&EPA
               United States
               Environmental Protection
               Agency
              Office of Research and Development
              Municipal Environmental Research
               Laboratory
              Center for Environmental Research
               Information
              Cincinnati OH 45268
Office of Water
Office of Water Program
 Operations
Washington DC 20460
                Technology Transfer
Design
Manual

Municipal
Wastewater
Stabilization
Ponds

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EPA-625/1-83-015
                                 DESIGN MANUAL


                   MUNICIPAL WASTEWATER STABILIZATION PONDS
                     U.S. ENVIRONMENTAL PROTECTION AGENCY

                      Office of Research and Development
                  Municipal Environmental  Research Laboratory
                 Center for Environmental  Research Information

                                Office of Water
                      Office of Water Program Operations
                                 October 1983

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                                    NOTICE                     >


This  document has  been  reviewed  in  accordance  with  the  U.S.  Environmental
Protection Agency's  peer  and administrative review policies and  approved for
publication.    Mention  of  trade  names  or  commercial  products  does  not
constitute endorsement or recommendation for use.
                                      ii

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                                   FOREWORD
The  formation  of  the  Environmental  Protection. Agency  marked a  new era  of
environmental awareness in America.  This Agency's goals are national  in scope
and encompass broad  responsibility in the  areas  of air and  water pollution,
solid wastes, pesticides,  hazardous wastes,  and  radiation.    A vital  part of
EPA's  national   pollution  control  effort  is  the  constant   development  and
dissemination of new technology.

It is now clear that only the most effective design and operation of pollution
control facilities using  the latest available  techniques will  be  adequate to
ensure  continued  protection of   this  Nation's  natural   resources.    It  is
essential   that  this  new  technology  be  incorporated  into  the  contemporary
design  of  pollution  control  facilities  to achieve  maximum benefit  from  our
expenditures.

The purpose of this manual is to provide the engineering community and related
industry a  new  source  of information to be used  in the planning,  design,  and
operation  of  present  and  future  stabilization  ponds  treating  municipal
wastewaters.  It is  the intent of the manual  to  supplement the existing body
of knowledge in this area.

This manual  is  one of  several  available from  Technology Transfer  to  describe
technological advances and present new information.
                                     iii

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                                ACKNOWLEDGMENTS
Many  individuals  contributed to  the preparation  and  review of  this  manual.
Contract  administration  was  provided  by the  U.S.  Environmental  Protection
Agency, Center for Environmental Research Information,  Cincinnati, Ohio.
CONTRACTOR-AUTHORS

     Major Author:
     Contributing
      Autho rs:
Dr.  E.  Joe Middlebrooks,  Newman Chair  of  Natural
  Resources Engineering, Clemson University

James H.  Reynolds,  James M.  Montgomery  Consulting
  Engineers, Inc.
Charlotte Middlebrooks,,  Middlebrooks  & Associates,
  Inc.
R.   Wane   Schneiter,    Kennedy/Jenks   Engineers
Richard J.  Stenquist, Brown  &  Caldwell  Consulting
  Engineers
Bruce    A.     Johnson,    Ch^M    Hill    Engineers
CONTRACT SUPERVISORS

     Project Officer:

     Reviewers:
Denis   J.    Lussier,    EPA-CERI,   Cincinnati,   OH

Edwin  F.  Barth,  Jr.,  EPA-MERL,  Cincinnati,  OH
Ronald   F.   Lewis,   EPA-MERL,   Cincinnati,   OH
Sherwood   c.    Reed,    COE-CRREL,    Hanover,   NH
Richard  E.   Thomas,   EPA-OWPO,   Washington,   DC
TECHNICAL PEER REVIEWERS

     Dr. Ernest  F.  Gloyna - University of  Texas-Austin,  Austin,  TX
     George   W,    Mann   -   City   of   Kissimimee,   Kissimmee,   FL
     Dr. Walter  J.  O'Brien -  Black & Veatch  Engineers,  Dallas,  TX
     Dr.  A.   T.  Wallace  -   University  of   Idaho,   Moscow,   ID


Review comments  were  compiled  and summarized by Mr. Torsten Rothman,  Dynamac
Corp., Rockville, MD.
                                      iv

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                                   CONTENTS

Chapter                                                             Page
           FOREWORD                                                  111'
           ACKNOWLEDGMENTS                                            iv
           CONTENTS                                                    v
           LIST OF FIGURES                                           vll
           LIST OF TABLES                                             xi

           INTRODUCTION

           1.1  Background and History                                 1
           1.2  Manual Objective and Scope                             1
           1.3  Types of Ponds                                         2
           1.4  Nutrient Removal Aspects                               7
           1.5  References                                             7

           PROCESS THEORY, PERFORMANCE, AND DESIGN

           2.1  Biology                                                8
           2.2  Biochemical Interactions                     ,         11
           2.3  Controlling Factors                                   16
           2.4  Performance and Design of Ponds                       20
           2.5  Disinfection                                          53
           2.6  Odor Control                                         -64
           2.7  References                                            71

           DESIGN PROCEDURES

           3.1  Preliminary Treatment                       ,          75
           3.2  Facultative Ponds                                     75
           3.3  Complete Mix Aerated Ponds   •    •                     98
           3.4  Partial Mix Aerated Ponds                            114
           3.5  Controlled Discharge Ponds                           129
           3.6  Complete Retention Ponds        •                     135
           3.7  Combined Systems                                  .   143
           3.8  References                                           144

           -PHYSICAL DESIGN AND CONSTRUCTION

           4.1  Introduction                                         147
           4.2  Dike Construction                                    147
           4.3  Pond Sealing                                         150
           4.4  Pond Hydraulics                                      182
           4.5  Pond Recirculation and Configuration                 185
           4.6  References                                           190

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                              CONTENTS  (continued)

Chapter


   5       ALGAE, SUSPENDED SOLIDS, AND NUTRIENT REMOVAL

           5.1   Introduction
           5.2   In-Pond Removal Methods
           5.3   Filtration Processes
           5.4   Coagulation-Clarification Processes
           5.5   Land Application
           5.6   References

   6       COST  AND ENERGY REQUIREMENTS

           6.1   Capital Costs
           6.2   Cost Updating
           6.3   Energy Requirements                  ,
           6.4   References.

APPENDIX   EVALUATION OF DESIGN METHODS

           A.I   Facultative Ponds
           A.2   Aerated Ponds
           A.3   References
Page
 192
 192
 202
 247
 259
 271
 280
 285
 288
 290
 292
 312
 327
                                      vi

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                                   FIGURES

Number.                                                              Page


2-1        The Nitrogen Cycle                        _                13
2-2        Calculated Relationship Among pH, C02, C03~, HCC^",
             and OH~                                                  15
2-3        Changes Occurring in Forms of Nitrogen Present in
             Pond Environment Under Aerobic Conditions                18
2-4        Schematic Flow Diagram and Aerial Photograph of the
             Facultative Pond System at Peterborough,
             New Hampshire                                            21
2-5        Schematic Flow Diagram and Aerial Photograph of the
             Facultative Pond System at Kilmichael, Mississippi       23
2-6        Schematic Flow Diagram and Aerial Photograph of the
             Facultative Pond System at Eudora, Kansas                25
2-7        Schematic Flow Diagram and Aerial Photograph of the
             Facultative Pond System at Corinne, Utah                 26
2-8        Facultative Pond BODr Effluent Concentrations              37
2-9        Facultative Pond SS Effluent Concentrations                29
2-10       Facultative Pond Fecal Coliform Effluent Concentrations    31
2-11       Schematic Flow Diagram and Aerial Photograph of the
             Aerated Pond System at Bixby, Oklahoma                   40
2-12       Schematic Flow Diagram and Aerial Photograph of the
             Aerated Pond System at Pawnee, Illinois                  41
2-13       Schematic Flow Diagram and Aerial Photograph of the
             Aerated Pond System at Gulfport, Mississippi             42
2-14       Schematic Flow Diagram and Aerial Photograph of the
             Aerated Pond System at Koshkonong, Wisconsin             44
2-15       Schematic Flow Diagram and Aerial Photograph of the
             Aerated Pond System at Windber, Pennyslvania             45
2-16       Aerated Pond BODg Effluent Concentrations                  46
2-17       Aerated Pond SS Effluent Concentrations                    48
2-18       Aerated Pond Fecal Coliform Effluent Concentrations        49
2-19       Chlorine Dose vs. Residual for Initial Sulfide
             Concentrations of 1.0-1.8 mg/1                           55
2-20       Changes in Soluble COD vs. Free Chlorine Residual —
             Unfiltered Pond Effluent                                 56
2-21       Chlorine Dose vs. Total Residual—Filtered and
             Unfiltered Pond Effluent                                 57
2-22       Total Coliform Removal Efficiencies—Filtered and
             Unfiltered Pond Effluent                                 58
2-23       Combined Chlorine Residual at 5°C for Coliform =
             104/100 ml                                               60
2-24       Conversion of Combined Chlorine Residual at Temp. 1
             to Equivalent Residual at 20°C                           61
2-25       Conversion of Combined Chlorine Residual at TCOD 1 and
             20°C to Equivalent Residual at TCOD = 60 mg/1 and 20°C   62
2-26       Determination of Chlorine Dose Required for Equivalent
             Combined Residual at TCOD = 60 mg/1 and 20°C             63
                                     vii

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                             FIGURES  (continued)

Number                                                              Page-


2-27       Conversion of Combined Chlorine Residual at TCOD 1 and
             5°C to Equivalent Residual  at TCOD = 60 mg/1 and 5°C     65
2-28       Determination of Chlorine Dose Required When S = 1.0
             mg/1, TCOD = 60 mg/1, and Temp. = 5°C            .        66
2-29       Sulfide Reduction as a Function of Chlorine Dose           67

3-1        Wehner and Wilhelm Equation Chart                          93
3-2        kct vs. C0/Cn for,Complete Mix Model                      102
3-3        Layout of One Cell  of Complete Mix Aerated Pond
             System                                                  113
3-4        Layout of Surface Aerators in First Cell of Partial
             Mix System                                              127
3-5        Layout of Aeration System for Partial Mix Diffused
             Air Aerated Pond Systemn                                128
3-6        Portion of Advected Energy (Into a Class A Pan)
             Utilized for Evaporation                                138
3-7        Shallow Lake Evaporation as a Function of Class A Pan
             Evaporation and Heat Transfer Through the Pan           139

4-1        Eroded Dike Slopes on a Raw Wastewater Pond in a
             Dry Climate                                             149
4-2        Top Anchor Detail--Alternative 1, ATI Linings             167
4-3        Top Anchor Detail—Alternative 2, All Linings             168
4-4        Top Anchor Detail—Alternative 3, All Linings             169
4-5        Top Anchor Detail—Alternative 4, All Linings Except
             Asphal t Panel s                                          170
4-6        Top Anchor Detail--Alternative 5, All Linings             171
4-7        Seal at Pipes Through Slope—All Linings                  172
4-8        Seal at Floor Columns--Asphalt Panels                     173
4-9        Pipe Boot Detail--All Linings Except Asphalt Panels       174
4-10       Seal at Inlet-Outlet Structure--All Linings               175
4-11       Mud Drain Detail—All Linings                             176
4-12       Crack Treatment—Alternatives A and B                    "177
4-13       Wind and Gas Control                                      178
4-14       Cost Comparison for Linings in the United States          179
4-15       Special Fiberglass Plug                            ?.      184
4-16       Common Pond Configurations and Recirculation Systems      187
4-17       Cross Section of A Typical Recirculation Pumping
             Station                                  •        E       189

5-1        Length of Filter Run as a Function of Daily Mass
             Loading for 0.17 mm Effective Size Sand         ....       206
5-2        Length of Filter Run as a Function of 'Daily Mass  '':"
             Loading for 0.4 mm Effective Size Sand         V       207
5-3        Length of Filter Run as a Function of Daily Mass  t
             Loading for 0.68 mm Effective Size Sand                 208
                                    vi i i

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                             FIGURES  (continued)

Number                                                              Page
5-4        Length of Filter Run as a Function of Daily Mass
             Loading for Pond Effluents Having Calcium
             Carbonate Precipitation Problems                        209
5-5        Sand Grain Size vs; Sand Size Distribution                213
5-6        Sand Grain Size vs. Sand Size Distribution for
             AASHO M6 Specifications                                 216
5-7        Cross Section of a Typical Intermittent Sand Filter       217
5-8        Common Arrangements for Underdrain Systems                219
5-9        Typical Upflow Sand Washer and Sand Separator
             Utilized in Washing Slow and Intermittent Sand
             Filter Sand                                    ,         223
5-10       Plan View, Cross-Sectional View, and Hydraulic
             Profile for Intermittent Sand Filter                    229
5-11       Biochemical Oxygen Demand (BOD5) Performance of
             Large Rock Filter at Eudora, Kansas                     232
5-12       Suspended Solids Performance of Large Rock Filter
             at Eudora, Kansas                                       232
5-13       Rock Filter Installation at California, Missouri          233
5-14       Schematic Flow Diagram of Veneta, Oregon
             Wastewater Treatment System                             234
5-15       Performance of California, Missouri Rock Filter
             Treating Pond Effluent                                  236
5-16       Veneta, Oregon Rock Filter                                237
5-17       Performance of Veneta, Oregon Rock Filter       , ,         238
5-18       SS Removal vs. Hydraulic Loading Rate at
             Veneta, Oregon                                          239
5-19       Dual-Media Filter Effluent Turbidity Profile              245
5-20       Dual-Media Filter Headless Profile                        245
5-21       Effect of Alum Dose and pH on Flotation
             Performance                             ,                254
5-22       Effect of Alum Dose and Influent SS on Flotation
             Performance                                             254
5-23       Conceptual Design of Dissolved Air Flotation
             Tank Applied to Algae Removal                           256

6-1        Actual Construction Cost vs. Design Flow for
             Discharging Stabilization Ponds                         281
6-2        Actual Construction Cost vs. Design Flow for
             Nondischarging Stabilization Ponds                      282
6-3        Actual Construction Cost Vs. Design Flow for
             Aerated Ponds                                           283

A-l        McGarry and Pescod Equation for Area! BOD5 Removal
             as a Function of BODc Loading                           295
A-2        Relationship Between 6005 Loading and Removal
              Rates--Facultative Ponds                               296
                                      ix

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                             FIGURES  (continued)

Number                                        !                      Page


A-3        Relationship Between COD Loading and Removal Rates-
             Facultative Ponds '                                      297
A-4        Relationship Obtained with Modified Gloyna Equation-
             Facultative Ponds                                       300
A-5        Arrhenius Plot to Determine Activation Energy             302
A-6        Plot of Reaction Rate Constants and Temperature to
             Determine the Temperature Factor                        304
A-7        Relationship Between Plug Flow Decay Rate and
             Temperature--Facultative Ponds                          305
A-8        Relationship Between Complete Mix Decay Rate and
             Temperature—Facultative Ponds                          306
A-9        Plug Flow Model--Facultative Ponds            ,            307
A-10       Plug Flow Model--Facultative Ponds                        308
A-ll       Complete Mix Model--Facultative Ponds                     309
A-12       Complete Mix Model--Facultative Ponds                     310
A-13       Wehner and Wil helm Equation Chart                         311
A-14       Relationship Between Wehner and Wilhelm Decay Rate
             and Temperature--Facultative Ponds                      314
A-15       Relationship Between Plug Flow Decay Rate and
             Temperature—Aerated Ponds                              317
A-16       Relationship Between Complete Mix Decay Rate and
             Temperature—Aerated Ponds                              318
A-17       Relationship Between Wehner and Wilhelm Decay Rate
             and Temperature—Aerated Ponds                          319
A-18       Plug Flow Model--Aerated Ponds                            320
A-19       Complete Mix Model--Aerated Ponds                         321
A-20       Schematic View of Various Types of Aerators               324

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                                     TABLES

Number                                                              Page


1-1        Wastewater Stabilization Ponds                              3

2-1        Design and Actual  Loading Rates and Detention Times
             for Selected Facultative Ponds                           22
2-2        Summary of Design  and Performance Data—Selected
             Facultative Ponds                                        34
2-3        Influent Wastewater Characteristics at Selected
             Facultative Ponds                                        37
2-4        Annual Average Ammonia-N Removal by Selected
             Facultative Ponds                                        37
2-5        Influent Wastewater Characteristics at Selected
             Aerated Ponds                                            39
2-6        Design and Actual  Loading Rates and Detention Times
             for Selected Aerated Ponds                               39
2-7        Comparison of Various Equations Developed to Predict
             Ammonia Nitrogen and TKN Removal  in Diffused-Air
             Aerated Ponds                                            52
2-8        Summary of Chlorination Design Criteria                    68

3-1        Facultative Pond Design Equations                          77
3-2        Assumed Characteristics of Wastewater and
             Environmental Conditions for Facultative Pond Design     79
3-3        Variations in Design Produced by Varying the
             Dispersion Factor                                        95
3-4        Summary of Results from Design Methods                     96
3-5        Motor PowerN Requirements for Surface and Diffused
             Air Aerators                                            126
3-6        Climatological Data for Calculating Pond Evaporation
          !   and Precipitation                                       137
3-7        Calculated Pond Evaporation Data                          140
3-8        Volume and Stage of Pond at Monthly Intervals for
             Design Conditions and A = 142,300 m2                    141
3-9        Volume and Stage of Pond at Monthly Intervals for
             Average Conditions and A = 142,300 m2                   143

4-1        Reported Seepage Rates from Pond Systems                  151
4-2        Seepage Rates for Various Liners                          153
4-3        Trade Names of Common Lining Materials                    156
4-4        Sources of Common Lining Materials                        159
4-5        Summary of Effective Design Practices for Placing
             Lining in Cut-and-Fill Reservoirs                       161
4-6        Classification of the Principal Failure Mechanisms
             for Cut-and-Fill Reservoirs                             181

5-1        Labor Requirements for Full-Scale Batch Treatment of
             Intermittent Discharge Ponds                            195
5-2        Intermittent Sand Filtration Studies                      203
                                      xi

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                              TABLES  (continued)

Number                                                              Page
5-3        Sieve Analysis of'Filter Sand                             211
5-4        Gradation Requirements for Fine Aggregate in the
             AASHO M6 Specification                           -       215
5-5        Summary of Intermittent Sand Filter Design Criteria       226
5-6        Summary of Design Criteria and Costs for Existing and
             Planned Intermittent Sand Filters Used To Upgrade
             Pond Effluent                                           231
5-7        Performance of Rock Filter at California,
             Missouri                                                235
5-8        Summary of Performance of 1-micron Microstrainer
             Pilot Plant Tests            .                           241
5-9        Performance Summary of Direct Filtration with Rapid
             Sand Filters                                            243
5-10       Performance of the Napa-American Canyon Wastewater
             Management Authority Dual-Media Filters                 246
5-11       Summary of Coagulation-Flocculation-Settling
             Performance                                             248
5-12       Performance of the Napa-American Canyon Wastewater
             Management Authority Algae Removal Plant                249
5-13       Summary of Typical Coagulation-Fl otettion Performance      251
5-14       Comparison of Site Characteristics for Land
             Treatment Processes                                     260
5-15       Comparison of Typical Design Features for Land
             Treatment Processes                                     261
5-16       Summary of BOD and SS Removals at Overland Flow
             Systems Treating Pond Effluents                         263
5-17       Summary of Nitrogen and Phosphorus Removals at
             Overland Flow Systems Treating Pond Effluents           264
5-18       Removal of Heavy Metals at Different, Hydraulic
             Rates at Utica, Mississippi                             265
5-19       BOD Removal  Data for Selected Slow-Rate Systems
             Treating Pond Effluents                                 266
5-20       Nitrogen Removal Data for Selected Slow-Rate Systems
            - Treating Pond Effluents                                 266
5-21       Phosphorus Removal Data for Selected Slow-Rate
             Systems Treating Pond Effluents                         267
5-22       Trace Element Behavior During Slow-Rate Treatment of
             Pond Effluents                                          268
5-23       Nitrogen Removal Data for Selected Rapid Infiltration
             Systems Treating Pond Effluents                         270
5-24       Fecal Coliform. Removals at Selected Rapid Infiltration
             Systems Treating Pond Effluents                         270

6-1        Average Nonconstruction Cost Ratios for New
             Wastewater Treatment Plants                             284
6-2        Comparative Costs and Performance of Various Upgrading
             Alternatives and Pond Systems                           286
                                     xi i.

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                              TABLES  (continued)

Number                                                              Page


6-3        Expected Effluent Quality and Total  Energy
             Requirements for Various Sizes and Types of
             Wastewater Treatment Ponds Located in the
             Intermountain Area of the United States                 289

A-l        Mean Monthly Performance Data for Four
             Facultative Ponds                                       293
A-2        Mean Monthly Performance Data for Five
             Partial Mix Aerated Ponds                               313
A-3        Types of Aeration Equipment for Aerated Ponds             323
A-4        Calculation of Oxygen Demand and Surface Aerator
             Size for Aerated Ponds                                  325
                                     xiii

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                                   CHAPTER 1

                                 INTRODUCTION
1.1  Background and History


Stabilization ponds  have  been employed  for treatment of wastewater  for over
3000 years.   The  first recorded construction  of  a pond system  in  the United
States  was  at  San  Antonio, TX,  in 1901.   Today, almost  7000 stabilization
ponds are  utilized in  the United  States for  treatment of  wastewaters (1).
They are  used to treat a variety of wastewaters  from  domestic wastewater to
complex industrial  wastes, and they  function under  a  wide  range  of weather
conditions,  from  tropical  to  arctic.     Ponds   can  be   used  alone  or  in
combination with  other wastewater  treatment  processes.   As  understanding of
pond operating  mechanisms has increased,  different types  of  ponds  have been
developed for application  to specific situations.


1.2  Manual Objective and  Scope


This manual   provides  a  concise  overview  of  wastewater  stabilization  pond
systems  through  discussion of  factors   affecting  treatment,  process  design
principles  and  applications,  aspects of physical  design  and  construction,
suspended solids  (SS) removal alternatives, and cost and energy requirements.

Chapter 2 provides a review of physical and biological factors associated with
wastewater stabilization  ponds.   Empirical  and rational  design equations, and
their ability to  predict  pond performance, are also discussed.

Actual  design examples employing the rational equations presented in Chapter 2
are outlined in Chapter 3.   These examples encompass  essentially all  types of
wastewater ponds  currently  in use in the  United States.

Physical design  and  construction criteria are  discussed  in Chapter 4.  These
criteria  are  vital  to effective  pond performance  regardless of  the design
equation employed and must be considered  in facility design.

High  SS concentrations   in  pond  effluents  have  traditionally  represented  a
major drawback  to their  use.    Alternatives  for  SS  removal   and  control  are
presented in Chapter 5.

Chapter 6 contains  cost and energy requirements information to aid in process
selection and justification.

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An  evaluation  of  various  facultative  and aerated  pond  design  methods  is
presented in an Appendix.   This  evaluation  was; performed using data collected
on the four facultative and five aerated pond  systems presented in Chapter 2.


1.3  Types of Ponds


Wastewater  pond systems  can  be  classified  by dominant  type of  biological
reaction, duration  and frequency of  discharge,  extent of  treatment  ahead  bf
the  pond,  or arrangement among  cells (if more  than  one cell is used).   The
method used  in  this manual  is based on  that provided  by  Oswald (2)  and  is
believed to be the most flexible approach to pond classification.

Ponds are classified below on the basis of dominant biological reaction, types
of influent, and outflow conditions.  Classification according to flow pattern
(e.g., series, parallel) and the amount and type of recirculation is discussed
in Chapter 4.

Table 1-1  summarizes information on  pond  application, loading, and  size for
each of the pond types discussed in this section.


     1.3.1  Biological Reactions


The  most basic  classification  involves  description of the dominant  biological
reaction or reactions that occur in the pond.  Four principal types  are:

     1.   Facultative (aerobic-anaerobic) ponds \

     2.   Aerated ponds

     3.   Aerobic ponds                         :,

     4.   Anaerobic ponds


         1.3.1.1  Facultative Ponds


The most common type of  pond is  the facultative pond.  Other  terms  which are
commonly applied are oxidation pond,  sewage (or wastewater treatment) lagoon*
and photosynthetic pond.  Facultative ponds  are  usually 1.2 to 2.5 m  (4  to 8
ft)  in  depth,  with  an aerobic  layer  overlying  an  anaerobic  layer,  often
containing sludge deposits.   Usual  detention time  is  5  to  30 days.   Anaerobic
fermentation occurs in the lower layer and aerobic stabilization occurs in the
upper layer.    The  key to facultative  operation is  oxygen  production  by
photosynthetic  algae  and surface reaeration.  The oxygen  is  utilized  by the
aerobic  bacteria  in  stabilizing the organic  material  in  the  upper  layer.
Algae present in pond  effluent represent one  of  the  most serious performance
problems associated with facultative ponds.

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                                                                   TABLE  1-1

                                                     WASTEWATER STABILIZATION PONDS
CO
       Pond Type            Application

     Facultative     Raw municipal wastewater
                    Effluent from primary
                      treatment, trickling
                      filters, aerated ponds,
                      or anaerobic ponds

     Aerated         Industrial wastes
                    Overloaded facultative
                      ponds
                    Situations where limited
                      land area is available
     Aerobic         Generally used to treat
                      effluent from other
                      processes, produces
                      effluent low in
                      soluble BODc and high
                      in algae solids
     Anaerobic       Industrial wastes
     Typical  Loading
        Parameters

   22-67 kg BOD5/ha/d
 8-320 kg  BOD5/1000 m3/d
   85-170 kg BOD5/ha/d
160-800 kg  BOD5/1000 m3/d
 Typical
Detention
  Times

 25-180 d
  7-20 d
 10-40 d
 20-50 d
   Typical
  Dimensions

1.2-2.5 m deep
   4-60 ha
  2-6 m deep
   30-45 cm
 2.5-5 m deep
           Comments  -

Most commonly used waste
  stabilization pond type
May be aerobic through  entire
  depth if lightly loaded
Use may range from a supplement
  of photosynthesis to an
  extended aeration activated
  sludge process
Requires less land area than
  facultative

Application limited because of
  effluent quality
Maximizes algae production and
  (if algae is harvested)
  nutrient removal
High loadings reduce land
  requirements

Odor production usually a problem
Subsequent treatment normally
  required

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Facultative  ponds  find the  most widespread  application.   They  are  used for
treatment  of raw  municipal  wastewater  (usually  small  communities)   and for
treatment of primary  or secondary  effluent (for small or large cities).  They
are  also  used,  in  industrial  applications,,  following  aerated  ponds  or
anaerobic ponds  to  provide additional  stabilination  prior  to  discharge.   The
facultative  pond  is  the  easiest  to  operate  and  maintain,   but  there  are
definite  limits  to its performance.   Effluent  BODs values range  from 20 to
60 mg/1,  and SS  levels  will  usually  range  from 30  to 150  mg/1.    It  also
requires  a  very  large   land  area to  maintain  area!   8005   loadings  in  a
suitable  range.    An  advantage,  where  seasonal   food  processing  wastes are
received during summer, is that allowable  organic loadings  are generally much
higher in summer than in winter.

The  total  containment pond  and the controlled discharge  pond are  forms of
facultative ponds.  The total containment pond is  applicable in climates where
the  evaporative  losses  exceed the rainfall.   Controlled discharge  ponds have
long hydraulic  detention  times and the  effluent  is  discharged once  or twice
per year when the effluent quality is satisfactory.


         1.3.1.2  Aerated  Ponds


In an aerated pond,  oxygen is supplied mainly  through  mechanical  or diffused
air  aeration rather  than  by photosynthesis  and surface  reaeration.   Many
aerated  ponds  have evolved  from overloaded  facultative ponds  that  required
aerator  installation  to   increase  oxygenationi  capacity.  Aerated  ponds  are
generally 2 to 6 m (6 to 20 ft) in depth with detention times of 3 to 10 days.
The chief advantage of aerated ponds is that they  require less land area.

In some cases, both photosynthesis and mechanical  aeration can be effective in
providing  oxygen.     At   Sunnyvale,  CA,   for  example,  mechanical   cage-type
aerators were  installed  at  the  effluent  points to  eliminate  local  anaerobic
conditions   during   seasonal   increased   loads   from  a   canning   plant.
Photosynthesis  and surface  reaeration provide  the  necessary oxygen  in the
remaining areas of the pond  (3).
                                               I
Aerated  ponds  can  also be classified  by the  amount of mixing  provided.   If
energy input is  sufficient to keep  all  solids in  suspension, and if secondary
clarification  with  sludge  return is  utilized,  the   system  approaches  an
activated 'sludge  process  with the  associated  high  BOD5 and  SS  removal.
Power costs  for this system  become  very  high,   however,  and  operation and
maintenance complexity increases.

Aerated  ponds are  used in both municipal  and  industrial  wastewater treatment
applications.  For  the former situation, they  are often resorted  to  when an
existing  facultative  system becomes  overloaded  and there  is  minimal  land
available for expansion.   For industrial wastes,  they are sometimes used as a
pretreatment step  before  discharge to a  municipal  sewerage system.   In both
municipal  and industrial   applications,  aerated  ponds  may  be  followed  by
facultative ponds.                              I

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         1.3.1.3  Aerobic Ponds


Aerobic ponds, also called  high  rate  aerobic ponds, maintain dissolved oxygen
(DO) throughout  their  entire depth.  They  are  usually 30 to 45  cm  (12 to 18
in)  deep,  allowing  light  to  penetrate  the full  depth.    Mixing  is  often
provided  to   expose  all  algae  to sunlight and  to  prevent  deposition  and
subsequent anaerobic  conditions.   Oxygen  is provided by  photosynthesis  and
surface reaeration, and aerobic  bacteria  stabilize  the waste.  Detention time
is short, three to five days being usual.

High-rate aerobic  ponds  are limited to warm, sunny climates.  They  are used
where  a high  degree  of  6005  removal  is  desired  but land  area  is  limited.
The chief advantage of the high-rate aerobic pond is that it  produces a stable
effluent with low land  and energy requirements  and  short  detention  times.
However, operation is  somewhat  more complex than for  a  facultative  pond and,
unless  an algae  removal  step is provided,  the  effluent will contain high SS.
Short detention times also mean that very little coliform die-off will result.
Because of their  shallow  depths,  paving or covering the bottom is required to
prevent weed growth.


         1.3.1.4, Anaerobic Ponds
Anaerobic ponds receive such a  heavy  organic  loading that there is no aerobic
zone.   They  are usually 2.5 to  5  m (8 to  15  ft)  in depth and have detention
times of 20 to 50 days.  The principal biological reactions occurring are acid
formation  and  methane fermentation.   The  smaller  of the  two Sunnyvale, CA,
cells was originally an anaerobic cell providing treatment of  seasonal cannery
wastes.   Effluent  from  the  anaerobic cell  enters  the  larger  and shallower
facultative cell.

Anaerobic  ponds  are  usually  used  for  treatment  of  strong  industrial  and
agricultural   wastes,  or  as  a pretreatment  step  where  an  industry   is  a
significant contributor to a municipal system.   Because  they do not have wide
application to  the  treatment of municipal  wastewaters,  they are not discussed
further in this manual.

An  important disadvantage  to  anaerobic  ponds is  the  production  of odorous
compounds.   Sodium nitrate  has been  used to combat  odors,   but  it is quite
expensive and in some cases has not proven  effective.  Another common approach
is  to  recirculate  water  from a  downstream  facultative  or  aerobic  pond  to
maintain a thin aerobic layer at the surface of the anaerobic  pond, preventing
transfer  of  odors  to  the  air.    Crusts   have  also  proven  effective,  either
naturally  formed  as with  grease, or  formed from styrofoam balls.   A further
disadvantage of  the anerobic pond is  that the effluent must usually be given
further treatment prior to discharge.

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     1.3.2  Pretreatment


Ponds  can also  be  characterized by  the  degree  of  pretreatment which  the
wastewater receives before discharge into a pond system:

     1.  None.   Ponds  receiving  raw untreated wastewater direct from the
         municipal sewer are often used by small communities to avoid the
         added  expense of pretreatment.   Care  must be  taken  to ensure
         that  odors  do  not  occur  from  anaerobic  conditions,  mats  of
         rising  sludge near the  pond  inlet,  or from  greasy  scum at the
         shoreline.                           |

     2.  Screening.   Screening or comminution may  be  employed; however,
         this is not common practice.

     3.  Primary sedimentation.   Where primary sedimentation is used, the
         pond provides a  form of secondary treatment,  usually  at a much
         lower cost than other forms of biological treatment.  The Davis,
         CA,  pond system  is  an  example  of  sedimentation before  pond
         treatment.

     4.  Secondary  treatment.    Ponds  receiving secondary  effluent  are
         normally associated  with trickling  filter  and activated sludge
         effluents.    Effluent  8005  concentrations  from  high-rate  rock
         media  trickling  filters may  be  40  to 75 mg/1, making ponds
         practical  for  further  removing  and   stabilizing the  organic
         material.  Ponds can  also  be considered for use after trickling
         filters  when  loading  increases or  discharge  requirements  are
         tightened.  Activated sludge  and trickling  filter effluents  can
         be further treated by ponds for nutrient removal.


     1.3.3  Discharge  Conditions


Ponds may also be classified on the basis of discharge conditions:
                                               i
     1.  Complete retention.   These  systems  rely on  evaporation and/or
         percolation to reduce  the liquid volume at a rate equal  to  or
         greater than  the influent accumulation.  Favorable geologic and/
         or climatic conditions are prerequisite.

     2.  Controlled  discharge.    These  systems  have  long   hydraulic
         detention times,  and effluent is discharged when receiving water
         quality  will   not  be   adversely  affected  by  the  discharge.
         Controlled discharge  ponds  are designed to hold the  wastewater
         until the effluent and receiving water quality arecompatible.

     3.  Continuous  discharge.   These  systems  have   no  provision  for   ;
         regulating  effluent  flow  and  the  discharge rate  essentially
         equals the influent rate.

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1.4  Nutrient Removal  Aspects


Both nitrogen  and phosphorus  in  wastewater are  affected by  passage  through
waste  stabilization  ponds.   Nitrogen  can  undergo a  number of  chemical  and
physical  processes,   including   settling  (in  organic   particulate   form),
assimilation into  algae  cells, ammonification  (conversion of organic nitrogen
to  ammonia),  nitrification,  and  denitrification.   Phosphorus  is  removed  by
assimilation  into algae  cells and  by  precipitation.    When the  alkalinity
increases during the daylight hours, phosphate is precipitated and will settle
out of  the wastewater.   A reduction in alkalinity  at night can result in some
of  the  phosphorus being  dissolved  from the sediment.   In general, the  pond
effluent phosphorus concentration is less than half of the influent wastewater
concentration.

Nutrient removal  can be  accomplished  in ponds  using water hyacinths, duckweed
and other plants.   Details on the  use  of aquaculture in wastewater treatment
are presented in Chapter 5 and elsewhere  (4).


1.5  References


  1.  The 1980  Needs  Survey.  EPA-430/9-81-008,  NTIS No. PB  82-131533,  U.S.
      Environmental  Protection Agency,  Office  of  Water  Program Operations,
      Washington, DC,  1981.

  2.  Oswald, W.  0.  Quality Management by  Engineered Ponds.   In: Engineering
      Management  of Water Quality, P. H. McGauhey, ed., McGraw-TTTIl, New York,
      NY, 1968.

  3.  Upgrading   Lagoons.    EPA-625/4-73-001b,  NTIS   No.   PB  259974,  U.S.
      Environmental  Protection  Agency,  Center  for  Environmental  Research
      Information, Cincinnati, OH, 1977.

  4.  Aquaculture Systems for Wastewater  Treatment: An Engineering Assessment.
      EPA-430/9-80-007,  NTIS  No.  PB  81-156689,  U.S.  Environmental  Protection
      Agency, Office of Water Program Operations, Washington, DC, 1980.

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                                   CHAPTER 2

                   PROCESS THEORY, PERFORMANCE, AND DESIGN
 2.1   Biology
 Enumeration  of types  of organisms  occurring in  wastewater  ponds  possesses
 some  inherent  limitations.   Species  identification  reflects the  selective
 nature  of the isolation method,  as well as  the  particular interests  of the
 researcher.  Also, seasonal  changes  in  pond operation and influent wastewater
 characteristics  produce  variations  in  the  naicrobial  populations.   Despite
 these  limitations,  general   observations   pertaining to  macro-  and  micro-
 organisms  in  wastewater ponds  are  valuable  in  understanding  the  process
 theory.


     2.1.1  Bacteria


         2.1.1.1  Aerobic Bacteria
                                              I

 Bacteria found in an aerobic zone of a  wastewater  pond are primarily  the same
 type as those found in an activated sludge  process or in  the zoogleal  mass  of
 a trickling  filter.   The most frequently isolated bacteria  include  Beggiatoa
 alba,   Sphaerotilus   natans,   Achromobacter,  Alcali genes,   Flavqbacterium,
 Pseudomohas,  and  Zoogloea spp.   (1)   These  organisms  decompose the  organic
materials present in the aerobic zone into oxidized end products.


         "2.1.1.2  Acid Forming Bacteria


Acid forming  bacteria  are  heterotrophs  that convert  complex organic  material
into simple alcohols and acids.  These  acids  are primarily acetic,  propionic,
and  butyric  (2).  The  activity of  these  bacteria  is  important  since  they
provide one of the substrates for the final reduction of  the organic  material
into methane gas by  the  methanogenic  bacteria.   Acid forming  bacteria  do not
limit the rate of the anaerobic decomposition and  do  not  require  thermophilic
temperatures for optimum growth as do  the  methanogenic  bacteria.  Addition-
ally, the acid forming bacteria are  able to maintain a near-optimum  pH range
for their existence through  their own acid production.

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         2.1.1.3  Cyanobacteria


Cyanobacteria  are  commonly known  as blue-green  algae.   Like  algae,  cyano-
bacteria  are able  to assimilate  simple  organic compounds  while  utilizing
carbon  dioxide as  the  major carbon  source,  or to   grow  in  a completely
inorganic medium.   Cyanobacteria produce  oxygen  as  a by-product  of  photo-
synthesis, thus providing an  oxygen  source for other organisms in the  ponds.
Ability  of  the Cyanobacteria to utilize  atmospheric  nitrogen  accounts for
very  broad  distribution  in  both  the  terrestrial  and  aquatic  environment.
Cyanobacteria  appear in  very  large numbers as  blooms  when  environmental
conditions are suitable (3).


         2.1.1.4  Purple Sulfur Bacteria


Many  species of Chromatiaceae,  the  purple sulfur bacteria, are actually pur-
ple,  but others  may  be  dark  orange  to brown or  various  shades  of pink  or
red.  Purple  sulfur bacteria may  grow  in  any aquatic environment  to which
light of the required wavelength  penetrates, provided that  carbon  dioxide,
nitrogen, and a reduced  form  of sulfur,  or hydrogen,  are available.   Purple
sulfur bacteria occupy  the anaerobic layer below the algae,  Cyanobacteria,
and  other aerobic  bacteria  in  a  pond.   Wavelengths  of  light  used  by the
purple sulfur bacteria are  different  from those used by the Cyanobacteria or
algae; thus the sulfur bacteria are able  to grow  using light that has  passed
through  the  surface layer  of water or  sediment  occupied by  aerobic  photo-
synthetic organisms.  Purple  sulfur bacteria are commonly  found at a specific
depth, in a thin layer where  light  and  nutrition  conditions are  optimum (3).
Conversion of odorous sulfide compounds to  elemental  sulfur or  sulfate  by the
sulfur bacteria is  a significant factor for  odor control  in facultative and
anaerobic ponds.


         2.1.1.5  Pathogenic Bacteria


Pathogenic bacteria  frequently  discussed with  reference  to  wastewater ponds
include  SalI monel1 a,  Shi gel!a,  Escherichia,  Leptospi ra,  Francisell a,  and
Vibrio.   (Viruses and certain protozoa  are also pathogenic,  but  scant  inf or-
mation exists.)  Water is not the  natural  environment of  the pathogenic bac-
teria, but instead  a means  of transport to a new host.   Pathogenic  bacteria
are  usually  unable  to  multiply or  survive  for extensive  periods  in  the
aquatic  environment.  The  decline  in  numbers of microbial  pathogens with
time,  within  the  aquatic  environment, involves  sedimentation,  starvation,
sunlight, pH, temperature, competition,  and predation (1).

The  most probable  number  (MPN)  of coliform organisms present in  a given
volume of a waste is the commonly accepted  index of  the pathogenic quality of
an effluent.  Most literature concerning the  performance of ponds report very
high  reductions  in  coliform  bacteria,  often as  high as 99.9  percent,  in

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 facultative  ponds.  Caution  should  be exercised  in interpreting  these  fig-
 ures, however, as  large absolute numbers of coliform may still be present.


     2.1.2  Algae


 Algae  constitute  a  group of  aquatic organisms  that may  be unicellular  or
 multicellular,  motile  or immotile,  of  which  practically  all  have  photo-
 synthetic  pigments.   Being  autotrophic,  algae  utilize  inorganic  nutrients
 such as phosphate,  carbon  dioxide,  and  nitrogen.   Algae  do not  fix  atmos-
 pheric  nitrogen, but  require  inorganic nitrogen  in  the form  of  nitrate  or
 ammonia.   Also,  some  algal  species  are  able  to use ami no  acids and  other
 organic nitrogen compounds.   Inorganic  nutrients  utilized by  algae are  photo-
 synthetically converted into  cellular organic  materials, with oxygen  produced
 as a by-product.
                                               i
 Algae  are generally divided  into  three  major groups,  based on  the  color
 imparted  to  the cells by  the  chlorophyll  and  other pigments  involved  in
 photosynthesis.  Green algae  include  unicellular,  filamentous,  and  colonial
 forms.    Brown   algae  are  unicellular  and   flagellated,  and   include   the
 diatoms.   Certain  brown  algae  are  responsible  for toxic red  blooms.   Red
 algae  include  a few unicellular forms,  but  are primarily  filamentous  (3).
 Green  and brown algae are common  to  wastewater ponds,  with  the red  algae
 occurring  infrequently.   The  predominant algal  species  at  any given time  is
 thought to be  primarily  a  function  of temperature,  although the  effects  of
 predation, nutrient  availability, and toxins are also important.

 It has  been generally  accepted that algae and bacteria together  comprise the
 essential   elements  of a  successful   stabilization  pond operation.   Bacteria
 break down the complex organic waste  components aerobically and  anaerobically
 into simple products which  are then available for  use by  the algae.   Algae,
 in turn, produce the oxygen necessary for maintaining the aerobic  environment
 necessary for the bacteria to perform oxidative functions.

 Due to  the cyclic  biochemical  reactions of biodegradation  and mineralization
 of nutrients by  bacteria, and  synthesis of new organics  in  the form  of  algae
 cells,   it is  feasible that  a  pond  effluent  could  contain  a  higher  total
 organic content  than the  influent.   However,  this could occur only under the
most optimum algae growth conditions, which would seldom  occur in  practice.


         2.1.3  Animals


Although  bacteria  and algae  are the  primary  organisms  through  which waste
 stabilization is accomplished, higher, life forms  are of importance as well.
 Planktonic Cladocera and  benthic Chironomidae  lhave  been suggested as  the  most
 significant faunaTn  the pond  community, in terms  of  stabilizing  organic
matter.  The Cladocera feed on  the  algae and promote  flocculation and  set-
tling of  particulate matter.   This   in turn   results  in better  light pene-
                                      10

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tration and algal growth at greater depths.  Settled matter  Is  further  broken
down and stabilized by  the benthic feeding Chironomidae.  Predators, such  as
rotifers, often  control  the  population levels of certain  of the lower  forms
in the pond, thereby influencing the succession of predominating species.

Mosquitoes  do  present a problem  in some  ponds.   Aside  from their  nuisance
characteristics, certain mosquitoes are  also  the  vector for  such diseases  as
encephalitis, malaria,  and yellow  fever,  and constitute  a  hazard to  public
health which must be controlled if ponds are to be utilized.  The most  effec-
tive means  of  control  is  the  control  of  emergent  vegetation.   Gambusia,  or
mosquito  fish,  have  beeen  successfully  employed  to   eliminate   mosquito
problems in some ponds in warm climates (4) (5).


2.2  Biochemical Interactions


     2.2.1   Photosynthesis


Photosynthesis  is  the process whereby  organisms  are able to grow  utilizing
the  sun's   radiant  energy  to  power  the  fixation  of  atmospheric  C02 and
subsequently provide  the reducing power to convert  the C02 to organic  com-
pounds.  Photosynthesis is  usually associated with the  green plants;  however,
certain  bacteria as well  as  algae carry  out  photosynthesis.   In  wastewater
ponds, the  photosynthetic  organisms of interest are  the algae,  cyanobacteria
(blue-green algae),  and the purple sulfur bacteria (5).

Photosynthesis may  be  classified  as oxygenic  or  anoxygenic  depending on the
source of reducing  power used by a particular organism.   In oxygenic  photo-
synthesis,  water serves  as the source  of  reducing power, with oxygen  being
produced as  a  by-product.   The  equation representing oxygenic  photosynthesis
is:
                                   2H+ + 2e-                             (2-1
Oxygenic photosynthesis occurs in green plants, algae, and cyanobacteria.   In
ponds,  the oxygenic  photosynthetic  algae  and cyanobacteria  convert carbon
dioxide to  organic  compounds that serve  as  a source of  chemical  energy,  in
addition to organic waste matter,  for  most other living organisms  (3).   More
importantly, the by-product oxygen produced in oxygenic photosynthesis allows
the  aerobic bacteria  to  function  in  their  role  as  primary  consumers  in
degrading complex organic waste material.

Anoxygenic  photosynthesis  produces  no  oxygen  as  a  by-product,  thus   oc-
curring  in  the  complete  absence  of  oxygen.   The  bacteria  involved  in
anoxygenic  photosynthesis are  largely  strict  anaerobes,  with  reducing power
supplied  by  reduced  inorganic  compounds.   Many  anoxygenic  photosynthetic


                                      11

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bacteria utilize  reduced  sulfur compounds or  elemental  sulfur in  anoxygenic
photosynthesis according to the fpllowing equation:


            H2S  -*•  SO + 2H+ + 2e-                                       (2-2)

                                                                           '
     2.2.2  Respiration


Respiration  is  a  physiological   process  in   which   organic   compounds   are
oxidized mainly  to  carbon dioxide and  water.   However,  respiration does  not
only lead  to  the production  of carbon dioxide, but to the synthesis of cell
material as  well.  Respiration is  an orderly  process,  catalyzed by enzymes
such  as the  cytochromes  and  consisting of  many integrated  step  reactions
terminating  in  the  reduction  of  oxygen to water (6).  Aerobic  respiration,
common  to  species  of  bacteria,  protozoa,   and  higher  animals,  may  be
represented by the following simple equation:



         C2H12°6 + 602     enzyt"es >    6C02  +  6H20 + new  cells            (2-3)


The  bacteria  involved in aerobic  respiration  are primarily  responsible  for
wastewater stabilization in ponds.

In  the  presence  of  light,  respiration  and photosynthesis can occur simul-
taneously  in  algae.   However,  the respiration rate is low compared with  the
photosynthesis rate,  resulting in  a  net consumption  of  carbon  dioxide  and
production of oxygen.   In the  absence  of light,  algal  respiration  continues
while photosynthesis  stops,  resulting  in  a  net  consumption   of  oxygen  and
production of carbon dioxide.


     2.2.3  Dissolved Oxygen  (DO)


Oxygen  is  a  partially soluble  gas, and solubility varies  in  direct propor-
tion  to the  atmospheric  pressure  at  any given temperature,   and  in inverse
proportion to temperature for  any given atmospheric  pressure.   DO concen-
trations of approximately 8 mg/1 are usually considered  the maximum  available
under  ambient  conditions.   In  mechanically  aerated  ponds,  the  limited
solubility of oxygen is a  significant factor,  since  it  determines the oxygen
absorption rate and, therefore, the cost of  aeration (7).

The  two natural   sources  of DO in ponds are  surface reaeration  and photo-
synthetic oxygenation.  In areas of low wind activity, surface  reaeration  may
be  relatively unimportant,  depending  on  the  water  depth.    Where surface
turbulence is created from  excessive wind  activity,  surface  reaeration  is
significant.   Observation has shown that DO in wastewater ponds varies almost
directly with  the level  of photosynthetic  activity,  being low at night  and


                                      12

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early  morning  and rising  during  daylight hours  to  a  peak  in  the  early
afternoon.   At  increased  depth,  the  effects  of  surface  reaeration  and
photosynthetic  oxygenation  decrease,  since  the  distance  from  the  water-
atmosphere  interface   increases  and  light  penetration  decreases.   This  can
result   in   a   vertical   gradient  in  DO   concentration   accompanied   by  a
segregation of microorganisms.



     2.2.4  Nitrogen Cycle



A simplified nitrogen cycle is represented by Figure 2-1.




                                  FIGURE 2-1

                              THE  NITROGEN CYCLE



       organic-N	ammonification 	^ammonium  §
E E          ^                                         -^    •     —
CD O
OVr-
O +•>
S~ (O
I ^ \s
     nitrogen gas-*-
                               denitrification


In a wastewater  pond,  organic nitrogen and  ammonium nitrogen enter with  the
influent  wastewater.   Organic  nitrogen  in  fecal  matter and  other  organic
materials in the wastewater undergo conversion to ammonia  and ammonium ion by
microbial  activity.   The  ammonium  in  turn  is  nitrified to  nitrite   by
Nitrosomonas and  then  to nitrate by  Nitrobacter.   The  overall  nitrification
reaction is:



            NH4+ + 202   -»•  NOg  + 2H+ + H20                             (2-4)
The nitrate  produced  in the nitrification  process,  as well  as  a portion  of
the ammonium produced from ammonification, can be assimilated by  organisms  as
a nutrient  to  produce cell protein  and other nitrogen-containing compounds.
The nitrate is utilized  in  denitrification  to form nitrite and then  nitrogen
gas.   Several   bacteria  may  be  involved  in  the  denitrification   process
                                      13

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including Pseudomonas, Micrococcus, Achromobacter, and Bacillus.   The  overall
denitrification reaction"??!
            6N03" + 5CH3OH  -»•  3N2 + 5C02 + 7H20+ 60H"                  (2-5)
Nitrogen  gas  is  "fixed"  to  form  organic  nitrogen by  cyanobacteria,  thus
making the nitrogen available as a nutrient and completing the cycle (8).

Nitrogen removal in facultative wastewater ponds can occur by  any  of the  fol-
lowing processes:   (1)  gaseous ammonia stripping  to the atmosphere,  (2)  am-
monium assimilation in algal biomass,  (3) nitrate  uptake  by  plants and algae,
and (4) biological  nitrification-denitrification.  Ammonium  assimilation  into
algal biomass depends on the biological activity in  the  system and is affect-
ed by several  factors  such  as  temperature,  organic load, detention  time,  and
wastewater  characteristics.   The  rate  of  gaseous  ammonia  losses  to   the
atmosphere is  primarily  a  function of pH,  surface to volume  ratio,  tempera-
ture, and  the mixing conditions.   An  alkaline pH shifts the  equilibrium  of
ammonia gas  and ammonium  ion  towards gaseous  ammonia  production, while  the
mixing conditions affect the magnitude of the mass transfer coefficient.


     2.2.5  pH and Alkalinity


In wastewater ponds,  the   hydrogen  ion concentration,  expressed  as pH,  is
controlled  through  the   carbonate  buffering  system  represented   by   the
following equations:


            C02 + H20  t  H2C03  £  HC03" + H+                           (2-6)
                                              I

            M(HC03)2  ?  M++ -i- 2HC03"                                    (2-7)



            HC03" £  C03=  + H+               ;                           (2-8)


where:  M s metal  ion


            C03= + H20  t  HC03"  +  OH"                                 (2-9)



            OH" + H+  £  H20                                            (2-10)
                                      14

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The equilibrium of this system  is  affected by algal photosynthesis.  In pho-
tosynthetic metabolism by algae, carbon dioxide is  removed from the  dissolved
phase, forcing  the equilibrium of  the first  expression  to  the  left.   This
tends  to  decrease the  hydrogen ion  concentration  and also  decrease bicar-
bonate alkalinity.   The  effect of  the   resultant  decrease  in  bicarbonate
(HC03~) concentration  is to  force the  third equation to  the left and the
fourth to  the  right,  both  of  which  decrease  total  alkalinity.   Figure 2-2
shows a typical  relationship between pH,  C02,  HCOs", C0=, and OH~.
The decreased  alkalinity associated with  photosynthesis  will  simultaneously
reduce the  carbonate hardness present  in  the  waste.   Because  of  the  close
relationship  between pH  and  photosynthetic  activity,  considerable  diurnal
fluctuation in pH is observed.
                                 FIGURE 2-2


        CALCULATED RELATIONSHIP AMONG pH,  C02,  C03=,  HC03",  and  OH~  (7)
                 100  -
                  80  -
             u>
            ~    60  -
             CO
            o
            o
            CO
            O

            J2.    40
            .9
                  20  -
                         7.0
8.0
 9.0

pH
10.0
11.0
                                      15

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 2.3   Controlling Factors


      2.3.1   Light                             ,

                                              !
 The  intensity and  spectral  composition of  light  penetrating a  pond  surface
 significantly  affects  all  resident  microbial  activity.   The  available  light
 determines,  to a  large  degree,  ,the  level  of  photosynthetic activity  and,
 hence,  oxygen  production.   Oxygen   availability  to  the  aerobic  bacterial
 organisms  is  vital.   In   general,   photosynthetic  activity  increases  with
 increasing  light  intensity  until  the  photosynthetic  system  becomes  light
 saturated.   The  rate at  which photosynthesis increases  in proportion to  an
 increase  in  light  intensity,  as  well  as the  level at  which an  organism's
 photosynthetic  system  becomes  light saturated,  depends  upon the  particular
 biochemistry of the species  (1).  . In ponds, photosynthetic  oxygen  production
 has  been  shown  to  be  relatively constant  within  the  range  of  5,380  to
 53,800 lumen m2   (500   to   5,000:  foot-candles)  light   intensity  with   a
 reduction occurring at higher and lower intensities (5).
                                  \
 The  spectral  composition of  available light is also crucial in  determining
 photosynthetic activity.   The  ability of photosynthetic  organisms  to  utilize
 available  light  energy  primarily depends upon  their ability  to absorb  the
 available wavelengths.  This absorption ability  is determined  by  the  specific
 photosynthetic pigment of the  organism.  The main  photosynthetic  pigments  are
 the  chlorophylls  and  the phycobilins.   Bacterial   chlorophyll  differs  from
 algal chlorophyll  in both  chemical structure and absorption  capacity.   These
 differences  allow   the  photosynthetic  bacteria  to   live  below  dense  algal
 layers where they can utilize light not absorbed  by the algae (1).

The quality  and quantity  of light penetrating the pond  surface  to any  depth
 depends on the presence of  dissolved and  particulate matter  as  well, as  the
water  absorption   characteristics.   The organisms   themselves  contribute  to
water turbidity, further limiting  the depth of light penetration.   Because  of
 these  restrictions,  photosynthesis  is significant  only in the  upper  pond
 layers.  This  region of net photosynthetic  activity is  called the  euphotic
zone (1).

Light  intensity  from   solar  radiation  varies  with  the  time   of  day   and
difference  in  latitudes.   In  cold  climates,  light  penetration  can   be
drastically reduced by  ice  and snow cover—thus  the  prevalence of  mechanical
aeration in these regions.


     2.3.2  Temperature


Temperature is a very  important factor in the aerobic environment  of a  pond
and will,  at or near  the surface,  determine  the  succession  of predominant
 species of algae,  bacteria,  and other  aquatic organisms.   Algae can survive
at temperatures of  5°C  to  40°C.  Green algae show  most  efficient growth and
                                      16

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activity  at temperatures  near 30°C  to  35°C.   Aerobic  bacteria  are  viable
within the temperature range of 10°C to 40°C, with 35°C  to  40°C  being  optimum
for cyanobacteria (10)(11).

Solar  radiation  is  a  major  source  of  heat,  generally  resulting  in   a
temperature gradient with respect to depth.  This can  influence  the  anaerobic
decomposition of  solids settled  to the  bottom of  the  pond.   The bacteria
responsible for anaerobic  degradation,  ideally requiring temperatures  within
the  range  of 15°C  to  65°C,  are  exposed to  the lowest temperatures,  thus
greatly  reducing  their  activity.   The  other  major  source  of  heat  is the
influent.   In  sewerage  systems  having  no  major   inflow  or   infiltration
problems, the influent temperature  is higher than that of the pond  contents.
Cooling  influences  are exerted by  evaporation,  contact  with cooler  ground-
water, and wind action.

Overall effects of  temperature,  combined with  light intensity,  are  reflected
in the fact that  nearly all investigators report improved  performance  during
summer  and  autumn  months  when  both  temperature  and  light  are  at  their
maximum.   The  maximum practical  temperature of  wastewater  ponds  is  likely
less  than  30°C,  indicating that  most  ponds  operate  at less  than  optimum
temperature for anaerobic activity (12).

Temperature  changes in  nonaerated  ponds  result in  vertical stratification
during certain  seasons  of  the year.   Stratification results because of  an
increase in  water density  with  depth caused  by a  decrease in  temperature.
During the summer, the upper waters are warmed and the  density decreased, and
stratification  results.   The  temperature of  the  upper layer  of  water  is
relatively  uniform  because of  mixing  by  the  wind.   Temperatures   change
rapidly  in  the  thermocline, and  the zone is  very resistant  to mixing.   As
temperatures decrease  during  the fall,  stratification is  decreased and the
pond  is  mixed  by wind  action.   This phenomenon  is  referred to as  the  fall
overturn.

The  density of water  decreases as  the temperature  falls  below  4°C,  and  a
winter stratification  can occur.  As ice cover breaks up  and  the water warms,
a spring overturn can  also occur.

During  both the  spring  and  fall   overturns,  significant  odors caused  by
anaerobic material being brought to the surface can stimulate complaints  from
neighbors.    Overturn  phenomena are  the reasons  for  regulatory  requirements
that  nonaerated ponds  be located downwind {based  on  prevailing winds  during
overturn periods)  and  away from dwellings.


     2.3.3  Nutrient Requirements and Removal


Growth and,  to  some extent, activity of microorganisms  is  controlled by the
availability of essential nutrients such as  carbon, nitrogen, phosphorus, and
sulfur and a variety of other substances required in  small  quantities.   These
nutrients may be  classified as inorganic  or organic.  Nitrogen,  phosphorus,
                                      17

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and  sulfur  represent the inorganic nutrients, while organic  carbon compounds
represent the organic nutrients.
         2.3.3.1  Nitrogen
Nitrogen  can  be  a  limiting  nutrient  for  primary  productivity  involving
algae.   Figure 2-3  represents  the  various  forms  that  nitrogen  typically
assumes over time  in  wastewater ponds.   The conversion  of organic nitrogen to
various other  nitrogen forms  results  in a net loss  in total  nitrogen  (13).
This nitrogen  loss may be due  to  either algal  uptake  for metabolic  purposes
or to bacterial  action.   It  is likely that each mechanism contributes to  the
overall total  nitrogen  reduction.   As  previously  discussed,  another  factor
contributing to  the reduction of total  nitrogen is  gaseous  ammonia  stripping
under favorable  environmental  conditions.  Regardless of  the  specific  removal
mechanism  involved,  ammonia  removal  in  facultative  wastewater  ponds  may
approach 99 percent,  with  the major removal  occurring in the  primary cell  of
a multicell pond system (9).
                                 FIGURE 2-3

           CHANGES OCCURRING  IN FORMS OF NITROGEN PRESENT IN A POND
                  ENVIRONMENT UNDER AEROBIC CONDITIONS  (7)
                                   Time, days
                                      18

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         2.3.3.2  Phosphorus


Phosphorus   is  most   often   the   growth-limiting    nutrient   in   aquatic
environments.   Municipal   wastewater,  however,  is  normally  quite  rich  in
phosphorus  even  though  current  restrictions  on  phosphorus  compounds  in
detergents  has   resulted  in   reduced  concentrations.   Nonetheless,   the
concentration is still  adequate to stimulate growth in aquatic organisms.

In aquatic  environments,  phosphorus  occurs  in  three  forms:   (1)  particulate
phosphorus,  (2)  soluble  organic  phosphorus,  and  (3)   inorganic  phosphorus.
Inorganic  phosphorus,  primarily  in  the  form  of  orthophosphate,  is  readily
utilized by aquatic organisms.   Some  organisms may  store excess  phosphorus as
polyphosphates for future  use.   At the  same time,  some phosphate is  contin-
uously lost to sediments,  where it is locked up in insoluble precipitates  (1).

Phosphorus  removal  in  ponds  may result from  physical mechanisms  such  as
adsorption,  coagulation,   and  precipitation.   The  uptake  of  phosphorus  by
organisms  in  metabolic functions  as  well   as  for storage  can also  add  to
phosphorus removal.  Phosphorus  removal  in wastewater ponds has  been  reported
to range from 30 to 95  percent (13).

Like nitrogen, phosphorus  held by  algae discharged in  the final effluent may
be introduced  to receiving  waters as organic  phosphorus.   Excessive algal
"afterblooms" observed  in waters  receiving effluents  have,   in some  cases,
been attributed to nitrogen and  phosphorus compounds remaining in  the  treated
wastewater.  Phosphorus removal  in aquaculture  is discussed  in Chapter  5.


         2.3.3.3  Sulfur


Sulfur is  a vital  nutrient  for  microorganisms,  but  is usually plentiful  in
natural  waters.   Because  sulfur  is   rarely   limiting,  its   removal   from
wastewater  is  usually  not  considered  necessary,   Ecologically,  sulfur  is
particularly -important since compounds such  as hydrogen sulfide and  sulfuric
acid are  toxic,  and since the  oxidation of certain sulfur  compounds is  an
important energy source for some  aquatic bacteria (1).


         2.3.3.4  Carbon


The decomposable organic carbon  content of  a waste is  traditionally measured
in terms  of its  biochemical oxygen  demand (BOD),  or   the amount of  oxygen
required under  standardized conditions  for the  aerobic biological   stabili-
zation  of   the  organic matter  in a  waste.   Since  the  time  required   for
complete  stabilization  by  biological  oxidation,  depending  on  the  organic
material   and  the  organisms  present,  can   be  several  weeks,  the   standard
practice  is to  use the   five-day biochemical  oxygen   demand   (BODs)  as  an
index  of  the organic  carbon content or organic  strength  of a waste.   The
                                      19

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 removal   of  BOD5   is  also  a  primary  criterion  for  evaluating  treatment
 efficiency.

 BODg  reductions in wastewater ponds ranging from  50  to 95  percent  have been
 reported  in  the literature.   Factors affecting  the reduction  of BOD5  are
 numerous.   A  very  rapid  reduction   in  BODs  occurs  in  a  wastewater  pond
 during  the  first   five  to  seven  days.   Later reductions  take  place at  a
 sharply  reduced rate.  BOD5 removals  are generally much  lower during winter
 and  early spring  than  in summer  and  early fall.  This  is due  primarily  to
 lower temperatures during these periods.  Many  regulatory agencies recommend
 that  ponds  be  so operated as to prevent discharge during cold periods.


 2.4   Performance and Design of Ponds


      2.4.1  Facultative Ponds

                                              i                             i
 Performance  results from existing pond  systems  located at  Peterborough,  NH;
 Kilmichael, MS; Eudora,  KS; and  Corinne,  UT, are  presented in  this  section
 (14-17).   These  studies  encompassed   12  full  months  of  data  collection,
 including   four  separate  30-consecutive-dayj,  24-hour   composite   sampling
 periods, once  each  season.


      2.4.1.1   Site  Description                !


         a.  Peterborough, New Hampshire


 The  Peterborough  facultative  waste  stabilization pond   system  consists  of
 three  cells  operated  in  series  during  the  evaluation   of the  performance
 described in  this  chapter.  The option  to operate the cells  in  parallel  or
 combination of series  and parallel is available.   The total surface  area  is
 8.5 ha  (21  ac) and the effluent is chlorinated.   A schematic drawing  of  the
 facility 'is  shown  in Figure 2-4.  An  effluent chlorine residual  of 2.0 mg/1
 is maintained  at all  times.  The  facility was designed in  1968 on an  areal
 loading  basis   of  20 kg  BOD5/d/ha   (18  Ib  BOD5/d/ac)  with   an  initial
 average hydraulic  flow of 1,890 m3/d  (0.5 mgd).  At  the  design depth  of  1.2
m (4 ft), the theoretical hydraulic detention time  for the system  would be  57
 days.   The  results of  the study conducted  during   1974-1975  indicated  an
 actual mean  area  loading of 15 kg  BODs/d/ha (14  Ib BODs/d/ac)  and  a  mean
hydraulic  flow  of  1,011   m3/d  (0.27  mgd),,   The  theoretical   hydraulic
 detention time based  upon  the flow  entering the  plant   was  107 days.  The
 loading rates and  detention times  for  the  first  cell  in the series  are  shown
 in Table 2-1.
                                      20

-------
                           FIGURE 2-4

SCHEMATIC FLOW DIAGRAM AND AERIAL PHOTOGRAPH OF THE FACULTATIVE
           POND  SYSTEM AT PETERBOROUGH, NEW HAMPSHIRE
              To chlorine contact tank
                               21

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                                  TABLE 2-1

             DESIGN AND ACTUAL LOADING RATES AND DETENTION TIMES
                       -FOR SELECTED  FACULTATIVE! PONDS
                           Organic Loading Rate	         Theoretical
                                      Actual   	     Hydraulic Detention
                                 TotalFTrst            Time
     Location          Design   System        Gel1     DesignActual

Peterborough, NH
Kilmichael, MS
Eudora, KS
Corinne, UT

20
67*
38
36
kg BOD5/ha/d
15
15
17
12
I
1
1
36
23
43
30

57
79
47
180
days
107
214
231
70
apirst cell.
         b.  Kilmichael, Mississippi


The Kilmichael  facultative  waste stabilization pond system consists of  three
cells operated  in  series with a total surface  area  of 3.3 ha (8.1 ac).   The
effluent is not chlorinated.  A  schematic drawing of the  facility  is shown in
Figure 2-5.

The design  load as specified by the State of  Mississippi  standards for  the
first  cell  in  the  series  was 67 kg  BOD5/d/ha  (60  Ib  BOD5/d/ac).    The
second cell was designed with a  surface  area  equivalent to 40 percent of  the
surface area of the first cell.  The third cell was  designed with a  surface
area equivalent to 16 percent of the first cell.  The  system  was designed  for
a hydraulic flow of 690 nr/d (0.18 mgd).  The  average depth  of the cells  is
approximately  2 m  (6.6  ft).   This  provides  for  a  theoretical  hydraulic
detention time of 79 days.  The  result of the  study indicated that the actual
average  organic load  on  the  first  cell  averaged 23 kg  BOD5/d/ha  (21   Tb
BODs/d/ac)  and that  the  average  hydraulic  inflow  to   the  system was  280
m3/d  (0.07 mgd).    The  theoretical  hydraulic  detention  time based upon  the
flow entering the  plant was 214 days.   Loading rates and detention times  are
summarized in Table 2-1.                                                    ;
                                       22

-------
                          FIGURE 2-5

SCHEMATIC FLOW DIAGRAM AND AERIAL PHOTOGRAPH OF THE FACULTATIVE
            POND SYSTEM AT KILMICHAEL, MISSISSIPPI
                               23

-------
             c.   Eudora, Kansas


The  Eudora  facultative  waste  stabilization pond  system  consists  of  three
cells  operated  in series with  a total surface area  of  7.8 ha  (19.3  ac).   A
schematic  diagram of the  system is shown in Figure 2-6.  The  effluent is  hot
chlorinated.

The  facility was designed on  an area! loading basis  of 38 kg  BODs/d/ha  (34
Ib  BODs/d/ac)  with  a hydraulic  flow  of  1,'510 m3/d   (0.4  mgd).   At  the
design  operating depth of 1.5  m (5  ft), the theoretical  hydraulic  detention
time would be 47  days.   The results  of  the study indicated that the actual
mean  organic load on  the   system  was  17   kg  BODs/d/ha  (15  Ib  BOD5/d/ac).
The  actual mean  hydraulic  flow to  the  system was 500  m3/d (0.13 mgd),  and
theoretical  hydraulic  detention time  in  the system was  231 days.  A  summary
of the  loading rates and detention times are shown in  Table 2-1.


             d.   Corinne, Utah

                                               j
The  Corinne facultative  waste  stabilization pond system  consists  of  seven
cells  operated  in series with  a total surface area  of  3.8  ha  (9.5  ac).   A
schematic  drawing of the  system is shown in Figure 2-7.  The  effluent is  not
chlorinated.

The  facility was designed on  an area! loading, basis  of 36 kg  BODs/d/ha  (32
Ib BOD5/d/ac) with a hydraulic  flow of 265 m3/d (0.07  mgd).

With a  design  depth of 1.2  m  (4 ft),  the system has  a  theoretical  hydraulic
detention  time   of  180 days.   The results  of  the study indicated that  the
actual  mean  organic  load  on the   system was  12  kg  BODs/d/ha   (11   Ib
BODg/d/ac).  The actual average hydraulic  flow  to the  system  was 690 m3/d
(O.T8 mgd),  and  the  theoretical  hydraulic detention time in the  system was  70
days.   Loading rates and detention times are summarized in Table  2-1.


        -2.4.1.2 Performance                  ;


             a.   BODs Removal


The  monthly average  effluent  BODs  concentrations for   the  four  previously
described  facultative  pond  systems are presented in Figure 2-8.    In general,
all  of the  systems were  capable of  providing  a monthly average effluent
BODs  concentration of less than  30 mg/1  during  the major  portion  of  the
year.   Monthly   average  effluent  BODs  concentrations  ranged  from 1.4 mg/1
during  September 1975  at the Corinne,  UT, site,,  to 57 mg/1  during March 1975
at  the Peterborough,  NH, site.  Monthly  average effluent  BODs concentra-
tions tended to  be higher during January, February,  March, and  April  at all
                                      24

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                           FIGURE 2-6

SCHEMATIC FLOW DIAGRAM AND  AERIAL PHOTOGRAPH OF,THE FACULTATIVE
                 POND SYSTEM AT EUDORA, KANSAS
     Effluent
                                                     Influent
                               25

-------
                             FIGURE  2-7

 SCHEMATIC FLOW DIAGRAM  AND AERIAL PHOTOGRAPH OF THE FACULTATIVE
                    POND SYSTEM AT CORINNE, UTAH
           Effluent
©
O Sampling station
    (TYP.)
-©

Cell No. 7
0.34 ha J
f
©1
Cell No. 6
0.405 ha
f
/"^"™"'\
(e)

Cell No. 5
0.405 ha
_^^^,
•^^^^
Cell No. 2
0.405 ha

®i

\
Cell No. 3
0.405 ha
®J
1
Cell No. 4
0.405 ha
© ;
00




Cell No. 1
1.49 ha
\
\










\
\
[.•M***"* •* ™" " \ Influent
; ©
\
                                 26

-------
                                        FIGURE  2-8

                    FACULTATIVE POND BOD5 EFFLUENT CONCENTRATIONS
O)
E
 in
Q
O
CO

c
0)
01
d>
OJ
CD
c
o
           N    D    J    F   M   A   M

               1974-1975
            Eudora, Kansas (3 cells)
	D	Kilmichael, Mississippi (3 cell)
	A	 Corinne, Utah (7 cells)
	•-	  Peterborough, New Hampshire (3 cells)
                                                                               N
D   J     F
1975'1976

-------
of  the  sites.   This  was  especially evident at the Peterborough  site  when  the
cells were  covered over by ice due  to freezing temperatures.  The ice  cover
caused  the  cells to  become  anaerobic.  However,  even when  the ponds at  the
Corinne  site were covered  over with  ice the monthly  average effluent  BODs
concentration did not exceed 30 mg/1.

None of  the systems  studied was significantly affected by  the fall  overturn;
however,  the spring  overturn  did  cause  significant increases  in  effluent
BODc concentrations  at  two of the sites.  At the Corinne  site  two  different
spring  overturns occurred.  The  first occurred  in  March  1975,  with a  peak
daily   BODs  concentration   of   36 mg/1.    The  second   occurred   during
April 1975,  with a  peak daily effluent  BOD5 concentration  of 39 mg/1.   At
the  Eudora  site,  the   peak  daily  effluent  BOD5  concentration  of  57  mg/1
occurred  during April 1975.  The  Kilmichael  and  Peterborough sites  were  not
severely affected by  the spring overturn period.

