WATER POLLUTION CONTROL RESEARCH SERIES • 17010ELQ08/71
ADVANCED WASTE WATER
TREATMENT AS PRACTICED
AT SOUTH TAHOE
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
-------
WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes
the results and progress in the control and abatement
of pollution in our Nation's waters. They provide a
central source of information on the research, develop-
ment, and demonstration activities in the Water Quality
Office, Environmental Protection Agency, through inhouse
research and grants and contracts with Federal, State,
and local agencies, research institutions, and industrial
organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Head, Project Reports
System, Office of Research and Development, Water Quality
Office, Environmental Protection Agency, Room 1108,
Washington, D. C. 202H2.
-------
ADVANCED WASTEWATER TREATMENT
AS PRACTICED AT SOUTH TAHOE
by
SOUTH TAHOE PUBLIC UTILITY DISTRICT
SOUTH LAKE TAHOE, CALIFORNIA
for the
WATER QUALITY OFFICE
ENVIRONMENTAL PROTECTION AGENCY
Project 17010 ELQ (WPRD 52-01-67)
August 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 - Price $3.25
-------
EPA Review Notice
This report has been reviewed by the Environ-
mental 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 or commercial
products constitute endorsement or recommen-
dation for use.
-------
ABSTRACT
This report presents the results from three years operation of a
7.5 mgd advanced wastewater treatment plant at the South Tahoe Public
Utility District in South Lake Tahoe, California.
Two principal purposes of the project are to evaluate the recovery
and reuse of lime as a coagulant in tertiary treatment, and to investigate
ammonia stripping as a means for nitrogen removal from tertiary effluent.
The work also includes a comprehensive study of the efficacy,
reliability, and economy of a tertiary sequence of treatment consisting of
conventional activated sludge, followed by lime treatment for phosphate
removal, ammonia stripping, two-stage recarbonation, mixed media fil-
tration, granular activated carbon adsorption of dissolved organics, and
chlorination. Granular carbon is thermally regenerated and reused, spent
lime mud is recalcined and reused, and all waste organic and chemical
sludges are incinerated to sterile, inert ash.
Quality of the reclaimed water is consistently very high. It is
sparkling clear, low in algal nutrients, free of color, odor, bacteria, and
viruses, and is suitable for many, if not all, types of reuse.
The project clearly demonstrates that all of the necessary technol-
ogy is now available to completely control water pollution from all domes-
tic and most industrial wastewaters provided that a genuine desire exists
to do so, and that adequate leadership and financing are provided.
This report was submitted in fulfillment of Project Number 17010
ELQ, Grant WRPD 52-01-67, under the partial sponsorship of the Water
Quality Office, Environmental Protection Agency.
iii
-------
CONTENTS
Section Title page
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION 5
IV HISTORY, PURPOSES, AND IMPLEMENTATION OF THE
TAHOE PROJECT 7
HISTORY 7
Local Conditions 7
Seeking A Plan 10
Advanced Waste Treatment 10
Plant Overloaded 11
Solids Disposal System 11
Nitrogen Removal 12
Effluent Disposal 12
Alternate Export Routes 13
IMPLEMENTATION 15
PURPOSES 15
Local Purposes 15
Broader Purposes 18
V SELECTION AND INTEGRATION OF UNIT PROCESSES 19
General 19
Effluent Quality Required 21
Reliability 22
Status of Process Development 24
Requirements for Ultimate Disposal of Sludge 25
Process Compatibility 26
Process Flexibility 28
Costs 28
Awkward Process Combinations 29
Storage 31
Disinfection 32
Summary 32
VI THE TAHOE PROCESS FOR WASTEWATER RECLAMATION 33
Water Reclamation Plant 33
Liquid Processing 33
Solids Handling System 38
v
-------
CONTENTS
Section Title pages
VII PLANT DESIGN DATA 41
VIII EXPORT SYSTEM 47
Description 47
DC OPERATOR TRAINING 53
Introduction 53
South Tahoe Training Program 53
Operator Goals 55
X SAMPLE COLLECTION AND ANALYSIS 57
Automatic Sampling System 57
Schedule of Sampling and Testing 57
XI TEST PROCEDURES 63
GENERAL 63
CALCIUM OXIDE (EDTA Method) 63
Procedure 63
Calculation 63
Reagents 63
Standardization 64
APPARENT DENSITY TEST FOR ACTIVATED CARBON 64
CARBON ASH ANALYSIS 65
Procedure 65
Notes on Method 65
CARBON ISOTHERM PROCEDURE 65
THE IODINE NUMBER OF ACTIVATED CARBON 67
Procedure 67
Notes on Method 68
Reagents and Equipment 68
XII PRIMARY TREATMENT 71
Physical 71
Treatment Efficiency 71
XIII ACTIVATED SLUDGE SECONDARY TREATMENT 73
Physical 73
Operational Practices 73
Treatment Efficiency 73
VI
-------
CONTENTS
Section Title Page
XIV DEWATERING AND INCINERATION OF WASTE
ORGANIC SOLIDS 77
Physical 77
Operational Practices 77
Stack Sampling Results 79
XV CHEMICAL TREATMENT 81
Primary Treatment 81
Activated Sludge 82
Lime Coagulation and Clarification of
Secondary Effluent 84
Methods Used For Data Collection 85
Optimum Lime Dose 86
Effects of Recycle Water 86
Maintenance of Lime Mud Lines 101
Additional Benefits of Chemical
Coagulation and Cferification 101
Point of Polymer Application 116
Summary and Conclusions 116
XVI TWO STAGE RECARBONATION 119
Methods Used for Data Collection 119
Results of Jar Tests 122
Results of Plant Scale Testing 128
Calcium Stability 134
Desired pH Level 135
Chemical Addition 135
Summary and Conclusions 136
XVII LIME RECOVERY AND REUSE 139
General 139
Physical System 139
Operating Practice 143
Lime Mud Thickening 143
Lime Mud Classification
and Dewatering 144
vii
-------
CONTENTS
Section Title page
XVII Chemical Addition 144
(cont.) Classification Evaluation 144
Classification Evaluation Results 145
Lime Mud Recalcining 153
Optimum Furnace Conditions 155
Conclusions 161
XVIII NITROGEN REMOVAL 163
General 163
Ammonia Stripping Tower Physical
Description 163
Tower Performance 166
Operational Problems 172
Tower Off-Gases 175
Summary and Conclusions 175
XK MIXED MEDIA FILTRATION 177
General 177
Filter Role 178
How Mixed-Media Filters Act 179
Separation Beds at South Tahoe 180
Special Separation Bed Evaluation 184
Test Results Separation Bed Evaluation 186
Summary - Separation Bed Evaluation 192
Filtration Summary 196
XX GRANULAR ACTIVATED CARBON ADSORPTION AND
REGENERATION 199
Carbon Adsorption System 199
Carbon Regeneration System 201
Carbon Adsorption Operating Practices 206
Carbon Regenerating Operating Practices 208
Carbon Column Maintenance 210
Carbon Regeneration Maintenance 211
Sampling and Data Collection 211
Average Results of Carbon Adsorption and
Regeneration 213
Effect of Carbon Regeneration Cycles on
Organics Removal 215
viii
-------
CONTENTS
Section Title Page
XX Carbon Column Loading Rate Investigation 218
(Cont.) Carbon Loading and Regeneration Over an
Extended Period of Time 218
Long Range Ash Build-Up 240
Carbon Losses Due to Regeneration and
Physical Handling 242
Summary and Conclusions 252
XXI VIRUS REMOVAL 257
General 257
Design Consideration for Virus Removal 266
Actual Virus Removals in Plant Operation 267
XXII DISINFECTION 271
General 271
Chlorine Feed Facilities 273
Results of Chlorination 273
XXIII FINISHED WATER QUALITY 277
Sampling and Analysis ' 277
Summary Finished Water Quality 298
XXTV INDIAN CREEK RESERVOIR 301
General 301
Study and Monitoring Procedures 301
Visual Observations 303
Physical and Chemical Tests 304
Irrigation 311
Rainbow Trout Fishery 311
Results of Lake Tahoe Area Council Study 315
Recreational Use 319
ix
-------
CONTENTS
Section Title Page
XXV CAPITAL AND OPERATING COSTS FOR CONVENTIONAL
AND ADVANCED WASTE TREATMENT 323
Introduction 323
Assumptions for Capital Costs 324
Capital Costs 324
Assumptions for Operating Costs 326
Operating Cost Data Collection and Analysis 327
Unit Operating Costs 329
Primary Treatment 329
Secondary Treatment 329
Organic Sludge Dewatering 332
Organic Sludge Incineration and Disposal 332
Overall Costs - Organic Sludge Dewatering,
Incineration, and Disposal 336
Lime Coagulation 336
Lime Mud Dewatering 336
Lime Mud Recalcining 340
Overall Costs - Lime Dewatering and
Recalcining 340
Nitrogen Removal by Ammonia Stripping 340
pH Adjustment by Recarbonation 343
Mixed Media Filtration 343
Carbon Adsorption 347
Carbon Regeneration 349
Disinfection by Chlorine 353
Summary 353
Increase in Construction Costs at South Lake
Tahoe ' 354
XXVI ACKNOWLEDGEMENTS 361
x
-------
CONTENTS
Section Title Page
XXVII REFERENCES 365
XXVIII LIST OF PUBLICATIONS RESULTING FROM
DEMONSTRATION GRANT PROGRAM 379
APPENDIX
A TABULATION OF VISITORS TO PLANT 383
APPENDIX
B TABULATIONS OF DAILY LABORATORY
AND FLOW DATA 385
APPENDIX
C CARBON ADSORPTION ISOTHERMS 419
xi
-------
TABLES
No. Title Pace
1 Effluent Quality Required 21
2 Average Raw Sewage Characteristics 1970 71
3 Average Plant Performance for COD Removal 75
4 Organic Sludge Furnace Operating Data 79
5 Stack Sampling Results 80
6 Plant Scale Effect of Recycle Streams on Average
Phosphorus Removals 91
7 Effect of Recycle Water on Turbidity vs Lime Dose 93
8 Average Effect of Recycled Water on Chemical
Clarifier Efficiency 95
9 Average Effect of Very High Turbidity and Phosphorus
in the Recycle Water 98
10 Average Efficiency of Chemical Clarifier with Recycle
Water Added to Floe Basin 99
11 Average Efficiency of Chemical Clarifier with Recycle
Water Added to Primary Clarifier 100
12 Stability Index and Marble Test - Scrubber Water
and Lime Mud Thickener Overflow 102
13 Average Performance of The Two Stage Recarbonation
System 132
14 Scrubber Water Ortho Phosphorus Content, mg/1 PO4-P 152
15 Lime Recalciner Operating Data 154
16 Effect of Temperature on Recalcined Lime Activity
at a Constant Feed and Rabble Rate 158
17 Effect of Rabble Rate on Recalcined Lime Activity
at a Constant Feed Rate 159
18 Effect of Feed Rate on Recalcined Lime Activity at
1900° F and 1.5 RPM Rabble Rate 160
19 Design Data Full Scale Ammonia Stripping Tower 164
20 Low Temperature Ammonia Stripping at South Lake
Tahoe Plant 167
21 Typical Removals by Separation Beds 185
22 Removal Efficiencies of Two Separation Beds in
Series at 8 - 64 ppm Dry Alum Dosages 185
23 Pounds of Various Substances Removed Per Pound of
Dry Alum Fed 192
24 A Comparison of COD and MBAS Removal Efficiency
Between First Cycle CC-5 and Third Cycle CC-6 216
xii
-------
TABLES
Title Page
A Comparison of COD and MBAS Removal Efficiency
Between Second Cycle CC-5 and Fourth
Cycle CC-6 217
26 Average Carbon Efficiency Per Regeneration Period 222
27 Average Carbon Furnace Parameters Per Regeneration
Period 228
28 Organic Loading and Reactivation Effect on Iodine
Number 234
29 Furnace Operating Conditions for Four Batch
Regeneration Cycles 236
30 Percent Ash Over Four Carbon Regeneration Cycles 241
31 Carbon Losses During Batch Regeneration Periods
Which Included Regeneration of First Cycle
Make-up Carbon 245
32 Average Mean Particle Diameters of Carbon 247
33 Mean Particle Diameter of Carbon at Various Points
in Regeneration System 248
34 Sieve Analysis of Third Cycle Carbon from CC-6 at
Various Points in the Regeneration System 250
35 A Comparison of Water Quenching of 4th Cycle
Regenerated Carbon with Air Cooling 251
36 Virus Sampling - 1969 South Tahoe Public Utility
District Water Reclamation Plant 268
37 Monthly Summary of Bacteriological Tests 275
38 Reclaimed Water Quality April - September 1968 278
39 Reclaimed Water Quality October 1968 -
March 1969 279
40 Reclaimed Water Quality April - September 1969 280
41 Reclaimed Water Quality October 1969 -
March 1970 281
42 Reclaimed Water Quality April - September 1970 282
43 Reclaimed Water Quality October - December 1970 283
44 Summary of Laboratory Analyses 8 July 1968 -
1 October 1968 284
45 Summary of Laboratory Analyses 1 October 1968 -
1 January 1969 285
46 Summary of Laboratory Analyses 1 January 1969 -
1 April 1969 286
47 Summary of Laboratory Analyses 1 April 1969-1 July 1969 287
48 Summary of Laboratory Analyses 1 July-1 September 1969 288
xm
-------
TABLES
No. Title Page
49 Summary of Laboratory Analyses 1 October 1969 -
1 January 1970 289
50 Typical Quality of Reclaimed Water 297
51 Effluent Storage Reservoir Laboratory Analyses 1968 305
52 Effluent Storage Reservoir Laboratory Analyses
March 28, 1969 306
53 Temperature and Dissolved Oxygen Profiles of
Indian Creek Reservoir 307
54 Water Quality of Indian Creek Reservoir and
Stevens Lake 308
55 Capital Costs for Conventional and Advanced Waste
Treatment Plant at 7.5 MGD Design Capacity 325
56 Percent Operational Labor Division per Treatment
Phase 328
57 Unit Costs 1969 and 1970 330
58 Operating and Capital Costs Primary Treatment at
7.5 MGD ' 331
59 Operating and Capital Costs Secondary Treatment at
7.5 MGD 333
60 Operating Costs Organic Sludge Dewatering at
7.5 MGD 334
61 Operating Costs Organic Sludge Incineration at
7.5 MGD 335
62 Operating and Capital Costs Organic Sludge
Dewatering and Incineration at 7.5 MGD 337
63 Operating and Capital Costs, Lime Coagulation at
7.5 MGD 338
64 Operating Costs Lime Mud Dewatering 339
65 Operating Costs Lime Mud Recalcining at 7.5 MGD 341
66 Operating and Capital Cost Lime Mud Dewatering
and Recalcining 342
67 Actual Operating and Capital Cost Ammonia Stripping
at 7.5 MGD Under Intermittent Conditions 344
68 Operating Costs For Ammonia Stripping at
7.5 MGD For Continuous Operation 345
69 Operating and Capital Costs Recarbonation at
7.5 MGD 346
70 Operating and Capital Costs Filtration at 7.5 MGD 348
xiv
-------
TABLES
No. Title Page
71 Operating and Capital Costs Carbon Adsorption
at 7. 5 MGD 350
72 Operating and Capital Costs Carbon Regeneration
at7.5MGD 351
73 Operating and Capital Costs Carbon Regeneration
per Ton of Carbon Regenerated 352
74 Total Operating Costs Conventional Wastewater
Treatment at 7.5 MGD 355
75 Total Operating Costs Advanced Wastewater
Treatment at 7.5 MGD 356
76 Total Operating and Capital Costs for Conventional
and Advanced Waste Treatment at the South
Tahoe Water Reclamation Plant for the 7.5 MGD
Design Capacity in 1969 and 1970 357
77 Miscellaneous Operating Costs for Conventional
and Advanced Waste Treatment 358
78 Actual Construction and Equipment Costs at the
7.5 MGD South Lake Tahoe Water Reclamation
Plant by Contract Completion Dates 360
xv
-------
FIGURES
No. Title Page
1 Aerial View of South Lake Tahoe 8
2 South Tahoe Public Utility District Service Area 9
3 Organization for Project Implementation 16
4 Board of Directors in Session 17
5 Schematic Flow and Process Diagram 34
6 Luther Pass Pump Station 48
7 Indian Creek Reservoir During Initial Filling 50
8 Iodine Correction Curve 70
9 Solids Handling - Primary and Secondary Sludge 78
10 Chemical Rapid Mix and Clarifier with Secondary
Clarifier in Foreground and Nitrogen Removal
Tower in Background 83
11 Phosphorus Removal from Secondary Effluent versus
Lime Dose 87
12 Turbidity Removal from Secondary Effluent versus
Lime Dose 88
13 pH versus Lime Dose 89
14 Effect of Recycle Water on Phosphorus Concentration
vs Lime Dose 92
15 Total Phosphorus Removal vs Calcium Oxide Dose 96
16 Total Phosphorus Removal vs Clarifier Overflow Rate 97
17 Pounds of Total COD Applied vs Percent COD Removal 103
18 Total BOD Removal vs Lime Dose 105
19 Soluble BOD Removal vs Lime Dose 106
20 Particulate BOD Removal vs Lime Dose 107
21 Total COD Removal vs Lime Dose 108
22 Soluble COD Removal vs Lime Dose 109
23 Particulate COD Removal vs Lime Dose - Recycle
Stream to Floe Basin 110
24 Total COD Removal vs Lime Dose - Recycle Streams
to Primary HI
25 Soluble COD Removal vs Lime Dose - Recycle Streams
to Primary 112
26 Particulate COD Removal vs Lime Dose - Recycle
Streams to Primary 113
27 Organic Suspended Solids Removal vs Lime Dose 114
28 Organic Suspended Solids Removal vs GJarifier
Overflow Rate 115
xvi
-------
FIGURES
No. Title Page
^^HVMIBM ^^
29 Recarbonation Schematic 120
30 Ammonia Stripping Tower and Recarbonation Basins -
Normal Operation 121
31 pH vs Reaction Time 123
32 pH vs Sludge Produced 124
33 pH vs Total Hardness 125
34 Sludge Produced vs Hardness Reduction 126
35 pH vs Alkalinity 127
36 Poly electrolyte Dosage vs Sludge Produced 129
37 Alum Dosage vs Sludge Produced 130
38 Hardness vs Alum Dosage in Jar Tests 131
39 First Stage pH vs First Stage Stability Index 134
40 Solids Handling Building 140
41 Solids Handling - Lime Sludge 141
42 Furnace Control Panel 142
43 Percent Solids Captured vs Flow Rate to Centrifugal 146
44 Effect of Centrifugal Capture on the Change in
Calcium Oxide Content of the Centrifugal Cake 148
45 Percent Solids Captured vs Percent of Usable Calcium
in Feed Conveyed to Furnace 149
46 Percent Solids Captured vs Percent of PO^ in Feed
Wasted in Centrate 150
47 Percent Solids Captured vs Percent of Magnesium in
Feed Wasted to Centrate 151
48 Virgin Lime Slaking Rate Test 157
49 Nitrogen Removal Tower 165
50 Percent Ammonia Removal vs Cubic Feet of Air per
Gallon Wastewater Treated for Various Depths
of Packing 169
51 Percent Ammonia Removal vs Surface Loading Rate
for Various Depths of Packing 170
52 Effect of Water Temperature on Ammonia Stripping 171
53 Mixed Media Filter Before and After Initial
Backwashing 181
54 Separation Beds Filter Cycle 182
55 Exterior View of Separation Beds, Decanting Tank,
and Tertiary Building 183
56 Percent Removal of PO4-P vs Dry Alum Dosage
Across Both Separation Beds 187
xvii
-------
FIGURES
No. Title Page
57 Percent Removal of Soluble PC>4-P vs Dry Alum
Dosage Across Both Separation Beds 188
58 Percent Removal of COD vs Dry Alum Dosage Across
Both Separation Beds 189
59 Percent Removal of BOD vs Dry Alum Dosage Across
Both Separation Beds 190
60 Length of Separation Bed Run vs Dry Alum Dosage 191
61 Pounds of PO4 Removed Per Hour vs Pounds of PO4
Applied Across Both Separation Beds 193
62 Pounds of Suspended Solids Removed Per Hour vs
Pounds of Suspended Solids Applied Across
Both Separation Beds 194
63 Pounds of Turbidity Removed Per Hour vs Pounds of
Turbidity Applied Across Both Separation Beds 195
64 Carbon Columns 200
65 Carbon Columns Normal Upflow Operation 202
66 Section Through Carbon Column 203
67 Carbon Furnace and Quench Tank 204
68 Carbon Regeneration System 205
69 Carbon Defining Tank 207
70 MBAS Removal for Controlled Loading Rates 219
71 COD Removal for Controlled Loading Rates 220
72 A Comparison of COD Efficiency, Iodine No., and
Carbon Dosage by Carbon Regeneration Periods 223
73 A Comparison of MBAS Efficiency, Iodine No., and
Carbon Dosage by Carbon Regeneration Periods 224
74 Increase in Spent Carbon Iodine Number by
Thermal Reactivation 225
75 Carbon Regeneration Cycles 226
76 Isotherms for Virgin and Regenerated Carbon 230
77 Isotherm Spent and Regenerated Ultimate COD
Capacity vs Four Regeneration Cycles 231
78 Isotherms for Regenerated Carbon 232
79 Isotherms for Regenerated Carbon 237
80 Isotherm Spent and Regenerated Ultimate MBAS
Capacity vs Four Regeneration Cycles 238
81 Isotherms for Regenerated Carbon 239
82 Percent Loss of Carbon vs Carbon Regeneration
Cycles 244
xviii
-------
No. Title Page
83 BOD Removals Through Plant - 1969 290
84 COD Removals Through Plant - 1969 291
85 Suspended Solids Removals Through Plant - 1969 292
86 MBAS Removals Through Plant - 1969 293
87 Phosphorus Removals Through Plant - 1969 294
88 Ammonia Nitrogen Removals Through Plant and
Reservoir - 1969 295
89 Aerial View of Indian Creek Reservoir 302
90 Rainbow Trout From Indian Creek Reservoir 312
91 Sailboating on Indian Creek Reservoir 320
92 Swimming in Indian Creek Reservoir 321
xix
-------
SECTION I
CONCLUSIONS
1. In actual practice, reclaimed wastewater has been used to
create a recreational lake in which algal growths have been successfully
controlled by nutrient removal in the treatment plant and reservoir.
2. The reclaimed water is safe for all water contact sports such
as fishing, boating, swimming, and water skiing, and has been officially
approved for such purposes by the California Water Resources Control
Board.
3. Chemical treatment, mixed media filtration, and granular car-
bon adsorption are efficient, reliable, and economical processes for tertiary
wastewater treatment. The reliability and ease of control of these methods
are very much greater than those for conventional biological treatment pro-
cesses.
4. By appropriate selection and sequencing of unit processes and
by proper plant design, wastewater treatment can be made fail-safe. Plant
bypasses can be eliminated. A degree of reliability and flexibility in oper-
ation can be attained which is comparable to that achieved in power genera-
tion facilities and in water purification plants supplying water to the public.
5. Bacteria and virus can be entirely eliminated from adequately
pretreated wastewaters by small doses of chlorine, properly applied, even
in the presence of relatively high concentrations of ammonium ion.
6. Organic sludges from primary and secondary wastewater treat-
ment can be incinerated to insoluble sterile ash without creating air pollu-
tion problems.
7. Lime used in wastewater treatment can be recalcined and re-
used. In small plants, such as the one at Tahoe, this avoids the problems
and saves the costs which would otherwise be involved in lime sludge dis-
posal. In larger plants, it can also reduce the cost of lime. Lime can be
reclaimed in a multiple hearth furnace without air pollution.
8. Granular activated carbon used to adsorb organics from waste-
-------
water can be thermally regenerated and successfully reused. Stack gases
can be scrubbed to meet air pollution control standards.
9. Operation of advanced wastewater treatment processes as
employed at Tahoe is less difficult than the operation of activated sludge
systems. On the job training of locally available personnel has provided
eminently satisfactory plant operation. The plant has operated without in-
terruption for 3 years with the production of a reclaimed water which has
continuously and without exception met the extremely high water quality
standards established by the regulatory agencies.
10. The Tahoe plant has clearly demonstrated the fact that there
is no need for wastewaters or their treatment by-products to pollute the en-
vironment in any manner. The means are available to prevent it. The Tahoe
Process has only three end products; high quality water, insoluble sterile
ash, and harmless stack gases.
11. The cost of even the highest degree of wastewater treatment is
not a valid argument against it, rather it is a weak excuse for inaction. At
a 7.5 mgd scale, the cost of treatment as practiced at Tahoe is slightly
more than twice the low cost of conventional secondary treatment, but the
cost benefits resulting from completely pollution-free operation are more
than doubled. The cost of treatment is only one part of the total overall
costs for wastewater collection, transport, and disposal. Even with the
most advanced treatment, the cost of sewer service is the least of all com-
mon utilities including electric power, water, gas, and telephone. The
costs to provide the necessary degree of treatment are reasonable and
should not be a deterrent to the solution of pollution control problems.
12. To satisfy discharge and other environmental requirements
less stringent than those at Tahoe, the advanced treatment processes can
be appropriately reduced to suit local conditions with a resulting lowering
of the costs involved.
13. The successful completion of pollution control projects de-
pends on many important factors. The foremost of these is the genuine
desire and determination of the members of the politically responsible gov-
erning body to solve the problem. They must also know how to solve the
problem, and how to gain the necessary public support. They must have the
benefit of competent engineering, legal, and financial advice. They must
seek, train, and retain qualified personnel to properly operate and maintain
the completed facilities.
-------
SECTION II
RECOMMENDATIONS
The great motivating force for the Tahoe Demonstration Project
was to find practical solutions to water pollution control problems. Al-
though basic and applied research was involved to a limited extent, the
principal effort at Tahoe has been to bridge the gap between scientific
knowledge and discovery and its practical use and application in the field.
This was basically an engineering design problem to develop methods and
equipment to make use of new processes which had progressed only to the
laboratory or pilot plant stage. This has been done. Chemical treatment
for clarification or phosphorus removal, ammonia stripping (at temperatures
above 32°F and with provisions for scale removal), recarbonation, mixed
media filtration, granular carbon adsorption, lime recovery and reuse,
sludge incineration, and carbon regeneration and reuse have all been shown
to be efficient, reliable, and economical processes for use where required.
Proven methods are now at hand to solve most, if not all, water pollution
problems. The crying need at this time is for the widespread use of these
demonstrated techniques to provide clean water. This is the message and
principal recommendation of this report.
It is obvious from a reading of this report that nitrogen removal
is the area which presently requires the most attention at this time. De-
spite the temperature limitations of ammonia stripping and the scaling
problems involved, this method for nitrogen reduction for large concentra-
tions of ammonia is by far the most economical and reliable to be develop-
ed to date. Unless, or until, other methods are developed which may prove
to be better, further development and demonstration work should be done in
this area. One approach to the calcium carbonate scale removal problem is
simply to design or use a tower in which the packing is accessible for
cleaning .• At Tahoe it is proposed that the planned future second section
of tower be built to provide full treatment capacity using a steel frame and
plastic pipe packing. The packing would be factory pre-fabricated in mod-
ules which can be rolled in and out of the tower structure for cleaning by
hosing down with a pressure stream of water. If this proves to be satis-
factory, then the existing section of tower would be repacked with the new
-------
material. At times when the air temperature is below 32°F and the tower
is not operative, the ammonia would be removed by break-point chlorina-
tion as described in the final report of FWPCA Grant WPP-85 for an earlier
(1965-67) Tahoe project. It is recommended that this work be done immed-
iately.
Indications are that water of quality suitable as a supplemental
source of supply for potable water purification plants can be produced from
wastewater by advanced treatment systems. However, much further study
is needed of the tolerable levels of biological and chemical substances
that may be present in wastewater; such as trace elements, pesticides,
carcinogens, antibiotics, hormones, viruses, and materials not yet stud-
ied. The effects of various commercial and industrial wastes found in many
urban wastewaters also need considerable investigation. The findings of
studies in these areas will also be valuable in evaluating the safety of
badly polluted surface water supply sources. Extensive studies are urgent-
ly needed in this area. They are principally of a research nature and are
of a type which can be done by only a relatively few persons, most of whom
are employed by EPA, by universities, or by private research organizations.
It is strongly recommended that this research be done, so that when it be-
comes necessary in the future to supplement water supply sources with re-
claimed water the questions regarding safety will all be answered.
-------
SECTION III
INTRODUCTION
Today there is widespread public recognition of the gross in-
adequacies of conventional secondary sewage treatment processes in
protecting the environment under many circumstances and the need for
the practical application of new treatment methods which produce re-
claimed water of superior quality.
At Lake Tahoe this need became apparent about ten years ago
because of special local conditions which will be described in more
detail later in this report. As a result, research and pilot plant studies
were undertaken in 1961 to reveal possible new processes for waste-
water reclamation. It was found that a tertiary sequence of treatment
including conventional activated sludge followed by chemical treatment,
mixed-media filtration, and granular carbon adsorption produced remark-
able improvements in water quality. These improvements included
virtually complete removal of suspended solids, BOD, bacteria, and
other substances only partially removed by secondary treatment. In
addition, good removals were obtained of COD, color, odor, viruses,
phosphates, MBAS, and other substances which are relatively unaffected
by secondary treatment.
In 1963, a 2.5 mgd tertiary plant was designed for the South
Tahoe Public Utility District incorporating these processes, plus facil-
ities for thermal regeneration of granular activated carbon for flows up
to 10 mgd. This plant was built in 1964 and 1965 and was placed into
operation during the summer of 1965.
In April 1965, further laboratory, pilot plant, and full-scale
plant studies were initiated at Tahoe with WQO, EPA demonstration grant
funds. These studies included recovery and reuse of coagulant, nitro-
gen removal, and data collection in connection with full-scale carbon
regeneration and reuse.
In 1966, plans and specifications were prepared to expand the
capacity of the entire South Tahoe plant from 2.5 to 7.5 mgd. Facilities
were planned for the recovery and reuse of lime as a coagulant and for
the incineration of all sludge produced. These plant additions were
completed and placed into operation on March 31, 1968. Also an exper-
imental ammonia stripping tower with a nominal capacity of only 3.75 mgd
(one half that of the basic plant) was built and placed into operation in
November 1968.
-------
This 7.5 mgd Water Reclamation Plant of the South Tahoe Public
Utility District is the largest and most complete scale advanced waste-
water treatment plant in the world, and was the first to be placed into
operation. It has been designated as a National Demonstration Plant
by the WQO, EPA under the Clean Waters Restoration Act.
WQO, EPA Demonstration Grant WRPD 52-01-67 not only provides
for studies of recovery and reuse of lime as a coagulant and ammonia
stripping, but also for complete detailed studies and reporting of the
entire plant operation including costs for a three year period ending Feb-
ruary 1971.
This report includes: a discussion of the history and purpose of
the Tahoe project, a description of the process used, design data for the
plant and export system, an outline of the on-the-job training of plant
personnel, a description of sample collection techniques and test pro-
cedures employed, detailed descriptions of each liquid processing step
and each solids handling procedure, detailed results of treatment and
plant operation, complete data on actual construction and operating
costs, information on the prolonged storage of reclaimed water in Indian
Creek Reservoir, conclusions and recommendations, and other miscell-
aneous related information.
-------
SECTION IV
HISTORY. PURPOSES. AND IMPLEMENTATION OF
THE TAHOE PROJECT.
HISTORY.
Local Conditions. Lake Tahoe is a beautiful alpine lake
located high in the Sierra Nevadas straddling the California - Nevada
boundary. Tahoe has not joined the list of ruined lakes. It is still one
of the clearest purest lakes in the world. During the past decade many
individuals have exercised great effort to assure its long and useful life,
not to be sullied by the activities of man. This is the story of one group
which has devoted the past ten years to developing a project to collect,
treat and remove the treated sewage from the south shore area of Lake
Tahoe.
Lake Tahoe Basin has an area of 506 square miles - 314 are land
and 192 represent the water surface. The lake's man-made boundaries
make a complex political problem; they include two states, five counties
and over 65 local, State and Federal agencies - each exercising some
jurisdiction over the land and water in the basin. Six local public
agencies provide some degree of sewerage service. Three of the agen-
cies are in Nevada and three in California. The South Tahoe Public
Utility District is the largest and most active of the six agencies.
The District organized in 1951, consisted of 140 acres, with an
assessed value of $1.14 million. It now contains over 21,000 acres,
assessed at more than $80 million.
The District represents over half the developable land in the
basin. The area has grown rapidly due to the increase in leisure time
and year-round recreation, coupled with improved all year access by
automobile and other forms of transportation. Figure 2 shows the present
boundaries and location of the District.
In I960, the District started operating a new 2^-mgd activated
sludge treatment plant, which replaced two redwood septic tanks that
had served as treatment facilities since 1956. The new plant, although
capable of producing a high quality secondary effluent, did not permit
discharge to the lake. Effluent disposal was accomplished by spray
irrigation on land.
-------
Figure 1
AERIAL VIEW OF SOUTH LAKE TAHOE
:
-------
EL DORA.DO CO
R6CLA.MWRO
PL/MJT
SOUTH TA.HOE
PUBLIC UTILITY
DISTRICT BOUKIPAJ^Y
EFFLUEK1T EXPORT
FIPBLIKIE
CREEK.
RESERVOIR
FIGURE 2
SOUTH TAHOE PUBLIC UTILITY DISTRICT
SERVICE AREA
s
-------
Although no official water quality policy had been adopted for
Lake Tahoe in 1960, it appeared that land disposal of effluent within the
lake basin would be acceptable for many years. This conclusion was
based on three factors: State regulatory agencies would never permit
direct discharge of conventionally treated effluent to Lake Tahoe or its
tributaries; removal of the treated effluent from the lake basin would be
impossible due to legal restrictions on water rights and legal complica-
tions involved in disposing of sewage effluent in another state or water-
shed; and secondary treated effluent would not meet quality standards
necessary to protect the high quality water in the receiving streams.
Seeking A Plan. In April, 1961, the District Board of Directors
asked its consulting engineers to investigate alternatives and to recom-
mend a plan for permanent effluent disposal. After a detailed investi-
gation, the engineers recommended the following:
To continue with land disposal for the next several years.
Although the method did not afford complete protection of the lake, it
was the only alternative available for interim use.
Develop an advanced method of waste treatment that
might ultimately permit disposal within the lake basin, or permit removal
of the effluent from the basin, if necessary.
Study available routes for effluent removal from the basin
and seek an agreement that would permit disposal outside the basin.
The plan was approved and its implementation was started.
Existing land disposal areas were enlarged and a new area con-
structed. This was sufficient for the next several years. With the
interim element completed, efforts were devoted to the final two elements
of the plan, which were more time consuming and difficult.
Advanced Waste Treatment. In order for sewage effluent to be
acceptable for export, it would have to be essentially of drinking water
quality. If in-basin disposal were ever to be permanently allowable,
maximum removal of phosphate and nitrogen would be required. Since
there were few, if any, plants in the country that could meet such stan-
dards, the District decided to initiate a research program and develop a
tertiary treatment process that would meet the objectives.
The consulting engineers undertook a program to develop a pro-
cess utilizing chemical coagulation, filtration through multimedia filters
10
-------
and finally adsorption on activated carbon beds. By the end of 1963,
pilot plant tests had developed to a point where the District believed
that it would be possible to build and operate a tertiary treatment plant
at a cost it could afford, and authorized the design of a full scale 2.5
mgd plant. The plant was constructed in 1964 and placed into service
in July, 1965. The facility operated successfully; effluent quality was
equal to or exceeded the expected quality and operating costs were with-
in the predicted range.
Plant Overloaded. The completion of the tertiary plant coin-
cided with the culmination of an unprecedented growth within the District.
The existing activated sludge plant was overloaded during the summer of
1965. The 2.5 mgd plant was receiving flows up to 4 mgd. Plant perform-
ance suffered and the tertiary facility could not continuously perform
adequately with poor quality secondary effluent.
By the summer of 1966, it was mandatory that the treatment plant
be expanded. That fall, plans and specifications were authorized for
expansion of plant capacity to 7.5 mgd. Construction began the following
summer. Three major contracts were let: One provided for expansion of
the primary, secondary and tertiary plants; another for construction of a new
solids disposal system; and the last for construction of an experimental
ammonia stripping system for nitrogen removal, which was build for only
one half plant capacity, or 3.75 mgd.
The primary and secondary plant expansion consisted of adding
one primary clarifier, two aeration basins, one secondary clarifier, a
return sludge pump station, a chemical flocculation basin, chemical
clarifier, waste activated sludge thickener, lime mud thickener and a
final effluent pump station.
The tertiary plant expansion included adding four separation beds,
six new activated carbon columns and new secondary effluent pumping
facilities.
Solids Disposal System. Operation of the original tertiary
plant posed a problem in disposing of the alum sludge produced. At first
it was planned to reclaim and reuse the alum, but this proved to be not
feasible. To overcome the problem, lime is used as a coagulant in the
expanded plant.
In addition to the chemical sludge problem, the original plant had
trouble disposing of biological sludge because its digesters and drying
bed were inadequate, particularly in the winter.
11
-------
For these reasons, a new solids disposal system was incorpor-
ated into the expanded plant. Biological sludge is incinerated in a six-
hearth, 14.5 foot diameter furnace. Waste activated and primary sludge
is dewatered to about 19 percent solids by a concurrent flow solid bowl
centrifuge.
The lime sludge is reclaimed by recalcining the lime in a second
multiple hearth furnace. It is thickened in a gravity flow thickener,
then dewatered to about 50 percent solids by a centrifuge.
The biological furnace and the lime furnace are fired by natural
gas.
The lime centrate contains most of the phosphates, which are
removed by feeding the centrate to the primary clarifier and collecting
this portion of the lime sludge with the biological sludge. The phos-
phate sludge is then incinerated along with the biological sludge, and
the phosphate is disposed of as an insoluble rock phosphate in the ash.
Nitrogen Removal. Treating the secondary effluent with the
high lime dose (about 300 mg/1) necessary for maximum phosphate re-
moval and clarification raises the pH to about 11.0. At this high pH,
calcium carbonate could be deposited on the piping and filter beds, so
the effluent is recarbonated until the pH reaches 7.5. This is accom-
plished by a two-stage system utilizing CO2, which is obtained from
the furnace stack gas. Prior to lowering the pH, the lime treated efflu-
ent is pumped through a cooling tower where ammonia nitrogen is stripped
from the water and released to the atmosphere as a gas. The stripping
tower will remove up to 95 percent of the ammonia nitrogen.
The plant expansion, with the exception of the ammonia stripping
tower, has been operating since March 31, 1968. The tower was placed
in service in November 1968.
Effluent Disposal. Until 1964, the District continued to study
the effluent disposal problem. State and Federal regulatory agencies
were urging that export, or removal of the effluent from the Lake Tahoe
Basin, be carried out since this would positively eliminate any danger
to the lake from nutrient enrichment by sewage.
In November of 1963, the Governors of California and Nevada met
to consider solutions to the potential pollution problem of the lake. As
a result of the meeting, each State pledged its resources to carrying out
a program of effluent export. The South Tahoe Public Utility District
12
-------
was selected as the first target, and California issued an edict telling
the District to export by 1965. Unfortunately, the Governor's edict did
not present a solution, but only added to the urgency of the problem.
Alternate Export Routes. The District had available at least
three alternative routes for export. All routes were feasible, but each
presented problems that were beyond the District's control.
The first route to be considered was a pipeline extending south
from the water reclamation plant approximately 40,000 feet to discharge
over Echo Summit into the South Fork of the American River. The total
elevation rise would be 1,080 feet. This route offered the least annual
cost and, accordingly, was recommended by the engineers.
In April of 1964, the District applied to the State of California
to discharge effluent of drinking water quality into the South Fork. After
a detailed investigation of the application, a public hearing was held by
the Central Valley Regional Water Quality Control Board. Practically all
agencies and individuals concerned protested the proposed discharge.
As a result, the regional board prohibited any discharge, direct or in-
direct, into the South Fork of the American River at any point above
Placerville. Since the town of Placerville is 45 miles downstream from
Echo Summit, the first cost of the plan changed radically and the District
was forced to discard the plan.
The next choice was to export to the north over Dagget Pass into
Douglas County, Nevada. This route would involve a 40,000-foot pipe-
line and a change in elevation of about 1,030 feet. The District applied
to the State of Nevada for permission to export the effluent to this loca-
tion. The Nevada State Health Department indicated that a discharge of
effluent of the indicated quality would be acceptable. The District then
began negotiations with a counterpart in Nevada, the Douglas County
Sewer Improvement District No. 1, to provide for construction of a joint
export system over Dagget Pass. After several months, it appeared that
negotiations of a successful joint project would not be possible due to
legal and political considerations. It also appeared that the District
would obtain greater State and Federal financial assistance if the project
were constructed in California. Therefore, the District decided that the
Dagget Pass route would be unsatisfactory.
The final choice was a route extending southerly and easterly
from the water reclamation plant over Luther Pass into Alpine County,
California. This route was approximately 75,000 feet long to Luther
Pass, and involved an elevation change of 1,440 feet.
13
-------
The District, in 1965, applied to the State of California for
permission to dispose of effluent of drinking water quality, into the
Hope Valley area adjacent to the West Fork of the Carson River, just
over Luther Pass. The Lahontan Regional Water Quality Control Board,
after an investigation and public hearing, approved the plan. The
District at last thought an acceptable plan had been reached, even
though the cost would be greater than the other alternates. However,
the County of Alpine did not agree with the State Board. The County,
under California law, had the right to establish standards and require-
ments for effluent disposal beyond those set by the State. Alpine County
immediately passed a series of stringent ordinances establishing a water
quality control policy. Among these ordinances was one prohibiting any
effluent discharge into the Hope Valley region. After several months of
negotiations between Alpine County, the State of California, and the
District, final agreement was reached on an effluent disposal project.
The agreement contained the following major points:
1) The point of discharge could not be in Hope Valley, but
would be in Diamond Valley approximately 12 miles below Luther Pass.
2) The effluent must be from a tertiary treatment plant and be
essentially of drinking water quality.
3) The effluent must be stored in a suitable location so that
discharge will occur only during the irrigation season.
4) All effluent must be made available for irrigation use.
5) Effluent disposal would be accomplished in Alpine County and
done in a manner which would allow recreational use of the impounded
water, if approved by the appropriate health agencies.
6) The project, as finally designed, must be approved by all
State and Federal agencies involved in water quality control of Lake
Tahoe.
Even though the conditions imposed involved appreciably greater
expenditures than originally anticipated, the District agreed to accept
the project as approved, subject to obtaining financial aid from the State
and Federal governments.
The design of the export system was authorized by the District in
late 1965. The time schedule contemplated placing all elements of the
system under construction during 1966, with completion of construction
14
-------
scheduled by the end of 1967.
The export system involved four separate major projects: The
Luther Pass Pipeline, Luther Pass Pump Station, Indian Creek Pipeline
and the Indian Creek Dam.
IMPLEMENTATION.
The novel scientific and engineering aspects of the South Tahoe
Water Reclamation Project have been widely publicized and have received
considerable attention. While these aspects are the principal subjects
of this report, it must be pointed out that this project would not have
been successfully completed without the unusual vision, determination,
and leadership of the Board of Directors of the South Tahoe Public Utility
District. A brief summary of the organization and teamwork involved in
implementing the project might be valuable to other political subdivisions
contemplating similar undertakings.
Figure 3 is a diagram which illustrates the mode of operation
followed by the Board in coordinating and directing the efforts of various
groups working on the project. The Board of Directors are the hub of the
operation. Technical advice comes to them from the consulting engineers,
district management, and in cooperation with State and Federal water
pollution control agencies. Financial planning is a Board responsibility
based on information supplied by bond counsel, the consulting engineers,
and district management, and on the availability of federal grants and
state loans. Public support is a direct responsibility of the Board.
Public support and confidence are vital to all phases of the work, partic-
ularly to adequate financing and staffing of the project. The Board also
has an important role with their legal advisors in securing the necessary
political support of elected officials at the local, state, and national
levels. All of these relationships are depicted in Figure 3.
PURPOSES.
Local Purposes. The local purposes of the South Tahoe Water
Reclamation Project may be summarized as follows:
1. The preservation of Lake Tahoe against any possibility what-
ever of pollution or accelerated eutrophication from wastewater discharge.
15
-------
ADVANCED WASTE
WATER TREATMENT
PROCESS AND
PLANT DESIGN
PUBLIC
SUPPORT
,
COOPERATION
WITH POLLUTION
CONTROL AGENCIES
CONSULTING
ENGINEERS
L
FINANCIAL
SUPPORT
FINANCIAL
PLANNING
LEADERSHIP
BOARD OF DIRECTORS
SOUTH TAHOE
PUBLIC UTILITY DISTRICT
DISTRICT
MANAGEMENT
POLITICAL
SUPPORT
LEGAL
COUNSEL
THE SOUTH LAKE
TAHOE WATER
RECLAMATION PLANT
I
BOND
COUNSEL
Figure 3. Organization For Project Implementation,
-------
Figure 4 BOARD OF DIRECTORS IN SESSION
-------
2. Compliance with the export edict of the Nevada, California,
and Federal governments.
3. Compliance with the effluent disposal standards of Alpine
County which provides for water of such quality that unrestricted recrea-
tional use of stored water is permitted.
4. The development of a treatment process which will make it
possible in the future to benefically reuse the reclaimed wastewater
within the Tahoe Basin.
Broader Purposes. Because the South Tahoe Plant is the first
full scale plant of its kind and incorporates many new treatment process-
es and much new equipment, and since the water it produces is so far
superior in quality to conventional secondary treated effluents, there is
world-wide interest in the techniques employed in the advanced treat-
ment, the practical operational results, and the actual costs involved in
construction and operation.
In view of this interest and the relation of the Tahoe Project to
national water pollution control problems and goals, the Plant is desig-
nated by the Environmental Protection Agency as a National Demonstration
Plant under the Clean Waters Restoration Act. Federal grants were made
to aid in construction and to assist in the collection of data on the opera-
tion of the plant and the associated costs which will be useful in planning
other similar works.
18
-------
SECTION V
SELECTION AND INTEGRATION OF UNIT PROCESSES.
General. This Section discusses the reasoning used in select-
ing and sequencing the unit wastewater treatment processes which are
incorporated in the South Tahoe plant.
A partial check list of factors which may influence selection and
sequencing of processes follows:
1. Effluent quality required
a. present
b. possible future
2. Reliability and simplicity of unit processes
a. effects of changes in flow, temperature, and applied
water quality
b. required operator skill and attention
c. process sequence interrelationships
( 1 ) effects of secondary treatment upsets
3. Status of process development
a. laboratory experiments
b. pilot plant
c. operating full-scale plants
( 1 ) design data and equipment specifications
(2 ) actual operating experience
( 3 ) firm cost data
4. Requirements for ultimate disposal of sludge.
a. land disposal
( 1) raw sludge
(2 ) digested sludge
(3 ) dewatered sludge
b. incineration
( 1 ) sludge dewatering characteristics
(a) primary sludge
(b) waste activated sludge
(c) chemical sludge
(d) organic-chemical sludge mixtures
19
-------
(2) sludge conditioning
(a) digestion
(b) heat treatment
5. Process compatibility.
a. optimum points for chemical application
b. optimum pH for each unit process
c. recycling of process water and waste streams
(1) centrate
(2) filtrate
(3) scrubber water
(4) filter backwash water
(5) carbon rinse water
(6) miscellaneous
6. Process flexibility.
a. alternate modes of operation
b. standby units
c. provisions for servicing and repair
d. fail safe features
(1) process monitoring
(2) restricted bypass arrangements
(3) alarms
7. Costs.
a. capital
b. operating
c. plant capacity or size of units
(1) powdered vs granular
(2) gravity vs pressure units
(3) materials of construction
(4) throwaway vs reuse of chemicals
8. Awkward process combinations. (Carrying out two or more pro-
cesses simultaneously in a single treatment unit.)
a. general problems
(1) loss of individual process control and optimization
(2) loss of flexibility
(3) loss of reliability
b. mixing, flocculating, settling, and internal solids recycling
in a single basin (solids contact basin)
c. chemical-primary treatment
d. chemical-activated sludge treatment
e. carbon contactor-filter
f. sludge incineration - lime recalcining in a single furnace
20
-------
Effluent Quality Required. The first consideration in the selec-
tion of unit processes is the degree of treatment required at present and
that which may be required in the future. Once the required water qual-
ity is established, then unit processes must be selected to accomplish
the desired result. Obviously, for almost every situation, there are a
number of combinations of unit processes which may satisfy the needs.
The requirements to be met immediately by the plant for water
exported to Alpine County, Calif, as established by the Lahontan Region-
al Water Quality Control Board and the Board of Supervisors of Alpine
County are given below.
TABLE 1
EFFLUENT QUALITY REQUIRED
Description
MBAS, mg/1, less than
BOD, mg/1, less than
COD, mg/1, less than
Susp. S., mg/1, less than
Turbidity JU, less than
pH , units
Coliform, MPN/100 ml
Requirements
Alpine Co.
0.5
5
30
2
5
6.5 to 8.5
Adequately
Disinfected
Lahontan R . W . Q . C . B .
percent of time
50
0.3
3
20
1
3
80
0.5
5
25
2
5
100
1.
10
50
4
10
6.5 to 9.0
Median less than 2
Max. No. Consecutive
samples greater than
23, 2.
21
-------
These standards do not include any requirement for phosphorus or
nitrogen removal. However, Alpine County, the recipient of the reclaimed
water, included provisions in their contract with the District which clearly
indicated that the receiving reservoir on Indian Creek was to be used for
recreation. Since this was the case, it was decided to include provisions
in the plant for the maximum degree of phosphorus removal which was
feasible. The Consulting Engineers were of the opinion that phosphorus
removal alone could control algal growths in the reclaimed water. This
was based on "batch" algal growth tests of pilot plant effluent. It has
since been verified by three years of observation of the water in Indian
Creek Reservoir.
Because of the potential future beneficial reuse of the reclaimed
water in the Tahoe Basin and the potential savings in electric power costs
which could be realized from elimination of export pumping, it was de-
cided to evaluate methods for nitrogen removal, since it appears that the
regulatory authorities will require some degree of nitrogen removal for
waters to be reused in the Basin.
Reliability. The simplicity and reliability of unit processes and
sequences thereof are top priority factors. While simplicity and reliabil-
ity are not synonymous, they are very closely related. The simpler the
process is to operate and control, the more likely it is to operate success-
fully and continuously. Regardless of how highly efficient a process may
be when operating at its very best under conditions rigidly controlled by
experts, if it is sensitive to minor changes in flow, temperature, or ap-
plied water quality, or if it requires constant attention and adjustment,
then it is not likely to operate as intended all of the time in practical
plant application.
The operation of conventional secondary treatment plants is often
very erratic. Settling basins are subject to upsets. The design of ad-
vanced wastewater treatment processes which follow must take this fact
into account. They must be able to accept these variations in performance
and still produce an effluent of uniform quality.
To secure a high degree of treatment with a high degree of reliabil-
ity, it was apparent early in project planning that efficient filtration would
be a necessity. Indeed, without the use of filters in advanced waste treat-
ment flow sheets, there unquestionably will be a loss of quality in the
finished water, and a serious loss of reliability in the continuity of the
entire treatment process. In 1961, when this work was started, a search
of the literature revealed that there was at that time no satisfactory way
to filter sewage, although many attempts had been made over a period of
22
-------
50 years or more to do so. Failure of these attempts resulted generally
from either the rapid plugging of the filter surface or plugging over a per-
iod of time due to slime growths. Rapid sand filters, slow sand filters,
and intermittent sand filters had all been used with a notable lack of
success. In 1961, Raymond Pitman and Walter Conley were using in
water purification at the Hanford Atomic Works in Richland, Washington
a dual media (coal-sand) filter which produced a very high clarity water.
This dual media filter differed from earlier versions in that it was a mixed
dual media rather than a layered dual media. It utilized to a limited
extent the principle of coarse-to-fine filtration. Later work by Conley,
Archie Rice, and others for Microfloc, Inc. led to a major improvement in
the mixed media filter for water treatment by the use of three materials,
coal, sand and garnet. Proper gradation and combination of these ma-
terials results in a filter in which the pore space is uniformly graded from
top to bottom of the filter and which allows storage of solids removed
from the water throughout the full depth of the filter bed. The trial and
adaptation of the mixed media filter to wastewater treatment at Tahoe was
really the key that opened the door to practical, reliable advanced treat-
ment. Experience in the operation of the full-scale plant has verified the
fact that the filters are one of the most important parts of the entire treat-
ment process. During normal plant operation it appears at times that
filtration might be eliminated from the process with little loss in finished
water quality. The full value of filtration is demonstrated when preceding
processes are upset due to shock hydraulic or organic loads, equipment
failure, human error, or other factors which are universally prevalent.
Under these conditions filtration is indispensable. Filtration not only
compensates for failures in preceding processes without interruption of
treatment, but also protects processes which follow, such as carbon
contact, against failure. Mixed-media filtration is the one important
difference between an advanced waste treatment scheme which works and
one which does not work. It should also be noted that the differences
between the reliability and performance of a mixed-media filter and a
dual media filter are greatest in favor of mixed-media when the poorest
water is being filtered, that is, at those times when filtration is most
needed.
Granular activated carbon adsorption of organics is a highly re-
liable process provided it follows filtration. Granular carbon can take
shock hydraulic or organic loads without difficulty. However, downflow
columns subject to high turbidity loadings can be troublesome. At
Tahoe, upflow carbon contactors are used following mixed-media filtration
which has proved to be a good arrangement. Upflow co'untercurrent carbon
columns are also by far the most efficient from the standpoint of carbon
use as will be discussed in detail later.
23
-------
Following activated sludge treatment with high lime treatment is
a good sequence because any biological floe carryover is usually settled
out along with the lime. Following activated sludge treatment with carbon
treatment equalizes variations in BOD or COD content.
Status of Process Development. The state of development of a
process, particularly the number of full-scale plants from which engineer-
ing design and equipment information, actual operating results, and cost
data can be obtained, has a great influence on the degree of reliability
which may be expected of it. Obviously, if new approaches are not tried
on a plant-scale, little progress will be made. However, engineers and
clients embarking in new areas should be aware of the degree of uncer-
tainty involved. The acceptable risk level must be determined individ-
ually for each project.
The first tests of any new treatment method are usually made in the
laboratory. The next step is pilot plant operation on a continuous flow
basis. Pilot plant work gives a good insight into the results to be ex-
pected from liquid processing. Unfortunately, it does not always ade-
quately evaluate sludge problems or problems associated with recycled
process streams or return solids. Only a few advanced wastewater treat-
ment processes have been tested on a plant scale. It is only at plant
scale than many engineering design problems and the practical operation
problems are faced for the first time. The transformation of pilot plant
data gathered by biologists, engineers, chemists, and laboratory tech-
nicians into workable engineering designs is a difficult and demanding
task, and one not to be taken lightly or for granted. It is here, in the
hands of the sanitary engineering designer, that the project either fails
or succeeds. The success depends not only on how well he selects and
combines the unit processes, but more importantly how well he selects
and specifies the performance of equipment, and how well he executes
the excruciating details of design. Actually, the development of this
engineering design knowhow is the great gap in the application of new
and better methods for wastewater treatment. There is a great backlog
and wealth of information and scientific research which cannot be used
until it is transformed into actual working plants. This transformation
requires the design of new structures and equipment, and the provision of
sufficient safety and flexibility in the design to allow for any contingen-
cies which may not be apparent at pilot scale.
Because the problems involved in going from pilot to full scale are
difficult, it is sensible to take full advantage of all prior knowledge.
24
-------
There are many unknowns still remaining upon completion of pilot scale
experiments which become readily discernable upon completion and oper-
ation of the full scale plant. For maximum reliability, the designers of
future plants must take advantage of the prior art, modifying proven de-
signs as necessary to meet different conditions as to size and other
design variables.
The Tahoe plant designers had to rely principally on prior art in
other industries, since it was the first full-scale advanced wastewater
treatment plant. For example, the experience of the sugar refining in-
dustry provided some guide lines in the design of carbon contacting ves-
sels, carbon transfer equipment, and carbon regeneration equipment and
procedures. The waterworks industry provided much information on chem-
ical treatment, recarbonation, and plant controls, and with the paper
manufacturing industry supplied some data on lime recalcining and reuse.
Ammonia stripping tower design relied principally on experience with coot-
ing towers, even though there are some important functional and operation-
al differences.
Plants which follow Tahoe will, of course, have the benefit of the
Tahoe experience. In this report the difficulties as well as the successes
at Tahoe will be discussed because they are of great importance to the
designer. Each designer should have the privilege of making his own
mistakes rather than repeating old ones.
Requirements for Ultimate Disposal of Sludge. Of major import-
ance in process selection are the circumstances related to the handling
and ultimate disposal of the sludge produced. In locations where there
are available remote, large areas of land, almost any kind of sludge,
wet or dry, stable or decomposing, can be, and isy disposed of by haul-
ing or pumping to these land disposal sites. In many places this crude
method for sludge disposal probably will not be tolerated indefinitely, but
might suffice for the time being. Ocean disposal of sludge has long been
an easy way to evade the knotty problems involved in proper sludge dis-
posal. However, the nuisances which have been created and the damages
wrought to beaches and coastal waters have aroused the public to the
point where this method is now in almost universal public disfavor.
All of the more acceptable methods for sludge disposal involve
dewatering of the sludge. The ease with which sludge may be dewatered
is a prime factor in unit process selection. There are many alternate ways
to process the liquid component of wastewater to secure the desired re-
sult at about equal costs, but there are very few ways to satisfactorily
25
-------
and economically dewater sludge. In sludge from certain wastewaters,
dewatering of mixtures of organic-chemical sludges may be satisfactory,
but care must be taken to check this out before designing a full scale
plant. Favorable pilot plant test results are an important prerequisite.
Another approach which has been used successfully is to keep
entirely separate all organic sludge from all chemical sludges. Then,
conventional equipment used for either of these types of sludge can be
installed. Pilot tests are still highly desirable, even with this approach.
Heat treatment or anaerobic digestion of organic-chemical sludges
may condition these mixtures to make possible use of a wide range of de-
watering equipment. Chemical conditioners may accomplish this same
end, but dosages must be determined to ascertain economic feasibility.
At South Tahoe, the choices in sludge disposal were: incineration,
or digestion and hauling the sludge out of the basin provided a disposal
site could be found. Because of the long haul involved in sludge export,
the descision to incinerate all waste organic and chemical sludges was
quite easy as it was favored both by esthetics and economics. Existing
sludge digestors for the original 2.5 mgd plant were utilized in the ex-
panded plant for emergency storage of sludge. They also can be used to
pretreat sludge for easier dewatering if necessary.
One of the greatest single factors favoring the tertiary sequence
of treatment (in which advanced treatment follows conventional biological
treatment) is the sludge handling problem. At Tahoe, mixtures of primary,
waste activated, and chemical sludges proved to be prohibitively expen-
sive to dewater, but organic sludges and chemical sludges which were
kept separate dewatered readily and at low cost. This is one of the most
important factors to be evaluated prior to final plant design, particularly
in the decision between physical-chemical treatment and the tertiary
sequence.
Process Compatibility. Another consideration in process selec-
tion is the compatibility of the process with other unit processes used in
the overall treatment scheme. The possible effects of waste streams or
recycled solids is very important.
The optimum pH for various unit processes is a factor which in-
fluences their compatibility, and may affect placement of processes in
the plant flow sequence. There are many examples of this point. Vari-
ous chemical coagulants operate best within certain pH ranges. In this
case , the choice may be to adjust the pH or change the chemical
26
-------
used. Also it is possible to broaden the effective pH range of chemicals
by use of coagulant aids, such as activated silica or polymers. Biolog-
ical processes may be adversely affected by pH values above 9.3, al-
though activated sludge cultures have great buffer capacity and it may be
possible to allow the pH of the influent to activated sludge basins to
exceed 9.3 so long as the pH in the aeration tank itself does not exceed
this value. Phosphorus removal by lime requires raising the pH to values
of 9 to 11. Ammonia stripping also is most efficient at pH values of 10.5
to 11. Calcium reaches minimum solubility at a pH near 9.3 . Carbon
adsorption of organics is best at low pH values, and is very poor at pH
values above 9.0. Chlorination is more effective at low pH values, at
low turbidities, and in waters with low chlorine demand. Granular acti-
vated carbon adsorption is favored by good clarification of the applied
water. Granular activated carbon will adsorb chlorine. With information
on process interrelationships and pH effects, then, a logical process se-
quence for maximum reliability and effluent quality would be biological
treatment followed by advanced treatment, or the so-called tertiary se-
quence. Although the costs may exceed those of approaches combining
certain steps, there are at least three advantages to this arrangement
which must be given due consideration: the pH is favorable for biological
treatment; the organic sludges are kept separate from the chemical sludges
which usually minimizes sludge dewatering problems; and the polyphos-
phates in the raw wastewater are converted to orthophosphate before chem-
ical coagulants are applied, thus avoiding potential interference with
chemical coagulation.
In considering compatibility, attention must be given to the point
in the overall process at which centrate, filtrate, backwash water,
scrubber water and other plant process water and recycle streams are
introduced. It is wise to provide more than one point of return for some
of these streams, particularly to take care of those times when certain
plant units are temporarily out of service.
In the South Tahoe plant, the processes are compatible. Fortu-
nately, sufficient flexibility was built into the plant to allow some pro-
blems in this regard to be worked out under actual plant operation. For
example, an optional point of lime application to the primary tank influent
was not used due to sludge dewatering problems which lime addition cre-
ated. Several points of centrate (from sludge and lime centrifuges) re-
turn were provided including points to be used with certain plant units out
of service. Several points for return of flue gas scrubber water were pro-
vided, but the best point for both return waters has proved to be the rapid
mix. Filter backwash water is returned to the rapid mix basin, but, again,
alternate points of return are provided.
27
-------
As previously mentioned, at Tahoe, chemical treatment follows
biological treatment which has the advantages of reducing sludge de-
watering problems and taking care of biological floe carryover by chem-
ical flocculation and settling. Also at Tahoe, once the pH of the water
is raised to 11.0 with lime for phosphorus removal, the water passes
through the ammonia stripping tower which requires the same high pH.
Thus, one lime application serves two purposes. Two stage recarbon-
ation, which follows, then lowers the pH to a value suitable for subse-
quent filtration, carbon adsorption, chlorination, and stabilization.
Process Flexibility. The capability should be provided in ad-
vanced wastewater treatment plants for as many alternate modes of oper-
ation as possible. Each basin and each piece of equipment must be
taken out of service at some time for servicing or repair, and provisions
must be made in the design to operate the plant under these conditions.
In many cases, duplicate or standby units may be provided. The plant
should include as many fail-safe features as possible, including equip-
ment for process monitoring and alarms to signal plant failures. Bypasses
around individual units are essential, but no bypass should be provided
which will allow water of unacceptable quality to leave the plant.
This scheme has been followed in the design of the Tahoe plant.
It is fail-safe. It has no plant bypass. It has operated for 3 years with-
out interruption in the high quality of water produced, even though every
plant unit and piece of equipment has been down at some time for service
or repair. There is no reason why wastewater plants cannot be just as
reliable as power generation stations or water purification plants if they
are designed and operated with this intent.
Costs. Capital and operating costs are important factors in
process selection. It is obviously false economy to use a process which
will not do the job merely because it is cheap to install and operate. If
the designers has a choice between a proven process with a high degree
of reliability and a process which may be cheaper, but is of unknown or
questionable reliability, then prudence is on the side of the more costly
but workable process.
Plant size exerts some influence on process selection. The capac-
ity of the Tahoe plant justifies the use of granular activated carbon with
regeneration facilities, where smaller plants might use powdered carbon
on a once-through, throw aw ay basis. The size of plant and distance to
28
-------
sludge disposal sites also dictates the use of equipment for recalcining
and reuse of lime, while smaller plants or other locations might indicate
alternate sludge handling methods or the use of chemicals other than
lime.
Awkward Process Combinations. One special word of caution is
appropriate with regard to the attractive and tempting possibility of com-
bining various processes into a single process or into a single structure.
By reducing the total number of structures, there are obvious savings in
construction costs. Actually, this initial cost saving is usually the only
advantage of combining processes, and there may be many disadvantages.
The history of water and wastewater treatment is replete with failures to
satisfactorily combine two or more processes. Yet, some of these mis-
takes are perpetuated in present day designs, and new unworkable combi-
nations may be devised. This is not to say that some of these efforts may
not end in success, but only to inject a word of caution and to point out
some of the inherent weaknesses in making one process out of two or more.
First of all, there is invariably a loss of control or flexibility in operation
by combining two processes. A change which benefits one of the process-
es may interfere with or reduce the efficiency of the other. Also, in plant
operation, it is much more difficult to relate cause and effect, which is
necessary to make treatment adjustments, because of the greater complex-
ity introduced by the combination. There are many specific examples
which can be presented.
Upflow solids contact basins of the sludge blanket type combine
the four processes of rapid mixing, flocculation, settling, and solids re-
cycling in a single unit. They have been applied successfully to treat-
ment of a constant flow of waters (principally well waters) which are of
constant physical and chemical quality, at a considerable savings over
the use of four separate operations. However, these sludge blanket bas-
ins are often not stable when operated at varying flow rates, or with
waters which have significant variations in chemical composition or phy-
sical characteristics, such as temperature or organic content. It may be
difficult to change the point of chemical addition in this type of basin if
it becomes necessary. Also with changes in flow rate, chemical compo-
sition, or physical character of the applied water, or with the accumula-
tion of organics in the sludge blanket, the chemical dosages required to
maintain a sludge blanket of the proper density change so frequently and
rapidly as to present an impossible operating condition, and the basin
fails to function as a settling device. Wastewaters possess properties
which make operation of sludge blanket clarifiers difficult. Some plant
experiences indicate that this type of equipment can be used satisfactorily
29
-------
for wastewater treatment if the overflow rates are the same as for a con-
ventional horizontal flow clarifier, and if the sludge is removed from the
basin as rapidly as it reaches the bottom of the tank. Separate rapid mix-
ing, flocculation, and settling basins with provisions for external sludge
recirculation appear to be more satisfactory than solids contact basins for
treatment of wastewater. Mutual interference is avoided, and complete
flexibility of operation and control is afforded.
Difficulties and high costs may be involved in dewatering organic-
chemical sludge mixtures in some wastewaters. Combining high lime or
alum treatment with primary settling with the elimination of a separate
chemical clarifier, or even going further and eliminating biological treat-
ment, offers potential savings which are quite substantial. The possibil-
ities certainly warrant investigation in each instance to see of there is a
sludge dewatering problem, and, if so, if there is an economical solution
to it. This should be done on a pilot plant scale before undertaking the
building of a full scale plant.
Combining chemical treatment with activated sludge treatment for
phosphorus removal also presents some practical difficulties at full plant
scale which should not be overlooked, even though there may be ways to
solve the problems. Additon of lime or alum to aeration tanks secures
excellent phosphorus removal. The difficulty is that the inert chemical
sludge accumulates and selectively displaces the culture of activated
sludge organisms over a period of a few weeks, and normal biological
treatment ceases. Because of the differences in specific gravity between
the chemical and biological sludges it may be possible to separate them
and return or waste them as necessary to control the process, but this re-
mains to be demonstrated on a plant scale.
Combination downflow carbon contactor-filters are used success-
fully in water treatment plant practice where there are low suspended
solids in the applied water. However, the carbon contactor-filter is a
surface filter, and not an in-depth filter, and as such is subject to the
same limitations as any other surface filter in filtering wastewater. The
use of granular carbon as a contactor-filter has all of the same disadvan-
tages of other surface filters plus the additional one of being a much deep-
er bed, which is more difficult to properly clean by backwashing than a
shallower bed. Also, the use of carbon as a filter to remove suspended
and colloidal matter from the water is likely to blind the carbon pore open-
ings and require removal of the carbon from the bed before its full adsorp-
tive capacity is exhausted.
Flocculation and settling of organics and lime sludge in the same
30
-------
basin poses another problem if the lime is to be recalcined and reused.
Calcium carbonate has been recalcined and organics incinerated suc-
cessfully in a single furnace. However, this means that the recalcined
lime contains considerable inert ash. There are two choices, the ash can
be recycled with the recalcined lime, or some means can be devised to
separate the lime from the ash. If the ash is recycled with the lime it
becomes wet again and there are extra costs for fuel for repeated drying
of the ash on subsequent cycles. It is necessary to waste about 25 to
35 percent of the recalcined lime on each cycle of use to rid the system
of phosphates, and a similar portion of the recycled ash would automat-
ically be wasted in the same operation. This would be an acceptable way
to operate, and the decision as to whether to settle and incinerate organ-
ics and chemical sludge together or separately can be resolved by a rigid
cost analysis including, of course, all capital and operating costs.
Whether to attempt to separate the ash from the reclaimed lime as opposed
to recycling the ash with the lime also is strictly a matter of comparative
costs, assuming that either a wet separation or a dry separation can be
made successfully.
These examples should serve to illustrate some possible problems
which may be encountered when attempting to combine two or more unit
processes into a single unit. Combining processes usually complicates
operation and control and decreases reliability, while the designer should
be seeking to simplify operation and control, provide maximum flexibility
of operation, and insure greater reliability. There is no point in combin-
ing two perfectly good unit processes into one poor one. Because of the
potential savings, efforts to determine workable combinations should
certainly continue.
In the South Tahoe plant separate basins are provided for chemical
mixing, flocculation, and clarification. External sludge recirculation is
provided. Separate filters and carbon contactors are used. These arrange-
ments have proved to be eminently satisfactory.
Storage. One way to reduce capital costs for construction of
advanced wastewater treatment plants is to introduce storage of waste-
water at some point in the system. This should be done after the water
has received sufficient treatment so as not to create a nuisance on stand-
ing. Sufficient storage should be provided to allow the sections of the
plant which follow the storage to operate at the average rate for the design
maximum day rather than at the peak hourly rate for the maximum day. A
rough rule of thumb for separate sanitary sewer systems is to build at
least 1.5 to 2.0 million gallons of storage for each 10 mgd of plant cap-
acity. The exact requirements vary for each individual collection system,
31
-------
and the rule of the thumb does not apply to systems receiving sanitary
sewage plus storm water.
At Tahoe, about 2 mg of storage is provided just after secondary
recarbonation and just ahead of filtration. This provides storage for back-
washing water and equalizes flow through the filters and carbon columns
which are designed to handle maximum daily rather than peak hourly flows.
Disinfection. Virus and bacterial removal are important con-
siderations in wastewater treatment. At Tahoe, removal of these organ-
isms is virtually complete before chlorination so that the high quality
water, which has a very low chlorine demand, is ideal for complete disin-
fection by chlorination.
Summary. Since 1967, when the Tahoe treatment process was
finalized, the unit processes and their sequence have been under constant
observation and review both in the light of plant operating experience and
new developments in the field at other locations. There is a constant
search for improving the process. However, despite this concern and
continuous reevaluation and reexamination, under the conditions at Tahoe,
this flow sheet still appears to be the best. It must be pointed out that
other conditions will require other solutions to optimize results and costs
to accomplish different treatment objectives. In general, it is believed
that these solutions to be used under other conditions will consist of elim-
inating certain steps which are unnecessary rather than in combining them
or in changing the sequence of unit processes.
32
-------
SECTION VI
THE TAHOE PROCESS FOR WASTEWATER
RECLAMATION
Water Reclamation Plant. The South Tahoe water reclamation
plant is the most advanced full-scale wastewater treatment plant In the
world, although other similar plants are now under construction In other
places.
Treatment of wastewater consists of two basic parts, liquid
processing and solids handling. The first two steps of liquid processing
are the conventional ones of primary,or solids separation, and secondary,
or biological oxidation. In addition, the advanced treatment provides
chemical treatment and phosphate removal, nitrogen removal, mixed-
media filtration, activated carbon adsorption, and disinfection.
The solids handling system provides for incineration of biolog-
ical sludge, regeneration and reuse of granular activated carbon, and
recalcining and reuse of lime, all by means of multiple hearth furnaces.
The furnaces are equipped with scrubbers and after-burners to prevent
air pollution.
A detailed description of the treatment plant processes will be
given in the normal order which they occur in flow through the plant,
first for the liquid processing and then for the solids handling.
Figure 5 is a schematic flow and process diagram.
Liquid Processing. All wastewater Is pumped to the reclam-
ation plant. Plant influent may be prechlormated for odor control. The
raw wastewater is then passed through a barminutor which screens and
shreds the coarse solids, then through Parshall flumes which measure
the plant inflow.
The water then passes to either or both of two primary settling
tanks where the liquids and solids are separated by sedimentation. In
addition to the raw wastewater, the primary tanks may also receive the
overflow from the lime mud thickener, and the centrate from the lime
centrifuge or the sludge centrifuge. If desired, lime or polymer may be
33
-------
SECONDARY
TREATMENT
(BIOLOGICAL
TREATMENT)
PRIMARY
TREATMENT
(SOLIDS
SEPARATION)
CHEMICAL TREATMENT
AND
PHOSPHATE REMOVAL
MAJOR TYPES
OF TREATMENT
PROVIDED
NITROGEN
REMOVAL
OM6 EMERGENCY
HOLDING POND.
RECLAIMED
WATER TO
INDIAN
CHEEK
RESERVOIR
RETURN TO
SECONDARY BALLAST
POND AT PLANT
FLOWM
MO DIVISION
BMMINUTORS
AMMONIA
STRIPP1NO
TOWER
LUTHER PASS -
BOC-STER PUMP
STATION
WASTE WATER
FLOW
THROUGH
PLANT
SECONDARY
CLARIFIERS
TERTIARY
PVHf
STATION
PLANT INFLUENT
FORCE MAINS
PRIMARY
SLUOOE PUMPS
SECONDART\
SLUOOE PUMPS
BACKWASH
WATER
DECANTING
TANK
* SLUDGE FLOW
DIVISION BOX
WASTE ACTIVATED
SLUOOE
SOLIDS
HANDLING
LIME AND
CARBON
RECLAWA'ION
BIOLOGICAL
SLUOCE PUMP
RECALCINED LIME
TO RE-USE
REGENERATED
CARBON TO
RE-USE
FIGURE 5
SCHEMATIC FLOW AND PROCESS DIAGRAM
-------
added ahead of the primary tanks. One of the primary tanks is a rectang-
ular basin, and the other Ls a circular basin. Both are equipped with
mechanical collectors for continuous sludge removal.
The next step in the process is secondary treatment or biological
oxidation. One-third of the plant capacity utilizes the conventional plug-
flow activated sludge process with diffused air. The other two-thirds of
the secondary treatment capacity is provided by a complete mix system
using a combination of diffused air and mechanical mixing, or surface
aeration. Secondary settling takes place in either of two circular basins,
each of which has its own sludge recirculation pump station. Chlorine
may be added to the secondary settling basin influent for control of sludge
bulking as necessary.
Secondary settling is the end of the processing in conventional
treatment plants, so that the additional treatment provided beyond this
point is all in the nature of advanced waste treatment.
The secondary effluent together with waste filter backwash water
enters a rapid mix basin where violent mechanical stirring occurs, and
where lime is added to pH=ll+, which corresponds to a dosage of about
400 mg/1 of lime. Next comes a period of slow mixing and flocculation
by air agitation. Following this, a polymer is added, usually in the
amount of about 0.1 mg/1, as the flocculated high-pH water flows to the
chemical clarifier. The chemical clarifier, a circular basin, separates
the liquid from the rather large quantities of lime sludge.
Overflow water from the chemical clarifiers flows by gravity to
a sump where either of two pumps lifts it to the top of the nitrogen re-
moval tower, the first tower of its kind used in a municipal wastewater
plant. The tower has a nominal capacity of 3.75 mgd (one-half plant
capacity), and is the only part of the full-scale plant which is still con-
sidered to be experimental in nature. Water pumped to the tower has
pH=ll+, indicating that the ammonia is virtually all present as dissolved
gas, rather than as ammonium ion in solution. Large quantities of air
must be circulated through the tower for best efficiency, so that an open
packing must be used in the tower to minimize head losses and power
requirements for the circulating fan.
The water is distributed uniformly from a horizontal tray across
the top of the packing, which is made of treated hemlock slats spaced at
1.5 in. vertically and 2 in. horizontally. As the water strikes a slat,
droplets are formed. Surface film thickness in the droplets is at a mini-
mum as they are forming, and this favors the escape of ammonia gas from
the droplet. By circulating a great amount of air through the tower, the
35
-------
air surrounding the droplet is kept at a low ammonia concentration, pro-
moting a maximum transfer of ammonia from the water to the air. Once
droplets are fully formed, very little further transfer of ammonia takes
place, so the droplets are coalesced on top of the next slat below and
new droplets are formed as the water falls off the slat, allowing further
escape of the ammonia. This process is repeated about 240 times in one
pass through the 24-ft-high tower.
Air in the tower flows across the descending droplets. The air
enters through the side louvers and travels horizontally to a central
plenum, where it is discharged vertically upward through a fan that has a
maximum capacity of 700,000 cfm. Tower loading rates are about 2.9gpm
of water per square foot, and about 390 cfm of air per gallon of waste-
water. The efficiency of the tower in removing ammonia will vary from
30 to 98 percent, depending principally upon air and water temperatures
and to a lesser extent upon hydraulic loading and air supply.
From the catch basin beneath the nitrogen removal tower, the
tower effluent passes over a weir for flow measurement, and then into
another basin beneath the tower, which contains three sections. The
first section is the primary recarbonation basin. Here, carbon dioxide
gas, supplied by compressing stack gasses in the incinerator building,
is dissolved in the water to lower the pH from 11 to 9.6. The recarbon-
ated water is then held in a contact basin for 30 minutes or more to allow
complete formation and some settlement of calcium carbonate. This basin
is equipped with equipment for continuous sludge removal. The third
section of the basin is the secondary recarbonation chamber, where the
pH is reduced from 9. 6 to any desired level, usually 7.5, by further
addition of carbon dioxide.
The recarbonated water then flows through two ballast ponds in
series. The ballast ponds are used to store water for backwash ing the
mixed-media filters, and to reduce peak flows to the filters and carbon
columns.
Water is pumped from the ballast ponds to the filters and carbon
columns. Ordinarily about 5 mg/1 of alum are added to the filter influent
water. Three pairs of mixed-media filter beds, developed especially for
filtering waste water, handle the plant flow.
The mixed-media bed, with pores graded coarse to fine in the
direction of flow, is composed of coarse coal, with a specific gravity of
1.4; medium-sized sand, with a specific gravity of 2.65; and fine garnet,
with a specific gravity of 4.5. A properly graded bed made of these
materials i~nvides an almost ideal coarse-to-fine filter. Because of the
different specific gravities of the three materials, the particles retain
their desired position in the depth of the bed during backwash ing. The
36
-------
fine filter media is supported on a conventional bed of graded gravel, to
which has been added an important new feature, a 3-in. layer of 16-mesh
garnet. This extremely heavy material (specific 4.5) positively prevents
any movement of the gravel bed below, and also prevents any penetration
of the fine garnet above into the gravel supporting bed. The filters are
equipped with rotary surface washers, and rotation indicator lights. Good
surface wash is essential to proper operation of the coarse-to-fine filters
because of the large quantities of particulates removed from the water and
stored throughout the depth of the bed.
