EPA-600/2-75-038
October 1975
Environmental Protection Technology Series
        LIME  USE  IN WASTEWATER TREATMENT:
                           DESIGN AND COST  DATA
                        Municipal Environmental Research Laboratory
                                    Office of Research and Development
                                   U.S. Environmental Protection Agency
                                        Cincinnati, Ohio 45268

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                                   EPA-600/2-75-038
                                   October 1975
     LIME USE IN WASTEWATER TREATMENT:

           DESIGN AND COST DATA
                    by

   Denny S. Parker, Emilio de la Fuente,
     Louis O. Britt, Max L. Spealman,
 Richard J. Stenquist, and Fred J. Zadick

            Brown and Caldwell
      Walnut Creek, California  94596
          Contract No.  68-03-0334
              Project Officer

            James E. Smith, Jr.
       Wastewater Research Division
Municipal Environmental Research Laboratory
          Cincinnati, Ohio  45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
    OFFICE OF RESEARCH AND DEVELOPMENT
   U.S. ENVIRONMENTAL PROTECTION AGENCY
          CINCINNATI, OHIO  45268

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                          DISCLAIMER
     This report has been reviewed by the Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency,  and
approved for publication.  Approval does not signify that the
contents necessarily reflect the views and policies of the  U.S.
Environmental Protection Agency, nor does mention of trade  names
or commercial products constitute endorsement or recommendation
for use.
                               11

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                              FOREWORD
     Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise, and other forms of pollution,
and the unwise management of solid waste.  Efforts to protect the
environment require a focus that recognizes the interplay between
the components of our physical environment—air, water, and land.
The Municipal Environmental Research Laboratory contributes to this
multi-disciplinary focus through programs engaged in

     O    studies on the effects of environmental contaminants
          on the biosphere, and

     O    a search for ways to prevent contamination and to
          recycle valuable resources.

     The research reported here was performed for the Ultimate Disposal
Section of the Wastewater Research Division to provide design and cost
data on lime use, reuse, and recovery in wastewater sludge handling and
disposal operations.  The information presented in this report is of
immediate use to the treatment plant designer and should make possible
improved operation as well as operation at a reduced cost.
                                  111

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                                  ABSTRACT
This report presents design and cost information on lime use in wastewater
treatment applications. It includes design and cost information on lime handling,
liquid processing, solids generation and dewatering, lime recovery and ultimate
ash disposal.  The report takes a design manual approach so that the information
presented has maximum usefulness to environmental  engineers engaged in both
the conceptual and detailed design of wastewater treatment plants.

Design data on alternate sludge thickening and  dewatering  processes  are
presented with special emphasis on wet classification  of calcium carbonate from
unwanted materials and on maximizing the dewatering of wasted solids.

Alternative recalcining techniques are assessed  and problem areas identified. A
relatively  new technique for beneficiation of the  recalcined product is presented.
Approaches to heat recovery are presented that minimize the  net energy require-
ments for recalcination and incineration.

A computer program for computation of solids balances is included as a design
aid and two case histories are presented which portray the cost of lime treatment,
sludge processing and lime reclamation.

This report was submitted in fulfillment of Project Number CI-73-0131, Contract
Number 68-03-0334, by Brown and Caldwell, Consulting Engineers, under the
sponsorship of the U.S. Environmental Protection Agency.  Work on the first
draft was completed as of June, 1974.
                                    IV

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                                  CONTENTS


                                                                       Page

Abstract    	     iv

List of Figures  	     viii

List of Tables	     xii

Acknowledgments	     xvi

Sections

I       Conclusions	     1

II      Recommendations	     3

III      Introduction	     4
            Purpose and Scope	     5
            Background 	     5
            References	     6

IV      Fundamentals of Lime	     7
            Definitions	     7
            Lime in Wastewater Treatment   	     8
            Lime Slaking	     8
            Selection of Lime   	     13

V      Handling of Lime   	     15
            Lime Delivery	     15
            Lime Unloading and Storage	  .     16
            Lime Feeders	     19
            Dissolving of Lime	     25
            In-Plant Transport Methods   	     28
            Safety Considerations	     31
            References	     32

VI      Liquid Processing with Lime	     33
            General Considerations   	     33
            Process Chemistry	     33
            Lime Addition	     47
            Control of Lime Dosage	     48
            Flocculation	     52
            Alternate Processes for Primary Application	     53
            Recarbonation	     63
            Tertiary Applications	     66
            Design Considerations for Primary Clarifiers	     66
            References	     72

                                      v

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                           CONTENTS  (continued)


Sections                                                                Page

VII     Lime Sludge Thickening and Dewatering   	      77
            General Considerations   	      77
            Sludge Thickening	      77
            Sludge Dewatering	      85
            Sludge Cake Conveying	      125
            References	      128

VIII     Slime Sludge Recalcination and Waste Sludge Incineration  .  .      131
            General Considerations   	      131
            Lime Sludge Recalcination	      132
            Handling of Reclaimed Lime   	      148
            Related Processes	      157
            Summary of Lime Recovery Case Histories	      164
            Waste Sludge Incineration	      171
            Energy Considerations	      171
            References	      184

IX     Air Quality Considerations	      188
            References	      192

X      Mass Equilibrium Balances of Solids Processing
        Systems by Digital Computation	      193
            Description of Program	      197
            Derivation of Equations and Program Mechanics	      205
            Material Balances for Several Cases	      209
            References	      216

XI     Ultimate Disposal of Ash	      217
            Ash Characteristics	      217
            Uses of Sludge Ash   	      217
            Ash Handling Prior  to Disposal	      220
            Final Disposal Sites	      221
            References	      222

XII     Development of Cost Estimates	      223
            General Considerations   	      223
            The Lower Molonglo Water Quality Control  Centre   ....      224
            The CCCSD Water Reclamation Plant	      226
            Cost Estimates for the CCCSD Water Reclamation Plant  . .      228
            References	      244

XIII     List of Inventions and Publications	      245

XIV     Glossary	      246

XV     Appendices	      248
                                     vx

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                        CONTENTS  (continued)





                                                                Page




APPENDIX A. LISTING OF SOLIDS 1A	     249



APPENDIX B . OUTPUT FOR CASES	     257
                                vn

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                                   FIGURES

 No.                                                                Page

 5- 1    Positive/Negative Pneumatic Conveying System                   20

 5- 2    Typical Screw Type Volumetric Feeder                          23

 5- 3    Typical Belt Type Gravimetric Feeder                           24

 5- 4    Typical Detention Type Slaker                                  27

 5- 5    Typical Paste Type Slaker                                     29

 6- 1    Effect of Phosphate Form on Calcium Carbonate
        Precipitation                                                  35

 6- 2    Effect of Solids Concentration on Calcium Removal                36

 6- 3    Lime and Iron Dose vs .  Supernatant Quality for
        CCCSD Wastewater                                            41

 6- 4    Phosphorus Removal for Low pH Operation lime and Iron
        Treatment of CCCSD Wastewater                                44

 6- 5    Effect of Lime Treatment on Salt Lake City Wastewater             45

 6- 6    Calcium Loss to Supernatant and Phosphorous Precipitation        46

 6- 7    Location of Lime Slakers at the CCCSD Water Reclamation Plant    49

 6- 8    Lime Dosage Control Diagrams                                  50

 6- 9    Lime Dosage Control Diagram - Feed Forward
        Control Mode                                                 51

 6-10    Air Supply - Shearing Relationship for Preaeration-Flocculation   54

 6-11    Phosphorous Removal as a Function of Lime Dose                 56

 6-12    Lime Requirement for pH  11 as a Function of Wastewater
        Alkalinity                                                    61

 6-13    Typical Solids-Contact Clarifier                                 67

6-14    Primary Treatment Units at CCCSD Water Treatment plant         69

7- 1     Relationship between Increase in Solids Concentration
        and Moisture Removal                                          78
                                  Vlll

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                             FIGURES (continued)

No.                                                                 Page

7- 2     Settling Characteristics of High Lime Sludge
        at the Blue Plains Pilot Plant                                    80

7- 3     Typical Gravity Thickener                                      81

7- 4     Gravity Sludge Thickener at CCCSD Water Reclamation Plant       82

7- 5     Schematic Diagram of the  Dissolved Air Flotation Process          84

7- 6     Effect of Moisture Content on the Cost of Sludge Combustion        86

7- 7     Effect of Moisture Content on the Cost of Sludge Combustion        87

7- 8     Conventional Plural Purpose Furnace Flow Sheet                  88

7- 9     ATTF Solids Processing System                                  89

7-10    Solid-Bowl Conveyor Centrifuges                                91

7-11    Vertical Centrifuge Installation at the CCCSD
        Water Reclamation Plant                                         93

7-12    Summary of Constituent Recoveries During Wet Classification
        without Lime Recycle                                           97

7-13    Summary of Constituent Recoveries During Wet Classification
        with Lime Recycle                                            100

7-14    Effect of Feed Rate on Solids Recovery                          102

7-15    Effect of Pond Setting on Dewatering at pH 11                    102

7-16    Effect of Conveyor Speed on Polymer Requirement               103

7-17    Effect of Centrifugal Force on Solids Recovery                  104

7-18    Effect of Feed Rate on Solids Recovery                          105

7-19    Effect of Polymer Dosage on Lime Recovery                      107

7-20    Effect of Polymer Dosage on Solids Removal                     110

7-21    Schematic Diagram of Belt Type Vacuum Filter                  111

7-22    Dewatering of Lime Sludge by Vacuum Filtration                113
                                    IX

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                              FIGURES (continued)



 No.                                                                 Page


 7-23    Effect of Drum Speed on Cake Solids Concentration               115

 7-24    Effect of Drum Speed on Filter Loading                          116

 7-25    Effect of Drum Speed on Solids Capture                         117

 7-26    Schematic Diagram of a Pressure Filtration System               119

 7-27    Relationship between Solids Concentration and
        Specific Weight                                               127

 8- 1    Effect of Excess Air on the Cost of Sludge Incineration            133

 8- 2    Decomposition of Calcium Carbonate to Calcium Oxide            134

 8- 3    Typical Multiple Hearth  Furnace                               137

 8- 4    Schematic Diagram of a Pellet Bed Calcining System              141

 8- 5    Typical Fluidized Bed Calciner                                 144

 8- 6    Schematic Diagram of a Sand Bed Calcining System               146

 8- 7    Typical Rotary Kiln Calciner                                   149

 8- 8    Particle Size Distribution of Recalcined Lime                    151

 8- 9    Two Types of Air Classifier                                   152

 8-10    Dry Classification of Recalcined Lime                           154

 8-11    Auxiliary Equipment for MHF  at the CCCSD Water
        Reclamation Plant                                             159

8-12    Lime Recovery at the South Tahoe Water Reclamation Plant       166

8-13    Piscataway Tertiary Treatment Plant                            168

 10-1    Effect of Blow down  on Recovered CaO                          212

10-2    Effect of Blowdown on Primary Sludge Production for Cases       213
                                    x

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                             FIGURES (continued)



No.                                                                Page



11-1     Particle Size Analysis of Wastewater Sludge Ash                 219



12-1     Flow Diagram of the CCCSD Water Reclamation Plant             227
                                    XI

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                                    TABLES
  No.
                                                                     Page
 4- 1    Characteristics of Lime Chemicals                                9

 4- 2    Characteristics of Main Grades of Quicklime                      10

 4- 3    Characteristics of Quicklime and Hydrated Lime                  14

 5- 1    Sizing Data for Screw Conveyors and Bucket Elevators            17

 6- 1    Solubility Products of Heavy Metal Salts                         39

 6- 2    Effect of Primary Clarifier pH on Performance at Waterford,
         New York                                                     55

 6- 3    Operating Parameters for Primary Treatment in "PEP" Plants      58

 6- 4    High pH Treatment of CCCSD Wastewater                        60

 6- 5    Lime and Iron Treatment of CCCSD Wastewater                   62

 6- 6    Maximum Clarifier Design Parameters                           70

 6- 7    Recommended Clarifier Design Parameters                       71

 7- 1     Some Basic Materials of Construction Used in Sharpies
         Centrifuges                                                   90

 7- 2     Classification Data for Water Treatment Plant Sludges             95

 7- 3     Run Data for Wet Classification                                  98

 7- 4    Centrifuge Performance Summary - Lime Sludge Recycle
        Project                                                        99

 7- 5    Effect of Flocculation pH on Second Stage Cake Dryness          105

 7- 6    Dewatering of High Lime "IPC" Solids after Centrifuge
        Classification                                                 106

7- 7    Dewatering of "IPC" Waste Solids (Whole Sludge)                 108

7- 8    Pressure Filtration of Centrate at Blue Plains                    121

7- 9    Pressure Filtration of Centrate at CCCSD                        121
                                   xii

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                             TABLES  (continued)


 No.                                                                 Page

7-10     Comparison of Machine and Floor Area Requirements for
        Alternate Flow Sheets at 1.31 CU M/SEC                        122

7-11     Comparison of Water Evaporated  for Alternate Dewatering
        Systems at 1.31 CU M/SEC                                     124

8- 1     Typical Temperature Profile in Six Hearth Furnace              138

8- 2     Temperature Profile  in Lime Recalcination Furnace for CCCSD     138

8- 3     Standard Multiple Hearth Furnace Sizes                         140

8- 4     Size Distribution Analysis of Recalcined Lime from a MHF         150

8- 5     Comparison of Accepts and Dust Composition during ATTF
        Test Work                                                   155

8- 6     Component Recoveries in Classification Tests during ATTF
        Test Work                                                   155

8- 7     Typical Size Distribution for Pellets from a Fluidized
        Bed Calciner                                                 156

8- 8     Typical Heat Values  of Fuel Oils                                161

8- 9     Typical Sound  Levels                                         162

8-10    Permissible Noise Exposures                                  163

8-11     Sound Pressure Level of MHF Equipment                        163

8-12    Comparison of Primary Sedimentation Performance with and
        without Lime Recycle                                         170

8-13     Materials Balance for MHF in Recalcine Mode                    173

8-14    Heat Balance for MHF in Recalcine Mode                         174

8-15     Summary of Heat Balances for MHF in Recalcine Mode            177

8-16     Materials Balance for MHF at Three Moisture Levels
        of Second Stage Cake                                         179

8-17     Summary Heat Balance for MHF at Three Moisture Levels
        of Second Stage Cake                                         179
                                  XI11

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                              TABLES (continued)


  No.

  8-18   Auxiliary Fuel Requirements of MHF after Heat Recovery         180

  8-19   Overall Materials Balance for Fluidized Bed Calciner             182

  8-20   Overall Heat Balance for Fluidized Bed Calciner                  183

  9- 1   Solids Composition of Lime Furnance Off-Gases,  Percent         189

 10- 1    Common Prefixes Used in Program "Solids 1A"                   194

 10- 2    Common Suffixes Used in Program "Solids  1A"                   195

 10- 3    Other Symbols Used in Program "Solids 1A"                     196

 10- 4    Format for Data File "Dat. 1"                                   201

 10- 5    Format for Data File "Dat. 2"                                   202

 10- 6    Format for Data File "Dat. 3"                                   202

 10- 7    Materials Balance Description for Magnesium Oxide
         in the Primary Sludge                                         207

 10- 8    Solids  Processing Sequence Options for Various  Cases           210

 10- 9    Materials Balance Comparisons for Various Solids
         Processes Cases                                              211

 10-10   Calculated Solids Balances for Cases 100, 117, 120, 121
        and 122                                                      215

 11- 1   Physical Properties of Sludge Ash                              218

 11- 2   Classification of Ash Particles by "BAHCO" Micro Particle
        Size Analyzer                                                 218

 11- 3   Particle Size of  "FBR" Ash                                     218

 12- 1   Design Data for Flocculation - Sedimentation Basins at the
        Lower Molonglo  WQCC                                         225

12-2    Cost Comparison Between Solids - Contact Clarifiers and
        Rectangular  Flocculation - Sedimentation Tanks                  225

12- 3   Design Data for the CCCSD Water Reclamation Plant              229
                                   xiv

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                             TABLES  (continued)
 No.
12- 4    Capital Cost for Lime Treatment and Recovery at the CCCSD
        Water Reclamation Plant                                       233

12- 5    Capital Cost of Alternate Dewatering Process at the CCCSD
        Plant - Vacuum Filters in a Plural Purpose Furnace Flow Sheet    235

12- 6    Capital Cost of Alternate Dewatering Process at the CCCSD
        Plant - Filter Presses Substituted for Centrifugal Dewatering in
        the Second Phase                                             236

12- 7    Operation and Maintenance Cost for Lime Treatment and
        Recovery at the CCCSD Water Reclamation Plant                 238

12-8    Operation and Maintenance Cost for Alternate Dewatering
        Process at the CCCSD Plant - Vacuum Filters                    239

12- 9    Operation and Maintenance Cost for Alternate Dewatering
        Process at the  CCCSD Plant - Filter Presses                     240

12-10   Fuel Requirements for Alternative Cases                        241

12-11   Comparison of Total Annual Costs for Lime Treatment and
        Solids Processing                                            242

B-l     Case Descriptions                                            258
                                   xv

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                             ACKNOWLEDGEMENTS


The report was prepared by Brown and Caldwell, Consulting Engineers,  of
Walnut Creek, California. Project Manager and Project Engineer for this work
were Dr. D.S. Parker and Mr. E. de la Fuente, respectively.  Other contributors
were Messrs. L.O. Britt, M.L. Spealman, R.J. Stenquist, andF.J. Zadick.  This
report reflects the design and research experience of both Brown and Caldwell
and Caldwell Connell Engineers, an Australian affiliate. Indirect contributors to
this report were the engineers of those two  firms who have worked on lime
applications to wastewater treatment.  In addition to those already named, these
engineers include Dr. D.H. Caldwell and Messrs. R.C. Aberley, J.A. Cotteral,
D.L. Eisenhauer, M.J.  Flanagan,  W.Henry,  R.B. Sieger,  K.E. Train,  and
W.R. Uhte.

Mr. R.B. Thompson, of Industrial Pollution Control, Inc., Westport, Connecticut,
served as a special consultant on fluid bed recalcination.

The Central Contra Costa Sanitary District's  interest in lime treatment led to the
operation of its Advanced Treatment Test Facility (ATTF) .  The experience gained
in this operation of ATTF has broadened this effort considerably.

A  number of manufacturers contributed valuable information, principal among
these are BIF, Dorr-Oliver, Inc., Envirotech Corp., Passavant Corp., Nichols,
Sharpies-Stokes and Wallace and Tiernan, Divisions of The Pennwalt Corp.,
Komline-Sanderson  Engineering Corp., Walker Process Equipment and
Bird Machine Co.

Mr. Robert Boynton, Executive Director of the National Lime Association,
volunteered his time and reviewed the final draft of this report.

A number of individuals and agencies were kind enough to host site visits of
their facilities and/or offer their comments on  lime treatment processes.  These
included:  Messrs.  F.  Krause and C.W. Bellows, Board of Water and Light,
Lansing, Michigan;  Messrs. P. Hinkley, C.E.  Kilpatrick and H. Munn,  S.D.
Warren Co., Muskegon, Michigan;  Mr. L. Martin, City of Holland, Michigan,
Mr. W. Ranson,  City of Hastings, Michigan; Mr.  J.L. Hall, Dade Water and
Sewer Authority, Hialeah, Florida; Messrs. T. Saygers and R.C. Stout of the
City of Dayton, Ohio; Messrs. D.F.  Bishop, S.M. Bennett, T. Pressley, and
T.P. O'Farrell of the EPA-DC Blue Plains Pilot  Plant, and Dr. C. Lewis,
Consultant to the U.S. Lime Division of the Flintkote Co.

Dr. James E.  Smith  Jr.,  of the U.S. Environmental Protection Agency's
Municipal Environmental Research Laboratory (MERL),  Cincinnati, Ohio,
served as Project Officer for this study.  Dr.  Eobert B. Dean, also of
the MERL, provided  early inspiration to this investigation.
                                   xvi

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                                   SECTION I

                                 CONCLUSIONS
The purpose of this report is to present design  and cost information on lime
handling, liquid processing, solids generation and dewatering, lime recovery and
ultimate ash disposal.  Since the report takes a design manual approach rather
than a research investigation approach, the conclusions are of a different nature
than those which would normally be found in most Office of Research and
Development reports.  The following conclusions were drawn:

    1.  Lime treatment of raw sewage is an attractive process with many
        advantages, has wide applicability, is state-of-the-art technology and
        should be evaluated in the selection procedure of treatment alternatives.

    2.  The choice of coagulants to be used in waste treatment processes should
        be based on cost and performance comparisons. The selection process
        should consider both chemical costs and the costs  of sludge processing,
        as considerable savings can be made by careful choice of operating pH
        and supplemental metal salts for coagulation.

    3.  Combined sludges generated by lime coagulation in a chemical primary
        sedimentation  tank can be effectively wet classified into two components
        with a solid bowl centrifuge.   One component, the cake, contains the
        bulk of the calcium carbonate and silica.   The other component, the
        centrate, contains the bulk of the organics and other chemical pre-
        cipitates.  Wet classification produces a cake ideal for recalcination,
        as it is high in calcium carbonate and low in moisture content.

    4.  Sludge handling processes incorporating wet classification  are more
        effective in reducing the total water to be evaporated in furnaces than
        processes not  employing wet classification.

    5.  Sludge handling processes incorporating wet classification  coupled with
        pressure filtration of the centrate are less costly than processes where
        whole sludge recovery is practiced.

    6.  Lime recovery through recalcination can produce a readily  reusable
        quicklime that can significantly reduce chemical costs in larger plants.

    7.  The multiple hearth furnace (MHF) is well established in  the wastewater
        sludge recalcination field as a result of operational experience with
        tertiary lime sludges and large-scale recycling tests with raw  wastewater
        lime sludges.  The fluidized bed reactor (FBR) has been  used  in similar
        applications, but operating experience has not yet been obtained in the
        wastewater field.  Developmental work will have to be done to establish
        the FBR as a working tool.  The rotary kiln needs substantial research
        and development work before it can be applied with confidence to waste-
        water sludge applications.

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 8.  When applied with energy recovery features, both the MHF and the FBR
    can be competitive, on an energy basis, with the industrial production of
    lime from limestone.

 9.  Recalcined lime applied in the primary sedimentation process causes more
    complete phosphorus removal and improves the softening reactions when
    compared to the use of "new" lime alone.

10.  Sludge handling processes incorporating wet classification recycle
     substantially less unwanted solids  than processes not employing wet
     classification.

11.   When centrifugation and pressure filtration are used,  the use of recalcined
     lime  has been shown to improve the dewatering of waste sludges generated
     in lime treatment.

12.   When centrifuges are used for wet  classification or whole sludge recovery,
     dry classification of the recalcine furnace product is essential for control-
     ling  the level of silica in the system.   High levels of silica recycle cannot
     be tolerated due to centrifuge wear.

13.   Relative effectiveness of the alternative dewatering processes for the
     centrate from the wet classification step are as follows:  pressure filtration,
     vacuum filtration and centrifugation.  However, vacuum filtration rates are
     low and the cake does not separate easily from the septum.

14.   As a rule, the pH of operation of the chemical primary tank must be con-
     siderably in excess of pH 9.5 to generate enough calcium carbonate to
     justify lime recovery.

15.   Low  lime treatment plants are considerably less efficient in phosphorus
     and organic removal than either high lime treatment plants or plants
     incorporating the use of lime with other metal salts.

16.   Flocculation pH influences the dewatering processes significantly.  A pH
     greater than 11.0 adversely affects the dewatering of the wet classification
     centrate.  Higher filter yields on nonclassified  whole sludges are obtained
     with high pH sludges (pH >11.5) than with low pH sludges  (pH < 11.5) .

17.   Rectangular sedimentation tanks incorporating  preaeration for grit
     removal and flocculation are lower in capital cost than circular tanks
     with separate grit removal.

18.   The quantity of sludge produced where lime is  used in a primary
     sedimentation tank can be accurately estimated  by high-speed digital
     computation.

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                              SECTION II

                          RECOMMENDATIONS
1.   The Energy Crisis has brought to the forefront the need for consideration
    of the impact that the choice of a particular treatment process has on
    energy demands.  Rapid application and development of the use of heat
    recovery in incineration systems is justified. The full  economic and
    environmental benefits of such applications should be investigated.

2 .   Lime treatment is not a new-untried technology;  the environmental
    engineering profession should adopt it as  one of its standard techniques.

3.   As lime treatment techniques advance in their development, this develop-
    ment should be  documented to expand the  data base,  especially in the
    areas of economics and long-term plant operating data.

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                                  SECTION III

                                INTRODUCTION


 Increasingly,  waste treatment systems are being designed to produce effluents of
 substantially higher quality than can be obtained by conventional primary or
 secondary processes.  These new,  "advanced waste treatment"  systems are
 oriented toward the removal of sewage constituents which are not significantly
 removed by conventional treatment processes.  These advanced waste treatment
 systems often  incorporate the addition of coagulant chemicals for enhanced
 phosphorus, solids, grease or heavy metals removal.  Coagulant chemicals that
 are commonly in use today include iron  (ferrous  or ferric) ,  aluminum  (alum or
 sodium aluminate) ,  and calcium  (lime) .

 Lime is an attractive chemical for utilization in advanced waste treatment systems,
 and has been selected as the chemical of choice in a number of situations.  In some
 locales lime costs may be lower than either aluminum or iron compounds, and lime
 sludges are generally easier to dewater than ferric and alum sludges .  The use of
 lime allows higher surface overflow rates on sedimentation tanks than does an iron
 or aluminum salt, and this is an important factor for upgrading existing treatment
 plants. In all cases, however, coagulant choice should be based on an engineering
 economic evaluation of  each  alternative.

 Lime was used in waste treatment long before the present era of "advanced waste
 treatment" (AWT) .  An example of this was  the Laughlin Process, which was used
 during the 1930's and employed lime in a first stage system followed by ferric
 chloride in a second stage.   Chemical treatment was considered a competitive
 process to biological treatment in the 1920's and early 1930's but was supplanted
 in later years  by  refinements of the activated sludge and trickling filter processes
 which seemed to be  more promising  for strictly BOD removal.

 Interest  in lime treatment rekindled in the 1960's when environmental concern
 began to be  expressed about other sewage constituents such as phosphorus, heavy
 metals and viruses.  This concern  spawned the present AWT era in the tech-
 nology of sewage  treatment.  The use of  lime in the treatment scheme enhances
 removals of  phosphorus, metals  and viruses over that obtained by conventional
 primary and biological  treatment schemes.

 Initial full-scale applications of lime treatment  in  the AWT era were so-called
 "tertiary" applications and followed conventional biological treatment. An example
of such a practice is at  South Lake Tahoe.  Generally, these  applications were
primarily intended for phosphorus removal, but heavy metals, suspended solids
and virus removals were also obtained .  In the particular case of South Lake Tahoe,
pH elevation for ammonia stripping was also desired . Some of the later applications
of lime in AWT have integrated lime precipitation into an earlier stage, the primary
stage of the  treatment  system. In terms of historical perspective, this could be
considered a partial reversion to the chemical treatment systems of the 1920's and

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1930's.  The main difference is that downstream processes normally polish the
chemical primary effluent.  The advantage gained from moving lime forward from
the tertiary stage is that one or more treatment stages can be eliminated, making
the overall treatment system less complex.
                              PURPOSE AND SCOPE
This report is basically concerned with the design of treatment facilities where
lime is incorporated in the primary stage of treatment.  Tertiary applications have
been well documented in the literature.  Examples of primary stage applications
are:

    1.   Low level lime addition into the  primary for phosphorus removal followed
        by biological treatment for organic reduction.

    2.   Moderately high level lime addition into the primary for organic reduction
        to permit nitrification in a biological treatment step.

    3.   Lime addition into the primary,  followed by filtration and activated
        carbon adsorption.

    4.   Lime addition into the primary for improved organics,  grease, and heavy
        metals removal, followed by ocean disposal of the lime clarified effluent.

This review presents design and cost information on lime handling, liquid proces-
sing, solids generation and  dewatering, lime recovery and ultimate disposal.
                                 BACKGROUND
Much of the information contained in this manual has been derived from the
experience of Brown and Caldwell, of Walnut Creek, California and Caldwell
Connell Engineers of Melbourne, Australia, gained in the design of four treatment
plants which will employ lime in the primary stage of treatment. Two of these
plants, the Central Contra Costa Sanitary District (CCCSD)  plant and the City of
Livermore plant,  are located in the State of California and are oriented towards
water reclamation.  Two other plants, Canberra and Darwin, are located in
Australia and are oriented towards water pollution control.  Practical operating
experience has been gained in full-scale operations in conjunction with the CCCSD
at the CCCSD Advanced Treatment Test Facility (ATTF) !'2 where chemical pri-
mary flows average up to 2.5 mgd. Full scale liquid and solids processing
studies have  been conducted at the ATTF .  Additional information was compiled
from the literature covering lime use in water and wastewater treatment,
manufacturers data and information data supplied  by the Environmental
Protection Agency, and from site visits made during the project.  These sources
are specifically referenced where used and summarized in the acknowledgments
section.

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                         REFERENCES
Horstkotte, G.A., D.G. Niles, D.S. Parker, and D.H. Caldwell. Full-
Scale Testing of a Water Reclamation System.  Journal Water Pollution
Control Federation, 46, 181  (1974).

Parker,  D.S., K.E. Train and F.J. Zadick. Sludge Processing for
Combined Physical-Chemical-Biological Sludges.  Environmental
Protection Agency. Washington, D.C. Report No. EPA-R2-73-250.
July, 1973, 141 p.

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                                  SECTION IV

                            FUNDAMENTALS OF LIME
DEFINITIONS

Lime is a general term applied to several chemical compounds that share the
common characteristic of being highly alkaline. In the water and wastewater
treatment fields, the term is usually applied to quicklime and hydrated lime.
Both types of lime are frequently used and are readily available throughout the
United States. The definitions given below are intended to clarify the confusing
terminology often found when dealing with different forms of lime.  Standard
definitions used  in the industry follow.

Limestone is the basic compound from which usable lime forms are derived.
There are two kinds of limestone:  (1) high calcium limestone which is almost
entirely calcium; and (2) dolomitic limestone  which is a double carbonate mineral
of calcium and magnesium containing 35 to 45  percent of the latter, expressed as
magnesium oxide.

Quicklime is derived from high calcium limestone by a high temperature calcina-
tion process .  Quicklime contains about 90 percent  calcium oxide, and for  this
reason is also called calcium oxide.  Two other terms sometimes applied to
quicklime are burned lime and unslaked lime. Quicklime does not react uniformly
when applied directly to water or wastewater  but must first be converted to the
hydrate Ca  (OH)2.

Hydrated  lime or slaked lime is a dry powder obtained by a chemical reaction
that occurs when sufficient water is added to quicklime to satisfy its affinity for
water.  This form of lime is  also  referred to as hydrate.  The chemical composition
of hydrated lime depends on the calcium oxide content of the quicklime from which
it is derived.  A high calcium quicklime will provide a high calcium hydrated
lime containing 72 to 74  percent calcium oxide and 23 to 24 percent water of
hydration.

Pebble or crushed lime  is the most common form of quicklime, and the  effective
diameter of the pebbles varies from about 1/4-inch  to 2 inches.  This lime is
produced mostly in  rotary kilns.

Lump lime is the product whose pebbles or lumps range in effective diameter from
eight  down to two or three inches. Lump lime is produced in stationary vertical
kilns  and is crushed after burning.

Recalcined lime  is the product recovered after burning lime sludge from a water
softening or wastewater plant.  Calcination takes place in a rotary kiln or  any of
several types of  furnaces available in the industry. (See Section IX) .

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So far, no standard specifications have been issued for lime to be added to
wastewaters.  American Water Works Association (AWWA) Standard B202-54, for
quicklime used in water works, can be followed when specifying lime for waste-
water treatment.  Tables 4-1 and 4-2 summarize the main characteristics of lime
chemicals in general, and of quicklime in particular.

LIME IN WASTEWATER TREATMENT

Chemical treatment of municipal wastewaters has been practiced for almost a
century.  It is usually employed as a simpler and more flexible alternative to
secondary biological processes, although it is  not as effective in removing soluble
organic matter.  While chemical treatment has  never been widely practiced, it was
found particularly useful when colloidal solids and finely divided suspended
matter could not be removed by plain sedimentation, and coagulants had to be
added to the wastewater.   Chemical treatment has found its widest application in
the treatment of industrial wastes, where its flexibility, lower cost and simplicity
of operation and maintenance were all attractive assets to industry. The fact that
some trade wastes are either not amenable to biological treatment or toxic to the
microorganism population has also contributed to the wide application of chemical
treatment in the industrial  wastes field.

The advent  of AWT processes has brought a new popularity to chemical treatment.
The inability of conventional biological treatment to effectively remove nutrients,
i.e., nitrogen and phosphorus, and other organic and inorganic pollutants, paved
the way for  physical-chemical-biological treatment. These combined processes
have put the goal of wastewater reclamation and reuse well within the confines  of
present day technology-  The use of lime as a  coagulant in AWT is due to its well
established  efficacy in removing phosphorus from raw wastewaters.  Additional
benefits derived from lime  coagulation in the primary  treatment stage include the
increased removal of organic matter,  which decreases the organic load on
subsequent biological processes;  the  enhanced removal  of heavy metals and
viruses; and, as the pH  value is raised above  9.5, precipitation of magnesium
as magnesium hydroxide.  The addition of lime to raw wastewater is treated in
detail in Section VI.

LIME SLAKING

Slaking is a chemical process which makes quicklime reactive in water and
wastewater. "Slaking" and hydration are synonymous terms from a chemical
standpoint. As used in the lime industry, however, slaked lime is hydrated
quicklime containing considerable excess water. In contrast commercial
hydrated lime is a dry, ultrafine white powder, more concentrated than aqueous
forms of slaked quicklimes; however, chemically both are the same, i.e.   hydro-
xides .

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              Table 4-1.  CHARACTERISTICS OF LIME CHEMICALS
Chemical
Common name
Formula
Quicklime
CaO











Recovered lime
CaO



Dolomitic lime
CaO • MgO
(MgO content
varies)



Hydrated lime
Ca(OH)









Carbide lime
Ca(OH)2



Dolomitic hydrated
lime
Ca(OH), + Mg(OH)
z z







Limestone
(unbumed Itrne)
CaCO_
3


Dolomite
CaCO. • MgCO



Shipping data
Available
forma

Pebble
Crushed
Lump
Ground
Pulverized








Pellets




Pebble
Crushed
Lump
Ground
Pulverized


Powder
(Passes
200 mesh)








Powder
70 - 90%
(200 mesh)
Slurry


Monohydrated
powder
slaked at
atmos. press.
Dihydrate
powder
slaked at
high press .
and temp .


Powder
Granules
Ground


Lump or
crushed
Ground
Powder
Containers
and
requirements

Moisture proof
bags - 80-100
Ib . ; wood bbl . ;
bulk - CA .
Store dry max.
60 days; keep
container
closed.





Bulk delivery
direct from
kiln to
storage bin

Bags, 50-60
Ib.; bulk -
CA; bbl.