The monthly average  effluent  BODs concentration  of  the  Corinne pond  system
never exceeded  30  mg/1  throughout the  entire study.   The Eudora pond  system
monthly  average effluent  BODs concentration exceeded 30 mg/1  on  only  two
occasions during the study.   The  Peterborough  pond  system monthly  average
effluent BOD5 concentration exceeded 30 mg/1  in 4  of the 12 months studied.

Although  these  systems  are subject  to seasonal  upsets,  they are capable  of
producing an effluent sufficiently low in BODj that  discharge to a  waterway
is, in  many cases, acceptable.   It should  be noted  that  three  of  the  four
systems were underloaded based on a comparison of  design vs. actual  organic
and  hydraulic   loadings,  as  shown  in Table  2-1.    The  Corinne  system  was
grossly underloaded from an  organic standpoint and grossly overloaded from  a
hydraulic standpoint.


            b.   Suspended Solids Removal


The monthly average  effluent SS concentrations for each  system  are presented
in Figure 2-9.                                  i

In  general, the  SS   concentration  in  facultative  pond  effluents  follows  a
seasonal  pattern.   Effluent SS  concentration is  high during summer months
when algal  growth  is intensive and  also during  the  spring  overturn  periods
when settled solids are  resuspended  from  bottom sediments due to mixing.   The
monthly average  SS concentration  ranged  from 2.5 mg/1  during September 1975
at Corinne to 179 mg/1 during April  1975, also at Corinne.  The high  value of
179 mg/1  occurred  during   the   spring  overturn  period,  which  caused   a
resuspension of settled  solids.

Eudora and  Kilmichael illustrate  the  increase in  effluent SS  concentration
due to algal growth during the warm  summer months.  However,  Peterborough  and
Corinne were not  significantly  affected by  algal  growth  during  the summer
months.    In general, Corinne  and  Peterborough  produced a  monthly  average
effluent SS concentration of less  than 20 mg/1.   During  10  of the 13 months
                                      28

-------
                                                              FIGURE  2-9

                                          FACULTATIVE POND SS  EFFLUENT CONCENTRATIONS
ro
                      o>

                      (0
                      CO
0>
_3
£
(U
o>
(0

I
                      o
100

 90

 80

 70

 60

 50

 40

 30

 20

 10


  0
                                                                  4, 179
                                              _L
                                                         i
                                                                                                         ..A
                                                                                                    ..A-"
                                                                                               "A"''  I     I
                                     0
                                  .-n
                                  ..A
                    N    D    J    F
                       1974-1975
                                    M
M
0    N
                     Eudora, Kansas (3 cells)
                  •- Kilmichael, Mississippi (3 cells)
                  • •  Corinne, Utah (7 cells)
                  -•  Peterborough, New Hampshire (3 cells)
D    J
 1975

-------
 studied,  the monthly  average effluent  SS  concentration at  the  Corinne site
 never  exceeded   20mg/l.    However,   the  monthly   average   effluent   SS
 concentration  at  Eudora  was never  less than  39 mg/1   throughout  the entire
 study.

 The  results of these studies indicate  that facultative ponds  can  produce an
 effluent  which has  a  low SS concentration;  however,  effluent SS  concentra-
 tions will  be high at various  times  throughout the year.   In general, these
 SS  are composed  of algal  cells  which may  not  be  particularly  harmful  to
 receiving  streams.  In areas where effluent SS standards  are stringent, some
 type  of polishing device  or controlled  discharge  will  be  necessary to reduce
 SS concentrations  to acceptable levels.


            c.  Fecal Coliform Removal


 The  monthly  geometric  mean  effluent  coliform concentrations  for the  four
 facultative pond  systems  are compared  with a  concentration of 200/100 ml  in
 Figure  2-10.

 Only   the   Peterborough,  NH,   system  provides  chlorine   disinfection.   As
 illustrated  in Figure 2-10,  the  chlorinated  effluent  at  Peterborough never
 exceeded  20 fecal  coliform organisms/100  ml.   This  clearly  indicates  that
 facultative   pond  effluent  may  be   satisfactorily   disinfected   by  the
 chlorination process.

 For  the three  systems without  disinfection  processes,  the  geometric  mean
monthly    effluent   fecal    coliform    concentration    ranged    from   0.1
 organisms/100 ml  in June  and  September 1975, at  the Corinne,  UT,  lagoon
 system  to  13,527  organisms/100 ml  in  January  1975, at the  Kilmichael,  MS,
 lagoon  system.    In  general,   geometric  mean   effluent   fecal   coliform
concentrations  tend to  be  higher  during the  colder periods.   The  fecal
coliform  die-off  during  periods  of   ice  cover can be  expected   to   be
 significantly less than normal due to the reduced  amount of sunlight reaching
 the  organisms.   The Eudora,  KS,  and  the Kilmichael,  MS,  geometric mean
monthly  effluent  fecal  coliform concentrations  consistently  exceeded  200
organisms/100 ml during winter operation.

The fecal  coliform concentration  in  the Corinne  effluent never exceeded  10
organisms/100  ml   even though  this  system  did  not  include  any  form   of
disinfection.   This system is composed  of seven cells in series.  Analysis  of
the fecal  coliform  concentrations between  the  seven   cells  indicated that
fecal  coliforms were essentially  absent after  the fourth  cell in  the series
 (17).   The other two systems without disinfection  only  utilize three cells  in
series; however;  fecal  co'liform  die-off is  primarily   a  function  of  actual
hydraulic residence time  rather  than  the absolute number of cells  in series.
                                      30

-------
                         FIGURE 2-10

FACULTATIVE  POND FECAL COLIFORM  EFFLUENT CONCENTRATIONS
IVJ
105
"5
o —
Q> i-
3 \
3= o
^ 103
sj
Monthly Geometric
Coliform Conceni
D § Q 9
\J
v
1 I 1 I 1 I 1 1 1 1 1 I 1 I 1 I t I I
r^^ '^""VA /
/ V-v
: / /\ :
n — c/ \ n
p^ \ / V \ / Ns x
/ • .7 '•. •« A. •' .-A.
A./ ..A. ..\.A- '. v' /•. •'^''
./ \ ; X'"'\ / "'A-.. .•'' *"•« ..-A
i i + * + y i V i i i v i t i i t" i i
1 AS ON DJFMAMJ J AS ONDJFM
1974-1975 1975«1976
	 O- 	 Eudora, Kansas (3 cells)
	 D 	 Kilmichael, Mississippi (3 cells)
Peterborough, New Hampshire (3 cells) (unchlorinated)
Peterborough, New Hampshire (chlorinated)

-------
 The results of these  studies  indicate that facultative pond  effluent  can be
 chlorinated to  produce fecal  coliform  concentrations  less  than 10  organ-
 isms/100  ml.   Two  of the  systems  studied  could  not produce  an  effluent
 containing  less than  200  fecal  coliforms/100 ml.   This  was  probably  due to
 hydraulic  short circuiting;  however,  the Corinne,  UT,  system study  clearly
 indicated   that facultative  pond  systems  can  significantly  reduce  fecal
 coliform concentrations by natural, processes occurring in the pond.


        •2.4.1.3   Design Criteria  for  Organic Loading and Hydraulic
                   Detention Time


 Canter  and  Englande (18)  reported  that  most  states have design  criteria  for
 organic  loading   and/or   hydraulic  detention   time  for   facultative   waste
 stabilization  ponds.   These design criteria  are established by  these  states
 in  an  effort  to  ensure   that  the   quality  of  pond  effluent  would meet
 applicable  state  or  Federal  standards.   Effluents  from  ponds  constructed
 according  to  these  design  criteria  repeatedly  fail to  meet  the  quality
 standards,  thus  indicating  deficiencies  in  the  current  design  criteria.
 Reported  organic  loading  design  criteria  averaged 29  kg  BODs/ha/d   (26  Ib
 BODs/ac/d)  in   the  north  region  (above  42°  latitude),  49  kg BODs/ha/d  (44
 Ib  BOD5/ac/d)  in  the southern  region (below 37°  latitude),  and  37   kg
 BODs/ha/d   (33   Ib  BODs/ac/d)   in  the  central  region.    Reported   design
 criteria for  detention time averaged  117 days  in the north,  82  days  in  the
 central, and 31 days in the south region.      !
                                               u
 Design  criteria for  organic  loading  in New Hampshire  was  39  kg  BODs/ha/d
 (35  Ib  BODs/ac/d).   The   Peterborough treatment system  was  designed  for  a
 loading of  20  kg  BOD5/ha/d  (18 Ib  BOD5/ac/d)  in   1968  to  be  increased  as
 population  increased  to   40  kg  BODs/ha/d   (35  Ib  BODs/ac/d)  in  the year
 2000. .  Actual   loading during  1974-1975 averaged   15 kg  BOD5/ha/d  (14   Ib
 BODs/ac/d)  with the  highest monthly  loading being  21  kg  BODs/ha/d  (19 Ib
 BODc/ac/d).  Although  the  organic  loading was substantially  below the  state
 design  limit,   the  effluent BOD5 exceeded  30 mg/1  during  the  months   of
 October 1974 and February,  March, and April  1975.

 Mississippi's   design  criteria  for   organic  loading. was  67  kg  BODs/ha/d
 (60 Ib BODs/ac/d)  in  the  first  cell.   Based on  an  overall  loading rate,  the
 Kilmichael   treatment   system  was   loaded   at   43   kg   BODs/ha/d  (38   Tb
 BOD5/ac/d).   Actual  loading during 1974-1975 averaged  15  kg BOD5/ha/d  (13
 Ib  BODs/ac/d)   with  a   monthly  maximum   of   25   kg   BODs/ha/d  (22   Ib
 BODs/ac/d),   and yet  the  effluent BODs exceeded  39  mg/1  twice  during  the
 sample year (November and July).

 The design  load for the Eudora, KS, system was  the  same  as the state  design
limit,  38   kg  BOD5/ha/d   (34   Ib   BOD5/ac/d).    Actual   loading   during
1974-1975 averaged only 17  kg  BODs/ha/d (15 Ib  BODs/ac/d)  with  a maximum
of  31  kg   BOD5/ha/d  (28  Ib   BOD5/ac/d).   The   effluent  BOD5  exceeded
30 mg/1  three months during the  sample year  (March,  April, and August).
                                       32

-------
Utah  has both  an  organic loading  design  limit,   45  kg  BODs/ha/d  (40  Ib
BOD5/ac/d) on  the  primary cell and  a winter  detention  time design  criteria
of 180 days.   Design  loading  for the Corinne  system was  36 kg BOD5/ha/d  (32
Ib  BOD5/ac/d),  and  design  detention  time  was  180   days.   Although   the
organic  loading  averaged 30  kg  BODs/ha/d  (34  Ib BODs/ac/d)  on  the  primary
cell, during  two  months of the  sample year it exceeded  56 kg BOD5/ha/d  (50
BODs/ac/d).    Average  organic  loading   on  the   total   system  was  12   kg
BODij/ha/d   (11   Ib  BOD5/ac/d),  and   the  hydraulic   detention  time   was
estimated to be 88 days during the winter.   Regardless of the  deviations  from
the state design criteria, the average monthly 8005  never exceeded 30  mg/1.

A summary of  the state design  criteria  for each location  and actual design
values for  organic  loading and hydraulic  detention time are  shown in Table
2-2,  Also included is a list of the months  the Federal effluent  standard  for
BODs  was exceeded.   Note  that  the  actual  organic  loading  for all   four
systems  are  nearly equal, yet  as the  monthly effluent  BODs  averages shown
in  Figure 2-8  indicate,  the  Corinne  system consistently  produced a higher
quality  effluent.  This  may be a function of the larger number  of cells  in
the Corinne system—seven  as  compared  to three for  the  rest of  the  systems.
Hydraulic short circuiting  may  be  occurring in   the  three  cell  systems,
resulting in  a  shorter actual  detention  time  than exists  in  the   Corinne
system.  Detention time  may also be affected  by  the location  of  cell inlet
and outlet structures.  As shown in Figure 2-7, the  outlet  is at  the  furthest
point possible from the inlet in the Corinne, UT, system.   At the Eudora,  KS,
system shown in Figure 2-6, large "dead zones" undoubtedly  occur  in each cell
due to the unnecessarily short distance between inlet and outlet.   These dead
zones result in decreased hydraulic detention and increased effective  organic
loading rate.


         2.4.1.4  Nitrogen Removal


            a.  Theoretical Considerations


Differences   between   influent  and   effluent  .nitrogen   concentration    in
facultative   stabilization  ponds  occur  principally through   the  following
processes:


     1.   Gaseous ammonia stripping to the atmosphere

     2.  Ammonia assimilation  in algal  biomass

     3.  Nitrate assimilation  in algal  and other plant biomass

     4.   Biological  nitrification-denitrification
                                       33

-------
                                                       TABLE  2-2

                           SUMMARY OF DESIGN AND PERFORMANCE  DATA—SELECTED FACULTATIVE  PONDS
co
                                   Organic Loading
Theoretical Hydraulic
    Detention Time
Locati on

Peterborough, NH
Kilmidael, MS
Eudora, KS
Corinno, UT
Design
Standard
kg
39
56
38
453
Design
BOD5/ha/d
20
67h
43b
38
363
Actual
(1974-1975)

16
27a
I8b
19
34a
15b
Design
Standard

None
None
None
180
Design
days
57
79
47
180
Actual

107
214
231
70
88C
Months Effluent
Exceeded 30 mg/1 BODs

Oct/Feb/Mar/Apr '
Nov/Jul
Mar/Apr/Aug
None
        aPrimary cell,
        bEntire system.
        cEstimated  from  dye  study.

-------
The following design equations are based on  equations  describing  the  loss of
gaseous ammonia to the atmosphere; however, the design parameters also reflect
the influence of all processes associated with ammonia nitrogen removal.   The
rate of  gaseous  ammonia losses  to  the atmosphere depends  mainly on the  pH
value, surface to volume ratio, temperature,  and  the  mixing conditions in the
pond.   Alkaline pH shifts the  equilibrium equation  NH3° + H20  £   NH4+ + OH~
toward gaseous  ammonia production,  while  the mixing  conditions  affect  the
magnitude of  the mass  transfer  coefficient.  Temperature  affects  both  the
equilibrium constant and mass  transfer  coefficient.

Ammonia removal in ponds can be  expressed by  assuming  a  first order reaction
(19)(20).  A  conceptual  development  of the  mathematical  model is  presented
elsewhere (21).  The final  design equations are given below:


For temperatures of 1°C to  20°C;


             ^e=__	1	   (2-11)

             Co   T  +^ (0.0038 + 0.000134T)e(1-041 + 0-044T)(PH-6.6)



For temperatures of 21°C to 25"C:



             ^e=  	1	                  (2-12)

             co~  1 ^(B.osBxio-V1-540^-6'6'


             C0 =   influent concentration of  (NH.  + NHg ), mg/1  as  N


             Ce =   effluent concentration of  (NH4  + NH3°), mg/1  as  N

                                              p
             A  =   surface area  of the pond,  m

             Q  =   flow rate,  m  /d

             T  =   temperature,  °C
                                       35

-------
             b.  Pond Systems

                               • V'  ?:ANr> •'    '   :;.    ' '
The  stabilization pond systems located  in Peterborough, NH; Eudora, KS;  and
Corinne,  UT, described earlier, are  exposed to similar  climatic  conditions.
During  the  winter the water  temperatures  range between 1°C and 5°C  (between
34°F  and  41°F),  and ice cover  is  experienced during the winter.   During  the
summertime  the water  temperature is  approximately  20°C  (68°F)  and  isgenerally
less  than 25°C  (77°F).   The fourth'  system at  Kilmichael,  MS, was  excluded
from  the  analysis because of the  different aeration systems and  much  milder
climate.

The  characteristics of  the wastewater  entering these  systems were  signif-
icantly different, as shown  in  Table  2-3.   The Eudora wastewater is a typical
medium-strength   domestic  wastewater;  the  Corinne  wastewater  is  slightly
alkaline; and Peterborough  has  a neutral  unbuffered wastewater. The  pH value
in the  ponds has a marked  effect  on  ammonia-N removal. In  the Corinne ponds
the  pH  values were above  9, while  in the  Peterborough  system the  pH value
during the summer was 6.7 to 7.4, which is low compared with other ponds.


             c.  Ammonia-N Removal


The  annual   average  percentage nitrogen   removals,  calculated  as  ammonium
nitrogen, at the Eudora and  Corinne facultative pond  systems  were about  95
percent,  and at  the Peterborough  ponds  it was about 46 percent.   The major
removal occurred  in the primary cells.  Table 2-4 summarizes these  results.

During  the  months  of  June through September,  ammonia-N  removal   in  the
Peterborough system reached  67  percent, while at Eudora ammonia-N  removal was
almost 99 percent.  In the  winter  period  of December to March  in  the primary
cell   of the Peterborough system,  there was  no ammonia-N removal,  and  in  the
total system there was  approximately 19  percent  ammonia-N  removal.    In  the
Eudora and  Corinne systems, during  this  period, there  was  about 90 percent
ammonia-N removal with 53-62 percent removal occurring  in the primary  cells.


     2.4.2  Aerated Ponds                      ;

                                               i       :
Results of   intensive aerated porid performance  studies of  aerated ponds  at
Bixby, OK; Pawnee,  IL; North Sulfport,  MS; Lake Koshkonong, WI; and  Windber,
PA (22-26)  are  presented  in this section.   Data  collection   encompassed  12
months  with  four  separate  30-consecutive-day,  24-hour  composite  sampling
periods, once each season.
                                       36

-------
              TABLE 2-3

INFLUENT WASTEWATER CHARACTERISTICS AT
      SELECTED FACULTATIVE PONDS
Parameter
BOD, mg/1
COD, mg/1
NH4, mg/1
pH
Alkalinity, mg/1 as CaC

Peterborouqh
NH
138
271 .
21.5
7.0
03 107
TABLE 2-4
Eudora
KS
270
559
25.5
7.7
428

ANNUAL AVERAGE AMMONIA-NITROGEN REMOVAL
SELECTED FACULTATIVE PONDS
Parameter
NH4-N, mg/1
Influent
Cell #1 Effluent
Final Effluent
NH4-N Removal , percent
Cell #1
Total System
Theor. Detention Time,
Cell #1
Total System
Peterborough
NH
21.5
16.5
11.5
23.3
46.5
days
44
107
Eudora
KS
25.5
9.2
1.1
63.9
95.7
92
231
Corinne
UT
74
128
7.5
8.4
576

BY
Corinne
UT
7.5
1.4
0.2
81.3
97.3
29
70
                  37

-------
 Aerated ponds are  medium-depth,  manmade basins  designed for  the biological
 treatment of  wastewater.   A  mechanical  aeration  device is  used  to supply
 supplemental  oxygen  to the  system; -  Well-mixed  aerated  ponds  are  aerobic
 throughout their  entire depth.   The  mechanical  aeration  device may  cause
 turbulent  mixing  (i.e.,   surface  aerator)  or  may  produce  laminar  flow
 conditions (diffused air systems).  The five aerated ponds were considered to
 be partial mix  systems by  the  investigators,  although data  describing  the
 mixing characteristics  were not collected.

 The  North Gulfport system  contains surface  aerators; the average depth of the
 aerated cells is 1.9 m (6.3  ft).  Diffused-aiir aeration systems  are  used in
 the  other ponds,  and the average  depth  is 3.0  m (10 ft).  The Bixby and North
 Gulfport systems  consist of two aerated cells  in  series and  the others, three
 cells  in series.   The aerated  cells of  the  North  Gulfport system are followed
 by settling ponds and a chlorine  contact pond.  The operating conditions  for
 these  systems  and  the influent  wastewater  characteristics  entering  these
 systems  were significantly different as shown in Tables 2-5 and 2-6.


          2.4.2.1  Site  Descriptions
                                               i

           a.  Bixby, Oklahoma


 A  diagram of  the  Bixby, OK,  system is shown in Figure  2-11  (22).   The system
 consists  of two  aerated cells  with  a total surface  area  of 2.3  ha  (5.8  ac)
 designed  to treat  335   kg  BOD5/d (737 Ib  B0[>5/d)  with a  hydraulic  loading
 rate of 1,550  m3/d (0.4 mgd).  The  design  organic  loading rate on the  first
 cell  is  shown  in  Table   2-6.  There  is  no  chlorination  facility at the  site.
 The design hydraulic retention  time was 32 days.


         b.  Pawnee, Illinois


 A  diagram of the Pawnee, IL, system  is  shown in Figure  2-12  (23).   The system
 consists  of three aerated  cells in series with a  total surface area  of 4.45
 ha  (11.0  ac).   The  design  flow  rate  1,890  m3/d  (0.5 mgd) with  a  design
 organic  load  of   386  kg  BOD5/d  (850  Ib   BOD5/d)  and  a  design  hydraulic
 retention time of 60 days.  The design  organic loading  rate  on  the first cell
 is  shown   in   Table  2-6.    The  facility  is  equipped  with   chlorination
 disinfection and  a  slow sand filter  for  polishing  the  effluent.   The  filter
was removed following the study.   Data  reported below were collected prior  to
 the filters and represent only  pond performance.


         c.  North Gulfport, Mississippi
                                               i


A  diagram of the  North Gulfport, MS,  system  is shown in Figure 2-13  (24).
The system consists  of  two aerated cells  in series with a total surface area

                                      38

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                                   TABLE  2-5

                    INFLUENT WASTEWATER CHARACTERISTICS AT
                            SELECTED AERATED PONDS
Parameter
BODg, mg/1
COD, mg/1
TKN, mg/1
NH4-N, mg/1
pH
Alkalinity, mg/
Pawnee
IL
473
1,026
51.4
26.32
6.8-7.4
1 242
Bixby
OK
368
653
45.0
29.58
6.1-7.1
154
Lake
Koshkonong
WI
85
196
15.3
10.04
1.2-1 A
397
Windber
PA
173
424
24.3
22.85
5.6-6.9
67
North
Gulf port
MS
178
338
26.5
15.7
6.7-7.5
144
       as CaCOa
                                    TABLE 2-6

               DESIGN AND ACTUAL LOADING RATES AND DETENTION TIMES
                           FOR SELECTED AERATED  PONDS
                        Organic Loading Rate on First Cell
  Total System
Theor. Hydraulic
  Detention Time
Location

Pawnee, 11
Bixby, OK
Lake Koshkonong, WI
Windber, PA
North Gulf port, MS
Design Actual
kg BOD5/ha/d
154a 150
284b 161
509b 87
497b 285
375C 486
Design
kg BOD5/1
5.8
12.0
20.2
18.6
19.3
Actual
,000 m3/d
5.6
6.7
3.6
9.8
25.1
Design Actual
days
60 144
32 108
30 73
30 48
26d 18
aEqualed or exceeded 7 of the 12 months monitored.
"Not exceeded.
cExceeded 11 of the 12 months monitored.
d Aerated cells only.
                                      39

-------
                                    FIGURE 2-11 I

         SCHEMATIC FLOW DIAGRAM AND  AERIAL  PHOTOGRAPH OF THE AERATED
                         POND SYSTEM AT BIXBY, OKLAHOMA
                 Pump 1
Screen
                    Lift
                   station
                 Pump 2
    Legend

   I   Influent
   E  Effluent
   R  Return Ref.
   A  Air
   D  Drain
   Ep Plant Eff.
   E1 Lagoon 1 Eff.
   E2 Lagoon 2 Eff.
   E° Overflow and emergency eff.
                                        FM
I
I
I
I
Blower
house
j
i
i
i
E2
Cell No. 1
1.18 ha
A® J> A

I I
A| |A
<
R
Cell No. 2
1.18 ha
® ® D
«-
I
E1

E°
D^^
Ep
To river
                                        40

-------
                            FIGURE 2-12

SCHEMATIC  FLOW  DIAGRAM AND  AERIAL  PHOTOGRAPH  OF THE  AERATED
                POND SYSTEM AT PAWNEE, ILLINOIS
            m
                              Cell No. 1
                   Baffle
2.5 ha

Cell No. 2
1 .3 ha
^
Cell No. 3
0.73 ha



                          1 Manhole
                          2 Wet well
                          3 Compressor house
                          4 Chlorine contact tank
                          A Sampling station (typical)
                                 41

-------
                            FIGURE 2-13
SCHEMATIC  FLOW DIAGRAM  AND AERIAL PHOTOGRAPH OF  THE AERATED
             POND  SYSTEM AT  GULFPORT, MISSISSIPPI
          15"dia.
4^   Flow monitoring station
/lA   Sample monitoring station
(i)   Aerator (HP)
=1   Weir Box
 O   Manhole
                                 42

-------
                                                      a  theoretical  detention
                                                      it  1,890 nrVd  (0.5  mgd)
of 2.5  ha (6.3 ac)  followed  by settling ponds with
time of  five  days.  The  system was  designed  to  treat
with a  total  theoretical hydraulic  retention  time  of 26  days.
organic loading rate on  the first cell in the series  is  shown in
The system is equipped with a chlorination facility.
                                                                   The  desi<
                                                                   Table  2-t
           d.  Lake Koshkonong, Wisconsin
A  diagram  of the Lake  Koshkonong,  WI, system is  shown
The system consists  of three aerated cells with a  total
ha  (6.9  ac)  followed  by  chlori nation.  The
mgd) with  a  design  organic  load of  463 kg
design hydraulic detention time  of  30 days.
on the first cell is shown in Table 2-6.
                                                         in Figure 2-14  (25).
                                                          surface area of  2.8
                                              design  flow was  2270  m3/d  (0.6
                                              BODs/d  (1,020 Ib  BOD5/d)  and a
                                              The design organic loading  rate
           e.  Windber, Pennsylvania
The  Windber,  PA,  system consists  of  three cells  in  series with  a  total
surface  area  of  8.4  ha (20.7  ac)  followed by  chlori nation  (Figure 2-15)
(26).  The  design  flow rate was  7,576 m3/d  (2.0 mgd)  with a design  organic
load  of  approximately  1,540  kg  BOD5/d  (3,400  Ib  BOD5/d).    The   design
organic loading rate  on the  first cell  is  shown in  Table 2-6.  The  design
mean hydraulic  residence  time was  30  days for the  three  cells operating  in
series.
         2.4.2.2  Performance
           a.
                    Removal
The monthly  average  effluent BODs  concentrations  for the
described aerated pond systems are presented in Figure 2-16.
                                                              five previously
In general, all  of the systems, except the Bixby, OK, system, were capable  of
producing  monthly   average   effluent  BODs  concentrations   of  less   than
30 mg/1.   Monthly  average effluent  BODs concentrations  appear  to  be  inde-
pendent  of influent  BODs concentration  fluctuations and  not  significantly
affected by seasonal  variations in temperature.

Monthly  average  influent BODs  concentrations  at  Bixby,  OK,  ranged  from
212 mg/1  to  504 mg/1  with   a  mean  of  388 mg/1  during  the   study   period
reported.  The  design influent BODs  concentration  was  240 mg/1,  or only  62
percent of the  actual  influent  concentration.   The  mean flow rate during the
period  of  study was  520  m3/d  (0.12  mgd),  which is less  than one-third  of
                                       43

-------
                              FIGURE 2-14

SCHEMATIC  FLOW DIAGRAM AND AERIAL  PHOTOGRAPH  OF  THE  AERATED
           POND  SYSTEM AT LAKE  KOSHKONONG,  WISCONSIN
»V  r^"]
 0  l_ — I
                                             Comminutor and
                                             pumping station
                              By-pass -
                Drainage ditch
                to Rock River
                 1370L.F. 12" Outfall
                               By-pass -
                                          T — r- 3000 L.F. 12" Force main
                                          f——'	;
                        Chlorinators
                                             Cell No. 1   I
                                              0.91 ha   !
                                             •	  4
                                            tell No. 2
                                             0.91 ha
                                             Cell No. 3
                                              0.91 ha
                                    44

-------
                                        FIGURE 2-15

         SCHEMATIC  FLOW DIAGRAM AND AERIAL PHOTOGRAPH  OF THE  AERATED
                       POND  SYSTEM  AT WINDBER,  PENNSYLVANIA
Highland
trunk line
      Baffle

45 cm Outfall
 60cm
 Outfall
 Recirculation
.line 10% of
 flow
                                                  30 cm Gravity flow

                                                  • i .•
                                            Pump line
                              Cell No. 1 Drain
                              Cell No. 2 By Pass
                           A Sampling Site No. 1 (Plant Influent)
                           B Sampling Site No. 2 (Cell No. 1 Effluent)
                           C Cell No. 2 Effluent
                           D Cell No. 3 Effluent
                           E Plant Effluent (After Chlorination)
                                                         Manhole
                                                         Parshall flume

                                                         Grinder & Screen

                                                         Grit removal unit
                                             45

-------
                                                     FIGURE'2-16

                                      AERATED POND BOD5 EFFLUENT CONCENTRATIONS
cr>
   100


     90


^   80
o>
£
 to
Q
O
m

c
Q)
_3

UJ
O)
(D

<5
70


60


50


40


30
         |   20
          o

              10
              0
                                                     l
                                                 i
                                                 1
1
                                     Pawnee, Illinois

                                     Gulfport, Mississippi
                                     Bixby, Oklahoma
                                  —  Windber, Pennsylvania

                                  —  Lake Koshkonong, Wisconsin
                                       ..... A..
                                              ' -A
                               .-DN
                 ON    DJ    FMAMJ     J

                           1975 • 1976
                                                           A    S    0    N   D    J     F

                                                                                1976-1977

-------
the  design  flow rate.  The Bi'xby system was  designed to treat 336  kg BODs/d
(740  Ib  BOD5/d),  and  apparently  a  load  of  only  203  kg  BOD5/d   (446  Ib
BODs/d)  was  entering the  lagoon.    The  only  major  difference  between  the
Bixby and other aerated lagoons is  the number "of cells.  Bixby has  only  two
cells in  series.  Based upon  the results of studies with  facultative  ponds
which  show  improved  performance  with  an   increase  in  cell  number,  this
difference in configuration could account for the relatively poor  performance
by  the  Bixby system.  However,  there are  other  possible  explanations,  i.e.,
operating procedures and short circuiting.

The  results  of  these studies  indicate that  partial  mix aerated ponds  which
are  properly  designed,  operated, and  maintained  can consistently produce  an
effluent  BOD5  concentration  of  less than  30  mg/1 .   In  addition,  effluent
quality is not  seriously affected by seasonal  climate variations.


            b.  Suspended Solids Removal


The monthly  average  effluent  SS concentrations  for each system are  presented
in Figure 2-17.  With  the  exception of the  Bixby system,  the ponds  produced
relatively constant effluent SS concentrations throughout the entire  year.

Mean monthly effluent SS concentrations ranged  from  2 mg/1 at Windber, PA,  in
November  1975,  to  96 mg/1  at  Bixby, OK,  in  June  1976.    The  mean  monthly
effluent  SS  concentration  for  the  Windber,   PA,  site never  exceeded  30 mg/1
throughout the  entire  study  period  and, at  Pawnee,  IL, and  Lake  Koshkonong,
WI, only exceeded 30 mg/1 during one of the  months reported.

The  results  of  these  studies  indicate  that   aerated  pond  effluent   SS
concentrations  are   variable.    However,   a  well -designed,  operated,   and
maintained aerated  pond can  produce final  effluents  with low SS concentra-
tions.


            c.  Fecal Col i form Removal


Only  two  monthly  geometric  mean  fecal  col i form values  were available  for
Bixby, OK.  The monthly geometric mean effluent fecal  coliform concentrations
compared to a concentration of  200  organisms/100  ml  for all   five systems  are
illustrated in Figure 2-18.

All  of  the aerated  pond systems except  Bixby,  OK,  have  chlorine  disinfec-
tion.  These  data  show  that  aerated  pond  effluent can be   disinfected.   In
general, the Windber PA, and  the Pawnee,  IL, systems produced final  effluent
monthly  geometric   mean  fecal   coliform concentrations  of  less   than  200
organisms/100 ml.   The  nonchlorinated Bixby, OK, effluent  had  a  high  fecal
coliform  concentration.   The  Gulfport,  MS,  system  produced  an   effluent
containing more than 200  fecal  coliforms/100 ml   most of the time,  but  the
fecal  col i forms were measured  in   effluent samples  from  a holding pond
                                      47

-------
                                                    FIGURE 2-17

                                      AERATED POND SS EFFLUENT CONCENTRATIONS
               100
00
                                                                               Pawnee, Illinois
                                                                               Gulf port, Mississippi
                                                                            ••• Bixby, Oklahpma
                                                                            — Windber, Pennsylvania
                                                                            — Lake Koshkonong, Wisconsin
                        N    D    J    F
                           1975. 1976
M
M
N    D   J    F   M
    1976.1977

-------
                                                            FIGURE 2-18

                                     AERATED POND FECAL COLIFORM EFFLUENT CONCENTRATIONS
4s.
                      105
                 15    104
                 o
                 0)
                      103
                 C'Z
                 (0  .
                 0) C
                 S-,2-
                   4~t
                 U CO
                 1-5
                 E o
                 o c
                 0) o
                 c±:
                 fg
102
101
10°
                       0
                         0
                                                Pawnee,.-ll. (No CL2)
                                                Pawnee, Illinois (CLa)
                                                Gulfport, Mississippi
                                                Windber, Pennsylvania (No CL2)
                                                Windber, Pennsylvania (CL2)
                                    i     j     i     i     r   r    i     i      r^
                                    —,..j?	  Lake Koshkonong, Wisconsin (No CL2)
                                           • —  Lake Koshkorjpng, Wisconsin (CL2)
                                                Bixby, Oklahoma (No CL2)
         N    D    J    F
             1975. 1976
O
N     D   J     F   M
    1976 . 1977

-------
 with  a  long  detention   time   following   the  addition  of  the  chlorine.
 Aftergrowth  of   the   fecal   col iform   probably   accounted   for   the  high
 concentrations.    Aerated  pond  systems   are  capable  of  producing  effluents
 containing  less  than 200 fecal col iforms/100 ml without  disinfection.


             d.   Summary


 From the performance  data currently available,  it appears  that  (1)  aerated
 ponds  can produce  an  effluent BODs  concentration  of less  than  30  mg/1,  (2)
 aerated pond SS  concentrations are relatively  stable throughout the  year, and
 (3)  an aerated pond effluent  can  be produced  containing  less  than  200 fecal
 coliforms/100 ml.


          2.4.2.3   Design Criteria


 Most  partial  and  complete  mix  aerated ponds  have  been  designed  using  a
 complete  mix  hydraulic  model  and  pseudo-first  order  removal  rates.   The
 Ten-State Standards (27),  which  is  the basis for the  majority  of  the  states'
 standards,  recommend  that  a   complete mix  formula  be  used.   The  U.S.  Army
 Corps  of  Engineers has designed  most of  its aerated  ponds using  the complete
 mix  formula.  Results presented  in  the  Appendix  indicate  that this  formula
 does  not give the best fit  of  the  performance  data  for the five  selected
 partial mix  aerated pond systems discussed above.

 A plug  flow-first  order  kinetic model  best  described the performance of these
 five partial mix aerated ponds.  Use  of  the plug  flow model  is  illustrated  in
 a design example in Chapter 3.

 Performance  data  were not  collected for  complete  mix  aerated  ponds, but
 experience has shown that when adequate  mixing  is  applied,  the complete mix
 hydraulic model  and pseudo-first order  kinetics  can  be  used for design.   A
 design example based on the complete mix model  is presented in Chapter  3 (28).

 The development and analyses of the  complete mix, plug flow,  and other models
 used  to design aerated  ponds  are presented in the  Appendix.   Environmental
 conditions have a  significant effect on  the design  of aerated ponds.   Some  of
 the effects  of environmental  factors were discussed earlier  in this chapter,
 and others are discussed in Chapter 3 and in the Appendix.


            2.4.2.4  Nitrogen  Removal


                a.  Theoretical Considerations
Ammonia nitrogen exists in aqueous solutions as ammonia or ammonium  ions.   At
a pH value of 8.0, approximately 95 percent of the nitrogen is in the  form  of


                                       50

-------
 ammonium ion.  Therefore,  in  biological  systems such  as  aerated ponds where
 the pH values are usually less than 8.0, the majority of the ammonia nitrogen
 is in the form of ammonium ion.

 Total   Kjeldahl  nitrogen  (TKN)   is  composed  of the  ammonia,  ammonium,  and
 organic nitrogen.   Organic nitrogen  is a  potential   source  of  ammonia  and
 ammonium nitrogen because of  the  deamination  reactions during the metabolism
 of organic matter in wastewater.

 TKN reduction in  aerated  ponds can occur through several processes:


      1.   Gaseous  ammonia  stripping to the atmosphere

      2.   Ammonium assimilation in  biomass

      3.   Biological nitrification

      4.   Biological denitrification

      5.   Sedimentation of insoluble organic nitrogen

      6.   Nitrate  assimilation
Table 2-7  contains  a summary of selected equations  developed  by Middlebrooks
and  Pano  (29) to  predict ammonia  nitrogen  and  TKN removal  in  diffused-air
aerated ponds.   All  of the  equations  have  a common data base;  however,  the
data were used differently to  develop  several of the equations.   The "System"
column in  Table  2-7  describes the cell or series of cells that were used to
develop the equation.  The description  "Cells 1,  2,  and  3" indicates that the
influent concentrations of TKN or  ammonia nitrogen  were  used  in conjunction
with the effluents from the  first cell, second  cell, and third cell  in  series
to estimate  the  removal  or  detention  time necessary to  achieve  the measured
removal.  The description  "Total System"  indicates that  only the influent and
final  effluent  from  the   system  were  used  to  develop   the  equations.   The
description "All Data" indicates that  all possible combinations  of the  system
were used.   In  this combination, the  results  developed  under "Cells  "1,  2,
and  3,"  as well as  the  results  developed  from  the intermediate cells,  are
incorporated.   For  example,  the  ammonia  nitrogen  concentration in   the
effluent from the first  cell  of the  pond  system  would  be  considered  the
influent to the second cell, and this  influent  concentration and the effluent
from the  second cell would  then be  used in  the formulas  to calculate  the
detention time  or  removal rates.   These  combinations of data were analyzed
statistically, and the  equations presented in  Table 2-7 were selected based
upon the best statistical  fit of these  data for the  various  combinations  that
were tried.   Therefore,  although the  combinations  of data  are  not directly
comparable, the comparison presented in Table  2-7 does take into  account  the
best statistical  fit of the data.

All   of  the relationships  for TKN  removal  are  statistically  significant  at
levels  higher than one percent.  Because of the  small  difference  in  detention


                                       51

-------
en
                                                              TABLE  2-7

                COMPARISON  OF VARIOUS EQUATIONS DEVELOPED TO PREDICT AMMONIA NITROGEN  AND TKN REMOVAL IN
                                                 DIFFUSED-AIR AERATED PONDS (48)
Hydraulic
Equation Used to Estimate Correlation Detention
Detention Time Coefficient Time
(Days)
TKN Removal
% TKN Removal » 130-2,324 (Hydraulic Loading Rate)
% TKN Removal = 137-6,511 (I/Detention Time)
In Ce/CQ » -0.0129 (Detention Time)
TKN Removal Rate * 0.809 (Loading Rate)
TKN Removal Rate * 0.0946 (BODg Loading Rate)
TKN Fraction Removed = 0.0062 (Detention Time)
Ammonia-N Removal
% NH4-N Removal = 139-2,498 (Hydraulic Loading Rate)
% NH4-N Removal = 147-7,032 (I/Detention Time)
In Ce/C0 = -0.0205 (Detention Time)
NH4-N Removal Rate = 0.869 (Loading Rate)
NH4-N Removal Rate = 0.0606 (BOD5 Loading Rate)
NH4-N Fraction Removed = 0.0066 (Detention Time)
0.998
0.993
0.911
0.983
0.967
0.959
0.996
0.995
0.798
0.968
0.932
0.936
142
114
125
132
113
129
129
105
79
92
132
121
Compari son
with Max
Detention
Time (% Dif
0
19
12
7
20
9
2
20
40
30
0
8
System
Total System--
Mean Annual Data
Total System-
Mean Annual Data
Cell 1, 2, and 3—
Mean Monthly Data
Total System--
Mean Monthly Data
Total System-
Mean Monthly Data
Cells 1, 2, and 3—
Mean Monthly Data
Total System-
Mean Annual Data
Total System--
Mean Annual Data
All Data-
Mean Monthly Data
Total System--
Mean Monthly Data
Total System--
Mean Monthly Data
Cells 1, 2, and 3-
Mean Monthly Data
                              ;  Detention  Time = days;   Loading   Rate =-g/m3/d;  BODs * g/m3/d;   Removal
Rate - g/m3/d;  C« = Effluent  TKN   or  Ammonia-N  concentration,  mg/1 ;   C0 =  Influent  TKN   or   Ammonia-N
                 Hydraulic   Loading  Rate «
                            ;   C«
                 concentration, mg/1.

-------
times calculated using all  of the expressions, there is a good basis to apply
any of  the  relationships  in design of ponds  to  estimate  TKN removal.  Using
the  mean   annual   data  for  diffused-air   aerated   ponds  yields  a  more
conservative design when  employing the  hydraulic  loading rate  relationship.
However,  the values  obtained using  the  reciprocal   of  the  detention  time
relationship yields  a  value  slightly   lower  than that  recommended  by   the
majority  of the  other expressions.   In  view  of  the error that  might  be
introduced  by  taking  annual means,  the results based upon  the mean annual
data are  in excellent  agreement with  the results obtained using  the  mean
monthly data.   Using any  of  the  above  expressions  will  result in  a  good
estimate of  the TKN removal  that is likely to  occur  in diffused-air aerated
ponds.

The  relationships  developed   to  predict  ammonia   nitrogen  removal  yielded
highly  significant  (1  percent level) relationships for all  of  the  equations
presented  in Table  2-7.   However,  the  agreement  between  the calculated
detention times for ammonia nitrogen removal differed  significantly from that
observed for the  TKN  data.   This variation is not surprising  in view of  the
many mechanisms involved in ammonia nitrogen production and  removal  in waste-
water ponds, but  this  variation  in  results  does  complicate the  use  of  the
equations  to estimate  ammonia  nitrogen  removal   in  aerated  ponds.   Sta-
tistically, a justification exists to use  either of the expressions in Table
2-7 to  calculate  the detention  time  required to  achieve  a given percentage
reduction in ammonia nitrogen.


2.5  Disinfection


     2.5.1  Introduction


Since chlorine,  at present,  is  less expensive  and  offers  more  flexibility
than other  means  of disinfection, chlorination  is the most practical method
of  disinfection.   Basic principles  of  chlorination  are  presented  elsewhere
(7M29H39).


     2.5.2  Effects of Chlorinating Pond Effluents


White (31)  suggested  that  chlorine demand increases with  high concentrations
of algae commonly  found in pond effluents.  A chlorine dose  of 20-30 mg/1  was
required  to satisify  chlorine  demand  and  to  produce  enough   residual  to
effectively disinfect algae-laden wastewater within 30-45 minutes.  Kott (32)
reported increases in demand as  a  result of algae, but found that a chlorine
dose of 8 mg/1  was  sufficient  to produce  adequate   disinfection  within  30
minutes.   If contact times  are  kept  relatively  short,  no serious chlorine
demand  by  algae cells  is  encountered  (32).  For  pond  effluents, a chlorine
demand of only 2.6 to 3.0 mg/1 was exerted after 20 minutes  of contact (33).
                                      53

-------
At  low chlorine  doses,  very  little  increase  in  chlorine  demand  is  attri-
butable to algae, but at higher doses,  the  destruction  of  algal  cells  greatly
increases  demand  (34).    This occurs  because  dissolved  organic   compounds
released  from  destroyed  algal   cells  are oxidized  by  chlorine   and  thus
increase chlorine demand (35).

Another concern  regarding  the chlorination  of pond effluents are the  effects
on  BOD and COD.  Conflicting  results  have  been reported  (32-37),  indicating
that  either  an increase or  decrease  in BOD and COD  occurred with  increased
chlorine   concentrations.    A  conclusion  would  be   that   the  effect   of
chlorination  on BOD  and  COD  is  a  function  of wastewater  characteristics,
chlorine application methods and contact time, and  other undefined parameters.

The formation  of toxic chloramines is  also of  concern in chlorinating  pond
effluents.   These  compounds  are  found in  waters  high  in ammonium  nitrogen
concentration  and are  extremely  toxic  to   aquatic  life  found  in  receiving
water.  For  example, a  chloramine concentration  of  0.06 mg/1  is  lethal  to
trout  (38).

Not all of the side effects  of  chlorination pond  effluents  are detrimental.
Kott  (39)  observed reductions  of  SS  as a result of chlorination.   Reductions
of  volatile  suspended solids  (VSS)  by  as   much as  52  percent  and  improved
water  clarity  (reduced  turbidity)  by 32   percent  were  observed   following
chlorination  (33).  Chlorine may  enhance  the flocculation of algae masses  by
causing algal cells to clump together (35).

Four  systems  of identically  designed  chlorine mixing  and contact tanks,  each
capable  of  treating  190  m3/d   (50,000  gpd),  were  used  to  study  the
chlorination of  pond effluents (40).   Three of the four chlorination  systems
were  used  for  directly  treating the pond effluent.   The effluent  treated  in
the fourth system was filtered through  an intermittent sand  filter to  remove
algae  prior  to  chlorination.   The filtered  effluent was  also  used  as  the
solution water for all  four chlorination systems.

Following  recommendations  of  others  (41-45),  the chlorination  systems were
constructed to  provide  rapid initial  mixing  followed  by chlorine  contact  in
plug flow reactors.   A serpentine  flow configuration having a length to width
ratio  of  25:1, coupled with  inlet and outlet baffles, was  used  to  enhance
plug  flow  hydraulic performance.   The  maximum theoretical  detention time for
each  tank  was 60 minutes, while  the  maximum  actual  detention time averaged
about 50 minutes.

The pond  effluent was chlorinated at doses  ranging  from 0.25  to  30.0 mg/1
under  a  variety  of  contact  times,   temperatures,   and   seasonal  effluent
conditions from  August  1975 to August  1976.   Some of  the  major findings  of
this study are summarized below.
                 "- •                            i

1.   Sulfide,  produced  as  a  result  of  anaerobic conditions  in   the ponds
during winter  months  when the ponds  are frozen over,  exerts  a significant
                                      54

-------
chlorine  demand   (Figure 2-19).    For   sulfide  concentrations  of   1.0   to
1.8mg/l, a  chlorine  dose of  6 to  7 mg/1  was required  to produce  the  same
residual as a chlorine dose of about 1  mg/1  for conditions with no sulfide.
                                 FIGURE 2-19

               CHLORINE DOSE vs. RESIDUAL FOR INITIAL SULFIDE
                       CONCENTRATIONS OF 1.0-1.8 mg/1
         15
     0>
     0)
     DC
     0)
     o
      . Residual = 1.552 + 0.346 (dose)
             r = 0.956
            0
       10            15

Chlorine Dose, mg/l
2.   For  all  concentrations  of  ammonia encountered,  adequate  disinfection
could be  obtained  with combined  chlorine  residual  in 50  minutes or less  of
contact  time.   Therefore,   breakpoint  chlorination,  and   the  subsequent
production  of free  chlorine  residual, was  rarely,  if  ever,  necessary  in
disinfecting pond effluent.

3.   Total COD concentration  in a pond effluent was virtually  unaffected  by
chlorination.   Soluble  COD increased with  increasing concentrations of  free
chlorine only.  This  increase was attributed to the  oxidation of SS by  free
chlorine.  Increases  in  soluble COD vs. free  chlorine residual  are shown  in
Figure 2-20.
                                       55

-------
                                  FIGURE 2-20

             CHANGES IN SOLUBLE COD vs. FREE CHLORINE RESIDUAL -
                           UNFILTERED POND EFFLUENT
        30

        24

        18

        12
     I  6
     8
     o
  0

 -6


-12

-18

-24

-30
                     • o
            r •
                                               I
                      Y = 4.692 X -2.948
                       r = 0.547


                      	I
           0
        234

Free Chlorine Residual, mg/l
4.   Some  reduction  in SS, due  to the breakdown  and oxidation, of  suspended
particulates,  and  resulting  increases   in   turbidity  were   attributed   to
chlorination.   However,  this   reduction  was  of   limited   importance  when
compared with  reductions  of SS  resulting  from settling.   SS were reduced  by
10 to 50 percent by settling in the contact tanks.

5.   Filtered  pond effluent exerted a lower  chlorine demand than unfiltered
pond  effluent, due  to  the removal  of  algae (Figure 2-21).   The  rate   of
exertion of  chlorine  demand was  directly  related to chlorine dose and  total
chemical oxygen demand.

6.   A  summary of total  coliform  removal  efficiencies  as  a  function  of  a
total chlorine residual  for filtered and  unfiltered effluent  is  illustrated
in Figure 2-22.  The rate of disinfection was a function of  the chlorine dose
                                      56

-------
                      FIGURE  2-21

CHLORINE DOSE vs.  TOTAL RESIDUAL -  FILTERED  AND
              UNFILTERED POND EFFLUENT
  Tj
  '55
   0>
  OC
   0)


  I

  o
      15
      10
          0
       15
   3   10
   0)
   oc
   03
  •6
   I
          o
                 ——   17.3 Min Contact Time, r = 0.933
                 — —i   35.0 Min Contact Time, r = 0.933
                 .. —  49.6 Min Contact Time, r = 0.932
Y = 0.534 X + 0.062

Y = 0.505 X + 0.007
Y = 0.479 X+0.010
              10
               15
                 20
                   Applied Chlorine Dose, mg/l
                       (a) Filtered Effluent
 Y = 0.507 X +0.139

 Y = 0.481 X + 0.098

 Y=^ 0.460 X +0,076
             17.3 Min Contact Time, r = 0.847
        • —  35.0 Min Contact Time, r = 0.833
        — •  49.6 Min Contact Time, r = 0.822
           I 	I         I
  6
12
18
24
30
                  Applied Chlorine Dose, mg/l
                     (b) Unfiltered Effluent
                           57

-------
                        FIGURE 2-22

TOTAL COLIFORM REMOVAL  EFFICIENCIES -  FILTERED AND
                UNFILTERED POND  EFFLUENT
      0.0
      -1
      -2
  a, -3
     -4,
     -5
  o
 0,0


-1.0


-2.0


-3.0


-4.0


-5.0
                           17.5 Min. Contsict Time, r = 0.922
                      — — 35.0 Min. Contact Time, r = 0.939
                      	49.6 Min. Contsict Time, r = 0.908
                                    Y==-1.139x
                                    Y==-1.807x
                                    Y==-2.161x
                   1
          4
                   Total Chlorine Residual, mg/l
                        (a) Filtered Effluent
                           17.5 Min. Contact time, r = 0.876
                           35.0 Min. Contact Time, r = 0,843
                           49.6 Min, Contact Time, r = 0.823 .
Y = -0.726x
Y = -0.992x
Y=,-1.098*
                                             8
                  10
                  Total Chlorine ResiduEil, mg/l
                      (b) Unfiltered Effluent
                            58

-------
 and  bacterial  concentration.   Generally,  the  chlorine demand  was about  50
 percent  of  the  applied  chlorine  dose  except  during  periods  of  sulfide
 production.

 7.   Disinfection  efficiency was  temperature  dependent.   At  colder  tempera-
 tures,  the reduction  in the  rate of  disinfection was  partially offset  by
 reductions in  the  exertion  of  chlorine demand; however, the net  effect  was a
 reduction in the chlorine  residual  necessary  to achieve adequate disinfection
 with increasing temperature for a specific contact period.

 8.   In  almost all cases,  adequate disinfection  was  obtained with  combined
 chlorine  residuals of  between 0.5  and l.Omg/1  after a  contact period  of
 approximately  50 minutes.   This indicated that disinfection can  be  achieved
 without  discharging excessive  concentrations of toxic  chlorine residuals into
 receiving waters.


     2.5.3  Predicting Required Residuals


 Using  the  data from  the study summarized  in  section  2.5.2,  Johnson et  al.
 (40) developed a model  to  predict  the chlorine residual required  to  obtain a
 specified bacterial kill.  The model was used  to  construct  a series of design
 curves for  selecting  chlorine doses  and  contact  times for  achieving  desired
 levels of disinfection.   An  example  may best illustrate  how these  design
 curves are applied.

 Assume that a  particular lagoon effluent  is  characterized  as  having  a  fecal
 coliform  (FC)  concentration of 10,000/100 ml,  0  mg/1  sulfide, 20 mg/1  TCOD,
 and a  temperature  of  5°C.   If  it is necessary to  reduce the FC counts to  MPN
 of 100/100 ml, or  a 99 percent bacterial reduction, and an  existing  chlorine
 contact  chamber  has an  average  residence time of  30  minutes, the  required
 chlorine  residual   is  obtained  from  Figure  2-23.   A 99  percent  bacterial
 reduction corresponds  to log  (Ng/N)  equal  to 2.0.   For a  contact period  of
 30 minutes, a  combined chlorine residual  of  1.3 mg/1  is  required.   This  is
 indicated by Point 1 in Figure 2-23.

 Going  to Figure  2-24, it  is  determined that  if  a  chlorine dose produces  a
 residual  of  1.30 mg/1  at  5°C,  the same  dose would  produce   a   residual   of
 0.95 mg/1 at 20°C.  This is because  of the faster rate  of reaction  between
 TCOD and chlorine at the higher temperature.  This  is  indicated by Point 2  in
 Figure 2-24.   For  an  equivalent chlorine  residual  of  0.95  mg/1  at 20°C  and
 20 mg/1  TCOD,  it is determined from  Figure 2-25  that  the  same chlorine dose
would  produce  a residual  of  0.80  mg/1  if the TCOD  were  60  mg/1.   This  is
 because  higher concentrations  of TCOD  increase the rate of chlorine  demand.
 Points  on Figure 2-25  corresponds  to  this  residual.   The  chlorine dose
 required to produce an equivalent   residual of  0.80 mg/1  at 20°C  and  60 mg/1
 TCOD is  determined from Figure  2-26.   For a  chlorine contact  period of  30
minutes,  a  chlorine dose  of 2.15  mg/1  is  necessary   to produce  the  desired
 combined residual  as  indicated by  Point  4  on Figure 2-26.   This dose will
 produce  a  reduction in FC  from 10,000/100 ml  to  100/100 ml  within 30 min  at
 5°C and with 20 mg/1 TCOD.


                                       59

-------
                              FIGURE 2-23

COMBINED CHLORINE RESIDUAL  AT 5°C FOR COLIFORM  =  104/100 ml
      5.0
      4.0
      3.0
      2.0
      1.0
                 No. Fecal= 10V100 ml
                 No. Total = 10V100ml

                 Fecal Coliform

                 Total Coliform
                              Combined Chlorine Residual 1.5 mg/l
                                                       f

                                                   /     1.5mg/^T
                                                                   60
                                   60

-------
                           FIGURE 2-24

    CONVERSION  OF COMBINED CHLORINE RESIDUAL  AT TEMP.  1
                TO EQUIVALENT  RESIDUAL  AT 20°C
3.5 r-
         0.5
1.0     1.5     2.0     2.5     3.0

    Combined Chlorine Residual at Temp. 1, mg/l
                                                          4.0
                                                                 4.5
                                61

-------
                                                         FIGURE 2-25


                               CONVERSION  OF COMBINED CHLORINE RESIDUAL AT TCOD  1  AND 20°C

                                    TO EQUIVALENT RESIDUAL AT TCOD  =  60 mg/1 AND 20°C
                    3.5 l-
01
ro
                              0.5
1.0       1.5      2,0      2.5      3.0      3.5


  Combined Chlorine Residual at TCOD 1 and 20°C, mg/l
4.0

-------
                             FIGURE 2-26


   DETERMINATION OF CHLORINE DOSE  REQUIRED FOR EQUIVALENT
         COMBINED RESIDUAL AT TCOD  = 60 mg/1 AND 20°C
   5.0 i-
    4.0  -
O)



"(5
3
T3
°35
0>
tr

<0


_0


o

T3
0>
c
3

o
o
3.0
2.0
    1.0
                      Chlorine Dose = 10.0 mg/l
                 10
                       20
                                   Chlorine Dose = 7.0 mg/l
                               Chlorine Dose = 5.0 mg/l
                                   Chlorine Dose = 3.0 mg/l
                                     I
30        40


Time, min
50
60
                                   63

-------
 If,  in the previous example,  the initial  sulfide concentration were 1.0 mg/1
 instead of 0 mg/1, it would be  necessary  to go  directly  from Figure 2-23 to
 Figure 2-27.   Here,  chlorine  residual  of 1.30 mg/1  at the TCOD of 20 mg/1 and
 a temperature  of 5°C  is  converted  to an  equivalent  chlorine  residual  of
 1.10 mg/1  for a TCOD of  60 mg/1  and  5°C.   This  is  represented by Point 5 on
 Figure 2-27.   Going  to Figure 2-28, which  corresponds to an  initial  sulfide
 concentration of 1.0 mg/1,  it is determined that a  chlorine  dose of 6.6 mg/1
 is  necessary  to produce  an equivalent chlorine residual of  1.1  mg/1  after a
 contact period of 30 min.  Point 6  on  Figure  2-28  corresponds to this dose.
 The  sulfide  remaining  after  chlorination  is  determined to be  0.4 mg/1  from
 Figure 2-29 as indicated  by Point 7.


     2.5.4


 The primary  objective  of good chlorine  contact tank design is  to  design for
 hydraulic performance which will  allow for a minimum usage  of chlorine with a
 maximum exposure  of microorganisms  to the  chlorine.   An  evaluation  of  a
 number of  chlorine contact tanks  indicates  that mixing, detention  time,  and
 chlorine dosage are the  critical factors to  consider  in  providing adequate
 disinfection.   Good  design not  only  optimizes; disinfection  efficiency,  but
 should also   minimize  the concentration  of  undesirable   compounds  being
 discharged to the environment and  reduce  the  accumulation  of solids  in  the
 tank by keeping the  flow-through velocity  high enough to prevent solids  from
 settling (46).   A discussion of  chlorine contact chamber hydraulic character-
 istics  is   presented elsewhere  (9)(30).  Table 2-8  presents  a summary  of
 chlorination  design criteria.


 2.6  Odor Control


     2.6.1   Introduction


 Odors  are. usually created  at  wastewater ponds because  they  are overloaded,
 excessive surface scum has been  allowed to accumulate,  or  aquatic and  pond
 slope  weeds are completely uncontrolled.  All  three of  these causes can  be
 eliminated  by  adequate  design,  including  design  features  for  effective
 operation and maintenance.


     2.6.2  Overloading


 Process  design considerations are  discussed  in  Chapter 3.   Careful  design
which   incorporates  the  requirements   set  forth   in   that   chapter   should
 eliminate  pond  overloading.   These  requirements include  (1)  selection  of
 loading  criteria  applicable   to  the  influent  loads  and  the  operational
 limitations created by local land use  and climatic conditions,  and  (2)  design
 of a layout which assures the effective  utilization  of all pond volume.   Dead
areas which do  not maintain adequate circulation or  flow must  be  eliminated.

                                      64        i

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                                                       FIGURE 2-27


                             CONVERSION OF  COMBINED  CHLORINE RESIDUAL AT TCOD 1  AND 5°C

                                   TO EQUIVALENT RESIDUAL AT TCOD = 60 mg/1  AND  5°C
               3.5 r-
Ol
01



la

T3
'
-------
                            FIGURE 2-28

    DETERMINATION  OF  CHLORINE  DOSE REQUIRED WHEN  S  =  1.0  mg/1,
                  TCOD = 60 mg/1, AND TEMP. = 5°C
4.0 r-

-------
                    FIGURE 2-29
SULFIDE REDUCTION AS A FUNCTION OF CHLORINE DOSE
                                                    0—o.
                                           Limit of detectability
                                     J_
         J_
                   8        10       12
                 Chlorine Dose, mg/l
14
16
18
20

-------
                                  TABLE 2-8  .

                   SUMMARY .OF CHLORINATION DESIGN CRITERIA

Mixing

     I.  Rapid  initial  mixing  should:be accomplished within  5  sec and before
         liquid  enters  contact  tank.   Design  hydraulic  residence  time >^ 30
         sec for tanks using mechanical mixers,;           ,

    II.  Methods available
            1.  Hydraulic jump in open channels;.
            2.  Mechanical mixers located  immediately below  point of chlorine
                application.
            3.  Turbulent flow in a restricted reactor.
            4.  Pipe flowing full.  Least  efficient  and should  not be used in
                pipes with diameter > 7.6 cm (> 30 in).

Contact Chamber                                ;

     I.  Hydraulic residence time              v    •    ••  .     .
            1.   j> 60 minutes at average flow rate.
            2.   ^ 30 minutes at peak hourly flow rate.

    II.  Hydraulic performance
            1.  Model value obtained in dye studies ^0.6, tp/T > 0<6.
            2.  Efficiency of disinfection increases as tp/T increases.
            3.  Design for maximum economical tp/T.                         ;

   III.  Length to width ratio                 ;
            1.  L/W _> 25:1.                                   .
            2.  Cross-baffles  used  to  eliminate  short  circuiting  caused  by
                wind.                                   .-•-.-

    IV.  Solids removal
            1.  Baffles arranged to remove floating solids.                 '•
            2.  Provide drain to remove solids and liquid for maintenance.
            3.  Provide duplicate contact chambers.
            4.  Width between  channels  should  be  adequate for  easy  access  to
                clean and maintain chamber.

    V.    Storage of chlorine
            1.  Provide a  minimum of  one  filled   chlorine  cylinder for  each
                one in service.
            2.  Maintain storage area at a temperature > 13°C (>_ 55°F).
            3.  Never locate  cylinders  in direct  sunTight  or apply  direct
                heat.
tp «= Time for tracer at outlet of contact tank to reach peak concentration.
 T * Volume of contact tank/flow rate = theoretical detention time.
 L - Length of contact tank.
 W s Width of contact tank.

                                       68

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                          TABLE 2-8 (continued)
VIII,
  IX.
          6.
          7.
          8.
       Limit maximum  withdrawal 'rite*  from 45-
       150-lb) cylinders to 18 kg/d (40 Ib/d).
       Limit   maximum  withdrawal   rate   from
       cylinders to 182 kg/d (400 Ib/d).
       Provide scales to weigh cylinders.
       Provide cylinder handling equipment.
       Install automatic switchover sytem.
                                                       and  68-kg (100-  and

                                                         909-kg   (2,000-lb)
  VI.  Piping and valves
          1.  Use Chlorine Institute approved piping and valves.
          2.  Supply piping between  cylinder  and  chlorinator should be  Sc.
              80  black  seamless  steel  pipe  with  2,000-lb  forged  steel
              fitting.   Unions should be ammonia type with lead gaskets.
          3.  Chlorine  solution  lines  should be  Sc.  80 PVC,  rubbeHined
              steel,  Saran-lined  steel, or  fiber  cast  pipe  approved  for
              moist chlorine  use.   Valves  should be PVC,  rubber lined,  or
              PVC lined.                                                   ,
          4.  Injector  line between  chlorinator and  injector should be  Sc.
              80 PVC  or fiber  cast  approved for  moist chlorine  use.

 VII.  Chlorinators
          1.
          2.
       Should be sized to provide dosage _> 10 mg/1.
       Maximum  feed  rate  should  be determined  from  knowledge  of
       local
                                      should  be  used  only in  small
                    conditions.
              Direct feed  gas chlorinators
              installations.    Check   state
              certain states.
              Vacuum feed  gas chlorinators
              much safer.
              Hypochlorite solutions should
              where safety is  major concern.
          used
regulations.
      in
Prohibited
                                      are most  widely  used  and  are

                                      be considered  in  installations
Safety equipment and training
   1.  Install an exhaust fan  near  floor level with  switch  actuated
       when door is opened.
   2.  Exhaust fan should be capable of one air exchange per  minute.
   3.  Gas mask located outside chlorination room.
   4.  Emergency chlorine container  repair kits.  .
   5.  Chlorine leak detector.
   6.  Alarms   should   be   installed   to   alert   operator   when
       deficiencies or hazardous conditions exist.     ;
   7.  Operator should  receive detailed hands-on  training with  all
       emergency equipment.

Diffusers                                             ,.  	
   1.  Minimum velocity  through  diffuser holes >  3-4 m/sec  (> 10-12
       ft/sec).                                     / L
   2.  Diffusers  should   be   installed   for  convenient   removal,
       cleaning, and replacement.
                                      69

-------
 Whenever possible,  influent  loadings should  be shared  with  other  cells  by
 means  of forced recirculation.   Mechanical  aeration should be  used to supple-
 ment natural  photosynthesis  whenever  conservative loading rates cannot  be
 applied.   The intermittent operation of an influent cell  mechanical  aeration
 unit can often be  adjusted to compensate for  conditions which could  not  be
 anticipated  during  design.   Its  availability  can then  be an excellent tool  to
 eliminate  odors.    Temporary  relief  from  odors can be  obtained  by  applying
 sodium nitrate to the pond  influent on spreading  over  the  surface.   Details
 on  the application of sodium nitrate,  other  chemicals,  and other methods  of
 odor control  are  presented  in Reference (47).


         2.6.3  Scum Accumulation


 Scum often accumulates  on  pond surfaces  from  debris which  enters  from  the
 influent  sewer,  dead  or  decaying  algae  which remains  buoyant,  and  debris
 which  enters  from  surrounding  areas.   Such  surface scum  often  decomposes
 without  sinking if the  surface  is quiescent  or the  scum attaches itself  to
 riprap,  floating  debris,  or aquatic  growth.   Small  clumps  of scum,  spread
 over a fairly large surface, will  not usually create sufficient  odor  levels
 to be  an offsite  nuisance.

 One  effective  way  of  eliminating  stabilization  pond   scum  buildup  is  by
 providing  a means of mechanical  agitation.  Another means of eliminating  scum
 accumulation  is  through  the  use  of  recirculation.   The   Sunnyvale,   CA,
 secondary oxidation ponds have been  receiving a major  portion  of that plant's
 stabilized sludge over the past  several years  (48).  The  pond  recirculating
 system  is  designed  to maintain  mixing  throughout, and the  pond has never
 experienced any significant scum  accumulation in any of  its supply and  return
 channels or cells.


         2.6.4  Scum Attachment


 One  of the most  significant effects of aquatic plants   is  their ability  to
 support  scum accumulations.   If a  pond  were  heavily loaded,  the resulting
 scum would certainly have  no chance  of  dissipating,  and odors  would result.
 Good housekeeping,  which means control of  aquatic  weeds  and  berm weeds,  is
 essential  to  odor control.  Raw wastewater poinds where  scum  accumulation  is
 expected should not have riprap which allows scum to accumulate  in cracks and
 crevices.  A  concrete  or asphalt  apron  can  be used  to protect the embankment
where scum accumulation is expected.
                                       70

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2.7  References


 1.  Lynch,  J.  M.,  and  N.  J.  Poole.   Microbial   Ecology,   A  Conceptual
     Approach.  John Wiley & Sons, New York, NY,  1979.   266 pp.

 2.  Brockett,  0.   D.  Microbial  Reactions  in  Facultative  Ponds  -  I.   The
     Anaerobic   Nature   of  Oxidation   Pond   Sediments.   Water   Research
     10(l):45-49, 1976.

 3.  Gaudy,  A.  F.,  Jr., and  E.  T.  Gaudy.   Microbiology for  Environmental
     Scientists and Engineers.   McGraw-Hill, New York,  NY, 1980,  736 pp.

 4.  All rich, A.  H. Use  of Wastewater  Stabilization  Ponds  in Two  Different
     Systems.  JWPCF 39(6):965-977, 1967.

 5.  Pipes,  W.  0.,  Jr.  Basic   Biology  of  Stabilization Ponds.   Water  and
     Sewage Works 108(4):131-136, 1961.

 6.  Stanier, R. Y., M.  Doudoroff,  and  E.  A. Adelberg.   The Microbial  World.
     2nd ed., Prentice-Hall, Englewood Cliffs,  NJ,  1963.   753 pp.

 7.  Sawyer,  C.   N.,   and   P.    L.   McCarty.   Chemistry  for   Environmental
     Engineering.   3rd ed.,  McGraw-Hill,  New York,  NY,  1978.  532 pp.

 8.  Process  Design Manual  for Nitrogen  Control.   EPA-625/1-75-007,   U.S.
     Environmental   Protection   Agency,  Center  for   Environmental   Research
     Information,  Cincinnati, OH, 1975.

 9.  Middlebrooks,  E. J., C. H.  Middlebrooks,  J. H. Reynolds, G.  Z.  Watters,
     S. C.  Reed, and D.  B.  George.   Wastewater Stabilization Lagoon Design,
     Performance and Upgrading.  Macmillan  Publishing  Co.,  Inc.,  New  York,
     NY, 1982.

10.  Anderson,  J.   B.,  and  H.   P.  Zweig.   Biology  of  Waste   Stabilization
     Ponds.  Southwest Water Works Journal 44(2):15-18, 1962.

11.  Gloyna,  E. F.,  J.  F. Malina,  Jr.,  and  E.  M.  Davis.    Ponds   as  a
     Wastewater Treatment  Alternative.   Water  Resources  Symposium No.  9,
     Center  for  Research   in   Water  Resources,   College  of   Engineering,
     University of  Texas, Austin, TX,  1976.   447  pp.

12.  Oswald, W. J.  Quality  Management by Engineered Ponds.  In:   Engineering
     Management of Water Quality, P.  H.  McGauhey.  McGraw-HilTT New York, NY,
     1968.

13.  Assenzo, J. R., and G. W.  Reid.   Removing Nitrogen and  Phosphorus by
     Bio-Oxidation   Ponds  in  Central  Oklahoma.   Water  and  Sewage   Works
     13(8):294-299, 1966.
                                      71

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14.  Performance Evaluation of  Existing Lagoons-Peterborough, New  Hampshire.
     EPA-600/2-77-085,  NTIS  No.  PB  272390,  U.S.  Environmental   Protection
     Agency,  Municipal   Environmental  Research  Laboratory,  Cincinnati,   OH,
     1977.                                                                  ;

15.  Performance Evaluation of Kilmichael Lagoon.  EPA-600/2-77-109, NTIS  No.
     PB 272927, U.S. Environmental Protection Agency,  Municipal  Environmental
     Research Laboratory, Cincinnati,  OH, 1977.
                                               \
16.  Performance Evaluation of  an Existing Lagoon System  at Eudora,  Kansas.
     EPA-600/2-77-167,  NTIS  No.  PB  272653,  U.S.  Environmental   Protection
     Agency,  Municipal   Environmental  Research  Laboratory,  Cincinnati,   OH,
     1977.

17.  Performance  Evaluation  of  an  Existing   Seven  Cell  Lagoon   System.
     EPA-600/2-77-086,  NTIS  No.  PB  273533,  U.S.  Environmental   Protection
     Agency,  Municipal   Environmental  Research  Laboratory,  Cincinnati,   OH,
     1977.

18.  Canter, L. W.,  and A. J.  Englande.  States' Design  Criteria for Waste
     Stabilization Ponds.  JWPCF 42(10):1840-1847, 1970.

19.  Stratton, F.  E.  Ammonia Nitrogen  Losses  from  Streams.  J. Sam't. Eng.
     Div., ASCE, SA6, 1968.

21.  Pano,  A.,  and  E.   J.   Middlebrooks.    Ammonia  Nitrogen  Removal   in
     Facultative Wastewater Stabilization Ponds.   JWPCF 54(4):344-351,  1982.

22.  Performance Evaluation of  Existing Aerated Lagoon System  at Bixby,   OK.
     EPA-600/2-79-014, NTIS No.  PB 294742,  Municipal  Environmental Research
     Laboratory, U.S. Environmental  Protection Agency,  Cincinnati,  OH,  1979.

23.  Performance Evaluation of the Existing Three-Lagoon Wastewater  Treatment
     Plant  at  Pawnee,   Illinois.   EPA-600/2-79-043,   NTIS  No.  PB  299740,
     Municipal   Environmental   Research   Laboratory,  U.S.    Environmental
     Protection Agency,  Cincinnati,  OH,  1979.

24.  Performance Evaluation of  the  Aerated Lagoon System  at North  Gulfport,
     Mississippi.     EPA-600/2-80-006,   NTIS  No.  PB  80-187461,   Municipal
     Environmental  Research Laboratory,  U.S. Environmental   Protection  Agency,
     Cincinnati, OH,  1980.