Each pair of beds comprises a filter unit, and they operate in
series both during filtration and backwash. A total depth of 6 ft of fine
media is provided in each pair of beds. With coarse-to-fine filters, the
length of filter run is almost directly proportional to the depth of fine
media, so that the length of run for the two beds in series is about double
that for a single bed. By backwashing the two beds in series, about half
as much backwash water is discharged to the decant tank and then return-
ed at a slow rate to the rapid-mix basin for reprocessing.
When a pair of filters is plugged or no longer produces a high
quality effluent, it is automatically taken off the line, backwashed,
filtered-to-waste, and restored to service. This is all done automatically
and monitored through a control panel located in the filter building.
The filtered water next flows under pressure to the eight carbon
columns, which operate in parallel. Each column is 12 ft in diameter by
24 ft high, and contains about 22 tons of 8 X 30 mesh granular activated
carbon. Flow in the columns is of the moving bed, countercurrent type -
that is, water flows from the bottom to top of the column, while movement
of the carbon is down, the fresh carbon being added at the top and the
spent carbon removed at the bottom. This system permits frequent removal
and corresponding addition of carbon for maximum operating efficiency.
The water is in contact with the carbon for a period of 15 to 25
minutes, during which the adsorption of organics by the carbon takes
place. The carbon column effluent is colorless, odorless, low in organics,
and sparkling clear.
The high quality of the water following complete treatment vastly
improves the efficiency of chlorination, the final step in the liquid pro-
cessing. As compared to chlorination of ordinary secondary effluent, the
chlorination of the reclaimed water at South Tahoe is many times more ef-
fective, as virtually all of the chlorine-demanding materials, except am-
monia, present in the secondary effluent have been removed. With rapid
violent mixing at the point of chlorine application, good disinfection can
37
-------
be accomplished in the presence of ammonia. One explanation offered is
that chlorine reacts more rapidly with bacteria and viruses than with am-
monia .
Solids Handling System. As mentioned previously, all solid
plant wastes are processed in multiple hearth furnaces. The biological
and waste chemical sludges are incinerated, the lime mud is recalcined
and reused in the process, and the spent granular carbon is regenerated
and reused.
The materials to be incinerated include primary and waste activ-
ated sludge, waste chemical sludge, screenings, skimmings, and the
centrates from the lime and sludge centrifuges.
A mixture of all of these materials is pumped to the sludge cent-
rifuge, which operates at about 1,600 rpm, where a polymer is added and
the sludge is partially dewatered to a solids content of about 19 percent in
the cake. The cake is conveyed by belt to a multiple hearth furnace; the
fuel is natural gas. The furnace is operated at about 1,600 °F and re-
duces the sludge to an insoluble sterile ash, which may be disposed of on
the plant grounds. The furnace stack gas is cooled to 110°F and scrubbed.
There is no odor, smoke or steam plume, and the discharges meet all air
pollution codes. "When the sludge dewatering or incineration equipment is
out of service, the old sludge digesters may be used for sludge storage.
Handling of the spent lime mud is similar to that just described
for biological sludge. Lime sludge from the chemical clarifier is pumped
to a sludge thickener which thickens the sludge to about 8 percent solids.
The thickened sludge is then pumped to a centrifuge for further dewatering
at 1,600 rpm. The cake contains about 40 percent solids. The lime is re-
calcined at about 1,850°F to a calcium oxide content of about 50 to 80 per-
cent. Again the stack gas is cooled and scrubbed so that there is no air
pollution. Only about 75 percent of the lime sludge is recalcined and re-
used. The other 25 percent is wasted, mostly hydroxyapatite, in the cen-
tra te to the primary clarifier and thence to the sludge furnace, or directly
to the sludge furnace. Alternately, the centrate from the lime centrifuge
can be dewatered in a second centrifuge and the cake incinerated in the
sludge furnace.
The recalcined lime is conveyed pneumatically to a storage bin,
and then reused in the process. Makeup lime is unloaded from trucks
pneumatically and stored in a separate bin. Separate gravimetric feeders
and slakers are provided for the recalcined and makeup lime. Many of the
furnace operations are controlled from a panel on the main floor of the in-
cineration building.
38
-------
The carbon regeneration equipment is located in the filter build-
ing. After the carbon becomes saturated with materials removed from the
wastewater, it loses its capacity to absorb certain organics, and must be
regenerated. Originally in 1965, a break-through of MBAS (or detergents)
was the indicator that regeneration was needed. With the advent of the
soft detergents, a high COD content in the carbon column effluent has
become the indicator. In regeneration a carbon column is pressurized
and the carbon slurry is drawn off the bottom of the column to one of the
dewatering bins. Here the free moisture drains off in about 10 minutes,
leaving carbon with a moisture content of about 40 percent, which is
suitable for introduction of carbon to the furnace. Spent carbon is fed to
the furnace at a controlled rate by a screw conveyor equipped with vari-
able speed drive. The carbon regeneration furnace is operated at about
1,700°F in a limited oxygen atmosphere with the addition of steam. The
rate of feed to the furnace and the hearth temperatures are controlled by
the apparent density of the regenerated carbon, which is held at 0.48 to
0.49. As a check on regeneration efficiency, iodine numbers ( a relative
measure of adsorptive capacity) are run on carbon samples in the laboratory.
The carbon is regenerated to full virgin activity with an attrition loss that
is about 8 percent per cycle. The regenerated carbon is cooled in a quench
tank, pumped by a diaphragm slurry pump to wash tanks, washed to remove
carbon fines, and then returned to the top of the carbon column.
39
-------
SECTION VII
PLANT DESIGN DATA
The principal design criteria for the South Tahoe Water Recla-
mation Plant are tabulated below.
Item
Amount
Plant design average flow
Peak flow rate (except as noted below)
Peak flow rate (filters and carbon columns)
Maximum hydraulic rate
Plant design BOD (summer)
Plant design BOD (winter)
Plant suspended solids (summer)
Plant suspended solids (winter)
Water temperature (summer)
Atmospheric pressure (elevation 6,300 ft)
7.5
15.0
8.2
20.0
325
250
200
150
17°
11.6
mgd
mgd
mgd
mgd
mg/1
mg/1
mg/1
mg/1
C
psi
Primary clarifier No. 1
Surface area
Flow
Overflow rate
Primary clarifier No. 2
Surface area
Flow
Overflow rate
Aeration basins 1,2, and 3, plug flow
Flow
Volume
Detention (without recycle)
BOD loading
2,350 sf
2.7 mgd
1,150 gpd/sf
7,850 sf
4.8 mgd
610 gpd/sf
2.7 mgd
115,000 cf
7.5 hrs
50 lbs/1,000 cf
41
-------
Item
Amount
Aeration basins 4 and 5, complete mix
Flow
Volume
Detention (without recycle)
BOD loading
Secondary clarifier No. 1
Surface area
Overflow rate
Secondary clarifier No. 2
Surface area
Overflow rate
Sludge recirculation
Secondary clarifier No. 1
Secondary clarifier No. 2
Sludge
Primary, dry solids
Waste activated, dry solids
Rapid mixer, mechanical
Chemical feed equipment
Gravimetric lime feeders and slakers
Recalcined lime
Makeup lime
Liquid alum feeders
Two, each
Polymer solution feed pumps
Four, each
Chemical storage
Recalcined lime
Makeup lime
Liquid alum
4.8 mgd
137,000 cf
5 hrs
70 lbs/1,000 cf
2,830 sf
900 gpd/sf
7,850 sf
700 gpd/sf
1,380
3,840
8,130
9,760
30
1,500
1,500
50
50
35
35
10,000
gpm
gpm
Ibs/day
Ibs/day
seconds
Ibs/hr
Ibs/hr
gph
gph
tons
tons
gals
42
-------
Item
Amount
Flocculation chamber
Air Mix
Chemical clarifier
Flow
Surface area
Overflow rate
Lime sludge pumps
Centrifugal
Progressive cavity displacement
Lime mud thickener
Flow
Surface overflow rate
Surface dry solids loading
Thickened sludge solids
Ammonia stripping tower, cross-flow
Wastewater flow
Fill (packing):
Area
Height
Splash bars
Spacing, between centerlines
Vertical
Horizontal
Recarbonation, two-stage with
intermediate settling
Flow
Carbon dioxide compressors
No. 1
No. 2
No. 3
Reaction basin
Detention
Surface overflow rate
Ballast pond capacity
No. 1
No. 2
4.5
mins
7.5 mgd
7,850 sf
950 gpd/sf
450
100
gpm
gpm
450 gpm
1,000 gpd/sf
200 Ibs/day/sf
8-20 %
3.75
900
24
3/8" x :
1.33"
2"
7.5
500
1,000
950
mgd
sf
ft
mgd
cfm
cfm
cfm
30 mins
2,400 gpd/sf
1.0
1.5
mg
mg
43
-------
Item
Amount
Pumps to tertiary plant
No. 1
No. 2
No. 3
Surface wash booster
Mixed media filters
Flow
Units, 3 sets of 2 series beds
Hydraulic loading
Backwash rate
Area each bed
Surface wash flow
Waste backwash water receiving tank
Capacity
Carbon columns (8),upflow counter current
Flow
Carbon volume, each column
Carbon depth, effective
Contact time
Hydraulic loading
Chlorination equipment
Three feeders, each
Carbon regeneration furnace, 6-hearth,
54-inch diameter, gas-fired
Capacity, dry carbon
Sludge dewatering equipment, concurrent
flow centrifuges, 24" x 60"
Organic sludge
Number
Capacity, each, dry solids
Lime sludge
Number
Capacity
1,900
3,800
4,200
500
8.2
gpm
gpm
gpm
gpm
mgd
5 gpm/sf
15 gpm/sf
380 sf
0.6 gpm/sf
80,000 gals
8.2
1,810
14
17
mgd
cf
ft
min
6 .5 gpm/sf
2,000 Ibs/day
6,000 Ibs/day
450 Ibs/hr
1,650 Ibs/hr
44
-------
Item Amount
Sludge incineration furnace, 6-hearth
14'-3" diameter, gas-fired
Capacity, dry solids 900 Ibs/hr
Lime recalcining furnace, 6-hearth
14'-3" diameter, gas-fired
Capacity, dry CaO 10 tons/day
45
-------
SECTION VIII
EXPORT SYSTEM
Description. The export system involved four separate major
projects: The Luther Pass Pipeline, Luther Pass Pump Station, Indian
Creek Pipeline and the Indian Creek Dam.
The Luther Pass Pipeline extends approximately 77,000 feet
from the treatment plant at South Lake Tahoe to Luther Pass. This line
has an initial design capacity of 7.5 mgd and is designed for expansion
to 15 mgd when necessary. The line is 55,000 feet long between the
water reclamation plant pump station and the Luther Pass Pump Station.
This section, consists of 2 4-inch-diameter pipe and has a maximum oper-
ating pressure of 170 psi at design flow and a static head of 265 feet.
The section from the Luther Pass Pump Station to Luther Pass is
about 22,000 feet long; the first 10,000 feet is a 20-inch line, and the
remainder, 24-inch. The pipeline leaving the station rises rapidly from
elevation 6,500 to elevation 7,400 in a horizontal distance of 6,500 feet.
The pipeline continues to rise, climbing from elevation 7,400 to elevation
7,700 in the next 6,000 feet. The last portion of the line is quite flat,
rising from elevation 7,700 to elevation 7,735 at Luther Pass in a distance
of 10,000 feet. Construction of the Luther Pass Pipeline began in Septem-
ber, 1966 and was completed in December, 1967.
The Luther Pass Pump Station is located near the end of the •
Upper Truckee Valley at the bottom of Luther Pass. It is the main export
station and lifts the water from elevation 6,500 to elevation 7, 735-at the
summit of Luther Pass, a static head of 1,235 feet. The total operating
head at design flow is 1,320 feet. The station has an initial design
capacity of 7.5 mgd, and can be expanded to an ultimate capacity of 15
mgd. Three pumps were initially installed; one 1,000 hp and two 700 hp.
The pumps are horizontal, double volute, multi-staged, centrifugal type,
driven by constant speed electric motors - the motors are 3, 500 rpm,
2,300 volts. The pump operation is automatically controlled by water
level in an adjacent 1, 000,000-gallon steel reservoir. The control system
provides for staged pump operation with one or more pumps running,
47
-------
Figure 6
LUTHER PASS PUMP STATION
48
-------
depending on the incoming flow rate. The station is designed for auto-
matic operation, incorporating a variety of alarms and automatic shut-
down features, all of which are transmitted to the water reclamation plant.
The pumps are normally started, or stopped, through pump con-
trol valves designed to provide a controlled opening and closing time to
eliminate pressure surges in normal operation. In the event of power
failure or any circumstance involving pump failures, pressure surges of
dangerous magnitude will be prevented by surge suppressor valves located
upstream of the pump control valves. In the event of power failures, the
pump control valves close immediately, due to check valve action; the
surge suppressors open within a few seconds and allow the pipeline to
discharge to atmosphere. The surge suppressors then close slowly through
a timed operating cycle, and allow the water column to be brought to rest
without pressure surges. Construction on the station started in September,
1966 and was completed in January, 1968.
The Indian Creek Pipeline begins at the summit of Luther Pass
and extends approximately 62,000 feet easterly into the Diamond Valley
area of Alpine County. This line has a design capacity of 15 mgd and
consists of 18-inch and 21-inch cement-mortar-lined steel pipe. The line
is designed for gravity flow, and the average slope exceeds 5 percent.
The elevation at the beginning is 7,735, and at the terminus, 5,600.
Construction began in June of 1967 and was completed in December 1967.
The final project in the export system is the Indian Creek Dam.
This dam is located on a normally dry tributary of Indian Creek. This
project actually contains two dams. The main dam extends 67 feet above
stream bed with a crest length of 1,440 feet. In addition, there is a
saddle dam approximately 20 feet high and 800 feet long. Both dams are
of earth and rock-fill construction, utilizing native materials from within
reservoir site. The dam creates a reservoir with a maximum capacity of
3,225 acre-feet at a water surface elevation of 5,600 feet with a surface
area of 165 acres. The reservoir will provide storage of the reclaimed
water which will be disposed of on downstream ranch lands during the
irrigation season. The irrigation function is a definite asset for this area
of Alpine County. In addition to the irrigation benefits, a rainbow trout
fishery has been established in the Reservoir. The State regulatory
agencies, including the California State Department of Public Health,
have approved the use of the Reservoir for all water contact sports and
fishing. Construction of the dam and reservoir started in July, 1967, and
the project was completed in December, 1967. Filling of the Reservoir
began in March 1968. It was opened for trout fishing on May 2, 1970.
See Figure 7.
49
-------
Figure 7
INDIAN CREEK RESERVOIR
DURING INITIAL FILLING
50
-------
These four projects represent the backbone of the reclaimed
water export system. The system is unique in that it transports water
sufficiently pure, so that it can be directly reused, out of the Tahoe
Basin, over mountains requiring a 1,600-foot pump lift to a point 27 miles
from the treatment plant for final disposal.
51
-------
SECTION IX
OPERATOR TRAINING
Introduction. The successful performance of any wastewater
treatment plant depends largely upon the training and ability of the men
who are responsible for its operation, and upon the effort and attention
which they devote to their duties. Good performance is also dependent
upon the consulting engineer to design a plant which is capable of pro-
ducing a finished effluent which satisfies all requirements for discharge
or reuse, including those minimum criteria established by local, state,
and federal regulatory agencies. Further, the owner or operating agency
must provide sufficient funds for proper operation and maintenance of the
treatment facilities. Once these preliminaries have been accomplished
by the engineer and owner, then the success or failure of the plant in ful-
filling its objectives is in the hands of the operating staff. The operators
are responsible for the quality of the treated wastewater and its effects
upon the receiving natural waters. They are also responsible for the
service life of the plant and equipment, costs for operation and mainten-
ance, appearance of the buildings and grounds, keeping of adequate
records, and for establishing and maintaining good public relations.
Good plant operation requires not only the ability to operate,
maintain, and repair mechanical equipment, but also a working knowledge
of hydraulics, bacteriology, and chemistry. Except in very large waste-
water treatment plants, it is unusual to find a graduate engineer, chemist
or bacteriologist involved in operations. Most wastewater treatment
plant operators must be hired locally and trained on the job. The engineer
and owner must recognize the benefits which accrue from good operation
and provide adequately financed and supervised on-the-job training.
This training must start even before the plant is first placed into operation
and must continue as required in order to train new employees and to in-
form experienced operators of new developments.
South Tahoe Training Program. Prior to startup of the 7.5 mgd
advanced waste treatment plant, an on-the-job operator training program
was conducted. This course consisted of 33 two-hour sessions which
were held during a seven week period. Duplicate sessions were held,
53
-------
one from 7 to 9 A.M. and the other from 4 to 6 P.M., in order to accommod-
ate operators from all shifts. Operators were paid for their time in class.
This should be done to indicate to the operators that management recog-
nizes that adequate training is important. There is no substitute for on-
the-job training for this work. It can be supplemented by academic
training or short courses, but some on-the-job orientation is absolutely
necessary. The instructors for the training course included the district
manager, and representatives of the consulting engineers, construction
contractors, and major material suppliers. All of these people were also
paid for their time spent in the school.
The main text for the course was an Operations Manual which
was prepared by the consulting engineers and paid for by the District.
This manual contained more than 200 pages of material including: a dis-
cussion of the purposes of treatment and the plant processes provided to
accomplish the desired result; complete illustrations of plant flow patterns
under normal operating conditions, alternate flow patterns, and flow rout-
ings for emergency situations; complete description of each part of the
plant process and the equipment provided for carrying it out; a discussion
of all methods for control of plant operation including sampling and labor-
atory tests; and forms for reporting analyses, recording flow and operating
information, and summarizing all plant data on a monthly or weekly basis.
Other source materials were also provided including: copies of
the preliminary report; the construction plans and specifications; shop
drawings; and all suppliers' catalogs and installation, operation, and
maintenance instructions. Recent text books on water and sewage treat-
ment and technical magazines in the field were also provided. In labora-
tory training, only two or three operators were assigned to each instructor,
so that each operator could actually perform all of the tests under close
supervision. The results of this training program were excellent. If the
training had not been provided the plant doubtless never would have been
operated successfully. During three years of plant operation there has
been virtually no turnover in operating personnel, and the quality of opera-
tion as reflected in plant performance continues to improve.
To recruit and maintain a staff of good operators and maintenance
men, they must be adequately paid and otherwise compensated. The
current 1970-1971 pay classifications at South Tahoe are tabulated below:
54
-------
1970 - 1971
Job Classification Salary Range
Chief Operator $880 - $1,134
Senior Operator 763- 1,007
Operator, Grade I 715-885
Operator, Grade II 647 - 795
Solids System Operator, Grade I 737-912
Solids System Operator, Grade II 668-827
Plant Maintenance Supervisor $737 - $ 9 12
Plant Maintenance Mechanic 668 - 827
Plant Electrician 822- 1,071
Utility Man II 615 - 763
Operator Goals. In situations where there is a need for advanc-
ed wastewater treatment/as at Tahoe, there is also a need for much better
and more consistent operation than is commonly provided in primary or
secondary plants. The operation of primary and secondary plants is not-
ably erratic and subject to frequent interruptions and shutdowns, and many
suchplants are never operated to theirfull capability or maximum efficiency.
In general, the public is either not paying for good operation or is not
getting the kind of operation that could reasonably be provided within
available funds.
One of the objectives at South Tahoe was to demonstrate that a
wastewater plant could be operated as efficiently and particularly as con-
sistently as, say, a power generation station or a water purification
plant. Before the Tahoe plant was placed in service many people were
quite skeptical about the ability to keep what appeared to be a rather
complex plant in continuous, uninterrupted operation and to produce con-
sistently the high quality of water obtained in pilot plant tests of the
process. It was thought that the extensive on-the-job operator training
program would play an important part in securing the desired goal of good
operation. The Board of Directors, the District employees, and the con-
sulting engineers were all determined that the great effort and expenditures
which had gone into conceiving, designing, financing, and constructing
the plant would not be lost due to failure to properly operate or maintain
the facilities. There is no doubt that this attitude and determination on
the part of all parties directly involved with plant startup and its day-to-
day operation and maintenance were essential to the complete success in
all respects which was attained from the very start and during all three
55
-------
years of plant operation to date.
In almost every way the advanced treatment processes are
easier to operate, control, and maintain than are the conventional biolog-
ical processes of activated sludge and anaerobic sludge digestion. The
plant was designed to be fail-safe. Sufficient flexibility in modes of
operation and duplication of units are provided so that the plant can con-
tinue to operate with any unit out of service for servicing or repair. There
are by-passes around individual plant units, but there is no way to by-
pass the entire plant.
As will be seen later upon examination of the detailed operating
results, the South Tahoe Water Reclamation Plant has operated for the
three-year period to date continuously and without interruption, and the
high quality standards set by the regulatory agencies for the finished
water have been met continuously and without exception. There is no
longer any question whatever about the ability to practically operate the
advanced wastewater treatment processes incorporated in this plant to
their full theoretical potential. To do so does require adequate financing,
the determination on the part of everyone involved in operation and main-
tenance, and the transfer of the knowledge from the plant designers to
the operating personnel as to how the plant is intended to operate. There
is no doubt that a formal,organized,on-the-job training program is essen-
tial. At .South Tahoe,the dedication of the operating and maintenance staff,
the skills they have developed and demonstrated, and the pride they have
taken in setting a record of outstanding performance are a source of great
satisfaction to all concerned with the project.
56
-------
SECTION X
SAMPLE COLLECTION AND ANALYSIS
Automatic Sampling System. An automatic flow-integrated
sampling system was operated from June 1968 to February 1971 by means
of a flow activated timer. The rate of sewage flow entering the plant is
measured by Parshall flumes. The signal from the flumes is received by
an integrator-recorder which continuously records the gallons of sewage
passing and transmits a signal to activate the time for the sampling
system.
Pumps have been installed to supply a continuous stream of raw
sewage, primary effluent, secondary effluent, carbon column effluent, and
recarbonation basin effluent to the sample points. When the time is actu-
ated, a solenoid valve opens for a pre-selected time and the sample stream
flows into a one-gallon container. The sample containers are stored in
refrigerators until they are ready for use. Samples of filter effluent and
chlorinated final effluent are collected in a similar manner although pumps
are not used.
Schedule of Sampling and Testing. During the course of the
project there were two schedules used, one for the period of April 1968 to
July 1970, and the other for July 1970 to February 1971, when the number of
samples taken was reduced.
LABORATORY TESTING PROGRAM
April 1968 to July 1970
GRAVEYARD SHIFT
I, Pick up composite or grab samples (as necessary) from the follow-
ing plant streams: Raw, Primary Effluent, Secondary Effluent,
Separation Bed Effluent, Carbon Column Composite and Individual
Column Effluents, and Chlorinated Effluents.
57
-------
II. Unless specif Led, perform the following analyses on Monday,
Tuesday, Wednesday, Thursday, Friday:
P.O. - Basins 1, 2, 3, 4, 5 & weir (all days)
Settleable Solids - Mixed liquor, activated sludge (all days)
Suspended Solids - Mixed liquor, activated sludge (all days)
B.O.D. - Raw, Sep. Bed Eff., Final Eff. (Monday & Wednes.)
Prim. Eff., Sec. Eff. (Tuesday & Thursday)
Raw, CCComp., CC1-8, Final Eff. (Friday)
MBAS - Prim. Eff., Sec. Eff. , Sep. Bed Eff. , CC Comp. ,
CC1-8 (Tuesday & Thursday)
NO2~ Raw, Sec. Eff., CC Comp,
NO3~ Raw, Sec. Eff., CC Comp.
Alkalinity - Raw, Sec. Eff., CC Comp.
pH - CC Comp. (all days)
DAY SHIFT
I. Pick up grab samples, as necessary, to do required analyses.
II. a. Collect total solids samples from Primary under Flow 1 & 2,
day tank, sludge centrifuge cake and centrate, and lime
centrifuge cake. (Set up tests, Swing Shift will finish
them.)
b. Measure sludge centrifuge feed rate by drop in day tank at
time of sample collection.
c. Measure lime centrifuge cake feed rate and wet density
when collecting lime centrifuge cake sample.
III. Unless specified, perform the following analyses on Monday,
Tuesday, Wednesday, Thursday, Friday:
58
-------
P.O. - Basins 1, 2, 3, 4, 5 & weir (all days)
Settleable Solids - Mixed liquor, activated sludge (all days)
Suspended Solids - Mixed liquor, activated sludge (all days)
Chlorine - Final Eff., Luther Pass
COD - Prim. Eff., Sec. Eff., Chem. Clar. Eff., Sec. Recarb,
Eff., Sep. Bed Eff., CC Comp., CC1-8
PO4~Raw, Prim. Eff., Sec. Eff., Chem. Clar. Eff., Sec.
Recarb. Eff., Sep. Bed Eff., CC Comp.
Turbidity - Final Eff. (all days)
Total Solids - Final Eff. (See also Paragraph n a)
SWING SHIFT
I. Pick up grab samples, as necessary, to do required analyses.
II. Unless specified, perform the following analyses on Monday,
Tuesday, Wednesday, Thursday, Friday:
P.O. - Basins 1, 2, 3, 4, 5 & weir (all days)
Settleable^ Sol ids - Mixed liquor, activated sludge (all days)
Suspended Solids - Mixed liquor, activated sludge (all days)
Raw, Prim. Eff., Chemical Clar. Eff.,
Sec. Recarb. Eff., Sep. Bed Eff., Final
Eff., (Monday, Tuesday, Wednesday,
Thursday, Friday)
CaQ - Feed lime, recalcined lime from furnace, new lime
from truck.
Color - Sep. Bed Eff., CC Comp., CC1-8
Volatile Suspended Solids - Mixed liquor
59
-------
Total Volatile Solids - Sludge cent, cake
Total Solids - See Paragraph II a, Day Shift
Ca Hardness - Raw, Sep. Bed Eff., CC Comp. (Monday,
Wednesday, Friday)
Chlorides - CC Comp. (Tuesday, Thursday)
Sulfates - CC Comp. (Tuesday, Thursday)
NH3 - Raw, Sec. Eff., Strip Tower Eff., Final Eff.
LABORATORY TESTING PROGRAM
July 1970 to February 1971
GRAVEYARD SHIFT
I. Pick up composite or grab samples (as necessary) from the follow-
ing plant streams: Raw, Primary Effluent, Secondary Effluent, Re-
carbonation, Separation Bed Effluent, Carbon Column Composite
and Individual Column Effluents, and Chlorinated Effluents.
II. Unless Specified, perform the following analyses on samples
which were collected on Sunday, Monday, Tuesday, Wednesday
and Thursday:
P.O. - Basins 1, 2, 3, 4, 5 & weir (all days)
Settleable Solids - Mixed liquor, activated sludge (all days)
Suspended Solids - Mixed liquor, activated sludge (all days)
B.O.D. - Sep. Bed Eff., CC1-8, CC Comp., Final Eff.
MBAS - Sep. Bed Eff., CC1-8, CC Comp.
NO£ - CC Comp.
NO3 - CC Comp.
60
-------
Alkalinity - CC Comp.
pH - Floe basin, 1st Stage Recarb., 2nd Stage Recarb. ,
CC Comp. (all days)
DAY SHIFT
I. Pick up grab samples, as necessary, to do required analyses.
II. a. Collect total solids samples from Primary under Flow 1 & 2, day
tank, sludge centrifuge cake and centrate, and lime centrifuge
cake. (Set up tests, Swing Shift will finish them.)
b. Measure sludge centrifuge feed rate by drop in day tank at time
of sample collection.
c. Measure lime centrifuge cake feed rate and wet density when
collecting lime centrifuge cake sample.
III. Unless specified, perform the following analyses on Monday,
Tuesday, Wednesday, Thursday, Friday:
P.O. - Basins 1, 2, 3, 4, 5 & weir (all days)
Settleable Solids - Mixed liquor, activated sludge (all days)
Suspended Solids - Mixed liquor, activated sludge (all days)
Chlorine - Final Eff., Luther Pass
COD - Prim. Eff., Sec. Eff., Chem. Clar. Eff., Sec. Recarb
Eff., Sep. Bed Eff., CCComp., CC1-8
PO4 - Raw, Prim. Eff., Sec. Eff., Chem. Clar. Eff., Sec.
Recarb. Eff., Sep. Bed Eff., CC Comp.
Turbidity - Final Eff. (all days)
Total Solids - Final Eff. (See also Paragraph II a)
61
-------
SWING SHIFT
I. Pick up grab samples, as necessary, to do required analyses.
II. Unless specified, perform the following analyses on Monday,
Tuesday, Wednesday, Thursday, Friday:
P.O. - Basins 1, 2, 3, 4, 5 & weir (all days)
Settleable Solids - Mixed liquor, activated sludge (all days)
Suspended Solids - Mixed liquor, activated sludge (all days)
Raw, Prim. Eff., Sec. Eff., Chem. Clar.
Eff., Sec. Recarb. Eff., Sep. Bed Eff.,
Final Eff. (Monday, Tuesday, Wednesday,
Thursday, Friday)
CaO - Feed lime, recalcined lime from furnace, new lime
from truck.
Color - Sep. Bed Eff., CC Comp., CC1-8
Volatile Suspended Solids - Mixed liquor
Total Volatile Solids - Sludge cent, cake
Total Solids - See Paragraph II a, Day Shift
Ca Hardness - Raw, Sep. Bed Eff., CC Comp. (Monday,
Wednesday, Friday)
Chlorides - CC Comp. (Tuesday, Thursday)
Sulfates - CC Comp. (Tuesday, Thursday)
- Raw, Sec. Eff., Strip Tower Eff., Final Eff.
62
-------
SECTION XI
TEST PROCEDURES
General. The test procedures used in the course of this project,
with minor exceptions, are those prescribed by, "Standard Methods for the
Examination of Water and Wastewater", as prepared and published jointly
the American Public Health Association, the American Water Works Assoc-
iation, and the Water Pollution Control Federation, Twelfth Edition, 1965,
except for those test procedures which are described in detail, hereinafter.
CALCIUM OXIDE.
Procedure.
1. Crush lime and weigh 1.000 gm sample.
2. Disperse in 200 ml volumetric flask with small amount of
distilled water.
3. Add 50 ml Ammonium Chloride (NI^Cl) and mix with mag-
netic stirrer for 3 minutes.
4. Dilute to 200 ml, mix, and take 25 ml sample.
5. Add about 100 ml of distilled water to the 25 ml sample, add
3 to 4 drops of a 20% solution of triethanolamine, and adjust the pH to
12.0+with 20% NaOH.
6. Stir rapidly on magnetic stirrer and add Calcon indicator to
medium red color.
7. Titrate with EDTA to pure blue end point while stirring
rapidly to eliminate magnesium hydroxide floe interference.
8. If the end point is a violet color, and will not turn blue, the
sample has too much magnesium in it and a smaller aliquote than 25 ml
will be necessary. The percent available CaO should be corrected by
the ratio of 25 ml to the number of ml used in the smaller aliquote.
Calculation. % Available CaO=(mls EDTA) (Correction Factor)
Reagents.
1. Ammonium Chloride (NH4C1) - 10 percent. Add 100 gm
NH4C1 to small amount of water and dilute to 1 liter.
2. Sodium Hydroxide (NaOH) - 20 percent. Add 100 gm NaOH
to small amount of water and dilute to 500 ml.
3. EDTA (N
63
-------
Add 8.3 grams EDTA to about 500 ml water and put into
solution by adding NaOH pellets. Dilute to 1 liter.
4. Triethanolamine - 20 percent. Dilute 200 ml of triethan
olamine to 1 liter with distilled water
Standardization . Weigh out carefully 0.2 to 0.3 gms Calcium
Carbonate (CaCC^) and dissolve in 50 ml of water using concentrated
Hydrochloric Acid (HC1). Perform normal CaO analysis beginning with
step 3 . Record mis EDTA
Correction Factor = ***
, ^
(mis EDTA for Stand
)
.)
<56>
APPARENT DENSITY TEST FOR ACTIVATED CARBON .
1 . Weigh the 100 ml graduate cylinder supplied with the car-
bon shaker apparatus and record the weight in grams. (Weigh on trip
balance) .
2 . Pour a sufficient amount of the carbon to be tested into
the funnel at the top of the shaker, place the graduated cylinder under
the shaker, and fill to the 100 ml mark at the rate of 1 ml/sec.
3 . Weigh the graduate cylinder and carbon and record the
weight in grams.
4. To calculate the apparent density, determine the weight
of carbon in the full graduate and divide by 100.
Weight Carbon = Weight Full _ Weight Empty
Graduate Graduate
Apparent Density =
Carbon
5. Example
Weight Empty Graduate
Weight Full Cylinder
Weight Carbon
Apparent Density -
128.0 gm
176.6
48.6
0.486 gm/ml
64
-------
CARBON ASH ANALYSIS. Ash is defined as the mineral oxide con-
stituents of the carbon. Heating a sample to a temperature of 1750° F in
an oxidizing atmosphere will completely oxidize all carbon and convert
the mineral constituents to their respective oxides.
Procedure.
1. Grind a representative sample of carbon until 90 percent or
more will pass a 325 mesh screen (by wet screen analysis).
2 . Weigh 1.000 gram of pulverized sample into a weighed
Vycor glass crucible without cover (see Note 1).
3. Place crucible and contents into a muffle furnace, set at
1750°F for 3 hours.
4. Remove from furnace, cool indesiccator and weigh. (Save
crucible and ash for iron analysis, if desired).
5. Percent Ash is calculated as follows;
% Ash = 100 (final weight of crucible) - (original weight of empty crucible)
N ote s on MethpcL
1. Although it is preferable to use Vycor glass, 30 ml capacity
crucibles in this test, platinum or porcelain crucibles may also be used.
CARBON ISOTHERM PROCEDURE.
1. Pulverize a representative sample of the granular carbon
(a 10-20 gram sample is usually adequate) so that 95 percent will pass
through a 325 mesh screen. Oven dry the pulverized sample for three
hours, at 150°C.
2. Obtain a representative sample of separation bed effluent.
3 . Transfer four different weights of the oven dried pulverized
carbon to the test containers. Spent carbon use 15,30,50, and 100
milligrams. Regenerated carbon use 5,10,25, and 50 milligrams.
Stopped flasks or pressure bottles are satisfactory containers.
4. To one container add 500 ml of separation bed effluent
from a graduate cylinder, and clamp the container on a mechanical shaker.
65
-------
The samples must be constantly agitated during the isotherm test and a
mechanical shaker is desirable. A Burrell Wrist Action Shaker, Catalog
No. 75-775, is satisfactory. Agitate the mixture for the chosen contact
time. The container may be filled and placed on the shaker at ten or
fifteen minute intervals to give the analyst sufficient time to filter each
sample immediately after the contact time has elapsed. The same volume
of wastewater should be added to a container without carbon and subject-
ed to the same procedure in order to obtain a blank reading.
5. After the chosen contact time has elapsed, filter the con-
tents of the flask through either a laboratory pressure filter fitted with
asbestos disk or through a Buchner funnel containing a filter paper
(Whatman No. 3 or equivalent) inserted in a filter flask connected to a
vacuum. The blank should be filtered in the same manner as the other
samples. It is desirable to discard the first and last portions of the
filtrate and save only the middle portion of analysis.
6. Immediately initiate procedure for determination of the
chemical oxygen demand of the filtrate. MBAS (Methylene Blue Active
Substances) may also be determined at this time.
7 . Tabulate the data as shown in the following table. The re-
sidual solution COD or MBAS concentration, c, is obtained directly from
the filtrate analysis. The amount adsorbed on the carbon, x, is obtained
by subtracting the value of c from that of co, the influent concentration.
Dividing x by m, the weight of carbon used in the test, gives the amount
adsorbed per unit weight of carbon.
Tabulation of Isotherm Data
m ex x/m
Weight of Carbon Residual COD COD Adsorbed COD Adsorbed
(mg/1000 ml solu- mg/1 mg per Unit Weight
tion)
8 . On log paper plot c on the horizontal axis against x/m on
the vertical axis and draw the best straight line through the points , to
obtain the isotherm.
9. The theoretical ultimate adsorptive capacity l£| c0 can
be obtained by finding on the vertical axis the point where the influent
concentration, co, intercepts the isotherm.
66
-------
THE IODINE NUMBER OF ACTIVATED CARBON. The Iodine Number Is
defined as the milligrams of iodine adsorbed by one gram of carbon when
the iodine concentration of the residual filtrate is 0.02 normal.
Procedure.
1. Grind a representative sample of carbon until 90% or more
will pass a 325-mesh sieve (by wet screen analysis).
2. Dry the sample for a minimum of three hours in an electric
drying oven maintained at 150°C.
3. Weigh 1.000 gram of dried pulverized carbon (see Note 2).
4. Transfer the weighed sample into a dry, glass-stoppered,
250-ml Erlenmeyer flask.
5. To the flask add 10 ml of 5%-wt HC1 acid and swirl until
carbon is wetted.
6. Place flask on hotplate, bring contents to boil and allow
to boil for only 30 seconds.
7. After allowing flask and contents to cool to room tempera-
ture, add 100 ml of standardized 0.1 normal iodine solution to the flask.
8. Immediately stopper flask and shake contents vigorously
for 6 minutes.
9. Filter by gravity immediately after the 6-minute shaking
period through an E & D folded filter paper.
10. Discard the first 20 or 30 ml of filtrate and collect the re-
mainder in a clean beaker. Do not wash the residue on the filter paper.
11. Mix the filtrate in the beaker with a stirring rod and pipette
50 ml of the filtrate into a 250-ml Erlenmeyer flask.
12. Titrate the 50-ml sample with standarized 0.1 normal sod-
ium thiosulfate solution until the yellow color has almost disappeared.
13. Add about 2 ml of starch solution and continue titration
until the blue indicator color just disappears.
67
-------
14. Record the volume of sodium thiosulfate solution used.
15. Calculate the Iodine Number as follows:
x _ A - (2 . 2B x ml of thiosulfate solution used)
m weight of sample (grams)
_ N2 x ml of thiosulfate solution used
50
v
Iodine Number = ~ D
X/m = mg. iodine adsorbed per gram of carbon
NI = normality of iodine solution
N2 = normality of sodium thiosulfate solution
A = N! x 12693.0
B = N2 x 126.93
C = residual filtrate normality
D = correction factor (obtained from attached graph)
Notes on Method.
1. The capacity of a carbon for any adsorbate is dependent of
the concentration of the adsorbate in the medium contacting the carbon.
Thus, the concentration of the residual filtrate must be specified, or
known, so that appropriate factors may be applied to correct the concen-
tration to agree with the definition.
2. The amount of sample to be used in the determination is
governed by the activity of the carbon. If the residual filtrate normality
(C) is not within the range 0.008 N to 0.035 N, given on the Iodine
Correction Curve, the procedure should be repeated using a different size
sample.
3. It is important to the accuracy of the test that the potassium
iodide to iodine weight ratio is 1.5 to 1 in the standard iodine solution.
Reagents and Equipment. Hydrochloric Acid, 5%-wt - 445 ml of
distilled water add 55 ml of reagent-grade concentrated hydrochloric acid.
Sodium thiosulfate, 0.1 normal - In a one-liter volumetric flask
dissolve 24.82 grams of reagent-grade sodium thiosulfate crystals
68
-------
(Na2S2O3- 5H2O) in distilled water. Add about 0.1 gram of reagent-grade
sodium carbonate and dilute to the one-liter mark. This solution should
be allowed to stand for a few days before standardizing.
Standardize with reagent-grade metallic copper. Dissolve about
0.2 gram of copper, weighed to the nearest 0.1 mg, in 5 ml of concentrated
nitric acid and boil gently to expel brown fumes. Dilute to about 20 ml with
distilled water and add ammonia water dropwise until the solution is a
deep blue color. Boil again until the odor of the ammonia is faint. Neu-
tralize with acetic acid until the precipitate which forms with the acid
dissolves and add 5 or 6 drops in excess. Again bring to boiling. Cool
to room temperature. Add solid potassium iodide in sufficient amount to
redissolve the copper iodide precipitate which forms. Titrate with sodium
thiosulfate until the iodine fades to a light yellow color. Add starch in-
dicator and continue the titration by adding the thiosulfate dropwise until
a drop produces a colorless solution. Calculate the normality of the
sodium thiosulfate as follows:
Normality of sodium thiosulfate = msto x 0.06354
Iodine Solution - Dissolve 12.7 grams of reagent-grade iodine
and 19.1 grams of potassium iodide in distilled water. (See Note 3.)
Dilute to one liter in a volumetric flask. To standardize the iodine solu-
tion, pipette 25.0 ml into a 250-ml Erlenmeyer flask and titrate with the
standardized 0.1 N sodium thiosulfate. Use the starch indicator when
the iodine fades to a light yellow color. Then finish the titration by add-
ing the thiosulfate dropwise until a drop produces a colorless solution.
Calculate the normality of the iodine solution as follows:
, . ml thiosulfate x normality thiosulfate
Normality of iodine solution = - 25 - -
Starch Indicator - Mix one gram of soluble starch with1 a few mis
of cold water. Pour the mixture into one liter of boiling water and allow
boiling to continue for a few minutes. This solution should be made up
fresh daily for best results.
Filter Paper - E & D, Folded, filter paper, 18.5 cm, No. 192.
Burrell Corporation Catalog No. 34-390.
69
-------
FIG. 8
IODINE CORRECTION CURVE
1.35
1.30
1.25
1.20
e
o
o
o
Ul
DC
§ 1-05
1.00
0.95
0.90
0.85
_\
.005 .010
.015 .020 .025 .030 .035
RESIDUAL FILTRATE NORMALITY (C)
-70-
-------
SECTION XII
PRIMARY TREATMENT
Physical. Primary treatment facilities include a 2.7 mgd rectang-
ular clarifier (No. 1) and a 4.8 mgd circular clarifier (No. 2). At design
flow the rectangular clarifier has a detention time of 1.4 hours and an over-
flow rate of 1150 gpd/sf. The circular clarifier at design flow has a deten-
tion time of 2.4 hours, and an overflow rate of 610 gpd/sf. The weir load-
ing for both clarifiers is 15,300 gal/ft/day. Each clarifier is provided with
mechanical sludge collection. The rectangular clarifier is equipped with
water spray scum collection, and the circular clarifier is equipped with
both water sprays and mechanical scum collection. Active lime or alum can
be fed to both clarifiers. A discussion of lime addition to the primary clar-
ifiers is included in the chemical treatment section. Excess activated slud-
ge is wasted to the primary clarifier. The primary clarifier underflow con-
sisting of primary and waste activated sludge is degritted with a cyclone
degritter before dewatering and incineration.
Treatment Efficiency. The raw sewage entering primary treatment
is largely domestic and relatively low in strength. Average strength of the
waste is shown in Table 2.
Table 2
Average Raw Sewage Characteristics
1970
BOD mg/1 140,
Suspended Solids mg/1 225
Phosphorus (mg/1 PO4~P) 11
Total Dissolved Solids mg/1 315
NHa-N mg/1 22
NO2-N mg/1 .1
NO3-N mg/1 -4
COD mg/1 200
MBAS mg/1 6
71
-------
For the last 12 months of the grant period primary clarifier removals
averaged 30% for BOD, 60% for Suspended Solids, 5% for Phosphorus, and
NH3-N, NO2~N, NO3~N increased very slightly.
72
-------
SECTION XIII
ACTIVATED SLUDGE SECONDARY TREATMENT
Physical. Three plug-flow (0.9 mgd each) and two complete mix
(2.4 mgd each) aeration basins, all in parallel, followed by two circular
clarifiers at 2.0 mgd and 5.5 mgd comprise the conventional secondary
facilities. For the plug flow basins at 2.7 mgd and 50% return sludge, a
5.1 hour aeration period is provided. The volumetric aeration period with
50% return sludge for each of the complete mix basins is approximately 3.5
hours, however, since the characteristics of complete mix basins result in
the contents of aeration tank and the effluent being homogeneous, the act-
ual aeration period will be shorter at design flows. The 2.0 mgd second-
ary clarifier has a detention time of 2.9 hours, a surface area of 2830 sf,
and overflow rate of 700 gpd/sf, and a weir loading of 10,600 gal/ft/day.
The 5.5 mgd secondary clarifier has a detention time of approximately 2.6
hours, a surface area of 7850 sf, an overflow rate of 700 gpd/sf, and a
weir loading of 17,500 gal/ft/day. The 2.0 mgd secondary clarifier has a
maximum sludge recirculation of 1380 gpm, and the 5.5 mgd secondary has
a maximum rate of 3840 gpm.
Operational Practices. In order to achieve good ammonia removals
through the ammonia stripping tower, it is necessary to operate the activ-
ated sludge system to prevent nitrification. To prevent nitrification, the
load factor or food to microorganism ratio is usually maintained above 0.35,
the mixed liquor suspended solids at 2000 mg/1, and the sludge age at 4-
6 days. Also periodically the mixed liquor prior to clarification is dosed
with 2 mg/1 of chlorine to retard nitrifying bacteria. These practices have
kept the secondary effluent NO2~N concentration less than 0.1 mg/1 and
the NOs-N less than 0.5 mg/1, with very little change in the NH3~N across
the secondary process.
Treatment Efficiency. During the year 1969, average percent re-
movals across the secondary process included approximately 5% for Phos-
phorus, 60% for MBAS (Methylene Blue Active Substances), 65% for COD,
70% for BOD, and 75% for Suspended Solids. Across the entire conventional
primary and secondary treatment process average percent removals were ap-
proximately 10% for Phosphorus, a slight decrease for Ammonia Nitrogen,
60% for MBAS, 65% for COD, 85% for BOD, and 90% for Suspended Solids.
73
-------
It is important to recognize the effect of conventional treatment
for organics, detergents (MBAS), and solids removal on the advanced waste
treatment processes. The various advanced waste treatment processes
normally remove a fairly constant percent of the organics, detergents, and
solids applied to each process, with the exception of the mixed media fil-
ters which are nearly 100% efficient regardless of the solids concentration
in the influent. If there are biological or mechanical malfunctions in the
conventional processes, the concentration of chemical dosages, the num-
ber of backwashes, and the carbon dosage for the advanced waste treat-
ment processes must all be increased or the final effluent quality will de-
teriorate. Since an effluent of constant quality and reliability is required
for wastewater reuse, the provision for a possible poor quality water en-
tering the advanced waste treatment processes must be considered in de-
sign.
An excellent example of the effect of secondary treatment on the
advanced waste treatment processes is shown in Table 3. An approximate
baseline for normal plant COD removals is depicted in the first line by
showing the average removals for the entire year of 1969. In 1969, the
secondary averaged 70% removal, 65% across chemical coagulation, re-
carbonation, and filtration, and 53% across the activated carbon. In com-
parison for the period March 23 to May 28, 1970, there was an apparent
upset in the activated sludge process resulting in removal efficiencies
around 30% for most of the period. Although the settleability and
solids concentrations were normal, the effect of the poor secondary
treatment on the activated carbon process and degree of carbon sat-
uation is evident in Table 3. For instance, from March 23 to April 6,
the secondary averaged 34% removal, chemical treatment through fil-
tration 79%, and 39% for activated carbon. This period was immediate-
ly prior to a batch carbon regeneration and the carbon column effluent in-
creased to 19 mg/1. The effect of carbon regeneration on the carbon col-
umn effluent with approximately the same prior treatment efficiencies is
shown for the period April 7 to April 19. With the freshly regenerated car-
bon at the top of the columns, the carbon treatment efficiency increased
to 68%, with an effluent value of 10 mg/1. From April 20 to May 10, there
was an apparent increase in the strength of the waste, and the activated
sludge process responded with near normal treatment efficiency. However,
since the carbon was heavily loaded, the average carbon column effluent
increased to 14 mg/1. For the next period, May 11 to May 28, the waste
strength was normal, but the secondary efficiency decreased to 30%. How-
ever, the columns had freshly regenerated carbon at the top of the bed and
the average carbon column effluent concentration decreased to 12 mg/1.
From May 29 to June 22, the activated sludge was performing better at a
55% removal efficiency, which resulted in a lower COD concentration ap-
plied to carbon, 22 mg/1. However, it was at the end of a loading period
74
-------
-J
Cn
TABLE 3
THE AVERAGE PLANT PERFORMANCE FOR COD REMOVAL
January 1, 1969 to December 31, 1969
March 23, 1970 to June 22, 1970
Period
Primary Secondary Sep. Bed Car. Col.
Effluent Effluent Effluent Effluent
Comments
1-1-69 - 12-31-69 200
3-23-70 - 4-6-70 222
4-7-70 - 4-19-70 186
4-20-70 - 5-10-70 340
5-11-70 - 5-28-70
5-29-70 -6-22-70 180
60
147
138
121
132
81
19
31
31
32
32
22
9 Plant performance for the year 1969,ap-
proximately normal treatment efficiencies.
19 Poor secondary efficiency, normal chem-
ical treatment and filtration, prior to a
batch carbon regeneration.
10 Poor secondary efficiency, normal chem-
ical treatment and filtration, after a
batch carbon regeneration.
14 Abnormally high secondary loading with
near normal efficiency, normal chemical
treatment and filtration, prior to a batch
carbon regeneration.
12 Poor secondary efficiency, normal chem-
ical treatment and filtration, after a
batch carbon regeneration.
12 Near normal secondary efficiency, nor-
mal chemical treatment and filtration,
before a batch carbon regeneration.
-------
for the carbon prior to regeneration, and the carbon treatment had a 45%
removal efficiency, with an effluent concentration of 12 mg/1. From Table
3 , it is readily apparent that activated carbon plays an important role in
maintaining an effluent of uniform quality in spite of normal, but undesir-
able, fluctuations.
The ammonia stripping process is dependent upon the operation of
activated sludge system to prevent nitrification, so that the majority of
the nitrogen present in the waste will be the ammonium ion, which can be
converted to ammonia gas by pH adjustment and then air-stripped. Phos-
phorus removal does not necessarily depend upon conventional processes
for initial removals, but the efficiency of phosphorus removal can be de-
creased by such problems as a considerable carryover of organic solids in-
to the chemical coagulation process as a result of an upset in the activat-
ed sludge process.
76
-------
SECTION XIV
DEWATERING AND INCINERATION OF WASTE ORGANIC SOLIDS
Physical. During normal operation, one 24" X 60" solid bowl,
concurrent flow centrifuge is used to dewater the organic sludge mixture of
primary and waste activated sludge. Incineration of the sludge is accom-
plished in a six hearth, 14.3 foot diameter, natural gas fired furnace. The
furnace also dries the classified waste inert solids from the lime solids
stream and the grit removal process. The waste lime, organic solids, and
the grit pass through the furnace from top to bottom (hearth 1 at the top/
and hearth 6 at the bottom). The furnace will have a maximum fuel con-
sumption of 2.7 X 106 BTU/hr handling 21,000 Ibs/day of waste solids at
design capacity of 7.5 mgd and a cake solids content of 19%. After incin-
eration and drying, the inert ash from the grit, waste organic and lime sol-
ids is carried by a bucket conveyor to an ash bin on the exterior of the in-
cineration building. The ash bin is provided with a screw conveyor for
loading dump trucks. Final disposal is to a private land fill. Two 45-foot
diameter digesters, constructed in 1961 with the original conventional plant
construction, are used for emergency storage of waste solids in the event
of a breakdown in the dewatering or incineration system. See Figure 9.
Operational Practices. Excess activated sludge is wasted to the
primary clarifier, where it settles with the primary sludge. The sludge
combination is pumped from the primary clarifier at 1-2% solids through
a cyclone degritter to a small holding tank. The solids are pumped from
the holding tank at the same concentration to the centrifuges and dewater-
ed, with over 90% capture, resulting in a cake solids concentration of ap-
proximately 18%. The centrate is returned to the primary. Approximately
2 to 5 Ibs of a polyelectrolyte per ton of dry solids are required during the
dewatering process. The organic solids cake and the waste inert lime sol-
ids from centrifugal classification of the lime solids stream are carried to
the furnace by a belt conveyor. The waste lime solids have a solids con-
tent of approximately 30%. The grit from the cyclone degritter is conveyed
with a screw conveyor directly to the top of the incineration furnace. In
routine operation of the furnace, drying of the waste solids is accomplish-
77
-------
CENTRATE
TO PRIMARY
CLARIFIER
INFLUENT
CHANNEL
SEWAfiE
SLUDGE FROM
PUMPS IN
PRIMARY
PUMP AND
EQUIPMENT
ROOM
SCRUBBER
ND. 2
CENTRIFU6E
FOR SEIAGE
VPOLYELECTRO-
LYTE FEED
REVERSIBLE
SCREW
CONVEYER
TO LIME
ftECALCINlNfi
FURNACE
REVERSIBLE^
FEED CONVEYOR
^-BYPASS-
BEWATERED
SEIAGE SLUOGE
CHUTE
ASH SCRE1
CONVEYOR
AND WATER
SPRAY FOR
DUST
CONTROL
SLUDGE
INCINERATOR
FURNACE
FURNACE RABBLE
ARM DRIVE
BUCHET ASH
ELEVATOR
SHAFT
COOLING
AIR FAN
COMBUSTION
AIR BLOWER
FIGURE 9
SOLIDS HAMDLING
PRIMARY AMD SECONDARY
SLUDGE
78
-------
ed on the first two hearths, incineration of the organic solids takes place
on the third hearth, with possibly some on the fourth, and cooling on the
fourth, fifth, and sixth hearths. A typical furnace hearth temperature
profile would be:
Hearth No. 1 700°F
Hearth No. 2 1200°F
Hearth No. 3 1500°F
Hearth No. 4 1400°F
Hearth No. 5 1300°F
Hearth No. 6 500°F
The ash temperature leaving the furnace is approximately 200°F, and is
naturally cooled in the conveying process to 100°F before it enters the
ash bin. Table 4 shows the operating data for December 1969 to Decem-
ber 1970.
TABLE 4
ORGANIC SLUDGE FURNACE OPERATING DATA
December 1969 - December 1970
Plant Influent, mgd 2.45
Centrifugal
Feed, % Solids .2.0
Cake, % Solids 17.0
Capture, % 91.0
Polyelectrolyte,lbs/ton( * ) 5.1
Electricity,KWHR/day( 2 ) 600
Organic Sludge Incinerator
Feed, tons dry solids 921
Fuel requirements,BTU/lb( 3 ) 7,640
Ash, cubic yds 970
Electricity ,KWHR/day( 4 ) 460
( 1) Tons of dry solids to furnace.
( 2 ) Includes energy and demand charges for feed pumps, centrifugal,
and sludge conveyor.
( 3 ) Natural gas at 18 psia and 860 BTU/ft3.
( 4 ) Includes energy and demand charges for furnace support motors
and ash conveying system.
Stack Sampling Results. On November 10, 1970, three one hour
stack sampling runs were made on the scrubber effluent of the multiple
hearth incinerator. At the time of the sampling, the incineration furnace
79
-------
was being fed a combination of organic solids from the primary clarifier
and waste lime from the centrifugal classification process of the lime sol-
ids recovery stream. The sampling and analysis of the stack gases were
performed by a private laboratory, Ultra-Chem. The results of the samp-
ling and analysis for sulfur compounds calculated as sulfur dioxide
(SO2) in ppm and combustion contaminants in grains per cubic foot of gas
calculated to 12 percent carbon dioxide (CO2) are shown in Table 5. Al-
so the standards for the above parameters from Rule 53 of the Los Angeles
County Air Pollution Control District Rules and Regulations are presented
in Table 5.
TABLE 5
STACK SAMPLING RESULTS
MULTIPLE HEARTH INCINERATOR WITH COMBINATION LIME-
ORGANIC SOLIDS FEED
November 10, 1970
Combustion Contaminants:
Grains/SCFM at 12% CO2
Oxides of Sulfur:
(as SO2) ppm
Oxides of Nitrogen
(as
Test A Test B Test C Rule 53
.026 .014 .014 0.3
2.2 2.3 3.2 2000
52
65
The average of the three runs for combustion contaminants was
.018 grains/SCFM, which is 6% of that permitted by Rule 53. The aver-
age for'oxides of sulfur was 2.6 ppm, which is less than 1% of the al-
lowable according to Rule 53.
80
-------
SECTION XV
CHEMICAL TREATMENT
During the period of the grant, chemical treatment studies consist-
ed of active lime addition to the primary clarifier and to the secondary
effluent. The addition of active lime to the primary clarifier was discon-
tinued approximately five months after the grant studies were initiated be-
cause of problems in dewatering the lime-organic sludge mixture. This is
described in detail later in this section. Lime coagulation and clarifica-
tion of the secondary effluent was initiated at the start of the grant period
and continues to the present. Excellent phosphorus removals plus addi-
tional solids and organics removals have been attained with the lime co-
agulation and clarification of the secondary effluent.
Primary Treatment. During the first five months after the expanded
7.5 mgd Water Reclamation Plant was put on line, recalcined lime was add-
ed to the primary clarifier to study its effect on clarification, as a wasting
procedure to maintain the proper CaO content in the recalcined lime, and
for phosphorus removal. Shortly after the addition of lime to the primary
clarifier was initiated, problems arose in dewatering the mixture of primary,
waste activated, and waste lime sludge in the centrifuges. Centrifuge
problems included high torque and chatter, excessive wear on the convey-
ors, a high demand for sludge conditioners (polyelectrolytes), a wet cen-
trifuge cake, and highly dispersed fines in the centrate. Several attempts
were made to remedy the problem with different mixtures of the organic
and lime sludges, but the above problems persisted. Also the centrate
from the dewatering of the organic-lime sludge mixture was directed back
to the primary clarifier during this period. This often resulted in increased
concentrations of suspended solids and phosphorus in the primary effluent
as compared to those found in the raw sewage. As a result of the dewater-
ing problems, the practice of adding recalcined lime to the primary was dis-
continued in September, 1968. Since that time the lime and organic sludges
have been dewatered separately with few problems.
During the latter portion of the period when recalcined lime was
added to the primary, an attempt was made to dewater the organic-lime
sludge mixture with a pilot (10 square foot) vacuum filter. The sludge
mixture had a high demand for ferric chloride or for polyelectrolyte, which
81
-------
was thought to be a result of the waste lime in the organic sludge. It was
determined that the chemical demand could be markedly reduced by adding
sulfuric acid to the sludge mixture before adding the conditioners. How-
ever, the end result was that filtrate quality was no better than the centrate
from the centrifuges and dewatering costs were approximately the same for
both dewatering methods.
In spite of the dewatering problems, some intermittent data was
collected across the primary clarifier during the recalcined lime addition
period. For this period the pH in the primary effluent ranged from 7.5 to
11.0, with the majority of the results 9 .5 or lower. When reasonable data
was available across the primary clarifier, that is phosphorus and suspend-
ed solids removals, not increases, were attained, the phosphorus removals
averaged about 20% and the suspended solids removals averaged slightly
less than 50%. During the last 18 months of data collection at the end of
the grant period when lime was not added to the primary, the phosphorus
and suspended solids removals across the primary average less than 5%
and between 50-60%, respectively.
After the decision was made to discontinue adding recalcined lime
to the primary clarifier, the lime centrifuges have been used to classify
inert materials out of the feed to the recalcining furnace. This has proven
to be a more economical and effective way of maintaining the desired act-
ive lime content in the recalcined feed lime, rather than dewatering and
recalcining the entire lime recovery solids stream and wasting a portion of
the entire stream. A more detailed discussion of the centrifugal classifi-
cation of the lime solids stream is included in the section on Lime Recov-
ery and Reuse.
Activated Sludge. During the period when recalcined lime was add-
ed to the primary clarifier, the activated sludge continued to satisfactorily
perform and produce the normal degree of treatment for organics removal.
However, because of the earlier described dewatering problems with the
primary sludge and the many variables such as sludge return rate, organic
and solids loading, aeration period, and many others, very little specific
data could be collected across the activated sludge system.
During the intermittent recalcined lime addition to the primary, at
times the pH of the primary effluent reached above 11. Grab samples were
taken of the return sludge-primary effluent mixture just before entering the
aeration basins and approximately five feet into the aeration basins. When
the mixture of primary effluent and return sludge was above pH 11.0, the
pH five feet from the entrance was 8.5-8.6. Hence, it appears the activ-
ated sludge mixed liquor has a considerable buffering capacity for the high
82
-------
Figure 10
CHEMICAL RAPID MIX AND CLARIFIER
WITH SECONDARY CLARIFIER IN FOREGROUND AND
NITROGEN REMOVAL TOWER IN BACKGROUND
83
-------
primary effluent pH under the lime addition to the primary mode of opera-
tion.
Lime Coagulation and Clarification of Secondary Effluent. The pur-
pose of lime coagulation at South Tahoe are phosphorus removal from sec-
ondary effluent, clarification, and preparation of this effluent for ammonia
stripping.
Recalcined and makeup lime are stored separately in identical 35
ton bins. Each bin is equipped with gravimetric lime feeders and pug-mill
type slakers with 1500 Ib. CaO/hr capacities. Bulk 16 X 50 mesh granular
quicklime is used as makeup. The Ca(OH)2 slurry is approximately one-
fourth makeup and three-fourths recalcined lime. The slurry flows by grav-
ity to the rapid mix chamber. Boxes are provided on the line to provide ac-
cess for cleaning. Enough lime is added to raise the pH to about 11. This
requires a lime dose of approximately 300 mg/1 of calcium oxide. Lime
feed rates are controlled by continuous pH measurement.
Rapid mixing is accomplished in a partitioned corner of a square
20 X 20 X 8 feet deep flocculation basin. At design flow of 7.5 mgd, there
will be 30 seconds of rapid mixing, and 4.5 minutes of flocculation.
After flocculation, the lime treated secondary effluent flows to a
conventional clarifier for removal of phosphorus rich lime mud and clarifi-
cation. To improve clarification a polymer is added just as the water leav-
es the flocculation chamber. The polymer dose varies between 0.1 and
0. 3 mg/1.
The clarifier is equipped with both a center sludge hopper and suc-
tion pipes attached to the clarifier mechanism. To date only the center
sludge draw off has been needed. During the study period, the clarifier
overflow rate ranged from 395 to 600 gal/ft2/day, and detention times
ranged from 4.6 to 3.0 hours. At the design capacity of 7.5 mgd, the
overflow rate is 950 gal/ft2/day and 1.9 hours detention time.
A discussion of the recycle streams and their point of addition to the
process at South Tahoe is necessary before the data collection methods
and results can be evaluated. There are six significant recycle streams:
1. Furnace Stack Gas Scrubber Water
2. Separation Bed Backwash
3 . Lime Mud Thickener Overflow
4. Recycle Sludge from Chemical Clarifier
5 . Organic Sludge Centrate
6 . Lime Mud Centrate
84
-------
The water reclamation plant effluent is used for supply of scrubber
water to clean the sludge incineration and lime recalcining furnaces stack
gases. This quantity is fairly constant, being about .65 mgd. The scrub-
ber water is high in particulate material and has a temperature of about
80°F. The scrubber water can be returned to the process at primary clari-
fication, the flocculation basin, or to the ballast ponds.
Separation bed (filter) influent is used to backwash the beds. The
backwash water is collected in a 80,000 gallon tank. The tank can be op-
erated as a decant tank with a variable period for clarification. The low
turbidity water in the top two-thirds of the tank can be decanted back to
the ballast ponds by means of a floating decant arm. The high turbidity
water in the bottom of the tank can be drained through a sludge valve to
the primary clarifier or the flocculation basin. The tank also can be oper-
ated to drain the entire contents of the tank through the sludge valve with-
out clarification. Each backwash produces about 74,000 gallons of highly
turbid water. There are an average of four backwashes every 24 hours.
The overflow from the lime mud thickening process can be return-
ed to the primary or the flocculation basin. The overflow is clear and
averages about .2 mgd.
A portion of the lime mud drawn off the chemical clarifier can be
returned directly to the flocculation basin for seeding purposes. This flow
is approximately 5 gpm. The centrates from the lime and organic sludge
centrifuges are about 20 and 35 gpm, respectively. Both centrates are re-
turned to primary clarification.
The major recycle flows, scrubber water, back wash, and lime mud
thickener overflow, when mixed together, have a total quantity of over 1
mgd, a turbidity of approximately 70-100 Standard Jackson Units, and a to-
tal phosphorus concentration of about 7 mg/1 PO4-P. It is important to
note that the recycle streams of scrubber water, lime mud thickener over-
flow," and decant tank sludge are all mixed together in a flow splitter box,
before they are added to the plant processes. From this splitter box, the
three flows may be introduced into either the primary clarifier or the lime
flocculation basin. The scrubber water and/or the decant tank low turbid-
ity water may also be returned to the ballast ponds which are situated be-
tween the lime coagulation and filtration systems.
Methods Used for Data Collection. Three methods of sampling were
used to evaluate the efficiency of the chemical clarifier. For the first me-
85
-------
thod, jar tests were performed to determine the optimum lime dose, and
amount of recycle water for phosphorus and turbidity removal. Secondly,
24-hour composite samples were collected to evaluate on a plant scale,
the efficiency of the chemical clarifier in removing not only phosphorus,
but also organic materials and suspended solids under two different recy-
cle schemes. Finally, grab samples were collected across the chemical
clarifier for over a year to study the effect that the reintroduction of re-
cycle water at different points in the plant had on phosphorus removal.
All the jar tests were performed in the following manner on 500 ml
samples. Lime was added in varying amounts to each sample. The sam-
ples were flash mixed for 30 seconds at 100 rpm and flocculated for 5 min-
utes at 35 rpm. No polyelectrolytes were added. After one hour of clari-
fication with no mixing, the clear liquor was analyzed.
A number of tests were run for which soluble, particulate, and total
concentrations were reported. Materials passing a 0.45 micron filter were
assumed to represent the soluble fraction. Particulate concentrations were
determined by subtracting the concentration of the filtered sample from a
parallel unfiltered sample.
Optimum Lime Dose. Lime doses from 200 to 700 mg/1 CaO were
added to 500 ml samples of secondary effluent to determine the optimum
lime dose for phosphorus and turbidity removal. Figures 11 and 12 show the
results of these tests.
Figure 11 indicates the optimum lime dose for phosphorus removal at
South Lake Tahoe would be about 300 mg/1 as CaO. An increase in lime
dose from 200 to 300 mg/1 CaO produced a seven percent increase in phos-
phorus removal; whereas an increase to 400 mg/1 produced only a three
percent increase in phosphorus removal. If the goal for phosphorus remov-
al with excess lime treatment was greater than 86%,lime doses in excess
of 200 mg/1 CaO would be required in secondary effluents similar to those
at South Lake Tahoe. Figure 13 shows the corresponding pH values.
A comparision of the turbidity removals, Figure 12, obtained during
the same set of jar tests show that 300 mg/1 CaO is close to the optimum
dose.
Effect of Recycle Water. In an effort to improve phosphorus remov-
als, the project staff, in July 1969, began recycling lime mud from the chem-
ical clarifier to the lime rapid mix. Prior to this time, the average PO4-P
concentration in the final effluent had been 0.22 mg/1. During the next
eight months after the addition of recycled lime mud, the final effluent
averaged 0.16 mg/1 PO4-P-
86
-------
FIGURE 11
100
PHOSPHORUS REMOVAL FROM SECONDARY EFF. VS LIME DOSE
(Jar Test)
00
xl
BO
LI
-.<
DC
O
1 6°
O
a
I
% 40
in
u
Q
20
INITIAL P04-P 11.7 MG/L
100
200
300 400 500
LIME DOSE, MG/L CaO
600
700
800
-------
FIGURE 12
TURBIDITY REMOVAL FROM SECONDARY EFF. VS LIME DOSE
(Jar Test)
100
80
CD
EC
2 60
•'
(
!U
tr
40
H
IJI
o
ce
20
INITIAL TURBIDITY - 12 SJU
100
200
300 400
LIME DOSE,MG/LCaO
500
600
700
800
-------
FIGURE 13
pH VS LIME DOSE
0
CD
<
•
INITIAL CONDITIONS
pH - 7.5
TOTAL ALKALINITY - 226 MG/L AS CaCO3
100
200
300
400
500
600
700
800
900
LIME DOSE, MG/L CaO
-------
Ortho phosphorus (PO4-P) studies of another recycle stream, scrub-
ber water from the sludge and recalcining furnaces revealed a total con-
centration of 12.8 mg/1, of which 12.3 mg/1 was particulate and 0.5 mg/1
was soluble. Since the filters are capable of removing approximately 81%
of the soluble PC^-P and 91% of the particulate PO4~P, as described in
the filtration section later in this report, the recycle scrubber water was
returned to the rapid mix where higher efficiencies could be obtained.
After the scrubber water change had been made in March, 1970, the final
effluent average PO^-P concentration dropped from 0.16 mg/1 to 0.09 mg/1.
In June, 1970, all recycle streams were changed to the primary clar-
fier. A comparison of final effluent average PO4~P concentrations show-
ed an increase from 0.09 mg/1 to 0.31 mg/1. In August, 1970, the recycle
streams were changed back once again to the rapid mix. The final effluent
average PO^-P concentration then dropped back to 0.07 mg/1.
With the exception of the period when the recycle flows were return-
ed to the primary, grab samples of the chemical clarifier effluent showed
that average PO4~P concentrations ranged between 0.35 and 0.40 mg/1.
During the perioa when the recycle water was returned to the primary, the
chemical clarifier effluent average PC>4-P value increased to 0.76 mg/1.
Since the increase could not be explained by inadequate lime dose or other
circumstances, the effect of the recycle water on the removal of phosphor-
us was included in the detailed study of chemical clarifier efficiency. The
effect of the recycle streams on phosphorus removal is summarized in Table
6.
Jar tests were performed to determine what effect the amount of re-
cycle water had on phosphorus removal at different lime doses. The re-
sults of these jar tests are shown in Figure 14. The recycle water used
for the jar tests contained normal amounts of scrubber water, filter back-
wash water, and lime mud thickener overflow. A recycle ratio of four parts
secondary effluent to one part recycle water showed the best results of the
ratios tested: no recycle, 6 to 1, 4 to 1, and 3 to 1. Turbidity removals
were generally unaffected by the different recycle ratios. Table 7 shows
the variation of turbidity with recycle concentration.
To further evaluate the effect of recycle water on phosphorus remov-
al, twenty-four hour composite samples were collected around the chemi-
cal clarifier. These samples were collected during periods when the recy-
cle water was being reintroduced at the floe basin and when it was being
added to the primary clarifier. The polyelectrolyte dose was held between
0.1 and 0.16 mg/1 throughout the period.
90
-------
TABLE 6
PLANT SCALE EFFECT OF RECYCLE STREAMS
ON AVERAGE PHOSPHORUS REMOVALS
Test Period
Point of Re-introduction of
1. Scrubber Water (*)
2. Filter Backwash (2)
3. Thickener Overflow(3)
4. Clar. Underflow (4)
Ratio of Plant Influent to Recycle
Flow at Floe Basin
Phosphorus Concentration in Secondary
Effluent, Effluent as mg/1 PO4-P
(24 hr. composites)
Phosphorus Concentration in Chemical
Clarifier Effluent as mg/1 PO4-P
(Daily grab @ 10:00 hrs.)
Phosphorus Concentration in Final Efflu-
ent as mg/1 PO4-P
(24 hr. composites)
1 Jan. 69 1 July 69 16 Mar. 70 10 June 70 26Aug. 70
to to to to to
ljuly 69 14Mar.7Q 8 June 70 24Aug. 70 18Sept.7Q
Ponds^ Ponds Floe Basin Raw Sewage Floe Basin
FlocBasin Floe Basin
none
4.5
1
6.0
0.22
4.7
1
8.6
0.40
0.16
1.8
1
9.0
0.35
0.09
8.4
0.76
0.31
2.4
1
12.8
0.35
0.07
(1) Scrubber water is from sludge and lime recalcining furnaces.
(2) Filter backwash water is from mixed media separation beds.
(3) Thickener overflow is from lime mud thickener.
(4) Clarifier underflow is a small sludge recirculation stream around the chemical clarifier.
(5) Ponds are ballast ponds located between the chemical clarifier and the separation beds
-------
FIGURE 14
to
ro
>;>
a.
s?
EFFECT OF RECYCLE WATER
ON PHOSPHORUS CONCENTRATION
VS
LIME DOSE
(Jar Test)
100
200
300
400
500
600
700
800
LIME DOSE, MG/L CaO
-------
Lime Dose mg/1 CaQ
TABLE 7
EFFECT OF RECYCLE
WATER ON TURBIDITY
VS
LIME DOSE
( Jar Tests )
Settled Water
Turbidity SJU
Ratio: Secondary Effluent/Recycle Water
1/0
4/1
6/1
0
200
300
400
500
600
700
12
7
3
3
3
2
2
26
3
3
3
3
3
3
23
3
3
3
5
4
3
20
3
2
4
10
3
2
Secondary Effluent 12 SJU
Recycle Water 67 SJU
93
-------
Table 8 shows that adding the recycle water to the floe basin great-
ly improved the removal of phosphorus reported as particulate phosphorus.
The removal of soluble phosphorus was not affected by the point of
recycle water addition, by calcium oxide dosages between 200 and 500
mg/1, or by clarifier overflow rates between 400 and 600 gal/ft^/day. How-
ever, the removal of total phosphorus, and the particulate phosphorus was
affected by the point of recycle water addition and by calcium oxide dose.
Between 400 and 500 gal/ftVday the overflow rate appeared to have very
little effect on total phosphorus removal. Figure 15 shows that the calcium
oxide dose affected total and particulate phosphorus removals when the re-
cycle water was returned to the primary clarifier, and that CaO dose did
not materially affect phosphorus removals when the recycle water was in-
stead returned to the floe basin. Total phosphorus removals, as shown by
Figure 16, were not changed by the overflow rates studied. The effect of
adding the recycle water to the floe basin is also shown in Figures 15 and
16.
During the period when all recycle waters were being returned to the
floe basin, thickened lime mud overflowed into the lime mud thickener
launder continuously for several 24 hour periods. Twenty-four hour com-
posite samples were collected around the lime coagulation system and
analyzed. These results were not included in the previously reported re-
sults since they did not represent normal operating conditions. It is, how-
ever, interesting to compare the average of these results with those of
normal operation. In Table 9 it can be seen that although the chemical clar-
ifier effluent phosphorus concentration increased slightly, the percent re-
moval of phosphorus across the chemical clarifiers improved because of
the higher phosphorus concentration in the recycle water.
In Tables 10 and 11, the removal efficiencies for several parameters
are shown for the two points of recycle water addition. It is important to
note the similarities in the total and ortho phosphorus concentrations shown
in the two tables. Practically all of the phosphorus measured is ortho,
with very little polyphosphate present.
Although recycling the scrubber water back to the lime flocculation
basin improved the plant phosphorus removal, this procedure led to higher
lime costs due to the increased flow (0.65 mgd) and to the accelerated for-
mation of hard scale in the transport line, which was difficult to remove.
Tests for the stability index (2 pHs-pH) and Marble Test were per-
formed on the lime mud thickener and the sludge and lime furnace scrubber
94
-------
TABLE 8
THE AVERAGE EFFECT OF RECYCLE WATER
ON CHEMICAL CLARIFIER EFFICIENCY
Parameter
pH Floe Basin
Ortho Phosphorus
Soluble (1)
P articulate
Total
Total Suspended
Solids
Organic Suspended(2)
Solids
Turbidity
Recycle Water Returned
To Floe Basin
11.0
% Removed
99.4
73.4
93.4
51.5
89.2
70.4
% Added
Recycle Water Returned
To Primary Clarifier
10.9
% Removed
99.7
85.8
87.5
% Added
177.
68.
•
20
(1) Measured after filtration with .45 m filter
(2) Pretreated to pH 2 with HC1
95
-------
FIGURE 15
TOTAL PHOSPHORUS REMOVAL
VS
CALCIUM OXIDE DOSE
IUU
—J
O
SI 90
DC
tn
D
DC
O
I
Q.
Q
-r- on
X oU
H
O
1-
i_
m 70
DC
UJ
Q.
Kn
*
^^
^^*"^
f
I
'
^^ ^*^
^^ ^^^
*^
O
O
^ •• ^
^^Illl^" ^
+
4-
f\
¥
— -^-^" """"""
__ _ +
i
O - RECYCLE TO FLOG BASIN
+ - RECYCLE TO PRIMARY
1 1
100
200
300
400
500
CALCIUM OXIDE DOSE MG/L
-------
FIGURE 16
TOTAL PHOSPHORUS REMOVAL
VS
CLARIFIER OVERFLOW RATE
100
00
NJ
I
<•'
X
0
CL
Ul
C
I
D
i
'i
u
90
BO
JO
60
300
RECYCLE TO FLOC BASIN
RECYCLE TO PRIMARY
400 500 600
CLARIFIER OVERFLOW RATE \N GAL/FT2/DAY
700
-------
TABLE 9
THE AVERAGE EFFECT OF VERY HIGH TURBIDITY AND
PHOSPHORUS IN THE RECYCLE WATER
Normal Operation High Solids Overflow
Of Lime Mud Of Lime Mud
Pararneter Thickener Thickener
Total Phosphorus, mg/1
Sec Effluent 11.3 9.9
Recycle Water 6.8 36.6
Chemical Clar. Eff. .7 .8
Percent Removal of
Total Phosphorus % 93.7 95.2
Turbidity of Recycle
Water SJU 69 600
pH 11 11
98
-------
TABLE 10
AVERAGE EFFICIENCY OF
CHEMICAL CLARIFIER WITH RECYCLE
WATER ADDED TO FLOG BASIN
Parameter (mg/1)
BOD
Soluble
P articulate
Total
COD
Soluble
P articulate
Total
Total Phosphorus^1)
Soluble
P articulate
Total
Ortho Phosphorus
Soluble
P articulate
Total
Total S.S.
Organic S.S.(2)
Turbidity SJU
Color(3)(Cobalt Std.)
Alkalinity, as CaCO3
Hardness as CaCO3
PH
Average Concentrations
Sec. Eff.
15.5
23.8
39.3
44.3
44.6
88.9
10.33
0.97
11.30
8.79
1.81
10.60
38.
33.
16
33
183
73
7.2
Recycle
9.3
12.8
22.1
23.2
29.5
52.7
0.53
6.28
6.81
0.35
5.49
5.84
166
29
69
7
250
152
7.7
ChemXff.
5.1
3.8
8.9
30.8
3.8
34.6
0.03
0.68
0.71
0.04
0.62
0.66
38.
6
9
11
249
145
11
Percent
Removed
54.5
80.5
73.5
26.4
91.0
57.8
99.7
67.8
93.7
99.4
73.4
93.4
51.5
89.2
70.4
(1) Acid Digestion
(2) Pretreatment of sample to pH 2 with HC1
(3) Filtered at 0.45 microns
99
-------
TABLE 11
AVERAGE EFFICIENCY OF
CHEMICAL CLARIFIER WITH RECYCLE
WATER ADDED TO PRIMARY CLARIFIER
Parameter (mg/1)
BOD
Soluble
Particulate
Total
COD
Soluble
Particulate
Total
Total Phosphorus^1)
Soluble
Particulate
Total
Ortho Phosphorus
Soluble
Particulate
Total
Total S.S.