Bags - 50 Ib.;
Bbl. - 100 Ib.;
Bulk - C/L
(Store dry)







Bulk





Bags - 50 Ib . ;
Bbl.
Bulk - CA
(Store dry)







Bags - 50 Ib.;
80 Ib.
100 Ib. drums;
Bulk - CA

Bags - 50 Ib.;
Drums
Bulk - CA

Physical and chemical characteristics
Appearance
and
properties

White (light grey,
tan) lumps to
powder.
Unstable, caustic
irritant .
Slakes to hydrox-
ide slurry evolv-
ing heat .
Air slakes to
CaCO
Sat. Sol.
pH 12.4

Light grey, tan
Same properties
as quicklime


Same appearance
and properties as
quicklime,
except MgO
slakes slowly


White, 200-400
mesh; powder
free of lumps;
caustic, dusty
irritant;
absorbs H.O and
CO from air to
form Ca(HCO ) .
Sat. Sol.
pH 12.4

Coarse, grey
powder; grey
slurry (35%
solids)


Tan to white
powder free
of lumps
(-200 mesh);
caustic, dusty
irritant; Sat . Sol .
pH 12.4




White amorphous
powder; Sat. Sol.
pH 9 - 9 . 5


White, grey, tan;
Sat. Sol.
pH 9 - 9.5

Weight
Ib./cu. ft.2
(bulk density)

55 to 75
To calculate
hopper capacity -
use 60;
Sp.G., 3.2-3.4













Pebble, 60-65
Ground, 50-75
Lump, 50-65
Powder, 37-63,
Avg. 60
Sp.G., 3.2-3.4

35 to 50
To calculate
hopper capacity -
use 40; some 20
to 30 - use 23;
Sp. G., 2.3-2.4





35 to 55





Monohydrate
25 to 37;
Dihydrate
27 to 43;
To calculate
hopper capacity -
use 40;
Sp.G. , 2.65-2.75



Powder, 35-60;
Granules, 100 -
115;
Sp.G., 2.65-2.75

87 to 95;
Sp.G. , 2.8-2.9


Commercial
strength

70 to 96% CaO
(Below 88% can
be poor quality)










75 to 90% CaO




CaO -
55 to 57.5%;
MgO -
37.6 to 40.5%



Ca(OH)
82 to 98 %;
CaO -
62 to 74%
(Std. 70%)






95% Ca(OH)2





Monohydrate
Ca(OH) - 62%
MgO - 34%;
Dihydrate
Ca(OH) - 54%
Mg(OH) - 42%
(approx.)




96 to 99%




Varies



Solubility
in water
g/100 ml. @ 25°C

Reacts to form
Ca(OH)
Each Ibf of
quicklime will
form 1.16 to 1.32
Ib. of Ca(OH) ,
with 2 to 12%
grit, depending
on purity.




Same as
quicklime



Slakes to form
Ca(OH)2 slurry
plus MgO, which
slakes slowly



0.18 @ 0°C
0.16 @ 20°C
0.15 @ 30°C
0.077 @ 100°C







Same as Ca(OH)





Same as Ca(OH)










0.0013 @ 20°C
0.002 @ 100°C



Approx. same as
limestone


 Reproduced by permission of BIF, a Unit of General Signal Corporation.
' 1 Ib/cu ft = 16 kg/cu m

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          Table 4-2. CHARACTERISTICS OF MAIN GRADES OF QUICKLIME1
Grades
High calcium
Medium calcium
Low calcium

Dolomitic
Magnesium
Calcium content
> 88% CaO
75 - 88% CaO
<60 - 76% CaO

51 - 58% CaO
35 - 41% MgO
5 - 35% MgO
Dolomitic lime could also be
classed as a low calcium lime.
Form
Lump
Lump crushed
Pebble

Pellet
Ground
Pulverized

Particle size
3" - 8" and smaller
1/2" - 2 1/2" to dust
1/4" - 1 1/2" and smaller
to dust
20 to 100 mesh
-8 to -100 mesh
+100 to -200 mesh

      Burned or
       calcined
   Calcination temperature degrees F
 Slaking characteristics
       Soft


       Normal

       Over

       Hard
Calcined Just above the decomposition
temperature necessary—1,800 to 2,400°F
in a minimum time.
Calcined at about 2,400 to 2,600°F in a
minimum time.
Calcined at 2,500 to over 2,600°F.  If
lower, then time would be longer.
Calcined above 2,600°F.  If at a lower
temperature, time would be longer.
Very quick slaking and
temperature rise


Fast to medium slaking
and temperature rise
Medium to slow slaking
and temperature rise
Slow to very slow slaking
and temperature rise
        Reproduction by permission of BIF, a Unit of General Signal Corporation.

        Time of calcination, type of kiln, composition of limestone and the composition
        of the surrounding atmosphere (CO2 content in kiln), are all factors in the type
        of burned lime produced,  as to reactivity, etc. At a lower ratio (say 2.5 - 1)
        reaction could be quicker or at least similar.  Air slaking will increase slaking
        time and decrease the temperature rise.
Depending upon the proportions in which quicklime and excess water are com-
bined, the hydration process can yield a milk-of-lime, a lime slurry, or a viscous
lime paste of varying degrees of consistency.  As will be seen later, the different
types of slaked lime lend their names to the mechanical equipment used to mix
quicklime and water.  Predictably, this type of equipment is called a lime slaker
and it is described in Section V.
                                        10

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Lime slaking provides two available hydroxyl ions that react readily. The
process is exothermic, i.e., appreciable heat is emitted during the chemical
reaction.  The progression from limestone to slaked lime is shown below.
           Limestone
              Heat
                                  Calcination
         Carbon dioxide
                                           CaCO,

                                             +

                                             At

                                             I
                                            CO.
Quicklime



Quicklime

    +

  Water
           Slaked  lime
                              Slaking (Hydration)
                                                       CaO
                                                       CaO
                                                       H20
                                          Ca(OH)2
              Heat
                                             At
Several variables influence the required slaking time and quality of the resulting
hydrated lime. The National Lime Association lists the following:

    1.  Reactivity of the quicklime:  whether the quicklime is hard, soft, or
        medium burned will influence the speed of slaking and temperature
        attainment.

    2.  Particle size  and gradation of quicklime:  whether the quicklime is lump,
        pebble, ground, pulverized, or run-of-the-mill gradation is important.
        The finer sizes of the same  quality slake most rapidly.

    3.  Optimum amount of water:   whether too much or too little water is used.
        Limes vary in their optimum water: lime ratio.
                                     11

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    4.   Temperature of water:  whether slaking water is too cold or possibly
        too hot (steam) for the particular slaking conditions can affect the
        product.- Slow reacting limes need heated water; reactive limes do not.

    5.   Distribution of  water: the manner in which water  is introduced into the
        slaking chamber is a factor, and an even flow is desired.

    6.   Agitation:  too vigorous or insufficient agitation of  quicklime and water
        is undesirable.  Some agitation is necessary.

The standard tests to determine the optimum slaking conditions for a given type of
quicklime are AWWA B-202-65 and ASTM specification C110 on Physical Tests of
lime. The reactivity of quicklime in water is expressed as  the number of minutes
required for a temperature rise of 40 degrees Centrigrade  (104 F) .  Reactivity is
classified as follows:

    High-reactivity lime will  show a 40 C temperature rise in 3 minutes or less
    and will complete the reaction within  10 minutes.

    Medium-reactivity lime will show a 40 C temperature rise in 3 to 6 minutes
    and will complete the reaction in 10 to 20 minutes.

    Low-reactivity lime will require more than 6 minutes to show a 40 C
    temperature rise and will require more than 20 minutes to complete the
    reaction.

Under AWWA B-202 the particular quicklime will be  rejected if the sample tested
fails to produce more than a 10 C (50 F) rise in temperature in 3 minutes or  fails
to reach the maximum temperature in 20 minutes when slaked under test conditions
It should  be pointed out that these rules are applicable to commercial grades of
quicklime and are not intended to cover recalcined limes.  The standard test has
aroused considerable controversy.  A leading manufacturer of paste-type slaking
equipment has  the following comments:

     "This test  is intended to predict the slaking characteristics of quicklime.  It
     is obviously  slanted toward the slurry slaker approach, as it uses a 4: 1
     water: lime ratio.  We question its value.  As an example, an oyster-shell
     lime barely qulified as a low-reactive lime. When the  water was reduced to
     a 2: 1 ratio, it qualified as a medium-reactive lime. When repeated at 120 F,
     it reacted almost violently.  This same lime is being successfully slaked in
     a paste slaker."

The effect of water temperature and water-lime ratios on the slaking process will
 be further discussed when describing lime slakers in  (Section V) .
                                       12

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SELECTION OF LIME

As mentioned earlier, quicklime and hydrated lime are frequently used in water
and wastewater treatment.  Which type to use in a particular situation is influenced
by a number of factors, such as scale of operation, method cost, transportation
cost, and availability.  Material cost depends on whether bagged or bulk lime,
hydrated or quicklime  is used.   The choice between purchasing lime in bags or
in bulk is a direct function of rate of use.  Where chemical requirements are small,
bagged lime is preferred.  Conversely, at the larger treatment plants it is more
efficient and economical to handle bulk lime.  More details about lime delivery
and handling will be given in the next chapter.

The selection of quicklime or hydrated lime also depends on economics and avail-
ability.   The cost of hydrated lime  is about 30 percent greater than the cost of a
quicklime with the same calcium oxide content. The difference is due to the higher
production cost of the former and to higher transportation charges;  on the other
hand, the capital cost of the slaking equipment required when quicklime is used,
will  tend to offset the savings in material cost.   The  source of supply and  its
relation to transportation costs  also play an important  role in determining whether
quicklime or hydrated lime should be selected.  Other factors to consider are
storage space  available at the treatment plant, plant process layout in relation to
storage location, material handling problems, and the storage requirements of the
two types of lime.

In analyzing the factors discussed above,  the National Lime Association offers the
following comments:

    1.  Where lime consumption is small,  such  as 50 to 1,000 Ib/day, i.e., 1 to
        20 50-lb bags, bagged  hydrated lime is clearly indicated.  Probably this
        limit could be  extended to  1,500 Ib/day, but at this point, if lime is being
        consumed seven days a week, consumption will reach  22^ tons/month.
        Then, the economy of truck load bulk shipments of 15 to 20 tons starts to
        become attractive.  But then bulk silo storage and unloading facilities
        may have to be purchased  and installed.  If headroom is unavailable for
        a silo and there is ample ground floor space for storing bags, then the
        use of bagged  hydrate  may be justified  up to 2,000 Ib/day or even more.

    2.  With respect to bulk lime,  hydrate is generally indicated  up to 3 to
        4 tons/day (100-125 ton/month) over quicklime.   At this point the
        inherent economy of quicklime, in spite of slaking expense, should be
        considered. Again, due to peculiar plant conditions the use of hydrate
        up to  200 tons/month may be warranted; however,  above this figure it
        is quicklime's  province. Many of those plants that use quicklime in the
        lower ranges suggested for hydrate may be saving little or nothing due
        to greater losses of lime through air  slaking and recarbonation. This is
        particularly true if the quicklime is highly reactive, of small particle
        size,  and is used under humid conditions.  Hydrate is more stable and
        stores better.
                                      13

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   'j5  u6 ^S! W^th m°St en9ineering decisions, selection of the type of lime to be
used should be based on a detailed economic analysis, taking into account all the
factors just mentioned.  Table 4-3 summarizes the characteristics of quicklime
and hydrated lime.
      Table 4-3.  CHARACTERISTICS OF QUICKLIME AND HYDRATED LIME

Formula
Molecular Weight
Physical State
Particulate Size
Bulk Density, Ib/cu ft
Specific Gravity
Affinity for Water
Solubility
Stability in Bagged Storage
pH of Saturated Solution
Quicklime
CaO
56.1
White solid
Pulverized to lump
55 to 75
3.-2 to 3.4
Reacts quickly to form
Ca(OH)2 with heat of
formation, 490 Btu/lb.
Slightly, varies inversely
with temperature
In multiwalled bags, max.
60 days
12.4
Hydrated Lime
Ca(OH)2
74.1
White solid
Power, 200 to 400
mesh
35 to 50
2.3 to 2.4
Absorbs H2O and CO2
from air to form
CaCo3
Slightly, varies inversely
with temperature
Up to 6 months.in dry
tight bags
12.4
                                     14

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                                   SECTION V

                               HANDLING OF LIME
LIME DELIVERY

Lime can be delivered either in bags or in bulk. The choice between these two
forms depends mostly on the rate of chemical use at the treatment plant. Bagged
lime is delivered in truck or rail car.  Once at the  treatment plant, the bags are
transferred by hand truck, fork lift, or overhead crane to storage.  When  a large
number of bags are used, it is advantageous to purchase lime in palletized ship-
ments and use fork lift trucks to take the  pallets to storage.  In addition to saving
space and labor, this procedure also minimizes bag breakage. Other methods of
handling bagged lime will be reviewed when discussing in-plant transport
practices .  When lime use justifies bulk shipments, delivery can be made by
using covered hopper railroad cars, container and box cars, and a variety of
specially designed trucks.  Bulk delivery offers many advantages:  lower initial
cost; faster unloading; reduced labor cost for  handling; elimination of losses due
to torn bags and spillage; and improved safety, operating, and housekeeping
conditions.

The method of transport to  the plant is based primarily on economics.   When
railroad access is feasible and the rate of use justifies the cost of railroad  siding
and unloading facilities,  delivery by rail is usually cheaper since a railroad car
has three times the load carrying capacity of a bulk truck. The CCCSD water
reclamation plant-1- includes a complete in-plant railroad system connected  to the
Atchison, Topeka and Santa Fe railway mainline.   Three chemical unloading
platforms are being provided to unload lime, chlorine, ferric chloride, methanol,
and carbon dioxide.

Where a railroad siding is not practical or the  distance from the shipping point is
relatively short, a.trailer truck is a fast and economical way to deliver bulk ship-
ments.  Unlike rail cars, trucks can have access to nearly all areas within the
treatment plant; therefore,  there is more flexibility in selecting the location for
storage. Also, the length of unloading lines can be kept at a minimum  by parking
trucks close to the storage  facilities.  The pneumatic truck is available in two
basic  designs.  The more widely used is the self-unloading type, in which con-
veying air  is supplied by a positive displacement blower  mounted on the trailer.
Lime is  blown from the truck directly to storage through a 4-inch pipeline. The
second type of pneumatic truck requires an external souce of compressed air,  or
a separate mechanical conveyor  system, to  transfer lime to storage. Blower
trucks are  available in capacities varying from 20 to 36 cu m (700 to 1,300 cu  ft) .
The latter can deliver up to 20 tons of hydrated lime and 24 tons of quicklime. 2
The larger capacities are accommodated by dividing the trailer into compartments,
each provided with a sloping or hoppered bottom to facilitate material outflow.
Further details on  truck design an available in the literature.
                                     15

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LIME UNLOADING AND STORAGE

Unloading bagged lime is a simple operation and was previously described under
Lime Delivery.  The following storage precautions are recommended by the
National Lime Association:

    "Storage areas  for bagged materials must be covered to prevent rain
    from wetting the bags.  Hydrated lime is normally packed in multiwall
    paper bags which are not resistant to free water or humid air.  Quicklime
    is also packaged in multiwall paper bags,  one or more of the plies moisture
    proofed. This  moisture proofing is effective in preventing the entrance of
    humid air but is not usually designed to be effective against liquid water.
    This is particularly true at the  valve where humid air or liquid water may
    enter more readily  and start slaking the lime; and the heat and swelling
    will cause the bags to burst.  Hence, quicklime storage must be designed
    to avoid any accidental contact  with water. As an example,  in one storage
    warehouse, a good tight roof was provided, but the bags were stored close
    to the door. This door was inadvertently  left open a few inches during a
    driving rain which wetted the bags at the  bottom of the pile. These broke
    open and the pile collapsed, resulting in an expensive clean-up operation
    together with considerable loss of lime. Because of the heat generated in
    accidental slaking of lime, bagged quicklime should never be  stored
    adjacent or too close to combustible materials."

    "Hydrated lime may be stacked  as much as twenty bags high without
    injuring the bottom bags (higher when palletized) .  In  dry  storage,
    hydrate may be stored for periods up to one year without encountering
    serious deterioration.  When stored for  extended periods, a slight
    increment of carbon dioxide may be found at the corner of the bag near
    the valve.  This carbonation  during storage is usually evident only after
    storage for at least sbc months  and then does not penetrate more than
    about one-half  inch into the bag near the valve."

     "Quicklime will deteriorate in storage at a much more rapid  rate than
    hydrated lime.  Under good storage conditions,  with multiwall moisture
    proofed bags,  quicklime may be held as long as  six months, but in
    general should not be stored over three months.  Care should  be
    exercised to use the material in the order  it is received, rather than
    maintain an inactive reserve  stock which may not be consumed for
    several months."

 Bulk shipments of  lime can  be unloaded from rail cars or trailer trucks by
 mechanical or pneumatic equipment.  The latter method has  gained wide accept-
 ance because of its simplicity and high unloading speed. Either system can be
 used to unload lime when effective particle diameters are smaller than 2^-inch
 (6.4  cm)  but H-inch (3.2 cm) or smaller is preferable for efficient pneumatic
 conveying.2
                                      16

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Mechanical handling usually involves several steps.  Lime is first transferred
from delivery car or truck into a receiver hopper. From this hopper, some type
of conveyor (screw, belt, etc.) is used to feed the material to the elevating
equipment  (bucket elevator, screw-lift, etc.) which finally discharges it into the
storage bin or silo.  The basic equipment can be arranged in a variety of ways to
suit each particular situation,  e.g.,  an inclined screw conveyor can be used to
transfer lime directly from receiving hopper to storage bin  when headroom is
available and the silo is of limited height. Table 5-1  gives information published
by the National Lime Association for preliminary sizing of mechanical conveyors
and elevators.  Mechanical handling  of lime will be discussed in more detail under
In Plant Transport Methods .
    Table 5-1 .  SIZING DATA FOR SCREW CONVEYORS AND BUCKET ELEVATORS
                              Screw Conveyor Data
Screw size
(inches)
6
9
12
16
Normal rpm
50
50
50
50
Tons quicklime
(per hour)
2 - 2-1/2
7-8
15 - 20
45 - 50
                              Bucket Elevator Data
Bucket size
(inches)

6x4
8x5
10 x 6
12 x 7
14 x 7
Bucket spacing
cm
33
41
46
46
48
inches
13
16
18
18
19
Speed
m/min
69
70
82
93
110
ft/min
225
230
270
305
360
Tons quicklime
(per hour)

8-10
15 - 20
30 - 35
58 - 65
50 - 60
                                     17

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Lime unloading which uses pneumatic conveying equipment usually results in a
simpler and more flexible arrangement than  that obtained by mechanical con-
veyors.  Dusting, a common occurrence around lime unloading operations, is
reduced to a minimum and can be completely eliminated where a negative pres-
sures system is used.  These advantages have to be weighted against greater
power requirements  for pneumatic than for mechanical conveying systems of
equal capacity.  Safety considerations also favor the pneumatic approach, since
there are no moving parts and,  therefore, no  risk of injury to the operator.  The
pneumatic conveyor transports material in suspension by means of a high velocity
air stream.  For quicklime and hydrated lime, this velocity varies from 914 to
1520 meters per minute  (3,000 to 5,000 fpm) .  The higher values are required to
blow quicklime because of its higher bulk density (880-960 kg/cu m or 55-60 lb/
cu ft) than pebble quicklime bulk density (400-560 kg/cu m or 25-25 Ib/cu ft) for
hydrate.

Two types of in-plant pneumatic systems are commonly used to unload dry
chemicals:  negative pressure (vacuum) and  positive/negative pneumatic con-
veyors.  The equipment is commonly provided as  a package.  The lighter units
can be mounted on skids, casters,  or wagon type  trailers when the application
calls for a portable unit. The higher capacity unloading systems are normally
stationary.  The negative pressure unloading system consists of an intake nozzle,
a receiver-separator, a vacuum pump, accessories, and interconnecting piping.

To unload a rail car or truck, the intake nozzle is attached to the vehicle hoppers
through quick-opening couplings.  The intake assembly is usually mounted on a
skid base to facilitate handling.  Lime is drawn directly into the conveying line
by air flow under the suction created by the vacuum pump.  The air stream then
conveys  the  fluidized material to  the  receiver-separator (usually a bag-type
filter) .  In the filter  receiver lime separates from  the air by cyclonic action,  drops
to the cone shaped bottom and is discharged to the storage silos through a rotary
valve feeder.  Conveying air is cleaned as it flows through the filter bags and,
after passing through the vacuum pump, is exhausted to the atmosphere.

Vacuum systems are limited to operating pressures of 25 to 30 cm of  (10 to 12 in.)
Hg below atmospheric pressure and by the number of storage bins which can be
filled from a single  receiver-separator.  When pressure losses exceed 30cm
 (12 in.)  Hg,  or when lime is stored in a large number of silos, a positive/negative
pneumatic conveyor is required .

Positive pressure conveyors are normally used when material must be delivered to
several separated storage bins located at considerable distances from the delivery
station.  In a positive pressure system,  the conveying stream is created by the air
discharged from a blower,  and  this air "pushes" the solids through the conveying
line.  Normally, a rotary positive displacement unit or, less frequently, a cen-
trifugal blower is used. Most positive pressure systems operate within the range
of the positive displacement blower or up to 1.05 kg/sq cm (15 psig)
                                     18

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A positive/negative pressure pneumatic conveyor has certain features of the
vacuum system and the distribution flexibility of the positive pressure system.
A vacuum system can be converted to a combination system by connecting the
vacuum pump exhaust pipe to the rotary valve feeder of the receiver-separator.
Thus material collected in the separator is discharged into a positive conveying
line. The rotary valve acts as an air lock between the negative and positive sides
of the system.  Material is then distributed to the storage bins through individual
feed lines or through a series of two-way diverter valves.  A typical positive/
negative pneumatic conveyor is shown in Fig. 5-1.

Quicklime and hydrated lime can be stored in hopper-bottom concrete or steel
facilities since both are noncorrosive materials. The interior of storage vessels
should not be painted to avoid the possibility of product contamination.  Storage
bins or silos must be airtight to prevent air slaking caused by the moisture con-
tent of atmospheric air. In this  respect,  hydrated lime is  more stable than
quicklime when stored for extended periods.  There are some  differences between
quicklime and hydrated lime which must be considered in  designing the storage
facilities.  Quicklime lime is generally free-flowing and will discharge readily
from storage bins if the hopper bottoms have a minimum slope  of 60  degrees from
the horizontal.  This  value is related to the  angle,of repose of quicklime which, on
the average, can vary between 50 to 55 degrees.   Nevertheless, it  is considered
good practice to provide some type of flow-aiding device to regulate material dis-
charge under all conditions. Hydrated lime, on the other  hand, has a tendency to
arch because of its physical characteristics and much smaller particle size.
Therefore, more elaborate mechanical or aeration activators are necessary to
insure a continuous discharge of material from storage. Detailed descriptions of
the various types of devices commonly used to facilitate free flow of material from
storage can be found in references 2 and 4.

Sizing of storage facilities should be based on daily lime demand, type and
reliability of delivery, future chemical requirements, and flexibility of expansion.
A minimum sufficient storage should be provided to supply a 7-day  lime demand,
however, sufficient storage to supply lime for 2 to 3 weeks is desirable.  In any
case, the total storage volume should be at least 50 percent greater  than the
capacity of ±he delivery rail car or truck to  insure adequate lime supply between
shipments.  Average bulk density values used in structural design are 640 kg/
cu m (40 Ib/cu ft) for hydrated lime  and 960 kg/cu m  (60 Ib/cu ft) for quicklime.3

LIME FEEDERS

The term feeder, as used in this report, refers to the mechanical devices employed
to continuously deliver a measured amount  of dry lime to  the mixing equipment.
Solution feeders are mostly  limited to the smallest treatment plants,  where bagged
hydrated lime is  handled and process lime is prepared in  batch or intermittent
form.

There are two basic types of dry chemical feeders:  volumetric and  gravimetric.
Each type is  in turn available in a variety of designs and models, according to
the preferences of equipment manufacturers.  Regardless  of type, all dry feeders
share two essential components:
                                      19

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                                    DUST COLLECTOR
   FILTER -
   RECEIVER
ROTARY
AIR LOCK
                            TYPICAL
                            DIVERTER
                            VALVE
                                             INTAKE MANIFOLD
                              BLOWER AND MOTOR
       MATERIAL
       UNLOADING NOZZLE
           Figure 5-1  Typical positive-negative pneumatic conveying system

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    1.   A day storage hopper, where material is transferred from the lime silos
        to provide a uniform supply to the feeding element. This hopper has a
        contracting bottom through which the chemical flows by gravity.

    2.   An adjustable feeding element to vary the rate of chemical feed.  The
        feed  rate is controlled by volume (volumetric feeder) or by weight
        (gravimetric feeder) .

When hydrated lime is used,  a solution tank is frequently added to mix lime with
water and form a slurry, which is then fed to the process.  If quicklime is used,
the solution tank is replaced  by the slaking equipment.

Day Storage  Hoppers

The capacity  of the day hopper should be sufficient to store no less than eight
hours' supply at the  maximum feed rate.  In most cases, the hopper bottom  slopes
at least 60 degrees.   This  angle  would normally assure free flow of quicklime
independent of particle size.  On the other  hand,  hydrated lime will tend to
arch or bridge, even if the bottom slope is steeper than  60 degrees.  Closely
related to bridging is the phenomenon of flooding which occurs when an arch of
material suddenly collapses and inundates the feeder. Various types of agitating
devices are used to prevent arching.  Several manufacturers of chemical feeders
 (Bif, Infilco,  Wallace & Tiernan, among others) incorporate paddle type (internal)
or pulsating diaphragm type  (external) agitators as part of their feeding equip-
ment.  When the storage hopper is not included with the feeder,  three general
classes of agitators are available:  electromagnetic or electromechanic vibrators
as manufactured, by Eriez, Jeffrey,  Syntron and others; aerators  (air pads and
air diffusers) ,  as manufactured by Airnetics, Bibco, National and others;  and
the live-bottom bins  originally developed by Vibra Screw.  Regardless of their
operating principle,  agitators aim at promoting the flow  of bulk materials that
tend to pack in storage containers.  It is  critical to stop  agitation when the feeder
is not  in use,  since  continuous vibration could actually defeat its purpose by
deaerating the material and increasing its density  (packing) .

The flood prevention device most commonly used is the rotary vane inlet valve
which allows  only a fixed amount  of material to discharge from the storage hopper
at any given time. The rotary valve is also utilized as a volumetric feeder.

Volumetric Feeders

Volumetric feeders deliver a  constant, preset volume of  chemical regardless of
changes in material density.  The accuracy of the volumetric feeder is closely
related to the physical characteristics of  the chemical and is greater for uniform,
cohesive materials which tend to flow readily. On  the other hand, this type of
feeder is less reliable when the density of the material handled varies. Varia-
tions in density can be compensated by recalibrating the feeder whenever a
change occurs.  Nevertheless, in the case of hydrate and quicklime, which
exhibit wide variations in bulk density, the error of a volumetric feeder is
normally in the 5 percent range by volume.
                                      21

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Most volumetric feeders operate on the principle of displacing a predetermined
volume of chemical from the point where it leaves the storage hopper to the point
of material discharge.  The method used to move the material can be a travelling
 (Wallace & Tiernan) or vibrating  (Vibra-Screw)  belt;  a screw-type feeder (BIF,
Vibra-Screw  W&T);  an oscillating throat at the base of a hopper  (BIF); a roll-
type feeder (W&T); a rotary vane or paddle (BIF); or a vibrating feeder    _
 (Syntron)   Although a few other types of volumetric feeders are still found in
treatment plants,2 the types listed above are the most frequently used._ The
screw or helical conveyor appears to have gained wide acceptance in lime feeding
applications and each of the leading manufacturers offer several modifications of
the basic configuration.  A screw feeder is a positive displacement device that
delivers a constant stream of chemical from the storage hopper.  Feeder capacity
can be varied by simply adjusting the speed of the screw shaft.  Fig.  5-2
illustrates a typical screw type feeder.  The capacity range of volumetric feeders
varies widely from as low as  6 to 1 for  the roll-type, which is driven by a con-
stant speed motor, up to 200 to 1 for a screw feeder which is equipped with
variable speed drive.  For best results, lime feeders should be selected to
operate in the 40 to 1 range.  Volumetric feeders are considerably cheaper than
the gravimetric type, therefore their application can be justified when only
limited funds "are available or when greater chemical feeding accuracy is not
required.

Gravimetric Feeders

A gravimetric feeder is indicated when chemical dosage must be accurately and
reliably measured.  In this type  of feeder,  the quantity of material discharged in
a unit of time is continuously weighed and the  speed of operation automatically
adjusted to maintain  a constant weight.  Consequently, feeder accuracy is not
affected by changes in bulk density and variations in particle  size.  Despite its
higher first cost, a gravimetric lime feeder is  often warranted, even for small
treatment plants. Apart from eliminating the need for recalibration, savings in
chemicals are frequently achieved due to greater feeding accuracy and reliability,
i.e.,  operation and maintenance  costs are reduced.

Gravimetric feeders are available in three types:  pivoted belt, rigid belt and
loss-in-weight hopper. The two belt types include an endless traveling  belt
conveyor  supported on weighting scales, a counter-weight assembly to balance
the load on the belt and controls  to automatically adjust the rate of feeding.  The
loss-in-weight type uses the loss of weight in  a hopper, rather than the
instantaneous  weight on a belt conveyor, to adjust the material feed rate.  Belt
type gravimetric feeders are available from a number  of manufacturers including
BIF, Jeffrey, Syntron, Vibra-Screw and W&T. Flow of material is normally
regulated  by throttling an inlet gate located in the passage between storage
hopper and belt;  by changing the speed of  a rotary inlet valve, or by changing
the belt speed. Control action can be achieved by mechanical, pneumatic,
electric or electronic means.  Fig . 5-3  shows a typical gravimetric feeder.
                                      22

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Ul
                                MOTOR
                         GEAR REDUCER
                 FEED RATE REGISTER AND
                    FEED ADJUSTING KNOB
                      SOLUTION CHAMBER
                                                                                               HOPPER
ROTATING AND
RECIPROCATING
FEED SCREW
                                                                                               JET MIXER
                                                                                    DWG. NO. 1643
                    Figure  5-2  Typical screw type volumetric feeder  (courtesy of Wallace & Tiernan,

                                division of Pennwalt Corporation)

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Figure 5-3  Typical belt type gravimetric feeder (courtesy of Wallace & Tiernan,
           division of Pennwalt Corporation)

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The standard capacity range of a gravimetric feeder  (10-100 to 1) can be greatly
increased by combination of control modes or the addition of equipment options.
For instance, Wallace & Tiernan inlet gate or rotary valve control (10 to 1 range)
can be combined with a variable belt speed control (20 to 1)  for a combined range
of 200 to 1.  This can be further increased by adding a 10 to 1 gear box for a
resultant capacity range  of 2000 to 1.  The loss-in-weight type, developed by
BIF, is electronically controlled and has a capacity range of 10 to 1.  Most
manufacturers of gravimetric feeders will guarantee a minimum accuracy of
within + 1.0 percent, by weight, of the  set rate. For uniform and free flowing
materials, the error can  be reduced to + 0.25 percent.

DISSOLVING OF LIME

As indicated previously, before a measured amount of lime is fed to water or
wastewater, it is first mixed with water either in a dissolving tank (hydrated
lime) or in a slaker  (quicklime) . In each case,  mixing of lime and water is done
for different reasons. Hydrated lime is  prewetted to facilitate transport to the
point of application and improve dispersion and  efficency after it is added to the
process.  In general quicklime does not react uniformly with water and therefore
should  never be applied  dry.  The only exception would be a high calcium, soft
burned quicklime of small particle size and  uniform grading.  (The most common
form of commercial lime is the crushed or pebble type,  which ranges in effective
partial diameter from about 2 to 1/4 inches)  .

Lime Dissolvers

Both volumetric and gravimetric feeders handling hydrate can be readily fitted
with dissolving or solution tanks.  Dissolvers are often supplied as part of a
packaged feeder-solution system.  Dissolvers are usually sized to provide three
to five minutes of detention at  the maximum  rate  of feed.  Concentration of lime
solution is usually kept at or below 6 percent. Mixing and agitation is
accomplished by water or compressed air jets at a minimum pressure of 2.8 kg/
sq cm  (40 psi) or by mechanical agitators.   Depending on the solution tank
size, one or two impeller type agitators  are provided to effect a more rapid and
thorough mixing of lime and water. Due to the noncorrosive properties of lime
solutions, dissolving tanks are usually  made of steel.

Lime Slakers

A lime slaker is used to add water to quicklime and accomplish the slaking
reaction. Two basic types of slakers are available:   detention type which pro-
duces a lime slurry, and pug mill or paste type  which produces  a viscous,  paste-
like product.  Both types are provided with dilution tanks to lower the concentra-
tion of slaked lime to that of a  milk-of-lime  (thin slurry) .  They  also include grit
removal equipment, vapor and dust separators,  and thermostatic controls for
personnel safety.
                                     25

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The major difference between the two types of slakers rests in the ratio, by
weight, in which  water and lime are  mixed.  In detention slakers this ratio
averages 3i to 1 on a weight basis, while in paste slakers, the proportion of
water to lime is about 2 to 1.  In  mixing water  and quicklime, two extreme con-
ditions  should be avoided. When too much water is added, i.e., water-lime
ratios in excess of 6 to 1,  the surface of the material hydrates rapidly forming
a coating which hinders water penetration to the center of the particle disintegra-
tion.  This reaction is commonly called  "downing" and results in delayed or
incomplete slaking and coarser hydrate particles.  Downing is more likely to
occur when cold slaking water is used.  On the other hand,  if insufficient water
is added, "burning" will occur as a result of excessive reaction temperature
 (120-260 C) . Some slaking water escapes as  steam and this loss  will leave a
considerable portion of particles unhydrated.

Dentention Slakers - The detention type slaker is manufactured  in the
United States by BIF and Dorr-Oliver at the present time.  The BIF unit is divided
in two,  three, or four compartments, depending on slaker capacity and detention
time needed for complete hydration.  Quicklime is fed continuously to the first
compartment where water is added and the mixture blended  by a propeller-type
agitator. The lime slurry formed overflows into the second compartment where
the slaking process is completed. Mechanical  agitation is provided to promote
hydration by continuously exposing lime  particles to moisture.  In case  a third
and fourth  slaking compartment is required, the principle of operation is the  same
and each additional compartment will be equipped with a separate agitator. From
the last slaking compartment the hot slurry overflows into a  separation chamber
where it is further diluted and agitated by water jets to  promote settling of  grit
particles.  In the large capacity models, i.e.,  above 450 kg/hr  (1000 Ib/hr) ,  a
helical  screw, driven by an electric motor,  is recommended for continuous
removal of grit.  Below 1000 Ib/hr (450 kg/hr)  grit removal is done manually.
Finally, the milk-of-lime slurry flows over a weir into the outlet. Fig.  5-4 shows
the BIF  detention slaker .

Due to the higher water-to-lime ratio, a detention type slaker operates at a much
lower temperature than a paste slaker;  consequently, the slaking process requires
a longer retention time to reach completion (about 20 to 30 minutes as compared to
5 to 10 minutes for paste slakers) . To accelerate the hydration reaction, the  body
of a detention slaker is insulated to reduce heat losses. A coil type heat exchanger
is also offered as an option to preheat the slaking water by recovering some of the
heat of hydration from the mixing compartment.  If hot water is available, it can
be blended with slaking water to obtain a desirable process temperature of 77-
88 C .  It should be pointed out that the ideal slaking temperature is closely related
to the reactivity of quicklime.   If the material handled is a  quick reacting lime
("soft" burned) , water at ambient temperature would still produce quick slaking
and temperature  rise.  Conversely, "hard" burned  quicklime would normally
slake very  slowly  and the addition of  cold  water will tend  to further delay the
reaction.
                                     26

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ro
                      LIME  FEEDER
              ACCESS COVER
               GRIT
               REMOVER
               HEAT  EXCHANGER
                   (OPTIONAL)
                                                                                   FEEDER
                                                                                    INLET
                                                                                        WATER
                                                                                        CONTROL
                                         DISCHARGE
                                            WEIR
                                                                                     MIXER
         DUST AND
         VAPOR
         REMOVER

DILUTION  WATER
              Figure 5-4  Typical detention type slaker (courtesy of BIF, a unit of General Signal Co.)

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Several methods can be used to control the supply of slaking water.  Manual
control is the simplest and can be used when the rate of lime feed is fairly constant.
As will be seen later however, feeder operation is often controlled by variables
such as wastewater flow and pH;  then the amount of water of hydration has to be
adjusted accordingly to maintain  the required water-to-lime ratio.

