen
(nitrification) can occur simultaneously with carbonaceous metabolism in activated sludge
systems. The effect of nitrification on subsequent tertiary treatment of secondary
effluent can be either beneficial or detrimental.
Nitrogen in the form of the ammonium ion is oxidized to the nitrate ion in a two step
reaction by the autobiophic bacteria nitrosomonas and nitrobacter [11]. The reactions
can be summarized as follows:
-14-
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Step 1
2NH4 + 3O9 nitrosomonas 2NO? + 4H + 2H->O
t z, - ~ -*- L £
Step 2
2NO2" -i- O2 nitrobacter . 2NOo"
Overall Energy Reaction
2NH4+ + 4O9 — 2NO^" + 4H+ + 2H9O
" *— J 4*
In addition to being an energy source, the ammonium ion is also assimilated by the
bacteria for synthesis of cell tissue. McCarty [12] represents the autotrophic synthesis
reaction as follows:
Synthesis
4CO? + HCOo" + NH4+ + H0O — CcH7NO7 + 5O?
A. -> t ^ J / .i z.
Based on both theoretical calculations and laboratory data, McCarty [12] has proposed
the following overall reaction to describe the autotrophic nitrification reaction:
22NH4+ + 37O2 + 4CO2 + HCO3" — C5H7NO2 + 21NO3" + 20H2O + 42H+
The extended aeration activated sludge process can provide an environment well suited
for nitrification. The conditions that are reported to favor nitrification include
[13,14,15]:
1. Long sludge age, Tg — 5 to 20 days
2. Low organic loading - 0.15 to 0.25 Ibs BOD5/day/lb MLVSS
3. D.O. level - 1.0 to 3.0 mg/1
4. Temperature — 10 to 20 degrees C
5. Slightly alkaline pH - 7.2 to 8.0
6. Inorganic carbon source — HCO^
The nitrifying autotrophic bacteria have considerably slower growth rates than the
heterotrophic bacteria in the activated sludge floe. The sludge age at a given temperature
must be greater than the reciprocal growth rate, if nitrification is to occur. The low
organic loading improves the competitive position of the autotrophic bacteria with
respect to other heterotrophic organisms.
Oxygen tension is also critical. Wuhrman [16] reports D. O. levels of 1.0 to 1.5 adequate
for nitrification. Carlson [13] and others indicate D.O. concentrations of 3.0 to 4.0
mg/1, however, may be necessary for complete nitrification of available ammonia
nitrogen. While a slightly alkaline pH is more favorable to nitrification, lower operational
values (6.5 to 7.0) have been reported [11].
-15-
-------
The synthesis reaction in nitrification results in a net release of hydrogen ion (H ).
Bicarbonate ion (HCO3 ), if available, will be converted to carbonic acid (F^CC^) in an
amount equivalent to the hydrogen ion released
H+ + HCO3" — H?CO3
resulting in a reduction in pH according to the equilibrium relationship:
PH = pK, + log [HC03 ]
[H2C03]
Kj is the equilibrium constant for the carbonic acid - bicarbonate buffer system. At 25
degrees C, pKj has a value of 6.35.
Both the formation of alum floe and the efficiency of alum-phosphate precipitation are
dependent upon pH. The reduction in alkalinity and consequent pH depression resulting
from nitrification can be either beneficial or detrimental to subsequent tertiary treatment
of secondary effluent. Formation of hydrous aluminum floe is restricted to a pH range of
about 5 to 9.5 [29]. Optimum conditions for alum-phosphate precipitation occur
between pH 5 to 6 [31,32].
In highly alkaline wastewater, nitrification can aid alum-phosphate precipitation and alum
coagulation by reducing the pH to a more favorable level. In low alkalinity wastewater,
however, the pH may be depressed below the range where these reactions can occur. The
addition of soda ash or other source of alkalinity may be necessary to maintain pH
control under these conditions.
Alum is also acidic. Sufficient alkalinity must be available in the secondary effluent to
buffer the alum dosage required to produce the level of phosphate removal desired in the
tertiary process.
TUBE CLARIFICATION
GENERAL-Tube type clarifiers were used for liquid/solids separation in both the
secondary and tertiary treatment systems. Practical application of tube type clarifiers as
an efficient sedimentation device is a relatively recent development in gravity separation
of solids from liquids.
A thorough discussion of the fundamental principles of sedimentation has been prepared
by Fair and Geyer [17]. Hansen and Gulp [18] and Hansen et al. [19] have applied
shallow depth sedimentation theory to the development of tube clarifiers. The following
is a summary of sedimentation theory and the development of tube clarifiers.
SEDIMENTATION THEORY-In developing a fundamental understanding of
sedimentation, Hazen [20] recognized that the removal efficiency of discrete particles
settling unhindered in a basin is solely a function of (1) the settling velocity of the
-16-
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particles, (2) the surface area of the basin, and (3) the flow velocity through the basin.
The surface area combined with the flow velocity constitutes the basin surface loading or
surface overflow rate. The removal efficiency is independent of the detention time of the
basin.
Camp [21] suggested the model on Figure 1 to describe unhindered settling of discrete
particles in a rectangular settling basin. All particles having a settling velocity, vs, equal or
greater than VQ = Q/A fall through the full depth, hQ, of the basin and are removed.
Particles with a settling velocity, vg, less than VQ, can also be removed if they are
introduced at or below a height h = vstQ above the sludge zone. The fraction of yo
particles having a settling velocity, vs, less than vo that are removed, y/yo, is equal to the
ratio of the velocities VS/VQ.
^oho Vo vo
INCLINED TUBES- Sedimentation in water and wastewater treatment has conventionally
been performed in large basins having detention times of 2 to 8 hours and requiring
particles to settle through depths of 8 to 16 feet in order to be removed. Since
sedimentation efficiency is primarily a function of surface loading, Hazen [20] suggested
that an ideal settling basin should be as shallow as possible. Inserting a number of closely
spaced horizontal trays in a settling basin would reduce the distance through which a
particle must travel to be removed and substantially decrease the basin detention time.
Following Hazen's suggestion, several attempts [19] have been reported to utilize shallow
trays or false bottoms in the design of settling basins. Flow distribution and sludge
removal problems, however, limited the practicality of these designs.
To overcome the problems associated with wide, shallow trays, small diameter tubes
packed parallel in bundles and inclined at various angles have been developed [18,19,22].
Longitudinal flow through tubes with diameters of a few inches optimizes hydraulic
conditions for sedimentation and overcomes flow distribution problems associated with
tray type settling basins. The tubes have a large wetted perimeter in relation to
cross-sectional area, resulting in low Reynolds numbers and insuring laminar flow. A
Reynolds number of 500 is thought to be adequate for settling [23] .
As an example, a two-inch diameter tube, four feet long, operating at an equivalent
surface loading of 235 gpd/sq ft has a Reynolds number of 48. The detention time is
approximately three minutes at these flow conditions.
Flow distribution through parallel tubes is self-regulating. As solids deposit in a tube, the
cross-sectional area decreases, resulting in increased velocities and a slightly higher head
loss through the tube. If the solids accumulation is greater in one tube than another, the
differential in head loss forces more flow to those tubes containing less settled solids.
Thus, the flow and solids loading over the entire tube bundle is evenly distributed.
-17-
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SURFACE AREA, A*
DIRECTION OF FLOW
OUTLET Q
FIGURE 1
IDEALIZED SETTLING OF DISCRETE PARTICLES IN
A HORIZONTAL FLOW BASIN
ANGLE OF INCLINATION
FIGURE 2
IDEALIZED SETTLING OF A DISCRETE PARTICLE IN
AN INCLINED TUBE
-18-
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Inclining the tubes in the direction of flow allows the solids that have settled to the
bottom surface to slide down and eventually discharge from the tubes. As in the
horizontal basin, the path traced by the particle as it settles is the vector sum of the
velocity of flow, V, and the settling velocity of the particle, v§. In inclined tubes,
however, the vectors are not at right angles, as illustrated on Figure 2. The settling
velocity has a component, v^, parallel and opposite to the direction of flow. If V > vg,
the length of settling surface decreases as the angle of inclination increases from zero up
to about 25 to 30 degrees (at V = 2.5 vs,) and then increases approaching infinity at 90
degrees. For V < vs, the tube length continues to decrease with increasing angle.
Experiments [18,19,22] with tubes demonstrated that an inclination of 45 to 60 degrees
is necessary for continuous gravity removal of settleable material from the tubes (Figure
3a). A countercurrent flow pattern is established in which particles are carried upward as
they settle, until becoming entrapped by the downward flowing stream of concentrated
solids. In separating flocculant material, this countercurrent flow is thought to aid in
agglomerating the smaller particles into a larger, heavier, more rapidly settling floe [19],
Tubes inclined only slightly in the direction of flow (five to eight degrees) have been
successfully cleaned by periodically draining the tubes (Figure 3b). The falling water level
hydraulically scours the accumulated solids from the bottom surface of the tubes.
In this research and demonstration project, both steeply and slightly inclined tubes were
utilized for liquid-solids separation. Tubes inclined at 60 degrees were used in the
aeration-surge basin for separation and return of mixed liquor suspended solids. Slightly
inclined tubes (7-1/2 degrees) were used in the tertiary process to remove chemically
coagulated and flocculated solids prior to filtration. Cleaning of the tertiary tube settler
was combined with the mixed- media filter backwash operation.
TERTIARY TREATMENT
GENERAL—Tertiary treatment as applied to this project was a polishing process to
remove suspended solids (turbidity) and soluble phosphate remaining in the secondary
effluent. Tertiary treatment was accomplished by a four step process:
1. Alum coagulation and phosphate precipitation
2. Flocculation
3. Tube sedimentation
4. Mixed-media filtration
The theory of tube (shallow depth) sedimentation has been discussed above. A review of
chemical coagulation and flocculation, aluminum-phosphate precipitation and
mixed-media filtration theory is presented in the following paragraphs. More detailed
discussions of chemical coagulation and precipitation have been developed by Fair and
Geyer [24] and Stumm and Morgan [25]. A thorough discussion of the theory and
development of mixed-media filtration has been presented by Gulp and Gulp [26] and
Tchobanoglous [27].
-19-
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INFLUENT
EFFLUENT
SETTLED SOLIDS DRAWOFF
(a)
INFLUENT
EFFLUENT
TUBES PERIODICALLY DRAINED
TO REMOVE SETTLED SOLIDS (b)
FIGURE 3
BASIC TUBE SETTLER CONFIGURATIONS, (a) STEEPLY
INCLINED TUBE SETTLER, (b) SLIGHTLY INCLINED TUBE SETTLER
-20-
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CHEMICAL COAGULATION-The terms coagulation and flocculation are often used
interchangeably. In this report, coagulation is considered to be the formation of complex
hydrous oxides and the destabilization (or neutralization) of charged colloidal particles,
resulting from the addition of floe-forming chemicals such as aluminum and iron salts.
Coagulation is a complex process involving both chemical and electrostatic reactions. The
reaction occurs rapidly and is essentially complete within the time necessary to physically
disperse the coagulating chemicals into the liquid being treated.
Flocculation is defined as the process of agglomerating the coagulated particle into a
larger mass of sufficient size to settle by gravity. This agglomeration results from the
collision and sticking together or bridging of the destabilized particles. Flocculation is a
time dependent reaction. Under quiescent conditions, colloidal size particles collide with
each other as a result of Brownian movement. More rapidly settling particles overtake and
entrap slower settling ones as the floe forms and grows. The rate of growth is very slow,
however. Gentle agitation of the chemically coagulated water increases the opportunity
for contact of the destabilized colloids. Gentle stirring can decrease the time required for
flocculation to between 10 and 15 minutes. The addition of polyelectrolytes can also
assist the flocculation process by increasing the shear strength of the floe and hastening
floe formation.
A certain amount of suspended material remains in the secondary effluent after
clarification. The majority of these particles are colloidal in size, ranging from 2 x 10"' to
5 x 10" 5 cm, and account for the turbidity in the water. This finely divided material
consists of aggregates or single large organic molecules, such as protein, starch and tealike
color compounds; cell tissue fragments; bacteria and clay particles.
The two distinguishing features of colloidal particles that affect their removal from the
suspending medium are:
1. Size
2. Large surface to mass ratio or specific surface area
Colloidal particles cannot be removed by conventional filtration, but can be separated by
ultrafiltration or dialysis through membranes. The surface of the particle tends to
preferentially adsorb ions, usually H+ and OH", becoming electrostatically charged with
respect to the surrounding medium. Due to the large specific surface area, the repulsion
of like charged colloids and Brownian motion are sufficient to prevent gravity settling.
Under these conditions, the particles are said to be "stabilized."
Chemical coagulation is a complex equilibria involving:
1. The colloids dispersed in the water being treated
2. The pH and ionic composition of the water or dispersion medium
3. The coagulating chemical or collecting medium
The mechanism of coagulation involves:
1. Reduction of the zeta potential of the colloid
-21-
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2. Neutralization of charge through the addition of oppositely charged hydrated
metal oxide colloids or polyelectrolytes.
In addition, the destabilized hydrous oxides and polyelectrolytes produce gelatinous
binder material to form a floe matrix during the subsequent flocculation process.
The term zeta potential is used to describe both the charge (magnitude) on the colloidal
particle and the distance into the solution through which the effect of the charge
extends. So long as the zeta potential exceeds a certain critical value, the colloid is stable.
Below this value coagulation occurs.
The zeta potential can be reduced by:
1. Decreasing the distance of charge effectiveness
2. Neutralizing the electrostatic charge on the colloid
The distance through which the charge is effective is primarily dependent on the ionic
concentration of the solution. The addition of di- and trivalent ions has a much greater
effect on coagulation than ions of single charge. Reduction of zeta potential is brought
about by the introduction of oppositely charged colloids into the suspending medium.
Electrostatic attraction decreases the net charge resulting in coalescence of the colloidal
particles.
Chemical coagulation of colloidal suspensions in water and wastewater can be
accomplished by adding floe-forming chemicals such as alum, Al^SO^^ . 18H2O; ferrous
sulfate, FeSC>4. 7H?O, ferric sulfate,
ferric chloride FeCl? and
polyelectrolytes. The initial reaction is one of solution. For alum, the reaction is:
A12(SO4)3 • 18H2O
2A1
3+
3SO,
ISH^O
The addition of both aluminum and sulfate ions increases the ionic concentration of the
medium. The net effect is a lowering of the zeta potential, creating a more favorable
coagulation condition.
The second and more important reaction is hydration of the metal ion. Many metals will
coordinate four to six H2O molecules around each ion. Depending on the pH of the
medium, the hydrated complex may be positively, neutrally, or negatively charged.
Pfeiffer [28] in the very early 1900s visualized the hydrolysis of trivalent metal ions,
such as aluminum and iron, to be represented by the equilibria:
\
OH
H_O-Me-OH
\
H00
OH
3+ _
OH
H~0
2
OH
\ /
H-O-Me-OH.
2 / \
OH
H-O
\
OH
H_O-Me-OH
\
H2O
OH
OH"
HO
OH
H,O-Me-OH
£. / \
(S,
OH'
-22-
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The degree of dissociation, the species present, and the anion associated with the metal
depend upon the pH and ionic composition of the solution.
Stumm and Morgan [29] have proposed a more complex model for the aluminum (III)
ion.
[AKH20)6
3 +
OH
[AHH20)5
-------
(a)
12
10
DISSOLUTION
COAGULATION
DISSOLUTION
I
/ ACID
/ BASE
FIGURE 4
AVERAGE CHARGE
2+ 1+ 0 1-
NAI(OH)
ALKALIMETRIC AND ACIDIMETRIC TITRATION OF
AL(OH)3 IN SOLUTION
2-
(b)
-------
Polyelectrolytes assist coagulation and flocculation by two general mechanisms - charge
neutralization and interparticle bridging. Polymers can act as a primary coagulant,
reducing the electrostatic charge of the colloidal particles. Interparticle bridging results
from the polymer becoming physically attached to adsorption sites on the surface of
individual particles forming a "bridge" between two or more particles. During
flocculation, the bridged particles become intertwined with other bridged particles. Both
the size and strength of the floe is increased, while the time required for floe formation
is reduced.
PHOSPHATE PRECIPITATION-The forms of phosphorus present in domestic
wastewater can be classified into three general categories: orthophosphate ion,
polyphosphates or condensed phosphates, and organic phosphorus compounds. Table 1
lists some of the phosphorus species in each of these categories.
Raw domestic wastewater usually contains a considerable amount (5 to 20 mg/1 as P) of
all three forms. During biological treatment, however, decomposition of organic matter
and hydrolysis of the condensed inorganic phosphates converts 50 to 90 percent of the
total phosphate to orthophosphate [30].
The valence of condensed inorganic phosphates and orthophosphates is determined by the
pH of the dissolving medium. Stumm and Morgan [25] have calculated the relative
concentration of the various orthophosphate species as a function of pH from equilibrium
data (Figure 5). Between pH 5 and 9, the normal range of domestic wastewaters, hbPO^."
and HPO4"~, are the predominant species.
Phosphates can be removed from solution by addition of multivalent metal ions including
Al(IIl), Fe(IlI), and Ca(ll). Chemical precipitation, coagulation, and adsorption have been
proposed as the removal mechanisms [24,25]. Depending upon the pH of the water being
treated, one, two, or all three phenomena may be involved. The solubility relationships of
the metal phosphate and metal hydroxide compounds, the hydrolysis of the metal ions,
and the acid-base equilibria of the phosphate ions are all pH dependent.
Chemical precipitation of orthophosphates with Al(IlI) under favorable pH conditions
follows the reaction:
A13+ + HnPO43-n ^ AlPO4(s) + nH+
Stumm and Morgan [25] have calculated the total phosphate solubility for AlPC>4(s) as a
function of pH (Figure 6) from solubility equilibrium and acidity constants, ignoring the
possible influence of phosphate-hydrous oxide complex formation. The minimum
solubility at pH 6 is calculated to be 0.01 mg/1. At pH 5, the calculated solubility
increases to 0.03 mg/1 and at pH 7, increases to 0.3 mg/1.
As discussed earlier, the aluminum ion also undergoes a competing hydrolysis reaction to
form a hydrous oxide according to the stoichiometric relationship:
-25-
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TABLE I
FORMS OF PHOSPHORUS IN DOMESTIC WASTEWATER
(After 31)
FORMS
Suspended or Insoluble Organic Phosphorus
Bacterial Cell Material
Plant Debris
EXAMPLES
Phospholipid
Phosphoprotein
Nucleic Acids
Polysaccharide Phosphate
Dissolved Organic Orthophosphates
Sugar Phosphates
Inositol Phosphates
Phospholipids
Phosphoamides
Glucose-1 -Phosphate
Adenosine Mono Phosphate
Inositol Mono and
Hexaphosphate
Glycerophosphate
Phosphatidic Acid
Phosphocreatine
Orthophosphate
-, HP042', P043'
Inorganic Condensed Phosphates
Pyrophosphate
Tripolyphosphate
Trimetaphosphate
HP2073-, P204'
HP3°104"- P3°105"
-26-
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PH
H3P04
-2
01
O
•6
-10
6
pH
8
10
12
FIGURE 5
EFFECT OF pH ON VARIOUS FORMS OF ORTHOPHOSPHATE
-3r
-7
FIGURE 6
SOLUBILITY OF ALUMINUM (III) PHOSPHATE
-27-
-------
A13+ + 6H2O ^± Al(H2O)3(OH)3(s) + 3H+
In neutral and alkaline solutions, AlPO4(s) is quite soluble, favoring the formation of the
hydrous oxide. Consequently, the stoichiometric efficiency of phosphate removal with
Al(III) would be expected to decrease with increasing pH above about 6.0. This
relationship has been experimentally observed by several investigators with the optimum
removal efficiency occurring between pH 5.5 and 6.0 [31,32].
In the lower pH range of effective precipitation, the AlPO4(s) formed is a negatively
charged colloid. Al(III) in excess of the stoichiometric requirement is necessary to
produce a positively charged hydrous oxide floe to coagulate and remove the precipitated
particles from suspension.
The precipitation mechanism alone cannot always account for the total phosphate
removed from solution. Aluminum and ferric hydroxides exhibit a strong tendency for
adsorption of both ortho- and polyphosphates [25]. The same type of chemical forces
involved in aluminum phosphate precipitation are likely responsible for this adsorption
phenomena. Phosphate adsorption onto Al(OH)3(s) generally increases as the pH
decreases, tending to conform to the AlPO4(s) solubility diagram on Figure 6.
Stumm and Morgan [25] explain the mechanism of adsorption to be a replacement of an
-OH group with a phosphate group in the hydrated metal oxide complex. As an example:
H2o OH I ]HOO OH
H0O-AI-OH
-
OH
/
/
H2O-AI-OPO3H2
OH
OH"
_1
(S)
-------
1. Mechanical straining and sedimentation
2. Physical-chemical adsorption between the suspended material and the filter
media.
Flocculation induced by the media and biological growth within the filter bed are
secondary factors that may also contribute to particle removal [33].
Filter performance and efficiency depend to a large extent on both the characteristics of
the suspended material being removed and the physical properties of the filter, including
filter-media grain size, shape, density and chemical composition, and filter bed porosity.
The characteristics of primary importance include:
1. Concentration
2. Particle size and distribution
3. Floe strength
4. Electrostatic charge of the particle
Of these, floe strength is commonly the dominant factor affecting- solids removal
efficiencies and filter performance.
Biological floe is generally much stronger than chemically induced floe. The strength of
biological floe increases as the mean detention time of the solids in the biological
treatment process increases. Thus, the suspended solids from an extended aeration
activated sludge system would be expected to be more cohesive than that produced in
contact stabilization or high rate activated sludge processes. Mechanical straining at or
near the surface of the filter is the principal mechanism responsible for removal of strong
floe.
Chemical floe tends to shear easily, penetrating into the filter bed. A combination of
straining and adsorption is involved in separating fragile floe. The addition of polymers
can add strength to the floe structure, improving particle capture in the filter bed.
Turbidity is an easily measured parameter frequently used to monitor filter performance.
Tchobanoglous and Eliassen [33] have demonstrated that within limits, the suspended
solids concentration can be correlated with turbidity measurements.
Rapid sand filters, using a single media with an effective particle size of between 0.35
and 1.0 mm, have conventionally been used for treatment of domestic water supplies,
with limited application to filtration of biologically treated wastewater. During the
backwash cycle the filter bed is hydraulically expanded to remove the entrapped
particulates. The finest media rise to the top of the bed while the coarser grain sizes tend
-29-
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to remain at the bottom. As a result, the media is sized from fine to coarse in the normal
direction of flow when filter operation is resumed (Figure 7). The effect of this gradation
is for most of the suspended solids in the water being treated to be removed at or near
the surface, with 75 to 90 percent of the head loss occurring in the upper inch of the
filter bed [26]. The single media filter is essentially a surface filtration device. Any
particles escaping the surface layer will likely pass through the bed and be present in the
filter effluent.
2
Rapid sand filters are conventionally sized for a surface loading of 2 gpm/ft and are
capable of effectively treating waters with turbidities in the range of 5 to 10 Jackson
Turbidity Units (JTU) [34].
To more fully utilize the full depth of the bed for removing and storing suspended solids,
the concept of multimedia filtration was developed in the early 1960's. Using filter media
of differing densities and particle sizes, a gradation of particle size generally from coarse
to fine in the direction of flow can be achieved. Figure 8 is an idealized illustration of a
mixed-media filter bed. Coarse media of low density form the upper layers while finer
grain size higher density media make up the lower levels of the filter bed.
Two or three separate media with specific gravities ranging from 1.55 to 4.2 and particle
sizes from 2.0 mm to 0.15 mm are commonly used. The types of media used include
activated carbon (sp. gr. 1.5), anthracite coal (sp. gr. 1.65), silica sand (sp. gr. 2.6), and
garnet (sp. gr. 4.2).
By carefully controlling the size distribution of each media, the average grain size will
gradually decrease from the top to bottom of the filter. Distinct layers do not develop.
Particles of each type of media can be found throughout the bed as illustrated on Figure
9.
The coarse to fine media distribution, or more correctly, the pore space distribution
between particles, provides "in depth" filtration and storage of suspended solids
throughout the entire depth of the bed. Compared to single media rapid sand filtration,
more suspended material can be removed by properly designed multimedia filters before
backwashing is necessary.
The decreasing void gradation of mixed-media filters allows higher filtration rates than
conventional rapid sand filters. In addition, the very finely sized media (0.15 mm)
provide a considerable amount of surface area for adsorption of colloidal size particles,
substantially increasing filter effluent quality.
Mixed-media filters are capable of operating at hydraulic loading rates of 5 to 15 gpm
and producing effluents containing one to 5 mg/1 suspended solids from extended
aeration activated sludge systems without chemical coagulation [26]. Chemical
coagulation of secondary effluent can produce treated wastewater essentially free of
suspended solids with turbidities in the order of O.I JTU [26].
-30-
-------
o
2
g
o
cc
Q
GRAIN SIZE
FIGURE 7
CROSS-SECTION THROUGH SINGLE-MEDIA BED
SUCH AS CONVENTIONAL RAPID SAND FILTER
o
z
g
o
LU
OC
Q
FIGURE 8
CROSS-SECTION THROUGH IDEAL FILTER
UNIFORMLY GRADED FROM COARSE TO FINE
FROM TOP TO BOTTOM
GRAIN SIZE
-31-
-------
TOP
iu
Q
Q
iu
CD
>*-COURSE PARTICLES
MEDIUM PARTICLES
FINE PARTICLES
20
40 60
PARTICLE DISTRIBUTION %
80
100
FIGURE 9
DISTRIBUTION OF MEDIA IN A PROPERLY DESIGNED
MIXED-MEDIA FILTER
-32-
-------
SECTION IV
TREATMENT FACILITIES
GENERAL DESCRIPTION
An aerial view of the Tualatin tertiary treatment plant is shown on Figure 10. The
photograph was taken at the completion of construction.
Domestic waste from the City's collection system flows by gravity to the plant through a
12-inch diameter sewer to the influent pump station (1). Industrial wastewater from the
Hervin Company also flows by gravity through an 8-inch diameter sewer to the influent
pump station. The combined raw wastewaters are lifted by two submerged pumps
through two 4-inch pipes to the headworks (2). Solids in the wastewater are normally
shredded by a comminutor (3). If the comminutor is out of service for maintenance or
repair, the raw influent can be bypassed through a stationary bar screen.
The flow from the headworks is split and continues by gravity to the aeration-surge basin
(4) through two 8-inch pipelines, having outlets under each floating mechanical aerator.
In addition to providing oxygen for biological treatment, the aerators evenly distribute
the incoming raw waste in the basin, maintaining a completely mixed system.
The aeration-surge basin allows the tertiary portion of the plant to operate at a constant
rate, as the basin water level rises and falls in response to changes in the influent flow
rate. The basin effluent flows upward through the tube type secondary clarifier (5)
located in the center of the aeration-surge basin, and into a collection pool above the
tubes. The water level in the clarifier is essentially the same as that in the surrounding
aeration-surge basin.
Activated sludge, separated from the treated wastewater in the clarifier, settles back down
through the tubes. The solids are continuously drawn from the bottom of the clarifier
into the aeration-surge basin by aerator induced velocity currents. Waste activated sludge
is pumped through two 3-inch pipelines located directly beneath the tube clarifier to the
waste activated sludge storage ponds (6). Supernatant from the sludge storage ponds is
returned by gravity flow to the plant influent pump station.
Clarified secondary effluent is withdrawn at a constant rate by the tertiary influent pump
(7) to an overflow box (8). The tertiary pump is automatically controlled by the water
surface elevation in the aeration-surge basin. A flow splitting arrangement in the overflow
box, returning a portion to the suction side of the tertiary influent pump, allows the
flow rate through the tertiary system to be varied. The effluent from the secondary tube
clarifier can also be discharged directly to the plant effluent pump station (14), bypassing
the tertiary system.