Organic S.S.(2)
Turbidity SJU
Color (3) (Cobalt Std.)
Alkalinity, as CaCOg
Hardness as CaCOg
PH
mg/1
Average Concentrations
Secondary Eff.
3.4
7.6
11.0
18.4
22.1
40.5
8.08
0.36
8.44
7.28
0.39
7.67
22
19
10
21
226
97
7.4
Chemical Eff.
0.8
0.8
1.6
12.6
4.2
17.2
0.04
1.24
1.28
0.02
1.08
1.10
37
3
12
12
286
137
10.9
Percent Removed
or Added (+)
76.5
89.5
85.5
31.5
81.0
57.5
99.5
2 54 . (+)
84.7
99.7
177 (+)
85.8
68.0 (+)
87.5
20 (+)
43
(1) Acid Digestion
(2) Pretreatment of sample to pH 2
(3) Filtered at .45 microns
100
-------
effluents. Table 12 shows that the thickener overflow had very high scale
forming tendencies whereas the scrubber effluents were in equilibrium or
slightly corrosive. It is suspected that the very large volume of warm,
low pH, CO2 rich scrubber effluent accelerated the scale forming tenden-
cies of the CO2 free, pH 11 lime mud thickener overflow.
Maintenance of Lime Mud Lines. About one year after plant start-
up and prior to the addition of scrubber water, an increasing problem with
calcium carbonate plating out on the lines handling lime mud and lime mud
thickener overflow was encountered. An example of such buildup was ob-
served in the 8 inch welded steel line which carried the lime mud thicken-
er overflow and decant tank sludge. In the year of operation the diameter
of this line had shrunk to 4 inches at the joint inspected. The lines were
first chemically treated with no success. A pipe cleaning contractor with
a cutting device that could be pulled through the pipe was tried next. The
amount of time it took to clean 25 feet of pipe made the costs prohibitive.
Finally, a device called a "Polly-Pig" manufactured by Knapp, Inc. was
attempted for pipe cleaning. The pig is made of a polyurethane foam us-
ually formed in a bullet shape with abrasive cutting edges on the exterior.
At Tahoe, water pressure is used to expand the pig and force it through the
pipe. The pigs can pass 90 degree turns, gate, check, and plug valves.
The experience with the pigs as a pipe cleaning device has been very suc-
cessful and cleaning of lime mud conveying lines has been established on
a scheduled basis.
Additional Benefits of Chemical Coagulation and Clarification. Dur-
ing the plant scale chemical clarifier evaluation, data on several paramet-
ers other than phosphorus were collected to determine what additional ben-
efits might be anticipated for removal of organics, particulate materials,
and detergents.
As shown in Tables 10 and 11 , Biochemical Oxygen Demand percent
removals were somewhat better when the recycle streams were added to the
primary clarifier. Particulate BOD removals were only slightly better, but
soluble BOD removals were markedly better under this mode of operation,
since the recycle streams had the benefit of biological treatment.
Chemical Oxygen Demand removals remained constant regardless of
the point of addition of the recycle streams. As shown in Table 10and 11 ,
the total removals averaged slightly less than 60%. Figure Vindicates the
total COD percent removals were from 50 to 70 percent throughout the range
of loadings.
Between 400 and 600 gal/ft2/days, percent removals of BOD and COD
were not affected by different flow rates.
101
-------
TABLE 12
STABILITY INDEX AND MARBLE TEST
SCRUBBER WATER AND LIME MUD THICKENER
OVERFLOW
Scrubber Water
Type of Sample
Sludge
Furnace
Lime
Furnace
Lime Lime
Mud Mud
Thickener Thickener
(heated)
Temperature ° F 62
Total Hardness , mg/1 as
CaCO3 162
Total Alkalinity, mg/1 as
80
52
Marble Test
Total Alkalinity, mg/1 as
CaCOs (a, untreated)
Total Alkalinity,mg/1 as
CaCO3 (b, treated)
Results:
255
255
324
330
50
242
326
346
80
242
CaCO3
Initial pH
Total Dissolved Solids,
mg/1
Stability Index (2pHg-pH)
Scaling <6.6> Corrosive
357
6.8
312
7.5
440
7.1
310
7.2
362
11.3
300
2.8
363
11.2
300
2.4
363
337
scale forming
X
X
corrosive
X
a = b
equilibrium
102
-------
FIGURE 17
POUNDS OF TOTAL COD APPLIED
VS
PERCENT COD REMOVAL
100
<* 8°
> —
0 U.
83 60
2 •"
UJ ill
DC u
UJ
o- 2:
40
9n
*
•
0 ^
O
f
o
*
o
D
0
O
O
• - RECYCLE WATER TO PRIMARY
0 - RECYCL
E WATER TO FL
OC BASIN
500
1500
2500
3500
4500
POUNDS OF COD APPLIED
-------
However, BOD and COD removals were affected by lime dosages be-
tween 205 and 450 mg/1 as CaO, and by corresponding pH values between
10.5 and 11.3. The removal of total BOD and COD improved with increas-
ing lime dosages. This result was expected since jar tests and plant
scale observations had shown that clarification improved with increasing
lime doses. At the same time, it was observed that the soluble BOD and
COD removals were poorer with increasing lime doses. For example, the
soluble BOD removal at 290 mg/1 CaO was 78% whereas the soluble BOD
removal at 450 mg/1 CaO was only 25%. Some effects of lime dose on sol-
uble and particulate BOD and COD removals can be seen in Figure 18
through Figure 26.
The slope of the soluble BOD curve, Figure 19 together with the cor-
relation with the two soluble COD curves, Figures 22 and 25, would seem
to rule out toxicity or nitrogen interferences as being responsible for the
resulting decrease in the removal of soluble organics with increasing lime
doses. Furthermore, all the samples were collected under the same con-
ditions, (24 hour composite with refrigeration), and analyzed by the same
procedures and analyst.
One explanation offered for poorer soluble organic removals with in-
creasing lime doses is that the OH~1 ion is converting some particulate
organic material to soluble forms.
Suspended solids removals were evaluated two ways. Before filter-
ing, one set of samples was acidified to pH 2 to determine the actual or-
ganic solids removal, and another set was filtered without acid pretreat-
ment. The pretreated samples indicated slightly below 90 percent remov-
als of organic suspended solids during both modes of process recycle ad-
dition. The removal rate of organic suspended solids was not materially
affected by lime dose or overflow rate within the ranges shown by Figure
27 and Figure 28. Since acid pretreatment was used to dissolve parti-
culate calcium and phosphate solids, the resulting organic suspended sol-
ids still contained some fly ash from the sludge furnace scrubber. Both
Figures 27 and 28 appear to show that generally slightly better organic sol-
ids removal could be obtained when the recycle water was returned to the
primary instead of the floe basin. This difference may be caused by the
additional removal of fly ash in the primary and secondary clarifiers when
the recycle water is returned to the primary clarifier.
The untreated samples indicated a 68 percent increase in total sus-
104
-------
FIGURE 18
TOTAL BOD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO FLOC BASIN
O
-'
100
o
-------
FIGURE 19
SOLUBLE BOD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO FLOG BASIN
100
o
DC —
LL
S£
LU O
i- i
Z 0
111 _
u z
tr
BO
60
20'—
200
300
400
500
600
LIME DOSE,MG/LCaO
-------
FIGURE 20
PARTICULATE BOD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO FLOG BASIN
100
i
O
ill
^ ec
Q Ul
LU <
< LU
Q. X
O
80
80
40
20
200
300
400
500
600
LIME DOSE,MG/LCaO
-------
FIGURE 21
TOTAL COD REMOVAL
VS
LIME DOSE
••>
is
£ LI-
CC E
§§
o z
I- III
II
u
DC
ii
0
RECYCLE STREAMS TO FLOC BASIN
80
70
',1 =
ill
200
300
400
500
600
LIME DOSE, MG/L CaO
-------
FIGURE 22
SOLUBLE COD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO FLOG BASIN
so
-J
4 fin
> oc
r~) *•* *
Q -1
O <->
uu *t 40
_J 0
3 "j
0 0
1- Z
m
g 20
LLJ
Q.
V
>
0
Sv
\
\.
^•v^
0
O
o
^-^>__^
0
200 300 400 500 601
LIME DOSE, MG/L CaO
-------
FIGURE 23
PARTICULATE COD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO FLOC BASIN
100
_J
o
5 90
UJ Q-
OC uj
O u.
° E
UJ -J
1- 0
<_J
3 < 80
O 2
F 2
^ 0
PERCENT
IN
,8 a
O
O
o
— e —
— e — '
c
>
10 300 400 500 60
LIME DOSE, MG/L CaO
-------
FIGURE 24
TOTAL COD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO PRIMARY
100
BO
> cc
O in
Q
O O
I
60
20
100
200
300
400
500
LIME DOSE, MG/L CaO
-------
FIGURE 25
SOLUBLE COD REMOVAL
VS
LIME DOSE
RECYCLE STREAMS TO PRIMARY
80
60
UJ u.
cc
0 <
8d
UJ -1
-J <
oo o
£z
UJ ~
o
II
III
a
40
20
\
100
200
300
LIME DOSE, MG/L CaO
400
500
-------
FIGURE 26
PARTICULATE COD REMOVAL
VS
LIME DOSE
I
O
5
-------
FIGURE 27
ORGANIC SUSPENDED SOLIDS REMOVAL
VS
LIME DOSE
<
|(C
5 m
I/)
u
U
~ —'
< O
100
BO
',0
40
20
• - RECYCLE WATER TO PRIMARY
O - RECYCLE WATER TO FLOC BASIN
100
200
300
LIME DOSE.MG/L, CaO
400
500
-------
FIGURE 28
ORGANIC SUSPENDED SOLIDS REMOVAL
VS
CLARIFIER OVERFLOW RATE
O1
5 LLJ
_
LLJ LL
* E
w<
in O
U -I
IT LU
z z
111 —
•
DC
Ui
a
100
80
60
40
300
0
3
• - RECYCLE WATER TO PRIMARY
O- RECYCLE WATER TO FLOG BASIN
400
500
600
700
OVERFLOW RATE, GAL/FT2/DAY
-------
pended solids with the recycle streams added to the primary and a 50 per
cent removal of total suspended solids when recycle was added to the
flocculation basin. Turbidity reductions correlated well with the untreated
suspended solids evaluations. When the recycle was added to the primary,
turbidity increased 20 percent, but when the recycle was added to the
flocculation basin, there was a 70 percent reduction of turbidity. As dis-
cussed earlier, the direct addition of the turbid recycle streams to the
flocculation basin succeeded in improving the settling characteristics of
particulate calcium and phosphate sludges.
The chemical clarifier effluent color concentration was the same for
both modes of recycle addition, averaging 12 color units. It appears the
color reduction is approximately 50 percent across the clarifier.
MBAS was also evaluated across the chemical clarifier for both modes
of recycle addition. Pretreatment of the pH 11 clarifier effluent to pH 7 was
necessary before the MBAS concentration was determined. The results in-
dicated MBAS is not affected by lime coagulation and clarification.
As was expected, alkalinity and hardness increased across the clar-
ifier with the excess lime treatment of the unsaturated wastewater with re-
spect to hardness.
Point of Polymer Application. One rather significant finding was
made regarding phosphorus removal, as influenced by mixing and the point
of polymer application. From April through August, 1968, both the lime
and polymer were added ahead of the mechanical rapid mix and the floccul-
ation basin. This procedure produced a large instantaneous floe which
settled very well in the chemical clarifier. Laboratory jar tests indicated
however that better phosphorus removal was obtained by smaller floe part-
icles. To utilize this on a plant scale, the point of application of the
polymer was changed in September, 1968 to the clarifier influent pipe fol-
lowing the rapid mix and flocculation chambers. This change allowed a
fine lime floe to be formed and then agitated for 5-15 minutes before the
polymer was added, which in turn caused the agglomeration of the floe in-
to larger particles as the water entered the chemical clarifier for settling.
The prolonged mixing of the fine lime floe in the wastewater provided great-
er opportunities for contact with the phosphorus, and resulted in a reduc-
tion in the final effluent residual phosphorus from about 0.7 mg/1 to about
0.15 mg/1 with no increase in chemicals used.
Summary and Conclusions. Chemical treatment with lime addition
to the primary clarifier and the secondary effluent at South Lake Tahoe have
demonstrated the following:
116
-------
1. The addition of active lime to the primary clarifier resulted in
a mixture of lime and organic sludge which proved to be very difficult and
costly to dewater with a full scale centrifugal or a pilot vacuum filter.
2. During the period when lime was added to the primary clarifier,
the pH averaged 9.3, with a range of 7.5 to 11.0 plus. Phosphorus remov-
als averaged 20% and suspended solids removals 50%. During normal op-
eration, without lime addition to the primary, phosphorus removals aver-
aged 5% and suspended solids removals ranged from 50%-60%.
3. When lime was added to the primary, the activated sludge sy-
stem continued to satisfactorily perform and produce a normal secondary
effluent. The activated sludge mixed liquor had a considerable buffering
capacity for the high pH primary effluent, reducing a pH of 11+ in the pri-
mary effluent-return sludge mixture to 8.5 within five feet of the aeration
basin entrance.
4. The optimum lime dose for phosphorus removal from the second-
ary effluent per pound of lime at the South Tahoe Public Utility District
plant is around 300 mg/1 CaO. Only slightly greater removals are avail-
able at dosages up to 700 mg/1. The clarity of chemical clarifier effluent
also reaches an optimum at around 300 mg/1.
5. During the study, the point of addition of the recycle waters had
a noticeable affect on final effluent phosphorus concentrations. When the
recycle waters were added to the floe basin, the final effluent PO4-P con-
centration averaged from .07-.09 mg/1. More efficient clarification was
attained with the turbid recycle waters added to the floe basin and hence
better phosphorus removals.
6. Measurements of total and ortho phosphorus indicate practic-
ally all of the phosphorus in the secondary effluent is of the ortho form.
7. Clarifier overflow rates between 400 and 600 gal/day/ft2 had
no affect on phosphorus, BOD, COD, organic solids, or turbidity removals.
8. BOD removals averaged about 80% and COD removals averaged
slightly less at 60%. Increasing lime doses provided better clarification
and hence better total COD and BOD removals. Organic suspended solids
removals from the secondary effluent average slightly less than 90%.
9. Soluble BOD and COD removals decreased with increasing lime
dosages. It is felt that the high lime dosages converted portions of the
organic particulates to soluble forms.
117
-------
10. Color removals from the secondary effluent averaged about
50%.
11. Detergents, reported as MBAS, were not affected by lime co-
agulation.
12. Scale formation in the lime mud lines was easily removed by
the routine use of a polyurethane pig with abrasive cutting edges.
118
-------
SECTION XVI
TWO STAGE RECARBONATION
The purpose of two stage recarbonation at South Tahoe is two-fold;
first to adjust the pH for maximum calcium recovery in the reaction basin,
and then to further adjust the pH for optimum filtration, calcium stability,
carbon adsorption and, finally, export to Indian Creek Reservoir.
The system, located beneath the ammonia stripping tower, is divid-
ed into three sections; first stage recarbonation, a reaction basin, and
second stage recarbonation. The tower effluent flows into the first stage
basin where compressed scrubbed stack gases from the lime recalcining
and sludge incineration systems are used to reduce the pH. Three com-
pressors can supply 2,450 cfm at 6200 feet elevation at plant capacity of
7.5 mgd. In the first stage, the pH of the tower effluent is reduced from
11.0 to 10.3 with five minutes contact time at design flows. In the re-
action basin, after approximately fifteen to twenty minutes, the dissolv-
ed CC>2 has completed its reaction with the first stage effluent and the
pH is approximately 9.6. At pH 9.6, maximum CaCC>3 recovery is attain-
ed, with a corresponding reduction in alkalinity, hardness and total dis-
solved solids. The detention time of the reaction basin at design flows
is thirty minutes. The basin is provided with sludge collection equipment.
Approximately 17% additional CaCOs is settled out in the reaction basin
with the two stage system as compared to single-stage recarbonation to
pH 6.8 - 7.5. This additional removal also decreases deposition of
CaCOS in the ballast ponds. The second stage reduces the pH from 9.6
to 6.8 - 7.5. The second stage basin is slightly smaller than the first,
providing a 4-minute contact time at design flows.
Methods Used for Data Collection. Two methods of sampling were
used to evaluate the efficiency of the two stage recarbonation system.
For the first method, jar tests were performed to determine the pH level in
the first stage effluent to achieve maximum calcium recovery, and to study
the chemical composition of the water in the reaction basin. Secondly 24
hour composite samples were collected to evaluate on a plant scale reduc-
tions across the recarbonation system for alkalinity, chemical oxygen
119
-------
•MAIN
STACKS
1.000 CFM
POSITIVE
DISPLACEMENT
COMPRESSOR
500 CFH
POSITIVE
DISPLACEMENT
COMPRESSOR
CHECK
VALVE
EMERGENCY
PRESSURE
RELIEF VALVE
TO STANDBY
RECAR80NATION
GRID IN CHEMICAL
CLARIFIER EFFLUENT
LAUNDER
TO PRIMARY
RECARBONATION
GRID AT STRIPPING
TOWER
TO SECONDARY
RECARBDNATION
GRID AT STRIPPING
TOWER
FIGURE 29
RECARBONATION
SCHEMATIC
-RECARBONATION
CONTROL VALVE -
(BLEED-OFF)
IMPORTANT:
THE SUCTION VALVE AND AT
LEAST ONE OF THESE VALVES
MUST BE OPEN WHEN A CO;
COMPRESSOR IS RUNNING IN
ORDER TO AVOID A SERIOUS
ACCIDENT IN CASE OF RELIEF
VALVE FAILURE.
THE POSITIVE DISPLACEMENT
COMPRESSORS CAN DEVELOP
PRESSURES IN EXCESS OF THE
BURSTING STRENGTH OF PIPE
AND EQUIPMENT WHEN OPERATED
AGAINST A CLOSED PIPELINE
120
-------
lALIfS
& OPEN
ONI I
PPIH6
1ER
TOIEI
PUMP
SUMP
EFFLUENT
SLUICE GATE
OPEN
FLOW
RECIRCOLATIOM
FLAP BATE
PRIMARY
RECARBOIATIOI
BASIN
SHOE
GATE
OPEN
TOIER
BYPASS
SLIDE
GATE
CLOSED
REACTION
BASIN
EFFLUENT
SLUICE
BATE
CLOSED
SECONDARY
RECARBONATION
BASIN
'TO BALLAST
POND SPLITTER
BOX
EFFLUENT
SLIDE GATE
OPEN
FIGURE 30
AMMONIA STRIPPING TOWER
AND RECARBONATION BASINS
NORMAL OPERATION
121
-------
demand, phosphorus, total dissolved solids, suspended solids, turbidity,
and total hardness.
All of the jar tests were performed in the following manner on 500
ml samples of chemical clarifier effluent. The samples were recarbonated
to various predetermined pH's and placed on the gang mixer. The samples
were mixed for approximately 30 minutes at 35 rpm to allow for the CO2
reaction to take place. Four runs were made, two utilized recarbonation
to various pH's, with no chemical addition. The third was made with
recarbonation to pH 10.3, and the polyelectrolyte, ST-270, used to aid
settling in the chemical clarifier was added in varying dosages at the
beginning of the mixing period. In the last run the chemical clarifier
effluent was recarbonated to pH 10.3 - 10.6, and varying dosages of alum
were added at the beginning of the mixing period. After an hour of qui-
escent clarification, the supernatant was analyzed for pH, phenolphtha-
lein and methyl orange alkalinity, turbidity, and total hardness. The re-
mainder of the supernatant and the clarified sludge were filtered on "What-
man Glass Fiber (GF/A) filter paper, dried and the amount of sludge pro-
duced was determined.
Results of Jar Tests. Initially, to determine the length of time for
the CO2 reaction to be completed, a CO2 reaction curve was established.
A sample of chemical clarifier effluent was recarbonated with CO2 gas in-
stantaneously to pH 10.3, and a stopwatch was started. The pH was deter-
mined at minute intervals up to 10 minutes, and at 15, 20, 25, 30 and 150
minutes. The curve established is shown in Figure31 . The pH of the
sample dropped from 10.3 and leveled out at 9.6 within 15 to 20 minutes.
Also it is important to note, the pH of the sample dropped one-half
unit (10.3 - 9.8) in about 5-6 minutes.
The results of the first two runs to determine the optimum pH for
calcium recovery and water chemical composition are shown graphically
in Figures 32 through 35 . In Figure 32 , the amount of sludge produced
reaches a maximum in the completed pH reaction range from 9.4-10.0.
The two curves have different magnitudes because the jar tests were run
on different days and the chemical clarifier effluent pH varied from 11.5-
11.8.
The chemical composition of the water also supports the best sludge
production pH range of 9.4-9.9. A discussion of the wastewater hardness
at South Tahoe is necessary before chemical composition and sludge pro-
duction can be explained. At South Tahoe, calcium hardness as CaCOS
constitutes the major portion of the total hardness, with only a small
amount of magnesium hardness present. This has been verified in the
122
-------
FIGURE 31
pH
VS
REACTION TIME
(Jar Test)
11.0
'-
INITIAL pH -11.5
C02 ADDITION TO pH -10.3
10.0
150
REACTION TIME, MINUTES
-------
FIGURE 32
pH
VS
SLUDGE PRODUCED
(Jar Test)
/uu
600
500
3
5
E PRODUCED
j-.
8
Q
3 300
CO
200
100
0
7
0^
X
/
/
^ — e-^e.
o
1
O - INITIAL pH -11.8
• - INITIAL pH-1 1.5
^
0 8.0 9.0 10.0 11.0 12.
FINAL pH (AFTER RECARBONATION)
-124-
-------
FIGURE 33
H
TOTAL HARDNESS
(Jar Test)
140
O INITIAL pH - 11.8
T. HARDNESS - 520 MG/L
• INITIAL pH - 11.5
T. HARDNESS - 198 MG/L
8.0
9.0
10.0
11.0
12.0
FINAL pH (AFTER RECARBONATION)
125-
-------
FIGURE 34
SLUDGE PRODUCED
VS
HARDNESS REDUCTION
(Jar Test)
600
450
o
Q
o
K
Q
LI I
a
5
3
300
150
150
225
300
375
450
525
600
HARDNESS REDUCTION MG/L CaCO3
-------
FIGURE 35
PH
VS
ALKALINITY
(Jar Test)
280
12.0
-127-
-------
plant lab and at other private laboratories. In Figure 33, the pH and total
hardness relationship, the minimum total hardness is attained around the
completed reaction pH of approximately 9.4-9.6, and correspondingly,
the minimum calcium hardness or maximum calcium recovery in the sludge.
In Figure 34, a good correlation between sludge produced and total hard-
ness reduction supports the above fact that the greater the total hardness
or calcium reduction, the greater the amount of sludge produced.
In Figure 35, showing the pH and alkalinity relationships, at the
completed reaction pH of 9.4-9.9, a water is attained with very little
bicarbonates, no hydroxide or caustic alkalinity, and high in carbonates.
At this pH range a substantial amount of CaCOs is formed which can be
recalcined and reused as active lime.
Figure 36 shows the effect of adding the polyelectrolyte to the re-
cently recarbonated chemical clarifier effluent to aid in settling the cal-
cium carbonate suspension. A slight improvement in sludge production
is attained, with the best initial sludge settling in the mixing period at
polyelectrolyte dose of 0.05 and 0.1 mg/1.
Results of alum addition to settle the calcium carbonate suspension
are shown in Figure 37. Again, a slightly greater amount of sludge is attain-
ed at 5-10 mg/1 dosage, but at higher dosages the sludge production decreas-
es slightly. At alum dosages of 30 and 40 mg/1, a larger heavy, rapid settl-
ing floe was formed, but a contrastingly lower amount of sludge was recov-
ered. The hardness and alum dosage relationship corresponds well with the
sludge recovery curve. Figure 38 shows a slightly higher total and calcium
hardness in the treated water at the higher alum doses, and hence a lower
sludge recovery.
From the laboratory studies, the optimum completed reaction pH for
maximum calcium recovery and treated water chemical composition is in
the range of 9.4-9.9. Also, the addition of the two chemicals studied
did not greatly benefit sludge recovery, and the alum at the higher doses
resulted in a slightly harder water.
Results of Plant Scale Testing. Two continuous testing periods
were used to evaluate the two stage recarbonation system. The first test-
ing period ran from September 30 to October 13, 1970, and the second per-
iod ran from November 22 to December 6, 1970. The combined results from
both testing periods are shown in Table 13.
Hardness reduction was found to be the most useful parameter when
comparing pH adjustment by recarbonation with removal of calcium carbon-
128
-------
FIGURE 36
POLYELECTROLYTE DOSAGE
V:>
SLUDGE PRODUCED
(Jar Test)
300
250
' 3
a
a
in
•
Q
O
<-.-
0
Q
-'
200
150
100
INITIAL pH - 11.6
CX>2 ADDITION TO pH - 10.3
.3 .4 .5
POLYELECTROLYTE DOSAGE, MG/L
I JO
-------
FIGURE 37
ALUM DOSAGE
VS
SLUDGE PRODUCED
(Jar Test)
300
250
O
Q
1U
o
Q
O
n:
a.
3
_i
M
200
150
100
INITIAL pH - 11.7
CO2 ADDITION TO pH - 10.6
ALUM DOSAGE, MG/L
-------
FIGURE 38
HARDNESS VS ALUM DOSAGE
(Jar Test)
-J
5
'&
ill
Q
DC
10
15
20
ALUM DOSAGE, MG/L
-------
TABLE 13
AVERAGE PERFORMANCE OF
THE TWO STAGE RECARBONATION SYSTEM
10/13/70 - 11/13/70 and
9/30/70 - 12/6/70
Flow; 2 .85 mgd
Composite Samples pH Alkalinity mg/1 COD PO^P TDS S.S. Hardness Turbidity
24 hours CaCO3 mg/1 mg/1 mg/1 mg/1 mg/1 as SJU Stability
w phenol methyl CaCOs Index
Influent 11.1(1) 259 302 23 .33 323 21 191 6.7 3.6
Effluent 7.0 0 258 23 .43 288 49 133 14.3 8.1
Percent Removal 14.5 0 - 10.8 - 30.4
(1) First Stage pH 10
-------
ate in the reaction basin. Since full scale plant layout did not permit
actual measurement of sludge volumes produced, the indirect method of
comparing hardness reduction with sludge production (Figure 34) was used.
Depending on the first stage recarbonation pH, the hardness values
in the second stage recarbonation effluent ranged between 102 and 174
mg/1 as CaCOs. The lowest hardness and indirectly the greatest sludge
production was found to occur when the instantaneous pH in the first stage
recarbonation effluent was kept between 10.1 and 10.6. Since at the South
Tahoe Public Utility District there is normally about a 10-minute delay
between sample collection and laboratory analysis, the best operating pH,
in consideration of Figure 31, for the first stage recarbonation at South
Tahoe was between 9.5 and 10.0.
Calcium Stability. The stability index 2 pHs-pH, (where pHs =
the pH at calcium carbonate stability) was computed for the first stage re-
carbonation effluent and plotted against the first stage pH. The resulting
curve showed that below pH 9.5 the first stage effluent had corrosive ten-
dencies; whereas above pH 10, the first stage recarbonation effluent had
scaling tendencies. Figure 39 shows the resultant graph. The graph re-
presents 24-hour composite samples; therefore, the pH shown is after the
first stage carbon dioxide has had an opportunity to completely react.
The stability index was also used to determine the stability of the
second stage recarbonation effluent. Throughout the testing period this
stability index ranged between 7.3 and 9.2, on a scale where values above
six indicate a corrosive tendency. The average stability index was 8.1.
Since March 31, 1968, when lime coagulation was initiated, the
separation beds (filters) and activated carbon columns have been monitor-
ed for deposition of calcium carbonate. In November 1969 the six beds
were opened for electrical maintenance on the surface wash arms. At this
time the surface of the filter media was examined for calcium carbonate
buildup. From visual examination there appeared to be no buildup of cal-
cium carbonate on the media. Further, no hardness reduction was noted
across the beds. Two of these beds had been in operation since the summer
of 1966. During the inspection of the oldest set, a sample of sand and coal
from the surface of the filter was ground up and analyzed for calcium oxide.
The available CaO was 0.6%. A duplicate sample was calcined at 1800°F.
and analyzed for CaO. The available CaO was 1.1%.
133
-------
FIGURE 39
8.0
FIRST STAGE pH
VS
FIRGT STAGE STABILITY INDEX
7.0
I
a
C.
a
z
j.O
TENDENCY
CORROS
8
o
5.0
a
<
4.0
3.0
8.0
U
Z
III
o
z
111
I-
(3
Z
J
•I
K
i
\
9.0
10.0
11.0
12.0
pH
-------
In nearly 3 years of operation there has been only one filter mainten-
ance problem traceable to calcium carbonate scale buildup. This problem
occurred in June of 1970. One of the 28 automatic butterfly valves con-
nected with separation bed operations failed to function because of scale
buildup. Inspection of the valve seat and piping to and from the valve
showed a scale buildup of approximately 1/8 of an inch.
In October and November, 1970, carbon columns 1, 2, 3, 4, 5, 6
and 8 were inspected. No visual signs of calcium carbonate scale were
observed on the vessel walls or influent and effluent screens. The in-
spection was accomplished by transferring all of the carbon from the col-
umn to be inspected to the empty reserve column. Further, no scale has
ever been observed on the spent carbon since the beginning of lime coagul-
ation treatment.
Desired pH Level. The desired pH level in the second stage re-
carbonation basin, in order to prevent deposition of calcium carbonate,
was evaluated from September 1969 to November 1970. The monthly averages
of the daily stability indices, taken from 24-hour composite samples,
ranged between 7 .1 and 8.2 . The fourteen-month average was 7.6 . In-
dividual days were examined to determine an approximate relationship of
pH with this stability index. The stability index was found to be below
six for only one 24-hour composite sample in the fourteen months of study.
The particular pH was 8.9 and the resulting stability index was 5.9. Gen-
erally speaking at pH values of 8.3 or above, the stability index was 6.1
to 6.2. Below a pH of 8.0, this index was above 7.
The calcium carbonate chemical balance or stability test (marble
test) was performed on several occasions using the final effluent. This
independent check indicated that the water was in equilibrium as to car-
bonate constituents.
Chemical Addition. Laboratory and plant scale tests were perform-
ed to determine the quantity of chemicals required to settle the suspension
of calcium carbonate formed in the first stage recarbonation basin. Alum
and a polymer, Calgon ST-270, were chosen for the evaluation.
The laboratory results as outlined earlier, showed that neither chem-
ical significantly improved the capture of calcium carbonate.
No chemicals had been used in plant operation because good clarity
135
-------
was obtained in the effluent and therefore, the added expense of chemical
addition was not justifiable. However, for the purposes of the grant, 10
mg/1 of alum was added to the plant reaction basin just after the first
stage recarbonation. Four days of 24-hour composite sampling showed no
improvement in suspended solids or hardness reduction. The chemical
addition was discontinued.
Summary and Conclusions. Studies of the two stange recarbonation
system have demonstrated the following:
1. At current flows approximately 17% additional CaCOs is settled
out in the reaction basin following the first stage of a two-stage recarbon-
ation system. The additional recovery above that of a one-stage system
provides a net cost savings of about $25/mg at current flows.
2. After first stage recarbonation with CC>2, 15-20 minutes is
needed before the reaction is completed. The total pH drop after initial
recarbonation is about 0.7 pH units. Seventy percent of the pH drop takes
place in the first 5-6 minutes following recarbonation.
3. The best pH range for maximum sludge productions after first
stage recarbonation and 15 to 20 minutes reaction time is 9.4 to 9.9. The
optimum pH is 9.6. At the South Tahoe Public Utility District, where the
pH of the first stage recarbonation effluent is normally read about 10 min-
utes after sample collection, the best pH range is 9.5 to 10.0.
4. In the laboratory a slight improvement of sludge production
was noticed with addition of 0.05-0.1 mg/1 of Calgon ST-270 or the addi-
tion of 5-10 mg/1 alum. At plant scale no improvement in sludge produc-
tion was observed when 10 mg/1 of alum was added to the first stage re-
carbonation effluent. Until alum was used on plant scale no chemicals
had been added to the reaction basin in 2 years of operation because it
was felt that the effluent clarity and solids recovery was excellent and
that the added chemical cost could not be justified.
5. The stability index on a scale of 1 to 14, with scaling tendencies
below 6 and corrosive tendencies above 6, was used to estimate the desir-
ed pH level in the second stage recarbonation basin. It was found that pH
values between 8.3 and 8.7 produced water which had slightly corrosive
tendencies, according to the test. One 24-hour composite sample showed
a very slight scaling tendency at pH 8 .9. Below a pH of 8 in the secondary
recarbonation effluent, the water showed definite corrosive tendencies.
However, the marble tests of the finished water showed it to be stable.
136
-------
6. For fourteen months of continuous 24-hour sampling, the month-
ly average of the daily stability indices ranged between 7.1 and 8.2. The
fourteen month average was 7.6.
7. Inspection of the separation beds (filters) and the activated
carbon columns after two to three years of continuous operation failed to
disclose any visual signs of scale formation of any kind.
137
-------
SECTION XVII
LIME RECOVERY AND REUSE
General. At a flow of 7.5 mgd through the water reclamation plant
approximately 17 tons (dry CaO basis) per day of lime mud would have to
be dewatered and disposed of. Since about 93% by weight of this lime mud
is in the form of calcium carbonate , disposal costs would include not only
dewatering and disposing of about 34 tons of water and solids but also the
loss of recoverable calcium oxide. By recovering the lime through recal-
cination, the total blow-down of waste solids is reduced to about 1.5 tons
of dry solids. The cost of recalcined lime as shown later would be slight-
ly more than that of new lime at 7.5 mgd; however, at this flow the reuse
of lime reduces by a factor of 20 the amount of water and sludge to be dis-
posed of and, therefore, effects a substantial cost savings.
Physical System. Lime mud is pumped from the chemical clarifier
and recarbonation reaction basin to a 30-foot diameter gravity thickener,
with a design overflow rate of 1000 gal/ft2/day. Thickened lime mud is
pumped to a 24" x 60" solid bowl concurrent flow centrifuge. The cake
from the centrifuge is carried by a belt conveyor to a 14.3 foot diameter,
six hearth furnace in which calcium oxide and carbon dioxide are produc-
ed. The recalcined lime is conveyed out of the furnace by gravity through
a crusher to a thermal disc cooler where lime temperatures are lowered
from 700°F to 100°-150°F, and then into a rotary air lock. The recalcined
lime is pneumatically conveyed from the rotary air lock to a 35-ton capac-
ity recalcined lime storage bin for eventual reuse. Stack gases, rich in
carbon dioxide, are scrubbed in a multiple tray scrubber before being ex-
hausted to the atmosphere. A portion of the gases are recycled to the re-
carbonation system. See Figure 41.
Solids wasting must be performed continuously to maintain an accept-
able calcium oxide content in the recalcined lime. Wasting can be accom-
plished by feeding recovered lime to the primary clarifier, by diverting
part of thickener influent to the primary clarifier, by conveying lime mud
cake from the centrifuge directly to the organic sludge furnace or by us-
ing the centrifuge to classify the phosphate and other inerts into the cen-
trate and the calcium carbonate into the dewatered cake conveyed to the
139
-------
Figure 40
SOLIDS HANDLING BUILDING
140
-------
MAIN
STAC*
SC«UBBE«
LIKE
RECALCININ6-
FUftNACE
FURNACE
RABBLE
ARI DRIVE
XXX
X X NX X "
BYPASS -
OEIUEREt $r S
LI HE SLUOCE^X^X /
STORAGE BIN y
TRUCK
LOAD INC
TO
SEItBE
SLUDSE
FURNACE
FROK
CHEHICAL
CLARIFIER
SLUOQE
PUHP
\v/ws/>>
COMBUSTION
AIR BLOIE*
SHAFT
COOLIN6
RECALCINED
LINE BLOIER
^THERMAL
OISC.
FRESH
LIKE TO
SPLITTER
BOX
SO
FIGURE
IDS HAN
IME SLU
41
DLI
DGE
NG
141
-------
Figure 42
FURNACE CONTROL PANEL
142
-------
recalciner. A second centrifuge dewaters the centrate from the first
machine and its cake is conveyed to the organic sludge furnace.
The centrate from the lead centrifuge may be returned to the prim-
ary clarifier instead of directed to the second machine. The second cen-
trifuge's centrate is returned to the primary. The spillage from the lime
conveyor belt is collected in a tray and returned to either the primary
clarifier or to the lime mud thickener.
Operating Practice. Since plant startup in 1968, steps have been
taken to remove all active lime or waste lime mud streams from the prim-
ary clarifier. As described in the "Chemical Treatment" section, feeding
active lime to the primary clarifier led to organic sludge dewatering prob-
lems and to some extent adversely affected primary clarification. Waste
lime mud streams being returned to the primary clarifier also affected, but
to a lesser extent, the dewatering characteristics of the raw and waste
activated sludges.
In January, April and May 1970, and from July 1970 to date, the
lime centrifuge has been used to classify inert materials out of the feed
to the recalcining furnace. At the same time, the classified centrate from
the first centrifuge has been dewatered and clarified in a second centri-
fuge and dried in the organic incineration furnace. The degree of classi-
fication and resulting economies are discussed later in this section.
Lime Mud Thickening. Total solids tests were used to evaluate
the efficiency of the lime mud thickener. To determine the amount of cal-
cium lost over the thickener launder the following procedures were used.
Basin overflows and sludge withdrawals were measured to determine the in-
fluent flow. The amount of calcium in the thickener influent was determin-
ed by heating the influent total solids samples in the laboratory muffle
furnace at 1850°F for two hours and then determining the available CaO
content. By this method, the calcium hydroxyapatite, Ca5OH(PO4)3, was
not included, and the value reflected only the calcium in CaCOs and
Ca(OH)2- Part of the influent sample was filtered 0.45 u millipore filter
and calcium hardness was run on the filtrate to determine the Ca(OH)2«
The difference in the two provided the pounds of usable calcium available
for thickening.
The pounds of usable calcium in the thickener overflow were found
by determining the difference in calcium content between acidified and fil-
tered samples.
143
-------
The amount of usable calcium lost over the thickener launder was
evaluated over an eight hour composite sampling period. Using the pro-
cedures described above, 0.04% by weight of the usable calcium coming
into the thickener was lost over the weir.
The true ability of the thickener to concentrate lime mud solids
could not be evaluated due to low plant flows. Thickener influent percent
solids were about 1% by weight. At chemical clarifier flows of 2.8 mgd
and thickener underflow rates of 36 gpm, the lime mud was thickened to
4.9% solids; whereas at 3.7 mgd through the chemical clarifier and 15 gpm
thickener underflow rate, lime mud was thickened to 8.3% solids.
Lime Mud Classification and Dewatering. During the lime centri-
fuge acceptance tests, three bowl speeds were evaluated to determine the
optimum centrifugal bowl speed. The three bowl speeds evaluated were
1600, 1800, and 2200 rpm. Each of the three evaluations were conducted
at 140:1 gear reduction ratio. The function of the gear unit is to drive the
conveyor at a fixed speed relative to the bowl. For the three bowl speeds
above, the conveyor revolved at approximately 11.5, 13, and 15.5 rpm. For
all three bowl speeds evaluated, the cake solids ranged from 36-38%, and
recovery or capture remained fairly constant. As a result, the lowest bowl
speed of 1600 rpm was chosen for plant operations because of the reduced
wear and maintenance problems.
Chemical Addition. Since the lime centrifuge is used primarily
for classification purposes and not dewatering, polyelectrolytes were not
used to condition the thickened mud prior to centrifuging. In the next
section the excellent classification results are discussed. The addition
of a polyelectrolyte to the centrifuge feed would defeat these purposes.
Classification Evaluation. Two methods were used to evaluate the
centrifugal classification of the inert calcium hydroxyapatite out of the
lime solids recovery stream. The first was to make four, ten-minute samp-
ling runs with high and low feed rates and pool depths within the centri-
fuge to optimize the classification process. An approximate twenty min-
ute interval was allowed after making adjustments to the centrifuge to
insure steady state conditions for a particular set of variables. The cen-
trifuge bowl speed was kept constant at 1600 rpm. During each ten-minute
period a sample was composited uniformly on the feed, centrate, and cake
steams. The centrifuge pool depth, cake volumetric flow rate and wet
144
-------
density, and centrate flow rate were recorded. The composited samples
were analyzed for total solids and then calcined in a muffle furnace at
1750°F. The total solids, percent capture and centrate flow rate were used
to compute the feed rate. After calcination, the samples were analyzed
for CaO, and samples were dissolved in acid and analyzed for magnesium
and orthophosphates.
With the volumetric flow rate and phosphate and calcium results,
balances were made around the centifuge for usable calcium, and the inert
materials, magnesium and phosphate.
The second method was to composite a sample of centrifuge feed,
centrate, and cake every two hours for an eight hour period. The centri-
fuge centrate flow rate was recorded every two hours also. As in the pre-
vious evaluation, the centrifuge bowl speed was maintained at 1600 rpm.
The resulting composite samples were analyzed for total solids, calcined
at 1750°F for 2 hours, and then the usable calcium was determined by an-
alyzing for percent calcium oxide. The dilutions and analysis for phos-
phate used for the first evaluation were repeated. The percent capture for
solids was computed with the analysis information, and the appropriate
balances around the centrifuge for usable calcium and phosphate were deter-
mined .
/
Classification Evaluation Results. A brief explanation of the eff-
ects of changing the pool depth in a centrifuge is necessary before the
classification results are explained. If the pool depth is increased, the
cake should get progressively wetter. It is possible to increase the pool
depth to the extent that the cake leaves the centrifuge as a wet slurry.
However, if the pool depth is decreased to just below this point, the
maximum capture should be attained. Conversely, if the pool depth is
decreased, the centrate should have a higher solids content, lower per-
cent solids capture, but the cake should be drier. The centrifuge pool
depth setting is on a scale of 1-10, with a low number corresponding to a
low pool depth and a high number, a high pool depth. As Figure 43 indi-
cates, the centrifuge performed as was expected, the higher pool depth
produced the higher captures for similar flow rates. The flow rate to the
machine also has a significant effect on the solids capture, with a mark-
ed decrease in solids recovery at the higher flows. The highest flow rate,
23 gpm, had a feed solids content of 6%, whereas the other four data points
had feed solids contents of 8%. Also the highest flow rate data point was
derived from an eight-hour sampling period, and the other four points were
from ten minute sampling periods.
145
-------
Q
UJ
OC
9
g
h
Ul
O
cc
FIGURE 43
PERCENT SOLIDS CAPTURED VS FLOW RATE TO CENTRIFUGAL
10 15 20
FLOW RATE TO CENTRIFUGAL, GPM
30
-------
The removal of inert materials by classification into the centrate
stream provides many benefits to the lime treatment and solids recovery
system. A significant savings in fuel usage is realized, which is des-
cribed later in the recalcining portion of this section. Also the size of
the waste stream is reduced, a smaller amount of usable lime is lost,
which results in lower makeup lime dosage and costs. The effect of sol-
ids capture or recovery in the centrifuge on the removal of inert materials
from the feed to the recalcination furnace by classification is shown in
Figures 44 through 47 . The data in Figures 44 and 45 is derived from the
two previous sampling runs described and from three runs of the optimi-
zation of the recalcination furnace described later. As would be expect-
ed, higher captures of solids from the centrifugal feed will result in a
lower percent increase in the usable calcium or active lime, CaO, in the
cake. At lower captures the lower specific gravity inert materials can be
separated from the usable lime. This is very evident in Figure 44, at 90%
solids capture there is only a 5% improvement in the percent CaO of cake
over the feed to the centrifugal. At 70-75% solids capture, a 12-15% im-
provement in the cake percent CaO over the centrifugal feed can be ex-
pected. Correspondingly in Figure 45, at 95% capture practically all of
the usable calcium is conveyed to the recalcination furnace, but so are a
majority of the inert materials. At lower solids recoveries a portion of
the usable calcium is lost in the centrate, but the higher active lime or
CaO content of the cake from better classification of the inerts more than
offsets this loss.
Since one of the high priorities of the treatment at South Tahoe is
to remove phosphorus from the wastewater, the logical question is how
efficient is the phosphorus removal from the lime solids recovery stream.
In Figure 46, the effect is shown of solids capture and classification on
the amount of phosphate wasted in the centrate. The four data points a-
bove 80% capture are taken from the ten-minute sampling periods and the
other point is taken from the eight-hour period. At 90% capture or 10% of
the solids entering the centrifuge being removed in the centrate, a 20%
reduction in phosphate in the cake can be expected. A centrate contain-
ing 20% of the solids entering the centrifuge will have almost 40% of the
phosphate entering the centrifugal. According to the trend indicated in
Figure 46, 90% of the phosphates in the centrifuge feed can be wasted
to the centrate at 75% solids capture or recovery, which corresponds well
with Figure 44, indicating a near maximum increase in the cake CaO over
the centrifuge feed CaO around 75% capture of solids. The removal of
magnesium from the centrifuge feed to the centrate by classification is
shown in Figure 47 . The four data points shown in Figure 47, are from
the ten-minute sampling runs; magnesium was not analyzed in the eight-
hour run. The fourth point in Figure 47 was disregarded in drawing the
147
-------
FIGURE 44
EFFECT OF CENTRIFUGAL CAPTURE ON THE CHANGE IN
CALCIUM OXIDE CONTENT OF THE CENTRIFUGAL CAKE
95
90
»
Q
LLI
E
EL
<
o
I
8
HI
o
o:
LLJ
a.
85
80
7'.
70
+5%
CaO
+10%
CaO
RELATIVE INCREASE IN CAKE CaO CONTENT
TO FEED CaO CONTENT
+15%
CaO
+20%
CaO
-------
FIGURE 45
PERCENT SOLIDS CAPTURED
VS
PERCENT OF USABLE CALCIUM IN FEED CONVEYED TO FURNACE
96
90
-u
to
(j
ui
rr
-j
O
u
o
H!
I
85
75
75 80 85 90 95
PERCENT OF USABLE CALCIUM IN FEED CONVEYED TO FURNACE
100
-------
FIGURE 46
PERCENT SOLIDS CAPTURED
VS
PERCENT OF P04 IN FEED WASTED IN CENTRATE
95
90
\
Ol
9
Q
01
DC
O
t/J
Q
V)
I-
UJ
O
tr
in
a.
85
80
75
70
20
40
60
80
100
120
PERCENT OF P04 IN FEED WASTED IN CENTRATE
-------
FIGURE 47
100
PERCENT SOLIDS CAPTURED
VS
PERCENT OF MAGNESIUM IN FEED WASTED TO CENTRATE
Q 95
UJ
K
1
<
O
3 90
8
o
cc
UJ
Q.
85
80
10
15
20
25
30
35
40
PERCENT OF MG IN FEED WASTED TO CENTRATE
-------
line, since the analysis for this run resulted in a 15% error in the magnes-
ium balance around the centrifugal. However, the same trend as the
wasting of phosphates in Figure 46 is indicated. At 80% capture, approxi-
mately 35% of the magnesium entering the centrifuge is classified into
the centrate.
To further exemplify the classification abilities of the lime centri-
fuge the organic sludge and recalcination furnaces' scrubber waters were
analyzed for ortho phosphorus (mg/1 PC>4-P) for three different periods of
operation. The first period was under normal classifying operations with
the lead lime centrifuge classifying and the swing centrifuge dewatering
the centrate and conveying the waste inert materials to the organic sludge
furnace. The second period was when the recalcination furnace was remov-
ed from service for a short period for maintenance, but the organic solids
furnace continued to operate. The third period was when the lead lime
centrifugal was not used for classifying, but dewatering only, and the re-
sulting cake was being recalcined. The average results of the three per-
iods are shown in Table 14 .
TABLE 14
SCRUBBER WATER
ORTHO PHOSPHORUS CONTENT, mg/1 PO4-P
Operation Mode Sludge Furnace Recalcination Furnace
Total Soluble* Total Soluble*
Classification 17.95 .56 2.4 .32
Not Recalcining 1.54 0.08 0.19 0.07
Lime Centrifuge 3.59 — 12.02
for dewatering only
* Soluble defined as passing a .45 u filter.
The water reclamation plant effluent is used for the source of sup-
ply for the furnace scrubbers. The normal ortho phosphorus content of
the plant effluent is in the range of .06 to 0.1 mg/1. When the recalcina-
tion furnace was out of service, it's scrubber water phosphorus content
was barely affected. During the same period, when the sludge furnace
was incinerating only organics, it's phosphorus content was 1.5 mg/1,
all particulate. When the lead lime centrifuge is used for dewatering
152
-------
purposes only, the lime centrate is directed to the primary where the lime
solids that are in the centrate settle out and are dewatered and dried or in-
cinerated with the organic sludges. During this period the phosphorus con-
tent of the sludge furnace scrubber water increased to 3.5 mg/1, as a re-
sult of the lime centrate being directed to the primary. Since the lime
centrifuge is operated with the highest possible solids capture when it is
used as a dewatering device, the majority of the inert materials are convey-
ed to the recalcination furnace with the lime cake. This resulted in a much
higher phosphorus scrubber water content of 12 mg/1. Only total ortho
phosphorus was analyzed during this period. During the period of normal
operations when the lead lime centrifuge is used for classification the
sludge furnace, drying the concentrated waste lime inerts increased to
18 mg/1, mostly particulate. Since the majority of the inert materials had
been classified out of the lime cake, the recalcination furnace scrubber
water content decreased to 2.4 mg/1, mostly particulate.
Lime Mud Recalcining. Since April 1968 the District has success-
fully recalcined lime mud from the lime chemical treatment process. Over
this period makeup lime has accounted for only 28 percent of the calcium
oxide used. Average monthly CaO values in the recalcined lime have rang-
ed between 51.0% and 74.7% with the average over the entire period being
66.0%. Table 15 shows the operating data for the lime mud recalciner. A
reduction of approximately 40% in fuel requirements was achieved when
centrifugal classification was used.
In an effort to measure the usable calcium losses in the recalcina-
tion furnace, the assumption was made that all the calcium lost as fly ash
would be captured in the wet scrubber. The increase in calcium and phos-
phate in the scrubber water as a result of fly ash consisting of usable cal-
cium and inert calcium hydroxyapatite was measured by acidifying the
scrubber influent and effluent samples to pH 2.0, filtering with a .45 u
filter, neutralizing the filtrate to pH 7 and analyzing for calcium hardness
and phosphate. The phosphate was measured to determine the amount of
calcium combined with the hydroxyapatite. The difference in terms of cal-
cium, of the calcium hardness and the calcium combined with the hydroxy-
apatite provided the amount of usable calcium loss from the furnace. By
measuring the amount of usable calcium in the centrifuge cake entering
the furnace, described earlier in the classification and dewatering portion
of this section, the percent calcium losses from the furnace can be deter-
mined. The amount of usable calcium loss from the furnace in the scrubber
water was evaluated over an eight hour composite period. Using the anal-
ysis procedures and assumptions described above, 3.7% by weight of the
usable calcium entering the furnace during the eight hour period was lost
from the furnace.
153
-------
TABLE 15
LIME RECALCINER OPERATING DATA
No Centrifugal Centrifugal
Classification Classification
Pertod Oct. 69 - May 71 July 70 - Nov.70
Chemical Clarifier Flow, MGD 2.95 3.63
Feed, Ibs/hour*1) 435 756
Feed, % Solids 33.3 42
Electricity KWHR/day^2^ 508
Fuel Requirements ,BTU/lb(3) 5500 3270
(1) Pounds of dry solids per hour
(2) Includes energy and demand charges for furnace support motors
and recalcined lime conveying system. February 70 to Decem-
ber 1970
(3) Natural gas at 18 psia and 860 BTU/ft3
154
-------
Optimum Furnace Conditions. Eades and Sandberg in their dis-
cussion of lime reaction parameters point out that, "Although the art of
lime burning has been practiced since ancient times, it was not until the
18th century that a scientific explanation of calcination was advanced. As
industrial and chemical technology developed, lime became an increasingly
important component in numerous reactions and processes. For these appli-
cations, the lime was judged primarily on its chemical purity, and minimal
amounts of silica, alumina, iron, and other impurities were desired. In
general, reaction rates were not thought important."
"Reaction rates of commercial limes became a matter of considerable
interest with the introduction of the basic oxygen converter steel furnace.
Operation costs for such converters are quite high, and steel producers
quickly began investigation of methods to lower the time per heat of steel.
Metallurgists became interested in the relationship between lime reactiv-
ity and slagging time. As a result of these and other studies, it quickly
became apparent that in steel making and many other industrial applications
reactivity of a lime was a more significant criterion for judging quality and
suitability of a lime than chemical purity."
The authors further state, "that pore space and calcium oxide (CaO)
crystallite size are the prime factors controlling reactivity of any given
lime. These in turn can be linked to calcining conditions with low tempera-
ture burning producing a highly porous, highly reactive lime and high tem-
perature burning producing a shrunken, dense lime with low porosity and
low reactivity".
According to the AWWA Standard for Quicklime and Hydrated Lime
(AWWAB202-65), high-reactive, soft-burned lime will show a temperature
rise of 40°C in 3 minutes or less and the reaction will be complete within
10 minutes when tested by the method given in the standard. A medium-
reactive, medium-burned lime will show a temperature rise of 40°C in 3 to
6 minutes and the reaction will be complete in 10-20 minutes. For low re-
active, hard-burned lime more than 6 minutes will be required for a 40°C
temperature rise and the complete reaction time will take longer than 20
minutes.
Since it is possible to produce quicklime with the same calcium oxide
content, but with very different slaking properties, tests were performed on
the lime recalcining furnace. The purposes of the tests were to'determine
the optimum recalcining temperature, feed rate and rabble rate in terms of
lime reactivity and furnace fuel requirements.
155
-------
The Rapid or EDTA Method for calcium oxide as described in Section
XI and the AWWA Slaking Rate Test at 400 rpm were used to determine the
reactive properties of the recalcined lime. At least an hour was allowed
after changes in process variables to permit the furnace to reach equilibrium,
A sample was then composited at 15-minute intervals from the No. 6 hearth
for an additional hour. Composite feed samples were also collected at the
same intervals and recalcined in the laboratory muffle furnace at 1800°F for
1 hour to insure that the potential input calcium oxide remained constant.
To establish a qualitative base line, calcium oxide and slaking rate
tests were performed on virgin makeup lime. The data presented in Figure
48 shows that the makeup 16 x 50 mesh granular quicklime used at South
Lake Tahoe is highly reactive. A 40°C temperature rise is reached in less
than 30 seconds and the reaction completed in seven minutes. Identical
results were achieved in three separate tests of the sample.
The effect of temperature on the recalcined lime activity at a constant
feed and rabble rate was first investigated. Table 16 shows that recalcin-
ing temperatures between 1600°F and 1900°F had a major effect on recalcin-
ed lime activity, although all three temperatures produced lime which, un-
der the AWWA standard, was considered to be highly-reactive. Within
this temperature range there was no indication that the lime was being over-
burned, since the total reaction time was well within the time requirements.
Recalcining lime at 1900°F as opposed to 1800°F produced a 5% increase in
available calcium oxide, but very little improvement in an already accept-
able slaking rate.
At 1600°F the flour-like recalcined lime showed pronounced tenden-
cies to agglomerate into soft, easily crushed particles of 1/4 inch to 3/4
inch diameter. Many of the particles contained centers of unburned organ-
ic sludge. Additional evidence of unburned organic sludge was observed
in the Dewar Flask after the slaking test.
For the second phase, the rabble rate was varied between 1.5 and
2.0 rpm while the temperature and feed rate were held constant. At both
1900°F and 1600°F the variation of rabble rate showed very little effect on
the recalcined lime activity. Once again temperature proved to be the maj-
or variable. Table 17 shows the results of varying the rabble rate.
Finally,to determine the effect of feed rate, the temperature and rab-
ble rate were held constant at 1900°F and 1.5 rpm, respectively. The feed
rate to the centrifugal was run at 870, 820, and 450 pounds of dry solids
per hour. Table 18 shows that the total slaking time doubled when the feed
rate was reduced from 870 Ibs/hr to 450 Ibs/hr with no significant change
156
-------
a\
FIGURE 48
VIRGIN LIME SLAKING RATE TEST
AWWA STANDARD B202-65
90
SLAKING TEMPERATURE °C
: g § 8 8 3 8
7
1
1
1
1
1
1
1
1
1
1
t
1
1
1
1
I
1
1
24.5°C
^
>—— 0 <
, o
-------
TABLE 16
Effect of Temperature On
Recalcined Lime Activity
At a Constant Feed and
Rabble Rate
No. 3 Hearth
No. 4 Hearth
No. 5 Hearth
Percent CaO
Recalcining Temperature °F
1640 1630 1450
1900 1710 1620
1900 1780 1600
86
81
76
Slaking Rate:
60 Sec. Temp. Rise, °C 50 48
Total Temp. Rise, °C 51.5 48
Total Reactive Time, min. 2 1
41
41
1
Feed Rate,
Rabble Rate, rpm
870
1.5
800
1.5
870
1.5
( 1 ) Dry solids to centrifuge
158
-------
TABLE 17
Effect of Rabble Rate
On Recalcined Lime
Activity At a Constant
Feed Rate
Rabble Rate, rpm
2.0 rpm 1.5 rpm
1900°F Avg Temp (D
Percent CaO 86 86
Slaking Rate
60 Sec. Temp. Rise, °C 51.5 50
Total Temp Rise, °C 52 51.5
Total Reaction Time, min. , 1.5 2
Feed Rate (2), Ibs/hr 940 870
1600°F Avg Temp Q)
Percent CaO 70 76
Slaking Rate
60 Sec. Temp. Rise, °C 39 41
Total Temp Rise, °C 39.5 41
Total Reaction Time, min. 2 1
Feed Rate (2), Ibs/hr 830 870
( 1 ) Average of No. 4 & No. 5 Hearth temperatures
( 2 ) Dry solids to centrifuge
159
-------
TABLE 18
EFFECT OF FEED RATE ON
RECALCINED LIME ACTIVITY
AT 1900°F (1) AND 1.5 RPM
RABBLE RATE
FEED RATE (2) Ibs/hr
870 820 450
Percent CaO 86 90 89
Slaking Rate
60 Second Temp. Rise, °C 50 50.5 50.5
Total Temp. Rise, °C 51.5 53.5 53.5
Total Reaction Time, min. 2 2.5 4
(1) Average of No. 4 and No. 5 hearth temperatures
(2) Dry solids to centrifuge
160
-------
in the calcium oxide content. All three feed rates produced highly-react-
ive recalcined lime under the AWWA standard. However, the lower feed
rate produced a less reactive lime.
The optimum furnace conditions in terms of recalcined lime activity
appear to be about 1900°F on the fourth and fifth hearths at 1.5 to 2.0 rpm
rabble rate for 800-900 Ibs/hr of dry solids to the centrifuge. The centri-
fuge was being used as a classifying device during this test period. On
the basis of the 75% capture that was obtained, the actual furnace feed
rate for the optimum conditions was 600 to 700 Ibs/hr.
A slightly less reactive lime was obtained at an average recalcining
temperature of 1750°F. At the same loading rates and taking into consider-
ation the higher natural gas consumption, increasing the calcium oxide
content from 81% at 1750°F to 86% at 1900°F saved approximately $2.00 per
ton of dry solids fed to the furnace.
The soft burned recalcined lime produced at South Lake Tahoe has,
as previously mentioned, a flour-like texture. Individual particles are not
easily seen without magnification. The large surface area to volume ratio
makes the recalcined lime very easy to slake. Tables 16, 17 and 18 all in-
dicate that the total slaking time was four minutes or less; whereas the
highly reactive 16 x 50 mesh granular makeup lime required seven minutes
for total slaking.
Conclusions. At the 7.5 mgd design flow about 34 tons per day of
dewatered lime would have to be disposed of if lime recovery and reuse
were not practiced. Through lime recalcination the total blow-down of
waste solids is reduced to approximately 1.5 tons of dry solids. The cost
of recalcined lime is slightly more than that of new lime, however, the
reuse has and will avoid the costs of disposal and purchase or production
of CO2- Lime recovery and reused at South Lake Tahoe has demonstrated
the following:
1. Lime recalcination provided not only 72 percent of the lime used
for the past three years, but also a usable source of carbon dioxide.
2. Industrial gravity type thickeners are an effective device for
thickening lime mud containing organic solids with very low weir overflow
losses of usable calcium.
3. A concurrent flow centrifuge can be used to separate or classi-
fy phosphate rich inerts and magnesium from reusable calcium carbonate.
161
-------
4. Three centrifuge bowl speeds, 2200, 1800, and 1600 rpm, were
used to determine optimum bowl speed. All three speeds produced approx-
imately the same percent cake solids and recovery or capture. Consequent-
ly the lowest bowl speed, 1600 rpm, was selected for plant operations to
reduce wear and maintenance costs.
5. The lime centrifuge performed as expected with high solids
captures at high pool depths and lower flows to the machine. Conversely,
at low pool depths and higher flows solids capture was less.
6. At 9 tons of solids to the furnace per day, the optimum recal-
cining conditions were 1900°F on the number 4 and 5 hearths with a 1.5-
2.0 rpm rabble rate.
7. Of the three parameters, recalcining temperature, rabble rate
and feed rate, temperature had the most effect on recalcined lime activity.
The CaO content in the recalcined lime was increased 15% by raising the
temperatures from 1600°F to 1900°F.
162
-------
SECTION XVIII
NITROGEN REMOVAL
General. Nitrogen removal appears to be the major remaining barr-
ier to disposal of reclaimed water in the Tahoe Basin. Since there is some
opinion that algal growths in Lake Tahoe are presently nitrogen limited, it
is quite possible that nitrogen removal must be successfully demonstrated
on a plant scale prior to any possible reconsideration of in-basin reuse or
disposal of purified wastewater. Also, in many water short areas of the
world, the need for an economical and reliable means of removing nitrogen
from wastewater has prompted many pilot studies of the various methods of
removing nitrogen from wastewater. Basically these were the reasons for
extensive ammonia stripping pilot studies carried out by Smith and Chap-
man at South Lake Tahoe. Upon completion of the pilot plant tests with a
24-foot countercurrent tower, it was decided to build a plant scale unit to
one-half total plant capacity to verify pilot plant results and to evaluate
such potential problems as freezing and calcium carbonate scaling. Al-
though after six months of testing, scaling on the pilot tower fill was not
evident, it was felt this problem might arise in a full scale tower, and the
possibility of altering the original design would be less difficult for a tower
built to one-half plant capacity. In the same light, tower freezing problems
in the winter and their possible solutions or alterations could be accomplish-
ed more easily on a smaller tower.
Ammonia Stripping Tower Physical Description. The principal de-
sign features of the Tahoe ammonia stripping tower are given in Table 19.
Although the pilot towers were countercurrent airflow towers, the full-scale
tower was designed as a cross flow unit.
The completed tower is shown in the photograph of Figure 49. The
overall dimensions of the tower are 32 feet x 64 feet x 47 feet high. Wat-
er, at pH = 11, is pumped to the top of the tower by one of two constant
speed pumps. These pumps are backflushed two or three times daily to
minimize buildup of calcium carbonate scale in the pump units. When the
163
-------
TABLE 19
DESIGN DATA FULL SCALE AMMONIA STRIPPING TOWER
Capacity:
Type:
Fill:
Air Flow:
Nominal, 3.75 mgd
Cross flow with central air plenum and vertical air
discharge through fan cylinder at top of tower
plan area, 900 square feet
Height, 24 feet
Splash bars:
material, rough sawn treated hemlock
size, 3/8" x 1-1/2"
spacing, vertical 1.33 inches
horizontal 2 inches
Fan, two-speed, reversible, 24-foot diameter, horizontal
Water Rate
Air Rate
gpm
1,350
1,800
2,700
gpm/sf
1.0
2.0
3.0
cfm
750,000
700,000
625,000
cfm/gpm
550
390
230
Tower Structure:
Redwood
Tower Enclosure: Corrugated cement asbestos
Air Pressure Drop: 1/2 inch of water at 1 gpm/sf
164
-------
Figure 49
NITROGEN REMOVAL TOWER
165
-------
plant inflow is less than the rate at which the pumps are delivering water
to the tower, some water is recycled from the tower effluent back to the
pump suction well. This avoids the need for variable speed pump control,
and at the same time provides some recirculation through the tower, which
improves ammonia removal.
At the top of the tower, the influent water enters a covered distribu-
tion box and overflows to a distribution basin. The distribution basin is a
flat deck with a series of holes fitted with plastic nozzles. Further dis-
tribution of the inflow is provided by diffusion decks immediately below
the distribution basin. At 6-foot vertical intervals in the fill there are three
other diffusion decks. The tower fill proper provides, theoretically, 215
successive droplet formations as the water passes down through the tower.
The tower effluent falls into a concrete collection basin which also forms
the base for the tower structure. From the collection basin, the tower ef-
fluent passes through a rectangular measuring flume into a chamber, where,
as previously mentioned, excess pumpage returns through a flap gate into
the tower pump sump to be recirculated through the tower. The remaining
flow passes from this chamber to the first stage recarbonation section.
Air enters the tower through side louvers, passes horizontally through
the tower fill and enters a central plenum. At the top center of the plenum
is a 24-foot diameter, six-bladed, horizontal fan. Fan blades and fan cy-
linder are both made of glass-reinforced polyester. The fan takes suction
from the plenum and discharges to the atmosphere through the fan cylinder.
The fan has a maximum capacity of about 750,000 cfm. It is equipped with
a two-speed, reversible 100 hp motor. The tower was constructed in the
summer and fall of 1968, and put on line October 29, 1968.
Tower Performance. Initially, tower operation was on an intermitt-
ent basis as a result of extreme cold and snow conditions in November,
1968. In the later part of November through January some operational re-
sults were obtained when weather conditions permitted. In Table 20 are
listed the operating parameters and the ammonia removal efficiencies ob-
tained during low temperature winter operation. The air/water ratio is
computed with a theoretical fan output curve provided by the manufacturer.
From the data tabulated in Table 20, the air temperature ranged from 31 to
43°F, the influent water temperature ranged from 48 to 52°F, and the aver-
age temperature drop through the tower was 14°F. The surface loading rate
averaged 1.9 gpm/sf, with a range of 1.2 to 2.9 gpm/sf. The theoretical
air to water ratio, cf/gal, averaged 535, with a range of 235 to 750 cf/gal.
The pH of the tower influent water averaged 10.7 with an average drop of
0.1 pH unit through the tower. The average percent removal of ammonia
was 64%, with a range of 47 to 89%. From the pilot plant data, Smith and
Chapman , indicated that the probable average lower limit of ammonia
166
-------
en
TABLE 20
LOW TEMPERATURE AMMONIA STRIPPING AT SOUTH LAKE TAHOE PLANT
Date
11-27-68
11-28-68
11-28-68
11-29-68
11-29-68
12-23-68
1- 3-69
1- 3-69
1- 3-69
1- 3-69
1- 4-69
1- 4-69
1- 6-69
Air
Temp
Op
41
38
39
40
41
34
43
41
31
43
42
40
39
Water Temp
Op
In Out
52
52
54
54
54
48
54
54
52
54
52
52
50
37
39
36
37
37
41
45
41
34
43
39
37
36
Flow
Rate
mgd^
3.8
3.3
1.7
1.7
1.7
3.0
3.8
2.6
2.6
2.2
1.9
1.9
1.5
Theo.
Load- Air/
ing Water
gpm/fl? c^gal
2.9
2.5
1.3
1.3
1.3
2.3
2.9
2.0
2.0
1.7
1.5
1.5
1.2
235
290
650
650
650
355
235
390
390
475
570
570
750
PH
In Out
11.
10.6
10.8
10.5
10.5
10.6
10.7
10.6
10.0
10.7
10.6
10.9
10.7
11.2
10.5
10.8
10.5
10.5
10.5
10.5
10.4
10.0
10.5
10.6
10.7
10.3
Ammonia Removal
o/
/o
In Out Removal
16.2
13.9
14.3
16.1
16.4
17.1
18.2
19.6
18.6
20.8
16.4
16.2
13.3
6.9
6.8
2.6
7.1
7.8
8.1
8.7
6.9
7.8
4.7
3.6
5.7
1.4
58
51
83
56
52
47
52
65
58
77
78
65®
89
(1) No Recirculation
(2) Ice Formation
-------
removals during winter conditions would be in the range of 50 to
60%. Consequently, the full scale tower data does compare quite well
with the pilot plant results. Also there was no recirculation for the data
in Table 20, that is the data represents one pass through the stripping
tower. In Figure 50 the data from the full scale tower is superimposed on
the pilot data from Smith and Chapman. The pilot data in Figure 50 is tak-
en from optimum summer temperature conditions, and the full scale data is
for the conditions shown. Figure 50 indicates the reduction in effective
packing depth as a result of the lower temperature. Although the waste-
water passed through the 24 feet of packing in the full scale tower, the
ammonia removal efficiency was comparable to passing through only about
15 feet of packing. This also indicates approximately the recirculation
required at low temperatures to achieve a desired ammonia removal. Fur-
ther, Figure 50 indicates to what extent the air to water ratio must be in-
creased during low temperatures to achieve a desired ammonia removal ef-
ficiency. For example, to achieve 90% ammonia removal for an air temper-
ature of 40°F, a water temperature of about 50°F, proper pH conditions,
and an air to water ratio of 750 to 800 cf/gal of water would be required.
In Figure 51, the full scale low temperature data is superimposed on
pilot data. At low temperature the full scale removals fall off sharply with
increased surface loading rate, and again compared with the removal ef-
ficiency of approximately 15 feet of packing, rather than the 24 feet of packing
which the wastewater actually passed through. The low rate of loading to
achieve a significant removal is also shown in Figure 51.
In Figure 52, full scale data is again superimposed on the Smith and
Chapman data for different tower depths. The full scale data compared very
well with the pilot data for ammonia removals at approximately the same
operating conditions of surface loading rate, air to water ratio, and influent
and effluent water temperatures. Only single points are shown on Figure 52,
since the full scale tower can only be operated at packing depth of 24 feet.
Unfortunately, after about three months of operation, the tower fill
started to become encrusted with calcium carbonate scale. Although the
scale could be easily removed from the splash bars with a water jet, the
structural members holding the fill in place prevent the scale from being
completely removed from the tower. The blocked portions of the fill re-
sulted in short circuiting the water and airflow, and hence lower ammonia
removals. As a result of the scale, ammonia stripping under optimum
168
-------
PILOT TOWER, OPTIMUM SUMMER CONDITIONS
FULL-SCALE TOWER, WINTER CONDITIONS
AVG AIR TEMP40°F
AVG WATER TEMP 11.5°C
AVG pH 10.7
24 FT DEPTH
WO' DEPTK
O
— 12 FEET OF PACKING PILOT
20 FEET OF PACKING PILOT
— 24 FEET OF PACKING PILOT
24 FEET OF PACKING
FULL SCALE
200 400 600 800
CUBIC FEET AIR/GALLON TREATED
FIGURE 50
PERCENT AMMONIA REMOVAL VS. CUBIC FEET
OF AIR PER GALLON WASTEWATER TREATED
FOR VARIOUS DEPTHS OF PACKING
1000
1200
-169-
-------
••-I
p
FIGURE 51
PERCENT AMMONIA REMOVAL VS. SURFACE LOADING RATE
FOR VARIOUS DEPTHS OF PACKING
1 fin . j. i i .
1 UU
80
>
O
z
LLJ fin
DC
z
o
^
2
5:
l~ an
2 ^u
LLJ
O
K
LLJ
O.
20
\ o — 0 — =*
\7
\
» 0
\A
\
4 \
o+ if__
>\* -f "^~"
\
^0^V •
\«
•\
\
\
4 \
X
v. «A *
*V-* '
\ A
•\
• \
x
5^
O ^^*'«*^,~r "^
^>^,
O
20' D
\ ^— FULLS
,
• ^^-
.
~
— + — 24' DEPTH PILOT
O 20' DEPTH PILOT
6 12' DEPTH PILOT
•— 24' FULL SCALE
o
*sss/s**. S
^"V. X^
^^^ 4
ys.
CALE
^^ ^1
"^••^. T
"~- «
A
^-24' DEPTH
s
s^
_V\
N
2' DEPTH
"^ ^ —
^•^ .
\ \
x^x
^Ox.
o^s. N
^s^
^*>
^ A
•— .. .
^^
S^^r--^
^^a-
A
' .
A
OPTIMUM
SUMMER CONDITIONS
FOR PI LOT TOWER
FULL-SCALE
WINTER CONDITIONS
AVG AIR TEMP -40°
AVG WATER TEMP -
11.5°
AVG pH -10.7
24 FT DEPTH
0 1 .0 2.0 3.0 4.0 5.0 6.0 7.0
SURFACE LOADING RATE - GPM/FT2
-------
100
75
,
•;
o
•;-
!
o
Z
fa
j
2
I'M
u
a
m
a
50
25
EFFLUENT
WATER
TEMPERATUFJES
• 24' FULL-SCALE
D 24' DEPTH, PILOT
O 20' DEPTH, PILOT
A 12' DEPTH, PILOT
-17°C
(PREVIOUS DATA)
|0C INFLUENT2
12°C
(20°C INFLUENT)
•9°C
(17°C INFLUENT)
(13°C INFLUENT)
"12° C INFLUENT1
OPERATING CONDITIONS
2.0 GPM/FT2, 480 FT3
AIR/GALLON)
1 FULL-SCALE TOWER
2.0 GPM/FT2, 390 FT3
AIR/GALLON)
2FULL-SCALE TOWER
1.7 GPM/FT2, 480 FT3
AIR/GALLON)
4 8 12 16 20
TOWER DEPTH, FEET
FIGURE 52
EFFECT OF WATER TEMPERATURE ON AMMONIA STRIPPING
•4
-------
warm weather conditions could not be evaluated properly. However, inter-
mittent data collected under optimum stripping conditions indicated the
tower could be 70% efficient in spite of the short circuiting. The scale
buildup and the attempted solutions are discussed in the subsequent sec-
tion.
Operational Problems. The intermittent dates of data collection in
Table 20 are a result of shortage of analysis time and are also due to freez-
ing conditions in the tower under which the tower would be removed from
service until the ambient wet bulb air temperature went above 32°F. The
freezing problem was, of course, recognized in pilot plant operation, but
could not be fully evaluated until the full scale tower was operated at low
air temperatures. Cooling towers similar in design to ammonia stripping
towers operate very successfully in severe winter climates in the northern
U.S. and Canada. This is done in several ways. One method is to use
large flow distribution orifices at the outside face of the tower. This con-
centrates a curtain of warm water at the point where the cold air first enters
the tower and gives some protection against freezing. If there is a slight
ice buildup on the outside tower face, the draft fan can be reversed, thus
blowing warm inside air to the frozen area and melting the ice. These are
satisfactory ways to prevent freezing, or to correct it, in a cooling tower
because the desired cooling of the water is still obtained.
These same methods were tried at Tahoe. The tower was able to
operate at temperatures as low as 25°F by reversing the fan at a slow speed
for 25 minutes every 1-1/2 hours. This method of operation created an ad-
ditional work load on the plant personnel and was discontinued. Larger
orifices were placed on the outside 18 inches of the tower distribution bas-
in to provide the sheeting effect. Although the modification seemed to
help, the freezing condition existed until the arrival of above freezing
temperatures. Also, at these low temperatures, the ammonia removals
drop to less than 30 percent, which is of questionable benefit. The oper-
ation of the plant-scale tower has demonstrated that it is not practical to
operate the tower at air temperatures below 32°F; unless large waste heat
sources are available, it is not practical to heat the air or water in order
to prevent ice formation on the tower because of the tremendous quantities
of heat required.
As briefly discussed earlier, the second problem encountered in tow-
er operation is the calcium carbonate scale deposition on the tower pump,
distribution deck, fill, and structural members. The countercurrent pilot
tower was checked very carefully periodically over a period of six months of
operation with lime adjustment at pH=10.8, and there was no evidence of
172
-------
scale buildup. However, several months after the full scale tower pumps
were started, a sharp decrease in pump efficiency was encountered due to a
buildup of scale on the impellers. Baffles were then installed in the first
stage recarbonation basin below the tower to prevent migration of CC>2 to the
pump sump. Although these baffles seemed to help, the problem was not
completely alleviated until the pumps were allowed to run without being
throttled and a regular schedule of pump backflushing was initiated. The
schedule of backflushing apparently solved the scale problem and the pumps
can be operated at lower flows without losing too much efficiency. The de-
position of calcium carbonate within the fill area of the tower has been the
most serious problem. The amount of material deposited on the splash bars
has been sufficient to restrict the flow of both air and water. The distri-
bution of water has been very uneven throughout the tower with some areas
receiving little or no water while sheeting occurs in other areas. Since the
scale which forms is soft and friable, it can be removed quite readily with
a high pressure spray. However, the tower structural members which hold
the splash bars in place prevent the scale from being completely removed
from the tower. In addition, three horizontal layers within the fill, each
approximately four inches thick, cannot be reached for cleaning because
of the tower's structural design. Droplets pool above these layers, flow-
ing to outer edges of the fill and then sheet down the sides of the tower.
The problem of how to clean these layers without repacking the entire tow-
er has not been solved.
Plastic fill was installed near the top of the tower to evaluate the
calcium carbonate incrustation on this type of material. It appeared the
buildup was similar in quantity to the amount deposited on the hemlock fill,
but the buildup was easier to remove from the plastic material with water
spray.
An attempt was made in January, 1970 to chemically clean the tower
fill of the calcium carbonate incrustation. After consultation with chem-
ical company personnel, it was decided to use a combination of pH shock
with sulfuric acid and a cooling system dispersant. The sulfuric acid was
used to increase the stability index of the batch solution to a corrosive
tendency, allowing the dispersant to penetrate through the incrustation and
physically remove it with the hydraulic flow. The stability index of the
water flowing through the tower during normal operation is around 3-4, hav-
ing a high scaling tendency. The stability index of the batch solutions used
for cleaning was between 7 and 8, having a moderately corrosive tendency.
An acid dosage of 210 mg/1 was used in the batch cleaning solution. A dos-
age of 300 mg/1 was used for the dispersant.
173
-------
The following procedure was used in the attempted chemical clean-
ing of the fill. First, the accessible portions of the fill and the tower
catch basin were cleaned with the water spray. Second, the ports between
the tower sump and the first stage recarbonation basin were blocked to
enable the entire batch cleaning solution to be recirculated over the tower.
Third, the tower sump was filled with No. 3 or plant effluent water, and
the acid and dispersant added to the sump. Initially the batch solution was
dark brown in color, and after recirculation through the tower from 3-6 hrs.
it became light yellow. The stability index changed from 7.9
to 7.2. The pH of the solution before and after was 7.2. Six batch solu-
tions were recycled over each side of the tower for about 6 hours each.