Paste Slakers - Paste type slakers are manufactured by Wallace & Tiernan and
Infilco.  The design and operation principle of these units are very similar so the
description now given applies to  both.  The slaker body is divided into two com-
partments . Quicklime and water  are  fed continuously to the inlet end of the
slaking compartment in a ratio of approximately 2 to 1  (water to quicklime) by
weight. The lime-water mixture is thoroughly mixed and moved to the discharge
end of this compartment by two sets of counter-rotating (pug mill) paddles. The
mixing paddle shafts are driven by a gear reduction unit.  The torque exerted on
the gear reduction unit controls the hydration water supply through a torque
actuated valve.  An increase in torque, indicating an increase in viscosity of the
paste, opens  the water valve and admits additional water to the inlet end of the
slaking compartment.  High consistency of the paste is maintained to carry grit
and inert material through the slaking compartment.  When it reaches the end of
the first compartment, slaked lime flows over a weir and drops into the grit
removal compartment.  As it moves over the weir, the heavy paste is broken by
water jets and diluted to a lime slurry.  Water-to-lime ratio of the slurry varies
with changes in slaker input, since the supply of dilution water is normally
constant.  Once in the second compartment, rakes attached to the same shaft as
the mixing paddles agitate the slurry to keep the lime particles in suspension.
The slurry then flows under a dust shield and over a weir to the discharge port
in the slaker. An external grit conveyor is attached to the discharge compartment.
A classifier is provided in the bottom section of the grit conveyor for separation of
the grit from  the slaked lime.  Water  is applied in the grit conveyor to continuously
wash lime from the grit particles. Fig. 5-5 shows the Wallace & Tiernan paste
slaker.

Because of the low water to quicklime ratio, more heat is generated during the
slaking reaction in a paste slaker than in a detention type unit.  Therefore the
former operates at higher temperatures  (190-210 F) and shorter detention times.
The high operating temperature also  eliminates the need to insulate the  slaker
body.  The lower detention time required by the paste slaker results in a more
compact design of this unit as compared  with a detention type slaker of the same
capacity.

IN-PLANT TRANSPORT METHODS

In the small treatment facility using bagged hydrated lime, in-plant handling is
commonly limited to taking bags from storage,  either manually or with the aid of
a hand truck or fork lift, and emptying them into the storage hopper of the
chemical feeder.  To facilitate bag dumping,  day hoppers can be equipped  with
a filling canopy which includes a bag splitter, a screen and a dust collector. As
both the treatment plant size and  the chemical requirements increase, the methods
of transporting lime become more elaborate.  In-plant transport systems can be
divided into two general groups:   mechanical and pneumatic.
                                      28

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    QUICKLIME
              \Q
TORQUE CONTROLLED WATER VALVE
         DUST SHIELD
                                                                                           RIT DISCHARGE
           PADDLES           DILUTION CHAMBER

SLAKING COMPARTMENT      SLURRY DISCHARGE SECTION

                                    CLASSIFIER
                     GRIT ELEVATOR
                                      WATER FOR GRIT WASHING
                               Figure 5-5  Typical paste type slaker
             (courtesy of Wallace £ Tiernan, division of Pennwalt Corporation)

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As was mentioned before,  mechanical conveyors require less power to operate
per ton of solids handled than pneumatic conveyors, and therefore the type of
transport system to use is a matter of careful evaluation.  It is common to combine
pneumatic and  mechanical units and retain the  best features of each method to
achieve flexibility, reliability and economy of operation.

Mechanical Transport

In-plant mechanical transport systems include a variety of conveying devices
used to move material from one point to another which is at either the same or a
different elevation.  Mechanical conveyors and elevators were briefly discussed
under lime unloading methods.   They find further application where chemicals
have to be transferred from storage to the point of usage. Where lime recalcination
is practiced,  mechanical conveyors can be used to return the reclaimed product to
storage and also to transport  the inert ash to a loading area prior to final disposal.
Of the various types of conveying and elevating equipment  found in industrial
plants, only a few have  been  used in water and wastewater treatment plants.  Belt
and screw conveyors, bucket elevators, Screw-Lifts, and combination conveyor-
elevator  (Bulk-Flo)  are the types most commonly seen in municipal applications.

Belt conveyors  are the most versatile and widely used type of mechanical conveyor
They can transport dry materials over paths beyond the capability of any other con-
veying device.  However, belt conveyors are not recommended for the transport
of lime, particularly hydrate  or reclaimed lime, because of dusting.   The dust
problem can be solved by  adding covers over the conveyor and an exhaust air
system to collect the dust. This  configuration however, eliminates some of the
basic  advantages of the belt conveyor concept and  there are simpler ways  to
approach a dusting situation .

Screw conveyors are one of the oldest and simplest methods of handling granular
materials which exhibit noncorrosive and low abrasion characteristics .  The basic
screw conveyor is compact and can be mounted in horizontal and inclined positions.
This versatility  is particularly advantageous  in congested locations,  when the
distance does not exceed about 60 meters (200 feet) , and the slopes are not greater
than about 35 degrees. Preliminary sizing information for  screw conveyors has
been given in Table 5-1.

Bucket elevators are widely used to elevate bulk materials.  Bucket elevators are
available in two types:  chain-mounted and belt-mounted, and the latter is used
when handling abrasive materials .  Data for preliminary sizing of bucket elevators
has also been given in Table  5-1.

The Screw-Lift is a vertical screw conveyor installed in a dust proof enclosure.
The unit is  compact and  it is used to elevate both granular and pulverized
materials. The Screw-Lift is normally fed by a horizontal screw conveyor, and
therefore it could also be considered as a combination conveyor-elevator.

Bulk-Flo is an enclosed elevator and conveyor which can carry bulk materials in
horizontal, vertical or  inclined  positions.  This flexibility can then  be used to
replace several straight line conveyors with a single unit.
                                      30

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Mechanical material  handling  is a specialized field and the final design of a
mechanical system for in-plant conveying of lime should be done in consultation
with the equipment manufacturers.   Rexnord (previously Rex Chainbelt) and
Link-Belt are two companies in the wastewater treatment field with extensive
experience in materials handling .

Pneumatic Transport

The basic types of pneumatic transport systems  were described earlier under the
section entitled Transport Methods.  Pneumatic conveying can also be used for
in-plant lime transport.  This  approach becomes more advantageous as the size of
the plant increases and chemical processes become more sophisticated.  Pneumatic
conveying is probably  the only streamlined means of moving  chemicals in a large
treatment facility where the process areas are interconnected  through piping
tunnels.  As an example, in  the CCCSD water reclamation plant,  quicklime and
recalcined lime will be handled in pneumatic conveying systems.  These systems
include quicklime unloading; transfer of a mixture of quicklime and recalcined
lime over a distance  of about 120 meters or 400 feet from the storage silos to the
slakers day hopper;  and  return of reclaimed lime to storage  (a distance of about
300 meters  or 1,000 feet)  . Also, inert ash is transported pneumatically  from the
sludge burning furnaces  to holding hoppers from where it is loaded into trucks
for final disposal.

Pneumatic conveying is still much as an  art as  it is a science. Design depends
largely on practical knowledge, and the judgment and experience of the equipment
manufacturers plays  a key role. A number of companies specialize in the pneumatic
field (Butler,  Fuller,  Semco,  Sprout-Waldron)  .  The more progressive manu-
facturers would normally size  a conveying system only after the particular material
has been tested in a  pilot plant.  Close cooperation between the purchaser and the
manufacturer is required to arrive  at  a  sound  design.  A satisfactory approach
could be  for the purchaser to prepare a comprehensive performance specification,
preceded by a careful assessment of the knowledge and experience of the equipment
manufacturers.

SAFETY CONSIDERATIONS

Although lime  is considered  a  nonhazardous chemical, certain precautions should
be  observed regarding the  caustic nature of the  material.   A comprehensive
review of safety practices can  be found in reference 2 of this section.
                                      31

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                             REFERENCES
1.   Brown and Caldwell.  Plans and Specifications for Water Reclamation
    Plant, Stage 5A-Phase 1.  Central Contra Costa Sanitary District,
    California, April,  1973.

2.   Lime Handling, Application, and Storage in Treatment Processes.
    National Lime Association.  Washington, D .C . Bulletin 213.  May, 1971.
    pG-18.

3.   Lime for Water  and Wastewater Treatment.  BIF .  Providence, R.I.,  Ref
    No. 1.21-24. June, 1969.  19 p.

4.   Kraus, M.N. Pneumatic Conveying-General Considerations, Equipment
    and Controls.  Reprinted from Chemical Engineering. New York, N.Y.
    31 p.  April, 1965.
                               32

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                                  SECTION VI

                         LIQUID PROCESSING WITH LIME
GENERAL CONSIDERATIONS

Lime can be added to wastewater either ahead of primary treatment or following
biological treatment. In the latter case,  lime addition is mostly practiced to
remove phosphorus, i.e. , as  part of a typical tertiary treatment sequence. 1

On the other hand, when the use of lime in the primary treatment stage is  coupled
with biological treatment, much of the organic carbon load is removed from sub-
sequent treatment processes.  This reduction in the organic carbon load reduces
the  needed  size of subsequent biological units and allows stable oxidation  of
ammonia to nitrate (nitrification) .2  Besides the removal of organic matter, lime
improves the removal of phosphorus, heavy metals ,  grease  and viruses .  Although
the  use of lime for phosphorus removal is less efficient with raw wastewaters than
it is in tertiary treatment, the residual phosphorus concentration in the primary
effluent  is sufficiently low for effective biological uptake in the activated sludge
process.3/4

The improved BOD and suspended solids removal associated with chemical addi-
tion greatly increases the mass of raw sludge settled in the primary tanks. When
excess sludge from biological treatment is returned to the primaries, the result-
ing  physical-chemical-biological precipitation contains all  of the sludge produced
in the liquid treatment phase.  Precipitation of all sludges  in a single basin can
simplify subsequent handling of solids.  It has generally been found that primary
sludges  more readily dewater than secondary sludges.^ Methods for computing
sludge quantities are presented in Section X.

PROCESS CHEMISTRY

Many chemical reactions  occur when lime is  added to raw wastewater. When
lime alone is added, the reactions producing most of the sludge involve calcium,
magnesium and phosphorus.  Other chemical reactions take place coincidentally,
such as  changes in alkalinity, and precipitation or  adsorption of heavy metals.
However, calcium, magnesium and phosphorus precipitation  are responsible
for  the bulk of the inorganic chemical sludge production.   At the same time,
chemical coagulation of the  raw sewage solids takes place,  resulting in the co-
precipitation of the organic sludge.  The chemistry of the process  is extra-
ordinarily complex, so only a process-oriented review is presented.
                                    33

-------
Calcium Carbonate  Precipitation
At moderate to high lime doses, the bulk of the calcium added to the process is
precipitated as calcium carbonate according to the reaction:
    Ca(OH)2 + Ca(HC03)2 - >2CaCO3 + 2^0                        (6-1)

Water chemistry equilibria would suggest much lower levels of soluble calcium
than do actually occur in chemical primary effluents where lime addition is
practiced.  In other words, the reaction indicated in equation  6-1 usually does
not closely  approach equilibrium conditions as might be  defined  by water
chemistry transposed from water softening theory.  Considering the host of con-
stituents in  raw wastewater not present in raw municipal water supplies, it is not
surprising to find that there may be competitive reactions that inhibit calcium
carbonate precipitation.

Schmidt and McKinney,3 in fact,  demonstrated with jar tests that polyphosphate
could completely inhibit calcium carbonate precipitation up to  a pH of 9.5 Ortho-
phosphate also caused inhibition of the reactions , as shown in Figure 6-1 .  The
theory cited for this  inhibition is that phosphorus is adsorbed on the growing
faces of the  calcium carbonate crystal, preventing further calcium carbonate
growth.  Schmid and McKinney concluded that lime  recovery is not justified for
low pH operations, since there is very little, if any, calcium carbonate preci-
pitation below a pH of 9 . 5 .

Control of nucleation of the calcium carbonate crystal and crystalline growth are
important factors governing the extent of completion of the reaction indicated in
equation 6-1.  Allowing the reaction to take place in the presence of calcium
carbonate crystals enhances both the  reaction rate and the extent of its comple-
tion.  In terms of the treatment process, crystals can be recycled from the sedi-
mentation tank underflow to encourage calcium carbonate precipitation.  This
principle has long been recognized in water treatment practice and has led to the
development of solids contact-type clarifiers.  For instance, Hartung7 found that
in a water softening  operation soluble calcium decreased when the solids concen-
tration in the reaction chamber was increased from  one and a half to two  percent
total solids by weight. Stone^ found in both laboratory and full-scale water
softening tests that the soluble calcium level was decreased by solids recycle.  It
was concluded that the lime dose  could be reduced for the same effluent hardness
with solids recycle;  or alternatively,  at the same lime dose, effluent hardness
could be reduced by solids recycle .

In a raw wastewater  application,  Horstkotte,  et al.9 found that with no  solids
recycle, the hardness increase  across the primary  sedimentation tank was 32
mg/1 at pH 11.0 operation. With solids recycle and  the maintaining of flocculator
solids in the 900 to 1500 mg/1 level, the hardness increase across the primary
was only 6 mg/1. Most of the change occurred in the calcium ion concentration.
                                     34

-------
            200
                                            INITIAL
                                      —X- 50 mg/l Poly- P04
                                            mg/l Ortho "
                                          25 mg/l Poly  "
                                      -0-50mg/l Orfho "
                                      -O--NO  po4
                                          200 mg/l C03=
                                          200mg/l CO**
                 8.5
                  Figure 6-1  Effect of phosphate form

                   on calcium carbonate precipitation
PressleyiO studied the effect of sludge recycle on coagulation in jar test experi-
ments of raw wastewater.  At a pH of 11.65, the rate of  removal of soluble
calcium was calculated as a function of time.  Fig. 6-2 shows the effect of solids
content on the rate of calcium removal.  As can be seen, little is gained in terms
of improving the calcium carbonate reaction rate by  increasing  the solids level
above 2500 mg/l.
                                      35

-------
to
'o 4
                                _o	——e	€>
 o:
 o
 LJ
              1         23456

                       TOTAL SOLIDS CONCENTRATION XI03mg/l


          Figure 6-2  Effect of solids concentration on calcium removal
The importance of solids recycle is not limited to hardness considerations.  If
the calcium carbonate reaction is  not complete, the effluent from the clarifier
will remain unstable with respect to calcium carbonate precipitation, unless pH
adjustment is made.  The result of this instability is that the calcium carbonate
will plate out on the clarifier itself and downstream structures.  For instance,
at the South Tahoe Plant,  where a tertiary lime application is made and only
minimal solids recycle is practiced, copious quantities of solids are deposited
on the weirs, piping, and distribution trays above the ammonia stripping tower.
Similar scaling has been observed in clarifier weirs prior to pH adjustment at
the CCCSD's ATTF.  In comparison, far less scale formation has been reported
at Envirotech's Salt Lake City pilot plant where solids contact units have been
employed.  In the latter case, between 0.2 to 1.2 percent TS has been employed
in the reaction zone, 12 a level which is much greater than the cited solids
recycle applications.

The stability of the effluent is exceptionally important in those treatment systems
employing ammonia stripping for  nitrogen removal,  as calcium carbonate scaling
on the tower media has been one of the major operating difficulties of the ammonia
                                     36

-------
stripping process.  It should be recognized that ammonia is stripped at high pH.
Even effluents which have been stabilized to calcium carbonate at pH 11 will
contain free Ca(OH)2 which can react with CC>2 from the air producing scale.

Calcium Phosphate  Precipitation

Precipitation of calcium phosphate creates another lime coagulant demand and
leads to further sludge precipitation.  The exact nature of the precipitate is the
subject of continuing controversy.  Up until recently, the nearly universal
opinion has been that the form of calcium phosphate precipitated was crystalline
hydroxy apatite, which has the formula CasOH (PC^) 3.  Recently, Menar and
JenkinsS evaluated  calcium phosphate and calcium  carbonate precipitation
phenomena in both "chemically defined" water systems and in actual wastewater
coagulation.  Crystalline hydroxy apatite could not  be detected either by x-ray
diffraction techniques or by solubility tests.  Rather, the solubility data suggested
the formation of an amorphous tricalcium phosphate, Ca^ (POq) 2 • Further, in the
chemically defined systems, where  raw sewage organics were absent,  Menar and
Jenkins found that a phase change eventually took place, whereby crystalline
tricalcium phosphate (Ca3 (PC^) 2  • 41^0) was  formed.  The extent of completion
of the reaction was  not evaluated, nor could the presence of the crystalline phase
be detected in the wastewater systems tested.

In explaining the absence of hydroxyapatite Menar  and Jenkins^ make  the follow-
ing statement:

    "Magnesium appears to inhibit the  nucleation of calcium phosphate, to slow
    down the formation of apatite  from  amorphous calcium phosphate, and to
    stabilize the formation of tricalcium phosphate."

For the purposes of this report, the simplifying assumption is made  that all
phosphate precipated is present in the  form of amorphous tricalcium phosphate
according to the reaction:

    3Ca(OH)2 + 2POJ  	> Ca3  (PO4) 2  + 6 OH~                         (6-2)

Obviously, this is not the only  phosphorus  removal mechanism operative, since
there are other forms of phosphorus than orthophosphate present in  raw sewage.
As with calcium carbonate solids  recycle, the presence of preformed calcium
phosphate solids has a catalytic effect on the formation of the calcium phosphate
solid phase.  Albertson and Sherwood^ showed with jar tests  run on waste-
water that .solids recycle significantly reduces residual phosphate concentration
at constant pH up to a pH of 11. Further, in one case, the effect of solids re-
cycle was to reduce by 50 percent the dose required to achieve the same  residual
soluble phosphate.  Menar and JenkinsS showed that the activity product or
solubility of tricalcium phosphate decreased with increased solids levels in
"chemically defined" systems in experiments conducted up to  a pH of 8.
                                     37

-------
Contrary to the results of previous investigators, Pressley^O found that soluble
phosphate  residuals increased with the level of solids recycle in jar tests and
that the "organic phosphorus" fraction in the recycle solids accounted for the
increase in the systems studied.  No increase in orthophosphorus residuals was
observed.

Magnesium Hydroxide Precipitation

For most wastewaters, magnesium is not precipitated until enough lime is added
to raise the pH above 10.0.  The chemical reaction involved is:

    Mg++ + Ca (OH) 2	> Mg (OH) 2 + Ca++                          (6-3)

Soluble magnesium levels are a function of pH and typical values follow:

    pH                    Soluble Mg as CaCO,,, mg/1
                                              O

    10.0                               370
    10.2                               145
    10.4                                 57
    10.6                                 22
    10.8                                 9
    11.0                                 4

In raw sewage applications,  the magnesium hydroxide reaction does not closely
approach the equilibrium predicted on the basis of Mg (OH) 2 solubility.  For
instance, at the CCCSD's ATTF, the effluent magnesium averaged 33 mg/1 at pH
11.0, when a supplemental coagulant dose of 14 mg/1 of ferric chloride was
added.  Apparently the magnesium hydroxide reaction is inhibited, although
the specific inhibition mechanism is as yet undefined.

Trace Metals Precipitation

Of the unit processes available for waste treatment today, lime precipitation is
one of the most effective methods for removing heavy metals and, as a rule, is
more effective than either iron or aluminum . 13,14,15  Trace metals are of
significance in water pollution control because many are toxic to the biota in the
receiving waters,  either at their discharge concentration or through concen-
tration in living cell tissue. Other metals  are  micronutrients essential for
biological growth.

Lime removes trace metals from wastewater through adsorption, flocculation, or
by conversion of soluble  metals to an insoluble precipitate.   Most metals form
insoluble hydroxides, oxides, carbonates, sulfates,  or chlorides. 14 Solubility
data were summarized by Argaman and Weddlel4 ancj are presented in Table 6-1
for  the common trace metals and their  precipitates.  As can  be seen, silver,
cadmium, cobalt,  copper, iron, mercury,  manganese,  nickel, lead and  zinc
ought to form relatively insoluble hydroxides or oxide precipitates when lime
treatment is practiced. Actual performance often does not match predicted
chemical equilibrium because of slow rates of reaction or the formation of
                                    38

-------
                         Table 6-1 .  SOLUBILITY PRODUCTS OF HEAVY METAL SALTS
Metal

Ag, Silver

Ba, Barium


Cd, Cadmium
Co, Cobalt

Cu, Copper

Fe, Iron

Hg, Mercury

Mn, Manganese

Ni, Nickel
Pb, Lead

Zn, Zinc
Oxide or Hydroxide
-8
AgO 1.9x10

_ _

-14
Cd(OH) 2. 0x10
Co(OH) 1.6xlO~15
-19
Cu(OH) 1.6x10
-39
Fe(OH) 2. 0x10
G
-26
HgO 4. 0x10
-13
Mn(OH) 1.6x10
-15
Ni(OH) 2. 0x10
Pb O(OH) 1.3xlO~15
£i 2
Zn(OH) 1.6x10" 6
Carbonate

-
-9
BaCO0 1. 6x10
3

-
-

-

-

-

-

-
PbCO0 1. 5xlO~13
o
-10
ZnCO 2. 0x10
Sulfate

-
-10
BaSO 1. 1x10
4

-
-

-

-

-

-

-
PbSO, l.Sxlo"8
4
-
Chloride
-10
AgCl 2.8x10

-_ _


-
-

-

-

-

- -

-
_ _

-
Sulfide
-51
Ag S 1.0x10
2

_ _

-28
CdS 1.4x10
-
-38
CuS 4. 0x10

FeS
-53
HgS 3. 0x10
-16
MnS 7. 0x10

-
PbS 7.0xlO~

ZmS 4. 5x!0"24
Chromate
-13
Ag CrO 7.1x10
-10
BaCrO 2. 1x10
4

-
-
-6
CuCrO 3. 6x10
4

-
-9
HgCrO 2. 0x10

-

-
PbCiO S.OxlO"13
4
-
Ar senate

-

_ _


-
-

-

-

-

-
-2fi
Ni(AsO ) 3.1x10
PbHAsO 4. OxlO~36
4
Zn(AsO ) 1. 3xlO~38
LO

-------
complexes  (chelation) .  In other instances, removals may exceed predicted levels
through adsorption or coprecipitation on other compounds.

Two metals, barium and chromium, may pose problems in lime precipitation
systems.  Barium does not form a hydroxide precipitate,  and it is often not
removed efficiently with lime.  In fact,  Maruyama, et al.  found, in pilot testing,
that ferric  sulfate removes barium more efficiently than lime, since barium forms
an insoluble precipitate as a sulfate.15 Chromium in the  hexavalent form exists
as an oxide (chromate or dischromate anion) , which forms a soluble salt with
most cations found in wastewater.14 if reduced to the trivalent form, the metal
may precipitate as an insoluble hydroxide (solubility product of 1.0 x 10  du) .

Coagulation

Unlike the  situation in water treatment, lime is not added to raw wastewater for
the exclusive purpose of precipitating calcium or  magnesium.  Rather,  lime is
ordinarily  used for precipitation of phosphorus or metals, and for coagulation
of raw sewage solids.  Only when water reclamation is to be practiced do hard-
ness considerations influence process operation.9 Criteria for coagulation of
raw sewage solids and precipitation of phosphorus compounds  may set quite
different operating criteria than that for treatment of water hardness alone.

When pH is controlled at 10 or  below and lime is the only  coagulant, effluents
tend to be very turbid and have high concentrations of finely divided or dis-
persed solids.  In other words, the effluents do not appear to be well coagulated.
This solids loss results in lower phosphorus removal, since some precipitated
phosphorus is lost over the effluent weirs.  For cases where a very high degree
of phosphorus removal is required in primary treatment,  the encouragement of
magnesium precipitation is  often recommended. The  reason is that magnesium
hydroxide  forms  a gelatinous  matrix that binds  the  precipitated  calcium
phosphate  and  calcium carbonate together into readily settleable floes. This
normally requires a pH  of 10.5 or greater,  depending on  the  raw water
magnesium content.

Menar and  Jenkins^ have suggested that additional coagulants be employed for
high phosphorus  removal below  pH 10.  Since above pH  8 to 9.6, calcite
(calcium carbonate) carries a net negative charge, a cationic material was
suggested for coagulation.  While they showed that a  high calcium ion concen-
tration could fill this role, they suggested that cationic polymers or alum or
ferric salts could be more efficient coagulants.

Jar tests conducted at the ATTF have demonstrated that the  addition of ferric
chloride and its precipitation as ferric hydroxide  could be substituted for the
high pH conditions conducive to magnesium hydroxide precipitation, while
obtaining similar supernatant turbidity and phosphorus levels.  The jar test
were conducted on CCCSD raw sewage utilizing both  lime and iron at the doses
and pH levels indicated in Figure 6-3.  As can be  seen in Figure 6-3, the
turbidity at a pH of 9.6 is equal to that obtained at a pH of 11.4.  The high
clarity obtained at a pH of 9.6 was due to the use of 25 mg/1 of FeCl3 as a
supplemental coagulant. To obtain effluent phosphorus levels less than 1 mg/1
                                     40

-------
11.0
IO.O
pH
9.O
8.0
75c
3.0
? 2.0
H
Q
00
tr
H I.O
°(
9.6
0.8
0.7
^ O.6
o
a" 0.5
1 0.4
0.
I 0.3
0.2
°'C
25mg/l FeCI3 ,ja-V~"^ /
\ B^t \ HIGH LIME CONTROL
\ ,,—*•"' — \ ATOm9/l FeCI3
^^•*^^"^ I0mg/l FeCI3-^
CONTROL POINT
' (NO CHEMICAL ADDED)
i l 1 1 1 1 1

) 50 100 150 200 250 300 350 400
CONTROL POINT
' (NO CHEMICAL ADDED) H.L. CONTROL
AT Omg/l FeCI3 	 -,
25mg/l FeCI3— -7 I0mg/l Fe CI3— 7 1
"^^^ ®^,^__/^_ 	 i
l i l 1 i l l

D 50 100 150 200 250 300 350 4OO
CONTROL POINT H.L.CONTOL
•• TOTAL P-P045 TOTAL P AT Omg/l
AT Omg/l Fe CI3 FeCI3^^^_^^
yA^ ^V*^ TOTAL PAT
TOTAL PAT /^ v \ ^fe>»^~'<-)rTI9''' Fe ^'3
25mg/IFeCI3 	 ' \ \ \ \
v ^ \ \
PO/ AT /^ \ « / / H.L.CONTROL-^
OK / c r, X \ f / P04= AT Omg/l
25mg/eFeCI3 — ^ \ ' / Fe Cl
X / // 3
\ / £_P04S AT 10
IS mg/l FeCI3
1 1 1 1 1 1 1

) 50 100 150 200 250 300 350 40O
                       LIME DOSE Ca(OH)2,mg/l

Figure 6-3  Lime and iron dose vs. supernatant quality for^CCCSD
            wastewater
                                41

-------
32O
> 300
z\
^E 280
*£
<8 260
Ouj 240
220
2OO
(
200
8 ISO
Ul _
If 160
I ro
s8 140
2 a
yo
 120
o <
100
80*
<
100
I 90,
*i, 80
5 ro 7n
30 ru
§ ° 60
50
40
C
25mg/l IOmg/1
Fe CI3— ^. Fe CI3 — i
>• N\ R>^ \ HIGH LIME CONTROL
^•x ^> * ATOmg/l FeCI3— i
r CONTROL POINT
(NO CHEMICAL ADDED)
1 1 1 1 1 1 1



3 50 100 150 200 250 300 35O 4OO
25mg/l
\> I0mg/l
* \ \ HIGH LIME CONTROL
\ \ ATOmg/l FeCI3
_ CONTROL POINT ^&^ ^^^. S
(NO CHEMICAL ADDED) ^^/
i 1 1 1 1 1 T 1



3 50 100 150 200 250 300 360 40O
s — 25mg/l FeCI3
\ ./
' CONTROL POINT V A
- (NO CHEMICAL ADDED) \ S *
\ S \ S*^. HIGH LIME CONTROL
^ \ ^^""13^ ATOmg/l Fe Cl 3 	 1
V' /*^\i 1
I0mg/l FeCI3 	 ' \ /
\ '
1 I 1 1 I ^ I



' 50 100 150 200 250 300 35O 4OO
                         LIME DOSE Ca(OH)2,mg/l

Figure 6-3 (continued)  Lime and iron dose vs. supernatant quality
           for CCCSD wastewater
                                42

-------
P, however, the pH had to be raised to at least 9.85 (lime dose = 150 mg/1) .
Lower pH levels resulted in higher supernatant phosphorus as shown in Figure
6-4 for another jar test series.  Nonetheless, Figure 6-4 demonstrates that there
is a broad pH range where comparable phosphorus removals are obtainable as
long as appropriate iron doses are employed.

Other items of interest in Figure 6-3 are the alkalinity and hardness data.  Note
that there is no clear minimum solubility point for calcium,  rather there is a
broad range where the calcium concentration is roughly in the same range (pH
10.3 to 11.0) .   This is contrary to what would be predicted from water softening
experience which usually  indicates a minimum solubility point for calcium  in the
pH 9.5 to 10 range. Note also that magnesium is not completely removed at pH
11.4, contrary to solubility predictions.  Very little magnesium is precipitated
up to a lime dose of 250 mg/1  (pH = 10.1) ,  yet excellent clarity is obtained.  This,
again, is evidence that iron has substituted for magnesium as the coagulation aid.

Quite similar hardness relationships were reported by Burns and Shell-^ for
Salt Lake City wastewater when lime was used without supplemental coagulants.
Effluent calcium was lowest in a pH range from 10 to 11, with a minimum at pH
of 10.4.  Complete magnesium removal did  not occur even at a pH of 11.5
 (Figure 6-5) .

These hardness relationships led to the decision to select an operating pH  of 11.0
at the ATTF.   This was the point of minimum total hardness, which is a consid-
eration when the treatment product is  to be reused.  The data in Figure 6-3 on
CCCSD wastewater can be reworked to show another interesting relationship.
Knowing the lime requirement for phosphorus removal  (Equation 6-2) , and the
measured supernatant calcium, the loss of calcium to tricalcium phosphate
formation and to soluble calcium in the supernatant can be calculated.  Theoret-
ically, this loss when subtracted from  the lime dose, gives the lime precipitated
as calcium  carbonate.  Obviously, if all the calcium added is lost to the super-
natant and  phosphorus precipitation, there can be no lime recovery as no
calcium carbonate is precipitated.  In Figure 6-6, the calcium loss  is expressed
as a percent of the lime dose  (as CaCO3)  and plotted against the lime dose  (as
Ca(OH) 2) .  It can be seen that at pH 9.5 nearly all the calcium is lost.  Other
investigators have also found that  at pH 9.5 or less,  there is essentially no
calcium carbonate formation .3,6,12 jt can  aiso j-,e seen from Figure 6-6, that
the pH must be at least 10 for the loss  to be less than 30 percent, leaving 70
percent for lime recovery. In practice, losses occur in other parts of the
treatment system, and obtainable recovery  is even less.

Subsequent work done in  connection with the design of a wastewater  treatment
plant in Australia showed that either ferrous or ferric sulfate could be sub-
stituted for ferric chloride.  Also, an investigation at the ATTF showed that
alum or aluminate could be substituted for ferric chloride as the supplemental
coagulant.

The choice of  coagulants  to  be  employed  should be based on jar tests for
screening purposes, and if possible, final  selection should be based  on pilot
                                      43

-------
      4.0
     3.0
  r  2.5
  a   2.0
  o
  I   '•*
  Q.
     0.5
      0
               50mg/| FeCt3
  IOmg/1  FeCI3
                                           FeCI3
                                                  _L
                50      100      150      2OO     250
                              LIME DOSE Ca(OH)2,mg/l
                         300
                 350
400
pH
      12.0
      11.0
      10.0
     9.0
     8.0
     7.0
     6.0
                      LOW LIME W/
                      IOmg/1 FeCI3-
            LOW LIME W/
            25mg/l Fe CI3
                              LOW LIME W/
                              50mg/IFeCI3
_L
                                                            400mg/l Ca(OH)2
                                                            Omg/l Fe CI3
_L
               50       100      I5O     200      250

                              LIME DOSE Ca(OH)2,mg/l
                         300
                350
400
          Figure 6-4  Phosphorus removal for low pH operation.
                      Lime and iron treatment of CCCSD wastewater
                                      44

-------
 900-
               RAW WASTEWATER
               ALK= 240mg/l
                                                      12
                   LIME TREATMENT pH, UNITS


Figure 6-5 Effect of lime treatment on Salt Lake City

            wastewater
                          45

-------
LU

£
UJ
CL

C/T
(/)
O
o
    100
    80  -
60   -
    40  -
    20  -
     0
             50       100
                                   150       200      250

                                     LIME DOSE, Ca(OH)2
                                                                                 9.5
300      350     400
            Figure 6-6 Calcium loss to supernatant and phosphorus precipitation

-------
or plant scale testing.  Cost and performance comparisons should dictate
coagulant choice.

Hydrolysis

The discussion of lime treatment process chemistry would not be complete with-
out mention of the concept of "hydrolysis".  Certainly, no aspect of this subject
is more controversial than the role of hydrolysis. Zuckerman and Molof16 have
theorized that,  by managing the lime treatment stage, the downstream activated
carbon treatment or activated sludge treatment can be optimized. The procedure
suggested was that at high pH (11.5 in the wastewater studied)  high molecular
weight organics (e.g.,MW  >  1200) are hydrolyzed to low molecular weight
organics  (MW «"•- 400) .  Zuckerman and Molofl6 concluded that high molecular
weight organics are not efficiently adsorbed,  whereas low  molecular weight
organics are. It has also been suggested that the activated sludge process would
also benefit by hydrolysis in the chemical primary on the basis that low molecular
weight organics are more easily and completely degraded.

No other  investigators have documented or  supported the "hydrolysis"
concept as advanced by Zuckerman and Molof. In fact, reviewers and other
researchers have made contrary conclusions.  Weber, ' in a discussion,
questioned the character of the high molecular weight organics determined by
the gel-permeation chromatography and wondered if they were in fact colloidal
material.  If they were really colloidal material, they could have been removed
by coagulation rather than hydrolysis.  Weber disputed the molecular weight
concept as a determing factor in carbon efficiency for a number of reasons  (see
discussion) .  He also provided high pH data which showed no significant
hydrolysis effect at a pH of 11.5.  In a later discussion, Weber^ concluded that
hydrolysis-adsorption could not demonstrate  any advantage in terms of effluent
quality when compared to other physical-chemical effluents.  McDonald,  et al_,
found very little high molecular weight material in raw wastewaters from various
locations.  The proportion of this  material was always less than 10 percent, which
is contrary to the findings of Molof and Zuckerman.20 if there are essentially no
high molecular weight materials present, there can be no benefit from their
hydrolysis.  Westrick and Cohen^l found no benefit in high pH lime operation to
carbon adsorber efficiency as compared to low pH lime operation or ferric opera-
tion.  These findings are again contrary to the findings of  Zuckerman and Molof.
The weight of evidence appears to be against the concept of hydrolysis
significant effect in lime treatment of raw wastewater.
as a
LIME ADDITION

Lime is added in sufficient quantity to increase the wastewater pH to the level
required by the treatment process.  The amount of lime needed is a function of
wastewater flow, total alkalinity and calcium hardness.  When lime is fed ahead
of the primary clarifiers, the lime slurry should be added at a point of high
turbulence in the wastewater. This turbulence can be created by a sudden drop
in the hydraulic profile, as by passage of the liquid through a Parshall flume or
                                     47

-------
over a weir  or may be produced by a mechanical agitator or mixer.  The degree
of agitation is more important than the mixing period.  When using mechanical
rapid mixers,  scaling of the shaft and impeller is likely to occur.  Also, unless
removed,  rags will tend to wrap around it. Therefore, to facilitate maintenance,
provisions should be made for duplicate units.22

Where preaeration is provided for the removal of grit, the addition of lime ahead
of the preaeration tanks could offer several advantages.  When quicklime is used,
the lime slakers do not require grit removers, since grit particles will settle in
the preaeration tanks.  This arrangement saves power, simplifies maintenance
and provides a more compact equipment layout.   The savings in space can be
significant when paste type slakers are specified since, as was pointed out before,
they require considerably less floor space than  detention slakers.