25.  Performance Evaluation of Existing Aerated Lagoon System at Consolidated
     Koshkonong Sanitary  District,  Edgerton,  Wisconsin.    EPA-600/2-79-182,
     NTIS No. PB 80-189681, Municipal  Environmental Research Laboratory, U.S.
     Environmental  Protection  Agency,  Cincinnati,  OH,  1979.

26.  Performance  Evaluation  of  the  Aerated   Lagoon  System  at  Windber,
     Pennsylvania.     EPA-600/2-78-023,   NTIS   No.   PB   281368,    Municipal
     Environmental  Research Laboratory,  U.S. Environmental   Protection  Agency,
     Cincinnati, OH,  1978.
                                       72

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27.  Recommended Standards  for  Sewage Works.  A  Report of  the  Committee of
     Great Lakes-Upper Mississippi  River Board of  State Sanitary Engineers.
     Health Education Services,  Inc.,-Albany;- NY,  1978.

28.  Metcalf & Eddy, Inc.  Wastewater Engineering. McGraw-Hill, New York, NY,
  ..'  1979.         -;            .:  .,.   .*<::/.•<  : .            . -     .   . .'

29.  Middlebrooks,  E. J., and A.  Pano.   TKN  and  Ammonia Nitrogen  Removal in
     Aerated Lagoons.  Report submitted  to  Center for Environmental  Research
     Information, U.S.  Environmental Protection Agency,  Cincinnati, OH, 1981.

30.  White,  G.  C.  Handbook  of  Chlorination.   Van  Nostrand Reinhold   Co.,
     1972.  744 pp.

31.  White,  GJ  C.  Disinfection  Practices  in  the  San  Francisco Bay Area.
     JWPCF 46(1) :89-l 01,  1973.

32.  Kott, Y.  Chlorination Dynamics in Wastewater Effluents.  J. Sanit.  Eng.
     Div., ASCE 97(SA5):647-659,  1971.

33.  Dinges, R. and A. Rust.  Experimental Chlorination  of Stabilization  Pond
  -   Effluent.  Public Works 100(3):98-101,  1969.

34.  Brinkhead, C.  E. and W. J. O'Brien.  Lagoons and Oxidation Ponds.  JWPCF
     45(10):! 054-1059,  1973.

35.  Echelberger,  W.  F., J.  L.  Pavom", P.  C.  Singer, and  M.  W.   Tenney.
     Disinfection  of  Algal  Laden  Waters.   0.   Sanit.   Eng.   Div.,   ASCE
     97(SA5):721-730, 1971.

36.  Horn, L. W. Kinetics of Chlorine Disinfection in an  Ecosystem.  J. Sanit.
     Eng. Div., ASCE 98(SA1):183-194,  1972.

37.  Zaloum,  R.,  and K. L.  Murphy.  Reduction of  Oxygen Demand  of  Treated
     Wastewater by Chlorination.   JWPCF  46(12);2770-2777, 1974.

38.  Zillich, J. A.  Toxicity of  Combined Chlorine Residuals  to  Fresh Water
     Fish.  JWPCF 44(2):212-220,  1972.  ,

39.  Kott, Y.  Hazards  Associated  with the  Use  of Chlorinated Oxidation  Pond
     Effluents for Irrigation.  Water  Research 7:853-862, 1973.
                                                                     t
40.  Johnson, B. A., J. L.  Wight,  E. J.  Middlebrooks, J.  H.  Reynolds, and
     A.D.  Venosa.   Mathematical   Model  for  the   Disinfection  ,of  Waste
     Stabilization Lagoon Effluent.  JWPCF 51(8):2002-2015, 1978.

41.  Collins, H. F., R.  E.  Selleck, and G.  C.  White.   Problems  in Obtaining
     Adequate  Sewage  Disinfection*  J.  Sanit.  Eng.   Div.,  ASCE  97(SA5):
     549-562, 1971.

42.  Kothandaraman, V., and R. L. Evans.  Hydraulic Model Studies of Chlorine
     Contact Tanks.  JWPCF 44(4):626-633, 1972.


                                      73

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43.  Kothandaraman, V., and  R.  L.  Evans.  Design and Performance of  Chlorine
     Contact Tanks.   Circular 119, Illinois  State  Water  Survey, Urbana,  IL,
     1974.

44.  Kothandaraman, V., and  R. L.  Evans.   A Case  Study  of Chlorine  Contact
     Tank Inadequacies.  Public Works 105(1):59-62,  1974.

45.  Marske, D. M., and J. D.  Boyle.  Chlorine Contact Chamber  Design—A  Field
     Evaluation.  Water and Sewage Works 120(1):70-77, 1973.

46.  Hart,  F.   L.,  R.  Allen,  J.   DiAlesio,  and  J.  Dzialo.    Modifications
     Improve Chlorine Contact Chamber Performance, Parts I and  II.  Water  and
     Sewage Works 122(9):73-75 and 122(10):88-90, 1975.

47.  Zickefoose, C.,  and  R.  B. J.  Hayes.   Operations  Manual:   Stabilization
     Ponds.  Contract No.  68-01-3547,  U.S.  Environmental  Protection  Agency,
     Office  of  Water  Programs  Operations,  Municipal  Operations   Branch,
     Washington, DC, 1977.

48.  Process Design  Manual  for Sludge  Treatment and  Disposal.   EPA-625/1-
     79-011, U.S.  Environmental  Protection Agency,  Center  for  Environmental
     Research Information.,  Cincinnati, OH,  1979.
                                      74

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                                CHAPTER 3   •

                            DESIGN PROCEDURES
3.1  Preliminary Treatment
In  general the  only  mechanical  or monitoring  and  control  equipment
required  for wastewater  pond  systems  are  flow  measurement   devices,
sampling  systems, and pumps.  The flow  diagrams presented  in  Chapter  2
illustrate the  variety of  preliminary treatment options  in use.   Design
criteria  and examples for preliminary treatment components  are presented
in   several  other  publications   (1-6)  as   well   as  in   equipment
manufacturer's  catalogs.  Flow  measurement  can  be  accomplished  with
relatively simple  devices such as Palmer-Bowlus  flumes,  V-notch   weirs,
and  Parshall  flumes  used  in  conjunction  with   a  recording   meter.
Frequently,  flow  measurements  and  24-hour  compositing   samplers   are
combined in  a  common  manhole, pipe, or other housing  arrangement.   If
pumping facilities are necessary,  the wet  well  is sometimes used  as  a
point  to  recycle  effluent  or  to  add  chemicals  for  odor   control.
Pretreatment facilities should be kept to a minimum at pond  systems.
3.2  Facultative Ponds
Facultative pond  design is based upon BOD removal; however,  the majority
of  the suspended solids  will be removed in the  primary  cell  of   a  pond
system.  Sludge fermentation feedback of organic  compounds   to the water
in a  pond system  is significant and  has an  effect on the  performance.
During the spring and fall, overturn of  the pond  contents can result  in
significant quantities of solids  being resuspended.  The  rate  of   sludge
accumulation  is  affected  by  the liquid  temperature,   and  additional
        is added for sludge accumulation in cold  climates.   Although  SS
                  influence  on  the performance of  pond  systems,  most
                  simplify the incorporation  of  the influence of  SS  by
                  reaction rate constant.  Effluent  SS generally consist
of suspended organism biomass and do not include suspended  waste organic
matter.
volume
have a  profound
design equations
using an overall
Several  empirical  and rational models  for the  design   of   facultative
wastewater  ponds  have been proposed.   These  relationships  include   the
ideal  plug flow and complete  mix models, as well  as models   proposed by
                                    75

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Fritz et al., Gloyna,  Larson, Marais,  McGarry  and  Pescod,  Oswald  et  al.,
and  Thirumurthi  (7-14).  Of  these  models,  several  produce  satisfactory
results;  however,  use may   be  restricted  because  of  the  difficulty  in
evaluating specific coefficients  or  by   the  model  complexity.   Equations
from these sources are presented  in  the Appendix.

Because  of the many approaches   to  the design  of   facultative   ponds,  an
attempt will not  be made to  select  the "best"  procedure.  An  evaluation
of  several  design  formulas  with  the operational   data  presented  in
Chapter 2 failed  to  show that  any  of  the  methods are  superior   to the
others  in  terms of predicting  the  performance  of   pond  systems  (see
Appendix).  The design methods most  : often  referenced   are  summarized  in
Table 3-1.  Each of  these will  be   used to design  a  facultative pond for
the   domestic   wastewater   described   in    Table  3-2.    Following  the
calculations of  the  size of the  pond  system  by  each method,  a  summary
and comparison of the results will be presented.                        i


     3.2.1  Areal Loading Rate Procedure                               ;
                                          I

The  BODp. area!   loading  rate   recommended for   an   average  winter  air,
temperature  of less than  0°C   is   11-22 kg/ha/d  (10-20   Ib/ac/d) (Table
3-1).  The more   extreme the  environment, the lower the loading rate.  In
this hypothetical case, an  intermediate BODr loading rate  of  17  kg/ha/d
and a  minimum hydraulic  detention  time of  180 days was selected. The
minimum hydraulic detention time of 180 days was  selected  because of the
severe  climatic  conditions  and long  periods  of  ice cover when effluent
can  not  be  discharged.   The   detention  time must   be  selected  in
consideration of  the climatic conditions and  values  may  range from  no
minimum value specified up  to 180 days  as used  in   this  example.  The
organic loading rate on the first cell  in the  system will  be  limited  to
40 kg BODr/ha/d to avoid overloading and anaerobic  conditions and  odors.
                                   76

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                                         TABLE  3-1

                         FACULTATIVE  POND  DESIGN EQUATIONS
                         AREAL LOADING RATE
                                 (15)
                                              GLOYNA EQUATION
                                                    (8)
Design Equation
or
Parameter
Temperature
Adjustment of
Parameters
For Avg. Winter Air Temperature
of above 15°C (60°F)

BOD,- Loading = 45-90 kg/ha/d
   D           (40-80 Ib/ac/d)

For Avg. Winter Air Temperature
of 0-15°C (32-6p°F)

BOD,- Loading = 22-45 kg/ha/d
   3           (20-40 Ib/ac/d)

For Avg. Winter Air Temperature
of below 0°C (32°F)

BOOK Loading = 11-22 kg/ha/d
   b           (10-20 Ib/ac/d).

BOD,- Loading in first cell  is
usually limited to 40 kg/ha/d or
less and the hydraulic detention
time is 120 to 180 days in  climates
where the average air temperature
is below 0°C. In mild climates
(air temp. > 15°C) loadings on the
primary cell can be 100 kg/ha/d
Given above
   = t  =  0.035L.   9
                                                                          (35-T)
ff
     pond  volume,  m
     influent  flow rate,  1/d
     hydraulic residence  time,  d
     ultimate  influent  BQO  or COO, mg/1
     temperature coefficient =  1.085
     pond  water temperature, °C
     algal  toxicity factor
     sulfide oxygen demand  factor
                                                       BOD removal  efficiency = 80-90%
                                                       f  = 1.0 for domestic wastes
                                                       f  = 1.0 for SO. < 500 mg/1
                                                       Depth = 1 m  for calculation  of  surface
                                                         loading
                                                       Depth varies with climate
                                                       Depth = 1 m  for ideal conditions,
                                                         i.e., uniform temp., tropical to
                                                         sub-tropical, min.  settleable solids.
                                                       Depth = 1.25 m for same condition
                                                         as above but with modest amounts of
                                                         settleable solids.
                                                       Depth = 1.5  m for locations  with
                                                         significant seasonal variation in
                                                         temperatures.
                                                       Depth = 1.5-2 m for severe climates.
Included  in  equation

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                                                      TABLE 3-1



                                                      CONTINUED

Design Equation
or
Parameter
Temperature
Adjustment of
Parameters
MARAIS & SHAW EQ.
(COMPLETE MIX MODEL)
(10)
Cn F 1 >
Co [1 + Vn J
C = effluent BODg concentration, mg/1
C = influent BOD,, concentration, mg/1
k = complete mix_Jst order reaction
rate, days"
t = hydraulic residence time in each
pond, days
n = number of ponds in series
rr ) - 70°
lVmax 0.6d + 8
(C ) = maximum pond BODK cone.
e max consistent with aerobic
conditions, mg/1
d = depth of pond, ft
Max. efficiency in a series of ponds is
obtained when t in each pond is equal.
k = k (1.085)T~35
CT C35
k = reaction rate at rain, operating *
T water temperature
k 35= reaction rate at 35°C =1.2 day"
T = minimum operating water
temperature, °C
PLUG FLOW
MODEL
(16) (17)
CG - e-W
^ - e p
C = effluent BOD,- concentration, mg/1
C = influent BODg concentration, mg/1
? = base of natural logarithms, 2.7183
k = plug flow first order reaction
P rate, day"
t = hydraulic residence time, days
k varies with the BODg loading rate
P rate as shown below?
kp
BODg Loading Rate 20_1
kg/ha/d day
22 0.045
45 0.071
67 0.083
90 0.096
112 0.129
kp - kp (1.09)T"ZO
HT K20
kp = reaction rate at min. operating
T water temperature
k = reaction rate at 20°C
V20
T = minimum operating water
temperature, °C
WEHNER-WILHELM EQ. &
THIRUMURTHI APPLICATION
(13) (14) (18)
Ce 4 ae 1/2D
Co (Ha)2 ea/ZD - (l-a)Z e*/W
C = influent BOD- concentration, mg/1
C° = effluent BOD- concentration, mg/1
1 = base of natural logarithms, 2.7183
a = \/l + k t D _1
k = 1st order reaction rate, day
t = hydraulic residence time, d
D = dimensionless dispersion number
D =JL = I!! '":.
VL L2 ^ L
H = axial dispersion :coef., area per
time
v = fluid velocity, length per time
L = length of travel path of a typical
particle, length
kT = k?0 (1.09)1""20
k,. = reaction rate at minimum operating
water temperature i
k2Q= reaction rate at 20°C = 0.15 day"
T = minimum operating water
temperature, °C
00

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                            TABLE 3-2



     ASSUMED CHARACTERISTICS OF WASTEWATER AND ENVIRONMENTAL

             CONDITIONS FOR FACULTATIVE POND DESIGN
 Q = Design flow rate = 1893 m /d (0.5 mgd)



CQ = Influent BOD5 = 200 mg/1



C  = Effluent BOD,- = 30 mg/1
 €               D


 T = Water temperature at critical period of year = 0.5°C



T  = Average winter air temperature = <0°C
 a


 Light Intensity = adequate



 Evaporation - rainfall



 Suspended Solids = 250 mg/1




 SO  = <500 mg/1
                             79

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Design Conditions:  See Table 3-2.

Requirements:  Size a facultative wastewater treatment pond  to  treat  the
               wastewater described in Table 3-2, and specify the
               following parameters for the system.

                   1)  Detention time  in total system and first
                       cell, t and t,
                                    •*•      i
                   2)  Volume in total system and first cell,
                       V and V1

                   3)  Surface area,in total system and first cell,
                       A and A^            \.

                   4)  Depth, d            !

                   5)  Length, L

                   6)  Width, W

Solution:                                    ,                 .

     BOD, Loading = 200 mg/1 (1893 m3/d)(—°° jlters)(	^L	)
        &  •                                  md    ,   1 x 10°, mg

     BODg Loading = 379 kg/d
                                                   379 kg/d
                                                  40 kg/ha/d
     Surface area required in first cell = A, =


          AI = 9.5 ha = 95,000 m2 (23.4 ac)

     Total surface area required = A = (379 kg/d)/(17kg/ha/d)
                                                                        .,
          A  = 22.3 ha = 223,000 m2 ,(55.1 ac)
                            2
The surface area of 95,000 m  (23.4 ac)  required  in the primary  cells  is
larger than normally provided in one cell; therefore,  the system will  be
divided into two parallel systems with  a surface  area of 47,500  m   (11.7
ac) in  each primary  cell.   The remaining surface area requirement will
be divided  into  two parallel  systems with  three  equal size cells   in
series in each parallel system.

     Surface area in secondary cell = A2 = (223,000 - 95,000)/
        (2 parallel systems)(3 cells in series)

     A£ = A3 = A4 = 21,330 m2

Using  a length to width ratio of 3:1 and an embankment slope of  4:1, the
dimensions of the cells at the water surface and at  maximum depth can  be
calculated as follows:


                                    80

-------
     AX = Lj x Wx = L(L/3) = L2/3 = 47,500 m2
        Lx = 378 m (1240 ft)           '    !
        Wj = 378/3 = 126 m (413 ft)
        A2 = L2/3 = 21,330 m2
        L2 = 253 m (830 ft)
        W2 = 84 m (277 ft)
     Depth selection is usually control Ted by state  standards,  and
     depths specified will range from 1.0 to 2.1 m (3 to  7  ft)  in the
     primary pond to 2.5 to 3.0 m (8 to 10 ft)  in secondary ponds.
     Let the depth of primary pond = 2 m (6.6 ft)
     Depth includes 0.3 m (1 ft) for ice cover  and 0.3 m  (1 ft)  for
     sludge storage.
     The "effective" depth in the primary cell  = 1.4 m  (4.6 ft).
     Depth selection in the remaining cells is  also  controlled  by state
     standards, and most states will allow greater depths in  the
     secondary cells.
     Let the depth of the other cells = 3, m (10 ft)
     Depth includes 0.3 m (1 ft) for ice cover  and 0.3 m  (1 ft)  for
     sludge storage.
     The  "effective"  .depth  in the  secondary cells = 2.4 m  (7.9  ft).
The  volume  of the cells can be calculated using the  following  formula
for  the  volume  of  a rectangular basin with  sloped sides  and  rounded
corners,
     V = |(L x W.) + (L-2sd)(W-2sd) + 4 (L-sd)(W-sd)
where,
     V = volume, m
     L = length of pond at water surface, m
     W = width of pond at water surface, m
     s = horizontal slope factor, i.e., 3:1 slope, s = 3
     d = depth of pond, m
                                    81

-------
The  total  volume  of the  primary cells  includes  the sludge  and   ice
storage or  a total depth  of 2 m.  The "effective" volume is  based on a
depth  of 1.4 m and  is  the  vdltifiie  used  to calculate  the theoretical
hydraulic detention time.

     Total Volume in One Primary Cell (TVPC) =  (378)(126) +

         (378-2 x 4 x 2) + (126-2 x 4 x 2) + 4 (378-4 x 2)

            (126-4 x 2)
                        <


          TVPC = 87,363 m3 (3.09 x 10^ ft3)
     Effective Volume =  (378)(l26) * (378-2x4x1.4)(126-2x4x1.4)

          + 4(378-4 x 1.4M126-4 x 1.
••«] ¥
     Effective Volume = 62,786 m3 (2.22 x 106 ft3)                       :

     Theoretical hydraulic detention time in primary cell = t,

          tj = 62,7867(1893/2) = 66 days

The  total  volume of  the  secondary cells includes  the ice and  sludge
storage for a total  depth of 3 m (10 ft).  The "effective" volume of the
secondary  cells  is  based  on  a  depth  of  2.4  m (7.9 ft),  and  the
theoretical hydraulic detention time is calculated based  on  the  volume
of the cell at a depth of 2.4 m.
     Total Volume in One Secondary Cell (TVSC) =
                (253K84)
          (253-2 X 4 x 3)(84-2 x 4 x 3) + 4 (253-4 x 3)

            (84-4 x 3)If                   !
     TVSC = 52,200 m3 (1.84 x 106 ft3)

     Effective Volume in One Secondary Cell =
            (253M84) +
        (253-2 x 4 x 2.4) (84-2 x 4 X 2.4) + 4 (253-4 x 2.4)

                        2.4
           (84-4 x 2.4)
                         6
     Effective Volume = 43,535 m3 (1.54 X 106 ft3)
                                           j
     Theoretical hydraulic detention time i|n secondary cell =
                                    82

-------
          t2 = 43,5357(1893/2) = 46 d


          t  = effective total theoretical hydraulic detention  time


          t  - tj_ + tg + tg + t4


          t  = 66 + 46 + 46 + 46 = 204 d
The hydraulic residence  time  calculated for  the   selected  loading  rates
exceeds the minimum acceptable  residence time  of  180  days.    The system
can  be  designed for a  hydraulic  residence  time of   180  days  without
discharge during  the winter  months  and  discharge during  the  summer.
Another option  is to operate the  system as a  controlled discharge pond
system.  Results  such as these will occur frequently when the  design  is
based on conservative loading rates used in areas with  severe climates.

The  size of  the  pond  with  a  180-day  hydraulic detention  time  is
calculated as follows.

Volume of one primary cell  = same  as above because of loading  limit  of
40 kg BOD5/ha/d.

          Vj = 62,786 m3 (2.22 x 106 ft3)

          tj = 62,786 m3 (1893 m3/d/2) = 66 d

          t2 = 180 - 66 = 114 d

          Vp = volume in one secondary cell =

              114 d (1893 m3/d)/(2)(3) = 35,967 m3  (1.27 x  106  ft3)

There are numerous options as  to  how the ponds may be  arranged besides
the four cells in series selected  above.  The simplest,  but not  the best
option,  would be a  two  pond  system  without  baffles.    The hydraulic
characteristics of  the  two pond system  could be  improved  by  installing
baffles to  direct the  flow  patterns.  In  severe climates the use  of
baffles  must be conducted with  care because  of   the   potential for ice
damage.  The two  parallel systems with each processing one-half  of  the
flow is an excellent choice because of  the  flexibility provided by such
a flow configuration.  The four  ponds in series will provide a hydraulic
residence time that would approach the theoretical  value.

Many state standards  require that  a minimum  of 0*6 m (2   ft)  of  water
depth be  maintained in  ponds; therefore, the  volume   required  to  store
180 days  of wastewater flow is based on the volume above the 0.6-m  water
depth.   The volume allowed for sludge and ice storage  in the system will
satisfy this requirement.

The  dimensions of the two primary cells will  be  the   same  as  calculated
above,  or  378  m x  126  m  at the water surface  at maximum depth.  The


                                    83

-------
dimensions of  the  six  secondary  cells car   be   calculated   using   the
formula used  above to calculate the volume  of   a  rectangular  basin   with
sloped sides and rounded  corners.  Side slopes  are 4:1  and  the length to
width ratio is 3:1.
     V2 = 35,967 =
(L x L/3) + (L - 2 x 4 x 2.4KL/3 - 2 x 4 x 2.4)
          + 4 (L - 4 x 2.4KL/3 - 4 x 2.4)  -™

     L2/3 + (L - 19.2KL/3 - 19.2) + 4  (L - 9.6)(L/3  -  9.6)  =  89,918

     L2/3 + L2/3 - 38.4L + 368.64 + 4(L2/3 - 19.2L +.92.16)  =  89,918

     2 L2 - 115.2L + 737.28 = 89,918         ;

     Solve quadratic equation by completing the square.

     L2 - 57.6L -f 829.44 = 44,591 + 829.44

         (L - 28.8)2 = 45,420

             L - 28.8 = 213.1                                 :

                 L = 241.9 m, Use 242 m  (794 ft)
                                              .

                     W = 241.9/3 = 80.6  m, Use 81 m  (266  ft)

     Surface area of water surface in one secondary  cell  = 242  (81) =
        19,602 nT
                                             I       ••''••        o
     Surface area in all secondary cells = 19,602  (6) = 117,612  m

                                             i
     3.2.2  Gloyna Equation


The Gloyna equation and design parameters are summarized  in  Table 3-1.

Design Conditions:  See Table 3-2.

Requirements:  Size a facultative wastewater treatment  pond  to  treat  the
               wastewater described in Table 3-2,  and specify  the
               following parameters for  the system.           ^:  -

                   1)  Detention time in total system and first  cell,
                       t and t,

                   2)  Volume in total  system and  first cell,
                       V and V-L

                   3)  Surface area in  total system  and first  cell,
                       A and Ai


                                    84

-------
                   4)  Depth, d         ;  '  .. •
                      : .            •       •",'".'•   .    "          -       '
                   5)  Length, L                                     •

                   6)  Width, W

Solution:
                                            't  . ~ ':
Gloyna suggests that  the  ultimate BOD be   used in  the  equation,  and this
is  logical because   in treatment  units using extended  detention  periods,
the ultimate demand is  important.   The COD  is  the   logical  measure   of
oxygen demand if industrial wastes or  sulfate on other sulfur compounds
are  present.   Ultimate  BOD values usually  are not available, and  it  is
necessary to use  the COD  or  a multiplier to estimate the  ultimate BOD.
A multiplier of 1.2 will be used to estimate  the ultimate  BOD  (8).
       = t = 0.035L   9-    ff •
     x             «               ;,.....,

     L   = 1.2 (200 mg/1) = 240 mg/1
      a

      0  = 1.085

      T  = 0.5°C

      f  = 1.0

      f '  = 1.0                              .

      t  = 0.035  (240)  1.085(35~°*5)

      t  = 140 d

      V  = t (Q)  = 140  (1893 m3/d) = 265,000 m3  (9.36  x  1Q6  ft3)

Climate  is  severe;  therefore, the  depth should  be  2  m  (6.6 ft).   The
depth of 2 m includes approximately 0.3 m  (1 ft)  for  ice cover and 0.3 m
(1 ft) for sludge storage.

The effective depth  of  1 m is to be used  in  the calculations  of surface
loadings and surface areas.                          "    '

     Surface area = A = 265,000 m3/! m =26.5  ha  (65.5 ac)

     Surface area loading rate = 379 kg/d/26.5 ha

     Surface area loading rate = 14.3 kg BODc/ha/d
             ,-!.-..     ,    t  -  '        ?,         :
The length and width of individual cells can   be  calculated   as shown  for
the previous example.
                                   85

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More detail  on  the  arrangement of   ponds   as  perceived
available in several publications (8)  (19)  (20).
by  Gloyna  is
Gloyna  and  Tischler   (19) have  reported  that   facultative   ponds   are
effective only in a  water temperature  range  of   5 to  35°C;  therefore,  it
is unlikely that they would recommend the   use of  the Gloyna  equation  at
the design water temperature  of  0.5°C used  in  this  example.    However,
the  results agree well with the  areal  loading design  presented above.   A
comparison of  these  two  methods  as   well   as   others   presented  in  the
following  paragraph  is  presented  at  the  end   of  the  section    on
facultative ponds.
     3.2.3  Marais-Shaw Equation
The  Marais-Shaw equation   is based   on  a complete  mix  model  and   first
order  kinetics.    The  equation  and   conditions    necessary   for    its
application are shown in Table 3-1.

Design Conditions:  See Table 3-2.

Requirements:  Size a facultative wastewater treatment pond  to  treat the
               wastewater described  in Table 3-2, and specify the
               following parameters  for  the system.

                   1)  Detention time in total  system and  first cell,
                       t and ti

                   2)  Volume in total system  and first  cell,
                       V and V1

                   3)  Surface area  in total system and  first cell,
                       A and Ai                                   "

                   4)  Depth, d

                   5)  Length, L                      ,

                   6)  Width, W
Solution:

Marais and Shaw (21) proposed that the maximum BOD5 concentration  in  the
primary cells,  (Cjm=v,  be 55  mg/1  to  avoid  anaerobic  conditions  and
odors.            e max

The permissible depth of the  pond,  d in feet,  was found to  be  related  to
(C )    as follows: (Equation must be used with English units  because  of
the empirical constants that cannot  be converted to metric units.)
     "Vmax
                  700
               0.6 d + 8
                                     86

-------
          55 =
   700
0.6 d + 8
           d = 7.9 ft (2.4 m)
     Use ad = 8 ft (2.4 m)
Detention time in the primary cell is calculated as follows:
                         n
      'n
            (c0/cn)
                  c   n
                   1/n
                (1.085)
                       T-35
                  -1
         =1.2 day
         = 1.2 (1.085)0'5"35 = 1.2 (0.0599)
     ccT = 0.072 day'1
      .   = (200/55) - 1
       1     0.072
      tx = 36.6 d
      V1 = 36.6 (1,893 m3/day) = 69,300 m3
Calculate the surface area of the primary cell.
           69,300 m3
             2.4m
—   Aj = 2.9 ha (7.2 ac)
Determine , the number of ponds in series that will be  required  to  produce
an effluent containing 30 mg/1 of BOD,-.
                                   87

-------
     30/200  =
           n =
 1 + 0.072 (36.6)

1.5
                                  n
Two  ponds of equal volume  in  series with  a  depth  of  2.4   m  (8 ft)  and a
surface  area of  2.8 ha  (7.0  ac)  will  be required   (Mara (22) has  shown
that the most efficient series operation consists  of  equal  volumes).

Calculate the surface loading  rate being applied to the primary cell.    ,,.
Surface loading rate =
(200 mg/T)(1893 m3/d);
1000 liters
L >3 J

kg
1 x 106 mg
                                            2.8  ha
Surface loading rate = 135 kg of BODg/ha/d
The surface loading rate applied  to  the   primary  cell  is  much  higher than
the  value  of 40 kg BOD5/ha/d normally  recommended  as  the  maximum  for a
severe  climate  such as the environmental  conditions  specified   for this
design.  Because the  method  was  developed  in   a warm  climate,  it  is
likely  that the method cannot be  applied to  northern   areas.  This design
approach  does not make any allowance  for ice  cover  and/or  sludge storage
to determine  an "effective" depth.  If  t.he 'values   used  in the   previous
examples were applied here, the total  depth would approach  3m.

The dimensions  of  ponds designed by  this method are  also .calculated  as.
shown in the first design example  (Section  3.2.1).        •
     3.2.4  Plug Flow Model
The  plug  flow equation and  design  parameters   are  summarized  in   Table
3-1.                                       '•"--••

Design Conditions:  See Table 3-2.

Requirements:  Size a facultative wastewater  treatment  pond  to  treat the
               wastewater described in Table  3-2,  and specify the
               following parameters for the system.

                   1)  Detention time in  total system and  first  cell,
                       t and t.
                                     88

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                   2)  Volume in total system and first cell,
                      • V and Ml

                   3)  Surface area in total system and first cell,
                       A and A,
                              1

                   4)  Depth, d

                   5)  Length, L

                   6)  Width, W

Solution:
The difficult part of  using any of the design  methods  is  selecting   the
reaction  rate. The plug flow model  is no exception.  As shown   in Table
3-1, the value  of the  reaction  rate  varies  with  the organic  loading
rate.  The size  of the  pond system can be based on an  average  value  for
the tptal system,  or  the removal  in each stage of the system   and   the
organic loading rate to the succeeding  cell can  be  estimated   and   the
reaction  rate varied for each cell.  TheoreticaMy, the  latter approach
should be used; however,  in  most  cases an overall k   of  0.1  day"    is
                                                      P20
used to size the system.  Both approaches will be illustrated.


Variable kp:


In  severe  climates the  organic  loading rate  (kg  BODc/ha/d)  in   the
primary cell is limited to 40 kg/ha/d; therefore, a k /   value  of  0.071
    1                                                 29
day"  will  be used to estimate the removal  of  BODg  in the first cell.
The  size of the primary cell will be the same as the value calculated in
the design using organic loading rate criteria.

     At = (379 kg/d)/(40 kg/ha/d) = 9.5 ha (23.4 ac)

A total  depth  of  2 m  (6.6  ft)  is  selected based   on  the   criteria
described earlier.  The depth  includes  0.3 m   (1 ft) for  ice   cover  and
0.3 m  (1  ft) for sludge storage.  The "effective" depth   in the  primary
cell is 1.4 m (4.6 ft).

     Total Volume in One Primary Cell = 87,363 m3 (3.09  x 106 ft3)

     Effective Volume in One Primary Cell = 62,786 m3 (2.22 x 106  ft3)

     See Section 3.2.1 for the calculations of the above volumes.

     t  =62,786 m3/(1,893 m3/d/2) = 66 d         ,
                                    89

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Calculate the effluent quality  of  the  primary cell.

     kp   =  kp    (1.09)1""20                     .  .
      "r      P20                            i
                                             i'
     kD   =  0.071  (1.09)0'5"20
       T                                     ;•-

     kD   =  0.013  day"1
     C-,       -kp t
          =  e   T
     Cl      -0.013(66)
     200  " e


     Cj   =  200  (0.424)                     :                        !

     C-L   =  85 mg/1

The  hydraulic  detention time  required  to   remove the remaining BODg  is
calculated as  follows.  The organic  loading rate   on  the cells following
the primary cell  is much   lower  than  that  applied to   the  primary., cell .-
It is necessary to select a lower reaction  rate  of k    = 0.045 day  .
                                                     20
Calculate  the    t2  necessary  to   produce  an  effluent  with  a  BODg
concentration of  30 mg/1 .

     kp  =  0.045 (1.09)0'5"20
            0.0084
     30  _   -0.0084 t,
         -  e         2
     - 0.0084 t2 = - 1.041

              t2 = 124 d                     i

     V2  =  Qt2 = (1,893 m3/d)(124d)         !

     V2  =  234,700 m3 (8.29 x 106 ft3)                    .

Most  state  standards  permit   the   use   of   a   greater depth  in  cells
following  the  primary cell.    Depths  as  great  as  2.5m  (8  ft)   are
allowed.  A depth of  2.5 m will be   used  in  the  secondary  cells with an
"effective" depth of 1.9 m.
                                    90

-------
     d2  =  1.9 m
     A2  =  V2/d2  =  234,700 m3/!.9 m
     A2  =  123,500 m2 (30.5 ac)
The  total detention time  in  the system  is  190   days;   therefore,   the
minimum acceptable value of 180 days will  control,.  The  size  of  the  pond
system would be calculated the same way  as that  shown  in  Section  3.2.1.
Constant k

An average  value of kp   of 0.1 day"   will  be   used  to   size the entire
                       20
system.   The size of the  primary cell   is controlled by the limit of 40
kg of 80Dg/ha/d;  therefore,  the primary cell will be the  same size  as
that used in the design using the organic areal loading rate criteria.
     Aj  =  (379 kg/d)/(40 kg/ha/d) = 9.5 ha  (23.4  ac)
A depth of 2 m  (6.6 ft) is selected based on  criteria   described earlier.
The  depth includes 0.3  m  (1 ft) for   ice cover and  0.3 m  (1  ft) for
sludge storage.  The "effective" depth  in the primary  cell  is 1.4  m (4.6
ft).
     Effective  volume = 125,600 m3
     tj_  =  125,600 m3/l,893 m3/d = 66  d
Calculate the effluent quality of the primary cell.
     kp  =  kp    (1.09)1""20
      *T     *20
     kp  =  0.1 (1.09)0-5"20
     k0  =  0.019 day"1
      PT
     ci   _     -
              -0.019  (66)
          ™"  6
     Cj   =  57 mg/1
To  satisfy the effluent   standard  of   30  mg/1   of BOD,-,  a secondary pond
                                    91

-------
will be required.  The detention  time necessary   to   produce  an  effluent
BODg of 30 mg/1 is calculated as follows:

     Cx       -kp t

          •  e   T
     30   _   -0.019t
          ~  e
      t   =  34 d
                                                                          •
The effluent from the  secondary pond meets  the  .standard   of  30  mg/1  of
BOD(-;  therefore,  additional  ponds  would  not  be  required.   Using   a
two^pond system is  not  recommended, but  if such a system  were selected,
baffling would be necessary to improve  the hydraulic   characteristics  so
that the actual hydraulic residence time approached the  theoretical.


     3.2.5  Wehner-Wilhelm Equation         ;           '.   •,


The  Wehner-Wilhelm   (18) equation for  arbitrary  flow   was proposed  by
Thirumurthi  (14) as  a  method to design   facultative pond systems.  The
equation and design parameters  are summarized  in Table  3-1. Thirumurthi
developed the chart   shown  in Figure   3-1 to facilitate the use   of the
equation.  The  term  kt  is plotted versus the percent  BOD5 remaining  in
the  effluent for dispersion  factors varying from zero   for ideal   plug
flow  to infinity  for a complete  mix  reactor.  Dispersion factors  for
ponds range from 0.1  to 2 with most values not  exceeding 1.0.   Using the
arbitrary  flow equation is complicated in that  two  "constants"  must  be
selected,  the  reaction  rate (k)  and the dispersion  factor   (D).  The
influence of the dispersion  factor  can be illustrated  by  using  several
values to estimate  the detention  time required to reduce   the BOD5  from
200 mg/1  to 30 mg/1  as specified in the other  examples.  A value  of  0.15
day   was recommended for k2Q.


     kT  =  k2Q (1.09)T~20

     ky  =  0.15 (1.09)0'5"20

     k?  =  0.028 day"1

     C
     _§  =  Percent BOD,- remaining = (30/200) 100 = 15%
     Co                5

Values of kjt,  t, V,  and A for dispersion factors normally occurring  in
pond  systems are summarized in  Table  3.3.  A  depth   of 2  m (6.6  ft) was
selected  based on  the criteria outlined  in the area! loading  method  of
design.  The "effective" depth is 1.4 m (4.6ft).


                                    92

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                        FIGURE 3-1


          WERNER AND WILHELM EQUATION CHART (14)

-------
A typical  calculation  for a  D of 0.1 and a kj of  0.028  day    is  shown
below.  It is necessary to solve the equation by trial  and  error.

     Ce             4ae1/2D
     Co  "  (1+a)2 ea/2D - (1-a)2 e'3/20
      a  =  /1 + 4 kTtD
      a  =  1/1 + 4 (0.028K0.1) t  =  /T+ 0.0112  t


     First iteration:

          Assume t = 50 d
          a  =    1 + 0.0112(50) = 1.25


                            4(1.25)
                d+1.25)2 e1'25"2"0-"  - (1-1.25)2  e-1.25/(2)(0.1)
          0.15 ?«  -      - - =0.283
                  (5. 06355(518, 01) - (0.0625MO. 00193)

Agreement  is not satisfactory;  therefore,  niust perform iterations   until
two sides of equation agree.


     nth iteration;                         ;

          Assume t = 80 d
          a = Vl + 0.0112(80) = 1.377


                            4(1.377)  ,
                (U1.377)2 e1-377/^^0'"  -  (1-1.377)2  e-1'


          0.15 = -    817'46 - - =  0.148
                 (5.65)(977.50) - (0.142) (0.00102)

Agreement is adequate and the design detention  time is 80 days.
                                   94

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                                TABLE 3-3

     VARIATIONS IN DESIGN PRODUCED BY VARYING THE DISPERSION  FACTOR
D
kTt
t,days
V,m3
A,m2
0.1
2.3
80
151,400
108,200
0.25
2.6
93
176,000
125,700
0.5
3.0
107
202,600
144,700
1.0
3.7
132
249,900
178,500
The selection of  a  value  for  D can dramatically  affect   the  detention
time required to produce  a  given quality effluent.   The selection   of  a
design value for kpn can have an equal effect.

the  dimensions of ponds  based on this design method  are  calculated as
previously shown.


     3.2.6  Discussion of Design Methods


All  of the designs are based  on  parameters reported  in  the  literature
and  no  attempt  was  made  to  select   parameters  that   would  produce
consistent  results  in  all  of  the  methods.    Each  design   was   made
independently using the values of constants  recommended  by  the   author of
a method.

A  summary  of  the  results from the various design methods  is shown in
Table 3-4.  Numerous and varying requirements are  imposed on the  designs
by  the  conditions  under  which  the  methods  were  developed.    These
limitations  on  the design  methods  make it difficult  to  make   direct
comparisons; however, an  examination  of the hydraulic detention  times
and  total volume requirements  calculated by all  of   the   methods  shows
considerable consistency if  the Marais and  Shaw method  is  excluded  and  a
value of 1.0 is  selected for the dispersion factor  in the  Wehner-Wilhelm
method.

All  of the  design  equations have   limitations   and  several   have been
mentioned  in  the  design examples.  To  determine the limitations  of  a
particular method,  the  original  reference should  be  consulted.    The
major limitation of all the methods  is  the  selection  of a reaction rate
constant or other factors in  the  equations.  Even with this limitation,
if  the pond hydraulic system is  designed and  constructed such that the
theoretical  hydraulic detention time  is approached,  reasonable  success
can be assured with all of the  design  methods.   Short  circuiting is the


                                    95

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                                                        TABLE 3-4

                                         SUMMARY OF RESULTS FROM DESIGN METHODS
                                                                                           SURFACE LOADING RATE
10
CTl
DESIGN
METHOD
AREAL
LOADING
RATE
GLOYNA
MARAIS &
SHAW
PLUG FLOW
WERNER &
WILHELM
DETENTION TIME, d
Primary Total
Pond System
66a 180
140
37b 74
66a 180
66a 80-132
VOLUME^ m
Primary
Pond
125,600a
125,600a
69,300b
125,600a

125,600a
Total
System
386,800
265,000
138,600
386,800

151,400 to
249,900
SURFACE
Primary
Pond
9.5
- .
2.8
9.5
9.5
AREA, ha
Total
System
22.3
26.5
5.6
22.3
10.8 to
17.9
Depth
m
2
(1.4)
2
(DC
2.4
2
(1.4)
2
(1.4)
No.
Cells
in
Series
4
c
-
2 -
4
c 	 	
c 4
kg BOD5/ha/d
Primary Total
Pond System
40 17
14
135 , 68
40 25
30-48
     Controlled by state standards and is equal to value calculated for an areal loading rate of 40 kg/ha/d
     and an effective depth of 1.4 m.

     Also would be controlled by state standard for areal loading rate; however, the method includes a
     provision for calculating a value and this calculated value is shown.

    C                      •                "                  *    '
     Effective depth.

-------
greatest  deterrent to  successful   pond  performance,   barring any  toxic
effects.  The  importance  of  the  hydraulic design  of  a pond system cannot
be overemphasized.           ,j •   '

The surface  loading rate   approach  to   design  requires a minimum of input
data,  and   is based on   operational experiences  in various  geographical
areas of  the  country.    This  is probably the most  conservative  of the
design methods, but attention to the  hydraulic design is as important as
the selection  of the BODg loading rate.

The Gloyna method  is applicable only for 80  to  90  percent  BOD removal
efficiency,  and it  is assumed  that  solar energy for  photosynthesis is
above the  saturation   level.  Provisions for  removals outside this range
are  not  made;  however, an  adjustment  for  light  can   be  made  by
multiplying  the  pond  volume  by the  ratio of sunlight in the particular
area  to the average found in the Southwest.   Mara (23) has discussed the
limitations  of the  Gloyna  equation,  and  if a  detailed  critique  is
needed, the  reference should be  consulted.

The Marais and Shaw method of design is based  on  complete mix  hydraulics
and  first order reaction kinetics.   Complete mix  hydraulics  are  not
approached   in  facultative  ponds,  but   the  greatest  weakness  in  the
approach may lie in the calculation  of  the volume of a primary cell that
will  not  turn  anaerobic.   Mara   (22)   (23)  has  also  discussed  the
limitations  of  the  Marais  and  Shaw approach  and these references should
be consulted.

Plug flow hydraulics  and first  order  reaction  kinetics have been found
to describe  the  performance of many facultative pond systems (14) (16)
(17). As shown in the   Appendix, a plug  flow model   was found to  best
describe the   performance of the four  facultative pond systems summarized
in  Chapter  2.   Because of the arrangement   of most  facultative  pond
systems into   a series  of three or more  ponds, logically  it would  be
expected that  the hydraulic  regime  could  be approximated  by a plug  flow
model.

The  plug flow design reaction   rate used in the   above example was based
on values in the literature  (14) (16).   The 'reaction  rate (slope of the
line of best fit)  calculated from  Figure  A-9 in the Appendix,  adjusted
.for the temperature using the expression  in  Table 3-1 for the plug flow
model,  yields  a hydraulic  detention  time of  over 400 days.   This large
difference   in  detention times  (190  versus  400  days)  is   probably
attributable to  the  low  hydraulic   and organic  loading rates applied to
the four  systems.  These low loading rates  tend  to result in a  lower
value for, the  reaction   rate  (16).    This discrepancy in  reaction rates
further  illustrates  the difficulty   and  importance  of  selecting the
design parameters.

Use  of the  Wehner-Wilhelm  equation   requires  knowledge  of  both  the
reaction  rate and the dispersion  factor which  further complicates  the
design procedure.   If knowledge  of the  hydraulic characteristics  of a
proposed   pond   configuration   exists   or  can  be   determined,   the


                                     97

-------
Wehner-Wilhelm  equation  will  yield   satisfactory  results.     However,
because  of  the difficulty  of  selecting  both  parameters,  design  with one
of the  simpler  equations is   likely   to be   as   good   as  one using the
Wehner-Wilhelm equation.

In summary,  all  of  the design  methods discussed can   provide  a  valid
design, if the proper design parameters  are   selected and  the hydraulic
characteristics of the  system are controlled.


3.3  Complete Mix Aerated Ponds             |


Complete mix  aerated ponds  are  designed  and  operated  as   flow-through
ponds with or without solids recycle.   Most systems are  operated   without
solids  recycle;  however,   many systems   are   built with the option  to
recycle effluent and solids.  Even  though  the  recycle option  may not  be
exercised,  it is desirable  to  include   it   in   the design  to   provide
flexibility in the  operation of the system.   If  the solids are  returned
to the pond, the process becomes a  modified activated sludge process.

Solids in the complete  mix   aerated pond  are kept suspended  at all  times.
The  effluent from the  aeration  tank  will   contain from   one-third to
one-half  the  concentration of  the influent   BOD in the  form of solids
(3).   These solids  must be  removed by  settling before  discharging  the
effluent.   Settling is  an  integral part of  the aerated  pond   system.
Either  a  settling basin  or   a  quiescent portion of   one  of the  cells
separated by baffles may be  used for solids removal.

Six factors  are  considered in the design of  an  aerated   pond:   1)  BOD
removal, 2) effluent  characteristics,  3)  oxygen requirements, 4)  mixing
requirements, 5) temperature effects, and 6) solids  separation (3).  BOD
removal and  the effluent characteristics are  generally  estimated using a
complete  mix hydraulic  model  and first order  reaction   kinetics.  A
combination of Monod-type kinetics, first order kinetics,  and  a  complete
mix model has  been proposed,  but  there  is  limited  experience  with the
method  (3) (24).   The  complete mix   hydraulic  model   and   first  order
reaction  kinetics  will  be  used  in  the  following   example.    Oxygen\
requirements will be estimated using equations  based  upon mass balances;:
however, in a complete  mix  system  the  power input necessary to  keep the-
solids suspended is much greater  than  that required  to  transfer  adequate
oxygen.   Temperature   effects  are incorporated   into   the   BOD   removal
equations.  Solids  removal  will be accomplished  by installing a  settling
pond.  If  a higher quality  effluent   is  required,  the  solids removal
devices described  in Chapter  5 should be evaluated  and  one selected  to
produce an acceptable effluent quality.
                                    98

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     3.3.1  Complete Mix Model
The complete mix model  using  first order kinetics and  operating   in   a
series with n equal volume ponds is shown below.
               1 +
                   k_t
                    n
where,

     C
      n

     CQ  =  influent BODg concentration, mg/1

     k
   =  effluent BODr concentration in cell n, mg/1
n                 o
                                                          -i
      0

         =  complete mix first order reaction rate constant, day
            (assumed to be constant in all n cells) = 2.5 days"  at 20°C

      t  =  total hydraulic residence time in pond system, days

      n  =  number of ponds in series.

If other than a series of  equal  volume ponds are to be employed,  it   is
necessary to use the following general equation.
where,
      c  , k  , k    =  complete mix first  order  reaction  rate
       1    2    n     constant in each of n  ponds.   Because of  the
                       lack of better  information,  all  are  generally
                       assumed to be equal.

      -i» to» tn  ~  hydraulic residence time  in  each  pond,  days
     3.3.2  Selection of k
The selection of   a k   value   is  the  critical  decision   in  the  design of
any pond  system.  A Sesign value  should  be  determined for the  individual
wastewater  in bench  or pilot  scale  tests.   If this  is  impractical,   the
experiences  of others should  be evaluated.   As an   initial  estimate,  the
value of 2.5 days"  may be used for  a  complete  mix  aerated pond  system.
                                     99

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     3.3.3  Influence of Number of Ponds
When using the complete mix model,  the  number  of   ponds  in  series  has  ta
pronounced effect on the size of  the aerated ponds  required  to  achieve  a
specific degree of treatment.  The  decrease  in  total   volume of reactor
required to achieve a given efficiency by  increasing the  number  of ponds
in  series  can  best  be  illustrated  by  an   example.    Rearranging the
complete mix model  into the following form makes   it more convenient   to
calculate the total detention time.
     t =
                        1/n
where,

     t

     n

     k
            total hydraulic residence time  in  pond  systems,  days

            number of ponds in series

            complete mix first order reaction  rate  constant,
            2.5 days"1 at 20°C

            influent BOD5 concentration, mg/1

            effluent BOD,- concentration  in  cell n,  mg/1
When n
4-
L
When -n
4-
L
= 1,
!
2.5
/200V/1
1 30J
- 0
£•»
2
2.5
/200Y/2
. \30/

_i
—j.

1
~j.
                                  , = 2.27 d
                                   = 1.27 d
When n


     t
- 3,


=  3
  2.5
                             -1
                                   = 1.06 d
                                  100

-------
When n = 4,


          4
     t =
         2.5
When n = 5,
           -1
= 0.97 d
         2.5
'2_OoY/5

  30/
                             -1
= 0.92 d
Continuing to increase n  will result  in  the detention
to the  detention time  in a  plug  flow  reactor
days" .
                                      time being  equal
                                with a k  value of  2.5
                                        c
Figure 3-2 is  a plot  of the  complete mix  equation  for one to four ponds
in  series.   The  figure can  be  used   to   estimate the  performance  or
required detention  time when  the  reaction  rate  (k  )  has  been  selected.
When the influent (C ) and   effluent  (C  )   BOD,-  are  known,   the  value of
C /C  is calculated  and located on the   horizontal  axis of the  plot.  A
vertical line  is extended from this  point  to  intersect with the line for
the number of ponds in  series.  From this   point   a horizontal  line  is
drawn to intersect with the  k  t axis.    This value  of k t  is then divided
by the k  value to yield  the  total detention  time  required in n ponds in
series.  An example is shown on Figure 3-2.
     3.3.4  Unequal Volume  and  k
Mara (22)  has  shown that  a  number  of  equal  volume reactors in series is
more efficient than  unequal  volumes; however,  there may  be  cases where
it is  necessary  to construct   ponds of  unequal   volume.    When  this is
necessary,  the following example  for a  three  pond  series with half the
volume in the  first pond   and  one-fourth  in the  second  and third ponds
will  illustrate  how  to   calculate   the   needed   detention  time_., or
efficiency.   The reaction  rate  constant  is   assumed to be  2.5 days~  in
the  first  pond  and  1.5  days"    in  the   second and  third  ponds  to
illustrate  the procedure for varying   reaction rates in  the  event they
are available.
where,
     C3  =  30 mg/1
                                k   t
                        1 + k
                                    101

-------
                                                   FIGURE 3-2
                                       k t VERSUS  C /C  FOR COMPLETE MIX MODEL
                                        c          on
o
PO

-------
            200 mg/1

            1/2 t

            t3 = 1/4 t

            total hydraulic residence time in system, days
      30

     200
     0.15  =
1
1 + 2.5U/2)

1
1 + 1.5(t/4)

1
1 + 1.5(t/4)
                (1 + 1.25 t)(l + 0.375 t)(l + 0.375 t)
     0.15  =
                1 + 2 t + 1.079 t2 + 0.176 t3
     0.0264 t3 + 0.162 t2 + 0.3 t - 0.85 = 0

            t3 + 6.14 t2 + 11.36 t - 32.2 = 0
The cubic  equation  can  be solved by synthetic  substitution   as   shown
below or solved on a pocket calculator.
     2.0
1 + 6.14 + 11.36 - 32.2
  + 2.00 + 16.28 + 55.3
                 8.14 + 27.64 + 23.1
If the sum of  the  last two terms are equal to zero,  the   assumed  value
(2.0 in this example) is a root of the  equation.   In the above  iteration
the  assumed  value  is  too  large;  therefore, another  value  must   be
assumed.
     1.5
1 + 6.14 + 11.36 - 32.2
  + 1.50 + 11.46 + 34.2
             1 + 7.64 + 22.82 +  2.0
The  second estimated  value is  very close  to a  root   and   is  probably
accurate  enough,  but  to complete the  solution  another  trial will  be
completed.
     1.45
1 + 6.14 + 11.36 - 32.2
  + 1.45 + 11.00 + 32.4
1 + 7.59 + 22.36 +  0.2
                                   103

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For the conditions  described above, a total hydraulic detention  time of
1.45 days (t)'. would be  required.   The first pond would have a detention
time  of  0.72  days (t/2)  and the second and  third  ponds  would  have a
detention time of 0.36 days (t/4).


     3.3.5  Temperature Effects                     .


The  influence of  temperature on  the  reaction  rate  is  expressed  as
follows:
      C20
     1C"


where,
      CT   =  0W
               T.-20
     k_   =   reaction rate at design temperature, days"
       T                 •     •  '          .'."'"  •'" •   .  ':'" '•:''.. . .

     kr   =   reaction rate at 20°C, days"
       20

     9    =   temperature factor;, dimensionless = 1.085

     T,,   =   temperature of pond water, °C
      W                                  '            '          -    ,

The  impact  of mixing and the ambient  air temperature on the pond water
temperature can  be  estimated by  trial  and  error using  the following
equation developed by Mancini and  Barnhart  (25)  and  the  complete mix
model presented above.                       I

            AfT. + QT.                                '•'.'•
              Af + Q                         ;

where,                                       |

     T,,  =  pond water temperature, °C       ;
      W                            ,        '  \- -

     T,  =  ambient air temperature, °C
               •                              i
     T^  =  influent wastewater temperature, !°C

                                   2         i
     A   =  surface area of pond, m

     f   =  proportionality factor = 0.5

     Q   =  wastewater f 1 ow rate , m /d
                                    104

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An estimate of the surface  area  is  made   using  the   complete .mix  model
corrected for temperature,  and   then the water temperature  is calculated
using, the Mancini and Barnha'rt equation.  1

After  several iterations, when the water temperature  used  to correct the
reaction rate  coefficient  agrees  with  the  value calculated  with  the
Mancini  and Barnhart  equation,  the selection of the detention  time in
the aeration ponds is complete.


     3.3.6  Mixing and Aeration


Aeration is used to mix the  pond contents  and to transfer  oxygen ,to the
liquid.   In complete mix  aerated ponds the   mixing  requirements control
the power input to the system.  There is  no rational  method available to
predict the  power  input  necessary to keep   the solids   suspended.  The
best approach  is to  consult  equipment manufacturers' charts and tables
to  determine  the power input  needed to   satisfy  mixing   requirements.
Malina et al. (26) indicate that  a minimum, power  level of 5.9 kW/1000  m
(30 hp/Mgal) of aeration  tank volume is   required to   completely  mix aa
aerated pond cell.  Others  indicate that   approximately  2.96  kW/1000 m
(15 hp/Mgal) is  adequate to maintain  solids  in  suspension   (27).  These
values can be used  as  a guide to make  preliminary   estimates  of  power
requirements, but the  final sizing of aeration equipment should be based
on guaranteed performance by an equipment manufacturer. ...

There are  several rational  equations available   tp  estimate  the oxygen
requirements  for pond  systems,  and these'equations  can  be  found in many
text  books (3.)  (4) (20)  (24).   In  most cases,  the  use of   the BODg
entering  the  pond  as  a  basis to  estimate    the   biological  oxygen'
requirements,  is as  effective as other approaches and has  the  advantage
of being simple to calculate.

After determining  the  total horsepower   requirement   for   a  pond,  the
individual aeration units should  be located in the pond so  that   there is
an  overlap  of  the diameter  of influence providing complete  mixing.
Several  small  aerators are better than   one  or two  large  units.  Large
units  create  localized  mixing; therefore,   several   small units  would
likely  be  more efficient  and   economical.   Maintenance  and  repair of
small units would have  less  of  an  impact   on .performance, and such an
arrangement would provide more operational  flexibility.


     3.3.7  Design Example


The complete mix  model with four equal   volume  ponds in series will  be
used.   As  discussed  above,  equal  volume ponds   in  series  are  more
efficient  than  unequal volumes, and  increases  in  the number  of  ponds
beyond  four in a series does little to  reduce   the   required  hydraulic
detention times.  In  addition to the benefits of reducing   the required


                                    105

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detention  time,  four   ponds    in   series    improves   the    hydraulic
characteristics  of  the pond  system.  The following  environmental  and
wastewater characteristics are given:

     Q     =  1893 m3/d (0.5 mgd)

     CQ    =  influent BODg = 200 mg/1

     C     =  effluent BOD5 from the nth pond  in an n-pond series
              lagoon system = 30 mg/1

     k     =  k   (1.085)
      CT       C20                                      ,
     k_    =  reaction rate at design temperature, days'

       T                                        1
     k     ~  reaction rate at 20°C = 2.5 days
      C20
     T     =  pond water temperature, °C
      W                                     '                             :
,
al
           =  ambient air temperature in winter = 5°C

     T_    =  ambient air temperature in summer = 30°C
      a2
     T.    =  influent wastewater temperature = 15°C

     f     s  proportionality factor = 0.5  i
                                            i  • , .  .  -
     Elevation = 100 m

     Maintain a minimum dissolved oxygen concentration in ponds -
     2.0 mg/1                               !,'..,'
                                            i
Requirements:  Size a complete mix aerated wastewater pond system to
               treat the wastewater and determine the following
               parameters for the system.
                                            i                 • •
               1)  total detention time, t

               2)  Volume, total and for each cell , V, V^, etc.

               3)  Surface area, total and for each cell, A, Ap etc.

               4)  Depth, d                 :

               5)  Length of each cell, L

               6)  Width of each cell , W
                                            I
               7)  Aeration requirements
                                   106

-------
Solution:

     First iteration
          t  =
                               1/n
                                   -1
                               1/4
     Assume that t. = 5°C during the winter.
                  W
          k   =  2.5 (1.085)
           CT
                            5-20
          kr  =  0.74 day
           CT
                         -1
                 0.74
tr,
                                          = 3.3 d
                    , & tA = 3.3/4 =.0.825c'd
          Vx  =  0.825 (1893 m3/day) = 1562 m3 (5.5 x 104 ft3)

The pond  depth is limited  by the  ability of  the aeration equipment to
maintain the pond contents  at the desired  level  of mixing.  Acceptable
depths  for aerated  ponds  range from 1.5 to 4.5 m (5  to 15 ft).  A 3-m
(10-ft) depth is used in this example.

     Ax  =  1562 m3/3 m = 520 m2 (5597 ft2)

Check the  pond water temperature using the surface area  of 520 m  (5579
ft )  and  the  other  known  parameters  in  the  Mancini  and  Barnhart
equation.                                                 /
      w
      w
      w
       Af + Q

=  520(0.5H-5) + 1893(15)

       520(0.5)+ 1893

=  12.6°C (55°F)
                              -1300 + 28395

                                260 + 1893
                                   107

-------
     Second iteration                              "'.',.'.

As  the  winter  pond  water   temperature   increases,   the   surface  area,
detention  time, and volume of the   pond  will   decrease;   therefore,  the
next  estimate of  T   should  be approximately   equal   to   the  calculated
value of Tw of 12.6°C  (55°F).    :>r,- ;.     ';          '   :..    "  ••.
Assume T,
        w
  13°C in the winter.
      t   =
2.5 (1*085) -•
1.41 day'1
4
1.41
/200\1/4 ,
[W J
                        - 1.72 d
          =  1.72/4 = 0.43 d

          =  0.43  (1893) = 814 m3  (2.87  x  104 ft3)

          =  814/3 = 271 m2 (2900  ft2)
       w
       w
   271(0.5)(-5) + 1893(15)  =  -677.5 + 28395

      271(0.5) + 1893             2028.5

   13.7°C (57°F)                   i
The assumed value of  13°C   is   approximately  equal  to  the  results  of  the
second  iteration of  13.7°C.  The  limits  of   the  method do   not justify
attempting  to  balance  the temperatures   closer  than  to  the  nearest
degree.                                  '   ,

The temperature  will decrease   from  pond  1 to pond  2 and from pond 2 to
pond 3, etc., but the decrease is not   so   great that an average T   value
cannot be used.

     Final Size of Ponds
t  =  1.72 d

tp t2, tg &
                           =  0.43  d
          V  =  3256 m3  (11.5 x  104 ft3)
                           =  814' m3' (2.87  x  104  ft3)
          A  =  1084 m2  (11.67 x  103 ft2)
                                     108

-------
              A2, A3 & A4  =  271 m2 (2.92 x 103 ft2)
     Dimensions of Ponds           . .      \
Using the formula for the volume of a pond  with sloped side walls  for  a
square pond and the required  volume in each pond, the dimensions of  the
ponds can be calculated.  Use a slope of  2:1.
              (L x W) + (L-2 sd)(W-2 sd) + 4 (L-sd)(W-sd)
         =  volume = 814 m3 (2.87 x 104 ft3)
     V
where,
     V
     L   =  length of pond at water surface, m
     W   =  width of pond at water surface, m
     s   =  horizontal slope factor, i.e., 2:1 slope,  s = 2
     d   =  depth of pond  =  3 m (10 ft)
                                                           d
     814 =
             (LW) + (L-2x2x3)(W-2x2x3) + 4  (L-2x3)(W-2x3)
In a square pond L = W.
                   (L-12)a~l2) + 4 (L-6) (L-6)
     814 () = L2
          6L  - 721 + 288 » 1628
              L2 - 12L + 48 * 271.3
Solve quadratic equation by completing the square.
     L2 - 12L + 36 = 223.3 + 36
         (L-6)2 = 259.3
             (L-6) = 16.1
                 L = 22.1 m at the water surface  (72.5 ft)
A minimum of  0.6 m  (2 ft) of freeboard must be  provided; therefore, the
dimensions  of a single pond  will be 24.5 m x 24.5 m (80.4 ft x 80.4 ft)
at the top of the inside of the dike with a water depth of 3 m (10 ft).
There are  no rational design equations to predict the required mixing to
keep the solids  suspended  in an  aerated pond.  Using the mass of  BODg
entering  the system  as  a  basis  to  estimate  the  biological  oxygeH
requirements is simple and as effective as other  approaches.
                                   109

-------
Catalogs from equipment manufacturers  must  be  consulted  to   ensure  that
adequate mixing  is provided.   Additionally,,, all  types  of equipment must
be  evaluated to ensure that  the most  economical  and  efficient system  is
selected.  A  municipal  wastewater  treatment system  designed  to provide
complete mixing  of the pond  contents  requires  approximately  10 times  as
much  power as a system designed   to meet  the  oxygen requirements  only.
Therefore, an economic analysis along  with sound  engineering  judgment  is
required to select the proper aeration equipment.

The following relationship  is used to  estimate  aeration requirements:    >
a
                   - C
                      L
                          (1.025)
                   T. -20
where,
     N   -  equivalent oxygen  transfer  to  tapwater  at  standard  condi-
            tions, kg/hr

     N,  =  oxygen required to  treat  the wastewater, kg/hr
      a
     a   -  oxygen transfer in  wastewater   x   n  g
            oxygen transfer in  tapwater    ""


     C,   -  minimum DO concentration  maintained  in  the waste,  assume
      L     2.0 mg/1

     C_  ™  oxygen saturation  value of  tapwater  at  20°C and  one
            atmosphere pressure =  9,17  mg/1
                                            i
     T..  =  wastewater temperature, °C
      W

     C   =  B(C  )P = oxygen saturation value  of the waste,  mg/1


     R   _  wastewater oxygen  saturation value  =   n 9
     1    ~  tapwater oxygen saturation  value


     C   =  tapwater oxygen saturation  value at  temperature, T,
      ss                                                      w

     P   =  ratio of barometric pressure at plant site to  barometric
            pressure at sea level, assume  1.0  for the  elevation of
            100 m

The maximum oxygen transfer will be .required   in the summer  months.    The
Mancini  and   Barnhart  equation  can  be used to   estimate   the   pond
wastewater temperature during  the  summer.
                                    110

-------
     T   -  271(0.5)(30) +1893(15)
      w  ~     271(0.5) + 1893
     T   _  4065 + 28395  _
     'w  ~  -      -  '
     C   =  9.85 mg/1 at 16°C
      o o
BODC in the wastewater = C  x Q
   o                      o
         =  (200 g/m3) (1893 m3/d) (kg/1000 g) (day/24  hr)
         =  16 kg/hr
Assume that the oxygen  demand of the   solids  at   peak  flows   will  be 1.5
times the mean oxygen demand of 16 kg Op/hr.   Therefore,
     N   =  1.5 x 16 kg QJ\\r = 24 kg 00/hr
      a                  c.              c.
     ccu, =  0.9(9.85 mg/1) 1.0 = 8.87 mg/1*
      oW
                   24 kg 0?/hr
     N  =  - - - =  39.3 kg  09/hr
           0.9
"8.87 - 2.0-1
    9.17    J
(1.025)
                                    16-20
Manufacturers'  catalogs  suggest  1.9  kg  0?/kWh    (1.4   kg/hr/hp)   for
estimating  power requirements.  Therefore,  the  total  power  required   to
satisfy the oxygen demand in the pond system is:
     39.3 kg 0,,/hr
     	  =  20.7 kW  (27.8 hp)
     1.9 kg 02/kWh
The power required to meet requirements for liquid mixing  is  (27):
     minimum power =1.5 kW/1000 m  of volume
     power required =1.5 kW/1000 m3 (814 m3)  =  1.2 kW/cell
     power total  = (4 cells) (1.2 kW/cetl) = 4.8 kW  (6.4  hp)
The power required to meet requirements for solids suspension  is  (24):
                                 3
     minimum power = 15 kW/1000 m  of volume
     power required = 15 kW/1000 m3 (814 m3/cell) = 12.2 kW/cell
                      (16.4 hp/cell)
     power required = (4 cells)(12.2 kW/cell) = 48.8  kW(65  hp)

                                   111

-------
The  power required  to  maintain  solids suspension   exceeds   the   power
required both to meet  oxygen demand and for  mixing   of the pond liquid;
therefore, the  power requirement for solids suspension will   be used   to
select aerators.
                                            i_
Assuming  90  percent  efficiency  for aerator gearing,  the total   motor
power for solids suspension is:

     48W  =  54.2 kW (72.7 hp)
This value represents  an  approximate power  requirement  and  is  used   to
select aeration  equipment.   The power  actually  applied   to  the  pond
contents may  be more or  less  than this value  being  determined by  the
zone  of  complete  mixing requirements  in each  cell.   Using  the  data
presented in a catalog  by Aqua-Aerobic  Systems,   Inc.  (27),  six 2.2-kW
(3-hp) aerators for each cell would provide zones  of complete mix having
13-m  (42-ft)  diameters  and  would  not   require   a    draft   tube   or
anti-erosion assembly  in  a pond with a depth  of 3  m   (10 ft).   This
selection in aerators  and  aerator  placement   leaves small   areas where
solids suspension  might  occur.   However,  additional power  and, hence,
additional operating  cost  would not  significantly improve   efficiency.
Figure  3-3  depicts  aerator placement, zones   of  complete  mixing   for
solids suspension in  one  of the four ponds.    A  settling   pond  ,with  a
hydraulic detention time of two days is  provided after the fourth pond.

     Summary                      '  ..                  '

     V  =  3256 m3

     A  =  1084 m3

     t  =  1.72 d

     02 required for treatment                =  39.3 kg 02/hr (20.7 kW)

     Power required for liquid mixing         =  4.8 kW

     Power required for solids suspension     =  48.8 kW

     Power supplied via six aerators per cell =  13.4 kW
                                    112

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          FIGURE 3-3   ; j

LAYOUT OF ONE CELL OF COMPLETE MIX
        AERATED POND SYSTEM
                                        Zone of Complete
                                        Mixing for Solids
                                        Suspension
  Influent
                     Surface  Aerators (2.24 kW)
                 113

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3.4  Partial Mix Aerated Ponds


In the partial mix aerated pond  system,  no  attempt  is  made  to  keep all  of
the  solids in the  aerated ponds   suspended.   Aeration  serves   only  to
provide oxygen  transfer adeq'uatd iO  oxidize  the  BOD   entering the  pond.
Some mixing  obviously occurs and keeps  portions  of the  solids suspended;
however,  in the partial mix  aera'ted  pond,   anaerobic degradation of the
organic  matter  that  settles   dofes  occur.    The  system   is   frequently
referred to as a facultative aerated  pond system.

Other  than the  difference  in  mixing   requirements,  the   same   factors
considered in the complete mix aerated pond   system are  applicable to the
design  of  a   partial   mix    system,   i.e.,    BOD   removal,   effluent
characteristics, oxygen  requirements,   temperature effects,   and solids
separation.  BOD removal is  normally  estimated using  the   complete mix
hydraulic model  and first order reaction kinetics.   Recent studies (17)
have shown  that  the  plug  flow   model  and   first order   kinetics more
closely  predict the performance of partial mix ponds  using   both surface
and  diffused air  aeration.  HoWever, most   of the ponds   evaluated were
lightly  loaded and  the reaction   rates  calculated from  the  performance
data are  very conservative because of the  tendency of the  reaction rates
to decrease as  the organic  loading  rate   (surface loading  or volumetric
loading) decreases  (16).  Because  of  this  lack of  better design  reaction
rates, it is still  necessary to design  partial mix aerated   ponds  using
the complete mix model  discussed in  detail   in   Section  3.3. The  only
difference  in  applying  this   itiddel  to   partial  mix  systems   is the
selection of  a  reaction  rate  coefficient   applicable  to partial mix
systems.   Section 3.3 should be consulted  to  determine  the  effect of the
number of ponds in series (3*3.3)*  unequal  volumes  in  each  pond  (3.3.4),
and temperature effects (3.3.5).


     3.4.1  Selection of k
                                            I

As   mentioned  several  times,  the   selection   of the    reaction  rate
coefficient  is the most important  decision  in the design   of  any pond
system.   All other considerations  in the  design will   be   influenced  by
this selection.  If  possible, a design  k   should  be  determined   for the
wastewater  in pilot  or  bench  scale  tests.   Experiences   of  others with
similar wastewaters and environmental  conditions  should  be  evaluated.

The  "Ten States Standards"  (1) recommends k   values of 0.276  day"  at
20°C and  0.138 day   at  1°C.   Using   the t«<5   values  to   calculate the
temperature coefficient (9),  yields   a   9  value  of   1.036.   Boulier and
Atchison (28) recommend values   of  k     of  0.2 to  0.3 at 20°C and 0.1  to
0.15 at 0.5°C.   A temperature coefficient  of  1.036 results  when the two
lower  or  higher  values of  k     are   used  to   calculate  9.   Reid  (293
suggested a  k    value  of  0.18   at  20°C  and  0.14 at  0.5°C based  oh
research  withp partial  mix  ponds    in  central  Alaska    aerated  with
perforated  tubing.  These values   are essentially  identical  to  the "Ten


                                    114

-------
States Standards" recommendations.    In  the  example  presented  later,  the
values recommended by the "Ten States Standards" will  be  used.


     3.4.2  Mixing and Aeration


In  partial mix  aerated  ponds, aerators are used  to transfer  oxygen   to
the liquid  at the  rate necessary to maintain  aerobic conditions  in  the
ponds.   In a complete  mix system the   power input to each  pond  in  the
series must be  adequate  to keep  the   solids  suspended;  whereas,   in a
partial mix system  the power input  is   reduced from  pond to  pond  because
of  the  reduction  in  organic  matter  (BOD)  to  be oxidized   as   the
wastewater flows through the system.

The oxygen  requirements in  each pond can  be calculated  using  rational
formulas developed for activated sludge  systems (3) (24); however,  it   is
doubtful that  any  of the relationships are  more accurate   than  assuming
that  all  of  the influent  BOD,- entering  the  pond is  to  be oxidized.
After  calculating  the  required  rate  of  oxygen  transfer,   equipment
manufacturers' catalogs  should be   consulted to   determine  the  zone of
complete oxygen  dispersion by  surface, helical,   or air gun aerators or
the proper spacing of perforated tubing.


     3.4.3  Design Example


The design  of  a partial  mix aerated pond is performed  the  same  as  that
shown  for the  complete mix  system with  the exceptions   of   different
reaction rate  coefficients and less power  input requirements.   The  power
input is reduced from one pond to the  next to  account for the reduction
in  organic matter  (BOD) to be oxidized as the wastewater   flows  through
the system.