From the overflow box. the secondary effluent continues by gravity through the
flocculator tank (9), the tertiary tube settler (10), and mixed-media gravity filter (11)
-33-
-------
1. INFLUENT PUMP STATION
2. HEADWORKS
3. CQMMINUTOR
4. AERATION-SURGE BASIN
5. SECONDARY TUBE CLARIFIER
6. ACTIVATED SLUDGE PONDS
7. TERTIARY INFLUENT PUMP
8. OVERFLOW BOX
9. FLOCCULATOR TANK
10. TERTIARY TUBE SETTLER
11. MIXED MEDIA FILTER
12. ALUM STORAGE TANK
13. BACKWASH STORAGE TANK
14. EFFLUENT PUMP STATION
15. CHEMICAL SLUDGE HOLDING TANK
16. CHEMICAL SLUDGE PONDS
17. CONTROL BUILDING
FIGURE 10
TREATMENT FACILITIES
-34-
-------
Alum is added to the tertiary influent for phosphate removal and to improve suspended
solids reduction. A metering pump in the control building (17) feeds liquid alum from a
storage tank (12) to the suction side of the tertiary influent pump. Provisions are made
to add soda ash (sodium carbonate) on the discharge side of the tertiary influent pump
for pH adjustment as necessary. Polyelectrolyte can also be added to the secondary
effluent at the constant head box to aid flocculation. Both polyelectrolyte and soda ash
are stored and fed through metering pumps in the control building. The flash mixing
action of the tertiary pump and turbulence in the piping and overflow box disperse the
chemical coagulant and flocculation aids prior to flocculation.
The flocculator inlet flow enters at the bottom of the tank. Gentle agitation by paddle
blades brings the chemically coagulated solids and suspended material into intimate
contact, forming floe particles of ever increasing size.
Following coagulation and flocculation the wastewater passes through an outlet near the
top of the tank into the inlet of the tertiary tube settler-filter unit. The flow is split to
two rows of inclined settling tubes,where the bulk of the chemically coagulated and
flocculated solids are removed.
The effluent from the tube bundles collects in a center trough, discharging into the
mixed media filter compartment. Remaining particulate is separated from the wastewater
as the flow passes down through the filter bed. The spaces between the media grains
become progressively smaller in the direction of flow. Larger particles are entrapped in
the upper portion of the filter bed, while final polishing occurs in the lower levels. A
gravel support and pipe lateral underdrain system collect the filtered water. To improve
solids removal efficiency and control turbidity breakthrough, a small dosage of
polyelectrolyte is added just prior to filtration.
Filtered wastewater is piped away through the tertiary effluent pump to the backwash
storage and chlorine contact tank (13). A level controller-throttling valve system
modulates the effluent flow, from the settler-filter unit to maintain a constant water level
over the mixed media filter. This control system allows the effluent flow to be matched
to the influent flow, regardless of changes in the influent flow rate or pressure drop
across the filter as solids become trapped in the bed.
When the differential pressure across the filter rises to a preset value, the backwash cycle
is automatically initiated. Both the tertiary influent and effluent pumps are stopped and
the effluent valve closed. The waste valve from the tertiary tube settling compartment
opens, draining the unit by gravity to the chemical sludge holding tank (15).
The receding water level carries with it the settled solids stored in the tubes, leaving the
tubes clean and ready for the next filtration cycle. While the settler-filter unit is draining,
the filter surface wash and backwash operations are begun.
-35-
-------
The surface wash system consists of a fixed grid arrangement of nozzles directed
downward toward the filter bed. The surface wash pump delivers water from the
backwash tank to the high-pressure jets, breaking up solids deposited on the filter surface
and scouring the media.
The backwash pump, also drawing water from the backwash storage tank, reverses flow
through the filter underdrain system fluidizing the filter bed. A control valve maintains a
constant backwash flow. As the bed expands, the suspended solids trapped by the media
are carried upward out of the bed and into a wash water collection trough, discharging
into the tertiary settler compartment. The relatively high upward velocity of the
backwash water in the filter bed causes a rolling action of the media. The media rub
against each other, tending to scour and clean the individual grains.
The initial portion of the backwash flow, containing most of the filtered suspended
solids, is wasted to the tube settler compartment of the tertiary settler-filter unit scouring
the bottom of the tank. Before the backwashing operation is complete, however, the
waste valve is closed and the settling compartment partially refills with backwash water.
The tertiary influent pump is restarted at this time. About six minutes before the
backwash cycle is complete, the surface wash is discontinued to allow the media to
hydraulically level. When the tube settler and filter compartments are nearly full, the
backwash flow is stopped. The tertiary effluent pump is restarted and normal tertiary
operation resumed.
When the backwash storage tank has refilled, the filtered wastewater overflows through
an outlet near the top of the tank into the plant effluent pump station (14). Plant flow
is metered in the force main from the effluent pump station. Chlorination is provided in
both the backwash tank and the effluent pump station. The combined volume of the
backwash storage tank and the 6-inch force main to the Tualatin River provide a
minimum of one hour contact time at the average design flow to comply with the State
of Oregon disinfection standards. Chlorine storage and metering facilities are located in
the control building. (17).
The spent backwash water in the chemical sludge holding tank (15) is held for a
predetermined period of time, allowing the heavier solids to settle. The supernatant is
automatically pumped to the headworksfor return to the aeration-surge basin. Settled
chemical sludge is pumped from the bottom of the tank to the chemical sludge storage
ponds (16). The overflow from the chemical sludge storage ponds returns by gravity
through an 8-inch pipeline to the influent pump station.
An emergency bypass is provided around the plant between the influent and effluent
pump stations in the event of a power outage or major failure of the secondary-tertiary
system. The plant effluent can also be diverted to the chemical and activated sludge
storage ponds. In the design of the plant, provisions were made for an emergency
generator to provide standby power to the effluent pump station. The generator was not
installed during the research and demonstration phase of the project, however.
-36-
-------
Figure 11 is a schematic diagram of the treatment system, showing the flow pattern and
location of sampling points, flow metering, main control valves and pumps.
DESIGN CONCEPT
In addition to demonstration of a tube type clarifier for separation of biological floe in
an activated sludge system and chemical coagulation, flocculation, tube sedimentation,
and mixed media filtration as a tertiary treatment process for extended aeration systems,
the facilities were designed to minimize:
1. Construction and operating labor costs.
2. The necessity of highly trained operators.
3. Susceptibility to upset resulting from organic and hydraulic
shock loads and toxic wastes.
4. Waste solids handling, stabilization, and disposal.
To accomplish these objectives, the secondary-tertiary treatment system employed the
following design concepts:
Primary clarification and grit removal facilities were eliminated. Grit settles in the
aeration basin and will be removed by hydraulic dredging or other means when necessary.
A plastic (PVC) membrane was used to line the aeration basin in place of higher cost
reinforced concrete construction.
The complete mix extended aeration activated sludge process was selected for secondary
treatment to reduce susceptibility to process upsets from organic and hydraulic shock
loads and toxic wastes. Hydraulic surge capacity allowing two feet of fluctuation in water
level was provided in the aeration-surge basin, permitting the tertiary system to operate at
a constant rate.
Since tertiary treatment was required only during the warmer months of April through
October, weather protection was not provided for the tertiary facilities, including pumps
and control equipment. The majority of the tertiary piping was located above ground for
ease of installation and access.
The tertiary system as well as waste sludge pumping was completely automated to
minimize the necessity for operator attention.
Storage ponds were used for stabilization as well as storage of waste activated and
chemical sludges, eliminating the need for separate anaerobic or aerobic sludge digestion
facilities and greatly simplifying waste solids handling and disposal.
-37-
-------
^ EMERGENCY BYPASS „
f
RAW SEWAGE
INFLUENT^
/ ^
t
1
u-
cc
UJ
O
|
H
Z
ft
Ul
O-
^INFLUENT SECQNDARY
PUMP STATION ^||
AERATION-SURGE v
BASIN \
HEADWORKS ANO \
^-COMMINUTION UNIT \
\ ^
X
-^ i 1 ,
PMBM
*
T S-B -J (F
S-D(-
/
t
1
ACTIVATED SLUDGE -j
POND NO. 1 I"4 — "
1
ACTIVATED SLUDGE _
POND NO, 2 •* ra J
1
t
CHEMICAL SLUDGE -,
POND NO. 1 W
CHEMICAL SLUDGE ^
POND NO. 2 W
FIERx
1
^
)LEir
DECA
LIQU<
s
ALUM FEED
SODA ASH FEED
POLYELECTROLYTE FEED I , EFFLUENT
) /BACKWASH 1 PUMP STATION
/OVERFLOW i *^ "
/BOX i*-l
/ g
^A. ** .
^U: 8< .
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nx/FRFi r\\M —«, , .
TERTIARY
OVERFLOW
^ T xFORCE MAIN
^1 cc I to LU S-C, - . /
5LUuJQ
-------
DESIGN CRITERIA
The criteria used for final design of the City of Tualatin tertiary treatment plant are
listed in Table 2.
TABLE 2
DESIGN CRITERIA
FLOW
Design Average 280,000 gpd
Design Maximum 636,000 gpd
Peak Instantaneous 720,000 gpd
ORGANIC LOADING
Domestic
BOD5 460 Ibs/day
Population Equivalent' 2,700
Industrial
BOD5 170 Ibs/day
Population Equivalent 1,000
Total
BOD5 630 Ibs/day
Population Equivalent 3,700
EFFLUENT REQUIREMENTS (TERTIARY OPERATING)
Maximum BOD^ f 10 mg/1
Maximum Suspended Solids^' 10 mg/1
Soluble Phosphate (as P) 0.1 to 1.0 mg/1
Turbidity 1 JTU
t Based on 0.17 Ibs BODc/capita/day.
M Oregon State Department of Environmental Quality discharge standards for the Tualatin River are 10 mg/1 BOD,
and 10 mg/1 suspended solids.
-39-
-------
DESIGN FACTORS
The design factors used for the major units and equipment selection are listed in
Appendix A, Photographs of selected units are included in Appendix B. Appendix C lists
the manufacturers of major equipment items. The major treatment units are briefly
described below.
The aeration-surge basin is an earthen structure lined with 20 mil PVC plastic and
surrounded by a 4-foot high concrete ring wall. A typical section through the
aeration-surge basin is shown on Figure 12. The overall dimensions of the basin are
approximately 70 feet by 90 feet by 12 feet minimum depth in the center portion. Two
15 hp floating mechanical aerators supply oxygen for biological treatment. The basin
provides a minimum of 24 hours detention time at the design flow of 0.28 mgd, with an
additional surge storage capacity of approximately 75,000 gallons. This additional storage
allowance provides capacity to accommodate peak plant inflow rates in excess of the
tertiary design flow rate, backwash water from the tertiary system, storage of plant flow
during the backwash cycle when the tertiary unit is out of service, and supernatant
returned from the chemical sludge holding tank and sludge storage ponds.
The secondary tube clarifier is located in the center of the aeration-surge basin. The unit
consists of two tube bundles 6 feet wide by 20 feet long by 3-1/2 feet high, with one
bundle located approximately 1-1/2 feet above the other. An end view of the tube
clarifier is shown on Figure 13. Each tube bundle is made up of four separate modules
fabricated by solvent welding extruded plastic channels at a 60 degree inclination from
the horizontal between parallel plastic sheets. By alternating the direction of inclination
of each row of channels, the module becomes a self-supporting beam that need only be
supported at the ends. Each tube is 2 inches square. The plastic sheets are 0.010-inch
nominal thickness rigid calendared polyvinyl chloride (PVC). The plastic channels are
0.020-inch nominal thickness acrylonitrile butadiene styrene (ABS). An illustration of a
tube module resembling an egg crate is shown on Figure 14.
The tube clarifier is supported by an aluminum frame connected to a reinforced concrete
slab on the bottom of the aeration basin. The lower tube module is approximately 6 feet
above the basin floor. Effluent from the clarifier unit is collected in a 20-foot long,
6-inch diameter perforated collection pipe located in a collection pool above the upper
tube bundle. At the design flow of 235 gpm, the tube clarifier has an overflow rate of
approximately 2 gpm per square foot.
Flocculation of the secondary effluent is carried out in an 8-foot diameter by 10-foot
high steel tank resting on a concrete pad. Detention time at the design flow rate is
approximately 15 minutes. The flocculation mechanism consists of redwood paddles
bolted to steel angle arms clamped to a solid steel drive shaft. The flocculator mechanism
is mounted in a vertical position.
The tertiary tube settler and mixed-media filter are housed in a single rectangular steel
tank installed on a concrete pad. Figure 15 is an illustration of the tertiary tube
settler-filter unit.
-40-
-------
n>rHA!\IDRAIL
MAXIMUM WATER LEVEL
MINIMUM WATER LEVEL
BASIN
BOTTOM
COMPACTED
LINER BASE
GRAVEL
BACKFILL
NOTE: INSIDE SURFACE DIMENSIONS
OF BASIN 68'x88'
SCALE: %" = I'-O"
FIGURE 12
AERATION-SURGE BASIN
TYPICAL SECTION
-------
MAXIMUM
WATER LEVEL
MINIMUM
WATER LEVEL
BOTTOM OF
AERATION
SURGE BASIN
i • -if/ 3" DIAMETER v A i
SLUDGED/ SLUDGE WITH- \vSLUDGE
^-^DRAWAL PIPELINES
PERFORATED
COLLECTION
PIPE TO TERTIARY
INFLUENT PUMP
MIXED LIQUOR
TUBE MODULE
6" WIDE x 2' DEEP
BOTH SIDES
TUBE MODULE
6' WIDE x 20' LONG
x 3'-6" DEEP
AIR SPARGING
SYSTEM
FIGURE 13
TUBE CLARIFIER
TYPICAL SECTION
FIGURE 14
60° INCLIJMED TUBE MODULE
-42-
-------
±
BACKWASH OUTLET
1 9--0" (INSIDE) 1
1TIARY 1
LUENT
_ — j.
SS
5?
V
H
cr
g
5
<
I _
"7 "
Y
\ -
f ~
(-
Z
UJ
D
_i
u.
Z
\ -
- -»
V-2"
•\ \ N
\ > I.., —
I )
7%° INCLINED TUBE
SETTLER MODULE
I i
EFFLUENT COLLECTION TROUGH
•f f II /
7V1° INCLINED TUBE
SETTLER MODULE
; J
—/ -S
9'-3"
15'-11V4" (INSIDEI
A-
•>• \ FILTER B
^ /'"cblLEcric
u =
4- U
^ 0 ,
\
\
\^
ACKWASH
N^T'ROUGTT"/'
in
•*-^»
i 2
o-XJs — ii__
5'.6"
16--8"
>
• MIXED MEDIA
FILTER BED
_ FIXED GRID
FILTER SURFACE
WASH SYSTEM
FILTER
EFFLUENT
PLAN VIEW
MIXED MEDIA
FILTER COMPARTMENT
LF.VEL SENSORS
3" HIGH DENSITY
MEDIA
UNDERDRAIN PIPING
AND COLLECTION
SYSTEM
" GRAVEL
ELEVATION VIEW
FIGURE 15
TERTIARY SETTLER/FILTER UNIT
-------
The settler compartment contains two tube modules in addition to distribution baffles
and an effluent collection trough. The settling tube modules consist of a multiplicity of
hexagonal shaped channels 2 inches in depth, 39 inches long, and inclined at an angle of
7-1/2 degrees from the horizontal. The modules are fabricated from solvent welded 30
mil ABS plastic sheets. The settling unit has an overflow rate of less than 150 gpd per
square foot of settling area at the design flow rate. The total basin detention time at this
flow condition is approximately 30 minutes.
The mixed-media filter compartment is made up of a filter media bed, support gravel, a
pipe lateral underdrain system, and a surface wash system above the filter bed. The
rotary surface washarms originally installed were replaced midway through the project
with a fixed grid surface wash system.
The filter bed is 5-1/2 feet wide by 9-feet long by 51 inches deep. The filter media in the
top 30 inches of depth consists of 55 percent anthracite coal (1.5 sp.gr.), 30 percent
silica sand (2.6 sp.gr.) and 15 percent garnet sand (4.0 sp.gr.). The particle size of the
mixed-media ranges from 0.2 to 1.2 millimeters. The mixed-media is underlain by 3
inches of coarse garnet support gravel followed by 18 inches of graded stone, ranging
from 3/16 to 2 inches in. diameter. At the design flow, the filtration rate is
approximately 4.75 gpm per square foot. The filter is backwashed at a rate of
approximately 16 gpm per square foot.
Chlorination is provided in both the backwash storage tank and in the effluent pump
station. The combined contact time of the backwash storage tank and the outfall to the
Tualatin River at the average daily flow of 280,000 gallons per day is 65 minutes.
The control building houses plant control equipment, laboratory and office, a restroom,
Chlorination facilities, chemical storage and feeding equipment, and a workshop and
miscellaneous storage area. The plant is designed to operate to a large degree by
automatic control. The plant influent and effluent pump stations operate on water level.
A bubble type level sensor in the aeration-surge basin automatically starts and stops the
tertiary unit and chlorinator at preset water levels. The tertiary filter backwash system is
automatically initiated,when the filter head loss reaches a preset value. The backwash
cycle sequence of events is controlled by a mechanical programmer, which automatically
resets at the end of each backwash cycle.
-44-
-------
SECTION V
DEMONSTRATION PROCEDURES
PLANT STARTUP
Prior to startup, the aeration-surge basin was filled with tap water. On 1 April 1970,
wastewater from the Hervin Company was turned into the plant and the aerators
activated. At the same time, the aeration-surge basin was charged with two truck loads of
barnyard manure and approximately 4000 gallons of activated sludge to initiate biological
activity. The following week, the first domestic flow was received at the plant.
Formation of a biological floe and an increase in mixed liquor suspended solids (MLSS)
were observed during the first week after startup. Activated sludge was not intentionally
wasted in order to build biological solids in the basin.
The MLSS increased at a farily uniform rate from an initial value of 100 to 2200 mg/1 by
mid-May. During this period, the sludge volume index (SVI) dropped from 400 to 50.
The secondary treatment system was assumed to be completely acclimated within
approximately six weeks after startup, when BOD5 reductions of 95 percent were
achieved in the aeration-surge basin.
During the startup period, the tertiary system was operated without the addition of
chemicals.
OPERATION
After startup in April 1970, routine operation and data collection for the demonstration
phase of the program had to be delayed until August as a result of problems encountered
at the plant. In mid-April, the plant operator/research technician suffered a serious
accident and was not able to return to work full-time until mid-July. A temporary
operator who had minimal laboratory experience was employed part-time to maintain and
operate the facilities during the regular operator/research technician's absence. In
addition, an undetected leak in the aeration-surge basin liner allowed gas generation under
the membrane, causing it to tear and float. Repairs were not complete until mid-July.
During this period, low influent flows allowed the plant to be operated intermittently.
Normal plant operation was resumed in late July. The tertiary system operated
continuously until the last week in November, when freezing conditions damaged the
chemical decant pump. During December 1970, the tertiary system was operated
manually during the day. Cold weather forced suspension of tertiary operation from
January through March 1971. Modifications were made to the secondary tube clarifier
and tertiary equipment to improve performance while the tertiary system was out of
service.
Normal tertiary operation was resumed from April 1971 to the end of October 1971.
Table 3 is a detailed schedule of plant operation during the demonstration project.
-45-
-------
DETAILED OPERATIONAL SCHEDULE
DATE
APRIL 1970
MAY
JUNE
JULY
AUGUST
SEPTEMBER
OCTOBER
NOVEMBER
DECEMBER
JANUARY 1971
FEBRUARY
MARCH
APRIL
MAY
JUNE
JULY
AUGUST
SEPTEMBER
OCTOBER
AVERAGE
PLANT FLOW
(GPO)
39.300
31.400
22,300
34,300
43,100
81,300
109,100
88,700
112,300
1 18,500
97,600
115,100
87,900
73,400
94,800
88,900
115,200
1 16,600
107,300
AVERAGE
MLSS<"
IMG/L)
500
2,100
2,100
1,300
1,400
1,100
1,100
1,100
1,400
1,700
2,800
2,400
1,900
1,800
2,600
1,900
2,100
2.800
2,500
TERTIARY
FLOW RATE
(GPM)
80,90. 180, 200
70, SO, 200
80, 200
70, 80, 200
75
75, 135, 195
185, 195
0, 185
0, 185
0, 185
0, 120, 190
0,85, 165, 190
0, 190
190
190
110.190
110
140
140
CHEMICAL DOSAGE IMG/L)
ALUM(2)
0
0
0
0
0. 117
0, 29. 58, 96
1(6-119
0, 111, 137, 150.
155.184,212,
238. 262
0. 95, 155
0, 95, 155.208
0
0
0
0, 126, 155. 210
0. 155, 183
0, 94, 126, 155,
182. 240
0,63,94, 107, 126
155, 160, 215,242,
266, 315
0,56,81, 105-108,
135, 190, 217, 242
106, 146
83, 105
POLYELECTROLYTE
PRE-SETTLER
0
0
0
0
0
0
0
0, 0.52, 0.62. 0.95,
1.05, 1.6, 2.0, 2.7
0, 0.52, 0.55. 1.00,
2.0, 3.5
0
0
0
0. 1.0, 1.4, 1.9
0. 0.45, 0.50. 1.00
1.3. 1.4. 1.9
0, 0.45, 0.50, 1,0,
1.40, 1.90, 2.00
0, 1.1, 1.4, 1.5
0, 1.1, 1.5. 1.8
0, 0.50. 1.12
0
PRE-FILTER
0
0
0
0
0
0
0
0
0
0
0
0
0, 0.10, 0.22
0, 0.06. 0.10, 060
0, 0.06, 0.10
0, 0.03, 0.04
0, 0.03
0.03, 0.04, 0.05
0.04
SODA ASH(3'
0
0
0
0
0
0 - 18.3
0 - 56.7
0 -8.6
0
0
0
0
0 - 60.0
0
0
0 - 49.0
0
0
0
(1) MIXED LIQUOR SUSPENDED SOLIDS
(2) AI2(S04I3-14.3 H20
(3t Na 2C03
-------
The research and demonstration program was officially brought to a close at the end of
August 1971. However, data collected in September and October 1971 has been included
in this report to expand the data base for evaluating plant operation and performance.
SAMPLING SCHEDULE AND PROCEDURES
Samples were routinely collected at various locations throughout the secondary-tertiary
system. The locations of the sampling points are indicated on Figure 11 and are described
below. Table 4 lists the testing program and approximate sampling schedule followed
during the demonstration period.
PLANT INFLUENT
Composite samples of the plant influent were collected from the headworks at sample
point A (Figure II), located downstream of the comminutor. Samples of equal volume
were composited with an automatic sampler at regular time intervals from 10 August
1970 to 15 September 1970, 22 September 1970 to 7 January 1971, and 18 May 1971
to 16 August 1971. At all other times, influent samples were manually composited from
grab samples of equal volume collected 3 to 5 times during the normal daily 8-hour
operating period.
AERATION-SURGE BASIN
Daily grab samples were taken directly from the aeration-surge basin, sample point B, for
MLSS, SVI, and D.O. determinations.
SECONDARY EFFLUENT
Secondary effluent samples of equal volume were composited manually 3 to 5 times
during the daily 8-hour operating period. When the tertiary system was operating, the
secondary effluent samples were withdrawn from the tertiary influent pipeline ahead of
the chemical feed locations, sample point Cj with the aid of a hand-operated suction
pump. When the tertiary system was not in service, secondary effluent samples were
taken from the secondary bypass discharge to the effluent pump station, sample point
C2-
WASTE ACTIVATED SLUDGE
Grab samples were periodically taken from a tap on the discharge of the waste activated
sludge pump, sample point D.
TERTIARY (PLANT) EFFLUENT
Unchlorinated tertiary effluent grab samples of equal volume were taken from a tap
located in the discharge pipeline between the tertiary filter and the backwash tank,
sample point EI, and manually composited 3 to 5 times during the normal daily 8-hour
period. Chlorinated tertiary (plant) effluent samples were collected periodically at the
plant effluent pump station, sampling point E^-
-47-
-------
TABLE 4
ROUTINE SAMPLING AND TESTING SCHEDULE
(APPROXIMATE NUMBER OF TESTS PER MONTH)
SAMPLE
LOCATION
A PLANT
INFLUENT
AERATION-
B SURGE BASIN
CONTENTS
r SECONDARY
EFFLUENT
WASTE
D ACTIVATED
SLUDGE
E TERTIARY
EFFLUENT
SLUDGE
F POND
SUPERNATANT
OO
1- 00
12
12
12
P
O
LU
_J
O
!§
O co
12
Q
UJ
Q
Z in
LU Q
lo
20
20
20
p(3)
20
P
Q
LU
> Z
_J LLI
O C3
00
20
20
H
Z
h- ^
O-!
h- <
20
20
20
20
I
a
20
20
20
20
P
LU
cr
I-
LU
a.
LU
H
20
20
20
20
1/3
20
(1)
n
^ -C3
0
-------
SLUDGE POND SUPERNATANT
Grab samples were periodically taken of the combined sludge pond supernatant overflow
at the point of discharge into the influent pump station, sampling point F.
ANALYTICAL METHODS
All analyses, with the exception of nitrogen, phosphorus and coliform tests, were
performed in the treatment plant laboratory. Nitrogen and phosphorus analyses were
performed by the EPA at the Pacific Northwest Environmental Research Laboratory in
Corvallis, Oregon. A limited number of coliform tests were performed by the City of
Portland's Tryon Creek Sewage Treatment Plant and by the Public Health Laboratory of
the Oregon State Health Department. All routine analyses were performed in accordance
with Standard Methods [35].
NITROGEN AND PHOSPHORUS
Nitrogen and phosphorus tests were performed in accordance with the FWPCA manual
[36].
A list of laboratory equipment used for the analytical testing is included in Appendix C.
-49-
-------
SECTION VI
WASTEWATER CHARACTERISTICS
GENERAL
The domestic waste water collection system for the City of Tualatin was constructed
concurrently with the treatment plant. When the plant was started up in April 1970, a
population of less than 150 was connected and contributing flow to the City sewerage
system. In the initial months of the demonstration program, industrial wastewater from
the Hervin Company constituted the bulk of both the flow and organic load to the
plant.
Additional domestic connections were made periodically in the succeeding months of the
study, increasing the contributing population to approximately 1025 by August 1971.
The industrial flow, however, continued to be the major source of organic load,
substantially influencing the influent wastewater characteristics and plant performance.
The industrial flow was measured and recorded beginning the last week of September
1970 through October 1971. The strength of the industrial wastewater was not
continuously monitored, however. Only the combined industrial-domestic influent was
sampled on a regular basis. Therefore, direct analysis of the organic loadings contributed
by Hervin Company and from domestic sources was not possible.
INFLUENT CHARACTERISTICS
The following parameters of the combined industrial and domestic wastewater were
measured: flow; 5-day biochemical oxygen demand (6005); total suspended solids
(TSS); kjeldahl, ammonia, nitrite and nitrate nitrogen; ortho and total phosphorus; total
alkalinity; pH and temperature.
The data obtained during the demonstration program has been divided into five time
intervals, corresponding to warm and cold weather periods and changes in the influent
organic loading: (1) 3 August - 25 October 1970, (2) 26 October - 2 May 1971, (3) 3
May - 27 June 1971, (4) 28 June - 11 July 1971, and (5) 12 July - 31 October 1971.
The average, maximum, minimum, and standard deviation values for the parameters
measured in the plant influent during each time period and for the entire demonstration
program are listed in Table 5. In the final period, nitrogen and phosphorus
determinations were made during August 1971 only.
The Hervin Company normally operated on a five-day week schedule, Monday through
Friday, except for a two-week vacation period in late June and early July each year.
Influent samples were routinely collected during the week, but not on weekends when
the treatment plant was unattended. The data in Table 5 represent the characteristics of
the combined industrial and domestic flows to the plant, except for period (4). Only
domestic wastewater was received during this time interval.
-51-
-------
TABLE 5
COMBINED INDUSTRIAL AND DOMESTIC INFLUENT WASTEWATER CHARACTERISTICS
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
FLOW
-------
The Hervin Company suspended operations for two weeks each summer for annual
employee vacations. During these periods in both 1970 and 1971 influent samples were
collected to characterize the domestic contribution to the influent wastewater in the
absence of infiltration and to provide data to estimate BOD, nitrogen and phosphorous
loadings during the weekends. The results of these analyses, together with data from four
samples collected on other days, when only domestic wastewater was received by the
plant, are summarized in Table 6.
FLOW
Daily plant flow was measured in the effluent from the treatment plant. Due to the surge
capacity in the aeration-surge basin and the low flows experienced during the
demonstration period, the daily influent and effluent flows were not necessarily
equivalent.
The daily effluent flow averaged over the week, however, was considered to be
representative of the average daily influent flow.
The average flow during the demonstration program was about 0.10 mgd. The average
weekly flow varied from a minimum of 0.0359 mgd to a maximum of .1524 mgd. Figure
16 is a plot of the average weekly flow, rainfall, and population contributing to the plant
versus time for the demonstration period. The effect of infiltration during wet weather
periods, as well as the general increase in flow with population, is evident.