Also, if the slakers can be located nearby or directly above the point of chemical
application,  the difficulties of slurry handling can be largely eliminated. Pro-
blems associated with the transport of lime slurries derive from the fact that the
water in which lime is suspended, because of its high pH, undergoes a softening
reaction with the precipitation of calcium carbonate.  This forms a dense hard
scale which  in time will plug the solution lines.23 At the wastewater treatment
plant in Holland, Michigan,  the lime slurry line has to be cleaned with a special
polurethane tool ("Poly-Pig") every other  day to keep it clear.2^  The scale also
forms at the point where lime is added to the treatment process.^

Fig. 6-7 shows the 3600 kg/hr (8000 Ib/hr) paste slakers in the CCCSD water
reclamation plant2^ located above a steep channel. A hydraulic jump occurs in
this channel when the rapidly moving flow encounters the horizontal water surface
of the preaeration and flocculation tank. The turbulence created by the jump will
be used to mix lime,  ferric  chloride and polymer with the raw wastewater.

CONTROL OF LIME DOSAGE

Lime dosage control is normally based on one or more of the following measure-
ments:  plant flow, influent pH and effluent pH.  Because there is no correlation
between wastewater flow and wastewater characteristics (e.g., BOD,  suspended
solids, alkalinity,  and the like) , it is generally recommended that one of the
following three methods be  used to control lime  dosage to maintain a fixed pH
level in the flocculation tank:

    1.  Influent flow and off-line measurement  (i.e., periodic laboratory
        analysis of wastewater samples) of flocculator pH.

    2 .  Influent flow and on-line measurement  (i.e., continuous measurement
        by a pH sensor) or flocculator pH.

    3.  Influent flow and on-line measurement of influent and flocculator pH.

Fig. 6-8 (top)  is an example of open-loop feeder control whereby the lime dosage
ratio is automatically proportioned to the influent flow rate. The pH in the lime
flocculator is manually measured at preset time  intervals, and changes in the
                                     48

-------
   PNEUMATIC
   CONVEYING
   LINE
   DAY STORAGE
   HOPPER
    ROTARY
    VALVE
    FLEXIBLE
    HOSE
     WEIR
                                        AIR EXHAUST
                                        LINE
CYCLONIC
SEPARATOR
                                            LIME FEEDER
 LIME SLAKER
                            FLOCCULATION TANKS
                            DISTRIBUTION CHANNEL
Figure 6-7 Location of lime slakers at the CCCSD water reclamation plant
                           49

-------
              INFLUENT FLOWS OFF-LINE FLOCCULATION pH
>—1±3
INFLUENT
                                           V
                                             PH
                                 FLOCCULATOR
                                                      PRIMARY
                                                      CLARIFIER
              INFLUENT FLOW 3 ON-LINE FLOCCULALTION pH
INFLUENT
               Figure 6-8 Lime dosage control diagrams
                                 50

-------
dosage rate can be made by changing the setting on the ratio relay FY via manual
loading station HIK.  The control system shown in Fig.  6-8  (bottom)  is an example
of compound loop control whereby the dosage rate is proportional to  flow, and the
dosage controller AIC acts as a dosage trimming device, compensating for varia-
tions in lime demand as measured by the pH in the flocculator.  Optimum dosage
control is attainable with a feedforward control system with feedback trim. The
feedforward portion of the control system is used to calculate the desired lime
dosage per unit of influent flow based on the measurement of influent flow and pH.
Although there is not a consistent relationship between  influent pH and lime dose,
the feedforward control action results in a first approximation to the  required
dosage.

The feedback controller is then used to compensate for changes in wastewater
characteristics that have not been taken into consideration in the feedforward
calculation.  In addition, the feedback controller also compensates for inaccuracies
in the various transmitters and computing elements in the Control System.  For the
Control System  shown in Fig. 6-9,  the feedback controller AIC adjusts the ratio
setting of ratio relay UY, if the feedforward prediction, executed through relay
FY1, proves inaccurate as determined by the flocculator pH measurement.
                    ^J	
                      I
                          •LI ME FEEDER!
   INFLUENT
1
loH
i CA1T) -
1
™" ^™



"Vv /^\
(AIT)

FLOCCULATOR






PRIMARY
ri ARIFIFR

        Figure 6-9  Lime dosage control diagram - feed forward control mode
                                     51

-------
Symbols in Figs. 6-8 and 6-9 follow Instrument Society of American's (ISA)
Standard S5.1, Instrumentation Symbols and Identification.  A comprehensive
review of the principles of instrumentation and control and their practice in the
wastewater treatment field is presented in reference 26.

FLOCCULATION

The unit process of flocculation is concerned with the aggregation of particles
which have been destabilized -in a preceding coagulation  step .  In a flocculation
basin,  opportunities for particle collision are provided by inducing fluid motion
so that larger floes can be produced and separated in a subsequent  sedimentation
step .  Design considerations involve energy input  (such  as "G", the root mean
square (rms) velocity gradient) , detention time, degree  of flocculator compart-
mentalization, and the type of shearing device (such as paddle design) .
Consideration must be given to floe breakup  in addition to floe aggregation. In
general, the  rate of floe breakup varies with the level of  turbulence.  At Mgh
levels of turbulence floe breakup can predominate over floe aggregation.

Flocculation design concepts have been investigated in detail for other waste and
water treatment applications, but comparitively little work has been done with
flocculation processes in wastewater treatment using lime as the coagulating agent.
Parker and Niles28 found that a preaeration-grit removal tank could be used for
flocculation when lime was used as a coagulant.  The currents caused by the
release of diffused air in the grit removal tank encourage the formation of large
flocculant particles which settled readily. By using air instead of mechanical
means, the problems associated with rag fouling of mechanical flocculators  were
avoided.  The same has not  been found true when ferric chloride was used  as the
principal coagulant.  Indications were that maximum particle aggregation was pre-
vented due to floe breakup in the preaeration tank.29

When preaeration is used for flocculation, the coarse bubble air diffusers should
be of the swing arm type to allow maintenance without having to take the tank out
of service. Maintenance is required because of scaling inside the diffuser orifices,
which is caused by carbon dioxide in the preaeration air. Monthly  cleaning of
diffusers may be required,  although the maintenance period can be  extended to as
long as three months by providing a high pressure air or water connection for
blowing out scale deposits.

Critical design criteria for flocculation in the preaeration tank are detention time
and aeration  rate.  Detention time at average dry weather flow should be no less
than 10 minutes and preferably 20 minutes for  optimum results.  The air supply to
the preaeration headers should be separately regulated and provided with flow
metering.  Standard preaeration air requirements of 0.75 cu m per cu m (0.1 cu ft/
gal) of sewage are adequate as a maximum delivery capability for low pressure air.
While actual air usage has not been determined for applications such as  at the ATTF
air rates for flocculation are normally set lower than for standard preaeration.
Preliminary estimates indicate that air requirements may be lower than that
normally used in preaeration.  Care must be used to ensure adequate distribution
of turbulence throughout the preaeration tank to prevent  deposition of organics or
chemical precipitation with the grit.  A typical theoretical relationship (developed
                                      52

-------
for the ATTF)  between air rate and "G", the rms velocity gradient, is shown in
Figure 6-10.

Mechanical means may also be employed for inducing the turbulent shearing
necessary for flocculation.  When mechanical means are employed, extreme care
must be taken  in the design and operation of devices used for rag removal.  It has
been found that when  rags are screened, comminuted and then returned to the
sewage, rag fouling problems develop.  For instance at the Hatfield Township
Plant,  comminuted rags were found to reweave themselves and foul paddle-type
flocculators .30 Frequent maintenance was necessary. Rags have also fouled
turbine-type flocculators and draft tubes in solids contact units, such as at the
pilot plant at Salt Lake City .31  To overcome this problem, it is recommended that
rags be removed from the sewage after screening and disposed of separately when
mechanical flocculation is to be employed.

Another aspect of flocculation concerns solids contact. In addition to aiding
coagulation, solids contact promotes floe aggregation. Argaman and Kaufman
showed that the rate of flocculation was proportional to the number of particles,
the level of turbulence, "G",  and the nature of the floe, in addition to other
factors.32  By increasing the solids concentration,  flocculation efficiency may
be enhanced.

Solids contact may be promoted by two means,  solids recycle or integral recircula-
tion in a "solids contact clarifier". Solids recycle has been used at CCCSD's ATTF
to maintain the solids  concentration between 900 and 3900 mg/1.  Solids recycle
was accomplished by pumping a portion of the underflow solids back to the influent
to the preaeration tank.  Integral recirculation is described under primary clarifier
design.  Burns and Shell found that the solids level in the recirculation zone had to
be limited to 4000 to 6000 mg/1 to prevent prolonged contact and effluent deteriora-
tion due to septicity.  Common detention times  (based on influent flow) cited for  the
recirculation zone in a solids contact clarifier were  given as 15 to 30 minutes.-^

ALTERNATE PROCESSES FOR PRIMARY APPLICATION

Depending upon pH level, the addition of lime to raw wastewaters has resulted in
three distinct processes, each of which is intended to achieve different degrees of
basically the same objectives. These processes are: the Low Lime Process,  the
High Lime Process, and a process employing lime and other metal salts.

The low lime process  normally operates in a pH range of 9.5 to 10.5.  Phosphorus
removals are lower than for the high lime process,  since magnesium is not pre-
cipitated to coagulate the colloidal phosphorus.  Solids and organics removal are
also somewhat lower for the same reason.

The high lime process must operate at a pH of at least 10.5, so that magnesium
precipitation can aid coagulation. While the lower limit of operating  pH is given
as 10.5, operation for most applications has usually been at 11.0 or even higher
for  a number of reasons that will be discussed in detail.
                                      53

-------
1000
800
600
500
400
300
200
,_ 150
UJ
5
g 100
(= 80
3
£ 60
| 50
o" 40
30
20
15
10


	 1

FUNC

	









^

I 	 T 	 1 	 1 — i — riii 	 	 	 r 	
DESIRABLE OPERATING RANGE
;TION RATE.SCFM G, sec-'
PREAERATION (O.I CF/gol)
LIME REACTION,FLOCCULATION









^









^









S>










^









^










^



(
\
(
(
(





x"




3 =
i =
3 =
:FI»
:F
220
35-220





f




29
dil
CF
t/lo
rec




x*





.5
FfL
~H
P«
ict



^»r
y





/Q'h
ser dept
/CF rea
•r = 1.3 S
or= 539^
130 sec'1 .
30-130 _


^







h, 10'
ctor
>CFM
D


^








10      15    20    30   40  50 60   80  100
                     AIR RATE, SCFM
150  200   300
      Figure 6-10 Air supply - shearing relationship
                  for preaeration - flocculation
                           54

-------
The third lime process is a relatively recent development.  Lime is coupled with
another metal salt, such as iron, to enhance the removal of phosphorus, organics
and other solids.  The metal salt permits production of a high quality effluent
without the need to precipitate magnesium.  As a result, lower lime doses are
possible.  Operating pH normally will be between 9.5 and 11.0.

Low  Lime Process

The low lime process is a relatively economical method, from a chemical cost stand-
point,  to remove a large percentage of phosphorus from wastewater. Inspection of
the data in Fig. 6-11 shows that beyond a given initial removal  (eighty percent),
the incremental amount of lime required to precipitate incremental quantities of
phosphorus increases rapidly.  If the desired level of phosphorus removal falls
within the steeper portion of the curve, a relatively low dosage of coagulant will
be sufficient.  It can be observed that there is a minimum dose required before
normal primary treatment removals are exceeded. As an example, in jar tests
conducted by Tofflemire and Hetling33 it was observed that 85 percent removal
of phosphorus was obtained with a dosage of 125 mg/1 of Ca (OH) 2 at pH 10.
Albertson and Sherwood1* reported similar results.

Figure 6-11 is derived from a pilot treatment study at Kansas State University34
where the primary operation was at a low overflow rate of 12.2 cu m/day/sq m
 (300 gpd/sq ft) .  The allowable upper limits for overflow rate were not defined
in the  study.  Lower phosphorus removals have been reported by Burns and
Shell.    In one run, the removal was only  41 percent at pH 9.8,  at 270 mg/1
total alkalinity and a lime dosage of 270 mg/1 as Ca (OH) 2-

The  amount of lime required to precipitate phosphorus will normally cause
coagulation  also;  therefore, suspended solids are removed along  with phosphorus.
Table  6-2 gives the results reported by Tofflemire and Hetling for approximately a
month  of clarifier operation at each pH value shown.  Clarifier overflow rate was
16.3 cu m/day/sq m  (400 gpd/sq ft) .  Coagulation aids  have  been used to
increased the  settling velocity and to flocculate insoluble phosphorus.  The
former is achieved by adding small dosages  (lower than 1.0 mg/1) of organic
polyelectrolites. ^°
      Table 6-2.   EFFECT OF PRIMARY CLARIFIER pH ON PERFORMANCE
                  AT WATERFORD, NEW YORK
pH
9.9
10.3
10.8
COD
mg/1
542
548
782
Influent
COD
% Sol.
40.9
25.5
23.1
S.S
mg/1
240
356
548
Removals
COD
%
60.7
69.5
75.6
S.S
%
76.3
88.5
91.0
Effluent
Turbidity
JTU
36
20
27
                                      55

-------
   100



    90



    80



    70



    60



    50



    40



    30



°-   20



    10



    0
UJ
LU
CL
LU
IT
                                             8O% REMOVAL
      0
                50
100
150       200       250


  LIME DOSAGE, mg/l Ca(OH)2
300
300
400
450
                     Figure 6-11  Phosphorus removal as a function of lime dose

-------
Three full-scale plants (Holland, Mich.; Hastings, Mich, and Hatfield Township,
Pa.),  using the low lime process were surveyed in connection with this project.
All of the plants were designed around the "PEP" process patented by Dorr-Oliver
and feature sludge recirculation to the flocculator zone.  Operating data for these
plants are shown in Table 6-3.  As can be seen, primary performance in two of the
plants is low.  This may  be due to insufficient lime dose  (see Fig. 6-11) ,  or to
excessive overflow rate.

In general, design overflow rate for low lime applications is fairly low and runs
about 16-32 cu m/day/sq  m (400-800 gpd/sq ft)  at average dry weather flow.
Dorr-Oliver recommendation for overflow rates at peak wet  weather flow is 33 to
40 cu  m/day sq m (800  to 1000 gpd/sq ft) .

High Lime  Process

When  certain requirements on final  effluent water  quality demand raising the
wastewater pH to 11 or 11.5,  i.e.,  to increase lime dosages, the resulting pro-
cess is called the High  Lime Process.  The figures given in  Table 6-2 show the
improvement in BOD (COD) and suspended  solids removal with increased pH
values.  As was mentioned earlier, wastewater clarification in the high lime
process is directly related to the removal of magnesium in the form of magnesium
hydroxide.  The reaction of magnesium with calcium hydroxide requires a  pH
greater  than 10.5.   Clarification is further enhanced by the precipitation of
additionalcalcium carbonate which improves floe stability and settling charac-
teristics.    The high lime process also  aids in removing phosphorus, ammonia
nitrogen (via air stripping)  and certain viruses.  Phosphorus removal as a
function of lime dose approaches a logarithmic relationship. After the initial
fraction is removed, further unit precipitation of phosphorus occurs with
successively increasing lime dosage.

The efficiency of ammonia air stripping as a result of high lime treatment depends
on the pH of the wastewater.  The process requires a high pH to achieve efficient
removal of ammonia, because this nitrogen compound is very soluble in water and
is highly ionized at pH  7.0.  The following table illustrates  equilibrium conditions
between ammonium hydroxide and disassociated ammonia at various pH levels:

                pH                     NH4OH:
                 7.0                      0.0055:1
                 8.0                       0.055:1
                 9.0                        0.55:1
                10.0                         5.5:1
                11.0                          55:1

Since only the undisassociated ammonium hydroxide can be removed by air
stripping, the process is practical only at pH levels of 10.5 and higher.
                                     57

-------
                Table 6-3.  OPERATING PARAMETERS FOR PRIMARY TREATMENT IN "PEP" PLANTS
Plant
Hastings
Holland
Hatfield
Present ADWF ,
cu m/d (mgd)
3,030 (0.8)
15,140 (4.0)
8,320 (2.2)
Ca(OH)2
dose,
mg/1
297
166
394
PH
9.6
9.3
9.5
Present ADW
overflow rate,
cu m/day sq m
(gpd/sq f)
29 (700)
21 (520)
16 (390)
P
removal,
percent
68
34
58
SS
removal ,
percent
71
44
45
BOD
(COD)
removal ,
percent
58
(a)
77 (61)
Reference
No.
35
36
37
en
CO
       (a)  Not available

-------
The removal of virus through high lime treatment appears virtually complete.
Cooper, et al.^0 found that a pH of 11.0 resulted in no detection of inoculated
polio virus Type I.  Lower operating pH values resulted in detectable levels of
virus.  Other unit processes, such as activated sludge,  sand filtration, and
carbon adsorption did not completely remove the virus.

Table 6-4 summarizes the results obtained in the Contra Costa ATTF  when
operating in the high lime process.  The table shows the high degree of organics
removal possible when the high lime process is used. For comparison, results
from a control primary are shown.

As increasing quantities of lime are added to the wastewater, recovery of the
spent chemical by recalcination becomes economically attractive.  Basically,
calcination converts calcium in the lime sludge to calcium oxide.  Calcium must
be in the carbonate form for lime recovery to be a feasible process.  As was
mentioned earlier, it has been found that the pH has to be raised above 9.5
before calcium carbonate will begin to precipitate from the wastewater. Another
factor is  the alkalinity of the wastewater.  In highly alkaline wastewaters,
additional CaCO3 will be precipitated at high pH levels.   Therefore, for the same
lime dosage,  the flow at which lime recovery becomes feasible is smaller for plants
treating a highly alkaline wastewater.  Figure 6-12 illustrates the relationship
between  lime dosage and wastewater alkalinity in the high lime process .41

Lime and Other Metal Salts

The coupling of lime with other metal salts for wastewater coagulation is a fairly
recent development. It derives from the practice  in water softening plants, where
metal salts are used in the recarbonation stage to  improve the flocculation of the
finely divided calcium carbonate precipitate.  The first application of lime coupled
with iron was reported by Wuhrman.42  irOn (Fe++ ) was used at a dose of  1 to 2
mg/1 as a flocculation aid to improve phosphorus precipitation in the  pH range of
10.5 to 11.0.  The lime was applied to secondary effluents.  Wuhrman also noted
that excess biological sludge could effectively  be coprecipitated with the lime
sludge.  Lime has been coupled with alum in precipitation of oxidation pond
effluents  .43  A pilot plant operated by the Napa County Sanitation District
obtained  83 percent SS removal when operating at a pH of 10.8 the lime dose (as
Ca  (OH) 2) was 260 mg/1 and was coupled with an alum dose (as Al2  (804)3.
18H2O) of 50 mg/1.  Bishop, et al_., 44 employed ferric chloride with lime at low-
pH operation but has not repoTted the details.

Considerable experience has been gained at the Advanced Treatment Test Facility
in the use of lime coupled with ferric chloride. ^ Results are summarized in
Table 6-5. Comparing these results to those obtained with the use of lime alone
(Table 6-4) ,  it can be  seen that there is relatively little difference in the  removals
obtained  for the  conventional parameters  (BOD, SS, TOG) .  Moreover, it can be
seen that the phosphorus removal obtained at pH 10.2 with iron, exceeds  that
obtained  at pH 11.5 without iron. Chemical  dose, is of course, appreciably less
at the low pH. Further,  there is approximately 28 percent less solids generation
at pH 10.2 than 11.5.45  Grease removal is also considerably better with lime and
iron operation compared to lime alone.
                                      59

-------
                                 Table 6-4 HIGH pH TREATMENT OF CCCSD WASTEWATER

C onstituent
(mean value)


BOD5
SS
vss
Turbidity
TOC
Soluble organic carbon
Total phosphorus as P
Settleable solids
Calcium hardness6
Magnesium hardness6
Hardness increase6
Grease
o
pH 11.5 operation
Ca (OH) • 500 mg/1
£
Raw
sewage
mg/1
190
199
-
-
107
16
9.4
8.2d
76
96
-
57
Control primary

mg/1
103
57
43
35C
59
16
-
0.3d
-
-
-
32
%
removed
46
71
-
-
45
0
-
95
-
-
-
44
Chemical primary

mg/1
50
41
20
16C
37
23.4
0.96
nil
168
40
46
12
%
removed
74
79
-
-
65
-46
90
100
-
-
-28
79
pH 11.0 operation'3
Ca (OH)2: 400 mg/1
Raw
sewage
mg/1
192
195
-
-
118
17
9.2
9.5d
76
103
-
53
Control primary

mg/1
121
57
46
40C
68
21
-
0.2d
-
-
-
42
%
removed
37
71
-
-
42
-24
-
98d
-
-
-
21
Chemical primary

mg/1
60
47
25
26C
48
28
2.3
<0.1d
156
59
36
19
%
removed
69
76
-
-
59
-65
75
>99
-
-
-20
64
CTl
O
         December 22, 1971 to February 10, 1972, at average flow 1.30 mgd.
         February 11 to February 28, 1972, at average flow 1.12 mgd.
        °JTU
        dml/l
         as CaCC)

-------
   500
O

<5
0>


I

O
I
Q.

o:

£

D
UJ
a



s
ir

UJ

o
a

UJ
400
300
200
    100
                               _L
                                       _L
       0
               100         200         300


              WASTEWATER ALKALINITY mg/l-CaC03
400
                                                                 500
             Figure 6-12 Lime requirement for pH 11


               as a function of wastewater alkalinity
                                   61

-------
                             Table 6-5 LIME AND IRON TREATMENT OF CCCSD WASTEWATER
Constituent
(mean value)
BOD
O
ss
vss
Turbidity
TOC
Soluble organic carbon
Total phosphorus as P
Settleable solids
Calcium hardness as
CaCO
O
Magnesium hardness
as CaCO
O
Hardness increase as
CaC03
Grease
f\
pH 11.0 operation
Ca(OH) : 400; Fed : 14
Z 3
Raw
sewage
mg/1
210
305
130
23
9.5
13. 2d

75.5
90

-
146
Control primary
mg/1
109
69
49
45C
72
18
0.13d

-
-

-
-
%
removed
48
78
45
21
99

-
-

-
-
Chemical primary
mg/1
53
27
14
14C
37
24
0.85
nil

139
32.5

6
9.5
%
removed
75
91
72
-4
91
100

-
-

-4
94
pH 10.2 operation
Ca(OH) : 289; FeCl : 24
2i o
Raw
sewage
mg/1
178
235
117
20
9.4
12. ld

72
90

-
66
Control primary
mg/1
106
59
48
41C
68
17
.1

-
-

-
-
%
removed
40
75
42
15
99

-
-

-
-
Chemical primary
mg/1
59
31
19
15 c
43
25
0.68
<0.1d

148
70

56
8
%
removed
66
87
63
-25
93
>99

-
-

-34
88
to
            March 23, 1972 to April 5, 1972 at average flow 1.19 mgd.
            April 7, 1972 to April 30, 1972 at average flow 1.20 mgd.
           °JTU
           dml/l

-------
It is probable that future applications of lime to raw sewage coagulation will
increasingly employ supplementary dosages of other metal salts because of the
savings in chemical and solids handling costs.

RECARBONATION

Raising the pH of wastewater by lime will result in deposition of calcium scale on
surfaces with which the water comes in contract.  To prevent this the pH is
adjusted downward to a value of about 7 by the addition of carbon dioxide (CO2)
after the wastewater leaves the  lime treatment unit and before it undergoes other
treatment processes (an exception involves ammonia stripping which requires
high pH) .  The hydroxides and carbonates which have been produced in raising
the pH are reconverted to bicarbonates according to the following reactions:

                Ca (OH) 9 + CO9	>  CaCOQ + H0O
                       Z      Z              o    Z

                CaCO3 + CO 2 + H2O 	>Ca (HCOg) 2

Recarbonation is a process  which has been used for many years in water treatment
for downward adjustment of pH following lime-soda water softening. The recent
increase in the use of lime for treatment of wastewaters has resulted in recarbona-
tion being increasingly used in advanced waste treatment schemes.

Sources of Carbon Dioxide

There are three principal sources of carbon dioxide for recarbonation:  (1) liquid
carbon dioxide;  (2) combustion of a fuel such as propane or fuel oil, and  (3) stack
gas from either a lime recalcining furnace  or a sludge incineration furnace. In
most waste treatment applications, the latter source is usually used.  Stack gas
from sludge incineration contains 8-14 percent carbon dioxide, and gas from a
lime recalcining furnace contains  14-20 percent carbon dioxide.

It is interesting to  note that at the CCCSD's ATTF  sufficient carbon dioxide is
normally supplied  by  the biological oxidation reactions in the nitrification units  to
lower the pH to the desired value as the wastewater enters the aeration tanks.^
Liquid C02 is used on a standby basis when the pH in the aeration tanks becomes
too high for efficient biological  oxidation.  When external carbon dioxide is
required,  it is added  directly to the aeration tanks.

The quantities of carbon dioxide necessary for recarbonation can best  be deter-
mined by laboratory tests.  The best procedure is to bubble COo into a sample of
lime-treated wastewater under conditions likely to ensure nearly complete transfer
efficiency;  required dosage generally range from 200 to 400 mg/1. It is possible to
compute directly the dose of carbon dioxide necessary to lower the pH to 8.3 (i.e.,
to change hydroxide and carbonate alkalinity to bicarbonate alkalinity) if the initial
types and quantities of alkalinities present are known.  An example  of such a
calculation is given by Gulp and Gulp.
                                      63

-------
Recarbonation Equipment

Recarbonation equipment consists of a reaction basin for recarbonation to take
place,  equipment required to produce and deliver the carbon dioxide to the basin,
and a diffusion system to add the carbon dioxide to the wastewater.

Regarding reaction basin design,  it is important to note that the recarbonation
reaction is not instantaneous.  Although the COo gas may enter the water  as dis-
solved CO2 rapidly, the time required for recarbonation reactions to be completed
and the pH to be lowered to the desired value may be 10 to 15 minutes.  Thus,
sufficient detention time must be allowed in the basin or scale will form on the
surfaces  of downstream units and  piping.

Design of the reactor also depends on whether the pH adjustment is made  in one
or two  stages. When lime is used in tertiary treatment in high lime application, it
is common practice to recarbonate in  two steps. In the first step the pH of the
wastewater is usually reduced to a value near 9.3. This is the point of minimum
solubility of calcium carbonate in tertiary treatment applications.  This calcium
carbonate is then settled in the reaction basin and can be reclaimed by recalcin-
ing. At South Tahoe11 about  17 percent of the lime which is recovered comes
from the  recarbonation  settling basin.  In the second step of the recarbonation
process,  the  pH  is brough down to about 7.0 to provide a stable effluent.

If two-stage recarbonation is used, sufficient detention time must be allowed to
provide both reaction and settling in  the first stage. Gulp and Gulp   recommend
at least 30 minutes with an overflow rate of not more than 98 cu m/sq m/day
 (2,400 gal/sq ft/day) .  Provisions should be made for sludge removal in the
settling basin.  In single-stage recarbonation Gulp and Gulp recommend a
detention time of at least 15 minutes.  However, no provisions for settling and
collection of sludge are required.

The equipment required to deliver the carbon dioxide to the reaction basin will
depend on the source of the carbon dioxide.46 If liquid CO2 is used, it can be
fed in either the  gaseous or liquid form.  In either case,  pressure reduction cools
the carbon dioxide as it is withdrawn from its insulated, pressurized storage
container, and care must be taken to  prevent dry ice formation.  To prevent icing,
storage containers are provided with means to heat the unit. For gas feed, an
orifice plate in the feed line can be used to measure the flow.  For liquid feed,
equipment similar (except for materials) to solution-feed chlorinators may be used.

If fuel  is  burned  to produce carbon dioxide,  either underwater burners utilizing
natural gas or pressure generators, which can burn a variety of fuels, are usually
used.  Pressure  or forced-draft generators operate by compressing air and fuel in
a chamber at  sufficiently high pressure to allow discharge directly to the  water
after combustion.  With underwater burners,  air and natural gas are compressed
and then  burned at the point of application.  When stack gas from a furnace is used
as a source of carbon dioxide, the gas is passed through a wet scrubber to remove
paniculate matter and for cooling.  The gas is then fed through  a compressor in
order to attain sufficient pressure to feed against approximately 2.4m (8  ft) of
water.
                                      64

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The type of diffusion system utilized will depend in part on the source of carbon
dioxide.  For example, underv/ater burners act both to produce carbon dioxide
and to diffuse it into the wastewater; for liquid carbon dioxide,  cotton fabric hose
with controlled porosity may be used.

For dispersing gaseous carbon dioxide into the wastewater, commercial devices
such as those manufactured by Walker Process or Lightnin  (Mixing Equipment Co.)
are available.  These consist of a propeller mixer placed  above a sparger through
which carbon dioxide  is  added to the  wastewater. The  bubbles formed by such
systems are quite small (on the order of 1 mm) , and gas transfer efficiencies can
range up to 90 percent. Gulp and Gulp described an absorption system consisting
of a grid of perforated PVC pipe that is submerged 2.4m  (8 ft) in the wastewater.
Transfer efficiencies of 85 percent or greater can be obtained with 4.7 mm(3/16-in)
diameter holes that discharge 0.03 to 0.05 cu m/min (1.1  to 1.65 cfm) of gas.   They
recommend that the holes be spaced along the pipe at least  7.6 cm (3-in) apart,
and that the pipes be spaced 0.46 m  (1.5  ft) apart.

Since the recarbonation reaction takes considerable time  and gas transfer can be
accomplished fairly rapidly, it is often convenient to add gas only in the first
portion of the reaction basin. However, this may result in  incomplete transfer
unless pure COo is used.  The concentration of CC>2 which can be dissolved in
water depends on the partial pressure of CC>2 in the gas.  For example, if stack
gas is used, the equilibrium concentration of CC^ in the wastewater may be less
than the required dosage.  In order to overcome this, it may be necessary  to add
carbon dioxide over a large fraction of the detention time, so that as carbon dioxide
is removed from solution by the recarbonation reactions,  more can be transferred
from the gaseous phase into solution.

Single-Stage vs Two-Stage Recarbonation

When lime is applied to raw wastewater, it is doubtful that the recarbonation
should be carried out in two steps,  rather the pH be brought down to about 7 in
a single step .  Horstkotte, et aj.. ,9 found little difference  in hardness where two-
stage and single stage operations were compared during  studies at the ATTF for
pH less than 11.0.  From this observation, it can be deduced that very little cal-
cium carbonate precipitation will  occur after first-stage recarbonation for most pH
levels in the chemical primary. Studies at the Cleveland  Westerly Plant^7 tend to
confirm this conclusion.  When  the chemical primary clarifier was operated at
pH 10.5, it was found that very little sludge was precipitated in the second-stage
of 2-stage recarbonation.  Calcium hardness across the clarifier was reduced only
6 mg/1. However, when the operating pH was raised to 11.5 to 12 .0, large
quantities of calcium carbonate  were precipitated  in the second of the two recar-
bonation stages. When single-stage recarbonation was practiced, no significant
precipitation following recarbonation was observed. In Studies at Blue Plains,
O'Farrell^S found that two-stage recarbonation in raw sewage coagulation at a
pH of 11.4 to 11.7 resulted in sludge production of 0.9 kg/cu m  (7.5 lb/1000
gallons); when lime and iron were used at a pH of 10.5, only 0.4 to 0.5 kg/cu m
(3.5 to 4.0 lb/1000 gallons) of sludge was obtained.
                                      65

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In summary, two-stage recarbonation appears to have a role to play only in
tertiary treatment applications and in those few primary treatment applications
where the pH is considerably above 11.0.  Since effluents of the same quality can
be obtained where lime, at lower dosages, is used in combination with other salts,
two-stage operation at high pH is not economically justified.  The latter process
also produces  greater quantities of sludge than lime coupled with metal salts.

TERTIARY APPLICATIONS

Lime use in tertiary treatment applications has been covered in detail in References
1, 11  and 46, based mostly on the experiences gained at the South Tahoe Water
Reclamation Plant.  The main advantages of the tertiary treatment approach are
listed as greater flexibility of the operation because the biological and chemical
processes are separated; and the separation of the organic, i.e., primary and
secondary, sludges from the  chemical ones, which tends to facilitate subsequent
handling of the sludge and prevent the build up of inerts if lime  recovery is
practiced. It was acknowledged that the principal drawback of tertiary treatment
was its  high initial cost.

Although a comparison between the two lime processes is beyond the scope of this
manual, it should be pointed  out that two years of operation at the CCCSD's ATTF
have demonstrated the stability of a biological system,  i.e., nitrification-denitri-
fication, following the addition of lime to raw wastewaters. The test facility also
showed that combined sludges can be effectively classified with a solid bowl
centrifuge, thereby minimizing the problem of recycling inerts.   (See also
Section VIII) .

DESIGN CONSIDERATIONS FOR PRIMARY CLARIFIERS

When lime (or any other chemical)  is added to raw wastewaters to increase the
removal of suspended solids, phosphorus and toxic materials, the unit operations
required are similar to those  found in water treatment plants, i.e.,  rapid mixing,
flocculation, sedimentation and sludge  handling.  These four processes have often
been integrated into a single  unit resulting in the upflow solids contact clarifier or
sludge blanket clarifier. In connection with water treatment, it  has been stated
that the main advantage of this design, when compared to the separate tank
approach, is its lower construction cost.  Another important feature of the solids
contact  tank is the ability to bring the raw wastewater in contact with high  con-
centrations of  suspended solids. Figure 6-13 shows a typical solids contact unit.

It has often been stated that solids contact units are lower in capital cost than
primary sedimentation tanks.  However, detailed examination of this in Section XII
shows that there is no economic advantage to solids contact units.  It has now been
common practice for many years to provide grit chambers ahead of the main treat-
ment units y to protect mechanical equipment and, when sludge digestion is
practiced, to prevent grit accumulation in the digestion tanks.  Therefore,  grit
removal facilities  are usually required  and,  preferably, precede the primary
clarifiers.  As mentioned earlier, a preaeration and grit removal tank can perform
well as a flocculation basin.   This flocculation can be provided with conventional
                                      66

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primary tanks at no extra cost if preaeration is used for grit removal.  In com-
parison, the solids  contact unit must have previous grit removal so that the
functions of flocculation and grit removal cannot be combined.
                                  CHEMICAL FEED PIPING
  INLET
                                                              PERIPHERAL
                                                              LAUNDER

                                                                OUTLET
                                                                 SUPPORT
                                                                 RODS
                                                                RECIRCULATION
                                                                DRUM
                                            SLUDGE PIPE
                                            TO SUMP
                 Figure 6-13 Typical solids contact clarifier

                     (courtesy of the Eimco Corporation)
In lieu of grit removal tanks and a pumped grit slurry system, effective grit
separation can be accomplished by degritting the primary sludge. With this system
relatively thin primary  sludge is pumped to centrifugal cyclonic separators. The
grit separators would discharge the heavier ,  inorganic particles to a grit classifier
with both  the classifier  and centrifugal separator overflowing to a sludge sump.
Sludge would then be pumped from this sump to the thickening tanks.  Although
lower in first cost than  separate grit removal tanks, disadvantages of sludge
degritting include increased odor production because of an open  classifier and
sludge sump, plus more difficult maintenance of grit separation equipment due to
                                      67

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the higher concentrations of organic material which may cause fouling of the equip-
ment.  The lower sludge concentration also requires larger thickening tanks,  which
offsets some of the cost savings of sludge degritting.

Gulp and Culp46 have also pointed out that sludge blanket clarifiers are difficult to
control under varying flow rates or changing physical and chemical composition of
the wastewater.  Another operational problem in certain upflow clarifiers, when
used in primary lime applications, is the tendency of rags and similar materials to
wrap around the flocculator paddles.  Shuckrow and Bonner,46 based on pilot plant
studies at the Westerly WTP in Cleveland, have recommended against the use of
solids  contact units for the full-scale plant.  They found severe difficulties in
maintaining a sludge blanket in the clarifier and stated that this problem would
be further aggravated under variable hydraulic loadings.

Burns  and Shell have reported stable operation of a solids contact clarifier.12 This
was a  solids contact operation and not sludge blanket clarification operation; this
kept sludge out of the clarification zone.  Sludge  was kept at or below the bottom of
the reaction well  (Fig. 6-13) .