The  complete mix model  with four equal volume ponds  in series   will be
used (see Section 3.3.7 for justification).  The  following environmental
and wastewater characteristics are given:

     Q    =  1893 m3/d (0.5 mgd)

     C    =  influent BODK = 200 mg/1
      o                  o

     C    =  effluent BOD,- from the  nth  pond  in an  n-pond series
             pond system = 30 mg/1

                           T -20
     k    =  reaction  rate  at  design  temperature,  days"
                                    115

-------
     k    =  reaction rate at 20°C = 0.276 day"
      w
=  temperature of pond water, °C

=  ambient air temperature in winter = -5°C
     T    =  ambient air temperature in summer = 30°C
      a2
     T.   =  influent wastewater temperature = 15°C

     f    =  proportionality factor =0.5

     Elevation = 100 m
                                          I

     Maintain a minimum dissolved oxygen concentration in ponds =
     2.0 mg/1

Requirements:  Size a partial mix aerated pond system to treat the
               wastewater and determine the following parameters for
               the system.
          1) Total detention time, t

          2) Volume, total and for each cell, V,
                                                               etc.
                    3) Surface area, total and for each cell, A, A-, ,
                       etc.                                 ...

                    4) Depth, d

                    5) Length of each cell, L

                    6) Width of each cell, W

                    7) Aeration requirements
Solution:

     First iteration

t

t


n
k
pm
4
k m
pm
fC\ 1/n
1 ° 1 -1
c -1
Av
/200\1/4 .
1 30 / "-1
V /
     Assume that t  = 10°C during the winter.
                              ,10-20
          k    =  0.276 (1.036)
                                  116

-------
          k    =  0.194 day'
r
t
*2
4
~ O94
/200\ 1/4
N
= t3 = t4 = 12.5/4 = 3.
-1
1 d
                                           = 12.5 d
     Vj = 3.1 (1893 m3/d) = 5868 m3  (2.07 x 105 ft3)

Acceptable depths from partial mix aerated ponds  ranged  from  1.5  to 4.5 m
(5 to 15 ft).  A 3-m (10-ft) depth is used in this example.

Calculate the area of the pond.

The ideal configuration of  a  pond  designed  on the  basis  of  complete  mix
hydraulics   is a circular or  a square pond;  however,  even  though partial
mix  ponds are designed using the  complete   mix  model,  it  is  recommended
that the ponds be configured with a  length to width  ratio  of  3:1 or 4:1.
This is done because it  is recognized that the hydraulic  flow pattern in
partial mix  systems  more closely resembles the plug flow  model.   As more
field  data  become  available,  it  is   likely  that reliable   plug  flow
reaction rates will be developed, and the  plug flow model  can be used to
size partial mix systems.

Ponds with sloped side walls  (3:1)  and a length to  width ratio of   4:1
will be used.  The dimensions of the ponds can be calculated   using   the
formula  for the volume  of a rectangular pond  with side  slopes  that  was
presented in Sections 3.2.1 and 3.3.7.
     V =

where,
(LxW)  + (L-2sd)(W-2sd) + 4 (L-sd)CW-sd)
     V = volume of pond = 5868 m3  (2.07 x  105 ft3)

     L = length of pond at water surface,  m

     W = width of pond at water surface, m

     s = horizontal slope factor,  i.e., 3:1  slope,  s  =  3

     d = depth of pond = 3 m  (10 ft)
     L = 4W

     V |  = (4WxW)
          (4W-2x3x3)(W-2x3x3) + 4 (4W-2x3)(W-2x3)
     4W2 + 4W2 . 9QW + 324 + 16W2  -  120W +  144  =  2V
                                    117

-------
          241T  -  210W  =  2V  -  468

                W2 - 8.75W = 0.08333V  -  19.5

Solve the quadratic equation  by completing the  square.

     W2 - 8.75W + 19.14  = 469.5 +  19.14

        (W - 4.375)2 = 488.6

           W -  4.375 = 22.10

              W = 26.5 m (86.9  ft)

                  L = 26.5 x 4 = 106.0 m (348  ft)

     A = 106.0  x  26.5  =  2809  m2 (3.02 x 104 ft2)
Check  the 2pond water temperature   using   the   surface  area  of   2809   m
(30,236  f t ) and  the  other known  characteristics   in  the   Mancini   and
Barnhart equation  (Section 3.3.5).
                 QT1
      w
            Af + Q
     T  - 2809(0.5)(-5) + 1893(15)           !
     'w       2809(0.5) + 1893

     T,, = 6.5°C  (44°F)
      W


     Second iteration

The  temperature  of  the  pond  water  will  be  colder   than   originally
estimated; therefore, the pond area  required will  increase  and more  heat
will be lost.   The next estimate will be  lower than   the value resulting
from the first iteration.
Assume T.. = 5°C
        W
      pm

      cpm
=  0.276(1.036)

=  0.162 day"1
                         5-20
     4
   0.162
                       30 /
                      200
-1
                                   = 15.0 d
                       = 15/4 = 3.75 d
          3.75(1893) = 7099 m3(2.51 x 105 ft3)
                                    118

-------
     VT - 8.75W = 0.08333V - 19.5

          (W - 4.375)2 = 572.06 + 19.14

               W - 4.375 = 591.2                               .   ,

          W = 28.7 m (93 ft)

          L = 28.7 x 4 = 114.8 m (371 ft)

          A = 28.7 x 114.8 = 3295 m2 (3.55 x 104 ft2)

     T  = 3295(0. 5)(-5) + 1893(15)
     'w     3295(0.5) + 1893

     Tw = 5.7°C (42°F)

The second  value of T  of 5.7°C is in  close agreement with the  assumed
value  of   5.0°C,  ana   further  refinement  is  not  justified.    The
temperature will decrease as the  wastewater  flows from one pond to  the
next,  but  the change  is not  large enough to significantly  affect the
design based on an average temperature.

     Final Size of Ponds
          t  = 15.0 d
                            = 3.75 d
                28,396 m3 (1.00 x 106 ft3)
          Vj_ = V2
          V3 « V4 = 7,099 m3 (2.51 x 105.ft3)

A  = 13,180 m2 (1.42 x 105 ft2)


                            (3>55 x 1C)4 ft2)
          Al = A2 = A3 = A4 = 3295

A freeboard  of 0.6 m  (2 ft)  should be provided.  The  dimensions of  a
single cell at the top of the inside of the dike will be 40.7 m  x 126.8
m (131.4 ft x 409.5 ft).                                    .;        .

The  advantage of  a four cell system can  be demonstrated  by considering
the  detention  time  and  area that would  be  required for a   two -cell
system.   Using the  same assumptions as those  used in the  previous  case,
with n = 2 and TW = 5°C:
     First iteration
t
2
0.162
/ \
/ 200 \
L\30/
                         1/2
                                  = 19.5 d
                                    119

-------
     t, =
          t2 = 9.75 d
         ' 9.75 (1893) =18,457 m3. (6.5xl05 ft3)
          8.75W = 0.08333V - 19.5
          W2 - 8.75W = 1518.5
              (W - 4.375)2 = 1518.5 + 19.14
                   W - 4.375 = 39.2
         43.6 m (143 ft)
     W
     L = 4 x 43.6 = 174.4 m (572 ft)
     A-
          7604 m2 (81,850 ft2)
     Tw =
          7604(0.5)(-5) + 1893(15)
              7604(0.5) + 1893
        = 1.6°C (35°F)
Second iteration
Let Tw = 1°C
   k   = 0.276 (1.036)
   kpm = 0.141 day'1
                      1-20
   t =
  2
0.141
                 30
•Y/2i
'
                          =  22.4 d
     M1 = 11.2 (1893) = 21,202 m3 (7.49xl05 ft3)
     W2 - 8.75W = 0.08333(21,202) - 19.5
          (W - 4.375)2 = 1747 +19.14
              W - 4.375 =42.0
                  W = 46.4 m (152 ft)
                     L = 4 x 46.4 = 185.6 m (609 ft)
                       120

-------
          A = 46.4 x 185.6 = 8612 m2 (9.3xl04 ft2)

          T  = 8612(0.5)(-5) + 1893(15)
          'w       8612(0.5) + 1893
T  =
 W
                     (34°F)
The  assumed value  of  T  of 1.0°C is in  excellent  agreement   with   the
calculated value of 1.1°C; therefore,  the design  is  satisfactory.  Using
only  2 cells instead of 4  will increase the  detention  time required by
approximately 50% and will increase the surface  area   and volume required
by  a factor  of approximately  3.  This would be   undesirable  for  winter
operations in  cold  climates  because of the enhanced potential  for  ice
formation and the additional cost for construction.

Equations are available  to  estimate the  oxygen  requirements  in aerated
ponds; however, the  use of these equations requires  assuming two or more
parameters  which  have a wide  range  of  values  from which  to choose.
Experience has shown  that basing the biological oxygen  requirements   on
1.5 times the  mass of BOD,- entering  each cell  is  satisfactory in  a mild
climate such as  the  one  described in  this  example.  In cold climates
where  solids   accumulation  will  be  greater,   the  factor   should   be
increased to 2.0 kg O^/kg of BOD,- applied to each  cell.

Equipment  manufacturers'  catalogs  must  be  consulted   when   selecting
aerators.  All types  of equipment must be evaluated   to   ensure that  the
most  economical system  is  selected.   An  economic  analysis  and good
engineering judgment is required to select aeration equipment.

The following relationship is used to estimate aeration requirements:
          N  =
where,
a
"Csw-CL "
L GS J
T -20
(1.025) W
«
     N   = equivalent  oxygen  transfer  to  tapwater at  standard condi-
           tions, kg/hr

     N   = oxygen required  to treat  the wastewater,  kg/hr

            oxygen transfer in wastewater  =   n g
     a      oxygen transfer in tapwater


     C,  = minimum DO  concentration  maintained in the waste,  assume
      L    2.0 mg/1

     C   = oxygen saturation  value of  tapwater at 20°C and one
           atmosphere  pressure =  9.17  mg/1
                                     121

-------
     TW  = wastewater temperature, °C

C_,  = B (CCC)P = oxygen saturation value of the waste, mg/1
 bW       oo
     a   _  wastewater oxygen saturation value  _  0 g
         ~   tapwater oxygen saturation value   ~


     C__ =  tapwater oxygen saturation value at temperature, T  '
      SS           '                                           W

     P   =  ratio of barometric pressure at plant site to barometric
            pressure at sea level, assume.1.0 for the elevation of
            100 m

The maximum  oxygen transfer  will be.required in the summer months.  The
summer water temperature in the  ponds can be estimated using the Mancini
and Barnhart equation.

     T   =  3295(0.5)(30) + 1893(15)        !
     'w       3295(0.5) + 1893
                                            i                       ''"'•"
     Tw  =  21.98   22°C (72°F)             :

     Css =  8.72 mg/1

     BODC in the influent wastewater = C. x Q
        o                               o
         = (200 g/m3)(1893 m3/d)(kg/1000 g)(d/24 hr)

         = 16 kg/hr            -~           j".
                                                  •
     BOD5 in the effluent from pond number one can be calculated as
     follows:                                     ,


          Cn            1                   I''-''
          Co
          Cl
          200
                   0.162(3.75)  + 1
              =  124 mg/1
     BODg in the influent to pond number two =

          Cx x Q = 124 mg/1 (1893 m3/d)(kg/

     BODg in effluent from pond number two:
x Q = 124 mg/1 (1893 m3/d)(kg/1000 g)(d/24 hr) = 10 kg/hr
                                    122

-------
            _  .


          124      [0.162(3.75) + ll 2

                   I     2         J
          C2 = 73 mg/1


     BODg in influent to pond number three =



          C2 x Q = 73(1893)(1/1000)(1/24) = 6 kg/hr



     BODg in effluent from  pond number three:




          fa   .            i
          73       [6.162(3.75) + 11 3

                   [    3          J

          C3 = 42 mLg/l



     BODg in influent to pond number four =



          C3 x Q = 42(1893)(l/1000)(l/24) = 3  kg/hr
Assume that the oxygen demand of the wastewater   and  solids   at  peak  flow

will be 1.5 times the mean oxygen demand entering each  cell.   Therefore,



     N3  =  1.5 x 16 kg/hr = 24 kg/hr
      «1




     Na  «  1.5 x 10 kg/hr = 15 kg/hr


       2


     Na  =  1.5 x 6 kg/hr = 9 kg/hr





     Na  »  1.5 x 3 kg/hr = 4.5 kg/hr

       4



where, the subscripts 1 through 4 represent  ponds 1 through  4.



     Cei,  = 0.9 (8.72 mg/1) 1.0 = 7.85 mg/1
      5W




Qy Requirements
     Pond #1:




                   24 kg 0,,/hr
     ti ,  ___ . -     ',  . -'       C
                                            =   39.7 kg 02/hr
                                    123

-------
Pond #2:
15 kg 0,,/hr
N
_
2 Q 9|7.85
U'y 9.
L.
7 2'°1(1 025)22-20
I/ U.U^D;
Pond #3:
9 kg 0,,/hr
N
__
3 n Q7.85
U*y 9.
t_
7 2'°~(1 025)22'20
•J y ^ J. .UdO ^
                                             =  24.8  kg  02/hr
                                            =  14.9  kg 02/hr
     Pond #4:
                    4.5 kg 02/hr
               0.9
                   7.85 - 2.Q-
                      9.17
  (1,
         2232Q  =  7.4 kg 02/hr
The  use of  both  surface and diffused air  aerators will  be  illustrated.
Using surface aerators,  a value  of 1.9  kg  O^/kWh   (1.4 kg/hr/hp)   is,
recommended  to  estimate  the power  requirements.  A  value   of   2.7   kg!
02/kWh (2 kg/hp/hr) is recommended  for diffused  air   aeration systems  by;
tne  manufacturers.  The gas  transfer  rate  must  be  verified   for  the
equipment  selected.   The  total  power  required  to  satisfy the oxygen
demand in the ponds using surface aerators is:
     Pond #1:
          39.7 kg 02/hr
           1.9 kg 02/kWh
     Pond #2:
          24.8 kg 02/hr
           1.9 kg 02/kWh
     Pond #3:
          14.9 kg 02/hr
           1.9 kg, 02/kWh
     Pond #4:
           7.4 kg 02/hr
           1.9 kg 02/kWh
                            =  20.9 kW  (28.Q  hp)
=  13.1 kW (17.5 hp)
=  7.8 kW (10.5 hp)
=  3.9 kW (5.2 hp)
                                    124

-------
If diffused air aerators are to be used, the  same procedure  is performed
as shown above with the exception being to divide  by the value of 2.7 kg
Op/kWh.  The power requirements for a diffused air  system  is  calculated
as follows:
     Pond #1:

          39.7 kg 02/hr
           2.7 kg 02/kWh

     Pond #2:
                           =  14.7 kW (19.7 hp)
          24.8 kg 09/hr
          	  =  9.2 kW  (12.3 hp)
           2.7 kg 02/kWh

     Pond #3:

          14.9 kg CL/hr
          	  =  5.5 kW  (7.4 hp)
           2.7 kg 02/kWh

     Pond #4:

           7.4 kg 02/hr
           2.7 kg 09/kWh
                           =  2.7 kW  (3.7 hp)
The  surface  and  diffused  air  aerators  power  requirements  must   be
corrected  for  gearing  or  blower  efficiency.    Assuming   90   percent
efficiency for both gearing  and blower efficiency; the  total  motor  power
required is calculated as follows:

     Pond #1:

          20Q^9kW  =  23.2 kW (31.1 hp)


The values for the other ponds are calculated  as shown above.  The  motor
power requirements are summarized in Table 3-5.

The  values shown in  Table 3-5 represent approximate  power  requirements
and  are  used  to   select   aeration   equipment.   The   actual   power
requirements for the ponds using surface  aeration will  be  determined  by
using the  zone  of  complete  oxygen dispersion  reported  by equipment
manufacturers and the above power requirements.
                                     125

-------
                                TABLE 3-5

                  MOTOR POWER REQUIREMENTS FOR  SURFACE
                        AND DIFFUSED AIR AERATORS

                                    POWER REQUIREMENTS,  kW

   Pond Number        Surface Aerators       Diffused Air  Aerators
#1
n
#3
#4
TOTAL
23.2
14.6
8.7
4.3
5078
16.3
10.2
6.1
3.0
35.6
Using data presented  in  a catalog  by Aqua-Aerobic   Systems,   Inc.   (27),
ten 2.2-kW (3-hp)  surface aerators  in  the   first   pond  would  provide  a
zone of complete  oxygen dispersion with  a diameter  of  41.2   m (135  ft)
and  a zone of complete  mixing with  a  diameter  of  13 m  (42   ft) without
draft tubes or anti-erosion assemblies in  a pond  with  a depth  of 3   m  (10
ft).  The  arrangement of the  aerators   is   shown  in  Figure   3-4.    The
aerators provide  considerable overlap in  the  zones  of   complete  oxygen
dispersion  as  well  as providing   a zone  of  complete   mixing  at  even
intervals along the tank to disperse any channeling  of the flow that  may
develop.  Similar selections and arrangements can be  developed for  the
remaining  three cells but with decreasing power  requirements  as shown in
Table 3-5.  The  main concern in the selection  of aerators is that  there1
is considerable overlap of the zones of  complete  oxygen dispersion.

Diffused air aeration  requirements for  all four  ponds are 35.6  kW  (47.7
hp).  Manufacturers   supply motor-blower combinations  in  10, 15, 20, etc.
hp; therefore,  to meet the  47.7-hp  (35.6-kW)  requirement for aeration
and to  provide  flexibility in  maintenance  and  operation, three   15-hp
(11.2-kW) and two  10-hp  (7.5-kW)  motor-blowers  are   specified.    The
blowers are to be  operated in combinations   providing 50 hp (37.3  kW) of
aeration with the remaining blowers in reserve.

When the  air is distributed with fine   bubble  perforated tubing   (Hinde
Engineering Company)  the  quantity  of air  added   to  a  pond is   assumed to
be directly  proportional  to  the  length  of  tubing  placed  in  a   pond.
Approximately 50-60 percent  of  the tubing in  the  first pond is   placed
within the  first third of the  pond.  The tubing in  the remaining  ponds \
can  be  spaced  at equal  intervals  along the length  of the ponds   in
proportion  to the power requirements in each cell.    The distribution of
the tubing is shown in Figure 3-5.

Use  of  the  fine  bubble perforated tubing  requires  that   a  diligent
maintenance program   be established.  Many communities  have   experienced
clogging of the perforations, particularly in  hard  water areas. If this
method  of aeration is specified, the  design engineer must emphasize  the
importance of adhering to the maintenance  schedule.


                                    126

-------
             FIGURE  3-4


  LAYOUT OF  SURFACE AERATORS  IN

FIRST CELL OF  PARTIAL MIX SYSTEM
                                Zones of complete
                        x       oxygen dispersion
                             ^ Zones of complete mixing
                               where solids suspension
                               occurs
                               Loqatjon of aerators
                               varied to prevent
                               channel of flow
                Influent
                  127

-------
                                                   FIGURE 3-5



                                    LAYOUT OF AERATION SYSTEM FOR PARTIAL MIX

                                        DIFFUSED AIR AERATED POND SYSTEM
ro
oo
INFLUENT LJ

4-
1.5m j-
, i-
3m
t
l
V
Cell 1 	
























F Blower House Air Distribution Manifod ^
> i X.




Cell 2 	
LJ
















-^

-
V.
•$
Cell 3
•^tCPng-
i
J.
Cm
t









t >*


Cell 4
'
	





•^

; AFFLUENT
12m

-------
A settling pond with a two-day detention time is provided after the final
aerated pond.

     Summary

     V  =  28,396 m3

     A  =  13,180 m2

     t  =  15.0 d

     OP required for treatment (See Table 3-5)

     n  =  4


3.5  Controlled Discharge Ponds


No rational or empirical  design model exists specifically for the design
of  controlled   discharge   wastewater  ponds.   However,  rational  and
empirical  design models applied to  facultative pond design may  also  be
applied to the design  of controlled discharge ponds  provided  allowance
is  made  for the  required larger storage volumes.
result  from  the  long  storage  periods  relative
discharge periods.   Application of the  ideal  plug flow model developed
for  facultative ponds can  be applied to controlled  discharge ponds  if
hydraulic residence times of less than  120 days are considered.  A study
of  49 controlled  discharge  ponds in Michigan  indicated that discharge
periods very  from  less  than five  days  to  more  than  31  days,  and
residence times were 120 days or greater (30).
                                                     These larger volumes
                                                     to  the  very  short
The  following design and  operating information for controlled discharge
ponds were extracted  from a report entitled "Wastewater Treatment Ponds"
(15).  The unique features  of controlled discharge  ponds  are long-term
retention and  periodic,  controlled  discharge usually  once or  twice a
year.   Ponds  of  this type  have  operated "satisfactorily in the north-
central U.S. using the following design criteria:

     Overall organic  loading:  22-28 kg BOD,-/ha/d  (20-25  Ib
     BOD5/ac/d).                            °

     Liquid  depth:  not more  than  2 .m  (6  ft)  for the  first cell,
     not more  than 2.5 m  (8 ft)  for subsequent cells.

     Hydraulic detention:  At least 6 months  of storage above
     the 0.6-m (2-ft) liquid  level  (including  precipitation),  but
     not less  than the period of ice cover.

     Number  of cells:  At least  3  for reliability,  with piping
     flexibility  for  parallel  or series operation.
                                    129

-------
The design of the  controlled  discharge  pond must   include   an   analysis
showing that receiving stream water  quality  standards   will  be maintained
during  discharge  intervals,  and  that   the receiving watercourses   can
accommodate  the discharge  rate  from  the  pond.   The design must   also
include a recommended discharge schedule.

Selecting the  optimum day and hour  for  release  of the pond contents is
critical  to the success of this  method.  The  operation and maintenance
manual must include  instructions on  how to correlate pond discharge  with
effluent  and stream  quality.   The  pond contents  and stream   must  be
carefully examined,  before and during the release of the pond contents.

In  a  typical  program,  discharge  of effluents  follows   a  consistent
pattern for all ponds.  The following steps  are usually taken:

     1.  Isolate the cell to be discharged,  usually the final one  in the
         series, by  valving-off the  inlet line  from  the preceding cell.

     2.  Arrange to  analyze  samples for  BOD, suspended  solids,  volatile
         suspended   solids,  pH,  and  other parameters  which  may  be
         required  for a particular location.
     3.  Plan  to work  so  as  to  spend full
         discharge throughout the period.
time  on  control  of  the
     4.  Sample  contents of  the cell   to   be   discharged   for  dissolved
         oxygen, noting turbidity, color, and any  unusual conditions.

     5.  Note conditions in the stream  to receive  the  effluent.

     6.  Notify   the  state  regulatory agency  of    results   of   these
         observations and plans for discharge and  obtain  approval.

     7.  If discharge is  approved, commence  discharge,  and  continue  so
         long as  weather is favorable,  dissolved  oxygen  is  near or  above
         saturation values and turbidity is not excessive following the
        "prearranged discharge  flow  pattern among  the  cells.   Usually
         this consists of  drawing down  the  last two cells in  the series
         (if there are three or more)   to about  46 to  60  cm  (18  to 24 in)
         after isolation, interrupting  the   discharge  for a  week or more
         to divert  raw  waste  to a cell which  has  been  drawn down and
         resting the initial cell before its discharge.  When this  first
         cell is drawn  down  to about  60  cm  (24 in) depth, the   usual
         series  flow pattern,  without  discharge,  is   resumed.  During
         discharge  to the receiving waters,  samples  are taken   at  least
         three  times  each day  near the  discharge pipe  for   immediate
         dissolved oxygen  analysis.    Additional  testing may be required
         for suspended solids.

Experience with  these ponds is limited  to   northern states  with seasonal
and  climatic  influences on  algae growth.  The concept  will   be   quite
effective for BOD removal in  any  location.  The  process will also  work
                                    130

-------
with a more frequent  discharge  cycle than  semi -annually,  depending  on
receiving water  conditions and  requirements.   Operating   the  isolation
cell  on a fill-and-draw  batch basis is similar to the "phase  isolation"
technique discussed in Chapter 5.


     3.5.1  Design Example


In  areas of high evaporation rates  or high rainfall, the volume   of the
pond should be adjusted  to compensate for the water   loss   or   gain.   In
this  example,  it is assumed  that rainfall  is  equal  to  evaporation,
producing no net change  in volume.  This  example illustrates  the  design
of   a  controlled  discharge  pond  using  a  minimum  discharge   period
criterion.

Design Conditions:

     Minimum discharge period  = 30 d

     Q   = Design flow rate   = 1893 m /d  (0.5 mgd)

     C.  = influent BOD,-    = 150 mg/L
      0                0


                                                        "
     Ce  = effluent BODg    = 30 mg/L
     kp  = reaction rate for plug flow at 20°C = 0.1 day
      ^20
     T   = water temperature critical period of the year = 2°C

Requirements:   Size  a  controlled discharge  wastewater  pond system to
treat the wastewater and specify the following parameters:

     1)  Detention time, t

     2)  Volume, V

     3)  Surface area, A

     4)  Depth, d

     5)  Length, L

     6)  Width, W

Solution:  t = 365 d - minimum discharge period

             = 365 d - 30 d = 335 d

Discharge can occur when the effluent quality satisfies standards  or the
receiving  stream  flow rate is adequate  to  receive the effluent.  More
frequent discharge periods  than once a  year can be employed,  but  it is


                                   131

-------
necessary  to  evaluate  the  performance   of   the   system   for    shorter
hydraulic residence times.  The methods used to design   facultative  ponds
can be used to estimate the performance of  a controlled  discharge  pond.

Raw  wastewater is not added to the pond being  emptied.  Raw  wastewater
inlets and  effluent  withdrawal ports are  provided   in  each  cell of  the
system.  The cells  are  connected in  series to facilitate  operation  and
flexibility.  Three cells are used in this  example.

An  effective depth (d1) of 1.5  m (5 ft) and a total depth   (d) of  2  m
(6.6 ft) is  used.  This depth  allows for  adequate  light  penetration to
sustain  photosynthetic   oxygen   production,   providing    an    aerobic
environment through much of the pond contents.  The   aerobic  environment
enhances treatment  and  reduces odor problems.   Also,  to   control  odors
during discharge  periods, the pond is emptied  to  a minimum depth of  0.5
m (1.5  ft).   Additional volume must  be provided to compensate for this
minimum withdrawal depth.
     A/cell  =
 effective volume    _  Q x t   1893 m /d x 335 d

n x effective depth     3 x d1     3 x 1;5 m
     = 140,900 nT  (35 ac)           •        j      .

This  area is used to  calculate  the total   volume   for  the   pond   total
depth:

     d = 1.5 m + 0.5 m    = 2 m (6.6 ft)

     V/cell = (A/cell)(d) = (140,900 m2)(2 m)

                          = 281,800 m3  (74.4  x 106 gal)

Significant volumes  of  wastewater may be lost  through seepage   if  the
pond  bottom  is   not  scaled.   For   this   example   seepage   rates   are
considered minimal.

The length  to width ratio of  the cells in a controlled   discharge pond
has  less affect on the  performance of the   system than  in flow  through
systems.   Dimensions  for   the  cells are   selected   to  avoid   short
circuiting during discharge or  inter-basin transfer.  A  length to width
ratio of 2:1 was selected for this example.
Dimensions of Ponds
The dimensions  of  each  pond with side slopes of  4:1   and  a   length  to
width ratio  of  2:1 can be calculated using  the formula   first  presented
in Section 3.2.
                                   132

-------
     V =

where,
(L x W)  + (L - 2sd)(W - 2sd) + 4 (L - sd)(W - sd)l|
     Vj = volume of pond fl - 281,800 m3

     L  = length of pond at water  surface, m

     W  = width of pond at water surface, m

     s  = horizontal slope factor,  i.e., 4:1  slope,  s  =  4

     d  = depth of pond = 2 m (6.6  ft)

     (281,800) | = (L x -£•) + (L -  2x4x2) (jj- -  2x4x2)


          + 4 (L - 4x2)(?r - 4x2)


     3L3 - 721 + 512 = 845,400

          L2 - 24L = 281,630

Solve the quadratic equation by completing the  square.

     L2 - 24L + 144 = 281,630 + 144

        (L-12)2 » 281,774

            'L-12 = 530.8

                 L = 542.8 m (1780  ft)

                     W = 542.8/2 =  271.4 m (890 ft)

A freeboard  of 0.6 m (2 ft) should be  provided.    The dimensions of each
pond  at  the top of the inside of  the  dike  will  be 547.6  m x  276.2 m.
The three  ponds shall  be  interconnected  by   piping  for  parallel and
series operation.


Effluent Quality Prediction


In a pond  with  a  hydraulic  residence time  of  over 300  days,  it  is
obvious that an effluent with a  BOD,-   concentration of  less than 30 mg/1
can be achieved.  However, if  it  beBomes necessary to discharge at other
intervals of time,  some  method   of estimating the  effluent quality is
needed.  Controlled  discharge ponds are basically a  facultative pond,
and the effluent  quality can be predicted using the plug flow model used
to design a facultative pond in Section 3.2.

                                    133

-------
     co                                    !
where,
     Cg  = effluent BODg concentration,  mg/1
     C   = influent BODj- concentration,  mg/1
      O                0
     e   = base of natural  logarithms, 2.7183
     k   = plug flow first  order  reaction  rate,  day"
     t   = hydraulic residence  time,  d
                    T -20
     k   = k   (1.09) w
      Pt    P20
     k   = reaction rate at minimum operating water temperature,  day~
      pt
     kn  - reaction rate at 20°C  = 0.1 day"
      P20                                                               ;
     TW  = minimum operating water temperature,  °C.
Assume  that   it becomes necessary  to   discharge  from  the  ponds  after  a
mean  hydraulic  residence  time   of 100  days   when   the  mean   water
temperature  during the  period was 2°C.  What would  be the concentration
of BODg in the effluent?
     k   » 0.1 (1.09)2"20
      Pt
     k   = 0.021 day"1
      pt
     Ce     -0.021(100)
           e
     Ce  = 18 mg/1
                                           i
The BODg concentration of 18  mg/1  in  the   effluent  will   easily  satisfy
the staHdard  of 30 mg/1.   Suspended  solids concentrations will  have  to
be  monitored on site to ensure that the standards for  discharge are met.
The guidelines  presented  at  the  beginning  of this   example  must   be
followed in operating the controlled discharge pond system.
                                   134

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     Summary

     V  = 845,400 m3

     A  = (542.8)(271.4)(3) = 441,950 m2

     t  = 335 d


3.6  Complete Retention Ponds
In areas  of  the  U.S. where  the moisture  deficit,  evaporation  minus
rainfall,  exceeds  75   cm   (30  in)  annually,  a  complete   retention
wastewater pond may  prove to be  the most economical method  of  disposal.
Complete retention ponds must  be sized to provide  the  necessary surface
area  to  evaporate  the   total  annual   wastewater  volume    plus   the
precipitation  that  would  fall  on  the  pond.   The system  should   be
designed for the maximum wet year and  minimum evaporation year  of  record
if overflow  is not permissible under  any circumstances.  Less  stringent
design  standards may  be  appropriate  in  situations   where  occasional
overflow is  acceptable  or an  alternative  disposal  area  is   available
under emergency conditions.

Monthly evaporation and  precipitation  rates  must be known  to properly
size the  system.   Complete retention ponds  usually require large  land
areas, and  these areas are not productive once they have  been  committed
to this  type of system.  Land  for this-system must be  naturally flat or
be shaped  to provide  ponds  that are  uniform   in depth, and have large
surface areas.  The design  procedure for a complete retention wastewater
pond system is presented in the following example.


Design Conditions:

Table  3-6 presents data  from  NOAA  (31)  for estimating evaporation  and
precipitation in southern Arizona.   The air  temperature and  wind speed
data represent  mean  values over a 54- and 61-year period,  respectively.
The precipitation  data are the mean of the  five wettest   years over  a
60-year  period.  The pan evaporation data  represent the  year  with  the
lowest  evaporation  for  a  10-year  period.   These  values    generally
represent the worst case, thus providing for a conservative  design.

The  difference  between  the  surface  water  temperature   and  the   air
temperature is assumed to be  1°C.  The selection of this value can  have
a significant effect on  the evaporation losses   as  shown in Figure  3-7;
therefore, the value must be selected to reflect  local conditions.

Surface water temperature = T  = air temperature  (T ) minus  1°C.
                             0                     cl
                                   135

-------
     TQ - Ta = -1°C.

     Q = 950 m3/d (0.25 mgd)

Influent BOD& = 150 mg/1

Seepage = 0.80 mm/d  (0.2  in/wk)  (32).  Seepage  is   prohibited   in   some
areas.  State  agency wastewater facility standards may   require  the  pond
bottom be sealed with an impervious  liner, reducing seepage  to zero.

Elevation = 300 m (980 ft) above MSL.
Requirements:   Size  a  complete  retention  wastewater   pond  with    no
overflow for the given geographic  area.  Specify  the  following:          '.


     1   Are,  A	0  065 d/yr)	;	
             '      d-(Annual Precip.-Annual Evap.-Annual  Seepage)

     2.  Surface area, A

     3.  Depth, d

     4.  Length, L

     5.  Width, W

Solution:  The design procedure^consists of the following  steps:

     1.  Using  the data in Table  3-6 with Figure 3-6  (Elevation  = 305  m).
         and Figure  3-7, determine  the mean monthly  evaporation  from the
         pond.  The  calculation   of pond  evaporation  is   shown  on  the
         figures  by  dashed lines.  The  results are  presented in  Table
         3-7.                                                            ;

     2.  Using  the data presented in Tables 3-6  and   3-7, calculate  the
         area required  for  an  assumed  mean  depth  for  .one  year   of
         operation  under design   conditions.  The  mean   depth   (d)  may
         range from 0.1 to  1.5 m  (0.3  to  5.0 ft).   The  mean depth   is
         usually near 1 m (3 ft).

     3.  Use the A value determined  in step 2 to calculate  the   stage  of
         the  pond  at  the end of   each  month of operation  during  the
         design year.

     4.  Calculate   the  monthly    stage  of  the  pond   under    average
         conditions.   If  the pond  is designed  to  never   overflow, the
         average  yearly  evaporation  and seepage must exceed the inflow
         and precipitation entering  the pond.

     5.  Repeat steps  2  and  3   until  a  satisfactory   pond  depth   is
         obtained.
                                   136

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                                                      TABLE 3-6




                       CLIMATOLOGICAL DATA FOR CALCULATING POND EVAPORATION AND PRECIPITATION
CO
Month .
(Days in
Month )

January (31)
February (28)
March (31)
April (30)
May (31)
June (30)
July (31)
August (31)
September (30)
October (31)
November (30)
December (31)
TOTAL

Mean
Precipitation
mm/month
12.3
12.1
10.1
4.2
2.9
• 2.2
6.8
15.9
10.6
7.8
8.3
14.6
107.8


Air Temp.
°C
12.4
14.9
17.7
21.0
24.6
29.3
32.8
32.4
29.1
22.6
16.8
12.9



Wind Speed
kts.,daya
140.4
148.7
154.2
157.0
154.2
134.9
- 140.4
134.9
115.6
110.1
126.6
143.2


Minimum Ten-Year
Pan Evaporation
mm/month mm/ day
87.5 2.82
130.5 4.66
198.2 6.39
238.1 7.94
332.0 10.71
374.4 12.48
416.0 13.42
347.8 11.22
278.5 9.28
210.4 6.82
137.4 4.58
95.2 3.07
2847.0

Mean Ten-Year
Pan Evaporation
mm/month
105.0
177.5
220.0
271.4
.365.2
423.1
449.3
389.5
323.1
219.9
163.5
131.4
3238.9
           Kts = knots = total of nautical miles/hr of wind per day.

-------
                            FIGURE 3-6

PORTION  OF ADVECTED ENERGY  (INTO A CLASS A PAN)  UTILIZED  FOR
               EVAPORATION IN METRIC  UNITS (33)
    0,9 -ii
                                   ELEVATION = 3048 M. ABOVE MSL
         ELEVATION = 305 M. ABOVE  MSL I
    0,2
    0,1
                   2O     3O       0     10    20
                     PAN WATER TEMPERATURE, *C
                               138

-------
                           FIGURE 3-7

SHALLOW LAKE EVAPORATION AS A FUNCTION OF CLASS A PAN EVAPORATION
 AND HEAT TRANSFER THROUGH THE PAN IN METRIC UNITS PER DAY (33)
                               139

-------
                                Table 3-7
                    CALCULATED POND  EVAPORATION  DATA
 Month
January
February
March
April
May
June
July
August
September
October
November
December
TOTAL
ap  (Fig. 3-6)
     0.58
     0.62
     0.64
     0.66
     0.71
     0.74
     0.77
     0.77
     0.73
     0.58
     0.62
     0.58
Pond Evaporation (Fig. 3-7)
 mm/daymm/month
  1.7
  3.0
  4.1
  5.2
  7.2
  8.4
  9.0
  7.4
  6.2
  4.4
  2.9
  1.8
As a starting  point, select   a  mean  depth  of  0.4  m
required surface area to evaporate the wastewater.
        53
        84
       127
       156
       223
       252
       279
       229
       186
       136
        87
        56
      1568

to estimate  the
     A =
                (946 nr/d)(365 d/yr)
          0.4 - (0.1078 - 1.868 - 0.277)
       =  142,259 nr (35 ac)
Use A = 142,300  m  (35 ac) to calculate the  stage of  the  pond  at  the  end
of each month of operation.  Table 3-8  contains  a summary of the  results
of this procedure for the design  year of operation  assuming  the  pond is
empty at the beginning of the year.

An examination of  the pond stage  results  in  Table  3-8  shows  that   the
maximum depth of water in the  pond  during the design year (conservative
design data) would be 0.60 m (2  ft) plus  the depth at  the beginning of
the design year.  The  pond  stage  under average conditions is  shown in
Table 3-9.  Average  evaporation  and  seepage are  within 5  percent   of
inflow  and precipitation.   Assuming  that   several average  years would
occur in sequence, there  would  be  a small  accumulation  of water in  the
pond.   Because  of  the  imprecise  methods  available  to predict   the
sequence of occurrence of the  design  year,,  maximum, and average years,
the pond surface area  of 142,300 m  is large  enough  to prevent overflow
of the pond.

The depth  of  complete retention  ponds is   limited only   by groundwater
conditions,  economics, and evaporation  rates.   Generally maximum depths
range from 1.0 to 3 m (3 to 10 ft) with a freeboard of 0.6 m (2  ft).
                                   140

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                                TABLE 3-8

            VOLUME AND STAGE OF POND AT MONTHLY INTERVALS FOR
                  DESIGN CONDITIONS AND A = 142,300 nT
    Month
(No. of Days
  in Month)
Starting Date 1

September (30)
October (31)
November (30)
December (31)
January (31)
February (28)
March (31)
April (30)
May (31)
June (30)
July (31)
August (31)
TOTAL

Starting Date 2

January (31)
February (28)
March (31)
April (30)
May (31)
June (30)
July (31)
August (31)
September (30)
October (31)
November (30)
December (31)
   Inflow +
Precipitation'

    (m3)
    29,888
    30,436
    29,561
    31,404
    31,076
    28,210
    30,763
    28,978
    29,739
    28,693
    30,294
    31,589
   360,631
    31,076
    28,210
    30,763
    28,978
    29,739
    28,693
    30,294
    31,589
    29,888
    30,436
    29,561
    31,404
Evaporation
+ Seepage

  (m3)
  29,712
  22,706
  15,624
  11,322
  10,895
  14,981
  21,425
  25,443
  35,086
  39,104
  43,055
  35,940
 305,293
  10,895
  14,981
  21,425
  25,443
  35,086
  39,104
  43,055
  35,940
  29,712
  22,706
  15,624
  11,322
Storage
Volume

 (m3)
    176
  7,906
 21,843
 41,925
 62,106
 75,335
 84,673
 88,208
 82,861
 72,450
 59,689
 55,338
 20,181
 33,410
 42,748
 46,283
 40,936
 30,525
 17,764
 13,413
 13,589
 21,319
 35,256
 55,338
Pond.
0.00
0.06
0.15
0.29
0.44
0.53
0.60
0.62
0.58
0.51
0.42
0.39
0.14
0.23
0.30
0.33
0.29
0.21
0.12
0.09
0.10
0.15
0.25
0.39
alnflow = Q(no. of days/month); precipitation = (monthly precipitation)
b(A).
 Seepage  =  0.00076 m/d(no.  of  days/month)(A);  evaporation =  (monthly
 evaporation)(A).
 Storage V = cumulative sum  of (inflow  + precipitation)  -  (evaporation
 .+ seepage).
 Pond stage = storage V/A.
                                   141

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                          TABLE 3-8  (continued)

    Month                    •.?>:.
 (No.  of Days      Inflow +          Evaporation        Storag
   in Month)    Precipitation        + Seepage          Volume
Starting Date 3
                     (m3)               (m3)              (m3)         (m)
December (31)       31,404             11,322            20,082       0.14
January (31)        31,076             10,895            40,263       0.28
February (28)       28,210             14,981            53,492       0.38
March (31)          30,763             21,425            62,830       0.44
April (30)          28,978             25,443            66,365       0.47
May (31)            29,739             35,086            61,018       0.43
June (30)           28,693             39,104            50,607       0.36
July (31)           30,294             43,055            37,846       0.27
August  (31)         31,589             35,940            33,495       0.24
September  (30)      29,888             29,712            33,671       0.24
October (31)        30,436             22,706            41,401       0.29
November (30)       29,561             15,624            55,338       0.39
alnflow = Q(no. of days/month); precipitation  =  (monthly  precipitation)
b(A).
 Seepage  = 0.00076 m/d(no. of  days/month)(A);   evaporation   =   (monthly
 evaporation)(A).
 Storage  V = cumulative sum of (inflow +   precipitation)   -  (evaporation
j+ seepage).
 Pond stage = storage V/A.


The  maximum  depth required  will  depend  upon   the   time  of year   that
filling  of  the  pond begins and the  initial depth  of water in  the  pond
when the design  year occurs.  It is impossible  to  predict  accurately the
water  stage  in the  pond; therefore, it  is necessary to   exercise   goo|d
judgment  based upon the  constraints at particular locations.   Estimates
beyond the average and  design  year conditions  can  be made  by  analyzing
historical  data  for  the  site,  but  this   still is no  guarantee of
accuracy.

The water depth  in  the pond  after one year  of operation   under design
conditions will  be  equal  to  the mean depth plus the depth of  water at
the beginning of the year.  During certain  months   of the year,  the depth
may  exceed  the  mean  depth when filling  of   the  pond occurs  at   the
beginning  of the wet  season (Table  3-8).    Three beginning dates   are
shown in Table 3-8 to illustrate the effects of  startup date.    Using the
above procedure, it  is possible for the design  engineer  to   estimate the
stage of the pond under as many conditions  as  considered  necessary.

A maximum depth of 1.2 m (4 ft) would  be  adequate  to avoid overflow  from
the pond  by providing storage for  five average  years and a design  year


                                   142

-------
in  sequence.   It  is unlikely  that  five  average years  of   evaporation
would  precede the design  year.  The pond L and W values   are calculated
from the A.  No  restrictions are   imposed   on  the length  to  width  ratio.
Also,  the   need  to  divide  the  pond  volume  to    enhance  hydraulic
characteristics is eliminated.  The most economical design consists  of  a
single  pond  provided  the  system  can  be   isolated   enough  to   avoid
complaints about odors when solids decompose on exposed  slopes.

     A = L x W

     L = W = A1/2 = (142,300 m2)1/2 = 377 m  (1,237 ft)
Summary


     1 pond   A = 142,300 m2 (35 ac);L = W = 377 m  (1,237  ft)

              V = 170,800 m3 (45 Mgal);d = 1.2 m (3.9  ft)

                                TABLE 3-9

            VOLUME AND STAGE OF POND AT MONTHLY  INTERVALS  FOR
                  AVERAGE CONDITIONS AND A = 142,300 nT
            Inflow +
Month    Precipitation
              «_
Average Year
September
October
November
December
January
February
March
April
May
June
July
August
TOTAL
 (nr)'

 29,888
 30,436
 29,561
 31,404
 31,076
 28,210
 30,763
 28,978
 29,739
 28,693
 30,294
 31,589
360,631
Evaporation
 + Seepage
   (m3)
   33,947
   23,480
   17,976
   14,351
   12,404
   19,284
   23,413
   28,551
   38,259
   43,766
   46,231
   39,851
  341,513
Storage
Vpljume
 (m3)
 -4,059
  6,956
 18,541
 35,594
 54,266
 63,192
 70,542
 70,969
 62,449
 47,376
 31,439
 23,177
Pond
j>ta£e
 (m)
(no accumu-
0.00 lation)
0.05
0.13
0.25
0.-38
0.44
0.48
0.50
0.44
0.33
0.22
0.16
3.7  Combined Systems
In  certain  situations   it   is   desirable   to   design   pond   systems  in
combinations,  i.e.,   an   aerated   pond   followed  by a   facultative or  a
tertiary pond.   Combinations  of  this   type   are designed  essentially the
                                    143

-------
same as the individual  ponds.   For  example,  the aerated pond would  be
designed  as  illustrated  in  Sections  3.3 or  3.4,  and the  predicted
effluent quality from the aerated pond would  be the  influent quality for
the  facultative pond.  The facultative pond  would   be designed as  shown
in  Section  3.2.   For more discussion  on  combined  pond  systems  see
References 20, 28, and 34.                                               ,


3.8  References
 1.  Recommended Standards for Sewage Works.,  A Report  of the  Committee
     of  Great  Lakes-Upper Mississippi  River  Board  of State   Sanitary
     Engineers. Health Education Services,  Inc.,  P.O. Box   7126, Albany^
     NY, 1978.

 2.  Design Criteria  for  Mechanical,  Electric  and  Fluid  System   and
     Component Reliability. EPA  430/99-74-001, NTIS  Report  No. PB   227
     558, U.S.  Environmental Protection  Agency, Office of  Water Program
     Operations, Washington, D.C., 1974.

 3.  Metcalf  and Eddy.  Wastewater  Engineering. McGraw-Hill, New  York,
     1979.

 4.  Al-Layla,  M.  A., S.  Ahma'd,  and E.  0. Middlebrooks.   Handbook   of
     Wastewater  Collection  and Treatment:   Principles  and  Practices.
     Garland STPM Press, New York, 1980.

 5.  Water Pollution  Control  Federation   and  American Society  of Civil
     Engineers.  Wastewater Treatment  Plant;  Design. MOP/8,  Washington,
     D.C., 1977.

 6.  Water  Pollution   Control  Federation.  Preliminary  Treatment   for
     Wastewater Facilities. MOP/OM-2, Washington, D.C., 1980.

 7.  Fritz,  0. 0., A. C. Middleton, and D. D. Meredith.  Dynamic Process
     Modeling     of     Wastewater    Stabilization    Ponds.     JWPCF,
     •51 (11): 2724-2743, 1979.

 8.  Gloyna  E.  F.  Facultative Waste  Stabilization  Pond   Design.   In:
     Ponds  as  a  Wastewater   Treatment   Alternative.  Water  Resources
     Symposium No. 9, University of Texas,  Austin, 1976.                 ;

 9.  Larson, T.  B.  A Dimensionless Design Equation  for Sewage  Lagoons.
     Dissertation, University of New Mexico, Albuquerque, 1974.

10.  Marais,  G.  V.  R.   Dynamic   Behavior  of  Oxidation  Ponds.   In:
     Proceedings  of Second  International  Symposium for.Waste  Treatment
     Lagoons, Kansas City, Missouri, June 23-25, 1970.

11.  McGarry,  M.  C., and  M.  B.  Pescod.   Stabilization   Pond  Design
     Criteria   for   Tropical   Asia.   In:    Proceedings   of   Second

                                    144

-------
     International Symposium  for Waste  Treatment  Lagoons, Kansas City,
     Missouri, June 23-25, 1970.
                                          - i

12.  Oswald, W. J., A. Meron,  and M. D. Zabat.  Designing Waste.Ponds to
     Meet   Water   Quality   Criteria.   In:   Proceedings   of   Second
     International Symposium  for Waste  Treatment Lagoons,  Kansas City,
     Missouri, June 23-25, 1970.

13.  Thirumurthi, D.  Design  Criteria  for  Waste  Stabilization  Ponds.
     JWPCF, 46(9)=2094-2106, 1974.

14.  Thirumurthi, D.   Design Principles  of  Waste  Stabilization Ponds.
     Journal  Sanitary   Engineering  Division,  ASCE,  95  (SA2:311-330,
     1969.

15.  Wastewater  Treatment  Ponds.  EPA 430/9-74/001, U.S.  Environmental
     Protection  Agency,  Office  of Water Program Opertions, Washington,
     D.C., 1975.

16.  Neel,  J.  K.,  J.  H.  McDermott, and C.  A.  Monday.  Experimental
     Lagooning of Raw Sewage. JWPCF, 33(6):603-641, 1961.

17.,  Middlebrooks, E. J.,  C.  H.  Middlebrooks, J.  H.  Reynolds, 6.  Z.
     Watters, S. C.  Reed,  and D.  B.  George.  Wastewater Stabilization
     Lagoon Design, Performance,  and  Upgrading.   Macmillan  Publishing
     Co., Inc., New York, 1982.

18.  Wehner,  J.  F.  and  R.  H.  Wilhelm.  Boundary Conditions of  Flow
     Reactor.  Chem. Eng. Sc., 6:89-93, 1956.

19.  Gloyna,  E.  F.,  and  L.  F.  Tischler.  Waste  Stabilization  Pond
     Systems.   In:     Performance   and   Upgrading    of    Wastewater
     Stabilization Ponds.  EPA 600/9-79-011,  NTIS  Report No. PB 297504,
     U.S.   Environmental  Protection  Agency,   Municipal  Environmental
     Research Laboratory, Cincinnati, Ohio, 1979.

20.  Gloyna, E.  F.  Waste Stabilization Ponds.  Monograph Series No. 60.
     World  Health Organization, Geneva, Switzerland, 1971.

21.  Marais, C. V. R., and  V. A. Shaw.  A Rational Theory for the Design
     of  Sewage  Stabilization  Ponds  in   Central  and   South  Africa.
     Transactions, South  Africa  Institute  of  Civil Engineers,  3:205,
     1961.

22.  Mara,  D.  D.   Sewage  Treatment in Hot  Climates.   John  Wiley  &
     Sons, Inc., New York, 1976.

23.  Mara, D. D.  Discussion.  Water Research, 9:595, 1975.

24.  Benefield, L.  D., and C. W. Randall.  Biological Process Design for
     Wastewater Treatment.  Prentice-Hall, Inc., Englewood Cliffs,  N.J.,
     1980.


                                   145

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25.  Mancini, 0.  L., and E. L. Barnhart.  Industrial Waste Treatment  in
     Aerated   Lagoons.    In:    Ponds   as   a   Wastewater   Treatment
     Alternative.  Water Resources  Symposium No. 9, University of Texas,
     Austin, 1976.

26.  Malina, 0.  F., Jr.,  R.  Kayser,  W.  W.  Eckenfelder,  Jr.,  E. F.
     Gloyna,  and W. R. Drynan.  Design Guides  for Biological Wastewater
     Treatment Processes.  Report CRWR-76.  Center for Research   in Water
     Resources, University of Texas, Austin, 1972.

27.  Aqua-Aerobic Systems, Inc.  Aqua  Jet Aerators.  Rockford, Illinois,
     1981.

28.  Boulier,  G.   A.,   and  T.  J.  Atchison.   Practical  Design  and
     Application  of  the  Aerated-Facultative  Lagoon  Process.    Hinde
     Engineering Company, Highland Park, Illinois, 1975.

29.  Reid, L. D., Jr.  Design and Operation for  Aerated  Lagoons in  thei
     Artie and Subartic.  Report 120.  U.S.  Public Health Service, Artie
     Health Research Center, College, Alaska, 1970.

30.  Pierce, D. M.   Performance  of Raw Waste Stabilization  Lagoons  in
     Michigan  with   Long   Period   Storage   Before   Discharge.   In:
     Upgrading  Wastewater  Stabilization  Ponds  to  Meet New  Discharge
     Standards,  PRWG151,  Utah Water  Research  Laboratory,  Utah  Statfr
     University, Logan, 1974.                                            :

31.  NOAA. Climatic Survey  of  the United States. National Oceanographic
     and   Atmospheric  Administration,  U.S.  Department  of   Commerce,
     National  Climate  Center,   Federal  Building,   Asheville,   North
     Carolina, 1981.

32.  Middlebrooks,  E.  J., C.  D.  Perman, and I.  S. Dunn.   Wastewater
     Stabilization  Pond  Linings.  Special  Report  78-28,  Cold Regions
     Research  and  Engineering  Laboratory,  Army  Corps  of  Engineers,
     Hanover, New Hampshire, 1978.
                                                                         i
33.  U.S.  National  Weather  Service.   U.S.  Department   of  Commerce,
     National   Climate  Center,  Federal   Building,   Asheville,  North
     Carolina, 1981.

34.  Rich, L. G.  Design Approach to Dual-Power Aerated  Lagoons. Journal
     Environmental Engineering Division, ASCE, 108 (EE3):532, 1982.
                                    146

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                                  CHAPTER 4

                      PHYSICAL DESIGN AND CONSTRUCTION
4.1  Introduction


Regardless of the care taken to evaluate coefficients and apply  biological  or
kinetic models,  if  sufficient consideration is  not  given to optimization  of
the pond layout and construction,  the  actual  efficiency may be  far less  than
the calculated efficiency.   The physical design  of a  wastewater  pond is  as
important  as the  biological  and  kinetic  design.   The  biological   factors
affecting wastewater pond performance  are  primarily employed to estimate  the
required hydraulic residence  time  to achieve  a specified efficiency.   Physi-
cal factors,  such  as length  to  width ratio,  determine the actual treatment
efficiency achieved.

Length  to  width  ratios  are  determined according  to the  design model used.
Complete mix ponds should have a length to width ratio  near  1:1, whereas  plug
flow ponds  require length  to width ratios of  3:1  or greater.   The danger  of
groundwater  contamination  may  impose  seepage  restrictions,   necessitating
lining  or  sealing  the  pond.    Reuse of the pond  effluent in dry areas where
all water  losses are  to be  avoided may  also dictate the use of  linings.
Layout  and construction criteria should be established  to reduce dike erosion
from wave  action, weather7  rodent attack,  etc.  Transfer structure placement
and  size  affect  flow  patterns within  the  pond and  determine  operational
capabilities  in   controlling  the  water  level  and  discharge  rate.  These
important  physical design  considerations are  discussed in  the  sections  that
follow.


4.2  Dike Construction


Dike stability is most often affected by erosion  caused by wind-driven  wave
action  or  rain and  rain-induced weathering.   Dikes  may also be destroyed  by
burrowing  rodents.  A  good  design will anticipate these problems and provide
a  system which can,  through cost-effective operation  and  maintenance,  keep
all three under control.


     4.2.1  Wave Protection


Erosion  protection  should  be provided on  all  slopes;  however,  if winds  are
predominantly from one direction, protection  should be emphasized for those
areas  that  receive  the  full   force of  the   wind-driven  waves.   Protection


                                       147

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should  always extend  from at  least 0.3 m  (II   ft)  below  the  minimum water
surface  to  at least 0.3 m  (1  ft)  above  the  maximum water surface  (1).   Wave
height is a function  of wind  velocity and fetch (the distance over which  the
wind  acts  on  the  water).   The  size of  riprap  depends on  the  fetch  length
(2).  Riprap varies from river run rocks  that are 15-20 cm  (6-8  in) to  quarry
boulders that  are  7-14 kg  (15-30  Ib).   Uniformly  graded river  run material,
when  used  for riprap,  can  be quite  unstable.   River  run  rocks,   if   not
properly mixed with smaller material  and  carefully placed, can be  loosened by
wave  action  and   caused to  slip  down   the  steeper  sloped  dikes.    Broken
concrete pavement  can often be used  for  riprap  but  can make mechanical  weed
control very difficult.

Asphalt,  concrete, fabric,  and  low  grasses  can  also be  used  to  provide
protection  from wave  action.   When  riprap  is used  for wave protection,   the
designer must  take  into consideration its effect on weed and rodent  control,
and routine dike maintenance.


     4.2.2  Weather Protection                                              l


Dike  slopes must  be  protected  from weather erosion  as  much   as  from  wave
erosion  in  many areas  of  the  country.   The most common method  of weather
erosion protection when  large dike areas  are involved uses grass.   Because  of
large variations in depth  encountered in total  containment ponds, they often
have  large  sloped  dike areas  which  cannot  be  protected  in  a  more  cost-
effective way.   Ponds  which  have only  minimum freeboard and  have  constant
water depth are often  protected more cost  effectively  when  the  riprap  is
carried right  to the  top of  the  slope and serves for  both  wave and weather
protection.

In some  cases  climate and  soil  conditions  are   suitable  for completely bare
dike  slopes without  major  weather erosion  problems.   Figure 4-1  shows   the
erosion effects on  the bare slopes of a stabilization pond.

Weather erosion, unlike wave erosion, can  also affect the top and  outside
slopes of  the pond  diking sstem.   The   designer  should  make sure  that   the
all-weather road system for the  top of  the  dike  is of  sufficient width  to
allow traffic to pass  over every part of  the surface.  Too narrow a road will
result in ruts that can  create  runoff erosion problems  in  areas  of high rain
intensity.    Final   grading  should  be  specified  to   minimize  rutting   and
frequent maintenance and control surface  runoff  erosion.

It is also  necessary  to  protect the  exterior  surface of dikes.   A thin layer
of gravel may  be  used;  placement of topsoil and  seeding with  grass may  be
less  expensive initially   but  grass  requires   periodic   cutting.    In  some
locations sheep can be  used to  keep  exterior grass slopes maintained.  Other
native   groundcover  plantings may  also   be  used.   Local  highway   department
experience  on  erosion   control  for  cut-and-fill   slopes  can   be a guide.
                                      148

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                                 FIGURE 4-1

                           ERODED DIKE SLOPES ON A
                    RAW WASTEWATER POND IN A DRY CLIMATE
     4.2.3  Rodent Protection
If a stabilization pond is  located  in  an area that supports  an  exceptionally
high  population of  burrowing  animals,  such  as muskrats  and  nutria,  good
design can control this  threat of dike  stability.   Broken  concrete or  other
riprap that  does  not completely  cover the dike  soil  can become  a home  for
burrowing rodents.  Riprap design and  placement-should be aimed  toward  limit-
ing  the  creation  of voids  which  allow rodents  to  burrow  near  the  water
surface.

Varying pond  water depth can  discourage muskrat  infestation (3).  Muskrats
prefer a partially submerged  tunnel,  so design  provisions  to vary the  water
level over a  several-week  period will  discourage them from burrowing in  the
dike.  Such provisions will often add  to the  expense of riprap  placement  for
wave protection but can greatly reduce  operation  and maintenance  expenses.
     4.2.4  Seepage
Dikes should be designed and constructed to minimize  seepage.   Vegetation  and
porous soils should  be  removed and the embankment  should be well  compacted.

                                      149

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Use  of  conventional   construction  equipment  is  usually  suitable  for  this
purpose.

Seepage  collars  should be provided around any pipes penetrating  the  dike  (4)
(5).   The  seepage collars should extend  a minimum of  0.6 m (2 ft)  from  the
pipe.   Proper installation of  transfer  pipes can be  assured by building  up
the dike at least 0.6 m  (2 ft)  above  the  pipe elevation, digging  a  trench  for
the  pipe  and seepage  collar,  backfilling   the  trench,  and compacting  the
backfill.                                                                   ;

In some  circumstances  it may  be necessary to control seepage and ensure bank
stability  at  the exterior toe.   A  filter blanket material  can  be used  (6).
Another  method  of  preventing  seepage  where  embankment  material  cannot  be
adequately compacted  is  placement  of an  impervious  core  in  the levee with
imported material.


4.3  Pond Sealing


     4.3.1  Introduction


The  need  for a well-sealed  stabilization  pond has  impacted  modern pond
design, construction, and maintenance.   The  primary motive  for sealing ponds
is to  prevent seepage.   Seepage effects treatment capabilities  by  causing
fluctuation  in  the water  depth  and  can cause pollution  of  groundwater.
Although many types of pond sealers exist, they can be  classified into one  of
three  major  categories:   (1)  synthetic  and  rubber  liners,  (2)  earthen and
cement liners, and  (3)  natural  and chemical  treatment sealers.  Within each
category also exists a wide variety of  application characteristics.   Choosing
the appropriate lining for a specific site is a critical issue in pond  design
and seepage control.   Detailed  information  is available  from manufacturers,
and in other publications (4)(6).                                           ;


     4.3.2  Seepage Rates                                                   ;

                                                                            i
Stander et al. (7) presented a  summary of information (Table  4-1) on  measured
seepage rates in wastewater stabilization ponds.   Seepage is  a function of  so
many variables that it is impossible  to anticipate or predict rates even with
extensive  soils  test.   The  importance  of   controlling  seepage  to  protect
groundwater dictates that careful  evaluations be conducted  before construc-
tion of ponds to  determine the need for linings and the  acceptable types.

The Minnesota  Pollution  Control  Agency  (8)   initiated  an  intensive  study  to
evaluate  the   effects   of stabilization  pond  seepage from five  municipal
systems.
                                      150

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                                                                   TABLE 4-1

                                             REPORTED SEEPAGE  RATES  FROM POND  SYSTEMS (7)a
en



Location

Mojave, CA

Kearney, NBD
Filer City, MI

Pretoria, SAC

Windhoek, SWAd
Pond No. 5
Pond No. 6
Pond No. 7
Pond No. 8
Pond No. 9





Geology of
Pond Base

Desert soil
(sandy soil)
Sand and gravel
Sandy soil

Clay loam and
shale

Mica and schist
Mica and schist
Mica
Mica and schist
Mica and schist
with side wall
seepage to
river


Initial


Seepage
Rate
cm/d
22.4

14.0
—

__


0.41
0.43
0.04
0.15
0.58



m3/m2/d
0.19

0.12
—

0.13


0.003
0.003
0.0003
0.0013
0.005





Hydraulic
Load
n,3/m2/d
0.30

0.13
—

0.05


0.73
1.11
0.67
0.67
0.43



Seepage
Rate as % of
Hydraulic
Load

63

90
__

N/A


0.45
0.32
0.04
0.19
0.12





Settling-in Eventual Seepage Hydraulic
Period Rate Load
cm/d m3/m2/d m3/m2/d
9 mo 0.9 0.007 0.36

1 yr 1.5 0.013 0.04
Average over 0.9 0.007 0.009
5 yr
+ 1 yr 0.8 0.006 0.05


A —— — — — —
e
e
e
e



Seepage
Rate as % of
Hydraulic
Load

2

29
84

13


—
—
—
—
—



       aCourtesy of Ann Arbor Science Publishers, Inc., Ann  Arbor, MI.
       Evaporation and rainfall effects apparently not corrected for.  Seepage losses also influenced at times by a high water table.
       cConstructed in sandy soil for the express purpose of seeping away Paper Mill NSSC liquor.
       ^Constructed for the express purpose  of water reclamation.
       eSettling-in period is nine days after all ponds are  in full operation.

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The  five  communities  were  selected  for  study on  the  basis  of  geologic
setting,  age of  the system,  and past operating  history of  the pond.   The
selected  ponds  were  representative  of the  major geomorphic  regions in  the
state, and the age of the systems ranged from 3 to 17 years.                ;.

Estimates of seepage were calculated by two  independent methods for each  of
the  five  pond  systems.   Water  balances  were  calculated  by  taking   the
difference between  the  recorded  inflows  and outflows,  and  pond seepage  Was
determined by conducting  in-place  field  permeability  tests  of  the  bottom
soils at each location.  Good correlation  was obtained with both  techniques.
                                                                           i
Field  permeability   tests  indicated  that  the   additional  sealing  from   the
sludge blanket  was   insignificant  in locations   where  impermeable soils were
used in  the  construction process.   In  the case of more permeable soils, ;it
appeared that the sludge blanket reduced th£  permeability  of the  bottom soils
from  an  initial  level  of  10"^  or  10~5  cm/sec   to  the  order  of  10~6
cm/sec.  At all  five systems evaluated, the stabilization  pond was  in contact
with the  local  groundwater  table.  Local  groundwater fluctuations had a sig-
nificant impact on  seepage  rates.    Reduced groundwater gradient resulted  in
a reduction  of  seepage losses at  three of the  sites.   Contact with ground-
water possibly explains the reduction in seepage rates  in many ponds; in  the
past this reduction  in  seepage rates has  been attributed totally to  a  sludge
buildup.   In an area underlain by  permeable material where little  groundwater
mounding occurs, there  is  probably little influence  from  the  water  table on
seepage rates.   The buildup of  sludge  on  the   bottom  of a pond  appears to
improve the  quality of the seepage  water leaving the  pond.  Sludge accumu-
lation apparently increases the cation exchange  capacity of the bottom of  the
pond.

Groundwater  samples  obtained  from monitoring wells  did not  show any appre-
ciable  increases  in  nitrogen,   phosphorus,  or  fecal   coliform  over   the
background levels after 17  years  of operation.   The seepage  from the ponds
did  show  an  increase in soluble  salts  as great as  20  times over  background
levels.  Concentrations of 25  mg/1  to 527 mg/1  of chloride  were.observed.

A comparison  of observed seepage rates for various types of liner material is
presented in Table 4-2  (4).  If  an impermeable  liner is required, it appears
that one of the  synthetic materials must be used.       .   .                !


     4.3.3  Natural  and Chemical  Treatment  Sealing


The  most  interesting and  complex techniques  of pond  sealing,  either sepa-
rately or in combination,  are natural  pond  sealing  and  chemical treatment
sealing (5)(9).

Natural sealing of ponds has been  found to occur from three mechanisms:   (1)
physical  clogging of soil pores  by  settled solids,  (2)  chemical  clogging of
soil pores by ionic  exchange,  and (3) biological and organic clogging caused
                                      152

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                                  TABLE 4-2

                   SEEPAGE RATES FOR VARIOUS LINERS9 (4)b


                                                           Minimum Expected
                                                           Seepage Rate  at
                                                          6 m of Water Depth
Liner Material                          Thickness         After 1  Yr of Service
                                          cm                     cm/d
Open sand and gravel
Loose earth
Loose earth plus chemical treatment*
Loose earth plus bentonite*
Earth in cut
Soil cement (continuously wetted)
Gunite
Asphalt concrete
Unreinforced concrete
Compacted earth
Exposed prefabricated asphalt panels
Exposed synthetic membranes





10.2
3.8
10.2
10.2
91
1.3
0.11
244
122
30.5
25.4
30.5
10.2
7.6
3.8
3.8
0.76
0.08
0.003
  The data  are based  on actual  installation experience.   The  chemical and
  bentonite (*) treatments  depend on pretreatment  seepage  rates,  and in the
 btable loose earth values are assumed.
  Courtesy of John Wiley & Sons, Inc.,  New York,  NY.


by microbial growth at the  pond lining.   The dominant mechanism of the  three
depends on  the characteristics of  the  wastewater being  treated.   Chemical
treatment changes the nature of the bottom soil  to ensure sealing.

Infiltration characteristics  of anaerobic ponds were  studied  in New  Zealand
(10).   Certain  soil  additives were  employed (bentonite,  sodium carbonate,
sodium triphosphate) in  12  pilot ponds with  varying  water depth, soil  type,
and compacted bottom soil thickness.   It was found that chemical  sealing was
effective for  soils with  a  minimum  clay content  of 8  percent and  a silt
content of 10 percent.  Effectiveness increased with clay and silt  content.

Four different soil columns were placed at the bottom  of an  animal wastewater
pond to study physical  and  chemical  properties  of  soil  and sealing of  ponds
(11).  It was discovered that the initial sealing which  occurred at the  top  5
cm (2 in) of the  soil columns was  caused by  the trapping of suspended matter
in the  soil pores.   This was followed by  a  secondary mechanism of microbial
growth that completely sealed off the soil from water  movement.
                                      153

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A similar study performed in Arizona  (12) also  found  this  double mechanism of
physical  and biological  sealing.  Physical sealing of the pond was  enhanced
by  the  use  of an organic polymer united  with bentonite clay.  This  additive
could have  been applied with  the pond full  or empty,  although  it was more
effective when the pond was empty.

An  experiment was  performed in South Dakota  (13) in  an  effort to relate the
sodium adsorption ratio (SAR) of the in situ  soil to  the sealing mechanism of
stabilization ponds.  No definite quantitative  conclusions were formed.  The
general   observation  was made  that  the  equilibrium  permeability  ratio de-
creases by a factor of 10 as SAR varies from  10 to  80.  For 7 out of 10 soil
samples, the  following were concluded:   (1)  SAR did affect permeability of
soils studied; (2) as the SAR  increased,  the  probability that the pond would
seal  naturally  also  increased;   and (3)  soils with higher  liquid limits3
would probably be less affected by the SAR.                                 ,

Polymeric sealants  have been  used  to  seal   both  filled  and  unfilled ponds
(14).  Unfilled ponds have  been  sealed  by admixing a blend of bentonite and
the polymer directly into the  soil lining.  Filled  ponds have been sealed by
spraying  the  fluid   surface  with  alternate  slurries  of  the polymer  and
bentonite.   It  has been recommended  that the  spraying  take  place  in three
subsequent  layers:   (1)   polymer,   (2)   bentonite,   and  (3)   polymer.   The
efficiency of the sealant has been found  to be significantly affected by the
characteristics of the  impounded water.  Most  importantly, calcium  ions  in
the water exchange with sodium ions  in the bentonite  and cause  failure of the
compacted bentonite linings.

Davis et al.  (15)  found  that for liquid  dairy  waste  the biological clogging
mechanism predominated.  In a  San Diego  County study site  located  on sandy
loam, the  infiltration  rate of  a virgin pond  was  measured.   A  clean water
infiltration rate  for  the  pond was  122 cm/d  (48 in/d).   After two  weeks  of
manure water addition, infiltration  averaged  5,,8 cm/d (2.3 in/d);  after four
months,  0.5 cm/d (0.2 in/d).

A study  performed in  southern  California  (Hi)  indicated  similar  results.
After waste  material  was  placed in  the  unlined pond  in  an  alluvial  silty
soil, the seepage rate was   reduced.   The initial 11.2 cm/d  (4.4 in/d) seepage
rate dropped to  0.56  cm/d   (0.22  in/d)  after  three months, and to  0.30 cm/d
(0.12 in/d)  after six  months.


     4.3.4  Design and Construction Practice


         4.3.4.1   Lining Materials                                           i
                                                                            t

Presentation of recommended  pond sealing  design and  construction  procedures
is  divided  into  two  categories:   (1)  bentonite,   asphalt,  and soil  cement
  The liquid limit  is  defined as the water  content of a soil  (expressed  in
  percent dry weight) having  a  consistency such  that two sections of  a soil
  cake,  placed in a  cup  and separated by a  groove, barely touch but  do  not
  flow together under the impact of several sharp blows.

                                      154

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liners, and (2) thin membrane  liners.   This division was selected because of
the  major differences  between the  application  techniques.   There  is some
similarity between the application of asphalt panels and the elastomer  liners
and of necessity  there  will  be some repetition in  these two discussions.   A
partial listing of the trade names and  sources  of common lining materials is
presented in Tables 4-3 and 4-4.

Regardless of the type of material selected as  a  liner there are many  common
design, specification,  and  construction practices.   A summary  of the  common
effective design  practices  in  cut-and-fill  reservoirs  is given in Table 4-5.
Most of these practices are commonsense items and would appear to not require
mentioning.  Unfortunately, experience  has  shown  these items  to  be the most
commonly ignored.


            a.   Bentonite,  Asphalt, and  Soil Cement


The application of bentonite,  asphalt, and soil  cement as lining materials
for reservoirs and  wastewater  ponds  has  a  long  history  (4).   The following
summary  includes   consideration  of  the  method  of  using  the  materials,
resultant  costs,  evaluations  of  durability,  and effectiveness  in limiting
seepage.   The  cost analysis is  somewhat  arbitrary, since  this  cost depends
primarily on the availability of the materials.   A summary  of state standards
developed or being developed  to  control  the application  of these  types  of
materials is presented elsewhere (6).