The spent batch solutions were pumped to a drying bed to prevent possible
detrimental effects to plant treatment processes. The cleaning solution was
then introduced at very low flows back into the ballast ponds with no meas-
urable effect on the processes or final effluent quality.
Ammonia removal efficiencies after the chemical cleaning indicate
the tower is still about two-thirds as efficient as the tower was before
the initial calcium carbonate incrustation in February, 1969. Approximate-
ly 870 cubic feet of lime sludge was removed by the chemical treatment.
However, since some water sheeting is noticeable on the outside tower
face and since ammonia removals did not improve appreciably, it is sus-
pected that inaccessible areas trapped the chemically treated sludge,
thereby still interferring with proper droplet formation and air flow. An in-
teresting side light to the tower cleaning was the tower pump's discharge
pressure doubled, reaching its original 18 psig pressure, indicating the
pump had been thoroughly cleaned. Also several pieces of the scale ap-
proximately 1/2" thick, and rounded to conform to the pressure pipe lead-
ing to the top of the tower, were found on the tower's warm water deck.
This would indicate this line had also been cleaned. It would appear the
chemicals used were successful in removing the scale, but the chemically
treated sludge could not be completely removed from the tower fill. The
cost of chemicals for one cleaning of the tower was less than $200.00.
In ammonia stripping of waters which form this soft scale as at
Tahoe, it is a simple matter to provide for easy, inexpensive removal of
the deposits by providing complete accessibility to the fill, so that once
the scale is removed from the splash bars, it can be hydraulically carried
out of the fill area. The provision for complete accessibility of the fill
area might be facilitated by the following four possible alternatives of
cleaning the stripping tower of calcium carbonate scale. First, a system
of water sprays or nozzles incorporated into the tower design used speci-
fically for cleaning purposes, and operated at regular intervals. Second,
in place cleaning of a completely accessible tower fill with a high press-
ure spray to remove the scale from the splash bars and carry it out of the
174
-------
fill area. With this method, the maximum width of the fill should be a-
round 10 feet with access from both sides. Third, the fill could be design-
ed in modules, so it could be removed from the tower, cleaned and replac-
ed with little difficulty. Fourth, chemical cleaning of the fill could be
accomplished economically and with very little physical work, however,
once again, the tower design would have to permit complete removal of '
the sludge from the fill. Soft scale formation in the tower can be overcome
and therefore should not be a reason for eliminating ammonia stripping.
In the treatment of some waters hard scale may be formed which cannot be
removed. Stripping may not be feasible in locations where hard scale is
formed.
Tower Off Gases. Under most conditions the off gases from an
ammonia stripping tower will present no problems. Because of the high
air to water ratios required for efficient tower operation, the ammonia
concentration in the off gases will be less than 6 mg/cubic meter, while
the threshold for odor is about 35 mg/cubic meter. Under unusual condi-
tions where the atmosphere is already polluted with high concentrations of
sulfur dioxide, ammonia may react with the sulfur dioxide to form an aero-
sol or fog.
Ammonia may be washed out from air by rainfall, but not by snow-
fall. The natural background concentration of ammonia in the atmosphere
is 5 ugm/m , and in rainfall the natural background ranges from 0.2 mg/1
to 1.0 mg/1.
Calculations for the ammonia washout in a rainfall rate of 3 mm/hr
have been made for a stripping tower with a capacity to treat a flow of
15 mgd (ultimate design capacity at South Tahoe), or a source emission
rate of 4.7 x 104 gm/hr. The peak ammonia concentrations of ammonia in
the rainfall would be 2.0 mg/1 at a distance of 2,000 meters from the
tower and would be only 0.5 mg/1 at a distance of 5,000 meters (which is
approaching natural background). The ultimate fate of the ammonia which
is washed out by rainfall depends upon the nature of the surface upon
which it falls. Most soils will retain the ammonia. That portion, which
lands on paved areas will appear in the runoff from that area.
For the same conditions except no rainfall and assuming no dry
deposition, the surface air concentrations of ammonia would vary from
0.041 mg/m3 at 2,000 meters to 0.0065 mg/m3 at 5,000 meters. Thus it
is apparent that the surface air concentrations of ammonia are far below
the threshold odor level, and further, that no significant changes in the
atmospheric environment result from ammonia stripping.
Summary and Conclusions. Under the right climatic conditions and
with the proper precautions regarding scale prevention or removal, ammonia
stripping is a practical, reliable method for nitrogen reduction. One of the
greatest advantages of this method of nitrogen removal is its extreme sim-
175
-------
plicity and low operating cost. Water is merely pumped to the top of the
tower at pH=ll, air is drawn through the fill, and the ammonia is stripped
from the water droplets. The only control required is to maintain the pro-
per pH in the influent water. This simplicity of operation also very much
enhances the reliability of the process. Full scale testing showed the
following:
1. Performance of the full-scale tower closely parallels that of
the pilot tower insofar as ammonia removals are concerned. At similar hy-
draulic loadings, air flows, and water and air temperatures, the results
with the full-scale cross-flow tower are much the same as with the pilot
countercurrent tower.
2. During low temperature winter operations, before the presence
of calcium carbonate scale on the fill, the tower achieved an average of
64% removal efficiency with a range of 47% to 89%.
3. It is necessary to either recirculate wastewater or to reduce
the surface loading rate to about 1.0 gpm/sf and raise the air to water
ratio to 750-800 cf/gal to achieve 90% ammonia removals at low air tem-
peratures above 32°F.
4. Sheeting water down the side of the tower fill and reversal of
the induced air fan enable tower operation slightly below 32°F, but gener-
ally it is not economical or practical to operate the ammonia stripping
tower below 32°F wet bulb air temperature. In cold climates, if ammonia
stripping is used, and if nitrogen removal is required during freezing wea-
ther, then ammonia stripping may be used at temperatures above 32°F and
a supplemental method used at colder temperatures.
5. Calcium carbonate scale can be expected on the tower fill area
of a crossflow ammonia stripping tower. As a result of this fact, the tow-
er fill should be designed for complete accessiblity to provide for physi-
cal or chemical cleaning and removal of the scale from the tower.
6. It was not possible to properly evaluate ammonia stripping effic-
iency at optimum summer conditions in the present tower because of cal-
cium carbonate scale buildup.
176
-------
SECTION XK
MIXED MEDIA FILTRATION
General. The production of high quality reclaimed water from waste-
water requires the use of efficient filtration. The key to the successful
operation of the entire Tahoe plant is the good performance of the mixed-
media filters. The importance of filtration to the overall treatment scheme
was recognized by the consulting engineers from the very beginnings of
the project in 1961. For fifty or one hundred years, engineers had attempt-
ed without success to clarify sewage using fine screens, san, diatoma-
ceous earth, and other types of mechanical strainers or surface type fil-
ters. These efforts, and similar ones at Tahoe, failed because of the
tremendous volume of solids to be removed and stored and the fragile and
sticky nature of these solids. On any surface filter, solids accumulate
rapidly and blind the surface. This causes high head loss followed by
the breakthrough of particulates as operating pressures are increased.
The practical engineering solution of these problems came about by the
development of in-depth, coarse-to-fine filtration combined with the use
of alum or polymers as filter aids. The first successful sewage filter of
this type was the dual-media filter. It extended the effective depth of
filtration from the 2 to 6 inches available in a sand filter to 12 inches or
more. Further refinement and development produced the mixed media
filter which has pore space which is uniformly tapered from coarse-to-
fine throughout the full depth of the bed, so that solids are removed and
stored throughout the full 36 inches or more of bed depth. The use of a
filter aid such as alum or a polymer results in coagulation, flocculation,
and adsorption of not only more particulate matter in the filter but also
some dissolved materials as well. Granular beds containing grains which
are chemically coated with filter aid are excellent flocculation and adsorp-
tion devices as well as good strainers. The coarse-to-fine filter allows
the use of finer media in the bottom of the filter than could be used satis-
factorily in a single media bed because much of the solids load is removed
in the coarse media in the top of the bed, and the presence of fine materials
at the bottom thus does not involve high head losses. This also reduces
the risk of solids leakage. The use of fine materials, 50 to 100 mesh, in
the bottom of a mixed media bed as contrasted to the 30 to 50 mesh common-
ly used in the top of a sand filter, provides a much clearer filter effluent
and at the same time greatly extends filter runs between backwashings.
177
-------
At Tahoe, it was only when good mixed-media filter performance was dem-
onstrated at pilot scale that consideration was given to full-scale advanc-
ed wastewater treatment. The subsequent ten years of development and
experience in the operation of advanced treatment have reaffirmed and
strengthened the importance of mixed-media filtration to the overall pro-
cess. It should be emphasized that coarse media, deep-bed filtration is
not equivalent to mixed-media filtration in terms of water quality produced.
Process reliability also is not equivalent
Filter Role. A careful examination and evaluation of the role of
coarse-to-fine filtration in overall treatment schemes reveals several im-
portant filter functions, including:
1. Coarse-to-fine filtration adds greatly to overall plant re-
liability in terms of continuous operation and consistent effluent quality.
Solids carryover from secondary or chemical clarifiers or settling basins
is stopped without harm to subsequent treatment units or process or inter-
ruption of normal operation. Even major surges of suspended solids can
be handled by mixed-media filters without plant shutdown or sacrifice in
effluent quality. Filtration is an excellent back up to overcome irregular-
ities common to biological and chemical treatment.
2 . Coarse-to-fine filtration produces water of exceptionally
high clarity which can be accomplished in no other practical way. With
use of a filter aid, any desired turbidity down to 0.05 J.U. (Jackson Units)
can be maintained, although 0.2 to 0.3 J.U. are more realistic values for
normal operation.
3. Filtration prior to granular carbon adsorption protects the
carbon against fouling by suspended solids and colloidal matter and pre-
vents loss of carbon efficiency upon regeneration due to the residual ash
from incinerated solids. Prior filtration reduces the load of organics
applied to the carbon and thus will permit either greater overall removals
of organics with equal carbon contact time or shorter carbon contact time
for the same removals. Overall economics generally favor the sequence
of mixed-media filtration followed by carbon adsorption over combined
filtration-adsorption in carbon beds with the required increased contact
time.
4. The complete removal of suspended matter by filtration
permits more effective disinfection of the water, in addition to the esthe-
tic benefits realized from the production of a sparkling clear effluent.
178
-------
How Mixed-Media Filters Act. The first concept necessary to
understanding the performance of mixed-media filters is that mechanical
straining is a relatively unimportant factor. Efficient filtration is a
physical-chemical process involving particle destabilization and particle
transport similar to the mechanisms of coagulation. Good coagulants are
also efficient filter aids. The processes of coagulation and filtration are
inseparable and the interrelationships must be considered for best treat-
ment results. There are two basic approaches, ( 1 ) the coagulant dosage
must be optimized for maximum filtrability rather than settleability of the
floe produced, or, ( 2 ) a filter aid must be added to the filter influent to
adjust the water to optimum filtrability. The second method is favored for
wastewater treatment. The removal of suspended particles in a filter con-
sists of at least two steps, ( 1 ) the transport of suspended particles to the
solid-liquid surface of a grain of filter media or to another floe particle
previously retained in the bed, followed by (2) the attachment and adsorp-
tion of particles to this surface. For filter runs of practical length, filter
aid to coat filter grains must be added continuously (rather than pre-coat-
ed). When filter aids are used the filtration process is so effective that
conventional sand or other surface filters clog very rapidly. Effective
filtration without excessive head loss can be accomplished only by use
of a coarse-to-fine, in-depth filter, such as a mixed-media filter. To
differentiate this type of filter action (destabilization, attachment, and
adsorption) from plain mechanical filtration by simple straining or surface
filtration, mixed-media filters are commonly designated as separation beds,
For most lime treated wastewaters, a continuous feed of at least
one to ten mg/1 of alum is required to the filter influent as a filter aid.
At times it may be desirable to also use 0.01 to 0.05 mg/1 of Calgon ST-
270, Purifloc N-ll, or other similar polymer. For alum treated wastewaters
0.05 to 0. 5 mg/1 of ST-270 or other polymer may be required for best fil-
tration results.
One important difference between coagulation and settling by floc-
culation versus filtration is the fact that the removal efficiency of a bed
is independent of the applied concentration of particles while the time of
flocculation is concentration dependent. Therefore, separation beds are
capable of more effective and efficient removal of colloidal particles pre-
sent in dilute but objectionable concentrations. The head loss developed
during filtration is dependent upon media size, filtration rate, and the
concentration of particles to be removed. Deep coarse beds or coarse-to-
fine filters are required to avoid rapid and excessive head loss buildup.
179
-------
Separation Beds at South Tahoe. For the design flow of 7.5 mgd,
there are three sets of two pressure beds in series, each 10 feet in dia-
meter by 38 feet long. The design filter rate is 5 gpm/sf, but rates as
high as 8 gpm/sf have been employed at full treatment efficiency. The
backwash rate is 15 gpm/sf. Each pair of beds is washed as a unit in
series. The surface wash consists of four 7-foot diameter rotary filter
agitators per bed. Each bed consists of three feet of mixed-media (as
supplied by Neptune Microfloc), supported on 3 inches of coarse garnet
and 2 feet 4 inches of graded gravel.
Figure 53 shows a separation bed of fine media above a supporting
layer of coarse garnet. The column on the left shows the original place-
ment of layers of fine media, with coal at the top, sand in the center and
fine garnet below. The column at the right shows the appearance of the
bed after it has been hydraulically backwashed to produce the desired uni-
formly tapered coarse-to-fine pore space from top to bottom, the direction
of flow during the filter cycle. Figure 54 shows the flow pattern for the
filter cycle. The underdrains are perforated plastic pipe. The influent
rate-of-flow controller consists of a Dall flow tube and a rubber-seated
butterfly valve. Loss of head across each bed is continuously measured
and recorded. Turbidity of separation bed effluent is continuously measur-
ed by a Hach CR Turbidimeter to tenths of a JU (Jackson Unit) and recorded.
All filter operations are fully automatic. Backwash may be initiated by time
clock, high head loss, high turbidity, or manually. The manual mode is
used most of the time. The beds are backwashed, filtered to waste, and re-
stored on line automatically by a program timer. The filters are backwash-
ed with filter influent water by means of a pump. There is a pressure-
booster pump for surface wash supply. Waste wash water discharges into
an 80,000 gallon steel tank (which holds the water from 2 backwashes).
The water from this tank is returned to the treatment process slowly over
a period of about two hours. One pair of these beds has been in service
for five years, and the other two pairs have been in use for three years
at this writing (1971).
All except one end of each bed is installed out-of-doors. An
allowance was made in the design for the formation of 4 inches of ice
inside the steel filter shell. This ice then insulates the tank against
further freezing under conditions of normal water flow through the bed.
An exterior view of the separation beds, decanting tank, and tertiary
building is presented in Figure 55.
180
-------
FIGURE 53
MIXED MEDIA FILTER BEFORE AND AFTER
INITIAL BACKWASHING
OR1CJNAL PLACEMENT
OF MATERIALS IN
FILTER
COARSE COAL
SP. GR. - 1.4
t o
MEDIUM SAND
SP. GR. - 2.65
FINE GARNET
SP. GR. » 4
POSITION OF MATERIALS
IN FILTER AFTER
BACKWASHING
MIXED-MEDIA WITH PORE
SPACE GRADED COURSE-
TO-FINE IN DIRECTION OF
FILTRATION (TOP TO BOTTOM)
16-MESH GARNET SUPPORTING
SUPPORTING GRAVEL
-------
WASTE
SEPARATION BED INFLUENT -^
BACKWA
SECONDARY WASTE
FLOCCULANT VALVE ~
COMBINATION FEED POINT CLOSED
AIR-VACUUM \
RELEASE /
VALVE" ^(R) (s)
^- — '
1 1
— -^
/ T ^^
1 i
1 SEPARATION
V BED
\ 2 .
EFFLUENT \^^ ^/
FLOW METER. 1
\ 1
1
1
J
iL-!-*-^
r ^*v ' i '
' EFFLUENT ¥
VALVE V*-
OPEN
— — -^
BACK
/WASH
(VALV
;CLOS
/STRAINER
/
§
ff —
u
~"~ SURFACE
WASH
^^VALVES --
\ CLOSED /
\ r [
1 V
/ \
DRAIN i
VALVE I
E CLOSED
ED 1 *-
— FILTER-TO-
WASTE
VALVE
> CLOSED
BACKWASH WATER -^ TQ
TANK
SH (
INFLUENT
>%. RATE OF
i» FLOW
CONTROL 1
/VALVE 1
I OPEN
/"^ ^S. x-STRAlNER
^^~*> A \ /
? \ ff LI-
SEPARATION I (J V-^-tN3-.
BED / — J I
1 / SURFACE /
V^^^ WASHXVALV E/
PUMP QpEN /
I ALUM
* APPLICATION y-TN,
POINT- *" V-S
FILTER-TO-WASTE AND
DRAIN LINE TO BALLAST
PONDS
~N.
N ~.
BACKWASH
WASH WATER RATE-OF-FLOW
SUPPLY CONTROL VALVE FLOW
\ CLOSED \ _/METER
r VALVE
.CLOSED
A +L
SEPARATION
BED EFFLUENT
TO CARBON
COLUMNS
CARBON COLUMN
BYPASS TO FINAL
EFFLUENT PUMP
STATION
FIGURE 54
1
I
1
1
INFLUENT FROM
SECONDARY
EFFLUENT PUMPS
SEPARATION BEDS
FILTER CYCLE
-182-
-------
Figure 55
EXTERIOR VIEW OF SEPARATION BEDS, DECANTING
TANK AND TERTIARY BUILDING
183
-------
The performance of these beds and the control system has been
excellent. The length of filter runs vary from 4 hours under very bad
conditions to about 60 hours under good conditions. At one time they
were used with alum as the primary coagulant in pretreatment, and with
Calgon ST-270 or Purifloc N-ll (0.1 to 0.8 mg/1) as a filter aid. In normal
operation they are used with lime as the primary coagulant in pretreatment
and either alum (1 to 20 mg/1), or alum (1-2 mg/1) plus ST-270 or N-ll
(0.01 to 0.10 mg/1) as a filter aid applied directly to the filter influent.
Normally the beds are backwashed when the head loss through each bed is
about 8 feet (16 feet total). However, they have been backwashed suc-
cessfully after head losses through the two beds total as much as 40 feet.
This high head loss would be excessive for continuous operation.
Special Separation Bed Evaluation. As discussed in detail later in
this report under Plant Operation Results, a number of measurements of
performance were made at all times during operation of the separation beds,
In addition, during a special four month test period from December 1969
through March 1970, more intensive and exhaustive tests were made to
evaluate separation bed capabilities and performance. The removals of
some substances are shown in Table 21.
Two approaches were used in collecting the data during the special
tests. One approach was to collect data on daily operations having the
operators control alum feed according to their personal judgement. Sam-
ples of bed influent and effluent were composited for 24 hours and analyz-
ed. Total daily flow and amount of alum used were recorded.
The second approach was to collect data across one specific pair
of beds. For each test run the alum dosage was fixed at a constant rate
and the run was allowed to continue until a high turbidity (2.0 SJU) or
high headless (15 ft lead bed) alarm sounded to terminate the run. Grab
samples were taken from the influent to the two beds operating in series,
between the two beds and after the second bed. The samples of each
run were collected two hours after the beginning of the run. In addition
to the analyses and measurements previously described, particulate and
soluble PO4-P, and length of filter run were measured. Results are shown
in Table 22.
184
-------
TABLE 21
Typical Removals by the
Separation Beds
For Test Period - March 11 - April 5,
AVERAGE .CONCENTRATIONS
mg/1
1970
PO4-P, Total
COD
BOD
Suspended Solids
Hardness as
Turbidity SJU
Influent
32
8
9
157
5.6
57
7
2
Effluent
21
3
1
150
0.4
10
2
8
3
Removals, Percent
Range Average
57-99.5 82
14-50 35
27-77 54
68-100 86
80-95
93
TABLE 22
Removal Efficiencies of Two Separation
Beds in Series at 8 - 64 ppm Dry Alum
Dosages for
Test Period - Nov. 69 to Mar. 70
Substance
Average %
Removal Across
Lead Filter
Average %
Removal Across
Second Filter
Range of %
Removal Across
Second Filter
P04-P Total
PO4- Soluble
PO4- p Particulate
COD
BOD
SS
Turbidity
79
78
86
30
57
80
78
4
3
5
7
13
19
10
0
0
0
1
6
0
2
13
12
16
17
24
50
30
185
-------
Test Results - Separation Bed Evaluation. The flow rates to the
beds varied between 2.8 gpm/ft2 and 4.0 gpm/ft2, on an average daily
basis. Within this flow range, the removal efficiencies for phosphorus,
COD, BOD, suspended solids and turbidity were not affected.
Total removal efficiency across both beds dropped considerably at
zero alum dosage for all substances measured except suspended solids.
Across the second bed, at no alum dosage, particulate PO^-P showed
much higher than average removal efficiencies.
In the range of 8-64 mg/1 dry alum dosage, total and soluble PO4~P
and total COD removal showed slight variation with alum dosage. COD
and soluble PO^j-P removal efficiency increased slightly with increasing
alum dosage whereas total PO4~P appeared to decrease slightly. The
variations in removal efficiencies with alum dosage for total PO4-P, sol-
uble PO4-P, COD, and BOD are shown in Figures 56, 57, 58 and 59, respect-
ively.
The additional filter depth provided by the second separation bed
has been extremely useful during periods of higher solids loadings. The
second filter has permitted the plant to achieve near 100% suspended solids
regardless of treatment efficiencies upstream. During the test period when
the headless or turbidity alarms were used to terminate the test run, the
second filter was needed to reduce suspended solids concentrations to
zero when influent loadings to the first filter were greater than 5-6 mg/1
suspended solids.
As indicated earlier, alum feed concentration between 8-64 mg/1 did
not appear to greatly affect removal efficiencies; however, on waters with
similar solids loadings, increasing alum feed concentrations decreased
length of filter run. Figure 60 shows such an effect. Each of the filter runs
shown in Figure 60 were terminated by a headless alarm, except the 18 mg/1
suspended solids influent loading, which was terminated by turbidity of 2.0
SJU. A test run of 6 mg/1 suspended solids with.no alum dosage lasted a-
bout five hours. This run was also terminated by turbidity of 2.0 SJU.
It is suspected that most of the influent suspended solids were
algae cells from the ballast ponds. The suspended solids prior to volatil-
ization were slightly green on the filter pad. Tests showed that the sus-
pended solids were completely volatile.
186
-------
m
FIGURE 56
PERCENT REMOVAL OF PO4-P VS DRY ALUM DOSAGE
ACROSS BOTH SEPARATION BEDS
100
i
I eo
U.
C
3
-
at
o.
-in
0
I
••;
30 40
DRY ALUM DOSAGE MG/L
••
-------
FIGURE 57
PERCENT REMOVAL OF SOLUBLE PO^-P VS DRV ALUM DOSAGE
ACROSS BOTH SEPARATION BEDS
100
a
3
OL
DO
3
""
O
HI
DC
t-
ui
O
C
LU
CL
10
20 30 40
DRY ALUM DOSAGE MG/L
50
-------
FIGURE 58
PERCENT REMOVAL OF COD VS DRY ALUM DOSAGE
ACROSS BOTH SEPARATION BEDS
100
00
to
Q
O
o
•1
I
Z
m
'••
DC
M
0
II
20
30 40
DRY ALUM DOSAGE MG/L
61
-------
FIGURE 59
PERCENT REMOVAL OF BOD VS DRY ALUM DOSAGE
ACROSS BOTH SEPARATION BEDS
100
80
g
U-
O
-------
FIGURE 60
LENGTH OF SEPARATION BED RUN
VS DRY ALUM DOSAGE
bu
40
E
3
O
X ?O
-A- J\J
z
2
D
DC
LL
O
E 20
r ^w
z
a
10
n
O
7 mg/l SS
) 6.0 mg/l SS
O 5.5 mg/l SS
O 9.5 mg/l SS
O 7.5 IT
18 mg/l SS
g/l SS
6.5 mg/l SS
0
10
20
30 40
DRY ALUM DOSAGE MG/L
50
60
70
-------
Table23shows the pounds removed of various substances by the
filters for each pound of dry alum fed.
TABLE 23
Pounds of Various Susbstances Removed
Per Pound of Dry Alum Fed
Test Period - March 11 - April 5, 1970
Substance Average Range
Total PO4-P .019 .003 - .037
COD .36 .15 - .51
BOD .22 .02 - .37
Suspended Solids .28 .06-1.12
The removal rates for orthophosphorus, suspended solids, and tur-
bidity indicated the beds can remove higher loadings of these paramenters
with relatively no change in the removal rate. Figures 61,62, and 63 show
these results. Removal rates for COD and BOD were very erratic and no
correlations could be interpreted for the data obtained.
Summary - Separation Bed Evaluation. A summary of all parameters
studied during the separation bed evaluation indicated the optimum dry
alum dosage to be around 15-25 mg/1. In the range of 0-64 mg/1 alum
dosages used during the evaluation and in those parameters showing a
correlation, the percent removals at 60 mg/1 were not greatly different
than removals at 10 mg/1. When water of poorer filtrability is encounter-
ed in bed operations, the alum dosage may be increased up to 30-50 mg/1,
but effluent quality does not improve above levels normally encountered
when a better quality of water is applied to the beds. The removal effic-
iencies were not affected by filter rates between 2.8 and 4.0 gpm/ft^.
The use of two beds in series has shown slightly greater removal efficien-
cies than single bed.
192
-------
FIGURE 61
POUNDS OF PO4-P REMOVED PER HOUR VS
POUNDS OF P04-P APPLIED ACROSS BOTH
SEPARATION BEDS
1.4
1.2
1.0
DC
3
c
r
DC
UJ
CL
J
••'.
r
0
u.
D
C?
a
v.
a
z
2
.;••
I
10 15 20
POUNDS OF PO4-P APPLIED
!
30
-193-
-------
30
25
K
0
a
UJ
UJ
cr
8
o
Q
|
M
LL
O
M
Q
2
•0
16
10
FIGURE 62
POUNDS OF SUSPENDED SOLIDS REMOVED
PER HOUR VS
POUNDS OF SUSPENDED SOLIDS APPLIED
ACROSS BOTH SEPARATION BEDS
<9
100
200 300 400 500
POUNDS OF SUSPENDED SOLIDS APPLIED
600
700
-------
FIGURE 63
POUNDS OF TURBIDITY <11 REMOVED PER HOUR
VS POUNDS OF TURBIDITY APPLIED ACROSS
BOTH SEPARATION BEDS
CO
E
O
rr
in
ft
ci
III
>
O
111
K
5
oa
DC
W
O
2
< '
D
POUNDS OF TURBIDITY APPLIED
350
(1) ASSUMING 1 SJU = 1 MG/1
-------
In November 1969 the six beds were opened for electrical mainten-
ance on the surface wash arms. At this time the surface of the filter media
was examined for calcium carbonate buildup. From visual examination
there appeared to be no buildup of calcium carbonate on the media. Fur-
ther, no hardness reduction was noted across the beds. Two of these
beds had been in operation since the summer of 1966.
During the inspection of the oldest set, a sample of sand and coal
from the surface of the filter was ground up, and analyzed for calcium oxide,
The available CaO was 0.6%. A duplicate sample was calcined at 1800°F
and analyzed for CaO. The available CaO was 1.1%.
Polyelectrolytes have been used, only in limited quantities, in the
past to improve turbidity removal during unusually high solids loadings
and subsequent above normal numbers of backwashings. However, from
the past two years of experience and from data collected thus far, alum
applied to the beds appears to be well suited to the needs of the South
Tahoe Water Reclamation Plant.
Filtration Summary. Five years of continuous operation of full
plant scale mixed-media separation beds at South Lake Tahoe have demon-
strated the following:
1. Mixed-media filtration is a reliable, efficient, easily con-
trolled and economical process for clarification of wastewater. Suspend-
ed solids can be removed to a degree which will permit reclaimed water
to be used for the first time for many purposes not heretofore possible.
2. Separation beds exert a very important stabilizing effect upon
the entire wastewater treatment process. By virtue of the ability of separ-
ation beds to remove suspended and colloidal materials from applied water,
even with rapid, sizeable fluctuations in influent turbidities, upsets in the
operation of preceding settling basins or other treatment units can be handl-
ed without loss in filtered water quality or interruption in treatment.
3. Mixed-media filtration produces water of exceptionally low
turbidity (0.05 to 0.3 JU) which can be obtained in no other practical way.
Application of the high clarity filter effluent to granular carbon affords
maximum protection for the carbon against fouling and loss of efficiency,
and disinfection with chlorine is enhanced.
196
-------
4. Visual inspection of the beds and laboratory tests of the
media both indicate that the filter beds are still in excellent condition
after 5 years of continuous full time service.
5. The automatic filter controls perform very well and are quite
reliable.
197
-------
SECTION XX
GRANULAR ACTIVATED CARBON ADSORPTION AND REGENERATION.
The most important process at the Tahoe plant in terms of meeting
the stringent export requirements is the granular activated carbon adsorp-
tion of dissolved organics and detergents. Since thermal regeneration of
the granular activated carbon is necessary to operate the adsorption pro-
cess most economically, and to facilitate and clarify the data collection
results, the two processes of adsorption and regeneration will be discuss-
ed together.
The first portion of this section describes the particular physical
system and operating practices for the carbon adsorption and regeneration
processes used at the water reclamation plant during the grant period.
Following a description of the sampling program and methods of data coll-
ection during the grant period, there is a general discussion of the gross
loadings and operating parameters for the adsorption and regeneration sy-
stems. Finally, in reference to the grant requirements, there are specific
discussions concerning removal of organics over several carbon regenera-
tions, adsorption contact time, regeneration efficiency, inert material
build-up in the carbon, and carbon losses due to regeneration and physical
handling.
Carbon Adsorption System. The purpose of the activated carbon
adsorption system is the removal of dissolved organics from the separation
bed effluent to insure that the reclaimed water meets the stringent export
standards for Chemical Oxygen Demand, Biochemical Oxygen Demand, and
Methylene Blue Active Substances (Detergents).
The adsorption system includes eight carbon columns which operate
in parallel, each as upflow (countercurrent) columns in normal service.
Fig. 64 shows four of these columns. Flow may be reversed for flushing
the top screens, compacting the carbon bed or removing matter in the low-
er section of the column. Any or all of the carbon columns may be bypass-
ed. Effluent from the carbon columns normally passes on to disinfection
and the final effluent pump station, but may be diverted to the ballast
ponds, if desired. The valve positions for normal upflow operation of the
199
-------
Figure 64
CARBON COLUMNS
200
-------
carbon columns are shown in Figure 65. The valves are manually operated.
The flow rate through each carbon column is set by manual operation of a
butterfly valve on the carbon column discharge line. There is flow indic-
ation at this control valve location.
The separation bed effluent flows under pressure into the column
through a'series of eight, 12-inch diameter, stainless steel well screens
located on the periphery of the column at the bottom (Figure 66). In a
similar fashion the column effluent leaves the column through well screens
located at the top of the column. The system is designed to approach a
true counter current moving bed process at design flows, but at present
flows the carbon is withdrawn from the bottom, regenerated, and added to
the top of the columns on a batch basis. This method of operation makes
possible complete exhaustion of the carbon before withdrawal, as well as
final passage of the effluent over freshly regenerated carbon.
Each of the eight 12-foot diameter by 24 high steel columns contain
approximately 1600 to 1700 ft3 (24-26 tons) of 8 X 30 mesh granular activat-
ed carbon. In all considerations, the specific gravity of the carbon was
assumed to be 30 Ibs/ft3. The carbon type is Filtrasorb 300, a product of
the Calgon Corporation. The effective carbon bed depth in the columns is
14 feet, and the cross-sectional area is 113 feet^ . The design flow rate
through the columns of 735 gpm provides a 17 minute superficial contact
time, and a hydraulic loading of approximately 6.5 gpm/ft .
Carbon Regeneration System. Thermal regeneration of the granu-
lar carbon is required to make the adsorption process economically feasible.
Figures 67 and68 depict the regeneration system at South Lake Tahoe.
A slug of spent carbon is withdrawn in a water slurry and transferred
to a dewatering bin where the transfer water is allowed to drain off. Each
column is fitted with peripheral water jets at the bottom to insure uniform
withdrawal of the spent carbon.
The dewatering bin has a variable speed conveyor at the bottom,
in which the carbon is augered into the top hearth of a six hearth furnace.
The furnace is 4.5 ft in diameter and can operate at feed rates from 1000-
6000 Ibs. per day. Regeneration temperatures range from 1650° to 1750°F,
with natural gas as the heat source. Regeneration is accomplished in a
limited oxygen atmosphere with the addition of steam to produce more uni-
form temperatures on each hearth and better carbon regeneration. Organic
impurities in the carbon are volatized and driven off in gaseous form. The
furnace is provided with an afterburner and a wet scrubber to control ex-
haust emissions. In the carbon regeneration furnace, the carbon flows
downward through the six hearths in series. The hearths are numbered 1
to 6 from top to bottom. Burners are located on hearths 4 and 6 and are
201
-------
EFFLUENT
MANIFOLD -^
/
^TO FINAL
EFFLUENT
PUMP STATION
/
x y\
\ / N^
FLOW
METER^J
EFFLUENT
RATE-OF-FLOW
CONTROL
VALVE
OPEN
^»—
\
INFLUENT >v
MANIFOLD-^ \
\
3-WAY VAL
INFLUENT
HEADER -^
X,
^»— — ^"» X
^^
"^1
I
I
1
r
CARBON
COLUMN
(TYPICAL)
\
VE"^
/
/
t
|
1
"*
\
/
/
f
/
/
r
^*-
V
CARBON
COLUMN
BYPASS
t
/
3-WAY j
VALVE
CLOSED
^VALVE
CLOSED
_
INFLUENT
FROM
SEPARATION
BEDS
CARBON
COLUMN
^-INFLUENT
r HEADER
VALVE
OPEN
AND DRAIN LINE
TO BALLAST PONDS
FIGURE 65
CARBON COLUMNS
NORMAL UPFLOW OPERATION
-202-
-------
CARBON IN
J O
PRESSURE VESSEL
12 FT DIAMETER
± INLET SCREENS (8)
WATER TO
TRANSFER
HEADER
BOTTOM WAFER VALVE
CARBON OUT
FIGURE 66
SECTION THRU CARBON COLUMN
-203-
-------
Figure 67
CARBON FURNACE AND QUENCH TANK
204
-------
-XJ-
SPENT CARBON
SLURRY BIN
MAKEUP
CARBON-
MAKEUP
CARBON
SLURRY
BIN
HXh
I
I
^^
CARBON
SLURRY
PUMPS
SPENT CARBON FROM
CARBON COLUMNS
SPENT CARBON DRAIN
AND FEED TANKS
SCREWS
CONVEYORS
CARBON
REGENERATION
FURNACE «.
CARBON
SLURRY
PUMPS
REGENERATED CARBON
DE-FINING AND STORAGE
TANKS
REGENERATED CARBON
TO CARBON COLUMNS
FIGURE 68
CARBON REGENERATION SYSTEM
-205-
-------
equipped with automatic temperature controllers. The steam is supplied
to hearths 4 and 6.
The regenerated carbon is cooled in a quench tank and pumped by
an air diaphram slurry pump to carbon defining tanks. The carbon is wash-
ed in the tanks to remove carbon fines produced in the regeneration and
transportation. After defining the tank is pressurized and the carbon is
transferred in a slurry back to the top of the column. The defining tank is
shown in Figure 69 .
Carbon Adsorption Operating Practices. Six of the eight carbon
columns (Nos. 1, 2, 4, 5, 6 and 8) were used during the grant period.
Number 3 column was kept empty to permit inspection of the other six
columns and number 7 column was used to store virgin carbon. The seven-
th column except for holiday periods received no flow. The carbon volume
in each operating column was kept at 1600 to 1700 cubic feet. Since make-
up carbon requirements were only about 20 cubic feet per column per batch
regeneration period, makeup carbon was not added after each regeneration.
The flow to each column was held between 500 and 735 gpm at all
times. Columns were taken off or put on line to maintain this range. The
columns were also rotated to insure equal loading.
For several months the carbon column flow was permitted to range
between 200 and 500 gpm in the early morning hours. During the same
period the turbidity going on to the carbon ranged between 1.5 and 2.5
Jackson Units for several days due to lime clarification and CO2 produc-
tion difficulties. Hydrogen sulfide was produced and some mud balls were
observed in the spent carbon being withdrawn for regeneration. The odor
and mud ball problem was corrected within a month by chlorination of the
column influent at 2 ppm, and by regeneration of approximately 400 ftr of
carbon from each column. The problem could have been corrected much
quicker,had the need existed, by more rapid withdrawal of the affected
carbon. Prior to or subsequent to this period, no odors or mud balls have
ever been detected although on several other occasions turbidity going on
to the carbon had ranged above 1.5 SJU; however, the flow was always
maintained above 500 gpm.
As mentioned earlier, the flow can be reversed to down flow con-
figuration. When the headloss across the carbon column reached 12 ft of
water/the flow was reversed for about 1/2 hour. This action dropped the
headloss to its normal value of 5 ft. The frequency of down flushing the
columns varied with the quality of water going onto the carbon. During
normal conditions (0.1 - 0.5 SJU carbon column influent) the interval of
206
-------
FIGURE 69
CARBON DE-FINING TANK
EXIT FOR SCREEN
BACKWASH WATER-
REGENERATED CARBON
FROM QUENCH TANK
SCREEN
BACKWASH WATER
TOP WAFER VALVE
PRESSURIZING AND
WASH WATER VALVE
TRANSFER WATER
BOTTOM WAFER VALVE
REGENERATED CARBON
BACK TO CARBON
COLUMN
207
-------
down flushing ranged between 2-4 weeks. As the turbidity increased to
2.5 SJU, the frequency of down flushing increased to once a shift.
During the study, approximately 200 ft^ of spent carbon was with-
drawn from each column for regeneration at 4 to 8 week intervals. The
regeneration periods were initiated when the percent removal of COD
dropped to about 40% or when the final effluent began to approach its
export limits for COD and MB AS due to poor treatment by the secondary
system or changes in plant influent waste characteristics. During periods
when the secondary system was performing exceptionally well (carbon
column influent COD values 10-14 mg/1), COD removal efficiencies of
less than 40% were permitted. This practice appeared to give satisfactory
usage of the carbon and it produced excellent effluent results. However,
this practice, as demonstrated by later data, resulted in variable loadings.
Carbon Regenerating Operating Practices. At the beginning of a
regeneration period the carbon furnace was fired. As furnace temperature
was being raised to regeneration levals over a period of 24-48 hours, a
slug of carbon (about 200 ft3) was withdrawn from the bottom of the first
column to be regenerated and transferred to one of the two dewatering bins.
When the regeneration of the first slug was nearing completion, a slug
(200 ft3) was withdrawn from the next column and transferred to the remain-
ing empty dewatering bin and so on, through all six columns until the regen-
eration of a slug from each was completed, usually in 9 to 11 days. The
furnace was then slowly cooled down and shut off until the next regeneration
period.
To withdraw spent carbon from the bottom of a column, the flow in
the normal upflow direction was increased to more than 1000 gpm with the
effluent piped to waste, the peripheral water jets turned on, and the press-
ure raised from the 5 psig to 20 psig. After the transfer water was estab-
lished, spent carbon was introduced into the transfer line. Once the
transfer was complete, the column was operated upflow-to-waste for 30
minutes at normal pressures and 1200 gpm to remove additional carbon fines.
The column then was restored to service until the defined regenerated car-
bon was ready to be returned hydraulically to the top of the carbon column
from which it had previously been withdrawn.
Time periods between 1 and 48 hours were equally effective in dewat-
ering the spent carbon prior to regeneration. This confirms earlier work
which indicated that dewatering times between 1 and 26 hours produced
moisture contents of 40.3 to 43.7 percent on a wet weight basis.
Regenerated carbon leaving the furnace was continuously quenched
and was pumped by an air diaphram pump to one of two defining tanks simil-
ar to the one in Figure 69. After approximately 60 to 80 ft3 of regenerated
208
-------
carbon had been pumped into the tank, the feed was switched to the second
vessel. The carbon in the first tank was defined by washing, then the de-
fining tank was pressurized and the contents transferred by water slurry
back to column from which the carbon was originally withdrawn. Carbon
defining required approximately 1 hour with backwashing of the tank efflu-
ent screens about every 15 minutes.
By judicious use of the two dewatering bins and defining tanks and
by taking into account the furnace detention time (25-30 minutes), the
same carbon was kept in a given column throughout the grant period. At
the same time, the furnace was kept full of carbon all through a regenera-
tion period.
The carbon regeneration system is shown in Figure 67 and Figure 68.
The spent carbon slurry bin (Figure 68) was not used during the grant per-
iod in order to prevent mixing of spent carbon from different columns. Its
use would, however, have eliminated many of the carbon regeneration main-
tenance and makeup carbon costs associated with furnace start-up and
shut-down by permitting longer regeneration periods at less than design
plant flows. The makeup carbon bin was basically used to receive virgin
makeup carbon. After defining the virgin carbon was transferred to carbon
column No. 7 for storage. Once again, the makeup carbon slurry bin would
serve a very important function in a continuous regeneration scheme.
The amount of steam fed during the grant period was not measured
directly but was approximately one pound of steam per pound of dry carbon.
Early grant work showed that this markedly improved carbon regeneration.
Excess oxygen in the burners was held to 3% at the number 4
hearth and 1% at the number 6 hearth. In the early periods of the grant,
the excess oxygen was checked periodically. However, as the percent
carbon losses began to increase above 6% with second and third cycle
carbon regeneration, the Q£ concentration was checked before each regen-
eration to insure that excess oxygen was not contributing to the higher
losses.
The number 6 hearth was also kept under slightly positive pressure
conditions (+0.05 inches HzO-gage pressure) to further limit the possibil-
ity of excess oxygen entering the furnace.
209
-------
The regeneration furnace was designed such that the hearth tem-
perature, furnace feed rate, rabble arm speed and steam could be used
to control the carbon regeneration. The rabble arm speed of 0.92 rpm was
held constant throughout the grant, and steam at about one pound per
pound of carbon was used for each regeneration. Of the two remaining
parameters, feed rate and temperature, the feed rate was found to be the
most responsive control.
The apparent density of the carbon was used for plant control of
the carbon regeneration. It was found that hourly apparent density meas-
urements were necessary to keep the regenerated carbon apparent density
between 0.48 and 0.49 gms/ml, the desired range for the 8 X 30 mesh
virgin carbon. Hourly checks were necessary because of the different
regeneration cycles from column to column and because the carbon within
an individual slug from a column had been loaded differently due to posi-
tion within the column prior to regeneration. It is interesting to note that
as the regeneration cycles of the carbon increased, the differences bet-
ween columns and carbon within a slug decreased to the point that at the
time of this report very little change in either temperature or feed rate was
being made from the beginning to the end of a batch regeneration period.
Carbon Column Maintenance. Aside from some very early corros-
ion problems, the carbon columns have required very little maintenance.
The original two carbon columns (1965), coated with 8 mils of
coal tar epoxy, were inspected in January 1968, after about 30 months of
operation and were found to be severely pitted by electrolytic corrosion.
Pits to 3/16 inch deep occurred over wide spread areas of the upper half
of each column. The columns interiors were sand blasted to grey metal
and an improved coal tar epoxy material was applied to each column.
For experimental purposes, 28 mils of the new material was applied to
carbon column No. 1 and 18 mils to carbon column No. 2. The columns,
including five of the six new columns placed into service in March 1968
(Nos. 3-8), were reinspected between October and December 1970 after
32 months of continuous operation. Carbon columns No. 1 through No. 6
showed no signs of corrosion and No. 8 column showed only very slight
signs. No. 7 column which was being used to store virgin carbon was
not inspected.
At the time of the recoating in January 1968, it was felt that either
the dielectric strength of the original 8 mil coal tar epoxy was not suffi-
cient or that pin holes existed after its factory application. The fact that
the six new columns, installed in late 1967, were coated to the same 1965
specifications and that these later columns have been almost completely
210
-------
free of corrosion suggests that the original 8 mil coating (1965) was not
applied correctly. The experience to date also suggests the heavier re-
coatings were adequate.
Carbon Regeneration Maintenance. The carbon regeneration sy-
stem, like two of the separation beds, has been used since 1965. Refer-
ences describe its use from 1965 to 1968, hence this discussion will
carry the maintenance and modification experience forward from January
1968 to January 1971.
The unlined iron pipe carbon slurry transfer lines, some dating
back to 1965, have not been replaced to date. One 90° ell on the suction
side of a diaphram pump was replaced due to electrolytic corrosion. The
maintenance of the stack gas scrubber due to increasing carbon fines is
discussed later in the section on carbon losses. The carbon defining tank
screens have also been affected by the fines. Before each batch regener-
ation period, the tanks are entered and the Johnson well screens are wire-
brushed. After approximately every third period, since July 1969, the
screens have been removed and acid cleaned (10% HC1) in order to com-
pletely remove the carbon fines.
The furnace, aside from replacement of the gas burner zero govern-
ors in 1970, and the draft fan electric motor in 1969, has had no major
maintenance costs. However, because of the batch regeneration periods
resulting from grant studies and plant flows higher than normal, mainten-
ance labor costs have been associated with each furnace start-up.
Since 1968 several modifications have been made to the carbon
regeneration system. In July 1968 the Neva-Clog screens in the defining
tanks were replaced with Johnson well screens. The original screens
plugged very rapidly and eventually ruptured.
In July 1969, copper tubing was installed between hearths of the
carbon regeneration furnace and the atmospheric vent on each of the gas
burner zero governors. This simple but important change has eliminated
burner flame-outs. Prior to this modification, the burners were hard to
light during start-up and flamed-out numerous times during a given carbon
regeneration. Fluctuating pressure within the furnace was suspected to
have caused the flame-outs .
Sampling and Data Collection. Automatic twenty-four hour com-
posite samplers, paced on the flow through the separation beds and carbon
columns, provide daily composites of the separation bed effluent and the
211
-------
carbon column effluent. During the data collection period, the six col-
umns on line were individually sampled by manually compositing twenty-
four hour samples of each column's effluent at a two hour interval.
The laboratory analysis schedule for the above samples in relation
to frequency and parameters analyzed, is described in another section of
this report. The parameters analyzed across the carbon adsorption pro-
cess were COD, BOD, MBAS, and color. The parameters, with the flow
data, provided several different evaluations of the carbon process, which
are described later in the carbon section.
Daily, during the data collection period, the individual carbon
column effluent's flow rate and headless were recorded at two hour inter-
vals. Also at the same time the flow totalizer reading for all water pass-
ing through the separation beds, including filter-to-waste flows, was re-
corded.
For the first 15 months of the data collection period, March 31,
1968 to June 30, 1969, on an individual column basis, the daily total flow,
cumulative flow, flow passed since the previous regeneration, average
hydraulic loading, and the loading and removal efficiencies of MBAS and
COD were computed manually. From July 1, 1969 to November 30, 1970,
more extensive data collection and analysis were available.
During the grant period, twenty batch regenerations were necess-
ary to insure the water reclamation plant's effluent met the stringent ex-
port standards. In the first batch regeneration, carbon was withdrawn
from only three of six columns, and only four in the second regeneration.
In the last eightee.n regenerations, carbon was withdrawn uniformly from
each of the six columns.
Each time spent carbon was withdrawn from a column, an approxi-
mate one liter sample of spent carbon was composited during the transfer.
The composited sample was indentified and placed in a drying oven at 300°F.
After the spent transfer was completed, the surface of the carbon in the
dewatering bin was leveled, and the freeboard depth was measured to com-
pute the approximate volume of the transfer.
After the carbon had passed through the furnace, an operational
sample before quenching was taken hourly for apparent density determina-
tion. A fixed portion of each operational sample was composited through-
212
-------
out each individual column's batch regeneration. This composite was
also placed in the 300°F drying oven. After quenching and defining, the
freeboard in the defining tank was measured, and the volume computed.
The regenerated carbon was then transferred back to the respective col-
umn from which the spent was withdrawn.
At periodic intervals during the grant period the freeboard in each
carbon column was measured before spent withdrawal and after the regen-
erated carbon was added. A log of carbon transfer volumes and column
freeboard depths was also kept, which was used to provide a history of
each column. The history provided an accurate account of the volume of
carbon in each column at a given time, when a regeneration had taken
place, and the volumes of spent withdrawn and regenerated added, and
if any makeup carbon had been added. With these facts, the regeneration
cycle and regeneration losses of each individual column's carbon could
be determined.
To further evaluate carbon losses in regeneration and transport,
sieve analyses were performed on sixty composite samples of spent and
regenerated carbon from five batch regenerations of all six carbon columns.
Twelve additional sieve analyses were performed on carbon column six
regenerated composites around the quenching and defining systems.
During the actual regeneration period, a log was kept, giving the
dewatering bin from which carbon was being extracted, the numerical
setting on the variable speed carbon auger, the hourly apparent densities
and hearth temperatures, steam addition, and every four hours, the nat-
ural gas meter reading. A strip chart also provided continuous hearth tem-
perature readout. From this data the furnace feed rate, gas consumption,
and average hearth temperatures could be determined.
After drying at 300°F for at least three hours, the spent and regen-
erated composites were individually split a number of times to obtain a
representative sample. The sample was pulverized in a ball mixer-mill,
and iodine number and percent ash analyses were made. Also an average
apparent density was determined on each column's spent and regenerated
composite sample. From this data could be determined the efficiency of
a particular regeneration.
Average Results of Carbon Adsorption and Regeneration. During
the thirty-two month data collection period of 1 April 1968 to 1 December
1970, the activated carbon adsorption columns treated approximately 3600
million gallons of separation bed effluent. The monthly average for the
period was 113 MG, with the lowest monthly flow being 80 MG and the
213
-------
highest 154 MG. The average detention or superficial contact time was
19.2 minutes, which provided an average loading rate of 4.7 gal/min/ft^.
The average COD concentration in the separation bed effluent was
20.3 mg/1, which resulted in approximately 612,000 pounds of COD being
applied to the carbon during the period. The average COD concentration
in the carbon column effluent was 10.0 mg/1. Approximately 311,000
pounds of COD were removed by the activated carbon, which resulted in
a removal efficiency of 50.8%.
The average MBAS concentration in the separation bed effluent was
approximately 0.6 mg/1, which resulted in 18,800 pounds of MBAS being
applied to the carbon. The average carbon column effluent MBAS concen-
tration was slightly more than 0.1 mg/1, which provided a removal effic-
iency of 77%.
The average BOD concentration in the Separation Bed effluent was
about 4 mg/1, and the carbon column effluent BOD ranged from 1-3 mg/1.
The chlorinated carbon column effluent BOD concentration averaged 1.2
mg/1 over the period. Since reliability and accuracy of the BOD determin-
ation in these ranges is questionable, no further correlations for BOD were
made in the evaluation of the carbon adsorption system.
The average color concentration in the separation bed effluent was
slightly over 11 color units with the cobalt standard, and the average car-
bon column effluent color value was between 5 and 6 color units. The
color removal efficiency across the carbon averaged slightly below 50%
for the grant period.
Between October 1968 and January 1971, the carbon column flow
was 3,341 MG and 23,050 ft3 or 691,000 pounds of activated carbon were
regenerated, providing a carbon dosage rate of about 207 pounds of regen-
erated carbon per million gallons of carbon column flow. For the same
period, an average of 0.8 pounds of COD were applied per pound of re-
generated carbon, and 0.38 pounds of COD were removed per pound of
carbon. An average of 0.027 pounds of MBAS were applied per pound of
regenerated carbon, and 0.021 pounds of MBAS were removed per pound of
carbon.
The average furnace feed rate for the batch regeneration periods
was 176 pounds per hour, or about 6 cubic feet per hour. Fuel require-
ments per pound of carbon averaged 2900 BTU at 860 BTU per cubic foot
of natural gas at 18-20 psia. Numbers four and six furnace hearth tem-
peratures averaged 1650 and 1670°F, respectively. Carbon losses in the
214
-------
furnace and in transport to and from the furnace averaged 8%during the
period.
The virgin carbon, from the 1965 and 1968 purchases, had an aver-
age iodine number of 935, an apparent density of .485 gms/ml, and an
ash content of 5.0 percent. The spent carbon before regeneration had an
average iodine number of 583, an apparent density of .571 gms/ml, and
an ash content of 6.4 percent. The regenerated carbon had an average
iodine number of 802 , an apparent density of 0.487 gms/ml, and ash
content of 6.8 percent.
The oldest carbon at Tahoe had been regenerated four times and
the newest carbon two times. In the batch regeneration used at Tahoe,
it took approximately one year for an entire column to pass through one
regeneration cycle.
Effect of Carbon Regeneration Cycles on Organics Removal. As
a result of the batch regeneration procedures used at South Lake Tahoe,
two different carbon column historys are required to evaluate the efficiency
of the activated carbon to remove organics over several regeneration cycles
Since it takes approximately an average of one year for one entire carbon
column to pass through one regeneration cycle, carbon purchased in 1965
and 1968 was used for this evaluation. Both carbons are the same brand
and type, Calgon Filtrasorb 300, 8 X 30 mesh. The carbon in Carbon Col-
umn Six (CC-6) is from the 1965 purchase, and the carbon in CC-5 is from
the 1968 purchase. When the grant's extensive data collection program
was initiated on March 31, 1968, CC-6 was in its second regeneration
cycle, and CC-5 was virgin. At the end of the data collection program,
CC-6 was in its fifth cycle and CC-5 was in its third cycle. Since the
regeneration cycles of CC-5 and CC-6 are not identical chronologically,
only the portions of each cycle that are identical in relation to loading
period are used. This method was used to eliminate the problems of var-
iable flow and waste strengths encountered in plant scale research.
The organic removal efficiencies for portions of four regeneration
cycles are shown in Tables 24 and 25 . Since the regeneration of approxi-
mately 50,000 Ibs of carbon is required before one regeneration cycle of
a column is complete, the comparison of first cycle CC-5 and third cycle
CC-6 (Table 24) represents 80% of the total regeneration cycle, and the
comparison of second cycle CC-5 and fourth cycle CC-6 (Table25) re-
presents 75% of the total cycle.
In Table 24, the comparison period of first cycle CC-5 and third
cycle CC-6, CC-5 was loaded slightly higher and had a slightly lower
215
-------
TABLE 24
A Comparison of COD and MBAS Removal Efficiency
Between First Cycle CC-5 and Third Cycle CC-6
Carbon Column
Regeneration Period
Regeneration Cycle
Total Flow in Period
Total Pounds of Carbon
Regenerated in Period
Ibs reg.
Carbon Dosage MG
Chemical Oxygen Demand
Influent mg/1
Effluent mg/1
Percent Removal
Ibs In
Ibs Removed
Ibs In/lb Carbon Reg.
Ibs Removed/lb Carbon Reg,
CC-5 CC-6
11/15/68 to 10/5/69
First
202.2
40960
202
18.2
9.5
47.8
30720
14695
.75
.36
Third
189.3
41100
217
18.2
8.0
55.0
28693
16084
.70
.39
Methylene Blue Active Substances
Influent mg/1
Effluent mg/1
Percent Removal
Ibs In
Ibs Removed
Ibs In/lb Carbon Reg.
Ibs Removed/lb Carbon Reg.
.55
.13
76.4
927
708
.023
.017
.55
.13
76.4
869
663
.021
.016
216
-------
TABLE 25
A Comparison of COD and MBAS Removal Efficiency
Between Second Cycle CC-5 and Fourth Cycle CC-6
Carbon Column
Regeneration Period
Regeneration Cycle
Total Flow in Period
Total Pounds of Carbon
Regenerated in Period
Ibs reg.
Carbon Dosage MG
Chemical Oxygen Demand
Influent mg/1
Effluent mg/1
Percent Removal
Ibs In
Ibs Removed
Ibs In/lb Carbon Reg.
Ibs Removed/lb Carbon Reg
CC-5
CC-6
1/7/70 to 8/6/70
Second
142.3
37170
260
22.6
12.3
45.6
26802
14556
.72
.39
Fourth
140.5
37170
264
21.7
12.1
44.3
25407
14145
.68
.38
Methylene Blue Active Substances
Influent mg/1
Effluent mg/1
Percent Removal
Ibs In
Ibs Removed
Ibs In/lb Carbon Reg .
Ibs Removed/lb Carbon Reg.
1.03
.32
68.9
1220
843
.033
.023
1.03
.25
75.7
1205
913
.033
.024
217
-------
COD removal efficiency, 0.36 Ibs COD removal/lb Reg. Carbon as oppos-
ed to 0.39 for CC-6, and a lower percent removal, 48% as opposed to 55%
for CC-6. MBAS removals are practically identical for the two cycles re-
gardless of flow.
In Table 25 / the comparison period of second cycle CC-5 and
fourth cycle CC-6, the applied loadings for both COD and MBAS are al-
most identical, and practically identical removal efficiencies for both
parameters were attained.
In summary, from the results shown in Tables 24 and 25 , the num-
ber of regeneration cycles of the carbon to date did not affect the removal
efficiencies. In general, if a wastewater of similar volume and waste
strength in terms of COD and MBAS were applied to all four cycles, ap-
proximately the same quality effluent would be attained in all four cycles.
Carbon Column Loading Rate Investigation. A controlled loading
rate investigation was performed by operating Column #1 at 2 gpm/ft2,
Column #2 at 4 gpm/ft2, and Column #4 at 6.5 gpm/ft2 representing con-
tact times of 45, 22.5 and 15 minutes, respectively. The three columns
used for this study all contained virgin carbon initially at the same depth.
As these columns were identical in size, it was not possible to separate
the effects of loading rate and contact time.
As shown in Figure 70 no obvious correlation was found to exist
between the loading rate and removal of MBAS. However, Figure 71 does
show that removal of COD at the lower rate was substantially better than
at either of the higher rates. All three loading ratings show a slight de-
crease in efficiency at about 40 MG of throughput.
Both capital expenditures, including the initial carbon charge,
and the carbon dosage would affect the economies of different loading
rates. A direct economic comparison, however, cannot be made since
the tests were terminated before each column had reached the same spec-
ific adsorption efficiency.
Carbon Loading and Regeneration Over An Extended Period of Time.
An extensive amount of data was collected during the grant period to eval-
uate the efficiency and quality of the twenty batch carbon regenerations.
The first portion of this section describes the specific data collected and
the results. At the end of the grant period, adsorption isotherms were
determined on selected samples from the twenty batch regenerations. The
results and discussion of the isotherm evaluations comprise the second
portion of this section.
218
-------
FIGURE 70
MBAS REMOVAL FOR
CONTROLLED LOADING RATES
uu
>
<
a
o
M
<
a
5
>-
Z
1 0
0.9
0.8
0.7
0.6
2 0.5
W
2
Z3
_l
LL
LL
III
0.3
K
UJ
>
< 0.2
0.1
4G
M/FT2 (22.E
MIN)
MIN)
10
20 30 40
THROUGHPUT. MG
60
70
219
-------
FIGURE 71
COD REMOVAL FOR
CONTROLLED LOADING RATES
Lb
i
d
8
LU
JJ
III
5
IT
LIJ
1 JJ
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
n
'
/
/ /
// 2
**
X
5PM/FT2 (45
^
MINI
- — — "
6.5 GPM/F-
4 GPM/FT2
'
2 (15 MINI
(22 .5 WIN)
^^"
10 20 30 40
THROUGHPUT , MG
70
220
-------
To demonstrate the ability to regenerate activated carbon over an
extended period of time, data was collected on carbon dosage, iodine
number, apparent density, ash buildup, as well as Chemical Oxygen
Demand (COD) and Methylene Blue Active Substances (MBAS), carbon
loadings, and efficiencies. The regeneration parameters of carbon feed
rate, fuel requirements and hearth temperatures were also recorded.
The data from each carbon column was combined and averaged for
each of the batch regeneration periods. Table 26 presents the average,
maximum, and minimum values based on the regeneration period averages
for November 1968 through January 1971.
The carbon dosage of 207 Ibs/MG (Table 26) is based on the total
flow passed through the carbon columns and the total amount of carbon
regenerated. Basically, the flow period was from September 1968 to Jan-
uary 1971. The time prior to September 1968 was used for flow rate studies.
An average of 90 MG through-put and one batch regeneration period occurr-
ed prior to September 1968. The through-put of the carbon columns includ-
ed more than 1 MGD of plant process recycle water that was not part of
plant influent or export flows.
The individual batch regeneration periods, on which Table 26is
based, are shown in Figures 72 and 73 . The average increase in iodine
number after carbon regeneration is shown by Figure 74 . Finally, the bar
graph in Figure 75 indicates the regeneration cycle of each carbon column
at the beginning of a batch regeneration period.
In Figures 72 and 73 the dates represent months during which batch
regeneration periods occurred. The iodine numbers are averages for a
specific regeneration period. The loadings and efficiencies for a particul-
ar date are averages of what occurred between the beginning of the pre-
vious regeneration period and the beginning of regeneration period repres-
ented by the date in question.
Several observations may be drawn from both Figures 72 and 73 . In
Figure 72 , the COD influent concentration and pounds applied to carbon
increased significantly from July 1969 to May or June 1970. At the same
time, the spent and regenerated iodine numbers began decreasing. Bet-
ween October 1969 and April 1970 no effort was made to compensate for
the increasing COD loadings by increasing the carbon dosage. Hence,
between October and April, the carbon efficiency also began to fall. In
May 1970, much higher carbon dosages were initiated. At the same time,
the influent COD began to drop. The net effect of increasing carbon dos-
ages during declining loadings was to bring about an improvement in the
iodine number and to some extent, COD efficiency. Toward the end of
221
-------
TABLE 26
Average Carbon Efficiency Per Regeneration Period
November 1968 Through January 1971
Parameter Average Maximum Minimum
Carbon Dosage
(Ibs.Reg./MG Treatedr ' 207 418 111
Iodine Number'-"-)
Spent Carbon 583 633 497
Regenerated Carbon 802 852 743
Apparent Density (gm/ml)^
Spent Carbon 0.571 0.618 0.544
Regenerated Carbon 0.487 0.491 0.478
Percent
Spent Carbon 6.4 7.0 5.8
Regenerated Carbon 6.8 7.2 5.8
Chemical Oxygen Demand
Percent Removal 49.9 63.3 30.1
Ibs . COD Applied 28,250 54,970 15,680
Ibs . COD Applied per MG 162 254 105
Ibs . COD Removed per MG 81 149 32
Ibs . COD Applied per Ib .
Carbon Regenerated^) 0.78 1.56 0.52
Ibs . COD Removed per Ib .
Carbon Regenerated^) 0.39 0.71 0.16
Methylene Blue Active
Substances (MBAS)
Percent Removal 77.0 93.0 58.0
Ibs . MBAS Applied 995 1675 457
Ibs . MBAS Applied per MG 5.7 10.7 2.6
Ibs . MBAS Removed per MG 4.4 8.2 1.6
Ibs . MBAS Applied per Ib .
Carbon Re generated (2) 0.027 0.045 0.012
Ibs. MBAS Removed per Ib.
Carbon Regenerated (2) 0.021 0.039 0.007
(1) November 1968 through November 1970
(2) Based on ft 3 of carbon fed to furnace at 30 Ibs/ft3
222
-------
FIGURE 72
A COMPARISON OF COO EFFICIENCY. IODINE NO.
AND CARBON DOSAGE BY CARBON
REGENERATION PERIODS
LJ ± 1 4. i__^
— I • -~ -"-^ I I > laurnat.f Mr--/-l
^T I f ~-~{-^ I REMOVED j \ |
-T 1—t 1 ! —~r—N-—-H---3,
223
-------
FIGURE 75
A COMPARISON OF MBAS EFFICIENCY. IODINE NO.
AND CARSON DOSAGE 8V CARBON
REGENERATION PERIODS
J. J_ 1 1 ' _J
nt
K
~
I I I I I I I
I I I I I I
i—i r—r—r
1 ] I APTLlEp
/TN.. kYE"AgfeAP?LH;0 .3
-------
FIGURE 74
INCREASE IN SPENT CARBON IODINE NUMBER
BY THERMAL REACTIVATION
300
' I
5 250
•
••••
:
•
200
150
\
8
•
8 §
8 8
<.
•
•
'
:
3
-
' )
i
Q
i
:
'
I
I
'"
'
•
-------
J-b
: U
O UJ
Z Q
no
in
8 8 8
c
;4-
FIGURE 75
CARBON REGENERATION CYCLES
^^
^g
I
| 1st REGENERATION
\//////////\ 2nd REGENERATION
KEY: R^SSSS^V^V^l 3rd REGENERATION
4th REGENERATION
5th REGENERATION
Y/////////////k'S$$^<$$$$$*
J
-------
the grant period, carbon efficiency for COD seemed to be effected more
by applied COD loadings than in earlier periods. Hence, the recovery in
efficiency was not as pronounced.
The ability of the carbon to remove ABS and alkyl sulfates is
shown in Figure 73 . Unlike COD, carbon efficiency for MBAS between
November 1968 and February 1970 was very dependent on the applied MBAS
loading. After February 1970 the applied loading appeared to have very
little effect on the carbon efficiency. From Figure 73 , one can see that
this change occurred shortly after the transition of 67% of the carbon to
the second cycle of regeneration and 33% to the fourth cycle. Further,
the MBAS efficiency was not effected by the increased carbon dosage
between May and August 1970.
Under variable loading conditions and carbon regeneration cycl es,
the regenerated iodine number seems to be leveling off at near 800. How-
ever, both Figures 72 and 73 show that the regenerated iodine number is
dependent on the spent iodine number, that is the change in iodine number
with regeneration is fairly constant.
Table 27 presents the average carbon furnace conditions from the
regeneration period in November 1968 through that in November 1970. The
higher feed rate and lower fuel and temperature requirements occurred dur-
ing the early stages of the grant. Conversely, it has taken higher tem-
peratures at lower feed rates to regenerate the carbon toward the end of
the grant.
A portion of the evaluation of the ability to regenerate activated
carbon over an extended period of time consisted of determining adsorp-
tion isotherms for four regeneration cycles and the virgin carbon. Chem-
ical oxygen demand and methylene blue active substance (detergents) ad-
sorption isotherms were determined on the virgin carbon, three batch re-
generation samples from carbon column five (CC-5), which were chronolog-
ically three total column regeneration cycles apart, and on one batch re-
generation sample from the fourth total regeneration of CC-8. The CC-8
sample was chosen because it was chronologically as far into its fourth
total column regeneration cycle as the third cycle sample of CC-5 was in-
to the third total regeneration. Also the CC-8 sample was of particular
interest because it had a very low spent and regenerated Iodine Number
compared to the average during the grant period.
The adsorption isotherm procedure used is described in Section
XI. Prior to determining the isotherms for the above samples, the length
of the shaking period or contact time required to reach equilibrium was
227
-------
TABLE 27
Average Carbon Furnace Parameters
Per Regeneration Period
November 1968 Through November 1970
Parameter
Average
Maximum Minimum
Furnace Feed
(Ibs/hr)
Fuel Requirements v
(BTU/lb carbon)
Hearth Temperatures ° F
No. 4 Hearth
No. 6 Hearth
176
2900
1650
1670
266
4510
1460
1560
139
1820
1720
1740
(1) Amount fed to furnace per hr at 30 lbs/ft3
(2) Natural gas requirements per Ib. of carbon fed to furnace
at 860 BTU/ft3 and 18 - 20 psia
228
-------
investigated by contacting equal volumes of separation bed effluent (500
mis) with equal volumes of carbon CC-5, second cycle, spent, (25 mg)
for 30 minutes, 1,2, and 3 hours. The results indicated that both COD
and MBAS reached equilibrium within 30 minutes to 60 minutes. A two
hour shaking period was chosen, and used for all the remaining isotherm
determinations.
Before the isotherms and their conclusions in reference to extend-
ed regeneration ability are revealed, a short discussion of the full scale
carbon column operation and isotherm theory is necessary.
First, because of the stringent export requirements the water re-
clamation plant effluent must meet, the carbon columns cannot be operat-
ed until their theoretical ultimate capacity or saturation is reached. Con-
sequently, the ultimate capacities attained in the laboratory with the iso-
therms are never reached in full scale operation.
Second, as is the accepted procedure, a ball mixer was used to
pulverize the carbon samples for the isotherm determinations, to eliminate
the variability of adsorption in accordance with the diameter of carbon
granules. Since the adsorption rate determining step is the migration of
the adsorbate from the surface of the carbon granule to the adsorption site
within, the larger 8 X 30 mesh granules require a longer adsorption time
and again, the theoretical ultimate capacity attained in the laboratory can
never be reached in full scale operation.
Third, the daily variation in the COD and MBAS strength of the
separation bed effluent will alter the theoretical ultimate capacity attain-
ed in the laboratory, since the adsorption driving force is higher for high-
er COD and MBAS concentrations applied to the carbon.
The COD adsorption isotherms attained for the above described
samples are shown in Figures 76 through 78 . In Figure 76, the COD iso-
therms attained with the virgin and three regenerated cycles of CC-5 and
fourth cycle of CC-8 are shown with the symbol "1", indicating the ulti-
mate capacity for each carbon. The variance of the COD concentration
in the separation bed effluent results in erroneous numerical results for
the ultimate capacity, since the 12-68 CC-5 regeneration has a capacity
greater than the virgin ultimate capacity which is highly unlikely. How-
ever, the slopes and position of the respective isotherms provide a more
reasonable basis for comparison. The isotherms indicate that for any COD
in the separation bed effluent from 20-100 mg/1, the ultimate capacities
for the regenerated samples would fall below the ultimate capacity for the
virgin sample. During the isotherm evaluations, the COD concentration
229
-------
VIRGIN AND THREE REGENERATION CYCLES
OF CC-5. DECEMBER 1968, JANUARY 1970, AND NOVEMBER 1970,
AND FOURTH CYCLE OF CC-8, JULY 1970
345678 910 20 304050 60708090100
C, RESIDUAL COD, MG/L
FIGURE 76
ISOTHERMS FOR VIRGIN AND REGENERATED CARBON
-230-
-------
FIGURE 77
ISOTHERM SPENT AND REGENERATED
ULTIMATE COD CAPACITY
VS
FOUR REGENERATION CYCLES
•
i
.
O
1
LU
:
a
m
:
'
•
ACTUAL REGENERATED
REGENERATED WITH ASSUMED
40 MG/L COD INFLUENT
VIRGIN
REGENERATION CYCLE
-------
THREE SPENT CYCLES OF CC-5
DECEMBER 1968, JANUARY 1970, AND NOVEMBER 1970,
AND FOURTH CYCLE OF CC-8, JULY 1970
3 45678910 20 30405060 708090100
C, RESIDUAL COD, MG/L
FIGURE 78
ISOTHERMS FOR REGENERATED CARBON
-232-
-------
in the separation bed effluent was averaging around 40 mg/1. If the ulti-
mate capacities at 40 mg/1 influent are plotted for the virgin, three sam-
ples of CC-5, and the fourth cycle of CC-8 from Figure 76 , the resulting
curve (Figure 77)of virgin and regenerated samples is derived. The trend
indicates that tne ultimate capacities in terms of COD decrease sharply
during the first regeneration and then appear to level off with only slight-
ly decreasing values. If the actual ultimate capacities obtained from
Figure 76 are plotted on the same Figure 77 , the same decreasing and then
leveling off trend results; but as indicated above, the virgin ultimate
capacity does not follow the trend, because of its low COD influent con-
centration .
The adsorption isotherms for the three spent cycles of CC-5 and the
fourth spent cycle of CC-8 are shown in Figure 78. The separation bed ef-
fluent COD concentrations for these evaluations were quite uniform, rang-
ing from 38-43 mg/1, providing an excellent comparison of the four spent
cycles. If the ultimate capacities derived from the isotherms of the spent
cycles are plotted against regeneration cycles as before, the resulting
curve for the spent samples is shown in Figure 77. The curve indicates a
similar downward and leveling off trend for the ultimate capacities as the
regenerated samples indicated.
The results of the four loading cycles of spent and regenerated
samples indicate that, for COD adsorption capacity, the capacity of vir-
gin carbon was not achieved by reactivation of the first cycle spent carbon.
At the same time, very little additional capacity was lost by continued
reaction of the carbon through the second, third or fourth loading cycles.
To further investigate the trends indicated by the isotherms, io-
dine numbers were determined on the identical samples of the first through
third regeneration cycles of CC-5, and the fourth cycle of CC-8. Table
28 shows the decrease in iodine number due to organic loading, the in-
crease in iodine number due to thermal reactivation, and the net change
in iodine number for each regeneration. After the first cycle regeneration,
there wasa net decrease in iodine number of 118, but the second through
fourth cycles indicated much smaller net decreases, which corresponds
well with the COD ultimate capacity trends shown in Figure 77.
Attempts were also made to correlate the actual pounds of COD
applied and removed, and carbon dosage during a regeneration cycle with
theoretical ultimate capacities attained with adsorption isotherms. How-
ever, correlations between actual full scale column loadings and the lab-
oratory results were unsuccessful.
233
-------
DATE
COLUMN
CYCLE
TABLE 28
ORGANIC LOADING AND REACTIVATION EFFECT
ON IODINE NUMBER
12/68 1/70 11/70 7/70
CC-5 CC-5 CC-5 CC-8
First Second Third Fourth
Virgin or Regenerated 972 854 805 794
Spent 678 568 588 530
Loading Decrease -294 -286 -217 -264
Regenerated
Spent
Reactivation Increase
854
678
+176
805
568
+237
794
588
+206
758
530
+228
Loading Decrease -294 -286 -217 -264
Reactivation Increase +176 +237 +206 +228
Net Change
-118
- 49
- 11
- 36
234
-------
Since organic loading and carbon dosage apparently did not effect
the considerable loss of COD adsorption capacity during the first cycle
regeneration, data was compiled on furnace operating conditions during
each of the batch regeneration periods from which the isotherm samples
were obtained.
The resulting information is listed in Table 29. There is consider-
able difference in all operating conditions between the first regeneration
period and the second through the fourth. In comparison, the furnace feed
rate is reduced to one-half, while the average hearth temperature required
for regeneration is about 50°F higher. The net result for the second through
fourth regeneration periods is that it takes longer to accomplish regener-
ation, and with the higher hearth temperatures, a considerable increase in
gas consumption results. In contrast, Figure 77 shows that at 40 mg/1,
regeneration of the first cycle, produced the lowest COD adsorption re-
activation efficiency, and that regeneration of the later cycles produced
more efficient results in terms of COD adsorption capacity.
As was described earlier, adsorption isotherms for MBAS were al-
so determined on the same samples at the same time as the COD isotherms.
The results of the MBAS isotherms for virgin and the four spent and regen-
erated cycles of CC-5 and CC-8 are shown in Figures 79 through 81. The
MBAS isotherms for the virgin and samples from the first three regeneration
cycles of CC-5 and a sample from the fourth cycle of CC-8 are shown in
Figure 79. It is readily apparent the ultimate capacities for the four regen-
eration cycles approach very closely to the ultimate capacity of the virgin
sample. This is graphically shown in Figure 80, in which MBAS ultimate
capacity is plotted against regeneration cycle. The straight horizontal
line indicates the carbon was always reactivated back to near the ultimate
adsorption capacity of the virgin carbon for MBAS regardless of regeneration
cycle.
The MBAS isotherms for the first three spent cycles of CC-5 and
the fourth spent cycle of CC-8 are shown in Figure 81. The results indic-
ate the ultimate capacity of the spent samples or their degree of being
spent were approximately the same. Again, if the MBAS ultimate capac-
ities for the spent sample are plotted against regeneration cycle as in
Figure 80, a curve is obtained which is approximately one-half the mag-
nitude of the line for the regenerated samples. Therefore, in terms of
MBAS removals, approximately one-half of the carbon's adsorption capac-
ity was expended each regeneration cycle in attaining the 77% overall
MBAS removal for the entire grant period.
235
-------
TABLE 29
FURNACE OPERATING CONDITIONS
FOR
FOUR BATCH REGENERATION CYCLES
COLUMN CC-5 CC-5 CC-5 CC-8
CYCLE First Second Third Fourth
BATCH REGENERATION
DATE 12/68 1/70 11/70 7/70
FURNACE FEED Lbs/Hour 286 164 146 142
GAS COMSUMPTION Btu/Lb 1980 2710 3330 3470
HEARTH TEMPERATURE OF
# 4 1660 1660 1700 1640
# 6 1650 1660 1700 1730
236
-------
FIGURE 79
ISOTHERMS FOR REGENERATED CARBON
VIRGIN AND THREE REGENERATION CYCLES
OF CC-5, DECEMBER 1968, JANUARY 1970, AND NOVEMBER 1970,
AND FOURTH CYCLE OF CC-8, JULY 1970
..
...
' !
Z
< '•
II!
a
i
:
D
a
.' i
Hi
m
i
u>
•
a
•
C, RESIDUAL MBAS, MG/L
.02 .03 .04 .05.06.07.08.09.1
01
.3 .4 .5 .6 .7 .8.91.0
3 4567891
-------
FIGURE 80
ISOTHERM SPENT AND REGENERATED
ULTIMATE MBAS CAPACITY
VS
FOUR REGENERATION CYCLES
ro
CO
00
.10
.09
1-
o .08
Q-
o .07
U)
29 .06
ui
£ .05
5
§ .04
1 .03
UJ
§ "
.01
0
r
t
— 1
<
r '
|
4
r-
t
— -,
— c
^-«
r— ~
— REGENERATED
i — SPENT
VIRGIN
2nd
3rd
4th
REGENERATION CYCLES
-------
z
to
a
-
o
a
HI
a
HI
.,,
i
••••
:v
0
-
•••>
xl E
FIGURE 81
ISOTHERMS FOR REGENERATED GAR-BON
THREE SPENT CYCLES OF CC-5
DECEMBER 1968, JANUARY 1970. AND NOVEMBER 1970
AND FOURTH CYCLE OF CC-8, JULY 1970
C, RESIDUAL MBAS, MG/L
.001
.01
.03 .04 .05 .06.07.08.oai
.3 .4 .5 .6 .7 .8.91.0
5 67891
-------
During the evaluation of the MBAS isotherms, attempts were made
to correllate pounds of MBAS applied and removed, and carbon dosage
with ultimate capacity of the spent and regenerated samples. Since the
MBAS loadings varied considerably for the regeneration cycles evaluated,
and the ultimate capacities for both spent and regenerated samples re-
mained relatively constant, these attempts were discontinued.
In summary, in relation to MBAS removal efficiency of the carbon,
the adsorption isotherms indicate the carbon is reactivated back to its
virgin adsorption capacity regardless of its age or regeneration cycle.