Conventional primary sedimentation basins are commonly of circular or rectangular
cross section, although some equipment manufacturers offer a square tank design.
Fig. 6-14 shows a typical section of the chemical primary treatment units designed
for the CCCSD Water Reclamation Plant.2^ A compact layout has been provided by
the common wall construction of rectangular tanks and by the separation of the
flocculation and sedimentation tanks by the distribution channel over an equipment
gallery. The gallery houses the grit, sludge and scum pumps, the preaeration
blowers and the associated pipine and appurtenances.  The primary sedimentation
tank in the ATTF  has two basic functions:  separation of the solids from the  liquid
and thickening of the solids. While the water reclamation plant under construction
will incorporate separate thickening stages, considerable thickening takes place
in the  primary sedimentation tank itself.

From the surface of the ATTF tank the sludge could be seen to settle out very
rapidly. Sludge profiles taken along the bottom confirmed that the bulk of the
sludge settled out in the first three-eighths of the primary tank.  Expansion of the
sludge layer  into the effluent end of the primary tank was taken as evidence of
sludge thickening failure, since no significant increase in underflow solids  con-
centration occurred at the time of layer expansion.  On this basis, it is estimated
that only 50 percent of the tank floor is effective in thickening.

Whenever sludge intruded under the effluent weirs or beyond, large floes immedi-
ately began appearing in the effluent. As long as the sludge layer was held in the
first half of the tank, no large floes appeared. This factor helps explain the
observed stability  of these clarifiers as a function of overflow rate.  Little deteri-
oration in effluent quality occurred up to a maximum hourly  overflow  rate of 90 cu
m/day/sq m (2200  gpd/sq ft) . During these tests, the average dry weather over-
flow rate was 59 cu m/day/sq m  (1440 gpd/sq ft) . The detention time at the peak
rate of  flow was only 0.9 hours.  The good separation of thickening and clarification
functions in the conventional rectangular primary allows relatively high overflow
rates to be obtained.

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                                         AGITATION AIR
                                           HEADER
       HELICAL SCUM  SKIMMER
                                                                    PIPE  CHASE
    PRIMARY
SEDIMENTATION
     TANK
           .Jb	
      PREAERATION ,
    FLOCCULATION 8
    GRIT  REMOVAL
        TANK
DISTRIBUTION
  CHANNEL
       LONG; TUDINAL
      SLUDGE COLLECTOR
                                           SCUM TO EJECTOR
                                              EQUIPMENT
                                                GALLERY
.^-AERATION
  HEADER
                                                                                  SLUDGE RECIRCULATION
                                                                                      LINE
 SLUDGE  CROSS  COLLECTOR
                                                                              GRIT HOPPER
                Figure 6-14 Primary treatment units at CCCSD water treatment plant

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The degree to which sludge could be thickened was affected by process pH. At
pH 11.0 and above when lime alone was added to the primary,  the sludge could be
thickened to as much as 9 or 10 percent total solids  (TS) .  However, at about 7 per-
cent total solids and above, coning and bridging occurred in the sludge hoppers,
and septic sludge zones developed.  This problem can be minimized by designing
steeper hoppers and providing positive feeding of sludge to the suction line of the
sludge pumps.  When the pH was dropped to 10.2, "thinner" sludges were obtained
The sludge could not be thickened to greater than 4.2 percent  TS .  However, when
an anionic polymer coagulant aid was employed at a dose of 0.25 mg/1,  6.0 percent
TS was attained in the underflow.  Burns and  Shell12 have reported on the solids
content of sludges over a slightly different pH range.  At pH values above 11.5,
the lime sludge thickening properties were significantly poorer than at pH 10.5 to
11.0.

Table 6-6 and 6-7  give maximum and recommended design parameters  respectively
to size primary clarifiers of both solids contact and rectangular design. The
rectangular tank design for which these figures are applicable is that which is
depicted in Fig. 6-14. Other rectangular tank designs may  have differing limiting
overflow rates and caution should be used in establishing  design overflow rates
unless specific test data is available. While solids contact type units are designed
at approximately the same surface overflow rates  as conventional rectangular pri-
mary tanks, considerably longer hydraulic retention times are employed.  This
translates into the need for deeper tanks when solids-contact units are designed.
Even  considering the separate preaeration and grit removal  tank (at 20 minutes
retention) as an addition to conventional tank cost,  solids-contact units require
greater structure size and therefore greater cost.


              Table 6-6  MAXIMUM CLARIFIER DESIGN PARAMETERS
Flow
Average dry weather
(ADWF)
Peak dry weather
(PDWF)3
Rectangular tank
Overflow rate
cu m/d/sq m (gpd/sq f)
59 (1,440)
90 (2,200)
Detention
time, hours
1.3
0.9
Solids contact clarifier
Overflow rate
cu m/d/sq m (gpd/sq f)
44 (1,080)
73 (1,800)
Detention
time, hours
2.5 3.0
1.5 2.0
     Peak flow during dry weather of 1  2 hour duration.

     Based on Reference 38.
It should be noted that Tables 6-6 and 6-7 apply to an operating pH of equal to or
greater than 10.5.  For both types of clarifiers, the design data are for highly
buffered wastewaters (alkalinity 200-300 as CaCO3) .  Low alkalinity wastewater
would result in lower calcium carbonate precipitation and different, as yet
undefined, criteria would apply.  Criteria for low lime applications are not as
well defined and were briefly discussed in a preceding section.
                                      70

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      Table 6-7  RECOMMENDED CLARIFIER DESIGN PARAMETERS
Flow
Average dry weather
(ADWF)
Peak dry weather
(PDWF) a
Peak wet weather
(PWWF)
Rectangular tank
Overflow rate
cu m/d/sq m (gpd/sq f)
49 (1,200)
73 (1,800)
147 (2,400)
Detention
time, hours
2.2
1.4
0.7
Solids contact clarifier
Overflow rate
cu m/d/sq m (gpd/sq f)
24 41 (580 - 1,010)

76 (1,870)
Detention
time, hours
1.4 2.8
-
1.4 1.9
Peak flow during dry weather of 1 - 2 hour duration.
Based on Reference 12.
Proportioned from Table 6-6.
                                      71

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                             REFERENCES


 1   Process Design Manual for Phosphorus Removal.  Black & Veatch,
    Consulting Engineers.  Washington, D.C. Environmental Protection
    Agency - Technology Transfer.  October, 1971.  pp. 10/23-10/27.

 2.  Parker, D.S., K.E. Train, andFJ. Zadick. Sludge Processing for
    Combined Physical-Chemical-Biological Sludge.  Washington, D.C.
    Environmental Protection Agency, Report Number EPA-R2-73-250,
    July, 1973. 141 p.

 3.  Schmid,  L .A. and R .E . McKinney. Phosphate Removal by a Lime-
    Biological Treatment Scheme. Journal of the Water Pollution Control
    Federation. 41, 1259-1276, July,  1969.

 4.  Albertson, O.E. and R.J. Sherwood. Phosphate Extraction Process.
    Journal of  the Water Pollution Control Federation.  41_, 1467-1490,
    August,  1969.

 5.  Adrian, D.D. and J.E. Smith, Jr. Dewatering Physical-Chemical Sludges.
    Applications of New Concepts of Physical-Chemical Wastewater Treatment.
    W.W. Eckenfelder, and L.K. Cecil.  New York, Pergamon Press, Inc.
    September, 1972. p. 273-289.

 6.  Menar, A.  and D. Jenkins. Calcium Phosphate Precipitation in Wastewater
    Treatment. Sanitary Engineering Research Laboratory, University of
    California, Berkeley, California, SERL Report No. 72-6.  June, 1972. 96 p.

 7.  Hartung, H.O.  Treatment Plant Innovations in St. Louis County, Missouri.
    Journal of  the American Water Works Association. 50:  965-974, July, 1958.

 8.  Stone, R.W.  The Effect of Lime  Sludge Return on Hardness Removal and
    Solids Carryover in the Lime  Softening Process. Thesis submitted to the
    University of Texas in Partial Fulfillment of the Requirements for the
    Degree of Master of Science in Environmental Health Engineering.
    January, 1968.

 9.  Horstkotte, G.A., D. G. Miles, D.S. Parker, andD.H. Caldwell. Full-
    Scale Testing of Water Reclamation System.  Central Contra Costa Sanitary
    District and Brown and Caldwell.  (Presented at the 45th Annual Conference
    of the Water Pollution Control Federation. Atlanta. October 12, 1972). 22 p.

10.  Pressley, T. Personal Communication to D .S . Parker.  Environmental
    Protection Agency - Blue Plains  Pilot Plant. October 11,  1973.
                                   72

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11.   Advanced Wastewater Treatment as Practiced at South Tahoe, South Tahoe
     Public Utility District. Washington, D.C. Project 17010 ELQ. Environ-
     mental Protection Agency.  August,  1971.  436 p .

12.   Burns, D.E. and G.E. Shell. Physical-Chemical Treatment of a Municipal
     Wastewater Using Powdered Carbon. Envirotech Corporation. Salt Lake
     City.  Report No. EPA-R2-73-264 for Environmental Protection Agency.
     August, 1973.  230 p.

13.   Nilsson, R. Removal of Metals by Chemical Treatment of Municipal Waste-
     water.  Water Research.  5:51-56, May, 1971.

14.   Argaman, Y. and C.L. Weddle. The Fate of Heavy Metals in Physical-
     Chemical Treatment Processes.  AICHE Symposium Series "Water 1973".

15.   Maruyama, T., S.A.  Hannah, and J.M. Cohen. Removal of Heavy Metals
     by Physical and Chemical Treatment Processes. (Presented at 45th Annual
     Conference of the Water Pollution Control Federation.  Atlanta.  October 12,
     1972) .

16.   Zuckerman, M.M. and A.H. Molof.  High Quality Reuse Water by Chemical-
     Physical Wastewater Treatment.  Journal of the Water  Pollution Control
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17.   Weber, W. J. Discussion of Paper 1-21.  In: Advances in Water Pollution
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18.   Weber, W.J.  Discussion. Journal of the Water Pollution Control Federation
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19.   McDonald, G.C., W.J. Greene, F.W. Hardt, R.D.  Spear, Washington,
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20.   Molof, A.H. and M.M. Zuckerman, High Quality Reuse Water from a Newly
     Developed  Chemical-Physical Treatment Process. In:   Advances in Water
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21.   Westrick, J . J . and J .M. Cohen. Comparative Effects  of Chemical Pretreat-
     ment on Carbon Adsorption.  (Presented at 45th Annual Conference of the
     Water Pollution Control Federation.  Atlanta.  October 11, 1972) .
                                    73

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22.  Gulp, G.L. Design of Facilities for Physical-Chemical Treatment of Raw
     Waste Water.  Gulp,  Wesner, Gulp. Corona del Mar. Environmental
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23.  Lime. Wallace & Tiernan .  Belleville, N.J.  Sales Services Department
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24.  Martin,  Larry. Personal Communication to D.S . Parker.  City of Holland,
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25.  Brown and Caldwell. Plans and Specifications for Water Reclamation Plant,
     Stage 5A - Phase 1.  Central Contra Costa Sanitary District.  California.
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26.  Babcock, R.H. Instrumentation and Control in Water Supply and Waste-
     water Disposal. Reprinted from Water and Wastes Engineering. 1968.
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27.  Parker, D .S ., W. J.  Kaufman, and D. Jenkins.  Floe Breakup in Turbulent
     Flocculation Processes. Journal of the Sanitary Engineering Division.
     Proceedings of the ASCE.  98_ (SA1): 79-99, February, 1972.

28.  Parker, D.S. andD.G. Niles. Full-Scale Test Plant at Contra Costa Turns
     Out Valuable Data and Advanced Treatment. Bulletin of the California
     Water Pollution Control Association. 9 (1):  25-27, July, 1972.

29.  Alternative Treatment Processes for Reductions of Turbidity, Color,
     Floatables, Grease and Settleable Matter. Brown and Caldwell, Consulting
     Engineers. Report for the City and County of San Francisco. September,
     1971. p. 23-53.

30.  Love, R. and F. Gaines.  Personal Communication  to D.S.  Parker.
     Hatfield Township Municipal Authority.  August 23,  1973.

31.  Burns, D .E . and D. J. Cook. Physical-Chemical Treatment of Municipal
     Waste. Progress Report No.  II. Envirotech Corporation, Salt Lake City.
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32.  Argaman, Y. and WJ. Kaufman.  Turbulence and Flocculation. Journal
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     241.  April, 1970.                                     ~~

33.  Tofflemire, T J. and L J ..Hetling .  Treatment of a Combined Wastewater by
     the Low Lime Process, Journal Water Pollution Control Federation,  45, 210
     (1973).                                                       —
                                   74

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34.  Pilot Plant Demonstration of a Lime-Biological Treatment Phosphorus
     Removal Method.  Department of Civil Engineering, Kansas State
     University.  Manhattan.  Project 17050 DCC .  Environmental Protection
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35.  Ranson, William.  Personal Communication to D .S . Parker.  City of
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36.  Martin, Larry.  Personal Communication to E . de la Fuente. City of
     Holland, Michigan.  October 26, 1973.

37.  Gaines, F.R. Personal Communication to E . de la Fuente.  Hatfield-
     Township Municipal Authority, Pennsylvania. October and December,
     1973.

38.  Shell, G.L.  Personal Communication to D .S . Parker .  Envirotech
     Corporation. Salt Lake City.  August 31, 1972.

39.  Convery, J.J.  The Use of Physical-Chemical Treatment Techniques for
     the Removal of Phosphorus from Municipal Wastewaters. (Presented at
     the Annual Meeting of the New York Water Pollution Control Association.
     New York.  January 29,  1970) .  39 p.

40.  Cooper, R.C., R.C.  Spear, andF.C. Schaffer.   Virus Survival in the
     Central Contra Costa County Water Renovation Plant.  School of Public
     Health, University of California.  Berkeley.  January, 1972.  38 p.

41.  Mulbarger, M.C., E. Grossman, III, R.B. Dean, andO.L. Grant.  Lime
     Clarification, Recovery, Reuse and Sludge Dewatering Characteristics.
     Journal of the Water Pollution Control Federation. 41_: 2070-2085,
     December,  1969.

42.  Wuhrman, K. Objectives, Technology, and Results of Nitrogen and
     Phosphorus  Removal Processes. In: Advances In Water Quality Improve-
     ment, E.F. Gloyna and W.W. Eckerfelder (eds.) . Austin.  University of
     Texas Press, 1968.  p 21-43.

43.  Caldwell, D.H., D.S. Parker,  and W.R.  Uhte. Upgrading Lagoons.
     Brown and Caldwell.  San Francisco. Environmental Protection Agency.
     Technology Transfer Seminar Publication.  August, 1973.  43 p.

44.  Bishop. D.F.,  T.P. O'Farrell, and  J.B. Stamberg.  Physical-Chemical
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     Federation.  44:  361-371, March,  1972.

45.  Parker, D.S., D.G. Niles, and F.J. Zadick. Processing of Combined
     Physical-Chemical-Biological Sludge. Brown and Caldwell and the Central
     Contra Costa Sanitary District.  (Presented at 46th Annual  Conference of
     the Water Pollution Control Federation. Cleveland. October 1,  1973) . 23 p.
                                    75

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46.   Gulp, R.S. and G.L. Gulp. Advanced Wastewater Treatment.  First
     Edition.  New York, Van Nostrand Reinhold Company, 1971.  310 p.

47.   Shuckrow, A.J. and W.F. Bonner. Development and Evaluation of
     Advanced Waste Treatment Systems for Removal of Suspended Solids,
     Dissolved Organics, Phosphate and Ammonia for Application in the City
     of Cleveland.  Battelle-Northwest, Richland.  Zurn Environmental
     Engineers.  June,  1971.  96 p.

48.   O'Farrell, Thomas. Personal Communication to D.S . Parker.  Environ-
     mental Protection Agency, Blue Plains Pilot Plant.  October 11, 1973.

49.   Sewage Treatment Plant Design.  Water Pollution Control Federation.
     Washington, D.C. Manual of Practice No. 8. 1959. 375p.
                                76

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                                  SECTION VII

                  LIME SLUDGE THICKENING AND DEWATERING
GENERAL CONSIDERATIONS

Sludge thickening and dewatering are preparation or pretreatment steps which
normally precede further sludge processing or final disposal.  In wastewater
treatment,  thickening and dewatering have often been considered as different
types of processes;  in fact, thickening is a dewatering process.  As currently
applied, however, sludge  thickening implies solids concentration with the aim
of reducing the volume of sludge to be handled in subsequent treatment steps.
Dewatering implies further removal of water, generally by mechanical means,
to produce a relatively dry sludge cake for further treatment or disposal.

Land methods of sludge  dewatering have not been included in this section, since
in the  majority of applications, they constitute the ultimate method of sludge
disposal. For a discussion of ultimate disposal of ash, see Section XI.

SLUDGE THICKENING

Although sludge thickening is a preliminary process, it removes a major amount
of liquid from the sludge.   The  curves presented in Fig. 7-1 show the  reduction
of water content under varying degrees of thickening.  For example, when the
sludge concentration is increased from 1.5 to five percent, over 70 percent of
the original moisture is  removed.

Two methods are commonly used to thicken sludge - gravity and air flotation. In
general, the gravity method is used to thicken primary sludges; i.e.,  sludges
that settle readily, while air flotation is employed when dealing with the lighter
biological sludges.
                                                      1  2
A third thickening method,  using centrifugal equipment,  '  is gaining accept-
ance, generally as an alternative to dissolved air flotation.  When centrifuges
are applicable, their use results in considerable savings in floor space require-
ments.  Power costs, however,  are likely  to be higher than with gravity or air
flotation thickeners.

Gravity Thickening

The results obtained at the CCCSD's ATTF in terms of thickening in the primary
clarifiers lead  to the conclusion that gravity thickening has clear advantages
when  dealing, with the  heavy lime  sludges generated  from primary treatment
applications.   This process is  not only simple to operate but also more econom-
ical than dissolved air flotation  or centrifugation.
                                     77

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       100
                   23456789    10    II
                INCREASE IN SOLIDS CONCENTRATION, PERCENT BY WEIGHT
    Figure 7-1  Relationship between increase in solids concentration and
               moisture removal (after Katz (12))


Scant information is available on gravity thickening of primary lime sludge.
Black and Lewandowski conducted a three-month plant scale operation at
Richmond Hill,  Ontario, where lime sludge concentrations of up to 12 percent
solids were achieved in gravity thickeners.^

Burns and Shell  have reported the results of eight months of laboratory
thickening tests at pH values between 9.8 and 11.6.  From these results they
conclude that "the moderate treatment pH (below 11.0)  sludges tested were
generally more concentrated than the high treatment pH sludges  (above 11.5) ."
Burns and Shell also stated that "it appears that the more concentrated the
chemical clarifier underflow (initial solids) the more the solids can be concen-
trated."  During the same work, Burns and Shell also evaluated  the effect of
polyelectrolytes as flocculation aids on thickener performance.  They concluded
that, although the continuous use of polyelectrolytes solely to reduce the thick-
ener size was probably unjustified, the addition of chemicals would maintain a
high underflow concentration under decreasing feed solids concentration.
                                    78

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At the time this report was being prepared, Burns and Shell were reevaluating
their  projections for  thickener performance.  A compression  zone analysis
indicated that to obtain ultimate sludge concentration  (18-25  percent TS) ,
thickener solids loading would  have to be reduced below  49  kg/sq m/day
(10 Ib/sq ft/day) , which is considerably lower than the 196  - 245 kg/sq m/day
(40 - 50 Ib/sq ft/day) previously recommended.5 This came to light when they
found that the results obtained in the laboratory tests could not be reproduced
in a 2.4m (8ft)  diameter gravity thickener .6, / Thickener performance was
erratic, varying from no additional concentration to about 35 percent increase
in the feed solids concentration.  The concentration of feed solids ranged from
8.1 to 12.0 percent TS.  Average thickener loading was 78 kg/sq  m/day (16 Ib/sq
ft/day) .   The most recent recommendations on the design of  gravity thickeners
based on the work at Salt Lake City are included  in Reference 8.

Investigators at EPA's Blue Plains pilot plant have conducted tests on the thick-
ening properties at high lime sludge.9  Interfacial settling velocity as a function
of total solids concentration is shown in Fig. 7-2.  Essentially,  no differences in
settling rates were observed between cases where recalcined lime was used and
where only new  lime was  used.  Using a batch flux method of analysis, it was
concluded that with a solids loading of 673 kg/sq m/day (138 Ib/sq ft/day) , 10
percent underflow solids could be obtained.  Similarly, at a solids loading of
430 kg/sq m/day (88 Ib/sq ft/day) , it was calculated that  20 percent total solids
in the underflow could be obtained. The investigators cautioned, however, that
this data had not been verified  in continuous thickening tests.

Gravity thickeners are commonly deep circular tanks provided with a rotating
arms  mechanism for sludge agitation and collection.  The feed sludge is intro-
duced into a circular  influent well and the overflow is usually collected over
peripheral weirs.  The  thickened underflow forms a sludge blanket so the unit
performs  not unlike a solids contact clarifier. Sludge is withdrawn, contin-
uously or intermittently, from a centrally located bottom hopper.  A typical
section of a gravity thickener is shown in Fig .  7-3.

To prevent septic  conditions in the thickener, the use of chlorine has been rec-
ommended. The dosage should produce a residual chlorine  concentration of
0.5 to 1.0 mg/1.2  Low pressure air has also been used to prevent septicity.
The gentle agitation provided by the compressed  air also aids in promoting
solids concentration by allowing entrapped water to escape through the sludge
blanket. 10  This approach is seen in Fig. 7-4,  which shows a cross section of
the lime sludge thickener at the CCCSD water reclamation plant.11  A 20-ft
deep  existing digester is being converted into a thickening tank.  Design
loading is 390 kg/sq m/day  (80 Ib/sq ft/day) and the lime sludge will be fed at
an approximate concentration of 6 percent TS .  Compressed  air can also be used
to fluidize the sludge blanket to control maximum solids concentration and to
allow low-torque starting of the rotating arms.
                                     79

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1
o
3
UJ
>
o
Ul
to
                             O  WITHOUT LIME REUSE

                             A  WITH LIME REUSE
     20  -
                          8
12
16
20
24
                        TOTAL SOLIDS, PERCENT
         Figure 7-2  Settling characteristics of high lime sludge
                    at the Blue Plains pilot plant
                                80

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               MANUAL ARM LIFT
               VERTICAL
               ADJUSTABLE^
               DIFFUSER
                                       ARM 8 CONCENTRATOR ASSEMBLY
          THICKENED  SLUDGE
    Figure 7-3  Typical gravity thickener (courtesy of Walker Process)
Although the concentration of solids that takes place in the primary sedimentation
tank (see Section VI)  could justify eliminating separate gravity thickeners, the
latter also perform as sludge flow equalization basins.  This function is as
important as solids concentration to smooth out the flow of solids to downstream
treatment processes.  Since sludge production varies during the day, removal
from the primary clarifiers is normally intermittent to insure that only well
compacted sludge is withdrawn.  The presence of thickeners then allows a
fairly constant sludge feed to the centrifuges or furnaces which is essential for
steady state operation.  It is under steady state conditions that the dewatering
and incineration equipment can achieve peak performance.

Surface skimming has not always been employed on gravity thickening tanks.
Surface skimming has been found to be mandatory on tanks receiving centrate
from a centrifuge classification step at the CCCSD's ATTF.  (See a  later
discussion  of classification in this  section) .  The centrifuge operation caused
                                     81

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00
                                                                                                                        Id EXHAUST
                                                                                                                        A/RUNE
                                                                                                                   •— A IK LINE. SPACING
                                                                                                                     TO as otreRM/NCD
                                                                                                                     BY MMUfjCTUKtR
                                                                                           /
-------
the incorporation of fine bubbles into the centrate, resulting in some foam flota-
tion.  This phenomenon has been used at Blue Plains^ to accomplish flotation
thickening, as is discussed in this section under Flotation Thickening.

Thickening data obtained to date have resulted in wide variations in terms of
design recommendations.  Therefore, development of firm design criteria will
have to await further investigation.

Flotation Thickening

Thickening of sludge by dissolved air flotation has seen wide acceptance in
recent years, particularly in waste activated sludge  applications.   To separate
solids from water by flotation, gas bubbles are formed by dissolving air into the
water at a pressure of approximately 2.8 kg/sq cm (40 psig) .  The air charged
stream is then mixed with the sludge where the pressure is  released forming
fine air bubbles which adhere to the solid particles.  Once introduced into the
tank, the lowered specific gravity of the solid particles causes them to rise to
the surface.  As the solids  accumulate,  a blanket of sludge is formed. An over-
head skimmer removes the  top of the sludge blanket, where  the high solids
concentration occurs, and discharges it to a sludge hopper. The relatively
clear underflow moves out of the separation zone under a submerged baffle and
flows over the effluent weir.  Fig.  7-5  shows a schematic diagram of the air
flotation process.^ The pressurized flow source may be recycled thickener
underflow,  plant effluent or some other process flow.

When centrifugal equipment is used for separation of calcium carbonate  from
other waste solids (see Wet Classification in this section) , the  high speed
centrifuge operation tends to aerate the sludge and to create fine bubbles in the
centrate.  These bubbles behave as air bubbles would in a conventional air
flotation system when the centrate enters a quiescent tank.  Bennett 9 has used
this effect to accomplish thickening of the centrate solids without a supplementary
air dissolution step. Centrate at 2-3 percent total solids, has been thickened by
this procedure to 4.7 to 7.3 percent total solids.  Bennett cautioned, however,
that the transfer of the centrate to the thickening tank must  be immediate to
prevent bubble  release from the sludge. To insure consistent operation, it  is
desirable to make provisions for standard air  dissolution equipment.

The application of conventional air flotation equipment to thicken lime sludges
must be approached with caution.  The introduction  of carbon  dioxide from the
pressurized air may cause  scaling of equipment with the accompanying  main-
tenance problems.  Purified oxygen or nitrogen might prove a better gas source
than ambient air for dissolved air flotation in this application, since they con-
tain a negligible quantity of carbon dioxide.

Specific design  criteria for flotation thickening of lime sludges have not been
published to date.
                                     83

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         SLUDGE
         FLOW
         TO BE
         THICKENED
CO
*>,
              PRESSURE
              REDUCTION
              VALVE
                                                                                 THICKENED
                                                                                ^SLUDGE
    BASIN
.THICKENER
 EFFLUENT
                                                        AIR
                                                        INJECTION
                                                       .   t
AIR
SOLUTION
TANK
                                 PRESSURIZED
                                 FLOW SOURCE
                                                               PRESSURIZATION
                                                               PUMP
                            ^-AIR-CHARGED
                              STREAM
                    Figure 7-5  Schematic diagram of the dissolved air flotation process

-------
SLUDGE DEWATERING

The main purpose of mechanical dewatering is to minimize the moisture content of
the sludge.  When oriented towards incineration,  a more specific purpose is to
increase the volatile content per pound of wet sludge.  Approximately 450 kg-cal
(1800 Btu) are required to evaporate a pound of water  (at an off-gas temperature
of 700 F);  therefore, excessive moisture increases the  thermal load on the incin-
eration process and the amount of auxiliary fuel required.  The influence of
moisture content on the cost of sludge incineration is shown in Figs. 7-6  and 7-7
for primary  sludge.2

Two  methods are  commonly used in the United States for sludge dewatering -
vacuum filtration  and centrifugation.  A third method,  utilizing filter presses,
enjoyed limited use in the past, 10 although in  recent years there has been
renewed interest  in pressure filtration for dewatering the more difficult sludges.
Pressure filtration of sludge has been practiced in Europe for many years.

The methods employed for sludge dewatering have a marked impact on the solids
processing design,  when  the objective is recovery of  lime from sludges. When
vacuum or pressure filtration is used to dewater the primary-generated sludge,
all of the sludge is  captured in a single dewatering stage.  Therefore, all of the
sludge must be recalcined in a Plural Purpose Furnace  (Fig. 7-8) .  Inerts (con-
stituents other than calcium carbonate or calcium  oxide) must be controlled from
building up  through recycling after several passes;  therefore, blowdown of a
portion of the recalcined product is mandatory with consequential loss of  a
portion of the reclaimed lime. 3 Dry classification, a process described in detail
in Section VIII, allows this ash blowdown to be somewhat more efficient in terms
of rejecting  silica inerts .

When centrifugation is employed, it is possible to classify the calcium carbonate
from most of the magnesium, phosphorus, and iron compounds as well as from
the organics. A high calcium carbonate  cake is produced which can be
recalcined (Fig.  7-9) to produce reclaimed lime.  Dry  classification can be
effectively employed in this flowsheet to  blow down silica.  The centrate  from
the wet classification step containing the waste solids can be disposed of  by a
number of procedures.  One alternate, shown  in Fig. 7-9, is to use another
centrifuge to separate the waste solids and use incineration to produce an ash
residue for final disposal. Another alternative would be to employ lime stabi-
lization of the solids prior to dewatering, followed by direct disposal of the cake
as land fill.   Alternately,  digestion of the centrifuge centrate could be used
before final  disposal.3

Centrifugation

Centrifuges  have  long been used for sludge dewatering, although at a limited
scale,  due mostly to their early design and construction deficiencies. 10  How-
ever, the development of the present efficient machines has led to the wide
acceptance of centrifuge equipment for mechanical dewatering applications.  The
theory of centrifugal separation has been presented in  References  10 and 13.
                                     85

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£  2
       10
       9  -
       8  -
       7  -
      6  -
                             DESIGN CONDITIONS



                             GAS EXIT TEMP	I500°F


                             EXCESS AIR	20%



                                  I. 1970 DOLLARS
                            $5.25
                                  (I)
       4  -
<  x  3  _
 -J  oS

 X  b
    ^  2  -
    O

    CM

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        I  -
       0
                 WITH  HEAT

                 RECOVERY AND

                 PREHEAT AIR TO

                 1000° F
                                      WITHOUT HEAT

                                      RECOVERY
                    % TOTAL SOLIDS  IN SLUDGE


          AT 75% VOL AND 5270KG-CAL/KG (9500 BTU/LB.) VOLATILE
Figure 7-6  Effect of moisture content on the cost of sludge combustion
                               86

-------
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                  % TOTAL SOLIDS VS. AUX FUEL


              EXIT TEMP AT 1500° F EXCESS AIR 20%




                       (I) 1970 DOLLARS
                  (I)

           $2.56/TON
                                          (I)

                                   $1.76/TON
                                                                  (I)

                                                          $0.92/TON
        25
                               275
                                                        30
                   % TOTAL SOLIDS IN  SLUDGE


         SLUDGE 75% VOL. AND 5500KG - CAL/KG (10,000 BTU/LB) VS.
  Figure 7-7  Effect of moisture content on the cost of sludge combustion
                                 87

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        MAKEUP LIME
        1
     L IME
    STORAGE
PRIMARY  CLAR IFIER
                 LAKERi
                              u
                RAW SEWAGE  A
                      FILTRATE
                         TO
                      PRIMARY
                         CAKE
                     J-
                            PRIMARY
                                                           EFFLUENT
                              MULTIPLE
                              HEARTH
                              RECALCINE;
                              FURNACE
               DRY
               CLASSIFICATION
JRECYCLE LIME TO  STORAGE
           VACUUM
           FILTER
              OR
           CENTRIFUGE
              OR
           FILTER PRESS
                                             GAS
                                            SCRUBBER
                                ASH
                  ASH
                  SLOWDOWN

                  ASH REJECTS
                                      ACCEPTS
    Figure 7-8  Conventional Plural Purpose Furnace flow sheet
                               88

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FROM
RECALCINING FURNACE
                 1
MAKEUP
LIME
WASTE
BIOLOGICAL
SOLIDS
                LIME
               STORAGE

S LAKER
W '
CENTRATE RETURN


RAW
SEWAGE

LIME
REACTOR
(PREAER-
ATION)


ATTF
PRIMARY CLARIFIER
. _--^
PRIMAR
EFFLUEf
                                             FIRST
                                             STAGE
                                            THICKENER
   WET
   CLASSIFICATION
                                        SECOND
                                        STAGE
                                        THICKENER
                                    2nd STAGE CENTRIFUGE
                                         OR
                                    FILTER PRESS
                                         OR
                                    VACUUM FILTER
                    MULTIPLE
                    HEARTH
                    RECALCINE
                    FURNACE
                                  'GAS
                             SCRUBBER
                     IRECALCINED
                      ASH
                             REJECTS
    DRY
    CLASSIFICATION
  RECYCLE LIME TO STORAGE
                                   CENTRATE TO
                                    PRIMARY
                                           MULTIPLE
                                            HEARTH
                                            FURNACE
       HIGH LIME
       ACCEPTS
                                                    ASH TO DISPOSAL
               Figure 7-9   ATTF solids processing system
                                      89

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Three general types of centrifuges are available today -  basket, disc, and solid
bowl.   However, only  the last type is  capable of producing both a dry sludge
cake and a well clarified centrate in a single step.
The main  elements of a solid bowl, scroll type centrifuge are the rotating bowl
and the conveyor mechanism.  The  solids, under the effect of the separating
force ("G" force)  settle in  the cylindrical-conical bowl, and are then picked up
by  the screw  conveyor which carries the settled solids to the discharge ports.
Solid bowl centrifuges used in sludge dewatering are available in two basic flow
configurations -  concurrent and counter-current.  In the concurrent design,  the
feed is introduced at one end and the liquid and solids travel together toward  the
outlet ports.  In the counter-current type, the feed is introduced near the conical
portion of the bowl (the dewatering beach) .  The solids are moved in one direction
while  the centrate is discharged in the opposite direction.  Fig. 7-10 shows both
types of centrifuges.
Solid bowl centrifuges can be manufactured of various alloys to provide protection
under abrasive or corrosive operating conditions .  Table 7-1 lists materials of con-
struction used by a major manufacturer of centrifuge equipment.  Where an abrasion
problem is more likely to occur, such as in the feed zone and conveyor flights,
hard surfacing techniques are often used to provide abrasion-resistant materials.
        Table 7-1.  SOME BASIC MATERIALS OF CONSTRUCTION USED IN
                    SHARPLES  CENTRIFUGES
          METALS
   ABRASION RESISTANT
       MATERIALS
CORROSION RESISTANT
     COATINGS
   Steel, Carbon & Alloy
   Stainless
      304, 304L, 316, 316L
      317L, 329, 17-4PH, 431
      (Miso PH Grades)
   Carpenter 20-Cb 3
   Titanium, C. P. Grades
      Ti (6 A1-4V,), Ti (0. 2% Pd)
   Hastelloy B; C-276
   Wiscalloy B, C (Low Carbon)
   Monel 400, K-500
   Inoaloy 800, 825
   Nickel 200
Tungsten Carbide (Solid)
Tungsten Carbide (Plasma Fused)
Tungsten Carbide Composites
  WC & Steel Matrix
  WC & Hastelloy Matrix
  WC & Ni, Dr, B, Matrix
  WC & Co, Cr, W Matrix
  Formaflex Coatings
Ceramics  (Solid)
Ceramics  (Plasma & Flame Sprayed)
Hard Chromium & Armaloy
Cobalt-Chrome-Tungsten
(Stellite-Stoody)
Nickel-Chrome-Boron
  (Colmonoy-Coast)
    Hard Rubber
    Neoprene
    Kynar
    TFE
    Penton
    Tin, Cadmium, Zinc
    Nickel (Electroless)
    Chromium
    Multiple Paint Systems
      Epoxy-Phenolic
      Urethane, Vinyl
      Alkyd, Plastisol
      Organic Zinc
                                        90

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                                                                  -f
                                                                 FEED
                       SOLIDS
                      DISCHARGE
                                                          CENTRATE
Concurrent flow centrifuge (courtesy of Bird Machine Company)
     LIQUIDS
    DISCHARGE
-Counter-current flow centrifuge (courtesy of Sharpies-Stokes

 Division of Pennwalt Corporation)



              Figure 7-10  Solid-bowl  conveyor centrifuges
                                   91

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Centrifuges are normally designed for horizontal installation, although one
manufacturer, Sharpies, offers a line of vertical units.  Among the advantages
attributed to the vertical centrifuge, when compared to the horizontal design,
are smaller floor space requirements and higher unit capacity.  The latter
feature is particularly advantageous in large installations where the required
number of horizontal machines can be replaced by a smaller number of vertical
units.  This reduction of equipment would often compensate for the higher initial
cost of the vertical centrifuges .  At the CCCSD water reclamation plant, the
capital cost of providing four vertical machines to wet classify 110,000 kg of dry
solids  (DS) per day  (242,000 Ib/day DS)  and to clarify 40,800 kg/day (90,000
Ib/day) DS (wet classification will be described later in this section) was 7.5
percent lower than the alternative to supply six horizontal machines to handle
the same sludge quantities.  Each alternative included the cost of the auxiliary
equipment normally required for centrifuge operation. Fig.  7-11 shows the
vertical centrifuge layout at the  CCCSD plant. H

Sludge dewatering by centrifugation is affected by both process and machine
variables. The Water Pollution Control Federation  (WPCF) manual on sludge
dewatering practices lists the following:

     "Process Variables:

         (a) sludge feed rate,
         (b) sludge solids characteristics,
         (c) sludge consistency,
         (d) sludge temperature, and
         (e) chemical addition."