Bentonite is a  sodium-type  montmorillonite  clay,  and  exhibits  a  high  degree
of  swelling,  imperviousness,  and low  stability  in  the presence  of  water.
Different ways  in  which bentonite may be used  to line ponds  are listed below.

     1.  A suspension of bentonite  in  water  (with  a bentonite concentration
         approximately 0.5  percent  of   the  water  weight) is placed over the
         area to  be lined,  and the bentonite  settles  to  the  soil  surface
         forming a thin blanket.

     2.  The same procedure as (1), except  frequent harrowing  of the surface
         produces   a  uniform soil  bentonite  mixture on the  surface of the
         soil.     The   amount  of  bentonite  used   in  this   procedure  is
         approximately 4.5  kg/mz (1 lb/ft2)  of soil.

     3.  A gravel  bed approximately 15  cm (6  in)  deep  is  first prepared and
         the bentonite  application performed  as in  (1).  The  bentonite will
         settle through the gravel layer and seal  the void spaces.

     4.  Bentonite is spread as a membrane 2.5  to 5  cm  (1 to  2 in) thick and
         covered with a 20 to  30  cm (8  to 12  in)  blanket of earth and  gravel
         to protect  the membrane.  A  mixture  of earth and  gravel  is more
         satisfactory than  soil  alone,  because of  the  stability  factor and
         resistance to erosion.
                                     155

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Trade Name

Aqua Sav


Armor last


Armorshell


Armortlte


Arrowhead


Biestate Liner


Careymat


CPE (resin)


Cover!ight


Driliner


EPDM (resin)


Flexseal


Geon (resin)


Griffolyn 45


Griffolyn E
                 TABLE 4-3

TRADE NAMES OF COMMON LINING

   Product Description

   Butyl rubber
   Reinforced neoprene
     and Hypalon

   PVC-nylon laminates
   PVC coated fabrics
   Bentonite
   Biologically stable PVC
   Prefabricated asphalt
     panels

   Chlorinated PE resin
   Reinforced butyl  and
     Hypalon

   Butyl  rubber
   Ethylene propylene
     diene monomer resins

   Hypalon and reinforced
     Hypalon

   PVC resin
   Reinforced Hypalon
   Reinforced PVC
MATERIALS (4)a

     Manufacturer

   Plymouth Rubber
   Canton, MA

   Cooley, Inc.
   Pawtucket, RI

   Cooley, Inc.
   Pawtucket, RI

   Cooley, Inc.
   Pawtucket, RI

   Dresser Minerals
   Houston, TX

   Goodyear Tire & Rubber Co.
   Akron, OH

   Phillip Carey Co.
   Cincinnati, OH

   Dow Chemical Co.
   Midland,-MI

   Reeves Brothers, Inc.
   New York, NY

   Goodyear Tire & Rubber Co.
   Akron, OH

   U.S. Rubber Co.
   New York, NY

   B. F. Goodrich Co.
   Akron, OH

   B. F. Goodrich Go.
   Akron, OH

   Griffolyn Co., Inc.
   Houston, TX

   Griffolyn Co., Inc.
   Houston, TX
                                     156

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Trade Name

Grfffolyn V


Gundline


Hydro!i ner


Hydromat


Hypalon (resin)


Ibex


Koroseal


Kreene


Meadowmat

@>
National Baroid


Nordel (resin)


Panel craft


Paraqual


Petromat



Pliobond


Polyliner


Red Top
        TABLE  4-3  (continued)

Product Descri pti on            Manufacturer
Reinforced PVC, oil
  resi stant
                             Griffolyn Co.,  Inc.
                             Houston, TX
High density polyethylene    Gundle Lining Systems,  Inc.
                             Houston,  TX
  (HOPE)

Butyl rubber
Prefabricated asphalt
  panels

Chlor9sulfonated PE
  resin

Bentonite
PVC films


PVC films
Prefabricated asphalt
  panels with PVC core

Bentonite
Ethylene propylene
  diene monomer resin

Prefabricated aspahlt
  panels

EPDM and butyl
Polypropylene woven
  fabric (base
  fabric-spray linings)

PVC adhesive


PVC-CPE, alloy film


Bentonite


                 157
                             Goodyear Tire & Rubber Co.
                             Akron, OH

                             W. R.  Meadows, Inc.
                             Elgin, IL

                             E. I.  Du Pont Co.
                             Wilmington, DE

                             Chas.  Pfizer & Co.
                             New York, NY

                             B. G.  Goodrich Co.
                             Akron, OH

                             Union  Carbide & Chemical  Co.
                             New York, NY

                             W. R.  Meadows, Inc.
                             Elgin, IL

                             National Lead Co.
                             Houston, TX

                             E. I.  Du Pont Co.
                             Wilmington, DE

                             Envoy-APOC
                             Long Beach, CA

                             Aldan  Rubber Co.
                             Philadelphia, PA

                             Phillips Petroleum Co.
                             Bartlesville, OK
                             Goodyear Tire & Rubber Co.
                             Akron, OH

                             Goodyear Tire & Rubber Co.
                             Akron, OH

                             Wilbur Ellis Co.
                             Fresno, CA

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Trade Name
         TABLE  4-3 (continued)
Product Description            Manufacturer
Royal Seal
SS-13
Sure Seal
Vinaliner
Vinyl Clad
Vi squeen
Void ay
Water Seal
EPDM and butyl
Waterborne dispersion
Butyl, EPDM, neoprene,
and Hypalon, plain
and reinforced
PVC
PVC, reinforced
PE resin
i
Bentonite
Bentonite
U.S. Rubber Co.
Mishawaka, IN
Lauratan Corp.
Anaheim, CA
Carlisle Corp.
Carlisle, PA
Goodyear Tire & Rubber Co.
Akron, OH
Sun Chemical Co.
Paterson, NJ
, Ethyl Corp.
Baton Rouge, LA
American Colloid Co.
Skokie, IL !
Wyo-Ben Products
Billings, MT :
aCourtesy of John Wiley & Sons, Inc., New York:, NY.
                                     158

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                                  TABLE 4-4

                    SOURCES OF COMMON LINING MATERIALS (4)a
Material

Bentonite
Butyl and EPDM
Butyl and EPDM,
  reinforced
CPE, reinforced

Hypal on
Hypalon,
  reinforced
EPDM

EPDM, reinforced


Neoprene
Neoprene,
  reinforced
    Manufacturer

American Colloid Co.
Archer-Daniels-Midland
Ashland Chemical Co.
Chas. Pfizer & Co.
Dresser Minerals
National Lead Co.
Wilbur Ellis Co.
Wyo-Ben Products, Inc.

Carlisle Corp.
Goodyear Tire & Rubber Co.

Aldan Rubber Co.
Carlisle Corp.
Plymouth Rubber Co.
Reeves Brothers, Inc.
   Location

Skokie, IL
Minneapolis, MN
Cleveland, OH
New York, NY
Houston, TX
Houston, TX
Fresno, CA
Billings, MT

Carlisle, PA
Akron, OH

Philadelphia, PA
Carlisle, PA
Canton, MA
New York, NY
Goodyear Tire & Rubber Co.   Akron, OH
San Jose, CA
Akron, OH

San Jose, CA
Carlisle, PA
Akron, OH
Canton, MA
New York, NY
Burke Rubber Co.
B. F. Goodrich Co.

Burke Rubber Co.
Carlisle Corp.
B. F. Goodrich Co.
Plymouth Rubber Co.
J. P. Stevens Co.

See  "Butyl and EPDM"

See  "Butyl and EPDM,
  reinforced"
Carlisle Corp.               Carlisle, PA
Firestone Tire & Rubber Co.  Akron, OH
B. F. Goodrich Co.           Akron, OH
Goodyear Tire & Rubber Co.   Akron, OH

Carlisle Corp.               Carlisle, PA
B. F. Goodrich Co.           Akron, OH
Firestone Tire & Rubber Co.  Akron, OH
Plymouth Rubber Co.          Canton, MA
Reeves Brothers, Inc.        New York, NY
                                      159

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Material

PE



PE, high quality

PE, reinforced

PVC
     TABLE  4-4 (continued)

Manufacturer
                                Location
PVC, reinforced
Prefabricated
  asphalt panels
3110
Monsanto Chemical Co.
Union Carbide, Inc.
Ethyl Corp.

Gundle Lining Systems, Inc.

Griffolyn Co., Inc.

Firestone Tire & Rubber Co.
B. F. Goodrich Co.
Goodyear Tire & Rubber Co.
Pantasote Co.
Stauffer Chemical Co.
Union Carbide, Inc.

Firestone Tire & Rubber Co.
B. F. Goodrich Co.
Goodyear Tire & Rubber Co.
Reeves Brothers, Inc.
Cooley, Inc.
Sun Chemical Co.

Envoy-APOC
Gulf Seal, Inc.
W. R. Meadows, Inc.
Phillip Carey Co.

E. I. Du Pont Co.
                         St.  Louis,  Mo.
                         New York, NY
                        .Baton Rouge, LA

                         Houston,  TX

                         Houston,  TX

                         Akron, OH
                         Akron, OH
                         Akron, OH
                         New York, NY
                         New York, NY
                         New York, NY

                         Akron, OH
                         Akron, OH
                         Akron, OH
                         New York, NY
                         Pawtucket,  RI
                         Paterson, NJ

                         Long Beach, CA
                         Houston,  TX
                         Elgin, IL
                         Cincinnati, OH

                         Louisville, KY
aCourtesy of John Wiley & Sons, Inc., New York,  NY.
                                       160

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                                  TABLE  4-5

          SUMMARY OF EFFECTIVE DESIGN PRACTICES FOR PLACING LINING
                         IN CUT-AND-FILL RESERVOIRS


 1.  Lining must be  placed  in  a  stable structure.

 2.  Facility  design  and  inspection   should  be   the   responsibility  of
     professionals with backgrounds  in  liner applications  and  experience in
     geotechnical  engineering.

 3.  A continuous underdrain to  operate  at atmospheric pressure is recommended.

 4.  A leakage tolerance should be  included  in  the specifications.   The East
     Bay Water Company of  Oakland,  CA  (East  Bay  Municipal  Utility District)
     developed the  following  formula   for  leakage  tolerance which  can  be
     modified by  inserting more stringent  factors in the  denominator,  i.e.,
     100, 200, etc.  The equation is empirical  and its  use must  be  based on
     experience.


                                Q=   A_VH
                                      80

     where,
            Q = maximum permissible  leakage  tolerance, gallons/minute
            A = lining area,  1000  ft2
            H = maximum water depth, ft

 5.  Continuous, thin, impermeable-type linings should be placed  on  a smooth
     surface of concrete,  earth, Gunite, or  asphalt concrete.

 6.  Except for asphalt panels all  field  joints  should  be made perpendicular
     to  the toe  of  the  slope.   Joints  of  Hypalon formulations  and  3110
     materials  can   run   in  any  direction,   but  generally   joints   run
     perpendicular to the  toe of the slope.

 7.  Formal  or  informal anchors  may be used  at the  top of the  slope.   See
     details in Figures 4-2 to 4-6.

 8.  Inlet  and  outlet structures must  be  sealed  properly.   See  details  in
     Figures 4-7 to 4-11.

 9.  All   lining punctures and cracks  in  the  support  structure should  be
     sealed.  See details  in  Figures 4-12  and 4-13.

10.  Emergency  discharge  quick-release  devices should  be provided  in  large
     reservoirs [7.6(104)  to  1.2(10*'') m3].

11.  Wind problems  with exposed  thin  membrane liners  can  be  controlled  by
     installing vents built into the lining.  See details  in Figure 4-14.

12.  Adequate protective fencing must be installed to control vandalism.
                                      161

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       5.  Bentonite  1s mixed with  sand at  aproximately  one to eight  volume
          ratio.  The  mixture is, placed in a  layer  approximately  5 to 10  cm
          (2 to 4 in)  in thickness on  the  reservoir  bottom  and  covered  with a
          protective cover of  sand  or  soil.   This method  takes  about  13.5
          kg/m2 (3 Ib/ft2) of bentonite ,(17).


 In  methods  (4)  and   (5)  above,  certain  construction practices  are  recom-
mended.  They are as follows:


       1.  The section  must be overexcavated [30 cm  (12 in)] with drag lines
          or graders.

       2.  Side  slopes   should  not  be  steeper  than  two  horizontal  to  one
          vertical.

       3.  Subgrade surface  should be  dragged to remove large rocks  and sharp
          angles.  Normally two passes  with  adequate equipment  are  sufficient
          to smooth the subgrade.
                                               I                             :f
       4.  Subgrade should be rolled with a smooth steel roller.              ;

       5.  The subgrade should be sprinkled to eliminate dust problems.

       6.  The membrane of bentonite or soil bentonite should then be  placed.

       7.  The  protective  cover should  contain  sand   and  small  gravel,  in
          addition to  cohesive,  fine  grained  material so  that it will  be
          erosion resistant and stable.


The performance of  bentonite linings  is greatly affected  by  the  quality  of
the bentonite.   Some  natural  bentonite deposits  may  contain  quantities  of
sand,  silt,  and clay  impurities.   Wyoming-type  bentonite,  which is  a  high
swelling   sodium   montmorillonite  clay,    has   been  found   to   be   very
satisfactory.  Fine  ground  bentonite  is  generally more  suitable  for  the
lining  than  pit run  bentonite.  If  the  bentonite  is finer  than   a  No.  30
sieve, it may be used  without specifying size  gradation.  But if the material
is coarser than the No. 30 sieve, it  should  be well  graded.  Bentonite  should
usually  contain   a  moisture  content  of  less  than  20   percent.   This  is
especially  important  for  thin  membranes.  Some  disturbance,  and  possibly
cracking  of  the  membrane,   may  take  place  during  the  first year  after
construction due  to settlement of. the subgrade upon  saturation.   A  proper
maintenance program, especially at  the  end  of the  first  year, is  necessary
(16).

Bentonite  linings  may be  effective   if  the  sodium  bentonite  used  has  an
adequate amount  of exchangeable  sodium.  Deterioration  of the  linings  has
been  observed  to  occur in  cases where  magnesium  or calcium  has  replaced
sodium as adsorbed ions.   A thin layer, less than  15 cm (6 in), of  bentonite
on the soil  surface  tends to  crack  if  allowed  to  dry.  Because of this,   a


                                      162

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bentonite soil  mixture with a cover of fine grained soil  on top, or a thicker
bentonite  layer,  is  usually  placed  (18).   Surface  bentonite  cannot  be
expected to be  effective  longer than two to four years.   A buried bentonite
blanket may last from 8 to 12 years.    .

The quality of  the  bentonite used  is a primary consideration  in the success
of bentonite membranes.   Poor quality bentdnite deteriorates  rapidly  in the
presence of  hard  water,   and  it  also  tends  to  erode  in  the presence  of
currents or waves.   Bentonite  linings must often  be placed by hand  and this
is a costly procedure in areas of high labor costs.

Seepage  losses  through  buried bentonite blankets  are  approximately  0.2
to 0.25 m3/m2/d  (0.7   to  0.85  ft3/ftz/d).   This   figure   is  for  thin
blankets and represents about a 60 percent improvement  over  ponds with  no
lining.

Asphalt linings may  be  buried on the surface and may be  composed  of asphalt
or a prefabricated asphalt.  Some possibilities are  as follows:

      1.  An  asphalt  membrane  is  produced  by   spraying  asphalt  at  high
          temperatures.   This lining may be either  on  the surface  or buried.
          A large  amount  of  special  equipment  is needed  for  installation.
          Useful lives of  18 years  or greater have been  observed  when these
          membranes are carefully applied  and covered with  an adequate layer
          of fine grained soil.

      2.  Asphaltic  Membrane Macadam.   This  is  similar to   the  asphaltic
          membrane, but it is covered with a thin layer of gravel, penetrated
          with  hot blown asphalt cement.

      3.  Buried  Asphaltic  Membrane.   This  is  similar  to  (1),  except  a
          gravel-sand cover  is  applied  over the  asphaltic  membrane.   This
          cover  is  usually  more   expensive  than  cover  in   (2)  and  less
          effective in discouraging plant growth.

      4.  Built-up  Linings.   These  include  several   different   types  of
          materials.   One type  could  be  a  fiberglass  matting,  which  is
          applied  over  a  sprayed   asphalt layer  and  then  also  sprayed  or
          broomed with  a  sealed coat of asphalt or  clay.   A 280-g (10-oz)
          jute burlap has  also been  used  as  the interior layer between two
          hot  sprayed  asphalt  layers.    In  this  case  the   total  asphalt
          application  should be  about  11.3 liters/m2   (2.5  gal/yd2).   The
          prefabricated lining may  be on the surface or  buried.  If buried,
          it could  be covered  with a  layer  of soil  or, in   some  cases,  a
          coating of All ox, which is a stabilized asphalt  (19).

      5.  Prefabricated Linings.  Prefabricated asphalt linings consist of a
          fiber or  paper  material  coated  with  asphalt.   This  type  of liner
          has  been  used   as  both   exposed and  covered  with  soil.   Joints
          between the  material  have  an  asphaltic  mastic  to  seal  the  joint.
          When  the  asphaltic material is  covered,  it is more effective and
                                     163

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          durable.  When  it is  exposed  it should  be coated with  aluminized
          paint  every three to  four years  to retard  degradation.   This  is
          especially  necessary above  the  water line.   Joints also have to  be
          maintained  when not  covered with fine grained  soil.   Prefabricated
          asphalt membrane  lining  is approximately 0.32  to  0.64 cm  (0.13  to
          0.25 in  thick.   It may  be  handled  in much the same  way as  rolled
          roofing with  lapped  and cemented joints.   Cover for  this  material
          is generally earth and gravel,  although  shot-crete and macadam  have
          been utilized.

Installation  procedures  for prefabricated  asphalt membrane linings  and  for
buried  asphalt  linings  are  similar to  those  stated  for  buried bentonite
linings.   The preparation  of  the  subgrade  is  important and  it  should  be
stable and adequately smooth for the lining.

Best  results  are  obtained  with  soil cement  when the  soil  mixed  with  ;the
cement is sandy and well graded to a maximum size of about 2 cm  (0.75  in).

Soil  cement should  not  be placed in  cold weather  and it  should be cured  for
about seven days after placing.   Some  variations of the soil  cement  lining
are listed below.

      1.  Standard  soil  cement  is compacted  using  a  water content of  the
          optimum  moisture  content9  of  the   soil.   The  mixing  process  is
          best accomplished by  traveling  mixing machines  and can be handled
          satisfactorily in slopes up to four to  one.   Standard soil  cement
          may be on the surface or buried.

      2.  Plastic soil cement  (surface  or buried)  is a  mixture  of soil  and
          cement with a consistency  comparable  to  that   of  Portland  cement
          concrete.  This is accomplished  by  adding a considerable amount  of
          water.    Plastic  soil  cement  contains  from three  to  six  sacks :of
          cement per cubic meter and is  approximately  7.5  cm  (3  in) thick.

      3.  Cement modified soil contains two to six percent volume of cement.
          This may  be used with  plastic  fine grained  soils.   The treatment
          stabilizes the soil in  sections subject to erosion.   The lining  is
          constructed by  spreading  cement on   top  of  loose soil  layers by a
          fertilizer-type spreader.  The cement is then mixed with loose  sqil
          by  a  rotary  traveling  mixer  and   compacted  with  a  sheeps  foot
          roller.   A seven-day  curing  period  is  necessary   for a  cement
          modified soil.

Soil cement has been used successfully in some cases  in mild climates.  Where
wetting or drying is a factor,  or  if  freezing-thawing cycles are present,  the
lining will deteriorate  rapidly (20).
  Water content  (expressed in  percent dry weight) at which  a  given soil can
  be  compacted  to  its maximum  density  by  means  of  a  standard  method of
  compaction.                                                              ;
                                     164

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Linings of  bentonite  and asphalt are  sometimes  unsuitable in  areas  of high
weed growth, since weeds and tree roots puncture  the material readily  (20).

Many  lining failures  occur as  a  result  of  rodent  and  crayfish holes  in
embankments.  Asphalt  membrane  lining  tends to  decrease the  damage,  but, in
some cases, harder  surface  linings  are necessary to  prevent  water loss from
embankment failures.

Linings of  hot  applied buried asphalt  membrane  provide one of the  tightest
linings  available.   These   linings deteriorate less  than  other   flexible
membrane linings (20).

Asphalt linings composed of prefabricated buried materials are best for small
jobs,  since  there  is  a  minimum  amount  of  special  equipment  and  labor
connected  with  installation.    For larger  jobs  sprayed  asphalt   is  more
economical.

When  fibers and  filler are  used  in   asphalt  membranes,  there  is  greater
tendency  to  deteriorate   when   these  fillers  are   composed  of  organic
materials.   Inorganic  fibers  are,  therefore,  more   useful   (20).   Typical
seepage volume through  one  buried asphalt  membrane  after  10 years of service
was consistently 0.02 m3/m2/d (0.08  ft3/ft2/d) (21).

Asphalt membrane linings can be  constructed at any time of the year.  It is
usually convenient,  because of  low water  levels in  ponds,  to  use  the late
fall and winter seasons  for installing  linings.  Fall  and winter installation
may dictate the use of the buried asphalt membrane lining  (20).

Buried  asphalt  membranes usually  perform  satisfactorily  for  more  than  15
years.  When these  linings  fail, it is generally  due to one or more of the
following causes:

     1.  Placement of lining on unstable side slopes
     2.  Inadequate protection of the membrane
     3.  Weed growth
     4.  Surface runoff
     5.  Type of subgrade material
     6.  Cleaning operations
     7.  Scour of cover material
     8.  Membrane puncture


         b.  Thin Membrane  Liners


Plastic  and  elastomeric membranes are  popular  in   applications requiring
essentially zero permeability.   These  materials  are  economical, resistant to
most  chemicals  if  selected  and installed properly,  available in large  sheets
simplifying  installation,   and  essentially  impermeable.   As   environmental
.standards  continue  to become more  stringent,  the  application  of  plastic and
elastomeric membranes as pond  liners  will  increase  because  of  the  need to
                                      165

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guarantee  protection  against  seepage.   This is particularly true for  sealing
ponds  containing toxic  wastewaters  or  the sealing  of landfills  containing
toxic solids and sludges.

Typical standards being  developed for the  application of liners  are presented
elsewhere  (6).   A partial  listing  of  the  trade names, product  description,
and  manufacturer of  plastic  and  elastomer lining  materials  is presented!  in
Tables 4-3 and 4-4.

The  most  difficult design problem encountered  in  liner application  involves
placing  a  liner  in  an  existing  pond.    Effective  design   practices  ;are
essentially the  same  as  those used in  new systems,  but additional  care must
be  exercised  in the  evaluation  of the existing structure  and the  required
results.   Lining  materials  must  be   selected  so  that  compatibility   is
obtained.  For example,  a badly cracked concrete lining to be covered with  a
flexible synthetic material must be properly sealed and the  flexible material
placed  in such  a way  that  additional movement  will  not  destroy  the  new
liner.  Sealing  around  existing columns,  footings, etc.,  are  other examples
of items to be considered.

The  following paragraphs are  a condensation of the  discussion  by Kays (4)  of
effective design practices which have been  summarized in Table  4-5.  Emphasis
is  placed  on  the details describing  the  installation  of  plastic or  elasito-
meric materials.

Formal  and informal  anchor  systems  are  used  at  the  top  of  the  slope  :or
dikes.  Details of three types of formal anchors are presented  in Figures 4-2
through 4-4.  Recommended informal  anchors  are  shown in  Figures  4-5  and 4-6;

When the  lining  is pierced,  seals can  be  made  in  two  ways.  The  techniques
illustrated in Figures 4-7 and 4-8 are  commonly used, and a second  technique
utilizes a pipe boot which is sealed to  the liner and clamped to  the entering
pipe as shown in Figure 4-9.

It  is  recommended that inlet-outlet   pipes  enter  a   reservoir  through   a
structure such as  that  shown  in Figure  4-10.  A better seal  can be produced
when the  liner  is attached  to  the top of the  structure.   However,  such |an
arrangement can  result in  solids  accumulation, and direct  free entry into:  a
wastewater pond is better.

A drain near  the outlet can  be  constructed as  shown in  Figure 4-11.  Large
reservoirs  containing  7.5  x  104 to   1.0 x  105 m3  (2.5   to   4.0 mgal)
should be equipped to  empty quickly in case of  an emergency.  .              :

The structure supporting the liner must be  smooth enough to prevent damage to
the  liner.   Rocks,   sharp  protrusions, and   other  rough  surfaces must  be
controlled.  In  areas with  particularly rough surfaces, it  may be necessary
to  add  padding  to protect  the  liner.   Cracks can be  repaired  as shown  in
Figures 4-12 and 4-13.

Thin membrane  liners  may have  problems with  wind on the  leeward  slopes.
Vents built into  the  lining control  this problem and serve  as  an outlet for
gases trapped beneath  the liner  (Figure  4-14).

                                      166

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                        FIGURE 4-2

      TOP ANCHOR DETAIL—ALTERNATIVE  1, ALL LININGS (4)

      Courtesy of John Wiley & Sons,  Inc., New York, NY
      Mastic
Mechanical anchor system
1/4"x2" aluminum or 3/16"x2"
galvanized steel or
stainless steel bars with
stud anchor bolts
12" max O/G. Use driven
studs only for asphalt
panel linings (2"  metal
washers req'd.
    Cast
concrete
structure
 Lining to concrete
 Adhesive Systems
  8" Min. for asphalt panels
  3" Min. for PVC & Hypalon
  6" Min. for all other linings
                                  Stable compacted
                                     soil or existing
                                 concrete, gunite or
                                   asphalt concrete
                         NOTE

         1.  Top of concrete should be smooth and
             free of all curing compounds.

         2.  Use min.  1/32." * 2" gasket (mat'l
            compatible with lining) between bar and
             lining, except no gasket required for
             asphalt panels or other linings thicker
             than .040".
                            167

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                            FIGURE 4-3

         TOP ANCHOR DETAIL—ALTERNATIVE 2, ALL LININGS  (4)

         Courtesy of John Wiley &  Sons, Inc., New York, NY
Min. 8" wide
x 1/32" thick
     chamfer
        strip
     Cast
 concrete
structure
Mechanical anchor system
1/4" x 2" aluminum or 3/16" x 2" galv.
or stainless steel bars with bolts

Min. 1" radius on new concrete
deburr old concrete

Wall lining
   Anchor system same as
   above - bar should be compatible
   with liquid contained
   Min. 6" wide x 1/32" elastomer
   lining boot - half on wall
   and half on slope with
   compatible concrete adhesive
                                               Note 2
                                                   Slope
                                                   lining
                                              Stable compacted
                                              soil or existing
                                              concrete, gunite
                                              or asphalt concrete
                      NOTE

     1.  All concrete at seals shall be smooth
          and free of all curing compounds.

     2.  Use compatible adhesive between slope
          lining and elastomer boot, and 3" min.
          width of compatible adhesive between
          slope lining and concrete.
                               168

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                           FIGURE  4-4

        TOP ANCHOR DETAIL—ALTERNATIVE 3, ALL LININGS  (4)

        Courtesy of John  Wiley & Sons, Inc., New York, NY
         m
   Cast concrete
   anchor beam
approx 12" deep
   depending on
    climatic and
  soil conditions
                                Mechanical anchor system -
                                1/4" x 2" aluminum or 3/16" x 2"
                                galvanized steel or
                                stainless steel bars with
                                bolt anchor
                                studs 12" max. O/C. Use driven
                                studs only for asphalt
                                panel linings  (2" 0 metal
                                washers req'd  )
                               Stable compacted
                               soil or existing
                               concrete, gunite
                               or asphalt concrete
Lining
                      NOTE

 1.  Top of concrete should be smooth and
     free of all curing compounds.

 2.  Use min. 1 /32" x 2" gasket (mat'l compatible with
     lining) between bar 8 lining except no
     gasket required for asphalt panels or other
     linings thicker than .040"
                               169

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                       FIGURE 4-5

  TOP ANCHOR DETAIL—ALTERNATIVE 4,,  ALL LININGS EXCEPT
                   ASPHALT PANELS (4)

    Courtesy of John  Wiley &  Sons, Inc., New York, NY
1% slope
             Trench cut by trenching
             machine - insert lining
             backfill and compact
                    12"
Top of slope
           Stable, compacted soil
           or existing concrete,
           gunite or asphalt
           concrete
                                                   Lining
                                                  w
                          170

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                        FIGURE 4-6

     TOP ANCHOR DETAIL— ALTERNATIVE ,5, ALL LININGS (4)

     Courtesy of John Wiley & Sons, Inc., New York, NY
                          Trench cut by tilted blade
                          of bulldozer, motor patrol,
                          etc., insert lining backfill
                          and compact
1% slope
Top of slope
   12" to 16"
                                                  Lining
                                Stable compacted
                                  soil or existing
                              concrete, gunite or
                                 asphalt concrete
                             171

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                    FIGURE 4-7

    SEAL AT PIPES THROUGH  SLOPE, ALL LININGS (4)

  Courtesy  of John Wiley & Sons, Inc.,  New York, NY
Lining
1/8" x 1" Short segments
of T/304 stainless
steel butt joined bars
with bolt anchor studs
6" 0/C. (see note)
                                     Mastic
              Concrete collar
                 or structure
                           Lining to concrete
                           adhesive system:

                            8" Min. for asphalt panels
                            3" Min. for PVC
                            6" Min. for all other linings
                       NOTE

      For asphalt panel linings, percussion
    driven studs thru 2" min. dia. x 1/16" thick
    galvanized metal discs at 6" O/C encased
    in mastic may be substituted for anchor shown.
                        172

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                  FIGURE 4-8

    SEAL AT FLOOR COLUMNS—ASPHALT PANELS (4)

Courtesy of John Wiley & Sons,  Inc., New York,  NY
                                   Concrete or
                                   steel column
                                    Asphalt mastic
                                     Asphalt panel
                                     lining
                    ...       .
Asphalt
primer and
adhesive
                             I1BWL
                                         Stable
                                         compacted
                                         subgrade
                               Concrete footing
                   NOTE

        Mechanical fasteners not required
                      173

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                      FIGURE  4-9

PIPE BOOT DETAIL—ALL LININGS EXCEPT ASPHALT PANELS (4)

   Courtesy of John  Wiley  & Sons,  Inc., New York, NY
                 Lining
                              Lining to lining
                              adhesive
                                       Pipe boot
     Stable compacted
    substrate concrete,
        gunite, asphalt
              concrete
                                                       1/4" Wide
                                                       stainless
                                                       steel band
                                                   Metal to
                                                   lining adhesive
                                                   4" wide
                                                   (see note)
                          NOTE

            Clean pipe thoroughly at area of
            adhesive application.
                         174

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                             FIGURE  4-10

           SEAL AT INLET-OUTLET STRUCTURE—ALL LININGS (4)

          Courtesy of John Wiley & Sons, Inc., New York, NY
Lining
                               1/8" x 1" T/304 stainless
                               steel bars, with 1" gap
                               between  bars. Anchor
                               with bolt anchor
                               studs, 6" O/C. (See note)
  Pipe
        Concrete
        structure
Lining to concrete	
adhesive system
 8" Min. for asphalt panels
 3" Min. for PVC
 6" Min. for all other linings
                                NOTE

                   With asphalt panel linings, percussion
                 driven studs thru 1" min. dia. 1 /16" thick
                 galvanized metal discs at 6" O/C,
                 encased in mastic may be substituted for
                 anchor shown.
                                175

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                  FIGURE 4-11

        MUD  DRAIN DETAIL—ALL LININGS  (4)

Courtesy of  John Wiley & Sons,  Inc., New York, NY
                          1/4" x 1 1/2" Aluminum bar,
                          1/2"* bolts6"0/Cor
                          bolt anchor studs
                          w/solid washers

                          Mastic
*
M
=: I
/
(Hill
I
^ / /
rr
K^-'-vir-*-
o" ••'•.'»••'.. T'.',«
£>'M&
\\
Concrete collar — * \
Concrete primer 	 *
81 adhesive, 4" wide
s
! 	
!
T
cd»
'-•» f. :«.- -.* •> • ||(^ l|EdUfe=JI[f=:||{ I T
' •• »• ••-. '+ ... !ii5|ii illjii^f'' lilfr.jilLL


•"• •>•'•'•%**•; .' •"»' IJJ =^/ r=r
/ ^tnhlo nnrth
or other
substrate
i
with valve
!
                      176

-------
                             FIGURE 4-12

              CRACK TREATMENT—ALTERNATIVES A AND B (4)

          Courtesy of John Wiley & Sons, Inc., New York, NY
Firm setting
heavy bodied
mastic
                                      Flexible
                                   continuous
                                        lining
•  1 1/2"min.
  * •
            Exist.
            crack
;.-.:A •••>/•».•. »>V. '^
                                         /
                                                            "V" cut
                                                            crack at
                                                            top
                                            Exist, concrete
                                            A.C. or gunite

                                            Heavy duty, high tensile
                                            curing mastic or
                                            cement grout - use
                                            concrete adhesive
                        Alternative A
r      Flexible
      continuous
      lining
                                       Metal plate
                                       see note)
                    	Percussion driven
             	           studs - 6" O/C - one
             —           side of crack only

                            NOTE

              Metal plate must be able to span
            crack without buckling from weight of
            water bridging the crack. Copper 8
            stainless steel are most common choices.

                        Alternative B
                               177

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                          FIGURE 4-13
                     WIND AND GAS CONTROL
Courtesy of Burke Rubber Company,  Burke  Industries, San Jose,  CA
        12" to 18" 12" to 18"
                        Anchor trench
                             &
                         Air-gas vent
                              178

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                                                             4-1 4
                          COST  COMPARISON FOR  LININGS IN THE UNITED STATES (1977  U.S. $j
                                 Courtesy of John Wiley & Sons,  Inc.,  New  York, NY
to
                                                   In-Piace Cost,  $/ft2                                 v
                            0.0 0.1  0.2 0.3 0.4 0.5  0.6  0.7  0.8  0.9 1.0  1.1  1.2 1.3 1.4  1.5  1.6 1.7
          Polyethylene
                 PVC
                3110
       Butyl, Epdm, Ept
 Reinforced Butyl, Epdm
              Hypalon
             Neoprene
             Concrete
           Steel Tanks
        Asphalt Panels
               Gunite
      Asphalt Concrete
                 CPE
       Compacted Clay
           Soil Cement
             Bentonite
  Waterborne Treatment
\       With  Bentonite
                                                  I    I
                                 I    l    1    I    1   I    I    I
I    I    I    I    I    I    I   I    I
                             0   1    2   34   56   7   8   9   10   11  12  13  14  15  16  17  18  19
                                                 In-Place Cost, $/m2

-------
Protection  of  a thin membrane  lining is essential,  and  Kays (4)  recommends
that a  fence at least 2 m  (6.6  ft)  high be placed on the outside  berm  slope
with the  top of the  fence  below the top elevation  of the dike  to keep :the
membrane out of sight of vandals.

In  addition to those manufacturers  presented in  Table  4-4,  there are many
firms  specializing in  the  installation  of  lining  materials.  Most  of the
installation -companies  and  the  manufacturers   publish   specifications  and
installation instructions and design  details.  Most of the recommendations by
the  manufacturers  and  installers  are  similar,  but  there  are  differences
worthy  of  consideration when designing  a system  requiring a  liner.   Consult
the manufacturers for details.
                                                                          F
New products continue to be developed, and with each new material the  options
available  to designers continue to  improve.   The future  should  bring even
more versatile and effective liners for  seepage control.   If  care and  common-
sense  are  applied to  the  application  of  liners,  the  control  of  seepage
pollution should become a minor problem in the future.


         4.3.4.2  Failure Mechanisms


Kays  (4)   presented   a  classification  of  the  principal   failure  mechanism
observed in cut-and-fill  reservoirs   (Table  4-6).  The list is extensive and
case histories  involving  all of the categories are  available;  however, the
most frequently observed failure mechanisms  were the lack of  integrity in the
lining suppport structure and abuse of the liner.


         4.3.4.3  Cost of Linings


The cost of linings  for ponds are approximations and  are  estimated based on
values at specific jobs (1978 U.S. $).

Bentonite   linings  cost   approximately   $1,.10   to   $2.20/m2   ($0.10   to
$0.20/ft2)  when  applied on  the surface.   The greater cost  will  occur for
harrowed „  blankets.     Buried   blankets    cost    approximately   $3.10/m2
($0.30/ft2).

The average cost  of  buried asphalt  membrane  linings with  adequate cover is
about $4.20/m2 ($0.40/ft2).                                                |

Prefabricated asphalt  materials  are  generally cheaper  than  buried asphalt
membrane linings if the prefabricated material can  be obtained for  less than
$1.10/m2 ($0.10/ft2).

Figure 4-14 presents a  cost comparison  for  the various types of  liners used
in the United States  (4).                                                  '
                                     180

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                                  TABLE 4-6

              CLASSIFICATION OF THE PRINCIPAL FAILURE MECHANISMS
                        FOR CUT-AND-FILL RESERVOIRS*
Supporting structure problems

  Underdrains
  Substrate
    Compaction
    Texture
    Voids
    Subsidence
    Holes and cracks
    Groundwater
    Expansive clays
    Gassing
    Sloughing
    Slope anchor stability
    Mud
    Frozen ground and ice
  Appurtenances

Operating problems

    Cavitation
    Impingement
    Maintenance cleaning
    Reverse hydrostatic uplift
    Vandalism
    Seismic activity
Lining problems

  Mechanical  difficulties
    Field seams
    Fish mouthsb
    Structure seals
    Bridging
    Porosity
    Holes
    Pinholes
    Tear strength
    Tensile strength
    Extrusion and extension
    Rodents,  other animals, and birds
    Insects
    Weed growths
  Weather
    General weathering
    Wind
    Wave erosion
    Ozone
 kCourtesy of John Wiley & Sons, Inc., New York,  NY.
  Separation  of butyl-type  cured  sheets at  the joint because  of  unequal
  tension in the two sheets.


Cover  material  over  buried  membranes is  the  most expensive  part  of  the
placing  procedure.   The  cover  material  should,  therefore,  be  as  thin as
possible  and  still  provide  adequate  protection for   the  membrane.   If a
significant hydraulic current  is present  in the  pond,  the  depth of  coverage
should be greater  than  25 cm  (1  ft), and this  minimum  depth should only be
used  when the  material  is  erosion  resistant  and  also  cohesive.   Such a
material  as a clayey gravel is suitable.  If the material is  not cohesive, or
if it is fine grained, a higher amount of  cover is needed (20).

Maintenance costs  for  different types  of  linings are difficult to  estimate.
Maintenance should  include repair of  holes, cracks,  and deterioration,  weed
                                      181

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control expenses and animal damages, and damages caused by  cleaning the pond,
if  that is  necessary.   Climate,  type of  operation, type of  terrain,  and
surface conditions also influence maintenance costs.  Plastic soil cement 7.5
cm (3 in) thick costs about $3.50/m2 ($0.33/ft2).

Cost  comparisons  of  various  liners  indicate  that natural   and   chemical
sealants  are  the  most  economical   sealers.   Unfortunately,   natural  ;and
chemical sealers are dependent upon local soil  conditions for seal efficiency
and never  form a  complete  seal.  Asphalt-type and  synthetic  liners compete
competitively  on  a cost  basis,  but  have  different  practical   applications.
Synthetic liners are most practical  for zero or minimum seepage  regulations,
for industrial waste that might  degrade concrete  or  earthen liners,  and |for
extremes in climatic conditions.


4.4  Pond Hydraulics


     4.4.1   Inlet and Outlet Configuration


In  the  past,  the majority  of  ponds  were  designed   to   receive   influent
wastewater through a  single pipe, usually  located toward  the  center of the
pond.   Hydraulic and  performance studies (22-25)  have shown that the center
discharge is  not the  most  efficient method  of introducing wastewater  to  a
pond.   Multiple inlet arrangements are preferred even in small  ponds  [<0.5 ha
(1.2 ac)].   Outlets  should be located  as  far as  possible  and  preferably by
means of a  long diffuser.  The  inlets and outlets should  be  placed  so that
flow through  the pond  has a uniform velocity profile between  the next inlet
and outlet.

One form of multiple  inlet, used for ponds as  large  as  20  acres, uses inlet
head loss to  induce internal  pond  circulation and initial  mixing.  The inlet
pipe,  laid on  the pond bottom, has multiple ports  or  nozzles all pointing in
one direction  and at a slight angle above  the horizontal.   Port head loss is
designed for  about 0.3 m  (1 ft)  at average  flow,  resulting in  a velocity; of
2.4 m/sec (8 ft/sec).

Single inlets  can  be used successfully if the  inlet  is  located the  greatest
distance possible from the  outlet  structure and baffled  or  the flow  directed
to avoid currents and short circuiting.  Outlet structures  should be  designed
for multiple  depth withdrawal, and  all  withdrawals  should be a  minimum of
0.3 m (1 ft) below the water surface.


            4.4.1.1  Pond  Transfer Inlets and Outlets


Pond transfer  inlets and  outlets should be  constructed  to minimize head loss
at peak recirculation rates, assure uniform distribution to all pond  areas at
                                     182

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all  recireulati'on  rates, and  maintain water-surface  continuity  between  the
supply channel, the ponds, and the return  channel.

Transfer pipes should be numerous and large enough to limit peak head loss to
about  7-10  cm  (3-4  in) with  the pipes  flowing about  two-thirds  to  three-
quarters   full.   Supply-  and  return-channel  sizing  should  assure  that  the
total  channel  loss is  no  more  than  one-tenth of  the transfer-pipe losses.
When such a ratio is maintained, uniform distribution  is  assured.

By  operating with  the  transfer pipes  less  than  full,  unobstructed   water
surface  is  maintained  between the channels  and ponds,  which  controls  scum
buildup in any one area.  If the first cell  is designed to remove scum,  then
the transfer pipes must be submerged.

Transfer inlets and outlets  usually are made  of  bitumastic-coated, corrugated
metal  pipe,  with seepage collars located near  the midpoint.  This  type of
pipe is  inexpensive,  strong enough to  allow for the differential settlement
often encountered in pond-dike construction.

Specially made  fiberglass  plugs can  be  provided to  close  the  pipes (Figure
4-15).   The  plugs  may  be installed from a boat.  Such  plugs  permit any  pipe
to  be  closed without  expensive  construction  of  sluice  gates  and  access
platforms at each transfer point.  Launching  ramps  into each pond and channel
are  recommended  to  assure  easy  boat access  for  sampling,  aquatic   plant
control,  and pond maintenance.


     4.4.2  Baffling


Better treatment is obtained when the flow  is guided more carefully through
the pond.  In  addition  to treatment efficiency,  economics and esthetics  play
an important role in deciding whether or not baffling  is  desirable.

Because there  is little horizontal force  on baffling except  that caused by
wave action,  the baffle structure need  not be  particularly  strong.   It may
also be placed  below  the pond  surface  to help overcome  esthetic objections.
A typical type  of  baffle to consider might be a  submerged  fence attached to
posts driven into the pond bottom and covered with  a heavy plastic, flexible
membrane.  Commercial   float-supported  plastic  baffling  for  ponds   also is
available.

In general, the more baffling  that is  used,  the  better the flow guidance and
treatment efficiency.   The lateral spacing and length of  the baffle should be
specified so that the  cross-sectional  area  of  the  flow is as  close  to a
constant as possible.

Baffling has an  additional virtue.  The  spiral  flow induced when flow  occurs
around the  end  of the  baffles  enhances  mixing and tends  to  break  up or
prevent any stratification or tendency to  stratify.
                                     183

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                                 FIGURE 4-15

                          SPECIAL FIBERGLASS  PLUG
'/4n FIBERGLASS RE INF.
  PLASTIC PLUG
                            CLAMPS AND SLOTS, SEE SECTION I
                            -30  CMP

                    SIDE ELEVATION
                                                     END ELEVATION
       '/Z " * 2" FIBERGLASS
       REINF. PLASTIC CLAMP-
V*.
, 9"± '/is
li. e'/z"
*,r
J&>\
^
^/^ ,
1
\
k-51.

•>«--»
J*

L
— p
E

'&
, *
ROVIDE Z'/4" * 3/i" SLOTS AT INTAKE
WS OF ALL TRANSFER PIPES
                                    SECTION(7)
                           TYPICAL  PLUG  DiETAIL
                                     NO SCALE
                                     184

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Winter ice  can damage  or destroy  baffles  in cold  climates.  Care  must be
exercised when designing baffles for a cold  climate.


         4.4.3  Wind Effects


Wind  generates  a circulatory  flow in  bodies of  water.   To  minimize short
circuiting  due to  wind,  the  pond  inlet-outlet  axis  perpendicular  to  the
prevailing  wind  direction  should  be  aligned.   If   for   some  reason  the
inlet-outlet  axis  cannot be  oriented  properly,  baffling  can  be  used to
control,  to some  extent,  the wind-induced circulation.   It  should be kept in
mind  that in  a constant depth  pond, the surface current  is  in the direction
of the wind and the return flow is in the upwind  direction along the bottom.


         4.4.4  Stratified Ponds


Ponds  that  are  stratified because  of  temperature  differences  between  the
inflow  and  the  pond  contents  tend  to behave  differently  in  winter  and
summer.  In summer, the inflow is  generally colder than the  pond  so it sinks
to the pond bottom  and  flows toward the outlet.   In the  winter,  the  reverse
is generally  true and the inflow  rises to  the surface and  flows toward the
outlet.

A  likely  consequence of  this  behavior is  that  the  effective volume  of the
pond  is  reduced  to  that  of the  stratified  inflow  layer (density current).
The result  can be a drastic decrease in detention time  and an  unacceptable
level of treatment.

One strategy to employ is  to use  selective  pond outlets positioned vertically
so that outflow is  drawn from  the layer with density  different  from that of
the inflow.   For  example,  under summer  conditions  the inflow will  occur along
the pond  bottom.   Hence,  the  outlets  should  draw from water near  the  pond
surface.   This concept  has not  been  tested but seems  likely   to   improve
performance over  "full-depth" outlet structures.

Another approach  is to premix the inflow with pond water while in the  pipe or
diffuser  system,  thereby  decreasing  the density  difference.  This  could be
accomplished by regularly  constricting  the  submerged inflow diffuser pipe and
locating openings in the  pipe  at  the constrictions.   The low pressure at the
pipe  constrictions  would  draw  in  pond water  and  mix  it with the  inflow to
alter  the density.   However, clogging  of openings with solid material could
be a problem.


4.5  Pond Recirculation and Configuration


Pond  recirculation  involves  interpond and  intrapond  recirculation as  opposed
to mechanical  mixing in  the pond cell.  The effluents  from  pond  cells are


                                      185

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mixed  with  the influent to  the  cells.   In intrapond recirculation, effluent
from a single cell is  returned  to the influent to  that cell.  In  interpond
recirculation, effluent from another pond is returned and mixed with influent
to the pond (Figure 4-16).

Both methods  return active  algal  cells to the  feed area  to  provide photo-
synthetic oxygen  for satisfaction  of  the organic  load.  Intrapond recircu-
lation allows the pond to gain some of  the advantages that a completely mixed
environment would  provide  if it were  possible  in  a pond.   It helps prevent
odors and anaerobic conditions in the feed zone  of  the pond.

Both  interpond  and intrapond  recirculation  can  affect  stratification  in
ponds,  and  thus  gain   some benefits  ascribed  to  pond  mixing,  which  is
discussed later.   Pond  recirculation  is  not generally as efficient  as are
mechanical systems in mixing facultative ponds.

Recirculation  is  used  principally  in  overloaded or  improperly  sized ponds.
Other  than  for  dilution  in  the case  where  pond  influents  with  very high
concentrations  of  wastes  are being treated,  in most cases  the  increased
energy costs associated with recirculation would  dictate against its  use.

Three  common  types  of  interpond-recirculation  systems  (series, parallel, and
parallel  series)  are  shown in Figure  4-16.   Others have  been suggested but
seldom used.

One objective  of  recirculation in  the  series arrangement  is  to decrease the
organic loading in  the  first cell  of the  series.  While the loading per unit
surface  is  not  reduced by  this  configuration,  the retention  time of the
liquid  is reduced.  The method  attempts  to  flush the  influent  through the
pond  fa~s?er  than   it  would  travel  without  recirculation.   The  first-pass
hydraulic retention time  of the influent  and  recycled  liquid  in  the first,
most heavily loaded, pond in the  series system is:
                           t-     V
                                (1+ r) F
where V is the  volume  of pond cell, F is  the  influent  flow rate, r, or R/F,
is the recycle ratio, and R is the recycle flow rate.

Another advantage  of recirculation in the series configuration  is  that the
BOD  in  the  mixture  entering the  pond  is  reduced,  and  is  given by  the
expression:
                                      186

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                      FIGURE  4-16
COMMON  POND CONFIGURATIONS AND RECIRCULATION  SYSTEMS
                      Recycle ^^^ Pump station
                     	[v>*-]  (typical)
                 Intrapond recirculation

                Recycle
                                          Lj
                        SJeries
          Parallel               Parallel series
                Interpond recirculation
                           187

-------
where  % is the  BOD  of the mixture,  $3  is the effluent  BOD from the  third
cell,  and S-jn  is the influent  BOD.   Thus, Sm would  be only  20 percent  of
Sjn  with  a 4:1  recyle  ratio,   as  $3  would  be   negligible in  almost  all
cases.   Thus,   the  application of organic  load in  the pond is spread  more
evenly throughout the ponds, and organic  loading and odor  generation  near the
feed  points are  less.   Recirculation  in the»  series  mode has  been  used  to
reduce   odors   in  those  cases  where  the  first  pond  is  anaerobic.    The
recirculation ratio is selected  based  on  the  loading rate applied to  the cell
that will not cause a nuisance.

The  parallel  configuration more  effectively  reduces pond  loadings than  does
the  series  configuration, because the mixture of  influent is  spread evenly
across all  ponds instead of the first pond  is a  series.   Recirculation  has
the same benefits in both configurations.

For  example,  consider  three  ponds,  either in series  or  parallel.   In  the
parallel  configuration,   the  surface  loading  (kg  BODs/ha/d)  on  the  three
ponds  is one-third  that of the  first  pond  in the series configuration.   The
parallel  configuration,  therefore,  is less likely  to  produce odors  than  the
series configuration.  However,  the  hydraulic improvements in design using  a
series configuration generally will offset  the  benefits  of  reduced  loading in
parallel configuration.

Based  upon  the  analyses  of  performance  data  from  selected  aerated  and
facultative ponds (see the Appendix and Chapter 2), four ponds  in  series  are
desirable  to  give  the  best  8005  and  fecal  coliform  removals  for  ponds
designed as plug  flow systems.    Good performance can be  obtained in a smaller
number  of ponds  if baffles  or  dikes are  used  to  optimize  the hydraulic
characteristics of the system.

Recirculation  usually  is  accomplished with  high-volume,  low-head propeller
pumps.   Figure  4-17  presents   a  simplified cross   section  of   such  an
installation.   In this  design, the cost  and  maintenance problems  associated
with large discharge flap gates  are eliminated by  the siphon discharge.  An
auxiliary pump  with an  air eductor maintains  the siphon.   Siphon breaks  are
provided to ensure positive backflow  protection.

Pumping  stations  of this  type  can be  designed to  maintain full  capacity  with
minimal  increase in  horsepower   even  when  the inlet  and  discharge  surface
levels  fluctuate over  a  range  of  1.0-1.2  m  (3-4 ft).   Multiple- and/or
variable-speed  pumps  are  used to adjust  the  recirculation rate to  seasonal
load changes.

Pond configuration should allow  full  use  of  the wetted pond  area.   Transfer
inlets  and  outlets  should be  located  to eliminate  dead  spots  and   short
circuiting  that  may  be  detrimental  to  photosynthetic  processes.    Wind
directions should be  studied  and transfer outlets located  to  prevent   dead
pockets where scum will tend  to  accumulate.  Pond  size  need  not be  limited,
as long as proper distribution  is maintained.
                                     188

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                                                   ...    FIGURE 4-17


                              CROSS SECTION OF  A TYPICAL RECIRCULATION PUMPING  STATION
                                      4-inch air and vacuum
                                          release valve
                                                                         2-inch eductor
00
to



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4.6  References


 1.  Upgrading   Lagoons.    EPA-625/4-73-001,    NTIS   No.   PB-259974,   U.S.
     Environmental  Protection  Agency,   Center   for   Environmental   Research
     Information, Cincinnati, OH, 1977.

 2.  Uhte,  W.  R.   Construction  Procedures and Review  of  Plans  and  Grant
     Applications.   In:   Proceedings  of  Symposium on  Upgrading  Wastewater
     Stabilization  Ponds   to   Meet  New  Discharge  Standards,  Utah  State
     University, Utah Water Research Laboratory,  Logan, UT, 1974.

 3.  Operations  Manual  for Stabilization  Ponds.  EPA-430/9-77-012, NTIS  No.
     PB-279443,  U.S. Environmental  Protection Agency, Office  of  Water  Program
     Operations, Washington, DC, 1977.

 4.  Kays, W. B. Construction of  Linings  for Reservoirs,  Tanks,  and Pollution
     Control  Facilities.   Wiley-Interscience Publishers,  John  Wiley  &  Sons,
     Inc., New York, NY, 1977.

 5.  Thomas,  R.  E., W.  A. Schwartz,  and  T.  M.   Bendixen.   Soil Changes  and
     Infiltration  Rate  Reduction  Under  Sewage   Spreading.   Soil  Sci.   Soc.
     American Proc. 30:641-646,  1966.                                      ,

 6.  Middlebrooks,  E.  J.,  C.  D.  Perman,  and  I.  S.   Dunn.   Wastewater
     Stabilization  Pond  Linings.    Special  Report  78-28.   U.S.  Army   Cold
     Regions Research and Engineering Laboratory, Hanover, NH, 1978.

 7.  Stander, 6. J., P.  G.  J. Meiring, R.  J. L.  C.  Drews, and H. Van  Eck.   A
     Guide to Pond  Systems  for  Wastewater  Purification.   In:   Developments  in
     Water Quality  Research,  Ann Arbor Science  Publishers,  Inc., Ann Arbor,
     MI, 1970.

 8.  Hannaman, M. C., E. J. Johnson, and M. A,   Zagar.  Effects  of  Wastewater
     Stabilization  Pond  Seepage on  Groundwater  Quality.   Prepared by Eugene
     A. Hickok  and Associates,  Wayzata,   Minnesota,  for  Minnesota  Pollution
     Control  Agency, Roseville,  MN, 1978.

 9.  Bhagat,  S.  K.,  and  D.  E.  Protector.  Treatment  of  Dairy  Manure  by
     Lagooning.   JWPCF 41(5):785-795, 1969.

10.  Hill,  David J.   Infiltration  Characteristics  from  Anaerobic Lagoons.
     JWPCF 48(4):695,  1976.

11.  Chang, A.  C.,  W.  R.  Olmstead, J.  B. Johanson,  and  G.  Yamashita.    The
     Sealing Mechanism of Wastewater Ponds.  JWPCF 46(7):1715-1721,  1974.

12.  Wilson,   L.  G.,  W.  L.  Clark, and   G.  Gi.   Small.    Subsurface  Quality
     Transformations  During Preinitiation of  a  New  Stabilization  Lagoon.
     Water Resour.  Bull. 9(2):243-257,  1973.
                                      190

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13.  Matthew, F. L., and  L.  L. Harms.   Sodium  Adsorption  Ratio Influence on
     Stabilization Pond Sealing.   JWPCF 41(11)  Part  2:R383-R391, 1969.

14.  Rosene, R. B., and C.  F.  Parks.  Chemical Method  of  Preventing Loss of
     Industrial and Fresh Waters from Ponds, Lakes and  Canals.  Water Resour.
     Bull. 9(4):717-722,  1973.

15.  Davis, S., W. Fairbank, and  H.  Weisbeit.   Dairy Waste Ponds Effectively
     Self-Sealing.   Trans. Am.  Soc. Agric.  Eng.  16:69-71,  1973.

16.  Robinson,  F.  E.  Changes  in  Seepage Rate  from an  Unlined  Cattle  Waste
     Digestion  Pond.   Trans.  Am.  Soc. Agric.  Eng.  16:95,  1973.

17.  Rollins, M. B., and  A.  S. Dylla.   Bentonite  Sealing Methods Compared in
     the Field. J.  Irr. &  Dr. Div., ASCE  proceedings  96(IR2):193, 1970.
                       /
18.  Dedrick, A. R.  Storage Systems for Harvested Water.  U.S. Department of
     Agriculture.   ARS W-22,  1975. p. 175.

19.  Asphalt Linings  for  Seepage Control:   Evaluation  of Effectiveness  and
     Durability of Three Types  of   Linings.   Tech.  Bull.  No.  1440,  U.S.
     Department of Agriculture, 1972.

20.  Linings for Irrigation Canals, U.S.  Department  of the  Interior,  1963.

21.  Buried Asphalt  Membrane  Canal   Lining.   Research  Report No.  12,   U.S.
     Department of the Interior,  1968.

22.  Mangel son, K. A.    Hydraulics  of  Waste  Stabilization   Ponds  and  Its
     Influence   on  Treatment  Efficiency.    PhD   Dissertation,   Utah  State
     University, Logan, UT, 1971.

23.  George, R. L.  Two-dimensional  Wind-generated  Flow Patterns,   Diffusion
     and Mixing in a Shallow  Stratified Pond.  PhD Dissertation,  Utah State
     University, Logan UT, 1973.

24.  Mangelson, K.  A., and  6.  Z.   Watters.   Treatment Efficiency  of  Waste
     Stabilization Ponds.   J. Sanit.  Eng. Div.,  ASCE  98(SA2),  1972.

25.  Finney, B. A., and E.  J.  Middlebrooks.   Facultative Waste Stabilization
     Pond Design.   JWPCF 52(1):134-147,  1980.
                                      191

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                                   CHAPTER 5

                 ALGAE, SUSPENDED SOLIDS, AND NUTRIENT REMOVAL


5.1  Introduction


Stabilization  ponds  are  an  effective means of  treating wastewater, reducing
BOD5  and  coliforms,  but  can  have  an  occasional  high  concentration  of
suspended solids (SS) in  the effluent.  During some months of the year, the SS
concentration  exceeds the secondary effluent standards specified by  regulatory
agencies.  SS  concentrations  can exceed  100 mg/1,  but  such high  levels are
usually  limited to  two  to four  months  during  the year.   In  the standards
established on October 7, 1977, small flow pond  systems  were excluded from ;the
Federal  SS  effluent requirements.  For  discharge  to  water quality  limited
streams, removal may be required.

A discussion taken from many  sources  is  presented of the various alternatives
available for  upgrading the effluent quality from existing ponds and designing
original systems to  meet water quality standards (1-3).                    :

                                                                           I
5.2  In-Pond Removal Methods


There are several factors  to  be  considered for in-pond  removal  of particulate
matter:

     1.  Subsequent  degradation  of settled  matter by microorganisms  to
         produce dissolved 8005,  which  could then  have  an  effect on the
         receiving water.

     2." Possibility that settled material will not remain settled.

     3.  Lack  of positive control Of effluent SS.

     4.  Problem of  eventually filling the pond.                            ;

     5.  Possibility that anaerobic reactions within the settled material
         will  produce malodors.                                             ;

At  first glance,  it seems  that  some of  these problems could  be  resolved by
rather simple  changes in  operation.   In  ponds that have cells  in series, the
settled  material  could   be  removed  from  the  bottom of  the  last cell  and
transferred  to  the  anaerobic  cell  or   primary   cell  in  which  biological


                                      192

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 degradation is  encouraged.    Positive  control  could  be achieved  by  adding
 coagulants  to  the final cell  to  ensure that settling  of  the SS takes  place.
 For example,  chemicals such as limes  ferric chloride, and alum might  be  used
 in  this  manner.   Generally,  complete containment ponds have  a  life  expectancy
 of  about 20 years (4).   In  areas short of  land,  filling could be  a  problem,
 but it might  be possible to dredge and  remove  the  solid material  after 10  to
 20  years have  elapsed and to restore the pond  to  its  initial  state.   In areas
 where  land  is  available and  land  cost  is not prohibitive,  filling would not  be
 a problem.


      5.2.1  Series Ponds


 Series ponds  are recommended by  some state  regulatory  agencies  to provide for
 algae  sedimentation  within cells.   The efficiency of  sedimentation in  cells,
 however, is limited by factors such  as wind mixing and  algae  species.  Small
 cells  usually  result in less mixing  (5).


      5.2.2  Series Ponds  with  Intermediate  Chlorination


 Chlorination  is  normally used to disinfect  effluent, but  it  has been  observed
 that chlorine added  to pond effluent will  also  kill  algae and cause settling.
 In  1946 a study  was  conducted of a series of four oxidation  ponds followed  by
 a  chlorine-contact  pond near  Dublin,   CA.   At  a flow  of  14,200 m3/d  (3.75
 mgd) the chlorine-contact pond had a retention  time  of 13.5  hr.  All  the algae
 were  reported killed  with  a chlorine  dose  of  12 mg/1.   In  addition,  between
 chlorine-contact pond  inlet  and  outlet, the BOD5  was reduced  from 45 to  25
 mg/1,  SS from 110 to  40 mg/1,  and turbidity from 170 to 40 JTUs (6).   Similar
 reductions  were  reported in  a later study,  which found that  volatile  SS could
 be   reduced 52  percent and  turbidity  32  percent  through  Chlorination  (7).
 Laboratory  tests with varying chlorine doses  showed  that  18 to 28 mg/1  of
 chlorine could be added without  producing  a chlorine  residual  above  0.5  mg/1
 in  the  effluent.   In  these tests,  a 67 percent SS removal  (24  mg/1  in the
 effluent)  and  68   percent   8005  removal   (5   mg/1   in  the  effluent)  were
 reported.  The  flocculating  effect of chlorine is  thought  to  result  from
 rupture  of the  algae cell  wall  and  release of cellular  metabolites  that may
 serve as flocculants (8).

 Recent studies at Utah State  University on the Chlorination  of pond  effluent
 do  not  confirm  the  concerns expressed  earlier by Echelberger et al.  (8) and
 Horn (9)  that  destruction of  algae  and lysis  of cells  will  occur with  high
 doses of chlorine.   Rather, these were  found to occur only when free residual
 chlorine is available (10)(11).   These studies have  shown  relatively  little
 COD released  to  the effluent  by the  Chlorination of  algae-laden waters  with
 chlorine dosages adequate  for disinfection, and  dosages as  high  as  30  mg/1
 with  63  mg/1   of  SS  have produced very  little change  in  the  COD.   In  general,
 COD   increased  with   free  available   chlorine   residual   but,  at  residual
•concentrations less than 2  mg/1, there appeared to be no consistent pattern.
 With  a  reasonable degree of  dosage  control, disinfection or  killing  of algae


                                       193

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should  improve settling  and  reduce effluent  6005  and SS.   The  use  of high
doses of chlorine could  result in  the  production of toxic chlorinated organic
compounds which may cause problems in receiving streams.


     5.2.3  Controlled Discharge Ponds


Controlled  discharge  is  defined as limiting the  discharge  from a pond system
to   those   periods   when   the  effluent   quality   will   satisfy  discharge
requirements.  The usual practice is to prevent discharge from the pond during
the winter, and during spring  and fall  overturn periods.

The  operations  of 49 controlled  discharge ponds in  Michigan have  been well
documented  (12).    Ponds  at   that  latitude usually  have low  BODs  loadings,
averaging  about  22   kg/ha/d   (20  Ib/ac/d).   All  the  systems  studied  were
designed  for  discharge  twice  yearly,  with effluent retention  between late
November and mid-April and from about mid-May to mid-October.  Discharge times
coincided with  periods  of low al gae-SS levels.   Mean effluent concentrations
were about 15 mg/1 BOD and 30 mg/1 SS.

A similar  study of controlled discharge  pond  systems was also  conducted in
Minnesota (12).   The  discharge practices  of the 39  installations studied were
similar  to  those  in Michigan.    The  results  of  that  study  from  the  fall
discharge period  indicated that  the  effluent  BODs concentrations for  36 of
the  39  installations  sampled were  less   than  25  mg/1  and  the  effluent SS
concentrations were  less than 30 mg/1.   In addition,  effluent fecal  coliform
concentrations were measured  at  17  of  the  installations studied.  All  of the
17 installations  reported  effluent  fecal  coliform concentrations of  less than
200/100 ml.                                                                  '

The  controlled  discharge  of  pond effluent   is   a   simple,  economical  and
practical method of protecting receiving water quality.  Routine monitoring ,of
the  pond contents  is necessary  to determine the  proper  discharge  period.
These discharge periods  may extend throughout  the  major  portion of  the year.
It may be necessary  to  increase the storage capacity  of continuous-flow pond
systems if  conversion to controlled discharge  is contemplated.   However, many
pond systems already  have sufficient freeboard and thus storage capacity which
could be utilized without significant physical  modification.

Controlled  discharge  is  an excellent  way  to control  algae  concentrations in
pond effluents where  the problem  is  seasonal.   Most  facultative  ponds  can be
operated as controlled discharge ponds  for certain periods of the year, and in
many cases this is all that would be required to control  the effluent SS.
                                                                            !

         5.2.3.1  Chemical Addition                                         !

                                                                            I

A  series of  reports distributed  by  the   Canadian  government  has  indicated
success  with  the  treatment of controlled  discharge  ponds by  adding  various
coagulants  from  a  motorboat  (13-15).     Excellent  quality  effluents  are


                                     194

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produced,  and  the  costs are  relatively  inexpensive.   The  cost  of  in-pond
treatment and the long  detention  times required must be balanced against the
alternatives  available.    Man-hour  requirements   for  the  full-scale  batch
treatment systems employed in Canada are summarized in Table 5-1.
                                   TABLE 5-1

               LABOR REQUIREMENTS FOR FULL-SCALE BATCH TREATMENT
                      OF INTERMITTENT DISCHARGE PONDS (13)
                                             Man-hours per
                                                        appli cati on

            Alum, liquid             2          1.6         16

            Ferric Chloride,
             liquid                  1.5        1.2         16
             powder                 13          9.6         16

            Lime,
             dry chemical method    24         17.7        125
             Haliburton method       1.7        1.4         16
In addition to the usual design considerations applied to controlled discharge
ponds, the following physical design requirements were recommended  (13):

     1.  A  roadway to  the  edge  of  each cell  with  a  turn-about area
         sufficient to carry 45 metric tons (50 tons) in  early spring and
         late  fall  or a piping  system to  deliver  the chemical  to each
         eel 1  and  a  road  adequate enough to  get the boats  to  the pond
         edge.

     2.  A boat ramp and a small dock installed in each cell.

     3.  Separate  inlet  and  outlet facilities to allow  diversion of raw
         wastewater  during  treatment  and  draw-down  in  multiple-cell
         installations for maintaining optimum effluent quality.

     4.  A low-level  outlet  pipe  in the  pond  to  allow complete  drainage
         of the cell contents.

     5.  An  outlet pipe from the  pond of sufficient  size  and design to
         allow drainage of the treated area over a 5- to  10-day period.

     6.  In  new,  large  installations,  a  number of medium-sized  cells of
         4-6  ha  (10-15  ac) would  be  better suited  to  this  type  of
         treatment than one  or two large  cells.  These medium-sized cells


                                    ' 195

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         could  be  treated individually and  drawn  down  over a relatively
         short  period  of  time,  thus  maintaining optimum water quality in
         the effluent.

Using  the  typical  wastewater stabilization  pond design  required  in the State
of  Utah  with 120  days  retention time for  cold weather storage  and  the most
severe conditions  likely  to occur, three chemical treatments per year would be
required.    Designing  a  system  for  1,140 nr/d  (0.3   mgd)  operation  would
result  in  approximately  136,000 m3 (36 x  10& gal) of  stored  wastewater per
treatment.   Applying alum at  a rate  of  150 mg/1   would result  in  20,400 kg
(44,900 Ib) of  alum  required  per treatment assuming that the hydraulic design
would control the  sizing  of the  storage ponds and neglecting evaporation.  The
installations would  require approximately  8 ha (20 ac)  of pond surface with a
depth  of 1.8 m (6 ft).   Assuming  that  a  relatively  small  boat  and supply
system would be adequate to  distribute and mix the chemicals with  the pond
water, a  capital   investment  of approximately  $33,000   (1978  US  $)  would ,be
required  to  obtain  the  tank  trucks,  storage  facilities,  boat  and  motor to
carry  out  the  operation.   Amortizing  the  equipment  for a useful  life  of [ 10
years  and  assuming 7 percent interest, it  would cost $4,700/yr.   Liquid alum
costs  approximately  $116/metric ton ($105/ton)  (equivalent dry)  and  using 62
metric tons  (68 tons) annually would  cost  $7,, 140.   Approximately  136,000 m3
(36 x  10°  gal)  of wastewater would  be treated before each  discharge.   Using
the  requirements   shown  in Table  5-1  of  1.6 man-hours/10^  gal  and  16 man-
hours  for  setup  and  cleanup  per application  results   in  a  total  labor
requirement of  221 man-hours/yr.  At labor costs of $20/hr, the cost would be
$4,420/yr.   Adding all  of the  above costs,  exclusive of the capital  cost of
the  pond  system,   results   in  an  annual   cost   of  $16,260  or  $0.040/m3
($150/106 gal)  of wastewater treated.                                      ;

The  above  costs  do not  include  storage  facilities  for  the  alum  and  the
additional  design  requirements  to  accommodate the  alum  handling equipment and
the boats.   However,  even  doubling the estimated  costs it is  apparent that
intermittent discharge  with chemical  treatment,  is  a  viable alternative where
applicable.

In addition to the cost advantages outlined  above,  batch chemical  treatment of
intermittent discharge  ponds  can  produce  an effluent containing less  than  1
mg/1 of  total  phosphorus.  SS and B005 concentrations  of less  than  20 mg/1
can be  produced consistently and  only occasionally did  a  bloom  occur durilng
draw down  of the  pond.    Rapid draw  down  would overcome  this  disadvantage.
Sludge buildup  was  insignificant  and  would  allow years of  operation before
cleaning would be required.                                                 •


     5.2.4  Continuous Overflow  Ponds with Chemical Addition


Studies  of in-pond precipitation  of phosphorus, BOD5,  and SS  were conducted
over a two-year period  in Ontario, Canada  (16),  The primary objective of the
chemical  dosing  process  was  to   test  removal   of  phosphorus  with  ferric
chloride, alum, and  lime.   Ferric  chloride doses of 20 mg/1 and alum doses of
225 mg/1, when continuously added to the pond influent,  effectively maintained


                                     196

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pond effluent phosphorus levels below 1 mg/1 over a two-year period.  Hydrated
lime, at  dosages up  to 400 mg/1,  v/as not  effective  in  reducing  phosphorus
below 1 mg/1  (1  to 3 mg/1 was achieved) and  produced  no 8005 reduction and a
slight increase  in SS concentration.   Ferric chloride  reduced  effluent BODs
from  17   to   11  mg/1  and  SS  from  28  to  21  mg/1;  alum  produced  no  B005
reduction and a slight SS reduction  (43  to 28-34  mg/1).   Consequently,  direct
chemical  addition appears to be effective only for phosphorus removal.

A six-cell pond  system  located in  Waldorf, MD,  was modified to operate as two
three-cell systems  in parallel  (17).   One system was  used as a control  and
alum was added to  the other for  phosphorus removal.   Each system contained an
aerated first cell.   Alum addition to  the  third cell of  the  system proved to
be more efficient in removing total phosphorus, BOD,  and SS than alum addition
to the first  cell.   Total  phosphorus reduction averaged  81  percent when alum
was added at the inlet to the third cell and 60 percent when alum was added to
the inlet of  the first  cell.  Total phosphorus  removal  in  the  control  ponds
averaged 37 percent  when  alum was  added to the third cell and 50 percent when
alum was added to the first cell.  The effluent total phosphorus concentration
during the period when  alum was  added  to the first cell was 4.1 mg/1 compared
to  4.8  mg/1   total  phosphorus  concentration  in  the  control  system effluent.
When  alum  was  added  to  the   third   cell,  the  effluent  total  phosphorus
concentration averaged  2.5  mg/1  with the  control  pond  effluent averaging 8.3
mg/1.  Improvements in BOD and SS removal  by alum addition were more difficult
to detect and, at times, increases in effluent concentrations were observed.


     5.2.5  Autoflocculation and Phase Isolation


Autoflocculation of algae, predominantly Chlorella, has been observed (18-21).
Laboratory-scale continuous-flow experiments with mixtures of activated sludge
and  algae  have  produced  large  bacteria-algae  floes  with  good  settling
characteristics (21)(22).