In relation to COD removal efficiency, the isotherms indicate
there is a considerable loss in COD adsorption capacity during the first
regeneration. However, during the second through the fourth cycle, the
COD capacity loss decreases and appears to reach equilibrium in reactiv-
ating the carbon back to the previous regeneration cycle's regenerated
COD adsorption capacity. Also the furnace operating data indicates the
first regeneration is accomplished relatively easily with a high furnace
feed rate, low gas consuption, and hearth temperature, but the net
regeneration recovery efficiency is lower than later periods. During the
second through fourth regeneration periods, in comparison to the first,
the feed rate is lower, the gas consuption is much greater, and the
hearth temperature required for regeneration is higher. However, in the
later regeneration periods, a much better regeneration recovery efficiency
is attained.
Long Range Ash Build-Up. As was the case for the evaluation of
organics removal over several regenerations, the same two carbon column
historys (CC-5 and CC-6) will be used to evaluate the change in percent
ash during the grant period. As described earlier, CC-5 was filled with
carbon from the 1968 purchase and CC-6 was filled from the 1965 purchase.
The grant objective was to evaluate any long range build-up of
ash in the carbon as a result of the higher calcium content in the carbon
column influent. The calcium concentration in the raw wastewater enter-
ing the water reclamation plant is approximately 100 mg/1 as CaCOs. The
calcium concentration in the carbon column influent is around 150 to 160
mg/1 as CaCOs, as a result of the lime chemical treatment for phosphor-
ous removal and ammonia stripping.
In Table 30, the percent ash is shown for four regeneration cycles
of the carbon and the two virgin purchases. The ash content of the vir-
gin carbon from the 1968 purchase was 5.2%. After one complete regener-
ation of the column, the average ash content of spent carbon before regen-
240
-------
TABLE 30
Percent Ash Over Four Carbon Regeneration Cycles
"^\_^^ Carbon Column and
^^\^^ Regeneration Period
Parameter "~"~\^
Regeneration Cycle
Percent Ash
Spent
Regener-
ated
1968
Purchase
Virgin
-
5.2
CC-5
3/31/68
to
10/4/69
1st
x
5.7
6.4
CC-5
10/4/69
to
9/18/70
2nd
6.5
6.9
1965
Purchase
Virgin
-
4.8
CC-6
11/15/68
to
2/9/70
3rd
7.0
7.2
CC-6
2/9/70
to
11/12/70
4th
6.8
7.1
-------
eration was 5.7%, which might indicate a slight increase in ash content
as a result of the higher calcium content in the column influent. How-
ever, the greatest increase in ash content was through the regeneration
process, as the average ash content of the regenerated carbon was 6.4%.
Since the inert portion of the carbon granule would remain the same through
the regeneration furnace, the percent increase in ash content indicates a
slight amount of the carbon was burned in the furnace. In moving from
the first cycle to the second, within the accuracies of the analysis, the
first cycle regenerated and the second cycle spent are identical. This
would indicate there was no build-up of ash as a result of the calcium
in the influent. Again, through the furnace for the second regeneration
there was an increase in ash content as a result of burning the carbon,
but not as great as the first cycle regeneration.
From the second to the third regeneration cycle, bearing in mind
the change in columns and the age of the carbon, but not the type of car-
bon, the regenerated from the second cycle and the spent from the third
are basically identical, indicating no build-up as a result of the calcium.
In the third pass through the furnace there was only a slight increase in
ash due to burning of the carbon.
From the third to the fourth regeneration cycle, there was a slight
decrease in ash content from the third regenerated cycle to the fourth
cycle spent. A possible explanation for this is virgin makeup carbon
entering the picture. Again, through the furnace there was a slight in-
crease in ash content as a result of burning the carbon.
In summary, it can be concluded, within the accuracies of the
analysis, a slight increase in ash can be expected from the calcium con-
tent in the influent, for the first regeneration cycle, but the greatest in-
crease can be attributed to burning the carbon in the furnace in the first
pass through the furnace. After the first regeneration, the calcium con-
centration in the influent has no effect on the ash content, and the burn-
ing of the carbon in the regeneration process decreases until it is practic-
ally negligible for the older carbon. To date, there have been no physical
signs of calcium carbonate scale in either the columns or the dried spent
carbon.
Carbon Losses Due to Regeneration and Physical Handling. From
September 1968 through December 1970 detailed records on carbon regnera-
tion losses and carbon sieve sizes were kept in order to determine the long
range carbon losses due to regeneration and physical handling of the car-
bon. The period included four complete regeneration cycles of the carbon
with the carbon from columns Nos. 1, 2, 4 and 5 being completely regen-
242
-------
erated two times and columns Nos. 6 and 8 four times. A total of
705,500 Ibs. of carbon was regenerated during this period.
Two methods were used to determine the long term losses. First,
on the basis of carbon on hand and that purchased during the 2-3/4 years,
7.3% of the carbon was lost. Whereas, if the amount of carbon lost dur-
ing each regeneration was totalled, the carbon lost over the entire period
was 8.9%. Makeup carbon costs, as discussed later in this report, were
based on the amount of carbon lost during each regeneration.
Over the entire grant period it was observed that carbon regenera-
tion losses increased with each regeneration cycle, that the activated
carbon was becoming smaller with repeated regeneration and that some
carbon fines were being released from the carbon columns to the final
effluent.
In the following paragraphs the observed increases in carbon re-
generation losses and the decreases in carbon particle diameters are dis-
cussed in detail.
As pointed out in the discussion of regeneration practices, every
effort was made to insure that optimum conditions were present in the
furnace and that accurate carbon transfer measurements were made. Des-
pite the efforts of the grant and District personnel carbon regeneration
losses continued to increase.
Figure 82 shows the effect of repeated regeneration cycles on car-
bon losses. An individual point reflects the average loss for a given re-
generation cycle. The number within the parentheses indicates the num-
ber of batch regeneration periods that occurred within a particular regen-
eration cycle. The complete regeneration of a given column or columns
represents the regeneration cycle. The batch regeneration period refers
to the regeneration of a slug of carbon (about 200 ft^) from the bottom of
each column.
Virgin makeup carbon was added five different times during the
grant. The first four additions were part of regeneration periods during
the grant. Since these four regeneration periods did not reflect regener-
ation of a normal carbon cycle for that period, the four regeneration periods
of virgin carbon were not included in Figure 82; but rather, they are shown
in Table 31 .
From Figure 82 it appears that when no virgin makeup carbon is
added the maximum carbon loss of 10% to 11% is reached after the third
243
-------
FIGURE 82
PERCENT LOSS OF CARBON
VS
CARBON REGENERATION CYCLES
12
REGENERATION PERIODS
-244-
-------
TABLE 31 Carbon Losses
During Batch Regeneration Periods Which
Included Regeneration of First Cycle Make-up Carbon
Regeneration Period Carbon Loss
May 1969
Feb. 1970
June 1970
July 1970
2.5%
6.2%
5.9%
8.6%
Amount Originally Added
not recorded
333 ft3
238 ft3
87 ft3
(1) About 1200 ft3 of carbon is included in a regeneration period.
245
-------
to fourth regeneration of the carbon. If makeup carbon were added after
each batch regeneration period, to replace the lost carbon, one would
expect the carbon losses to fall between 8% and 9% as shown by the last
entry in Table 31. Approximately 110 ft3 of carbon is lost during each
batch regeneration period.
Increasing carbon losses with regeneration cycles was also
accompanied by an increasing occurrence of carbon fines in the regener-
ation furnace stack gas scrubber and by decreasing carbon particle dia-
meters .
To help evaluate the physical losses of carbon that occurred dur-
ing handling and regeneration, sieve analyses were performed on differ-
ent samples of spent and regenerated carbon. Mean particle diameters
were then computed for each sieve analysis.
In Table 32 the average mean particle diameter for spent and regen-
erated carbon is compared with regeneration cycle and original purchase
date. Table 32shows for both the 1965 and 1968 carbon that the carbon
is becoming finer with each regeneration cycle.
Table 32 also shows an apparent shift to coarser particle diameters
between the carbon entering the furnace and that leaving the furnace; and
at the same time, a shift to finer particle diameters is shown between the
hot carbon leaving the furnace and that being returned to the carbon column
and eventually being withdrawn once again for regeneration. For example,
if one looks at the second cycle 1965 spent carbon entering the dewatering
bin just prior to regeneration, this cycle of carbon has an average mean
particle diameter of 1.51 mm. After regeneration, but prior to quenching,
pumping, and defining, the mean particle diameter of the second cycle
hot carbon has increased to 2.02 mm. When this same second cycle car-
bon is returned to the dewatering bin for its third cycle regeneration, its
mean particle diameter has dropped back to 1.58 mm.
Special composite samples were collected during several batch
regenerations of carbon column six (1965) in an effort to determine where,
between the exit of the hot regenerated carbon and its eventual return as
spent carbon to the dewatering bin, the carbon was being broken up.
Table 33 shows the results of this special sampling program.
Table 33 once again demonstrates that the finer carbon is being
carried out of the furnace with the hot gasses. It also points out that
the majority of the decrease in particle size takes place in either the
rapid water quench of the hot carbon or in the air diaphram pump-water
246
-------
TABLE 32
Average Mean Particle Diameters of Carbon
From September 1968 to December 1970
Reported in Millimeters
CO
Regeneration
Cycle
1 st
2 nd
3 rd
From Virgin Carbon
Purchased in 1965
Spent Carbon Regenerated
EnteringDewatering Carbon Prior
Bin to Quench
1.69
1.51
1.58
2.02
1.85
From Virgin Carbon
Purchased in 1968
Spent Carbon
Entering Dewatering
Bin
1.61
1.43
Regenerated
Carbon Prior
to Quench
1.81
1.60
4 th
5 th
1 .44
1.65
Virgin (Before Defining)
1.58
1.67
-------
TABLE 33
Mean Particle Diameter of Carbon
At Various Points in Regeneration System
Reported in Millimeters
to
£*
00
Sampling Point
Spent Carbon Entering
Dewatering Bin
Spent Carbon Entering
Furnace
Regenerated Carbon
Prior to Quench
Quenched Regenerated Carbon
Entering Defining Tank
Defined Regenated Carbon
Entering Carbon Column
Virgin Carbon
First Cycle Carbon
From CC 6 and
1.69
1.70
1.66
1.58
February 1969
3rd Cycle Carbon
From CC-6
1.57
1.87
1.63
1.63
1.67(2)
November 1970
5th Cycle Carbon
From CC-6
1.40
1 .65
1.46
1.40
(1) Calculated from A.Slechta and G.Gulp, Progress Report, PHS Demonstration Grant 84-01 "Plant
Scale Regeneration of Granular Activated Carbon" ,April 1 - Oct.l 1965 p. 29
(2) Virgin carbon purchased in January 1968, 121 tons (before defining)
(3) Virgin carbon purchased in May 1969, 15 tons (before defining)
-------
slurry transfer system which moves the quenched carbon to the defining
tank. The defining operation and transfer back to the carbon column
shows no significant change in mean particle diameter. For further am-
plification, the sieve analysis of the February 1969 third cycle regenera-
tion is shown in Table 34.
To evaluate where the break-up of the carbon between the carbon
furnace and the defining tank might be taking place, an experiment to
compare water quenching with air cooling was performed. During the re-
generation of carbon column six in April 1970 (fourth regeneration cycle)
a hot sample leaving the furnace at 1740°F was split in such a manner
that a portion was water quenched in a bucket and a portion was trapped
in a dry container and then air cooled. The water temperature in the
bucket was 60°F before carbon quenching and 70°F after quenching. Water
temperature in the regular quench tank was 66°F at that time. Table 35
indicates that the difference in the two methods of cooling appears to be
insignificant. The data in Tables 34 and 35 suggests that the air diaphram
carbon slurry pumps and/or the carbon slurry transfer line leading to the
defining tank may be responsible for the shift to finer carbon particles.
The decrease in particle size as shown by Table 32 has not caused
a noticeable increase in headless across the carbon columns. In fact,
the headloss has been lower to date than it was at the beginning of the
grant period.
There has been, however, a noticeable increase of carbon fines
build-up in the stack gas scrubber and its water drain. In July 1969 the
diameter of the scrubber drain was found to have been reduced from 2 in.
to 1/2 in. by a build-up of carbon fines. Since 1966, fourteen batch
regeneration periods had occurred prior to this build-up. Six batch re-
generation periods later, in March 1970, the scrubber was opened for the
first time since 1966 to remove a carbon build-up and the scrubber drain
line was again replaced. In July 1970, following four additional batch
regenerations, the scrubber again was found to be plugged with carbon
fines. Since July 1970 scrubber inspection and cleaning has become part
of the routine maintenance prior to carbon furnace start-up. In January
1971, the scrubber drain line was again replaced. Seven batch regenera-
tion periods had occurred since its last replacement in March 1970.
Most of the carbon fines in the final effluent can be related to
regeneration periods during which carbon was being removed or added to
the carbon columns. These carbon fines have not been detected in Indian
Creek Reservoir nor to date have they caused any insurmountable problems
with operation of the water reclamation plant or export system.
249
-------
TABLE 34
Sieve Analysis of Third Cycle Carbon
From CC-6 at Various Points In
The Regeneration System
February 1969
Sampling Point
ro
en
o
Sieve No:
Spent Carbon Entering
Dewatering Bin
Regenerated Carbon
Prior to Quench
Quenched Regenerated Carbon
Entering Defining Tank
Defined Regenerated Carbon
Entering Carbon Column
Virgin Carbon
January 1968
Percent Retained on Given Sieve
4 8
4.5
0
8.3
4.8
4.9
7.2
10
15.2
28.3
17.7
19.3
16
53.2
55.7
56.0
54.0
66.4
30
25.0
7.4
20.0
18.8
24.2
40 50
1.6 0.3
0.1 0
0.9 0.2
1.5 0.3
2.0
-------
TABLE 35
A Comparison of Water Quenching
of 4th Cycle Regenerated Carbon (U
With Air Cooling
Sample Mean Particle
Diameter, mm,.
Spent Carbon
Entering Dewatering Bin 1.51
(Composite sample)
Water Quenching at 60°F
Hot Regenerated Carbon 1.61
Leaving Furnace at
1740°F (grab sample)
Air Cooling of Sample (same 1.63
grab sample as water quench)
(1) Carbon column No. 6, April 1970
251
-------
Trace amounts of carbon fines will probably always be present in
plant effluents where in-house carbon regeneration is practiced.
Should the removal of these carbon fines be necessary, solutions
such as more efficient defining, post-filtration, or quiescent settling in
reservoirs could be considered. Laboratory and field experience at South
Lake Tahoe has shown quiescent settling to be very effective in removing
the carbon fines.
Summary and Conclusions. Three years of continuous plant
scale granular activated carbon operation with twenty batch carbon regen-
erations providing four complete carbon regeneration cycles have demon-
strated the following:
1. Upflow, countercurrent, granular activated carbon contactors
provide the most efficient use of the carbon since only the required amount
of the saturated carbon from the lower portion of the column is withdrawn,
regenerated, and placed at the top of the column, where it polishes the
treated water prior to exit from the column. This enables the use of the
more flexible parallel column configuration, and obviates the need for
many columns in series.
2. Granular activated carbon was successfully regenerated
through four complete regeneration cycles. The organic adsorption ulti-
mate capacity of virgin carbon, as measured by the Iodine Number and
COD adsorption isotherms, was not recovered during the first regeneration
cycle; however, no additional capacity was lost by subsequent regenera-
tion cycles. The loss in Iodine Number and ultimate COD isotherm capac-
ity did not appear to effect the ability of regenerated carbon to remove
COD, BOD, detergents, or color.
3. Except during periods of very low organic loadings a regen-
eration period was initiated when the percent removal of COD dropped to
about 40% or when the carbon column effluent began to reach the export
limits for COD and MBAS due to changes in prior treatment upstream.
This practice provided satisfactory carbon usage but resulted in variable
organic loadings.
4. Eight mils of coal tar epoxy, provided it has the necessary
dielectric strength and has been applied correctly, will provide adequate
corrosion protection in the carbon columns. Early corrosion problems in
two of the columns was caused by improper application of the coating.
252
-------
5. Unlined iron pipe carbon slurry transfer lines and fittings
proved to be satisfactory. None of these lines have been replaced since
they were installed in 1965.
6. Perforated screens, when used in the carbon defining tanks,
plugged very rapidly, and eventually ruptured. The substitution of John-
son well screens has proved to be very satisfactory.
7. The carbon adsorption system has treated a total of 3,600
million gallons at a carbon dosage of 207 pounds of regenerated carbon
per million gallons of flow. The carbon removed an average of 0.38
pounds of COD and 0.021 pounds of MBAS per pound of carbon regenerated.
The removal efficiency for COD was 50.8% and 77% for MBAS. The effluent
concentrations averaged 10 mg/1 for COD and 0.1 mg/1 for MBAS.
8. The average carbon furnace feed rate was 176 pounds per
hour on the basis of 30 lbs/ft3. Fuel requirements per pound of carbon
averaged 2900 BTU at 860 BTU per cubic foot of natural gas at 18-20 psia.
Regeneration temperatures averaged 1670°F.
9. One manufacturers 8 X 30 mesh carbon was used throughout
the grant. The regeneration of this spent carbon brought the average io-
dine number back from 583 to 802 and the average apparent density from
0.571 gms/ml to 0.487 gms/ml. The ash build-up was 1.8% over three
years. By the end of the grant period, carbon purchased in 1965 had been
regenerated four complete times and carbon purchased in 1968 (the beginn-
ing of the present grant) had been regenerated two complete times.
10. Hourly apparent density tests were used to monitor the re-
generation. Carbon furnace feed rate was found to be the most positive
means to control the apparent density of the regenerated carbon.
11. For the same long term carbon dosage and applied organic
loading, the removal efficiency of the regenerated carbon was not mater-
ially affected by the number of regeneration cycles.
12. A controlled loading rate investigation showed that the re-
moval of COD at 2 gpm/ft2 was substantially better than at either 4 or
6.5 gpm/ft2, and that MBAS removal was not affected by loading rate.
As the columns tested were identical in size and volume, it was not poss-
ible to separate the effects of loading rate and contact time. The average
efficiencies reported for the entire grant period were at an average loading
rate of 4.7 gpm/ft2 .
253
-------
13. Spent carbon was fed to the carbon furnace at near the de-
sign capacity of 6,000 Ibs/day at 1600-1650°F during the first regenera-
tion cycles to maintain apparent densities in the 0.48 to 0.49 gin/ml
range. Whereas for similar organic loadings during the third and fourth
regeneration cycles, feed rates and temperatures of 3400 Ibs/day at
1700°F were necessary.
14. In relation to MBAS removal efficiency of the carbon, ad-
sorption isotherms indicate that the carbon is reactivated back to its vir-
gin adsorption capacity regardless of its age or regeneration cycle.
15. The adsorption isotherms indicate that for COD removal
efficiency, there is a considerable loss in COD adsorption capacity dur-
ing the first regeneration. However, during the second through fourth
regeneration cycles, the COD capacity loss decreases and appears to
reach a point where all the capacity lost during the adsorption cycle is
recovered by regeneration. Iodine numbers show the same effect.
16. During the grant period, there were no physical signs of
calcium carbonate scale in either the columns or in the dried spent carbon.
Ash analyses of the carbon show that prior to the first regeneration there
is a slight increase in ash content, possibly due to calcium salts. After
the first regeneration cycle the calcium concentration in the water has no
effect on the ash content of the carbon.
17. Based on the total amount of carbon on hand and that pur-
chased, 7.3% of the carbon was lost due to regeneration and physical
handling during the grant period. Whereas, if the amount of carbon lost
during each regeneration period is computed across the furnace and de-
fining tanks, the carbon lost amounts to 8.9%.
18. Carbon losses increased with the number of regeneration
cycles. Without the addition of virgin makeup carbon, a maximum carbon
loss of 10% to 11% was reached after the third to fourth regeneration of
the carbon. If makeup carbon were added after each batch regeneration
period to replace the lost carbon, one would expect the carbon losses to
be between 8% and 9%.
19. Sieve analyses showed an apparent shift to coarser carbon
particle diameters between the carbon entering the furnace and that leav-
ing the furnace. At the same time, a shift to finer particle diameters was
observed between the hot carbon leaving the furnace and that being return-
ed to the columns. Other sieve analyses suggest that the decrease in car-
bon particle diameters was being caused in part by the air diaphram pump
in the pumping of quenched carbon to the defining tank.
254
-------
20. During the grant period, the mean particle diameter of the
carbon dropped from 1.69 mm to 1.44 mm.
255
-------
SECTION XXI
VIRUS REMOVAL
General. One of the most frequently asked questions about
the safety of water reuse for purposes involving human contract or ingest ion
of the water is that of the possible transmission of viral disease. Even
though water is not an important mode of transmission of viral disease,
and despite the fact that certain sewage and water treatment processes or
combinations thereof can remove viruses, wastewater reclamation plants
must be properly designed to assure complete virus inactivation or removal.
A review of the water literature reveals many important consider-
ations .
In a 20-month study of the removal of polio virus Type I from
water, Robeck, Clarke, and Dostal made several noteworthy ovservations
in their paper, "Effectiveness of Water Treatment Processes in Virus Re-
moval", which appeared in the Journal AWWA for October 1962 . Their work
disclosed clearly that "coagulation and filtration are really one process
and must be studied together" . This is now a widely accepted and applied
principle. They further state, "Though smaller than coliform organisms,
the polio virus organism is removed by flocculation and filtration with about
the same efficiency as coliforms" . They also presented in tabular form a
summary of polio virus removal by various water and wastewater treatment
techniques as shown here.
They noted that, "If a low but well-mixed dose of alum was fed
just ahead of the filters operated at 6 or 2 gpm/sq. ft., more than 98 per-
cent of the viruses were removed by 16 in. of coarse coal on top of 8 in.
of sand".
"If the alum dose was increased and conventional floccuJators
and settling were used, the removal was increased to over 99 percent."
They reported that polyelectrolyte doses to filter influent as low
as 0.05 ppm increased floe strength and helped prevent filter breakthroughs
of virus. Their results are summarized in the tabulation which follows.
257
-------
Summary of Polio Virus Removal
Removal,
Process Per Cent.
Die-off (under experimental conditions-20°C) £?5-10 in 24-48 hr
Activated sludge 90-95
Polluted stream 99.9 in 18 days
Filtration or seepage
Through unsaturated sand at 20-40 gpd/sq ft >99.99
Ground water movement
Upflow- 9 gpd/sq ft (3 ft/day) ^99.99
Downflow- 12 gpd/sq ft (4 ft/day)
Slow sand filter rates - 50 gpd/sq ft 22-96
Rapid filter rates - 2,880-8,640 gpd/sq ft
(2-6 gpm/sq ft )
Without alum 1-50
With alum
Without settling 90-99
With settling <99.7
Flocculation and settling (varies w/dose & time) 95-99
Chlorination (varies w/dose & contact) 99.99
In discussing the above paper, in the same publication, H.O.
Hartung had this to say:
"The article by Robeck, Clarke, and Dostal contributes materially
to the growing evidence that the public water supply can be processed to
remove or inactivate viruses of public health significance. This evidence
258
-------
is consistent with epidemiological studies of waterborne diseases which
indicate that viral infections from the use of properly treated public water
supplies are unlikely at the present. Both laboratory and epidemiological
studies show that the possibility of waterborne viral outbreaks seems to
be linked to the presence of gross viral pollution in raw water sources,
and to the absence of reliable water treatment procedures at the local water
treatment plants for reducing viruses below infectious levels. All of these
studies indicate, however, that under circumstances of gross raw water
pollution and some existing water treatment methods, a bacteriologically
safe water may not be virally safe."
"The article is a very important addition to a series of studies
which evaluate unit water treatment processes as to their viral removal
capacity. This study has examined filtration. It shows again that surface
phenomena are important in the removal of animal viruses from waters.
Other studies have indicated that activated sludge sewage processing,
chemical coagulation, and chlorination, when properly applied and rigidly
controlled, are also factors in virus removal. "
"Viral pollution in raw water supplies can be materially reduced
through activated sludge processing of sewage prior to disposal in the
public raw water supply. Clarke and others observed that 90 percent or
more of enteric viruses added to sewage were removed by activated sludge
processing in laboratory experimentation. They found that, for a safe water
supply, the remaining viruses must be removed by additional processing of
the sewage treatment plant effluent or in the public water supply treatment
plants. It is important to note that viruses were not significantly removed
in primary sewage treatment plants. "
"Chlorination under controlled conditions is also effective for
viral removal. However, chlorination for bacteria disinfection may not
always be a dependable viricide. Free chlorination is considerably more
viricidal than combined chlorine. The free residuals required for inactiva-
tion depend upon pH, temperature, contact time, and other factors. For
example, Kabler and others report that, 'At 25°C and at pH 7, 6 ppm of
combined chlorine with a 1-hr contact period was necessary for inactivation
of polio virus' . On the other hand, ' Studies indicate that, at a tempera-
ture of approximately 20°C and pH values no higher than 8.0-8.5, a free
chlorine residual of 0.2-0.3 ppm will destroy most of the tested viruses
in 30 min. At temperatures below 10-15°C and pH values greater than 8.5,
effective virus kills with free chlorine residuals of 0.2-0.3 ppm are prob-
ably not obtainable without long detention periods.' "
"Coagulation in some instances has also been observed to be
effective in removing viruses. Chang and others found that two-stage
259
-------
coagulation of Ohio River water - using 25 ppm of alum, and 25 ppm of
ferric chloride coagulants with very good floe formation at 25°C, and pH
about 7.3 - was effective in removing 99.9 percent of Coxsackie viruses
added to water. During such coagulation studies it was observed that
coagulant doses adequate for turbidity removal are not necessarily high
enough to insure efficient virus or bacterial removal. For virus removal
it was found that the dosage of coagulant must be adequate to insure good
floe formation, even though such floe might not be necessary for turbidity
removal. Also, pH regulation to control speed of floe formation and stir-
ring rate were found to be important. "
"In their article the authors prefer to consider coagulation and
filtration as one process for virus removal. They show that virus removal
is accomplished by good, high strength floe formation followed by filtration.
Filter breakthrough was found to be an indication of failure of the combined
flocculation-filtration process to remove viruses. Sand filtration at 2 gpm/
sq ft was not dependably effective in removing viruses until the water
applied to the filters was properly coagulated. The great variability of the
effectiveness of sand filtration in certain flow-velocity ranges indicates
the weakness of the forces of adhesion between virus and filter media. "
In an interesting paper on "High-Quality Water Production and
Viral Disease" in the Journal AWWA, October 1962, H. E. Hudson, Jr.
reached the following conclusions:
"1. Filtration plants operated to attain a high degree of removal
of one impurity tend to accomplish high removals of other suspended mater-
ials. Examples of parallelism in removal of turbidity, manganese, micro-
organisms , and bacteria are cited. "
"2. Speed and simplicity make the turbidity measurement a
valuable index of removal of other materials. Plants producing very clear
water also tend to secure low bacterial counts accompanied by low incid-
ence of viral diseases."
"3. The production of high-quality water requires striving to-
ward high goals as measured by several - not just one or two - quality
criteria. These criteria include filtered-water turbidity, bacteria as indic-
ated by plate counts and by presumptive- and confirmed-coliform determin-
ations, and thorough chlorination. "
"4. The operating data for plants treating polluted water indic-
ate that low virus disease rates occur in cities where the water treatment
operators aim to produce a superior product rather than a tolerable water."
260
-------
In discussing Hudson's paper, R. L. Woodward made some points
which are of interest here. They are as follows:
"Turbidimeters measuring the quality of the output of each filter
unit, either continuously or at frequent intervals, are needed to obtain the
best possible plant performance."
"If the best effluent clarity is wanted, there is also merit in fil-
tering to waste for a short time after backwashing. This practice has large-
ly been discontinued in this country, but it remains true that water produced
during the early part of the filter cycle is not as clear as water produced
later. A monitoring turbidimeter can be useful in guiding operations if this
practice is followed. "
"Although infectious hepatitis is sometimes transmitted by water,
there is general agreement among epidemiologists that its principle mode
of transmission is by more direct fecal-oral contact. The possible function
of water in causing scattered primary cases, which may then give rise to
further spread in the community by contact, can only be speculated on. "
In the October 1969 Journal AWWA a Committee report by Clarke,
Berg, Liu, Metcalf, Sullivan and Vlassoff summarizes very well and com-
pletely the status of viruses in water. Excerpts from this report follow:
"Any virus excreted and capable of causing infection when ingest-
ed could be transmitted by water. Practical conditions would seem, how-
ever, to indicate that we should be concerned with only those viruses that
can multiply in the intestinal wall and that are discharged in large numbers
in feces. This means that the recognized viruses with which we should be
concerned are the members of the enteric virus group: polioviruses, Cox-
sackie viruses, ECHO viruses, the virus (es) of infectious hepatitis, the
adenoviruses, and the reoviruses. The total number of virus types that
compose these six major groups is around 100 and, with the exception of
the agent(s) of infectious hepatitis, they have been shown present in sew-
age."
"What can be said about gastroenteritis .and the related diarrheal
diseases? Many epidemics have been conveniently ascribed to viruses,
although very, very few have been thoroughly studied to identify causative
agents. Experimental work does, however, indicate that some gastroenter-
itis or diarrheal disease is caused by viruses and that, under the proper
circumstances, it could be waterborne. Weibel and coworkers have listed
142 epidemics of these diseases that occurred in this country from 1946 to
1960, with more than 18,000 persons afflicted. Thus, in terms of number
261
-------
of persons afflicted, gastroenteritis and diarrhea appear quite important.
This is an area where laboratory and epidemiological research is obvious-
ly needed."
"Finally, something must be mentioned about the unknown, un-
discovered, or nonhuman viruses that some scientists have said may be in
our water supplies and transmitted through drinking water. Berg has point-
ed out that viruses native to fish and bacteria abound in water and that
plant viruses must be almost as plentiful. He also indicates that viruses
native to wild life and farm and domestic animals must also be washed in-
to waterways. The suggestion is then made that, since we know certain
viruses can cause cancers in species foreign to them, and that other viruses
may infect generically distant hosts, we cannot ignore the large number of
viruses of nonhuman origin in our natural waters and be unconcerned that
these viruses are probably consumed by man. Of course, we cannot ignore
these viruses; they should be studied! There is, however, no reason to
panic; there is no reason to suspect that modern water treatment processes
cannot remove or inactivate these viruses from our drinking water - if they
are present. Certainly, on the basis of all evidence available, the assoc-
iation of cancer viruses in water with the production of tumors in man is
not warranted at this time. "
"A question repeatedly asked those involved in research on the
problem of viruses in water, and probably those involved in supplying the
public with drinking water, is 'Is water that meets USPHS bacteriological
drinking water standards free from disease-producing levels of virus ?'
This question can perhaps be answered if the following factors are consid-
ered:
1. What are the relative numbers of indicator bacteria and vir-
uses in water and sewage?
2. What is the relative survival time of the two groups of micro-
organisms ?
3. What is the relative effectiveness of water and sewage treat-
ment processes on indicator bacteria and viruses ?
4. What epidemiologic evidence do we have that water that
meets or does not meet the standards can be responsible for virus disease
or infection in humans ? "
" Relative numbers of coliform bacteria and enteric viruses in
water and sewage have been discussed by Clarke, et al. These authors
262
-------
have calculated coliform-virus ratios to be about 92,000: 1 in sewage and
about 50,000: 1 in polluted surface waters. Coliform organisms greatly
outnumber enteric viruses in sewage or polluted surface waters and there-
fore appear to be a far better indicator of pollution than enteric viruses."
"The relative survival times of bacteria and enteric viruses in
various types of water have been discussed by Clarke, et al. and by Berg.
The data available do not permit generalizations on the comparative surviv-
al times of viruses and indicator bacteria. In some waters viruses survive
much longer than coliform organisms; in other waters, coliforms survive
longer than certain enteric viruses do. Additional studies are needed be-
fore any broad generalizations can be made on survival times of viruses
and indicator bacteria in water. "
"A considerable amount of literature is available regarding the
relative effectiveness of water and sewage treatment processes on indica-
tor bacteria and viruses. The viricidal efficiency of water disinfectants
has been summarized by Kabler, et al. The conclusions in this paper in-
dicate that different enteric viruses show rather wide variations in their
resistance to chlorine. Additionally, certain types of Coxsackie viruses,
polioviruses, or ECHO viruses are more resistant to chlorine than indicator
bacteria are. This, however, is no cause for alarm. Clarke and Chang
have stated that, in the prechlorination of raw water, any enteric virus so
far studied would be destroyed by a free chlorine residual of about 1.0 ppm,
provided this concentration could be maintained for about 30 min and that
the virus was not embedded in particulate material. They further state
that, in postchlorination practices where relatively low chlorine residuals
are usually maintained, and in water of about 20°C and pH values not more
than 8.0-8.5, a free chlorine residual of 0.2-0.3 ppm would probably des-
troy in 30 min most viruses so far examined. These statements are reassur-
ing, but there still is need for assessing the effect of chlorine on other
viruses, particularly the virus(es) of infectious hepatitis, once a reliable
method of handling this agent in the laboratory becomes available."
"The effectiveness of chemical flocculation and filtration in remov-
ing viruses and bacteria from water has been reviewed by Clarke, et al.,
and Berg. Chemical flocculation generally seems to be as effective in re-
moving a Coxsackie virus as in removing coliform organisms from water.
Slow sand filtration removes both coliform bacteria and enteric viruses
quite well but, with increasing filtration rates and no chemical pretreatment,
virus removals become erratic. Note also that, although rapid sand filtra-
tion also results in a decrease in coliform removals, this decrease is not
of the magnitude observed with viruses. This rapid sand filtration is not
as effective in removing enteric viruses from water as it is in removing
263
-------
coliforms. Rapid sand filtration, combined with chemical flocculation is,
however, effective in removing bacteria and viruses from water."
"The numerous reports of waterborne outbreaks of virus disease
have been summarized by Mosley. He states, 'There are very few viruses
for which epidemiological evidence suggests transmission by drinking
water1. Mosley also states that infectious hepatitis is the only disease
caused by an agent having the characteristics of a virus for which evidence
of waterborne transmission has been accepted by all workers in the field.
A somewhat different feeling, however, has been expressed by Stevenson,
who states, "Unfortunately they (the epidemiologists) have not sharpened
their tools to the point where they can tell us the significance of small
quantities of viruses in water...' At this point in time, nobody can be
sure which of these viewpoints is indeed correct, although true epidemics
of waterborne virus disease are extremely rare and are usually the result
of a breakdown in treatment procedures, if any treatment is normally used. "
"Certainly, waterborne infectious hepatitis does occur, but in
the United States most of these outbreaks have been the result of obvious
contamination of small, private water supplies. There have been ten re-
ported outbreaks of infectious hepatitis in the United States in which a
public supply was involved. In seven of these outbreaks, the reports give
no indication of the type of treatment used, if any, or if there was evidence
of crossconnection with a toilet or other evidence of definite sewage con-
tamination. In the remaining three outbreaks the supplies were reported
chlorinated."
"In the infectious hepatitis epidemic reported by Hayward, no
coliform data were presented. Chlorine residuals of 0.7 to 0.9 ppm were
reported present in the treated water. All in all, the basis for accepting
this epidemic as being waterborne is really inadequate; it has the char-
acteristics of person-to-person transmission. "
"Mosley has described an epidemic of infectious hepatitis that
apparently was waterborne and that resulted from using an unapproved
water source, with coliform MPN's of "240 plus". The major portion of
this supply was chlorinated, but there was evidence that the portion of the
supply from the contaminated source was never chlorinated and did not have
opportunity to mix with the chlorinated portion. "
"The epidemic reported by Polkanzer and Beadenkopf is especially
interesting, since it seems to be associated with a chlorinated public sup-
ply with an excellent record of 'no coliforms1. In the year preceding this
epidemic and for 6 months following it, all reported coliform counts were
less than 2.2/100 ml. All samples except one, examined about a month
264
-------
after the probable contamination of the water supply, were also negative
for coliforms. The one positive sample was collected from a greenhouse
tap and had an MPN of 15/100 ml. The treatment plant records indicated
'residual free chlorine levels daily ranged from 0.35 to 0.6 ppm by the
orthotolidine test using the flash method'. Other records indicated the
plant was meeting the New York State Department of Health recommenda-
tions of 'a minimum concentration of free chlorine for a disinfecting period
of at least 10 min ranging from 0.2 ppm at a pH of 6.0 to 0.8 ppm at a. pH
of 10.0'. It appears that, in this epidemic, chlorine residuals (no other
treatment was used) were adequate to control the bacteriologic quality of
the water. The epidemic has been ascribed to inadequate chlorination,
but it is also possible that the virus could have been protected from the
chlorine by particulate matter. This epidemic is in some aspects compar-
able to the New Delhi, India hepatitis disaster. To some, it might appear
that treated water may, under certain circumstances, transmit infectious
hepatitis. In the reported epidemics, however, it is very doubtful that
the water was adequately treated, as it could have been by applying al-
ready known procedures."
"There is no doubt that water can be treated so that it is always
free from infectious microorganisms-it will be biologically safe. Adequate
treatment means clarification (coagulation, sedimentation, and filtration),
followed by effective disinfection. Effective disinfection can be carried
out only on water free from suspended material. The importance of this
latter point has been vividly pointed out by Sanderson and Kelly. They
describe a situation in which coliforms were consistently isolated from
waters containing from 0.1-0.5 mg/1 free chlorine and between 0.7-1.0
mg/1 total chlorine after 30 min contact time. This water had turbidity
values of from 3.8 to 84 units, contained iron, rust, and occasionally had
biological organisms of 2,000 units. Viruses, because of their small size,
would probably more easily become enmeshed in a protective coating of
turbidity-contributing matter than bacteria would. For most effective dis-
infection, turbidities should be kept below 1 Jackson Unit; indeed, it
would be best to keep the turbidity as low as 0.1 unit, as recommended by
AWWA water quality goals. The limit of 5 Jackson Units of turbidity spec-
ified in the USPHS 'Drinking Water Standards', 1962, is meant to apply to
protected watersheds and not to filtration plant effluents. With turbidities
as low as 0.1 to 1, a preplant chlorine feed need be only enough to have a
1 mg/1 free chlorine residual after 30 min contact time. Postchlorination
practice would depend upon the ability to maintain such residuals through-
out the distribution system. "
"In conclusion, there does not appear to be cause for panic or
overreaction to the problem of viruses in water. Under certain conditions,
265
-------
infectious hepatitis can be transmitted by treated water, but the evidence
indicates that in such cases treatment was inadequate. The evidence for
the transmission of other enteric viruses by treated water is, for the most
part, speculative, with the possible exception of viral gastroenteritis and
diarrhea, and nothing much is known about these viruses. These state-
ments, however, do not mean we can be smug or complacent. There is
still considerable room for research, both laboratory and epidemiologic,
to determine if there is a problem in virus disease transmission by water;
to determine if the coliform index is always adequate {positive coliform
test may not indicate freedom from viruses); to devise better techniques
for measuring viruses in water; to develop a laboratory method of detect-
ing small numbers of viruses in large volumes of water. "
Design Considerations For Virus Removal. The preceding litera-
ture review points to several factors that must be considered in the design
of water reclamation facilities. In the reference section of this report, a
total of 29 references are listed relating directly to virus removal. A sear-
ch of these additional references will reveal several other important items
which warrant attention in plant design.
Basically the Tahoe plant is a good secondary sewage treatment plant
followed by an efficient water purification plant followed by activated car-
bon adsorption. On the face of it, then, this process should remove virus
based on the experience of numerous existing water works which receive
raw water containing raw, primary, or secondary treated sewage. Actually
it does more than this because the sewage treatment portions of the plant
are designed and the plant is operated with the specific aim of producing
a safe water from wastewater. The addition of provisions for adsorption of
organics on carbon is another plus factor.
Relating the Tahoe design to the literature quoted, one point is
that the close interrelationships of coagulation and filtration have been
recognized and utilized in the plant design. A coagulant, alum, is added
continuously to the filter influent water following the high lime treatment
in such a concentration that maximum filtrability is assured. At times, a
polymer is also applied at this point. The mixed-media separation beds
in the plant are even more efficient than the coal-sand media tested by
Robeck, et al. in removing virus. Recalling the close relationship between
virus removal and turbidity reduction which was pointed out by several in-
vestigators, it should be mentioned that the Tahoe separation beds have
under test produced filtered water with turbidity as low as 0.02 J.U. .
266
-------
Ordinarily, they are operated at about 0.2 J. U. The turbidity of the water
is continuously monitored and recorded. Provisions are made to filter-to-
waste after each filter backwash as recommended in Woodward's articles.
If the water were intended for potable use, then polymer could be used
continuously to increase floe strength and to maintain even lower turbid-
ities and to further improve virus removal.
The fact that particulates are almost completely removed minimizes
the chance that viruses can escape chlorine contact by encapsulation in
particulate matter. Again, if the reclaimed water was intended for potable
use, double chlorination with several hours or even days of intermediate
contact would provide even further assurance of virus removal.
Also at Tahoe, the pH of the water is lowered to about 7.0 prior to
chlorination to improve disinfection efficiency. The high pH of 11.0 in the
chemical treatment may also have some benefits in virus removal in addi-
tion to its bactericidal effects .
Actual Virus Removals in Plant Operation. Despite the confidence
of the designers in the ability of the Tahoe Process to completely remove
virus, everyone involved with the project was quite anxious to have this
ability confirmed under actual field conditions by appropriate sampling
and testing. Fortunately the staff at the WQO laboratory in Cincinnati
agreed to cooperate in furnishing information on proper sample collection
and transportation of the virus samples to their laboratory, and especially
to perform the laboratory tests for virus in the water samples.
Between May 29 and October 2, 1969, nine sets of water samples
were collected and submitted to the Cincinnati laboratory for virus exam-
ination under the direction of Dr. Gerald Berg. Each set consisted of 4
samples, one each from primary effluent, secondary effluent, carbon col-
umn effluent and reclaimed water. Counts in the primary effluent varied
from 3 to 207 units. In one sample of secondary effluent, there was no
recovery of virus. In the other samples of secondary effluent, the counts
varied from 18 to 430 units. Virus were recovered from two of the nine
samples of carbon column effluent with counts of 1 and 9 units. All nine
tests of the chlorinated reclaimed water were negative for virus. No virus
has been recovered from the water being exported to Indian Creek Reservoir
in two summers of sampling. While this does not necessarily mean that the
water is free of virus, at least all of the results to date are favorable. Table
36 is a tabulation of the 1969 virus testing results. Detailed results for the
1968 sampling are not tabulated, but all chlorinated reclaimed water samples
were negative for virus. Admittedly this is only a small amount of data, but
in an area where the total test data are meager, any bit of information is
helpful.
267
-------
TABLE 36
VIRUS SAMPLING - 1969
SOUTH TAHOE PUBLIC UTILITY DISTRICT
WATER RECLAMATION PLANT
Primary
Date effluent
Virus Recovered (PFU)**
Secondary Carbon Column Final
effluent effluent (U) effluent(C)
Sample
size (liters)+
May 29 3 0
June 5
June 12
Aug. 20 3 18
Aug. 2 7
Sept. 11 —
Sept. 18 179 14
Sept. 25 NRD 430
Oct. 2 207 320
1
0
0
NRD*
NRD
0
9
0
0
0
0
0
0
0
0
0
0
0
1P,S,U,C
2P,S,U,C
2P,S,U,C
4P,4S 20U,20C
12C
27U, 19. 7C
4P,4S, 29U,29C
4S, 32U, 32C
4P,4S, 32U,32C
* No reliable data
+ P=primary, S=secondary, U=unchlorinated final, C=chlorinated final
** Tests performed by the FWPCA Laboratory at Cincinnati, Ohio
PFU=Plaque forming units
268
-------
Complete virus removal or inactivation at Tahoe is finally de-
pendent upon adequate chlorination. Again, this parallels bacterial re-
moval which is also dependent on chlorination to complete the task. In
both cases, complete disinfection cannot be successfully carried out
without proper pretreatment of the water by clarification, removal of
chlorine demanding substances, and adjustment of pH to a low range
favorable for best use of chlorine. Successful disinfection in the pres-
ence of ammonia, the usual condition in treating wastewater, depends to
a very great extent upon the use of rapid, violent, and thorough mixing
of the chlorine solution and the water being treated, as well as adequate
chlorine dosages. Less chlorine is required for viral and bacterial dis-
infection of wastewater than might be estimated based upon its ammonia
content. At Tahoe the application of only 2 mg/1 of chlorine is adequate
to produce the results reported in the presence of 2 to 15 mg/1 of ammonia
nitrogen.
In addition to attempts to recover virus from reclaimed water,
epidemiological data is also needed. The use of reclaimed water for
supplemental drinking water supply as presently practiced in Windhoek,
South Africa should yield a great deal of extremely valuable results along
this line.
269
-------
SECTION XXII
DISINFECTION
General. To make water suitable for many type s of reuse , it
must be adequately disinfected.
In the disinfection of water chlorination depends on several
factors including:
1. Time of contact.
2. Concentration of disinfectant.
3. Concentration of organisms.
4. Temperature of disinfection.
5. Concentration of interfering substances.
6. pH of the water.
7. Chlorine application and mixing procedures.
Primary and secondary treated effluents contain particulate matter
and have high chlorine demands which interfere with chlorination and make
it impossible to properly disinfect such waters. Advanced wastewater
treatment (AWT) as practiced at Tahoe eliminates these interferences and
makes it possible to completely destroy bacteria, virus, and other organ-
isms. Chemical coagulation, settling, and filtration remove particulate
matter which could otherwise prevent contact between chlorine and the
organisms. Specifically, the turbidity of the separation bed effluent is
about 0.2 J.U. as compared to 10 to 50 for secondary effluent and 20 to 80
for primary effluent.
AWT also greatly reduces the concentration of organisms to be
killed, thus enhancing the disinfection process. Secondary effluent can
contain 2 million or more coliforms per 100 ml as compared to 20 to 200 per
100 ml in the carbon column effluent at Tahoe prior to chlorination.
AWT also reduces markedly the concentration of other substances
which interfere with chlorination. Activated carbon adsorbs organics
which would otherwise exert considerable chlorine demand and thus inter-
fere.
271
-------
The tertiary effluent still contains ammonia nitrogen in concentra-
tions of 2 to 20 mg/1. Despite the reactions which occur between ammonia
and chlorine in water, good disinfection is secured. This was an unexpect-
ed result. This efficiency probably is explained by the influence of the
rapid, violent, and thorough mixing of the chlorine with the reclaimed wat-
er which is provided.
A chlorine concentration of only about 2 mg/1 is required for disin-
fection of the tertiary effluent as compared to 20 mg/1 or more commonly
used in treating primary and secondary effluents.
As previously mentioned, the complete removal and destruction of
bacteria and other organisms from wastewater depends ultimately on proper
disinfection with chlorine more than any other single factor, as it does in
water purification practice.
When chlorine is added to water containing ammonia-nitrogen, the
ammonia reacts with the hypochlorous acid formed by the addition of chlor-
ine to produce chloramines. Further addition of chlorine to the "breakpoint"
converts the chloramines to nitrous oxide, an insoluble gas which is re-
leased from the water to the atmosphere. Equations illustrating these re-
actions are given below:
NH3 + HOCl^rNH2Cl + H2O monochloramine
NH3 + 2HOC1^NHC12 + H2O dichloramine
NH2C1 + NHC12 + HOCl^rN2O + 4 HC1
To reach the "Breakpoint" and to complete the conversion of all ammonia-
nitrogen to nitrous oxide, about 10 mg/1 of chlorine must be applied to the
water for each one mg/1 of ammonia -nitrogen present in the wastewater at
the point of chlorine application. Based on a chlorine cost of 0.0365 per
pound, the chemical cost for ammonia removal by breakpoint chlorination is
about $3 per million gallons of water treated for each mg/1 of ammonia-
nitrogen removed. It is obviously rather expensive to treat waters high in
ammonia by this method. For example, water containing 15 mg/1 of ammonia
would cost $45 per million gallons for complete treatment by this process.
However, the cost for removing 0.5 mg/1 of ammonia-nitrogen by this means
is only $1.50 per million gallons, as the required chlorine to ammonia ratio
does not change at extremely low concentrations. Trace amounts can be
removed at the same proportionate cost as larger amounts of ammonia . This
272
-------
ability of breakpoint chlorination to remove trace amounts of ammonia to
zero concentration is unique. Other nitrogen removal processes either
cannot remove the ammonia completely, or can remove trace amounts only
at greatly increased costs as compared to costs for securing the initial
reduction in concentration. For this reason, regardless of the method used
for removing the bulk of the nitrogen, breakpoint chlorination will undoubt-
edly be used as a supplemental process to remove the last traces of ammon-
ia where this is necessary.
Chlorine Feed Facilities. Chlorine is purchased and fed from
ton containers. There are three chlorinators installed each with a maximum
capacity of 2,000 pounds per day, or a total of 6,000 pounds per day. The
three chlorinators are connected to distribution headers in such a way that
chlorine solution may be applied to each or all of four points in the treat-
ment process. Ordinarily it is applied only to two points, ( 1) to the activ-
ated sludge mixed liquor in a splitter box preceding secondary settling to
control filamentous growths and nitrifiers, and ( 2 ) to the carbon column
(final) effluent. In the final effluent pump sump there is a chlorine solution
distribution header which introduces the chlorine to the reclaimed waste-
water between the inlet to the wet well and immediately adjacent to the
final effluent pump suction lines. The turbulence in the wet well and pass-
age through the turbine pumps provides the excellent rapid mixing of the
chlorine and the water which is essential to good utilization of chlorine in
the presence of ammonia. Chlorine contact is provided in 27 miles of pipe-
line and a one million gallon equalizing reservoir (covered steel tank) as
the water is pumped in two stages to Indian Creek Reservoir. Chlorine may
also be fed for odor control to the raw sewage in the plant influent rising
well, or to the separation bed influent, if necessary to extend filter runs
and to aid in maintaining clean filter media in the separation beds.
Results of Chlorination. Chlorine has been used at times at all
four points of application. Dosages of 2 to 5 mg/1 to the raw sewage when
necessary have controlled odors at this point in treatment. Dosages of
1 to 8 mg/1 to the activated sludge mixed liquor have prevent filamentous
growths and have also helped (along with maintaining a high load factor) in
maintaining nitrogen in the ammonia form for improved stripping efficiency by
controlling the growth of nitrifying bacteria in the return activated sludge.
It has been necessary to use chlorine ahead of the filters on only one or
two occasions for one or two days to assist in cleaning the beds. By far
the most important aspect of the utilization of chlorine has been in the dis-
infection of the finished water. The use of about 2 mg/1 of chlorine has
produced excellent results in eliminating bacteria, virus, and other organ-
isms from the exported water. After two years of plant operation, in 1970,
in recognition of the good bacteriological record and other measures of
plant performance, the various State of California regulatory agencies.
273
-------
including the State Water Resources Control Board and the State Department
of Health, approved Indian Creek Reservoir (the receiver for reclaimed
water) for all water contact sports including swimming, boating, fishing,
water skiing, and the like, and the reservoir has in fact been used for all
these purposes to some extent even prior to completion of planned recreat-
ional facilities at the site.
Table 37 summarizes the bacteriological test results from April 1968
through December 1970.
The tabulation of bacteriological data reveals several items of
interest. First of all, the bacteriological quality is excellent and from
this standpoint of quality, as well as from many others, it is unquestion-
ably the best ever produced by a full-scale wastewater treatment plant
anywhere. It is also of interest to note the improvement in the consistency
in bacteriological removal which has occurred in the 33 months of contin-
uous plant operation. This is due to the perfection of operator skills as
they gained experience in operation of the plant. This same improvement
is also reflected in other results of plant operations as will be described
later in this report.
For 8 of the 33 months all bacteriological samples collected dur-
ing the month were found to be free of coliform bacteria. From June 15,
1970 through September 29, 1970, a period of 107 consecutive days, a total
of 105 bacteriological samples were collected, all of which were found to
be free of coliform organisms.
Despite this excellent record, there is still room for some further
improvement in bacteriological quality. If reclaimed water is to be recycled
to supplement water supplies used for potable purposes then there are two
simple additional steps which could be taken to add further safety and
reliability in this regard. One is retention time following the initial chlor-
ine treatment. The more time the better. A few hours would be good, a
few days even better. Then, the water could be again chlorinated. Such a
sequence of double chlorination with intermediate storage would provide
fail-safe disinfection satisfactory for any proposed water reuse from the
standpoint of bacteriological quality.
274
-------
TABLE 37
MONTHLY SUMMARY OF BACTERIOLOGICAL TESTS
Number of Samples
With Coliform MPN/100
Month
1968
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
1969
Jan.
Feb.
March
April
May
June
luly
Aug.
Sept.
Oct.
Nov.
Dec.
1970
Jan.
Feb.
March
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Total
13
23
17
23
21
21
23
14
17
19
20
25
22
21
21
22
21
17
31
30
30
31
24
31
30
31
30
31
29
30
31
30
31
less than
2.2 or 2.0
11
15
15
12
9
19
14
14*
14
17
16
22
21
20
18
17
20
17*
30
30*
24
30
24*
29
27
31*
29
31*
29*
29
26
30*
28
2.1 or
2.2
1
1
1
1
4
1
1
0
2
1
0
1
1
1
1
3
0
0
0
0
5
1
0
0
2
0
0
0
0
0
0
0
1
5.1, 5.0,
or 4.4
0
3
1
1
1
0
2
0
1
1
3
2
0
0
1
2
1
0
0
0
1
0
0
0
0
0
2
0
0
0
2
0
0
8.8 or
9.2
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
1
0
0
0
0
0
1
1
0
1
ml of
1 5 or more
16 than 16
0
1
0
0
1
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
0
3
0
7
6
1
4
0
0
0
1
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
"
24 or
38
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
1
* All bacteriological samples collected during the month were found to
be free of coliform organisms.
275
-------
SECTION XXIII
FINISHED WATER QUALITY
Sampling and Analysis. Previous sections of this report des-
cribe in detail the methods and frequency of all sampling and analyses
for the project, and report the results of bacteriological and virus tests.
This section reports and interprets the results of chemical and other tests
which have been made during 33 months of operation of the 7.5 mgd plant.
Included in the results are concentrations in the reclaimed water
of BOD, COD, SS, MBAS, turbidity, pH, chlorine residual, nitrogen
(ammonia, nitrate, and nitrite), phosphorus, alkalinity, hardness, chlor-
ide, and sulfate. The daily results have been tabulated on a form for
each month together with plant flow data. The monthly reports of daily
results from April 1968 through December 1970 form Appendix B to this
report.
In addition, monthly summaries have been prepared which compare
a few parameters of plant performance with the quality standards as estab-
lished by the Lahontan Regional Water Quality Control Board and Alpine
County. The monthly summaries of plant effluent quality data have been
condensed, six months to a page, in Tables 38 through 43.
Laboratory analyses were also made of water samples collected at
various stages in the treatment process to show the efficiency of individ-
ual units within the plant. Tests were made on raw sewage and primary,
secondary, separation bed, and carbon column effluents. These results
are summarized in Tables 44 through 49 for 3 month periods beginning in
July 1968 to January 1, 1970. These tables show average, median, maxi-
mum and minimum values for each quarter.
To show the effectiveness of various unit processes and their con-
sistency, or lack of it, the data for the calendar year 1969 from the pre-
ceding tables have been plotted in Figures 83 through 88. In looking at
the BOD removals through the plant in Figure 83, note that the average
BOD of the chlorinated carbon column effluent is 1.0 mg/1 or 99.5% re-
moval as compared to an average of 28 mg/1 and 80% removal in the acti-
vated sludge effluent. Even though the maximum BOD of secondary efflu-
ent reached 83 mg/1 the final product never contained more than 4.9 mg/1.
277
-------
Table 38
to
*J
00
SOUTH TAHOE PUBLIC UTILITY DISTRICT
ADVANCED WASTE WATER TREATMENT PLANT
RECLAIMED WATER QUALITY
Aprtl - Sept. 1968
DESCRIPTION
APRIL || MAY
; Per Cent ol^Ttrne for uent ot 'iLime
SO 60 100 . SO 80 loo
MBAS, mo/1, lass than .01
?,
BOD, mg/1, less than t 1.3
COD, mg/1, less than
SUSP. S.,mg/l, less than
18
2*
TURBIDITY, JU, less than 1.3
i|
PHOSPHORUS, mg/1. less than 0.4
pH, units, range
Coltform bacteria
MPN/100 ml. Median,
Plant Flow, million gals.
.03
2.9
21
5*
1.6
O.S
.06 .13
4.8
22
11*
2.0
0.7
7.6 to 9.0
less than
2.2
55. 1
1.9
11
0
0.6
1.0
.17
3.3
16
2
0.7
2.3
.28
3.5
19
S
1.3.
2.7
6.6 to 7.9
less than
2.2
JUNE
per uent ot lime
$g, sd lob
.13
4.5
7
0
0.4
1.0
.17
5.4
10
1
O.S
1.3
.24
6.4
12
4
1.0
1.6
6.9 to 8.2
less than
2.2
60.8 72.4
r
i JULY
rer uent ot Time
56 80° IdO
.12 .18
1
| 0.4 : 1.1
13 17
1 2
0.3 O.'S
1.2 1.7
.20
2.2
18
7
1.0
1.8
i
7.0 to 8.1
less than
2,2
82.6
AUGUST SEPTEMBER
f er cent ot Time Per uent ot 11 me
50 80 100 SO dn Ion '
.18
0.5
13
0
0.1
0.4
.19
0.9
15
1
.19 14 .16
1.5 0.4 0.8
17 9 10
3 0 1
0.2 : 0.3 0.1 ' 0.2
0.7
1.2 0.10 i 0.14
.19
1.4
13
2
0.4
0.8
I
7.0 to 8.4 6.8 to 7.7
less than !i less than
2.2 2.2
76.7 '• 58.2
* Carbon fines from new carbon columns
-------
Table 39
ISO
VJ
to
SOUTH TAHOE PUBLIC UTILITY DISTRICT
ADVANCED WASTE WATER TREATMENT PLANT
RECLAIMED WATER QUALITY
OCTOBER 1968 to MARCH 1969
DESCRIPTION
MBA,i,mg/l, less than
BOD mg/1, less than
COD, mg/1, less than
SUSF.S.,mgA less than
TURPIDITYJU, ler» than
PHOSPHORUS, mg/l.less than
pH, units, range
Coll.'orm bacteria
MPN/100 ml. Median
Plan Flow, million gals.
OCTOBER 1968
Per Cent of Time
50 80 100
0.09 0.09 0.09
1.0 1.4 3.2
12 17 20
0 0 1
0.3 1.4 1.9
0.15 0.53 0.64
6.8 to 8.8
less than
2.2
48.3
NOVEMBER
Per Cent of Time
50 80 100
0.13 0.15 0.26
0.3 1.2 2.0
15 17 23
008
1.4 1.7 2.9
0.42 0.75 4.9
6.9 to 9.1
less than
2.2
46.4
DECEMBER
Per Cent of Time
50 80 100
0.11 0.13 0.15
0.5 0.6 0.8
7 11 13
000
0.9 1.1 1.7
0.10 0.46 0.52
6 . S to 7.8
less than
2.2
49.8
JANUARY 1969
Per Cent of Time
50 80 100
0.16 0.28 0.35
1.6 2.9 3.1
11 13 19
000
1.5 2.7 6.2
0.15 0.26 0.54
6.4 to 8.9
less than
2.2
69.0
FEBRUARY
Per Cent of Time
50 80 100
0.20 0.27 0.28
1.6 1.6 1.6
11 16 25
000
0.7 1.2 3.0
0.13 0.31 0.49
6.6 to 7.4
less than
2.2
53.9
MARCH
Per Cent of Timf
50 80 100
0.11 0.13 0.20
0.9 1.5 1.7
9 12 16
0 00
0.3 0.4 0.3
0.22 0.28 0.51
6.6 to 8.5
less than
2.2
57.5
-------
Table 40
00
O
SOUTH TAHOE PUBLIC UTILITY DISTRICT
ADVANCED WASTE WATER TREATMENT PLANT
RECLAIMED WATER QUALITY
April - Sept. 1969
DESCRIPTION
MBAS,mg/l, less than
3OD,mg/l, less than
COD, mg/1, less than
SUSP. S., mg/1, less than
TURBIDITY JU, less than
PHOSPHORUS, mg/1, less then
pH, units, range
Coliform bacteria
MPK/100 ml, Median
Plant Flow, million gals .
APRIL
Per Cent of Time
SO 80 100
0.09 0.11 0.13
0.5 0.7 1.1
5 7 11
000
0.2 0.3 0.8
0.21 0.39 0.49
6.6 to 8.5
less than 2.2
76.8
MAY
Per Cent of Time
50 80 100
0.16 0.25 0.27
0.5 0.9 1.0
tO 12 15
000
0.4 0.6 1.0
0.21 0.58 0.70
6.8 to 8.1
less than 2.2
63.9
JUNE
Per Cent of Time
50 80 100
0.09 0.12 0.14
0.9 1.5 4.1
7 9 10
0 0 0
0.1 0.4 0.8
0.16 0.23 0.86
6.7 to 8.8
less than 2.2
81.0
JULY
Per Cent of Time
50 80 100
0.19 0.21 0.23
0.7 0.8 1.8
13 15 19
000
0.3 0.6 1.0
0.11 0.29 1.1
6.6 to 9.4*
less than 2.2
75.9
AUGUST
Per Cent of Time
50 80 100
0.10 0.15 0.27
0.8 1.0 4.9
7 13 16
000
0.2 0.4 0.8
0.07 0.09 0.90
6.5 to 8.1
less than 2.2
82.3
SEPTEMBER
Per Cent of Time
50 80 100
0.04 0.12 0.14
1.1 1.7 3.8
8 10 15
000
0.1 0.2 0.4
0.08 0.12 0.24
6.8 to 7.4
less than 2.2
61.9
* Only one reading above 8.8
-------
Table 41
CO
CO
SOUTH TAHOE PUBLIC UTILITY DISTRICT
ADVANCED WASTE WATER TREATMENT PLANT
RECLAIMED WATER QUALITY
OCTOBER 1969 to MARCH 1970
DESCRIPTION
M8AS,mg/l, less than
BOD,mg/l, less than
COD, mg/1, less than
SUSP. S., mg/1, less than
TURBIDITY, JU, less than
PHOSPHORUS, mg/l,less than
pH, units, range
Col form bacteria
MPK/100 ml, Median
Plart Flow, million gals.
OCTOBER
Per Cent of Time
50 80 100
0.09 0.20 0.20
0.9 1.3 1.4
3.9 7.8 12.8
000
0.2 0.3 0.8
0.12 0.16 0.29
6.7 to 8.1
less than
2.0
55. 6
NOVEMBER
Per Cent of Time
SO 80 100
0.19 0.35 0.35
1.0 2.5 3.9
9.0 10.4 21.7
000
0.4 0.5 1.3
0.06 0.12 0.27
6.6 to 8.7
less than
2.0
50.2
DECEMBER
Per Cent of Time
50 80 100
0.00 0.13 0.18
0.5 1.8 6.7
8.9 11.3 24.0
0 x 0 0
0.3 1.0 1.5
0.13 0.20 0.68
6.6 to 8.3
less than
2.0
63.9
JANUARY 1970
Per Cent of Time
50 80 100
0.07 0.09 0.09
0.3 0.4 2,4
5.7 13,3 18,1
000
0.7 1.0 1.8
0.19 0.51 0.75
7.4 to 8.4
less than
2.0
87.0
FEBRUARY 1 MARCH
Per Cent of Time li Per Cent of Tirr.e
50 80 100 l| SO SO IOC
0.10 0.14 0.14
2.2 2.8 5.0
7.3 11.5 20.7
000
0.3 0.4 0.6
0.19 0.27 0.43
7.1 to 8.2
less than
2.0
65.5
0.24 0.25 0.53
2.2 3.3 4.5
12.2 18.5 30.7
000
0.4 0.8 1.1
D.15 0.21 0.63
6.5 to 8.1
less than
2.0
71.7
-------
Table 42
to
CO
CO
SOUTH TAHOE PUBLIC UTILITY DISTRICT
ADVANCED WASTE WATER TREATMENT PLANT
RECLAIMED WATER QUALITY
APRIL - SEPTEMBER 1970
DESCRIPTION
MBAS,mg/l, less than
BOD mg/1, less than
COD, mg/1, less than
SUSP. S., mg/1, less than
TURBIDITY.JU, less than
PHOSPHORUS, mg/1, less than
pH, vnlts, range
Coltform bacteria
MPN/100 ml, Median
Plant Flow, million gals .
APRIL
Per Cent of Time
SO 80 100
0.25 0.3S 0.35
2.7 2.9 5.0
13.3 16.2 18. ^
000
0.5 0.5 1.0
0.07 0.09 0.19
6.4 to 7.8
less than
2.0
61.6
MAY
Per Cent of Time
50 80 100
0.30 0.45 0.46
4.7 4.7 4.8
12.6 17.2 22.7
000
0.3 0.5 1.0
0.09 0.15 0.30
6.7 to 8.3
less than
2.0
66.5
JUNE
Per Cent of Time
50 80 100
0.35 0.42 0.46
2.1 2.8 2.9
12.6 14.8 24.5
000
0.5 1.0 2.0
0.12 0.32 0.61
6.8 to 7.9
less than
2.0
75.5
JULY
Per Cent of Time
50 80 100
0.21 0.24 0.40
1.1 2.0 4.3
14.8 17.0 28.7
000
0.3 0.7 1.0
0.25 0.46 0.7S
7.0 to 8.9
less than
2.0
85. 3
AUGUST
Per Cent of Time
50 80 100
0.10 0.15 0.22
0.7 1.2 3.5
10.5 13.3 20.0
000
0.3 0.3 0.4
0.24 0.39 0.65
6.8 to 8.3
less than
2.0
93.6
SEPTEMBER
Per Cent of Time
SO 80 100
0.19 0.21 0.25
0.7 1.4 2.6
9.6 10.5 12.5
000
0.2 0.2 0.3
0.06 0.09 0.20
6.8 to 8.3
less than
2.0
74.1
-------
Table 43
SOUTH TAHOE PUBLIC UTILITY DISTRICT
ADVANCED WASTE WATER TREATMENT PLANT
RECLAIMED WATER QUALITY
OCTOBER - DECEMBER 1970
oo
CO
DESCRIPTION
MBA5,mg/l, less than
BOD mg/1, less than
COD, mg/1, less than
SUSP.S.,mg/L less than
TURBIDITY, IU, less than
PHOSPHORUS, mg/1 .less than
pH , -units , range
Collform aacteria
MPN/100 ml. Median
Plant Flow, million gals.
OCTOBER
Per Cent of Time
SO 80 100
0.11 0.14 0.17
1.1 1.2 1.7
8.1 10.0 13.?
000
0.2 0.2 0.2
0.04 0.06 0.39
6.9 to 7.6
less than
2.0
64.0
NOVEMBER
Per Cent of Time
50 80 100
0.10 0.17 0.23
0.80 1.2 1.7
6.8 8.9 14.3
0 0 0
0.2 0.2 0.6
0.08 0.12 1.0
6.9 to 8.1
less than
2.0
62.0
DECEMBER
Per Cent of Time
50 80
0.32 0.41
1.2 1.4
14.8 18.7
0 0
0.3 0.6
0.09 0.12
6.9 to 7
100
0.52
2.1
26,0
0
0.7
0.20
.7
less than
2.0
70.7
-------
Table 44
00
SUMMARY OF LABORATORY ANALYSES
8 July 1968 - 1 October 1968
(1)
Parameter
mg/1
P
NH3
N03
N02
MBAS
COD
BOD
Alk. as CaCO3
Ca Hardness
as CaCOs
Susp. Solids
Color (Units)
Raw Sewage
Ave. Range
12 5-21
0.01 0-0.03
0.02 0-0.03
7 4-9
281 144-371
43 33-56
233 118-590
Primary Eff.
Ave. Range
1 7 \2/ c 09
J. 3 O ftlt
21 12 - 27
217 110-320
97 38-164
67(3) 33-82
100 32-268
Secondary Eff.
Ave. Range
10 5-13
7 1-12
0.5 0.2-0.8
37 17-57
167 145-210
26 1-111
Chem.Clar. Eff.
Ave. Range
0.7 0-5
Sep. Bed Eff.
Ave . Range
0.4 0.2-0.6
18 10-31
20 15-25
Carbon CoL Eff.
Ave. Range
0.7 0-3
7 0.8-8
7 6-10
2 1-4
0.15 0.1-0.2
12 2-18
lp. 7™ 0.01-2
232 146-275
144 10 197
0
<5 0-5
1. Average daily flow 2.30 mgd. Range 1.60 to 3.05
?. CaPQi wasted to primary for part of period
3. Lime centrate returned to primary
4. "ollowing chlorination
-------
Table 45
CO
Cn
Parameter
SUMMARY OP LABORATORY ANALYSES
1 October 1968 to 1 January 1969
Raw Sewage
Primary Eff.
Secondary Eff. NH3 Strip.Tow. Eff
1. Average dally flow 1.57 mgd. Range 0.76 to 2.42 mgd
2. Chlorinated effluent
Sep. Bed Eff. Carbon Col.Eff.
mg/1
PO4 - P
NH3 - N
NO3 - N
NO2 - N
MBAS
COD
BOD
Total
Alk.as CaCO3
Hardness
as CaCO 3
Susp. Solids
Color (Units)
Av. Range
9 2-14
0.43 0-1.7
O..I9 0.05-0.2
8 5-11
175 125-250
184 156-228
76 44-114
250 62-674
Av. Range
7 3-14
6 5-10
184 128-281
120 96-152
126 24-390
Av. Range
17 14-21
••
12 4-29
Av. Range
Av. Range
0.5 0.04-3
0.7 0.2-1.2
23 13-29
146 92-184
3 0-22
13 5-20
Ay. Range
0.5 0.02-5
0.17 0-0.6
0.1 0-0.5
0.17 0.1-0.8
12 2-25
(2} (2]
0..81' 0.1-3V ;
233 113-427
134 44-200
2 0-23
S 5
-------
Table 46
CSJ
CD
Parameter
SUMMARY OF LABORATORY ANALYSES
1 January 1969 to 1 April 1969
Raw Sewage
Primary Eff.
Secondary Eff.
Recarb. Eff.
Sep. Bed Eff. Carbon Co.Eff.
mg/1
PO,; - P
NH3 -N
N03 -K
N02 -N
MBAS
COD
BOD
Total
Alk.as CaCO3
Hardness
as CaCO3
Susp. Solids
Color (Units)
Turbidity SJU
Avg. Range
6 3-10
0.3 ..1-.8.
0.08 .03-. 2
156 110-210
144 112-160
161 108-234
69 44-120
156 51-500
Avg. Range
7 <« 2-11
S 4-7
158 100-235
108 84-147
77 42-182
Avg. Range
5 1-9
15.6 11-21
2 1-4
53 31-88
18 10-24
Avg. Range
38 34-47
Avg. Range
0.3 .02-. 6
0.6 .3-1.2
20 12-37
3 1-5
144 50-188
1.6 0-10
9 4-15
Avg. Ranee
0.2 .01-. 5
0.2 0-.5
0.06 0-.5
0.13 .02-. 3
10 3-19
0 8(2) 3-1 7U
U • O • O 1 • /
248 131-340
124 54-178
0.4 0-2
5 2-5
0.5 .l-l.-l
1. Average dally flow 2.21 mgd. Range of average dally flows: 1.26 to 6.02 mgd
2. Chlorinated effluent
3. Lime centrate returned to primary
-------
Table 47
to
CO
SUMMARY OP LABORATORY ANALYSES
1 April 1969 to 1 July 1969
Parameter Raw Sewage Primary Effluent Secondary Effluent Sep. Bed Effluent Carbon Column r.ff.
mg/1
PO4-P
NH3-N
NO3-N
NO2-N
MBAS
COD
BOD
Total Alkalinity
as CaCO3
Hardness
as CaCOj
Susp. Solids
Color (Units)
Turbidity(SJU)
avg . med . range
7.4 7.2 4-13
.46 .32 0-2.6
.09 .09 .03-. 2
140 127 110-265
166 163 119-288
77 78 48-118
233 206 60-660
avg . med . range
7.7<3) 8.0 3-11
4.9 4.9 2-8
173 155 86-723
75 78 31-105
76 62 16-228
avg. med. range
6.9 7.2 4-9
14 14 \1-18
.60 .28 0-2.5
.16 .04 .01-.9
1.8 1.9 .4-3.2
20 20 7-28
183 182 150-261
15 12 4-44
avg. . med. range
.2 .2 .02-.6
.3 .3 .1-.7
15 15 10-20
2.6 3.0 1-4
127 135 64-150
2 0 0-11
6 6 4-10
avg, mod. ran^e
.2 .2 .02-. 6
.18 .08 0 -.8
0.15 0.10 0 -.3
7.7 7.4 3-19
(2U .8 .2-1.5
214 218 134-283
126 126 74-152
.5 0 0-7
3 3 2-5
.3 .3 .1-1.2
1. Average daily flow 2.5 mgd. Range of average daily flows: 1.7 to 3.8 mgd.
2. Chlorinated effluent.
3. Lime centrifuge centrate returned to primary.
-------
Table 48
SUMMARY OF LABORATORY ANALYSES
1 July 1969 to 1 Sept. 1969
Parameter
Raw Sewaoe
Primary Effluent
Secondary Effluent Sep. Bed. Effluent Carbon Column Eff.
mg/1
PO4-P
NO3-N
M3AS
COD
BOD
8.5 8.5 4.6-15.8
19.7 19.6 16.1-22.5
.39 .23 0-5.5
.08 .06 0-.5
M40 140 103-172
Total Alkallnltyj
as CaCO3 177 159 122-276
Hardness
as CaCOg
Susp. Solids
Color(Unlts)
Turbidlty(SJU)
71 60 42-160
167 136 37-936
9.8 9.9 6.4-12.9
6.0 5.8 2.6-9.6
238 230 60-465
88 93 58-112
117 76 12-800
av. me>A . ranm
8.9 8.6 4.6-14.2
20.9 21.1 15.8-25.9
1.6 .91 0 - 5.5
0.29 .13 0- 5.0
2.0 1.8 .4-5.2
57 54 4-128
33 30 23-52
188 186 141-227
24 16 0-248
av _ med .
.2
.1 0-1.14
.85 .52 .12-4.2
17.5 15.4 9.4-36
2.2 2.2 .4-6.8
126 138 50-188
4-27
mp> •? . rangp
.16 .08 0-1.14
13.5 13.4 2.9-18.'
2.4 1.8 0-7.8
.23 .14 0-.62
.13 .12 0-.27
9.5 8.2 3.2-18.!
®1.2 .8 .2 - 4.S
204 205 102-262
131 136 38-174
4 4 1-10
.3 .2 .1-1.0
1. Average daily flow 2.4 mgd. Range of average dally flows: 1.8 to 2.9
7.. Chlorinated effluent.
,1. Litiic ccntril'ugo con'rcitc returned to primary.
-------
Table 49
SUMMARY OF LABORATORY ANALYSES
1 Oct. 1969 to 1 Jan. 1970
00
(JO
.... P?raT)et?r .... Raw Sewacre Primarv Effluent Secondary Effluent^5) Sen. Bed Effluent Carbon noh,mn r.ff.
mg/1
P04-P
NH3-M
NO2-N
NO3-N
MBAS
COD
BOD
Total Alkalinity
as CaCO3
Hardness as
Susp. Solids
Color (Uni's)
Turbidity (SJU)
avg. med. range
10.7 10.6 3.6-20.4
21.0 20.6 13 -30
.08 .08 .02-. 23
.34 .28 0 -2.1
134 130 79-229
199 193 114-285
106 106 60-146
232 204 24-608
avg. med range
10.8® 10.6 6.1-17.9
6.1 6.0 3.1-7.8
210 208 59-420
115 110 78-140
107 88 16-376
avg. med. range
8.7 8.8 2.8-17.9
21.1 20.8 11-28
.06 .04 0 - .3
.22 .12 0-1.4
3.1 3.7 .2-6
98 78 16-321
42 36 20-83
189 190 110-293
33 25 1-124
avg. med. range
.15 .12 0 - .7
14® 13.1 6-22
19.8 16.9 9-68
2.5 2.1 .1-5.8
161 162 96-204
0
11 10 5 -28
avg. med. range
.12 .11 0 - .7
17.4 16.8 8-28
.11 .07 0 -.39
.84 .48 0 -3.9
.13 .11 0 -.4
8.0 7.8 .6-24
1 .3&) .9 .2-3 .9
233 230 156-356
151 156 108-178
0
5 5 3-15
.4 .3 .1 -1.5
1. Average daily flow 1.85 mgd. Range of average daily flows : 1.07 to 3.37 MGD
?.. Chlorinated effluent
3. Lime centrifuge centrate containing PO4~P returned to primary
4. Ammonia stripping tower effluent - data includes values when tower wasn't running
5. Biological upset
-------
300
FIGURE 83
BOD REMOVALS THROUGH
PL ANT-1969
REMOVAI
f EAR = 99.5%
RAW PRIMARY SECONDARY SEPARATION CHLORINATED
BED CARBON COLUMN
EFFLUENT
-290-
-------
FIGURE 84
COD REMOVALS THROUGH PLANT -1969
700
600
500
-
0
o
u
400
300
200
100
PRIMARY SECONDARY SEPARATION
BED
EFFLUENT
CARBON
COLUMN
-291-
-------
FIGURE 85
SUSPENDED SOLIDS REMOVAL THROUGH PLANT -1969
J
C
_
a
2
LL
~
900
800
700
600
500
400
300
200
100
SUSPENDED SOLIDS ARE
COMPLETELY REMOVED
BY THE FILTERS, BUT
CARBON COLUMNS WILL
ADD CARBON FINES TO
THE WATER AT TIMES.
RAW PRIMARY SECONDARY SEPARA-
TION
BED
EFFLUENT
-292-
-------
FIGURE 86
MBAS REMOVALS THROUGH PLANT - 1969
10
-
PRIMARY
AVERAGE
DURING YEAR
SECONDARY
SEPARATION
BED
CARBON
COLUMN
EFFLUENT
-293-
-------
FIGURE 87
PHOSPHORUS REMOVAL THROUGH PLANT
1969
a.
in
<
c
z
_
u
a
u
03
E
c
r
^
M
a
ET
ID HblUHN
C5NTRATE TO
RAW
PRIMARY
SECONDARY
FILTER
CARBON
COLUMN
EFFLUENT
-294-
-------
FIGURE 88
AMMONIA NITROGEN REMOVALS THROUGH PLANT
AND RESERVOIR - 1969
JO
20
° 15
1
1 3
*NOTE: AMMO
TOWER TREAT!
OF FLOW AND I
ATED DURING
WEATHER.
AVERAGE
YEAR (INCLUC
IN INDIAN
= 86%
>IIA STRIPPING
ONLY PART
SNOTOPER-
:REEZING
REMOVAL FOR
NG STORAGE
CREfcK RESERVOIR)
RAW
SECONDARY
STRIPPING
TOWER *
INDIAN
CREEK
RESERVOIR
EFFLUENT
-295-
-------
The much greater consistency and reliability of the treatment in the
tertiary section of the plant and the greater ease of operation of this
part of the plant are even more apparent from day to day observation of
plant operations than from the curves.