BIOCHEMICAL OXYGEN DEMAND
The BODg of the combined industrial-domestic weekday influent flow averaged 534 mg/1
and varied between a minimum of 96 mg/1 and a maximum of 1520 mg/1 during the
demonstration period. The BODj of the domestic flow, determined from influent samples
collected when Hervin Company was not operating and infiltration was not a factor,
averaged 230 mg/1. Figure 17 is a plot of the average weekday BOD^ concentration
versus time.
Also shown on Figure 17 is the 7-day average weekly BOD^ concentration, weighted to
include the weekend domestic flow. The 7-day average weekly BOD$ concentration was
calculated from the following equation:
7-day average BOD (mg/l) = [5 day BOD x Q5 x 8.34] x 5 + [POP x P.E.] x2
t x 8.34 x 7
-53-
-------
TABLE 6
DOMESTIC WASTEWATER INFLUENT CHARACTERISTICS
PARAMETER AVERAGE RANGE
BOD (MG/L)
TSS (MG/L)
KJEL-N (MG/L)
NH3-N (MG/L)
ORG-N (MG/L)
N02-N (MG/L)
NO3-N (MG/L)
TOTAL-N (MG/L)
ORTHO-P (MG/L)
TOTAL -P (MG/L)
230.
275.
54.1
38.9
15.2
0.051
0.04
54.2
11.1
16.5
158.
148.
45.0 -
31.0 -
12.1 -
0.01 1 -
0.005 -
45,0 -
8.8 -
12.8 -
355.
512.
69.3
54.0
18.5
0.12
0.12
69.3
17.0
20.0
-------
1500
O
1000
5? 50°
O
°- o
4.0
3.0
53J
< in
OCX 2.0
UJ
III
1.0
0
0.2
Q
i
~ 0.15
O
0.1
UJ
UJ
a
< 0.05
DC
UJ
PERIOD
YEAR
0.0
AUG. I SEPT.
T
OCT. | NOV
1970
DEC.
JAN.
3 "4 I
MAY j JUNE ] JULY
1971
FEB. | MAR. | APR.
FIGURE 16
POPULATION, RAINFALL AND FLOW VERSUS TIME
AUG. | SEPT. | OCT.
-------
a"
8
UJ
O
1500.0
1200.0
CC
>_ 900.0
1-1 600.0
r-
O
300.0
0.0
1500.0
1200.0
CC
S£-» 900.0
600.0
if)
PERIOD
YEAR
300.0
0.0
5 DAY
7 DAY
5 DAY AVERAGE
7 DAY AVERAGE
/
w/v
/A
1
AUG. | SEPT.
OCT.
1970
NOV. I DEC. I JAN.
2
! FEB.
~~ '"" I 3" T 4~1 " 5
MAR. ' APR. ! MAY JUNE JULY | AUG. | SEPT. OCT
1971
FIGURE 17
INFLUENT BOD AND TSS CONCENTRATION VERSUS TIME
-------
Where: 5 day BOD = Average weekday BOD$ concentration (mg/1)
C?5 = Average weekday flow (mgd)
Q-y = Average 7-day weekly flow (mgd)
POP = Average monthly population connected to the plant
P.E. = Calculated population equivalent, or per capita,
BOD loading (Ibs/cap - d)
8.34 = Conversion constant ([Ibs/10 gal] )/ [mg/1])
This equation was also used to calculate 7-day weekly averages for influent TSS.
The per capita loadings were developed from the domestic wastewater characterization
data in Table 6 and are discussed in more detail later in this section.
TOTAL SUSPENDED SOLIDS
The TSS concentration averaged 517 mg/1 for the combined industrial and domestic
influent flow over the demonstration period and ranged between a minimum of 93 mg/1
to a maximum of 1730 mg/1. The average TSS concentration determined for the domestic
flow only was 275 mg/1. The average weekday TSS concentration and 7-day average
weekly TSS concentration are also shown on Figure 17.
NITROGEN
The influent nitrogen was present mainly as organic nitrogen and ammonium ion. The
total nitrogen content of the combined industrial and domestic influent averaged 54.4
mg/1 (as N) during the project, varying from a minimum of 24.0 mg/1 to a maximum of
117 mg/1. The average nitrite plus nitrate nitrogen for the combined influent was 0.17
mg/1. The total nitrogen content of the domestic only contribution averaged 54.2 mg/1
with nitrite and nitrate nitrogen constituting less than 0.1 mg/1.
PHOSPHORUS
The ortho and total phosphorus concentrations of the combined influent averaged 7.7
and 11.2 mg/1 (as P), respectively. The orthophosphate levels ranged between 1.18 and
17.0 mg/1 and the total phosphate concentrations between 1.60 and 21.0 mg/1. The
average ortho and total phosphorus contents for domestic flow only were determined to
be 11.1 and 16.5 mg/1, respectively.
NUTRIENT RATIO
The average BODjinitrogeiXas N):phosphorus (as P) ratio in the combined industrial and
domestic influent for the demonstration period was 100:10.2:2.1. The average nutrient
ratio of the domestic waste contribution was 100:23.6:7.2.
-57-
-------
TOTAL ALKALINITY AND pH
The total alkalinity tended to increase during the course of the project from an average
value of 148 mg (as CaCO3) during August-October 1970 to 235 mg/1 in the period
August-October 1971. The average value of the alkalinity was 187 mg and ranged from
52 to 359 mg/1. The pH ranged between 6,55 and 8.30. The median pH value of the
influent was 7.25.
TEMPERATURE
The influent temperature ranged from 10 to 31 degrees C and averaged 20 degrees C,
LOADING
The daily flow (mgd) and BODg TSS, total nitrogen and total phosphorous loadings (Ibs
per day) of the combined industrial and domestic influent were averaged weekly for the
five week days (Monday - Friday). Average daily flows and loading were also calculated
on a 7-day week basis, to include the effect of domestic flow only on weekends. The
seven-day week average daily loadings were calculated using the following equation:
7-day week average daily loading (Ibs/day) =
[Average weekday loading (Ibs/day)] x 5 + [POP x P.E.] x 2
7
Where: POP = Average monthly population connected to the plant
P.E. = Calculated population equivalent (Ibs/cap - d)
The average, maximum, minimum, and standard deviations for each of the loading
parameters are summarized in Table 7 for the five separate time periods and for the total
duration of the demonstration project.
FLOW
The average weekday flow for the demonstration period was 0.1019 mgd and varied from
a minimum of .0419 during the week of 24-28 August 1970 to a maximum of .1704
mgd during the week of 12-16 October 1970. Over the 7-day week, the daily flow
averaged 0.0972 mgd for the demonstration period. The minimum and maximum 7-day
week average daily flows of 0.0359 mgd and 0.1524 mgd occurred during the same
respective weeks also.
BOD
The average weekday BOD5 loading ranged from 110 Ibs per day during the week of 5-9
July when Hervin Company was shut down for annual employee vacations, to a
maximum of 1,340 Ibs per day in the week of 11-15 January 1971. The average weekday
-58-
-------
TABLE 7
INFLUENT LOADINGS
5-DAY WEEK (MONDAY-FRIDAY]
AVERAGE MAXIMUM MINIMUM
7-DAY WEEK (MONDAY-SUNDAY)
MAXIMUM MINIMUM STD. DEV.
PERIOD
FLOW
BOD5
TSG
TOTAL-N
TOTAL-P
PERIOD
FLOW
BODg
TSS
TOTAL-N
TOTAL-P
PERIOD
FLOW
BOD5
TSS
TOTAL-N
TOTAL-P
PERIOD
FLOW
BOD5
TSS
TOTAL-N
TOTAL-P
PERIOD
FLOW
BODg
TSS
TOTAL-N
TOTAL-P
PERIOD
FLOW
BOD5
TSS
TOTAL-N
TOTAL-P
(MGD)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
0.0822
259.
247.
30.9
5.6
0.1704
481.
370
51.6
9.2
0.0419
125.
106.
17.9
2.5
3 AUGUST - 25
0.0406
117.
78.8
9.9
1.8
OCTOBER 1970
0.0788
207.
195.
26.5
5.3
0.1524
366.
284.
41.5
8.0
0.0359
110.
94.
17.0
3.2
0.0384
84.
57.
7.2
1.3
26 OCTOBER 1970-2 MAY 1971
(MGD)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(MGD)
(LBS/DAYI
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(MGD)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(MGD)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(MGD)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
(LBS/DAY)
0.1081
456.
420.
40.1
8.4
0,0893
478.
507.
47.1
9.4
0.0720
111.
176.
32.3
9.7
0.1161
670.
607.
63.3
12.9
0.1019
470.
438.
42.6
8.7
0.1410
1340.
916.
81.1
15.6
0.1159
943.
924.
77.9
15.9
0.0738
113.
181.
35.9
10.6
0.1323
1211.
1235.
75.4
15.9
TOTAL
0.1704
1340.
1235.
81.1
15.9
0.0739
184.
121.
20.8
4.6
0.0732
185.
229.
15.5
4.7
28 JUNE
0.0702
110.
170.
28.6
8.7
0.0905
380.
357.
43.8
9.5
0.0204
278.
175.
14.8
2.9
3 MAY -27
0.0171
237.
229.
21.6
3.8
0.1030
352.
322.
33.8
7.6
JUNE 1971
0.0848
377.
392.
40.8
8.9
0.1520
983.
676.
63.0
12.7
0.1082
721.
699.
65.0
14.2
0.0689
157.
110.
20.3
4.9
0.0691
161.
188.
16.7
5.1
0.0210
198.
125.
10.5
2.1
0.0151
177.
171.
17.2
3.2
- 11 JULY 1971 (DOMESTIC WASTE ONLY)
0.0025
2.
8.
5.1
1.4
12 JULY - 31
0.0122
212.
192.
11.2
1.8
DEMONSTRATION PROJECT -
0.0419
110.
106.
15.5
2.5
0.0266
269.
213.
17.7
3.5
0.0746
728.
166.
32.6
9.8
OCTOBER 1971
0.1101
538.
483.
56.6
12.7
3 AUGUST 1970
0.0972
373.
343.
37.1
8.2
0.0778
128.
169.
34.9
10.6
0.1225
930.
937.
66.1
15.1
- 31 OCTOBER
0.1524
983.
937.
66.1
15.1
0.0714
128.
163.
30.3
9.1
0.0921
333.
297.
41.1
10.5
1971
0.0359
110.
94.
16.7
3.2
0.0045
0.
4.
3.2
1.1
0.0096
154.
139.
8.8
1.3
0.0251
201.
160.
14.6
3.2
-59-
-------
BODc loading for the demonstration period was 470 Ibs per day. The absence of
industrial flows on weekends reduced the daily loads averaged over a 7-day period by
about 20%. Daily BOD loadings averaged over the 5-day and 7-day week are plotted
versus time on Figure 18.
The treatment plant experienced organic overload conditions (design capacity 630 Ibs
BOD per day) during one or more weeks in all but the first three-month period. During
August through October 1971, the average weekday BOD loading was 689 Ibs per day.
As a result, satisfactory D.O. levels could not be maintained in the aeration-surge basin.
Secondary treatment performance was impaired, particularly during the later phases of
the demonstration program. The effect of organic overloading on plant performance and
operation is discussed in Sections VII and VIII.
TSS
The average weekday TSS loading ranged from 106 Ibs per day during the week of 17-21
August 1970 to 1235 Ibs per day during the week of 6-10 September 1971. The weekday
TSS loading averaged 438 Ibs per day for the demonstration period. When averaged over
the 7-day week, the domestic weekend flow reduced the weekday TSS load by
approximately 22 percent. The 5-day and 7-day week average daily TSS loadings are
shown on Figure 18.
TOTAL NITROGEN
The weekday total nitrogen loading averaged 42.6 Ibs per day over the total
demonstration period and varied from a minimum of 15.5 Ibs per day during the week of
31 May-4 June 1971 to a maximum of 81.1 Ibs per day during the week of 28 December
1970-1 January 1971. Averaging the total nitrogen loading over 7 days reduced the
average weekday loading approximately 12.5 percent. The 5-day and 7-day week average
daily nitrogen loadings are plotted versus time on Figure 19.
TOTAL PHOSPHORUS
The weekday total phosphorus loadings ranged from 2.5 Ibs per day during the week of
19-23 October 1970 to 15.9 Ibs per day during the weeks of 21-25 June 1971 and 2-8
August 1971. The average weekday total phosphorus loading for the demonstration
period was 8.7 Ibs per day. Averaging the total phosphorus loading over a 7-day week
reduced the 5-day average loading by approximately 4.5 percent. The 5-day and 7-day
week average daily total phosphorus loadings are plotted versus time on Figure 19.
INDUSTRIAL WASTEWATER
Both the flow and BOD of the industrial wastewater from Hervin Company varied
widely. The daily flows ranged from 1,600 to 101,800 gpd. The average daily flow from
the last week of September 1970 through August 1971 was 26,400 gpd. BOD analyses
run on industrial wastewater samples during and after the demonstration period ranged
between 840 and 3400 mg/1. It is estimated that between 50 and 65 percent of the
organic load, applied to the treatment plant during the demonstration program, resulted
from industrial wastewater.
-60-
-------
1500.0
5 DAY AVERAGE
7 DAY AVERAGE
5 DAY AVERAGE
7 DAY AVERAGE
PERIOD
YEAR
AUG. | SEPT. | OCT. | NOV. | DEC.
1970
JAN. | FEB. ] MAR. I APR, I MAY | JUNE I JULY AUG. I SEPT.
1971
FIGURE 18
INFLUENT BOD AND TSS LOADINGS VERSUS TIME
-------
100.0
2
LU
O
£ <
- £ 75.0
Z! jf\
II
Z 50.0
25.0
in
o
cc
0.0
20.0
15.0
10.0
in
ccz
5 1 "
>- -I
<
o
in
PERIOD °°
YEAR
1 I
AUG. I SEPT. t OCT. I NOV. I DEC.
1970
2 I 3 I 4 I 5
JAN. I FEB. I MAR. I APR. I MAY I JUNE I JULY I AUG. I SEPT. I OCT.
1971
FIGURE 19
INFLUENT NITROGEN AND PHOSPHOROUS LOADINGS VERSUS TIME
-------
DOMESTIC PER CAPITA LOADINGS
In August 1971, approximately 365 single-family dwellings were connected to the City
sewerage system, contributing an average flow of 95,000 gpd to the treatment plant. The
effect of infiltration on the total influent flow during the month was negligible due to
the dry weather conditions of the preceding three months. The 1970 census indicated an
average of 2.8 population per dwelling in the City of Tualatin. From these data the
average per capita flow was calculated to be 93 gallons per day.
Using the average influent BOD, TSS, nitrogen, and phosphorus values determined for the
domestic wastewater (Table 6), the following influent per capita loadings were calculated:
BOD - 0.178 Ib/cap/d
TSS - 0.213 Ib/cap/d
TOTAL - N - 0.042 Ib/cap/d
ORTHO - P - 0.0086 Ib/cap/d
TOTAL - P - 0.0128 Ib/cap/d
INFILTRATION
Infiltration contributed a significant flow to the treatment plant, during the prolonged
wet weather of winter and spring. An estimate of the average daily infiltration flow was
made for each month from November 1970 through May 1971. The infiltration flow was
assumed to be the difference between the total plant flow and the combined industrial
and domestic wastewater flows. The industrial wastewater contribution was measured
directly. The domestic flow was estimated by applying the per capita flow of 93 gpcd to
the estimated population connected to the plant each month. The average daily total
plant flow and infiltration flow for each month and the total monthly rainfall are shown
on Figure 20.
-63-
-------
n
120 -
TOTAL PLANT FLOW
1970
1971
FIGURE 20
EFFECT OF INFILTRATION ON TOTAL PLANT FLOW
-64-
-------
SECTION VII
TREATMENT PLANT PERFORMANCE
GENERAL PLANT PERFORMANCE
Although the plant was started up in April 1970, problems with the aeration-surge basin
liner delayed routine testing and data analysis until August 1970. With the exception of a
brief period in June and July when repairs were being made to the aeration-surge basin
liner, the secondary portion of the treatment plant operated continuously during the
demonstration project.
The tertiary system was operated on a routine basis from August 1970 through the end
of November 1970, when freezing weather damaged several pieces of equipment. During
December 1970 through March 1971, the tertiary unit was operated intermittently. With
the onset of warmer weather in April the tertiary system was reactivated and run
continuously for the duration of the project.
At the beginning of the project, both the hydraulic and organic loadings applied to the
plant were considerably below the design capacity of the system.
During the course of the project, however, the organic loading frequently exceeded the
aeration capability of the secondary system, resulting in a degradation in secondary
effluent quality. The increased organic loading was primarily due to expansion of Hervin
Company's production facilities and the inability of their pretreatment system to reduce
the strength of the industrial wastewater to the level anticipated at the time the
treatment plant was designed.
The continual addition of domestic connections to the Tualatin wastewater collection
system, particularly during the months of June, July and August of 1971, added to the
overload condition. This increase in domestic connections had been anticipated and
allowed for in the design of the plant. The increased industrial waste load, however, used
up most of the capacity allocated for the domestic flow.
The hydraulic capacity of the plant was never reached during the demonstration program.
The maximum daily flow recorded was 0,256 mgd. During the peak flow month of
January 1971, the average daily flow approached 45 percent of the design hydraulic
capacity.
Two additional problems also affected secondary treatment performance. Excessive
electrical current draw caused the aerators to kick off periodically, interrupting the
oxygen supply to the aeration-surge basin. Although modifications were made to the
aerators, this problem was never satisfactorily resolved during the demonstration program.
-65-
-------
Entrapment of biological solids in the tube bundles of the secondary clarifier and
subsequent septic conditions greatly increased the suspended solids content of the
secondary effluent at various times in the first half of the program. Modifications made
to the secondary tube clarifier in March 1971 substantially alleviated this problem.
Even though poor performance of the secondary system at certain times severely taxed
the tertiary unit, a consistent, high quality final effluent could be maintained with the
addition of chemicals.
SECONDARY TREATMENT SYSTEM
GENERAL
The following parameters were routinely monitored throughout the demonstration
program to provide a basis for analysis of secondary treatment system performance:
Aeration-Surge Basin: Temperature, pH. alkalinity, dissolved oxygen (D.O.),
mixed liquor suspended solids (MLSS), sludge volume
index (SVI), and waste sludge.
Secondary Effluent^: BOD; TSS; kjeldahl, ammonia, nitrite, and nitrate
nitrogen; ortho and total phosphorus, pH and alkalinity.
The secondary treatment system data was separated into the same five time periods for
analysis and presentation as the plant influent data:
1. 3 August - 25 October 1970
2. 26 October 1970 - 2 May 1971
3. 3 May - 27 June 1971
4. 28 June - 11 July 1971
5. 12 July - 31 October 1971
Combined industrial and domestic wastewaters were treated during weekdays in periods
1, 2, 3, and 5. In period 4, Hervin Company's operations were suspended for annual
employee vacations. Only domestic wastewater was treated in this two week period.
Nitrogen and phosphorus determinations were not made in September and October 1971. Aeration-surge basin
temperatures were not recorded in September 1971.
-66-
-------
The secondary system performed reasonably well, producing an acceptable effluent for
tertiary treatment most of the time during periods 1, 3, and 4. Solids accumulation
problems in the secondary clarifier degraded the secondary effluent quality much of the
time in period 2. The modifications made to the secondary tube clarifier considerably
improved performance after March 1971.
In the final period, the organic loading frequently exceeded the aeration capacity of the
plant. As a result, secondary treatment performance degenerated toward the end of the
program.
AERATION-SURGE BASIN PERFORMANCE
The data obtained from the aeration-surge basin are summarized in Table 8. The average,
maximum, minimum and standard deviations for the parameters measured are listed for
each of the five time periods and for the entire demonstration project.
TEMPERATURE-The average weekly temperature of the aeration-surge basin varied
from a maximum of 22.5 degrees C during the second week of August 1971 to a
minimum of 8.1 degrees C in the second week of January 1971. The average temperature
for the demonstration period was 15.5 degrees C. The daily aeration-surge basin
temperature versus time is shown on Figure 21. The range of temperatures experienced
by the secondary system did not appear to measurably affect treatment performance. The
relatively long sludge ages and low F/M's tended to minimize the effects of temperature.
pH AND ALKALINITY-The pH and alkalinity were directly affected by the extent of
nitrification in the aeration-surge basin. When D.O, levels were adequate to support full
oxidation of the ammonia nitrogen fraction, the pH remained between 6.4 to 6.8 and the
alkalinity between 40 to 80 mg/1. When nitrification was inhibited, the pH stabilized
between 7.3 to 7.5 and the alkalinity remained above 200 mg/1. Continual monitoring of
pH and alkalinity provided a reasonably good qualitative assessment of the extent of
nitrification. The daily values of pH and alkalinity are plotted versus time on Figure 21.
Return of the tertiary backwash from the chemical sludge holding tank also affected the
aeration-surge basin pH and alkalinity. During the first period (3 August-25 October
1970), low levels of alkalinity resulting from nitrification could not provide sufficient
buffer capacity to offset the acidity of the backwash water, when alum was being fed to
the tertiary system. Lime was added at the comminutor basin during September and
October 1970 to control the aeration-surge basin pH.
To prevent pH depression in the aeration-surge basin during the spring and summer of
1971, the entire filter backwash volume was pumped directly to the chemical sludge
storage lagoons. Algal activity maintained the pH of the lagoons above 7, effectively
neutralizing the backwash water.
•
There was a tradeoff, however, to this mode of operation. The lagoon return supernatant
was at times heavily laden with algae. A significant amount of algae appeared to pass
-67-
-------
TABLE 8
AERATION-SURGE BASIN DATA SUMMARY
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM .
MINIMUM .
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
TEMP.
(DEC. C)
17.2
19.1
15.5
1.0
12.0
15.1
8.1
1.8
17.0
20.0
14.2
1.9
16.0
16.2
15.9
0.2
19.3
22.5
13.5
2.8
15.5
22.5
8.1
3.6
(1)
pH
6.90
7.45
5.70
0.50
6.85
7.65
6.05
0.32
7.20
7.40
6.80
0.16
6.80
7.30
5.90
0.50
7.40
7.50
5.40
0.28
ALK.
(MG/L)
43.
90.
15.
22.
106.
223.
34.
51.
159.
230.
112.
39.
28
85.
142.
28.
80.
233.
273.
116.
50.
D.O,
(MG/L)
1.5
3.9
0.2
1.0
1.6
4.3
0.2
1.1
0.8
1.6
0.2
0.5
MLSS WASTE SLUDGE u' SLUDGE A
(MG/L) SVI (LBS./DAY) (GPD)
3 AUGUST TO 25 OCTOBER 1970
1210 69 253. 18,200
1810 105 675. 41,710
920 46 95. 6,910
245 15 187. 11,060
26 OCTOBER 1970 TO 2 MAY 1971
1860 96 176. 7,060
3130 134 711. 30,170
750 65 0 0
706 18 178. 7,680
3 MAY TO 27 JUNE 1971
2250 82 265. 9,770
3250 93 615. 27,430
1600 71 0 0
587 7 189. 8,980
(DAY!
12.0
31.1
6.4
7.2
12.3
23.7
4.1
5.6
17.6
31.3
8.1
8.0
JUNE TO 11 JULY 1971 (DOMESTIC WASTE ONLY)
2.5
2.9
2.0
0.6
0.4
2.1
0.1
0.5
2060 99 260. 9-970
2150 102 496. 18.680
1980 97 24. 1.260
118 3 334. 12,320
12 JULY TO 31 OCTOBER 1971 (5'
2320 203 364. 16,510
2890 380 H54, 56,710
1680 100 45. 1i710
352 89 269. 13,820
TOTAL DEMONSTRATION PROJECT - 3 AUGUST 1970 - 31 OCTOBER
7.40
7.65
5.40
0.55
118.
273.
15.
73.
1.2
4.3
0.1
1.0
1910 116 250. 11,860
3250 380 1154. 56.710
750 46 0 0
656 68 216 11,150
27.7
31.1
24.4
4.7
12.0
23.3
4.6
4.8
1971
13.3
31.3
4.1
6.6
(II AVERAGE VALUE IS MEDIAN pH
(21 DAILY AVERAGE COMPUTED FROM WEEKLY AVERAGE.
(31 SLUDGE AGE DEFINED AS TOTAL SUSPENDED SOLIDS (LBS)
IN THE AERATION-SURGE BASIN DIVIDED BY THE TOTAL
SUSPENDED SOLIDS (LBS/DAYI LOST FROM THE SECONDARY
TREATMENT SYSTEM. SLUDGE AGE COMPUTED ON A TWO
WEEK MOVING AVERAGE.
0.102
0.198
0.047
0.050
0.144
0.281
0.046
0.083
0.098
0.136
0.038
0.033
0.025
0.026
0.024
0.001
0.136
0.229
0.088
0.041
0.122
0.281
0.024
0.063
(4) FOOD TO MICROORGANISM RATIO (F/M) DEFINED
AS TOTAL INFLUENT 5 DAY BOD (LBS/DAY) DIVIDED
BY THE TOTAL SUSPENDED SOLIDS (LBS) IN THE
AERATION-SURGE BASIN.
(5) TEMPERATURE RECORDED FOR JULY, AUGUST,
AND OCTOBER ONLY.
-68-
-------
PERIOD
YEAR
FEB. I MAR. I APR.
FIGURE 21
3 [ 4
MAY I JUNE I JULY
1971
AERATION-SURGE BASIN TEMPERATURE, pH AND TOTAL ALKALINITY VERSUS TIME
-------
through the aeration-surge basin and into the secondary effluent. The larger volume of
lagoon return supernatant, resulting from putting all of the filter backwash in sludge
holding lagoons, had the potential to increase the suspended solids loading to the tertiary
system.
DISSOLVED OXYGEN-The D.O. in the aeration-surge basin fluctuated between 0 to 4
mg/1, varying with the influent BOD load. The daily values of D.O. are shown on Figure
22. From September to mid-November 1970 and January through May 1971, D.O. levels
above 0.5 mg/1 could generally be maintained. The increased organic load during the
summer and fall of 1971 held the D.O. about 0.2 mg/1, except for the two week period
in June and July when the industrial flow to the plant was temporarily suspended.
SLUDGE VOLUME INDEX-The SVI tended to increase during the demonstration
program, ranging from a minimum weekly average of 46 in August 1970 to a maximum
of 380 in October 1971. The average SVI for the demonstration period was about 116.
The daily values of SVI versus time are shown on Figure 22. The increase in SVI
appeared to correspond with a decrease in D.O.
MIXED LIQUOR SUSPENDED SOLIDS-The variation in the daily MLSS is shown on
Figure 23. The weekly average of the MLSS ranged from a minimum of 750 mg/1 to a
maximum of 3,250 mg/1. The average MLSS for the program was 1,910 mg/1.
WASTE ACTIVATED SLUDGE—Biological solids were wasted from the aeration-surge
basin through two suction lines located beneath the secondary tube clarifier. The mixing
pattern created by the aerators tended to sweep the settled solids out from under the
clarifier and into the basin. As a result, thickening was limited to about 1.2 times the
MLSS concentration.
An attempt was made to thicken the solids by shutting down the aerators and allowing
the MLSS to settle for 15 minutes before wasting. At SVI levels of 60 to 100, the MLSS
could be thickened to between 6,000 to 9,000 mg/1. Thickening waste activated sludge in
this manner had several limitations, however. After 15 to 30 minutes of wasting, the
compacted sludge around the suction lines was withdrawn and the solids concentration
rapidly decreased. With high organic loads frequently taxing aeration capacity, turning off
the aerators only aggravated the difficulty of maintaining adequate D.O. in the
aeration-surge basin. For these reasons, this method of thickening waste activated sludge
was not generally practiced.
An average of 250 pounds per day of solids was intentionally wasted from the secondary
treatment system.
SLUDGE AGE-The sludge age, defined as the total suspended solids in the aeration-surge
basin divided by the total suspended solids lost from the secondary treatment system
(secondary effluent and intentional wasting), ranged between 4 to 31 days. The average
sludge age for the entire demonstration period was 13 days. Sludge age was calculated on
a two week moving average. Data for the week in which the sludge age was determined
was averaged with the data from the previous week. This method of calculation was
-70-
-------
8.0 !
6.0 I
> i I
x 4.0 i!
o I i
2 i i
2.0
0.0
500.0
400.0
300.0
c/3
200.0
100.0
PERIOD
YEAR
0.0
,1 I 2 1 3 H 4T 5
AUG. | SEPT. I OCT. I NOV. i DEC. I JAN. I FEB. I MAR. I APR. I MAY I JUNE i JULY I AUG I SEPT.