Floating  algae blankets  in the  presence  of chemical  coagulants   have  been
reported  (23)(24).   This phenomenon may be caused  by  the  entrapment  of gas
bubbles  produced  during metabolism or  by  the   fact  that  in  a  particular
physiological  state  the algae have  a  neutral  buoyancy.    In  a 3.2-liter/sec
(50-gpm)  pilot plant  (combined  flocculation  and sedimentation),  a floating
algal blanket occurred  with  alum  doses of  125 to  170 mg/1.   About  50 percent
of the algae  removed were skimmed from the  surface (24).

Because   of   the   infrequent   occurrence  of   conditions   necessary   for
autoflocculation, and poor  understanding of the  actual  mechanism involved, it
is not a viable alternative for removal of  algae from ponds at this time.

Phase  isolation  is an  attempt  to design  a pond  system  in  which the various
processes involved in  wastewater  ponds are  separated,  and  ponds  performing
these  special  functions  are  placed   in   series.    Field  studies  of  phase
isolation have yielded  inconclusive results  (25)(26).
                                      197

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     5.2.6  Aquacul ture


Aquaculture is a centuries-old technique for producing food and fiber products
for direct or indirect human consumption.  Application of waste materials, for
their nutritive value, to  aquaculture systems has been a  common  practice for
many years  in  some  parts of  the world.   The  use  of  designed  aquaculture
systems for treatment and  management  of  municipal  wastewaters is  a relatively
new  concept.    As  recently  as  1978, Duffer  and Moyer  (27)  concluded  that
additional  developmental   research  was  needed  to establish  reliable  design
criteria.    They   presented   a  comprehensive   literature  review  and  were
optimistic  that  several  types  of aquatic organisms  could be  developed  that
would  be  attractive  in  terms  of treatment  effectiveness,  cost,  and  energy
usage.    A 1980 engineering assessment of aquaculture systems  for wastewater
treatment is available (28).                                               ',

Although  aquaculture  shows  promise  as  a  potential   wastewater  treatment
process, much remains to be learned at this time regarding removal mechanisms,
design parameters,  and overall  applicability.   The following sections present
results from recent research utilizing various types of organisms (29-33).


         5.2.6.1  Invertebrates


Invertebrate organisms which feed on  algae include Daphnia and related species
(water fleas), Artemia (brine shrimp), and assorted bivalve mollusks (oysters,
clams,  and mussels).

Design considerations for  culturing invertebrates must take into account their
environmental  requirements.   These include pond  site selection,  construction
of  berms  and  baffles,    inlet  and  outlet  structures,  mixing  and  depth,
substrate, and pH regulation.   Culture ponds require rigid operational control
and extensive management (34).

Based upon  the  experiences with  invertebrates  in wastewater ponds  to  remove
algae,  their use does not  appear to be feasible at this time.


           5.2.6.2  Water  Hyacinth                                         '


Water hyacinth is an aquatic plant native to South America that was introduced
into the United  States  in  1884.    The  species  currently   grows  throughout
Florida,  Southern  Georgia, Alabama,  Mississippi,  Louisiana,  and  in  parts  of
Texas and California.  Temperatures  below freezing will  kill the  plant.   The
plants form dense mats, interfering with most uses of waterways;  the hyacinth
has been  designated a noxious weed by the  U.S. Government.   Under favorable
conditions, the  total  plant mass  can double  in  periods  of a  few  weeks.   In
order to support this  rapid plant growth, hyacinths  consume  large amounts  of
nitrogen  and  phosphorus,   making  it  a potentially  useful  means  for  nutrient
removal from pond effluent.

                                      198

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Dinges  (35)  experimented  with using  water hyacinths  cultivated in  shallow
basins  for  treating  pond effluent   from  the  Williamson  Creek  Wastewater
Treatment  Facility  at  Austin,  TX.     Effluent   BODs  levels  through  the
experimental  system were reduced by 97 percent;  SS by 95 percent; and  COD by
90  percent.   Mean  effluent 8005  and SS levels were  less  than 10 mg/1  and
effluent total  nitrogen was less than 5 mg/1.

Wolverton and McDonald (36) diked off a 2.0 ha (5.0 ac) portion of a pond with
an average depth of  1.2 m  (4  ft)  and  stocked  it with water hyacinths.   Before
the hyacinths were  introduced  the pond produced no reduction  in  effluent SS
and  a  76  percent  reduction  in  6005.    After   the  water  hyacinths  were
introduced, SS were  reduced an average of 87  percent and BOD5  an  average of
94 percent.

Chambers (37) experimented  with water  hyacinths  at the Exxon Baytown Refinery
over a two-year period.  Following introduction  of water  hyacinths in  August,
a 78 percent reduction in  effluent SS  was obtained in September.  The tops of
plants  were  damaged  by   coots,   a  duck-like   bird,   by   early  November.
Subfreezing weather killed  the  tops in the  winter and surface coverage by the
hyacinths was reduced  from 80 percent of the  pond to 50 percent  in January.
After  mechanical  harvesting  in  late January   as  planned,   surface  coverage
dropped  to  zero  in  March  and  effluent  quality was  the same  as in  control
ponds.   Experience the next  year was  similar.   This  study  demonstrates  the
seasonal nature and  some of the potential management problems associated with
water hyacinths.
                                           >
Water hyacinth systems are capable of removing high levels of BOD, SS,  metals,
and  nitrogen,  and  significant  removal  of  refractory  trace  organics  (28).
Removal  of phosphorus is  limited to  the plant needs  and  probably will  not
exceed  50  to  75  percent  of  the  phosphorus  present  in  the  wastewater.
Phosphorus removal  will  not even approach  that range  unless there  is  a very
careful  management  program with  regular  harvests.    In  addition  to  plant
uptake, the  root  system  of the water  hyacinth  supports a very  active  mass of
organisms that assist in the treatment.  The plant leaves also shade the water
surface and limit algae growth by restricting  light penetration.

Multiple-cell pond  systems where water hyacinths  are used on  one  or  more of
the  cells  are  the  most   common  system   design   (28).    Based  on  current
experience,  a pond  surface  area of  approximately  1600 ha/106  m^  ^5  ac/
10"  gal)  seems  reasonable  for  treating primary  effluent  to secondary  or
better  quality.    An area  of  about 500  ha/106 m3  (5  ac/106  gal)  should be
suitable for  systems  designed to polish secondary  effluent  to  achieve higher
levels of  BOD  and SS removals.  For  enhanced  nutrient removal  from secondary
effluent,  an area  of approximately   1300  ha/106  m3   (12  ac/106  gal)  seems
reasonable.   Effluent  quality  from such a  system  might achieve: <10 mg/1  for
BOD and SS, <5 mg/1 for N,  and approximately 60  percent P removal.  This level
of  nutrient  removal  can  only be obtained with  careful  management and harvest
to yield 110 dry metric tons/ha (50 tons/ac) per year.

The organic loading  rates  and  detention times  used for water hyacinth systems
are similar  to those  used  for conventional  stabilization ponds  that treat raw
wastewater (28).   However,  the  effluent from the water hyacinth system can be

                                     199

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much   better  in  quality  than   from   a  conventional   stabilization  pond,
particularly  with   respect   to  SS  (algae),   metals,   trace  organics^  and
nutrients.

Harvest of  the  water hyacinth or duckweed plants may be essential to maintain
high levels  of  system performance  (28).   It is essential  for  high  levels' of
nutrient  removal.    Equipment  and  procedures  have been   demonstrated  for
accomplishing these  tasks.   Disposal and/or reuse  of the  harvested materials
is  an  important  consideration.   The water  hyacinth plants have  a moisture
content  similar to  that of  primary sludges.   The  amount   of  plant biomass
produce  (dry basis)  in  a  water hyacinth pond  system is about  four times the
quantity  of  waste  sludge produced  in conventional  activated sludge secondary
wastewater   treatment.      Composting,   anaerobic   digestion   with  methane
production,  and processing  for  animal   feed   are  all  technically  feasible.
However,  the economics  of these  reuse   and  recovery operations do not seem
favorable at this time.  Therefore  only a portion of the solids disposal costs
will be recovered unless the economics can be improved.                    ;

The major cost  and energy  factors for water hyacinth systems are construction
of  the  pond  system,   water   hyacinth   harvesting  and  disposal  operations,
aeration  (if provided), and  greenhouse   covers  where utilized  (28).   Evapo-
transpiration in arid climates  can  be a  critical  factor.   The water loss from
a water  hyacinth system will  exceed the evaporation from  a comparably sized
pond with open water.  Greenhouse structures may be necessary where  such water
loss and related increase in effluent TDS are a concern.

Mosquito  control  is  essential  for  water hyacinth  systems and  can  usually be
effectively  handled  with Gambusia or other mosquito  fish.   Legal  aspects are
also a concern.  The transport or sale of water hyacinth plants is  prohibited
by Federal and  state law in many situations.   The  inadvertent  release of the
plants from  a system to  local  waterways  is a potential  concern to a number, of
different agencies.   A  fixed  barrier can  be   used  to  prevent escape  of the
plants to the  outside environment.  Water   hyacinth plants  cannot survive or
reproduce in cool  waters  so  the  concept is limited  to  "warm"  areas  unless
climate  control  is   provided.    Other  floating  plants,  such  as  duckweed,
alligator weed,  and  water  primrose, have a  more extensive  natural  range but
only limited data on their performance in wastewater treatment are available.


         5.2.6.3  Fish


In Asia, fish, most  commonly members of the carp family, have been cultured; in
highly enriched water for centuries.   Schroeder (38) has shown  that fish can
be  effectively  combined with  plankton  and  bottom  fauna to  produce a system
that is biologically balanced with  stable DO and pH levels.

Experiments  at   the  Exxon  Baytown  Refinery  using  Golden   Shiners,  fathead
minnows, Tilapia noloticia, and mullet were unsuccessful; in fact, effluent SS
levels increased.Stomach analysis  of the fish revealed that,  in addition to
algae, they fed on alga-feeding invertebrates.  Reid (39) concluded that there
                                      200

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was  a   serious   gap   between  fish  culture   and   constraints   of  sanitary
engineering, pointing towards the need for further research.

Preliminary   experiments   at   Benton,   AR,   compared   parallel   three-cell
stabilization ponds receiving equal  volumes  of the  same wastewater (BOD - 260
mg/1, SS  -  140  mg/1)  (28).   The  cells in one set  were  stocked  with silver,
grass, and  bighead carp while the  other set  received no fish and was operated
as a conventional stabilization  pond.   The comparative  study  continued for a
full annual  cycle.  Results indicated generally similar performance of the two
systems but the fish culture units consistently performed somewhat better than
the  conventional  pond.    For example, the effluent BOD from  the  fish system
ranged from  about 7  to 45  mg/1  with values  less  than 15  mg/1  obtained more
than 50  percent of the time.   The conventional pond  system  had  effluent BOD
ranging from 12  to 52 mg/1  with values less  than 23 mg/1  about  50 percent of
the  time.  SS were very similar in  the  effluents  for both systems  except in
July when the concentration was  about 110 mg/1 for  the  conventional  pond and
60 mg/1 for the fish system.

In the second  phase  of the study  at Benton,  the  six cells were all connected
in series and a baffle constructed in each to reduce short circuiting.  Silver
carp and bighead carp were stocked in the last four cells and additional grass
carp, buffalofish,  and  channel  catfish  in  the  final  cell.   No  supplemental
feed  or   nutrients  were  added  to  the fish  culture  cells.    Estimated fish
production after 8 months  was over 3,300 kg/ha (7,200 Ib/ac).

Effluent quality steadily improved during passage through the six-cell system.
BOD  removal  for  the  entire system averaged  96 percent for the 12-month study
period.   About  89  percent  of  that  removal  was achieved in  the  first two
conventional  cells.    SS  removal  averaged  88  percent in  the  entire system,
with  73  percent occuring  in  the  two conventional   cells.    It  is  not clear
whether  the fish  or the  additional  detention time  or some  combination is
responsible  for  the  additional  7 percent BOD  removal  in the  final  four fish
culture cells..  The  final  average effluent  BOD concentration of about 9 mg/1
is typical for a six-cell  conventional stabilization pond system of comparable
detention time.   It seems  very  likely that the fish contributed significantly
to the low  SS in the final effluent (17 mg/1) via  algal  predation.   A value
two  or three  times that high  might be expected for conventional stabilization
ponds.


         5.2.6.4  Integrated Systems


Experiments  have  been   conducted  on  combinations  of   several   types  of
algae-reducing   organisms.    Ryther  (40)   concluded  that  highly  enriched
environmental systems were relatively unstable and difficult to control, often
failing to  develop a diversified biological community.

A  prototype  integrated  aquaculture  treatment  system  was  constructed  in
Hercules,  CA,  by  Solar   AquaSystems,   Inc.   (41).    Startup  problems  were
encountered   because   of    poor   construction  practices   and  efforts  were
                                      201

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unsuccessful  to  make the system  function  parallel  to  the  experiences of ;the
pilot facilities.  The system has been abandoned.


     5.2.7  Baffles


The  encouragement  of attached  microbial  growth  in  ponds  is  an  apparent
practical  solution  for  maintaining  biological  populations,  obtaining  the
desired treatment, and reducing the SS level.  Although baffles are considered
useful  primarily  to  ensure  good   mixing   and  eliminate  the  problem  of
short-circuiting, they may  also provide a  surface on  which bacteria, algae,
and other  microorganisms can grow.   In a study  of  anaerobic and facultative
ponds  with baffling,  the  microbiological  community  consisted  of  an  algae
gradient,  from  photosynthetic  chromogenic  bacteria  to  nonphotosynthetic,
nonchromogenic bacteria  (42)(43).   In these baffle  experiments,  the presence
of  growth  attached  to  the  baffles was  the  reason attributed  for  the higher
efficiency of treatment than that found in a nonbaffled system.


5.3  Filtration Processes


     5.3.1  Intermittent Sand Filtration


         5.3.1.1  Summary of Investigations


Literature  reviews   are  available  discussing  the   history,  theory,  design,
operation,  performance,  modeling, and  economics of intermittent sand,  slow
sand, rapid sand, and  other media filtration of  potable  water and wastewater
(44-58).   The following  is a condensation  of  these  reviews  and contains  a
brief  history of  intermittent  sand  filtration  of  wastewater as  well  as  a
summary  of studies  concerning  intermittent  siand filtration to  upgrade  pond
effluents  (see Table 5-2).

These  studies  indicate  that, with proper  design and  operation,  intermittent
sand fiftration  is  an effective  and  economical  process to  upgrade wastewater
stabilization pond effluent to meet present and future  discharge requirements.
The  effective sand  size  has been  found  to  be  the most  important variable
relative  to quality  of  effluent  and  the  ability  of the  process  to  meet
effluent requirements.  Hydraulic loading rate does not have a  great effect;on
the  effluent  quality but does  play  an important  role  in the  economics  of
filter  run  time.   Lengthening the filter  run  time  requires either a decrease
in  loading rate, which  in  turn  creates  a  larger  initial   construction  cost
along  with increased  maintenance costs,  or  a  sacrifice  in  the quality  of
effluent.   Neither  variation guarantees any consistent run time  because  pond
effluent quality  can fluctuate  greatly during  the  year and  can  increase  or
decrease the filter run time.
                                      202

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                                                                   TABLE  5-2


                                                  INTERMITTENT  SAND FILTRATION STUDIES
o
co

Pond Type

Facultative


Facultative





Facultative


Facultative


Aerated

Anaerobic*5


Facultative

Load! ng
u* Rate
.mgad
5.8 0.1
0.2
0.3
9.74 0.2
0.4
0.6
0.8
1.0
1.0
6.2 0.5
1.0
1.5
9.73 0.25
0.5
1.0
9.73 0.5
1.0
HA 0.1
0.35
0.5
9.7 0.2
0.4

Influent
rag/1
13.7
13.7
13.7
30.3
30.1
34.0
23.9
28.5
24.3
32.4
32.4
32.4
70.7
197
108
158
68.7
353
208
194
23.0
20.8
SS
Effluent
rag/I
4.0
4.8
6.0
3.5
2.9
5.9
4.7
5.1
3.7
8.6
7.8
6.4
10.1
15.6
11.8
52.5
32.9
45.5
46.5
45.1
2.7
3.5

Removal
percent
71
65
56
88
90
83
80
82
85
74
76
80
86
92
89
67
52
87
78
77
88
83

influent
ntg/1
9.2
9.2
9.2
23.0
22.5
25.9
15.2
21.5
18.6
21.9
21.9
21.9
38.8
155
83.0
71.1
36.6
264
162
175
17.8
18.5
VSS
Effluent
™9/1
2.0
2.1
2.3
1.3
3.4
3.1
1.2
2.5
1.6
3.3
3.2
3.3
6.5
11.9
8.8
13.2
11.3
28.1
35.3
35.7
1.0
2.3

Removal
percent
78
77 >
75
94
85
88
92
88
91
85
85
85
83
92
89
81
69
89
78
80
95
88

Influent
mg/1
6.3
6.3
6.3
19.5
20.6
25.6
2.8
13.5
6.1
10.7
10.7
10.7
20.2
71.4
34.0
34.4
19.6
123
108
107
10.9
11.5
BOD
Effluent
~~rog7l
1.2
1.3
2.0
1.9
2.5
4.2
1.8
2.6
2.2
1.8
2.0
2.3
6.6
9.4
13.0
5.1
, 11.7
19.5
43.7
67.6
1.1
2.6

Removal
percent
82
80
69
90
88
84
36
81
64
83
82
79
67
87
62
85
40
84
60
37
90
77

Reference

44


47





48


49


49

50


51

            aResults for best overall performing 0.17 mm e.s. filters.

            ''Dairy waste.

            *u = uniformity coefficient.

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         5.3.1.2  General Design Considerations
*>                                   .-.'•.-                '

 In  general, the  design  and construction  of intermittent  sand  filters  ;for
 polishing  pond  effluents is  similar  to that used  for conventional  slow sand
 filters used in potable water treatment.  Because pond systems are designed to
 be  relatively  low-maintenance systems, intermittent  sand  filters  designed to
 augment pond systems should  also  be designed as  low-maintenance systems.  The
 initial capital cost of constructing intermittent sand filters will be reduced
 substantially  if filter  material  (i.e.,   embankment,  sand  and  gravel)  are
 locally available or can be  processed on site.  It is obvious that importation
 of  these  materials  to the  construction site will  significantly increase  the
 cost  of  construction.    In  such  instances,  a complete economic comparison of
 various pond effluent polishing techniques  should be performed.

 Basically,  there  are two  different configurations employed  for intermittent
 sand  filtration  of  pond  effluent,  single-stage and  series.   Single-stage
 intermittent  sand filtration  consists  of  passing  pond  effluent through  a
 single intermittent  sand  filter employing  a reasonably small  (0.20 mm to 0.30
 mm)  effective  sand  size.    Series  intermittent  sand filtration  consists  of
 passing pond effluent  through two or more  separate  intermittent sand filters
 with  each  filter employing a  different  effective  sand  size.    The  initial
 filter sand  size in a  series  operation is  relatively large  (0.60 mm to 0.70
 mm) while the subsequent filters employ smaller sands (0.15 mm to 0.40 mm).


         5.3.1.3  Configuration   ;


 The decision to  use  a single-stage  or  a series  intermittent  sand filtration
 system should  be based  on  the effluent  quality required, desired  length of
 filter run, hydraulic head  available, and  availability of  various  filter sand
 sizes.  Each of  the  above considerations  has a  direct impact on the economics
 of the configuration selected.                                             :

 The effluent quality produced by an intermittent sand filter is almost totally
 a function of  the filter  sand  size employed.  The smaller  filter sand  sizes
 also  plug  faster  and thus  reduce  the length of  filter run.   In  areas  where  a
 high  quality   effluent  is  not required   (i.e.,  8005 £30 mg/1)  and SS  <30
 mg/1), a  single-stage  filter with  a  medium filter sand  size will  produce  a
 reasonable  filter run  length  and the  required  effluent quality.    If a high
 quality  effluent is desired (BOD5- <10 mg/1 and SS  <10  mg/1), 'then  series
 intermittent sand filtration with a small  final  stage Tilter sand  size should
 be considered.   In addition, series intermittent sand filtration is applicable
 in cases where the lower  operation  and  maintenance costs associated with long
 filter run lengths are desirable at the expense of initial  capital  costs.  •

 Series intermittent  sand  filtration  may  also  not  be  economically  feasible
 where sufficient hydraulic head is not available to allow flow from one filter
 to  the next.   Siphons  and  pumps  may  be  used to  transfer effluent  from  one
 filter to  the  next  in  series; however, the operational  costs involved should
 be closely examined.

                                      204                                   :

-------
Series  intermittent  sand filters may  not be  economically feasible  in  areas
where  different  filter  sand sizes  are  not  readily  available.    Again,  an
economic comparison should be made.

In general,  series intermittent  sand  filtration is  capable  of  producing  an
effluent equal to or better than a single-stage filter and will  generally have
longer  filter  runs.   Tjhe costs of series  intermittent  sand  filtration may  be
more than those associated with single-stage intermittent sand filtration.  To
date,  there  is  more  reliable  design  and operational  data  for  single-stage
intermittent sand filtration than for series filtration.       ,


         5.3.1.4  Hydraulic Loading  Rate                       •


The removal efficiency  by  an intermittent sand  filter  does  not  appear  to  be
seriously  affected  by variations in hydraulic  loading  rates  (44-47)(59)(60).
Effluent  quality deteriorated  only  slightly  with   significant   increases  in
hydraulic loading rate (48).

The length of filter  run  is also not  directly affected  solely  by nydraulic
loading rate.   Rather,  length of filter  run  is  affected by a combination  of
hydraulic loading rate and influent SS concentration.  Attempts have been made
to relate the time a filter  performs between  cleanings  to  the mass  of organic
material  removed or applied,  i.e.,  (hydraulic  loading  rate)  x  (influent  SS
concentration)  (45-47).    Experience  with  full-scale  units  summarized  in
Figures 5-1  through  5-4 represent the  relationship between mass loading and
the time between cleaning  the filters (47)(51)(61).  Figures  5-1 through 5-3
represent  the performance  of filters with  sands  of  various effective  size
located in an area with  relatively soft water (total  hardness <250  mg/1), and
Figure  5-4  applies  to  areas  with  hard  waters   where  calcium' carbonate
precipitation is likely to occur during periods of active algal  growth (61).


            a.  Single-Stage


Information  available  from  full-scale  operations   indicates  that  hydraulic
loading  rates of  0.37  to  0.56  m^/m^/d  (0.4  to  0.6  mgad)  may be  employed
using single-stage intermittent sand filtration.  In areas where high influent
SS  concentrations  are  anticipated   (above  50  mg/1  average)   lower hydraulic
loading  rates,   0.19  to 0.37 nr/m2/d  (0.2  to  0.4 mgad),  are  recommended.
These  lower  hydraulic  loading  rates are suggested to  increase the  time  of
filter  run.   If the  time  a filter  will  perform is not a  significant design
consideration,  i.e.>  when   filters  are  very  small,  less than  90 m2   (1000
ft2),  the  higher  loading   rates  may  be  employed; however,  operation  and
maintenance costs will increase.

In areas  where land  is relatively inexpensive,  lower  hydraulic  loading rates
are suggested so that the time  between filter  cleanings may be  increased.  In
this case, the  initial  capital  costs will be  higher, but the annual operating
costs will be  significantly  lower.   This  is especially  true  for  cold weather

                                     205

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                            FIGURE 5-1


    LENGTH OF  FILTER RUN AS A FUNCTION OF DAILY MASS LOADING
              FOR 0.17 mm EFFECTIVE SIZE SAND (61)
    300 r
    200
CO
-a
O)


"c
CO
_03

O

c
0)
0)
CO
(
o.
    100
            days = 2529 (SSL)
               r = 0.801
                                             -1.733
        0
10
20
30
40
50
                          SS Loading (SSL), g/mVd
                               206

-------
                                                  FIGURE 5-2



                           LENGTH OF FILTER RUN AS A FUNCTION OF DAILY MASS LOADING

                                     FOR 0.4 mm EFFECTIVE SIZE SAND (61)
                 200
ro
o
               to
               TJ
O)
C

'c
03
jl)

O

c
0)


I
              m

              T3
               O

              'C
               0)
              Q.
                 100
                    0
                                                days = 8859 (SSL)-1-625

                                                r = 0.900
                     0
                                  50


                               SS Loading (SSL), g/mVd
100
130

-------
                                                  FIGURE  5-3


                            LENGTH OF FILTER RUN AS A FUNCTION  OF  DAILY MASS  LOADING

                                      FOR 0.68 mm EFFECTIVE SIZE SAND  (61)
                  200
ro
o
oo
 w

 CO
•o

 CO
 0>


'c
 co
JB

o

 c
 0)
 0)

B
 d>
m
                  100
                                                             days = 12,350 (SSL)'1-445

                                                             r = 0.979
                    0
                      0
                                  50                         100

                               SS Loading (SSL), g/mVd
                                                                                            130

-------
                                                    FIGURE 5-4


                  LENGTH  OF  FILTER RUN AS A FUNCTION OF DAILY MASS  LOADING FOR POND EFFLUENTS
                 HAVING CALCIUM CARBONATE PRECIPITATION PROBLEMS  (0.17 mm EFFECTIVE SIZE SAND)
                50 r
ro
o
             CO
             T5

             to
             O)
             co
             O

             c
             CD
             0)
             •o
             o
             *l_
             CD
             CL-
                40
                30
                20
                   0
                                     days = 319 (SSL)-1-119
                                     r = 0.948
                                                     I
                                   I
10
20         30          40

       SS Loading (SSL), g/mVd
50
60
70

-------
climates.   The optimum design  in cold weather climates would  allow for Jong
filter  run times  during  the  freezing  months  to  eliminate filter scraping
during  this  period of the year.   A single-stage filter at  Logan,  UT,  with a
hydraulic  loading  rate  of  0.19  m3/m2/d  (0,2  mgad)  operated  for  189  days
during the winter season before scraping was necessary (45).


            b.  Series Operation


Series  intermittent  sand  filters  have  been  used  only   on  a  pilot-scale.
Details of this experience can be obtained elsewhere (48).


            c.  Seasonal Variations


Because  length of  filter runs are affected by  a  combination of hydraulic
loading  rate  and influent SS concentration,  seasonal  variations  in hydraulic
loading  rates  may  be  advantageous.   Higher  hydraulic  loading  rates  may  be
employed  during  periods of  low influent SS concentration.    However,  filter
design must be based on the minimum hydraulic loading rate employed during the
year.                                                                     ;


         5.3.1.5  Filter Size and Shape


The total filter area required for a single-stage intermittent sand filtration
system  is obtained  by  dividing   the  anticipated  influent  flowrate  by  the
hydraulic  loading  rate selected  for the  system.   For  a  series  intermittent
sand filtration system, the  total  area thus obtained  must  be supplied by each
stage of  the  filtration system.  Thus,  if the  same hydraulic  loading rate is
specified  for  a  single-stage system and a three-stage  series  system treating
the same influent flowrate, the total area required for the three-stage series
system  would  be three  times  greater  than the total  area required for : the
single-stage system.   However,  in practice, the  same  hydraulic  loading rates
would not be employed to design both filter systems.

Depending upon the work  schedule  during cleaning operations, a  filter  may be
totally  out  of service  for several days.   Thus,  at least one  spare  filter
should  be  included in  the  system  to  accommodate  the  cleaning  schedule.
Alternately, sufficient holding capacity could be included in the pond  systems
to allow storage of filter influent during filter cleaning operations.  In any
event,  provisions  must be made to  accommodate  down  time  during  the cleaning
operation.  No system should have less than two  filters, and three filters are
preferred.

The  exact size  of  an intermittent'sand filter  will  depend on  the influent
flowrate and the hydraulic loading  rate.   However, if  it  is anticipated that
sand scraping  and filter  cleaning  operations  are  to be achieved by mechanical
means, the filters should  be large enough to allow relatively easy movement of


                                     210                                 ;  ..

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machinery on the filter surface.  For very small systems, sand scraping may be
accomplished by  hand.   In  such  systems the maximum  surface area  per filter
should  not  exceed  approximately  90  m2  (1,000  ft2).    For  mechanically
scraped  filters,  Huisman  and  Wood   (62)  recommended  that  it  not  exceed
approximately 5,000 m2 (55,000 ft2).

The design  of  odd or random shaped filters to  make  the  best use of available
land  may  benefit the  initial  capital  cost  of construction;  however,  if
mechanical  cleaning  is anticipated, equal  size  rectangular beds are preferred
(59).   Equal sized beds allow  the  alternation of loading between filters with
a minimum  of  upset to the  total  system operation.   In addition, cleaning and
operational procedures may be standardized with equal sized filters.


         5.3.1.6  Sand
Selected sand  is  generally used  as a  filter  media; however,  other granular
substances,  such  as crushed  coal  and  burnt rice husks, have  been  used when
suitable sand  was  not  available (62).  The  use of materials  other  than sand
should be  carefully  evaluated in a pilot-scale  filter  before being  used in a
prototype intermittent sand filtration system.

Filter  sands  are  generally  described by  their  effective  size (e.s.)  and
uniformity coefficient (u).   The  e.s.  is  the 10 percentile size, such that 10
percent of the filter  sand  by weight  is less than that  size.   The uniformity
coefficient  is the  ratio  of the 60 percentile  size to the 10 percentile size.
An example  procedure for determining  e.s.  and u  for  a specific  filter sand
follows:

     Problem:  For a sand with the characteristics shown in Table 5-3,
               determine effective size (e.s.)  and uniformity coefficient
               (u).
                                   TABLE 5-3

                         SIEVE ANALYSIS OF FILTER SAND
            U.S.  Sieve           Size of Sieve           Percent
            Designation              Opening              Passing
                No.                     mm

               3/8 in                  9.53                 10.0
                 4                     4.76                  95
                 8                     2.38                  66
                16                     1.19                  41
                30                     0.59                  20
                50                     0.297                  6
               100                     0.149                  1
                                      211

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       Solution:

     1.  Construct  a plot  of sand  grain size  (size of  sieve opening)
         versus  sand size  distribution  (percent passing)  as  shown  in
         Figure 5-5.

     2.  Determine  the  10  percentile  size,  PIQ»   by   reading  the  10
         percentile line intersection on the  curve in Figure 5-5.

                                PIQ = 0-38 mm

     3.  By definition, PIQ is equivalent to  e.s.

                             e.s. = PIQ = 0.38 mm

     4.  Determine the 60 percentile size, Pg0, by reading the 60
         percentile line intersection on the  curve in Figure 5-5.
                                    = 2.00 mm

     5.  By definition, u is P5Q divided by

                                 " = P60/Pl0

                                   =2.00 mm/0.38 mm

                                   = 5.22

Filter  sand  of the  required  e.s.  and u may  be produced  from  stock sands by
removing a given fraction that is either too large or too  small.  Alternately,
the  specified  sand  may  be  produced  by  mixing  two   sands  with  different
characteristics.   Mixing of the  sands  must be carried out  very thoroughly,
preferably  in  a   concrete  mixer.     The  procedures   for  mixing  and  the
calculations for determining the  proper  portions for producing a given filter
sand are described  elsewhere (62) (63).                                     ;

The  filter may  be  clean  river,  beach,  or bank  sand  with  either  sharp ; or
rounded  grains.    It  should be   free  from  clay,  dust,   dirt,  and  organic
impurities.  It is  desirable that the filter sand be washed prior to placement
in the filter bed.   If the sand has  not been  washed prior to installation,  a
poor  quality  filter  effluent  will  result during  the   first  few weeks 'of
startup.  The deterioration in quality is  caused by  washing of fine inorganic
and  organic  material  from  the sand.   However, once  this material  has   been
washed  from  the sand,  a high quality  effluent can be  expected.    The   sand
grains  should  be  of a  hard material  which will not break down  with wear and
contact with water.                                .     ....

Experience indicates  that,  generally, pit  run concrete sand is  suitable for
use in intermittent sand filters, provided the e.s. and u  are suitable.  Costs
may be  reduced  substantially  if  a sand source can be located which  does not
require screening  or washing.    It is strongly  recommended that  a  natural iOr
pit run sand not requiring specialized grading be employed where possible.


                                     212

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                                     FIGURE 5-5

                     SAND GRAIN SIZE  vs SAND  SIZE DISTRIBUTION
    98
 0
_N
"tf)
 o>

 0>
 CD
•D
 C
 CO
 +->
 en

 o>
 c
'(/)
 CO
 CD
 Q.
 +->

 CD
 O

 03
•.. Q. '
 CO
 u
 C/5
 JD
 CD
 .Q
 O
 CD
 E
95  h-


90
50
     10
     0.1
   0.01
        0.1
                 I        I     I    |   I   I  I  I  |

           Effective size = e.s. = P10 = 0'.38 mm

           Uniformity coefficient = fj=^-= ^-00 mm _ g
                                    "10   O.Jo mm
                                                                          I     r
          P60 = 2.00 mm
          P10 = 6.38 mm
                     I
                         1    il    I   1   I   111
                                                             I
                                 0.5          1.0

                Sand Grain Size (size of sieve opening), mm
                                         213

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            a.  Single-stage                                               ;


Filter sand  for  a single-stage intermittent  <;and filter should have  an e.s.
ranging from  0.20 to 0.30 mm, a  uniformity  coefficient of  less than 7.0, and
less  than  1  percent of  the sand  smaller  than  0.1  mm.    A  higher  quality
effluent will be  produced  from  filter sand with an e.s. near  0.20 mm while a
slightly poorer quality effluent  will  result  from using a  filter sand with an
e.s.  near  0.30  mm.   Most of  the  recent  research  on   intermittent  sand
filtration has been conducted using a 0.17 mm e.s. sand  (44-47)(60).

Previous reports  (44)(45)(63) have recommended u values of 1.70 to 3.27, and u
for  slow  sand  filters  for  potable  water  treatment  of  less  than  2.0 are
suggested by  Huisman and Wood (62).   However, the recent work with polishing
pond  effluents  utilized filter sand  with  a u  of 9.74  (45-47).   Hill et al.
(48)  employed filter sands with  u values  ranging from less than  2.0  to 9.74
with little effect on effluent quality.

It  appears  that the u  has little effect on the  quality of effluent produced
from an intermittent sand  filter.  However, u values  greater  than 7.0 should
be avoided.   In general, u values ranging between 1.5 and 7.0 are acceptable.


            b.  Series Operation


In  a  series operation,   the filter  sand  e,s.   should decrease  with  each
succeeding stage  of the filter.   Very little  data  exist  to  determine exact
filter sand  sizes for  series operation.   Hill et al.  (48) reported  using a
0.72  mm  e.s. sand in  the first-stage  filter,  a 0.40 mm  e.s.  sand  in the
second-stage filter, and a 0.17 mm e.s. sand in the third-stage filter., Based
on these data for a three-stage series operation,  the range of e.s. values for
the  first-stage  filter  should  be  0.65   to   0.75  mm,  the   range  for  the
intermediate stage 0.35 to 0.45 mm, and the  range for  the  final stage 0.20 to
0.30 mm.

A careful pilot-scale study  should  be conducted before determining the filter
sand  e.s.  for a  two-stage  series filter operation.    The  u values  for sands
used  in  series  filter  operations  should  be  similar  to  those  used  in
single-stage intermittent sand filtration.


            c.  Use of Highway Sand


Many  highway  specifications  require  that fine aggregate for concrete  conform
to  the  requirements  of  the  American  Association  of  State  Highway  and
Transportation  Officials     (AASHO  M6)  (64).    Such  sand   is  applicable  ,in
intermittent  sand  filters  used  to  polish pond effluents.    The  AASHO  M6
gradation requirements are shown  in Table 5-4.
                                     214

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                                   TABLE 5-4

                   GRADATION REQUIREMENTS FOR FINE AGGREGATE
                       IN THE AASHO M6 SPECIFICATION (64)
                  U.S.  Sieve                  Percent
                  Designation                  Passing
                     3/8 in                      100
                       4                        95-100
                      16                  •      45-80
                      50                        10-30
                     100                         2-10
The sand size distribution of this sand at the specific upper and lower limits
of specification  are  shown  in Figure 5-6.   Analysis  of this figure indicates
that the e.s. of this sand will range from 0.15 to 0.30 mm with u ranging from
4.23 to 5.39.

As can  be  seen  in Figure 5-6, the  No.  50 and No. 100  sieve are the critical
points of gradation.  The 10  percentile  sand size must  lie  between  these two
sieve  sizes  because the  e.s.  is determined  by  the  10  percentile  size  sand.
Generally, a filter  sand with an e.s. of  between 0.20 and  0.30 mm  should  be
used for single stage and the final  stage in series intermittent sand filters.-
The restrictions  on  u  for sand  employed  in intermittent sand  filtration are
not severe.  Thus, the limit on gradations for the No. 4 and No. 16 sieves are
not exceptionally  critical.  However, 100  percent of the  sand should pass  a
3/8-inch sieve.


         5.3.1.7  Filter Bed


The filter  bed  consists of the  filter  sand and  the  gravel  layer  between the
filter  sand  and  the   underdrain  system.    A   cross  section  of  a  typical
intermittent sand filter is shown in Figure 5-7.


            a.   Filter Sand Bed


In general, the filter sand should conform to the e.s. and u criteria outlined
above.  The sand depth should be sufficient to produce a high quality effluent
and also  provide a  sufficient  reserve  to allow  for  several cleaning cycles.
It has  been  reported that at  least  45 cm (18 in) of  filter  sand are required
to produce an adequate quality effluent (44).  Huisman and Wood (62) recommend
at  least 70 cm  (28  in) of  filter sand  be provided  for   slow sand filters

                                      215

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                                   FIGURE 5-6

                 SAND GRAIN  SIZE vs SAND SIZE DISTRIBUTION FOR
                             AASHO M6 SPECIFICATIONS
 99.99
   99.9
                                  i  r I  i
                                                      1    r
                                         i  r


(0
W
(0
Q.
*-•

CD
(0
O
0)
CO
X)
O
ol
"5
E
Specification
Upper Limit
Lower Limit
Effective SiEe
(mm)
0.15
0.30
Uniformity
Coefficient
4.23
5.39
99

98

95

90
50
£   10
 2

 1
          Upper Limit
                                                             Lower Limit
    0.1


   0.01
                   J_
I   I   I  I I I  I
I
I    I   I   I  I  I  I
       0.1
                          0.5        1.0
                 Sand Grain Size (size of sieve opening), mm
                                                10
                                     216

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                                  FIGURE  5-7

           CROSS SECTION OF A  TYPICAL  INTERMITTENT SAND FILTER
                Liner
                                     1.8 cm Max dia. rock
                                  ^3.8 cm Max dia. rock
       Section 2-2
Sand and gravel placement
                       Supply
                       line —v
N f
1
I

N. '

/
i



j
k. ™ t
i\ !
/ » \
1 1 \
I
_iner and filter bed >
I \ '
O ~*.


V
\
i
i
\!

^ j
'\ '
N


\
/

\
1 \ III N
1\ 1 ' \
\ \\~
t lir

1

33 1 between
er and pipe
           — Seal
      .Seal between
     Section 1-1
    Liner section
                                                   Liner
                             Seal between drain pipe       X
                             and liner with suitable
                             material
Drain
                                     217

-------
treating potable water.   Research  studies using a minimum of 60 cm (24 in) of
filter sand have produced a high quality effluent (45-48)(60).  Based upon the
above data, it appears that an intermittent sand filter should not be operated
with less than 45 cm (18 in) of filter sand.

In addition, sufficient  sand  for  at least one year  of  cleaning  cycles should
be provided.  Approximately 2.5 to 5 cm (1 to 2 in) of sand are removed during
each cleaning cycle.   If the  anticipated  length of filter run is  30  days, at
least  an additional 30 cm  (12  in) of  filter sand  should  be provided.  ; In
.general, the total  initial depth of  filter sand employed on intermittent sand
filters  is 90 cm (36 in).


            b.  Gravel  Bed


In general, a graded gravel layer 30 to 45 cm (12 to 18 in) in depth separates
the filter sand from the underdrain system.  If the underdrain system consists
of  perforated  pipe  as opposed  to  a  conventional  tiled or  block underdrain
system,  the gravel  will  completely enclose  the  drain pipe.   The gravel system
is built up  of  various layers, ranging from fine  at the  top  to  coarse at the
bottom.   The -layers are designed  to  prevent filter  sand from  entering  and
plugging the  underdrain system.    In general,  the bottom  gravel  layer should
consist  of particles  with an  e.s.  at  least four  times  greater  than  the
openings into the  underdrain  system.  Each successive  layer  should be graded
so that  its  e.s.  is not more than  four  times  smaller than that  of  the layer
immediately below.

The research  on polishing pond  effluents at Logan, UT, was  conducted with a
gravel bed 30 cm  (12 in)  deep composed of three  10-cm  (4-in)  layers  (45-47).
The bottom layer  consisted of gravel  ranging  from 1.9  to  3.8 cm  (0.75 to 1.5
in) in diameter, the middle layer consisted of  1.3 to  1.9  cm  (0.5 to  0.75 in)
diameter gravel, and the  top  layer  consisted  of 0.32 to 0.64 cm (0.12 to 0.25
in) diameter gravel.  This arrangement has proven to be satisfactory.


            c.  Underdrain Systems


The underdrain  system  may consist  of  porous  or  perforated  unglazed  drainage
tiles,   glazed  pipes  laid  with  open  joints,  or  perforated  asbestos  or
polyvinyl chloride   (PVC)   pipe   (62).     Experience  has  indicated   that  a
corrugated, perforated PVC pipe (similar to that used for irrigation drainage)
provides an adequate drain system for  minimum  cost.   If drain pipes  are used,
they should be placed  within  the  bottom  gravel  layer of the filter to collect
the flow as  it  infiltrates  through the  sand.    Filter bottoms  should  slope
toward the drainage pipe for efficient collection of effluent.

Typical  drain schemes are shown in Figure 5-8.   The drain pipes should be laid
with sufficient slope  to  produce  "scour  velocity" in the  pipes  under average
flow  conditions.    This  will  allow the drain  system to be  self-cleaning  and
thus reduce maintenance costs.


                                     218

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                  FIGURE 5-8



COMMON ARRANGEMENTS FOR UNDERDRAIN SYSTEMS (62)
1 1 1
t 1 1
1 1 1
i ' 1
1
|i!
! i t
— - *•
i '
i i
> i
! -
!
! !
i i
«l .!.•!•.
                     III
                     219

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 The drains should  be  designed so that they are fully exposed  to  the  air.   It
 is imperative that air be able to circulate through  the  drain  system  into;the
 sand filter  bed.    Intermittent  sand filters are  an aerobic  system  and  thus
 must have an  adequate air circulation if they are  to perform properly.  Outlet
 drains  should be exposed to the atmosphere and not submerged.


          5.3.1.8  Influent System


 The influent system may be  gravity  flow,  or  utilize  pumps or automatic dosing
 siphons depending on the configuration of operation  and  the  topography of jthe
 site.    When  a  relatively  large amount  of  slope  is not associated  with  the
 filter  site,  series intermittent sand  filtration operations  will  require  a
 pump lift station between filters to  lift the effluent  from one filter to  the
 influent level  of the next filter in the series.

 The influent  system should be  designed with  sufficient  capacity to  enable  the
 total  daily hydraulic load to 'be applied to  the filter in less than  6  hr.   For
 filters less than  90 m2  (1,000  ft2) in  area,  the  daily hydraulic  load  may
 be applied to the filter in  less than 1 hr  for a  relatively small investment.
 For larger filter systems,  the dosing time should  be accomplished in less  than
 6 hr.   This method  of operation  allows  the  maximum head buildup on  the filter
 and also,  because  the  influent  will drain  through the  filter  quickly,  the
 maximum  bed   aeration   time  is  achieved.    Influent  velocities  should r be
 sufficient to prevent settling of solids in  the lines.

 The influent  distribution system need not be complicated or elaborate.   Even
 distribution  of the influent across  the filter surface will  be accomplished  by
 the water buildup on the  filter caused by the short dosing time (i.e.,  less
 than 6 hr).  Water may  not be distributed evenly  across  the entire filter  at
 first,  but within a short time after loading begins the  water will be  standing
 several  centimeters deep over the entire filter surface.                   '<  .

 Simple  channels which overflow at regular intervals across the filter  bed will
 provide adequate  distribution of the  influent.    Discharge  velocities  from
 these   channels  onto the  fil ter  surface shoul d  be smal1  enough  to  prevent
•serious sand erosion.   Splash  pads  may be necessary in some  cases to reduce
 sand erosion  near  inlet structures.   In addition,  inlet channels should  be
 equipped with drains or "weep holes"  so  that they  may drain  completely  dry
 during  periods  of freezing  temperatures.   This should  prevent the  buildup lof
 ice within the  influent  channels.

 The influent  system should  be  fully  automated   so  that pumps,  siphons,   or
 transfer  structures may  be activated  routinely  without continual  personal
 supervision.   Provisions  should  be  made  so  that  the system can be  operated
 either  during day or night.   Flexibility should  be designed  into the system  so
 that each  filter may operate  independently.   Series intermittent  filtration
 influent  systems  should be  constructed  so  that   operation  can be  either  ;in
 series  or  in parallel   as  a  single-stage filtration  system.     In  addition,
 manual  overrides should  be  provided  for all  systems in case  of  power failures.
 Alternatively,  an  auxiliary  power source should be available.  Spare pumps  and

                                      220                                    :

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metering  systems  should  be  provided.    In  general,   the  same  degrees  of
flexibility  should  be  provided  for  a  pond  system  as  that  found  in  a
conventional  treatment plant.


         5.3.1.9  Filter Walls


Filter walls  may be constructed  as  earthen embankments or  from conventional
building materials  such as concrete,  steel, or  wood.    In general,  earthen
embankments are  much  more  economical,  especially for larger filters,  and are
recommended  for  most  designs.    Steel  or  concrete  filter  walls  may  be
applicable  for  small   filters  where  embankment  materials are not  readily
available or space is limiting.

When materials  other  than  earthen  embankment  are  employed  for filter  wall
construction,  care  must  be  exercised   to  prevent "short-circuiting,"  the
downward  percolation  of  water  along  the  inner  wall   face  without  passing
through the filter bed.  Short-circuiting may  cause deterioration of "effluent
quality  and   is  a  particular problem  in  small   sand   filters.    Structural
precautions  should be  taken  to  guard  against it.   It  is  no  problem  with
sloping walls  or earthen wall embankments  because  the  sand tends  to settle
tightly against these types of walls.  However, with smooth vertical  walls, it
may be necessary to incorporate devices such as built-in grooves or artificial
roughening of the  internal  surface.  The most effective precaution is to give
the walls a slight outward batter, so as  to obtain the advantages of a sloping
wall (62).

Earthen  filter embankment construction  should be  similar  to  that  used  in a
normal well-designed pond system.  Embankments  are  usually designed  with side
slopes from 6:1  to 2:1 with  3:1  being the  most common.   Embankment top width
should be  at  least 3 m  (10 ft)  and  provide a  30-cm (1-ft)  thick all-weather
gravel road.   Road surfaces  should  be crowned  to assure rainwater runoff and
minimum erosion.

The interior  embankment should  be impervious to  prevent both  exfiltration of
filter   influent   and   infiltration  of   seepage   groundwater.     Most  state
regulatory agencies  have a standard for  maximum  seepage losses.   Figure 5-7
illustrates  the use  of a  liner to create an  impervious  embankment.   Such
liners are only economically feasible on relatively small  intermittent sand
filtration systems.   In general,  an  impervious clay layer or similar material
used  to  seal  the  pond  system  would   be  sufficient  to  seal  the  filter
embankment.

Interior slopes should  also be designed to prevent erosion due to wave action.
Erosion  protection  can  be  provided  by  cobbles,  broken  or  cast-inplace
concrete,  wooden  bulkheads, or  asphalt strips.   Emphasis  should be placed on
shoreline  control  and reduction  of  aquatic  weed  growths.    In  addition, each
filter should  be  provided  with a ramp  for easy access and routine maintenance
of the system.  The ramp can  be  used for both  entry of  cleaning equipment and
as a boat  ramp.
                                      221

-------
Embankments should provide at least 30 cm  (1 ft) of head on the filter and 0.5
to 1 m  (1.6  to 3.3 ft) of freeboard to prevent wave  action  from washing over
the dike.


         5.3.1.10  Sand Cleaning


An  intermittent sand  filter  is considered  to  be  plugged when  the amount of
water applied to the filter will not percolate through the sand bed before ;the
next dose  is  applied.   When  the filter is plugged, it is taken out of service
and the  top  2.5 to 5 cm (1 to  2  in)  of sand are  removed or  scraped from the
filter surface.

Huisman  and Wood (62) present a review of  the current practice of sand washing
associated with  slow sand filters employed  in  potable water  treatment.   The
design engineer should become thoroughly familiar with the current  practice of
sand  reclamation  before  proceeding  with  the  design  of  intermittent  sand
filters.   Sand  from  an intermittent  sand filter may be washed by conventional
means, used  as a  soil  conditioner,  or disposed  of in  a  landfill.   In most
cases,  economic considerations  will  dictate  that  the sand  be  cleaned and
reused  rather than  discarded.    A typical  sand  washing device is  shown  in
Figure  5-9.     Basically,  these  sand  washing  devices consist  of  an  upflow
clarifier  with sufficient velocity  for  removal   of  organic  matter,  without
washing  away  the  sand.   The  organic matter  washed  from  the  sand may  be
recycled back through the pond system.  Once the sand has been cleaned, it can
be stockpiled and eventually recycled to the filter.

Whether  to dispose of or reuse the  spent filter  sand is largely dependent on
the local  availability of the  filter sand.   When  sand  costs are  high, the
removed  sand  should  be stockpiled, washed, and recycled.  Storage of the  sand,
in layers approximately 30 cm (1 ft) in depth and washing with 20 cm (8 in) or
more of  clean water, has successfully refurbished used sand on an experimental
basis (65).   Consideration of this approach appears particularly attractive in
wet climates.   It is also possible that filter effluent could be used to  clean
the sand by this technique.

The sand washing equipment should  be  sized to  accommodate  the  sand  washing
over several   days at a time.  Thus, the equipment may be smaller than required
for immediate sand washing.

The use  of the spent  sand as  a  soil  conditioner  has been investigated  on, a
limited  basis (65).    The  sand  is rich  in nutrients and organic  matter, and
appears  to  be a good  conditioner, especially  for clay  soils.    If  the pond
effluent is high in  heavy metals  concentrations,  use of the spent filter sand
as a  soil  conditioner may be  restricted  since  these metals  may  precipitate
from the sand particles.

The  disposal   of  the  spent  filter  sand  in   a   land  disposal   site  may  be
economically  feasible  for very  small  sand  filters where replacement  filter
sand is  readily available.   However, a careful  economic  evaluation should :be
conducted before complete sand  disposal is practiced.   In  addition, there may


                                     222

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                                FIGURE 5-9

   TYPICAL  UPFLOW SAND WASHER AND SAND  SEPERATOR UTILIZED IN WASHING
               SLOW AND INTERMITTENT SAND FILTER SAND  (63)
                 Water carrying
                 sand to be washed
                            Water carrying
                            washed sand
   Sand settles
  against rising
         water.
Pressure water,
     to ejector.
                 r
Water
rises ,,
to   4
overflow
Overflow
carrying
washings
or fine
sand
     Overflow
       water
Tn
  i
                           \
       Water carrying
       .iwashed sand
                       I
                                               Sand
                                               settles
           t
    Displaced
   water rises
.Sand
                       • Shear gate


                         Fluid sand
                     Make-up water
                     if needed
                   (A)
              Sand washer
                           (B)
                     Sand separator
                                  223

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be  regulatory agency  restrictions  against placing  the spent  filter  sand in
landfills due to possible leaching of heavy metals and  other toxic materials.

The filter media and  the  filtered matter provide an excellent environment for
weeds  and  grass  to grow.  Weed  control  during the growing season is achieved
by complete weed removal using manual labor or with mechanical raking devices.
The best method  of weed control  is continuous monitoring and removal of early
growth.

When a filter is observed to  be  plugged or approaching plugged conditions, it
is necessary  to  rejuvenate  the  filter surface.  Two approaches are available.
The first method consists of raking the media surface and breaking the surface
mat of filtered  matter.   Raking  makes the cleaning process more economical by
obtaining optimum  use of the media surface  prior to removal.   Raking  can be
accompl i shed  manual ly wi th a  garden rake or  wi th a tractor  and  a 1 andscape
rake.  A maximum of two rakings before cleaning is recommended.

When the raking  process no longer rejuvenates  the filter surface  due  to the
accumulation  of  the  filtered  matter  in  the top layer of the media, removal of
the solids  laden layer is  necessary.   The  removal  process can  be performed
manually or  with mechanical  devices.  A  four-wheel-drive  garden size tractor
equipped with a hydraulically  operated  scraper,  bucket loading  device,  and
either  flotation-type tires  or   dual  rear tires  works well  (59).   A small
floating dredge  has  been proposed as a  means  of cleaning a  large [4-ha  (10-
ac)] system  in  Wyoming  (66).   Heavy equipment such as road  graders or heavy
front loaders should not be used  on the filter.


         5.3.1.11  Winter Operations                                       ;


Winter operations  are  basically the same as  summer   operations  except that
cleaning of  the filters  during  the  winter  is  far more difficult.   The cold
season should be started with clean  filters  and in most instances the filters
will operate  through  the  cold weather without a cleaning being required.  The
system must  be  designed  to  prevent  the  accumulation of water in  the  filter
underdrain to a depth near the media surface where freezing can occur.

Operation  of experimental  intermittent  sand  filters   at  Logan,   UT,  during
freezing and  sub-zero  temperatures was  investigated by  Harris et al. (45-47).
Experience with  these experimental  and full-scale  systems  indicates that the
systems operated without any preparation of the sand surface.  If severe water
conditions  are   expected,  the  most  economical  method for winter  operation
appears to be the "ridge and furrow" technique.

The ridge and furrow technique requires that the sand filter surface be plowed
into small  ridges and furrows.  The ridges are spaced approximately 0.6 to 1.0
m (24 to 40  in)  apart with  30 to 45 cm (12 to  18  in) deep  furrows in between
each ridge.   The basic  idea  of  the ridge and furrow technique is to allow the
formation of a floating ice cover which will  settle on the peaks of the ridges
as the water percolates through  the  sand filter bed.   The  furrows  allow the
influent water to run under the  settled  ice  cover during the filter hydraulic

                                      224

-------
loading period and thus  float  the  ice cover.   Occasionally, the ice cover may
break up due to its own weight as it  rests upon the  ridges.   This also allows
the influent water to infiltrate through the sand surface.

For  very  small   filters  it  may  be  economically  feasible  to  construct  an
insulated cover  over the filter for  winter operation.   With such  a  covered
structure,  it  might  also  be  feasible  to provide  auxiliary heat  to  prevent
freezing.   In  severe  climates with  long  freezing  periods,  insulated filter
covers may be essential for winter operation.

Covered filters also  prevent algal  growth  on the  filter surface during summer
periods.  Thus, the length of filter runs may be substantially increased.


         5.3.1.12  Operational  Modes


Length of filter  runs may be  increased if the filter  influent SS are  low.  It
may  be  advantageous,  therefore,  to  hold  pond effluents  during  high  algal
periods and discharge during  periods  of low algal growth (i.e.,  early spring
and  late fall).   These  periods may  not result  in  a  high quality  of pond
effluent  in  terms  of  6005,  but  the  filter is   capable  of  significantly
reducing  the  6005.   Loading the filters at night rather than  during  the day
has also  increased length of  filter  runs.   This  is due to  the  reduction  of
algal  growth on the  filter itself during dark hours.


         5.3.1.13  Summary of Design  Considerations


A summary of intermittent sand filter criteria is presented  in Table 5-5.


         5.3.1.14  Typical Design of  Intermittent Sand Filter


            a.  Assumptions


1.  Design Flow =  378.5 m3/d (0.1 mgd).

2.  Hydraulic Loading Rate (HLR) = 0.29 m3/m2/d (0.3 mgad).

3.  Minimum Number of Filters =  2  (Table 5-5).

4.  Designed to minimize operation and maintenance.

5.  Gravity flow.

6.  Topography and location are  satisfactory.
                                      225

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                                     TABLE  5-5

              SUMMARY OF INTERMITTENT  SAND FILTER DESIGN CRITERIA
      Design Topic

Hydraulic Loading Rate


Filter Size/Number


Filter Shape


Depth of Filter Media
Size of Filter Media
and Underdrain Media
Filter Containment
Influent Distribution
Underdrain System
Maintenance
Considerations

Maintenance Required
Cleaning Frequency
Method of Cleaning
                Typical  Description

Equal  to  or less  than  0.47 m3/m2/d  using two or  more
equal dosings per day.

Minimum of two filter units.  Area of individual filters
<0.4 ha.

Dependent upon site plan and topography with rectangular
shape desirable to improve distribution of wastewater.

Large  gravel-minimum  cover of  10 cm  (leveled),  medium
gravel  -  10  cm,  pea  gravel  -  10 cm  ,  filter  sand  -
0.6-1.0 m.

Large  gravel  (avg.  dia.  = 3.3 cm), medium gravel  (avg.
dia.  = 1.9  cm),  pea gravel (avg.  dia.  =  0.64 cm),  sand
(0.15 mm to 0.30 mm e.s., u <7).

Compacted earthen bank of reinforced concrete; freeboard
X).5 m.

Dosing basin with siphon or electrically actuated  valves
with  timer  control  and  piping to  gravel  splash  pads.
Splash pad  gravel  should be 3.8-7.6 cm in diameter and
surface area and  depth  should  be 1.2  m^  and  25  cm.

Network of clay tile  or  perforated PVC pipe  at a slope
of 0.025 percent serve as laterals.  Pipes are placed in
sloped ditches and  attached to larger  drain manifolds.
Minimum lateral size  is  15 cm in  diameter and manifold
should be  adequate to  transport  design  flowrate at  a'
velocity  of 1.0-1.2  m/s  when flowing  full.  Maximum
spacing of laterals is 1.4 m.
Grass  encroachment,  rodent  activity,
access to filter by cleaning devices.
serviceability,
Removal  of vegetation  on filter  surface.   Raking  and
cleaning of top 2-5 era of filter sand when plugged.

Dependent   on  hydraulic   loading   rate   and   the SS
concentration in the applied water (1 month to  >1  year).

Raking maximizes the efficiency of the cleaning by fully
utilizing  the  top  layer of sand.  Manual  or mechanical
equipment cleaning can be used.
                                       226

-------
7.  Adequate land is available at reasonable cost.
8.  Filter sand is locally available.
9.  Filters are considered plugged when, at the time of dosing, the water
    from the previous dose has not dropped below the filter surface.

            b.  Calculate Dimensions of Filters

                  Area of Each Filter = design flow/HLR
                                      = (378.5 m3/d)/(0.29 m3/m2/d)
                                      = 1,357 m2  (14,800 ft2)
                 Letting L = 2W, Area = 2W2
                                    W = (Area/2)0-5
                                      = (l,357/2)°-5
                                      = 26 m (86 ft)
                                    L = 2W
                                      = 2(26)
                                      = 52 m (172 ft)
Construct two  filters  26  m x 52 m  (86  ft x 172  ft)  side-by-side  as  shown in
Figure 5-10.

            c.  Influent Distribution System

Assumptions:
     1.  Use of dosing basin with gravity feed to the filters.
     2.  Loading  sequence will  deliver one-half the  daily flowrate
         to each filter unit per day in two equal doses.
     3.  Loading  system  will consist  of two  electrically activated
         valves that  are  operated  alternately  by a simple electronic
         control   system   triggered  by   a   float   switch   or  two
         alternating dosing  siphons.
     4.  Pipe  sizes  are  selected   to  avoid  clogging  and  to  make
         cleaning convenient.  Hydraulics do not control.
                                     227

-------
Dosing Basin Size:
                   Design Flow Rate = 378.5 m3/d/2 filters
                                    = 189.3 m3/d (0.05 mgd)                ,
                  Dosing Basin Volume = 189.3 m3/d/2 doses/d
                                      = 95 m3 (25,000 gal)                 !
Use a square shape and a water depth of 1.0 m (3.3 ft) to minimize velocity in
distribution system.   Use 0.3 m  (1  ft)  freeboard and  install  overflow pipe.
Total depth = 1.3 m  (4.3 ft).
                       Dosing Basin Area = volume/depth
                                         = 95 m3/1.0 m
                                         = 95 m2 (1030 ft2)                I
                       Dosing Basin Width = (95 m2)0-5
                                          = 9.75 m (32.2 ft)
       Dosing Basin Size = 9.75 m (32.2 ft) square x 1.3 m (4.3 ft) deep
Distribution manifold  from the two  valves  leading to  the  individual  filters
would be  20-cm  (8-in)  diameter pipe.  Each  of  the outlets  from  the manifold
will  serve  6 m  (20  ft)  of the  long  side of the  filter unit.   The manifold
outlets will discharge  onto  splash  pads constructed  of gravel  3.8  to  7.6 cm
(1.5 to  3 in)  in diameter placed in  a  75-cm  (2.5-ft) square configuration at
each outlet opening.

            d.  Filter Containment and Filter Underdrain System
                (See Figure 5-10)

Use  a  reinforced concrete  retaining  structure or a 20-mil plastic  liner to
prevent infiltration and exfiltration to adjacent groundwater.
Slopes of filter bottom are dependent on  drain  pipe  configuration using 0.025
percent slope with lateral collection lines 4.6 m (15 ft) on center.
Utilization  of  15-cm  (6-in)   diameter   perforated   PCV  pipe  as  collecting
laterals and 20-cm (8-in)  diameter collection manifolds will provide adequate
hydraulic capacity and ease of maintenance.
Minimum Freeboard Required:
           Depth = volume/area = 95 m3/!,357 m2 = 7.0 cm (2.8 in)
                                      228

-------
                                      FIGURE  5-10

                 PLAN  VIEW,  CROSS SECTIONAL  .VIEW, AND HYDRAULIC
                       PROFILE FOR INTERMITTENT  SAND  FILTER
Plan view
                             Influent
                Alternating    manifold
                    dosing
                   siphons "Y
           Influent •
                          Overflow
                              pipe
                                        A-*-
           15 cm Perforated laterals
           @ 0.025 percent slope
           spaced 4.6 m
      Laterals
         Influent
         outlet

0.7m x 0.7m Gravel
splash pads
                                        A-*-
                       r
20 cm Collection
    manifold
                                  Effluent
Sectional view A-A

       0.3m Freeboard
                           Influent manifold
                            /—Splash pad
 0.6m Filter sand

   Underdrain media
                         tic liner J
                     Plastic liner
                             Drain manifold
                                               Laterals •
                                                                 •Ground
                                                                  level
                                                               Reinforced concrete wall
Hydraulic profile
Influent
elev 100m
Inve
srph
Bottom
99.1m
y
rted'
ons
Yuverriow pipe
,
*" Top of sand
I Media
'— 	 	 ._
98.2m

	 	 -_
                                                        -96.2m
                                          229

-------
Minimum freeboard required to accommodate wastewater when filter is plugged at
time of application of the dose  is  7.0  cm  (2.8 in).   However, with infrequent
inspection by  an  operator it is recommended that a safety factor be specified
and the value  of 30 cm (1 ft) mentioned above be used.
         5.3.1.15  Summary of Design Criteria for Existing and Planned
                   Filters
A  summary  of  the  design  criteria and  costs  associated  with  existing  and
proposed  intermittent  sand  filters  used to upgrade pond effluent is presented
in Table  5-6.
     5.3.2  Rock Filtration
A rock filter operates by allowing pond effluent to travel through a submerged
porous rock bed, causing algae to  settle  out  on  the rock surface and into the
void  space.    The accumulated  algae are  then biologically  degraded.   Algae
removal with  this  system filter has  been studied  extensively  at Eudora, KS,
beginning in 1970 (67)(68).                                                :

Two experimental  rock filters at Eudora  used  a  submerged rock depth of 1.5 m
(5 ft)  and  rock of 1.3  cm  (0.5  in)  in one and  2.5 cm (1.0  in)  in  the other
filter  (68).    Influent to  the  filter  submerges the  rock  bed,  which  is
contained in a diked area, and effluent is drawn off at the bottom of the bed.
The period  of peak efficiency of  the rock filter  is  in  the  summer and early
fall  and  hydraulic  loading  can be increased  in  this period.    The  filters  at
                                    rates   up  to  1.2 m3/m3/d (9 gpd/ft3) I in
                                    decreased   to  0.4 m3/m3/d (3 gpd/ft3)  in
                                    pond  effluent  having a BOD5 of 10  to  35
                                     showed that the rock filter reduced 8005
by only a relatively small amount (however, the final concentration was always
below 30 mg/1)  and  would reduce  SS to 20 to 40 mg/1 (Figures 5-11  and 5-12).
It  was  concluded  that   the  rock  filter  could be  operated   to  meet effluent
requirements  of 30  mg/1 BOD5  and  it was  doubtful  that the  filter  could
consistently reduce the SS to 30 mg/1. It was postulated  that the filter would
not become plugged for more than 20 years.  One  drawback is  the production  of
hydrogen  sulfide during  the  summer  and  early  fall when the  filter  becomes
anaerobic.  Aeration of the effluent would be required prior  to discharge.
Eudora  were  operated  at  loading
the  summer  and  this loading  was
the  winter  and  spring.   Tests  on
mg/1 and SS level  of 40  to 70 mg/1
A  rock filter  was  constructed  at  California,  MO,  in  1974  to upgrade  an
existing  pond  (67).   This was  placed  along one  side  of a  tertiary  pond  as
illustrated  in  Figure 5-13.   The  rock  filter was  designed for  a  hydraulic
loading  rate  of  0.4  m3/m3/d  (3  gpd/ft3).     In   1975,   a  757  mr/d  (0.2
mgd) rock  filter  was constructed in Veneta, OR.  In  1977 and  1978,  extensive
monitoring  programs were  conducted by  Oregon  State University  to  determine
removal mechanisms and efficiency of this filter (69)(70).  A schematic of the
Veneta system is presented in Figure 5-14.
                                     230

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                                                            TABLE 5-6

                                     SUMMARY OF  DESIGN CRITERIA  AND COSTS FOR EXISTING
                                        AND PLANNED INTERMITTENT  SAND FILTERS USED TO
                                                  UPGRADE  POND EFFLUENT  (59)
co
Location
Covello, CA
Mt. Shasta, CA
Tonal es, CA
dmarron, NM
Cuba, NM
Mori arty, NM
Portal les, NM
Roy, NM
Adel, GA
Alley, GA
Cummings, GA
Douglas County, GA
School
Nursing Home
Shellman, GA
Stone Mountain, GA
Huntington, UT
Design
Flow
1/s
3.5
0.7Lb
1.8
6.6
6.1
8.8
87.8
2.5
48.3
3.5
8.8
0.6
1.5
6.6
0.9
13.2
Pond
Type9
F
A
A
F
ASF
ASF
ASF
F
A
F
ASF
F
F
F
F
F
Retention
Time
days
49
20L>>
29
55
20
20
20
60
30
70
36
5
45
55
1
214
Filters
Number

4
3
2
• 2
4
8
3
2
2
2
4
2
2
4
1
3
Size
ha
0.048
0.405
0.012
0.04
0.02
0.028
0.405
0.028
0.405
0.06
0.06
0.008
0.012
0.032
0.081
0.271
Loadl ng
Rate
m3/m2/d
0.48
0.67
0.55
0.76
0.57
0.57
1.91
0.72
0.48
0.38
0.29
0.29
0.48
0.48
0.14
0.19
e.s.
mm
0.6-0.7
0.37
0.15-0.30
NA
NA
0.2
0.4
0.4
.0.25
0.25
0.25-0.80
0.3
0.35-0.75
0.35-0.75
0.45-0.55
0.2-0.25
u

NA
5.1
1.5-2.5
NA
NA
4.1
3.2
3.2
3.4
3.3
<4
3.67
<3.5
<3.5
H.5
<3
Sand
Depth
m
0.6
0.6
0.9
0.6
0.6
0.6
0.8
0.6
1.2
0.8
0.7
0.8
0.8
0.9
0.8
1.2
Filter Costs
capital USM
lotai Year
$/m3 flow
0.11
0.05 0.01
0.07
-
0.04C
0.03 0.01
—
0.01
0.02
0.05 0.01
0.03
0.04
0.01
0.03
0.04
1977
0.06 1976
1978
1975
1976
0.04 1976
1976
1976
1978
0.06 1976
1978
1976
1978
1979
1976
1976
          aA = Aerated.
          F = Facultative.
          I>L = Dry Weather Flow.
          cTwenty percent of total capital cost.

-------
                                  FIGURE 5-11
             BIOCHEMICAL OXYGEN DEMAND (BOD5) PERFORMANCE  OF  LARGE
                       ROCK FILTER At EUDORA, KANSAS (68)
                                             I    i     i    I

                                              POND EFFLUENT

                                              FILTER  EFFLUENT
CO
Q
_J
O
CO

O
UJ
Q
z
UJ
a.
CO
:D
CO
AS   ON

   MONTH

FIGURE 5-12!
                SUSPENDED  SOLIDS PERFORMANCE OF LARGE ROCK  FILTER
                            AT EUDORA, KANSAS (68)
                                                                 M    AM
                                               POND  EFFLUENT

                                               FILTER  EFFLUENT
            MAMJJ    ASONDJ
                                    232

-------
                       FIGURE 5-13

ROCK  FILTER INSTALLATION AT CALIFORNIA,  MISSOURI  (67)
     Effluent
    discharge

'condary




— _ —



Tertiary

^?£PS?
\
cell i
i
Q 	 •> J
\ , -^/

_j 	 A
\
i
u 1
cell i
1
:!p'i~*i^|-^'?;^/

1
^





Pri-
mary
Cell
-s

                ~  ^:                \:    ~ •
                       '
                        Single per-
                  • A    forated pipe
                               Double per-
                               forated pipe
                      9.37 m
                          5.03 m
1.68 m.

                                                  1
MRock Mat
                   11.89 m
                                       ^-Effluent
                                         Structure
                          Section A-A
                         233

-------
                           FIGURE 5-14

      SCHEMATIC FLOW  DIAGRAM OF VENETA,  OREGON WASTEWATER
                      TREATMENT SYSTEM  (69)
      Raw_
wastewater"
                  Cell No. 1
                   4.51  ha
                  Cell No. 2
                   1.47 ha
                                     Pond
                                     effluent
                                     samples
Rock filter
effluent
samples

Pump
stat.



Rock
filter
0.57 ha
I Discharge
1 Tom River
                                               Cl,
                             234

-------
A  performance  evaluation  of  the  California,  MO,  rock  filter  was  conducted
during March and  April  1975 (67).   The  results of  that  evaluation  indicated
that  the  actual  average  hydraulic load on  the filter was  0.25 m3/m3/d (1.9
gpd/ft3).    A  summary  of  the  rock  filter  performance is  reported  in  Table
5-7.   During  the  evaluation  period,  the  rock filter average  effluent 8005
concentration  was  only  21 mg/1.    The   rock filter  average  influent  SS
concentration  was  69  mg/1   while   the  rock  filter  average  effluent  SS
concentration was 22 mg/1.
                                   TABLE 5-7

            PERFORMANCE OF ROCK FILTER AT CALIFORNIA, MISSOURI (67)
                     BODfi                 SS                  DO	
               Ijif 1 uent EffluenT   Influent Effluent'   Influent Effluent
                     mg/1                mg/T                mg/T

      3/5/75      15        8         35       24         19       6.6
      3/13/75     14        6         64       26         16.8     7.9
      3/19/75     19        7         80       24          —     12.9
      3/26/75     25       13         94       20         12.9     5.2
      4/2/75      30       15         74       16         13.3     4.6

      Average     21       12         69       22         16       7.4
A routine monitoring program for the California, MO, rock filter was initiated
by  the  Missouri  Department of  Natural  Resources (71) in March  1975,  and the
results of this work are summarized in Figure 5-15.  All  solids determinations
were made  on grab  samples.   The performance of the  rock  filter was sporadic
and  failed  to meet the  federal  discharge standard  of 30  mg/1  of  SS  in the
effluent on  11 of the 19 sampling dates.