Figure 84 shows the COD removals through the plant. The
average residual COD for 1969 was 8.8 mg/1 which represents an aver-
age removal of 95.5% during the year. The COD remaining in the re-
claimed water depends on the concentration in the applied water, the
time of contact, and the period of time since fresh carbon was added to
the columns, so that there is a great deal of control which can be exer-
cised in this regard. Just after regenerated carbon or makeup carbon is
added to the columns the COD of the carbon column effluent is often less
than 3 mg/1 and had been as low as 0.6 mg/1. These minimum COD val-
ues of the reclaimed water are lower than the COD values of many tap
waters.
As indicated in Figure 85, suspended solids are completely removed
through the separation beds. The test procedure for suspended solids is
not good at very low values, and turbidity measurements are a better guide
to the clarity of the reclaimed water. At times, particularly immediately
after addition of carbon to columns, some carbon fines are carried out in
the carbon column effluent and are measured by the SS and turbidity tests.
The occasional presence of carbon fines in the treated water is not as sig-
nificant, of course, as an equal quantity of sewage solids which might
escape removal. If the reclaimed water is to be used for ground water
recharge, then the possible effects of carbon fines in plugging the re-
ceiving aquifer should be evaluated.
High MBAS removals through the plant are dependent principally upon
adsorption by the carbon as shown by Figure 86. On the average in 1969,
97.5% of the influent MBAS was removed by the plant. The average final
concentration was 0.13 mg/1. About 60% of the MBAS was removed by bio-
degradation in secondary treatment and 37.5% by carbon adsorption. On
many occasions no MBAS (less than 0.00 mg/1) could be detected in the
reclaimed water.
Phosphorus removals (measured as orthophosphate) through the plant
for 1969, as shown by Figure 87, averaged 98%. The average residual was
0.2 mg/1. More recently (1970-71) the average phosphorus content has
been reduced to 0.06 mg/1. The maximum concentration of phosphorus
measured in the plant effluent was 1.14 mg/1, and the minimum was 0.00
mg/1. As discussed in detail elsewhere in this report, the experience and
skill of the operators as well as subtle changes in treatment are important
296
-------
in reducing phosphorus concentrations from 2.0 mg/1, which is easily ob-
tained, to the 0.06 mg/1 value which is now the average. The removal of
phosphorus is one operation which is better at full plant scale than it was
in pilot plant tests.
Figure 88 shows the removals of ammonia nitrogen through the plant
plus Indian Creek Reservoir. As shown by the curves the average removal
during 1969 in the plant was about 25% and in Indian Creek Reservoir an-
other 61% was removed. When the stripping tower was operating and plant
flows were within its design capacity ammonia nitrogen removals as high
as 90% were obtained through the plant alone. The average nitrate nitrogen
in the plant effluent was 0.9 mg/1, and the average for nitrite nitrogen was
0.01 mg/1.
To summarize, the typical quality of reclaimed water now (1971)
being produced by the Tahoe plant is shown in Table 50, together with a
comparison of these results with those from secondary treatment.
TABLE 50
TYPICAL QUALITY OF RECLAIMED WATER
% Average Removals
Tertiary Treatment,
Secondary Tertiary Aver, final content
Parameter Treatment Treatment (mg/1 unless shown)
BOD
COD
MBAS
Suspended
Solids
Color
Odor
Phosphorus
Turbidity
Coliforms
MPN/100
85
65
60
89
Incomplete
Incomplete
10
96
ml 95
99.8
96.0
98.0
100.0
100.0
100.0
99.5
99.9
99.99+
0.7
9
0.15
0
< 5 units
None
0.06
0.6 Ju
<2.0
297
-------
Summary - Finished Water Quality. The 1\ million gallon a day
water reclamation plant has been in continuous operation since March 31,
1968, with the exception of the nitrogen removal tower, which was com-
pleted in November of 1968. The plant has been operating without inter-
ruption for the entire period. The quality of water is excellent and has
exceeded at all times the high standards set by the regulatory agencies.
During the first three years of operation, the plant processed more than
2 .5 billion gallons of wastewater from which the following materials
were removed:
(1) 72 tons of detergent (MBAS)
(2) 2,250 tons of suspended solids
(3) 150 tons of phosphorus
(4) 2,550 tons of oxygen consuming substances
(5) All color, odor, and coliform bacteria
All of the solid materials removed from the wastewater have been
incinerated at temperatures of 1,200 to 1,600° F. to insoluble, sterile
ash.
About 2,000 tons of lime mud and 260 tons of spent activated
carbon have been reclaimed and reused in the treatment process.
The reclaimed water quality has without exception exceeded the
requirements of the export standards .
While there were no regulatory requirements for removal of phos-
phorus or nitrogen, phosphorus was removed in order to restrict algae
growths in Indian Creek Reservoir which receives the reclaimed water.
For the first few months of plant operation, phosphorus concentrations in
the reclaimed water ranged from 0.5 to 2.0 mg/1. Operations have been
steadily improved, and currently the average final phosphorus content is
in the range of 0.06 mg/1. The phosphorus level has been low enough at
all times to secure the desired control of algal growth in the Reservoir.
Action within the Reservoir itself has kept nitrogen levels well within
acceptable limits.
In December, 1969 following close observation of 9 months oper-
ation of the plant and after consultation and receipt of recommendations
from the California State Department of Health, the Lahontan Regional
298
-------
Water Quality Control Board formally approved and authorized use of
Indian Creek Reservoir for "unrestricted recreational purposes" including
fishing, boating, water skiing, swimming and other water contact sports.
Previously the water had been used for irrigation of alfalfa, hay, and
pasture land.
There is no question that the water could also be used for any
domestic, municipal, agricultural, or recreational use that does not
involve drinking of the water or food processing packaging.
The high quality of the water, which technically meets the U.S.
Public Health Service Drinking Water Standards, and the fact that sew-
age treatment plant effluents inadvertently find their way into water
supply sources in many instances, invariably raises the question of the
possible reuse of the reclaimed water as a supplemental source of public
water supply. There is some logic in this question, certainly, since
intentional reuse has an advantage over inadvertent reuse in that water
renovation techniques are applied with the idea of reuse in mind. Also
continuous recycle to supplement potable water supplies would be limited
to about one-third of the total supply, as this procedure would avoid pro-
gressive increases in total dissolved solids and the need to add a costly
demineralization process to advanced wastewater treatment. Planned
reuse can and should provide a time barrier by storage of reclaimed water
to allow monitoring, analysis, and diversion, if necessary, in case of
accidental spills.
Unfortunately, this question of possible potable reuse of reclaim-
ed wastewater creates in the mind of the great majority of people a
great and immediate barrier, based on aesthetics, to any consideration
of beneficial reuse of the water whatever. This reaction tends to obscure
the primary purposes and usefulness of advanced wastewater treatment,
which are complete elimination of water pollution and health hazards and
the reuse of reclaimed water for purposes other than for potable water
in order to free an equal quantity of high quality water for potable supply.
Indications are that water of quality suitable as a supplemental
source of supply for potable water purification plants can be produced
from wastewater by advanced treatment systems. However, much further
study is needed of the tolerable levels of biological and chemical sub-
stances that may be present in wastewater; such as trace elements, pes-
ticides, carcinogens, antibiotics, hormones, viruses, and materials not
yet studied. The effects of various commercial and industrial wastes
found in many urban wastewaters also need considerable investigation.
The findings of studies in these areas will also be valuable in evaluating
the safety of badly polluted surface water supply sources.
299
-------
Obviously, some hazardous industrial wastewaters either alone
or mixed with domestic sewage will present special problems in recla-
mation, or will even prevent certain reuse.
These and a number of other good reasons favor delaying the use
of reclaimed water for drinking until there is absolute necessity to do
so. Morbidity and mortality data for populations using water supplies
which conform to the U.S. Public Health Service Drinking Water Stand-
ards support the reliability of these finished water standards as applied
to supplies taken from ground and surface water sources, since acute
health effects have not yet been attributed to waters that have met these
standards. Questions that have been raised on chronic health effects of
drinking such water are currently being investigated only to a very limited
degree , and funds are needed to greatly expand this work.
The U.S.P.H.S. Drinking Water Standards are based on the pre-
mise of sanitary survey of the raw water source to assure that the supply
was taken from'themost desirable source which is feasible, and effort
should be made to control pollution of the source. If the source is not
adequately protected by natural means, the supply shall be adequately
protected by treatment". As water sources become increasingly polluted,
more data can be obtained on the applicability of the Drinking Water
Standards to various dilutions of wastewater. These data, if collected,
will be valuable in developing criteria, monitoring techniques, and
standards for the safety of reclaimed wastewater, since the Drinking
Water Standards may not be applicable in this situation.
Delay in the use of reclaimed wastewater to supplement water
supply sources will also gain time in which to further establish the re-
liability and consistency of plant scale water reclamation treatment
processes, as well as time in which to secure further reduction in the
costs of water reclamation.
It is possible that situations will develop in the future where
wastewater must be reclaimed to increase drinking water supplies but in
the meantime the reclamation processes will continue to undergo rapid
and substantial improvement, which will result in greater reliability and
confidence in them, and better public acceptance, when the time comes
that they must of necessity be used to supplement drinking water supplies.
Also, in the interim, reclaimed water can be used to satisfy other
needs, and high quality water supplies can be reserved for production of
drinking water .
300
-------
SECTION XXIV
INDIAN CREEK RESERVOIR
General. Out of the ten years of research and development and the
three years of demonstration at South Tahoe, the single most important
fact revealed is that algal growths in Indian Creek Reservoir (which is com-
posed almost entirely of reclaimed water) have, in actual practice, been
controlled effectively by nutrient removal. The importance of this basic
fact must not be lost in reviewing the great mass of detailed laboratory and
plant data which is presented herein.
There will continue to be discussions as to precisely why there are
no nuisance algal blooms, or specifically what was done that prevented
such growths, but there is no longer any question whatever that proper
treatment of wastewater can provide satisfactory control of algae - this
has been demonstrated conclusively.
It is the unanimous judgement of the project personnel that phosphor-
us removal alone is the key to the successful limitation of algae in the re-
claimed water. Nitrogen, carbon, and dissolved organics must also re-
ceive some consideration under certain conditions, but it appears that
these substances are not effective stimulants when phosphorus concentra-
tions are less than about 0.3 mg/1.
Study and Monitoring Procedures. Indian Creek Reservoir was stud-
ied in three ways: (1) general observation, (2) limited sampling and testing
program under this grant, and (3) a detailed scientific study by the Lake
Tahoe Area Council (LTAC) through their Board of Consultants, Dr. P. H.
McGauhey, Dr. E. A. Pearson, and Dr. G. A. Rohlich and their project
staff, Dr. D. B. Porcella, Dr. G. L. Dugan, and Dr. E. J. Middlebrooks.
This third phase of the work was done under a separate grant from the En-
vironmental Protection Agency.
The first phase of study, that of general observation of the appear-
ance of the Reservoir, is the most important phase because it determines
the degree of public and political acceptance which the Reservoir and the
301
-------
Figure 89
AERIAL VIEW OF INDIAN CREEK RESERVOIR
302
-------
project receives.
The second phase, sampling and testing under this grant, was aim-
ed principally at getting information which would allow an evaluation of
the safety and suitability of water in the Reservoir for irrigation and re-
creation uses.
The objectives of the study by the LTAC were: to determine the eff-
ects of the reclaimed water on biological, physical, and chemical char-
acteristics of the Reservoir; to relate these characteristics of the Reser-
voir water to the nutrient concentrations of the influent water; to evaluate
the relative effects of biostimulants to the treated water and those added
by exchange from the underlying soils and sediments; and finally to at-
tempt to correlate the data on actual algal growth obtained from Reservoir
Studies with laboratory and pilot plant growth potential tests of the re-
claimed water. The results of the LTAC study are reported completely in
"Eutrophication of Surface Waters - Indian Creek Reservoir", First Progress
Report (FWQA Grant No. 16010 DNY), May 1970, Lake Tahoe Area Council,
South Lake Tahoe, California, and will not be duplicated herein, but only
drawn upon as necessary to complete this report.
Visual Observations. Prior to filling Indian Creek Reservoir with
reclaimed water, there was, of course, a great deal of speculation about
what would happen when it was filled. Engineers and others connected
TWith the project had collected bottles and jugs of pilot plant effluent which
had been exposed to sunlight for several months on window ledges or desks
and which had shown no signs of algal growth. Also, plastic drums had
been filled with various dilutions of Lake Tahoe water and tertiary effluent
and little if any growth was detected. The favorable results of these crude
batch tests did not necessarily mean that there would be no nuisance blooms
of algae in the Reservoir, where dynamic rather than static conditions pre-
vailed. Some engineers and other visitors were predicting that the Reser-
voir would quickly become a "green slimy mess", principally on the basis
that no nitrogen removal was being practiced in the treatment plant during
most of the initial filling period and ammonia nitrogen concentrations gen-
erally exceeded 15 mg/1. Fortunately, these prophesies of doom did not
come true, and no objectionable growths of algae have occurred.
The Reservoir was subject to very close scrutiny not only by project
personnel but any an almost continuous parade of visitors including laymen,
conservationists, politicians, engineers, and others from many fields of
endeavor. The water has always been quite clear. Objects can be per-
ceived on the bottom of the Lake at depths of 3 to 19 feet. There never has
been any odor from the water in the Reservoir. The color varies from a
dark blue under the best conditions, to a light blue under most conditions,
303
-------
to a very light green for very short times immediately following the runoff
of snow melt into the Lake. Most of the algae which grow appear to be
single-cell greens and they are present in very small numbers. Strings,
clumps, or mats of algae have not been seen in the Lake.
Immediately adjacent to Indian Creek Reservoir there is another lake,
Stevens Lake, which receives only natural runoff from the Indian Creek
watershed. Indian Creek Reservoir always presents as good an appearance
as Stevens Lake does.
During the first year or two of the project color photographs were
taken of the Reservoir (water's edge at dam and shoreline, and general
overall view) at different seasons in order to compile a record of the true
condition of the lake at all times.
Physical and Chemical Tests. In Appendix B a daily record is giv-
en of flows entering and leaving Indian Creek Reservoir. The general plan
of Reservoir operation is to fill it in winter and spring, and to draw it down
for irrigation of pasture lands during summer and fall. At spillway level
the Reservoir contains about one billion gallons of water, the maximum
water depth is 56 feet, and the surface area is 160 acres. At minimum
pool or conservation level the Reservoir contains about one-third billion
gallons, has a maximum depth of 40 feet, and a surface area of about 95
acres. The Reservoir has now been filled completely and drained down to
recreation pool level twice and is in the process of being filled for the
third time. At this time, it is believed that the leaching of nutrients from
the topsoil beneath the Reservoir has decreased substantially over that
originally taking place and that the effects on water quality probably are
now negligible.
In 1968, samples of reservoir water were collected on a more or less
regular schedule from late June through early December. The results of
the laboratory analyses are shown in Table 51 .
Snow and ice conditions made the Reservoir inaccessible from Dec-
ember 1968 to March 28, 1969 when the Lake was reached by snowmobile.
The water along the reservoir shore was extremely clear. Table 52
shows the laboratory analysis of a grab sample collected at the water and
dam interface. Ice conditions on the reservoir surface prevented collec-
tion of off-shore samples.
304
-------
TABLE 51
EFFLUENT STORAGE RESERVOIR
LABORATORY ANALYSES - 1968
Alkalinity
(mg/1 as CaCO3)
Date DO pH HCO3 CO3 Total Temp. NO3N P
mg/1 mg/1 mg/1
6/28
7/10
7/17
7/24
8/14
8/21
8/28
9/4
9/24
10/1
10/9
10/23
10/30
11/7
11/26
12/12
6.5
7.2
11.0
7.9
5.6
7.3
10.7
11.0
9.0
8.5
12.3
8.9
9.4
8.3
10.7
8.3
8.1
8.7
8.9
8.3
8.4
8.2
8.5
8.0
8.1
8.1
8.2
8.1
8.3
8.3
8.5
23
143
119
95
162
170
145
108
166
190
192
200
185
165
147
32
4
52
62
14
14
38
58
24
20
20
20
30
34
44
55
147
171
157
176
184
183
166
190
210
212
220
215
199
191
182
0.40
14°C 3.6 0.003
12'C 2.65
9°C
6°C 0.18
2°C 0.114
305
-------
Approximately 1/2 billion gallons of water was impounded on this
date.
Table 52
Effluent Storage Reservoir-Laboratory Analyses
March 28, 1969
Dissolved Oxygen 10. 2 mg/1
pH ' 7.2
Total Alkalinity 82 mg/1 as
Temperature 42°F
Nitrite 0.04 mg/1 as N
Nitrate 0.67 mg/1 as N
Ammonia 2.1 mg/1 as N
Phosphorus 0.04 mg/1 as P
Temperature and dissolved oxygen profiles of the Reservoir on Aug-
ust 1 and September 16, 1969 are shown in Table 53 .
Data from Stevens Lake and Indian Creek Reservoir are shown in
Table 54. Stevens Lake is located in the adjacent watershed to the reser-
voir and has been used as a control for the data collection program. The
lake was constructed for irrigation storage about 20-30 years ago and is
well established to the run off conditions of the area.
On October 28, 1969, dissolved oxygen and temperature profiles
were performed at the reservoir. Dissolved oxygen ranged from 7-9 mg/1
and temperatures from 47 to 49°F.
In January 1970 a Hinde Air-Aqua System was installed in Indian
Creek Reservoir. This system consists of ten 1/2 hp air compressors and
ten sections of perforated aeration tubing each about 250 feet long locat-
ed in the central deep-water part of the Lake just upstream from the dam.
Each compressor has a capacity of about 3 cfm of air. The principal pur-
pose of this aeration, turnover system is to prevent the formation of com-
plete ice cover over the Reservoir surface. It also can be used to prevent
or correct thermal or oxygen stratification in the Lake water. The system
has been very effective and its operation has been simple and trouble-free.
When the equipment arrived the Reservoir was completely covered with ice
which ranged in thickness from 6 to 12 inches. Holes were chopped in
the ice to install the air tubing. Eight of the compressors were operated
at one time, and within four or five days a major portion of the ice had
been melted due to the action of the turnover system in circulating warm
306
-------
TABLE 53
TEMPERATURE AND DISSOLVED OXYGEN PROFILES OF INDIAN CREEK RESERVOIR
(4)
August 1, 1969
September 16, 1969
Co
O
Station
Depth (ft
Surface
3.3
6.6
9.9
13.0
16.4
18.0
19.7
23.0
26.2
27.0
33.2
39.4
44.3
1
)
72
72
71
70
70
67
66
66
65
65
64
63
Temp.
Op
2
74
73
72
71
71
67
67
Dissolved Oxygen
mg/1
3123 Station
73
73
72
72
71
69
66
66
65
65
8
5
2
1
1
8 8
7
7 ' 7
1
1
Surface
5
10
15
17
20
25
30
35
38
40
45
A
64
63
63
63
65
64
64
64
64
64
Temp.
Op
B C
64 63
64 63
63 63
63 63
62
63
63
63
62
62
Dissolved Oxygen
mg/1
ABC
6 6
6
6
6 5.5
5
5
(1) 44.3 ft. A. 45 ft. (depth of reservoir at sampling station)
(2) 18.0 ft. B. 38 ft.
(3) 27.9 ft. C. 17 ft.
(4) Courtesy California Department of Fish & Game.
-------
TABLE 54
WATER QUALITY OF INDIAN CREEK RESERVOIR
AND STEVENS LAKE - 1969^)
Indian
7/16
2400
70
17
11
7.5
5.8
0
7.8
0
105
.05
3.4
1.9
0.11
Creek Reservoir
8/7
2380
68
15
7
7.3
6.2
0
7.5
0
116
.07
2.4
.25
1.7
.06
9/16
2050
63
25
10
4
4.7
0
7.4
0
116
.08
4.3
.36
1.1
.01
Stevens
7/1 6e)
73°
10
10
6.9
8.7
12
43
.015
.3
0
0
Lake
8/7
70°
10
5
10.8
6.6
9.2
13
43
.02
0
0
.8
.04
Sample Dates
Volume (acre-ft.)
Surface lfemp.(0 F)
Color (filtered)
Turbidity (SJU)
Secci Disk Depth (ft.)
D.O. mg/1 @ 5' below
surface
Chlorine, mg/1
PH
Alkalinity as CaCO3
phenolphthalein mg/1
methyl orange mg/1
P04 -P mg/1
NH3 -N mg/1
NO 2 -N mg/1
NO3 -N mg/1
MB AS, mg/1
(1) Courtesy California Department of Fish and Game
(2) All samples taken at 5 ft. depth, except 7/16 samples at Stevens
Lake which were taken at 2 ft. depth
308
-------
water from the deep part of the Lake to the surface under the ice. In 1971
the intermittent use of the aeration system has successfully prevented
development of complete ice cover. Ice which forms around the edges of
the Lake can be quickly melted by use of the system. This assists in main-
taining the dissolved oxygen levels necessary to support the trout fishery.
On January 5, 1970, the Hinde Air-Aqua System was put in operation
at the reservoir to melt the layer of ice and keep the surface free of ice.
The next day dissolved oxygen and temperature profiles indicated the res-
ervoir was near saturation with no stratification. Dissolved oxygen and
temperatures ranged from 8-11 mg/1 and 40-44 F, respectively. The ice
cover was very clear and the near saturation values were probably attribut-
able to a combination of natural photosynthesis and mechanical aeration.
On March 12, 1970, dissolved oxygen and temperature profiles rang-
ed from 13-15 mg/1 and 40-43°F, respectively.
In June 1970, the project quarterly report read as follows:
"The expanded 7.5 mgd water reclamation plant has now for 2-1/2
years continuously produced reclaimed water of very high quality, exceed-
ing the stringent export requirements. "
"On numerous occasions the orthophosphate content of the reclaim-
ed water was measured at values in the range of 0.002 to 0.005 mg/1 as
phosphorus, which approaches the quality of Lake Tahoe water in this res-
pect. At the start of plant operations two years ago, residual phosphorus
content to less than 0.01 mg/1 has been accomplished through several min-
or but important changes in plant operating procedures, without any in-
crease in the amount of chemicals used in treatment of the wastewater. "
"The clarity of the one billion gallons of water reclaimed by our plant
which is now stored in Indian Creek Reservoir is excellent. An 8-inch
white Secchi disc can be seen at depths of 3 to 19 feet in the Lake. This
improvement in clarity of the water in the Reservoir probably is due to two
factors. First is the fact that the initial filling of the Reservoir has been
virtually complete for several weeks now, and nutrients are no longer be-
ing leached by the water from topsoil which was inundated for the first
time. The second factor is that removing one algal nutrient, phosphorus,
from the reclaimed water to a satisfactory level has restricted algal growth
in the Reservoir. The success of this means for control of algae, by phos-
phorus removal, is in accordance with predictions of the effectiveness of
this method made by the District's Consulting Engineers in their prelimin-
ary reports on the project several years ago. The judgement of the Con-
309
-------
sultants that the growth of algae could be controlled by phosphorus remov-
al alone, and without the need for complete nitrogen removal is also borne
out to date by field observations and laboratory examination of Reservoir
water quality. "
"Trout fishing in Indian Creek Reservoir has been excellent. During
the first two days of the season which opened May 2, State Fish and Game
official, Robert Tharratt, reported that 920 anglers landed more than 1,250
rainbow-cutthroat trout which averaged over 12 inches in length and one
pound in weight* The Lake was stocked last summer with 38,000 trout
ranging in size from fingerlings to sub-catchables. An additional 92,000
trout have been planted in 1970, to bring the total trout planted to 100,000.
The largest recorded catch to date was a 3-1/4 pound, 19 inch trout."
The October 1970 quarterly report includes the following:
"The recent report, 'Eutrophication of Surface Waters-Indian Creek
Reservoir', as prepared and published by the Lake Tahoe Area Council,
contains what we consider to be a very significant finding by Dr. P. H.
McGauhey and his colleagues. This is the fact that an unanticipated 75
percent ammonia removal is taking place in the Reservoir. The ammonia
nitrogen content of reclaimed water entering the Reservoir is about 15 mg/1
while that of the water in the Reservoir is now 3 mg/1 (nitrates=l to 3 mg/1,
nitrites=less than 0.1 mg/1). The ammonia nitrogen content of the raw
wastewater averages about 30 mg/1, so that overall combined removal of
ammonia by the plant and Reservoir is 90 percent. Apparently the ammonia
in the influent water to the Lake is being converted first to nitrate and then
to nitrogen gas (which escapes harmlessly from the Reservoir to the atmo-
sphere) by the organisms in the benthic deposits in the Reservoir through
bacterial nitrification-denitrification processes. This is confirmed by nit-
rogen inventories of the lake environment. To date this means of nitrogen
removal in the Reservoir appears to be more reliable and economical than
any known plant process designed for this purpose. It is this phenomenon
which has made it possible for the trout fishery to be established in the
Lake. It appears that the continuing study of the biology of Indian Creek
Reservoir now in progress by the Lake Tahoe Area Council may well lead to
better understanding of the principles involved in nitrogen removal and
their more widespread practical use in wastewater reclamation. "
Ordinarily upon conversion of the ammonia to nitrate in the Lake wat-
er, algae could be expected to assimilate the nitrate nitrogen and incorpor-
ate it in cell growth, thus interrupting the nitrogen cycle at this point and
preventing the conversion of nitrate to nitrogen gas. One explanation which
is advanced to explain the fact that the nitrogen cycle proceeds in Indian
310
-------
Creek Reservoir is the very low phosphorus content of the water. This
phosphorus shortage appears to limit algal growth and allows the nitrogen
cycle to proceed without serious interference through action of benthic
organisms to production of free nitrogen gas (rather than algae) from the
nitrates. The nitrogen gas then escapes harmlessly to the atmosphere.
Another explanation offered is that there is direct release of ammonia
gas at the Reservoir surface. However, because of the low pH of the Lake
water this does not appear to be a significant nitrogen loss mechanism.
Irrigation. About 2 billion gallons of water has been withdrawn
during three summers of Reservoir operation for irrigation of pasture, hay,
and alfalfa. The availability of this water for irrigation was especially
valuable in 1968, which was a very dry year. Three cuttings of alfalfa
were obtained where only one could have been harvested without the use
of the reclaimed water.
Rainbow Trout Fishery. One of the hallmarks of public acceptance
of the reclaimed water and acknowledgement of its high quality was the
opening of the trout fishing season on May 2, 1970. The fishing in Indian
Creek Reservoir was established by the California Department of Fish and
Game through the enthusiastic cooperation of Robert Tharratt and his co-
workers. See Figure 90.
The July/August, 1970 issue of "Outdoor California" carries a story
by Mr. Tharratt about the "Exciting New Era" of trout fishing in the "pio-
neering wastewater reclamation lake". Excerpts from this account follow:
"The opening of the 1970 trout season may well have marked the be-
ginning of an exciting new era for California fishermen and recreation is ts.
About 900 trout anglers were on hand to try their luck in California's new-
est 'fishing hole', Indian Creek Reservoir, and they were not disappointed.
By sundown Sunday of opening weekend more than 1,200 trout averaging 13
inches long and more than one pound each had been creeled by the lucky
anglers. "
"Born out of the Lake Tahoe water controversy, this 160-acre Alpine
County lake represents the ultimate in the concept of water reutilization
and provides a prime example of environmental enhancement through man's
technology. "
"Indian Creek Reservoir, situated in the eastern foothills of the Si-
erra Nevada in Diamond Valley near Markleeville, is the culmination of a
311
-------
Figure 90
RAINBOW TROUT FROM INDIAN CREEK RESERVOIR
312
-------
10-year program of the South Tahoe Public Utility District to preserve the
clarity of Lake Tahoe. "
'The lake water is reclaimed waste water produced by a tertiary treat-
ment process in one of the world's most advanced waste treatment plants
on Tahoe's south shore. Following treatment, the water is transported
through 27 miles of buried 18-inch to 24-inch pipeline, including a lift of
nearly 1,300 feet over 7,700-foot Luther Pass to the reservoir site on Indian
Creek."
"The Lake Tahoe pollution control effort began in 1960 when the South
Tahoe Public Utility District began operating a conventional secondary
treatment plant. The effluent was sprayed on Forest Service and private
lands in the basin. "While solving the immediate problem of waste treat-
ment, it did not guarantee the higher goal of preventing nutrient enrichment
of the lake/ which might stimulate algae growth and thus impair for all time
the clarity of one of the world's most beautiful fresh water lakes."
"A program was initiated by the utility district in 1961 to improve the
waste treatment process. This work led to the development of advanced
wastewater treatment processes which were incorporated into the plant in
1965. Further additions to the treatment process were added, and the plant
was expanded to a total capacity of 7.5 million gallons a day by 1968."
"While the plant expansion was underway, local, state, and federal
regulatory agencies and political entities involved made the decision that
the only completely safe way to protect Lake Tahoe within existing technol-
ogy was to export all sewage and solid wastes out of the Tahoe Basin."
"Work was initiated on the export system. The pipeline was laid
from the plant to the reservoir site in Alpine County, a pumping station was
built at Luther Pass, and a dam and reservoir were constructed on a small
tributary at Indian Creek. The water reclamation plant was completed and
in operation in 1968. "
"The effluent water of the Tahoe plant is of very high quality and is
generally indistinguishable from water occurring naturally in other lakes.
Although it meets Public Health Service standards for drinking water, re-
cycled water is not now used for domestic purposes but is used only for
recreation and irrigation. The high quality of the water is evidenced by the
fact that rainbow trout are thriving. "
"The first trout were planted by the Department of Fish and Game in
October 1968, but none survived the winter. Apparently the heavy and pro-
313
-------
longed winter ice cover led to a series of conditions whereby the lake's
oxygen supply was depleted, and the fish suffocated. Additional fish
tests were made in 1969 by the DFG, and when it was determined the water
was satisfactory for trout, the DFG planted 8,000 fingerlings in August."
"A 'preview of coming attractions' was evident in October 1969 when
DFG netting revealed that the four-inch fingerlings planted 75 days before
were nine inches long 1"
"Even more startling was the growth of the smaller fingerlings plant-
ed by a DFG airplane at the same time. These rainbow-cutthroat trout hy-
brids were air dropped at a size more than 400 fish to the pound. When
sampled in October, these fish were six inches long and had increased in
weight 40 times, averaging nearly two ounces each!"
"Things looked bright indeed for the fishing at Indian Creek, but the
winter loomed ahead. Could the fish survive the winter?"
"Technology once again came to the fore. The South Tahoe Public
Utility District, at the suggestion of the Department of Fish and Game, a-
greed to install an aeration system in the reservoir to provide oxygen dur-
ing the freeze-over and to hasten the breakup of ice once it had formed. "
"The plan included the onshore installation of an engine-driven com-
pressor system and a series of weighted plastic hoses laid on the reser-
voir bottom. In operation the system would deliver compressed air over
the bottom of the lake, providing oxygen for the fish and causing a grad-
ual circulation of water."
"Water is heaviest at 39 degrees F, and hence a frozen lake is "warm-
er" on the bottom than at the surface just under the ice. The circulation of
this warm bottom layer to the surface tends to help melt the ice."
"Indian Creek Reservoir froze over completely near the end of Dec-
ember before the air hoses were installed. It was necessary to break holes
in the ice to get the aeration lines in place. The pumps were turned on the
first week in January, and within 24 hours the small holes cut in the four-
inch thick ice had enlarged to several feet in diameter."
"Several fish were observed jumping at rising air bubbles, and chem-
ical tests throughout the lake revealed that oxygen was plentiful in all ar-
eas. The aeration system was doing the job. With continued pumping and
a coincidental break in the weather, the lake was entirely free of ice in
less than two weeks and stayed that way the rest of the winter."
314
-------
"Nets were set in the lake in March 1970 to see if the trout had sur-
vived. Fat, scrappy rainbow trout to nearly a foot in length attested to
the success of the operation. "
"What about the future?"
"Indian Creek owes its success to the fine cooperation among feder-
al, state, and local agencies. The California Water Commission recently
approved recreation grants of $180,000 under the Davis-Grunsky program,
administered by the Department of Water Resources for part of the construc-
tion cost of the reservoir project and for the construction of initial water
supply and sanitary facilities for the recreation area."
"The Bureau of Land Management, which administers the project
lands, is seeking funds to build and operate the recreational complex con-
sisting of a campground, picnic area, and boat launching ramp."
"Alpine County plans to construct a new road to the nearby county
airport, which will improve access to the lake. All of the above facilities
should be in operation within two or three years."
"The South Tahoe Public Utility District and its consultants, Clair
A. Hill and Associates, have provided assistance in many ways, including
project planning, water monitoring, and the aeration system. "
"Add to this the planned interim stocking of approximately 30,000
trout annually by the Department of Fish and Game, and the future does
indeed look bright for the California sportsman. "
Results of the Lake Tahoe Area Council Study. The LTAC report
one "Eutrophication of Surface Waters - Indian Creek Reservoir", First
^Progress Report (FWQA Grant No. 16010 DNY), May 1970, in Chapter VI,
Summary and Conclusions, contains 37 conclusions and observations which
are reproduced here for the convenience of the reader. For the detailed
data on which these conclusions and observations are drawn, the reader
is referred to the Report.
"1. The water impounded in Indian Creek Reservoir during 1969 was
approximately 20 percent surface runoff and 80 percent reclaimed water.
Consequently its quality was more influenced by reclaimed water than by
surface runoff.
2. Because the drainage area above the reservoir is small (1700
acres) it may be expected that as the volume of exported water increases,
315
-------
the quality of impounded water will increasingly be influenced by reclaim-
ed water.
3. Estimates of runoff and evaporation rates previously reported to
the STPUD by its engineering consultants appear to be sufficiently valid to
permit a reasonable water budget estimate for Indian Creek Reservoir.
4. Year round observations designed to establish more accurate
runoff and evaporation rates should be made in order to refine the limnol-
ogical knowledge of the reservoir as it matures.
5. Infiltration rates of mid-1969 were of the order of 0.035± ft
of water per day, a value which is reasonable.
6. The clarity of Indian Creek Reservoir water during the period of
observation was typical of shallow impoundments of relatively good quality
water. During the period June 1969 through March 1970 it varied from 0.84
to 3.46 meters (Secchi disk). In April 1970 it was as great as 6 meters.
7. Water temperatures in the upper stratum of the reservoir, where
light and other environmental factors are most favorable to plankton growth,
reach an 18°-22°C range also favorable to biological activity. In winter
they fall below the lower limit for biological activity.
8. With only minor exceptions, the observed data on physical
characteristics of the reservoir are in line with typical and explainable
phenomena, although not in sufficient detail to permit statistical evalua-
tions .
9. The importance of wind movement in describing and evaluating
the limnology at Indian Creek Reservoir is such that a more detailed and
continous observation of wind director and velocity should be a part of
any continued surveillance of the reservoir.
10. Chemical analyses of impounded and discharge water show
that there was little difference in conservative chemical quality from top
to bottom. Dissolved oxygen declined with depth in July as did alkalinity
(carbon source) and ammonia (nutrient source).
11. COD in reservoir water was not demonstrably related to VSS or
any other of the parameters evaluated.
12. There is good evidence that iron in Indian Creek Reservoir
316
-------
played an important role in the life cycle of biota which appeared in the
surface stratum of the impounded water.
13. pH is a sensitive parameter of the limnological characteristics
of Indian Creek Reservoir, however, it varied in impounded water only from
7.7 to 8.5 as compared to 7.4 to 8.8 in the influent reclaimed water.
14. In terms of conductivity and chemical components the water
impounded at Indian Creek Reservoir is of good quality for irrigation water.
15. Differences in concentration of conservative quality factors
such as chloride and calcium in influent and impounded water in Indian
Creek Reservoir were clearly the result of dilution.
16. Substantial evidence was found that bicarbonate alkalinity was
used as a source of carbon by the biota of Indian Creek Reservoir during
the period of study.
17. Prior to September 1969 the impounded water was poorly mixed
and the oxygen profile reached zero at the bottom level.
18. The reservoir became well mixed in September 1969. There-
after results of horizontal and vertical distribution of oxygen indicated
that a single observation at one sampling station was a sufficient basis
for computing the oxygen resource of the impounded water mass.
19. The impounded water was quite homogeneous during the period
of study. Consequently only the dissolved oxygen concentration in the
water mass was particularly changed by mixing of the reservoir.
20. It is not yet known whether poor mixing was a seasonal phen-
omenon or an aspect of a new limnologically immature impoundment. Con-
tinued observation of the reservoir during another season should answer
this question and so make possible predictions of water quality in the re-
servoir .
21. Phosphorus was considered the limiting nutrient in reservoir
waters. N/P ratios of influent reclaimed water were of the order of 150/1.
In the impounded water the ratio remained above 29/1 during the period of
study.
22. With but little aid from dilution the NHs-N concentration chang-
ed from 15 mg/1 in the influent water to some 4 mg/1 in the impounded wat-
er. Evidence is submitted to show that the reduction was almost certainly
due to nitrification-denitrification rather than growth of biomass.
317
-------
23. Influent reclaimed water exported to Indian Creek Reservoir
proved toxic to trout in field tests, and to algae in laboratory assays.
Nevertheless, trout planted in the reservoir after October 1968 showed no
effects. Ammonia concentration in the reclaimed water was the presumed
toxic material.
24. A benthic invertebrate survey by the FWQA in October 1969
showed an average of 464 dipterous larvae per square foot in the 17 areas
sampled. These were all essentially of three species of low-oxygen toler-
ant types, although a previous condition of low oxygen in the bottom strat-
um of water was overcome as early as September 1969 .
25. Although the benthic invertebrate survey showed a high yield
of biota, the diversity of biota was unusually limited. The same was ob-
served in Indian Creek itself just below the discharge of Indian Creek Re-
servoir.
26. There is evidence that although the water mass was severely
phosphorus limited, benthic organisms made use of phosphorus in the soil
underlying the reservoir.
27. In the impounded water rainbow trout flourished at an NH^-N
level of about 4 mg/1, although 2 mg/1 is often considered a maximum for
such species. Trout planted in Indian Creek Reservoir in August 1969 in-
creased in length from 1.7 to 6 in., and from 4.5 to 8.9 in., in length by
October 1969.
28. Bioassays of impounded water showed limited growth, probab-
ly because of unfavorable N/P ratios, although a seasonal pattern of a
readily explainable nature was evident.
29. Essentially no growth occurred in laboratory bioassays of un-
diluted reclaimed water, indicating the presence of some toxic material.
When diluted to one percent concentration with Lake Tahoe water the toxic
effect was overcome to the extent that algal growth proceeded.
30. From plankton samples taken over a period of time it is evident
that a varied plankton population indicative of good productivity had devel-
oped in Indian Creek Reservoir by July 1969.
31. A plankton survey of impounded waters and bottom muds made
in April 1970 showed a species distribution characteristic of impounded
water. However, the reservoir appeared to be a highly productive body of
water.
318
-------
32. The plankton survey showed Indian Creek near the reservoir
dam to have a biota characteristic of an enriched water.
33. Monitoring of Indian Creek Reservoir, including benthic sur-
veys, should be continued to reveal any changes which may result from:
a. greater removals of nitrogen at the STPUD water reclam-
ation plant.
b. greater releases of impounded water during the summer
season.
c. reduction in soil phosphorus as a source of phosphorus.
34. Observation of Indian Creek over a period of time may make it
possible to design water reclamation processes capable of producing a wat-
er of balanced quality suited to a broad spectrum of recreationa 1 uses yet
not subject to algal blooms.
35. A major finding of the study is that by simple impoundment of
the water exported from the Tahoe Basin, its quality was changed from that
untenable to fish and certain algae, to one of good productivity of both,
within the limits of available nutrients.
36. In evaluating the results of the study it should be borne in
mind that the nitrogen content of the exported water did not represent the
ultimate degree of removal to be expected in water reclamation by the
STPUD, and that Indian Creek Reservoir may be expected to undergo furth-
er changes in the process of maturing.
37. Waste water reclamation at South Tahoe has progressed to the
point where under normal circumstances water would not be exported. How-
ever, because Lake Tahoe is more unique than normal Indian Creek Reser-
voir provides a good proving ground outside the Tahoe Basin in which to
evaluate the processes and develop the scientific knowledge needed to
permit its future use within the Basin if desired."
Recreational Use. As previously mentioned, the Lahontan Regional
Water Quality Control Board has formally approved and authorized use of
Mian Creek Reservoir for "unrestricted recreational purposes" including
fishing, boating, water skiing, swimming, and other water contact sports.
This approval was granted only after 9 months of observation of plant per-
formance, water testing, and observation of the Reservoir, and after con-
sultation and receipt of recommendations from other state agencies includ-
ing the California Department of Health.
319
-------
Figure 91
SAILBOATING ON INDIAN CREEK RESERVOIR
320
-------
Figure 92
SWIMMING IN INDIAN CREEK RESERVOIR
321
-------
SECTION XXV
CAPITAL AND OPERATING COSTS FOR CONVENTIONAL AND ADVANCED
WASTE TREATMENT
Introduction. The increasing interest by the general public in the
quality of the environment has stimulated several questions concerning
water pollution abatement. One of the most significant questions is what
the cost of cleaning up our nation's lakes and rivers will be. In some in-
stances, the addition of secondary treatment will be sufficient to reduce
the problem; however, in other areas one or more of the various advanced
waste treatment processes will be required to eliminate a pollution prob-
lem. A knowledge of the costs for the various degrees of conventional
and advanced waste treatment is essential in planning the nation's water
pollution abatement needs.
The purpose of this section is to present in detail the actual costs
of conventional and advanced waste treatment and to briefly review the
benefits of the plant scale conventional-advanced waste treatment scheme
used continuously since 1968 at South Lake Tahoe.
This section will show that the total cost at 7.5 mgd was $166/mg
for conventional waste treatment and $217/mg for advanced waste treat-
ment. These costs are based on producing the extremely high quality re-
claimed water described in earlier sections with 100 percent reliability.
Lesser requirements should demonstrate lower costs. Thus at South Lake
Tahoe, the cost of advanced waste treatment is approximately 30 percent
greater than the cost of conventional treatment.
The conventional and advanced waste treatment phases, with the
exception of the ammonia stripping tower, are designed for 7.5 mgd. The
ammonia stripping tower design capacity is 3.75 mgd.
Conventional treatment includes primary clarification, and both
plug flow and completely mixed activated sludge secondary treatment.
The activated sludge process is operated with a high organic loading and
low mixed liquor suspended solids and sludge age, to prevent nitrification
323
-------
and to keep the majority of the nitrogen in the ammonium ion form. The
mixed liquor is chlorinated at 2 mg/1 before clarification if nitrifying or-
ganisms begin to proliferate. Raw and waste activated sludges are de-
watered in centrifugals and then incinerated.
Advanced waste treatment begins with phosphorus removal and clar-
ification of the secondary effluent, using lime. The spent lime mud is
thickened in a gravity thickener, dewatered by centrifuging, and then re-
calcined in a multiple hearth furnace for reuse. Phosphorus rich lime mud
is classified in the centrifugal and wasted to the organic sludge system.
The effluent from the lime clarifier flows through an ammonia strip-
ping tower to a two-stage recarbonation system. Scrubbed stack gases
from the lime recalcining and sludge incineration furnaces are used to neu-
tralize the high pH water. The recarbonated effluent then is pumped to
mixed media filters and carbon columns. Two ballast ponds, each one
million gallons in capacity, float on the system in order to provide flow
equalization and supplemental filter backwash water. Spent carbon is
withdrawn periodically from the carbon columns, thermally reactivated in
a separate multiple hearth furnace, and then returned to the carbon col-
umns . The carbon column effluent is dosed with 2 mg/1 of chlorine and
then lifted 1,500 feet and through 27 miles to Indian Creek Reservoir in
Alpine County, California.
Assumption for Capital Costs. The capital costs include all equip-
ment and construction costs. They do not include design costs. The
equipment and construction costs were taken from District records of act-
ual contracts awarded for the various treatment phases. These contracts
were completed at various periods between 1960 and 1968. The EPA
Sewage Treatment Plant Construction Cost Index, Base Year 1957-1959=
100, was used to adjust the capital costs to 1969. It was assumed that
the San Francisco Region Indexes were equivalent to South Lake Tahoe.
All costs were adjusted to 1969 San Francisco Index and then to the Nat-
ional Average Index for 1969. The 1969 Index values used were 136.2 for
San Francisco and 127.1 for the Nation. The 1969 replacement costs per
million gallons were based on the national average at 7.5 mgd design ca-
pacity assuming capital amortization of all the costs at 5 percent for 25
years and no federal assistance. In fact, the capital costs to the District
were much lower since federal grants from the USPHS, EDA, and EPA fin-
anced approximately 46 percent of the total construction cost for conven-
tional and advanced waste treatment.
Capital Costs. The capital costs are shown in Table 55 and also
later in the operational cost tables. Included in the capital cost figures
for a specific treatment phase are items common to several processes.
324
-------
TABLE 55
SOUTH TAHOE PUBLIC UTILITY DISTRICT, CALIFORNIA
CAPITAL COSTS FOR CONVENTIONAL AND ADVANCED WASTE TREATMENT PLANT
7.5 MGD DESIGN CAPACITY
Treatment Phase
Actual
Contract
Total Construction
Cost Per Phase (21
Estimated
National Average
Replacement Construction
Cost for 1969
Estimated
Replacement
Costs Per MG
for 1969
CONVENTIONAL TREATMENT
Primary
Activated Sludge
Organic Sludge151
Chlorination
TOTAL, Conventional Treatment
$ 692,000
1,247,000
583,000
9,000
$2,531,000
$ 753,000
1.300,000
545,000
11,000
$2.609,000
$ 19.60
33.60
14.10
0.30
$ 67.50
ADVANCED TREATMENT
Nutrient Removal
Phosphorus Removal
Lime Treatment
Lime Recalcining lsl
SUBTOTAL, Phosphorus Removal
Nitrogen Removall7'
Recarbonation
SUBTOTAL, Nutrient Removal
Filtration
Carbon Treatment
Carbon Adsorption I8!
Carbon Regeneration
SUBTOTAL, Carbon Treatment
TOTAL. Advanced Treatment
401,000
552,000
$ 953,000
327,000
162,000
$1.442,000
705,000
656,000
193,000
$ 849,000
$2.996,000
378,000
516,000
$ 894,000
310,000
152,000
$1.356,000
687,000
632,000
199,000
$ 831,000
$2,874,000
9.70
13.50
$ 23.20
8.00
4.00
$ 35.20
17.80
16.30
5.20
$ 21.50
$ 74.50
TOTAL WATER RECLAMATION
Conventional Treatment
Advanced Treatment
2,531,000
2,996,000
2,609.000
2,874,000
67.50
74.50
TOTAL. WATER RECLAMATION
$5,527,000
$5,483,000
[2] Construction costs are taken from District records of actual contracts awarded for various phases. Contracts for construction
various periods between 1960 and 1968. These costs have not been adjusted to a common year.
[S| Indudes sludge handling, dewatering, incineration, and ash disposal.
[(] Includes lone mud handling, dewatering, and recalcining.
[7] Ammonia stripping.
|g) Includes initial carbon costs to fiD all carbon columns.
$142.00
completed at
325
-------
These items include buildings, electrical systems, piping, and controls
not specifically identifiable in the construction contracts. Both area and
volume relationships are used to proportion this capital cost to specific
treatment phases.
Total capital costs, based on 1969 national average replacement
costs, were 67.50 $/mg for conventional treatment and 74.50 $/mg for
advanced treatment. The 20 acre site where the present conventional and
advanced waste treatment processes are located was acquired in conjunc-
tion with the construction of the original 2.5 mgd primary and secondary
plant in 1960. Since the records did not show the site acquisition as a
separate item, the cost of the 20 acres was included only in the capital
cost of conventional treatment.
Assumptions for Operating Costs. The operating costs included in
this section are based on the plant design capacity of 7.5 mgd from Feb-
ruary 1969 to December 1970. During this period, the actual average mon-
thly influent flows varied between 1.79 mgd and 3.15 mgd. As a result of
recycling water from scrubber flows, backwashing filters, and backflowing
carbon columns, the filtration and carbon adsorption flows during the same
period varied between 3.13 mgd and 5.22 mgd.
To compare operating costs on the common basis of the plant design
capacity, it was assumed the total cost for fuel, chemicals, make-up lime,
and make-up carbon would increase in proportion to the flow. However,
the same assumption could not be made for electricity, operating and main-
tenance labor costs, equipment repair, and instrument maintenance. Costs
per day for electricity were adjusted upward to reflect the equipment char-
acteristics at 7.5 mgd. The cost per day for operating and maintenance
labor, repair materials, and instrument maintenance were assumed to be
the same as at present and design flows.
The assumption that the plant is staffed as though it were operating
at design capacity was made for the following reasons. During the grant,
three individuals were required per shift to operate the plant. One oper-
ator spent approximately five hours in the laboratory analyzing samples
for the District's FWQA research grant, and three hours performing plant
related duties. The second operator spent an hour per shift measuring
flows and keeping track of expendables for the grant, and seven hours in
plant operation. The third individual controlled the operations within the
incineration building, which did not vary with flow. This extensive data
collection would not be taking place at 7.5 mgd nor would it be the usual
practice at other advanced waste treatment plants. Maintenance labor
and repair materials would be affected by equipment age but not necess-
326
-------
arily by flow since most of the equipment is running today. Because it
was the basic purpose of this section to show costs at 7.5 mgd in 1969
and 1970, age was not considered to be a factor.
It was assumed, however, that emphasis placed on each treatment
phase by the first two operators would be different during carbon regener-
ation periods when this additional phase must be covered.
No District operating and capital costs associated with sewers,
pump stations, janitorial work in administrative areas, minor plant modi-
fications, effluent export, FWQA research grant, and general Utility Dis-
trict administration were included. It is felt that these costs were not
typical operating costs for actual waste treatment.
Operating Cost Data Collection and Analysis. Each month the com-
puter provided machine listings of the individual operating costs per treat-
ment phase for current and design plant flows. The computer also deter-
mined and printed the average to date costs for the current and design
flows.
The monthly labor rates for the operations and maintenance included
the actual monies paid by the District to or in behalf of the individual for
straighttime, overtime, standbytime, holidays, vacation, sick leave, pre-
mium pay, Social Security, retirement fund, medical insurance, unemploy-
ment tax, and Workmen's Compensation. The labor rates represented all
monies paid divided by the actual hours worked.
Two methods were used to allocate labor costs to the various treat-
ment phases. For maintenance labor, the actual hours spent within a
specific treatment phase were fed into the computer. Overhead time, such
as supervision, lunch, coffee breaks and unreported time, was prorated
among the various treatment phases on the basis of actual hours reported.
The maintenance group included six individuals.
Operating labor was divided among the various treatment phases by
fixed percentages. Three shifts were used, seven days per week. The
basic shift included three operators. A total of 15 operators were needed
to cover the three shifts, chief operator, and vacation and sick leave make-
up. The fixed percentages used to allocate the operational labor hours
are shown in Table 56. The fixed percentages were based on personal in-
terviews with each of the operators, and on observations by the authors
and the District administrative staff. Again, these percentages were stor-
ed in the computer as variable constants.
327
-------
TABLE 56
PERCENT OPERATIONAL LABOR DIVISION
PER TREATMENT PHASE
Without Carbon During Carbon
Treatment Phase Regeneration Regeneration
PLANT EXCLUDING INCINERATION BUILDING - 2 Operators/Shift
Primary Treatment 20.80 13.53
Secondary Treatment 25.00 17.70
Lime Clarification 4.17 .83
Ammonia Stripping 2.10 .42
Recarbonation 2.08 .83
Filtration 6.25 4.17
Carbon Adsorption 6.25 4.17
Carbon Regeneration 25.00
INCINERATION BUILDING - 1 Operator/Shift
Organic Sludge Dewatering 6.25 6.25
Organic Sludge Incineration 4.17 4.17
Lime Mud Dewatering 4.17 4.17
Lime Mud Recalcining 12.50 12.50
Lime Clarification (Slakers) 4.17 4.17
Recarbonation (CO2 Compressors) 2.09 2.09
TOTAL 100.00 100.00
-------
Operator responsibilities include process monitoring and adjust-
ments, chemical mixing, routine equipment servicing, and inside cleanup.
Electrical costs were divided among the treatment phases on the
basis of ampere-hours per month. The actual running time for each elec-
trical motor was one of the inputs for each month. The amperes for each
motor were stored in the computer as variable constants.
Cubic feet of natural gas used by the sludge incinerator, lime re-
calciner and carbon furnace and the amounts of chemicals used each month
were each measured separately.
Instruments were maintained by an outside contract. The costs per
treatment phase were determined by the number of instruments repaired or
calibrated per treatment phase. The contract included labor, parts, and
instrument replacement.
Repair material costs included replacement costs, material, repair
equipment purchase, and rental costs. This category also reflected out-
side labor cost, as well as material costs for work done outside the plant,
such as rewinding electric motors.
Unit Operating Costs. Costs of all commodities at Lake Tahoe are
high in comparison to the average of commodity costs in the USA. This is
due in large measure to the location in a mountainous area and to the Ta-
hoe area's tourist-based economy. In order to permit comparison with
costs which might be anticipated in other areas, Table 57 has been prepar-
ed to show the present cost of various commodities at Lake Tahoe. These
unit costs were stored in the computer as variable constants.
Primary Treatment. Raw sewage entering the plant passes through
a barminutor, a parshall flume and then into the primary clarifier. A rec-
tangular 2.7 mgd clarifier equipped with water spray scum collection and
a 4.8 mgd, 100 foot diameter circular clarifier with mechanical scum coll-
ection can be used. The underflow is degritted with a cyclone degritter.
Table 58 shows the operating and capital costs for primary treatment.
The barminutor, primary clarifier, degritter, and sludge and scum withdraw-
al pumps were considered to be part of primary treatment.
Secondary Treatment. The primary effluent flows by gravity to the
activated sludge secondary treatment system. This system consists of
three plug flow aeration basins (0.9 mgd each), two completely mixed
aeration basins (2.4 mgd each) all in parallel, and two circular secondary
clarifiers, 2.0 and 5.5 mgd, respectively. Activated sludge is wasted to
329
-------
TABLE 57
UNIT COSTS^1) 1969 AND 1970
Labor
Operations $ 6.11 /hour
Maintenance 5.05 /hour
Electricity (3) 12.10/1,000 kwh
Fuel^ 0.0543/therm
Make-up Lime (Quicklime)^5) 28.83/ton CaO
Chemicals
Chlorine 114.00/ton
Polymer - Sludge Dewatering 2.53/lb
Polymer - Lime Coagulation 1.92/lb
Polymer - Filtration 1.92/lb
Alum - Filtration (Liquid)(6> 0.014/lb
Activated Carbon Make-up^7) 0.305/lb
(1) All appropriate unit costs are f.o.b. South Lake Tahoe and include
a 5% California sales tax.
(2) Labor costs include all direct and indirect monies paid upon the
employees behalf. The rates are averages for 1969 and 1970.
(3) Includes energy and demand charges.
(4) Natural gas at about 860 BTU/cu ft at 6,200 feet elevation and
billed on the basis of interruptable service.
(5) Average calcium oxide content 93.6%.
(6) Liquid alum weight 11.08 Ibs/gal. Dry alum equivalent 49%.
(7) Activated carbon at 30 Ibs/cu ft.
330
-------
TABLE 58
OPERATING AND CAPITAL COSTS
PRIMARY TREATMENT AT 7 . 5 MGD
OPERATING COSTS
Electricity
Operating Labor
Maintenance Labor
Repair Materials
Instrument Maintenance
Total Operating Cost
$/Day
4.99
80.38
6.61
3.24
1.43
96.65
TOTAL COSTS PER MG
Operating
Capital
Total
$/MG
12.89
19.50
32.39
331
-------
the primary clarifier.
The average secondary effluent concentrations were 70 mg/1 of COD,
25 mg/1 of BOD and 25 mg/1 of Suspended Solids. Total efficiency of the
primary and secondary treatment phases for COD, BOD, and Suspended
Solids were 65, 85, and 90 percent, respectively.
The aeration basins, blowers, mechanical mixers, secondary clari-
fiers, and sludge return pumps were included in secondary treatment.
Table 59 presents the operating and capital costs.
Organic Sludge Dewatering. Raw and waste activated sludges are
pumped through a cyclone degritter at 1 to 2 percent solids to a holding
tank. From the holding tank the sludges are then pumped to one or two
24 by 60 inch solid bowl centrifugals for dewatering to about 18% solids.
A polymer is used in conjunction with centrifuging. The second centrifug-
al may also be used for dewatering lime mud; or as has been the practice
since February 1970, this second machine may be used to dewater the
phosphate rich lime centrate coming from the lead lime mud centrifugal.
In this later mode, the low calcium, high phosphate cake coming from the
second centrifugal is combined with cake from the organic centrifugal and
carried by belt conveyor to a multi-hearth incinerator.
Table 60 shows the cost of dewatering organic sludge. The sludge
holding tank, centrifugal feed pumps, organic sludge centrifugal (s), poly-
mer feed system, and sludge conveyor belts were considered to be part of
sludge dewatering costs. Maintenance labor and repair costs primarily
reflect the cost of periodically cleaning the sludge holding tank, and re-
pairing the sludge feed pumps and organic centrifugal (s).
Organic Sludge Incineration and Disposal. Dewatered organic
solids and waste lime are incinerated in 14.3 foot diameter, six hearth
furnace at 1500°F. The maximum furnace capacity is about 10.5 tons of
dry solids per day. Ash from the furnace is conveyed by bucket elevator
and screw conveyor to a hopper located outside the incineration building.
To date, ash (organic and waste lime) has been produced at the rate of
30.7 ft3 per million gallons of plant influent.
Table 61 shows the operating cost for organic sludge incineration
and disposal. The incineration and ash conveying systems were consid-
ered to be the organic sludge incineration system. The costs include the
expense of drying the waste lime mud and its disposal. The dumping
charges at the disposal site, 3 miles from the plant, were not included.
332
-------
TABLE 59
OPERATING AND CAPITAL COSTS
SECONDARY TREATMENT AT 7.5 MGD
OPERATING COSTS $/Day
Electricity 125.99
Operating Labor 101.90
Maintenance Labor 8.10
Repair Materials 5.85
Instrument Maintenance 4.75
Chlorine 6.04
Total Operating Cost 252.63
TOTAL COSTS PER MG $/MG
Operating 33.68
Capital 33.60
Total 67.28
333
-------
TABLE 60
OPERATING COSTS
ORGANIC SLUDGE DEWATERING AT 7 . 5 MGD
ORGANIC SLUDGE DEWATERING $/Day
Electricity 16.26
Polymer 138.47
O perating Labor 32.18
Maintenance Labor 22.27
Repair Materials 19.61
Instrument Maintenance .78
Total Operating Cost 229.57
TOTAL OPERATING COST
Per MG Plant Influent $ 30.61 /MG
Per Ton of Dry Solids Dewatered $ 23.24
334
-------
TABLE 61
OPERATING COSTS
ORGANIC SLUDGE INCINERATION AT 7.5 MGD
ORGANIC SLUDGE INCINERATION $/day
Electricity 5.63
Natural Gas 97.11
Operating Labor 21.47
Maintenance Labor 6.20
Repair Materials 1.84
Instrument Maintenance 2.58
Ash Disposal
Labor 2.47
Trucking^1) .82
Total Operating Cost 138.12
TOTAL OPERATING COST
Per MG Plant Influent $ 18.41 /MG
Per Ton of Dry Solids Dewatered $ 13.98 /ton
(1) Based on hourly truck rate during loading, 2 way hauling, and
dumping. Dumping charges at disposal site not included.
Hourly trucking charges included 5 yr amortization of capital
cost for 5 ton dump truck plus 5% of capital for maintenance.
335
-------
Overall Costs - Organic Sludge Dewatering, Incineration, and
Disposal. The operating and capital costs shown in Table62 represent
the total cost for organic sludge handling and disposal excluding dump-
ing charges.
Lime Coagulation. Chemical coagulation (with lime) of the secon-
dary effluent to pH 11 is accomplished with a rapid-mix flocculation basin,
followed by a 100 foot diameter conventional clarifier. To reach pH 11 for
the South Lake Tahoe wastewater, a lime dose of 300 mg/1 of calcium
oxide is required. A polymer, at a 0.1 to 0.3 mg/1 dose, is added just as
the water leaves the flocculation chamber to improve clarification.
The lime coagulation system typically removes 95 percent of the
phosphorus it receives. In the clarifier effluent, phosphorus concentra-
tions range between 0.2 and 0.7 mg/1 PO4~P and turbidity levels between
1 and 10 SJU.
Table 63 shows the specific operating and capital costs for this
treatment phase. The lime storage bins, slakers, floe basin, clarifier,
polymer feed system, and sludge draw-off pumps were considered to be
part of the lime coagulation system. As shown in Table 56, operating lab-
or from both the general plant and the incineration building were charged
to lime clarification. Maintenance labor and repair material costs for
1969 and 1970 represented primarily costs associated with the slakers,
lime buildup on the flash mixer, sludge removal from the lime mixing bas-
in, and cleaning of the lime slurry line from the slakers to the flash mix-
ing basin.
Lime Mud Dewatering. Lime mud is pumped from the chemical clar-
ifier and reaction basin to a gravity thickener for solids concentrations.
In turn, the thickened mud is pumped by either of two variable speed pump
units to a 24-inch x 60-inch solid bowl centrifugal for dewatering. Phos-
phorus is wasted from the system in the form of calcium hydroxyapatite by
operating the lime centrifugal so that 10-30 percent of the solids entering
the machine come out in the centrate. A second centrifugal clarifies the
centrate and the phosphorus-rich cake is conveyed to the organic sludge
furnace.
Operating and capital costs for the dewatering phase of lime recal-
cination are shown in Table 64 . The items of equipment included in this
phase were the thickener, lime sludge pumps to the centrifugal, the cen-
trifugal itself and lime cake conveyor to the furance. In 1969 and 1970,
most of the maintenance labor and repair costs were related to lime mud
line cleaning and centrifugal repair. The dewatering costs also included
the second centrifugal when it was being used to dewater lime centrate for
336
-------
TABLE 62
OPERATING AND CAPITAL COSTS
ORGANIC SLUDGE DEWATERING AND INCINERATION AT 7.5 MGD
ORGANIC SLUDGE DEWATERING $/MG< 1 ) $/TON^ 2
Operating Costs 30.61 23.24
Capital Costs 4.81 3.65
Total Costs 35.42 26.89
ORGANIC SLUDGE INCINERATION
Operating Costs 18.41 13.98
Capital Costs 9.29 7.05
Total Costs 27.70 21.03
TOTAL OPERATING AND CAPITAL COSTS 63.12 47.92
( 1 ) Per MG of plant influent
( 2 ) Per ton of dry solids dewatered
337
-------
TABLE 63
OPERATING AND CAPITAL COSTS
LIME COAGULATION AT 7 .5 MGD
OPERATING COSTS
$/DAY
Electricity
Make-up Lime
Polymer
Operating Labor
Maintenance Labor
Repair Materials
Instrument Maintenance
Total Operating Cost
5.22
168.19
22.18
30.67
9.59
3.14
3.04
242.03
TOTAL COSTS PER MG
$/ MG
Operating
Capital
Total
32.27
9.70
41.97
338
-------
TABLE 64
OPERATING COSTS
LIME MUD DEWATERING AT 7 . 5 MGD
LIME MUD DEWATERING $/DAY
Electricity 8.92
Operating Labor 21. 47
Maintenance Labor 16.04
Repair Materials 8-81
Instrument Maintenance 0* 00
Total Operating Cost 55. 24
TOTAL OPERATING COST
Per MG Plant Influent $ 7.37/MG
Per ton CaO Recalcined 5.49/ton
CaO
339
-------
the lead centrifugal.
The costs for drying and disposing of the dewatered high phosphate
lime mud were included in the costs for organic sludge incineration and
ash disposal.
Lime Mud Recalcining. Dewatered lime mud is conveyed from the
centrifugal to a 14.3 foot diameter,six hearth furnace for recalcining at
1800-1900°F. The maximum capacity of the furnace is about 20 tons of
dry solids per day. The recalcined lime exits by gravity through a crusher
into a thermal disc cooler, and then is pneumatically conveyed to the re-
calcined lime storage bin for eventual reuse.
For the purpose of determining operating and capital costs, all
equipment and functions from the lime furnace to the lime storage bin were
considered to be part of the lime recalcining system. These costs are
shown in Table 65. The majority of the maintenance costs were associat-
ed with the conveying of recalcined lime from the furnace to the storage
bin.
Oyerall__Costs_ - Lime Dewatering and Recalcining. The operating
and capital costs shown in Table 66 represent both dewatering and recal-
cining costs. If lime mud dewatering costs are considered common to any
lime clarification process, then the costs of lime recalcining are compet-
itive with buying new lime, particularly when disposal costs are included.
At South Lake Tahoe new lime was purchased at $28.83/ton CaO, whereas
lime recalcination cost $31.61/ton CaO.
Nitrogen Removal by Ammonia Stripping. Following lime clarifica-
tion, ammonia stripping is utilized at South Lake Tahoe to remove the nut-
rient nitrogen from the wastewater. The stripping process includes two
constant speed pumps, a cross flow cooling tower with a two-speed re-
versible 24-foot fan, a concrete collection basin below the tower, and a
flow measurement weir on the basin exit. The tower has an average de-
sign air-to-water ratio of 250 cu ft/gal, and a nominal capacity of 3.75
mgd.
Tower removal efficiencies have varied from 30 to 90 percent, de-
pending on air temperature and extent of calcium carbonate buildup on the
fill before cleaning. During the winter when the air temperature is lower
than 32°F (O°C.), the tower is bypassed to prevent ice buildup on the
fill. Tower influent NH3~N concentrations have ranged from 15 to 30 mg/1,
with effluent values from 3 to 15 mg/1.
340
-------
TABLE 65
OPERATING COSTS
LIME MUD RECALCINING AT 7 .5 MGD
LIME MUD RECALCINING $/DAY
Electricity 6.55
Natural Gas 142.83
Operating Labor 64.36
Maintenance Labor 12.68
Repair Materials 8.31
Instrument Maintenance 3.63
Total Operating Cost 238.36
TOTAL OPERATING COST
Per MG Plant Influent $ 31.78 MG
Per Ton CaO Recalcined 23.70/ton
CaO
341
-------
TABLE 66
OPERATING AND CAPITAL COST
LIME MUD DEWATERING AND RECALCINING
AT 7 . 5 MGD
LIME MUD DEWATERING $/MG $/Ton CaO
Operating Costs 7.37 5.49
Capital Costs 2.90 2.16
Total 10.27 7.65
LIME MUD RECALCINING
Operating Cost 31.78 23.70
Capital Cost 10.60 7.91
Total 42.38 31.61
TOTAL OPERATING AND CAPITAL COSTS 52 .65 39 .26
342
-------
The operating and capital costs of nitrogen removal for both inter-
mittent and continuous operation are listed in Tables 67 and 68, respect-
ively. Operating labor included backflushing of tower pumps and clean-
ing the distribution deck to remove CaCOs precipitation, routine chart
changing, process inspection, lubrication, and daily determination of
tower ammonia removal efficiency. Maintenance costs, to date, reflect
the costs of removing calcium carbonate scale from the influent pumps and
tower fill.
pH Adjustment by Recarbonation. The next unit in the liquid pro-
cessing stream is the two-stage recarbonation of the ammonia stripping
tower effluent. The system, located beneath the ammonia stripping tower,
is divided into three sections: first-stage recarbonation, a reaction basin,
and second-stage recarbonation. In the first-stage basin compressed
scrubbed stack gases from the lime recalcining and sludge incineration
systems are used to reduce the pH from 11.0 to 9.6, the minimum solubil-
ity of CaCOs. Approximately 17 percent additional CaCOs can be settled
out in the reaction basin with the dual-stage system. This additional re-
moval also decreases deposition of CaCOs in the ballast ponds and on the
filter media and activated carbon. The second-stage reduces the pH from
9.6 to 6.8-7.5, also with scrubbed stack gases.
Operating and capital costs for two-stage recarbonation are shown
in Table 69. The costs included the CO£ compressor system, first- and
second-stage recarbonation, and the reaction basin with its sludge coll-
ection system. Operator time included pH control associated with com-
pressor gas flow, servicing the compressors, and removal of lime sludge
from the reaction basin. The maintenance costs principally reflected com-
pressor repair costs.
Mixed Media Filtration. The secondary recarbonation effluent is
pumped to the mixed media filters at about 5 gpm/sq ft. There are three
pairs of mixed media beds which operate in parallel. Each pair of beds
comprises a unit, and the two beds are operated in series during all three
operational cycles; that is, during filtration, backwash, and filter-to-
waste. Normal operation of the beds (or filters) is controlled automatical-
ly from a control panel. The filter medium is a special patented (Neptune
MicroFLOC, Inc.) coarse-to-fine medium containing coal, sand, and gar-
net. Alum is applied to the filter influent at 10 to 30 mg/1 to obtain the
desired turbidity in the finished water. Polyelectrolyte (or secondary
flocculant) may be added as a filter aid to control floe breakthrough.
After a predetermined time or throughput, each pair of beds is auto-
matically taken off line (one pair at a time in sequence), backwashed, and
343
-------
TABLE 67
ACTUAL OPERATING AND CAPITAL COST
AMMONIA STRIPPING AT 7. 5 MGD
UNDER INTERMITTENT CONDITIONS W
OPERATING COSTS PER DAY $/Day
Electricity (1) 41.12
Operating Labor 4.63
Maintenance Labor 5.17
Repair Material .78
Instrument Maintenance .94
Total Operating Cost 52 .64
TOTAL COST PER MG $/ MG
Operating 7.02
Capital 8.00
Total 15.02
(1) Intermittent conditions due to air temperatures below 32° Fat
which the tower freezes. Only electricity is affected.
344
-------
TABLE 68
OPERATING COSTS FOR
AMMONIA STRIPPING AT 7.5 MGD
FOR CONTINUOUS OPERATION
OPERATING COST PER DAY
Electricity (!)
Operating Labor
Maintenance Labor
Repair Material
Instrument Maintenance
Total Operating Costs
$/Day
60.78
4.63
5.17
.78
.94
72.30
TOTAL COST PER MG
Operating
Capital
Total
$/MG
9.64
8.00
17.64
Average cost per day at 7.5 mgd from months of continuous operation,
i.e., May through September 1969, and 1970.
345
-------
TABLE 69
OPERATING AND CAPITAL COSTS
RECARBONATION AT 7. 5 MGD
OPERATING COSTS PER DAY $/Day
Electricity 12.15
Operating Labor 16.87
Maintenance Labor 7.14
Repair Materials 3.11
Instrument Maintenance .65
Total Operating CostsU) 39.92
TOTAL COST PER MG $/MG
Operating 5.32
Capital 4.00
Total 9.32
(1) Stack gases from lime recalciner and/or sludge incinerator
supply the CO2.
346
-------
returned to service. The beds are backwashed at 15 gpm/sq ft with filter
influent water. The filtration cycle, depending on the influent water,
may last from 15 to 60 hours.
The contribution of the filters towards improving the final plant ef-
fluent can be shown by the following values. Phosphorus concentrations
in the filter effluent average 0.1 mg/1 with removal efficiencies of 50 to
99 percent. Effluent concentration for suspended solids average less than
one mg/1 and for turbidity about 0.5 Standard Jackson Units.
The major contribution, however, can only be seen through practical
plant operating experience. Both the filters and the carbon adsorption col-
umns, for the past 3 years, 24 hours a day, have enabled this plant to
produce an extremely high quality effluent despite complete activated
sludge failures and minor chemical clarification problems.
The operating and capital costs for filtration are shown in Table 70.
These costs include pumping the recarbonated effluent against a static
head of about 100 feet, surface and backwash pumps, separation beds,
and chemical feed. The high pumping head results from site location,
filter headless, and carbon column headless. Since the average valves
of headless across the filters and carbon columns are about the same, 50
percent of the pumping costs have been assigned to each of these two
functions.
Operating labor included manually initiating filter backwashes, per-
iodic monitoring of the filtration and backwash cycles, general cleaning,
and equipment servicing. Maintenance costs for 1969 and 1970 included
rewinding electric motors on two influent pumps, an inspection of the mix-
ed media beds, repair of the surface wash arms and minor automatic valve
work.
Carbon Adsorption. Activated carbon adsorption follows mixed med-
ia filtration. The activated carbon system includes eight steel columns,
each containing 22-25 tons of 8 x 30 mesh granular activated carbon. The
separation bed effluent flows under pressure upflow through the columns.
Chemical oxygen demand concentration in the separation bed efflu-
ent averaged 20 mg/1 with approximately 50 percent removal across the
activated carbon. MBAS concentrations in the separation bed effluent
averaged 0.6 mg/1, and the carbon column effluent concentration was a-
bout 0.1 mg/1. Biochemical Oxygen Demand (BOD) concentrations in the
separation bed effluent ranged from 3 to 6 mg/1, and carbon column efflu-
ent concentrations ranged from 1 to 3 mg/1. Color removals across the
347
-------
TABLE 70
OPERATING AND CAPITAL COSTS
FILTRATION AT 7 . 5 MGD
OPERATING COSTS PER DAY
Electricity
Chemicals - Alum/Polymer'-*-)
Operating Labor
Maintenance Labor
Repair Materials
Instrument Maintenance
Total Operating Costs
$/Day
47.34
73.66
24.53
9.83
3.32
10.67
169.35
TOTAL COST PER MG
Operating^2)
Capital
(1)
(2)
Total
$/MG
22.58
17.80
40.38
Insignificant amount of polymer used
Total operating cost per MG of water filtered would be 18.25
MG. Includes 7.5 mgd plant influent, plus recycle streams.
348
-------
carbon averaged 50 percent, with a range of 10-15 units on the influent
and 4-7 units on the effluent.
Operating and capital costs for activated carbon adsorption are
shown in Table 71.
Operational labor included flow monitoring, sampling, and backflow-
ing of columns. Maintenance included instrumentation calibration, corros-
ion inspection of the interior of the columns, and repair of appurtenances.
As mentioned in the filtration section, 50 percent of the pumping costs,
including maintenance for pumping through the filters and carbon columns
were assigned to the carbon adsorption system.
The initial carbon charge for the carbon columns was included in
the capital cost.
Carbon Regeneration. After an average dosage of 207 pounds of
carbon per million gallons has passed through the columns, a batch of 3
tons was withdrawn from each column for regeneration in sequence. From
past experience, this dosage appears to give optimum usage of the carbon
but is high enough to prevent a COD, MBAS, or color wavefront breakthrough.
Spent carbon is regenerated at 1,650° to 1,750°F in a multiple hear-
th furnace. The furnace can be operated at feed rates of 100 to 6,000 Ibs
per day. After regeneration, the activated carbon is returned to the col-
umns. Carbon losses used for the cost analysis averaged 8.9 percent.
Operating and capital costs for activated carbon regeneration are
shown in Tables 72 and 73 . As shown in Table 73 , the total combined op-
erating and capital cost of carbon regeneration is about 10 cents per Ib of
carbon regenerated.
Electricity included power used for instrumentation, driving rabble
arms, and fans for shaft cooling, induced draft, and combustion air. Nat-
ural gas and make-up carbon are self-explanatory. Operational labor in-
cluded furnace operation, defining, transferring spent and regenerated
carbon, and regeneration efficiency analysis. Maintenance labor and re-
pair material were for the furnace, instrumentation, and carbon transfer
appurtenances. Maintenance costs for 1969 and 1970 included furnace
startup and shutdown every 4 to 8 weeks, cleaning carbon dewatering and
defining screens, carbon slurry pumps and stack-gas scrubber. The ex-
tensive maintenance of furnace startup and shutdown would be eliminated
if regeneration were continuous.
349
-------
TABLE 71
OPERATING AND CAPITAL COSTS
CARBON ADSORPTION AT 7.5 MGD
OPERATING COSTS PER DAY
Electricity
Operating Labor
Maintenance Labor
Repair Material
Instrument Maintenance
Total Operating Cost
$/Day
47.34
24.53
3.27
1.15
4.24
80.53
TOTAL COST PER MG
Operating^ '
Capita^2 ^
(1)
(2)
Total
$/MG
10.74
16.30
27.04
Total operating cost per MG of water treated would be 8.77/MG.
This figure includes 7.5 mgd plant influent, plus recycle streams.
Includes initial carbon charge.
350
-------
TABLE 72
OPERATING AND CAPITAL COSTS
CARBON REGENERATION AT 7. 5 MGD
OPERATING COST PER DAY
Electricity
Natural Gas
Make-up Carbon
Operating Labor
Maintenance Labor
Repair Material
Instrument Maintenance
Total Operating Cost
$/Day
2.23
6.15
70.39
91.90
16.21
1.17
1.90
189.95
TOTAL COST PER MG
Operating
Capital
(1)
Total
$/MG
25.33
5.20
30.53
Total operating cost per MG of water treated would be 19.28/MG.
This figure includes 7.5 mgd plant influent, plus recycle flows.
351
-------
TABLE 73
OPERATING AND CAPITAL COST OF
CARBON REGENERATION PER TON OF
CARBON REGENERATED
OPERATING COST PER TON $Aon
Electricity 1.73
Natural Gas 4.72
Make-up Carbon 53.98
Operating Labor 68.74
Maintenance Labor 39.52
Repair Material 2.36
Instrument Maintenance 1.43
Total Operating Cost 172 .48
TOTAL COST PER TON $/Ion
Operating 172.48
Capital 29.76
Total 202.24
352
-------
Disinfection by Chlorine. The quality of water from advanced
waste treatment has a major effect on chlorine disinfection and the amounts
needed. Since the chlorine demand of the District's final effluent is very
low, instantaneous chlorine values of 2-3 ppm insured complete disinfec-
tion. Gaseous chlorine is added to the final effluent as it is pumped to
the main export pump station at Luther Pass.
The District must maintain high coliform count (MPN/100 ml) stan-
dards. Over the period covered by this grant, the median has always been
less than 2.0 and there have been no consecutive samples above 23.
In 1969, nine sets of water samples were collected and submitted to'
the FWPCA laboratory in Cincinnati for virus examination. Although virus-
es were found in the secondary effluent, all nine tests of the reclaimed
water after chlorination were negative for virus. No virus has been recov-
ered from the water being exported to Indian Creek Reservoir in two sum-
mers of sampling. While this does not necessarily mean that the water is
free of virus, at least all of the results to date are favorable.
The operating costs from February 1969 to December 1970 at 7.5 mgd
were $2.72/MG and the capital cost was $0.30/MG. These costs are in-
cluded in this section as part of the conventional waste treatment costs.
Summary. At the time the water reclamation plant was designed,
very little experience was available to aid in estimating full-scale plant
efficiencies. Approvals of the plant design by the various regulatory a-
gencies also included stringent export requirements on the plant effluent
quality. For the 3 year period covered by this grant the plant effluent was
continuously well below the export requirements.