1970 ' FIGURE 22 1971
AERATION-SURGE BASIN DISSOLVED OXYGEN AND SVI VERSUS TIME
' OCT.
-------
4000.0
3000.0
2000.0
1000.0
0.0
35.0
V)
I
a
Ul
CO
5
UL
30.0
25.0
20.0
15.0
10.0
5.0
0.0
0.3
0.2
0.1
PERIOD
YEAR
o.o
1 I 2 | 3 4
AUG. | SEPT. I OCT. I NOV. I DEC. I JAN. I FEB. I MAR I APR. I MAY I JUNE i JULY
1970 I FIGURE 23 1971
MLSS, SLUDGE AG£ AND F/M VERSUS TIME
AUG.
SEPT. 1 OCT.
-------
necessary to dampen the effects of infrequent activated sludge wasting. Sludge age versus
time is shown on Figure 23.
F/M-The average weekly F/M varied between 0.024 to 0.28. The average F/M over the
demonstration program was 0.122. F/M versus time is also shown on Figure 23.
DETENTION TIME -The hydraulic detention time in the aeration-surge basin averaged
about 2.6 days, ranging from 7.1 days at the beginning of the program to about 1.2 days
during peak flows in mid-January 1971.
SECONDARY EFFLUENT
The secondary effluent data are summarized in Table 9. The average, maximum,
minimum and standard deviations of the parameters routinely measured are listed for
each of the five time periods and for the total demonstration program.
BIOLOGICAL OXYGEN DEMAND-The BOD5 removal in the secondary treatment
system averaged 84 percent over the demonstration program. This poor BOD removal is
attributed to several factors, including organic loadings in excess of the aeration capacity,
aerator malfunction, and high solids carry-over in the secondary effluent.
Nitrification was also suspected in many of the secondary and tertiary effluent
tests, producing high readings. Simultaneous measurement of both the carbonaceous and
nitrogeneous components in the 8005 analysis would considerably bias the test results.
As a result, the percentage removals of the carbonaceous BOD fraction only were likely
much higher than the test results indicated, particularly during May through October
1971.
Secondary effluent BOD5 versus time is plotted on Figure 24. From August through
October 1970 and for brief time intervals during other periods, total BOD5 removals
approached 92 to 95 percent.
*
To estimate actual soluble BOD5 removal, a plot was made of the secondary effluent
total BOD5 versus suspended solids (Figure 25) for days when the D.O. was 1.0 mg/1 or
greater and nitrification had essentially gone to completion in the aeration-surge basin.
From Figure 25 the average soluble BOD5 concentration was determined to be about 3.0
mg/1, correlating well with tertiary effluent soluble BOD5 measurements made during the
same time periods. In terms of secondary effluent soluble BOD5 removals exceeding 99
percent were possible, when adequate aeration was available.
SUSPENDED SOLIDS-The level of suspended solids in the secondary effluent varied
widely, from a minimum of 20 mg/1 to a maximum of 820 mg/1. The daily suspended
solids content of the secondary effluent versus time is shown on Figure 24.
-73-
-------
TABLE 9
SECONDARY EFFLUENT CHARACTERISTICS
BOD5
(MG/LMLBS/DAY)
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
PERIOD
AVERAGE
MAXIMUM
MINIMUM
STD. DEV.
TSS KJEL-N(1) NH3-N ORG-N NOg-N NOg-N
(MG/LULBS/DAY) (MG/U (MG/U (MG/U (MG/U (MG/U
TOTAL-N ORTHO-P121
(MG/U (MG/U
TOTAL-P
(MG/U
pH<3>
ALK<4>
(MG/U
DAILY
FLOW
(MGD)
3 AUGUST - 25 OCTOBER 1970
28.
111.
12.
20.
102.
400.
17.
101.
74.
151.
22.
36.
65.
104.
29.
31.
79.
178.
27.
40.
73.
400.
12.
66.
24.5
118.
1.7
24.4
110.
676.
7.7
137.
57.3
143.
16.0
38.1
40.8
86.4
10.6
32.3
82.5
202.
25.5
45.8
71.9
676.
1.7
85.0
68.
477.
21.
69.
187.
820.
25.
220.
56.
141.
26.
28.
81.
404.
22.
121.
108.
585.
20.
96.
116.
820.
20.
148.
53.6
405.
4.8
69.7
184.
1,260
11.7
248.
43.0
134.
10.0
29.8
31.5
92.0
9.9
24.2
105.
586.
18.7
94.
TOTAL
107.
1.260.
4.8
162.
10.5
36.0
1.0
6.3
17.8
46.3
1.8
13.9
22.0
35.1
6.4
9.3
28
14.9
44.7
2.7
16.0
36.2
60.8
2.9
15.5
1.5
6.4
0.1
1.5
26
5.9
24.1
0.2
7.3
10.7
20.5
0.1
6.7
9.0 0.41 16.6
33.6 3.54 32.0
0.9 0.080 0.16
5.7 0.63 8.7
OCTOBER 1970 - 2 MAY 1971
11.9 0.38 8.8
41.3 2.05 22.1
1.5 0.002 0.01
9.8 0.49 6.7
3 MAY - 27 JUNE 1971
11.3 0.23 2.1
25.8 0.98 19.0
5.3 0.005 0.005
5.8 0.30 5.1
JUNE - 11 JULY 1971 (DOMESTIC WASTE
6.6
24.1
0.1
9.4
12
22.0
34.0
0.1
9.4
8.3 8.4 14.7
30.0 25.2 33.6
2.5 0.069 0.03
9.0 10.2 15.5
JULY - 31 OCTOBER 197l'5'
14.2 0.20 3.3
45.2 3.80 38.2
0.9 0.006 0.003
9.7 0.66 10.0
DEMONSTRATION PROJECT - 3 AUGUST 1970 -
21.5
60.8
1.0
15.5
10.3
34.0
0.1
10.9
11.2 0.93 9.1
45.2 25.2 38.2
0.9 0.002 0.003
7.7 3.5 10.7
27.4
47.7
9.0
9.2
27.0
61.7
12.5
12.5
24.4
. 35.3
12.3
7.4
ONLY)
38.0
44.8
31.3
4.2
39.6
60.9
11.7
11.5
- 31 OCTOBER
31.4
61.7
9.0
11.3
6.80
12.0
0.24
3.69
3.84
7.92
0.90
1.98
4.45
7.80
1.79
2.07
6.62
9.40
3.60
2.32
6.52
12.6
2.10
3.01
1971
5.88
12.6
0.24
3.15
7.6
15.7
0.52
3.8
7.0
13.0
1.32
2.9
6.0
9.7
2.65
1.9
8.0
10.5
4.70
2,2
8,3
15.0
3.91
3.4
7.6
15.7
0.52
3.2
7.05
7.40
5.75
0.46
7.10
7.65
4.50
0.42
7.50
7.60
6.95
0.17
6.9
7.60
6.20
0.58
7.40
7.55
6.80
0.14
7.5
7.65
4.5
0.55
39.
104.
6.0
28.
77.
208.
8.0
44.
130.
193.
50.
37.
69.
181.
9.0
71.
192.
257.
44.
45.
111.
257.
6.0
73.
0.0739
0.1876
0.01 14
0.0499
0.1030
0.2249
0.0302
0.0366
0.0849
0.1658
0.0256
0.0351
0.0746
0.1200
0.0270
0.0300
0.1101
0.2561
0.0429
0.0268
0.0973
0.2561
0.0114
0.0391
(1) NITROGEN REPORTED AS N (M.W. 14.01)
(2) PHOSPHORUS REPORTED AS P 1V.W. 30.98)
(3) AVERAGE VALUE IS MEDIAN pH
(4) ALKALINITY REPORTED AS EQUIVALENT CaCO,
(M.W. 100.09)
(5) N AND P DETERMINED FOR JULY AND AUGUST ONLY.
-------
900.0
PERIOD
YEAR
AUG i SEPT
OCT
1970
"1 3" [4l "5
FEB. I MAR. I APR. I MAY I JUNE ' JULY I AUG. I SEPT,
FIGURE 24 1971
NOV. I DEC I JAN
'
SECONDARY EFFLUENT BOD AND TSS CONCENTRATION VERSUS TIME
OCT.
-------
o
o
00
40
35
30
25
20
15
10
cc
<
Q
8 *
LLJ
00
0 o
NOTE: DO > 1.0 MG/L, NITRIFICATION
ESSENTIALLY COMPLETE.
I
10
20 30 40 50 60 70
SECONDARY EFFLUENT TOTAL SUSPENDED SOLIDS (MG/L)
80
90
100
FIGURE 25
SECONDARY EFFLUENT TOTAL BOD VERSUS SUSPENDED SOLIDS
-------
With the exception of the first week in October 1970, the secondary effluent suspended
solids level remained consistently below 85-90 mg/1 and averaged 60 mg/1 from August
through mid-November 1970. From mid-November until the air sparging modifications to
the secondary clarifier were completed in March, large quantities of solids were
periodically carried over, presumably as a result of solids accumulation and gassification
in the tube modules.
Daily sparging for 15 minutes prevented solids build-up in the tubes and considerably
improved the effluent quality. Except for a two week period toward the end of June
1971, the secondary effluent suspended solids concentration averaged 48.5 nig/1 until the
last week of July 1971. From this point on through the end of the program, the
secondary effluent quality degenerated primarily as a result of the inability to maintain
adequate D.O. levels in the aeration-surge basin.
The suspended solids removal in the secondary treatment system averaged 75 percent
over the demonstration program. For the period following modification of the secondary
clarifier, the suspended solids removal averaged 84 percent.
The possible effects of MLSS concentration, temperature, surface overflow rate, pH and
extent of nitrification on the secondary tube clarifier performance and effluent suspended
solids concentration are discussed in Section VIII.
NITROGEN -The total, ammonium and nitrate concentrations measured in the secondary
effluent are shown versus time on Figure 26. The long sludge ages, at which the
secondary treatment system was operated, presented ideal conditions for nitrification. So
long as sufficient D.O. was available, nitrification approached completion. The extent to
which D.O. controlled nitrification can be seen in comparing the D.O. levels on Figure 22
with the ammonium and nitrate concentrations on Figure 26. At D.O. levels above 1.0
mg/1 the ammonium concentration generally remained below 1.0 mg/1. Reducing the D.O.
to around 0.2 to 0.4 mg/1 effectively inhibited nitrification, limiting the nitrate
concentration to less than 0.5 mg/1.
The total nitrogen content of the secondary effluent ranged between 9.0 and 61.7 mg/1
and averaged 31.4 mg/1, representing a 42 percent reduction in influent total nitrogen.
The higher total nitrogen levels were primarily due to large suspended solids carryover in
the secondary effluent.
The soluble nitrogen content - ammonium, nitrite and nitrate - varied between 2.6 and
40.4 mg/1 and averaged 18.5 mg/1. Filtering the secondary effluent to remove suspended
solids could potentially have increased the total nitrogen removal to 66 percent.
PHOSPHORUS-The ortho and total phosphate concentrations of the secondary effluent
versus time are also shown on Figure 26. The secondary effluent total phosphate
concentration ranged from 0.52 to 15.7 mg/1 and averaged 7.6 mg/1. This represents an
average reduction of 32 percent of the influent total phosphorous load.
-77-
-------
TOTAL P
ORTHO P
AUG. I SEPT. \ OCT. I NOV. ! DEC.
JAN. I FEB. I MAR. I APR. I MAY I JUNE \ JULY ! AUG. I SEPT. I OCT.
1970
FIGURE 26
1971
SECONDARY EFFLUENT NITROGEN AND PHOSPHOROUS CONCENTRATIONS VERSUS TIME
-------
The orthophosphate varied from a minimum of 0.24 mg/1 to a maximum of 12.6 mg/1
and averaged 5.88 mg/1.
The difference in the ortho and total phosphate concentrations is believed to be due to
the high level of suspended solids in the secondary effluent. The hydraulic detention
times in the aeration-surge basin were such that polyphosphates would likely have been
hydroly/.ed to orthophosphate. The negligible difference between the ortho and total
phosphate in the tertiary effluent, when virtually all of the suspended solids were
removed, tends to support this conclusion.
The total influent phosphate and secondary effluent orthophosphate loadings were
averaged on a weekly basis and compared to evaluate phosphate removal in the
aeration-surge basin, assuming complete separation of secondary effluent suspended solids.
The phosphate removals varied considerably from 0 to 87 percent and averaged 48
percent. The possible effects of pH and alkalinity on phosphate removal in the secondary
treatment system are discussed in Section VIII.
VELOCITY PROFILES
Velocity measurements were made at 21 locations in the northeast quadrant of the
aeration-surge basin at depths of 1, 6 and 9 feet. The velocity profiles shown on Figures
27, 28. and 29 were constructed from these data. Since the basin was symmetrical, the
velocity profile of the northeast quadrant was assumed to be typical of the other three
quadrants.
Velocity measurements were made with a Hydro Products Model 451 current meter. Only
the horizontal component of velocity could be determined with this instrument. The
resultant velocity of both the horizontal and vertical components may well have been
higher than those indicated on the profiles. Both aerators were operating when the
velocity measurements were made.
At a depth of 1 foot below the surface, the minimum horizontal velocity of 0.1 feet per
second occurred at a point along the secondary effluent withdrawal pipe approximately 5
feet inboard from the aeration-surge basin nngwall. The maximum horizontal velocity of
0.7 feet per second was measured about 20 feet radially out from the aerator.
The horizontal velocities measured at a depth of 6 feet ranged from 0.7 feet per second
at basin Liner, decreasing to 0.3 feet per second within 5-10 feet of the aerator.
At a depth of 9 feet the horizontal velocities increased from 0.3 feet per second at the
liner to about 0.6 feet per second within 4 feet horizontally of the aerator.
The velocity data indicate that adequate mixing was provided throughout the basin.
Solids deposition would be expected in the low velocity areas between the ends of the
secondary clarifier and the basin ringwall.
-79-
-------
oo
9
NOTES:
1. VELOCITY IN FEET PER SECOND
2. DASHED LINE INDICATES CONTOUR
BASED ON INTERPOLATION.
MECHANICAL
AERATOR
FIGURE 27
AERATION-SURGE BASIN VELOCITY PROFILE
AT 1 FOOT DEPTH
TUBE
CLARIFIER
-------
MECHANICAL
AERATOR
oo
NOTE:
VELOCITY IN FEET PER SECOND
-TUBE
CLARIFIER
FIGURE 28
AERATION-SURGE BASIN VELOCITY PROFILE
AT 6 FOOT DEPTH
-------
oo
MECHANICAL
AERATOR
-TUBE
CLARIFIES
NOTE:
VELOCITY IN FEET PER SECOND
FIGURE 29
AERATION-SURGE BASIN VELOCITY PROFILE
AT 9 FOOT DEPTH
-------
SOLIDS ACCUMULATION
A high ground water table prevented dewatering of the aeration-surge basin to determine
the solids accumulation. An attempt was made to profile the material deposited on the
bottom of the basin by taking soundings. A weighted flat plate was suspended by a
calibrated rope and lowered through a pulley system until the plate rested on the basin
floor. Using this method the northeast quadrant was sounded at 21 locations.
The area of deposition is shown on Figure 30.
The solids accumulation was found to be minimal. The depth of the material varied from
about 3 inches at a distance of 7 feet measured radially from the aerator to about 12
inches at the north end of the secondary clarifier. The average depth was estimated to be
6 inches. The location of the deposit is consistent with velocity profiles determined for
the aeration-surge basin.
From these measurements and the total flow recorded for the 17-1/2 months the basin
was in service, the solids accumulation rate was conservatively estimated to be about 0.32
cubic yards per million gallons. This value is within the range of grit loading experienced
by other sewage treatment plants in the area.
TERTIARY TREATMENT SYSTEM
GENERAL
Alum coagulation supplemented with anionic polyelectrolyte. tube sedimentation and
mixed media filtration was demonstrated to be an effective process for removing
suspended solids and phosphate from the effluent of an extended aeration activated
sludge system. The physical and chemical characteristics of the secondary effluent varied
widely. This variability was attributed to the wide range of oxidative and sludge age
conditions in which the secondary treatment system operated and certain performance
limitations of the secondary tube clarifier.
The following tertiary effluent parameters were monitored on a regular basis throughout
the demonstration program:
Temperature
PH
Total alkalinity
D.O.
TSS
-83-
-------
00
MECHANICAL
AERATOR
AREA OF
SOLIDS
DEPOSITION
TUBE
CLARIFIER
FIGURE 30
AERATION-SURGE BASIN SOLIDS ACCUMULATION
-------
Total BOD5
Dissolved BOD 5
Ortho and total phosphate
Kjeldahl, ammonia, nitrite and nitrate nitrogen
Turbidity, filter run time, and filter head loss were also monitored on a regular basis from
March 1971 through completion of the project.
Tertiary system performance is summarized in Table 10. The average, maximum and
minimum values of the tertiary effluent quality parameters, throughput volume and solids
removal per filter cycle are listed for various alum feed conditions. Because of the limited
amount of data for each alum dosage range, standard deviations were not computed,
JAR TESTS
Jar tests were performed at the beginning and repeated several times during the course of
the project to establish the alum dosages necessary for coagulation and phosphate
removal. The alum dosage required to effect coagulation varied between 50 to 140 mg/1,
depending on the alkalinity and pH of the secondary effluent. The orthophosphate
concentration could generally be reduced to less than 1 mg/1 with alum dosages of 80 to
120 mg/1. The degree of phosphate removal appeared to be strongly affected by pH, with
optimum removals occurring in a pH range of 5 to 6.
A series of jar tests was also run to evaluate the effect of polyelectrolyte on coagulation
and floe formation. Initially, several anionic, nonionic and cationic poly electrolytes were
screened to determine the type best suited to complement the coagulation process.
Anionic polymers enhanced the formation of a large cohesive floe. Nonionic polymers
had little or no effect on floe formation and cation ionic polymers appeared to act as a
dispersant.
Anionic polymers of several manufacturers were then evaluated to select a polyelectrolyte
to be used during the project. The polymers tested included Dow Chemical Company
Purifloc A21 and A23; American Cyanamide Company Magnifloc 835A, 836A and 837A;
and Rohm and Haas Company Primafloc A10. Of these, A23, 836A and A10 produced
the best results in aiding floe formation at dosages of 1.0 to 2.0 mg/1. American
Cyanamide 836A was selected as the polyelectrolyte for use in the tertiary system,
because of its availability from a local distributor near the treatment plant.
CHEMICAL FEED RATES
During August 1970 and for several brief intervals during the project, the tertiary system
was operated without chemicals to establish a performance base line for the unit. On 31
August 1970, alum was introduced into the tertiary influent and on 9 October
polyelectrolyte was added to the flocculator.
-85-
-------
TABLE 10
TERTIARY PERFORMANCE SUMMARY
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
AVERAGE
MAXIMUM
MINIMUM
BODS
SOL.
(MG/U
5.0
8.6
2.8
—
—
-
—
-
-
6.2
13.9
2.8
4.1
5.2
3.0
4.0
8.4
1.9
2.2
3.5
1.0
4.3
9.2
1.6
4.4
10.8
2.2
6.5
17.6
0.8
6.1
13.0
1.3
TOT.
(MG/U
12.1
19.2
7.0
_
-
-
8.3
11.8
4.8
8.8
17.3
3.5
7.8
30.0
0.5
4.4
8.9
1.8
2.6
3.5
1.7
5.3
9.8
2.6
5.5
11.8
3.4
7.4
19.1
1.3
9.4
19.0
2.9
TSS
(MG/U
12.3
28.0
2.3
2.7
4.5
.9
1.4
2.8
.6
6.8
22.0
0.7
1.6
10.4
0.2
3.2
13.1
0.1
0.7
2.0
0.0
2.1
J5.0
0.0
1.3
3.2
0.1
1.4
4.0
0.1
2.0
9.3
0.1
FLOW
VOLUME
(GAL. /RUN)
148,700
478.000
38,000
33,500
44,700
22,200
50,100
78,100
23,100
46,000
57,500
34,200
42,700
67,200
25,200
41,100
60,800
20,900
48,300
58,600
41,800
36,500
57,000
25,600
33,200
40,400
24,700
31,600
41,800
14,200
34,300
50,900
23,100
TSS
REMOVED ORTHO-P
(LBS./RUNi (MG/L) %
NO CHEMICALS
106. 6.07
237. 8.30
23.2 3.40
ALUM 63 MG/L
14.8 5.28
19.7 6.56
9,8 4.00
ALUM 80-83 MGfL
22.7 l.tO
41.6 1.40
4.6 .80
ALUM 94-96 MG/L
34.5 1.96
40.7 6.05
22.5 0.19
ALUM 105-108 MG/L
35-4 1.11
123. 1.99
13.7 .23
ALUM 126 MG/L
22.5 0.68
99.0 2.20
7.3 0.09
ALUM 135 MG/L
40.5 0.16
58.6 Q.25
22.6 0.07
ALUM 155 MG/L
16.1 0.65
46.2 3.57
4.9 0.01
ALUM 182-184 MG/L
11.8 0.12
17.5 0.25
7.8 0.02
ALUM 211-217 MG/L
24.1 0.23
38.2 0.65
9.1 0.01
ALUM 238-242 MG/L
33.2 034
81.5 1.87
11.4 0.01
(as P|
REM.
17.3
28.6
2.4
45.9
57.4
34.4
79.2
85.6
72.9
73.2
93.3
45.5
84.2
93.0
75.4
89.8
97.9
68.1
96.2
98.3
942
86.7
99.6
8.3
96.8
98.9
95.5
95.1
98.4
90.6
93.6
99.1
87.3
TOTAL
MG/L
6.28
8.90
3.45
5.22
6.35
4.10
1.12
1.40
.83
2.05
6.0
0.24
1.22
2.20
0.23
0.69
2.20
0.11
0.16
0.25
0.07
0.73
3.84
0.03
0.16
0.27
0.04
0.26
0.66
0.02
0.39
1.90
0.03
P (as P!
% REM.
32.7
39.8
23.3
53.1
6T.O
45.2
81.9
85.8
78.0
75.9
96.1
54.5
85.2
94.4
76.1
91.4
98.4
73.2
96.4
38.6
94.2
88.0
99.0
8.6
96.9
97.9
94.8
95.1
97.8
92.0
94.6
97.9
87.3
TURBIDITY
(JTU)
3.2
3.5
2.7
1.8
2.0
t.3
1.3
1.6
2.0
1.3
1.1
1.8
0.8
1.0
2.1
0.4
1.2
.6
1.8
.35
0.7
0.9
0.5
0.65
0.85
0.55
1.0
2.4
0.4
-86-
-------
Low secondary effluent alkalinity conditions in September and October 1970 limited the
alum dosage that could be fed to the tertiary system and still maintain a pH condition
compatible with alum floe formation. The chemical metering pump assigned to add
polyelectrolyte between the tertiary tube settler and mixed-media filter was used to feed
soda ash (sodium carbonate) to the tertiary influent, as a supplemental source of
alkalinity.
Polyelectrolyte could not be added prior to filtration, until a fourth metering pump was
installed on 7 April 1971.
Polymer dosages in the tertiary influent (presettler) were varied from 0.4 to 3.5 mg/1.
Polymer dosages introduced immediately ahead of filtration (prefilter) ranged from 0.02
to 0.22 mg/1. Figure 31 shows the feed rates of the various chemicals added to the
tertiary system during the demonstration program.
FILTRATION RATE
The tertiary system was operated within four flow rate ranges during various periods of
the demonstration program, resulting in the following filter surface hydraulic loadings:
1.4 - 1.8 gpm/ft2 (70 - 90 gpm)
2.2 - 2.3 gpm/ft2 (110 - 115 gpm)
2.8 - 3.2 gpm/ft2 (140 - 160 gpm)
3.6 - 4.0 gpm/ft2 (180 - 200 gpm)
The tertiary flow rates and corresponding time periods during the project are shown on
Figure 32.
In general the filtration rate did not appear to substantially influence the throughput
volume per filter cycle or effluent quality. The wide variation in the secondary effluent
characteristics and the range of alum and polyelectrolyte dosages applied allowed only a
qualitative assessment to be made, however.
The total volume filtered per run at rates of 2.2 - 2.3 gpni/ft- and 3.6 - 4.0 gpm/ft- are
listed in Table 11 for similar suspended solids, pH and chemical feed conditions.
-87-
-------
SI
LLJ
O
K -I
2-
5
8
n
D< I
^ n» M
i «t
0.20;
i
j
0.15 j
I
0.1 i
I
0.05 i
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
90.0
70.0
50.0
30.0
10.0
0
300.0 i
260.0
220.0
180.0
140.0
100.0
60.0
20.0
0
i
AUG.
SEPT. I OCT. I NOV. I DEC.
1970 '
JAN.
FEB. I MAR. I APR.
"prr
MAY | JUNE I JULY
1971
OCT.
FIGURE 31
TERTIARY CHEMICAL DOSAGES VERSUS TIME
-------
200,0
160.0
in
h-
o: 120.0
O
>
DC
<
80.0
40.0
0.0 I
20.0
V)
EC
D
O
X
C3
<
CC
LU
PERIOD
YEAR
15.0
10.0
5.0
0.0
1
AUG. I SEPT.
OCT. I NOV.
1970
DEC.
JULY
JAN. I FEB. I MAR. I APR.
FIGURE 32
TERTIARY FLOW RATE AND FILTER RUN TIME VERSUS TIME
MAY I JUNE
1971
AUG. I SEPT.
OCT.
-------
TABLE 11
FILTRATION RATE COMPARISON
FILTRATION RATE
(GPM/FT2)
ALUM FEED
(MG/L)
0
126-135
155-160
182-190
240-242
2.2-2.3
AVG. VOL.
FILTERED
(GAL/RUN)
118,800
44,600
44,700
35,400
34,300
SEC. EFF.
TSS
(MG/L)
92
61
34-60
87
70-78
TER. EFF.
TSS
(MG/L)
11
2
1-5
1
1
PH
7.2
6.4
6.5-6.7
6.25
6.5-6.6
3.6-4.0
AVG. VOL.
FILTERED
(GAL/RUN)
1 24,300
48,000
39,800
33,600
35,100
SEC. EFF.
TSS
(MG/L)
43-92
31-63
45-51
29-66
39-75
TER. EFF
TSS
(MG/L)
6-15
1-4
1-3
1-3
1
PH
6.8-7.5
6.1-6.5
6.4-6.8
6.0-6.3
6.1
The tertiary effluent quality depended primarily on the characteristics of the secondary
effluent and the chemical dosages applied, and did not appear to be affected by filtration
rate. As an example, at an alum dosage of 155 to 160 mg/1, the tertiary effluent
suspended solids averaged 1.2 mg/1 at a flow rate of 110 gpm and 1.6 mg/1 at 190 gpm.
Additional study is needed to verify these observations, where the influent characteristics
can be more closely controlled.
FILTER CYCLE
Filter run times ranged from a maximum of 106 hours at a flow rate of 75 gpm without
the addition of chemicals to less than 2 hours at a flow rate of 190 gpm and alum
dosages of 155 to 242 mg/1. The length of filter cycle was affected by several factors,
including solids carryover from the tertiary tube settler, secondary effluent suspended
solids concentration, and chemical feed rates. The influence of each of these factors is
discussed in Section V1I1.
EFFLUENT QUALITY
BOD AND TSS-The total BOD5 and TSS in the tertiary effluent depended on the
chemical dosages applied and effectiveness of coagulation. Alum dosages of 80 to 105
mg/1 were generally sufficient to reduce the total BOD5 to less than 10 mg/1 and TSS to
Jess than 5 mg/1. At these levels, the overall reduction of BOD5 and TSS approached 99
percent. The soluble BOD^ averaged about 6 mg/1 and was dependent on the
performance of the secondary treatment system.
Nitrification is suspected to have occurred in some of the tertiary BOD tests.
Simultaneous oxidation of the nitrogeneous and carbonaceous fractions would produce a
considerably higher oxygen demand than the carbonaceous phase alone, resulting in an
apparent high BOD$. During periods when the secondary effluent was completely
nitrified and tertiary effluent TSS was less than 3 mg/1, the tertiary effluent total BOD5
averaged about 5 mg/1.
-90-
-------
Tertiary total and soluble BOD5 and TSS are shown versus time on Figure 33.
NITROGEN AND PHOSPHORUS-As would be expected, the concentration of
ammonium, nitrite, and nitrate in the secondary and tertiary effluent were essentially
identical. The residual organic nitrogen (total kjeldahl less ammonia nitrogen) depended
on the residual TSS of the secondary effluent.