     "Machine Variables:

         (a) bowl design;
            i   L/D  ratio,
            ii  bowl angle,
            iii flow pattern
         (b) bowl speed,
         (c) pool volume,
         (d) conveyor design, and
         (e)  relative conveyor speed ."

The effects of some of these variables will be covered in detail under Wet Classi-
fication .  The best way to evaluate all of the variables listed above is through
pilot plant testing. Test centrifuges are available from several equipment
manufacturers, which use a scale-up factor, £ , to predict results at full scale
ope ration.14
                                    92

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                          SHAFT COOLING\
                            AIR DUCT
                            MULTIPLE
                             HEARTH
                              FURNAC
                                                                    CENTRIFUGE
                                                                    DRIVE MOTOR
  TYPICAL
SCREW CONVEYOR
    DRIVE
 CASING VENT
                                                    TYPICAL
                                                  WORKING PLATFORM
                                   PLAN
CENTRIFUGE
FEED
                    BELT DRIVE
                     GUARD
                       GRATING
                                                CENTRATE
                                                DISCHARGE
                                           -SHAFT COOLING
                                           AIR DUCT
                                HEARTH   1
                              (AFTERBURNER)
                                HEARTH  2
                                HEAR
                                    TH  3
                                     TRANSFER SCREW
                                        CONVEYOR
FEED SCREW
CONVEYOR
                             ELEVATION
Figure 7-11  Vertical centrifuge installation at the CCCSD water reclamation
              plant
                                      93

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Scaling  Factors -
                               14
The equation for £ is as follows:
                        4R1 +  4ix2
                        v
  where: L  =  bowl length, cm
         R! =  radius of the liquid surface, cm
         R2 =  radius of the inner wall of the bowl, cm
         w  =  rate of rotation, rad/sec.

These terms have been represented in Fig. 7-10.   The  £ factor represents the
area, in sq cm, of a theoretical gravity sedimentation tank having equivalent
clarification characteristics to the centrifuge.  Thus,  £  can be used to relate
capacities of different centrifuges, such as the filtering surface area which is
used in sizing vacuum filters .

There  is some controversy among centrifuge manufacturers concerning the
appropriate bowl length to be employed in the  S  equation.  Some manufacturers
use the total bowl length, some  include the portion of the dewatering beach
that is wetted, and still others include only that portion of the beach between
the liquid discharge and the mid-point of the feed ports. From a theoretical
standpoint,  the effective clarification length is most closely approximated by
the latter definition  for the counter-current design (see Fig. 7-10) .  At any
rate,  if machines of different manufacturers are to be compared,  I> must be
calculated on the same basis for each.  The calculation of the SL factor  is one of
the essential steps in comparing equipment proposals of different manufacturers.
However, it must be  remembered that the value of 
-------
From the above calculation, it would be expected that it would take four of
Manufacturer A's machines to do the job that three of Manufacturer B's machines
would do.

Wet Classification
The problem in recovering lime from raw sewage sludge is that many constituents
are precipitated with the sludge besides calcium carbonate.  As explained in
Section VI, organics, phosphorus, magnesium, iron, and other constituents are
coprecipitated with calcium carbonate. These constituents, if left with the
calcium carbonate during recalcining, are returned to the process.  Eventually,
these "inerts" build up to such a magnitude that the solids processing facilities
are overwhelmed.  This problem has been the major reason that recovery of lime
added in the primary sedimentation tanks has not been practiced. 15 The problem
of lime recovery has also been a deterrent to the use of lime in raw sewage
coagulation.

Sludge solids vary greatly both in size and density and as a result, they settle at
widely different rates.  The process whereby the sludge constituents are
separated into various categories  based on this spread in settling rates is  called
wet classification.  Centrifugal action magnifies the  difference in settling of solids
particles; therefore, centrifuges are particularly suitable for wet separation.
The ability of centrifuges to classify particles on the basis of both size and
density has been used in industrial applications for many years. 16  Wet classi-
fication has been used for over three decades to control inerts buildup in water
softening plants practicing lime reclamation.I7/18,19  Classification data from
three studies where Bird centrifuges were employed are shown in Table 7-2.
Except for anamolous behavior with silica, good rejection of all components was
obtained, while retaining silica.  The procedure for calculation of the recoveries
has been described previously.3
        Table 7-2.  CLASSIFICATION DATA FOR WATER TREATMENT
                    PLANT SLUDGES
Plant
Constituent
Total Solids
Calcium
Magnesium
Iron
Aluminum
Silica
Recovery of stated constituent, percent
Wright Aeronautical
Corp. , Cinncinati, Ohio
Run 1
74
84
51
43
17

Run 2
81
88
57
11
40

Run 3
96
100
36
53
<1
38
Columbia Steel
Corp. , Provo, Utah
Run 1
92
96
3
51
50
92
Run 2
85
90
3
47
58

Marshalltown,
Iowa"
Control
80
89
16
62


Cycle 1
75
98
20
58


Cycle 2
75
95
9
66


Cycle 3
77
92
20
70



Findlay
Ohioc

73
77
40



    Reference 17
   ^Reference 18
   cReference 19
                                      95

-------
In the case of lime sludges, the purpose of wet classification is to maximize
recovery of calcium carbonate in the centrifuged cake while rejecting the other
components to as great an extent as possible.  The calcium carbonate crystals
settle more rapidly than the other solids .  Consequently, a partial recovery of
the total solids with a centrifuge concentrates the calcium carbonate along with
the heavy inert solids in the cake.

Classification  Efficiency - Classification efficiency of a centrifuge is expressed
in terms of the percentage of the particular constituent in the feed that is
recovered in the cake.  Good classification efficiency is achieved when calcium
carbonate recovery is high and when recovery of the other constituents is low.

In pilot plant studies at the CCCSD's ATTF,3'20 the  recovery of each component
was compared with the total solids recovery, to get an indication of  the efficiency
of component classification. The relationships derived from this analysis are
shown in Fig. 7-12.  From the figure, it can be observed that there  is a fairly
broad range in which fairly high calcium  carbonate  recovery is coupled with
reasonable classification. For instance, at 50 percent total solids recovery, 70
percent of the calcium carbonate is recovered with less than 30 percent of the
other major constituents,  while at 70 percent total solids recovery, almost 90
percent of the calcium carbonate is recovered with less than 50 percent of the
other major constituents,  except the acid insoluble inerts.  The one constituent
without good classification characteristics is the acid insoluble inerts.  Re-
coveries shown  in Table 7-3 range from 41 to  100 percent recovery.   Quite wide
variation in recovery of these inerts was obtained, perhaps because of variations
in composition of these inerts in the feed sludge. In subsequent work21 where
recalcined lime was recycled, the acid insoluble inerts were found to be com-
prised primarily of silica (80 to 90 percent) .

Data obtained  at the CCCSD's ATTF on classification during a representative
period of lime reuse are shown in Table 7-4.21  During this work, specific tests
on the silica levels in the sludge allowed the determination of silica recovery at
85 percent. This means that there is essentially no rejection of silica; it is
recovered at nearly the same level as calcium carbonate.   A plot of the classi-
fication relationships  determined during the ATTF test work on lime recycling
is shown in Fig. 7-13.  Classification for all constituents, except ferric
hydroxide and silica, was similar to that experienced without lime recycle
(Fig. 7-12) .   With silica, it was found that recovery increased from less than
the calcium carbonate recovery prior to lime recycle to a level  greater than
the calcium carbonate recovery after lime recycle.21  Apparently, the furnace
operation altered the classification characteristics of the silica  recycled to the
process. Iron recoveries were consistently greater than experienced previously,
even during the period prior to the actual implementation of lime recycle.  It is
felt that this was due to the addition of iron to the downstream nitrification
system, so that iron precipitates entered the primary incorporated into the  waste
activated sludge, rather than as a supplemental coagulant as in previous work.
                                     96

-------
     too
                    20
             RECOVERY
OF
40
TOTAL
    6O          8O
SOLIDS,  PERCENT
                                        IOO
  Figure 7-12  Summary of constituent recoveries during wet classification
              without lime recycle
Besides demonstrating the feasibility of wet classification of lime sludges,  the
data presented in Table 7-3 show the wide range in degree of classification
attained.  These variations are due primarily to differences in centrifuge
operating conditions.  The principal variables are feed rate, centrifugal force
and pond depth setting.
                                     97

-------
                                                   Table 7-3.   RUN  DATA  FOR VJE'-  CLASSIFICATION
Process Parameters
Hun
'2-7
2-5
2-1
2--J
2-32
2-]2a
Machine
Sharpies
P-liOO




Sharpies
N~1 P-3000
.1-4
S-12
8-9
8 -is
n-5
8-41
8-40
4-3-72
4-134
4-106
4-105
4-123b


Sharpies
P-600



Centrifugal
fo rcc
per Ib
mass, R'.S
2100



1050
2100
2100





1500
1500
3050
2100


Conveyor
speed,
AliPW
an



35
IB
2(i







05
50

9
Conveyor
pitch,
in.
2




3







1



Pond
number
1

3

1
3
1

2

3

1

1


4
Feed
rate ,
gpmc
s
10
10
12
9
3
23
49
25
49
21
49
19
43
10
5
7
14
4
Floccula-
tion
Pll
11.5




11 .0








10.2


Recoveries in Cake, percent
Total
solids

-------
      Table 7-4.  CENTRIFUGE PERFORMANCE SUMMARY-LIME SLUDGE
                 RECYCLE PROJECT
Date
7-27
29
31
8-2
4
6
8
10
Mean
Total
Solids
Recovery
Percent
62. 9
61. S
60.4
57. 7
53.4
55.2
56,6
53.0
57.6
Recoveries in Centrifuge Cake, Percent
CaC03
87.4
82. 1
82.7
78.8
77.9
78.3
76.8
84.7
81.0
Volatile
Matter
42.8
38.5
40.4
35.7
32.0
33.2
35.9
29.0
35. 9
Ca3(P04)2
18.0
21.8
17. 8
21.5
19.7
23.4
21.4
19.5
20.4
Mg(OH)2
7.5
28.9
41.8
30.3
25.6
25.6
36.3
18.7
26.8
Fe(OH)3
62. 9
54.0
48.3
43.2
53.4
55.2
51.9
53.0
52.7
Si02
66.2
75.8

99.6
82. 3
94.0
84.1
90.0
84.6
Otherb
(100)
61.8
84.6
69.2
(100)
47.3
75.5
63.7
75.3
  Operational pH in the primary was 11. 0; the machine was the Sharpies P3000
  operating at 2100 G, a pond setting of 1, and an influent flow rate ranging
 .from 2. 2 to 2. 5 I/sec (35. 2 to 40. 0 gpm)
  Acid insoluble inerts other than silica
Effect of Feed  Rate -  One of the most important parameters in the design of
equipment is the feed rate and the effect of variations in feed rate. Fortunately,
wide variation in feed rate can be tolerated for the purpose of constituent
classification.  Examination of the data in Table 7-3 reveals that for runs made
under the same conditions, except for feed rate, there was only a slight deteri-
oration in constituent classification with an increase in feed rate.

Effect of Centrifugal  Force - Another important variable in centrifuge opera-
tion is  the centrifugal force.  Most of the runs were made at a centrifugal force
per unit mass of 2,100 times the acceleration of gravity  (G) . However,  a few
runs were made at different G levels.  Over the range of about 1,000 to 3,000
G, recovery of calcium carbonate increased only slightly with an  increase in
centrifugal force.

Effect of Pond  Setting  -  The depth of the liquid layer in the centrifuge bowl
would be expected to  be an important variable.  Increasing the depth of the
liquid  (increasing pond number) had an adverse effect on the separation of
constituents.  The best constituent separation was always attained at the
lowest  pond setting.  For  example, runs 8-4 and 8-5  (Table 7-3)  held all
process parameters constant except pond setting. The pond setting of 1 as
compared to 3 gave a higher recovery of calcium carbonate and a  greater
rejection of all other components .

Effect of Lime  Dosage, or pH  - There is some indication that calcium carbonate
is more easily classified from the other components at a high pH than at a low
pH.  Further, calcium carbonate recovery was better at a high pH than at a
low pH.  However, some of the other variables were also changed simultaneously
with pH, and the pH effect could therefore not be firmly established.  For
example, runs made at pH of 10.2 and 11.5 were made with different machine

                                      99

-------
conveyors, while runs made at pH 11.0 were made with the larger of the two
machines.  Also,  the concentration of the various constituents in the sludge
was substantially different at the various pH levels, and that also could account
for the differences in degree of classification.
      100
   LU
   O
   £T
   UJ
   CL
   CO
   I-

   LLl
   Z3
   j-

   h-
   co

   o
   U.
   O
   a:
   UJ
   >
   o
   o
   LU
   o:
       0
                    20         40          60          80         100

               RECOVERY  OF  TOTAL  SOLIDS,  PERCENT
  Figure 7-13 Summary of constituent recoveries during wet classification
              with Iime recycle
                                   100

-------
Dewatering  During Wet Classification -

Besides classifying the individual constituents of the solids,  the dewatering of
the recovered cake must also be considered.  Factors which are important are
the centrifuge operating conditions and the lime dosage or pH level used in the
primary treatment from which the sludge is produced.  As with the classifica-
tion of solid constituents, the extent of dewatering is affected by several
centrifuge operating variables.  The effects of feed rate, centrifugal force and
pond setting have been studied to determine their relative importance.

Effect of Feed Rate  -  As was noted in the discussion of constituent classifica-
tion,  feed rate can be varied over a wide range with only a minor effect on
classification.  Feed rate was also found to have little effect on total solids
recovery at  all pH levels.  For instance at pH 11.0 (Fig. 7-14) total solids
recovery at  a pond setting of 1,  decreased only from 63 to 54 percent when
flows increased from 0.9 to 3.2  I/sec  (15 to 50 gpm) , more than a threefold
range.

Effect of Centrifugal Force - For constituent classification,  centrifugal force
seemed to have a slight influence.  For dewatering and solids recovery, how-
ever, the tests showed that centrifugal force is an important variable.  In-
creasing the centrifugal force improved dewatering  (Fig. 7-14 and 7-15) .  A
centrifugal force of 2100 appears to be adequate for dewatering.

Effect of Pond Setting - The liquid depth (pond setting)  had a substantial
effect on cake dryness (Fig. 7-15) .  For dewatering, as in classification, the
best results were obtained with  as shallow a liquid depth as possible (pond
setting No.  1) .

Centrate Processing by  Centrifugation -

One alternative for processing the centrate from the  wet classification stage is
to dewater the centrate in a second stage centrifuge  and incinerate the cake.
In addition to dewatering the rejected solids from wet classification,  a high
recovery of  solids in the second stage is necessary to prevent a large return
of solids to the primary treatment process.  The solids to be captured in the
second centrifuge stage are the  slow-settling  solids which were rejected in
the first centrifuge stage.  Different operating conditions must therefore be
used in the second stage than in the first stage. Efficient capture  requires
the addition of a polymer and a high centrifugal force to improve the settling
characteristics.   Since it was found that with high recoveries the extent of
classification among the constituents was small, the major concern is the de-
watering and capture of the solids .

Effect of Conveyor Speed  - Since the solids separated by centrifugal force are
removed from the bowl with a conveyor, its speed relative to the bowl speed
(A rpm) is one of the important operating variables.  An example of the effect
of conveyor speed is shown in Fig. 7-16.  The polymer requirement to  attain
an 80 percent recovery of solids was reduced to about half by increasing the
conveyor  speed from 8 to  12 A rpm. However, the extent of dewatering was
                                     101

-------
 100
  90 -
a
lu
o

-------
reduced  by the increased conveyor speed.  Apparently there is an optimum
conveyor speed that gives the best balance between polymer usage and extent
of dewatering for a given feed and set of operating conditions.
   100
    80
  kl
  
-------
  100
   8O
 a
 UJ
 o
 cc
 kl
 Q.
   60
 Uj
 i>
 o
 CO
 Q
   20
Conveyor pitch, In.: 3 for P-3000
               1  for P-600
  Polymer: ICI Atlasep 2A2
                   _L
SYM
BOL
©
A
H
A
PH
11.0
1 1.0
11.0
11.2
11.2
MACHINE
P-3000
P-3000
P-3000
P-600
P-600
FEED RATE,
gpm
30.7
29.0
30.7
3.5
3.5
POND
SETTING
4
4
4
3 '/2
CONVEYOR
ARPM
18
11
16
10
10
FORCE,
g
3200
2100
I5OO
3O50
2100
CAKE,
% SOLIDS
16.0- 17.1
15.5- 17.4
11.4- 11.8
12.8-13.8
II. 4-12. 8
                   23456
                  POLYMER DOSAGE, IB / TON  DRY SOLIDS
           Figure 7-17 Effect of centrifugal force on solids recovery


Effect of Feed Rate - In the centrifuge test runs shown in Fig. 7-18, the feed
rate was varied from 0.9 to 1.8  I/sec (14 to 29 gpm) with no significant change
in polymer requirement or percent of solids recovered.  There was an apparent
slight increase in cake water content at the higher feed rate. At the low feed
rate of 0.7  I/sec (11 gpm), about a third of the maximum rate used, solids
recovery was slightly better, and the polymer requirement was reduced. Fig.
7-18 shows that a wide range of feed rates can be used without changing the
efficiency to any great extent, which will lend flexibility to prototype operation.

For the runs at different feed rates, the conveyor speed was also varied to
maintain a relatively constant ratio of feed rate to conveyor speed.  Since the
concentration of solids in the feed was essentially constant, the amount of solids
removed per conveyor revolution was also maintained constant, thereby essen-
tially eliminating the effect of conveyor speed on cake dryness.

Effect of Flocculation pH - No relationship was found between flocculation pH
and the polymer dose required to attain a given recovery level. However,
significant differences occurred in the observed dewatering.  A flocculation pH
greater than 11.0 had a detrimental effect on second stage water content as
shown  in Table 7-5.  This difference would have a significant impact on sludge
incineration costs and would be a drawback to lime recovery with a flocculation
pH greater than 11.0.
                                    104

-------
        Table 7-5,  EFFECT OF FLOCCULATION pH ON SECOND STAGE
                   CAKE DRYNESS

pH

11.2 to 11.5
11.0
10.2
Total solids in cake, percent

Range
11.0 to 14.4
15.5 to 19.6
13.7 to 20.3

Median
11.8
17.2
18.4
 100
  80
Uj
  60
ct
lu
  40
to
Q
-j
O
  20
Machine;  Sharpies  P 3000
Pond • 4
Conveyor  pitch , in : 3
Centrifugal  force, g: 2100
Polymer : Atlasep 2A2
SYMBOL
0
0
A
FEED RATE
gpm
29.0
14.0
1 1.0
CONVEYOR
RPM
11
6
4
FEED,
% SOL IDS
1.6
1.5
1.6
CAKE,
% SOLIDS
15.5-17.4
16.8-19.0
16.4-18.0
                     23456
                  POLYMER  DOSAGE, LB/TON  DRY SOLIDS
            Figure 7-18 Effect of feed rate on solids recovery
                                  105

-------
Sludge Recarbonation - Some lime sludge processing flow sheets include pH
adjustment of the sludge with carbon dioxide  ("recarbonation") prior to sludge
processing.  The purpose of recarbonation is to dissolve the magnesium hydroxide
fraction which may hinder dewatering if left in the sludge. 1  Parker, et al.3
investigated recarbonation of the sludge prior to second stage centrifugation.  In
general, there appeared to be little, if any, benefit derived from recarbonation
of the first or second stage feed sludge.  The  lowest pH investigated by  Parker
et al. was 9.0.  At this level, there was  essentially no magnesium hydroxide
disTolved from the sludge.  Therefore the findings of no change in sludge de-
watering properties by these  investigators is  not surprising.

Thompson and Black22 investigated dissolution of magnesium  hydroxide from
water treatment plant sludge. It was found that a pH of 7.3 was required for
complete dissolution.  They reported that the  partial pressure of carbon dioxide
determined the rate of magnesium dissolution.  Considering the work of
Thompson and Black,22 it appears that future work on  sludge  recarbonation
should be done with pH levels lower than that used by Parker, et al.3 Special
attention should be given to whether other materials (such as phosphate, calcium
or organics) are released in the process.  The effects of centrate return to the
plant should also be evaluated.

Effect of Lime Recycle - Bennett evaluated lime sludge recalcination and reuse
at the Blue Plains pilot plant on sludge generated from  raw sewage coagulation.9
Limited centrifuge data indicate a marked reduction in polymer requirements
when reclaimed lime was  reused. (See Fig. 7-19) . The favorable influence on
sludge dewatering of recycling the inerts with the reclaimed lime can be com-
pared to the planned use of fly ash in other dewatering applications. Additional
data from the Blue Plains pilot plant on centrate treatment is given in Table 7-6.
       Table 7-6.  DEWATERINC OF HIGH LIME "!PC" SOLIDS AFTER
                   CENTRIFUGE CLASSIFICATION
Dewatering Method
Vacuum Filter
Filter Press3"
Centrifuge
Vacuum Filter
Filter Pressa
Centrifuge
Lime
Reuse
No
No
No
Yes
Yes
Yes
Feed Solids
Cone. , % TS
7. 7
7.5
5.7
5.2
2.6
6.6
Loading
7. 3-9. 8 kg/sq m-hr
(1. 5-2. 0 Ib/sq ft-hr)
1,169 kg/cu m (73
Ib/cu ft) 197 min cycle
35-48 ton DS/day
4. 9 kg/sq m-hr
(1. 0 Ib/sq ft-hr
1,202 kg/cu m (75
Ib/cu ft) 155 min cycle
35-50 ton DS/day
Cake Solids
Cone. , % TS
24-25
29-34
14-16
25-26
34
14-16
Chemical
Cost, $/ton
None
None
4-5
None
None
1-4
   Xichols 1 sq ft filter press
   Sharpless P600 centrifuge operated in high recovery mode.
                                     106

-------
    100
LU
O
o:
UJ
CL
o:
UJ

O
o
uu
cc
                                         POLYMER DOSAGE, LB/TON
                        Figure 7-19 Effect of polymer dosage on lime recovery

-------
Whole Sludge Recovery with Centrifuges  -

In addition to its classification capability, a centrifuge can also be used for whole
sludge recovery.  A typical flow sheet for this application has been shown in
Fig. 7-8.  Typical data from the Blue Plains pilot plant on operation for whole
sludge recovery is given in Table 7-7.
      Table 7-7.  DEWATERING OF "IPC" WASTE SOLIDS (WHOLE SLUDGE)
Sludge Source
IPC High Lime
IPC Low Lime
Vacuum Filter
Cake
Solids,
% TS
35-36
28-29
Loading,
kg/sq m-hr
(Ib/sq ft-hr)
30-45 (6-9)
10-15 (2-3)
Centrifugea
Cake
Solids,
% TS
28-32
28-29
Recovery, %
98-99
91-99
Cake
Production,
ton/day
43-90
85-90
Filter Press
Cake
Solids,
% TS
44-45
45-4Y
Cycle,
hrs.
1.0-1.2
2.6-3.6
Bulk Density,
kg/cu m (Ib/cu ft)
1378-1794 (86-112)
1250-1314 (78-82)
   'Sharpies P600 centrifuge in high recovery mode
    [chols 1 sq ft filter press
, on;
bNi.
Shuckrow and Bonner^ have reported the results of dewatering tests on primary
lime sludges in a 5.7  I/sec (90 gpm) pilot plant located in Cleveland.  The pH
of the centrifuge feed was 10.5.  When the centrifuge was operated at 5,000 rpm
 (2,120 G) ,  solids capture ranged from 50 to 80 percent solids and  the solids
concentration in the cake varied from 20 to 45 percent. Centrifuge performance
at 3,500 rpm  (1,020 G)  produced only a one percent drop in cake solids concen-
tration. Shuckrow and Bonner found that to increase solids capture to 95 per-
cent, approximately 0.55 to 0.75 kg (1.2 to 1.7 pounds)  of polymer per ton of
dry solids were required.  It was found that at 5,000 rpm the required polymer
dose was 30 percent lower than at 3,500  rpm for equal centrate quality. De-
watered sludge solids content was dependent on solids capture; solids content
averaged 26 percent at 70 percent capture and 22 percent at 90 percent capture
when using polymer conditioning .

Brown and Caldwell24 tested whole sludge recovery on sludge generated at pH
10.2 at the  ATTF.  In order to obtain 90 percent recovery at 2,000 G, it was
necessary to use 0.7 to 0.9 kg of anionic  polymer per  ton of dry solids  (1.5 to
2.0 Ib/ton)  . Cake  solids varied from 19.5 to 28.4 percent TS.

Sludges generated  in a two-stage lime treatment system processing partially
clarified raw wastewater have been tested at a 0.6 to 1.2  I/sec (10 to 20 gpm)
pilot plant at the CCCSD treatment plant.25 it was found that sludge generated
at pH 10.2 dewatered more easily than sludges at pH 10.8. To obtain 90 percent
recovery required  0.14 to 0.45 kg of anionic polymer per ton DS (0.3 to 1.0 lb/
ton) . Inspection of the data at pH 10.8 indicates that increasing the "G" level
from 750 to 2,100 improved  recoveries from 72 to 90  percent at a polymer dose
of 0.17 kg per ton DS  (0.38 Ib/ton) .  Cake dryness  was strongly related to
recovery in the centrifuge. At 90 percent recovery, 24 percent TS in the cake
                                    108

-------
was obtained; at 80 percent recovery,  28 percent TS was obtained;  at 70 percent
recovery, 33 percent TS was obtained; and at 60 percent recovery, 37 percent
TS was obtained .
        found that a pH of 10 was optimum for good centrifuge results on primary
lime sludge.  He obtained average cake concentrations of 33 percent and solids
recoveries of 78 percent without the use of polymers .  However, centrate quality
was poor  (1.3 percent SS) .  Addition of an anionic polyelectrolyte resulted in
reductions of centrate solids in proportion to the polymer dose.  Fig.  7-20 shows
the effect of polymer addition on suspended solids removal.

Tofflemire and Hetling27 conducted centrifuge dewatering tests using primary
sludge from a 0.3  I/sec (5 gpm) low lime pilot plant. Solids recoveries were
excellent, ranging from 93 to 100 percent at a conveyor speed of 4,600 rpm and
86 to 100 percent at 5,000 rpm.  The pH varied from 8.6 to 12.3.  Contrary to
the results obtained at Cleveland, 23 Tofflemire and Hetling found that, as long
as fresh lime sludge was fed to the centrifuge, the addition of an anionic polymer
did not appear to affect the recovery of solids .

Vacuum Filtration

Historically,  vacuum filtration has found wide acceptance for dewatering muni-
cipal and industrial sludges.  In the municipal field, the leading role of vacuum
filters has only been recently challenged by the increasing use of centrifuges
in sludge  dewatering applications .  An excellent review of the theory of sludge
filtration is given in Reference 10 .

Basically, a vacuum filter consists of a rotating drum partially (20 to 40 percent)
submerged in a sludge tank or pan.  The drum cylindrical surface is  covered
with the filter medium and a vacuum of about 25 to 65  cm  (10 to 26 inches)  of Hg
is applied between the drum compartments and the filter medium .  As the drum
passes through the pool of sludge, solids are attracted to the drum surface by
the vacuum effect forming a sludge mat (filter cake) .  Moisture (filtrate)  is
extracted  and filtered through both sludge cake and filter medium .  As the drum
rotates, the captured solids undergo further  dewatering.  Before the next pick-
up and dewatering cycle begins, filter cake is scraped off the drum surface and
falls into a mechanical conveyor . This conveyor then carries the dewatered
sludge to a loading area, to storage, or to further processing stages . The
filtering medium is usually a cloth or metal belt (belt-type filters) , or a double
layer of stainless steel coil springs (coil-type filters) . Several variations of
these basic designs are also available.  Fig.  7-21 show a typical belt-type
filter .

The performance of a given vacuum filter installation  depends both on the
sludge characteristics and on the filter operating variables.  Sludge type,  age,
solids concentration, and chemical composition are some of the sludge charac-
teristics that  affect the vacuum filtration process . Operating variables include
applied vacuum, filter submergence,  chemical conditioning, type of filter media,
and drum  rotational speed.  All these sludge and operating variables influence
                                    109

-------
     IOO<
     90
 3 Z e°
 o LU
     70
     60
              O.I      0,2     0.3      0.4      0.5
           POLYMER  DOSAGE, LBS/DRY  TON SOLIDS
                                                    O.6
  10,000
I
Q.

<0
Q
O
to
Q
Ul
Q
a
ki
0.
8,000 —
6,000 -
   4,000 —
   2,OOO —
                                                        CENTRIFUGE CONSTANTS
     Feed  Rate
     Bowl  RPM
          RPM
     Pond  Depth
  24  GPM
  3250
- 27
  3'/2
              O.I      0.2
            POLYMER  DOSAGE,
                           0.3     0.4     O.5
                          LBS/DRY  TON  SOLIDS
                                                    0.6
   10,000
 -  8,000 	
   6,000	
   4,000 	

-------
                  FILTER DRUM
                                                                        EQUALIZATION BAR

                                                                                DISCHARGE
                                                                                ROLL  DRIVE
                                                                                    DISCHARGE ROLL
                                                                                  ^-FILTER CAKE

                                                                                 CLOTH SPRAY PIPES

                                                                               PERFORATED WASH  ROLL
                                                                             WASH TROUGH

                                                                   DISCHARGE BRACKET
FILTER VAT-
VFILTER AGITATOR
       Figure 7-21 Schematic diagram of a belt type vacuum filter (courtesy of Komline-Sanderson
                   Engineering Corporation)

-------
the filtration process performance expressed in terms of sludge cake moisture
content, solids recovery,  cake thickness, filter yield, and filtrate clarity.

Although lime  has been intensively used in vacuum filtration of sludges,  either
alone or, more commonly, coupled with ferric chloride, its role has been
primarily as a conditioning agent to improve the dewatering and handling charac-
teristics of the sludge.  Dewatering of primary generated lime sludges by vacuum
filtration is a far less common practice.  Burns and Shell6 conducted numerous
vacuum filter tests, using the test leaf method, 10 on both moderate « 11.0) and
high (> 11.5)  pH treatment sludges.  The results of these tests, adjusted by a
scale up factor, together with the operating conditions, are given in Fig. 7-22.
Conditioning the sludge with 0.09 to 0.27 kg (0.2 to 0.6 Ib) of anionic polymer
per ton of dry solids increased the vacuum filter yields from 30 to 70 percent
above the values obtained from Fig. 7-22.

Mulbarger  et al. *  used filter leaf tests following gravity thickening to determine
the dewatering characteristics of lime sludges during bench scale studies of
lime clarification,  recovery,  and reuse.  The sludges had been produced by lime
treatment of secondary effluent.  Two-stage treatment was selected for study at a
pH equal to or larger than 11. The  investigators found that reclaimed limes pro-
duced sludges which were easier to filter than new lime sludges. They attributed
this to the  presence of recycled inerts acting as a filter aid. Filter cake solids
varied between 28  and 45 percent for the range of lime dosage studied. Recovery
efficiencies of the gravity  thickener-vacuum filter  system for total solids,  calcium,
phosphorus, and magnesium varied between 96 and 100 percent  (without sludge
carbonation) .

Leaf tests on polymer conditioned centrate from a centrifugal classification step
were conducted at the CCCSD's ATTF .  The centrate was difficult to dewater
and resulted in extremely low filter yields, ranging from 1.75 to 2.20 kg/sq
m/hr (0.36 to  0.45 Ib/sq ft/hr) .  The feed solids concentration was only 2.4
percent.  Other tests produced even lower filter yields, ranging from 0.98 to
1.46 kg/sq m/hr (0.2 to 0.3 Ib/sq ft/hr) .  Also, the discharge characteristics
of the filter cake were poor.3

Best media in the ATTF tests on centrate was a synthetic fabric (Eimco Dynel
DY453) .  The  centrate solids did not contain enough fibrous material to allow
solids capture on the coil filter medium tested.

Whole high-lime sludge  (pH  11) was somewhat easier to dewater, with filter
yields  ranging from 8.8 to 13.2  kg/sq m/hr (1.8  to 2.7 Ib/sq ft/hr) without
polymer conditioning.  These yields are consistent with the data of Burns and
Shell (Fig. 7-22) since the feed solids for the ATTF tests ranged from 3.0 to
3. 6 percent total solids .

Investigators at Blue Plains have extended  considerable effort towards defining
vacuum filtration operating parameters for lime sludge generated by an indepen-
dent physical-chemical system (IPC) .9  The IPC System consisted of lime
coagulation, flocculation,  sedimentation, filtration, and activated carbon
adsorption. Vacuum filtration data on whole primary  sludge are shown in
                                     112

-------
CT
(O
100.0
90.0
80.0

70.0

60.0

50.0

40.0


30.0



20.0
^

uT
2
O

I
Ld
O
CO
10.0
 9.0
 8.0
 7.0

 6.0

 5.0

 4.0


 3.0



 2.0
     i.O
                 OPERATING CONDITION:

                  3/16 INCH CAKE
                  33% DRUM  SUBMERGENCE
                  20 INCHES OF HG VACUUM
                  0.8 SCALE-UP FACTOR

                  NO CONDITIONING CHEMICALS
               FILTER CAKE
               MOISTURE CONTENT
               68-72% BY WGT.
                                             FILTER CAKE
                                             MOISTURE CONTENT
                                             65-68% BY WGT.
                                             O = DATA AT pH > 11.5

                                             A = DATA AT pH
-------
Table 7-7.  Consistent with the experience of Burns and Shell,5 high lime sludge
filtered at a higher rate than low lime sludge.   Similar experience was gained at
Blue Plains on centrate (Table 7-6) ,  as found at the ATTF . Filter yields were
higher, 4.9 to 9.8 kg/sq  m-hr (1.0 to 2.0 Ib/sq ft/hr) compared to 0.98 to
2.2 kg/sq m/hr (0.20 to 0.45 Ib/sq ft-hr)  at the ATTF, but feed solids were
greater at Blue Plains as  a result of flotation thickening.

In summary, the leaf-test data of Burns and Shell (Fig. 7-22) stand up well
compared to the results of other investigators and can be used for design purposes
on vacuum filters treating lime sludge from primary applications.  However, two
features on Fig.  7-22 should be highlighted.  First, there is variation in filtration
rates above and below the trend lines shown, reflecting day-to-day variations in
sludge characteristics.  Since sludge quality will be subjected to variations, some
conservatism in the application of Fig . 7-22 is justified.  The other design factor
apparent in Fig. 7-22 is that the filtration  rate is strongly affected by feed solids
concentration.  To obtain an economic filter loading, for example 24 kg/sq m/hr
 (5 Ib/sq ft/hr) ,  the feed  solids concentration must be between 10 and 13 percent
total solids. This requires consistent performance out of the preceding thick-
ening step.  If thickener  performance should deteriorate, the allowable vacuum
filter loadings would be lower, and the sludge inventory will build up in the
thickener.  This in turn might result in further thickening deterioration.  Stand-
by vacuum filtration capacity should  be provided to avoid overloading of filters.