All of the reclaimed water has been exported to Indian Creek Reser-
voir. The man-made lake has been approved by local and state regulatory
agencies for all water contact sports. The reservoir supports a thriving
population of rainbow trout and a state grant has been awarded for C9n-
struction of recreational facilities. The water in the reservoir is sparkl-
ing clear, and Secci disc observations have been recorded as high as 20
feet.' The low level of phosphorus in the plant effluent appears to be giv-
ing adequate control of algal growth. During the irrigation season, a por-
tion of the water in the reservoir is released for irrigation of forage crops
by the ranches below the reservoir.
The benefits of advanced waste treatment in a water-short area or
where it is essential to conserve the ecology of an area far outweigh the
costs of advanced waste treatment.
353
-------
A summary of the costs required to meet state effluent or export
standards and to produce the reclaimed water of exceptionally high quali-
ty are shown in Tables 74 and 75 and 76. Several miscellaneous items
were not included in the preceding operating cost categories. Table 77
lists these items and their related costs.
A very valuable water resource for recreation, irrigation, and per-
haps some day for direct reuse has been produced at an additional cost of
$217/MG which is approximately 30 percent greater than for conventional
treatment. Furthermore, the costs do not reflect the benefits of actual
federal assistance or resale of the product water. If the assumption is made
that the average sewage flow per person is 110 gpd, the total cost for ter-
tiary waste treatment per person per month is about 75 cents. Put another
way, the cost of tertiary waste treatment adds less than $9.00 per person
per year to the total cost of waste collection and treatment.
Increase in Construction Costs at South Lake Tahoe. The South
Tahoe Public Utility District pays an above normal price for construction
of improvements due to the geographical and climatological conditions of
the Lake Tahoe Basin. Construction costs in the basin are 15% to 30%
higher than costs in the nearest industrialized areas which are 50 to 100
miles away. The higher costs are primarily a result of the remote location,
climate and altitude, and a correspondingly short construction season.
As a result of the remote location, the majority of the labor force
must be imported. Subsistence of 9.50 to 11.50 per man-day is required
by union contracts. Since the cost of living is higher in the basin, super-
visory and semi-permanent personnel are paid an additional rate for the
increased cost of living. The resulting total labor cost may be as much
as 40% higher than less remote areas. Also since the workmen are away
from home, they are more likely to engage in the gambling and night life
readily available at the lake, which results in lower working efficiency.
Shipping costs are much higher because all highway mountain passes are
above 7100 feet elevation. The remote location also decreases the avail-
ability of construction materials. Concrete delivered to the project site
costs approximately double of that of less isolated areas. At times there
is an extended downtime of men and equipment while waiting for parts and
materials.
354
-------
TABLE 74
TOTAL OPERATING COSTS
CONVENTIONAL WASTEWATER TREATMENT AT 7 . 5 MGD
OPERATING COSTS
Electricity
Natural Gas
Chemicals - Polymers
Chlorine
Operating Labor
Maintenance Labor
Repair Materials
Instrument Maintenance
Total Cost per Day
$/Day
152.87
97.11
138.47
23.58
235.93
46.38
31.75
11.30
737.39
TOTAL OPERATING COST
Per MG Plant Influent
$/MG
98.32
355
-------
TABLE 75
TOTAL OPERATING COSTS
ADVANCED WASTEWATER TREATMENT AT 7. 5 MGD
OPERATING COSTS
Electricity^
Natural Gas
Chemicals (Alum and Polymer)
Make-up Lime
Make-up Carbon
Operating Labor
Maintenance Labor
Repair Materials
Instrument Maintenance
Total Cost Per Day
$/Day
170.87
148.98
95.84
168.19
70.39
278.96
79.93
29.79
25.07
1,068.02
TOTAL COST PER MG
$/MG
Total Cost per MG Plant Influent 142.40
(1) Based on intermittent weather conditions for ammonia stripping.
If NH 3 stripping operated continuously, total electricity would
have been $190.53/day.
356
-------
TABLE 76
TOTAL OPERATING AND CAPITAL COSTS FOR
CONVENTIONAL AND ADVANCED WASTE TREATMENT AT THE
SOUTH TAHOE WATER RECLAMATION PLANT FOR THE
7.5 MGD DESIGN CAPACITY IN 1969 and 1970
CONVENTIONAL WASTE TREATMENT^ $/MG
Operating Costs 98.32
Capital Costs 67.50
Total 165.82
ADVANCED WASTE TREATMENT
Operating Costs 142.40
Capital Costs 74.50
Total 216.90
MISCELLANEOUS OPERATING COSTS 11.57
TOTAL OPERATING AND CAPITAL COST 394.29
(1) Includes chlorination costs of final effluent and disposal phos-
phorus rich lime mud.
357
-------
TABLE 77
MISCELLANEOUS OPERATING COSTS
FOR CONVENTIONAL AND ADVANCED TREATMENT
Item
Uniforms
Laboratory Supplies
Fire Insurance
Telephones
Standby Propane
Miscellaneous Supplies
Plant Grounds-Cleanup
TOTAL
$/Day
10.97
8.22
41.10
6.85
2.74
10.97
5.90
86.75
$/MG at
7.5 MGD
1.46
1.10
5.48
.91
.37
1.46
.79
11.57
358
-------
The alpine climate and 6300 foot elevation of the area results in a
favorable construction season of only six months in length, usually May
through October. The contractor must mobilize and demobilize his oper-
ations each year, which requires extensive overtime. In order to retain
key personnel, the contractor must finance construction retentions through
the unproductive winter months. The quality of the work force may be
lessened because normally better workmen work in areas with longer con-
struction seasons and less severe climates. The heavy snow load re-
quires stronger permanent and temporary construction buildings. The in-
clement weather reduces equipment and labor production and efficiency.
In Table 78 the actual construction and equipment costs for the 7.5
mgd capacity water reclamation plant are listed, and manifest the increas-
ed construction costs as a result of the unique geographical and climatol-
ogical situation of the Lake Tahoe Basin.
359
-------
TABLE 78
ACTUAL CONSTRUCTION AND EQUIPMENT COSTS AT THE 7.5 MGD
SOUTH LAKE TAHOE WATER RECLAMATION PLANT
BY CONTRACT COMPLETION DATES
CONVENTIONAL TREATMENT - COST ADVANCED TREATMENT - COST
Primary Treatment
1960 $ 430,000
1968 262,000
$ 692,000
Secondary Treatment
I960 $ 508,500
1965 56,500
1968 682,000
$1,247,000
Organic Sludge (Handling,
dewatering , incineration
and ash disposal)
1968 583,000
Chlorination
1960 8,000
1968 1,000
$ 9 000
S7 *J / \J \J \J
Lime Treatment
1965 $
1968
$
800
400,200
401,000
Lime Re calcining (dewa-
tering andrecalcining)
1968
Nitrogen Stripping
1968
Recarbonation
1968
Filtration
1965
1966
1968
$
Carbon Adsorption
1965
1968
$
Carbon Regeneration
1965
1968
$
552,000
327,000
162,000
267,000
72,000
366,000
705,000
159,000
497,000
656,000
191,000
2,000
193,000
360
-------
SECTION XXVI
ACKNOWLEDGEMENTS
Environmental Protection Agency Project WPRD 52-01-67 is close-
ly related to the entire South Tahoe Water Reclamation Plant project.
Therefore acknowledgements are made, first for the Demonstration Project
specifically, then for the development and construction of the Plant which
made the Project possible.
The Demonstration Project (1967 - 1971)
Local Sponsors; South Tahoe Public Utility District Board of Dir-
ectors: Robert W. Fesler (President), Robert Wakeman, Edward Hegarty,
Donald Kortes, and Jerry Ream.
Data Collection: Plant Operation: Engineers: David R. Evans,
Jerry C. Wilson, Robert L. Chapman, and Clinton E. Smith. Treatment
Plant Operators: Earl Hardie (Chief Operator), Les Baker, Vern Trujillo,
Al Kaufmann, Al Gunderson, Dick Miller, Ray Fieldcamp, Terry Guild, Lou
Nagy, Bob Miller, Chet Horning, Jim Gorbet, Jerry Trauner, Mike Guthrie,
Jim Dalecke, Tom Ontko, Everett Fox, and Kim Balbini. Plant Maintenance
Crew: Murle Spencer (Supervisor), Conrad Ross, Willard Brown, Dick
Vonderscher, and Merle Kobernus. Financial Data: David Callahan, Mary
Parsley, Ruth Mounier. Indian Creek Reservoir Data: (Lake Tahoe Area
Council) Dr. P. H. McGauhey, Dr. D. B. Porcella, and Dr. Gordon Dugan.
Final Report Preparation. Engineers: David R. Evans, Jerry C.
Wilson, and Russell L. Gulp. Stenographers: Charlotte Corday and Kay
Price.
Technical Advice and General Supervision. District: HarlanE.
Moyer, Russell L. Gulp, and Gene Suhr. EPA: Dr. Robert B. Dean, Dr.
David Stephan, Dr. Frank Middleton, Dr. Joseph Farrell, JohnC. Merrell,
Jerry Troyan, and Robert Wills .
The Advanced Wastewater Treatment Plant (1961 - 1971)
The Demonstration Project was made possible by the existence
of the advanced wastewater treatment plant of the South Tahoe Public
Utility District. The total effort which culminated in the completion of
this plant includes ten years of research, pilot plant work, process devel-
opment, engineering design, construction, and operation. It also involved
361
-------
leadership, public support, political support, financial planning, counsel-
ling, management, and cooperation among many local, state, federal,
and private agencies . In all facets of the work hundreds of people were
involved, so that it is not possible to give individual recognition in all
cases but only to list some by organization title.
Leadership . South Tahoe Public Utility District, Directors:
Robert W. Fesler, Robert Wakeman, Donald H. Kortes, Edward Hegarty,
Jerry Ream, Donald L. Clarke, Frank C. Souza, Thomas L. Stewart, and
Donald Bickle.
Research and Unit Process Development. Original Concept:
Ralph E. Roderick, Cornell, Rowland, Hayes & Merryfield (C^M) . Lime
Treatment for Phosphorus Removal: Russell L. Gulp, CH^M. Lime Recal-
cining: CH2M, Gene Suhr, Russell L. Gulp; B-S-P Corp. Ammonia Strip-
ping: CH2M, Russell L. Gulp, Gordon Gulp, Robert Chapman, David
Evans; Glair A. Hill & Associates, Al Slechta, Clinton Smith, Jerry Wilson,
Two-Stage Recarbonation: CH2M, Russell L. Gulp, Gene Suhr. Mixed-
Media Filtration: Microfloc, Inc., Walter Conley, Archie Rice; C^M,
Ralph Roderick, Russell L. Gulp. Granular Activated Carbon Adsorption:
U. S. Public Health Service, Dr. Frank Middleton; Pittsburgh Activated
Carbon Co., Don Hager; Microfloc, Inc., Walter Conley, Archie Rice;
CH2M, Gene Suhr, Russell L. Gulp. Granular Carbon Regeneration: Car-
bon Manufacturers, Pittsburgh Activated Carbon Company, Atlas Chemical
Company, and others; EPA, Dr. Frank Middleton; C^M, Gene Suhr,
Russell L. Gulp; Pomona Project, Frank Dryden; Nassau County Project,
John Rose.
Process Sequencing and Integration. Microfloc, Inc.: Walter
Conley, Archie Rice. CH2M: Ralph Roderick, Russell Gulp, Gene Suhr.
Engineering Design of Plant. C^M: Russell L. Gulp, Gene
Suhr, William Ettlich, Richard Nichols, Gary Graham, Sid Clark, and many
others. Clair A. Hill & Associates: Harlan E. Moyer and others.
Financial Planning. Board of Directors , South Tahoe taxpayers ,
EPA, U. S. Public Health Service, Economic Development Administration,
State of California.
Political Support. U. S. Representative, Harold T. (Bizz) John-
son, State Assemblyman Gene Chappie, State Senator Stephan Teale, John
C. Weidman, Attorney, Supervisors of Alpine County, Supervisors of El
Dorado County, Councilmen of the City of South Lake Tahoe.
362
-------
Public Support. Local residents, Lake Tahoe Area Council,
League to Save Lake Tahoe, Sierra Club, local civic clubs, Tahoe
Daily Tribune, Sacramento Bee.
Cooperating Pollution Control Agencies. EPA: Dr. David
Stephan, Dr. Robert Dean, Dr. Frank Middleton, and others. California
Water Resources Control Board: Paul Bonderson, Jack Leggett, Fred
McLaren, David DuBois: Nevada State Department of Health: Wallace
White, Ernest Gregory.
Administration and Management. Board of Directors, South
Tahoe Public Utility District, Win Friday, Harlan E. Mover, David
Callahan, and Russell Gulp.
Legal Counsel. John C. Weidman; and firm of Wilson, Jones,
Morton, and Lynch, Robert Hill, Kenneth Jones, John Lynch.
Plant Construction Contractors. C. Norman Peterson Company,
California Filter Company, Rothschild, Raffin and Weirick, B-S-P Corpor-
ation, P-M-I Corporation.
Major Equipment Suppliers. Allis Chalmers Mfg. Company,
Autocon Industries, BSP Corporation, Bird Machine Company, Byron
Jackson Pump Division of Borg Warner Corporation, Certain-teed Products
Corporation and Johns - Manville Corporation, Chicago Bridge and Iron
Company, Dorr-Oliver, Inc., General Services Company - Flomatcher
Division, Komline-Sander son Engineering Corporation, Link Belt Company,
Marley Company, Neptune Microfloc, Inc., Pacific Clay Products, Rex
Chainbelt Company, Inc., United Concrete Pipe Corporation, U.S. Elec-
trical Motors, Inc., Wallace and Tiernan, Inc., Westinghouse Electrical
Corporation.
On-The-Tob-Traininq of Operators. CH2M: Russell L. Gulp,
Gene Suhr, Robert Chapman, David Evans. Clair A. Hill and Associates:
Clinton Smith, Jerry Wilson, Harlan E. Moyer. Neptune Microfloc, Inc.:
Walter Conley, William Ettlich. BSP Corporation: Richard Stroshane,
J.S. Roberts, Paul Cardinal, Bob Tillotson. Bird Machine Company: Ted
Durst, Jim Bailey, Cliff Amerro. Komline-Sanderson Engineering Corpor-
ation, W. E. Mayo. Dorr-Oliver, Inc.
Plant Operations and Maintenance. Plant operators and maintenance
crew as previously listed under "Data Collection".
363
-------
Operation and Maintenance of Collection System, Pump
Stations, and Export Facilities . Pump Stations and Export Facilities:
Lee Chada (Superintendent), Bernie Montbriand (Supervisor), Al Harris,
Lowell Hardie, Harry Hanson, Bob Eppler. Collection System: M. W.
Fagot, Norman Thomas, Gene Eppler, W. J. Bussboom, Richard DeVee,
Mike McCoy, Greg James, Brian Bethel.
364
-------
SECTION XXVII
REFERENCES
OPERATOR TRAINING.
1. Anon. , "Elementary Mathematics and Basic Calculations", Water &
Sewage Works Magazine. Scranton Publ. Corp., Chicago, Illinois.
2. Anon., "Operator Short Course", Water & Wastes Engineering. New
York.
3. Gulp, Russell L., "The Operator of Wastewater Treatment Plants",
Public Works Magazine. Ridgewood, N. J. (1970).
4. Texas Water & Sewage Works Association, Austin, Texas, Manual for
Sewage Plant Operators.
5. W.P.C.F., Washington, D.C., "Operation of Wastewater Treatment
Plants", WPCF Manual of Practice No. II.
6. W.P.C.F., Washington, D.C., "Wastewater Treatment Plant Opera-
tor Training Course Two", WPCF Publication No. 14.
TEST PROCEDURES.
7. American Public Health Assoc., New York City, Standard Methods for
the Examination of Water and Wastewater, 12th Edition.
INCINERATION OF WASTE SOLIDS.
8. Albertson, O. E. and Guidi, E. E., Jr., "Centrifugation of Waste
Sludges", Journal Water Pollution Control Federation, p. 607 (1969).
9. Alford, J. M., "Sludge Disposal Experiences at North Little Rock,
Arkansas", Journal Water Pollution Control Federation, p. 175 (1969).
10. Bird Machine Co., South Walpole, Mass., Operating Manual, (1966).
365
-------
11. Blattler, Paul X., "Wet Air Oxidation at Levittown", Water & Sewage
Works. p. 32 (February, 1970).
12. Cardwell, E. G., "Dewatering by Mechanical Means", Proc. 10th
San. Eng. Conf.
13. Ettelt, G. A., and Kennedy, T. J., "Research and Operational Exper-
iment in Sludge Dewatering at Chicago", Journal Water Pollution Con-
trol Federation, p. 248 (1966).
14. Genter, A. L., "Computing Coagulant Requirements in Sludge Condi-
tioning", Transactions, American Society of Civil Engineers, p. 641,
(1946).
15. Jones, W. H., "Sizing and Application of Dissolved Air Flotation
Thickeners", Water & Sewage Works. Ref. No. R-177-194 (Nov. 1968).
16. Jordan, V. J., and Scherer, C.H., "Gravity Thickening Techniques at
a Water Reclamation Plant", Journal Water Pollution Control Fed era -
ation, p. 180 (1970).
17. McCarty, P.L. , "Sludge Concentration-Needs, Accomplishments, and
Future Goals", Journal Water Pollution Control Federation, p.493(1966).
18. Nichols Engineering Co., Bulletin No. 238A, "Sludge Furnaces".
19. Schepman, B. A., and Cornell, C.F., "Fundamental Operating Vari-
ables in Sewage Sludge Filtration", Sewage and Industrial Wastes,
p. 1443 (1956).
20. Sharman, L., "Polyelectrolyte Conditioning of Sludge", Water and
Wastes Engineering,, p. 8 (1967).
21. Tenney, M. W., and Cole, T.G., "The Use of Fly Ash In Condition-
ing Biological Sludges For Vacuum Filtration", Journal Water Pollution
Control Federation, p. R281 (1968).
22. Tenney, Mark W., et al, "Chemical Conditioning of Biological Sludges
for Vacuum Filtration", Journal Water Pollution Control Federation,
p. Rl, (1970).
366
-------
23. Tomas, C. M., "The Use of Filter Presses for the Dewatering of Sew-
age and Waste Treatment Sludges", Paper presented at the 42nd Annual
Conference of the WPCF, Dallas, Texas (October, 1969).
CHEMICAL TREATMENT AND WASTE SOLIDS.
24. Camp, T. R. , "Flocculation and Flocculation Basins", Transactions
American Society of Civil Engineering, p. 1 (1955).
25. Camp, T. R. , "Floe Volume Concentration", Journal American Water
Works Association, p. 656 (1968).
26. Chemical Feeder Guide, BIF Co., Providence, Rhode Island (1969).
27. Hudson, H. E., "Physical Aspects of Flocculation", Journal American
Waterworks Association, p. 855 (1965).
28. LaMer, V. K., and Smellie, R. H., Jr., "Flocculation, Subsidence,
and Filtration of Phosphate Slimes", I. General. Journal Colloid
Science, p. 704 (1956).
29. Lea, W. L., Rohlick, G. A., and Katz, W. J., "Removal of Phosphates
from Treated Sewage", Sewage and Industrial Wastes, p. 261 (1954).
30. Mulbarger, M.C., et al, "Lime Clarification, Recovery, Reuse, and
Sludge Dewatering Characteristics", Journal Water Pollution Control
Federation, p. 2070 (1969)..
31. Morgan, J.J. and Englebrecht, R.S., "Effects of Phosphates on Co-
agulation and Sedimentation of Turbid Waters", Journal American Water
Works Association, p. 303 (1960).
32. O'Melia, C. R., "A Review of the Coagulation Process", Public Works
p. 87 (May 1969).
33. Rose, J.L., "Removal of Phosphorus By Alum", Presented at the FWPCA
Seminar on Phosphate Removal, Chicago, Illinois (June 26, 1968).
34. Sawyer, C.N., "Some New Aspects of Phosphates in Relation to Lake
Fertilization", Sewage and Industrial Wastes, p. 768 (1952).
35. Sebastian, Frank, and Sherwood, Robert, "Clean Water and Ultimate
Disposal", Water & Sewage Works, (August 1969).
367
-------
36. Schmid, L.A., and McKinney, R.E., "Phosphate Removal by a Lime-
Biological Treatment Scheme", Journal Water Pollution Control Feder-
ation, p. 1259 (1969).
37. Stumm, W. and Morgan, J.J., "Chemical Aspects of Coagulation",
Journal American Water Works Association, p. 971 (1962).
38. Walker, J.D., "High Energy Flocculation", Journal American Water
Works Association, p. 1271 (1968).
39. Wuhrmann, K., "Objectives, Technology, and Results of Nitrogen and
Phosphorus Removal", Advances in Water Quality Improvement, I,
University of Texas Press, Austin, Texas (1968).
40. Wukasch, R. F., "The Dow Process for Phosphorus Removal", Present-
ed at FWPCA Seminar on Phosphate Removal, Chicago, Illinois (1968).
RECARBONATION.
41. Anon., "Submarine Burners Make CO2 For Softening Recarbonation",
Water Works Engineering, p. 182 (1963).
42. Compressed Gas Assoc., Pamphlet G-6, "Carbon Dioxide", 2nd Edi-
tion, New York (1962).
43. Compressed Gas Assoc., Pamphlet G-6 IT, "Tentative Standard for
Low Pressure Carbon Dioxide Systems At Consumer Sites", New York
(1966).
44. Gulp, R.L., and Gulp, G.L., Advanced Wastewater Treatment, Van
Nostrand Reinhold Co., 450 W. 33rd St., New York, N.Y. (1971).
45. Fair,M.F. and Geyer, J.C., Water Supply and Waste Disposal, John
Wiley & Sons, Inc., New York, N.Y. (1954).
46. Handbook of Compressed Gases, Compressed Gas Assoc., Reinhold
Book Corp., New York (1962).
47. Haney, Paul D. and Hamann, Carl L., "Recarbonation and Liquid Car-
bon Dioxide", Journal American Water Works Association, p. 512 (1969),
48. Hoover, Charles P., Water Supply and Treatment, Eighth Edition,
Bulletin 211, National Lime Association, Washington, D. C.
368
-------
49. Ross, R.D., Industrial Waste Disposal. Reinhold Book Corp., New
York, N.Y. (1968).
50. Ryznar, John W., "A New Index For Determining Amount of Calcium
Carbonate Scale Formed by a Water", Journal of the American Water
Works Association. (April 1944).
51. Scott, L.H. , "Development of Submerged Combustion For Recarbona-
tion", Journal American Water Works Association, p. 93 (1940).
52. Walker Process Co., Bulletin No. 7-W-83, Carball CO? For Recar-
bonation, (May 1966).
LIME RECOVERY AND REUSE.
53. Aultman, W.W., "Reclamation and Reuse of Lime in Water Softening",
Journal American Water Works Association, p. 640 (1969).
54. Black, A.P. , and Eidsness, F.A. , "Carbonation of Water Softening
Plant Sludge", Journal American Water Works Association,p. 1343(1957),
55. Crow, W.B., "Techniques and Economics of Calcining Softening Slud-
ges-Calcination Techniques", Journal American Water Works Assocv
p. 322, (1960).
56. Eades, J.L. , and Sandberg, P.A., "Characterization of the Properties
of Commercial Lime by Surface Area Measurements and Scanning Elec-
tron Microscopy", The Reaction Parameters of Lime, ASTM SIP 472,
American Society for Testing and Materials, pp 3-24 (1970).
57. Mulbarger, M.C., et al, "Lime Clarification, Recovery, Reuse and
Sludge Dewatering Characteristics", Journal Water Pollution Control
Federation, p. 2070 (1969).
58
. Nelsen, F.G., "Recalcination of Water Softening Plant Sludge", Jour.
American Water Works Association, p. 1178 (1944).
NITROGEN REMOVAL.
59. Gillie, G.G. , et al, "The Reclamation of Sewage Effluents for Domes-
tic Use", Third International Conference on Water Pollution Research,
Munich, Germany, Section II, Paper I, WPCF, Washington, D.C.(1966)
60. Gulp, R.L. , "Nitrogen Removal by Air Stripping", Presented at the 2nd
Annual Univ. of Cal. Sanitary Engineering Research Lab. Workshop,
Tahoe City, California, (June 26, 1970).
369
-------
61. Gulp, R.L., and Moyer, H.E., "Wastewater Reclamation and Export
at South Tahoe", Civil Engineering, p. 38 (June, 1969).
62. Kuhn, P.A., "Removal of Ammonium Nitrogen from Sewage Effluent",
Unpublished MS Thesis, University of Wisconsin, Madison, Wiscon-
sin (1956).
63. Prather, B.V., "Wastewater Aeration May Be Key To More Efficient
Removal of Impurities", Oil and Gas Journal, p. 78 (Nov. 1969).
64. Prather, B.V., "Chemical Oxidation of Petroleum Refinery Wastes",
Presented at the 13th Industrial Wastes Conference, Oklahoma State
University, Stillwater, Oklahoma (Nov. 1962).
65. Prather, B.V., and Gaudy, A.F., "Combined Chemical Physical and
Biological Processes in Refinery Wastewater Purification", Presented
at the 29th Midyear Meeting of the American Petroleum Institute's
Division of Refining, St. Louis, Missouri (May 1964).
66. Sawyer, C.N., Chemistry for Sanitary Engineers, McGraw-Hill Book
Co., New York (1960).
67. Slechta, A.F. and Gulp, G.L., "Water Reclamation Studies At The
South Tahoe Public Utility District", T ournal Water Pollution Control
Federation, p. 787 (1967).
68. Smith, C.E., and Chapman, R.L., "Recovery of Coagulant, Nitrogen
Removal, and Carbon Regeneration in Wastewater Reclamation", Final
Report by South Tahoe PUD to FWPCA, Demonstration Grant WPD-85
(June 1967).
MIXED MEDIA FILTRATION.
69. Conley, W. R., Jr., and Hsiung, K., "Design and Application of Mul-
timedia Filters", Journal American Water Works Assoc., p. 97 (1969).
70. Conley, W.R., "Experiences with Anthracite Sand Filters", Journal
American Water Works Association, p. 1473 (December 1961).
71. Conley, W. R., and Pitman, R.W., "Innovations in Water Clarifica-
tion", Journal American Water Works Assoc.,p. 1319 (October 1960)
72. Conley, W.R., Jr., "Integration of the Clarification Process", Journ.
American Water Works Association, p. 1333 (1965).
370
-------
73, Gulp, G.L., "Secondary Plant Effluent Polishing", Water and Sewage
Works, p. 145 (April 1968).
74. Gulp, R.L., and Gulp, G.L., Advanced Wastewater Treatment, Van
Nostrand Reinhold Co., New York City (March 1971).
75. Gulp, R.L., "Filtration", Chapter 8, Water Treatment Plant Design
Manual, American Water Works Assoc.. 2 Park Ave .. N.Y. (1969).
76. Gulp, R.L., "New Water Treatment Methods Serve Richland", Public
Works, p. 86 (July 1964).
77. O'Farrell, T.P., Bishop, D.F., and Bennett, S.M., "Advanced Waste
Treatment at Washington, D.C. ", Presented at the 65th Annual AICHE
Meeting, Cleveland, Ohio (May 1969).
78. O'Melia, C.R., and Crapps, K.K., "Some Chemical Aspects of Rapid
Sand Filtration", JAWWA, p. 1326 (October 1964).
79. Rice, A. H. , and Conley, W.R. , "The Microfloc Process in Water
Treatment", Tappi, 167A (1961).
80. Robeck, G.G., Clarke, N.A., and Dostal, K.A., "Effectiveness of
Water Treatment Processes in Virus Removal", Journal American Water
Works Association, p. 1275 (October 1962).
81. Robeck, G.G., Dostal, K.A., and Woodward, F.L., "Studies of Mod-
ifications in Water Filtration", Journal AWWA, p. 198 (Feb. 1964).
82. Tchobanoglous, G., and Eliassen, R., "Filtration of Treated Sewage
Effluent", Journal Sanitary Engineering Division, American Society of
Civil Engineers, p. 243 (1970).
83. Yao, K.M., Habibian, M.T., and O'Melia, C.R., "Water and Waste-
water Filtration: Concepts and Application", submitted to Environmental
Science & Technology (October 1970).
GRANULAR ACTIVATED CARBON ADSORPTION.
84. Bishop, D.F. , et al, "Studies On Activated Carbon Treatment", Iburn.
Water Pollution Control Federation (Feb. 1967).
371
-------
85. Calgon Corp., "Water and Waste Treatment with Granular Activated
Carbon", General Catalog (1970).
86. Cooper, J.C., and Hager, D.G., "Water Reclamation With Activated
Carbon", Chemical Engineering Progress, p. 85 (Oct. 1966).
87. Cover, A.E., and Wood, C.D., "Appraisal of Granular Carbon Con-
tactors, Phase III", FWPCA Report No. TWRC-12, (May 1969).
88. Cover, A.E., and Pieroni, L.J., "Appraisal of Granular Carbon Con-
tactors, Phases I & II", FWPCA Report No. TWRC-11, (May 1969).
89. Gulp, R.L., "Wastewater Reclamation at South Tahoe PUD", Journal
American Water Works Association, p. 84 (1968).
90. Fornwalt, H.J., and Hutchins, R.A., "Purifying Liquids With Activat-
ed Carbon", Chemical Engineering, p. 155 (May 9, 1966).
91. Hassler, J. W., Activated Carbon, Chemical Publishing Co., New
York, New York (1963).
92. Hopkins, C.B., Weber, W.J., Bloom, Ralph, "A Comparison of Ex-
panded Bed and Packed Bed Adsorption Systems", Report No. TWRC-2.
FWPCA (Dec. 1968).
93. Hager, D.G., and Flentje, M.E., "Removal of Organic Contaminants
By Granular Carbon Filtration", Journal American Water Works Assoc.,
p. 1440 (1965).
94. Joyce, R.S., Allen, J.B., and Sukenik, V.A., "Treatment of Munici-
pal Wastewater By Packed Activated Carbon Beds", Journal Water
Pollution Control Federation, p. 813 (1966).
95. Morris, J.C., and Weber, W.J., "Adsorption of Biochemically Re-
sistant Materials From Solution", USPHS AWTR Publication No.9 (1964).
96. O'Farrell, T.P., Bishop, D.F., and Bennett, S.M., "Advanced Waste
Treatment At Washington, D.C. ", Presented at the 65th Annual AICHE
Meeting, Cleveland, Ohio (May 1969).
97. Parkhurst, J.D., Dryden, F.D., McDermott, G.N. and English, J.,
"Pomona Activated Carbon Pilot Plant", Journal WPCF. p. R70 (1967).
98. Rizzo, J.L. and Schade, R.E., "Secondary Treatment With Granular
Activated Carbon", Water & Sewage Works, p. 307 (August 1969).
372
-------
99. Slechta, A.F. and Gulp, G.L., "Water Reclamation Studies At The
South Tahoe Public Utility District", Journal WPCF, p. 787 (1967).
100. Smith, C.E., and Chapman, R.L., "Recovery of Coagulant, Nitrogen
Removal, and Carbon Regeneration In Wastewater Reclamation", Final
Report to FWPCA, Demonstration Grant WPD-85 (June, 1967).
101. Westvaco Bulletin, Activated Carbon and Wastewater, W. Virginia
Pulp and Paper Company (1970).
REGENERATION OF GRANULAR CARBON.
102. Gulp, G.L., and Slechta, A., "Plant Scale Reactivation and Reuse of
Carbon in Wastewater Reclamation", Water & Sewage Works, p. 425,
(Nov. 1966).
103. Gulp, R.L., "Wastewater Reclamation at South Tahoe PUD", Journal
American Water Works Association, p. 84 (1968).
104. Hassler, J.W., Activated Carbon, Chemical Publishing Co., New
York, New York (1963).
105. Juhola, A.J., and Tupper, F., "Laboratory Investigation Of The Re-
generation Of Spent Granular Activated Carbon", FWPCA Report No.
TWRC-7. (February 1969.)
106. Slechta, A.F., and Gulp, G.L., "Water Reclamation Studies At The
South Tahoe PUD", Journal Water Pollution Control Fed.,p.787 (1967).
107. Smith, C.E., and Chapman, R.L. , "Recovery Of Coagulant, Nitrogen
Removal, and Carbon Regeneration In Wastewater Reclamation", Final
Report to FWPCA, Demonstration Grant WPD-85 (June 1967).
lOS.Suhr, L.G., Chapman, R.L., and Gulp, R.L. , Operations Manual ,
For 7.5 MGD Water Reclamation Plant, South Tahoe PUD, (Sept 1967).
VIRUS REMOVAL.
109 Anon., "Transmission of Viruses by the Water Route", Interscience
Publishers, A Division of John Wiley & Sons, New York (1967).
110. Berg, G. , "Virus Transmission by the Water Route III. Removal of
Viruses by Water Treatment Procedures", Health Lab. Science, 3:170
(1966).
373
-------
111. Chang, S.L., et al, "Removal of Coxsackie and Bacterial Viruses in
Water by Flocculation", Amer. Journal Public Health, p. 51 (1958).
112. Chang, S.L., "Viruses, Amebas, and Nematodes and Public Water
Supply", Journal AWWA, p. 288 (March 1961).
113. Chang, S.L., "Waterborne Viral Infections and Their Prevention",
Unpublished manuscript.
114. Clarke, N.A., Berg, G., Liu, O.C., Metcalf, T., Sullivan, R. and
Vlassoff, L., "Committee Report, Viruses in Water", Journal AWWA,
p. 491 (1969).
115. Clarke, N.A., and Chang, S.L., "Enteric Viruses in Water", Journ.
AWWA. p. 1299 (October 1959).
116. Clarke, N.A., Berg, G-, Kabler, P.W., and Chang, S.L., "Human
Enteric Viruses in Water: Source, Survival and Removability", Ad-
vances in Water Pollution Research, Proc. Int. Conf., London, 1962,
Vol. 2, Pergamon Press, London (1964).
117. Clarke, N.A., et al, "Removal of Enteric Viruses From Sewage by
Activated Sludge Treatment", Amer. Journal Public Health, p.1118(1961).
118. Clarke, N. A., Stevenson, R.E., and Kabler, P.W., "Survival of
Coxsackie Virus in Water and Sewage", Journal AWWA, p. 677 (1956).
119. Dennis, Joseph M., "1955-56 Infectious Hepatitis Epidemic in Delhi,
India", Journal AWWA, p. 1288 (October 1959).
120. Dieterich, B.H., "A Study of the Adsorption Phenomenon in the Re-
moval of Bacterial Virus by Sand Filtration", unpublished thesis.
Harvard University, Cambridge, Massachusetts (1953).
121. Hayward, M.L., "Epidemiological Study of an Outbreak of Infectious
Hepatitis", Gastroenterology, p. 504 (1946).
122. Hsiung, G.D., and Melnick, J.L., "Plaque Formation with Poliomye-
litis, Coxsackie, and Orphan (Echo) Viruses in Bottle Culture of Mon-
key Epithelial Cells", Virology, p. 533 (1955).
123. Hudson, H.E., Jr., "High Quality Water Production and Viral Dis-
ease", Tournal AWWA, p. 1265 (1962).
374
-------
124. Kabler, P.W., Clarke, N.A., Berg, G., and Chang, S.L., "Viricidal
Efficiency of Disinfectants in Water", Public Health Reportsr p.565,
(1961).
125. Kelley, S. , Winsser, J. , and Winkelstein, W., "Poliomyelitis and
Other Enteric Viruses in Sewage", Amer. Tourn. Public Health.D.72
126. Kelly, S., Sanderson, W.W., "The Effect of Chlorine in Water on
Enteric Viruses", American Tournal Public Health, p. 1233 (1958).
127. Mosley, J.W., Schrack, W.D., Mafter, L.D., and Den sham, T.W.,
"Infectious Hepatitis in Clearfield County, Pennsylvania", American
Journal Medicine, p. 555 (1959).
128. Neefe, J.R. , and Stokes, J., Jr., "An Epidemic of Infectious Hepa-
titis Apparently Due to a Waterborne Agent", Tournal American Medi-
cal Association, p. 1063 (1945).
129. Pozkanzer, D. , and Beadenkopf, W., "Waterborne Infectious Hepa-
titis from a Chlorinated Municipal Supply", Public Health Reports.
p. 745 (1961).
130. Rhodes, A.J. , et al, "Prolonged Survival of Human Poliomyelitis
Virus in Experimentally Infected River Water", Can. Tournal Public
Health, p. 46 (1950).
131. Robeck, G.G., Clarke, N.A., and Dostal, K.A., "Effectiveness of
Water Treatment Processes in Virus Removal", Tourn. AWWA. p. 1274
(October 1962).
132. Sanderson, W.W. , and Kelly, S., "Discussion of Human Enteric
Viruses in Water: Source, Survival and Removability", Advances in
Water Pollution Research, Proc. Int. Conf., London, 1962, Pergamon
Press, London, Vol. 2 (1964).
133. Task Group Report, "Physiologic and Health Aspects of Water Qual-
ity", Tournal AWWA, p. 1354 (November 1961).
134. Taylor, F.G., Eagen, J.H., Smith, H.F.D., and Coene, R.F.,"The
Case for Water-Borne Infectious Hepatitis", American Journal Public
Health, p. 2093 (1966).
135. Vogt, J.E., "Infectious Hepatitis Epidemic at Posen, Michigan",
Tournal AWWA, p. 1238 (October, 1961).
375
-------
136. Weibel, S.R., Dixon, F.R., Weidner, R.B., and McCabe, L.J.,
"Waterborne Disease Outbreaks, 1946-1960", Journal AWWA, p.947,
(September 1964).
137. Weidenkopf, S.J., "Inactivation of Type I Poliomyelitis Virus with
Chlorine", Virology, p. 56 (1958).
DISINFECTION.
138. Bureau of San. Engineering, Calif. Dept. of Public Health, "Waste-
water Chlorination for Public Health Protection", Proc. 5th Annual
Sanitary Engineering Symposium (May 1970).
139. Collins, H.F., Selleck, R.E., and White, G.C., "Problems in Ade-
quate Sewage Disinfection", ASCE Natl. Specialty Conference on
Disinfection, University of Massachusetts, Amherst, Massa.
140. Meiners, A.F., Lawler, E.A., Whitehead, M.D., and Morrison, J.I. ,
"An Investigation of Light-Catalyzed Chlorine Oxidation for Treatment
of Wastewater", Robert A. Taft Water Research Center, Report No.
TWRO-3 (December 1968).
141. Moore, Edward W., "Fundamentals of Chlorination of Sewage and
Wastes", Water & Sewage Works Journal, p. 130 (1951).
142. Selleck, R.F., and Collins, H.F., "Disinfection in Wastewater
Reuse", Bureau of San. Engineering, Calif. Dept. of Public Health.
143. Smith, C.E., and Chapman, R.L., "Recovery of Coagulant, Nitrogen
Removal, and Carbon Regeneration in Waste Water Reclamation", Final
Report, FWPCA Demonstration Grant WPD-85 (June 1967).
INDIAN CREEK RESERVOIR.
144. Lake Tahoe Area Council, "Eutrophication of Surface Waters-Indian
Creek Reservoir", First Progress Report (EPA Grant No. 16010 DNY),
South Lake Tahoe, California (May 1970).
COSTS.
145. Evans, David R., and Wilson, Jerry C., "Actual Capital and Operat-
ing Costs for Advanced Waste Treatment", Presented to the Annual
Meeting of the WPCF, Boston, Massachusetts (1970).
376
-------
146. Smith, R., and McMichael, W.F., Cost and Performance Estimates
For Tertiary Wastewater Treating Processes. R. A. Taft Water Re-
search Center Report No. TWRC-9 (1969).
WATER REUSE.
147. Anon. , "Progress Report of Committee on Quality Tolerances of
Water for Industrial Purposes", Journal New England Water Works
Association, p. 1,021 (August 1958).
148. Bouwer, H., "Returning Wastes to the Land, A New Role For Agri-
culture", Journal of Soil and Water Conservation, 23 (Sept-Oct 1968).
149. Gillie, G.G., Van Vuuren, L.R.J. , Stander, G.J., and Kolbe, F.F.,
"The Reclamation of Sewage Effluents for Domestic Use", Proceedings,
Third International Conference on Water Pollution Research, Munich,
Germany, Published by the Water Pollution Control Federation, Wash-
ington, D.C. (1965).
150. Connell, C.H., and Forbes, M.C., "Once Used Municipal Water as
Industrial Supply, In Retrospect and Prospect", Water and Sewage
Works, p. 397 (1964).
151. Haney, Paul D., "Water Reuse for Public Supply", Journal American
Water Works Association, p. 73 (1969).
152. Kearns, J.T., "Water Conservation and Its Application to New Eng-
land", Journal American Water Works Association, p. 1379 (1966).
153. Merrell, J.C., Jr., and Katko, A., "Reclaimed Waste Water for San-
tee Recreational Lakes", Journal Water Pollution Control Fed. (1966).
154. Metzler, D.F., Gulp, R.L., et al, "Emergency Use of Reclaimed
Water for Potable Supply at Chanute, Kansas", Journal American
Water Works Association, p. 1021 (August 1958).
155. Parkhurst, J.D., and Garrison, W.E., "Water Reclamation at Whit-
tier Narrows", Journal Water Pollution Control Federation, p. 1094.
156. Stander, G.J., and Van Vuuren, L.R.J., "The Reclamation of Potable
Water from Wastewater", Journal Water Pollution Control Federation,
p. 355, (1969).
157. Steffen, A.J., "Control of Water Pollution by Waste Utilization: The
Role of the WFCF", Water and Sewage Works, p. 384 (1964).
377
-------
158. Stephan, D.G., and Weinberger, L.W., "Water Reuse-Has It Ar-
rived?", Journal Water Pollution Control Federation, p. 529 (1968).
159. U.S. Public Health Service, Draft Policy on Waste Water Reclama-
tion, Unpublished, (1968).
160. Water Quality Criteria, Edited by McKee, J.E., and Wolf, J.W.,
Resources Agency of California, State Water Quality Control Board,
Pub. No. 3-A (1963).
161. Whetstone, G.A., "Reuse of Effluent in the Future with an Annotated
Bibliography", Texas Water Development Board Report 8, Austin, (1965)
162. Wilcox, L.V., "Agricultural Uses of Reclaimed Sewage Effluent",
Sewage Works Journal, p. 24 (1948).
163. Wolman, A. , "Industrial Water Supply From Processed Sewage Treat-
ment Plant Effluent at Baltimore, Md. ", Sewage Works Journal (1948).
378
-------
SECTION XXVIII
LIST OF PUBLICATIONS
RESULTING FROM DEMONSTRATION GRANT PROGRAM
1. Gulp, G.L., and Hansen, S., "How To Clean Wastewater for Reuse".
American City, p. 96 (June 1967).
2. Gulp, G.L., and Slechta, A.F., "Nitrogen Removal From Sewage",
Final Progress Report, USPHS Demonstration Grant 86-01 (Feb.1966).
3. Gulp, G.L., and Slechta, A.F., "Nitrogen Removal from Waste Efflu-
ents", Public Works (Feb. 1966).
4. Gulp, G.L., and Slechta, A.F., "Plant Scale Reactivation and Reuse
of Carbon in Waste Water Reclamation", Water and Sewage Works.
pp 425-431 (November 1966).
5. Gulp, G.L., and Gulp, R.L., "Reclamation of Waste Water at Lake
Tahoe", Public Works. (February 1966).
6. Gulp, G.L., and Slechta, A.F., "Plant Scale Regeneration of Granular
Activated Carbon", Final Progress Report, USPHS Demonstration Grant
84-01 (February 1966).
7. Gulp, G.L., and Slechta, A.F., "Recovery and Reuse of Coagulant
From Treated Sewage", Final Progress Report, USPHS Demonstration
Grant 85-01 (February 1966).
8. Gulp, G. L. , and Slechta, A.F. "Tertiary Treatment Practices", Pres-
ented at the 38th Annual Conference of the California Water Pollution
Control Assoc. , Monterey, California (April 1966).
9. Gulp, G.L. , and Slechta, A.F., "Water Reclamation Studies at the
South Tahoe Public Utility District", TWPCF, pp 787-814 (May 1967).
10. Gulp, R.L., "A New Process for Wastewater Reclamation", Proceeds.
Fifth Texas Industrial Water and Waste Conference (June 1965).
11. Gulp, R.L., and Gulp, G.L., Advanced Wastewater Treatment. Van
Nostrand Reinhold Co. , New York (February 1971).
12. Gulp, R.L., "Design for Nutrient Removal", Sanitary Engineering Inst.
University of Wisconsin (March 1969).
379
-------
13. Gulp, R. L., "Integration of Advanced Wastewater Treatment Process-
es", FWQA AWT Seminar, San Francisco (October 1970).
14. Gulp, R.L., "Nitrogen Removal By Air Stripping", Second Annual Uni-
versity of Calif. Sanitary Engineering Workshop, Tahoe City Calif.
(June 1970).
15. Gulp, R. L. , "Nitrogen Removal and Recent Experience at South Tahoe",
CWPCA Conference, Anaheim (May 1969).
16. Gulp, R.L., "Nutrient Removal in Water Reclamation at South Tahoe"
Presented at the American Water Works Assoc. National Convention,
Atlantic City, New Jersey (June 1967).
17. Gulp, R. L., and Suhr, L.G., "Operations Manual for 7.5 MGD Water
Reclamation Plant", Cornell, Rowland, Hayes and Merryfield, and
Glair A. Hill and Associates (September 1967).
18. Gulp, R.L., "Phosphorus Removal in a 7-1/2 MGD Plant at South Tahoe",
FWPCA Phosphorus Removal Workshop, Chicago (June 1968).
19. Gulp, R. L. , "Reclaimed Water As A Resource", Seminar on Tertiary
Treatmentof Wastewater, University of Arizona, Tucson (January 1969).
20. Gulp, R.L., and Roderick, R.E., "The Lake Tahoe Water Reclamation
Plant", JWPCF, p. 147 (February 1966).
21. Gulp, R.L., "The Operation of Wastewater Treatment Plants1,1 Public
Works Magazine, (In three parts-October, Nov. and Dec. 1970).
22. Gulp, R.L., "The Present Status of Phosphorus Removal for Water
Pollution Control", Public Works, (October 1969).
23. Gulp, R.L., "The Tahoe Process for Nutrient Removal", 7th Industrial
Water and Waste Conference, Austin, Texas (June 1967).
24. Gulp, R.L., "The World's Most Advanced Wastewater-Purification
Plant", American City, p. 77 (August 1968).
25. Gulp, R.L., and Moyer, H.E., "Wastewater Reclamation and Export
At South Tahoe", Civil Engineering, p. 38 (June 1959.
26. Gulp, R.L., "Wastewater Reclamation by Tertiary Treatment", JWPCF
p. 799, (June, 1963).
27. Gulp, R.L., "Water Reclamation at South Tahoe", Water and Wastes
Engineering, p. 36 (April 1969).
380
-------
28. Gulp, R.L., "Wastewater Reclamation at South Tahoe Public Utility
District, JAWWA. Vol. 60, p 84 (January 1968).
29. Evans, D.R. , and J.C. Wilson, "Actual Capital and Operating Costs
for Advanced Waste Treatment", WPCF Nat.Meet.Boston (Oct.1970).
30. Hassler, A. , and Larsen, James, "Giving Our Lakes A Chance", World
Book Encyclopedia. 1971 Science Supplement, p. 138 (1971).
31. Moyer, Harlan E., "The South Tahoe Water Reclamation Project",
Public Works, p. 7 ( December 1968).
32. Friday, W., Moyer, H.E., and Gulp, R.L., "The Most Complete Waste-
water Treatment Plant in the World", The American City. 123 (Sep.1964).
33. Sebastian, P.P., and Sherwood, R.J., "Clean Water and Ultimate Dis-
posal", Water and Sewage Works, p. 297 (August 1969).
34. Sebastian, P.P., "Wastewater Reclamation and Reuse", Water and
Wastes Engineering, p. 46 (July 1970).
35. Stevens, Leonard, "Breakthrough in Water Pollution", Readers Digest.
(June 1971).
36. Smith, C.E., and Chapman, R.L., "Recovery of Coagulant, Nitrogen
Removal, and Carbon Regeneration in Waste Water Reclamation", Final
Report of Project Operations, FWPCA Grant WPD-85 (June 1967).
37. Smith, C.E. , "Use and Reuse of Lime In Removing Phosphorus and
Nitrogen from Wastewater", Annual Meet. ,Nat'l Lime Assoc., Phoenix.
38. Suhr, L.G., and Culp, R.L. , "Design and Operating Data for a 7.5
MGD Nutrient Removal Plant", Annual Conf., WPCF, Chicago(Sep. 1968).
39. Suhr, G.L., and Culp, R.L., "Nitrogen and Phosphorus Removal by
High pH Lime Coagulation", Presented at the Annual Convention of the
Pacific Northwest Water Pollution Control Assoc., Portland, Ore. (1966).
40. Tharratt, Bob, "An Exciting New Era", Outdoor California (Jul/Aug 1970).
41. Wakeman, R., "New Lake at South Lake Tahoe, California", Water and
Sewage Works, (August 1967).
42. Young, G., "Pollution, Threat to Man's Only Home", Nat'l Geographic
p. 758, 774, 775 (Dec. 1970).
381
-------
APPENDIX A
UNITED STATES VISITORS
SOUTH LAKE TAHOE WATER RECLAMATION PLANT
1964
Alabama
Alaska
Arizona
California 82
Colorado
Connecticut
Delaware
District of Columbia
Florida
Georgia
Hawaii
Idaho
Illinois
Iowa
Kansas 2
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada 17
New Jersey
New Mexico
New York
North Carolina
Ohio 2
Oklahoma
Oregon 1
Pennsylvania
South Carolina
Tennessee
Texas
Utah
Virginia
Washington
Wisconsin
Wyoming 1
Total 105
June
1965
1
188
2
2
1
2
1
10
3
1
1
2
1
30
1
5
5
8
5
5
1
2
277
1964
1966
119
3
4
2
3
1
2
10
3
1
1
8
5
3
165
to January
1967
68
1
2
2
1
2
6
2
1
4
2
2
3
5
1
1
1
1
2
107
1971
1968
179
1
2
3
1
11
5
2
3
3
1
8
2
8
3
1
7
4
1
2
5
1
4
257
1969
2
2
1
729
5
4
1
11
1
5
1
1
10
6
1
5
5
4
8
3
4
2
1
43
1
1
9
1
9
1
43
10
1
6
12
6
10
3
2
970
1970
1126
7
8
10
6
2
8
3
10
9
8
7
6
10
4
2
145
17
15
18
16
12
2
8
8
7
9
1483
Total
2
2
2
2491
16
9
16
28
8
7
11
5
38
16
8
1
31
22
15
20
5
8
4
2
257
26
1
39
1
38
3
86
41
2
2
16
28
14
30
6
7
3364
383
-------
FOREIGN VISITORS
SOUTH LAKE TAHOE WATER RECLAMATION PLANT
January 1965 - January 1971
COUNTRY
1965
1966 1967
1968
1969
1970
Total
Argentina
Australia
Belgium
Brazil
British Honduras
Canada
Czechoslovakia
Denmark
England (United Kingdom)
France
Ghana
Hong Kong
India
Indonesia
Israel
Italy
Japan
Netherlands
New Zealand
Norway
Poland
Republic of China
Russia
Singapore
Spain
Sweden
Switzerland
Thailand
Turkey
Union of South Africa
Uruguay
Venezuela
West Germany
West Pakistan
Totals
1
1 3
5
1 1
1 2 3
536
2
1 1
37 5
3
421
3
2
2 2
1
5
2
7 18 23 30
1
2
2
14
4
2
3
1
2
3
1
5
1
2
3
2
3
1
1
53
1
3
3
5
1
9
2
1
11
6
1
1
3
23
1
1
2
6
1
7
1
15
1
16
121
3
9
3
12
1
25
6
3
20
20
1
1
5
3
5
1
43
1
1
2
3
1
6
2
1
17
4
2
2
22
1
2
22
2
252
384
-------
APPENDIX B
TABULATIONS
OF
DAILY
LABORATORY AND FLOW DATA
385
-------
SOUTH TAIIOI: I'lwt.ic UTILITY DISTIUCT - WATIIU INNOVATION IMANT _Aijr.u
MONTin.Y TAIIUIATION OF ItOW AND IAHOKATORY OATA (Month)
l)y\-fE (First Month of Export)
196JL-
OO
00
en
Elant.JUov.'.-MG .
Peak Flow R.ito MGD
Flav.- I;ito I:-..!ij;i Crock
>?•-.-.• ->ir. MO
Flc.'.v Fron Indian Crock
.?.-::crvoir, MG
T'jMl Fl'j'.v From Other
O-:'Ms. MG
S-doy SOD (mg/1)
COD (mo/I)
ri'i-.-.'-.-.'V-l r,oll/ 1 P)
AlVili.nif/(rr.3/l CoCOj)
_ir--;.-!.TjS5(n-3/l C-.CO,)
_JT-.--.l.n!-:-:-5lv.'I.S'i1|iJ-!- /I,
„_!o 'ir,'i/l)
'yjrljo.i fir.';.", iron r QV.
..I
i.l
2.1
0
0
1.7
col
....2-
.Lil/
1,7
0
n
1.3
inns
LI
1»7
0
0
0.6
2_._1
2.1
0
0
0.6
- —
.....
S
2.1
2,1
0
0
1.0
_.6.
2.2
2.2
0
0
1.0
_J.
2.2
?..2
0
0
0.9
ra~
2.2
2.2
0
0
0.9
7.7
11*
0
1.3
8.0
1.8
.04
......
_9_
2.2
2.2
0
0
1.0
UL
5*
.01
1.3
7.7
l.S
J.O.
1.9
1.9
0
0
0.5
12
1
.01
1.5
7.9
2.0
1.3
....
..a.
2.2
A-JL
0
0
1.5
9.5
1
.01
0.5
7.9
2.5
1.5
17.
2.0
2.0
0
0
1.0
8.1
1
.01
0.5
7.8
2.5
1.5
.09
229
1.0
.13.
2.0
A, 6
2.0
0
0
0.6
.....
.1.4.
1.8
1..5
UP
0
0
0.7
....
1.5
2.0
S...3
2.4.P
0
0
1.5
11
1
.01
1.0
7.6
1.8
1.0
<2.?l
.IP.
0.6
._..
16
1.8
A,_Q
1.8
0
0
0.7
20
3<
.01
1.6
8.6
2.5
1.5
<2.2
27
<.l
—
17
2.0
:L7.
2.0
0
0
1.7.
21
1
.01
1.5
8.5
2.5
1.0
<2.2
0.4
—
-IB.
1.9
.-us
1.9
0
0
0.7
M
0*
.01
1.0
8.5
0.1
2.0
<2.2
0.3
-.13. 2.0
1.8
•LS>.
1.8
0
0
0.7
19
0
.03
0.9
8.7
1.0
2.0
9.2
0
21
0
0.5
265
2-18
34
2.4
A, .5
.2^
0
0
1.2
2.5
2.0
0.7
--
-.2.1.
1.9
5.5.
1.9
0
0
1.2
ZZ.._23.
1.9
4.J
1.9
0
0
1-JL
12
.06
1.3
9.0
2.5
2.5
<2.2
0.4
-
1.8
&.0
Lu?
0
0
2.9
22
.03
1.8
8.7
2.5
l.S
-------
00
SOUTH TAHOE PUBLIC UTIUTY DISTRICT - WATHR RENOVATION PLANT
MONTHLY TABUIATION OF FLOW AND LABORATORY DAT"A
DATE
_JM?iL.
(Month)
Wear)
_Eli;,' rinv, MO ,. . .
Peak Dow Rote MGD
How Into Indian Creek
Reservoir. MG
Flow Fro.-n Iivli.-m Crock
Reservoir, MG
Total Flow From Other
O-;'!'-t?. MG
5 -day BOD (rm/1)
COD (.T.g/1)
Susronde'i Solids (mg/1)
MBAS (rt!<3/l)
Turbidity, J U
pH (fH units)
Chlor.ne Residual (mi ' "ol vcd Sol ids Jnr^l
_Chloridr (mg/1)
•Ifate (n>7/l)
1^9
4.1
1.9
0
0
19
?.
.05
1.3
7.7
_
2.7
2.J1
(2.2
.03
2_
j-a
4.0
1.9
0
_D_
IS
0
.05
0.8
7.9
1.2
ZJH
<2,2
.03
3 4 S 6 7
? n
4.2
2.0
0
0
1.8
16
2
.05
0.6
7.7
3_i
2^.6
<2,2
18.(
0.1
.09
?in
130
328
35
2^2_
4.6
2.2
.JP_
_JL
7 ?
4.6
2,2
0
0
U
5.0
1,9
0
..Q_
flJl
16
1
,05
0.5
6.8
3.5
2.8
<2,2
.31
1.9
S.9
1,9
0
Q
Z_JL
11
2
,05
0.7
6.9
.
0.1
C2t2
.53
._8_
1.9
6.0
1.9
._Q_
JD...
0,7
n
4
,n^
1.0
7.1
4,3
0.1
5,1
.33
9 10
LJ.
4.3
LJL
0
0
Q^
13
2
.0?
0,5
7.1
1,2
1.1
<2.2
-
_
4.3
5,7
.43
1.9
5.9
1,9
0
0
QJL
R
1
,10
0.5
7.1
0,9
0.8
5.1
0
0
6.3
3.fl
.41
1S7
150
_
15
25
.11.
IA
4,9
2,1
o
0
12.
ZJ
5,4
z,i
0
0
2,0
1.3
2.2
.-11
1,9
5,5
1,9
0
0
1.4
S
1
.U
0.8
7.2
0.9
O.S
<2.2
.0
14 IS 16 17 1R 10 ?n 21 77. 71 74
2.0
4,6
2,0
JL
0
2.5
10
5
.15
0.6
6.8
1.2
0T3
5.1
0 :.
i
1.9
4,5
1 ,9
0
0
0.5
7
0
.17
1.0
7.0
1.7
U
1.2
1.9
5,8
1 ,t
-P_
0
O.f
9
0
.16
0.7
7.3
2.5
0.8
M6
2.0
2,0
4,0
2.JL
0
0
0.9
9
0
.17
0.7
7.2
2.9
1.1
<13.
0
0
12
Q.4
_
45
68
-
37
-
?_16
2 3
ua
4.6
1.9
0
n
2 n
IS
0
.14
0.7
7.5
1,5
1*5
<22
7, 7
?,n
5.1
x.n
_o_
0
•> '
16
0
.13
0.7
7.3
UL
>_J
16
? 7
1,9
4.
1.
_JL
0
l.n
17
0
.14
0.7
6.
JL.1)
U
2
1 ,
4,
1.9
.JL
0
o.n
13
0
,14
0.6
7.1
?,,?,
.LA
<2.2
_
0.3
6.9
0 fi
1 7
83
SO
60
33
18
..2.5.
2^4
5,4
?,,
Q
0
.26.
iJ
S,?
7
0
0
0.5
n i
0
<2.2
..?.?
JlJ
•i ?
1 9
0
'o
3.4
9
0
,16
0.3
7.1
? F
ja^j.
>16
1.2
-U
JLJ
1 i
? 1
0
0
,1.1
11
n
17
0.6
7.3
7
P ^
a. 2
1.5
19
JLJ
•1 1
? ]
JL
0
.1.S
13
n
?s
0.3
7.?
1 1
1 1
f?. ?
.10
7 1
^ ^
,> 1
0
0
.1.3
6
0
n
0.2
7.1
i •>
.
31^
UL
hi
2.4
0
P
3.S
11
0
.20
0.3
'.3
; _7
1 **
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT - WATER RENOVATION PLANT
MONTHLY ABULATION OF FLOW AND LABORATORY DATA
DATE
June
(Monti
1968
(Year)
CO
00
06
_ J>l,in» fin-.-/ Mrt
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir, MG
Flow Tro.'n In'lMn Greek
Rcsrrvoir, MG
Total 1'lov/ From Other
O'.'l.-ts, MG
>-'!.•>•/ r.OD (mi/\)
COD (rng/1)
Suspc-.ndod Solids (mg/1)
M3AS (mg/1)
Turbidity, J U
pH (pH units)
Chlorine Residual (mg/1)
Ir.;t4nt-ineous
30 Mln. Contact
I.uth
jLa
JL
0
r, 4
G.I
0
,24
0.4
7.4
0.4
0,4
i2_~2
O.S
2-J.
5.0
LJL
JL.
0
r. 7
5.8
0
.17
0,3
7.4
1.2
.58
-
0,7
2..0
5.1
I.JI
0
0
4.R
6.5
0
.13
0,3
7.4
2.1
.44
3
S'2,2
2.8
7.1
0.6
0.9
187
154
348
30
28
IS
2.6
5,4
2^.6.
_0_
0
"i
is
13.
5.4
2.J
0
0
0.5
7.5
0.9
,45
<2,Z
17
2.4
5.6.
2.4
0
0
5.9
12
0
.12
0.6
7.7
2.1
.44
<2,2
1.0
18
LJ.
5.7
2.5
0
0
5.4
11
2
.12
0.5
7.7
2.2
1.0
—
1 ,6
19 20 21 22 23 24 . 25 26 27 28 21
4^5.
LJL
4.8
0
0
r,.o
17
4
.16
0.5
8.2
—
1.4
2^.5.
5> 9
0
0
0
a
&
o
_ . ..
T_.a
2.0
6.0
0
0
0
]}
3
§
_
._
3.1
5,8
3.1
0
0
3.0
6,1
3.0
0
0
0.4
7 ,4
3.6
1.4
C2.2
?..?.
5.9
2.2
0
0
5.2
12
2
.13
0.3
fl n
1.7
2..1
C2.2
0.2
-
3.7
5,3
2.7
0
0
5,1
7
1
,13
0.3
7,6
5.6
2,6
&-JI
1.1
2,7
5,4
2.7
0
0
•1 S
8
0
.13
0.3
7 7
3.1
2.2
/2 . 2
0.4
?.a_
5.5
2.8
0
0
•1.4
S
1
.10
0.3
6.9
8.0
2.5
1.2
1.1
5.4
2.4
0
0
i ^
3.6
0
.11
1.0
7 ?
2.1
? ?
1 1 f
4.S
0.8
1 ,,1
246
140
324
33
25
LJL
5.4
3.0
0
0
30
2.7
5.3
2.7
0
0
0.4
6.9
3.6
•1 •»
, •» i
— U_.
1
!
• i
-
•
. ;
t
i
i
-------
00
00
(O
SOUTH TAIIOE PUBLIC UTILITY DISTRICT - WATF.R RENOVATION PLANT
MONTHLY \BULATION OF FL AND LABORATORY DAfA
DATE
IttLY
1969
jnth)
(Year)
EJant TJow^-MG
Peak Flow Rate MGD
Flow Into Indian Creek
R«<5T'/oir, MG
Flow From Indian Creek
Rrts^rvoir, MG
ToMl Flov/ From Other
Oi:'l»>ts, MG
5 -day BOD (mg/1)
COD (mg/1)
Suspended Solids (mo/1)
MBAS (ma/1)
Turbidity, I U
pH IpH units)
Chlorine Residual (mg/1)
Instantaneous
30 Mln. Contact
Luther Pass Station
Conforms (MPN/lOOml)
Uitroqen (mg/1 N)
XK33GQ9C *NOTE:
ammonia
nitrate
nitrite
Phosphate (mg/ I P)
AlXalinitytir.'j/l 00003)
Hardness(mg/l CaCO,)
TotM DissolvGdSoli'):;(-i'i/l
Chloride (mg/1)
Sulfate (mg/1)
_1 23 45 6 7 8 9 10 11 12
...I
5.7
2.6
0
0
3.6*
ft.n
1 .0
.13
0.3
7 S
1.9
2.1
<-2.2
1 R
- —
2..JL
5.5
2.6
0
0
4.3*
<1.2
2.0
.11
0.3
7 4
2.6
2.0
1-2.2
1 1
2..JL
5.5
2.8
0
0
3.7*
">.«
n.n
.10
0.2
7 ?
4.3
2.1
<2.2
Junr
of »
1 7
Z-l3.
5.7
2.9
0
0
4.*
0.2
3.5
2.5
4 t
astc
™
?-!-2.
6.1
3.2
0
0
3.5*
11.2
0.0
.10
0.3
7 I
2.8
2.6
<2.2
iru
watc
13.6
1.8
1 .9
1 'I
232
M6_
34.2_
29.5
30.0
111
6.7
3.3
0
0
July
'. a
2,JL
6.Z
2.9
0
0
0.5
1 A
2.8
1.7
>10
19,
ter
2..,6_
6.2
2_._6_
0
0
7.01
2.0
.12
0.5
7 n
2.6
1.5
<2.2
196
uly
1 R
2_,_6.
6.0
2_.6
0
0
6.4*
lfl.1
n.n
.10
0.5
1 I
1.3
1.0
2.2
_
>-o,
1 fl
Zji.
5.4
2.9
0
0
6.6*
io.n
2,0
.19
0.3
7,fi
1.7
1.3
<2.2
a 1st
SOD
1 fi
2^.9.
2.9
0
0
6.7*
in.i
2,0
.18
0.5
7 S
1.2
0.7
hlrj
s w
n n
2^.7
6.1
2.7
0
0
6.6*
16.(
4,0
.18
0.4
7,fi
1.4
0.7
<2.2
1, R
ire i
fi.3
5,1
3.5
1 1
208
138
260
21.3
22.8
JUJ-
!•_?.
6.1
3.2
0
0
3D
in o
r1-4'
?^.2.
5.6
2_.2
Q
0
0.5
7.4
1.3
0.9
<2.2
cadi
> sa
15, 16
2.9
5.6
2.9
2,2
0
6.6«
16.3
4.0
.20
0.3
7.5
1.5
1.1
2.2
igs
nple
1 7
2..9
5.8
2_J
7.1
0
7.0*
17.2
0.0
.20
0.3
7.5
1.0
1.3
>16
were
s cc
1 7
209
17.
2 . fl
5.9
.m
8,7
0
7.4*
12.3
1.0
.12
0.3
7.6
1.1
1.7
<2.2
obt
llect
i n
203
--
18 19 20 21 22 23
2^.7
6.0
2.7
8.7
0
S.4*
2.1
0.0
0.2
7.4
2.1
0.8
IPPC
;d a
n 4
22S
3^0
6.3
3.0
11,7
0
7.8*
12.6
7.0
.12
0.2
7.8
2.0
<2.2
bee
ter
9.6
1.7
1.0
187
134
303
63.8
27
3.0
6.1
3.0
(1,7
0
1USf
-hloi
3.1
5.9
3.1
8.7
0
0.2
1.8
1.0
<2.2
sni
Inat
J.9
6,0
2.9
4.3
0
L.2
11.2
2.0
.12
P. 2
8.1
1.1
1.0
>16
pips
on <
0.8
206
2.7
6,0
2.7
0
0
.01
1G.7
1.0
.09
0.2
7.5
2.1
1.2
9.2
wo
f w;
1.4
224
-2A
2_.2_
6,0
2.2
0
.0
0,4
10.9
1.0
.12
0.?
7.6
3.0
1.2
S.I
^ Ci
stew
I.I
226
rzs~
r-^O.
5.9
2.0
0
0
£J.
9.2
2.0
0.2
7.2
3.4
1.5
lice
a ter
0.8
213
.JZ.6_
L.?
5.4
2.2
3,8
0
0.2
1-1. •)
1.0
.12
1.0
7.1
2.0
!.•»
<2.2
Pd i
9.4
6,7
1.6
1.3
212
SO
179
42.5
52
ru
[?.,6
5,4
2.6
6.5
0
rlor
r"
[2.2
Li
2.2
6.5
0
0.3
7.7
3.9
3.1
>16
to c
,M
•» 1
1*1
2.2
0.5
0
16
ilori
0.6
208
..id
2.5
5,4
2.5
6.5
0
1.1
u.s
0.5
.16
9.2
7.5
3.5
2.9
>16
'.all,
0.8
193
H
r£
5.7
1.3
5.7
0
0.?
14. 5
o.o :
.18
Q.I '
7.6 i
1
3.2
1.2
>16
n
0.6
181
=
-------
SOUTH TAHOE PUr *C UTILITY DISTRICT - WATEP ^NOVATION PLANT
MONTHLY irtBULATION OF FLOW AND LABoi
Suspir.-Jod Sclids fl
3.9
1.0
173
112
190
39
2ft ..
2.3
5.1
2.3
0
0
2.3
5.0
2.3
0
0
0.3
7,5
1.6
1.3
5,1
2.4
5.1
2.4
0
0
0.4
1S.4
3,p
.19
0.2
7,6
1.9
1.9
>IL
0.8
202
2.5
5.1
2.5
0
0
0.4
11.8
QiQ
.19
0.2
7,4
1.8
1.6
>!!
O.S
217
2.6
S.3
2.6
0
0
0.6
11.9
0.0
49
0.1
7,5
2.0
1.8
2^2
0,2
212
2.5
6.1
2.5
0
0
1.3
U4
0.2
,19
0.2
7,3
2.8
1.9
_
0,3
221
2.4
5.1
2.4
0
0
1.0
13.1
1.0
,19
0.2
7.1
2.2
1,3
>}6
8.0
7 7
3.6
0,4
232
100
204
1?
-*--
2.4
5.5
2,4
0
0
2.3
5.1
2.3
0
0
0.3
7,2
2.8
1.0
>16
2.5
6.1
2.5
0
0
0.1
13.4
0,0
.Ifi
0.1
7,2
5.2
1.2
>16.
0,02
234
2.6
5.6
2,6
3.8
0
0.3
9.9
1,P
,)<»
0.2_
7,5
3.7
3.1
<2,2
0T4
228
2.7
6.5
2.7
9.4
0
0.6
9.3.
0.0
,11
0.2
7,4
3.3
2.2
<2,2
t?3
214
2.5
5.3
2.S
9.1
0
0.4
11 .n
0,0
.If)
0.2
7,4
2.8
2.8
—
0.4
226
2.3
5.8
2.3
9,4
0
0.9
15.0
0.0
.19
0.2
7,4
3.5
2.1
<2.2
R,4
6 0
2.7
0,3
236
2.8
5.6
2,B
9 4
0
-
2.5
5.4
2.5
94
0
0.2
7,0
1.7
2.3
<2.2
...
2.6
6.1
2.^6
9 4
0
O.-4
13.3
o.o
,1?
0.1
7,?
4.4
1.4
2.2
0.13
264
2.4
5.7
2.. .4.
9,4
0
0-1
11.5
1-P
,18
0.1
7,6
3.9
3.5
2.2
0.36
234
2.8
6.4
2...B
n 4
.07
0.4
If1, 5
0.0
,1?
0.1
7,5
2.9
2.6
<2.2
0.11
2_38
>•)
2.5
5.7
2.. 5
<) 4
.07
0.5
1-1,1
0.0
.lp
0.1
7,3
6.5
3,.1_
ajs.
fi.3
ft7
0.2
245
168
376
37
-34-
23 24 25 26 27 28 20 3n .11
2.5
5.6
?.. 5
o .1
.07
0.5
IP.?
0.0
_
0.1
—
5.6
4.2
<2.2
lii
5.6
2.G
0 4
0
2.4
6.1
2.4
9.-I
0
0.1
5.1
3.9
2,2
2.7
5.6
2.7
S.fl
.07
0,4
IP, 8
0,0
.
0.1
_
6.6
5.0
>16
0,4
2.5
S;8
2-5
0
.07
QJL
P,r>
O.C1
• >p
0.1
3.7
3.7
<2.2
---
0,7
2.5
5.7
2.5
0
.07
L.J
141
P.O
.
0.1
7,?
3.P
:.9
^2.2
0,8
257
2.3
6.1
2.3
P.
.07
0.6
7,
2.0.
+12.
0.1
7. 4
5.2
3.1
.
0,!>
257
1.9
s-7,
1.9
0
.07
Pf
IL.P
*13
0.1
7,?
4.6
3.4
<2.:
0,s
254
142
Tin
31
9
1,9
5.8
1.9
P
0
.....
-------
SOUTH TAHOE PUBLIC "TILITY DISTRICT - WATER RENOVATION PLANT
MONTHL'. ABL .TION OF FLOW AND LABORATO
DATE
September
1968
(Month)
(Year)
pl.-»n» flnvtfj Mf!
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir, MG
Flow From Indian Greek
Reservoir, MG
Total Flow From Other
Outlets. MG
5 -day BOD (mg/l)
COD (mg/l)
Suspended Solids (mg/l)
MBAS (ma/»
Turbidity, J U
pH (pH units)
Chlorine Residual (mg/l)
Instantaneous
30 Mtn. Contact
Luther Pass Station
Conforms (MPN/lOOml)
Nitrogen (mg/l N)
organic
ammonia
nitrate
nitrite
Phosi.'uto (mg/ 1 P)
Alkalinity(vi/l CaCO3)
ilGr-''ins-,(inrj/l CaCO3)
'olJ?!.1?*- !•.•<-'! ^iK'sfrng/l
Chloride (mg/l)
Sulfate (mg/l)
.1 23 45 6 789 If)
2,5
5.7
2.5
o
0
.19
0.3
6,8
3.0
2.7
?.Z
--
2,4
6.1
2.2
0
0.2
0.0
13.3
1.0
0.2
7.5
2.7
2.2
2.2
0.80
233
._.
2,1
5.3
2.0
3.7
0.1
0.7
9.7
1.0
.16
0.2
7.3
6.2
3.1
16
0.11
256
2.0
4.5
1.8
8.4
0.2
1.4
1.0
.11
0.1
7.3
0.2
(22
0.14
263
11.
2.0
4.3
1.9
8.4
0.1
0.3
0.0
.14
0.1
7.2
5.4
(22
0.11
250
r12
2,2
2.9
2.0
8.4
0.2
0.4
0.0
0.1
7.4
1.6
0.8
0.10
235
13 14 IS
1,8
3.0
1.7
8.4
0.1
0.5
Tjfi
1.0
.16
0.1
7.5
14.7
1.8
174
295
32
30
_2fl
2.
2.9
2.0
0
0
0.1
.20
1.
2.6
1.8
0
0
0.2
7.0
3.1
1.8
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT - WATER RENOVATION PUNT
MONTHLY TABULATION OF FLOW AND LABORATOR >AfA
DATE
Octobtr
(Month)
1968
(Year)
Ol»nf rlnv/4 MG
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir. MG
Flow From Indiin Creek
Rosorvoir, MG
Total flow From Other
Outlets. MG
5 -day BOD (mg/1)
COD (mg/1)
Suspended Solids (mg/1)
M2AS (mg/I)
Turbidity, J U
pH (pH units)
Chlorine Residual (mg/1)
Instantaneous
30 Mln.. Contact
Luther Pass Station
Coliforns (MPN/lOOml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/ 1 P)
Alkalinity (mg/1 CaCO3)
Hordnoss(mg/l CaCOj)
—TotaJ .P(s.so)v16
26.$
R
1 .7
3,9
1.7
0
0
1.4
7.5
0
0.3
7.4
2.0
0
>16
01,5
255
a
1 .7
4,2
1.7
0
0
0.4
8.0
0
0.3
7.2
4.9
0
>16
18.9
0.4'
0.48
0,14
226
10
1.7
3,8
1.7
0
0
1.3
8.3
Q
9,??
0.1
7.2
6.8
3.4
0,07
253
11
1.5
1.5
0
0
0.3
5.0
o
0.2
7.5
12.2
3.1
5.1
300
114
382
39
28
12
1.5
3,7
1.5
0*
0
1 .7
3,9
1.7
e
0
0.4
7.1
21.1
12.1
16
1.5
3,8
1.5
0
0
1.1
13.5
p
0.2
7.6
8.9
12.1
>23
2f)5
IS
1 .7
3,6
1.7
0
0
1.0
15.5
o
0.3
7.7
1.7
3.8
?16
2.6.3
16
1.1
3,7
1.4
0
0
1.2
n.i
o
0.3
7.6
3.4
1.4
5.1
2.27
17
I .4
4,0
1.4
0
0
0.7
11.3
o
1.4
7.8
2.7
0
_
W
1R
1 .1
3.9
1.4
0
0
0.5
17.8
o
1.7
8.4
8.9
3.6
(2.2
213
112
248
33.5
28.0
13
1.7
4.1
1.7
0
0
0.7
8.5
4.6
2.0
<22
20
1.3
4.0
1.3
0
g
21
2,0
3.9
2.0
0
0
0.1
_
f)
1.5
8.6
3.2
2.8
<2.2
0.64
?7P
,27.
4,1
1.7
0
P
1.0
17.0
P
1.5
8.7
5.0
2.9
(22
0.62
23.