The  Veneta  rock  filter  (Figure  5-16)  is  of  a  different  design  (69)(70).
Influent enters the rock filter  through  a  pipe  laid on the bottom and running
through  the  center of the  filter.   The  water  rises through  2  m  (6.6 ft) of
rock, 7 ...5 to 20 cm  (3 to 8 in) in diameter, and  is collected in effluent weirs
on  the  sides of the rock filter.  The Veneta rock filter can consistently meet
daily maximum  effluent limits  of  20 mg/1 BODg  and 20 mg/1  SS  for hydraulic
loadings  of  0.3  m3/m3/d   (2.2  gpd/ft3)  (Figure  5-17).     The  relationship
between the  SS removal  and  the hydraulic loading rate of  the Veneta facility
is  shown in  Figure  5-18.

Principal  advantages  of the  rock  filter are its  relativley  low construction
cost and simple operation.   Odor problems can occur,  and  the design life for
the  filters  and cleaning procedures have not yet been firmly established.
                                      235

-------
                                  FIGURE 5-15

               PERFORMANCE OF  CALIFORNIA, MISSOURI ROCK FILTER
                         TREATING POND EFFLUENT (71)
  150
                                                                  (173)
  100
A
                                 o Influent (pond effluent)
                                 • Effluent
O>
   50
    0
                                     \   -
                                      \   -
          M
O    N
                         D   J    F
                         1975-1976
M
A    M
                                    236

-------
                  FIGURE 5-16

       VENETA,  OREGON ROCK'FILTER (69)
•^ 	
^
Influent



<



\
/•



X
Effluent ^

^...,, ^
36.9 m
^7.3 m
Influent
pipe
V
r^ ^s
1
36.9 m




«^_
7.3 m ^
^
7.3m -
52.4m

y
7.3 m
_- if
^
7


y
\



I
                                             Effluent
                                             weir ••-
7.3 m
                   Plan
73.8m
7.3 m
                    Profile
                    237

-------
                                        FIGURE 5-17

                   PERFORMANCE  OF VENETA, OREGON  ROCK  FILTER  (69)
_  50
en
c
_o
2
•*-'
03
u

I
           • Influent SS
           • Influent BODg
           D Effluent SS
           o Effluent BOD5
                                                                                      >
                                                                                •-
                               '•   ••*    *  t»  I
       ••••


                                               on
1314 15 16 17 18 19
   11/77
1334567
    1/78
5 6 7 8 9 1011
    2/78
                                     I I  I   I I  I I I  I I   I  I I  I I  I I   I I  I I  I I  I
56 7 89 1011
    3/78
                                                      16 17 18 I92O2I22
                                                         4/78
                                                                  14 B 16 1718 192O 3O3 I  2 3 4 5
                                                                     5/78      7-8/78
                                          238

-------
                                                  FIGURE 5-18


                          SS REMOVAL vs HYDRAULIC LOADING RATE AT VENETA, OREGON (69)
CO
                    100
                     80
                  c
                  
-------
     5.3.3  Micros-trainers


Early experiments with microstrainers to remove algae from pond effluents were
largely  unsuccessful  (72-75).   This  was  generally  attributed to  the algae
being smaller than the mesh size of the microstrainers tested.

Envirex,  Inc. has  tested a one-micron  polyester  mesh  microstrainer for algae
removal  from  pond  effluents.   A portable  pilot  unit was used at 10 locations
in 1977 and 1978 (76).  The results of  seven  of  these tests are summarized in
Table  5-8.   Algae removal was  best for the  larger  species  of algae; smaller
species  of algae,  such  as  Chlorella,  were  removed only  when  a thin algal  mat
was maintained on the screerfl  SIime growth on the screen can  be controlled by
chlorine  without  harming  the  polyester mesh,.   SS  and  BODg  levels  below 30
mg/1 were consistently achieved during the test periods.

Unsuccessful  tests of one-micron and six-micron screens were reported by Union
Carbide  (77).  Algae samples taken several  days before and two weeks after the
tests  indicated that  predominant algae species removed were Aphanizomenon and
Lyngbya.  These algae both have a;width of one to two microns.  Heavy rainfall
accompanied  by  a  large amount  of colloidal  material  in  the  pond occurred
during the tests  and  there is some question  as  to  how  representative  the SS
content of the pond was at that time.   Addition of polymer in  relatively large
doses  (23 to 65 mg/1) was  necessary to  produce an effluent  SS <30 mg/1.  This
experience emphasizes the need to identify the algae species to be removed and
conduct pilot studies under representative conditions.

The  tests  represented  in  Table  5-8  are  of  relatively   short  duration.
Microstraining  performance and  reliability  at  pond  sites  over  an extended
period of time has yet to be proved.

The  first full-scale  microstrainer  application  to  pond  effluent, a  7,200
nr/d (1.9 mgd)  unit,  was placed in operation  at  Camden, SC,  in December 1981
(78H79).  Typical design  criteria  include  surface loading  rates of 90 to 120
m3/m2/d  (1.5 to  2.0  gpm/ft2)   and head  losses  up to  60 cm  (2  ft)  (76).
Other  process  variables include backwash  rate  and  pressure,  and  drum speed,
which  are normally  determined   depending  upon  influent quality  and  desired
effluent  quality.   The service  life  of the  screen  is reported to  be  longer
than five years; however,  actual  field experience on the one-micron screen is
limited.  For a 3  m by  3 m (10 ft x 10 ft)  unit  it  would take  12  to  16 man-
hours to replace all  the screens (77).  The microstrainer portion of the plant
at Camden cost $1.5 million  and  is estimated to  cost  $71,000/year to operate
(1979 US $).   Limited performance data are available, but the  results indicate
that the system can meet an effluent standard of 30 mg/1 BOD5 and SS (78).


     5.3.4  High Rate Filtration


Conventional  rapid sand or multimedia  filters have  been  used  both  for direct
filtration of algae-laden  waters and  for  polishing  filtration,  which  follows
coagulation-clarification.


                                     240

-------
ro
                                                     TABLE 5-8



                      SUMMARY OF PERFORMANCE OF 1-micron MICROSTRAINER PILOT PLANT TESTS (76)
Test Site

Adel , Georgia
Owasso, Oklahoma
Greenville, Alabama
Camcien, South Carolina
Gering, Nebraska
Blue Springs, Missouri
Gumming s, Georgia
Length of
Test
hr
60
60
50
22
90
90
100
Lagoon Effluent
SS
mg/1
69
58
44
126
44
64
26
BOD5
mg/1
72
30
45
38
—
32
—
Microscreen Effluent
SS
mg/1
9
15
12
19
13
22
6
BODc
mgTl
9
15
14
23
. —
16
—

-------
         5.3.4.1  Direct Filtration


Experiments with  direct sand  filtration  have  generally  resulted in  poor  SS
removals, as  indicated in Table  5-9.   Without coagulation, algae have  a low
affinity for  sand;  furthermore,  green algae  are  too small to  be efficiently
removed  by  straining.   The  larger diatoms  can  be removed effectively,  but
special  precautions must  be  taken in media  design  to  ensure that the filter
does not become rapidly clogged.

At  least one investigation  with  direct  filtration  has proved  successful.
Wilkinson tested  two   types  of mixed media  filters for  removing algae  from
stabilization pond effluent at the Exxon Baytown Refinery (80).   A 45-cm (1.5-
ft) diameter downflow deep bed was  constructed  using 45  cm (1.5 ft)  of gravel
support, 60 cm (2 ft)  of 0.6 to 0.75 mm sand, and 75 cm (2.5 ft) of 0.7 to 0.9
mm  anthracite coal.    A  downflow  43-cm  (17-in)   diameter  Neptune-Microfloc
shallow  bed  filter pilot unit was  also  used.   It  contained 30  cm  (1 ft)  of
gravel support, 7.6 cm (3 in) rough garnet,  11  cm (4.5 in)  of 0.33 mm garnet,
23  cm  (9 in)  of  0.4  to 0.6  mm sand, and  57 cm (22.5  in)  of  1.0 to 1.1  mm
anthracite c.oal.   Side-by-side comparisons  indicated no  run  length advantages
for deep  bed  filtration.   Acceptable  filter operation for both  filters with
influent SS in the range of 20 to 60 mg/1 was obtained using  alum with 0.5 to
1.0 mg/1 anionic or 1.0 to 2.0 mg/1  cationic polyelectrolyte.   Alum dosages of
25 mg/1 produced only marginal improvement,  while 40 to  50 mg/1 provided good
performance.   The  hydraulic  loading  rate  was 175 to  300 nrYm2/d   (3  to  5
gpm/ft2).    At a  constant  SS  feed of  30 mg/1,  tests  with  the  Neptune
Microfloc filter  indicated that  the  percent backwash  flow increased  from  8
percent  at  235  m3/m2/d   (4  gpm/ft2)  to  11.8 percent  at  350  m3/m2/d  (6
gpm/ft2),  and to  17.5  percent  at 470  m3/m2/d (8 gpm/ft2).     In  general,
work to  date  indicates that  direct  filtration  of oxidation pond  effluent  is
impractical  unless algae concentrations are low.


         5.3.4.2  Polishing Filtration


Use of a rapid sand  or multimedia  filter system to reduce  SS  concentrations
following  coagulation-clarification  is   very  effective,  achieving  final
effluent SS levels less than 10 mg/1 and turbidities less  than  4.0 JTUs (86).
Diatomaceous  earth  filters also  work  efficiently,   but  filter  cycles may  be
short  because  of  filter binding by algae and  other particulate matter.   This
results in excessive diatomaceous earth use and high operating costs.

Baumann  and Cleasby  (87)  have shown that,  while there are many  similarities
between  water filtration  (for  which  the most  information is  available)  and
wastewater  filtration, there  are  also  differences  that must  be  properly
accounted for  in design.   In  particular,  the quantity  of solids in wastewater
is generally higher and the characteristics much more variable than for water.
Furthermore,  filter effluent  turbidities  and SS concentrations  will  generally
be much lower for water treatment applications.   Therefore, direct application
of  designs  developed  for  water treatment  plants   may  result  in less  than
optimum operation and performance in wastewater treatment.

                                     242                                  :

-------
                                                     1HSBUE 5-8

                        PERFORMANCE  SUMMARY OF DIRECT  FILTRATION WITH'RAPID SAND FILTERS
CO
Coagulant
and Dose
mg/1
None
Fe: 7
None
None
None
None
None

None
None
None

Filter
Loading
m3/m2/d
11.7-117
123
28.8
28.8
111
111
117

64.5
29.3-58.7
29.3-176

Filter
Depth
cm
61
61
_.b
-_b
__b
— b
61

28
131
61


Sand

Size

Finding

Reference
mn
d50 =
d50 =
d50 =
d50 =
d50 -
d50 =
d50 =

dio =
d50 =
d!0 =
and
0.32
0.40
0.75
0.29
0.75
0.29
0.71

0.55
0.22
0.22
0.5
Removal declines to 21-45 % after 15 hr
50 percent al gae removal
22 percent algae removal
34 percent algae removal
10 percent algae removal
2 percent algae removal
pH 2.5, 90 percent algae removal
pH 8.9, 14 percent removal
0-76 percent SS removal
20 to 45 percent SS removal
22 to 66 percent SS removal
'
81a

82a



83a

75^
84d
85d

        aLab culture of algae.
        bNot available.
        C0xidation pond effluent.
        dUpflow sand filter.

-------
It  is  essential  for filter  runs  of reasonable length that  the  filter remove
solids  throughout  the  entire  depth  of  media  (deep-bed  filtration)  and  not
mainly  at the  filter surface.   Deep-bed  filters can be designed by using high
filtering  velocities,   up  to  350  m3/m2/d   (6  gpm/ft2)   which  permit  deeper
penetration of the  solids  into the filter,  and by  allowing  the  water to pass
through a  coarse-to-fine media gradation.   It is  advantageous  in wastewater,
filtration to  use  a greater  depth of filter  media *  150  to 175 cm  (60 to 70
in), than  in water  filtration,  75  to 130  cm (30  to  50 in),  to  allow  for
greater floe storage in the filter.

Backwashing operations  for .wastewater filtration will also  differ from those
techniques used  in water  filtration.    Auxiliary  agitation of  the  media  is
essential  to proper  backwashing.   Either air  scour shoul'd be  used or surface
(and  possibly  subsurface)  washers  should  be  installed   to  ensure  that  the
original cleanliness and grain classification is restored.

The ability of mixed media beds to capture large particles in the top layer of
the  bed  and   small  particles  in  the  lower  region,  allowing  for  greater
penetration  of the  suspended matter  throughout the  filter with  subsequent
lower  head  losses and  long  filter runs, has; been- demonstrated  by  several
researchers.                    :

A dual-media filter  consisting of 120 cm  (48 in) of anthracite  coal  (2.4-4.8
mm)  and  45  cm  (18  in)   of  sand   (0.8-1.0  mm)   was   used  for  polishing
flotation-tank type  effluent  in  a pilot  study at  Sunnyvale,  CA  (86).   The
loading rate  was  330  nr/nr/d (5.6  gpm/ft2).    Figure   5-19  shows  effluent
turbidity as a function of filter-run  duration.  Solids  breakthrough occurred
after  10 hours.  Figure 5-20  shows development of  the head  loss  profile with
time.   The uniform head loss  increase  at al 1 depths indicates that the filter
has  removed  solids uniformly  throughout the  filter depth.    This  factor  is
important in optimizing filter runs.
The average  SS  removal  performance was 89  percent  (3.0 to 6.0 mg/1  effluent)
using influent  with concentration of  32  to 62 mg/1/. Generally  one-half  to
two-thirds of the effluent SS was volatile solids.' '"•
                                                   • '*.&'
A  similar  type  of  filter was  used  by the Napa-American  Canyon (California)
Wastewater  Management  Authority  to  polish  effluent,  from  the  coagulation-
sedimentation process  (88).   Filter media .was  50 cm  (20 in)  of  1.0-1.2  mm
anthracite coal, 45 cm  (18 in) of 0>4-0.5 mm sand,  and  15  cm  (6 in)  of silica
gravel support material.  The  pla;nt  used  six  filters  with a combined capacity
of  58.300  m3/d  (15.3  mgdh    Filter  loading  rate  was  290  m3/m2/d  (5
gpm/ft2).   Table  5-10 presents  a* summary of  the data  from  the  treatment
plant for the first nine  months of operation.   BOD5 removal  data  through the
filter were  not  available,  but effluent 8005  values  were  reported.   There  is
consistent removal of SS.
                                     244

-------
                      FIGURE  5-19

 DUAL-MEDIA FILTER EFFLUENT TURBIDITY  PROFILE  (86)
£
I   2
.3
®
SE   i
111
<5
          i    i    ii
                             i    i     r   i
           i    i    i
                            _L
                                 _L
          2    46    8   10   12   14   16  18   20
                       f:ilter Run, hr
                      FIGURE 5-20

       DUAL-MEDIA FILTER  HEADLOSS PROFILE (86)
in
to
ca   5
I   <
i   *
     •i  i.
                                   Duration
                                   of filter
                                   run in
                                   hours
                  I
                    _l
                                 I
                  12      3

                     Filter Headless, ft
                         245

-------
                                  TABLE 5-10

               PERFORMANCE OF THE NAPA-AMERICAN CANYON WASTEWATER
                  MANAGEMENT AUTHORITY DUAL-MEDIA FILTERS (88)
             Month
             1978
              October
              November
              December

             1979
              January
              February
              March
              April
              May
              June

             Average
                           BOD5a
                                         SS
                  Effluent    InfluentEffluent
                           mg/l
                    5.5
                    4.4
                    3.8
                    4.3
                    5.2
                    7.3
                    3.2
                    5.7
                    5.2
                              mg/l
14
22
25
22
23
13
14
19
19

19
           mg/l
6.6
9.1
9.2
6.1
4.3
3.3
4.2
8.1
7.4

6.5
          Removal
          percent
53
59
63
72
81
75
70
57
61

66
             aFilter influent 8005 not monitored.
             bpirst 11 days of month, plant does not operate in
              summer.
The  importance  of  grain  size  selection  in  producing long  filter  runs  was
demonstrated  by  Hutchinson,  et a!.  (89).    It  was  found  that  diatoms  were
clogging the upper layers of mixed media filters.  By increasing the effective
grain size of the upper coal layer from 0.9 to 1.5 mm, while keeping the lower
sand layer at an effective grain size of 0.5  mm,  the  length  of filter run was
increased  from  5-12  hr  to  12-20  hr.   This  increase  was  attributed  to  the
ability of the new coal layer to capture the diatoms in a more uniform fashion
throughout  its  depth.   The quality of  filter  effluent  was  not  diminished
because the sand layer retained the ability  to  capture  the  smaller suspended
matter.
Design
(87).
procedures for  effluent filtration are  described  in detail elsewhere
                                     246

-------
5.4  Coagulation-Clarification Processes


     5.4.1  Introduction


Coagulation  followed  by  sedimentation  has  been  applied extensively  for the
removal  of  suspended and  colloidal  materials  from water.   Lime,  alum,  and
ferric  salts  are the most commonly used  coagulating  agents.  Each  of these
chemicals, alone or  in  combination with  others,  may be the  most appropriate
under  particular circumstances.   The  coagulant  chosen will  depend  on  pond
effluent  quality,  the type  and concentration  of predominant  algae,  process
considerations,  and  total  cost  (including  sludge  disposal).    Procedures
leading to coagulant selection include jar tests,  pilot tests, and engineering
feasibility studies.


     5.4.2  Coagulation-Sedimentation


Although  sedimentation has been used to clarify  many  types of wastewater, it
cannot by itself be used for algae removal.  Chemical coagulants must first be
added  to  destabilize the  algae.   The algae-coagulant  particles  must then be
aggregated  to  form  floes  large  enough   to   settle   and  be  removed  in  a
sedimentation  tank.   Thus,  the sedimentation  process  involves  three stages:
1) chemical coagulation, 2) flocculation, and 3)  settling.

A  number  of  investigators  have  obtained high  algae  removals  using  th;e
coagulation-flocculation-settling  sequence.    Representative  performance  data
are  shown  in  Table  5-11.   Overflow  rates  for  conventional  sedimentation
processes  have been  12  to  50  nr/m*/d  (0.2 to  0.8 gpm/ftO  with  hydraulic
detention times  of  three  to  four hours.   Flocculation tank  design criteria
that were found  to  be adequate were detention  times of 25 min with  a G value
of 36  to  51 sec  (81).  Underflow total solids have generally been in the range
of 1.0 to 1.5 percent when alum or iron is used.

Table  5-12 presents _month!y  averages  of daily  data collected at the Napa, CA,
algae  removal  plant  during its  first nine months of operation.  This facility
used   lime  coagulation-flocculation  followed  by   settling  and  dual  media
filtration.    The  effluent  COD and  BODg removal   percentages  apply  to  the
entire  algae  removal  plant whereas the SS  data .are for only the coagulation-
flocculation-settling process.   Influent SS varied  throughout  the year but a
consistent SS effluent quality from the clarifiers was maintained by adjusting
the chemical dosage.

As  shown  in Table  5-11,  most  applications  have  involved  alum or  lime.   In
.using  these  coagulants,  pH control  is important.   Golueke and  Oswald  (72)
found  that pH  for flocculation with alum was in the  range of 6.3 to 6.8.  This
pH range  applies whether  alum dosages  are relatively low,  as with the Golueke
and  Oswald  studies  (100  mg/1), of  relatively high,  as with the studies  at
Lancaster (240-360  mg/1).  When  lime  is added,  the major  effect is to raise
the pH to about 11 where  a magnesium hydroxide  [Mg(OH)2]  precipitate forms,

                                      247

-------
                                                   TABLE  5-11

                       SUMMARY OF  COAGULATION-FLOCCULATION-SETTLING  PERFORMANCE





r\>
-£>
oo
Location

Windhoek, South Africa (24)
Richmond, California (72)
Napa, California
Pilot Plant (88)
Napa, California
Prototype* (88)


Coagulant
Alum8
L1meb
Alum
L1me
Alum
L1me


Dose
mg/1
216-300
300-40QC
100
200
-------
                                                     TABLE 5-12

                                 PERFORMANCE OF THE NAPA-AMERICAN CANYON WASTEWATER
                                   MANAGEMENT AUTHORITY ALGAE REMOVAL PLANT  (88)
t\3
Ji>
UD


Month

1978
October
November
December
1979
January
February
March
April
May
Junec
Average


Influent
mg/1

39
32
27

27
23
44
36
45
61
37
BODa
Filtered
Effluent
mg/1

5.5
4.4
3.8

4.3
5.2
7.3
3.2
5.7
7.0
5.2


Removal
percent

86
86
86

84
77
83
91
87
89
85


Influent
mg/1

103
82
90

55
42
57
62
183
194
96
ssb
Clarified
Effluent
mg/1

14
22
25

22
23
13
14
19
19
19


Removal
percent

82
73
71

60
52
74
77
89
90
74
              following dual-media polishing filtration.
              bAhead of dual-media polishing filtration.
              cFirst 11 days of month, plant does not operate in summer.

-------
attaches to algae cells, and causes their sedimentation.  Required lime dosage
will fluctuate daily, generally from 200 to 400 mg/1.  Mean lime dosage at the
Napa, CA,  algae  removal  plant for the  first  six  months of 1979 was 246 mg/1;
monthly mean lime dosages during this period ranged from 200 to 300 mg/1 (88).

Tests  conducted  by  Al-Layla  and  Middlebrooks   (91)   found   that  the  most
significant  variables,  in  order  of  importance,  were  (1)  alum  dosage,  (2)
temperature, (3)  flocculatiori  time,  (4) paddle speed,  and (5) settling time.
They  found that  large  water  temperature  differences,  even   during  the  day,
could be important.                                                       ;

The  Los  Angeles  County  Sanitation  Districts  have  the   longest record  of
experience  with  a  coagulation-flocculation-settling  system at the Lancaster
Tertiary Treatment  Plant,  constructed in 1970.   The  Lancaster plant utilizes
alum  coagulation,  sedimentation,  and   dual-media  gravity  filtration.   The
system has consistently produced an effluent with turbidity below  1.7 JTUs,

In  designing  a  coagulation-flocculation-settling  facility,   care should  be
taken to ensure that conditions promoting autoflocculation are  not encouraged.
Floating  slujdge  in  the  sedimentation  tank  defeats  the  purpose  of  the
sedimentation  process.    To  prevent  this  effect,  supersaturation  should  be
relieved  by  preaeration   before   sedimentation,  and   photosynthesis   in  the
sedimentation tank should be prevented by covering the  tank surface.


     5.4.3  Flotation


The  flotation  process  involves  the  formation of  the  fine gas  bubbles  that
become physically attached to  the  algal  solids, causing them  to  float  to the
tank surface.  Chemical coagulation  results in the formation of a floe-bubble
matrix that  allows  more efficient separation  to  take  place in the flotation
tank.

Two  means  are available  for forming the  fine bubbles used in the flotation
process:   autoflotation  and  dissolved-air flotation  (DAF).    Autoflotation
results  from  the provision  of  a  region of turbulence  near the  inlet  of the
flotation tank (which causes bubble  formation  from dissolved  gases)  and  from
oxygen  'supersaturation  of   the  pond effluent.    In  DAF,  a  portion  of  the
influent (or recycled effluent) is pUmped  to  a pressure tank  where the  liquid
is  agitated  with  high  pressure air   to  supersaturate   the liquid.    The
pressurized stream is then mixed with the  influent,  the pressure is released,
and  fine  bubbles are formed.   These become cittached to the  coagulated algal
cells.   Table  5-13 presents  a  summary  of  operating  and  performance data, on
coagulation-flotation studies.


         5.4.3.1  Autoflotation


Autoflotation  is  the  natural  flotation  of  algae  brought  about  by   gas
supersaturation in stabilization ponds.   Information on autoflotation has  been


                                     250

-------
                                                                                5-13
                                           SUMMARY  OF  TYPICAL COAGULATION-FLOTATION  PERFORMANCE
ro
en

Location

Autoflotatlon
Windhoek, South Africa (91)

Stockton, California (92)


Dissolved A1r Flotation
Stockton, California (92)

Lubbock, Texas (93)
El Dorado, Arkansas (94)
Logan, Utah (95)
Sunnyvale, California (86)



Coagulant


Alum
C02
C02
Alum
Acid

Alum
Acid
time
Alum
Alum
Alum
Acid


Dose
mg/1

220 mg/1
to pH 6.5
to pH 6.3
200 mg/1
to pH 6.5

225 mg/1
to pH 6.4
150 mg/1
200 mg/1
300 mg/1
175 wg/1
to pH 6.0-
,.6.3
Overflow
Rate
m3/m2/d

205
106

117


158

__a
235C
76-1416
••::.ii/ -


Detention
Time
m1n

8
8

22


17b

12d
8C
__a-
11'



Influent
mg/1

12.1
12.1

	 a


46

280-450
93
	 a
	 a


BODg
Effluent
mg/1

2.8
4.4

	 a


5

0.3
<3
	 a
-.a



Removal
percent

77
64

~a


89

>99
>97
-.a
,.a



Influent
mg/1

— a
—a

156


104

240-360
450
100
150
~

ss
Effluent
mg/1

	 a
	 a

75


20

0-50
36
• 4 ;:
30



Removal
percent

—a
-_a

44


81

>79
92
96
80

••
              aNot available.
              blnclud1ng 33 percent pressurized (35^-60 pslg) recycle.
              ^•Including 100 percent pressurized recycle.
              •"Including 30 percent pressurized (50 pslg)-recycle.
              6Includ1ng 25 percent pressurized (45 pslg) recycle.
              flncludlng 27 percent pressurized (55-70 pslg) recycle.
              9lnclud1ng 50 percent pressurized recycle.

-------
developed  at Windhoek, South  Africa,  and Stockton,  CA (58)(92)(93)(95)(97).
For  autoflotation  to  be  effective,  the  DO  content of  the  pond must  exceed
about 13 to 15 mg/1 and the pH must be greater than 11.

Autoflotation  can  perform well  under  the  proper  circumstances.    The  major
disadvantage is  dependence on the  development  of  gas  supersaturation  within
the oxidation  pond.  At Windhoek,  the  tertiary  pond is  supersaturated around
the clock because of their light organic loading and the presence of favorable
climatic conditions.   At  Stockton,  the  required  degree of supersaturation was
present  only  intermittently,  and then  for  less  than  half  the  day.    The
Stockton pond  BODs  loadings  of 37 kg/ha/d (33  Ib/ac/d)  during the  summer are
closer to normal facultative pond loadings than those at Windhoek.

Generally, autofl otation  is usable only  for  a part of the day.   The only way
to compensate  is to store the effluent and  increase  the  number of flotation
tanks accordingly and  use the  process whenever it is operable.  The extra cost
for more  tanks will  favor the selection  of  dissolved air flotation in nearly
all instances.


       5.4.3.2  Dissolved Air Flotation (DAF)


The  principal   advantage   of   coagulation-DAF  over  coagulation-flocculation-
sedimentation  is the  smaller  tanks required.  Flotation can be undertaken in
shallow tanks  with hydraulic  residence  times of 7  to  20 minutes,  rather than
the 3 to  4 hours required for deep  sedimentation   tanks.   Overflow rates for
flotation  are  higher^ about  120  m3/m2/d  (2   gpm/ft2)   (excluding  recyclej
compared   to   50   nr/m2/d    (0.8  gpm/ft2)   or  less    for   conventional
sedimentation tanks.

Sedimentation,  however,  does  not require the  air  dissolution  equipment  of
flotation, making it a simpler system to operate and maintain.  This factor is
especially important for  small plants, and it was  crucial  in the selection of
sedimentation  over flotation  for  the Lancaster  Tertiary Treatment Plant (74).


Another  advantage  of flotation  over   sedimentation  is  that a  separate
flocculation  step   is  not  required.    In   fact,  a  flocculation  step  after
chemical  addition  and  before  introduction  of the  pressurized flow  into  the
influent has been found to be  detrimental (95)(98).


           a.  Optimization of DAF Operation


Ramirez et al.  (99) used electrocoagulation prior to DAF  and  achieved good
results.   The electrocoagulation  cell,  a   LectroClear  system,  supplies  a
current to  the influent  of 0.53  ampere-minute/I.   The  system  operates  on 24
volts and  has  a capacity of   3,000  amperes.   This  helps to  destabilize  the
algae's negative charge,  making chemical  coagulation more effective.
                                      252

-------
Operating  parameters used  in DAF  include surface-loading  rates,  air/solids
ratio, pressurization level, coagulant dose, and the coagulant-addition point,
the  choice  of influent versus recycle pressurization,  and  the design details
for  the  flotation  tank.   The last item is  important because most proprietary
tank  designs  were  developed for  sludge-thickening  applications,   and  some
manufacturers have not reevaluated designs for optimal  algae removal.


           b.  Surface Loading Rates


Studies  at Stockton  and Sunnyvale,  CA   (86)(93)(97)  and  at  Logan,  UT  (96)
indicate  that maximum surface  loading rates  generally vary  from 120 to 160
nr/nr/d   (2   to   2.7  gpm/ft2),   including  effluent   recycle,   where  used)
depending  on  tank  design.   Stone  et al.  (86)  found,  in prior studies  at
Sunnyvale,  that   loadings   greater   than  120  m3/m2/d  (2  gpm/ft2)  caused
deteriorating performance.   However,  the  flotation  tank used in the  study was
of poor hydraulic  design  and it  was  concluded  that  higher loading rates might
be  used  in  prototype  facilities.    It  was  also  concluded that   influent
pressurization produced better results than recycle pressurization and allowed
use  of  smaller  tanks  as well.    Bare  et  al.  (96)  found that  140^ m3/m2/d
(2.4  gpm/ft2) was  optimum  and Parker  et  al.   (93)  used  160 m3/
gpm/ft2) at Stockton, CA.  Alum was the coagulant used in all cases.
           c.  Pressurization and Air/Solids Ratio

          '"''•,.,-',''•;:'    -        -          '             '
     air/solids ratio  is  defined as  the weight  of  air bubbles  added to the
process  divided by the weight of SS entering the tank.  Values used generally
range  from  0.05  to  0.10  (93)(96).    The  air/solids  ratio is  dependent on
influent solids concentration,  pressure  level used, and percentage of  influent
or   recycled  effluent  pressurized,.     Pressurization  levels  used  in  DAF
-generally  range  from  1.7  to 5.4 atm.   Pressure may  be  applied  to all  or a
'portion  of  the flotation-tank  effluent, which  is then recycled  to  the  tank
influent.  The latter mode  has  traditionally been  used for sludge thickening
applications when  the influent  solids  have  been flocculated and pressurizing
the  influent might cause  floe breakup.


           d.  pH Sensitivity of Metal  Ion Flocculation


The  pH is  extremely  important in alum and iron coagulation.  It is possible to
lower  the wastewater  pH  by adding  acid (^$04), for  example, and  thus  take
full advantage of  the pH sensitivity of the coagulation  reactions.   The  acid
dose required to  reach a desired wastewater pH level  depends on the coagulant
dose and wastewater  alkalinity.

figure 5-21  shows  the effect of lowering the pH  ,on  effluent SS levels during
pilot  studies  at  Sunnyvale  (86),  using  alum  as  the  coagulant.    It was
concluded  that not much could be gained  by lowering the pH below 6.0,  and  that

                                      253

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                             FIGURE  5-21



    EFFECT  OF ALUM DOSE AND pH ON  FLOTATION PERFORMANCE  (86)
              100
           o>
               80
               60
           §   40
               20
                        I      I      I

                        lnfluentTSS=150mg/l
                               100 mg/l alum
                                          150 mg/l alum
                                Typical data

                                Sept. 19 and

                                Sept. 20
5.6    5.8    6.0
                                   6.2


                                   PH
                               6.4    6.6
              6.8
                             FIGURE 5-22



EFFECT  OF ALUM DOSE  AND INFLUENT SS ON FLOTATION PERFORMANCE (86)

           50
        o>
        E

       C/5
          40
30
        ®

        =  20
       7
       LLI
           10
                                                   T
                                    125 mg/l alum


                              ^S
                                    1150 mg/l alum
                               ^_A H
                                    175 mg/l alum
                   f            '
                                               200 mg/l alum
                        I
                         I
I
                              I
I
                  25    50    75   100   125   150

                            Influent TSS, mg/l
                                        175  200
                                254

-------
the range  of 6.0 to  6.3  could be used  for optimum performance.   Subsequent
neutralization can be accomplished by adding caustic soda.


           e.  Alum Dose


Pilot  studies  at  Stockton  (93)  and Sunnyvale  (86)  (Figure  5-22)  show  the
effect  of  influent TSS  and alum  dose  on  effluent  TSS concentrations.   The
results  presented  in Figure  5-22 show  that  influent  TSS  have a  relatively
minor  effect  on effluent quality.   The  benefit of increasing alum  doses  is
most  pronounced up  to  about  175 mg/1.    Beyond  that  range,  increased  alum
addition results in only marginal  improvement in effluent TSS levels.


           f.  Physical  Design


It  was noted  above  that proprietary  flotation  tank  designs  do  not  possess
certain features important  in  pilot- and full-scale  studies  of algae  removal.
Features incorporated in the flotation tank designs for Sunnyvale and  Stockton
are shown in Figure 5-23 and illustrate important design concepts.

      o  The location for alum addition is via orifice rings at the point
         of  pressure  release where  intense turbulence  is  available  for
         excellent initial  mixing of chemicals.   This  also  permits  the
         simultaneous  coprecipitation  of algae,  bubbles,  and chemical
         floe,  and results  in  excellent  flotation performance.   Altering
         this   position   of   chemical   addition  invariably   leads   to
         performance deterioration.

      o  The point of pressure  release  is in the  feedwell.   An orifice,
         rather than a valve, can be used on the pressurized line because
         the DAF tanks can  operate at constant  flow,  using  the ponds  for
         flow  equalization.   In   most  proprietary  designs,  a  valve  is
         provided on  the  pressurized line at the  outside tank wall,  and
         this  permits bubbles  to coalesce  in  the  line leading  to  the
         feedwel 1.

      o  Care  is  taken  to  distribute  the wastewater  flow  evenly  into
         the  tank.   An inlet  weir distributes the  flow around the full
         circumference of the  inlet  zone and a double  ring  of weirs  are
         used  to  dissipate turbulence.    One  full-scale circular  tank
         introduced  the , influent   unevenly,   causing   nearly  all   the
         influent to flow through one-quarter of the tank.

      o  Influent  is introduced  at the surface  rather than  below  the
         surface as  in  most proprietary  tank  designs.  The  buoyancy of
         the   rising   influent  introduced  below  the  surface  causes
         density currents that  result in short  circuiting  of solids into
         the effluent.
                                      255

-------
                                FIGURE  5-23

          CONCEPTUAL DESIGN  OF DISSOLVED AIR FLOTATION TANK
                        APPLIED TO ALGAE REMOVAL
Effluent
           Float scraper arm


              Float collection trough
Feedwell
                                                                  Alum feed
                                                                  orifice ring
                                  256

-------
      o  Provision of  sludge  and float scrapers and  positive  removal  of
         sludge and float will aid performance.

      o  Effluent  baffles ,  extending  down   into   the  tank   inhibit
         short circuiting of solids.

In  addition,   the  tank  surface  should  be protected from  wind currents  to
prevent movement  of  the  relatively light  float  across  the tank.    In  rainy
climates,  the  flotation  tank   should   be  covered   because   the   float  is
susceptible to breakdown by rain.   Alternatively,  the flotation  tank could be
shut  down during  rainy  periods,  which  would  necessitate larger tanks  to
accommodate higher flow rates in dry weather.


           g.  Float Concentration


It is necesary to remove and dispose of the chemical-algal  float that-rises to
the  water  surface.     Flotation general  ly  can  result in  a   higher  sludge
concentration  than does: sedimentation  for two reasons.  First,,  float removal
from the  flotation unit takes place on the liquid surface where the operator
has  good  visual  control over  the thickening   process.   Second,  the  float is
thickened  by  draining  the liquid  from the float, a  procedure, with a greater
driving force  promoting thickening  than the mechanism in sedimentation,  which
involves settling and compacting the loose algal-alum floe.

Bare et al. (96) reported float concentrations of 1>0 to 1.3 percent with alum
coagulation/DAF;  Concentrations .increased  to  about 2.0  percent  when a second
flotation  was  allowed  to  occur in the  skimmings receiving  tank.   Stone et al.
(86) reported  float concentrations of  1.3 to 2.1 percent in the  Sunnyvale, CA,
studies with specific gravitiejsL of 0.45 to 0.55.


         '  h.  Solids Handling and Treatment


Satisfactory  disposition  must be made of the  algal-chemical  sludge generated
by   coagulation-clarification   processes.      Application  of   conventional
solids-handling  and   treatment   processes  requires  increased   capital  and
operating  expenses.  This consideration was among those that led Middlebrooks
et al. (58) to recommend against using coagulation-clarification processes for
small plants.

Most of the relevant work  to  date has involved  alum-algal  sludges, with very
little  work   done  with  lime-algal   sludge.    Disposal  and   dewatering  of
alum-algal  sludge  are  notoriously  difficult,  which  is  not surprising  since
algal sludge and alum sludge  are difficult  to  process individually.

Both centrifugation  and vacuum  filtration  of  unconditioned  algal-alum sludge
have produced  marginal results because of dewatering  difficulties and the need
for  using  low process  loading  rates (72)(97).   Heat treatment  using  the
Porteous  process  at  temperatures of 193  to 213 °C has  been shown  to improve

                                     •257

-------
subsequent  vacuum filter yield  and cake  concentration  to a  limited  extent.
Filter  yield  was low  and  ranged  from  4.4  to  12.2  kg/m2/h  (0.9  to  2.5
Ib/ft2/hr).   Cake concentrations  during  the  study  were 8.3  to  21.6  percerit
total  solids,  using  raw sludge  with  a  solids  concentration  of  about  four
percent in the feed algal-alum sludge (97).

Use of Zimpro low-temperature oxidation, at temperatures of 180 to 220 °C, has
resulted  in vacuum  filter  cake  concentrations  of  15  to  19 percent  totaj
solids,  at  filter-yield  rates  of  3.3  to   14.9  kg/m2/h  (0.7  to  3.0  IB
ft2/hr) (97).

Zimpro high-temperature  oxidation,  with  temperatures ranging  from  220  to 275
°C, was also investigated  because  it would lead  directly to ultimate disposal
of the  sludge.   Evaluation  showed  that  cake concentrations and  filter yield
improvements   were  marginal,  indicating  that  ultimate  disposal   should
incorporate  ponds.   The high-oxidation  process  reduces  VSS in the  sludge by
about  97  percent,  which  is  important  in  producing  a  stable  end  product.
Although some of the volatile solids are made soluble in the liquid, the final
solids are stable and suitable for pond  storage (96).

Only limited- investigations  have  been made into  the  use of centrifugation for
concentrating  algal-chemical  sludges.    At Firebaugh,  CA,  a  Bird  solid-bowl
centrifuge  and a  DeLaval  yeast-type separator  were  used  to  dewater  sludge
(100).   Both  devices  were considered  failures,  although  the use of  sludge
conditioning aids, .such as  organic polymers, might be expected to   improve
their performance.   A DeLaval self-cleaning basket  machine, also tested, was
able  to  concentrate  a  two  to three percent  feed  to 10 percent  total  solids
with a recovery of 98 percent.

Centrifugation has been used for lime classification of raw wastewater sludges
(101M102),  but  the  only  report  on its  use  for algal-lime  sludge did not
present specific details (94).

Another  process  that has  been investigated  is  a chemical-oxidation  scheme,
called  Purifax,   that employs  chlorine  as  the  oxidant.    This  process  was
capable  of  stabilzing   the   sludge,  and  yielded a  product  that  could  be
dewatered  on  sand  drying  beds  or  in   a  pond;  however,  chlorine costs are
relatively high (97).

Initial work on anaerobic digestion of algal-alum sludge, at the University of
California,  indicated that  the  process  held  little  promise  for  future use
(103).  Volatile  matter  reduction  was  less than 44  percent, and  the  digested
sludge was unstable and slow to dewater.   Subsequent work has shown that algae
can  be  anaerobically degraded  successfully  if they are killed  before  their
introduction into the digester.

While these relatively complex processes have generally proved  unsatisfactory
there is a  comparatively simple,  and potentiality effective,  solution  to the
solids-handling problem—return  of the  algal-alum sludge  to  the  pond  (104,).
When algae-alum sludge is returned to a pond,  it must be distributed to  reduce
accumulation at  a single  point.   Furthermore, when air is contained  in the
sludge float,  procedures must be  found  to remove  it  before  introducing the

                                     258

-------
sludge  into the  pond,  or floating  sludge  problems  will  result.    Several
methods have been  investigated for breaking  down  collected  float,  including
the  use  of high-shear  pumps, pumps  using a  vacuum,  high-shear mixers,  and
water sprays (100).


           i.   Coagulant Recovery


Because  chemicals  are  used  in  large  quantities  for  coagulation,  their
regeneration and reuse may be a way to reduce overall operating costs.  Use of
acid to reduce pH to about 2.5 can result in a 70 percent alum recovery (100).
Because phosphorus  is  also released at low pH,  acid recovery will  be limited
to those situations where phosphorus removal is not required.

Although  efforts  in  coagulant recovery  from  algae sludges  have  only  been
exploratory thus  far,  there  is  evidence  that further  investigations  could
yield useful results.


5.5  Land Application


     5.5.1  Introduction


Land  application  systems  can be  classified  into   one  of  three  categories:
overland flow (OF)  (involving flow over grassed terraces); irrigation of crops
by conventional methods,  or slow-rate treatment (SR);  and rapid infiltration
(RI)  systems.    The   following   subsections   discuss   design  criteria  and
performance of  the three  system  types  when  used  in  conjunction with  pond
effluent.   Comparison of  typical  characteristics and design criteria  for land
treatment processes are presented in Tables 5-14 and 5-15 (105).


     5.5.2  Overland Flow


Overland  flow  is  a land  treatment process which can be  used specifically on
sites  containing   soils  with  limited  permeability.    In  an  OF  process,
wastewater  is distributed along the top portion of sloped terraces and allowed
to  flow  across  a  vegetated  surface  to  runoff   collection  ditches.    The
wastewater  is  renovated  as it  flows  in  a thin film  down  over the sloping
ground surface.  Since the  system  does  not  rely on  percolation into the soil,
overland  flow can  be used on clay  and  silty  type  soils with low infiltration
capacity.

The treatment mechanisms of an OF  system  are  similar in some respects to most
land  treatment  systems.    Biological   oxidation,   sedimentation,  and  grass
filtration  are the  primary removal mechanisms for organics and SS.  Phosphorus
and heavy metals are removed principally by adsorption, precipitation, and ion
exchange  in the  soil.   Some  are  also  removed by  plant uptake.   Dissolved

                                     259

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                                                     TABLE 5-14

                                       COMPARISON OF SITE CHARACTERISTICS FOR
                                           LAND TREATMENT PROCESSES (105)
ro
01
o
              Grade
              Soil
               Permeability
Depth to
 Groundwater
              Climatic
               Restrictions
Slow Rate

Less than 20% on
  cultivated land;
  less than 40% on
  noncultivated land

Moderately slow to
  moderately rapid


0.6-1.0 m minimum13
                 Storage often needed
                   for cold weather
                   and precipitation
Rapid Infiltration

Not critical;
  excessive grades
  require much
  earthwork

Rapid (sands, sandy
  loams)


0.3 m during flood
  cycle; 1.5-3.0 m
  during drying
  cycle

None (possibly modify
  operation in cold
  weather)
                                                                   Overland Flow

                                                                   Finish slopes 2-
Slow (clays, silts,
  soils w/impermeable
  barriers)

Not critical0
                                                  Storage often needed
                                                    for cold weather
                                                    treatment
              aSteeper grades might be feasible at reduced hydraulic loadings.
              bUnderdrains can be used to maintain this level  at sites with high groundwater table.
              clmpact on groundwater should be considered for more permeable soils.

-------
                                                               TABLE  5-15

                                             COMPARISON OF  TYPICAL  DESIGN FEATURES FOR
                                                    LAND TREATMENT  PROCESSES  (105)
ro
en
Application
Techniques
Application
Rate
Field Area
Requi red"
Typ. Weekly
Application
Rate
Minimum Pre-
appHcation
Treatment
Provided in
U.S.
Disposition
of Applied
Wastewater
Need for
Vegetation
Slow Rate
Sprinkler or
surface9
0.5-6.0 m/yr
23-280 ha
1.3-10 cm
Primary
sedimentation^
Evapotranspi ration
and percolation
Required
Rapid Infiltration
Usually surface
6-125 m/yr
3-23 ha
10-240 cm
Primary
sedimentation
Mainly
percolation
Optional
Overland Flow
Sprinkler or
surface
3-20 m/yr
6.5-44 ha
6-40 cmc
Grit removal and
comminution6
Surface runoff and
evapotranspiration
with some
percolation
Required
                                alncludes ridge-and-furrow and border strip.
                                bField area (not including buffer  area, road, or ditches) for 3,785 m^/d flow.
                                cRange includes raw wastewater to  secondary effluent, higher rate  for higher level
                                    of preapplication treatment.
                                dWith restricted public access; crops not for direct human consumption.
                                eWith restricted public access.

-------
solids are removed by plant uptake, ion exchange, and through leaching.  Algae
removal  by  OF  systems  has  been  inconsistent  and  it  should  be  evaluated
carefully before using OF as a means of algae removal.

Nitrogen  levels  can  also be  significantly reduced by  several  soil  and plant
processes.   An  aerobic  zone  is  maintained  in  the top layer of  liquid flow
where  ammonia  is oxidized  into  nitrite  and then  nitrate.   Immediately below
the soil surface, in the top few millimeters, an anaerobic zone is established
where  denitrifying bacteria convert the  nitrates into nitrogen gas, resulting
in high  overall  reduction in  the total  applied  nitrogen.   Plant  uptake  and
volatilization  under   proper   pH  conditions   are  other  important  removal
mechanisms, but permanent nitrogen removal by plant uptake is only possible if
the cover crop is harvested and removed from the field.

The basic differences between the OF systems cited in Tables 5-16 through 5-18
are the application methods and rates.   Two  types of  application can be used:
(1) sprinkler, or;  (2)  gravity surface  irrigation  by means  of grated pipe or
bubbling  orifice.   The most .common method  is  sprinkler, which  ensures even
distribution and can be automatically controlled.


     5.5.3  Slow-Rate or Crop Irrigation


In humid  climates, SR systems  are generally  designed  for the maximum possible
hydraulic loading  to  minimize  land requirements.   Systems of this  type have
been  successfully  designed for  forests,  pastures, forage grasses,  corn,  and
other  crop  production.   In  arid climates,  where water  conservation  is more
critical, wastewater is  often  applied  at rates  that just equal the irrigation
needs of  the crop.  Water  rights must also  be  given  careful  consideration in
arid  climates  prior  to  diverting  pond  effluent to another  location for land
treatment.

Design  of SR systems  for  typical  municipal  effluents  is  usually  based  on
either  the  limiting  permeability of  the in situ soils  or on  meeting nitrate
requirements in the groundwater,  if the  site overlies a potable  aquifer.  The
wastewater hydraulic loading  rate is calculated  for  both conditions,  and  the
limiting value then controls design (105).

Performance and design data for selected SR systems treating pond effluent are
summarized in Tables 5-19 through 5-22.


     5.5.4  Rapid Infiltration


The principal difference between RI and SR is that hydraulic loading rates  are
greater.    Highly  permeable   soils must be   available.    Nitrogen  removal
mechanisms rely less on  crop  uptake and  more on nitrification-denitrification
within the soil.   It has been suggested that such systems only be allowed when
groundwater quality is  either  of no consequence  or when the percolate can be
controlled (106).


                                     262

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                                                       TABLE 5-16


                                SUMMARY OF BOD  AND SS REMOVALS  AT OVERLAND FLOW  SYSTEMS

                                           TREATING POND EFFLUENTS3 (105)
ro
en
Location
f
Pauls Valley, OK
Utica, MS




Easley, SC
Slope
Length
m
46
46




46
Application
Rate
m^/m/hr
0.06
0.032
0.065
0.049
0.13
0.10
0.23
Hydraulic
Loadi ng
Rate
cm/d
1.66
1.27
2.54
2.54
5.08
1.27
3.58
Application
Period
hr/d
12
18
18
24
18
6
7
Frequency
d/wk
7
5
5
7
5
5
5
BOD
Influent

27.7
22
22
22
22
22
28
Effluent
mg/1
20.5
3.5
4.0
5.5
7.5
8.6
15
SS
influent

114
30
30
30
30
30
60
Effluent

72.8
5.5
8.0
13.0
13.0
6.4
40
          Performance during warm season.

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                                                       TABLE 5-17

                               SUMMARY OF NITROGEN AND  PHOSPHORUS REMOVALS AT OVERLAND
                                     FLOW SYSTEMS TREATING POND EFFLUENTS3  (105)
ro
Locati on

Pauls Valley, OK
Utica, MS




Easley, SC
Hydraulic
Loadi ng
Rate
cm/d
1.66
1.27
2.54
2.54
5.08
1.27
3.58
Total
influent

15.5
20.5
20.5
20.5
20.5
20.5
6.7
N
Effluent

11.4
4.3
7.5
7.3
10.0
7.0
2.1
Ammonia-N

Influent Effluent

1.7
15.6
15.6
15.6
15.6
15.6
1.0
mg/1
0.4
0.1
0.8
0.7
1.1
0.8
0.4
Nitrate-N
Influent Effluent

<0.1 0.2
<1.0 1.0
<1.0 2.6
<1.0 3.1
<1.0 4.8
<1.0 3.2
2.4 1.1
Total
Influent

6.3
10.3
10.3
10.3
10.3
10.3
3.8
P
Effluent

5.1
4.9
6.1
5.9
8.2
7.1
2.2
           aPerformance during warm season.

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                                                        TABLE  5-18

                                      REMOVAL  OF  HEAVY METALS  AT DIFFERENT HYDRAULIC
                                            RATES AT UTICA,  MISSISSIPPI (105)
                  cm/a

                  1.27
                  2.54
                  3.81
                  5.08
Cadmium

0.0046
0.0036
0.0079
0.0142
Nickel Copper
mg/1
0.0131 0.0129
0.0217 0.0293
0.0302 0.0382
0.0486 0.0524
Zinc

0.0558
0.0525
0.0757
0.0853
                                                                              Removal Efficiency
Cadmi urn
Nickel
Copper
Zinc
percent
85
91
78
63
92
88
80
66
93
82
74
64
88
87
79
75
en
on

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                                    TABLE 5-19

                 BOD REMOVAL  DATA FOR SELECTED SLOW-RATE  SYSTEMS
                          TREATING POND EFFLUENTS  (105)
   Location
Dickinson, ND
Huskegon, MI
Hydraulic
Loadi ng
Rate
cm/yr
140
130-260

290
Surface
Soil
Sandy loams
and loamy
sands
Sands and
loamy sands
Clay and
clay loam

In Applied
Wastewater
mg/1
42
24

89
BOD
In Treated
Wastewater
mg/1
1.3

0.7

Removal
percent
>98
94

99
Sampl i ng
Depth
m
<5
4

2.1
                                    TABLE 5-20

                  NITROGEN  REMOVAL DATA FOR SELECTED  SLOW-RATE
                      SYSTEMS  TREATING POND EFFLUENTS (105)
Location

Dickinson, ND
Helen, GA
San Angel o, TX
Total Nitrogen
1n Applied
Wastewater
mg/1 as N
11.8
18.0
35.4
Total Nitrogen
1n Percolate
or Affected
Groundwater
mg/1 as N
3.9
3.5
6.1
Removal
percent
67
80
83
Sampling
Depth
m
11
1.2
10
Total Nitrogen
in Background
Groundwater
mg/1 as N
1.9
0.17
—
                                      266

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                                                     TABLE 5-21

                              PHOSPHORUS REMOVAL  DATA FOR SELECTED SLOW-RATE  SYSTEMS
                                          TREATING POND EFFLUENTS3 (105)
PO
CTl


Location

Agricultural
Systems
Dickinson, ND


Muskegon, MI

Forest System
Helen, GA
Hydraulic
Loading
Rate
cm/yr


140


130-260


380

Surface
Soil



Sandy loams
and loamy
sands
Sands and
loamy sands

Sandy loam
P04
In Applied
Wastewater
mg/1 as P


6.9


1.0-1.3


13.1
Soluble P04
in Affected
Groundwater
mg/1 as P


0.05


0.03-0.05


0.22
Distance
Samp! 1 ng from
Removal Depth Site
percent m m


99 <5 30-150


95-98 1.5 0


98 1.2 0
Soluble P04
in Background
Groundwater
mg/1 as P


0.04


0.03


0.21
          aTotal phosphate concentration.

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                                                  TABLE 5-22

                                TRACE  ELEMENT  BEHAVIOR  DURING SLOW-RATE
                                    TREATMENT OF POND EFFLUENTS  (105)






ro
Ch
co
El ement

Cadmium
Chromium
Copper
Lead
Manganese
Mercury
Z1nc
EPA Drinking
Water Standard
mg/1
0.01
0.05
1.0
0.05
0.05
0.002
5.0
Raw Municipal
Wastewater
Concentration
mg/1
0.004-0.14
0.02-0.7
0.02-3.4
0.05-1.3
0.11-0.14
0.002-0.05
0.03-83
Muskegon,
Michigan3
Percolate
Concentration Removal
mg/1
<0.002
0.004
0.002
<0.050
0.26
<0.002
0.033
Percent
90
90
90
>40
15
95
San Antonio,
Percolate
Concentration
mg/1
<0.004
<0.005
0.014
<0.050
-- ;
0.102
Texasb
Removal
Percent
-d
>98
85
_.d
~
25
Melbourne,
Australia0
Percolate
Concentration Removal
mg/l
0.002
0.03
0.02
0.01
—
0.0004
0.04
Percent
80
90
95
95
—
85
95
aAverage annual concentrations (1975)  found 1n underdralns placed at a depth of 1.5 m below Irrigation site.
bAverage annual concentrations (November  1975 - November  1976) found In two seepage creeks  adjacent to the  irrigated area.
cAverage annual concentrations (1977)  found in underdrains placed at depths of 1.2 to 1.8 m below the irrigation site.
"Percent removal was not calculated since influent and percolate values are below lower detection limit.

-------
There  are  numerous  examples   of   rapid  infiltration  of  treated  effluent.
Hydraulic loading rates for secondary effluent range down from 2.1 m/wk (7 ft/
wk) at  Flushing  Meadows,  AZ, on sandy  soil  to 20 cm/wk (8  in/wk)  at Westby,
WI, on silt loam.  For primary  effluent, loading  rates  of  57 cm/wk (22 in/wk)
are used at Hoi lister, CA (105).

The few examples of RI with pond effluent  are  presented  in Tables  5-23 and
5-24.    Of particular concern would  be  whether the algae would clog  the soil.
The data  accumulated  so far at Flushing  Meadows seem  to  indicate that algae
have  a  greater clogging  potential  than an  equal mass  of SS from  secondary
treatment  (activated  sludge) at the  higher loading rates  employed  in  that
system.   This  fact is  ordinarily  of no  consequence  for  the  more  common
low-rate  systems applying  approximately  2.5  to 7.5  cm/wk  (1  to 3  in/wk).
However, Hicken  et  al.  (107) observed prolific algal growths on  nonvegetated
control  plots  at application rates of 5  to 15  cm/wk  (2  to 6  in/wk)  (100).
Contrary  to observations,  the  algal  mats  did  not increase  the  hydraulic
impedance  on  these  sites.    Perhaps the   explanation   lies  in  the  great
difference in application rate between the two systems.
                                     269

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                                   TABLE 5-23

              NITROGEN REMOVAL DATA FOR SELECTED RAPID  INFILTRATION
                      SYSTEMS TREATING POND EFFLUENTS (105)
Location

Brookings, SD

1X3
•-4
O
Total N
in Applied Loading
Wastewater Rate
mg/1
10.9

FECAL
m/yr
12.2

BOD:N

2:1
TABLE
Flooding
Time: Dry ing
Time

1:2
5-24
COLIFORM REMOVALS AT SELECTED RAPID
SYSTEMS TREATING POND EFFLUENTS (1
Renovated Water
NOri-N Total N
r- 	 •J. ,. , . . 	 "
mg/1
5.3 6.2

INFILTRATION
L05)
Total N
Removal
percent
43


Location

Hemet, CA
Milton, WI
Santee, CA
Soil Type

Sand
Gravelly
sands
Gravel ly
sands
Fecal Coliforms

Applied Wastewater Renovated Water
MPN/100 ml
60,000
TNTCa
130,000
130,000

11
0
580
<2
Distance of
Travel
m
2
8-17
61
762
aAt least one sample too numerous to count.

-------
5.6  References
  1.   Process Design Manual for Suspended Solids Removal.   EPA-625/l-75-003a,
      U.S.  Environmental  Protection Agency,  Center  for Environmental  Research
      Information,  Cincinnati,  OH,  1975.

  2.   Upgrading  Lagoons.     EPA-625/4-73-001b,  NTIS  No.  PB   259974,   U.S.
      Environmental   Protection  Agency,   Center  for  Environmental   Research
      Information,  Cincinnati,  OH,  1977.

  3.   Process  Design  Manual   for   Upgrading  Existing  Wastewater  Treatment
      Plants. EPA-625/l-71-004a, U.S. Environmental  Protection  Agency,  Center
      for Environmental Research Information, Cincinnati, OH,  1974.

  4.   Oswald, W.  J.   Advances  in Anaerobic Pond Systems Design.   In:   Advances
      in Water  Quality Improvement,  University of  Texas Press,""Austin,  TX,
      1968.   p. 409.

  5.   Goswami, S. R.,  and  W.  L. Busch.    3-Stage  Ponds Earn Plaudits.   Water
      and Wastes  Engineering 9(4):40-42,  1972.

  6.   Caldwell,  D.   H.    Sewage  Oxidation  Ponds.    Sewage  Works  Journal
      18(3):433,  1946.

  7.   Dinges,  R.,  and  A.  .Rust.   Experimental  Chlorination of  Stabilization
      Pond Effluent.  Public Works  100(3), 1969.

  8.   Echel berger,   W.  F.,  J,   L.  Pavoni,  P.  C.   Singer, and  M.  W.  Tenney.
      Disinfection   of   Algal   Laden  Waters.   J.   Sam't.   Eng.  Div.,   ASCE
      97(SA5):721-730,  1971.

  9.   Horn,  L.  W.   Kinetics of Chlorine Disinfection  in an  Ecosystem.   J.
      Sanit.  Eng. Div., ASCE 98(SA1):183-194, 1972.

 10.   Wight,  J. L.   A Field Study:  The Chlorination of Lagoon Effluents.   M.S.
      Thesis, Utah  State University, Logan,  UT, 1976.

 11.   Johnson, B.  A.   A  Mathematical  Model  for  Optimizing Chlorination  of
      Waste  Stabilization  Lagoon Effluent.   Ph.D.   Dissertation,  Utah  State
      University, Logan,  UT, 1976.

 12.   Pierce,  D. M.    Performance  of  Raw Waste   Stabilization  Lagoons  in
      Michigan with Long  Period Storage  Before  Discharge.     In:  Upgrading
    •  Wastewater Stabilization  Ponds to  Meet  New  Discharge Standards,  PRWG
      151,  Utah  Water  Research  Laboratory,  Utah State University,  Logan,  UT,
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 13.   Graham,  H. J.,  and  R.  B. Hunsinger.   Phosphorus Removal  in  Seasonal
      Retention Lagoons by Batch Chemical  Precipitation.   Project No.  71-1-13,
      Wastewater Technology Centre, Environment Canada,  Burlington,  Ontario,
      Undated.

                                      271

-------
14.  Polluted! Pollution Advisory  Services,  Ltd.   Nutrient Control  in Sewage
     Lagoons.  Project No. 72-5-12, Wastewater Technology Centre, Environment
     Canada, Burlington, Ontario, Undated.

15.  Polluted! Pollution Advisory  Services,  Ltd.   Nutrient Control  in Sewage
     Lagoons, Volume II.   Project  No.  72-5-12,  Wastewater Technology Centre,
     Environment Canada, Burlington, Ontario, 1975.

16.  Graham,  H.   J.,  and  R.  B.  Hunsinger.    Phosphorus  Reduction  From
     Continuous  Overflow  Lagoons   by   Addition  of  Coagulants  to  Influent
     Sewage.   Research  Report No.  65,  Ontario Ministry  of  the Environment,
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17.  Engel, W. T., and T.  T.  Schwing.   Field Study of  Nutrient Control  in a
     Multicell  Lagoon.     EPA-600/2-80-155,  NTIS , No.  PB  81-148348,  U.S.
     Environmental   Protection   Agency,  Municipal   Environmental   Research
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18.  Golueke,  C.  G.,   and  W.  J.  Oswald.     Harvesting   and  Processing
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19.  McGriff,  E.  C., and  R.  E.  McKinney.    Activated  Algae:   A  Nutrient
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20.  McKinney, R.  E., et  a!.    Ahead:   Activated  Algae?   Water  and Wastes
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21.  Hill, D. W., J.  H.  Reynolds, D. S. Filip, and E. J. Middlebrooks. Series
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22.  Performance Evaluation of Kilmichael Lagoon.  EPA-600/2-77-109,  NTIS No.
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23.  Shindala, A., and J. W. Stewart.  Chemical Coagulation of Effluents from
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24.  van  Vuuren,  L.   R.  J., and  F. A.  van Vuuren.   Removal   of Algae from
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25.  Koopman, B. L.,  J.  R. Benemann, and W.  J.  Oswald.   Pond  Isolation and
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26.  McGriff,  E.   C.    Facultative  Lagoon  Effluent  Polishing Using  Phase
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                                    272

-------
27.  Duffer,  W.  R.,  and J.  E.   Moyer.    Municipal  Wastewater  Aquaculture.
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28.  Aquaculture   Systems   for   Wastewater1   Treatment:      An   Engineering
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         • '                            -      }

29.  Dinges,  R.   The Availability of  Daphnia for Water  Quality Improvement
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30.  Frook,   D.  S.    Clarification of  Sewage  Treatment Plant  Effluent  with
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31.  Trieff, N. M.   Sewage Treatment by Controlled Eutrophication Using Algae
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32.  Prokopovich, N.  P.   Deposition  of Clastic Sediments  by  Clams.   Journal
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33.  Greer,  D. E.,  and C. D. Ziebell.   Biological  Removal  of  Phosphates  from
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34.  Duffer, W. R.    Lagoon  Effluent  Solids Control  by Biological Harvesting.
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35.  Dinges,  R.    Upgrading Stabilization  Pond Effluent  by   Water  Hyacinth
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36.  Wolverton, B.  C., and  R. C.  McDonald.  Upgrading Facultative Wastewater
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37.  Chambers, G.  V.   Performance of  Biological  Alternatives  for  Reducing
     Algae   (TSS)   in  Oxidation  Ponds   Treating   Refinery/Chemical   Plant
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38.  Schroeder,  G.   L.   Some  Effects  of  Stocking  Fish  in  Waste  Treatment
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39.  Reid,  G. W.    Algae  Removal by  Fish  Production.   In:    Ponds as  a
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                                     273

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40.  Ryther, J. H.  Controlled Eutrophication-Increasing Food Production from
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41.  Serfling, S.  A.,  and C. Alsten-   An  Integrated,  Controlled Environment
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42.  Reynolds, J.  H.   The  Effects of Selected  Baffle Configurations on the
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43.  Nielsen, S. B.  Loading and Baffle Effects on Performance of Model Waste
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44.  Marshall, G.  R.,  and E. J. Middlebrooks.   Intermittent Sand Filtration
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49.  Bishop,  R.  P., J.  H.   Reynolds,  D.  S.   Filip,  and E.   J.  Middlebrooks.
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50.  Messinger, S.  S.   Anaerobic  Lagoon-Intermittent  Sand  Filter  System for
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                                     274

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                                    275

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63.  Fair,  G.   M.,  0.  C.  Geyer,  and  D.  A.   Okun.    Water  and  Wastewater
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67.  O'Brien, W. J.   Algal Removal by Rock Filtration.  In: Transactions 25th
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68.  O'Brien,  W.  J.,   and  R.  E.  McKinney.   Removal  of  Lagoon  Effluent
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69.  Swanson, G. R., and  K. J. Williamson.  Upgrading Lagoon  Effluents  with
     Rock Filters.  J. Sanit. Eng. Div., ASCE 106(EE6):1111-1119, 1980.

70.  Williamson, K.  J., and G. R.  Swanson.   Field Evaluation of Rock Filters
     for  Removal  of  Algae  from  Lagoon  Effluents.    In:    Performance  and
     Upgrading of Wastewater  Stabilization Ponds,  EPA-6T5D/9-79-011,  NTIS No.
     PB 297504, U.S. Environmental Protection Agency, Municipal Environmental
     Reserach Laboratory, Cincinnati, OH,  1978.

71.  Forester,  T.   H.    Personal  communication.    Missouri:   Department  of
     Natural Resources, Jefferson City, MO,  1977.

72.  Golueke,  C.   G.,   and  W.   J.  Oswald.     Harvesting  and  Processing
     Sewage-Grown Planktonic Algae.  JWPCF 37(4):471-498, 1965.

73.  California Department  of Water Resources.   Removal   of  Nitrate  by  an
     Algal System.  EPA WPCRS, 1303ELY4/71-7, Washington, DC,  April 1971. :

74.  Dryden, F. D., and G.  Sterm.   Renovated Wastewater Creates Recreational
     Lake.  Environmental Science and Technology 2:268-278, 1968.

75.  Lynam,  G.,  G.   Ettelt,  and  T.  McAloon.   Tertiary  Treatment at  Metro
     Chicago by  Means of Rapid  Sand Filtration  and Microstrainers.   JWPCF
     41(2):247-279,  1969.

76.  Kormanik,  R.   A.,  and  J.   B.   Cravens.      Remove   Algae   through
     Microscreening. Water and Wastewater Engineering 15(11):72-74, 1978.
                                    276

-------
77.  Union  Carbide  Corporation.    Algae  Removal  from  the  Seadrift  Plant
     Wastewater Treatment System.   Port Lavaca, TX, January 1979.

78.  B. P. Barber &  Associates.   Recommended Design for  the  City  of Camden,
     South Carolina, Wastewater Treatment Facility.  Prepared for the City of
     Camden, SC, 1977.

79.  Harrelson, M.  E.,  and  J.  B. Cravens.   Use  of Microscreens  to  Polish
     Lagoon Effluent.  JWPCF 54(1):36-42, 1982.

80.  Wilkinson,  J.  B.     A  Discussion  of  Algae  Removal  Techniques  and
     Associated Problems and Process and Economic Considerations of Ponds for
     Treatment  of  Industrial   Wastewater.     In:    Ponds  as  a  Wastewater
     Treatment Alternative,  Water Resources  Symposium  No.  9,  University of
     Texas, Austin, TX,  1976.

81.  Borchardt,  J.  A.,  and  C.   R.   O'Melia.     Sand  Filtration  of  Algae
     Suspensions.   JAWWA 53(12), 1961.

82.  Davis, E., and  J.  A. Borchardt.   Sand  Filtration  of Particulate Matter.
     J. Sanit. Eng. Div., ASCE 92(SA5):47-60, 1966.

83.  Foess, 6.  W.,  and  J.  A.  Borchardt.   Electrokinetic  Phenomenon  in the
     Filtration of Algae Suspensions.  JAWWA 61(7), 1969.

84.  Forbes, J. H.   Algae Removal  by  Upflow  Filtration.   NTIS No.  PB 242369,
     University of  Nebraska, prepared for  the  Office of Water  Research and
     Technology, December 1974.

85.  McGhee, T. J.  Upflow Filtration of. Oxidation Pond Effluent.  University
     of Nebraska,  Water Resources Research  Institute,  Technical  Completion
     Report A-034-NEB, June  1975.

86.  Stone, R.  W.,  D.  S.  Parker,  and  J.   A.  Cotteral.   Upgrading  Lagoon
     Effluent  to  Meet  Best  Practicable Treatment.   JWPCF 47(8):2019-2042,
     1975.

87.  Wastewater Filtration Design Considerations.  EPA-625/4-74-007, NTIS No.
     PB   259448,    U.S.   Environmental   Protection   Agency,   Center   for
     Environmental Research  Information, Cincinnati, OH, 1974.

88.  Napa-American   Canyon   Wastewater  Management  Authority.     Personal
     Communication.  Napa, CA, 1979.

89.  Hutchinson, W.,  and  P.  D. Foley.   Operational  and Experimental Results
     of Direct Filtration.   JAWWA 66(2):79-87, 1974.

90.  Brandt,  H.  T.,  and   R.  E.  Kuhn.    Apollo  County  Park  Wastewater
     Reclamation  Project,  Antelope Valley,  CA.   EPA-600/1-76-022,   NTIS No.
     PB 252997, U.S. Environmental Protection Agency, Cincinnati, OH, 1976.
                                    277

-------
 91.  Al-Layla,  M.  A.,  and  E. J.  Middlebrooks.   Algae Removal  by  Chemical
      Coagulation.  Water and Sewage Works 121(9):76-80, 1974.

 92.  van Vuuren, L. R. J., P. 6. J., Meiring, M.  R.  Henzen,  and F.  F.  Kolbe.
      The Flotation of  Algae  in Water Reclamation.   International Journal  of
      Air and Water Pollution 9:823, 1965.

 93.  Parker, D. S., J. B. Tyler, and T. J. Dosh.  Algae Removal Improves Pond
      Effluent.  Water and Wastes Engineering 10(1):26-29,  1973.

 94.  Ort,  J.   E.    Lubbock  WRAPS  It Up.    Water  and Wastes  Engineering,
      9(9):63-66, 1972.

 95.  Komline-Sanderson  Engineering  Corp.    Algae  Removal   Application  of
      Dissolved Air Flotation, Peapac, NJ, August, 1972.

 96.  Bare,  W.  F. R.,  N.  B. Jones,  and  E.  J.  Middlebrooks.   Algae Removal
      Using Dissolved Air Flotation.  JWPCF 47(1):153-169,  1975.

 97.  Brown and Caldwell.  Report on Pilot Flotation Studies at the Main Water
      Quality Control  Plant.   Prepared for the City of Stockton, CA,  1972.

 98.  Ramani, A.  R.   Factors  Influencing Separation  of  Algal  Cells  from Pond
      Effluents  by  Chemical   Flocculation  and   Dissolved   Air  Flotation.
      Doctoral  dissertation,  University of California at Berkeley, 1974.

 99.  Ramirez,  E.  R.,  D.  L.  Johnson, and T.  E.  Elliot.  Removal  of  Suspended
      Solids and Algae  from  Aerobic  Lagoon  Effluent  to  Meet  Proposed  1983
      Discharge  Standards  to  Streams.     Proceedings of  Eighth   National
      Symposium on Food Processing Wastes, Seattle, WA, 1977.

100.  Parker, D.  S.   Performance of  Alternative Algae Removal Systems.   In:
      Ponds  as  a Wastewater Treatment Alternative,  Water  Resources  Symposium
      No.  9,  Center for Research  in  Water  Resources,  University of  Texas,
      Austin, TX, 1976.

101.  Parker, D.  S.,  D. 6. Niles,  and  F. J. Zadick.   Processing  of  Combined
      Physical-Chemical-Biological Sludge.  JWPCF 46(10):2281-2300, 1974.

102.  Parker, D. S., G.  A. Carthew,  and  G.  A. Horstkotte.   Lime  Recovery and
      Reuse   in   Primary   Treatment.      J.   Environ.   Eng.   Div.,   ASCE
      101(EE6):985-1004, 1975.

103.  Golueke,  C. G.,  W. J. Oswald, and H.  B.  Gotaas.   Anaerobic Digestion  of
      Algae.  Applied Microbiology 5(1), 1957.

104.  Parker,  C.  E.     Algae  Sludge  Disposal   in  Wastewater  Reclamation.
      Doctoral  dissertation.   University of Arizona, 1966.

105.  Process  Design   Manual   for  Land   Treatment  of  Municipal  Wastewater.
      EPA-625/1-81-013,  U.S.   Environmental  Protection Agency,  Center  for
      Environmental Research  Information,  Cincinnati, OH, 1981.