The concentration of orthophosphate remaining in the plant effluent after tertiary
treatment was a function of the secondary orthophosphate concentration, alum dosage,
and tertiary pH. The relationship of these three variables on orthophosphate removal is
discussed in Section VIII.
Orthophosphate residuals of less than 0.5 mg/1 (as P) could be maintained with alum
dosages of 100 to 200 mg/1. Under optimum pH conditions, orthophosphate
concentrations of less than 0.1 mg/1 (as P) were achieved.
Total phosphate residuals depended on the efficiency of TSS removal in the tertiary
system, as well as the secondary orthophosphate concentrations, alum dosage, and pH. At
tertiary TSS levels of 1-3 mg/1, the ortho and total phosphate concentrations were
essentially the same. The average total phosphate removal through the plant at alum
dosages above 125 mg/1 exceeded 95 percent.
The concentration of total nitrogen, ammonium, nitrate, orthophosphate and total
phosphate in the tertiary effluent versus time are shown on Figure 34.
pH, ALKALINITY AND TURBIDITY-pH (and its relationship with total alkalinity) was
perhaps the single most important variable to the control and performance of the tertiary
system. The alkalinity of the secondary effluent and pH of the tertiary effluent affected
alum coagulation, phosphate and TSS removal, and turbidity level of the tertiary effluent.
Tertiary effluent pH. total alkalinity and turbidity are plotted versus time on Figure 35.
The alkalinity equivalent of the alum [Al -,(804)3 • 14-3 H2°^ used durin8 the Pr°Ject
was determined experimentally to be about 0.36 mg/1 equivalent CaCO3 per mg/1 of
alum. In order for a chemical floe to develop, the secondary effluent alkalinity had to be
sufficient to offset the acidity of the alum dosage and maintain the pH above 5.0. If the
secondary effluent alkalinity was not adequate, sodium carbonate was added to the
tertiary influent to control pH.
The base turbidity on Figure 35 was the average turbidity of the tertiary' effluent. The
peak turbidity was the level recorded at the end of the filter run and indicates the
magnitude of turbidity breakthrough.
The lowest residual TSS and turbidity levels occurred in a pH range of 5.8 to 6.3, as
shown on Figure 36. The data plotted on Figure 36 represent the average of the observed
values at a given pH for alum dosages of 105 to 240 mg/1. This pH range is believed to
be the optimum zone for alum coagulation of the secondary effluent. Under these pH
conditions, negatively charged colloidal material suspended in the wastewater is
-91-
-------
in
a
8
2
o
50.0
40.0
:-. 30.0
8
>•
oc
cc
LU
CC
UJ
20.0
10.0
0.0
60.0
50.0
40.0
30.0
20.0
10.0
. fl
^ 1
\L
I
i
$MLl
i
i *
PERIOD
YEAR
0.0
V
TOTAL BOD5
SOLUBLE BODt
' \
. i
AUG. I SEPT. I OCT. I NOV. I DEC. I JAN. I FEB. I MAR. I APR. I MAY I JUNE I JULY I AUG. I SEPT. I OCT.
1970
FIGURE 33
1971
TERTIARY EFFLUENT TOTAL AND SOLUBLE BOD AND TSS CONCENTRATION VERSUS TIME
-------
ou.u
D
Z
§ 50.0
» CO
5 -" 40.0
O O
°5
oc s
= [i! 30.0
<
| * 20.0
> z
tt <
P 10.0
OC
UJ
l-
00
12.0
LU
^-
i
a.
0
I 9.0
CL
O
I
t-
8 =
Q
-------
PERIOD '
YEAR
n ' ' ' FEB' ' MAR- ' APR-
1970 FIGURE 35
TERTIARY EFFLUENT pH, ALKALINITY AND TURBIDITY VERSUS
MAY ' JUNE
1971
AUG
TIME
OCT.
-------
TERTIARY EFFLUENT TSS (MG/L)
TERTIARY EFFLUENT TURBIDITY (JTU)
m
30
H
3D
m
Tl
-n
r
c
m
Z
8 5
O
H
3D
00
m
30
CO
c
3D
m
CO
O)
13 J"
I o
o>
VI
b
o
o
o
-e-
•o
I o
O
O
O
N
b
u
b
-------
neutralized by positively charged hydrated aluminum ions. The result is a destabilization
and entrapment of the suspended solids, as the alum floe develops.
The tertiary effluent turbidity also correlated with the nitrate level in the tertiary
effluent as shown on Figure 37. This correlation is, at least partially, a reflection of the
pH and alkalinity conditions resulting from nitrification. The apparent relationship of
nitrate concentration to turbidity is presented here to illustrate the affect of secondary
treatment conditions, such as nitrification, on tertiary treatment system performance.
Nitrate ion may also have a possible secondary effect on chemical coagulation. As a
potential determining ion, it is conceivable that nitrate could reduce the zeta potential of
the hydrated aluminum colloid and promote coagulation.
POLYELECTROLYTE ADDITION-The affect of adding polyelectrolyte ahead of the
flocculator to assist floe formation was difficult to assess. In general, it did not appear
that applying polyelectrolyte at this point enhanced chemical floe formation, improved
the settling characteristics of the floe, or lengthened the filter run time.
The addition of 0.02 to 0.04 mg/1 of polyelectrolyte between the tertiary tube settler
and filter effectively controlled turbidity breakthrough. At dosages above 0.06 to 0.10
mg/1, the polyelectrolyte appeared to "bind up" the filter bed and appreciably shorten
the filter cycle.
The, effect of polymer on the tertiary treatment process is discussed in more detail in
Section VIII.
CHLORINATION
MPN-Plant effluent chlorination data are summarized in Table 12. Because of the very
limited amount of data obtained during the demonstration program, Table 12 has been
supplemented with data obtained from the Oregon State Department of Environmental
Quality collected after termination of the project.
A chlorine residual of 1.2 mg/1 or greater was adequate to reduce the total coliform
index to less than 1,000 MPM per 100 ml after a minimum of 0.9 hours contact time in
5 of 6 samples analyzed. Water of this bacterial quality is considered acceptable for
recreational purposes, including such water-contact activities as swimming and water
skiing, by several governmental regulatory agencies including the Ohio River Valley Water
Sanitation Commission (ORSANCO) [ 11 ]. In 4 of 5 samples the fecal coliform MPN was
less than 100 per 100 ml.
The sample collected on 15 May 1972 had an unusually high coliform count, even
though the chlorine residual was 2.5 mg/1. The chlorine residual measurement is suspected
to have been in error, considering the small dosage of chlorine applied. The high chlorine
residual measurement, however, may have resulted from much of the chlorine demand
being exerted by ammonium ion to form chloramines with little or no free chlorine
residual available for disinfection. The difference in plant influent and secondary effluent
alkalinity indicates that the secondary treatment system may not have been completely
nitrified. A considerable amount of ammonia likely remained in the secondary effluent.
-96-
-------
Q
QQ
CC
D
2
LU
CC
<
CC
UJ
10.0
20.0
TERTIARY EFFLUENT NITRATE (MG/L as N)
30.0
40.0
FIGURE 37
TERTIARY EFFLUENT TURBIDITY VERSUS NITRATE CONCF.NTRATION
-------
TABLE 12
PLANT EFFLUENT CHLORINATION DATA SUMMARY
DATE
8/12/70
10/27/70
7/15/71
9/13/71
5/15/72
6/6/72
6/20/72
7/17/72
CHLORINE
DOSAGE
(MG/L)
12.
5.
14.
7.
5.5
9.5
39.5
5.5
RESIDUAL
(MG/L)
0.6
0
2.3
1.8
2.5
1.2
2.3
0.15
CONTACT
TIME
(HRS.)
2.2
0.9
0.9
1.2
1.2
1.2
1.2
1.2
TOTAL ALKALINITY
INFLUENT
(MG/L)
180
166
206
196
200
180
167
200
SEC. EFF.
(MG/L)
35
53
136
199
121
57
38
110
TERTIARY EFFLUENT
BOD
11.2
10.3
-
-
3.0
1.4
-
-
TSS
5.8
5.9
1.6
0
8
1.0
2.0
3.0
KJEL-N
(MG/L)
2.4
2.4
1.9
-
-
-
-
-
NH3-N
(MG/L)
0.39
0.62
0.665
~
-
-
-
-
COLIFORM
(MPN/100 ML)
TOTAL
<45
24,000
8
<45
1,300
60
230
7,000
FECAL
<45
2,300
-
<45
1,300
<45
60
2,100
-------
Conversion of ammonia to nitrate in the secondary system will substantially reduce the
chlorine dosage required to reach the breakpoint and produce a free chlorine residual.
With complete nitrification occurring in the secondary treatment system, a chlorine
dosage of about 10 mg/1 or less was adequate to maintain a chlorine residual above 1.0
mg/1.
BREAKPOINT CHLORINATION TESTS-Three breakpoint chlorination tests were run
during June and July 1971. The results of the tests indicated breakpoint demands ranging
from 125 to 206 mg/1. During this period, the ammonium concentration varied between
14 to 23 mg/1 (as N). which undoubtedly increased the demand above that expected
when the secondary treatment system was completely nitrified. Difficulties in preparing
and standardizing reagents, however, make the data subject to question.
WASTE SOLIDS STORAGE
WASTE ACTIVATED SLUDGE STORAGE
GENERAL-Waste activated sludge (WAS) from the aeration-surge basin was stored in
two adjacent 42.000 gallon holding lagoons (Figure 10). WAS Lagoon No. 2 was
examined at the conclusion of the demonstration program to:
1. Determine the suitability of lagoons for storage of WAS from an extended
aeration system.
2. Estimate the volume and assess the feasibility of dewatering WAS in the
lagoons.
3. Characterize the solids after dewatering and estimate the loss of volatile solids
as a result of anaerobic decomposition.
4. Estimate cleaning frequency and recommend a method of disposal.
A record of the solids wasted to WAS Lagoon No. 2 was maintained during the
demonstration program. On 9 June 1971, the supernatant was decanted to the sludge
blanket. The sludge deposit was allowed to dry through the summer and the depth of the
sludge deposit measured at varying time intervals. A profile was made of the sludge
deposit on 16 September 1971 to determine the quantity and characteristics of solids
remaining in the lagoon.
No objectionable odors were detected from the storage lagoons at any time during the
project. During the dewatering operation, when a crust was beginning to form, a slight
"earthy," but unobjectionable, odor was observed when standing 10-15 feet downwind of
the lagoon.
-99-
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DEWATERING-Figure 38 shows the depth of the sludge deposit with time as the
material dewatered and dried. The depth of the sludge in the storage lagoon, measured
from the base of the outlet structure, decreased from 25 inches to 11-1/2 inches over a
period of approximately nine weeks. The ground water level is suspected to have
prevented the sludge from continuing to dewater.
As the sludge dewatered, a brown crust developed over the deposit. Within 3-4 weeks the
crust cracked and dried to a cinder-like material. Below the crust, the black sludge had
the consistency and appearance of thick chocolate pudding.
Photographs of the sludge storage lagoon taken at the time the lagoon was profiled are
contained in Appendix B.
SLUDGE CHARACTERISTICS-While the sludge deposit was being profiled, samples
were taken from five locations in the lagoon at various depths to determine the total
solids and total volatile solids content of the material. The results of these analyses are
summarized on Figure 39.
The material had an average total solids content of 18 percent. The solids were found to
be progressively more moist with depth, except for the bottom three inches where the
solids concentration appeared to increase. The volatile fraction of the solids averaged 52
percent. In the upper 10 inches the total volatile solids ranged between 54 to 60 percent.
Accumulation of inorganic materials in the bottom three inches reduced the volatile
fraction to around 34 percent.
SOLIDS ACCUMULATION-From plant records, approximately 25,000 pounds of total
(dry) solids were wasted to WAS Storage Lagoon No. 2. The profile of the sludge deposit
indicated an accumulation of approximately 57.2 cu yds at an average depth of about 13
inches. The bulk density was calculated to be 66 pounds per cubic foot assuming a
specific gravity of 1.4 for the dry sludge solids [11]. At this bulk density the quantity of
solids remaining was calculated to be 18,300 pounds. Approximately 27 percent of the
WAS was either destroyed by anaerobic decomposition, or lost as suspended solids in the
return sludge lagoon supernatant.
For comparative purposes, an attempt was made to balance the WAS with solids
accumulation in the lagoon based on ash content. The volatile content of the WAS for a
limited number of analyses performed in August 1971, averaged 73.5 percent. Assuming
this value was representative of the WAS over the entire demonstration program, the
inorganic fraction of the total solids wasted was estimated to be 6,625 pounds. At an
average ash content of 43.5 percent, the solids accumulation in WAS Storage Lagoon No.
2 contained approximately 8,000 pounds of inorganic material.
Comparing these estimates, it appears that either more solids were wasted to the storage
lagoons than recorded or the average volatile fraction of the WAS was closer to 68
percent.
-100-
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SLUDGE DRYING BEGUN
9 JUNE 1972
SLUDGE ACCUMULATION
PROFILED 16 SEPTEMBER 1971
40 60 80
ELAPSED TIME (DAYS)
100
FIGURE 38
WASTE ACTIVATED SLUDGE STORAGE LAGOON DRYING VERSUS TIME
V)
UJ
LLJ
O
D
D
_i
CO
1 _
4-
7-
13
///
1
%
w
isx
CONSISTENCY
TOTAL SOLIDS
DRY, BROKEN CRUST) 69%
THICK
PUDDING - LIKE
THIN
PUDDING - LIKE
THICK
PUDDING - LIKE
25%
19%
10%
18%
18%
AVG.
VOLATILE SOLIDS
54%
60%
58%
54%
34%
52%
AVG.
FIGURE 39
WASTE ACTIVATED SLUDGE STORAGE LAGOON PROFILE
-101-
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CLEANING FREQUENCY—At the plant design organic loading, removal of the solids
from both WAS sludge storage lagoons will be required at 9 to 12 month intervals.
ADDITIONAL SOLIDS DEWATERING STUDY-An additional study was conducted to
determine the ability of the stored WAS to dewater in a shallow bed. A drying bed
approximately 20 feet by 80 feet was improvised to the west of the aeration-surge basin
and filled with sludge from WAS Storage Lagoon No. 1 to an average depth of 6 inches.
The sludge dried to a cinder-like material in about 4-6 weeks. Analyses of the dried solids
indicated a moisture content of 9 to 12 percent and a total volatile solids content of
50-54 percent.
CHEMICAL SLUDGE STORAGE
GENERAL-Chemical sludge resulting from backwash of the tertiary unit was pumped to
the chemical sludge storage lagoons after a settling period of 2-4 hours in the chemical
sludge holding tank (Figure 10). Chemical Sludge Lagoon No. 2 was examined at the
conclusion of the demonstration program to:
I. Determine the suitability of lagoons for storing chemical sludge.
2. Estimate the volume and determine the dewatering and drying characteristics of
the accumulated solids.
3. Characterize the sludge after storage and dewatering.
4. Estimate cleaning frequency and recommend a method of disposal.
Except for short periods in October 1970, January, March, and May 1971, totaling
approximately 9 weeks, all of the chemical sludge produced from plant startup through
21 June 1971 was stored in Chemical Sludge Lagoon No. 2. During the last week of June
1971, the supernatant was decanted to the sludge blanket. Beginning 2 July 1971 the
sludge deposit was allowed to dewater by evaporation through the remainder of the
summer.
The sludge deposit in Chemical Sludge Lagoon No. 2 was profiled on 16 September 1971
to calculate the quantity and determine the total and volatile solids content of the
accumulated solids.
Chemical Sludge Lagoon No. 1 was used for temporary influent storage while repairs
were made to the aeration-surge basin and secondary clarifier. This lagoon was also used
for WAS storage on several occasions.
During the fall of 1970 and again in the spring of 1971, heavy algae blooms developed in
both chemical storage lagoons, particularly Chemical Sludge Lagoon No. 2. Algae in the
supernatant return from the lagoons passed through the aeration-surge basin and could be
seen in the secondary and tertiary effluent suspended solids determinations during April
and May 1971. The fraction of the suspended solids attributable to algae was not
determined, however. The alkalinity and pH of the return supernatant followed a
-102-
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predictable pattern as a result of algal activity. At the peak of the algae bloom in April
1971, the alkalinity was 58 and pH 8.8. As the bloom dissipated during the third week in
May, the pH dropped to 6.85 and alkalinity increased to 91.
Photographs of Chemical Sludge Storage Lagoon No. 2, taken at the time the lagoon was
profiled, are contained in Appendix B.
SOLIDS DEWATERING- The change in depth of the sludge deposit in Chemical Sludge
Lagoon No. 2 with time, as the lagoon dewatered, is shown on Figure 40. The depth,
measured from the base of the outlet structure, decreased from 26 inches to 10-1/2
inches over a period of approximately 8 weeks. Ground water prevented the material
from concentrating further and drying.
A floating mat 1/2- to 1-inch thick developed over about 80 percent of the surface of the
lagoon, as the sludge liquor concentrated. No objectionable odors were generated from
the lagoon, even during the dewatering period.
SOLIDS CHARACTERISTICS-Composite samples were taken from eight locations in
Chemical Sludge Lagoon No. 2. The total (dry) solids content of these samples average
4.0 percent, ranging between 2.9 to 5.1 percent. The volatile fraction of the dry solids
averaged 48.5 percent and varied from 40.8 to 51.8 percent. The bulk density of the
material averaged 59.8 pounds per cubic foot. The sludge was slightly more concentrated
around the influent pipe in the center of the lagoon and in front of the outlet structure.
The floating mat had a total solids content of 13-14.5 percent. The volatile content of
this material was about the same as the composite chemical sludge samples.
SOLIDS ACCUMULATION-The total amount of chemical sludge discharged to Chemical
Sludge Lagoon No. 2 was calculated to be 30,300 pounds, including both alum and
organic solids. From the profile made of the sludge accumulation, the quantity of solids
remaining in the lagoon was calculated to be 21,200 pounds. The 30 percent reduction is
attributed to anaerobic decomposition and loss of suspended solids in the supernatant
return.
An attempt was made to balance the inert fractions of the chemical sludge wasted to the
lagoon, the suspended solids lost in the lagoon supernatant return, and the solids
accumulation in the lagoon. The volatile content of the organic solids removed by the
tertiary system was assumed to average 73.5 percent, based on mixed liquor volatile
solids analyses. Sludge samples collected when the pond was profiled, had an average
volatile content of 48.5 percent. The suspended solids in the lagoon supernatant were
assumed to be 75 percent volatile.
Based on these data, the inert fraction of the chemical sludge discharged to the lagoon
less the inert fraction of the suspended solids in the supernatant return was calculated to
be 12,300 pounds. The inert fraction of the solids retained by the lagoon was calculated
to be 10,900 pounds.
-103-
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20
40 60
ELAPSED TIME (DAYS)
80
FIGURE 40
CHEMICAL SLUDGE LAGOON DRYING VERSUS TIME
27 JUNE - 25 JULY 1971
MATERIAL CRACKED
AND DRIED, EXPOSING
BOTTOM OF BED
TOTAL AND
VOLATILE
SOLIDS CONTENT
DETERMINED
CO
10 15 20
ELAPSED TIME (DAYS)
FIGURE 41
CHEMICAL SLUDGE ALIQUOT DRYING VERSUS TIME
-104-
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The agreement of these estimates to within 13% tends to add validity to the calculated
quantities of total chemical sludge wasted to and accumulated by the chemical sludge
storage lagoon during the project.
CLEANING FREQUENCY-At a design flow of 0.28 mgd, removal of solids from each
lagoon will be required at 2 to 3 year intervals.
ADDITIONAL CHEMICAL SLUDGE DEWATERING STUDY-A small drying bed (3 ft
x 3 ft x 1 ft) was constructed on the dike of Chemical Sludge Lagoon No. 2 to
determine the drying characteristics for a small aliquot of the chemical sludge, without
the influence of ground water. On 27 July 1971, the bed was filled to a depth of 8-3/4
inches with lagoon sludge having a dry solids content of 3.3 percent. Within 17 days the
depth of the bed was reduced to about 1 inch, at which point the material cracked and
dried to a whitish-gray cinder-like solid. After 27 days, the total solids content of the
dried solids was determined to be approximately 68 percent. The volatile fraction of the
dry solids averaged 45 percent.
The results of the aliquot drying study are shown on Figure 41. Photographs of the
drying bed at the end of the test period are contained in Appendix B.
COMBINED RETURN SLUDGE LAGOON SUPERNATANT
TSS, BOD and pH analyses were performed on samples of the combined return sludge
lagoon supernatant collected from the discharge to the plant influent pump station. The
results of these analyses are listed in Table 13 below:
TABLE 13
COMBINED RETURN SLUDGE LAGOON
SUPERNATANT CHARACTERISTICS
Average Maximum Minimum
TSSfmg/l) 73 160 30
BOD (mg/1) 51 96 26
pH(mg/l) 6.99 7.55 6.5
OPERATIONAL CONSIDERATIONS
A number of problems were encountered during the demonstration program which
affected plant performance and the overall conduct of the project. The more significant
problems are described in the following paragraphs.
-105-
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OPERATOR ACCIDENT
Two weeks after plant startup in April 1970, the treatment plant operator/research
technician was seriously injured. He was unable to return to work on a full-time basis
until the latter part of July 1970. A temporary operator was employed part-time to
operate and maintain the plant. His analytical experience was very limited, however, and
the scheduled sampling and testing program was suspended until the original operator was
able to resume work.
PVC LINER FAILURE
On 8 May 1970 the PVC liner in the east end of the aeration-surge basin floated as the
result of gas buildup under the liner. Inspection revealed that the liner had pulled away
from the footing, allowing seepage under the membrane. Subsequent septic conditions
and gassification caused the liner to float. The liner was repaired and reattached to the
aeration-surge basin ringwall footing.
On 22 June 1970 the liner was again found to be floating on the surface in the same
location of the aeration-surge basin. The liner was carefully inspected around the entire
perimeter of the basin. In addition to finding the liner pulled away from the ringwall
footing at several locations along the east end of the basin, a small cross-hatched cut was
detected in the liner. The cut had apparently been made to relieve entrapped air when
the liner was originally installed, but was not repaired.
It is suspected that mixed liquor had slowly leaked through this cut and under the liner.
Decomposition of organic material provided sufficient gas pressure to tear the liner from
the footing. This allowed more liquid to seep under the liner and accelerated
gassification.
When the liner was repaired for the second time, a gas relief system was also installed to
allow any gas forming under the liner to escape without damage to the membrane.
The second liner repair was completed in mid-July 1970. No further problems with the
PVC liner were encountered during the remainder of* the demonstration programs.
Pictures of the liner repair and gas relief system are included in Appendix B.
INFLUENT PUMPS
The submersible influent pumps jammed with rags and other debris on an average of 2-3
times each month. The pump had to be raised with the aid of a backhoe and the
impellers cleaned each time. Though not a difficult task, the periodic pump cleaning was
a considerable nuisance.
AERATION EQUIPMENT
Shortly after startup of the plant, the aerators began to periodically trip the thermal
overload circuit breakers, due to excessive current draw. The aerators were examined but
no evidence of debris binding or clogging the propellers could be found.
-106-
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Amperage recorders were placed on the power feed lines. A near linear increase in
current draw was observed over time periods lasting several hours to several days from
the time units were activated, until excessive current draw actuated the circuit breakers.
In March 1971, the aerators were pulled from the basin. The manufacturer changed the
pitch of the propellers in an attempt to reduce the current draw. The modification did
not completely resolve the problem. The aerators continued to kick off periodically,
especially during warm weather.
SODA ASH FEED
Periods of complete nitrification substantially reduced the aeration-surge basin alkalinity.
Under these conditions, soda ash was used, as necessary, to supplement the secondary
effluent alkalinity to maintain pH control in the tertiary system. A soda ash feed system
was devised using one of the polyelectrolyte metering pumps and the existing chemical
mixing and storage tankage.
SECONDARY TUBE CLARIFIER MODIFICATIONS
Solids accumulation in the secondary clarifier tubes had a pronounced effect on the
secondary effluent quality in the first half of the demonstration program. On 4 October
1970 gassification of the entrapped solids provided sufficient bouyancy to float the tube
modules in the clarifier structure. Restraining bands were added to hold the tube modules
in place.
In December 1970, MicroFLOC Corporation tested an air sparging system designed to
clean and prevent solids from collecting in the tube bundles of the secondary clarifier.
The tests were successful and a sparging system was installed during February and March
1971. Daily sparging of the tubes for a period of 15 minutes considerably improved the
performance of the unit.
At the same time the sparging system was being installed, the holes in the clarifier
draw-off pipe were enlarged. The reduction of the head loss in the tertiary influent line, as
a result of this modification, tended to correct an air entrainment problem,which caused
flow surges through tertiary influent pump.
FLOCCULATOR MODIFICATIONS
Air entrainment in the discharge from the overflow box to the flocculator tank caused
severe hydraulic short circuiting. An adjustable constrictive collar was placed in the
overflow box discharge line to maintain a constant water level over the discharge pipe
and prevent air from being drawn into the flocculator.
Sodium chloride tracer studies conducted by MicroFLOC after the constrictive collar was
put in however, indicated the actual mean detention time of the flocculator tank to be
about 50 percent of the theoretical value. To further reduce hydraulic short circuiting, a
horizontal baffle was installed in the flocculator tank in January 1971. Subsequent tracer
-107-
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studies indicated this modification increased the actual mean detention time to
approximately 75-80 percent of the theoretical value.
TERTIARY TUBE SETTLER/FILTER MODIFICATIONS
It appeared from visual observations that the chemical floe entering the tertiary tube
settler/filter unit was being broken up, due to high velocities created by constrictions at
several points in the inlet distribution system to the tube bundles. In January 1971,
modifications were made in the settler compartment to minimize these constrictions. It
was difficult, however, to determine the extent to which the modifications improved the
performance of the tertiary system.
The tertiary filter unit was originally installed with a rotating surface wash system to
break up and scour the surface of the bed during the backwash cycle. Repeated bearing
failures in the washarms, as well as a continual loss of media during the surface wash
operation, necessitated a design change. In April 1971, a fixed grid system was installed
over the filter bed, replacing the rotary washarms. This change considerably reduced
media loss and eliminated the previous maintenance problem.
CHEMICAL SLUDGE DECANT PUMP
The chemical sludge decant pump motor burned out on two occasions, as a result of
freezing weather conditions in November 1970 and February 1971.
SURFACE WASH DIAPHRAGM VALVE
Freezing conditions in January 1971 also damaged the surface wash diaphragm valve,
forcing suspension of routine tertiary operation until warmer weather.
OTHER MECHANICAL PROBLEMS
Water collection in the pneumatic control lines damaged the tertiary flowmeter pressure
transducer in December 1970. While the transducer was being repaired at the factory, a
manometer was used to monitor the tertiary flow rate. A refrigeration type air dryer was
installed to desiccate air for the plant pneumatic control systems.
On two occasions the plant flowmeter jammed. In both instances the unit was removed
and inspected. The causes for jamming could not be determined, however.
-108-
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SECTION VIII
DISCUSSION
SECONDARY TREATMENT SYSTEM
MICROBIOLOGY
So long as the D.O. remained above 0.5 mg/1, the relatively long sludge ages at which the
secondary system operated tended to produce a rather diverse population of organisms,
ranging from bacteria to rotifers.
During the latter phases of the program, when the D.O. hovered between 0.1 to 0.2 mg/1,
the higher forms all but disappeared. Surprisingly, few filamentous organisms were
observed at these low D.O. concentrations.
SLUDGE YIELD
The quantity and apparent resistance to biological breakdown of the influent suspended
solids had a significant affect on the gross sludge yield in the secondary treatment
system. The gross sludge yield is defined as the total pounds of solids (including
non-metabolized influent suspended solids as well as those biologically synthesized) lost
from the secondary system per pound of influent 800$ removed.
Figure 42 is a plot of gross sludge yield as a function of sludge age.
Each data point represents the 5-day weekly average of the solids lost and influent BOD^
removed over a temperature range of 8 to 22 degrees C. An average BOD5 removal of 98
percent was used in calculating the gross sludge yield, based on the average tertiary
effluent soluble BOD5 of 6 mg/1 measured over the demonstration period.
The considerable scatter in the data is attributed to several factors:
1. The majority of the BOD5 and TSS loading resulted from the industrial wastes
discharged by the Hervin Company. The TSS and BOD5 varied considerably
from day to day, depending upon the product being processed and production
rate.
2. Daily flows were measured at the plant effluent pump station. Due to the low
influent flows and surge capacity of the aeration-surge basin, the daily influent
and effluent flows were not necessarily equivalent. Thus, the actual daily BOD5
and TSS loads could not be accurately determined.