While both Burns and Shell^ and the  Blue Plains investigators^ found that
polymer conditioning was not required for vacuum filtration of whole sludge,
others have reported the  need for polymer addition.  Shuckrow and Bonner23
conducted pilot studies of lime sludge in a 3 ft diameter belt drum filter. Raw
sludges had been generated at a clarifier pH ranging from 10.0 to 12.2. They
found that vacuum filter performance was dependent on influent solids content,
polymer dose, and drum  speed.  The effect of these parameters is plotted in
Figs. 7-23, 7-24, and 7-25  for sludges generated  at pH 10.5.   Cake solids
ranged from 19 to 36 percent dry solids and filter loadings rates varied from
14.6 to 92.8 kg/sq m/hr  (3  - 19 Ib/sq ft/hr) .  Cake solids content was mainly
dependent on filter loading  rate.  The addition of less than 0.9 kg  (2 Ibs) of
polymer per ton of dry solids allowed loading rates up to three times higher
than without polymer conditioning.  Maximum loading rates were obtained at
the fastest drum  speeds  (50 rph) , but a wetter cake was produced causing it to
adhere to the filter medium. Solids capture was found to be strongly dependent
on solids content and only slightly dependent on drum speed.

It is recommended that facilities for polymer conditioning be provided to be used
in case actual operation demonstrates this  need. Polymer conditioning is some-
times required periodically only, as  is often found in treatment plants receiving
seasonal industrial wastes.  In any event, facilities for polymer addition provide
flexibility of operation and a margin  of safety in case that changes in sludge
characteristics might occur.  An additional benefit of polymer conditioning is
that, by increasing the filter loading, it allows  reduction of the filter area
required.
                                     114

-------
   38
   36
   34
   32
2  30


d
en

LU
^

3  28
   26
   24
   22
   20
                           6.3 % DS

                           0.9 LB/TON
                                           6.3 %DS 1.9 LB/TON
          9.9 %DS

          1.0-1.3 LB/TON
              10       20       30      40       50


                       DRUM SPEED (REVOLUTION/HR)
60
       Figure 7-23  Effect of drum speed on cake solids concentration
                                115

-------
   16
   14
   12
o:
I



O  '0
en

m
    8
Q

3
cc
   0
                                    9.9% DS
                                    1.0-1.3 LB/TON
                                   I3.4%DS-0.7LB/TON
                          6.3%DS-0.9 LB/TON
     0
10       20       30       40      50


         DRUM SPEED (REVOLUTION /HR)
                                                         60
          Figure 7-24  Effect of drum speed on filter loading
                                116

-------
   100
   96
   92
   88
   84
ui
o:
   80

3
en
Q
            '3.4 %     1,4 LR/THIM
                                                     9.9%   -I.O-I.3LB/TON
                              6.3%  -I.9LB/TON-
                                                       13.4%   -0.7LB/TOIM
   76
   72
      0
10
20        30       40       50


  DRUM SPEED (REVOLUTION/HR.)
60
            Figure 7-25 Effect of drum speed on solids capture
                                    117

-------
Although vacuum filtration seems to yield fairly dry cakes and achieve excellent
solids recovery, it does not permit classification of the sludge constituents prior
to lime calcination.  Consequently, a large proportion of inerts and other unde-
sirable solids are recycled through the treatment processes.  The amount of
recycled solids can be decreased either by wasting reclaimed lime ("blow down")
or by dry classification of the recalcination product.  However,  wet classification
is a more efficient process to separate calcium carbonate from the undesirable
components of the sludge cake.

Vacuum filtration of centrate from a classification step does not appear to be
economically attractive, since filter loading rates are so low. and the cake
discharge properties are poor.

Pressure Filtration

Filter presses are used extensively to dewater sludges from the chemical process
industry. As indicated before, they  have been used mostly in Europe for de-
watering municipal sludges.  In the U.S., pressure filtration has found limited
application in the water treatment field to dewater coagulant (i.e., alum)  sludges^
and in the wastewater field to dewater a digested  mixture of primary and trickling
filter sludges .29

Steward^O has listed two  installations where filter presses are being used to
dewater lime sludges and one that treats  a lime and ferric chloride sludge.
Although in two or these  plants the sludge cake is incinerated,  no attempt has
been made to recalcine and reuse the lime.

Pressure filtration is a batch process.  Basically, the process utilizes a high
pressure differential up to 15.8 kg/sq cm (225 psig) to produce a sludge cake
ranging between 30 and 65 percent solids.  Sludge  is fed to a series of filter
plates lined with the filter medium which typically has been precoated with a
filter aid, commonly fly ash.  The filter feed system is designed to satisfy
initial high volume-low pressure and final low volume-high pressure require-
ments.  Normally, the average dewatering cycle takes less  than two hours, after
which the hydraulic pressure is relieved and the filter opened.  The cake
formed inside the chamber then drops, through cutting bars, directly to a
loading truck or, more commonly, onto a belt conveyor underneath the filter.
If the cake is to be incinerated, the conveyor discharges it into a storage bin.
Since stored cake will tend to bridge over the  discharge opening and, in the
case of the wetter cakes,  to adhere to the bin walls, the design of the storage
facilities deserves special attention.   Fig.  7-26 shows a schematic diagram of
a pressure filtration system.  Media conditioning  by placing a protective layer
of porous material on the filter media before the dewatering step is often
practiced to prevent premature blinding  of the filter.   (Ash from a sludge
incinerator can be used as a pre-coat material, see Section XI)  .

In lime recovery application,  filter presses have the same limitation that vacuum
filters do, namely, their  inability to  classify the sludge solids prior  to incinera-
tion.  They present the added disadvantages of intermittent operation coupled,
in some systems, with  the need to clean the filter media after every cycle and to
                                     118

-------
  ASH
INFLUENT^
SLUDGE
              STORAGE
           IFEEDER
             V
               MIX
              TANK
                      CONTACT
                        TANK
FILTER
FEED  PUMP

 J_
          MEDIA
         CONDITIONING
        } (IF  REQUIRED)
       t
        l
        6
        L-.
PUMP
                                                                           EQUALIZING
                                                                                 TANK
          FILTER PRESS
           V
           I
                                                                       1
                                                                       I
                                                                       I	-*»
                                                                         FILTER
                                                                          CAKE
EFFLUENT FILTRATE
        RECYCLE
                                                         FILTRATE
                                                          TANK
 Figure 7-26 Schematic diagram of a pressure filtration system (courtesy of Passavant Corporation)

-------
pre-coat it before the next dewatering cycle can start. These drawbacks are
partially offset by the fact that the entire process can be automated.30  Data on
a whole sludge application are shown in Table 7-7.9

The greatest potential for pressure filtration in lime sludge applications seems
to lie in the dewatering of first stage centrate.  Bennett31 has reported filtrate
solids concentrations greater than 30 percent obtained on a 1 sq ft pilot filter
press operated at 7 kg/sq cm (100 psi) .  The pH of the lime  sludge fed to the
classifying centrifuge was 11.5.  Cake discharged from the filter  press without
difficulty and no conditioning chemicals  were required. Tables 7-6 and 7-8
present data obtained at the Blue Plains  pilot plant on  centrate filtration. One
of the principal advantages of pressure  filtration is evident in Table 7-8, namely
high filtrate clarity.   Lime recycle appears to reduce the cycle time required
for pressure filtration (Table 7-8) .  Apparently, the recycling of lime  to the
primary sedimentation tank is equivalent to the use of  fly ash for sludge condi-
tioning in terms of its effect on filter performance.  Comparable results have
been obtained at the CCCSD's ATTF on centrate  (Table 7-9)  .  Both the cycle
time and the obtainable cake solids are lower than obtained at Blue Plains when
no lime  was recycled; this difference is  likely due to differences in  quality of
the sludges.

Comparison of Dewatering  Techniques

As introduced at the beginning of this section, there are several approaches to
sludge dewatering.  The method of dewatering has a marked impact on the
recovery of lime. Of the alternatives considered, only the solid bowl centrifuge
allows control over the amount of inerts  recycled in the process.   If  a vacuum
filter or filter press is utilized, furnace products must be blown down  to con-
trol inerts which cause a loss of  reclaimed lime.

Equipment Requirements -

To compare equipment requirements for  the alternate flowsheets  (Figs. 7-8 and
7-9) ,  Table 7-10 was prepared.  To lend some reality to the  comparison, actual
manufacturers' equipment models were used for illustration  purposes.  In all
cases, the model chosen was the largest unit made by  the manufacturer. This
reduced the total number of machines required for each alternate. Machines of
other  manufacturers having similar  sludge processing capacity may be substi-
tuted  for those listed in  the table.

In the ATTF flowsheet, two types of solid bowl centrifuges are given for the
first dewatering  function, vertical and horizontal.  In the second  stage dewater-
ing step, vacuum filtration and filter pressing are presented as alternates.  In
the Plural Purpose Furnace flowsheet, centrifugation, vacuum filtration, and
filter pressing alternatives are illustrated.  The centrifugation alternatives are
based on those included in the plans and specifications for the CCCSD Water
Reclamation Plant. H The filter pressing alternatives  are based on CCCSD and
Blue Plains data  (Tables 7-8 and 7-9) .   Second stage vacuum filter loading is
based on ATTF and Blue Plains data.31  Vacuum filtration of whole sludge is
based on Cleveland Westerly data (Figs. 7-23, 7-24, and 7-25) .23
                                    120

-------
       Table 7-8.   PRESSURE FILTRATION OF CENTRATE AT BLUE PLAINS
Bun No.
1. No lime recycle,
thickened by flotation
2. No lime recycle,
thickened by flotation
3. Lime recycle, no
thickening
4. Only one recycle of
lime, thickened by
centrifugation
5. Only one recycle of
lime , thickened by
centrifugation
6. With one recycle,
thickened by flotation (2)
Feed
solids,
%
7.3

7.7

2.6

3.7


9.8


4.7

Cake solids, %
Outside
33.1

34.6

30.3

31.2


31. 8


31.1

Middle
29.9

37.3

34.0

28.2


31.6


29.0

Inside
26.6

32.4

26.6

27.6


31.1


26.5

Filtrate solids, %
SS,
mg/1
60



47

106


644


228

TS,
mg/1






1212


1630


588

Cycle
hrs
3.32

3.30

2.58

3.75


1.34


2.5

Bulk density
kg/cu m (Ib/cu ft)
1195 (74.6)

1149 (71.7)

1202 (75.0)

1158 (72.3)


1173 (73.2)


1136 (70.9)

No. of
cells
3

3

1

2


2


2

Temp. 11-15 C, (52-50 F) operating pressure 7 kg/sq cm (100 psi) test performed on 0. 09 sq m ( 1 sq ft) Nichols
      pilot filter press (2) thickened in the pilot 1 sq ft dissolved air flotation unit.
           Table 7-9.  PRESSURE FILTRATION OF CENTRATE AT CCCSD
Run no .
1
2b
3
4
5b
6
Filter3 cycle
time, hr
2.75
2.0
2.2
3.0
2.5
2.0
Feed solids,
percent
4.1
3.4
4.1
3.3
3.4
3.4
Cake solids ,
percent
26.5
24.1
24.6
23.0
26.6
24.8
Feed pHC
10.75
12.0
10.75
10.4
11.9
10.8
Cake thickness,
cm (inch)
2.54 ( 1.0)
2.54 ( 1.0)
2.54 ( 1.0)
3.18 (1.25)
3.18 (1.25)
2.54 ( 1.0)
     Tests performed with a Nichols 0.09 sq m (1 sq ft) filter press at 7 kg/sq cm (100 psig) .

     Tests performed with the addition of dry classification rejects on an 8 percent dry weight basis.

     Primary sedimentation operated at pH 10.8.
                                               121

-------
              Table 7-10.  COMPARISON  OF MACHINE AND FLOOR AREA REQUIREMENTS  FOR ALTERNATE FLOW
                               SHEETS AT 1.31  CD  M/SEC (30 MGD)
Plow sheet
CCCSD's ATTF
at pH 11 ,0d



Plural purpose
furnace at
20% ash
blowdown


First stage
sludge
dewatered,
kg/day
(lb/day)/
percent TS
101,729
(224,312)/8
98,806
(217,875)/8
96,783
(213,414)78
101,725
(224,312)78
133,064
(293,415)78
132,843
(292,928)78
126,835
(279,680)78
Machine
Centrifuge:
Sharpies
P68006
Centrifuge:
Sharpies
P68006
Centrifuge:
Sharpies
P6800
Centrifuge:
Sharpies
P5400
Centrifuge:
Sharpies
P68008
Vacuum filter
Elmco belt
12 x 20
Filter press
Nichols
72" x 48"
Loading ,
metric
(English)
14.4 I/sec
(221 gpm)
13.6 I/sec
(215 gpm)
13.3 I/sec
(211 gpm)
14.4 I/sec
(221 gpm)
18.2 I/sec
(289 gpm)
39 kg/sq m-hr
(8 Ib/sq ft-hr)
45% TS,
1 . 2 hr cycle
No. units
required
1
1
1
1
1
2
3
Floor area ,
sq m (sq ft)
each/total
6.9 (74)7
6.9 (74)
6.9 (74)7
6.9 (74)
6.9 (74)7
6.9 (74)
17.7 (191)7
17.7 (191)
6.9 (74)7
6.9 (74)
28.5 (307)/
57.0 (614)
25.7 (276)7
77.1 (828)
Second stage
sludge
dewatered ,
kg/day
(lb/day)/
percent TS
38,258
(84,363)/4
36,219
(79,865)/4
35,132
(77,469)/4
38,259
(84,363)/4
-
-

Machine
Centrifuge:
Sharpies
P68006
Vacuum filter
Elmco belt
12 x 20
Filter press
Nichols
72" x 48"
Centrifuge:
Sharp Les
P5400
-
-

Loading ,
metric
(English)
10.9 I/sec
(172 gpm)
4.9 kg/sq m-hr
(1 Ib/sq ft-hr)
25% TS ,
2.25 hr cycle
5.4 1/360
(86 gpm)
-
~
"
No. units
required
1
5
3
2
-
~
"
Floor area ,
sq m (sq ft)
each/total
6.9 (74)/
6.9 (74)
28.5 (307)/
142.5 (1,535)
25.7 (276)/
77.1 (828)
17.7 (191)/
35.4 (382)
-
~
"
Total
floor area,
both stages
sq m (sq ft)
13.8 (148)
149.4 (1,609)
84 (902)
53.1 (573)
6.9 (74)
57.0 (614)
77.1 (828)
Total no. of
machines
(both stages)
2
6
4
3
1
2
3
tsj
            See Section X for solids balances.
            Machine only, not including ancillary equipment such as chemical feed equipment, cake conveying equipment, piping, etc.
            Standby equipment is not included, normal practice requires standby capacity.
            Two furnaces are required.
            Vertical machine.
            Horizontal machine.
            Number of units per furnace.

-------
Comparing flowsheets, it can be seen from Table  7-10 that less  dewatering equip-
ment is required for the  Plural Purpose Furnace flowsheet than for  the ATTF
flowsheet.  Among the Plural Purpose Furnace flowsheet alternates, the least floor
area is required for the centrifuges. This reflects more compact equipment
arrangements possible with centrifuges.  Among the ATTF flowsheet alternatives,
the centrifuges also require the least number of machines and the least total floor
area.  The floor area requirements for  ancillary equipment,  e.g., sludge condi-
tioning equipment, feed pumps,  etc., are considered similar for each alternative
and are not included in the comparison.  As a general rule,  floor requirements
for auxiliary systems usually exceed those for the dewatering machines themselves

Maintenance -

Maintenance requirements will differ among the machine alternates and are
difficult to quantify.  High speed centrifugals, even with hard surfacing of the
conveyor, will require periodic  resurfacing. The operating period between
overhauls will depend on the amount of sandy material contained in  the feed
sludge.  Efficient grit removal is of paramount importance when dewatering
with centrifuges.  Vacuum filter belt and the filter medium  in filter presses
require routine cleaning and may eventually have to be replaced. Their service
life, however, is usually not affected by  grit. Pressure filtration, even with
the degree of automation provided in today's systems, requires more operator
attention than vacuum filtration or centrifugation. The presence of  an operator
is recommended during the cake discharge cycle  to make sure that all filter cakes
drop from the press plates.

Relative  Dewatering -

The alternatives must also be evaluated in terms of the basic dewatering objec-
tive, water elimination. This objective receives special emphasis when incin-
eration follows  dewatering, as approximately 450  kcal (1,800 Btu) are required
to evaporate a pound of water (at off-gas temperature of 700 F) .  Table 7-11 has
been prepared which presents an analysis of the weight of water which must be
evaporated in the furnaces for each alternate presented in Table  7-10.  Com-
paring the results  for the  ATTF flowsheet to the results for the Plural Purpose
Furnace flowsheet, it can be seen that there is no disadvantage in incorporating
the wet classification process into the ATTF flowsheet in terms of the energy
required to evaporate water. In fact,  there is a considerable advantage to the
ATTF flowsheet.

Employing pressure filtration in the second  dewatering stage of the  ATTF flow-
sheet has a substantial advantage over  vacuum filtration or centrifugation in
terms of the energy required for incineration. This factor will no doubt
encourage wider utilization of pressure filtration  in this energy-conscious age.

Flexibility -

The centrifugation process has demonstrated greater stability to  changes in
influent characteristics than either the  vacuum filtration process or  pressure
filtration.  This is partially indicated by the effect of influent solids level on
                                      123

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    Table 7-11.  COMPARISON OF WATER EVAPORATED FOR ALTERNATE DEWATERINC SYSTEMS
                  AT 1.31  CU M/SEC  (30  MCD)
Flow Sheet
and Dewatering
ATTFa
1st: centrifuge
2nd: centrifuge
ATTFb
1st: centrifuge
2nd: vacuum filter
ATTF°
1st: centrifuge
2nd: filter press
Plural Purpose Furnace
centrifuge
Plural Purpose Furnace6
vacuum filter
Plural Purpose Furnace
filter press
Dry Solids
Burned in
First Stage,
kg/day (Ib/day)
62,977 (139,950)
62,104 (138,011)
61,653 (135,945)
126,204 (278,281)
126,204 (278,281)
126,204 (278, 28i)
Percent
Total
Solids
58
58
58
24
28
44
Water
Evaporated
First Stage,
kg/day (Ib/day)
46,961 (101,343)
45,323 ( 99,939)
44,645 ( 98,443)
399,648 (881,223)
324,526 (715,580)
160,624 (354,176)
Dry Solids
Burned in
Second Stage,
kg/day (Ib/day)
33,136 (73,614)
33,782 (75,073)
34,782 (76,694)
-
-
-
Percent
Total
Solids
17
20
25
-
-
-
Water
Evaporated
Second Stage,
kg/day (Ib/day)
162,998 (359,410)
136,187 (300,292)
104,346 (230,002)
-
-
-
Total Water
Evaporated
kg/day (Ib/day)
209,960 (460,753)
181,510 (400,231)
148,991 (306,776)
399,468 (881,223)
324,526 (715,580)
160,624 (354,174)
jTCase 100, Section X
 Case 101, Section X
°Case 102, Section X
 Case 106, Section X
?Case 114, Section X
 Case 117, Section X

-------
filter yield for vacuum filters shown in Fig.  7-22 and the effect of influent con-
centration on cycle time for pressure filters  in Table 7-8.  This makes the vacuum
filters and pressure filters more dependent on the uniformity of operation of up-
stream thickening process than the centrifuge.

Choice -

Choice of the dewatering process must be based on evaluation of all the factors
listed in this section,  past experience and preferences of the operating agency
and the consulting engineer,  operator competence and training,  economics and
local factors.  The relative ranking of these  factors may be different for many
situations and lead to  quite different solutions.  The multiplicity of dewatering
designs in evidence today is testimony to the variability in solutions.

SLUDGE CAKE CONVEYING

Sludge cake can be pumped or transported by mechanical or pneumatic methods.
First stage centrifuge cake is usually too dry to be handled by pumps.  Attempts
to convey first stage cake from the ATTF with a progressive cavity, positive
displacement pump were unsuccessful.  Second stage cake, however, having the
consistency of a slurry, can be pumped with positive displacement units.  Cen-
trifugal,  torque-flow pumps  have also been used to handle lime sludge.  Aldworth32
has reported the use of this type of unit to recirculate lime sludges of up to 28
percent solids concentration, in digestion tanks.  He recommended abrasion-
resistant construction for this application.

Mechanical conveyors are similar to the ones used to move dry materials (see
Section V) .  Belt and  screw conveyors and bucket elevators are often employed
to transport the wet sludge cake to storage or to feed it to the incinerator.
Screw  conveying gave satisfactory results at the ATTF.   "Totally enclosed"
conveyor designs are  also available.  This type of mechanical conveyor features
a series of flights dragged by one or two hardened chains. The  conveying flights
are enclosed in a rectangular casing.  The return flights may be housed in the
same casing or in a separate one. Apart from the advantage of enclosed trans-
port of sludge cake, this conveyor is designed to change directions, a capability
not possessed by conventional belt or  screw conveyors. The degree and extent
of directional changes varies among the various designs.  As it was pointed out
in Section V, selection of mechanical conveyors should be done in consultation
with the equipment manufacturers .

The pneumatic conveying equipment used in wet sludge applications is  of the
pressure vessel (i.e., pneumatic ejector)  type.  Pneumatic ejection of sludge
cake offers several advantages.  The material is completely enclosed and can
be conveyed in any direction, above or below grade. The flexibility of trans-
port is particularly advantageous in multiple hearth furnace applications since
it permits locating the dewatering equipment at or near ground level instead of
above the top  (feeding)  hearth.  The saving achieved by eliminating the elevated
structures required to support the dewatering equipment can be substantial.

The key to successful application of pneumatic conveying techniques to sludge
cakes  lies in the characteristics of the sludge.  Although cakes at solid concen-
                                      125

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trations of 40 to 50 percent DS have been successfully handled in pneumatic
ejectors,33 some sludges are difficult to expel from the vessel.  In these cases,
the compressed air usually blows holes through the sludge mass instead of
forcing it through the discharge opening.  Some manufacturers of pneumatic
conveying equipment have pilot plant facilities33 where the suitability of the
sludge to pneumatic handling can be tested.

In sizing sludge conveyors,  the specific weight of the material is often required.
Fig. 7-2?34 was developed for converting from mass loading  rates to volumetric
loading rates. The data presented is for dense high calcium  carbonate cake.  In
those cases where the cake is crumbled prior to transport and air is entrapped,
a rule of thumb is to reduce the specific  weight by half.
                                   126

-------
   18
   16
-J
CQ
3;
CO

u]
u

o
Uj
CL
  14
   !O
   8
                                          SPECIFIC  WT- VS - % SOLIDS

                                          USING  2.4  g/ml  FOR SPECIFIC

                                          GRAVITY  OF SOLIDS (HIGH IN CaCOs)
    o
10
20
3O        4O        SO

PERCENT  SOLIDS
6O
70
80
9O
             Figure 7-27 Relationship between solids concentration and specific weight

-------
                          REFERENCES - SECTION VII


1.  Mulbarger, M.C., E. Grossman, III, R.B.  Dean, and O.L.  Grant.   Lime
    Clarification, Recovery, Reuse and Sludge Dewatering Characteristics.
    Journal of the Water Pollution Control Federation. 41_: 2070-2085, December
    1969.

2.  Balakrishnan, S ., D .E . Williamson, and R.W . Okey.  State of the Art Review
    on Sludge Incineration Practice. Resource Engineering Associates.
    Washington, D.C. Project 17070 DIV.  Federal Water Quality Administration.
    April 1970, 135 p.

3.  Parker, D.S., K.E. Train, andF.J.  Zadick.  Sludge Processing for Com-
    bined Physical-Chemical-Biological Sludges.  U.S. Environmental Pro-
    tection Agency, Washington, D.C.  Report No. EPA-R2-73-250, July 1973.
    141 p.

4.  Process Design Manual for Phosphorus Removal.  Black & Veatch, Consulting
    Engineers. Washington, D .C.   U.S.  Environmental  Protection Agency -
    Technology Transfer. October 1971.  pp.  10/23  - 10/27.

5.  Burns, D.E., andG.L. Shell.  Physical-Chemical Treatment of a Municipal
    Wastewater Using Powdered Carbon.  Envirotech Corporation.  Salt  Lake
    City. Report for U .S . Environmental Protection Agency.  Report No. EPA-
    R2-73-264.  1973. 230 p.

6.  Burns, D.E.   Physical-Chemical Treatment of Municipal Waste,  Progress
    Report No. 10.  Envirotech Corporation, Salt Lake City.  PRF-10.  March 8,
     1973. 26 p.

7.  Burns, D.E.   Physical-Chemical Treatment of  Municipal Waste, Progress
    Report No. 11.  Envirotech Corporation, Salt Lake City.  PRF-11.
    March 15, 1973.  32  p,

8.  Burns, D.E., G.L. Shell, D.J. Cook, and R. Wallace. Physical-Chemical
    Treatment of Municipal Waste.   Envirotech Corporation. Salt Lake City.
    Draft Report for the  U .S . Environmental Protection Agency.  Contract No.
    68-01-0183, 1974.

9.  Bennett,  S.M. Personal Communication to D .S .  Parker.  U .S . Environmental
    Protection Agency - Blue Plains Pilot Plant. October 11,  1973.

10.  Sludge Dewatering.  Water Pollution Control Federation . Washington, D .C .
    Manual of Practice No . 20 .  1969. 115 p.
                                    128

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11.  Brown and Caldwell, Consulting Engineers.  Plans and Specifications for
    Water Reclamation Plant, Stage 5A - Phase 1. Central Contra Costa
    Sanitary District. California.  April 1973.

12.  Katz, W.J., and A.  Geinopolos. Sludge Thickening by Dissolved Air
    Flotation.  Journal of the Water Pollution Control Federation.  39_, 946-957,
    June 1967.

13.  Kirk-Othmer.  Encyclopedia of Chemical Technology,  2nd Edition.  New York
    John Wiley & Sons,  1964.  Volume 4, p. 710-722.

14.  Perry, J.H. Chemical Engineers'Handbook.  Fourth Edition, New York,
    McGraw-Hill Book Co., 1963, p. 19-93.

15.  Gulp, G.L. Design of Facilities for Physical-Chemical Treatment of Raw
    Wastewater. Gulp,  Wesner, Gulp.  Corona Del Mar.  U .S . Environmental
    Protection Agency.  Technology Transfer  Seminar Publication. August 1973.
    29 p.

16.  Keith, F.W., Jr., andC.E.  Trump. Centrifugal Classification of Waste
    Sludge Components. Sharpies-Stokes  Division, Pennwalt Corporation,
     (Presented at the Annual Meeting of the New England Water Pollution
    Control Association, Hyannis, October 24, 1973) 19 p.

17.  Sheen, R.T. ,  and H.B. Lammers.  Recovery of Calcium Carbonate  or Lime
    from Water Softening Sludges.  Journal of the American Water Works Assoc.
    36:1145-1169,  November 1944.

18.  Pederson,  H .V .  Calcination Sludge From  Softening Plant.  Journal of the
    American Water Works Assoc.  36: 1170-1177, November  1944.

19.  Nelson, F.G.  Recalcination of Water Softening Sludge.  Journal of the
    American Water Assoc. 36_: 1178-1184,  November, 1944.

20.  Parker, D.S., D.G. Niles,  andF.J. Zadick.  Processing of Combined
    Physical-Chemical-Biological Sludge.  Brown and Caldwell and the Central
    Contra Costa Sanitary District.  (Presented at the 46th Annual Conference
    of the Water Pollution Control Federation.  Cleveland. October 1, 1973) .
    23 p.

21.  Brown and Caldwell, Consulting Engineers.  Final Report,  Lime Sludge
    Recycling study. Prepared for the  Central Contra Costa Sanitary District,
    Walnut Creek, California.  1974.

22.  Thompson, C.G., and A.P.  Black.  Demonstration of the  Magnesium
    Coagulation System  at Montgomery, Alabama.  In:  Minimizing and
    Recycling Water Plant Sludge, AWWA Seminar.  Proceedings. New York.
    American Water Works Association, 1973.  p. VI-1 to VI-45.
                                    129

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23.  Shuckrow, A.J., and W.F. Bonner.  Development and Evaluation of
    Advanced Waste Treatment Systems for Removal of Suspended Solids,
    Dissolved Organics, Phosphate and Ammonia for Application in the City
    of Cleveland. Battelle-Northwest. Richland, Washington.  Report to Zurn
    Environmental Engineers .  June 1971.  96 p..

24.  Parker, D.S . Internal Memorandum, Low Lime Centrifuge Test Results.
    Brown and Caldwell, San Francisco,  California.  May 1972.  7 p.

25.  Gibbs, O.J. Field Test Report,  Sewage Sludge  at the CCCSD Sewage
    Treatment Plant. Bird Machinery Co., Lafayette, California. Field Test
    Report No. WCD-38.  October 1971. 9 p.

26.  Smith, A.G. Centrifuge Dewatering of Lime Treated Sewage Sludge.
    Ministry of the Environment.  Toronto.  Paper No. 2030. May 1972. 22 p.

27.  Tofflemire, T.J., andL.J. Hetling .  Treatment of a Combined Wastewater
    by the Low Lime Process. Journal Water Pollution Control Federation, 45,
    210,  1973.

28.  Disposal of Wastes from Water Treatment Plants. American Water Works
    Association Research Foundation.  Washington, D.C.  Report Number 12120
    ERC. Federal Water Pollution Control Administration.  August 1969.  73 p.

29.  Gerlich, J.W., andM.D. Rockwell, Pressure Filtration of Wastewater Sludge
    with Ash Filter Aid. U.S . Environmental Protection Agency Report Number
    EPA-R2-73-231, June 1973.  153 p.

30.  Steward, C.R. Personal communication to D .S .  Parker. Passavant
    Corporation.  Birmingham, Alabama.  September 28, 1973.

31.  Bennett, S.M.  Personal communication to D .S . Parker.  U .S . Environmental
    Protection Agency -  Blue Plains Pilot Plant.  September 17, 1973.

32.  Aldworth, G.A. Some Plant Design Considerations in Phosphorus Removal
    Facilities.  James F. MacLaren Limited,  (Presented at the Phosphorus
    Removal Design Seminar, Toronto, Ontario, May 28 - 29, 1973)  19 p.

33.  Blanchard, C.T. Personal communication to E.  de la Fuente. CPC
    Engineering Corporation, Sturbridge, Massachusetts.  January 8,  1974.

34.  Foy,H.E.  Personal communication to D .S . Parker.  Envirotech Corporation,
    SanMateo. 1972.
                                    130

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                                  SECTION VIII

        LIME SLUDGE RECALCINATION AND WASTE SLUDGE INCINERATION


GENERAL CONSIDERATIONS

Lime recovery from chemical sludges has been practiced in the pulp and paper
industry and in the water softening field 1 for many years.   In wastewater treat-
ment however, the practice is much more recent dating back to 1968 when the
South Tahoe water reclamation plant began to successfully reclaim lime from the
tertiary treatment sludge.2

The economics of lime recovery from wastewater sludges are quite different than
for water softening  sludges.  In the latter case, since the softening reactions
cause calcium hardness to precipitate as calcium carbonate,  generally more lime
is produced than is added for treatment. As a result,  lime recovery operations
in the water softening industry often show a profit.!   On the other hand, due to
process inefficiencies and losses, which will be explained later,  only 50-70
percent recoveries  of the required lime  dose are usually possible from waste-
water lime sludges.  Consequently, new lime must be purchased to make up for
the losses.  Once steady state conditions are reached, the quantity of make up
lime  required can be expected to remain constant.

Lime recovery from wastewater sludge is attractive because  recalcination,  being
a combustion process,  can also be regarded  as a method of sludge disposal.
Therefore by recalcining the lime sludge, not only the spent chemical is re-
claimed to be used again, but also the expensive problem of process solids
disposal is greatly simplified at the same time.

In general, sludge incineration involves two steps,  (a) drying and (b)  com-
bustion. In turn, the drying and combustion processes consist of the following-
phases:   (1) raising the temperature of the feed sludge to 100 C (212 F) ,
(2) evaporating  water from the sludge,  (3)  increasing the water  vapor  and air
temperature of the gas,  (4) increasing the temperature of the dried sludge
volatiles to the ignition point,  and (5) combustion of the volatiles .  The end
products of combustion are water vapor, carbon dioxide, sulfur dioxide,
nitrogen gas and inert ash.

Another important consideration in incineration processes is the  required
amount of combustion air.  When any material burns, it combines with the
oxygen in the air.  The amount of air required can be  theoretically calculated
from the sludge  composition .3 This amount is called "theoretical air",  In
practice, however, it is necessary to supply more air  than is theoretically
required since it is not possible to distribute the air evenly over the burning
bed of material.   The amount of air supplied in addition to the theoretical air
is called "excess air" and is usually given as a percentage of the theoretical
                                    131

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air.  So, burning with 100 percent excess air means supplying twice as much air
as is theoretically necessary.   The fundamental requirement is that enough air
be admitted to the incinerator to ensure proper combustion of the sludge.  If not
enough  air is admitted, the sludge will burn with a smoky flame, produce pro-
ducts of incomplete combustion  such as carbon monoxide, and emit offensive
odors.  Insufficient air may also encourage formation of clinkers in certain types
of incinerators .  On the other hand, after the theoretically required air is supplied
the more excess air is admitted, the cooler the incinerator will become and the
more auxiliary heat will be required to maintain combustion.  Fig.  8-1 illustrates
the relationship between auxiliary fuel and excess air. 4 Gas costs are rising and
the fuel costs per ton can be proportionately increased over that shown in Fig.
8-1 to reflect local conditions .

LIME SLUDGE RECALCINATION

Recalcination of lime sludges is a  process in which sludge is burned to decompose
calcium carbonate to calcium oxide (lime)  for reuse in treating more wastewater.
The incinerator temperatures required to achieve this conversion are 871-982 C
(1600-1800 F)  and the decomposition is expressed by the following  equation:

        CaC03 	> CaO   +    CC>2  (gas)


Quantitatively this equation can be represented as a function of CC>2 concentra-
tion and temperature as shown in  Fig. 8-2.5 Since any incinerator will contain
10-20 percent CC>2 by volume it can be seen that active and energetic decomposi-
tion can be expected when the  solids reach temperatures above  760-816 C  (1400-
1500 F)  . Any hydrated materials  such as magnesium and iron hydroxides will
decompose to their respective oxides well below these temperatures.

During  the test work at the CCCSD's ATTF, it was found that the conversion
efficiency of calcium carbonate was related to temperatures in the recalcining
hearths of the multiple hearth furnace.6  To obtain 95 percent lime  recovery
efficiency, a temperature of 932 C (1710 F) in the  recalcining hearth was
required. The carbon dioxide content was 13-17 percent,  and Fig. 8-2 shows
that the practical recalcining temperature is considerably greater than the
theoretical value, because (a) a temperature difference is needed to transfer
heat between  the gas and the solids being recalcined and  (b)  the equilibrium
data  (Fig. 8-2) were obtained at long contact times and do not apply exactly  in
a practical circumstance where reaction time is net long.

Carbon  dioxide liberated during combustion can be collected and used for pK
adjustment, i.e. , recarbonaticn, in the lime treatment system.