4,0
1.7
o
P
-
lfi.3
p
1.0
8.6
2.9
<2.2
?1R
?A
3.9
l.S
P
P
0.2
19.0
p
0.8
8.3
5.6
0
_
77P
25
1,-t
4.0
1.4
0
P
0.1
17.3
P
1.2
8.7
17.8
3.8
<22
9,3
0
0,08
0.53
7?^
130
284
32
28
Zfi
1 .5
4.0
1.5
o
P
?,7
4.0
1.3
P
p
0.5
8.5
7.4
4.2
-------
SOUTH TAHOK PURLTC UTILITY PISrHTCT - V/ATCR Rl NOVATION PLANT
MONTHLY TAIUfUmON OI ROW AND LA'JOiV-TOKY DATA
NOVEMBER
""(Mor.thJ
1968
CO
CO
LO
V],-mt I'lov/ MCJ
Flov; Into Inc!ian Creel-,
f<"-:
Hardness (rr.g/1 CaCO3>
Total Dissolved Solldrfrng/1
Chlorldo (mg/1)
Sulfate (fi'O/1)
1 2 3 4 5 fi 7 8 9 10 11 1?. 13
i
1.8
0
0
0.9
16.1
0
0.26
1.6
9.1
3.6
3.1
14.2
0.22
0.37
190
108
310
39
45
1.8
2.6
0
0
2.2
2.6
2_.2
0
0
—
0.5
8.5
8.9
4.5
<22
1.5
2.9
1.5
0
0
0.2
16.8
2
1.0
8.4
4.3
6.9
,2_2
230
1.4
3.2
1.4
0
0
1.2
22.8
0
1.6
8'. 6
9.9
3,0
<2.2
228
1.3
3.2
1.3
0
0
0.4
13.8
0
1.4
8.6
2.0
1.8
(2.2
214
1.5
2.9
1.5
0
0
12.5
0
1.2
8.9
1.7
210
1.5
2.6
1.5
0
0.2
13.9
0
1.2
8.7
3.5
1,2
<2.2
193
138
306
29
28
1.8
2_.9
1.8
0
0
1.6
3.1
1.6
0
0
0.5
8.6
4.3
2,1
(2.2
1.7
3^8
1.7
0
0
0.0
15.9
8
I S
8.4
4.0
3,1
(2.2
218
1.8
3.6
1.8
0
0
0_.2
15.4
0
1 7
8.6
3.8
2,8
<2.2
214
1.7
2_.4
1.7
0
0
0.5
14.7
0
1 5
8.8
4.0
<2.2
235
14
l.S
2.4
0.7
0
0
0.3
17.3
0
1 R
8.7
3.1
2,9
213
15 16 17 IR 19 20 21 22
1.6
2.2
0
0
0
0.1
25.3
0
1.9
8.4
6.7
2,9
215
298
l.S
2.5
0
0
0
1.6
2.4
0
0
0
1.8
6.9
4.5
1.5
2.4
0
0
0
0.0
13.1
0
2.7
7.2
7.9
190
1.0
2.3
0
0
0
15.9
0
2.9
7.5
5.8
0
0.12
4.9
178
1.2
2.4
0.7
0
0
0.0
7.1
0
0.09
7.1
1.6
0.12
0.92
1.6
163
1,3
3.1
1.3
0
0
1.6
0.09
7.5
0.6
0.07
157
88
32
40
1.6
3.6
1.6
0
0
1.1
7.6
0.11
0.7
7.0
0
1.2
2.2
0.23
0.06
113
76
2£
40
23
1.4
5.3
1.4
,0
0
72
25
42
2-1 25 26 27 29 Z? 30 31
1.4
3.6
1.4
0
0
1.4
8.5
1.0
0.7
<2,2
118
Li
3.0
1.6
0
0
20.7
0.15
1.6
7.7
2.7
1.2
0.17
0.08
0.42
49
144
19
13
1.4
4.7
1.4
0
0
p.o
1.2
8.0
2.8
1.3
^2.2
0.4
0.07
0.62
42
152
31
l.S
3.2
l.S
0
0
1.8
11.5
0.25
1.1
8.6
2.4
1.5
'2,2
0.23
0.03
0.75
225
154
23
35 38
1.7(1.9
3.0J2.7
1.711.9
0
0
2.0
10.3
0.13
0.6
7.7
2.9
2.0
0.09
0.01
250
160
27
0
0
7.3
1.2
7.4
2.8
2.5
<2.2
0.22
0.04
235
154
23
33* 19
1.7
2.8
0
0
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT - WATER RENOVATION PLANT
MONTHLY "M1ULATION OF FLOW AND LABORATORY DATA
Pr.CEMRER
(Me
1968
(Year)
oo
to
pV»n[ F'°v' . W G
peaV. Flow Rote MGD
Flow Into Indian Creek
R^S^rvr^ir , IMG
T\'fii From Inrjlon Crock
H'jrx.T'/oIr , MG
Tot.-jl Flow From Other
Outlets. MG
5-doy HOD (mi/I)
COD (rrxj/l)
Su-,!i<-.-n')r."l !>ol|rl:i (nrj/1)
M B A S (mg/l)
Turbidity, I U
pH (pH units)
Chlorine RosiduaKmg/l)
Instantaneous
30 Kin. Contact
Luther Pass Station
Coliforms (MPM/100 ml)
N'itro'jon (mi/1 N)
organic
amnonia
nitrate
nitrite
Phosphate (mg/l P)
Alkalinity (mg/l CaCO3>
Hardness (mg/l CaCO3>
Total Dissolved Solldsfmo/l
Chloride (mg/l)
Sulfate (mg/l)
1
1,8
„
1.8
0
0
1.0
7.0
2,9
3,1
<2.Z
2
1,3
_
1.3
0
0
o.s
11.7
1.1
6.5
1,7
2.6
<2.2
0.12
0.01
0.52
260
164
26
21
3
I..1?
_
1.5
9
0
0,5
9.9
1.2
6.8
1,8
2.5
<2.2
0.52
160
22
25
4
1.2
_
1.2
0
0
9.2
Oil!
1.1
7.0
2,7
1.1
<2.2
0
0.01
0.46
271
162
21
32
5
1,1
4.9
1.4
0
0
0,1
7.9
1.0
6.9
3,3
2,3
0.0)
0.01
0.46
?• S3
162
25
32
6
1.6
6.5
1.6
0
0
o,n
6.6
run
0.8
7.1
3,1
2.0
<2.2
0
0.01
0.28
36.3
170
24
30
7
2.9
0
0
8
l.S
7.2
1.5
0
0
0 fi
o.s
6.8
2,R
1.3
?. 5
_
0.03
0.03
0.02
2.10
134
21
24
13
n 9
4,;
0,9
n
0
4.0
n n
1 .0
6,8
n
2,0
<2,2
0.03
0.02
30,5
116
24
24
14
3,0
n
0
is
i n
2.0
1.0
0
0
0.7
S.9
1.1
0,8
2.2
16
1 1
2.0
1.1
0
0
6.3
1.0
7,0
1.1
0,fl
<2.2
0.1?,
0.01
0.15
270
94
24
24
17
n R
2.0
0.8
0
0
6.1
1.0
7,2
1.0
0.7
5.1
O.fi
0.29
0.12
300
132
23
21
18
1 3
7.2
1.3
0
0
0.8
6.4
0.11
0.9
7,0
2.8
n,7
2.2
0.08
!62
160
25
24
19
1 9
2.3
1.9
o'
0
0.2
4.4
0.8
1.7
0,6
44
14
21
20
1 4
3.1
1.4
0
0
6.9
0.7
2.1
1,2
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT-WATER RENOVATION PLANT
MONTHL ABULATION OF FLOW AND LABORATORY DATA
IAN
(Month!
(Year)
oo
10
en
P]ant Flow. M G
ppfllc Flow Rate MOD
Flow Into Indian Creek
Tlv" From Irulbjn Creek
P.osirvoir. MG
7c/l;ii i'low from Other
Outlets. MG
S-'Uv ROD (mi/1)
COD (m'j/1)
Suspended Solids (mg/1)
M B A S (mg/1)
Turbidity. J U
pH (pH units)
Chlormo Rcsidual(mg/l)
Instantaneous
30 Min. Contact
Liitr.ir Pass Station
Cohforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOj)
Hardness (mg/1 CaCOs)
7ot.il Dissolved Solids(mgyl
SuUatc (rng/1)
1
,
.6
.2
0
0
1.6
1.2
fi 7
1.8
0,0
—
?fi?
104
19
24
2
9
4.B
1 ,1
0
0
12,0
2.7
7 2
1.4
0 0
00?
0.10
771
100
41
24
3
1
3.8
2,1
0
0
1 ft
01?
1.7
ff 4
1.3
0 fi
0.07
?7«1
ion
17
4
1 R
1.0
1 R
0
0
•
5
1 R
1.4
1 R
0
0
1.5
fi 5
1.9
1 1
<7?
6
1 fi
1.6
1 R
0
0
9 ,4
4.4
fi 5
1.7
0,9
<77
0.02
?9«.
15fi
49
7
1 5
1 S
0
0
0.6
7 R
Olfi
2.7
fi R
2.0
1 1
<7?
009
0.10
140
152
77
11
8
1 1
7,4
1 ,1
0
0
0.9
2.5
fi 4
3.1
1 ?
17
001
0.20
711
5fi
24
26
9
1 fi
1.7
1 fi.
0
0
15 fi
6 q
2.3
O.fl
001
0.18
7 Ifl
R?
26
23
10
1 fi
5 R
1 6
0
0
0.2
1? fi
fi R
2.1
1 1
m
2.7
0.38
002
0.15
71?
74
24
24
11
1 9
3.8
1 9
0
0
12
1 R
3.2
i fi
0
0
1.1
R q
1.3
1 ,0
C72
13
2.4
8,8*
? 4
0
0
1.3
11.0
7 0
1.8
1 .1
'??
0.48
0,15
0.17
?41
164
19
10
14
5!.S
*
fi.5.
7 5
0
0
—
11 fi
fi 7
1.6
0,9
<2.2
0.03
0.01
0.26
?lfl
4R
42
11
nftir
15
?. .0
4.1
2.0
0
0
1.1
13.4
7 ?
1.0
1 0
<•??
nil
110
.17
IB
16
1 .R
3.0
1.8
0
0
2.9
12.0
0,10
fi 7
2.0
0,6
_
0.18
01?
0,2 fi
11
27
17
1 .6
3.3
1.6
0
0
1.5
R.6
O.R
fi,R
?,,4
1 ,4
-------
SOUTH TAIIOE PUDLIC UTILITY DISTRICT - WATER RENOVATION PLANT
MONTHLY TABULATION OF FLOW AND LABORATORY DATA
February
(Month)
1969
(Year)
CO
CO
P|ar|t rlf", M <"•
Poafc Flow J?.it(« MCD
Fir// Into Indian Crock
Reservoir, MG
ri'/w From In'li-m Creek
Reservoir. MG
Total I'lov/ I'rom Other
Outlets. MG
S-diy BOD (ma/1)
COD (rm/0
SusponrJod Solids (mg/l)
M B A S (m-j/1)
Turbidity, I U
pH (pH units)
Chlorine Rasldual(mg/l)
Instantaneous
30 Min. Contact
Luther Pass Station
Collf',mr, (MPIJ/100 ml)
Nitrogen (mg/l N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/l P)
Alkalinity (mg/l CaCOj)
Hardness (mK,
0.12
0.01
0.13
304
54
15
28
1 9
3.4
1.9
0
0
0.5
] 7
3.5
1.7
0
0
0.7
6.1
2.7
0.8
0.0
„
0.09
i.»!
4.6
1.9i
0
0
7.2
0.13
6.8
? 1
1.8
S.1
J.I 61
246 J242
142 |120|
21
21
43 42
1
1
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT- WATER RENOVATION PLANT
MONTHLY TABULATION OF FLOW AND LABORATORY DATA
MARCH
(Month)
CD
vj
DATI:
PJant T\-yn . M G
Peak How Rato MGD
Flow Into Indian Creek
R"ST'/oir, MG
Flo*'/ from Indian Greek
Rosorvolr, MG
Total Flow From Other
O'Jttm . MG
5-d-r/ BOD (rw/l)
COD (mg/1)
Suspended Solids (mg/1)
M 3 A S (tr.7/1)
Turbidity, J U
pH (pH units)
Chlorine Restdual(mg/l)
Instantaneous
30 Min. Contact
Luther Pass Station
•Conforms (MPN/100 ml)
Nitrogen (rag/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOs)
Hardness (ng/1 CaCO3)
Total Dissolved Solldsfmcr/1
Chloride (mg/1)
Sullate (mg/1)
I 2 34567 8 9 10 11 12 13 14 IS 16 17 18 19 20 21 22 23 24
2.1
-
2.1
0
0
0.6
3.8
-
3.8
0
0
0.4
6.6
2.9
<2.2
1.9
-
1.9
0
0
1.5
3.2
0.3
6.7
4.4
<2.2
0.09
0.15
0.10
245
172
24
42
1.3
-
1.3
0
0
1.0
6.8
0.11
0.3
6.7
4.7
<2.2
0.00
0.06
0.13
258
1S6
28
44
1.8
3.3
1.8
0
0
8.8
3.3
6'. 9
7.6
<2.2
0.15
256
162
25
45
1.7
4.0
1.7
0
0
0.4
6.9
3.0
'I, R
<2.2
0.09
0.07
0.26
254
166
27
45
2.1
2.2
2.1
0
0
0.9
8.5
0.5
6.9
2.0
3 7
(2.2
0.09
0.2 S
245
172
28
48
2.0
4.7
2.0
0
0
0.4
2.0
3.6
2.0
0
0
0.5
6.8
3.6
7 0
C2.2
1.8
2.7
1.8
0
0
1,0
7.8
0.01
0.3
7.0
4.5
7 7
^2.2
0.32
0.09
0.15
292
148
23
?,fi
1.6
3.7
1.6
0
0
0,H
7.9
0.13
0.3
7.2
4,0
7 7
<2.2
0.38
0.38
0.15
277
144
27
34
1.7
3.8
1.7
0
0
1,4
11.8
0.10
0.3
7.3
4,3
7 I
<2.2
0.03
0.22
239
54
25
31
1.6
4.6
1.6
0
0
1.7
9.3
0.10
0.3
7.5
3.5
2.1
<2.2
0,22
0.27
260
170
29
30
1.9
4.1
1.9
0
0
0.7
9.6
0.3
7.7
2.4
3.1
<2.2
295
68
27
30
2,1
3.1
2.1
0
0
0.4
5.1
i
2,1
3.0
2.1
0
0
0.8
7.4
1.8
1.8
<2.2
2.1
2.2
2.1
0
0
7.0
0.1
7.0
5.1
2.8
S2.2
0.6
0.01
0.2 S
282
118
27
30
2,1
4.4
2.1
0
0
10.2
0.2
8.0
3.1
2.0
<2.2
0.47
0.22
319
128
30
18
2.0
3.8
2.0
0
0
8.1
Q.20
0.2
8.3
2.2
2.1
<2.2
0.38
0.13
0.16
226
148
25
18
2.0
3.9
2.0
0
0
0.5
8.5
0,17
0.2
8.2-
4.7
0.9
5.1
0,48
0.16
0.33
242
158
25
16
1.9
5.0
1,9
0
0
4.0
0.2
7.S
3.4
3.3
<2.2
0.38
0.07
0.51
220
78
24
24
2.2
3.7
2.2
0
0
0.2
2.2
4.8
2.2
0
0
0.3
7.2
2.5
0.9
1.9
4.2
1.9
0
0
6.7
0.2
7.2
0.8
1.2
S2.2
OZ2
0.05
0.20
162
206
26
14
25 26 27
2.2
4.1
2.2
0
0
10.7
0.2
0.9
1.0
\2.2
170
32
15
2.0
4.1
2.0
0
0
16.3
0.2
3.5
1.0
1,0
<2.2
0.4
0.00
0.26
131
78
2.3
3.7
2.3
0
0
16.1
0.2
1.4
0.9
<2.2
02 1
76
24 27
IS' 22
28 29 30 31
2.3
4.2
2.)
0
0
11.7
0.2
1.6
1.6
<2.2
0.19
118
25
2.7
3.7
2 -
0
0
0.2
3.0
4.4
3.0
0
0
0.9
7 "*
1.2
1.0
I
16
3.0
4.0
3.0
0
0
0.6
S.8
0.4
e.s
2.5
3.6
2.2
0.39
160
140
26
18
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT - WATER RENOVATION PLANT
MONTHLY TABULATION OF FLOW AND LABORATORY DATA
APRIL
(Month)
CO
CO
00
DATE
P1«;U Flovy. M f5
_P5»V, Fl MQD
Flov/ Into Indian Creek
Rcscrvpir. T/f5
Flov/ From Indian Creek
Rcr.orvolr, MO
Total Flow From Other
Outl°ts, MCS
S-day BOD (nvT/1)
COD (rm/l)
Suspended Solids (mg/1)
M B A S (riq/1)
Turbidity, I U
pll (p7! units)
Chlorine Resldual(ng/l)
Instantaneous
30 Mln. Contact
Luther Pass Station
Co!! forms O.'P.'I/IOO ml)
Nitroeicn (mg/1 N)
organic
amr.onla
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (rr.g/1 CaCO2)
Hardness (ng/1 CaCO3)
Total Dissolve! SolWsfrr.g/1
Chloride (rr.g/1)
Sulfate (r.g/1)
1
3.3
4,0
1.3
0
0
0.5
0,3
0.9
1.6
3.4
2.7.
0.07
0.17
142
120
23
20
2
2.4
4.6
2.4
0
0
_
0.06
0,3
7.B
3.1
2.0
7.2
0.&3
0.78
0.47
203
154
24
16
3
2.6
4,8
2.6
0
0
0.0
0,2
7.1
2.8
3.4
'•>..'/.
0.79
0.12
0.49
190
166
23
16
4
2.7
4.7
2,7
0
0
1.1
-------
C0
SOUTH TAIIOE PUBLIC UTILITY DISTRICT-WATER RENOVATION PLAN'"
MONTHLY TABULATION OF FLOW AND I.AI1OUATOKY DATA
MAY
196-9
(Month)
DATE
Flov/ Into Indian Crock
Flov/ From In'lUn Crrjrjk
\i^Z<"Tj\< fv'G
Tot--i! Flw From Other
riutlnttj VG
S-d-iy BOD (mfj/1)
COD (m'j/1)
Suspended Solids (rr.fj/1)
M B A S (rr.q/1)
Turbidity , I U
pH (pH units)
Chlvlnc: P.osl'JuaHrr.'j/l)
Instantaneous
30 Min. Contact
L'Jthcr Pass Station
Conforms (MPM/100 ml)
Nitrogen (rr.g/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOs)
Hardness (mg/1 CaCO3>
Total Dissolved Solidsfmg/
Chloride (mg/1)
Sulfate {mg/1)
1 2 34567 8 9 10 11 12 13 14
i n
? R
i n
0
n
6.7
014
0.2
?.n
0 R
0.3
<2.2
1.7 ^
0.14
0.12
180
134
20
16
2.4
i n
? 4
0
n
n,s
14.5
0.5
7.2
1 1
0.7
!^1
0.63
0.02
-
182
128
19
1.5
? 9
l.fi
? q
0
n
? s
1.3
7, ,S
0
n
0.7
7.2
1 1
0.4
—
? 4
2.4
0
0
n i
12.8
0,3
G.9
1L2
0.4
2.2
1.0
0.11
0.07
195
152
19
20
? 0
3.7
2.0
0
n
!Li
7.9
0,3
7.5
LuQ.
1.2
-------
SO'J'i'H TAHOE PUBLIC UTILITY DISTRICT - WATER INNOVATION PLANT
MONTHLY TABULATION Or FLOW AND I.ABORATORY DATA
JUNE
(Month)
O
O
Plarjt Flow. M G
Pc»y. ri'ftt Roto MOD
Flov/ Into Indian Creek
Reservoir, N'G
Tl'jrtt It'jtii Indian Cic-oK
Poservolr, Ml
Total Flow From Other
Outlets . MG
5-day BOD (mq/1)
COD (ng/1)
Suspended Solids (mg/1)
M B A S fmq/1)
Turbidity, J U
pH (pH units)
Chlorine Resldual(mg/l)
Instantaneous
30 Mln. Contact
Luther Pass Station
Conforms (MPfT/100 ml)
Nltro'jen (ng/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (ng/1 P)
Alkalinity fog/I CaCOj)
Hardness (mg/l CaCOj)
Total Dissolved Solids' tr.vA
Chloride (rr.<3/»
Sulfate (mg/1)
DMT
1 2 3 4 5 67 8 9 10 11 12 13 H 15 16 17 18 19 20
2,0
I.1)
2.0
0
0
0.6
7.S
0.6
0.8
2.3
5.0
2.3
0
0
8.1
0.00
0.4
7.1
0.6
0.8
<22
0.12
0.00
0.23
221
126
16
26
?..7
5.0
2.7
0
0
7.5
0.4
0.0
0.4
0.6
<2.2
0.05
0.24
203
124
19
28
2,5
O.C
2.5
0
0
2.0
9.0
0.12
0.4
n.4
0.9
O.f,
.q
0.06
0.1
7.4
1.2
0.0
<2.2
0.38
0.1
'0.16
222
150
17
15
2,1
4.7
2.1
0
0
n,2
6.0
0.09
0.1
6,7
1.3
0.0
<2.2
1.12
0.02
0.16
200
156
18
15
2,7
4.b
2.7
0
0
0,3
5.1
1.0
7.6
2.7
0.7
<£3.
O.Ofl
0. 4
0.61
211
136
17
18
3,0
4.b
3--°.
0
0
3,?
5.7
3.3
0
0
0.7
7.1
0.9
o.n
2.7
5.6
2.7
0
0
0.8
n.7
0.1
7.6
0.7
0.0
5.1
0.3
0.2
0.12
211
126
13
24
2.9
5.4
2.9
0
0
0.8
3.n
0.12
0.1
6.7
1.2
0.5
<2.2
4.4
0.32
0.18
161
132
11
20
2.9
5.0
2.9
0
0.
1.1
s.n
0.05
0.1
7.2
1.2
0.9
<2.2
3.06
0.31
0.15
209
140
19
18
2.7
5.7
2.7
0
0
G.C
0.1
6.8
1.1
0.7
<2.2
2.64
0.3
0.09
203
142
17
18
2,9
5.5
2.9
0
0
0.6
•1.2
0.1
8J..
1.0
O.-l
<2.2
0.75
0.08
0.02
216
21
3.0
4.9
3.0
0
0.
22
2.7
2.7
0
0
0.9
0.5
UL
0.9
0.7
23 24
2,7
5.7
2.7
0
0
3.0
9.0
0.12
0.1
2j_6.
O.-l
0.9
C2.2
14.1
0.03
0.02
0.28
229
124
13
18
2,7
4.6
?. .7
0
0
0.6
9.5
0.1
LJ.
0.7
0.0
C'2^2
15.3
0.00
0.00
0.23
239
146
21
18
25 26 27 28 29 30 31
3.8
5.4
s.n
0
0
9.5
0.09
0.1
?_J
0.7
0.5
16
0.28
0.19
0.37
2,5
4.2
c.s
0
0
10.6
0.1
7^5
0.4
0.0
<2.2
14.7
0.35
195 !l90
114
64
16 20
18
21
2.8
3.8
:.n
0
0
2.5
4.2
:.s
0
P
0.8
?.?
O.b
1.2
2.5
5.0
:.s
0
P
0.9
8.1
0.1
0.7
0.0
S2.:
11.5
0.16
76
14
20
-------
SOUTH TAHOE PUBUC UTILITY DISTRICT-WATCR INNOVATION PLANT
MONTHLY TABULATION OF I'LOW AND LABO 'OKY DATA
LULY_
(Month)
1969
(Year)
PJ-int Flov/, M G
Peak Flow Rote MGD
Flow Into Indian Creek
Ror.'Tvoir , r/'f»
flov/ From Indian Crook
P.iT.r.'rvolr, MI";
Totel Flov/ From Other
Outlof; . I/ir;
5-day HOD (mg/1)
COD (mg/1)
Suspended Solids (mg/1)
M B A S (mg/1)
Turbidity, J U
pH (pH units)
Chlorine Resldual(mg/l)
InEtontonoous
30 Mln. Cont.-ict
Luther Pass Station
Coliforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOj)
Hardness (mg/1 CaCOg)
Total Dissolved Sollds(mq/l
Chloride (mg/1)
Sulfate (mq/1)
1 2 34567 89 10 11
? ?
4.2
2.2
0
0
0.9
5.6
0.1
7.9
0.7
0.0
<"2.2
11.1
0.45
0.96
0.07
142
64
20
23
2.7
4.4
2.7
0
0
0.7
13.7
0.4
7.7
2.7
0.0
(7.2
11. S
0.52
2.64
0.08
144
108
21
23
2,r,
5.3
2.6
0
0
O.G
12.6
0.1
8.1
1 .7
0.0
-------
SOUTH TAIIOE PUBLIC UTILITY DISTRICT - WATER RENOVATION PLANT
MONTHLY TABULATION OF FLOW AND LABORA1. .IY DATA
AUGUST
(Month)
O
CO
Plant Flow. M C,
-£Sfk.VSf"-Es£2-MGn
Flow Into Indian Creek
Reservoir, r/fl
Flov/ From In'JI-m Crook
R'.-.iorvoIr, MC
Total Flov/ .'Torn Other
O'illit*. . MO
5-dv/ BOD (m'j/1)
COD (rr.y/1)
Suspended Solids (mg/1)
M E A S (mq/l)
Turbidity, J U
pH (pH I'nlts)
Chlorine ReslduoHmg/l)
Instantaneous
30 Mir,. Contact
L'jtbor Pair, Station
Conforms (Mf-fl/lOO ml)
Nitrogen (mg/l N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (n'j/1 CaCO3)
Hardness (.ivj/l CaC03>
Total Dlssol'/od Solid^rnrj/1
Chloride (mg/1)
Sulfatc (mg/1)
DATF
1 2 34567 8 9 10 11 12 13 14 IS 16 17 18 19 20 21 22 23 24
2^5
S.I
2.5
0
0
0.4
0.06
0.4
8.1
l.G
1.4
<2.2
7.6
0.4 C
0.02
201
134
20
24
2J
S.6
2.8
0
0
•LJ.
6.2
2.7
0
0
0.5
7.1
1.8
l.T,
lii
5.3
2.6
0
0
6.0
0.10
0.1
7.3
1.4
1.2
<2.2
7.8
0.12
0.09
192
146
25
22
IJ).
6.6
2.8
0
0
3.9
0.1
6,9
1.5
0.0
<2.2
4.8
0.01
0.03
182
146
17
40
2-J.
5.4
2.7
0
0
6.2
0.3
7.0
1.4
1.2
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT- WATER RENOVATION PLANT
' 'NTHI.Y TABULATION OP FLOW AND IABOUAT"-1RY DATA
September
1969
(Month)
CYear)
O
00
Plfnt F'QV/ , M G
Flow Into Indian Crook
Reservoir, MG
~ Total Flow From Other
Outlets. MG
5-day BOD (mg/1)
COD (rr,g/l)
Susporvk.''] Soli']!; (m'i/\)
M B A S (mg/1)
Turbidity, J U
pJ! (pll units)
Chlorlr.e P,csldual(rng/l)
Instantaneous
30 Min. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitrogen (rr.g/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alk'illnlty (mi /I CaCOj)
Hardness (mg/1 CaC03>
Total Dissolved Solldsfnvj/l
Chlorldo (mo/1)
Sulfate (rng/1)
1 2 34567
,4
.4
,8
0
9.0
0.2
7.0
1.8
1.2
2.2
0.02
0.15
186
130
?f>
21
,3
..1
,3
JL
n
.
0.2
6.9
1.7
1.2
1.2
1.9
026
193
136
n
20
.fi
1
.6
n
0
O.ff
6.1
0.2
6.8
2.2
0.6
<2.2
1.1
0.05
0.15
210
136
n
33
,4
.4
n
n
8.4
6.9
0.2
0.4
(2.2
0.9
0,05
192
126
11
23
2,3
2.3
n
f)
?,,5
r, i
2.5
n
0
—
2.3
r, ,1
2.3
0
0
0.3
0.1
7.1
2.8
1.6
.
1.0
0.05
192
136
n
20
&
?..?.
2.2
0
0
0.2
7.2
0.1
7.1
2.1
1.9
<2.2
1.8
0.11
0.05
192
128
26
22
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
2.4
r. .4
2.4
0
0
_
7.2
0.1
7.3
<2.2
10.7
0.05
250
136
JJ.
21
1.8
1 .8
0
0
_
8.3
0.1
7.1
2.2
1 .8
'7 ?
3.3
0.30
0.0 f
191
144
23
27
1.9
'J 2
1.9
0
0
_
4.3
0.4
7.0
1.7
2.6
m
2.4
0.18
024
163
128
26
26
1.9
5 7
1.9
0
0
_
_
2.2
5 7
2.2
0
0
2.1
5 3
2.1
0
0
6.1
0.1
f>.B
1.8
1.0
M
0.2
0.14
0.06
152
24
30
1.9
•1 .7
1.9
0
0
1.1
7.8
0.1
7.2
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT- WATER RENOVATION PLANT
3NTHLY TABULATION OF FLOW AND I-AnORATOUY DATA
OCTOBER
(Mont
1969
(Year)
Plant Flow. M G
Pjto MOD
Flow Into Irtdion Crock
Roscr/olr. MG
V'l'SH I'l'tm lli'li'in Cd;';K
Rr;sorvoir, MG
Total 1'low From Other
OutMs, MG
5-diy BOD (mi/I)
COD (rr,5/l)
SuspcnfJcd Solids (mg/1)
M B A S (ri'j/D
Turbidity, J U
pH (pH units)
Chlorine RoslcluaKrrjfj/1)
Instantaneous
30 Min. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitroyjn (rng/1 N)
or.ganic
ammonia
nitrate
nitrite
Phosphate (ir.g/1 P)
Alkalinity (mg/1 CaCOs)
Hardness (mg/1 00003)
Total Dissolved SolidrXmg/l:
Chlorldo img/1)
Sulfotc (mg/1)
DATE
1 2 34567 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
1.8
5.0
1.8
0
0
12. 5
0
0.1
7.1
1.8
1.2
<2.0
14.3
0.01
430
250
26
26
l.S
4.0
1.5
0
0
12.8
0
0.1
7.0
2.2
1.2
<2.0
12.3
0.09
415
152
340
2.8
4.9
2.8
0
0
0
<2.0
l.l
5.6
1.8
0
0_
0
8.8
2.0
6.0
2.0
0
0
9.9
0
0.2
7.1
1.2
1.4
(2.0
0.11
214
126
2.0
4.9
2.0
0
0
6.1
0
0.08
0.3
7.2
1.2
1.2
<2.0
15.1
0.5
0.02
0.29
356
264
22
18
1.7
4.6
1.7
0
P...
3.5
0
0.2
2.1
1.5
&?
17.4
0.21
108
330
i.e
5.7
1.8
0
0
5.3
0
0.1
7.0
2.5
1.6
<£l
16.4
0.19
220
330
23
21
1.8
5.1
1. 8
0
0 _
1.9
0
0.1
6.9
2.4
1.9
6I
23
18
1.7
4.0
1.7
0
0
3.0
0
0.2
7.-1
2.9
2.5
<2.0
19.6
1.4
0.35
0.11
276
148
1.7
4.0
1.7
0
0
0
2.0
4.7
2.0
0
0
0
<2.0
1.9
5.0
1.9
0
0
1.4
4.6
0
0.5
7.1
2.8
2.1
iM
16.2
1.1
0.12
246
152
1.5
3.7
1.5
0
0
3.2
0
0.20
0.4
7.2
2.3
2.0
iM
16.0
1.6
0.02
0.11
223
170 1290
28
J23
1.6
3.3
1.6
0
P
1.3
11.9
0
0.20
0.2
7.0
3.7
0.0
s2.0
18.6
1.9
0.14
0.01
250
176
310
1.9
3.3
1.9
0
0
1.7
0
0.19
0.3
6.7
2.2
0.4
N2.0
IS. 3
2.4
0.12
0.13
26S
370
124
23
29
1.6
3.5
1.6
0
0
1.2
7.8,
0
0.8
7.0
1.8
2.4
^2.0
IS. 3
1.3
0.14
0.15
255
158
450
21
1.6
4.0
1.6
0
0
0
iM
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT - WATfl ^NOVATION PLANT
MONTHLY TABULATION OF I LOW AND LAP. Yl'OKY DATA
NOVEMBER
(Month)
1969
O
cn
Plant Flow . M G
P?ak Flew Rate MGU
flvn Into Indian Crock
Reservoir, MG
Flow Frirr. Ifi'Ji.-iri Cronfc
Rosrsrvoir. MG
Total Flov/ From Other
Outlets. MG
5 -day EOD (na/1)
COD (ng/1)
Suspended Solids (mg/1)
M S A S (ng/1)
Turbidity, J U
pH (pH units)
Chlorine Resldual(mg/l)
Instantaneous
30 Min. Contact
Luther Pass Station
CoHformi (MPTI/1 00 ml) <
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOj)
Hardness (mg/1 CaCOj)
_Total Dissolved Soltds(m.2
15.3
1.6
0.12
0.02
234
168
410
3
1.7
4.1
1.7
Q
0
1.7
0
0.08
0,5
8.3
<2.2
12.4
1.8
0.09
0.04
250
390
31
38
4
1,5
4.4
1.5
o
0
2.5
0
0.3
8.4
2.1
2.0
(2.2
18.3
2.2
0.34
0.06
261
170
390
S
1,6
4.6
1.6
0
0
2.9
6.4
0
0.13
0.4
619
1.6
0.0
4
.1
0.01
.12
720
134
300
31
-------
SOUTH TAHOE PUULiC UTILITY DISTRICT - WATER INNOVATION PLANT
MONTHLY TABULATION QF FLOW AND LABC TORY DATA
DECEMBER
(Month)
O
CD
Plant Flow. M R
Peak Flov/ Rate MGD
Flow Into Indian Crock
Flov/ From Indian Creok
R'.-3'.-rvolr. MCJ
Total Flow From Other
Oijtlotn, Mr,
5-doy BOD (m-3/1)
COD (rr:7/l)
Suspended Solids (mg/1)
M B A S (n-3/1)
Turbidity, I U
pH (pi I units)
Chlorlr.o RoeldnoKmq/l)
Instantaneous
30 Mln. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitrogen (ng/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (nj/1 CaCOj)
Hardness (tr.g/1 CaCOj)
Jmlpmolvcd SolMsf-nj/l'
_C_Mortdo (mg/1)
Sulfatc (mo/I)
1
1.7
3.9
1.7
0
0
8.1
0,0
0,00
1.4
6,6
4.4
2.4
<2.0
22.3
0.9
0.01
0.13
230
290
25
32
2
l.S
3.7
1.5
0
0
0.3
D.9
0.0
1.0
7T8
0.7
2.3
<2.0
19.2
1.2
0.12
0.63
159
114
280
3
l.S
3.8
1.5
0
0
10.4
0.0
0.8
7.4
1.9
1.3
2.2
18.3
1.0
0.23
0.68
195
320
26
41
4
1.3
3.8
1.3
0
0
0.2
8.9
0.0
1.0
7.9
2.7
1.0
5.0
16.8
0.40
181
138
350
S
1.6
3.7
1.6
0
0
0,0
<;2.o
6
1.7
3.9
1.7
0
0
0.0
2.2
7
1.5
3.6
1.5
0
0
0.6
9.7
0.0
0.3
7.6
2.0
2.3
2.2
16.8
0.1
0.04
0.11
197
150
360
8
1.5
3.8
1.5
0
0
7.C
0,0
0,00
0.3
7.8
3.5
2.0
16.8
0.2
0.05
0.02
220
300
26
37
9
1.5
3.4
1.5
0
0
0.4
5.4
0.0
0.3
7.5
3.1
0.0
17..8
0.3
0.02
0.20
203
136
290
10
1.6
3.4
1 .7
0
0
6.2
5.0
0,00
0.3
6.8
3.8
2.7
2.2
18.9
0.1
0.03
0.02
192
300
38
31
11
1.7
3.7
1.7
0
0
0.5
11.3
0,0
0.3
7.1
2.4
?..R
18.2
0.0
0.02
0.13
156
142
320
12
1.7
3.3
1.8
0.
0
0,0
2.1
13
2.0
3.4
2.0
0
0
0.0
<2.0
14
1.0
3.2
l.fl
0
0
5.9
0.0
0.3
7.2
2.1
1.0
C2.0
22.0
0.5
0.10
0.12
230
156
340
15
1.8
3.3
i .n
0
0
9.4
0.0
0.10
0.3
7.2
2.6
2.2
(2.0
20.7
0.1
0.05
0.20
256
172
370
16
1.5
2.9
l.fi
0
0
3.1
9.1
0.0
0.3
6.8
3.3
1.9
ao
22.6
0.0
0.06
0.13
276
164
380
17
.4
3.2
3.2
0
n
2.9
0.0
0.3
7.2
3.3
1.9
<2.0
22.6
0.1
0.06
0.16
275
390
24
30
18
1.5
3.1
3.1
0
0
11,5
0.0
0.3
7.2
2.4
1.7
(2.0
21.2
0.2
0.05
0.06
293
168
19
2.1
S.5
S.S
0
0
0,0
<2.0
20
2.7
6.0
fi.O
0
0
0 0
<2.0
21
3.0
6.5
0.5
0
0
5.4
0 0
0.3
8.3
2,3
2.7
<2.0
13.5
0.5
0.06
0.16
200
168
22
2.3
5.3
5.3
0
0
fi.7
5.9
0 0
0,13
0.6
7.2
1,6
1.9
<2.0
15.0
0.0
0.03
0.05
204
178
23
2.3
5.0
5.0
0
0
l.fl
e.s
o n
0.5
7.1
1,7
1.4
<,,(,
14.5
0.5
0.16
0.06
195
174
294
24
3,4
7.1
r.l
0
0
10.9
n n
1.5
7.5
3,1
2.2
16.1
0.3
0.11
202
320
21
38
25
3,2
7.5
7.5
0
0
10.9
0.0
0.6
7.1
2.7
2,6
V,0
13.0
0.4
0.07
0.12
175
156
220
26
2.9
6.9
li.9
0
0
0.0
.1
0
0
15.?
0.0
0.5
7.1
1.9
2.1
21.1
0.2
o.oo
0.09
223
162
340
29
? 7
6.7
0 V
0
0
24. P
0.0
Oil
',4
4.7
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT - WATER RENOVATION PUNT
MONTHLY TABULATION Ol' FLOW AND LABO. lORY DATA
JANUARY,
1970
(Month)
Plant; Flw, M C
Ppak Flow Rate MGD
flow Into Indian Creek
Rosrrvoir, ?/f?
flow from Indian Creek
Pr;r.c-rv*lr ( ?/O
Total Flow From Other
OutlMr;. MO
5-c!3V liOU (nw/1)
COD (mg/1)
Suspended Solids (mg/1)
M B A S (mg/1)
Turbidity, I U
pH (pH units)
Chlorine Rosidual(rng/l)
Inst-mtancous
30 Min. Contact
Luther Pass Station
Conforms (MPri/100 rnl)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOs)
Hardness (mg/1 CaCO3)
Total Dissolved Solidsfmgyl
Chloride (mg/i)
Sulfate (mg/1)
1 2 3 4 S 6 7 8 9 10 11 12 13
3.0
5.6
\.n
0
0
0.2
2.6
0,f?
7.9
3.4
1.8
'? f
23.8
0.5
0.08
0.06
228
ISO
2.9
5.5
2._9
0
0
<2.0
2.G
6.5
2_.r,
0
0
<7 n
2.3
6.1
2.3
0
0
15.5
0.8
2.5
2.5
1,,fi
20.0
0.1
0.00
0.22
156
30(1
1.8
5.4
1...B.
0
0
13.3
1.8
7: 3
1.0
2.7
•.'?,.(
25.6
0.0
0.58
021
233
280
27
33
1.8
5.1
1...H
0
0
18.1
1.0
8.2
2.2
1.2
<•?.,<]
23.7
0.3
0.06
0.63
185
106
320
1,9
4.9
Ij..1).
0
0
17.0
1.0
8.4
4.4
1.4
'JLfi
13.5
0.2
0.52
0.52
190
33
34
1|7
5J.
1,7.
0
0
14.0
1.0
8.0
2.fl
1.9
i^g
17.5
1.1
0.32
0.51
222
152
320
2,fi
fi,6
2^6
0
0
c?,,n
2,4
fi 7
2^1
0
0
2.0
10.8
0.8
0.02
0.73
159
164
3.0
7.8
.1.0
0
0
4.7
0.09
0.3
7.0
3.6
3.0
>M_
1.0
0.04
0.07
166
15
19
3.1
5.3
3.2
0
0
2.2
0.3
7.3
2.8
2.7
iM
10.7
0.8
0.02
0.12
184_
160
4.6
8.0
•1 . C
0
0
1.8
0.07
0.3
7.2
0.4
1.5
<; 2. c
10.7
0.02
0.12
176'
16
27
3.3
8.1
J.3
0
0
SLA
1.1
0.3
7.1
2.0
1 .3
v?.o
8.6
0.6
0.01
0.14
191
156
3.3
6.2
3.3
0
0
s,2.0
3.1
6.8
J.3
0
0
%2.H
2.9
6.1
J.I
0
0
P,3
3.1
0.3
7.2
3.6
2.i;
•3. 0
13.5
1.1
0.03
0.06
190
150
2.8
S.9
^.9
0
0
3.1
0.3
7.2
4.1
2.6
v2,0
18.2
0.28
3.1
6.1
2.P
0
0
4.7
0.3
7.0
6.0
4.7
S2.0
12.9
0.0
0.4 S
0.46
185 J205
19
22
118
2..S.
".0
J.I
0
0
6.5
0,3
•>.«
2.'
i.£>
\2,C
2.4
S.S
_\5
0
0
P,4
3.1
7.9
>,2.e
14. /! 15. 8
0.3
0.01
C.I 9
199
24
20
1.1
0.1 P
0.0 f
214
2.4
5.9
:.4
0
0
^2.C
2.6
6.7
:.4
0
0
s?.o
-------
SOUTH TAHOE PUBLIC UTILITY DISTRICT- WATER RENOVATION PLANT
MONTHLY TABULATION OF FLOW AND LABO. :ORY DATA
FEBRUARY
1970
(Month)
(Year)
O
03
Plant Flow , _M <"!
Peak Tlvn R-ito MGD
Flow Into Indian Creek
Reservoir, MG
Flow i'rom Indian Cieok
Rer.orvolr, MG
Total Flow From Other
Outlets. MG
5-d-v/ BOD (/no/1)
COD (rag/1)
Suspended Solids (mg/1)
M B A S (.T.g/1)
Turbidity, J U
pH (pi! units)
Chlorine P.OEidual(mg/l)
Instantaneous
30 Mln. Contact
Luther far,?. Station
Coll for. T.S (MI'II/100 ml)
Nitrogen (m»j/l M)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOs)
Hardness (mg/1 CaCO3)
Total Dissolved Solids(m
-------
SOUTH IDE PUBI.IC UTILITY DISTRICT- WATHR RENOVATION -'ANT
MuNTIILY TABULATION Ol" FLOW AND [MORATORY DATA
1970
(Me .ch)
O
ID
PJ^nt F'OW, M O
£gak Flow Rate MGD
Flov/ Into Indian Creole
Resrryoir, MG
Mow Horn Indian Cioek
P'.-r.'-.-rvjIr. f/CJ
Total Flov/ From Other
Outlo'Sj Mf5
5-d-v/ BOD (mq/1)
COD (m-7/1)
Suspended Solids (rnrj/1)
M B A S (rr,S/l)
Turbidity, J U
pi! (pll units)
Chlorine Rosldual(mg/l)
Instantaneous
30 Mln. Contact
Luther Pass Station
Conforms (MPI.'/IOO rnl)
Nitrogen (rng/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCO3)
Hardness (ng/1 CaCO3)
_Total Dissolved Solldr/mci/l
_fflLlorld> (mg/1)
Sulfate (mfj/1)
DATE
1.2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
2.5
5.8
2.5
0
0
4.5
12.2
0.0
0.5
7.0
1.0
0.9
0
0
4,3
3.4
0,0
0.4
7.1
0.9
0.9
12..5
n.2
0.27
0.01
217
158
2-4
4.6
JLd.
0
0
2.5
0.0
0.4
7.2
1.3
_q.j4_
0.0
31
J.O
4.5
JJ1
0
0
15.0
0.0
6.5
4.1
0.0
<:.o
13.9
0.0
o.ojc'.oi
0.10
234
J29
0.09
237,
16S
-------
Sr tn TA1IOE PUBLIC UTILITY DISTRICT- WATER "^NOVATION PLANT
MONTHLY TABULATION Ol I'LOW AND 1AI.H il'OKY DATA
APRIL
(Mouth)
(Year
Plant flow. M G
Peak Flow Rate MGD
Flo-// Into Indian Crack
I'Jow Irom Indian Creel:
Total Fiow From Other
5-day BOD (rnrj/l)
COD (rng/D
Suspor.ctad Solids (mg/1)
M B A S (me/1)
Turbidity, J U
pll (plf units)
Chlorine Rosldual(mg/l)
Inst<9nt«noo..B
30 Kin. Contact
Luther Pass Station
CollforriB (MPfJ/100 ml)
Nitrogen (mg/1 N1)
organic
arr.rr.on'.a
nitrate
nitrite
Phosphate (.1.3/1 P)
Alkalinity (mg/l CaCOj)
Hardness (mg/1 CaCO3>
Total Dissolved Sollds/ma/l
_QhJorldoJng/l)
Sulfatc (mg/1)
1
4.8
2.0
0_._0
0.0
3.1
13.4
0
0.35
0.5
7.0
3.1
0.3
24.9
15.3
0.0
0.00
0.09
221
26
2
4.6
2.0
0.0
0.0
14.4
9
0.3
7.0
2.8
U9
<2.0
I9.fi
0.08
195
148
3
•L.SL
4.4
2.0
0.0
0.0
2.7
9
0.3
7.0
2.4
1-J.
<2.0
235
4
5.3
2.2
p_._o_
0.0
9
0.3
7.1
<2-«
220
S 6
LJ_
4.8
2.3
0.0
0.0
16.1
9
0.3
7:1.
1.8
p_..o
^2.0
?0 fi
0.02
230
64
2 l
5.1
2.1
0.0
0.0
15.7
0
o.s
5.9
2.0
0.0
.3.0
2S 0
0.05
195
32
19
7
5.4
2.2
o.n
0.0
7.2
0
1.0
7.0
6.1
P_-A
^z.o
19, R
0.11
210
142
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
LJL
4.4
1.1
0.0
0.0
7.7
o
7.1
0.7
-------
SOUTH -M-IOE PUBLIC UTILITY DISTRICT - WATtR INNOVATION "LANT
TABULATION Ol1 FLOW AND LABORATORY DAT.
(N .ith)
Plant Flov/. M G
Pcafc Flw Roto MOD
Flow Into Indian Crsok
Reservoir t MO
FlOY/ From In'Jitiri Creel'.
Reservoir, MO
Total How From Other
Outl';'."., MO
S-H.T/ non frvj/n
COD (rr/j/1)
Suspended Solids (my/1)
M B A S (mg/1)
Turbidity, J U
pH (pi! units)
Chlorine Residual(mg/l)
Inst-intfln^our;
30 Mln. Contact
L'jthor Pass Station
Conforms (?-/!!'N/100 ml)
Nitrogen (mo/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/I P)
Alkalinity (mg/1 CaCO-0
Hardness (mg/1 CaCO3)
_Total Dissolved SolldsdnqA
Chloride {mg/1)
_JLulfate (mg/1)
DATP
1 2 34567 8 9 10 11 12 13
2.1
5.4
2.1
0.0
0.0
<2.0
2,3
4.9
2.3
0.0
0.0
fi.n
2,3.
4.6
2.3
0.0
0.0
20,7
0
0.3
6.7
0.0
0.5
<2.r
14.7
0.3
0.05
0.09
198
154
?_.J.
4.6
2.1
0.0
0.0
IS 3
0
0T3
7.0
3.3
0.5
,'2.0
16.2
0.1
0.03
0.01
ill
.34
42
2,-CL
5.0
2.0
0.0
0.0
17?
o
0.3
7.0
3.0
1.8
<2.0
16.5
0.0
0.02
0.09
204
160
l,A
4.7
2.0
0.0
0.0
1? ft
0
0,3
7.2
3.6
1.6
(2.0
13.9
0.0
0.09
0.01
198
38
40
!ML
».S
2.0
0.0
0.0
10 4
0
0,3
7.. I
2.8
1.7
<2.0
15.9
0.2
0.04
0.01
195
162
ua_
4.1
1.9
0.0
0,0
<2.0
2.1
4.2
2.1
0.0
0,0
<2.0
2.2
4.0
2.2
0.0
0,0
14,4
o
0,3
7,0
3.5
2.7
<2.0
13.3
0.3
0.10
0.01
218
182
2.0
3.6
2.0
0.0
0,0
13, B
n
0,3
7.1
2.4
1.8
<2.0
18.3
0.1
0.05
0.11
223
35
44
3.0
4.3
2.0
0.0
0,9
R 4
0
n,4
7.0
2.6
1.6
<2.0
18.9
O.I
0.15
0.06
218
170
1 .1
4.4
1.9
0.0
0,0
17, fi
0
0.3
.LJL
2.2
1.9
<[2.0
17.1
0.0
0.01
244
43
45
J.4
2.0
4.2
2.0
O.o
0.0
16. U
n
0.4
7.0
2.5
1.1
<2.C
16.1
0.03
0.15
212
168
15
,. ....
2.
4.7
2.1
0,c
0.0
<2.0
16_
2.4
4.9
2.-.A
0.
0.0
<2.0
J.I-
3.0
4.6
3.0
0,0
0.0
4.7
7.6
0
0.5
7.1
1.5
1.0
<2.0
17.2
0.1
0.04
0.11
216
132
18 19 20 21 22
2.1
4.4
2.1
0,0
0.0
8.1
0
0.30
0.5
7.1
1.9
0.8
(2.0
17.7
0.0
0.01
0.08
218
28
44
2.1
4.5
LA
0.0
0.0
1,0
13.4
0
0.30
0.5
7.5
2.4
1.1
;2.0
18.0
0.2
0.01
0.1 S
194
154
2.0
4.3
2.1
0.0
0.0
11.7
0
7.4'
3.2
1.3
s2.C
16.9
0.2
0.01
0.19
257
28
36
2.0
4.2
2.0
0.0
0.0
4 ft
11.2
0
0.3
7.1
3.1
1.5
a.o
14.4
0.0
0.01
0.19
264
174
2.0
4.8
2.0
0.0
0.0
S2.C
23
7.7
4.6
2.3
0,0
0.0
\2.0
24 25 26 27 28
2.2
4.8
2.2
0.0
0.0
9.P
0
0.3
7.0
1.3
0.0
sZ.O
16.4
1.4
0.01
0.01
248
160
2.1
4.5
2.1
0.0
0.0
8.4
0
0.18
0.5
7.1
1.6
0.3
S2,0
0.0
0.01
0.09
230
30
36
2.1
5.0
2.1
0.0
0.0
22.7
0.31
0.5
7.1
2.5
0.5
S2.fl
17.8
0.0
0.01
0.02
2.0
3.6
2.P
0.0
0.0
9.3
0
0.26
0.4
7.2
N2.0
16.3
0.0
0.01
0.01
243J22S
172
25
36
29
2.0J2.3
4.3
2.C1
0.0
0.0
21.8
0
0.45
1.0
8.3
1.0
1.8
^2,0
14.9
0.30
235
154
4.8
2.3
0.0
0.0
s2,(?
30 31
2.7J2.2
4.5
2 T
0.0
0.0
i2,f
1
3.9
:.2
0.0
0.0
RS
0
0.46
0.5
7.1
1.4
0.0
l2,0
18.7
0.11
227
146
-------
SOUTH TAHOE r 'BUG UTILITY DISTRICT - WATER RENOVATION PLANT
MONTH Li rABUIATION OF FLOW AND IABORATORY DATA
JUNE
1970
(Month)
(Year)
Plant Flow. M G
Ppak Flpw Rate MGD
Flow Into Indian Creek
Reservoir. MG
Flow From Indian Creek
Reservoir. MG
Total Flow From Other
Outlets. MG
5 -dav BOD (mg/1)
COD (mg/1)
Suspended Solids (mg/1)
M B A S (mo/1)
Turbidity , I U
pH (pll units)
Chlorine Resldual(mg/l)
Instantaneous
30 Min. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOs)
Hardness (mg/1 CaCOs)
Total Dissolved Soltds(m<:iy4
Chloride (mq/1)
SulfnlC (irq/J)
HATE
1 2 3 4 S 67 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
2.1
3.9
1.9
0.2
0.2
2.9
14.6
0
0.5
7.2
2.1
0.0
S2.<
19.5
0.1
0.01
0.08
221
28
45
2.1
4.9
1.9
0.2
0.2
2.3
10.0
0
0.41
0.5
6.9
5.9
1.0
s2.0
15.9
0.0
0.01
0.06
224
158
2.1
3.9
1.1
1.0
1.0
2.1
12.1
0
0.45
0.5
7.0
4.0
1.9
S2.0
13.8
0.0
0.01
0.05
205
24
44
2.1
3.8
1.1
1.0
1.0
1.0
0.8
0
0.42
0.5
7.2
2.8
1.3
<2. 0
15.4
0.0
0.00
0.04
196
136
2.1
4,3
1.1
1.0
1.0
v2.n
2,3
4,2
1.3
L.O
1.0
<2,n
2,3
3,8
1.3
1.0
1.0
2.4
8.4
0
023
0.4
6.9
2.2
0.0
<2,(1
15.9
0.0
0.00
0.05
200
140
2.2
4.2
1.2
1.0
1.0
2.8
5.1
0
0.31
0.5
6.9
1.0
0.0
<2,0
16.1
0.0
0.05
0.03
183
31
53
2.5
4.2
1.5
1.0
1.0
2.8
10.1
0
0.46
7.0
0.0
0.0
<.?,0
17.4
0.04
195
1S2
?, 4
4.1
1.4
1.0
1.0
1.1
8.4
0
0.19
0.5
7.0
5,0
0.0
0.04
0.03
198
27
48
? ?
3.9
1.2
1.0
1.0
1.4
0
0.35
6.8
3.6
2.0
<8,(
16.2
0.0
0.00
0.09
181
146
2,5
4.1
1.5
1.0
1.0
<2.0
2. ft
4.2
1.6
1.0
1.0
4.0
?,,,•>
4.2
1.5
1.0
1.0
13,5
0
1.0
3.9
3.1
5.0
20.0
0,25
136
I \
6.9
1.4
1.0
1.0
10,5
g
0,41
1.0
7.6
3.6
1.9
2
Q
1.0
7.9
6.3
1.4
<2.()
19.2
0.20
217
132
^
2.2
4.2
0.0
2.5
2.2
13,6
0.0
2.0
7.2
4.4
0.0
(2.0
20.9
0.23
230
31
56
2.6
4.!
0.0
2.5
2.6
24,5
0.0
1.0
7.2
2.3
1.0
<;2.o
19.8
0.09
190
200
2.5
4.1
ofo
2.5
2.5
<;2.c
2.7
4.4
0.0
2.S
2.7
<,Z,0
2.7
S.2
9,0
2.5
2.7
1.6
15.4
0.0
0.5
6.8
1.9
0.8
<2.0
20.4
o.q
0.06
0.19
186
140
2.8
4.6
2.8
2.5
0.0
14,1
0.0
0.7
6.9
1.6
0.0
<2.0
21.'1
0.1
0.07
0.15
189
11,
42
2.9
6.0
2.9
2.S
0.0
14,8
0.0
1.0
7.3
2.1
0.7
<2.0
19.3
0.02
0.40
184
134
2.6
5.6
2.6
2.5
0.0
14.8
0.0
0.7
7.2
1.2
0.7
<2.0
203
0.0
0.02
0.41
197
24
41
2.7
S.5
2.7
2.5
0.0
12, 6
0.0
0.5
7.1
1.9
1.1
<2.0
18.8
0.29
210
144
3.1
5.5
3.1
2.5
0.0
<2,0
3.1
6.4
3.1
2.5
0.0
<2,0
1
2.5
6.1
2.5
2.S
0.0
12.5
0.0
1.0
7.1
3.0
1.1
<2.0
20.4
0.2
0.02
0.61
215
120
3.2
5.5
3.2
2.5
0.0
1.2
16,3
0.0
1.0
7.3
1.6
1.0
£.0
14.2
0.1
0.06
0.45
200
42
3.0
5.5
3.0
2.5
0.0
14,1
0.0
0.19
0.5
7.4
1.8
0.9
S2.0
0.0
0.05
0.32
194
124
-------
SOUTH TAHOE Pli' 1C UTILITY DISTRICT- WATER RH^OVATION PLANT
MONTHLY v.iiULATION OF FLOW AND LABORATORY DATA
(Month)
lam...
(Year)
Plant rlow. M G
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir, MG
Flow Prom Indian Creek
Reservoir. MG
Total Flow From Other
Outlets . MG
5 -day BOD (mg/1)
COD (mg/1)
Suspended Solids (mg/1)
M B A S (mo/1)
Turbidity , J U
pH (pTI units)
Chlorine Resldual(mg/l)
Instantaneous
30 Min. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCO3)
Hardness (mg/1 CaCO3>
Total Dissolved Sollds(mc]/l]
Chloride (mg/1)
Sulftitc (mg/1)
nATF.
1 2 3456
2.6
5.3
0.0
3.0
2.6
1.1
12.2
0.0
0.21
0.4
7.3
3.0
1.1
<2.0
19. 5
0.0
0.0:
0.16
230
29
40
2.7
s.o
0.0
3.0
2.7
0.8
022
0.3
7.2
1.9
0.9
<2.0
18.2
0.3
0.02
0.10
225
142
2.9
5.9
0.0
3,0
2.9
<2.{
3.3
7.3
0.3
3rO
3.0
C2.0
2.8
6.5
0.0
3,0
2.8
3.2
1S.9
0.0
021
0.8
7.1
1.9
0.7
-------
SOUTH TAHOE Pf 1C UTILITY 1MRTRICT - WATER R} "OVATION PLANT
MONTHT.Y i .BULATION OF FLOW AND LABORA OM DATA
AUGUST
(Month)
1970
(Year)"
Pl.irit Flov/. M G
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir j_MG
Flow From Indian Creek
Reservoir, MG
Total Flow From Other
Outlets. MG
5 -clay BOD (mg/1)
COD (mg/1)
Suspended Solids (mg/1)
M B A S (mq/1)
Turbidity, J U
pH (pll units)
Chlorine Residual (mg/1)
Instantaneous
30 Mln. Contact
Luther Pass Station
Coliforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCOg)
Harrlnoss (mg/1 CaCO3>
Totnl Dissolved Sollds(mgA
Chloride (nig/))
Snlfotf (i"ff/l)
DATI'
1 2 3 4 5 6 7 8 9 10 11 17. 13 14 15 16 17 18 19 20 21 22 23 24
3.0
6.9
0.0
10.0
3.0
1.9
0.0
<2.0
2.9
6.3
0.0
10.0
2.9
0.1
11.9
0.0
0.19
0.3
8.3
1.8
1.5
<2.0
20.6
0.1
0.19
0,28
315
136
2.7
6.6
0.0
10.C
2.7
3.5
10.8
0.0
0.3
2.7
1.8
<2.0
19.0
0.24
2<»
36
2,8
7.1
0.0
10. (1
2.8
1.7
14.0
0.0
0.12
7.3
3.3
2.1
<2.0
20.4
0.8
0.24
0.14
252
180
13
6.4
0.0
10.0
2.9
1.2
9.8
0.0
0.10
0.3
7.5
1.9
1.5
<2.0
19.5
0.21
252
32
34
2,9
6.4
0.0
10.0
2.9
3.1
10.5
0.0
022
0.3
7.8
2.4
1.4
<2.0
20.2
0.4
0.46
0.18
192
172
3,0
6.8
0.0
10.0
3.0
-------
SOUTH TAHOE PUr*TC UTILITY DISTRICT - WATER REfJQVATION PLANT
MONTHLY 'J..JULATION OF FLOW AND LABOR;!^»RY DATA
SEPTEMBER
1970
(Month)
(Yea,)
Pl^n^ Plow. M G
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir. MG
Flow From Indian Creek
Reservoir. MG
Total Flow From Other
Outlets. MG
S-day BOD (mg/1)
COD (mg/1)
Suspended Solids (mo/1)
M B A S (ma/1)
Turbidity. J U
pH (pll units)
Chlorine Rc8lduai(mg/l)
Instantaneous
30 Mln. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 P)
Alkalinity (mg/1 CaCO3)
Hardness (mg/1 03003)
Total Dissolved Solidsfmg/l
Chloride (mg/1)
Sulfate (mg/1)
JWE
1 '2 3 4 S 67 8 9 10 11 12 13.. 14 15 16 17 18 19 20 21 22 23 24 25 26
2.7
5.8
0.0
10.
2.7
2.0
9.2
0.0
020
0.1
7.4
3.2
1,3
(2.0
19.2
1.3
0.37
0.08
239
148
2.6
5.8
0.0
10.
2.6
7.1
0.0
049
0.1
7.4
4.1
1.3
CZ.O
18.4
1,3
0.3 0
0,06
229
43
23
2.6
6.6
0.0
10.
2.6
0.6
10.5
0.0
020
0.2
7.3
2.8
1.2
<2.0
15.1
1,1
0.49
0.04
220
138
2.9
7.0
0.0
10.
2.9
<2.0
J.O
6.8
0.0
10.
3.0
<2.0
».3
7.0
0.0
10.
3.3
0.8
9.6
0,0
0.14
0.2
7.2
1.9
1.2
<2.(
16.4
\,7
0.3 0
0.06
246
138
i.O
6.0
0.0
10.
3.0
0.3
7.1
0,0
0.19
0.2
7.1
2.8
1.2
CZ.O
18.6
1,5
0.44
0,00
265
30
22
2.4
6.0
0.0
10.
2.4
0.8
9.9
0.0
0.13
0.2
7.0
2.7
1.6
<2.0
18.2
1,3
049
0.13
235
146
2.5
S.8
0.0
10.
2.5
0.2
10.2
0.0
046
0.2
7.2
<2.0
12.6
1.6
0.45
Of19
244
26
33
2.4
5.0
0.0
10.
2.4
0.7
10.5
0,0
044
0.3
7.1
4.1
0.0
<2.0
15.4
0.6
0.45
O.p9
212
126
2.4
6.0
0.0
10.
2.4
<2.0
2.5
6.6
0.0
10.
2.5
<2.0
2.3
6.5
0.0
io.
2.3
0.9
0.0
021
7,5
2,3
1.9
<2.0
15,5
O.S
0.11
006
215
138
2.2
5.3
0.0
10.
2.2
O.S
9,0
0.23
7,5
3,0
1.8
<2.0
17,4
1.0
0.52
005
257
29
33
2.4
6.0
0.0
10.
2.4
2.2
9,0
021
7,2
?.?
2.6
<2.0
16.5
0.1
9.52
000
235
150
2.5
5.3
0.0
10.
2.5
0.7
9,0
0.20
M
2,7
2.5
0,0
14.4
1.5
0,35
0.00
244
26
26
2.3
5.2
2.3
0.0
0.0
1.1
9.6
0.0
044
7.5
2.7
2.1
<2,9
16.7
1.6
0.34
0.02
225
114
2.4
6,0
2.4
0.0
0.0
-------
SOUTH TA11OE PUP "0 UTILITY DISTRICT- WATHR P.VNOVATION PIANT
MONTHLY T/iuULAT/ON Oi 1'LOW AND LABORATORY DATA
OCTOBER
(Month)
O)
FJ-./jt rl '--•". -M..O.
H «••.-.>: Mo>/ IMI'! MC;u
rlov/ Into Inrll'in Crook
R'jRirvolr, MO
I'lov/ | roiii Indian Cicuk
Rr:r<--[./otr. Mf!
Total I'lov/ J'rora Other
Onti'f:;, MC;
5-d-v/ HOD ((fi',1/1)
COD (my/I)
Susp'.-n'led Soli'.l!t (rntj/1)
M B A S (rr.o/1)
Turbidity. J U
pi I (pi! units)
Chlorine P,esldual(mg/l)
InKtont'inoo'i.n
30 Min. Contact
I.utlior I'nss Station
Conforms (MPM/100 ml)
Ultro'j'in (mrj/1 M)
organic
ammonia
nitrate
riitrlto
Phosphate (rng/1 P)
Alkalinity (mo/1 CaCO3)
Hardness (mg/1 CaCO3>
Total Dissolved Solldsfmq/1
Chloride (mg/1)
Sulfato (ma/1)
1
2.2
4^0
2.2
0.0
0.0
0.0
0.06
7.1
3.1
1.9
<2.0
15.1
0.5
0.34
0.14
205
196
2
2j.O
5.3
2.0
0,0
0.0
<2.0
345
2... 3.
5.2
2.3
0.0
0.0
0.7
7.3
0.0
0.09
0.2
7.5
1.2
0.5
<2.0
17.4
0.3
0.02
0.04
215
116
2. -A
5.5
2.4
0.0
0.0
.1*3
(2.0
1,9
5.2
1.9
0.0
0.0
1.4
10.0
0.0
0.09
0.2
7.5
1.3
0.7
<2.0
0.3
0.11
0.16
195
25
28
PATT , - - •
67 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 25 29 30 31
?•!
5_.J)
2.1
0.0
0.0
-0,3
4.9
0.0
0.09
0.2
7.3
1.2
O.B
<2.0
0.6
0.02
0.06
249
140
2-1
4.3
2.1
0.0
0.0
Q..A
6.9
0.0
0.09
0.1
ZA
1 .4
0.9
<2.0
0.8
0.13
0.00
200
48
2,1
4.8
2.1
0.0
0.0
6.3
0.0
0.08
0.1
7.5
1 .4
1.0
<2.0
19.7
0.9
0.11
0.03
236
US.
2.1
4.9
2.1
0.0
0.0
—
—
<2.C
2.2
5.3
2.2
0.0
0.0
0.9
<2.0
2.1
5.0
2.1
0.0
0.0
1.1
8.2
0.0
0.10
0.2
7.5
0.8
1.0
<2.C
0.9
0.15
0.06
255
.111
2,0
4.9
2.0
0.0
0.0
1.2
6.0
0.0
0.11
0.2
7.5
2.3
1.0
<2.0
0.5
0.04
0.09
205
136.
24
28
2.0
4.9
2.0
0.0
0.0
1.2
5.6
0.0
0.11
0.2
7.6
1.7
1.1
<2.0
17.9
0.8
0.11
0.06
254
140
2.1
5.1
21
0.0
0.0
0.4
13.2
0.0
0.09
0.2
7.5_
1.5
0.9
<2.0
13.9
0.5
0.12
0.04
263
384
29
19
1 9
.lil
1.9
0.0
0.0
0.4
12.9
0.0
0.14
0.2
7.4
1.7
1.0
<£.0
17.0
0.4
0.12
0.02
235
148
304
? 1
.KI
2,1
0.0
0.0
1.7
1.0
5.0
? 1
4.7
2.3
HJL
0.0
<2.0
2.2
4.7
2.2
Q.I&
0.0
0.6
11.5
0,0
0.11
0.2
7.3
1.7
1.5
4.4
13.3
1.0
0.13
0.04
296
122
349
1.9
4.7
1.9
0.0
0.0
1.2
9.2
0.0
0.14
0.2
7.4
1.1
O.H
15.0
17.7
1.0
0.12
0.03
275
39
22
2.0
4.8
2.0
0.0
0.0
0.3
8.1
0.0
0.08
-------
SOUTH.TAIIOE PU"UC UTJUTY DISTRICT- WATi:R'R):NOVATION PLANT
MONTHLY .HULATION OF 1'l.OW AND J-ABOIV'TOKY DATA
(Month)
J12P._
(Year)
I'hint T\'jir. M C
PC.-..)- I -\'sn K»tn MOD
Flov/ ir.to Intifan CrocV.
fC.TX.-r/oIr, I/fi
rio'.v I ro:a In'Jinn. Cit'oV.
I'.r:r,«:rvo:r, MC
Totfl! r!ov; l"rr,m Othor
Out!'-'.!;. M
Total Dissolved Solldsfmq/l
Chloride (rng/1)
Sulfotc (rf3/l)
1 2 31567 8 9 10 11 12 13 11 15 • 16 17 18 19 20 21 22 23 24 25 26
2,0
6.3
2.0
P_,0
0.0
1.5
9.9
0
0.23
0.2
7.2
1.3
0.9
<2.0
21.2
1.1
0.16
0.07
296
154
1.6
4.9
1.6
0.0
0.0
0.8
10.6
0
0.14
0.2
7.2
1.0
1.0
<2.0
18.2
1.1
0.23
0.07
254
346
36
26
1.7
5.0
1.7
0_iO
0.0
L.O
9.9
0
0.15
0.2
7.3
1.4
0.6
<2.0
14.2
1.3
0.11
0.05
2S8
160
2.1
6.9
2.1
0.0
0.0
0.1
8.6
0
0.16
0.2
7.2
1.2
0.6
<2.0
19.2
1.4
0.02
0.06
248
338
26
26
2.2
5.8
2.2
0.0
0.0
0.6
6.9
0
0.19
0.2
7.1
1.4
0.6
<2.n
—
1.0
0.11
0.01
235
164
312
1.8
S.3
1.8
0,0
0.0
,"?.,n
2.4
6.0
2.4
0.0
0.0
-------
SOUTH TAHOF PUBLIC UTILITY DISTRICT - WATER RENOVATION PLANT
MONTHLY TABULATION OF FLOW AND LABORATORY DATA
DECEMBER
(Month)
1970
(Year)
Plant Tlow. MG
Peak Flow Rate MGD
Flow Into Indian Creek
Reservoir, MG
Flow From Indian Creek
Reservoir, MG
Total Flow From Other
Outleti,MG
5-day BOD (ma/1)
COD (mg/1)
Suspended Solids (mg/1)
M B A S (mg/1)
Turbidity, J U
pH (pH units)
Chlorine Resldual(mg/l)
Instantaneous
30 Mln. Contact
Luther Pass Station
Conforms (MPN/100 ml)
Nitrogen (mg/1 N)
organic
ammonia
nitrate
nitrite
Phosphate (mg/1 r)
Alkalinity (mg/1 CaCO3)
Hardness (mg/1 CaCO3)
Total Dissolved Sollds(mci/l
Chloride (mg/1)
Sulfatc (mg/1)
p ntrp
1
1.9
3.6
1.9
0.0
0.0
0.9
0
0.07
7.4
<2.(
22.3
O.S
0.02
0.04
325
134
2
1.9
3.8
1.9
0.0
0.0
0.2
3.4
0
0.09
7.3
(2.0
18.8
0.9
0.03
0.06
315
22
22
3
2.0
2.0
0.0
0.0
0.3
8.0
D
0.12
0.4
7.2
1.6
0.8
C2.0
19.5
0.9
0.05
0.04
235
126
4
2.0
2.0
0.0
0.0
an
s
2,2
2.2
0.0
0.0
<2,0
6
2.2
-Re
2.2
0.0
0.0
1.4
6.8
0
0.12
0.2
1.6
1.0
S6
199
00
-------
FIGURE C-1
COD ISOTHERM
VIRGIN CARBON
FEBRUARY 1968
9
:
3
e
E
4
§ 3
00
DC
O
u- 2
O
5
CC
Ul
0.
Q
DC .9
§ '8
< x/n
Q .6
O
(j 5
U.
O
(/j .4
s
x|E -3
:
.1
"~ •
>
X
X
/
^
y
/
/O O
/
7f
X
./
/
Co
3 4 5 6 7 8 9 10
20 30 40 50 60708090100
C, RESIDUAL COD, MG/L
-419-
-------
FIGURE C-2
COD ISOTHERM
CC-5 SPENT
DECEMBER 1968
0
03
•2.
<
O
U-
o
a
n
Ill
a
a
_
a
r
0
M
a
<
a
C
u
L_
C
u
a
"IE
1.0
E
B
7
.6
x5/n
4
3
;
.10
-':'
.08
.07
.06
.05
04
.03
.02
.01
10
20
30 40 50 60 708090100
3 4 56789 10
C, RESIDUAL COD, MG/L
-420-
-------
FIGURE C-3
COD ISOTHERM
CC-5 REGENERATED
DECEMBER 1968
9
B
;
,,
2 4
0
a
< 3
0
LL
0
^ O
ORBED PER N
' 1- '
0)
Q 9
< 8
->
8
it R
o
in. R
O
2 4
1
O 1
—
/
/
/
/
/
/
5
9
/
/
7\
7
1C
4 5 6 7 8 9100
200
3 4 5678910
C, RESIDUAL COD, MG/L
-421-
-------
FIGURE
-------
FIGURE C-5
COD ISOTHERM
CC-5 REGENERATED
JANUARY 1970
3
DC
<
L
a.
C
-
LU
_
DO
DC
a
-•
a
4
a
:
u
_
c
.
;-
5
• -
1.0
g
7
x/n
.6
-
4
3
.
10
:
40°° 50 60 70 80 90 100
C, RESIDUAL COD, MG/L
-423-
-------
FIGURE C-6
COD ISOTHERM
CC-5 SPENT
NOVEMBER 1970
1 .U
.7
.6
§ -5
O
OC .4
<
o
U- -3
o -J
O
DC x/n .2
ID
0.
Q
LU
00
DC
O
Q .10
** .09
§ -08
0 .07
S -06
o -05
.04
.03
.02
.01
!
/
/
y
/
rt
/
2 3456789 100 2 34567891
Co
C, RESIDUAL COD, MG/L
-424-
-------
FIGURE C-7
COD ISOTHERM
CC-5 REGENERATED
NOVEMBER 1970
o
Da
E
u
LL
3
3
1.0
S
B
.7
.6
5
03
O x/n
a
5
ia
[3
.2
1C
20
30 Co 40 50 60 70 80 90 100
C, RESIDUAL COD, MG/L
-425-
-------
1.0
.9
.8
.7
.6
.5
I *
C
2 3
IL
o
1 -2
£ x/n
0.
Q
UJ
CD
DC .1.0
g .09
.08
o -
0 .06
u. .05
O
8 -04
.03
xte
.02
.01
1
FIGURE C-8
COD ISOTHERM
CC-8 SPENT
JULY 1970
—
y
^
/
)
/
^
/
/
CD
3 20 30 40 50 60 70 8090100 2 3 4 56789 10
C, RESIDUAL COD, MG/L
-426-
-------
FIGURE C-9
COD ISOTHERM
CC-8 REGENERATED
JULY 1970
z
a
DO
a
<
u
a
a
LJ
CD
a
c
c
u
LJ-
0
c
2
I
*IE
1.0
.9
J
7
.6
x/n
3
.2
1C
20
30 Co40 50 60 70 80 90 100
C, RESIDUAL COD. MG/L
-427-
-------
FIGURE C-10
MBAS ISOTHERM VIRGIN CARBON
FEBRUARY 1968
8
6
5
4
00
DC
-------
FIGURE C-11
MBAS ISOTHERM CC-5 SPENT
DECEMBER 1968
.1
.09
.08
.07
.06
.05
g -04
DC
0 .03
LL
._ x/n
35 .02
DC
111
0.
Q
HI
DC .01
» .009
Q .008
: .007
< .006
00
! .005
LL
0 .004
(/)
0
5 .003
I
xlE
.002
.001
»•"
j*
i<
^
.*^
^^^
^f
^
*•
^^
^~
^
o
01
.02
.03 .04 .05 .0607.0a09.1
.2 .3 .4 .5 .6 .7 .8 .91 .0 Co
C, RESIDUAL MBAS, MG/L
5 6 7 8 9 10
-------
FIGURE C-12
MBAS ISOTHERM CC-5 REGENERATED
DECEMBER 1968
§
<
o
S
§
o
x/n
m
LL
O
XIE
0.1
.09
.08
-07
.06
.05
.04
.02
.01
01
.02 .03 .04 .05 .oaozoaoal
.2 .3 .4 .5 .6 .7 .8 .91.0
C, RESIDUAL MBAS, MG/L
Co 2
4 5 6 7 8 9 10
-------
FIGURE C-13
MBAS ISOTHERM CC-5 SPENT
JANUARY 1970
-U
CJ
z
O
OQ
DC
(D
5
DC
UJ
0.
0
UJ
00
g
S
<
x:E
1
.9
8
1
6
-
2
.:
09
.08
07
, ||
• i1
.04
.03
x/n
.02
.01
'
,*--*
(T^
^-*
.--
-
^r^
r
i .02 .03 .04 .05.06.07.0aoai .2 .3 .4 .5 .6 .7 .8 .9 1 .0 Co 2 3 4 5 6 7 8 9 1C
C, RESIDUAL MBAS. MG/L
-------
FIGURE C-14
MBAS ISOTHERM CC-5 REGENERATED
JANUARY 1970
it
CO
i
or
s
u_
O
u
DC
IN
a.
D
in
OB
DC
( >
M
D
tg
•i
CD
5
1/3
O
xlE
.01
I
g
a
/
6
x/n
01
4 5 6 7 8 9.1
2 3 4 5678 91.0
C, RESIDUAL MBAS, MG/L
Co 2
4 5 6 7 8 9 10
-------
FIGURE C-15
MBAS ISOTHERM CC-5 SPENT
NOVEMBER 1970
-
U
U
.1
.09
.08
.07
.06
-05
.04
x/n
.03
-02
.01
-009
.008
.007
.006
.005
.004
\ .003
xlE
.002
.001
CD
fe
CJ
5
LU
a.
Q
ill
CD
c
g
9
|
.02
.03 .04 .05 .06.07.0a09.1
.2 .3 .4 .5 .6 .7 .8 .91.0
C, RESIDUAL MBAS, MG/L
Co 2
5 6 7 8 9 10
-------
FIGURE C-16
MBAS ISOTHERM CC-5 REGENERATED
NOVEMBER 1970
.9
a
i
.6
Z .5
•4
0
u. .3
O
0
01
a.
O
01
00
DC
O .1
U) no
a .09
< .08
OT .07
m .06
5x/n
u. .05
O
to •'"
5
1 .03
xiE
.02
.01
<
—
^
^
^ff
**"
^"
^"
^
^
^^f
*er*
^
^
^-
si
-•-
r---
a
-?rf
^^
1 .02 .03 .04 .05 .06.07.0aOai .2 .3 .4 .5 .6 .7 .8 .9 1 .0 Co 2 3 4567891
C, RESIDUAL MBAS MG/L
-------
FIGURE C-17
MBAS ISOTHERM CC-8 SPENT
JULY 1970
.1
09
08
07
06
,06
04
11; i
x/n
02
.01
.009
.008
.007
.006
.005
.004
.003
.002
u.
i I'
(9
n
ill
oo
E
tn
a
'3
l/j
•i
ai
tn
a
:
i
xlE
.001
,01
4 5 6 7 8 9 .1
7. 3 4 567891.0
C, RESIDUAL MBAS, MG/L
Co2
4 5 6 7 8 910
-------
O
a
IT
c
iu
Q.
cc
§
3
8
x E
x/n
I
•I
8
/
e
.01
FIGURE C-18
MBAS ISOTHERM CC-8 REGENERATED
JULY 1970
1
.09
.08
.07
'06
.05
.03
.02
.(II
.02 .03 .04 .05.06.07.0aoai
.2 .3 .4 .5 .6 .7 .8.91.0
C, RESIDUAL MBAS, MG/L
Co 2
4 5 6 7 8 910
-------
Accession Number
Sn6;e<-f Field &. Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
South Tahoe Public Utility District, South Lake Tahoe, California
Title
Advanced Wastewater Treatment As Practiced At South Tahoe
1 Q Authors)
Gulp, Russell L.
Evans, David R.
16
21
Project Designation project NO.
Grant WRPD 52-01-67
17010 ELQ
Note
Wilson, Jerry C.
22
Citation
23
Descriptors (Starred First)
Phosphorus removal, ammonia stripping, recarbonation, mixed media filtration
carbon adsorption, lime recalcining, carbon regeneration, sludge incineration,
virus removal, algae control, water pollution control.
25
Identifiers (Starred First)
Water renovation, nutrient removal
s rac This report presents the results from three years operation of a 7.5 mgd ad-
vanced wastewater treatment plant at the South Tahoe Public Utility District in South
Lake Tahoe, California.
The work includes a comprehensive study of the efficacy, reliability, and economy
of a tertiary sequence of treatment consisting of conventional activated sludge, followed
by lime treatment for phos_phate removal, ammonia stripping, two-stage recarbonation,
mixed media filtration, granular activated carbon adsorption of dissolved organics, and
chlorination. Granular carbon is thermally regenerated and resued, spent lime mud is
recalcined and reused, and all waste organic and chemical sludges are incinerated to
sterile, inert a sh.
Quality of the reclaimed water is consistently very high. It is sparkling clear, low
in algal nutrients, free of color, odor, bacteria, and viruses, and is suitable for many, if
not all, types of reuse.
The project clearly demonstrates that all of the necessary technology is now avail-
able to completely control water pollution from all domestic and most industrial wastewaters
provided thata genuine desire exists to do so. and that adequate leadershinand financing are
Abstractor
Russell L. Gulp
Institution
South Tahoe Public Utility District
provided.
WR:I02 (REV JULY 1969)
WRSIC
SEND TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D C 20240
» 6PO: 1969-359-339
------- |