3. BOD5 analyses were normally made two or three days per week, while the TSS
was determined daily. Estimates of the influent BOD5 were made for those
days when BOD5 data were not available from plots of the influent TSS versus
BOD5.
-109-
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2.5
2.0
1.5
1.0
0.5
T
T
GROSS SLUDGE YIELD
SLUDGE AGE
TEMPERATURE
T
5 DAY WEEKLY AVERAGE
2 WEEK MOVING AVERAGE
8 TO 22°C
<9
CD
_L
10
15 20
SLUDGE AGE (DAYS)
30
FIGURE 42
GROSS SLUDGE YIELD VERSUS SLUDGE AGE
35
-------
4. The temperature in the aeration-surge basin varied from 8 to 22 degrees C,
averaging 15.5 degrees C. The data on Figure 42 were initially plotted for three
temperature ranges, but correlation of the data was not significantly improved.
While temperature undoubtedly had some affect on solids yield, the variability
introduced by the first three factors appeared to mask any changes due to this
parameter.
The gross sludge yield declined from about 1.5 pounds per pound of BODc removed at a
sludge age of 4 days, to J.O pounds per pound of BOD^ removed at a sludge age of 10
to 11 days. The gross sludge yield remained essentially constant from a sludge age of 11
to 31 days.
The influent suspended solids were suspected to be responsible for the larger than
anticipated solids production. An attempt was made to calculate the biologically
synthesized solids fraction of the gross sludge yield, by subtracting out the
non-metabolized influent suspended solids. Assuming the rate of degradation to be
dependent upon sludge age, the following equation was developed to estimate the
non-metabolized fraction of the influent TSS at a given sludge age and temperature
condition:
WAS + TSS/
-------
This relationship takes the form of the straight line equation:
y - fx + b
Where: y = gross sludge yield
x -
BOD(R)
b = net sludge yield (NSY)
f = slope (non-metabolized fraction of TSS(j\)
The gross sludge yield was plotted against TSS^/BOD^) to estimate the
non-metabolized fraction, f, of the influent TSS for various sludge age conditions. The
limited amount of data at any given sludge age necessitated using values obtained over a
temperature range of 8-22 degrees C. Figure 43 is an example of one of these plots for a
sludge age of 12-16 days.
The non-metabolized fraction, f, determined from these plots is shown as a function of
sludge age in Figure 44. It appears that essentially no degradation of the influent TSS
occurred at sludge ages less than 5 days and that only 20 to 22 percent of the influent
TSS was ultimately biologically metabolized at sludge ages greater than about 10 to 12
days.
The impact of the influent TSS on such operational parameters as the F/M and activated
sludge wasting rates can be significant, particularly in activated sludge systems where
primary treatment is not provided. At influent conditions where the TSS and BOD5 are
approximately equal, the apparent F/M based on MLSS may be lower by a factor of two
or more than the F/M considering only the biologically synthesized solids. The MLSS
level necessary to provide the concentration oi active biological solids desired must allow
for the non-degraded influent TSS. Consideration must also be given to the influent TSS
loading in estimating sludge wasting rates and sizing of sludge handling and storage
facilities.
The degradability factor, f, determined above was applied to the influent TSS to calculate
the net sludge yield for various sludge ages. The results are shown on Figure 45. The net
sludge yield decreased from about 0.4 to 0.25 pounds per pound of BOD5 removed
between sludge ages of 5 and 12 days. Beyond a 12-day sludge age, the net sludge yield
decreased at a much slower rate down to a minimum of about 0.17 pounds per pound of
6005 removed at about a 30 day sludge age.
-112-
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2.0
SLUDGE AGE - 12 TO 16 DAYS
TEMPERATURE - 8 TO 22°C
i
Q
O
LU
If)
Q
O
CO
< vo
O
O
f - 0.785
O
_J
LU
>
LU
O
D
C/5
O
CC
CP
J_
1.0
INFLUENT TSS
2.0
'LBS/DAY\
TOTAL BOD5 REMOVED VLBS/DAY/
FIGURE 43
GROSS SLUDGE YIELD VERSUS
INFLUENT TSS/TOTAL BOD5 REMOVED
-113-
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- -
28
.8
§
a
.6
,4
o
SLUDGE AGE - 1 WEEK MOVING AVERAGE
TEMPERATURE - 8 to 22°C
o
10 15
SLUDGE AGE (DAYS)
20
25
30
FIGURE 44
INFLUENT TOTAL SUSPENDED SOLIDS DEGRADATION VERSUS SLUDGE AGE
-------
D
co
CD
1
D
LU
O
D
0
O
cc
Q.
CO
Q
_J
8
D 1 r
--«. P. 3
CO
EC
I
Q
UJ
o 1.0
^jpl
Ui
oc
If)
Q
O
DQ
s — ^
Q 0.5
UJ
*"
UJ
0
D
to
• 0
I 1 I 1 I 1
SLUDGE AGE - 2 WEEK MOVING AVERAGE
TEMPERATURE- 8 TO 22°C
O
o
o
o
O C£>
o
^°°T>-^ 8 ° ° °
^^^^^ O Q O
jli ( . —Q^n
o°0 o o Q o -—
, ° ° 9 o° ° , o . i i °
) 5 10 15 20 25 30 3!
Z SLUDGE AGE (DAYS)
FIGURE 45
NET SLUDGE YIELD VERSUS SLUDGE AGE
-------
The sludge yield and endogenous coefficients were evaluated using the general form of
the equation developed by McCarty and Brodersen [10] and discussed in Section III:
A 0.8a
£1 = a -
F 1 + 1
bTs
Where: -p- = net biological solids synthesized
per pound of BOD removed
a = sludge yield coefficient
b = endogenous respiration coefficient
Ts = sludge age
The factor, 0.8 a, assumes 20 percent of the biologically synthesized solids are relatively
resistant to biological oxidation [10].
For sludge ages between 5 and 30 days and a temperature range of 8 to 22 degrees C,
the sludge yield coefficient, a, was calculated to be 0.60 and the endogenous coefficient,
b, to be 0.15. These values are in general agreement with values of 0.65 and 0.18
determined by McCarty and Brodersen for domestic sewage. Sludge yield and endogenous
constants of 0.70 and 0.1 were determined for a similar extended aeration system
treating a combined industrial and domestic waste at Dallas, Oregon [37].
SUBSTRATE REMOVAL
Substrate removal in the extended aeration system was evaluated in terms of the
following equation derived from the Michaelis-Menton relationship discussed in Section
III:
= ks
The substrate removal coefficient, k, is the slope of the straight line passing through the
origin produced by a plot of the substrate removal rate, R, expressed as total pounds of
BOD5 removed per day per pound of MLSS versus mg/1 of effluent soluble BOD5.
Figure 46a is a plot of the 5-day weekly average BOD^ removal rate versus the 5-day
weekly average effluent soluble BOD5 for all of the data obtained during the
demonstration period. As may be expected, the field data show considerable scatter. To
determine the substrate removal coefficient, a straight line from the origin was drawn
through the mean coordinates of the data points.
-116-
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0.3
<
Q
OC
LU
0.
Q
O
ill
e
in
Q
O
m
CO
m
0.2
0.1
0.0
O
TEMPERATURE - 8 TO 22 C
O
O
468
TERTIARY EFFLUENT SOLUBLE BOD (MG/L)
(a)
10
TEMPERATURE - 8 to 22 C
TERTIARY EFFLUENT SOLUBLE BOD (MG/L)
(b)
FIGURE 46
SUBSTRATE REMOVAL RATE VERSUS TERTIARY EFFLUENT
SOLUBLE BOD5
10
-117-
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Figure 46a represents data for a temperature range of 8 to 22 degrees C. Initially, separate
plots were made of the data in three temperature ranges. The substrate removal
coefficients determined from these plots did not show significant variation from each
other. It was concluded the variability due to temperature was within the variability
resulting from other factors, including influent suspended solids loading and the
characteristics of the industrial waste.
The average substrate removal coefficient, k, calculated from Figure 46a was 0.0235
pounds BOD5 removed per day per pound of MLSS per mg/I soluble effluent 8005.
Assuming the average volatile content of 73.5 percent determined for the WAS during
August 1971 was representative of the MLSS over the entire demonstration, the substrate
removal coefficient based on MLVSS was 0.032. This value is somewhat less than the
value of 0.041 reported for another extended aeration plant treating combined industrial
and domestic wastes [37]. The lower rate of substrate removal is attributed to the
industrial waste received from the pet food processor.
An attempt was made to improve data correlation by calculating the substrate removal
rate based on the biological solids fraction, Mg, of the MLSS. Mg was calculated from
the influent suspended solids degradation rate data in Figure 44 and the sludge yield data
in Figure 45 using the following relationship for various sludge age conditions:
y x BOD(I)
MB = y x BOD(I) + f x TSSa) x [MLSS]
Where: y = biological solids yield coefficient (Ibs solids
produced per day /Ibs BOD5 removed per day)
) = influent BODs (Ibs per day)
TSS(j) = influent TSS (Ibs per day)
f = non-metabolized fraction of TSS(j) at a given sludge
age and temperature condition
Tg = sludge age (days)
T = temperature (degrees C)
-118-
-------
Figure 46b is a plot of the pounds of BOD5 removed per pound of "biological" MLSS
(Mg) versus effluent soluble BOD$ concentration. Calculating substrate removal rate
based on Mg rather than total MLSS did not markedly improve the data scatter,
however. The substrate removal coefficient, k1 based on Mg, was calculated from a
straight line drawn through the mean coordinate of the data points and passing through
the origin. The value of k' determined from Figure 46b was 0.098 pounds BOD^
removed per day per pound Mg per mg/1 effluent soluble BOD^.
SLUDGE VOLUME INDEX
The sludge volume index was dependent to a large extent on the D.O. level in the
aeration-surge basin. Figure 47 is a plot of the average weekly D.O. and SVI. As long as
the D.O. remained above 0.5 to 1.0 mg/1, the SVI averaged about 80 and generally stayed
below 100. Below 0.5 mg/1 D.O., the SVI increased to values as high as 400.
Attempts were also made to relate SVI to F/M and sludge age. A correlation to either
parameter was not apparent.
Although the SVI did not appear to have a significant effect on the performance of the
secondary tube clarifier, high levels would undoubtedly reduce the degree of thickening
obtainable in a conventional secondary clarifier and substantially influence activated
sludge recycle and wasting rates.
SECONDARY CLARIFIER PERFORMANCE
The secondary effluent suspended solids concentration varied considerably, even after the
air sparger modification was made to prevent entrapment of the solids and clogging of
the tubes. Tube clarifier performance appeared to depend upon five variables:
1. MLSS concentration
2. Overflow rate
3. Temperature
4. pH
5. Extent of nitrification
Under a given set of conditions any of these parameters could become the controlling
variable or considerably influence clarification efficiency.
MIXED LIQUOR SUSPENDED SOLIDS-The MLSS level appeared to be the most
critical parameter. Figure 48 demonstrates the influence of MLSS on the secondary
effluent suspended solids concentration for overflow rates of 0.58 - 0.75 gpm/ft and
1.50- 1.67 gpm/ft2.
-119-
-------
®l
100
150
®
®
®
®
©
200
SVI
250
300
350
400
FIGURE 47
DISSOLVED OXYGEN VERSUS SVI
-------
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v 140
CD
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"" 120
10
t- 100
i-
ui 80
t 60
Ul
ir 40
D
§ 20
o
Ul
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i , , ,
GRAPH A
SURFACE OVERFLOW RATE - o.se TO 0.75 GPU/FT. 2
TEMPERATURE RANGE - 15° TO 22°C
^
-
\ ^°0 °
o°0° \ o
° OOO >sx^_^ °
^Jo o QC^ o o
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— i 1 1 1
(70-90 GP«)
-
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2000 2400 2BOO 3200
MLSS (MG/L)
^ 140
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- 120
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,_
ul 80
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It 60
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£ 40
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o 20
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GRAPH B
r SURFACE OVERFLOH RATE - 1.50 TO 1.67 GPU/FT. 2
TEMPERATURE RANGE - 8° TO !5°C
a
.
^. D D D D D
D ^""*n '-"-' ^
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2000 2400 2600 3200
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GRAPH C
.
SURFACE 0»ERFLO» RATE - 1,50 TO I.B7 GPU/FT.2
TEMPERATURE RANSE - 16° TO 22°
-
p a
^*"">>*>k D
""s^,^ D D
D PI iD T^^^^^
O D
D
0 400 800 1200 1EOQ
a
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a ° a ^ a
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a
•
__i 1 1 1
2000 2400 2800 3200
MLSS (MG/L)
FIGURE 48
SECONDARY EFFLUENT SUSPENDED SOLIDS VERSUS MLSS
-121-
-------
The effluent suspended solids concentration tended to decrease as increasing MLSS levels
approached 1,000 - 1,200 mg/1. One or both of two mechanisms are thought to be
responsible for this phenomenon: (1) An increase in MLSS concentration provides greater
opportunity for collision of suspended particles, enhancing coagulation. (2) The
coagulated solids collecting in the tubes form a filter bed, straining out smaller
particulate. A minimum concentration of 1,000 - 1,200 mg/1 is necessary to effect
optimum removal.
At MLSS levels of 2,200 to 2,400, a critical condition was reached above which solids
removal efficiencies sharply decreased. It is hypothesized that rising MLSS levels increase
the volume of material settling in the tubes. The upward flow cross sectional area is
reduced, resulting in an effective increase in the hydraulic surface loading. At a MLSS of
2,200 to 2,400 mg/1, a critical velocity condition is reached. Particles less than a given
size and density do not have sufficient time to settle out before being swept through the
tubes and into the collection pool above. The increased upward velocity may also be
sufficient to produce a scouring condition, resuspending settled material and contributing
to the solids carryover.
By modifying the clarifier design to increase the cross sectional area of the tubes or
change their geometry, it may be possible to increase the MLSS range of optimum
settling above the levels observed in this investigation. However, the constraint of MLSS
on suspended solids removal must be considered a limitation in application of tube
settlers to activated sludge clarification.
OVERFLOW RATE—The secondary tube clarifier operated within four overflow rate
ranges at various times during the demonstration program:
1. 0.58 - 0.75 gpm/ft2 (70 - 90 gpm)
2. 0.87 - 0.95 gpm/ft2 (105-115 gpm)
3. 1.12 - 1.16 gpm/ft2 (135-140 gpm)
4. 1.5 - 1.67 gpm/ft2 (180-200 gpm)
Within the optimum MLSS range (and at temperature of 16-22 degrees C) a secondary
effluent suspended solids level of 25 to 30 mg/1 was maintained at a surface overflow rate
0.58 - 0.75 gpm/ft^ (Figure 48). Increasing the surface overflow rate to 1.5 - 1.67
gpm/ftr at the same MLSS and temperature conditions increased the average effluent
suspended solids level to about 40 mg/1. At the higher flow rate, however, the upper limit
of the optimum MLSS range was extended from about 2,200 to 2,500 mg/1.
To provide a consistent effluent quality of less than 30 - 40 mg/1, these data indicate the
surface overflow rate should be limited to 0.75 gpm/ft or less at temperatures above 15
degrees C.
-122-
-------
TEMPERATURE-A decrease in temperature appeared to result in increased solids
carryover. Secondary effluent suspended solids are plotted versus MLSS for an overflow
rate of 1.5 to 1.67 gpm/ft2 and temperature ranges of 8 - 15 degrees C and 16-22
degrees C on Figure 48. Under optimum MLSS conditions, the secondary suspended
solids averaged about 40 mg/1 at water temperature of 16 - 22 degrees C. Reducing the
temperature range to 8 - 15 degrees C raised the average secondary effluent suspended
solids concentration to about 50 mg/1. The 10 mg/1 increase in solids carryover is
attributed to increased water viscosity at the lower temperatures.
pH AND NITRIFICATION-A correlation was observed between pH, the ammonium ion
concentration and the secondary effluent suspended solids concentration. Figure 49 is a
plot of pH versus secondary effluent concentration at overflow rates of 0.92 gpm per ft
and 1.12 gpm per ft^. The ammonium concentration versus suspended solids content is
shown on Figure 50 for all four overflow rates. The data presented in Figures 49 and 50
were limited to a MLSS range of 1,000 to 2,400 mg/1. Above and below these limits the
affect of MLSS on the secondary effluent concentration predominated over the influence
of the other variables.
The minimum secondary effluent suspended solids concentrations tended to occur
between pH 6.9 to 7.2 and at ammonium concentrations around 5 mg/1. Both pH and
ammonium concentrations were largely controlled by the extent to which the secondary
treatment system nitrified. The level of ammonium in the secondary effluent
corresponding to the minimum suspended solids concentrations occurred coincident with
the optimum pH for settling. Lower concentrations of ammonium, however, were also
recorded when the pH favored suspended solids removal. Thus, pH is suspected to exert a
greater influence on coagulation and settling than ammonium ion. It may be that the
ammonium concentrations corresponding to the lower secondary effluent suspended
solids levels are just a reflection of the pH conditions resulting from nitrification.
The stability and the surface charge or zeta potential associated with colloid_al particles_is
known to be affected by such potential determining ions as H , HCO3 and NH4 .
Adsorption of these ions onto the particle surface can decrease (or increase) the apparent
surface charge. Reduction in the surface charge and the resultant loss of stability
enhances the tendency for coagulation.
Bacteria organic matter resulting from the lysing and metabolism of cell tissue, and
inorganic colloids, such as clay particles, tend to have a net negative surface charge in a
slightly alkaline medium. Maintaining the pH within a specified range, together with the
presence of ammonium ion (NH4+), would be expected to neutralize the negative surface
charge and destabilize the suspended colloidal particles. Under these conditions,
coagulation and flocculation of the MLSS should be enhanced and clarifier performance
improved.
Further research is needed to more fully explore the effect of pH, the presence of
specific ions, and oxidative state on coagulation and secondary clarification of activated
sludge.
-123-
-------
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FIGURE 49
SECONDARY EFFLUENT SUSPENDED SOLIDS VERSUS pH
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A 1.12 SPH/FT.2 (135 6PI1)
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FIGURE 50
SECONDARY EFFLUENT SUSPENDED SOLIDS
VERSUS AMMONIUM ION CONCENTRATION
-124-
-------
NITRIFICATION
The relatively long sludge ages and temperatures in the secondary system produced an
ideal environment for nitrification. The oxidation of ammonium ion to nitrate went
virtually to completion, when adequate D.O. could be maintained in the aeration-surge
basin.
The extent of nitrification as a function of sludge age is shown on Figure 51. The degree
of nitrification is expressed as the ratio of nitrite plus nitrate to total dissolved nitrogen
(nitrite, nitrate, and ammonium). All of the data points in Figure 51 represent D.O. levels
of 0.8 mg/1 or above. A sludge age of about 5 to 6 days was sufficient to induce
nitrification within the temperature range of 8 to 22 degrees C.
Conversion of ammonium to nitrite and nitrate approached 98 percent of completion at a
sludge age of 10 to 12 days, with ammonium residual concentrations consistently less
than 1 mg/1.
The effect of dissolved oxygen on nitrification is shown on Figure 52. Below a D.O. level
of 0.4 to 0.6 mg/1, nitrification was effectively inhibited. At a D.O. of 1.0 to 1.5 mg/1
essentially complete (98 percent) oxidation was possible.
While warmer temperatures undoubtedly promote nitrification, particularly at the shorter
sludge ages, the effect of temperature over a range of 8 to 22 degrees C appears to be
less than the variability introduced in sampling and analysis in both Figures 51 and 52.
The effect of D.O. on the relative nitrite and nitrate concentrations was also examined.
The ratio of nitrite to nitrate as a function of D.O. is shown on Figure 53. Above a D.O.
of 0.6 to 0.8 mg/1 the oxidized form of nitrogen is essentially all nitrate.
A transition from a non-nitrified to highly nitrified condition occurred in late June 1971,
presenting an. excellent opportunity to observe the two step conversion of ammonium
nitrate as discussed in Section III. The industrial flows to the treatment plant were
suspended for two weeks. Only domestic waste was processed. The ammonium, nitrite
and nitrate concentrations measured during this period are shown on Figure 54.
Initially, ammonium ion was oxidized by the bacterium nitrosomonas to nitrite [11].
2NH4+ + 30^, nitrosomonas
-125-
-------
to
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D.O. 3* 0.8MG/L
10 12 14 16 18
SLUDGE AGE (DAYS)
20
22
24
26 28
30
FIGURE 51
NITRIFICATION VERSUS SLUDGE AGE
-------
5
1.0
1.5 2.0 2.5
DISSOLVED OXYGEN (MG/L)
FIGURE 52
NITRIFICATION VERSUS AERATION-SURGE BASIN DISSOLVED OXYGEN
-------
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1.4
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NITRIFICATION
INHIBITED
-
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0.5
1.0 1.5 2.0 2.5
DISSOLVED OXYGEN (MG/L)
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FIGURE 53
NO2/NO3 VERSUS AERATION-SURGE BASIN DISSOLVED OXYGEN
-------
£ 20 '
**• Ul
Q o
51
10 -
0246
8 10 12 14 16
TIME (DAYS)
18 20 22
FIGURE 54
SEQUENCE OF NITRIFICATION REACTIONS
-------
The concentration of ammonium decreased as the level of nitrite increased. About 48
hours after the start of nitrification, the bacterium nitrobacter began the conversion of
nitrite to nitrate [11].
2N02" + 02 nitroacter^ 2NO3"
The concentration of nitrite declined, corresponding with the increase in nitrate.
When normal production operations were resumed by the Hervin Company, after the two
week vacation period, the organic loading in the industrial flow exceeded the design
aeration capacity. The nitrate concentration immediately dropped as bacteria scavenged
for all available oxygen and the ammonium concentration began to steadily increase.
The bacterial oxidation of ammonium ion results in a net release of hydrogen ions and a
corresponding reduction in alkalinity. According to the autotrophic nitrification reaction
proposed by McCarty [12].
+ " ~ +
22NH4 + 37O2 + 4CO2 + HCO3 — C5H?NO2 + 21NO3 + 20H2
-------
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LU £5
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16-20°C
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16-22°C
NITRIFICATION
NITRIFICATION
INHIBITED
NITRIFICATION
O
LOW DISSOLVED OXYGEN
CONTENT INHIBITING
NITRIFICATION
10
15
20
25
30
35
SLUDGE AGE (DAYS)
FIGURE 55
NITROGEN REMOVAL IN AERATION-SURGE BASIN
-------
PHOSPHATE REMOVAL
An apparent correlation existed between pH and orthophosphate removal in the
secondary treatment system. Phosphate removal efficiency, expressed in terms of
orthophosphate in the secondary effluent and total influent phosphate is plotted versus
pH on Figure 56. Each data point represents an average of the phosphate removals
observed at a given pH condition.
Optimum orthophosphate removals occurred between a pH of 7.0 to 7.25. This is
approximately the same pH region in which optimum secondary clarification was
observed.
Whether the mechanism of orthophosphate removal is one of precipitation, adsorption, or
other phenomenon is a matter of conjecture. Analyses for cation precipitants, such as
calcium and aluminum, were not made. Therefore, it is not known whether a net loss of
these elements occurred in the secondary treatment plant to an extent which would
account for the observed orthophosphate reduction.
If orthophosphate removal was the result of precipitation with aluminum ion introduced
by discharge of the tertiary filter backwash to the aeration-surge basin, optimum removal
efficiencies, as observed in the tertiary system, should have occurred at or below a pH of
6.0 [25].
Because of the narrow pH range over which optimum phosphate removal occurred and
the coincidence with the pH region of optimum suspended solid removal, it is suspected
that the removal mechanism may be one of adsorption of orthophosphate on colloidal
particulate. Orthophosphate may be a potential determining ion affecting the stability of
suspended particulate. Considering the apparent effect of pH on coagulation of the
MLSS, it is conceivable that optimum orthophosphate adsorption could also occur in this
same pH regime.
AERATOR OXYGEN TRANSFER RATE
An estimate of the oxygen transfer rate of the floating aerators was made from the plot
of aeration-surge basin D.O. versus influent BOD5 shown on Figure 57. The following
assumptions were made in the oxygen transfer rate calculations:
1. The ultimate BODL was exerted (BODL = 1.47 BOD5).
2. The influent nitrogen underwent complete nitrification (1 mg N = 3 84 me
02).
3. At the average sludge age of 13 days for the demonstration program, 20
percent of the influent TSS were degraded and the BOD5 exerted the ultimate
demand.
-132-
-------
OJ
100
6.0
6,5
PH
7.0
7.5
FIGURE 56
SECONDARY TREATMENT SYSTEM PHOSPHATE REMOVAL VERSUS pH
-------
o
o
3 3
z
55
CO
ai
O
CC
? 2
i
o
CALCULATED TOTAL OXYGEN DEMAND
INCLUDING ALLOWANCE FOR INFLUENT
TSS DEGRADATION AND NITRIFICATION.
200
400 600 800
INFLUENT BOD5 (LB/DAY)
FIGURE 57
1000
1200
1400
AERATION-SURGE BASIN D.O. VERSUS INFLUENT BOD5
-------
The influent BOD5 and suspended solids concentrations were approximately equal, when
averaged over the demonstration period. The influent total nitrogen averaged 10 percent
of the influent BOD5- Based on the three assumptions above, the total average oxygen
requirement was calculated to be equivalent to 2.15 times the influent BOD5 as follows:
BODL = 1.47 mg/102/mg/lBOD5
TSS = 1.47 x 0.2 mg/1 O2/mg/l BOD5
N = 3.84 x 0.1 mg/1 O2/mg/l BOD5
Total 02Demand - 2.15 mg/1 O2/mg/l Influent BOD5
At the average temperature condition of 15.5 degrees C and a D.O. level of 1.0 mg/1 in
the aeration-surge basin, the field transfer rate for the two 15 hp aerators was calculated
to be 1 4" Ibs CH/hp-hr (nameplate hp basis). Assuming an a of 0.85 (ratio of oxygen
transfer rate into"waste to oxygen transfer rate in clean water) and B of 0.9 (ratio of
saturation D O in waste to saturation D.O. in clean water) the clean water transfer rate
of the aerators was calculated to be 2.13 Ibs O2/hp-hr. This transfer rate is somewhat
below that expected for draft tube type aerators.
The estimate of aerator oxygen transfer rate must be somewhat qualified, however. The
assumptions made in calculating the total oxygen demand allow for the maximum oxygen
utilization that could reasonably be expected and may be on the high side The data on
Figure 57 used in the calculations represent a temperature range of 8 to 22 degrees U
DO measurements were made only during the day, while the BOD5 analyses were made
from samples composited over a 24-hour period and represent the average BOD5 applied
to the plant. The diurnal variation in BOD 5 loading was not measured. Peak organic
loading conditions likely occurred during the daytime hours when the D.O. measurements
were made.
TERTIARY TREATMENT SYSTEM
TERTIARY SYSTEM PERFORMANCE
The cycle time of the tertiary unit was influenced by four factors:
1. Premature carryover of solids from the tertiary tube settler on to the filter.
2. Secondary effluent suspended solids concentration.
3. Alum dosage.
4. Excessive polyelectrolyte addition.
-135-
-------
SOLIDS CARRYOVER FROM THE TERTIARY TUBE SETTLER-The tertiary tube
settler did not have sufficient solids storage capacity to retain all of the settleable
chemical floe before entrapment of finer participate by the filter media required
backwashing of the bed. As a result, large quantities of chemical floe were prematurely
carried over onto the filter bed, causing a rapid rise in head loss and substantial reduction
in filter cycle time.
Figure 58 illustrates the effect of the solids carryover on filter performance. The
suspended solids content of the effluent from the tertiary tube settler, filter head loss
and tertiary effluent turbidity and suspended solids were monitored for one filter run.
The filtration rate was 3.8 gpm/sq ft. The secondary effluent contained a TSS of 65
mg/1, to which an alum dosage of 182 mg/1 was applied for coagulation. No
polyelectrolyte was added either presettler or prefilter.
At about 1-1/2 hours into the run, solids began to carryover from the settler onto the
filter. An increase in the rate of filter head loss buildup was observed at about 2-1/2
hours. At 3 hours, 56 minutes after start of the run, the head loss reached 8.3 feet, the
preset value initiating the backwash cycle and terminating the run.
A total volume of 44,840 gal was filtered during the run. Had the storage volume in the
tube settler been adequate to prevent carryover, extrapolation of the head loss buildup
during the first 2 hours of the run indicates the filter cycle could have been extended
from 4 to 16-1/2 hours.