                                     278

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106.  Wallace, A. T.  Land Application of  Lagoon  Effluents.   In:   Performance
      and Upgrading of Wastewater Stabilization Ponds,  EPA-60079-79-Oil,  NTIS
      No.   PB   297504,   U.S.   Environmental   Protection  Agency,   Municipal
      Environmental  Research Laboratory,  Cincinnati,  OH, 1978.

107.  Hicken,  B. T.,  R.  S.  Tinkey,  R.  A.  Gearheart, 0.  H.  Reynolds, D.  S.
      Filip,  and  E.   J.   Middlebrooks.     Separation  of  Algae   Cells  from
      Wastewater  Lagoon   Effluent,   Vol.  Ill:     Soil   Mantle Treatment  of
      Wastewater    Stabilization    Pond   Effluent—Sprinkler    Irrigation.
      EPA-600/2-78-097,  NTIS  No. PB  292537,  U.S.    Environmental  Protection
      Agency,  Municipal  Environmental  Research  Laboratory,  Cincinnati,  OH,
      1978.
                                     279

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                                  CHAPTER 6

                         COST AND ENERGY REQUIREMENTS


The costs  associated  with  wastewater treatment facilities  are usually divided
into capital costs and operations and maintenance  (O&M)  costs.   The 0AM costs
are significantly  influenced by energy  consumption in most  wastewater  treat-
ment  facilities.  Where  O&M costs  are  available,  the  data are  presented;
however, there is  a limited  amount  of data for the operation and maintenance
of wastewater  ponds.   The costs and energy  requirements  will   be  discussed
individually in the following sections.


6.1  Capital Costs


The majority of the cost data presented  in this section  were extracted  from  a
technical  report  distributed by  the  Environmental  Protection  Agency  (1).
These data  reflect the  grant-eligible costs associated with  the  construction
of publicly  owned wastewater treatment  facilities  and  were  derived  from  the
actual winning  bid documents.   These cost data  are  the  most complete  data
available and represent  all  types of wastewater processes.   If  comparison of
the pond costs are to be made with other.types of  treatment  facilities,  it is
suggested that the design  engineer consult the above-referenced  report,  which
has a  detailed  explanation of  the  data base  and  techniques used to analyze
the data.

These data are useful  for preliminary design  and planning purposes.  Conven-
tional estimating  procedures should be  used  during  final  design.  The  costs
shown  in Figures  6-1 through  6-3  are national   averaged  costs  indexed to
Kansas City/St.  Joseph,  MO,  during  the fourth quarter  of  1978.   Individual
data points are  included on  the graphs  to illustrate  the wide variation  that
occurred in construction costs around the country.

The results presented represent only construction costs  and  do not  show  other
costs.  These other costs  include eligible Step 1  and  Step   2 planning  costs
as well as those  associated  with  Step 3 construction  effort:  administration,
architect/engineer fees, contingency allowances, etc.   Table  6-1  contains the
average ratios of all these  Step  3  cost categories to the total  construction
costs for new projects.   There are 15 categories of costs  identified  in  Table
6-1.   Only  five  of these  cost  categories were found in  the majority of the
projects:  administrative/legal  costs,   architect/engineer basic fees,   other
architect/engineer fees, project  inspection  costs, and  contingencies.   These
five categories equal  approximately 20  percent of the construction costs as  a
national  average.  However,  including all  of the  15 categories,  the  national
average costs were approximately 50  percent  of the  construction costs.  In


                                      280

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                    FIGURE 6-1

  ACTUAL  CONSTRUCTION  COST vs DESIGN FLOW FOR
        DISCHARGING STABILIZATION PONDS
                 (COST BASE 1978)
                                  o
                              o
I    I   I   I  I I  I M
                                 I    I  I  I  I  I I I
                         o
        1  1  1  1 1 ll
                                       C=(1.31 X 106)Q°-77
                                       r = 0.78
              Note:  Nonconstruction costs not included


         1    1   I   1  I I  I I I       I    I   L 11111
        0.05
0.1               0.5     1.0

    Design Flow, Q (mgd)
5.0   10.0
                         281

-------
                              FIGURE  6-2


             ACTUAL  CONSTRUCTION COST vs DESIGN FLOW FOR

                  NONDISCHARGING STABILIZATION PONDS
                            (COST BASE 1978)
    1.0

    0.8


    0.6
_  0.4
c
E

2t  0.2
o
                       I    I   I  I  I I I  |


                                    O
                       o
                           O
                                         O
O
  I     i 0 I  I   I  I  I
                                                o
                                                00
                                                       o
o
c   0.1

I 0.08


t5 0.06
c
         —      o
CD
3
+-i
O
   0.04
   0.02
    0.01 L
       0.01
                       o
                       8
                                                C = (1.18X 106)Q°-75

                                                r = 0.74
                                   Note: Nonconstruction costs not included


                           I   I   I  I I I I         I     I   I  i  I  I  1 I
                            0.05      0.1

                            Design Flow, Q (mgd)
             0.5
1.0
                                   282

-------
                                                    FIGURE  6-3
ro
oo
to
 10.0


  8.0


  6.0



'  4.0
o

•(-?
(A
O
o

c
o
          2.0
          1.0
|  0.8


?  0.6
o
o

ro  0.4

1
          0.2
          0.1
             0.01
                                   ACTUAL  CONSTRUCTION COST vs  DESIGN FLOW FOR

                                                   AERATED PONDS

                                                  (COST BASE  1978)
                        I     I   I    I  I  I  I  I]
                                             O
                        I     I   I   I   I  I  I I  1
                                                I
                                                   o  o
I    II   llll|
                                                           O
     I  I  I  I  11
                                                      I
                                                                      o
                                                                              o
                  C = (2.47X 106)Q°-73

                  r = 0.87



          Note:  Nonconstruction costs not included


   I  I  I I  I  I I          I	I    I   I   I  I  I I
                           0.05      0.1                   0.5

                                          Design Flow, Q (mgd)
               1.0
5.0
                                                                                                 10.0

-------
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                                                  284

-------
addition  to  the  Step  3  nonconstruction  costs,  the  Steps   1  and  2  costs
(preliminary  and  detailed design)  must also  be included.   These  two  costs
were  calculated  as  a  fraction  of  the  total  construction  cost  and  are
presented at  the  bottom of Table 6-1.  The costs were  2.33 and 5.55  percent
for Steps 1 and 2,  respectively.   The information presented in Table  6-1  can
be  used to  estimate  the  nonconstruction costs  for a wastewater  treatment
facility by adding  the  total construction costs,  total  Step 3 nonconstruction
costs, as well as the Step 1  and Step 2 costs.


6.2  Cost Updating


The costs may be  updated to other  geographical  areas by using the  following
formul a:


                        Latest LCAT or SCCT Index
Total  Project Cost         for Desired Area	   = Updated Cost       (6-1)
from Figures 6-1    x  4th Quarter 19/8 LCAT or
through 6-3            SCCT Index for Desired Area


where

     LCAT  =  EPA large city advanced treatment index

     SCCT  =  EPA small city conventional  treatment  index

The  LCAT  and SCCT indexes  are  published  quarterly  by  the Environmental
Protection Agency.

The cost data  presented in Figures 6-1  through 6-3  do  not cover the  options
available to  upgrade pond effluents  to meet  secondary  or  advanced  secondary
levels.  Additional  data have  been collected  from  selected  projects  around
the country to provide individual  cost data for comparative purposes.

Cost and performance values  shown  in Table 6-2  represent the best  available
information for all  of  the processes  listed.   In several cases the  costs  are
based  on estimates  derived  from  pilot plant  studies  or engineering  esti-
mates.  Where  actual  bid prices are  available,  the  location  of the  facility
is  given.   All  costs are  site  specific  and can  be  expected  to vary  widely.
Costs are  reported as shown in  the literature, and  changes  in  value of  the
dollar are  not corrected for.   This was done to  allow  the reader  to  use  the
system  appropriate  for his/her area  to adjust  the  costs  to  a current  base.
Corrections were  made to all capital costs  to reflect  a  7 percent  interest
rate and a 20-year  life except for systems known to have shorter  operating
periods.  The exceptions are identified in Table 6-2.

The selection  of  the cost-effective alternative  must be made based  upon good
engineering judgment and local  economic conditions.  Cost variations in  one
                                     285

-------
                         TABLE 6-2

COMPARATIVE COSTS  AND PERFORMANCE OF VARIOUS UPGRADING
              ALTERNATIVES AND POND SYSTEMS

Process or System
and Location

Overland Flow0
EPA Estimate
EPA Estimate
Davis, CA
Surface Irrigation15
EPA Estimate
EPA Estimate
Spray Irrigation-Center Pivot1*
EPA Estimate
EPA Estimate
Spray Irrigation-Solid Set0
EPA Estimate
EPA Estimate
Rapid Infiltration
EPA Estimate
EPA Estimate
Intermittent Sand Filtration
Me tea If & Eddy Capital Cost
Est. and European OSM=
Huntlngton, UT
Kennedy, AL
Alley, GA
Mortarty, KM
White Bird, ID
Ht. Shasta, CA
Hlcroscreens
cMVIREX
Caroden, SC
Dissolved Air Flotation
Snider
Coaoulatlon-notatlon-
Sedlmentatlon-Fl itratlon
Los Angeles Co., CA




Rock Filters
Warden, HO

Delta. HO

California, MO
Luxemburg, MI
Veneta, OR
Design
Flow
Rate
m3/d

1,140
1,140
18,900

1,140
1,140

1,140
1,140

1,140
1.140
1,140
1,140


1,140
1,140 2,
318
303 5,
760 2,
114 3,
2,650 6,
6 440—8 520
' 7,200

3,030


1,890





303

303

1,360
1,510 0
830 0

Design
Loading


5 cm/wk
20 cm/wk
20 cm/wk

5 cm/wk
10 cm/wk

5 cm/wk
10 cm/wk

5 cm/wk
10 cm/wk
20 cm/wk
60 cm/wk


_
800 m3/ha/d
935 m3/ha/d
610 m3/ha/d
810 m3/ha/d
740 m3/ha/d
550 m3/ha/d
0 (


—


—





0.76 fl|3/
pop. eg.'
0.76 m3/
pop. eq.

.40 n3/m3/d
.27 m3/m3/d



Annual Costs'*
Capital


0.071
0.050
0.026

0.053
0.045

0.050
0.042

0.069
0.050
0.045
0.034


0.042
0.095
0.053
0.032
0.048
0.050
1?Q_n (T376
i£y— U.U-3/ w
0.038

0.037


0.034





0.011

0.013

0.011
O.OOSe
0.013
O&M
S/nr>

0.037
0.026
0.013

0.050
0.040

0.048
0.034

0.040
0.032
0.026
0.021


0.042

0.005
0.010

0.010

o!o27

0.016


0.079












Total


0.108
0.076
0.039

0.103
0.085

0.098
0.076

0.109
0.082
0.071
0.055


0.084

0.058
0.042

0.060

' 0.065

0.053d


0.113













Cost
Base


1973
1973
1976

1973
1973

1973
1973

1973
1973
1973
1973


1975
1975
1975
1975
1975
1978
1976
1 1 Q7O
J AJ/O
1979

1975


Cap
1970
O&M
1973
1974

1974

1974

1974
1975
1975


Referer


(2)
2)
(3)

(2)
(2)

(2)
(2)

(2)
(2)
(2)
(2)


(4)(5)
8$

(9)(1S
(10)
(18)

(24)

(12)


(13)





(14)

(14)

(15)
(16)
(17)
                                                              Effluent
                                                            Concentration
                                                              BOOc  SS
                                                             as
                                                             <30 <20
                                                             <30  <30
                           286

-------
                                               TABLE  6-2

                                               CONTINUED
Process or System
and Location

Intermittent Discharge-
Chemical Addition
Canadian Experience



Total Containment Ponds
Huntington, UT


Weilsville, UT
Tabiona, UT


Smithfield, UT


Southshore, UT
Facultative Ponds
Huntington, UT




Wardell, MO








Delta, MO

Unknown, ID
Long Valley, UT
Smithfield, UT
Challis, ID

Colfax, WA
Hampton-Princeton, ID
Tensed, 10
Aerated Ponds
Luxemburg, MI




Sugarbush, VA
Paw Paw, HI
Luxemburg-, Ml
White Bird, ID
Design
Flo*
Rate
m3/d


1,140




1,140


1,080
114


3,260


3

1,140




303








303

6,440
541
3,250
780

2,270
60
114

1,510




620
1,510
1,510
114
Design Annual Costs1
Loading Capital 04M Total
S/ra3


Alum: 0.011f 0.021 0.032
150 mg/1
Det. Time!:
120 days

0.0959


0.098
45 kg BOD5/0.372e
ha/d

45 kg BOD5/0.148e
ha/d

o.o?g

0.087




Primary Cell 0.077
38 leg 800s /
ha/d
2nd Cell
0.3 (Pri. cell
surface area)
3rd Cell
0.1 (Pri. cell
surface area)
Same as 0.108
Wardell
22/kg/ha/d 0.082
45 kg/ha/d 0.135e
45 kg/ha/d 0.1826
45 kg/ha/d 0.103e
in primary cell
0.0556
45 kg/ha/d 0.201e
67 kg/ha/d 0.122^

Det. time - 0.082s
35 days



1.127
0.069
36 kg BOOs/d 0.119 0.085 0.203
23 kg 80D5/d 0.370
Cost
Base



1976




1975


1974
1980


1979


1978

1975




1974








1974

1978
1979
1979
1978


1979
1978

1977




1974
1974
1978
1978
Effluent
Concentration
Reference 80Dr SS



(18)




(6)


(6)
(6)


(6)


" (19)

(6)




(14)








(W)

(19)
(6)
(6)
(10)

1977
(10)
(10)

(16)




(20)
(Anon.
(21)
(10)



<30 <10




No No
dis- dis-
charge charge

No No
dis- dis-
charge charge
No No
dis- dis-
charge charge


Varies Varies
with with
design design
& time & time
of yr of yr
















(10)



Varies Varies
with with
design design
& time & time
of yr of yr

)


aCosts amortized  at 7 percent and a 20-year life.
^Values can vary  by 50 percent and prices do not include land costs.
clncludes land costs with no credit for salvage value.
dExcludes sludge  disposal costs.
eEngineer's estimate.
fAmortized at 7 percent and a 10-year life.
9Bid  but not constructed.
                                                     287

-------
item,  such  as filter  sand or  land,  can change  the relative  position  of  a
process dramatically.  In brief, Figures 6-1  through  6-3  and  Table  6-2 cannot
6e substituted for good engineering.

All  of the processes  listed in Table  6-2  are capable  of meeting  secondary
standards,  and  several   are  capable   of  producing  a  much  higher quality
effluent.  Variations  in  design and operation also  alter the quality of  the
effluent  dramatically  in  most of  the  processes.   A  careful  study  of  all
alternatives  must  be  made   before  selecting  a   system.   The   literature
referenced  herein will  provide  all   details needed,  but  engineers should
remain  aware  of  current  developments  and  use other  alternatives  as  more
information becomes available.


6.3  Energy Requirements


Energy consumption is a major  factor in the  operation of  wastewater treatment
facilities.  Many of the  plans for water pollution  management in  the United
States were developed before the cost of energy and  the limitations of energy
resources became  serious  concerns  for  the   Nation.   As wastewater  treatment
facilities are built  or updated to incorporate  current treatment  technology
and  to  meet  regulatory   performance   standards,   energy  must  be  a   major
consideration   in  designing   and  planning  the  facilities.   Information  on
energy  requirements  for various systems must be made  available to  planners
and  designers in order  that  a  treatment   system  may  be  developed   which
incorporates the  most  efficient use of energy for each particular  wastewater
problem.


     6.3.1  Energy Equations


Equations of  the lines of  best  fit   for  the energy  requirements  of  pond
systems based on  the data  reported by Wesner  et  al.  (22) (25)  were used to
develop Table 6-3.  Details  about  the   conditions imposed  upon  the  equations
can be obtained from this  reference.


     6.3.2  Effluent Quality and Energy  Requirements


Table 6-3 shows the expected effluent quality and the energy  requirements  for
various  pond  systems.   Energy, requirements and  effluent  quality  are  not
directly  related.    Utilizing  facultative   ponds  and   land  application
techniques,  it is possible to obtain an excellent quality  effluent  and expend
small quantities  of  energy.
                                     288

-------
IN3
00
                                                        TABLE 6-3

               EXPECTED  EFFLUENT QUALITY  AND TOTAL ENERGY  REQUIREMENTS  FOR VARIOUS SIZES AND TYPES  OF
               WASTEWATER TREATMENT PONDS LOCATED IN THE INTERMOUNTAIN  AREA OF THE UNITED STATES  (23)
                                                             Total Energy Requirements at Various Flow Rates
Treatment Systems
Facultative Pond
+ Hicroscreens 23u
Facultative Pond
+ Intermittent
Sand Filter
Aerated Pond +
Intermittent
Sand Filter
Overland Flow-Facul-
tative Pond
Flooding
Rapid Infiltration-
Facultative Pond
Flooding
Slow Rate (Irri-
gation )-Fac.
Pond-Ridge and
Furrow Flooding
Effluent
BOD5
30
15
15
5
5
1
SS
30
15
15
5
1
1
Quality, mg/1
Total Total
Phos. Nttro-
as P gen as N
15
10
20
5 3
2 10
0.1 3
0.05 mgd
Elec-
tricity,
kHh/yr
11,300
5,840
20,800
5,700
1,540
2,800
Fuel,
Million
Btu/yr
148
150
151
148
148
149
0.1
Elec-
tricity,
kWh/yr
Z0.300
10,920
39,500
10,700
2,810
5,300
mgd
Fuel,
Million
Btu/yr
181
186
186
181
181
183
0.5
Elec-
tricity,
kHh/yr
83,100
50,540
184,800
50,070
12,140
24,700
mgd
Fuel,
Million
Btu/yr
320
345
345
320
320
330
1.
Elec-
tricity,
kHh/yr
154,600
99,270
364,500
98,810
23,050
48,050
0 mgd
Fuel,
Million
Btu/yr
433
483
483 1
433
433
• 453
3.0 mqd

Elec- Fuel,
tricity, Million
kWh/yr Btu/yr
419,800 745
291,800
,079,100
392,600
64,300
139,100
896
896 1
745
745
805
5.0
Elec-
tricity,
kWh/yr
670,900
482,200
,790,900
485,080
103,900
228,400
mgd
Fuel,
Million
Btu/yr
988
1,240
1,240
988
988
1,090

-------
 6.4   References


  1.   Construction  Costs  for Municipal  Wastewater Treatment Plants:  1973-1978,
      EPA-430/9-80-003,  NTIS  No.  PB  118697,  U.S.  Environmental  Protection
      Agency, Facility Requirements Division, Washington, DC, 1980.

  2.   Environmental  Protection  Agency.   Cost of  Wastewater Treatment  by  Land
      Application,  EPA-430/9-75-003,  NTIS  No.  PB  257439,   U.S.  Environmental
      Protection Agency,  Office of Water  Program Operations,  Washington,  DC,
      1975.

  3.   Brown and Caldwell.  Draft  Project Report,  City of Davis  - Algae Removal
      Facilities.  Walnut Creek, CA, November 1976.

  4.   Metcalf  & Eddy,  Inc.   Draft  Report to  National Commission  on  Water
      Quality  on Assessment of  Technologies  and  Costs  for  Publicly  Owned
      Treatment Works Under Public Law 92-500.   April 1975.

  5.   Huisman,  L.,   and   W.   E.  Wood.   Slow Sand  Filtration.   World  Health
      Organization, Geneva, Switzerland, 1974.

  6.   Valley Engineering.   Personal  communication.  Logan,  UT,  December  1976
      and 1980.

  7.   Gilbreath,    Foster    &    Brooks,     Inc.     Personal    communication.
      Tuscaloosa, AL, November 29, 1976.

  8.  McCrary Engineering  Corporation.   Personal  communication.  Atlanta,  GA,
      November 29,  1976.

  9.  Molzen-Corbin  &  Associates.  Personal  communication.  Albuquerque,  NM,
     1976.

10.   Hamilton  and  Voeller,   Inc.    Personal   communication.   Moscow,   ID,
     December 1978.

11.  Kormanik, R. A., and J. B.  Cravens.   Microscreening  and  Other  Physical -
     Chemical  Techniques  for Algae  Removal.   In:  Performance  and  Upgrading
     of  Wastewater Stabilization  Ponds,   EPA-"STTO/9-79-011,  NTIS  PB  297504,
      U.S.  Environmental  Protection  Agency,  Municipal   Environmental  Research
     Laboratory, Cincinnati, OH,  1979.

12.  Snider, E.  F., Jr.  Algae  Removal  by Air  Flotation.  In:  Ponds  as  a
     Wastewater Treatment  Alternative.   Water  Resources  Symposium  No.   9,
     University of Texas, Austin, TX, 1976.

13.  Parker, D.  S. Performance  of  Alternative  Algae  Removal  Systems.    In;
     Ponds as a Wastewater  Treatment Alternative.  Water  Resources  Symposium
     No. 9, University of Texas,  Austin, TX,  1976.
                                      290

-------
14.  Gaines,  6.  F.  Personal  communication.   C.   R.  Troter  and  Associates,
     Dexter, MO,  1977.

15.  Kays,  F.  Personal  communication.  Lane-Riddle  Associates,  Kansas  City,
     MO, 1977.  '

16.  Miller,  D.  L.  Personal  communication.   Robert  E.  Lee  and  Associates,
     Inc., Green  Bay, WI, 1977.

17.  Williamson,  K. J., and G.  R.  Swanson.   Field Evaluation of Rock  Filters
     for  Removal   of  Algae  from  Lagoon  Effluent.    In;    Performance and
     Upgrading of  Wastewater  Stabilization  Ponds, EPA-600/9-79-011, NTIS No.
     PB 297504, U.S. Environmental Protection Agency, Municipal  Environmental
     Research Laboratory, Cincinnati, OH,  1979.

18.  Middlebrooks, E. J., C.  H.  Middlebrooks,  J.  H.  Reynolds, G.  Z. Watters,
     S. C.  Reed,  and D. B. George.   Wastewater Stabilization Lagoon  Design,
     Performance,  and  Upgrading.   Macmillan Publishing Co.,  Inc., New  York,
     NY, 1982.

19.  Nielson, Maxwell & Wangsgard.   Personal  communication.   Salt Lake  City,
     UT, February  1981.

20.  Jupka,  J.   Personal   communication.    Lane-Riddle   Associates,  Kansas
     City, MO, 1977. •

21.  Robert  E.  Lee  &  Associates.    Personal  communication.   Green  Bay, WI,
     November 1980.

22.  Wesner,  G.  M., L.  J.  Ewing,  Jr.,  T.  S.  Lineck,  and   D.  J.  Hinricks.
     Energy   Conservation   in   Municipal   Wastewater   Treatment.    MCD-32.
     EPA-430/9-77-011,  NTIS PB  276989,  U.S.  Environmental  Protection  Agency,
     Office of Water Program Operations, Washington,  DC,  1978.

23.  Middlebrooks,  E.  J.,  and  C.  H,, Middlebrooks.   Energy  Requirements for
     Small Flow Wastewater Treatment Systems,  Special  Report 79-7.  Corps of
     Engineers, Cold Regions  Research  and Engineering  Laboratory, Hanover,
     NH/1979.

24.  Harrelson, M.  E., and J.  B.  Cravens.   Use  of Microscreens  to Polish
     Lagoon Effluent.  JWPCF 54(1):36, 1982.

25.  Middlebrooks,  E.   J.,  C.  H.   Middlebrooks,  and  S.  C.  Reed.   Energy
     Requirements     for   Small    Wastewater    Treatment   Systems.     JWPCF
     53(7):1172-1197, 1981.
                                     291

-------
                                  APPENDIX

                         EVALUATION  OF  DESIGN METHODS


A.I  Facultative Ponds


     A.1.1  Introduction


A  summary of  the  facultative  pond  performance data  used  to evaluate  the
various design methods  is  presented in Table A-l.  These  data were collected
for  the  four  facultative  pond  systems  described  in  Chapter  2.   "Only  the
characteristics of  the  influent  wastewater and  the effluent  from  the primary
(first) cell of the systems are presented in Table A-l for the four systems.

Most of  the kinetic analyses of  the systems are  limited to  the  performance
obtained  in the  primary  cell  because  BODs  and  COD  of the  primary  cell
effluent  appear  to represent performance  of the  systems far more  than  the
following  cells.   Algae  succession,  changes  in nutrient concentration,  and
the buffering capacity  of  the total system appear to exert more influence on
the cells  following the primary cell.  The  commonly  used design methods  are
discussed  individually  in the following sections.

Theoretically, most of  the models  evaluated  should have  a  line of  best  fit
that has  an  intercept of  zero or  unity,  but an analysis of  the  data infre-
quently yields such an  ideal relationship.  Therefore,  all of the  attempts to
fit the data to a  model were  evaluated with the least  squares technique with
an  intercept  and  with  the  line  of best  fit forced  through   an intercept of
zero.  The equations describing the lines of best fit  for  both cases are pre-
sented on  each figure  along with the  corresponding correlation coefficients.
In  general,  if  both  correlation  coefficients are  significant  (5  percent
level)  and approximately  equal,  it  can  be  assumed  that the intercept  is
approximately zero, and the data describe the model  to an acceptable degree.


     A.1.2  Empirical Design Equations


In a survey of the  first cell of facultative ponds in  tropical  and  temperate
zones,  McGarry  and Pescod  (1)  found  that  area! BODs  removal  (Lr,  Ib/ac/d)
may  be  estimated   through  knowledge  of  area! BODs   loading  (L0,  Ib/ac/d)
using

            Lr = 9.23 + 0.725 LQ                                          (A-l)
                                      292

-------
                       TABLE A-l



MEAN MONTHLY PERFORMANCE DATA FOR FOUR FACULTATIVE PONDS
MONTH
Jan
Feb
Mar
Apr
Hay
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Oan
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
INF
BOD
rag/1
122
107
58
49
62
52
40
40
92
87
85
99
140
332
258
303
400
326
303
373
284
209
179
270
298 ,
197
170
144
123
131
128
101
157
133
113
123
137
200
172
106
135
107
187
140
278
278
321
301
247
200
CELL
#1
BOD
31
38
57
33
33
30
29
36
35
34
30
21
21
41
49
41
53
56
35
49
44
57
42
55
69
43
46
48
65
70
68
50
36
38
37
30
25
23
24
21
20
27
16
17
26
25
31
15
17
14
INF
SOL
BOD
40
28
19
16
15
17
9
11
25
22
24
32
50
125
116
184
182
169
123
181
129
95
78
140
178
70
49
49
40
37
43
33
73
56
49
56
50
57
52
36
50
39
55
37
80
96
96
74
75
79
CELL
#1
SBOD
5
5
10
6
5
6
5
5
5
4
5
6
9
11
13
11
22
18
10
14
15
13
11
19
15
n
10
22
51
53
46
36
31
21
22
12
9
. 5
4
3
3
3
3
5
5
6
7
3
4
3
INF
COD
mg/1
173
140
135
114
105
78
75
81
141
178
132
189
192
633
552
576
614
573
631
635
580
375
458
533
544
334
303
245
204
201
263
181
425
249
223
315
313
254
333
204
232
225
470
312
628
626
746
572
535
458
CELL
#1
COD
118
125
126
113
117
95
131
162
168
146
114-
89
68
183
226
156
,163
174
180
186
172
284
204
265
246
203
207
155
158
154
151
128
110
174
213
230
161
138
123
120
128
164
103
90
89
121
140
52
108
102
INF
SOL
COD
81
64
47
46
40
37
35
38
54
SO
58
64
88
277
225
265
260
224
234
236
173
117
128
201
224
136
102
101
94
73
94
78
250
116
114
142
125
114
101
81
81
• 78
108
81
154
192
235
168
164
191
CELL
#1
SCOD
47
48
39
37
38
45
45
44
38
39
42
46
54
83
107
63
71
74
76
60
71
76
52
83
91
128
82
84
106
100
93
79
77
101
126
98
88
68
52
42
35
30
38
49
50
71
94
60
73
67
DET
TIME
DAYS
44.43
22.72
19.56
23.23
28.47
27.29
20.73
18.97
21.07
17.64
37.14
63.66
55.76
83.82
87.86
89.00
101.34
102.99
66.08
70.36
80.47
95.46
101.12
116.83
109.41
48.61
50.89
50.78
48.29
45.74
37.90
35.87
42.09
44.61
43.06
43.21
41.30
189.80
189.80
189.80
182.50
54.31
115.98
82.38
185.37
191.48
456.34
171.11
111.93
165.37
TEMP
°C
2
1
5
9
12
18
22
19
16
9
4
2
2
22
17
10
4
4
3
7
14
21
24
26
25
9
6
4
5
3
4
7
17
21
24
22
17
14
9
10
11
12
18
23
27
29
29
20
20
18
LIGHT
LAN
190
265
385
495
590
630
640
550
430
335
210
145
190
430
285
230
180
190
280
345
440
530
560
580
435
240
165
115
130
230
280
400
450
525
500
450
340
260
200
205
270
340
450
550
530
450
470
370
340
250
TSS
mg/1
52
61
55
69
74
56
65
87
95
85
66
27
18
89
124
79
71
84
74
112
85
130
121
172
137
70
74
44
27
26
21
23
37
47
63
76
49
57
82
86
74
107
65
47
52
43
55
46
33
28
VSS
mg/1
45
54
52
59
61
43
53
76
81
71
57
25
15
76
95
68
65
78
70
97
72
102
109
151
120
...
--
--
--
--
_-
_ —
—
..
—
--
— •
~
—
—
—
..
-•-
—
--

..
—
..
—
LOCATION
Corinne, UT
n
n
n
n
n
n
n
Eudora, KS
n
n
n
n
11
n
n
n
n
n
n
n
: n
n
n
"
Peterborough, NH
it
n
"
it
n
11
n
n
n
n
n
Kllmichael, MS
II
11
II
11
11 -
II
II
II
II
II
II
II
                           293

-------
The regression equation had a  correlation  coefficient of 0.995 and a  95  per-
cent  confidence  interval  of  + 33 kg/ha/d  (29  Ib  BODs/ac/d) removal  (Figure
A-l).  The  equation  was  reported to be valid for  any loading between 34  and
560 kg  BOD5/ha/d  (30  and 500 Ib  BOD5/ac/d).   McGarry  and  Pescod  (1)  also
found that,  under normal  operating ranges, hydraulic detention time and  pond
depth have  little influence  on percentage  or  area!  6005 removal.  With  such
a large 95  percent confidence  interval,  it is   impractical to  apply the  equa-
tion  to pond  systems loaded  at  rates  of  34 kg/ha/d  (30  Ib  BODs/ac/d)  or
less  as was the situation with  the majority of the  months  of operation  for
the four facultative pond systems described previously.

Relationships between organic  removal  and  organic  loading  for the lower  rates
observed  at the  four facultative  pond  systems  were  developed  using  BOD5,
soluble  biochemical   oxygen  demand  ($6005), chemical   oxygen  demand  (COD),
and soluble chemical oxygen demand  (SCOD).  Statistically  significant  rela-
tionships were observed  for  all four organic carbon  estimating analyses,  but
the best relationships were  observed when the  organic removals were  calcula-
ted   using   the   influent  6005   and   the  effluent   SBOD5   (ITBODs   and
ESBODs) and the  influent COD  and  the effluent SCOD  (ITCOD  and  ESCOD).   The
BODs  and  SBODs relationship  is shown in  Figure A-2,  and  the  COD and  SCOD
relationship is shown in  Figure A-3.   The  95 percent  confidence  intervals  for
the  BOD5-SBOD5 and  the  COD-SCOD relationships  are  much  smaller  than  the
value reported by McGarry and Pescod (1)  and are shown in Figures  A-2  and Ai-3.

Larsen  (2)  proposed  an  empirical design  equation,   developed  by using  data
from  a  one-year  study   at  the  Inhalation  Toxicology  Research  Institute,
Kirtland Air Force   Base,  NM.   The  Institute's  facultative  pond system  con-
sists of one 0.66 ha (1.62 ac) cell  receiving  waste  from 151 staff members,
1,300 beagle dogs, and several  thousand small animals.   Larsen found that  the
required  pond  surface   area   could  be  estimated  by use  of  the  following
equation.


       MOT  « (2.468RED + 2.468TTC + 23.9/TEMPR  + 150.0/DRY)*106          (A-2)

where the dimensionless products are:

                         2                          2    1/3
  MOT = (surface area, ft ) (solar radiation, Btu/ft  /d)     x n  0783  x  107)
        (influent flow rate, gal/d) (influent BODg, mg/l)1/3



             (influent BODC, mg/1) - (effluent  BOD,-,  mg/1)
       npn	0	O	
                        (influent BOD, mg/1)


        (windspeed,  miles/hr)  (influent BODC, mg/1)
  TTC =  	   5  *	  x 0.0879
                (solar radiation, Btu/ft^/d)1'1*
                                      294

-------
                              FIGURE A-l

ICGARRY AND PESCOD EQUATION FOR AREAL  BOD5 REMOVAL AS A  FUNCTION
                           OF BOD5  LOADING
        100
      0}
      DC

      Q
      O
          30     40      50     60      70     80      90     100

                       First Cell Areal BOD Loading (L0), Ib/ac/d
                                 295

-------
                                                           FIGURE A-2
ro
to
en

             70
             60
             50
           10
           Q
           O
             40
ui
           Q
           O
           CO
           t 30
           •O
           0
           §

           0)
           Q
           O
           CO
              20
              10
               0
                0
                                             RELATIONSHIP BETWEEN BOD5 LOADING AND
                                                REMOVAL RATES - FACULTATIVE  PONDS
                         Y = 0.940 X-1.04
                         r = 0.965
                 10
20          30          40

       BOD Applied (ITBOD5), Ib/ac/d
50
60
70

-------
                                                          .FIGURE  A-3


                                             RELATIONSHIP BETWEEN COD LOADING AND
                                               REMOVAL RATES - FACULTATIVE  PONDS
            110 r-
10
             90
          1
          CO
Q
O  70

CO
LU


O
O
O



I  50-

o
E

-------
     TEMPR =  (Pond liquid temperature,  °F)
                  (air temperature,  °F)

       DRY = relative humidity, percent

To determine the  effect  of  using  the Larsen equation on multicell facultative
ponds, it was applied to both  the  entire  system  and  the primary cell  for each
of the four  locations.   In each  case the Larsen  equation  underestimated the
pond  surface  area  required  for  a  particular  BODs  removal.   Prediction
errors for multiple  cell ponds  ranged from  190 to 248  percent.   Prediction
errors for the primary cell  surface areas ranged from  18 to  98 percent.  Use
of the Larsen equation is not recommended.

Gloyna (3) proposed the  following  empirical  equation for  the  design of facul-
tative wastewater stabilization ponds:
            V = 3.5 x 10~J QLa  ev°J~"  ff                             (A-3)
                               >—•      —/
where

     V  = pond volume (m^)

     Q  = influent flow rate (liters/day)

     La = ultimate influent BODU or COD (mg/1)

     e  = temperature coefficient

     T  = pond temperature (°C)

     f  = algal toxicity factor

     f' = sulfide oxygen demand factor

The 6005  removal  efficiency can be expected  to  be 80 to 90  percent  based on
unfiltered  influent  samples  and filtered  effluent samples.  A  pond  depth of
1.5 m is  suggested  for systems  with  significant  seasonal  variations  in  tem-
perature and major fluctuations  in  daily  flow.   Surface  area design using the
Gloyna equation should  always  be based on a  1-m  depth.   The additional  0.5 m
of  depth  is provided  to  store  sludge.   According to Gloyna (3), the  algal
toxicity factor (f) can be assumed  to  be  equal to 1.0 for domestic wastes and
many industrial wastes.  The sulfide  oxygen  demand (f)   is  also  equal  to 1.0
for S04=  ion  concentration  of less than  500 mg/1.  Gloyna  (3)  also  suggests
using the average  temperature  of the  pond  in the critical  or  coldest  month.
In  this  equation,  sunlight is not  considered to  be  critical in  pond  design
but may  be  incorporated  into the  Gloyna  equation  by  multiplying the  pond
volume by the  ratio  of sunlight in the  particular area  to  the  average  found
in the Southwest.
                                       298

-------
The  data used  to  evaluate the  Gloyna  equation  are  shown  in  Table  A-l.
Although ultimate  BOD data were  not available,  COD, SCOD,  BODs, and  SBODs
data were used.  Use of the Gloyna equation with  the  data  in  Table A-l failed
to produce  any  good relationships.   The relationships obtained with  the COD,
SCOD,  BODs, and  SBODs  data  were  statistically  significant,  but  the  data
points were scattered.  The relationship shown in Figure A-4 was  the  best fit
bbtained for the data, and the resulting design equation follows:

                                        LIGHT (35-T)

         V/Q = 0.035 (BOD5, mg/1) (1.099)   25°                          (A-4)
           t = detention time, days

         V/Q = t
where

           T = temperature, °C
       LIGHT = solar radiation,  langleys/day

           V = volume of primary pond, m
           Q = flow rate, m /d           *


The validity of the above  expression  is  questionable  because  of  the scattered
data,  but  the  relationship is  statistically  significant.  The  use  of  this
Relationship will be left to the discretion of the design engineer.

Although not directly comparable, the results  obtained with  this  equation and
fesults  obtained with  the relationship  shown  in  Figure A-2  are  presented
feelow to show the variation between the two approaches.

Assuming  a  design  flow  rate  of  3,785  m^/d   (1 mgd),  a  solar  radiation
ihtensity of  250 langleys, an  influent  BODs  concentration  of 300 mg/1,  and
4  temperature  of  10 C,  Equation  A-4 yields  a  surface area of 420,918  m2
(assuming a water  depth of 1m),  and the  organic  loading rate  relationship
(Figure A-2) yields a loading rate of 27 kg/ha/d (24  Ib/ac/d).   At this rate,
Organic  removal  will  be 24.1  kg/ha/d (21.5  lb/ac/d)  (Figure  A-2) or  an 89.7
percent  reduction  in  BODs. The percent reduction  is within  the  range  of 80
to 90  percent expected with a design using the  Gloyna equation.   The results
cfbtained with  Equation  A-4 appear to be conservative when compared  with the
6rganic  loading-removal  relationship  (Figure A-2) principally because of the
temperature correction  factor  in  Equation  A-4.   Although it  is  logical  to
expect  temperature  to exert an  influence on BODs removal, the plot  shown in
Figure  A-2  was  unaffected when temperature relationships were  incorporated
into  the relationship.   The most  logical  explanation for this  phenomenon is
that the systems are so  large that the temperature  influence  is  masked in the
process.  This observation is also pursued in the following section.
                                     299

-------
                                                            FIGURE A-4


                                     RELATIONSHIP OBTAINED  WITH MODIFIED  6LOYNA EQUATION

                                                FACULTATIVE PONDS (EQUATION A-4)
o
o
          I  4
            "
          in
          cs
Q
O
m

in
CO
           0)


          I  2

           c
           o
           •4-*

           §
           •!-•
           ID
          O
                                                                         n
                     Y = 0.0947 X (zero forced fit)

                     r = 0.913
D



a
                                          D
                                  a
                                                                                       a
                                                     a
                                                              a
                                                                        a

                                                                        a
              0
                                                           I
                             10
                                  15
                                        20

                                       35-T
25
30 ..
35

-------
     A.1.3  Rational Design Equations

Kinetic models based on plug flow and  complete  mix  hydraulics  and first order
reaction rates have been proposed by many  authors to describe  the performance
of wastewater  stabilization  ponds.   The basic models are  modified to reflect
the influence of temperature.  The basic models are:
Plug Flow;

     ^ = e  p                                                           (A-5)

or:  In Ce/CQ = -kpt                                                     (A-6)

Complete Mix;

                                                                         (A-7)
or:     f ~ - 1 )   = krt                                                (A-a)
          'e
where
     C0 = influent BQDs concentration, mg/1
     Ce = effluent BQDs concentration, mg/1
     k« B plug flow first order reaction rate constant, time"!
     t  = hydraulic Residence time, days
     e  = base of natural logarithms, 2.7183
     kc = complete mix first order reaction rate constant, time"-'-

The  influence of temperature on  the  reaction  rate constants is most frequent-
ly expressed by using the Arrhenius (4) relationship:
                RT
                                      301

-------
where
     k  s reaction rate constant
     Ea = activation energy, calories/mole
     R  = ideal gas constant, 1.98 calories/mole-degree
     T  « reaction temperature, -Kelvin
Integrating Equation A-9 yields the following expression:

     In k = - ^ + In B
where B is a constant.
(A-10)
Experimental  data can  be plotted  as shown  in Figure  A-5 to  determine the
value of  Ea.   Equation  A-9  can be  integrated between  the limits of  TI and
1*2 to obtain Equation A-ll.
                                 FIGURE  A-5
                ARRHENIUS PLOT TO DETERMINE ACTIVATION ENERGY
                             Slope = -E,/R
                                     1/T
                                      302

-------
                                                                        (A-ll)


In  most  biological  wastewater  treatment  processes,   it  is  assumed  that
         is a constant, C, and Equation A-ll reduces to
                                                                      ,  (A-14)


where e  = temperature  factor.   Plotting experimental  values  of the  natural
logarithms  of  l<2/ki  versus   (T2~T]J  as  shown  in  Figure  A-6,   the  value
of e can be determined.

The plug flow and  complete  mix models,  along with modifications suggested  by
various investigators, were evaluated using the data shown in Table  A-l.

The influence of temperature  on the calculated reaction  rates was  evaluated.
As shown in Figures A-7 and A-8,  the reaction rates calculated with  the  plug
flow and complete  mix equations were essentially independent of the  tempera-
ture.   This lack of  influence  by  the liquid temperature was also observed  in
the section on empirical design equations  (Figures A-2  and  A-3).  The logical
explanation for the lack of influence by temperature is that the pond systems
are so large  that  the temperature effect  is  masked  by other factors.   There
is  no  doubt  that  temperature  influences  biological  activity,  but  for the
systems  listed  in  Table  A-l,  the  influence  was  overshadowed  by  other
parameters that  may  include  dispersion,  detention  time,  light,  species  of
organisms, etc.

After observing the  lack  of influence by the  water  temperature,  the  data  in
Table A-l  were  fitted to the  plug  flow (Equation A-5)  and the complete mix
(Equation A-7) models  to  determine  if the systems could  be defined  by  these
simple relationships.  As shown in  Figures A-9 through A-12,  the  fit of the
data is  less  than  ideal  but  is  statistically  highly  significant   (1  percent
level).   Further  attempts to  incorporate  various  types of  temperature and
light intensity relationships into the plug flow and complete mix models  were
not successful.  The best  statistical  relationships obtained with the  data
are shown in Figures A-9 thorugh A-12.

Thirumurthi (5) stated  that a  kinetic model  based on  plug flow or  complete
mix hydraulics  should not be  used  for  the  rational  design of  stabilization

                                     3d3

-------
ponds.  Thirumurthi  found that facultative  ponds  exhibit nonideal  flow pat-
terns  and recommended  the  use  of  the following  chemical   reactor  equation
developed by Wehner and Wilhelm (6) for pond design:
                                                                        (A-15)
Co " (1+a)2 ea'2D - (1-a)
                                  2
where

     Ce s effluent BODs, mg/1

     C0 = influent BODs, mg/1

     a  =\/l + 4ktD
     k  = first order BODs removal coefficient, day1
                                  FIGURE A-6

              PLOT  OF  REACTION  RATE  CONSTANTS AND TEMPERATURE  TO
                       DETERMINE THE TEMPERATURE FACTOR
              c
              —I
                                         Slope = l_n 6
                                     T2-T,
                                      304

-------
                                                                     FIGURE  A-7

                                                    RELATIONSHIP BETWEEN PLUG FLOW  DECAY RATE
                                                       AND TEMPERATURE - FACULTATIVE  PONDS
CO
o
en
              -T3
                C
OC
                   2.0
                   1.5
                   1.0
                   0.5
      0.0
             Q~ -0.5
             J> Q
             Q
             IT'S


             |t -1-0




                  -1.5




                  -2.0
                  -2.5
                  Y = -0.0388 X (zero forced fit)
                  r = 0.659
                    Y =-0.0197 X-0.335
                    r = 0.263
                                D
                                                                       D
                                                             I
                     -5.0
                     0.0
5.0
10.0         15.0

     T2-T,
20.0
                                                                                      25.0
                                                                                                                30.0

-------
                                                                 FIGURE  A-8


                                              RELATIONSHIP  BETWEEN COMPLETE MIX DECAY RATE
                                                   AND  TEMPERATURE - FACULTATIVE  PONDS
CO
o
CTi
                2.0 i-
                 1.5  -
                 1.0

-------
                                                              yFIGURE A-9


                                                   PLUG FLOW MODEL  -  FACULTATIVE PONDS
CO
o
                                                                           Y = -0.0158 X (zero forced fit)
                                                                           r = 0.926

                                                                           Y = -0.0096 X - .0.722
                                                                           r = 0.746
                -3.0
                    0
                                                                                                         n
20
60
80      100      120

 Detention Time, days
140
160
180
200

-------
                                                                FIGURE A-10

                                                   PLUG FLOW  MODEL - FACULTATIVE  PONDS
CO
o
00
                0.0 K
                -0.5 -
                                                                            Y = -0.0279 X (zero forced fit)
                                                                            r = 0.904
                                                                            Y = -0.0113 X- 1.92
                                                                            r = 0.689
                -5.0
                    0       20       40       60       80       100      120
                                                        Detention Time, days
140      160
180     200

-------
                                                               FIGURE A-ll

                                                 COMPLETE MIX  MODEL - FACULTATIVE'PONDS
co
o
                100
                 90
                 80
                 70
1 60
 in
Q
O
CO
tu  50
 in
Q
O
EB  40
                30
                 20
                 10
                 0
              Y = 0.281 X (zero forced fit)
              r = 0.896
              Y = 0.269 X+ 1.35
              r = 0.738
                                                                        I
                   0       20       40       60      80       100      120
                                                       Detention Time, days
                                                                  140
160
                                                                                     I
                   I
180     200

-------
CO
I—»
o
                 20




                 18




                 16




                 14
JL 12
 in
o
o
CD

ID 10

 tn
Q
O

£  8
                  o
                                                                 FIGURE  A-12


                                                  COMPLETE MIX MODEL - FACULTATIVE PONDS
                Y = 0.0554 X (zero forced fit)

                r = 0.889



                Y = 0.0514 X + 0.462

                r = 0.714
                                                                                             D
Q
                                                                 n.
                                                                 n  a
                                                                                           I
                                                                                      I
                    0       20       40       60      80      100      120

                                                       Detention Time, days
                                                                  140
160      180
                                    200

-------
     t = mean detention time, days
     D = dimensionless dispersion number
     D-!L
         vL
Ht
7
where
     H * axial dispersion coefficient, area/time
     v « fluid velocity, length/time
     L = length of travel path of typical particle, length
Thirumurthi (5) prepared the  chart  shown  in Figure A-13 to facilitate the use
of Equation A-15.  The  dimensionless term  "kt"  is plotted versus the percent
BOD-5 remaining  for dispersion  numbers varying  from zero  for an  ideal plug
flow unit  to  infinity for  a  complete mix  unit.   Dispersion numbers measured
in stabilization ponds range  from 0.1 to 2.0 with  most  values  less than  1.0.

                                 FIGURE A-13
                      WEHNER  AND WILHELM EQUATION  CHART
                           4    6   8  10      20
                             BOD Remaining, percent
                                         50
                                      311

-------
The data  in  Table  A-l  were used to calculate values of  k  for three different
dispersion numbers  (0.1,  0.25,  and 1.0) by  an  iterative process.   The values
of k were normalized and plotted versus temperature as  illustrated in Figure
A-14.  Less  than 12  percent of  the  regression was explained by a linear rela-
tionship  indicating that temperature exerts  little  influence on  the  perfor-
mance of  the ponds.

Values of k  calculated using the influent  total  BODs  and  the  effluent solu-
ble BODc  concentrations with a dispersion number of  0.25 ranged  from 0.011
to 0.282/d with  a  mean vajue of  0.073/d  and a  median  value  ofo0.055/d.   The
mean temperature was 13.5°C and  the  median temperature was  12°C.   Using  the
design  data  presented with  the  Gloyna  equation  (Q   =  3.785  nr/d,  BODs  =
300 mg/1, and T =  10°C),  a k  of 0.055/d adjusted  linearly for  temperature to
yield a value of 0.046/d  (10°C/12°C x 0.055 = 0.046),  a dispersion number of
0.25,  and,  assuming   90   percent   removal   of  the   BOD5  (TBOD5-SBOD5),  a
detention time of  74 days  is  obtained.   This detention  time  is  less  than  the
value of  100 days  obtained with the Gloyna equation (Equation A-4),  but  con-
sidering  the differences in approach, agreement is reasonable.


A. 2  Aerated Ponds


     A. 2.1   Introduction

A summary of the  partial  mix aerated pond  performance data  used  to  evaluate
the various  design  methods is  presented in  Table A-2.  These data were  col-
lected at the five  aerated pond systems  described  in  Chapter  2.  Only  the
characteristics of  the influent wastewater and the effluent  from  the  primary
(first) cell of the  systems are presented in Table A-2.

Most of  the  kinetic analyses of  the systems are limited to the  performance
obtained  in  the  primary  cells because  BODs  and  COD  of the  primary  cell
effluent  appear  to  represent performance  of the systems  far  more than  the
following  cells.    Species  succession,  nutrient  concentrations,  and   the
buffering capacity  of  the  systems  appear to have  more of  an  effect  on  the
cells following the  primary cell.  The  more commonly  used  design  methods  for
aerating  ponds are discussed individually in the following paragraphs.


     A. 2. 2  Design Equations


The most  commonly  used aerated  pond design  equation is  presented  in  the  Ten
State Standards (7).
             2.3 k  (100-E)
                                      312

-------
                            TABLE A-2



MEAN MONTHLY PERFORMANCE DATA FOR FIVE PARTIAL MIX AERATED PONDS
MONTH
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Pec
Jan
Feb
Mar
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Dec
Jan
Feb
Mar
Apr
May
Jin
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
INF
BOD
mg/1
368
422
414
392
379
413
355
313
330
388
364
283
277
468
470
452
602
578
799
548
554
395
296
233
177
203
152
220
185
155
202
182
145
172
173
106
89
96
75
37
55
71
86
93
118
113
102
87
178
214
199,
192
178
175
171
134
151
170
171
206
CELL
#1
BOD
68
150
60
98
81
87
58
64
87
106
117
61
13
33
20
16
20
28
9
9
9
10
18
14
19
43
30
68
38
46
66
69
64
48
39
45
11
12
10
14
12
18
14
23
25
34
' 25
17
49
63
68
76
67
58
66
53
56
62
82
73
INF
SOL
BOD
222
244
227
127
136
122
140
105
142
136
147
119
58
75
89
'130
136
143
127
129
126
97
83
39
74
76
61
110
81
58
108
103
91
82
69
66
34
46
41
29
. 31
26
37
34
18
21
18
38
94
88
86
117
79
76
71
55
68
74
74
119
CELL
. #1
SBOD
55
87
40
23
9
13
14
9
5
8
7
9
7
17
10
10
11
10
5
5
4
5
- 1)
' 7
15
42
25
65
34
21
58
46
44
37
14
34
— •
'
—
—
—
—
—
—
—
—
—
—
32
41
46
35
36
31
37
30
36
38
41
42
INF
COD
mg/1
664
524
671
610
552
606
594
589
646
773
774
619
440
753
1147
1208
1921
1208
1572
1156
1115
779
649
367
267
376
211
192
206
270
435
431
356
749
1062
537
209
229
244
116
127
160
186
229
299
194
200
168
510
457
454
369
431
291
359
203
201
230
221
324
CELL
#1
COD
152
186
192
212
202
175
138
180
285
268
254
178
86
131
113
82
143
132
74
77
78
68
75
89
37
48
57
52
56
95
207
190
137
109
131
146
34
52
45
52
48
54
56
74
44
48
36
32
105
96
105
98
105
120
101
80
86
82
101
108
INF
SOL
COD
321
368
319
215
240
267
254
223
259
278
249
224
83
146
231
252
361
298
290
294
246
213
170
53
58
97
74
64
75
135
211
190
210
199
242
191
'34
46
41
29
31
26
37
34
18
21
18
38
144
120
115
138
112
102
92
69
86
89
86
151
CELL
#1
SCOD
68
133
101
79
61
104
54
62
68
57
71 ,
67
61
89
63
60
99
68
62
58
70
60
•59
61
33
36
47
35
38
16
97
101
77
65
52
52
22
44
37
30
28
24
29
36
25
26
21
27
60
56
55
52
55
56
46
46
51
49
57
69
DET
TIME
DAYS
66.59
68.26
60.26
45.87
52.49
66.94
59.92
33.32
52.89
59.58
55.28
49.85
85.15
77.53
82.36
86.40
83.69
88.44
86.61
96.76
87.09
115.11
76.36
66.57
29.73
29.53
14.81
14.47
15.71
14.'52
20.00
22.92
16.24
15.71
16.48
15.94
26.15
28.91
25.74
18.82
20.30
22.41
22.65
22.86
22.77
23.40
24.23
48.95
7.06
6.04
8.22
8.21
7.64
7.03
6.73
5.75
5.84
7.19
9.30
7.84
TEMP
°C
5
10
16
19
20
26
29
28
24
13
9
7
5
12
19
23
26
19
11
5
3
3
8
6
19
14
12
12
13
14
20
26
25
24
22
17
' 4
-1
1
4
11
12
21
23
22
16
12
7
12
14
19
16
22
23
28
29
29
27
24
18
LIGHT
LAN
190
250
350
435
590
600
560
550
470
350
265
200
520
485
415
555
510
395
255
220
165
245
320
345
140
110
135
225
275
470
460
500
510
470
345
225
85
150
225
290
415
510
590
575
530
400
255
180
240
250
365
280
505
490
550
480
475
400
345
255
TSS
rag/1
93
63
101
74
74
61
67
89
109
166
127
59
56
51
41
33
43
58
31
53
23
17
37
51
19
21
38
32
25
52
104
123
51
60
88
26
7
5
' 7
22
16
19
20
30
12
20
6
6
38
37
50
53
52
51
98
56
61
42
75
40
VSS
mg/1 LOCATION
64 Bixby, OK
40
63
59
74
53
50
76 ' "
78
140
103 ' "
44
20 Pawnee, IL
33
29
24
30
41 "
17
27
16
8
21
18
12 Windber, PA
13
28
22 "
18
37
72
81
31
41 "
73
21
6 Lake Koshkonong, WI
4 "
6 "
20
15
18 "
19 "
27
10
13
5
5 "
33 North Gulf port, MS
33
44 "
41
43
35
63 "
33 "
42
30
55
27
                             313

-------
                                                         FIGURE A-14


                                      RELATIONSHIP BETWEEN WEHNER AND WILHELM DECAY
                                         RATE AND TEMPERATURE - FACULTATIVE PONDS
co
                  2.5
                  2.0
            £    1-0
             go,

             



             I   -1.0
                 -1.5
                 -2.0
                   -5.0
                                  Y = -0.0242 X (zero forced fit)
                                  r = 0.554
                                         Y =-0.0227 X - 0.0263
                                         r = 0.342
         D
0.0
5.0
10.0
15.0
20.0
25.0
30.0

-------
where

     t  =   detention time, days

     E  =   percent BODs to be removed in an aerated pond

     fcl =   reaction  coefficient,   aerated   pond,   base  10.    [For  normal
            domestic  wastewater,  the  KI  value may be  assumed  to be  0.12/d
            at 20°C and 0.06/d at 1°C according to the standards (7).]

Equation  A-16 is  equivalent to  Equation A-8 presented  in  the  section  on
Rational  Design  Equations  for  facultative  wastewater  stabilization  pond
design.   By manipulating  Equation A-16 as shown  below,  it can be  shown  that
the two equations are equal.


         2.3  kxt = T/                                                    (A-17)
                                  100
         2.3 kxt = 	x  ^."/r  r ^	—                            (A-19)

                   100 -
                      100 - 100 C 1C
               t -
              l  ~ 100 - 100 t 100 C/C
         2.3 k,t = p  _ i                                               (A_2l)
              1     e

The  only  difference  between Equation A-16 and  Equation  A-8 is  that  the  con-
stant  in  Equation A-8 is  expressed in  terms  of  base  e and  the  other  is
expressed in terms of base 10.

Equation  A-8 is  the most  commonly used  equation  to  design  aerated  ponds.
Practically  every aerated pond  in  the  United  States  has been  designed  with
this  simple  complete mix  model.   In the design process, the  reaction  rate
coefficient  is  adjusted  to  reflect  the  influence  of  temperature on  the
biological reactions in the aerated ponds by using Equation A-14.

The  plug  flow  (Equation A-5),  complete  mix  (Ten State  Equation and Equation
A-8),  and Wehner-Wilhelm (Equation A-15) models were  evaluated  using the BOD
and  COD data shown  in Table A-2.   The  effect of water temperature on  the
reaction  rates  calculated with  each  of the models  using the  influent  total
                                     315

-------
      and the  effluent SBOD5  are shown  in Figures  A-15  through A-17.   The
Wehner-Wilhelm equation was solved using a dispersion number of 0.25.

Although  the relationships  between  decay  rates  and  temperature differences
are  statistically  significant at the  1  or 5  percent level, the  data points
are  scattered  and  less than 30 percent  of  the variation is explained by the
regression  analyses.   Using the  analyses for  the regression of  data through
the origin, temperature factors (&) of 1.07, 1.09,  and 1.07 were obtained for
the  plug flow, complete mix,  and Wehner-Wilhelm models, respectively,  using
the  influent  total  BODs  and  effluent  soluble  BOD5  to   estimate  the  sub-
strate strength, respectively.  The temperature factors are in  agreement with
values reported  in  the literature  (3)(8)(9).  The  above  values are recom-
mended for  use when  adjusting the reaction rates to  compensate  for tempera-
ture effects in aerated ponds.

The  relationships  shown in Figures A-15  through  A-17 were  the  best obtained
for  all  combinations  of  the  BOD and  COD  data.   Better   relationships  were
observed  between  the  reaction rates  and  temperature  for  the  aerated  ponds
than for the facultative ponds.   This  was  probably attributable  to the mixing
in   the   aerated   ponds.    The  relationships  between  the  plug  flow  and
Wehner-Wilhelm models'  reaction rates and  temperature provided   a better fit
of the data than the relationship observed  for the complete mix  model.  These
results  indicate  that the  plug flow  and  Wehner-Wilhelm  models  provide  a
better approximation  of the performance  of the  aerated  ponds  than  the  com-
plete mix  model.   All  of the  aerated  ponds were designed  using  the complete
mix model (Equation A-8).

Because  of the relatively  poor relationship  between the   reaction  rates and
temperature, the  data in Table A-2  were used to determine if the  plug  flow
and  complete mix  models  could be  used, to estimate  the  performance  of the
aerated  ponds.   As shown  in  Figures  A-18  and A-19,  the fit  of the  data  to
both the plug  flow and complete  mix models yields  statistically significant
(1  percent  level) relationships.  The data fit  the  plug  flow  model  better
than the complete mix model  even though the  complete mix  model was  used  to
design the systems.   This  is  not  surprising if  the flow  patterns  in  the
diffused  air aeration  systems is considered.  Ponds  using the  Hinde  Engi-
neering  Company  aeration  system (diffused air) are operated essentially  as  a
plug  flow,  tapered   aeration,   activated  sludge   system   without   cellular
recycle.  Therefore,  the  plug flow model  would  be  expected to  more closely
describe the performance of  these systems.  Surface  aeration systems could  be
designed so that either flow model would describe the  performance of a pond.
For example, an aeration basin with a  high  length to  width  ratio with surface
aerators  would approximate  a  plug flow pattern,  but a  circular  or square
basin  with  surface  aerators  would  be  expected  to  approach  complete  mix
conditions.  In  practice  the flow patterns in ponds are   imperfect  and  vary
with  each  system.   Logically,  a model  such  as  the  Wehner-Wilhelm equation
(Equation  A-15)   would be  expected  to  provide  the  best estimate  of  the
performance  of pond  systems.   Unfortunately,  none  of  the simple  models  is
obviously superior to the others.
                                      316

-------
                                                                  FIGURE A-15


                                                 RELATIONSHIP BETWEEN PLUG FLOW DECAY  RATE

                                                       AND TEMPERATURE - AERATED PONDS
oo
                    3.0  r
                    2.5
                    2.0
              So
              0) 03
              a ~
              ._
              O)
                    1.0
                    0.5
                    0.0
                   -0.5
                   -1.0
Y = 0.0707 X (zero forced fit)

r = 0.829

          -        :  n
                                                                                Y = 0.0416 X + 0.415

                                                                                r = 0.524
                      -5.0
  0.0
5.0
10.0
15.0
20.0
25.0
30.0

-------
                                                                   FIGURE  A-16
CO
t-»

00
                                                RELATIONSHIP BETWEEN COMPLETE MIX DECAY RATE

                                                       AND TEMPERATURE  - AERATED PONDS
      4.0





      3.5





      3.0





~    2.5


x —
 CM It)

~§  2.0



 0)111

 S-a  1.5
cc  c


 (0  ">
 oo  i n
 OJQ  i.u


_x —


ii  0.5
 QJ  t3
 +^  0}



 Is  o.o
            o
           o
                 -0.5




                 -1.0




                 -1.5
                 -2.0
                               Y = 0.0858 X (zero forced fit)

                               r = 0.724
                                         Y = 0.0362 X + 0.836

                                         r = 0.274
                                                a
                                                            I
                                        l_
                    -5.0
0.0
                                   5.0
10.0         15.0

      T2-ti
20.0
25.0
30.0

-------
                                                                  FIGURE  A-17

                                               RELATIONSHIP BETWEEN WEHNER AND  WILHELM DECAY
                                                    RATE AND  TEMPERATURE - AERATED PONDS
CO
c
_l _^
 . In

TOO
CC CD
                   3.0
                   2.5
                   2.0
                   1.5
             CD LU
             lo
             ^S
             E-   0.5
                   o.o
             c
                   -0.5
                   -1.0
                   -1.5
                                   Y = 0.0638 X (zero forced fit)
                                   r = 0.821
                                                                Y = 0.0498 X +0.312
                                                                r = 0.542
                     -5.0
                     0.0
5.0
10.0
15.0
20.0
25.0
30.0
                                                                 T2-Ti

-------
co
ro
o
                                                                   FIGURE A-18

                                                        PLUG FLOW MODEL  - AERATED PONDS
                                    D
                                            D
                                                                                          Y = -0.0501 X (zero forced fit)
                                                                                          r = 0.936
                                                                                          Y = -0.0344 X - 0.968
                                                                                          r = 0.822
Q
O
CO
H

 in
Q
O
CQ
(/>
UJ
                                                                    D
                  -5
                                                                    60

                                                           Detention Time, days
                                                                     80
100
120

-------
                        160r-
                        140
                        120
                                                            FIGURE A-19


                                               COMPLETE MIX  MODEL  - AERATED  PONDS
                                   Y = 0.654 X (zero forced fit)

                                   r = 0.816
                                   Y = 0.818 X- 10.1

                                   r = 0.745
                     "-  100
oo
ro
                     Q
                     O
                     CD
                     Q

                     O
                     00
                         80
                         60
                         40
                         20
                                                       I      Dl       I     "I
0      10     20     30    40
                                                             50      60    70     80

                                                             Detention Time, days
90    100    110    120

-------
     A.2.3  Oxygen Requirements


There is no rational design equations to  predict  the  mass rate of transfer of
DO and the  required mixing to keep  the  solids suspended in  an  aerated pond.
Using  the  mass  of  8005  entering  the  system  as a  basis  to calculate  the
oxygen  requirements is  simple  and  as  effective  as  other  approaches.   To
predict the aeration needed for  mixing,  it is necessary  to  rely  on empirical
methods  developed by  equipment manufacturers.   Oxygen  requirements   do  not
control  the  design  of  aeration  equipment  in  aerated  ponds  unless  the
detention time  in the  aeration tank  is  approximately one day.   Such  a short
detention time is- not recommended  for aerated  ponds;  therefore,  mixing is the
major concern in the design.

Catalogs  from  equipment  manufacturers   must  be consulted   to  ensure  that
adequate pumping, or mixing,  is provided.  The  types of  aeration equipment
available are  listed in  Table A-3  and  shown schematically  in  Figure A-20.
Graphs or tables  are available from all  aeration  equipment manufacturers, and
all types of  equipment  must be evaluated  to  ensure  that the  most  economical
and efficientssystem  is  selected.   The  oxygen  demand can be  estimated using
the  procedure  outlined  in Table  A-4.    Suspension  of  solids (complete  mix
system) will require approximately 10 times as much power for mixing than for
oxygen  supply.   Therefore,  an  economic  analysis   along  with  engineering
judgment must be used to select the proper aeration equipment.

The system  should be divided  into a minimum  of  three basins and  preferably
four  basins to   improve  the  hydraulic   characteristics  and  improve  mixing
conditions.  The  division of the basins  can be accomplished by using separate
basins or baffles.   There are simple plastic  baffles  commercially  available.
Aerators  should  be  selected  and  spaced  through   the  basins  to  provide
overlapping zones of mixing,  and spaced  in proportion  to the expected oxygen
demand (see Chapter  3).   The  oxygen  demand will  decrease  in  each  succeeding
cell.
                                     322

-------
                                                                                        TABLE A-3

                                                         TYPES OF  AERATION  EQUIPMENT  FOR AERATED  PONDS (10)
                                                    lb
                                            (Standard Condition)
                                                      Oxygen
                                                     Production

                                                      lb 02/hp
                                     Power
                                 Requirements
                                  hp/106 gal
Common
 Depth
  ft
                                                                                                                 Advantages
  Disadvantages
co
ro
co
              Floating Mechanical Aerator
                   High Speed
                   Low Speed
              Rotor Aeration Unit
                   (brush  type)
              Plastic Tubing Diffuser
                   Diffused Aeration
Air-Gun
              Helical  Oiffuser
                                  1.8-4.5/hp
                                  3.5/hp
                                0.2-0.7/100 ft
0.8-1.6/unit
                                1.2-4.2/unit
                                                         1;5           35
                                                     2.5  to 3.5        25
                                                    0.5 to 1.2       100
                                                        12-20
                                                 10-15    Good mixing and aeration
                                                          capabilities; easily
                                                          removed for maintenance
 3-10     Probably unaffected by
          freezing; not affected by
          sludge .deposits; good for
          oxidation ditches

 3-10     Not  affected by floating
          debris or ice; no ragging
          problem; uniform mixing
          & oxygen distribution

12-20     Not  affected by ice; good
          mixing
                                                  8-15     Not affected by ice;
                                                          relatively good mixing
Ice problems  during
freezing weather;
ragging problems with-
out clogless  impeller

Requires regular clean-
ing of air  diffusion
holes; energy conversion
efficiency  is lower

Requires regular clean-
ing of air  diffusion
holes; energy conversion
efficiency  is lower

Calcium carbonate build-
up blocks air holes;
potential ragging prob-
lem affected  by sludge
deposits   ;'

Potential ragging prob-
lem; affected by sludge
deposits'

-------
                       FIGURE A-20

SCHEMATIC VIEW OF VARIOUS TYPES OF AERATORS (10)
               Diffuser head
Motor

  Float
                  Propeller--' L	T— Intake volute

                     Floating surface aerator
   Rotor
                 Motor

                   Motor mount
                                                 I_
                                                     Water surface
                /-Rotor blades
                                  Air supply
                                  tubing
                  ^ Float

  Floating rotor aerator
                Water.
                 flow

               Air
               supply.
               Concrete
               base
   Helical aerator
                        Air gun aerator
                  Air hole
                 Pond bottom
                     Plastic tube aerator
                             324

-------
                                  TABLE A-4
   CALCULATION OF OXYGEN DEMAND AND SURFACE  AERATOR  SIZE  FOR AERATED PONDS

Design Conditions
     Design flow = 3,785 m^/d
     Influent BOD5 = 300 mg/1
     Pond temperature = 15°C
     Barometric pressure = 760 mm of mercury
Oxygen Requirements
     BOD5 in wastewater = (300 mg/1)  (3,785  m3/d)(l,000 Iiters/m3)/l06
                        = 1,136 kg/d
     Assume that 02 demand of  the solids and at  peak flows will be 1.5
         times the mean value  of 1,136  kg/d
     Oxygen requirements (Na)  = 1,136 x 1.5  = 1,703  kg/d
                              = 71 kg/hr
Aerator Sizing
After  determining Na,  the equivalent oxygen  transfer  to  tapwater   (N)  at
standard conditions in kg/hr can be calculated using the  following equation:
                              n  noc-
             a   - * -     (1.025)
               I  -  s   J
Wh re       oxygen transfer  to waste
          oxygen transfer to tapwater
    C-w = oxygen saturation  value of the waste  in mg/1 calculated
          from the expression:
    Where e = oxy9en saturation value  of  the waste
              oxygen saturation value  of  tapwater
                                      325

-------
         GSS ~ oxygen saturation value of tapwater at the specified
               waste temperature
         p   _ barometric pressure at the plant site
                 barometric pressure at »sea level
                                  \ "* "*'  .                ' '
         CL  = DO concentration to be maintained in the waste (mg/1)
         C-  = oxygen saturation value of tapwater at 20°C and 1
               atmosphere pressure = 9.17 mg/1
         T   « pond water temperature (°C)
The design conditions are:
         N   - 71 kg (Uhr        ,
          a           6.           •                  •..,..
         a   « 0.9                ,
         3   - 0.9
         P   » 1.0 atmosphere
         CL  = 2.0 mg/1
         T   = 15°C'           .   ' •   '"'.r:     :          \    '
             Csw = 0.9 (10.15) 1.0 = 9.14 mg/1
                        71                         71
             ha P9.14 - 2.01  h n«A  ~  °-9 x 0.78 x 0.884
             °'9 [_    9.U  J  °'884
             = 114 kg 02/hr
Assume 1.4  kg 02/hp-hr for  the aerator  for  estimating purposes  (taker) from
catalogs)
Total hp required is 114/1.4 = 81 brake horsepower (bhp) (60 kW)
Aerator drive units should produce at least 81 bhp (60 kW) at the shaft
     Assume 90 percent efficiency for gear reducer
     Therefore, total motor horsepower = 90 hp (67 (kW)
                                     326

-------
A.3  References


 1.  McGarry,  M.  6., and  M. B.  Pescod.   Stabilization  Pond  Design Criteria
     for  Tropical  Asia.   2nd  International  Symposium  for  Waste  Treatment
     Lagoons,  Missouri  Basin Eng. Health Council,  Kansas City, MO,  1970, pp.
     114-132.

 2.  Larsen,  T.  B.  A  Dimensionless  Design  Equation  for  Sewage Lagoons.
     Dissertation,  University of  New Mexico, Albuquerque,  NM,  1974.

 3.  Gloyna,  E. F.   Facultative Waste Stabilization  Pond Design.   In:  Ponds
     as a Wastewater  Treatment  Alternative.   Water Resources Symposium No.  9,
     Center for Research in  Water Resources, University of Texas, Austin, TX,
     1976.

 4.  Arrhenius, S.  Z. Physik. Chem. 1, 631,  1887.

 5.  Thirumurthi, D.   Design Criteria  for  Waste  Stabilization Ponds.  JWPCF
     46(9):2094-2106, 1974.

 6.  Wehner,  J. F.,  and  R. H* Wilhelm.   Boundary  Conditions of Flow Reactor.
     Chemical  Engineering Science 6:89-93, 1956.

 7.  Recommended  Standards for Sewage  Works.  A  Report of the Committee  of
     Great  Lakes-Upper  Mississippi River Board of  State Sanitary  Engineers.
     Health Education Services, Inc., Albany, NY,  1978.

 8.  Metcalf    Eddy,  Inc.   Wastewater  Engineering.   McGraw-Hill,  New York,
     NY, 1979.        ,

 9.  Oswald,  W.  J.  Syllabus  on  Waste Pond  Design  Algae  Project  Report.
     Sanitary Engineering   Research  Laboratory,   University   of   California,
     Berkeley, CA,  1976.

10.  Process  Design  Manual:   Wastewater Treatment  Facilities  for  Sewered
     Small  Communities.    EPA-625/1-77-009,  U.S.   Environmental   Protection
     Agency,  Center for Environmental  Research Information,  Cincinnati,  OH,
     1977.
                                       327
                                                 
-------