The existing tube settler was designed for a surface overflow rate of 143 gal per day per
sq ft. From the data in Figure 58, the tube settler surface area should be increased by a
factor of 4, reducing the overflow rate to about 35 gal per day per sq ft. The volume
required for backwash was 9,600 gallons. At a flow rate of 190 gpm and 4 hour filter
cycle, 21 percent of the tertiary, throughput was required for backwash. Optimizing the
size of the tertiary tube settler to provide more solids storage volume would reduce the
backwash requirement to about 5 percent of the throughput.
INFLUENCE OF SECONDARY TSS ON CYCLE TIME-Secondary TSS versus the
volume filtered per cycle without the addition of chemical is shown on Figure 59. The
throughput decreased exponentially at TSS concentrations above 60 to 70 mg/1 and
increased linearly at TSS below 60 mg/1. It is suspected that at the higher loadings, the
solids collected on the surface of the filter preventing "indepth" filtration throughout the
bed. Figure 59 illustrates the importance of providing efficient secondary clarification
when chemical coagulation and sedimentation are not provided prior to filtration. At a
secondary effluent TSS of 20-30 mg/1, the throughput across the 49.5 sq ft filter bed
approached 500,000 gal per cycle.
Increasing alum dosages reduced the influence of the secondary effluent TSS on the
length of filter run. Figure 60 is a plot of the volume filtered per cycle versus secondary'
effluent TSS for five alum feed conditions. Above an alum dosage of 183 to 190 mg/1,
the influence of the secondary effluent TSS to the tertiary system was minimal.
-136-
-------
FILTER RUN TIME (HOURS)
FIGURE 58
SUSPENDED SOLIDS, HEAD LOSS AND TURBIDITY VERSUS FILTER RUN TIME
-137-
-------
T T
O
260
220
180
1U
D
u.
til
c
Q 100
O
u
111
CO
60
20
I
I
I
NO CHEMICAL ADDITION
J_
I
40 80 120 160 200 240 280 320
VOLUME FILTERED PER CYCLE (GALxlO'3)
360
400
440
480
FIGURE 59
TERTIARY THROUGHPUT VOLUME VERSUS SECONDARY EFFLUENT TSS
CONCENTRATION (WITHOUT CHEMICAL FEED)
-------
X
V)
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50
40
30
20
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60
50
40
30
20
10
40
30
_ 20
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^. 10
40
30
20
10
0
40
30
20
to
HUM - 126 M6/L
O
ALUM • 155 MG/L
ALUM • 183-190 MG/L
O
o
Q>
o
o
ALUM - 240-242 MG/L
20
—40 60 BO TOO 120 HO 160 180
SECONDARY EFFLUENT TSS (MG/L)
FIGURE 60
TERTIARY THROUGHPUT VOLUME VERSUS SECONDARY EFFLUENT TSS
CONCENTRATION (WITH CHEMICAL FEED)
-139-
-------
INFLUENCE OF ALUM DOSAGE ON CYCLE TIME-Increasing alum dosages also
decreased the tertiary cycle time. Figure 61 is a plot of alum dosage versus the
throughput volume per cycle. The data points represent the average volume filtered at
each alum feed condition. The average throughput decreased nonlinearly from 50,000
gallons per cycle at an alum dosage of 53 mg/1 to 32,000 gallons per cycle at alum
dosages above 200 mg/1.
The reduction in the volume filtered per cycle may be explained by the fact that larger
alum dosages produced greater quantities of chemical floe, increasing the solids loading
on the tertiary settler/filter unit. Increased sedimentation capacity ahead of filter should
tend to minimize the effect of alum dosage on filter cycle.
PREFILTER POLYELECTROLYTE ADDITION-Addition of anionic polyelectrolyte at
dosages of 0.03 to 0.06 mg/1, after settling and prior to filtration, was effective in
controlling turbidity breakthrough. Figure 62 illustrates the application of polymer
prefilter. Three turbidity records were selected for identical alum and presettler polymer
dosages, but differing prefilter polymer feed conditions.
In Figure 62a, prefilter polymer was not applied. Breakthrough occurred about midway
through the filter run, with the turbidity increasing from 0.7 JTU to about 2.1 JTU at
backwash.
The prefilter dosage in Figure 62b was 0.03 mg/1. Breakthrough occurred in the last 25
minutes of the run and was only about 0.1 JTU above the base turbidity level.
Breakthrough was completely eliminated in Figure 62c with a prefilter dosage of 0.06
mg/1.
The turbidity control illustrated in Figure 62b is considered to be the optimum
condition, with breakthrough occurring simultaneously with or just prior to backwash.
While breakthrough was completely eliminated at the higher prefilter polymer dosage in
Figure 62c, the higher application rate may have been at least partially responsible for
the shorter filter run as compared to Figure 62b. The secondary suspended solids loadings
were essentially the same for both runs. The alkalinity and pH condition differed.
however. The feed conditions for the two runs were therefore not identical and a direct
comparison of the filter cycle times may not be totally valid.
Prefilter dosages of 0.1 mg/1 and above definitely reduced the filter run time. Figure 63
shows the head loss characteristics and effect on filter run time at prefilter polymer
dosages of 0 and 0.1 mg/1. At the higher application, the head loss increased more rapidly
and shortened the run time by 23 percent.
PRESETTLER POLYELECTROLYTE ADDITION-The addition of polyelectrolyte ahead
of the flocculator did not appear to appreciably aid the formation or improve the settling
characteristics of the chemical floe. Neither was there a noticeable increase in filter run
time as a result of presettler polyelectrolyte addition.
-140-
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250
200
LU
C
< 150
01
O
C
100
50
O
_L
_L
10
20 30 40 50
AVERAGE VOLUME PER FILTER CYCLE (GALx IO
60
FIGURE 61
EFFECT OF ALUM DOSAGE ON FILTER CYCLE
-141-
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2t APRIL 1971
CONDITIONS
FLO« RATE - 190 GPM
ALUK - 126 MG/L
POLY. P/S - 1.4 MG/L
PtILY P/F - 0 MG/L
SEC. TSS - 69 MG/L
TER. pH - 5.6
TER. TSS • 8.4 MG/L
'—I— RUN TIME 3;25 HRS
12N
2PM
4PM
6PM
(a)
DATE
7 JULY 1971
CONDITIONS
FID* RATE • 190 GPM
ALUM - 1 26 MG-'L
POLY. P/S - 1.4 »G,L
POLY. P/F - 0. 03 MG 'L
SEC. TSS - 46 MG/L
FER. pH - 5.4
TER. TSS
1 . 0 MG-'L
Q
CG
RUN TIME 5.20 HRS.
12N
2PM
4PM
6PM
1 0
I JUNE 1971
CONDITIONS
FLO* RATE
ALUM
POLY
POLY
SEC.
TER.
TER.
190 GPM
126 MG/L
P/S
P/F
TSS
pH -
TSS
1.4 MG/L
0 06 MG/L
42 MG/L
6.25
-------
CO
CO
O
UJ
I
EC
DATE
ALUM
SEC. TSS
POLY PIS
14 MAY 1971
183 MG/L
48 MG/L
1.4 MG/L
O
D
POLY P/F
0.1 MG/L
NO POLY P/F
1 2
RUN TIME (HOURS)
FIGURE 63
EFFECT OF PRE FILTER POLYELECTROLYTE
ADDITION ON FILTER RUN TIME
-143-
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Figure 64 is a plot of the secondary effluent TSS versus the pounds of secondary
suspended solids removed per filter run for three alum feed conditions and three levels of
presettler polymer addition - None, 0.5 to 1.0 mg/1, and 1.4 to 2.0 mg/1.
The data used in Figure 64 were limited to a prefilter polymer dosage of 0 - 0.06 mg/1 to
minimize filter "binding," due to excessive prefilter polymer addition and a reduction of
the filter run time.
At alum dosages of 126 mg/1, and 155 to 160 mg/1, there was a slight increase in the
solids removal at presettler polymer concentrations of 1.4 to 2.0 mg/1 over the addition
of alum only. From these data, it was concluded that presettler polymer additions did
not substantially improve tertiary performance.
The presettler polymer feed stream was introduced at the constant head box between the
tertiary influent pump and the flocculator tank. The alum feed stream was introduced on
the suction side of the tertiary influent pump. Sufficient time may not have been
provided for the alum to disperse and become hydra ted before the polymer was
introduced.
The chemical floe formed in the tertiary system was much smaller and appeared to be
less cohesive than that produced in jar tests at the same dosages of alum and anionic
polymer. From this observation, the point at which the presettler polymer was
introduced may not have been the optimum location.
In summary, the results of polymer addition to aid the flocculation process were
inconclusive. Further study is needed to better assess the potential benefits to be gained
by polymer addition in this phase of the tertiary process.
PHOSPHATE REMOVAL
Phosphate removal in the tertiary system was observed to be a function of at least three
variables: alum dosage, pH, and the initial concentration of orthophosphate in the
secondary effluent. The percentage removals generally increased at higher alum dosages.
The removal efficiency also improved with decreasing tertiary effluent pH. These
observations were confirmed by jar tests conducted periodically during the project.
An attempt was made to relate all three parameters - pH, initial (secondary effluent)
orthophosphate concentration and alum dosage-as shown on Figure 65. Log-log plots
were made of the observed removal efficiency (tertiary ortho P/secondary ortho P) versus
the molar ratio of Al (III) to secondary orthophosphate ion concentration for four pH
ranges: 5.35 to 5.5, 5.8 to 6.35, 6.5 to 6.65 and 6.7 to 7.0. Straight lines were placed
through the centroid of the data points and are replotted on Figure 66.
Although the data are somewhat scattered, the log-log relationship of removal efficiency
to [Al(IIl)]/[Ortho P initial] appeared to hold up to a molar ratio of about 2 to 3.
Above this range, the data varied widely.
-144-
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100
BO
60
1 DO
1 00
40 -
20
CHEMICAL ADDITION
ALUM 126 MG/L
POLY. PRE-FILTER 0-0. 06 MG/L
POLY. PRE-SETTLER
O NONE
« 0.5-1.0 KG/I
• 1 4-2.0 MG/L
CHEMICAL ADDITION
ALUM 155-160 MG/l
POLr. PRE-FILTER 0-0.06 KG/I
POLY. PRE-SETTLER
O NONE
0 0.5-1.0 KG/I
• 1.4-2.0 MG/L
CHEMICAL ADDITION
ALUM 182-190 KG L
POLY PRE-flLTER 0-0.06 HG/L
POLY PRE-SETTLER
O NONE
Q 0 5-1.0 MG. L
• 1 .4-2.0 MG L
10 20 3D
LBS SEC. EFF. TSS REMOVED PER RUN
FIGURE 64
EFFECT OF PRESETTLER POLYELECTROLYTE
ADDITION ON TERTIARY SOLIDS REMOVAL
-145-
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1.0
0.5 ^
1.0
a ».3
0.2
K)
*
c
:.
0.1
0.05
£ 0.03
0.02
0.01
0.1 0.2 0.3 0.5 1.0 2.0 3.0 0.1 0.2 0.3 0.5 1.0 2.0 3.0
1.0
0.01
0.1 0.2 0.3 0.5 1.0 2.0 3.0 0.1 0.2 0.3 0.5 1.0 2.0 3.0
[A|3+]/[P043- SEC.]
MOLAR CONCENTRATIONS
[A|3+]/[P043- SEC.]
MOLAR CONCENTRATIONS
FIGURE 65
EFFECT OF pH, ALUM DOSAGE AND SECONDARY EFFLUENT
ORTHOPHOSPHATE CONCENTRATION ON PHOSPHATE REMOVAL
-146-
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07
0 3 : -i
02
rt
(f
007
0.05
CT 0.03
o
•
J
0 02
0.01
O.OC7
0.005
0.003
0001
02 03 05 0.7 1.0 20 'S.O
[AI3fi/[INiTIAL PO43"]
50 70 10.0
FIGURE 66
RELATIONSHIP OF ALUMINUM (III), INITIAL
ORTHOPHOSPHATE CONCENTRATION AND
pH ON ORTHOPHOSPHATE REMOVAL
-------
From this observation, it was concluded that addition of alum at a molar ratio of Al(III)
to initial orthophosphate in excess of 2 to 3 did not improve removal efficiency.
Lowering the pH from 6.7 - 7.0 to 5.3 - 5.5 reduced the alum dosage required to achieve
a given orthophosphate removal by about 57 percent. Thus, a significant savings in alum
addition can be realized by tertiary operation at the lower end of the effective alum
flocculation pH zone. In addition, lower orthophosphate residuals can be achieved at the
maximum effective [Al (III)]/Ortho P initial] molar ratio of 2 to 3 at lower pH.
Recht and Ghassemi [32] have also demonstrated the effect of pH on phosphate removal
efficiency. They determined a molar ratio of [Al (HI)]/[Ortho P initial] of 2 to be the
upper limit of effective phosphate precipitation at a pH of 6.
Bicarbonate (HCC>3~) alkalinity is also thought to have some influence on phosphate
removal and may be responsible for some of the scatter in the data on Figure 65. The
effect of this variable could not be quantitatively established, however. It is suspected
that increasing concentrations of bicarbonate alkalinity at a given pH condition decrease
orthophosphate removal efficiency. The orthophosphate and bicarbonate ions would be
expected to compete with each other for adsorption sites on the alum floe, particularly
as the pH increases. This is an interesting area of alum-phosphate chemistry, which
deserves further study.
WASTE SOLIDS STORAGE AND DISPOSAL
The waste activated and chemical sludge storage lagoons were an effective means of
retaining waste solids on the plant site. No objectionable odors were detected from the
lagoons, even during the dewatering period at the end of the program. Unfortunately,
ground water conditions limited the extent of solids dewatering, particularly in the
chemical sludge lagoon.
Separate dewatering experiments using small drying beds demonstrated that both the
chemical and waste activated sludge could be dried to a cinder-like humus material in 4
to 6 weeks, during the dry summer months. From these experiments, it appears that
applying the stored solids to shallow drying beds at a depth of six to eight inches is an
economical method for sludge dewatering.
The stabilized and dried waste activated sludge humus material is a suitable soil
conditioner. Possible uses of this material include soil conditioning in the City's parks and
application on selected agricultural croplands.
The dried chemical sludge from the storage lagoons may also be suitable as a soil
conditioner. However, additional study is suggested to assess the possible adverse effects
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that may result from the aluminum present in the waste. In lieu of such tests, landfill is
the recommended method for disposal.
DESIGN MODIFICATION AND EQUIPMENT RECOMMENDATIONS
GENERAL
Design modifications and items of additional equipment and instrumentation to improve
the performance and operation of future secondary-tertiary treatment systems of the type
demonstrated by this project are discussed in the following paragraphs. Several equipment
design modifications made during the project have been discussed in previous sections.
Additional sampling and testing equipment was not included in the original plant design,
due to financial constraints. Considering the total capital investment of the treatment
plant, the cost of the research and demonstration program, and the improvement in data
quality and reliability that undoubtedly would have been attained, the minimal cost of
this equipment would have been more than justified.
FLOW MEASUREMENT
The plant effluent was the only wastewater flow accurately measured and recorded. In
plant designs where the aeration basin provides surge storage, as well as secondary
treatment, it is recommended that the influent flow be continuously measured and
recorded. The waste activated sludge should be metered and recorded to more accurately
control wasting rates and sludge age. Where sludge lagoons are used for waste activated
and chemical sludge storage, it is recommended provisions, such as a wier, be included to
measure the supernatant return flow.
SAMPLING
For treatment systems receiving combined domestic and industrial wastewater with large
fluctuations in both organic and hydraulic loadings, flow proportional automatic sampling
of the influent, secondary effluent and tertiary effluent is recommended. It is also
suggested that flow proportioned automatic samplers be installed to continuously monitor
the significant industrial waste flows. Additional tertiary system sampling taps should be
located in the flocculator effluent, between the tertiary tube settler and filter, and in the
chemical sludge holding tank decant and concentrated sludge lines.
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INSTRUMENTATION
Perhaps the most important control parameter for the tertiary process was pH. The
extent of nitrification in the secondary system considerably influenced the secondary
alkalinity and therefore, the tertiary effluent pH. It is recommended that the pH of the
flocculator effluent be continuously measured and recorded. Where the size of the
treatment facility can justify the cost, it is recommended that the aeration-surge basin
D.O. and ammonium ion concentration also be measured and recorded continuously.
Both flow rate and filter head loss indicators were provided with the tertiary system, but
neither parameter was recorded. A recording turbidimeter was borrowed during the
demonstration program to monitor tertiary effluent turbidity. To effectively regulate
chemical feed, assess tertiary system performance, and control plant effluent quality, it is
recommended that tertiary filter head loss and turbidity be recorded, as well as indicated.
In larger installations where limitations are placed on phosphate discharge, it is suggested
that automated monitoring and recording of the tertiary effluent orthophosphate
concentration, with feedback control to the alum feed system, be considered.
INFLUENT PUMP STATION
Debris clogged the submersible influent pumps on an average of 2 to 3 times each month,
requiring the units to be pulled and the impellers cleaned. A backhoe was brought in
each time to lift the pumps out of the wet well for servicing. Where this type of pump is
used in the influent pump station of small plants, it is recommended that a permanent
hoist be installed to facilitate maintenance.
AERATION-SURGE BASIN
AERATION CAPACITY-In extended aeration plants where industrial wastes cause wide
fluctuations in the influent organic loading, it is suggested that two speed, as opposed to
single speed, mechanical surface aerators be considered. Also, that more units of lower
horsepower be used than a lesser number of higher aeration capacity. This concept allows
the operator considerable flexibility in adjusting the air supply to satisfy the incoming
oxygen demand and can result in significant power savings. In larger installations
feedback control of the aeration system from continuous D.O. monitoring may be
justified.
GAS VENT SYSTEM-Where impermeable membranes, such as PVC, are used to seal the
aeration-surge basin, it is recommended that a venting system to provide gas relief under
the liner be included in the basin design.
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SECONDARY TUBE CLARIFIER
The air sparging system, installed during the demonstration program, proved to be an
effective means of cleaning the tube modules in the secondary clarifier. It is
recommended that an air sparger be included in the design, if steeply inclined tubes are
used for clarification of the secondary effluent. In addition it is recommended that
provisions be made for thickening waste activated sludge in the secondary clarifier design.
TERTIARY SYSTEM
FLOCCULATOR-Considerable short circuiting occurred in the flocculator tank. The
baffle modifications made midway through the project increased the mean detention time
from about 50 to 75 percent of the theoretical value. In future tertiary systems of this
type, it is recommended that careful consideration be given to preventing short circuiting
in the design of the flocculator. For small tertiary systems of 50,QOO to 300,000 gpd, it
may be convenient to include the flocculator as a part of the tertiary tube settler/filter
unit.
TERTIARY TUBE SETTLER-High velocity constrictions in the inlet system to the
tertiary tube settler were suspected to cause a breakup of the fragile chemical floe.
Modifications were made to the unit in an attempt to alleviate this problem. The
effectiveness of these changes was difficult to assess, however. It is recommended that the
inlet structure to the tertiary tube settler be redesigned to prevent turbulence from
damaging the chemical floe, once formed in the flocculator.
The tertiary tube settler did not have adequate storage volume for the solids loadings
encountered. The high suspended solids content of the secondary effluent undoubtedly
contributed to this condition. It is recommended, however, that the effective surface
overflow rate be reduced to about 35 gallons per day per square foot.
CHEMICAL SLUDGE HOLDING TANK SUPERNATANT-The supernatant from the
chemical sludge holding tank was normally pumped to the comminutor basin (Figure 11)
and combined with the influent flow to the aeration-surge basin. When the secondary
system was in a highly nitrified condition, the alkalinity in the aeration-surge basin was
not sufficient to buffer the acidity of the tertiary backwash water. As a result, the
aeration-surge basin pH could be depressed to intolerable levels of 5 and below.
To alleviate this condition, the entire backwash flow was pumped to the chemical sludge
storage lagoons. The increased lagoon supernatant return flow often contained high
suspended solids concentrations caused by dense algae blooms. A significant portion of
the algae appeared to pass through the aeration-surge basin placing an additional solids
loading on the tertiary system.
As an alternative to either of these methods of disposal, it is recommended that the
chemical sludge holding tank supernatant be returned, after settling, directly to the
tertiary influent line. Analyses of the supernatant indicate a suspended solids content of
10 to 20 mg/1 can be expected, following 3 to 4 hours of settling. The additional solids
loading placed on the tertiary system would be minimal.
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CHEMICAL FEED—Low secondary effluent alkalinity conditions, produced by
nitrification in the aeration-surge basin, required the addition of soda ash to the tertiary
influent to maintain pH control. It is recommended that the chemical feed system for
secondary-tertiary treatment plants of this type also include soda ash mixing, storage and
metering facilities.
Polyelectrolyte addition was not observed to improve alum flocculation. The point at
which polyelectrolyte was added to the tertiary influent may not have allowed sufficient
time for the alum coagulation reaction to reach completion. As a result, the
polyelectrolyte may have reacted as a primary coagulant, rather than effecting
interparticle bridging to aid flocculation. It is recommended that polyelectrolyte be
introduced sufficiently downstream of the alum feed point to allow at least 2 minutes of
reaction time. Soda ash should be introduced into the tertiary influent between the
points of alum and polyelectrolyte addition.
LABORATORY EQUIPMENT
It is recommended that the following laboratory equipment supplement the list contained
in Appendix C:
1. Dissolved Oxygen Analyzer
2. Muffle Furnace
3. COD Apparatus
4. Colorimetric Phosphate Test Kit
5. Specific ion probes for ammonium and nitrate ions or ammonium and
nitrite-nitrate test kits
6. Jar Test Apparatus
OPERATIONAL RECOMMENDATIONS
GENERAL
The tertiary process was demonstrated to be an effective and economical process for
removing phosphate and polishing the effluent from an extended aeration secondary
treatment system. The most significant variable affecting tertiary performance was pH.
Optimum phosphate removals were observed between pH 5.5 to 6.0. The minimum
tertiary effluent turbidity and suspended solids concentrations occurred around pH 6.0.
The extent of nitrification in the aeration-surge basin had a significant effect on the
operation of the tertiary system. Oxidation of ammonium to nitrate ion reduced the
secondary effluent alkalinity allowing the acidity of the alum to depress the pH into a
range more favorable to phosphate coagulation. Minimum tertiary effluent turbidity levels
tended to occur when nitrate concentrations were between 5 to 20 mg/1.
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Recommendations are offered for operation of the Tualatin secondary-tertiary system in
the following paragraphs. In general, these suggestions are also applicable to future
treatment systems of this type.
SECONDARY SYSTEM
MLSS-The MLSS should be held between 1,200 to 2,200 mg/1. Above and below these
limits, the secondary tube clarifier performance can be expected to degenerate.
SLUDGE AGE—A sludge age of 5 to 6 days is sufficient to induce nitrification.
Essentially, complete conversion of ammonium to nitrate ion will occur at sludge ages of
10 to 12 days, assuming adequate D.O. is available. Within the constraints imposed by
the allowable range of MLSS, it is recommended that the sludge age be held to between
8 to 10 days. If the secondary alkalinity is not sufficient to offset the acidity of the
tertiary alum dosage, the sludge age should be reduced by sludge wasting to limit the
extent of nitrification.
D.O.-A D.O. level of 1.0 to 1.5 mg/1 will support full nitrification. D.O. concentrations
of 0.4 to 0.6 mg/1 will inhibit nitrification and the SVI can also be expected to increase
under these low D.O. conditions.
pH-Optimum performance of the secondary tube clarifier was observed between pH 6.9
to 7.2. The highest removals of phosphate in the secondary system tended to occur
between pH 7.0 and 7.25. Insofar as practical, the aeration-surge basin pH should be held
about pH 7.0 by controlling the extent of nitrification through regulation of the sludge
age.
TERTIARY SYSTEM
ALUM ADDITION AND PHOSPHATE REMOVAL-Phosphate removal was determined
to be a function of the secondary effluent orthophosphate concentration, alum dosage
and tertiary effluent pH. These three variables are related as shown on Figures 65 and 66.
To effect optimum phosphate removal from a given secondary effluent quality, it is
recommended that the following procedure be followed:
1. Determine the total alkalinity of the secondary effluent.
2. Based on the experimentally determined acidity equivalent of 0.36 mg/1
[equivalent CaCO3l per mg/1 alum [A12 (SO4)3 x 14.3 H2O], calculate an
alum dosage which will leave 10 to 20 mg/1 of total alkalinity in the tertiary
effluent. This residual should be adequate to reduce the tertiary effluent pH
between 5.5 to 6.3.
3. After the tertiary pH stabilizes, trim the alum dosage as required to maintain a
tertiary pH of 5.9 to 6.1.
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If a lower phosphate residual is desired and sufficient alkalinity is not available in the
secondary effluent, add soda ash as necessary to increase the tertiary influent alkalinity
to the level required.
POLYELECTROLYTE ADDITION-High molecular weight, medium charge anionic
polyelectrolytes, were determined by jar tests to be the most effective flocculation aid to
enhance alum floe formation. However, unless the reaction time between alum and
presettler polyelectrolyte addition can be increased to 1-2 minutes, by relocating the
points of chemical addition in the tertiary influent, it is recommended that presettler
polymer addition be suspended.
Prefilter polyelectrolyte should continue to be added in an amount just adequate to
prevent turbidity breakthrough (Figure 62). The dosage is expected to be in the range of
0.03 to 0.06 mg/1.
SAMPLING AND TESTING
It is recommended that the sampling and testing schedule used during the research and
demonstration project continue to be followed. If the laboratory equipment
recommended earlier in this section can be purchased, it is recommended that the
following additional tests be performed:
SAMPLING
ANALYSIS LOCATION FREQUENCY
O2 Uptake Rate Aeration-surge basin Daily
MLVSS Aeration-surge basin 3 per week
COD Influent 3 per week
Secondary Effluent 2 per week
Tertiary Effluent 2 per week
Orthophosphate Secondary Effluent 3 per week
Tertiary Effluent 3 per week
Ammonium and Tertiary Effluent 3 per week
Nitrate
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FUTURE RESEARCH AND DEMONSTRATION
PROJECT RECOMMENDATIONS
Equipment and operational problems are inevitable in the startup of any research and
demonstration program involving new equipment and technology. This project was
certainly no exception. Difficulties encountered during startup and initial operation of
the plant, required the duration of the program to be extended several months in order
to fulfill the requirements of the EPA grant. Considerable additional expense to the
grantee resulted from this extension.
It is recommended that for future research and demonstration programs of this type, a
commissioning period of at least 3 to 6 months be allowed, as part of the overall project
schedule, to check out equipment and establish the operating characteristics of the
treatment system. This period is also necessary to familiarize the operator with new
processes and equipment. Once stable operation of the system has been achieved, the
scheduled testing and data acquisition phase of the project can proceed without repeated
delays.
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SECTION IX
FINANCIAL CONSIDERATIONS
The total capital cost of the treatment facility, including engineering, was $245,800. A
detailed breakdown of the engineering and construction costs is included in Appendix D.
The total capital cost of a conventional activated sludge treatment plant supplemented by
chemical coagulation, sedimentation and filtration obtained from Smith's curves [38] and
updated to January 1970 was $343,500. Comparison of these costs indicates the
substantial capital cost savings of this approach to secondary-tertiary treatment.
OPERATION AND MAINTENANCE COSTS
The total operation and maintenance cost for the first year of service (August 1970 to
July 1971) obtained from the City's accountant was $23,100. The cost includes
allocation of a portion of the salaries of members of the City's public works and
accounting staff, as well as the treatment plant operator.
Operation and maintenance costs for the plant, considering only the treatment plant
operator's salary and a minimal allowance for accounting personnel to process plant
records, was $19,400. This represents the actual annual cost to operate and maintain the
treatment facilities. A detailed breakdown of the operational costs is included in
Appendix D.
Operation of the tertiary portion of the plant was estimated to be $6,800, or 35 percent
of the total operation and maintenance costs.
RESEARCH AND DEMONSTRATION COSTS
The cost associated with the research and demonstration program, including additional
sampling and testing, supervision and data analysis was $31,800. This does not include
the cost of the nitrogen and phosphorus analyses performed by the EPA Pacific
Northwest Environmental Research Laboratory, or preparation of the final report.
TOTAL ANNUAL COSTS
The total annual costs of the combined secondary and tertiary treatment system for the
first year of operation (August 1970-July 1971) are summarized in Table 14. The annual
costs include:
1. Annual capital ammortization at a 5.5 percent interest rate over a 20
year period.
2. Annual operation and maintenance cost attributed to operation of
the plant only during the first year of operation.
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3. Equipment replacement and depreciation costs estimated to be 3
percent of the equipment capital cost.
TABLE 14
TOTAL ANNUAL COSTS
ANNUAL
ITEM COST
Capital Cost $245,800
Amortized Capital Cost (5.5% - 20 years) 20,600
Annual Operation and Maintenance
Salaries $10,200
Utilities 4,500
Chemicals 3,300
Laboratory Supplies 600
Insurance 800
$ 19,400
Estimated Equipment Replacement
and Depreciation 3,000
TOTAL ANNUAL COST $ 43,000
TREATMENT COSTS
At the beginning of the project, both the daily flow and organic loading were
considerably below the design capacity of the plant. The average daily flow through the
plant never reached the design condition. The design organic loading, however, was
exceeded for a substantial part of the demonstration program.
On the basis of total annual cost and the average flow and organic loadings of 0.10 mgd
and 467 Ibs BOD5 per day experienced over the demonstration project, the cost of
treatment was calculated to be SI. 18 per 1,000 gallons treated, or S0.25 per pound of
BOD5 removed.
The tertiary system, however, was operated at near the design flow rate for most of the
project and adequately demonstrated the ability to provide the design level of treatment,
even under severe loading conditions. Considering the low flows and wide range of
organic loadings applied to the plant during the demonstration program, a more realistic
calculation of treatment costs, which can be applied to future plants of this type, is one
based on the plant design conditions.
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At the design flow and organic loading of 0.28 mgd and 630 Ibs BOD5 per day, the cost
for treatment of the combined industrial and domestic wastes at Tualatin was calculated
to be $0.421 per 1,000 gallons treated, or SO. 187 per pound of BOD5 removed. The cost
of the secondary treatment was estimated to be $0.287 per 1,000 gallons and tertiary
treatment to be $0.1 34 per 1,000 gallons.
The following treatment costs were developed from Smith's curves [38], adjusted to
January 1971 cost levels, the mid-point of the demonstration program:
Conventional activated sludge secondary treatment - SO.306/1,000 gal
Coagulation, flocculation and filtration - SO. 197/1,000 gal
Total Treatment Cost - $0.503/1,000 gal
Comparison of the treatment costs developed from the R&D project with Smith's curves
demonstrates the economy of this approach to providing tertiary treatment of combined
industrial and domestic wastes for small municipalities.
Capital and treatment costs for the type of tertiary treatment facilities demonstrated at
Tualatin, Oregon have been developed for design capacities ranging from 0.1 to 3.0 mgd
in Figure 67, adjusted to June 1972.
The cost data in Figure 67 assume the following:
1. Alum dosage - 100 mg/1 <& S0.03/lb
2. Polymer dosage - 0.05 mg/1 applied prefilter only @ $1.90/lb
3. Chlorine dosage - 5 mg/1 @ S0.15/lb
4. Power @ $0.012/kWh
5. One full-time operator for plant sizes of 0.1 to 0.5 mgd graduating to
two full-time operators for a 2.0 mgd facility at the salary level
indicated in Table 14.
6. Other operating and maintenance costs contained in Table 14.
7. Waste activated sludge and chemical solids are stored in lagoons at
the treatment plant site. No costs were included for cleaning and
disposal of the solids. These costs will vary depending on location
and methods selected for ultimate disposal.
-159-
-------
100
J 90
C3 80
§ 70
S 60
I-
O 50
O
h-
Z 40
£ 30
20
10
LEGEND
C = CAPITAL COST, $105
T = TOTAL TREATMENT COST, it /1000 GAL.
A = DEBT SERVICE, $ /1000 GAL.
O&M = OPERATING AND MAINTENANCE COST, i/1000 GAL.
20
10
9
8
7
6
5
.15 .2 .25 ,3 .4 .5 .6 .7 .8 .9 1.0
DESIGN CAPACITY, MGD
1.5
2.
2.5 3
CO
O
CJ
4
FIGURE 67
CAPITAL COST, OPERATING AND MAINTENANCE COST AND
DEBT SERVICE VERSUS DESIGN CAPACITY ADJUSTED TO JUNE 1972
-160-
-------
SECTION X
ACKNOWLEDGMENTS
This project was supported by the Environmental Protection Agency Research and
Development Grant No. 11060 DLF. Appreciation is expressed to the administration and
staff of the City of Tualatin, Oregon; particularly to the treatment plant
operator-research technicians, Mr. Jim West and Mr. Dan Hanthorn; the EPA Pacific
Northwest Environmental Research Laboratory personnel, Neptune MicroFLOC, Inc. who
generously donated time and financial support to the project; and Cornell, Rowland,
Hayes and Merryfield/Clair A. Hill and Associates staff members for their cooperation
and assistance during this study.
-161-
-------
SECTION XI
REFERENCES
1. Glossary: Water and Wastewater Control Engineering, APHA, ASCE, AWWA, WPCF,
New York (1969). ~ "
2. Hawkes, H.A., Ecology of Waste Water Treatment, Pergamon Press, New York NY
(1963).
3. McKinney, R.E., Microbiology for Sanitary Engineers, McGraw-Hill Book Co New
York, N.Y. (1962X ~
4. Weston, R.F., and Eckenfelder, W.W., Application of Biological Treatment to
Industrial Wastes, I. Kinetics and Equilibria of Oxidative Treatment. Sewage and
Industrial Wastes. 27, 802(1955).
5. McKinney, R.E., Biological Design of Waste Treatment Plants, Presented at Kansas
City Section of ASCE Seminar, Kansas City, Mo. (1961).
6. McKinney, R.E., Mathematics of Complete Mixing Activated Sludge. Jour. San.
Engr. Div., Proc. Amer. Soc. Civil Engr., 88, SA3, 87(May 1962).
7. Eckenfelder, W.W., Comparative Biological Waste Treatment Design. Jour. San. Engr.
Div., Proc. Amer. Soc. Civil Engr., 93, SA6, 157(December 1967).
8. Lawrence, A.W., and McCarty, P.L., Unified Basis for Biological Treatment Design
and Operation. Jour. San. Engr. Div., Proc. Amer. Soc. Civil Engr., 96, SA3,
757(June 1970).
9. Eckenfelder, W.W., A Theory of Activated Sludge Design for Sewage. Proceedings of
Seminar at the University of Michigan, 72(February 1966).
10. McCarty, P.L., and Brodersen, C.F., A Theory of Extended Aeration Activated
Sludge. Jour. Water Poll. Control Fed.. 34. 1095(1962).
11. Metcalf & Eddy, Inc., Wastewater Engineering, McGraw-Hill Book Company, New
York (1972).
12. McCarty, P.L., Biological Processes for Nitrogen Removal: Theory and Application,
Proc. 12th San. Eng. Conf., University of Illinois, Urbana, (1970).
13. Carlson, D.A., Final Report for the Project Nitrate Removal from Activated Sludge
Systems, OWRR Project No. A026, University of Washington, Seattle (1970).
-163-
-------
14. Jenkins, D. and Garrison, W.E., Control of Activated Sludge by Mean Cell Residence
Time, Jour. Water Poll. Control Fed., 40, 1905(November 1968).
15. Downing, A.L., Factors to be Considered in the Design of Activated Sludge Plants.
Advances in Water Quality Improvement, Water Resources Symposium No. 1, E.
Gloyna and W.W. Eckenfelder, Eds., University of Texas Press, Austin, Texas (1968).
16. Wuhrmann, K., Objectives, Technology and Results of Nitrogen and Phosphorous
Removal Processes, Advances in Water Quality Improvement, Water Resources
Symposium No. 1, E. Gloyna and W.W. Eckenfelder, Eds., Univ. of Texas Press,
Austin, Texas (1968).
17. Fair, G.M. and Geyer, J.C., Water Supply and Waste-Water Disposal, John Wiley &
Sons, Inc., New York (1954).
18. Hansen, S.P. and Gulp, G.L., Applying Shallow Depth Sedimentation Theory, Jour.
Amer. Water Works Assn., 59, 1134(September 1967).
19. Hansen, S.P., Gulp, G.L. and Stukenberg, J.R., Practical Application of Idealized
Sedimentation Theory in Wastewater Treatment, Jour. Water Poll^ Control Fed. 41,
1421(1969).
20. Hazen, A., On Sedimentation, Trans. Amer. Soc. Civil Engr., 53, 45(1904).
21. Camp, T.R., Sedimentation and the Design of Settling Tanks, Trans. Amer. Soc.
Civil Engr., Ill, 895( 1946).
22. Gulp, G., Hansen, S. and Richardson, G., High-Rate Sedimentation in Water
Treatment Works, Jour. Amer. Water Works Assn., 60, 681 (June 1968).
23. Fischerstrom, C.N.H., Sedimentation in Rectangular Basins, Proc. Amer. Soc., Civ.
Eng., San. Eng. Div. (May, 1955).
24. Fair, G.M., Geyer, J.C. and Okun, D.A., Elements of Water Supply/ and Wastewater
Disposal, 2nd ed., John Wiley & Sons, Inc., New York (1971).
25. Stumm, W. and Morgan, J.J., Aquatic Chemistry. Wiley-Interscience, New
York(1970).
26. Culp, R.L. and Culp, G.L., Advanced Wastewater Treatment, Van Nostrand Reinhold
Company, New York (1971).
27. Tchobanoglous, G., Filtration Techniques in Tertiary Treatment, Jour. Water Poll.
Control Fed., 42, 604(April 1970).
28. Bailar, J.C., The Chemistry of the Coordination Compounds, Reinhold Publishing
Corporation, New York (1956).
-164-
-------
29. Stumm, W., and Morgan, J.J., Chemical Aspects of Coagulation, Jour. Anier. Water
Works Assn.. 54, 971 (August, 1962).
30. Process Design Manual for Phosphorus Removal. U.S. Environmental Protection
Agency, Technology Transfer Program, No. 1701GNP(October 1971).
31. Leckie, J. and Stumm. W.. Phosphate Precipitation, Advances in Water Quality
Improvement, Water Resources Symposium No. 3. E. Gloyna and W.W. Eckenfelder,
Eds., Univ. of Texas Press. Austin, Tex. (1970).
32. Recht, H.L. and Ghassemi, M., Kinetics and Mechanism of Precipitation and Nature
of the Precipitate Obtained in Phosphate Removal from Wastewater Using Aluminum
(HI) and Iron (HI) Salts, Environmental Protection Agency, Water Pollution Control
Research Series, 17010 EKI 04/70(1970).
33. Tchobanoglous, G. and R. Eliassen, Filtration of Treated Sewage Effluent, Jour. San.
Engr. Div., Proc. Amer. Soc. Civil Engr., 96. SA2, 243(April 1970).
34. Evers, R.H., Mixed-Media Filtration, Publication No. KT7212, Neptune MicroFLOC,
Inc., Corvallis, Oregon, (14 March 1968).
35. Standard Methods for the Examination of Water and Wastewater . APHA, AWWA,
WPCF, New York (1965).
36. FWPCA Methods for Chemical Analysis of Water and Wastes, Federal Water
Pollution Control Administration (1969).
37. Combined Treatment of Domestic and Industrial Wastes by Activated Sludge, EPA
Water Pollution Control Research Series 12130EZR 05/71(1971).
38. Smith, R., Cost of Conventional and Advanced Treatment of Wastewater, Jour.
Water Poll. Control Fed., 40, 1546(1968).
-165-
-------
SECTION XII
PUBLICATIONS
Thompson, H.W. and Dostal, K.A., Tertiary Treatment of Combined Domestic and
Industrial Wastes, Proceedings Third National Symposium on Food Processing Wastes,
EPA-R2-72-018 (November 1972).
-167-
-------
SECTION XIII
ABBREVIATIONS
mg/1
BOD
MLSS
MLVSS
mgd
TSS
VSS
SVI
D.O.
02
T..
Milligrams per liter
Biochemical oxygen demand
Mixed liquor suspended solids
Mixed liquor volatile suspended
solids
Million gallons per day
Total suspended solids
Volatile suspended solids
Sludge volume index
Dissolved oxygen
Oxygen
- Sludge age
-169-
-------
SECTION XIV
APPENDIXES
APPENDIX
A Design Factors
B Photographs
C Process and Laboratory Equipment
D Costs
-171-
-------
APPENDIX A
DESIGN FACTORS
-173-
-------
DESIGN FACTORS
INFLUENT PUMPS
Number
Type
Capacity
Total Head
HEADWORKS
Sewage Grinder
Number
Size
AERATION BASIN
Number
Depth (minimum)
Average Volume (including clarifier)
Detention Time
Design Organic Loadings
AERATION EQUIPMENT
Number of Aerators
Type
Size
Submersible raw sewage,
centrifugal
250 gpm
16.5 feet
15-inch
12 feet
280,000 gallons
24 hours
0.16 Ib BOD5/lb MLVSS/day
(16.8 Ib BOD5/1000 cubic feet/day
Floating, mechanical surface
15 hp
-174-
-------
SECONDARY TUBE CLARIFIER
Number
Surface Area
Surface Overflow Rate^
Solids Loading Rate3'4
Total Detention Time
Number of Tube Bundles
Tube Bundle Overall Dimensions
Number of Modules per Tube Bundle
Tube Module Dimensions
Individual Tube Dimensions
Cross-sectional Area (square,
2-inch/side)
Length
Angle of Inclination
(from horizontal)
WASTE ACTIVATED SLUDGE PUMP
Number
Type
Capacity
Total Head
TERTIARY INFLUENT PUMP
Number
Type
120 square feet
1.96 gpm/sq ft (2,820
gal/day/sq ft)
47 Ib/day/sq ft
30 minutes
10 ft (L) x 6 ft (W) x 3.5 ft (H)
10 ft (L)x 3 ft (W) x 3.5 ft(H)
4 square inches
48.5 inches
60 degrees
1
Self-priming, centrifugal
200
8.7 feet
Self-priming, centrifugal
-175-
-------
TERTIARY INFLUENT PUMP (continued)
Capacity
Total Head
FLOCCULATION TANK
Diameter
Height
Volume
Detention Time
TERTIARY TUBE SETTLER
Number
End Area Hydraulic Loading3
Surface Overflow Rate3
Detention Time3
Number of Tube Modules
Tube Module Dimensions
Individual Tube Dimensions
Cross-sectional Area (hexagonal,
one-inch/side)
Length
Angle of Inclination (from
horizontal)
MIXED MEDIA FILTER
Number
Surface Area
235 gpm
17.0 feet
8 feet
10 feet
3,540 gallons
15 minutes
1
1.49 gpm/ft2 (2,152 gal/day/sq ft)
143 gal/day/sq ft
27 minutes
2
9.25 ft (L) x 3.15 ft (W) x 8.5 ft (H)
2.6 square inches
39 inches
7-1/2 degrees
49.5 feet2
-176-
-------
MIXED MEDIA FILTER (continued)
Design. Filtration Rate-'
Backwash Rate
Filter Media Depth
4.75 gpm/fr
16 gpm/ft2
30 inches
Media Types
% of Total Bed Volume
Specific Gravity
Particle Size Range
High Density Support Gravel
Specific Gravity
Size
Depth
Low Density Support Gravel
Average Specific Gravity
Size
Depth
Anthracite
Coal
55
1.5
1.0-1.2 mm
Silica
Sand
30
1.6
Garnet
Sand
15
4.0
0.45-0.55 mm 0.2-0.3 mm
4.0
2.0 mm
3 inches
2.5
3/16 to 2 inches
18 inches
Total Bed Depth (including support material) 51 inches
TERTIARY EFFLUENT PUMP
Number
yype
Capacity
Total Head
Centrifugal
235 §Pm
35 feet
-177-
-------
BACKWASH PUMP
Number
Type
Capacity
Total Head
SURFACE WASH PUMP
Number
Type
Capacity
Total Head
BACKWASH STORAGE TANK
Diameter
Height
Volume
CHEMICAL SLUDGE HOLDING TANK
Diameter
Depth
Volume
Settling Time
CHEMICAL SLUDGE DECANT PUMP
Number
Type
Capacity
Total Head
1
Centrifugal
800 gpm
40 feet
1
Centrifugal
70 gpm
180 feet
12 feet
12 feet
9,600 gallons
11 feet
15 feet
10,000 gallons
0 to 5 hours
1
Self-priming, centrifugal
70 gpm
13 feet
-178-
-------
CHEMICAL SLUDGE PUMP
Number
Type
Capacity
Total Head
ALUM STORAGE TANK
Diameter
1
Self-priming, centrifugal
120 gpm
25 feet
8 feet
Height 11.5 feet
Volume 4,000 gallons
POLYELECTROLYTE AND SODA ASH FACILITIES
Mix Tank
Storage Tank
Auxiliary Storage Drum
CHEMICAL METERING PUMPS
Number
Type
Capacity
CHEMICAL SLUDGE STORAGE PONDS
Number
Area, each
Depth
Volume,each
Total
250 gallons
250 gallons
55 gallons
Variable stroke, diaphragm
540 gpd @ 25 psi
0.32 acres
4 feet
264,000 gallons
528,000 gallons
-179-
-------
CHEMICAL SLUDGE STORAGE PONDS (continued)
Supernatant Drainage
Operation
ACTIVATED SLUDGE STORAGE PONDS
Number
Area, each
Depth (maximum water level)
Volume, each
Total
Supernatant Drainage
Operation
CHLORINATION
Type
Control
CHLORINE CONTACT
Detention Time
Backwash Storage Tank
Outfall
Total
Return to Plant Influent Pump Station
Decant Supernatant to Sludge Blanket
and allow Sludge to Air Dry
0.10 acre
3 feet
42,000 gallons
84,000 gallons
Return to Plant Influent Pump Station
Decant Supernatant to Sludge Blanket
and allow Sludge to Air Dry
V-notch chlorinator
Tertiary Flow or Manual
49 minutes
16 minutes
65 minutes
-180-
-------
FLOW MEASUREMENT
Plant Flow
Tertiary Flow Rate
Waste Activated Sludge
Prop, meter, plant effluent
Orifice meter, tertiary effluent
Time clock, constant pumping rate
At average design flow of 280,000 gpd.
At 630 Ib BOD /day and 2,000 mg/I MLSS.
At tertiary design flow of 235 gpm.
At 2,000 mg/t MLSS.
-181-
-------
APPENDIX B
PHOTOGRAPHS
-183-
-------
oo
f-
INFLUENT
PUMP STATION
FIGURE B-1
INFLUENT PUMP STATION AND COMMINUTOR BASIN
-------
OVERFLOW
'BOX
CONTROL
BUILDING
FLOCCULATION
TANK
ALUM STORAGE
TANK
BACKWASH
STORAGE
TANK
TERTIARY
SETTLER-FILTER
UNIT
TERTIARY
INFLUENT
PUMP
FLOATING
MECHANICAL
AERATOR
AERATION
SURGE
BASIN
FIGURE B-2
AERATION-SURGE BASIN
AND TERTIARY SYSTEM
-------
FIGURE B-3
SECONDARY TUBE CLARIFIER AND WITHDRAWAL LINE
FIGURE B-4
SECONDARY CLARIFIER TUBE MODULE
-186-
-------
OVERFLOW
BOX
FLOCCULATIOIM
TANK
BACKWASH
STORAGE
TANK
MIXED
MEDIA
FILTER ,
COMPARTMENT*
TUBE
SETTLER
COMPARTMENT
TERTIARY
INFLUENT
PUMP
FIGURE B-5
TERTIARY SYSTEM
-------
oo
EFFLUENT
PUMP STATION
CHEMICAL SLUDGE
HOLDING TANK
FIGURE B-6
EFFLUENT PUMP STATION AND
CHEMICAL SLUDGE HOLDING TANK
-------
POLYELECTROLYTE
MIX TANK
TERTIARY
SYSTEM
CONTROL
PANEL
CHLORINE
FEED
SYSTEM
POLYELECTROLYTE
STORAGE TANK
CHEMICAL
FEED PUMPS
FIGURE B-7
CONTROL BUILDING
-------
,£
OUTLET
I I
•
/^STRUCTURE
. F
•I «• Jj
-Jam
**
. -
'***"" l»fP
FIGURE B-8
DEWATERED WASTE ACTIVATED SLUDGE
STORAGE LAGOON
OUTLET-
STRUCTURE
FIGURE B-9
DEWATERED CHEMICAL SLUDGE
STORAGE LAGOON
-190-
-------
FIGURE B-10
DRIED CHEMICAL SLUDGE IN TEST BED
-191-
-------
FIGURE B-11
AERATION-SURGE BASIN
LINER REPAIR AND INSTALLATION
OF GAS VENT SYSTEM
-192-
-------
APPENDIX C
PROCESS AND LABORATORY EQUIPMENT
-193-
-------
PROCESS EQUIPMENT
EQUIPMENT
Mechanical Surface Aerator
Activated Sludge Pump
Effluent Pump
Tertiary Influent Pump
Chemical Decant Pump
Chemical Sludge Pump
Filter Effluent Pump
Surface Wash Pump
Backwash Pump
Raw Sewage Influent Pumps
Compressor
Comminutor
Secondary Tube Clarifier
Tertiary Settler/Filter Unit
MODEL
5K6237xJ290C15
TypeK
T4A3-B
T4A3-B
13A2-B
12B2B
12B2B
3655
3655
3655
CP3100
23ANLF4, Type 30
12-4
MANUFACTURER
Ashbrook
Gorman-Rupp Co.
Gorman-Rupp Co.
Gorman-Rupp Co.
Gorman-Rupp Co.
Gorman-Rupp Co.
Goulds
Goulds
Goulds
Flygt
Ingersoll-Rand
Worthington
Neptune MicroFLOC, Inc.
Neptune MicroFLOC, Inc.
-194-
-------
EQUIPMENT
Balance
Blendor
Demineralizer
Drying Oven
Filter Apparatus
Magnetic Stirrer
pH Meter
Refrigerator (2)
Refrigeration - incubator
Conversion Unit
Vacuum Pump
LABORATORY EQUIPMENT
TYPE
Mettler HG Digital
Waring
Barnstead Bantam
Napco
Millipore, Pyrex
Magnestir
Coleman, Metrion IV
Westinghouse
HACH Incutrol
Cast, Rotary Air
Pressure and vacuum
RANGE
0- 160 g
0 - 50.0 ml
5 - 25 gal/hr
30 - 200 degrees C
0 - 14 pH
0-35 degrees C
1.3 cfm, 27 in Hg.
-195-
-------
APPENDIX D
COSTS
-197-
-------
CAPITAL COST BREAKDOWN
ITEM
Engineering
Survey
Soils Investigation
Engineering
Services During Construction
Resident Inspection
Construction
Additional Construction and Equipment
During Demonstration Program
Legal and Administrative
TOTAL CAPITAL COST
COST
$ 1,100
550
18,900
4,200
4,750
$ 29,500
210,100
4,900
1.300
$245,800
-198-
-------
CONSTRUCTION COST
ESTIMATED
ITEM COST
Move-In and Temporary Facilities $ 550
Bond and Insurance 1,550
Influent Pump Station 9,500
Comminutor Basin 800
Aeration-Surge Basin 16,600
Aerators (2) 7,800
Secondary Tube Clarifier 9,000
Flow Measurement 1,050
Comminutor 4,550
Raw Sewage Pumps 3>800
Self Priming Pumps 5»000
Control Building 15,200
Yard Piping 7'500
Electrical 12'000
Sludge Ponds 9'000
Painting 3'050
Force Main 13>000
Cleanup and Finish Grading 3»150
Access Road 85°
Fence 1'750
-199-
-------
CONSTRUCTION COST (continued)
ESTIMATED
ITEM COST
Effluent Pump Station 8,300
Tertiary' Treatment System 70.000
Laboratory Equipment and Reagents 3 QOO
Chlormation Facilities j 459
Miscellaneous Concrete 1 559
TOTAL CONSTRUCTION COST $210,100
-200-
-------
FIRST YEAR
OPERATION AND MAINTENANCE COSTS
(August 1970 - July 1971)
ITEM
Salaries
Operator-Research Technician
(Plant operation only - 3/4 salary)
Interim Operator1)
Operator Trainee^'
Public Works Superintendent'3'
Accounting^ '
Maintenance^)
Salary Overhead
Insurance
Utilities
Power
Water
Telephone
Chemicals
Laboratory Supplies
Miscellaneous Expenses
TOTAL FIRST YEAR O & M COSTS
(See attached page for footnotes).
COST
$7,470
680
1,690
2,930
1,170
650
3,320
800
360
$14,590
770
830
$ 4,480
1,380
620
. 400
S23,070
-201-
-------
FOOTNOTES
1) Interim operator hired temporarily when operator-research technician was injured in
an accident at the plant.
2) The operator-research technician left the employ of the City of Tualatin after the
completion of the R & D Program. An operator-trainee was added to the staff five
months prior to termination of the project.
3) The City of Tualatin allocated a portion of the salaries of the public works
superintendent, accountant and public works maintenance staff as part of the
operational cost of the wastewater treatment plant.
-202-
-------
RESEARCH AND DEMONSTRATION COSTS
(April 1970 - August 1971)
ITEM COST
Detailed Project Plan 5 4,920
Operator-Technician (R&D Data Collection
1/4 Salary) 3^530
Consulting Engineering Services (Does not
include preparation of final report) 21,770
Legal and Administrative 1 540
TOTAL RESEARCH AND DEVELOPMENT COST $31,760
Note: Preparation of Final Report not included in R&D costs.
-203- *U.S. GOVERNMENT PRINTING OFFICE: 1973 514-156/342 1-3
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
/. Report No,
3, Accession No.
4. Title
Tertiary Treatment of Combined
Domestic and Industrial Wastes
7. Author(s)
John W. Lee, Jr.
9. Organization
Cornell, Rowland, Hayes & Merryfield, Inc.
1600 S.W. Western Boulevard
Corvallis, Oregon 97330
5. Report Date
6.
8. Performing Organization
Report No.
10. Project No.
11. Contract I Grant No.
11060 DLF
/.>. 'i"y.'.ff oi Report and
Fericd Covered
15.
Sponsoring Organization
City of Tualatin, Oregon
Supplementary Notes
97062
i Environmental Protection Agency report
! number, EPA-R2-73-236, May 1973.
,' 16. Abstract
'operation of a secondary-tertiary treatment facility for combined domestic and pet food
manufacturing industrial wastewaters at the City of Tualatin, Oregon, was studied for 16
•months. The study demonstrated the feasibility of automated tertiary treatment for small
'communities treating a combined domestic and industrial wastewater at a reasonable cost.
:The system was designed for an average daily flow of 280,000 gpd and a BOD5 load of 630
ipounds per day. The extended aeration activated sludge process with a design detention
•time of 24 hours was employed for secondary treatment. An experimental 60 degree inclined
,'tube settler located in the aeration-surge basin provided secondary effluent clarification.
!The tertiary system consisted of a four step process: 1) alum and polyelectrolyte coagu-
jlation, 2) flocculation, 3) inclined tube sedimentation, and 4) mixed media filtration.
The tertiary system demonstrated the capability to produce an effluent quality of less
jthan 10 mg/1 BODs and 5 mg/1 suspended solids with a total phosphate residual of 0.1 to
jl.O mg/1 (as P).
iThe total capital cost of the facility was $245,800. Based on total annual cost, the cost
iof treatment at the design conditions was $0.42 per 1000 gallons processed and $0.19 per
'pound of BODs removed.
JThis report was submitted in fulfillment of Grant No. 11060 DLF, under the partial
*aponsoroh3:ff-of the Environmental Protection Agency.
17a. Descriptors
' * Waste Treatment, *Aerobic Treatment, Tertiary Treatment, Industrial Wastes,
' Activated Sludge, Domestic Wastes, Flocculation, Filtration, Chemical
! Precipitation, Phosphates
i
I
j 17b. Identifiers
\ Pet Food Processing Wastes, Mixed Media Filter, Tube Clarifier, Alum,
Polyelectrolyte, Treatment Costs, Phosphate Removal
17c. COWRR Field & Group
18. Availability
John W. Lee, Jr.
Abstractor
AIRSIC 102 (REV JUNE 1971)
19. Security Class.
(Report)
20. Security Class.
(Page)
21.
22.
No. of
Pages
Price
Send To:
W ATKR fJ£SOURC 1- S SCi '.'•'
US DEP^RTMEK': OF"HE
W ASM 1 Nil 1 ON. O C ?Ot^C
\lnstitution Cornell, Rowland, Hayes
Corvallis , Oreaon
•ric INH-WM *') KT-- C'lM i1 ' •••
I'iTtRIOR
& Merryfield, Inc.
G •> " ••
------- |