As indicated in Section VI, lime recovery is economically attractive in high lime
applications since the additional benefits derived from higher lime doses can be
justified when lime is to be recovered.  At this range of pH  (11-11.5) , the
precipitation of magnesium as magnesium  hydroxide is practically complete and
the calcined magnesium  (MgO)  does not react in water. Consequently,  unless-
the lime sludge is classified to  remove magnesium prior to incineration, the
                                     132

-------
  LL
  O

  O
  O
  O
  o:
  ui
  u
  O
  Q
_l Z
O <
O CD
tr o
^ E

d|

U- a

> £

< O
Zi O
  a:
  Z)
            % EXCESS AIR VS AUXILIARY FUEL

        SLUDGE AT 30% TS, 70% VOL 8 10,000 BTU/lb

            EXIT TEMPERATURE AT8I6C( I500F)
   .-  4
       0
                                                       $3.70/TON
                                                         :D
                                                 1970 DOLLARS
             $0.92/TON
                    I
                       (I)
                        I
           20         40         60


         % EXCESS AIR FOR SLUDGE


EXCESS AIR FOR NATURAL GAS AT 2O% (CONSTANT)
80
100
     Figure 8-1  Effect of excess air on the cost of sludge incineration
                                 133

-------
IOO
90
10
  400      500
600       700      800       900      IOOO
     TEMPERATURE.C
  Figure 8-2   Decomposition of calcium carbonate to calcium oxide
                                134

-------
recalcining process will render a product with a high percentage of unreactive
magnesium oxide. By contrast, wet classification of the lime sludge is expected
to reduce the proportion of magnesium oxide in the recalcined product to 5
percent or less by weight.?  However, even after wet classification,  other inerts
will build up in the system because complete rejection  of inerts is not achieved.
Inerts which build up are magnesium,  phosphorus, iron,  silica and other
compounds.  As a result,  the available lime in the recalcined product may be
only 60  to 77 percent.7,8

Inerts buildup can also be controlled by continuously purging ("blowing down")
a portion of the furnace product to equal the incremental increase in non-carbonate
solids added to the lime sludge during precipitation.9  Naturally, the blowdown
also wastes  a portion of the reclaimed calcium oxide so make up lime is required.
Solid balances presented in Section X, Table 10-10, show that in a flow sheet
without wet classification, 28 percent of the furnace product must be purged to
approximate the amount of solids generated in a system that incorporates wet
classification (Fig. 7-9) .  Also, at 28 percent ash blowdown, the makeup lime
requirements are 55 percent of the overall requirements;  in the flow sheet with
wet classification, makeup lime accounts for only 38 percent of the total require-
ments.  Thus, product purging is a wasteful means of  controlling inerts as the
overall  recovery of lime in the  process is  reduced.

Another means  for increasing the effectiveness of purging is to use dry classifi-
cation.  It may  be used alone or in conjunction with wet classification.  As
described later in this section, dry classification uses  particle size selection to
preferentially reject silica from the system.

Three types of  recalcining plants are used to recover lime from process sludges:
rotary kilns, fluidized bed reactors and multiple hearth furnaces.   The first
two types have been used extensively  in industrial and water softening appli-
cation.  The multiple hearth furnace seems to have taken the lead in lime
recovery applications from wastewater sludges.

Multiple Hearth Furnaces
                                                                 2
Multiple hearth furnaces  (MHF) are used at South Tahoe,  California,  Colorado
Springs, Colorado and Piscataway, Maryland for full scale recovery of lime
from tertiary treatment wastewater  sludge.  Four additional installations are
under different stages of construction  in the U.S. and  several more are in the
planning and design phases. 10 The MHF was initially developed  for use in
the mining industry for roasting ores. It has been widely used in  municipal
applications for disposal of both primary and biological sludges for over 40
years. H  Other solid products of wastewater treatment including grit, scum
and screenings have  also  been incinerated in the MHF .  The popularity of
multiple hearth units can  be attributed to their simple  design and flexibility
of operation under varying feed rates. ^

The multiple hearth furnace is  a circular structural steel shell lined with re-
fractory brick, and the interior is divided into separate compartments (i.e. ,
                                      135

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hearths)  by horizontal brick arches.  An air cooled central shaft supports the
cantilevered rabble arms (two or four) provided on each hearth.  Revolving
rabble arms move the sludge from hearth to hearth alternately inwards and
outwards so the sludge travels radially the full width of each hearth before
dropping to the next one.  This travelling pattern has been used to name the two
hearth types.  Those in which sludge enters near the periphery and exits through
openings around the center shaft are called "in-feed" hearths.  Those in which
sludge is rabbled from the center towards the hearth periphery, where the drop
holes are located, are called "out-feed" hearths.  Fig. 8-3 shows a typical MHF.

As the material passes down through the furnace, three  distinct zones are estab-
lished.  The upper hearths form a drying  and gas cooling zone. Here, vaporiza-
tion of some free moisture occurs as well as cooling of exhaust gases by transfer
of heat from the hot gases to the  sludge. Intermediate hearths form a high tem-
perature burning zone, or combustion zone, where all volatile gases and solids
are burned.  Combustion of most of the total fixed carbon takes place on the
lowest hearth of the combustion zone. The bottom hearths of the furnace function
as a cooling and air-preheating zone where ash is cooled by giving up heat to the
returned shaft cooling air.   The relative location of the zones will tend to shift
as the result of changes in the quality and quantity of the feed, i.e.,  the sludge
feed rate and the moisture content of the cake.  If there is enough combustible
matter in the sludge cake, sufficient heat will be liberated by the burning solids
to drive off the moisture in the sludge cake on the upper hearths to the point
where this material itself will ignite as it reaches the combustion zone.  Thus,
the incineration process may be  self-sustaining (autogenous combustion) .

A comprehensive thermal analysis of combustion in the MHF is given in Reference
11.   In general, sludge has to be 25-30 percent solids with a volatile solids
content of 70 percent  (and no solids to be calcined) for autogenous  combustion.
If afterburning is required to control air pollution  (see Section IX) , auxiliary
fuel is necessary to reach afterburning temperatures, although autogenous
combustion could still occur in the burning hearths.

A temperature profile across a typical sludge furnace is  given in Table 8-1. ^
For design purposes, excess air for  combustion of volatiles in the  sludge is
usually set at 50-75 percent.  Normal operation conditions may show a lower
percentage of excess air. 12

For a given solids load to a MHF, lime recalcination requires additional hearths
over the number normally required for sludge  combustion.  In the CCCSD water
reclamation plant,13 the furnaces will have ten hearths  (an eleventh hearth
will be used as an afterburner) .  Approximately two hearths are required to
dry the feed, two hearths to preheat the feed to calcining temperature  (899 C
(1650 F) solids temperature or about 1010 C (1850 F) gas temperature) , four
hearths to get complete calcination and two hearths to cool the  product.14
Excess air for  sludge  recalcination is normally set at 100 percent.  Table 8-2
gives the anticipated temperature profile for the CCCSD lime furnaces.
                                     136

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          EXHAUST GASES
          OUTLET
    TYPICAL
    IN-FEED
    HEARTH

    TYPICAL
    OUT-FEED
    HEARTH
    SHAFT
   COOLING
   AIR INLET
                                                      TYPICAL
                                                      RABBLE ARM
                                                      CENTRAL
                                                      SHAFT
 ASH
DISCHARGE
 PORT

 CENTRAL
SHAFT  DRIVE
Figure 8-3   Typical multiple hearth furnace (courtesy of BSP Division-
            Envirotech Systems, Inc.)
                               137

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 Table 8-1.   TYPICAL TEMPERATURE PROFILE
             IN SIX HEARTH FURNACE
Hearth No.
1 (Top)
2
3
4
5
6 (Bottom)
Temperature
C
427
649
899
788
649
149
F
800
1,200
1,650
1,450
1,200
300
   Table 8-2. TEMPERATURE PROFILE IN LIME
   RECALCINATION FURNACE FOR CCCSD
 Hearth No.

1 (Top)
2b
3
4
5
6
7
8
9
10
11 (Bottom)
C
76 Oa
427
677
899
1,010
1,010
1,010
1,010
1,010
677
399
F
l,400a
800
1,250
1,650
l,850e
1,850C
1,850C
1,850°
1,850C
1,250
750
Temperature
, Top hearth used as afterburner
 Feed hearth
 Test work indicates that a temperature
 as low as 932 C (1, 710 F) may be
 adequate.
                      138

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The MHF is sized based on solids loading per unit of hearth surface area. Sizing
is influenced by the characteristics of the sludge cake, including moisture, volatile
solids, inerts content, and calorific value.  34 to 59 kg of wet sludge per hour per
square meter of hearth area (7-12 Ib/hr/sq ft)  is the range of loading  rates com-
monly used in determining the required hearth area. 12  Rates for recalcining
furnaces are  generally in the low end of this range.  The somewhat lengthy pro-
cedure used to  size a MHF has been greatly simplified by the development of
digital computer routines .11/12

The modular  construction of MHFs allows their use in a wide range of  solids
loadings. Typically, additional capacity is obtained by increasing the furnace
diameter, increasing  the number of hearths, or both. Table 8-3 shows the
standard furnace sizes offered by a large manufacturer of the MHF . 12   The same
manufacturer has developed a "Plural Purpose" furnace (a  patented application) .^
This concept permits  the use of a single unit for both lime recalcination and
organic sludge incineration (Fig. 7-8) .  Scum, grit and screenings can also be
burned together with the lime and organic sludges.  The reclaimed lime is
separated from the inerts by  dry classification techniques.  12 Dry classification
will be covered in detail later in this section.

Fluidized Bed  Reactors

Fluidized bed reactors (FBR) are the type of recalciners most commonly used to
recover lime  from water softening  sludges. 1 The FBR is also used in  the pulp
and paper field and in other industrial applications such as ore roasting,
calcination of phosphate rock and limestone, etc.  In wastewater treatment,
fluidized bed techniques were first applied in Lynnwood, Washington  in 1963 to
burn both raw  sludge and scum. 16 The first full-scale application of  a FBR in
lime recalcination from wastewater sludge was started in Elkhart, Indiana in
1974.17

Basically, a FBR consists of a vertical steel shell internally divided into hori-
zontal compartments.  In general,  the number  of compartments depends on the
type of material burned in the reactor and its mode of operation.   A layer or
"bed" of the granular material (either lime pellets or sand) is placed at the
perforated bottom of a compartment.  As preheated air flows into the burning
section, its upward velocity suspends the solid particles and the bed expands.
This mixture of solids and gas is said to be fluidized since  it behaves  not unlike
a true liquid. 18  The physical appearance of the fluidized bed has been described
as similar to  boiling water due to the intense mixing between air and bed
material.  Combustion of either fuel or sludge takes place within this bed and
is completely dependent upon this intense mixing action.

Two distinct  types of fluid bed systems have been applied to lime recovery from
waste calcium carbonate  sludges .  The bed in one type of unit (Fig . 8-4) consists
of pellets of recalcined lime.  In the other type of unit, sand is used to form the
fluid bed.
                                      139

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      Table 8-3.  STANDARD MULTIPLE HEARTH FURNACE SIZES (COURTEST OF BSP DIVISION-
                 ENVIROTECH SYSTEMS, INC.)
I.D.
13"
20"
30"
39"
54"
5 1/2'
7'
8 1/2"
10 1/2'
12'
14 1/2'
16 1/2'
18'
20'
23 1/2'
26'
28'
O.D. for
wall thickness of
6"
18"
@ 2 1/2"
30"
@ 5"
3'
@ 3"
4'3"
5'6"
6'6"
8'0"
9'6"
11'6"
13'0"
15'6"
17'6"
19'0"
21'0"
24'6"
27'0"
29'0"
9"


44"
@ 7"
4.9.1
6'
71
8'6"
10'
12'
13'6"
16'
18'
19'6"
21'6"
25
27'6"
29'6"
13 1/2"



4'6"
6'9"
7'9"
9'3"
19'9"
12'9"
14'3"
16'9"
18'9"
20'3"
22'3"
25'9"
28'3"
30'3"
Col.
height3
1'
1'3"
1 1/2"
2 1/2"
4'
4'
51
6 1/2'
6 1/2"
6 1/2"
7'
7'
8'
8'
8'
8'
8'
Square feet of effective hearth area and "normal" shell height"
Hearths
1
1
2
4
7
15
24
32
47
80
97
143
181
215
269
382
463
610
2
2 1/4
1'8"
4
2'0"
8
2 '2"
14
3'6"
31
4'2"
47
4'8"
65
6'3"
94
6'3"
148
8'4"
195
6'9"
286
8'0"
363
8'4"
431
8'4"
538
9'6"
764
11'4"
926
12'7"
1,155
13'
3
2 1/4
6
12
19
42
63
96
138
227
287
422
534
634
790
1,145
1,389
1,690
4
3
3'4"
8
4'0"
16
4'4"
28
6'
63
7'4"
94
8'3"
130
lO'lO"
188
10' 8"
295
14'0"
390
11'8"
573
13'2"
727
14'3"
863
14'4"
1,077
16'1"
1,528
18'9"
1,852
20'9"
2,235
22'
5

10
20
32
74
110
161
235
374
487
716
908
1,078
1,346
1,909
2,315
2,770
6

12
6'0"
24
6'
37
8'6"
85
10'6"
125
ll'ld"
193
15'5"
276
IS'l"
442
19'8"
575
16'7"
845
18'7"
1,068
20'2"
1,268
20'2"
1,580
22'9"
2,292
26'2"
2,778
28'10"
3,315
31'
7


28
42
98
145
225
323
521
672
988
1,249
1,483
1,849
2,674
3,241
3,850
8


32
7 '8"
48
ll'O"
112
13'8"
166
15 '5"
256
20'0"
364
19'5"
589
24'4"
760
21'5"
1,117
24'1"
1,410
26'0"
1,660
26'1"
2,084
29'6"
3,056
33'7"
3,704
36'11"
4,395
40'
9


36
54
126
187
288
411
668
857
1 ,260
1,591
1,875
2,350
3,438
4,167
4,930
10


40
9'4"
61
13' 6"
140
16'10"
208
19 '0"
319
24'7"
452
23'10"
736
31'0"
944
26'4"
1,400
29'6"
1,752
31'11'
2,060
31'H1
2,600
36'2"
3,818
41'
4,630
45'
5,475
49'
11






351
510
815
1,041
1,540
1,933
2,275
2,860
4,200
5,093
6,010
12






383
560
883
36'8"
1,128
31' 2"
1,675
35'0"
2,090
37'9"
2,464
37'10"
3,120
42'11"
4,584
48'5"
5,556
53'1"
6,555
58'
Dimension H in Fig. 8-3 .
Dimension L in Fig. 8-3.

-------
  ,TO ATMOSPHERE
                     EXHAUST
                      FAN
                                                                                                       TO
                                                                                                     PRODUCT
                                                                                                     STORAGE
                                                                                                       BINS
                                                           FUEL OIL
                                                         V-A BLOWER
Figure 8-4   Schematic diagram of a pellet bed calcining system  (courtesy of Dorr-Oliver Incorporated)

-------
                                                                 17
A wide range of capacities can be accommodated with the FBR.  Lamb   has
reported 18 lime mud reburning installations as of March 1972,  ranging in
capacity between four and 220 tons of lime per day. The maximum capacity of a
single fluidized bed calciner is estimated at 250 tons of lime per day.  Sand bed
reactors have been built from four to 20 ft in internal diameter for the incineration
of wastewater sludges.

The FBR is sized on the basis of the gas velocity required to fluidize the bed
material. For pellet bed type units, velocities of approximately 1.8 m/sec
 (6 ft/sec) are usual whereas for sand bed units, the superficial reactor velocity
is about 0.6-0.9 m/sec  (2-3 ft/sec) .   Any given bed material will fluidize only
over a limited range of gas velocities and this fact imposes a limitation on the
flexibility of the FBR to accommodate variations in capacity much  beyond + 20
percent  of design without serious losses in efficiency.  In a practical sense the
capacity in terms of tons of sludge per square foot per hour is largely governed
by its moisture content and its calcium carbonate content—the two principal
contributors to heat requirements.

An attractive feature of the FBR is its ability to  restart quickly  on shut down.  The
fluidized bed acts like a large heat reservoir. Normally a hot sand bed will lose
only 0.5 C per hour during down time. 19 The FBR can also build up temperature
 rapidly due to the high  heat transfer properties of the gas-bed  mixture. Heat
transfer rates for an FBR bed are some 5 to  25 times that of gas alone. -^ As a
result of the heat properties of a FBR, shut  down-start up cycles  are  much
shorter than for a MHF .

Pellet Bed Units -

In the fluidized bed system that has been used to recover lime from water soft-
ening and pulp and paper mill sludges, the pellet bed reactor is only the
calcination and cooling part of the lime recovery system.  Essential to the
operation of the system  are some related processes which will now be described.
After passing through a thickening-dewatering stage (see Fig .  8-4 and Section
VII) , sludge cake is mixed with predried calcium carbonate in a paddle type
mixer.  Mixing with a dry product, required because dewatered cake is sticky
and difficult to  transport,  results in the formation of easily moveable lumps.
From the paddle mixer solids are discharged into a cage mill.  Here, the lumps
are broken up and the solids are exposed to a stream of exhaust gases from the
reactor.  The solid particles are rapidly dried by the hot gases and carried to
a cyclone where the dried carbonate is separated from the gas stream.  A
portion of the material collected in the  cyclone is returned to the paddle mixer
to condition dewatered cake  and the remainder is transferred to a dried sludge
storage bin.  From the storage bin, a pneumatic conveyor feeds the dried sludge
to the burning compartment of the FBR. Fuel, either gas or oil, is also injected
into this  compartment. Once in the burning compartment, where temperatures
are maintained at 816-927 C  (1500-1700 F) , the calcium carbonate  particles are
rapidly converted to calcium oxide. The CaO particles agglomerate into larger
particles, aided by the violent mixing in the bed.  To promote pellet formation
and to control its size, an agglomerating agent (soda ash) is normally introduced
                                     142

-------
along with the feed sludge.  Crushed lime pellets are added as seed particles.
Lime pellets are discharged from the calcining zone to the cooling section
through an internal transfer pipe. In the cooling compartment hot lime is
fluidized with incoming air which lowers the product temperature to 227 C  (440 F)
and in turn, preheats the air to that same temperature before entering the calcin-
ing section.   Cooled, dust free pellets are continuously transferred from the
cooling compartment to a storage bin through a bucket elevator.   Fig. 8-5  shows
a cross section of a typical fluidized bed calciner.

One attractive feature of the pellet bed unit is the heat recovery that is integral to
the system.  Hot off-gases from the reactor are used for flash drying of the cake
fed to the system.  Discharge gas temperature from the system usually is only
135 to 149 C (275 to 300 F) ,20,21 compared to the usual 427 C (800 F) in a MHF
(without after burning) or 816 C (1500 F) in a sand bed FBR.  As a consequence,
the pellet bed unit requires from one-half to one-third the fuel per ton of CaO of
a sand bed FBR.2^  The excess air required for the burning of either  or both the
fuel and  sludge is  only  20-30 percent as opposed to 70-100 percent in the MHF.

Up to the present time,  the pellet bed FBR has been applied strictly to paper pulp
mill and  water softening applications.  The process will be applied to  a tertiary
treatment lime sludge in a plant  currently under construction in Virginia.1'

The chief U.S . manufacturer of the unit, Dorr-Oliver Incorporated, is cautious
about the application of the pellet bed FBR to lime sludges generated in the
primary  sedimentation tank. The main concerns expressed are related to whether
excessive dusting would occur in the reactor due to the increased level of inerts
in a cake generated by primary processes as compared to tertiary processes.  In
one water softening application, granular silica in the raw influent increased
dust losses from the  normal 15 percent loss up to 25  percent. It was concluded
that if the pellet bed FBR is going  to be applied to lime recovery in raw waste-
water treatment, further research on the control of pelletization in the process
is required.22  The same note of caution is expressed by Krause.23  He noted
that even sludges from similar application, but different locations, differed in
their behavior in the pellet bed  FBR.  A considerable period must be  allowed
after start up for fine tuning and modification of the system to allow its full
performance to be obtained.

When the pellet bed reactor is applied to wastewater sludges, attention must also
be given to odor control in the unit.  During incineration of organic sludges, it
is often contended that the  combustion zone must be held at 649-816 C  (1200 to
1500 F) for effective  destruction of odorous substances (see Section IX) .  While
it is true that the pellet bed FBR operates at 816 C (1500 F) in the calcining zone,
the hot off-gases are used to dry the cake in a cage mill. As a result of the pre-
drying of the lime cake before it is fed to the reactor, the off gas temperature
ahead of the wet scrubber is in the range of 135 to 149 C  (175 to 300 F) . Conse-
quently, odors may be created in the drying zone from volatilization of organics.
Afterburning of the off-gases may  be required if the pellet bed FBR is applied to
lime recalcination of raw wastewater sludge. Afterburning will naturally reduce
its overall fuel efficiency -
                                     143

-------
HOT GAS TO DRYER
 PREHEAT BURNER
 TRANSFER PIPE
                                               RECYCLE CRUSHED PELLETS
                                                 GUNS
                                v^§?'ffl-_^FUEL GUNS
                                T. ~f- ^-'J -\ l^ •
                                            PELLETIZED PRODUCT


                                           AIR
             Figure 8-5  Typical fluldlzed bed calclner


                (courtesy of Dorr-Oliver Incorporated)
                                 144

-------
Due to lower levels of organic solids in tertiary lime sludges, afterburning may
not be required for tertiary treatment applications.

Sand  Bed Units  -

Originally, the sand bed FBR was developed to incinerate sludges from both
primary and biological treatment.  It has since been applied to lime sludges as
well.  Differences from the basic pellet bed unit are the elimination of the sludge
drying step, the dewatered cake being fed  directly to the burning zone of the FBR
by a positive displacement pump or a screw conveyor; and the replacement of the
bed of lime pellets used with  water softening and paper pulp sludges with a bed
of graded silica sand.  Fig. 8-6 shows the modified  flow sheet for applications
involving lime treatment of raw wastewater.

In the modified FBR for lime recalcination,  pellet formation is inhibited and all the
calcium oxide particles are carried by the exhaust gases to a hot cyclone where
CaO is separated from the gas stream.  From the cyclonic collector, lime dis-
charges into a quenching tank, where it is  slurried by the cooling water and then
discharged to  a collection tank.  Slaking of the lime to Ca(OH) 2 takes place in
this tank.  In this  tank, which also receives water discharged from the wet
scrubber and a conditioning ash slurry, the lime slurry is further diluted and
then pumped to an ash thickener.  In the process of dilution,  the lime is dis-
solved,  resulting in  a nearly saturated solution of calcium hydroxide and
leaving the other constituents in suspension.  Albertson24 has reported that the
separation of the suspended matter from the calcium hydroxide solution in the
thickener is extremely rapid. Overflow rates of 100 to 120 cu m/day/sq m (2500
to 3000 gpd/sq ft)  may be possible.  Supernatant from the thickener, containing
the calcium  hydroxide, is then returned to  the primary clarifier to recycle the
lime.  Thickener underflow is pumped to a  dewatering step prior to final  ash
disposal.

At the time this manual was being written,  no full-scale operational data were
available on the  modified FBR flow sheet shown in Fig. 8-6.  Albertson and
Sherwood-^ have reported the results of lime recovery tests conducted both  in
a 12-inch, laboratory scale reactor and  in a 4-ft FBR used to incinerate organic
sludge.  In these tests lime sludge, obtained during bench scale studies of lime
precipitation,  was mixed with centrifuged organic cake and the mixture was
fed to the reactor. Bed temperature was maintained at 871 C  (1600 F) .  The
combustion  gases then passed through a cyclone separator and a wet scrubber.
Laboratory analysis  of the  solids in the cyclone underflow showed that 79.6-90
percent available lime was captured in the  unit.

Experience  at Holland, Michigan -  As  mentioned before, there is no informa-
tion available  on full-scale operation of  a sand bed-type FBR on wastewater
sludges.  The closest operation similar to lime recalcination is the FBR in
operation at Holland, Michigan.  At Holland, the FBR is used for sludge
disposal  for a low  lime treatment plant rather than for lime recalcination.  As
a result, it does not  have the hot cyclone and recovery system shown in Fig.
8-6.   Nonetheless, the furnace is operated  at 816 C  (1500 F) ,26 This operating
                                     145

-------
                                                                         -TO ATMOSPHERE
01
                                       BOOSTER PUMP
                                              e?
                     FLUIDIZED BED REACTOR
             CENTRIFUGE
      THICKENED
      SLUDGE
                       lAAAAA/V
                        FEED SCREW
                         CONVEYOR
                      FUEL OIL
                       PUMP
                                                                                          ASH THICKENER OVERFLOW
                                                                                          RETURN  TO PLANT INFLUENT
                             Figure 8-6   Schematic diagram of a sand bed calcining system

                                           (courtesy of Dorr-Oliver Incorporated)

-------
temperature is sufficient for recalcination in a FBR.  Certain operating experiences
with this unit are worthy of discussion.

The FBR at Holland is a 4 m (13 ft) ID unit with a 1.5 m  (60-inch) expanded bed.
A total of 14 burners are provided.  Normally, a screw conveyor is used to feed
centrifuge cake.  In cases where the centrifuges are down, thickened slurry may
be fed through four feed ports using a Moyno pump. The unit has considerable
overload capacity.  It has been fed at 725 kg/hr  (1600 Ib/hr) without difficulty
while its design is for 408 kg/hr (900 Ib/hr) ,26

The current operating problem is that material is building up in the venturi
scrubber causing high head losses in the gas discharge from the unit.26  it is
likely that calcium oxide is slaking  in the scrubber, causing a deposit to form,
much as occurs in a lime slaker.  This condition requires at least semiannual
maintenance.

Some pelletization has occurred on the sand bed particles, and bed material must
be blown down to hold a constant bed volume in the system.  Martin26 stated that
a volume equal to the bed volume has been blown down in approximately a seven-
month period.  After this initial blowdown, the sand particles  seemed to have
reached a maximum size and no further removal  has been found necessary.27 n
has been found that 40 to 50 percent of the bed is calcium oxide. If pelletization
occurs in a sand bed FBR,  it defeats the intended mode of operation of the  unit
for recalcination, since product is removed from the effluent gases rather than
from the bed.   Dorr-Oliver states that pelletization has  not occurred in a recal-
cining application where the sludge contains  calcium carbonate from a tannery
waste treatment plant.   It is felt that the occurrence of unintentional pellet
formation is affected by the type of inerts in the waste sludge,  which may be
unique in each  application.22  Further research on pelletization is required to
define the conditions necessary for  its control in the sand bed  FBR before it can
be applied with  certainty to wastewater lime sludges.

Rotary Kiln Calciners

Until 1963, when the first fluidized  bed reactor was installed at S-.D. Warren Co.
in Muskegon, Michigan,20 the rotary kiln calciner  (RKC) was  the conventional
method to recover lime in the pulp and paper mill industry.  Rotary kilns have
also been successfully used to reclaim lime from water softening sludges. 1 To
date, no attempts have been made to apply the RKC to the recovery of lime from
wastewater sludges.

A typical RKC consists of a long  rotating  steel shell lined with  a refractory
material.  The shell is slightly inclined to facilitate movement of sludge along the
kiln.  Dewatered lime sludge is fed  and off-gases exhausted at the upper end of
the shell. This  section  is provided with a heat recovery chain to facilitate the
exchange of heat between the sludge cake and the hot exhaust  gases.  Sludge is
dried in this end of the  RKC.  After a residence time of one and a half hours  and
before being discharged at the lower, or firing end of the shell, sludge is
nodulized (i.e., agglomerated in round-shape lumps) and converted to calcium
oxide in the calcining zone. From the rotary shell, the  product enters a peri-
pheral tube  cooler from which it is mechanically transferred to storage.
                                     147

-------
The temperature of the calcining zone is maintained at approximately 1093 C
(2000 F) , considerably higher than the theoretical temperatures required for
recalcination.  Temperatures as high as 1371 C (2500 F) have been used in some
applications. Exhaust gases are emitted at 204 C  (400 F) .  In the integral tube
cooler, recalcined lime is cooled to approximately 316 C (600 F) .   The RKC
requires higher temperatures than the MHF or FBR because the particle size of
calcium carbonate in the rotary kiln is so much larger than in the other recal-
cining units. A higher temperature is required to provide the necessary force so
that carbon dioxide  can be driven out of the center of the larger clumps.  Uneven-
ness of particle sizes requires higher temperatures than necessary for the bulk
of the particles .28,29  A schematic diagram of a typical RKC is shown in Fig. 8-7.

It seems unlikely  that rotary kilns will find application in recovering lime from
wastewater sludges. The RKC requires appreciably more  area than either
multiple hearth furnaces or fluidized bed reactors.  Also,  the RKC would be
limited only to large installations processing more than 50  tons of product per
day.  Perhaps more important is  the fact that rotary kiln technology is completely
foreign to the wastewater treatment field whereas  the MHF  and the FBR have been
successfully applied to the disposal of wastewater sludges  for many years. 12,16
As a result, a wealth of experience has been gained in these installations and
important modifications have been made, and new designs  incorporated, to the
original equipment.  It could take the manufacturers of rotary kilns  a comparable
investment, both  in time and money, to develop the expertise  required to
satisfactorily recover lime from wastewater sludges.

HANDLING OF RECLAIMED LIME

The type of process used to recalcine wastewater sludges has a direct influence
on the way the reclaimed lime is handled.  In the case of the FBR, each type of
recalcine reactor  produces a unique product; consequently, product handling
differs among reactor types .

Handling of Lime from the MHF

As mentioned earlier, recalcined lime from a multiple hearth furnace is dis-
charged at the bottom hearth.  Unless  operating difficulties cause the formation
of lumps  (clinkers) , the lime discharged from the furnace  is a fine,  powder-like
product. Table 8-4 show the size analysis of a typical sample of recalcined lime
taken at Concord, California.6  As shown in Table 8-2, the discharge tempera-
ture of the recalcined product is approximately 399 C (750  F) .  To protect
operating personnel from injury and to avoid the need to use heat resistant
material in process equipment, it is advisable to cool the lime to a temperature
of 38-93 C (100-200 F) .  Several types of industrial coolers can be used for this
application. At the CCCSD water reclamation plant, water cooled, disc-type
coolers will be supplied.   After cooling, the reclaimed lime is either transported
to storage by mechanical or pneumatic conveyors  (see Section V) or it can be
classified, using dry techniques,  to separate inert solids and other undesirable
constituents from  the recalcined product.
                                    148

-------
  t
           SECONDARY
           SCRUBBER
    STACK
                    -WATER
I.D.FAN
             Y
             WASTE
CENTRIFUGE
                      PRIMARY
                      SCRUBBER
                                        SECONDARY AIR
 FILTER CAKE
 CONVEYOR
                                                            BUCKET_
                                                            ELEVATOR
                                                              NATURAL GAS
                                                                    PRIMARY
                                                                    AIR FAN
                                                        \f~~~~
                                                        LAAAAAAAAAAAAAAAA/\/g
                                                           PRODUCT SCREW
                                                                               LIME
                                                                              STORAGE
                                                                                BIN
                                                                                  PRODUCT
                       Figure 8-7  Typical rotary kiln calciner

-------
Table 8-4.  SIZE DISTRIBUTION ANALYSIS OF RECALCINED LIME FROM A MHh
Particle size
U.S. mesh3
100
140
200
270
325









b
Microns




44.00
34.48
31.22
24.77
15.57
11.12
7.55
3.34
1.36
< 1.36
Weight retained, grams
Sample 1
0.8100
1.3091
1.5756
3.1673
6.2182









Sample 2





3.3822
0.8490
2.5264
12.5030
22.8780
40.3914
51.0089
18.7903
e
Percent
retained
0.36
0.58
0.69
1.39
2.74
1.97
0.55
1.51
7.42
13.66
24.01
30.91
11.72
2.49
Cumulative
percent passing
99.64
99.06
98.37
96.98
94.24
92.27
91.72
90.21
82.79
69.13
45.12
14.21
2.49

   Sieve analysis

   Bahco analysis

  C Weight of sample:  227.0706 grams

   Weight of sample:  155 . 3664 grams

  6 Weight smaller than 1. 36yw.: 3.0362 grams

Dry  Classification  of Reclaimed Lime -

Dry  (i.e.,  air) separation of reclaimed lime can be used in lieu of the wet classi-
fication process described in Section VII or in addition to it.  In the former case,
this  method of solids separation can be used in conjunction with sludge dewater-
ing by vacuum filters or filter presses (Fig.  7-8) .  In the latter, dry classifica-
tion  aims at increasing the purity of the recalcined product beyond that obtained
by wet classification alone (Fig. 7-9) .  Dry classification has been found most
effective for blowing down silica from the system  shown in Fig. 7-9.6

Most air classifiers operate on the principle of centrifugal separation combined
with the effect of  opposing drag forces created by a current of  air. The settling
rates of particles  are increased many times when  centrifugal forces are used
in place of gravitational acceleration.  Once the difference in settling rate
between particles of two given sizes has been magnified, the classifier separates
them into two groups when centrifugal and drag forces reach equilibrium.  The
point of equilibrium, at which a particle of certain size is either accepted or
rejected by the classifier is called the "cut point".   The Envirotech Corporation
has found that a cut point at the 45  micron (>*)  particle size achieves a partial
classification of the acid insoluble inerts  (mostly  silica) from the other materials.
Fig.  8-8 shows the size distribution of a furnace product sample taken during an
extended test of lime sludge recycling at CCCSD.6  It can be seen for this single
sample that a fairly good rejection of silica can be obtained while recovering  the
                                      150

-------
bulk of the reclaimed lime at cut point points between 20 and 45 /* .  The selection
of the cut point is best established in field trials.   The accepts include fine dust
particles  ( < 5yU ) which normally must be retained for reuse in the  process.
This is accomplished by a second separation step that takes place in two stages.
First in a cyclonic separator where the solid particles are driven by centrifugal
force to the cyclone wall while the dust laden air escapes through the gas outlet.
Dust is subsequently removed,  in the second stage, in a bag type filter.   The
rejects (coarse) portion after discharge from the classifier is usually carried
directly to waste by mechanical or pneumatic conveyors.
  100 \—
                                                      Date Collected  8-6-73
              10
                  15
                       20   25    30    35    40
                          PARTICLE SIZE, MICRONS
                                                45
            Figure 8-8  Particle size distribution of recalcined  lime
Several types of classifiers are available which can successfully accomplish size
classifiction of the furnace product. Both the Bauer "Centri-Sonic" classifier and
the BSP Air Classifier have successfully been applied to this application.  The
Bauer machine  (shown in Fig. 8-9) is typical of conventional classification design
and operates with a rotating classifier section.  The feed,  admitted at the top,
first passes through a dispersing rotor which ensures that each individual
particle is free  to move in the classifier zone.  The particles then move downward
between the louver curtain and the rotating classifier  where they are intercepted
                                      151

-------
to
                         DISPERSING
                         ROTOR
                   LOUVER
                   CURTAIN
                                                  -DECK
                                                   SELECTOR
             • FINE ACCEPTS   •.". '. ; :-*T
                                REJECT FAN
                          BAUER "CENTRI-SONIC"
                                                                            BEND
CLASSIFYING
CHAMBER
                                                                         BAFFLE
                                                                         PLATE B
                                                                        SECONDARY
                                                                        AIR
                                                                                              FEED AND AIR
                                                                                              INTAKE
BAFFLE
PLATE A
                             EXHAUST
                             ORIFICE
                             (ACCEPTS)
              COARSE
              REJECTS


      BSP AIR  CLASSIFIER
                                        Figure 8-9   Two types of air classifiers

-------
by a controlled flow of air.  The air is forced through the classifier carrying with
it the fine particles and excluding the coarse particles which are held out by drag
forces.    The "cut point" in the Bauer design is determined by the air rate;  the
classifier speed;  the number of deck openings, as fixed by  the position of the
deck selector; and the rotating classifier design.

The BSP air classifier is unique in that it does not incorporate moving parts  (Fig.
8-9) . The sharp bend after the introduction of the feed moves the bulk of the
solid particles sliding against the  inside of baffle plate A  leaving a nearly clean
gas stream passing on the outside of this baffle plate,  next to the chamber wall.
At the bottom of baffle plate A,  the gas stream crosses a curtain of particles sliding
off the inside of the baffle plate producing a separation between the particles,
allowing each to react separately to  the drag and centrifugal forces induced on it
in the chamber.  Large  particles settle by gravity to the bottom of the chamber.
Intermediate size particles and fines flow with the gas in  a controlled spiralling
stream.  Each of these particles is subjected to a centrifugal force, tending to
move it  to the chamber walls, and to a drag force, created by the gas stream,
tending to move the particle to  the exhaust orifice. At the "cut point", the two
forces are equal.  Particles larger than the cut point are affected predominately
by centrifugal forces and flow outwardly until they impinge on the chamber wall
and settle by gravity to the classifier bottom. Particles smaller than the "cut
point" are affected mostly by drag forces and are swept out with the gas stream.
The BSP classifier "cut point" is controlled by the chamber dimensions, rate of
air flow and secondary  air flow.

Fig. 8-10 shows the adaptation of the basic air classification system to the separ-
ation of calcium carbonate from inerts in applications involving lime recovery
from wastewater sludges.

Using sludge generated at the ATTF, full-scale tests on air classification were
conducted at Concord, California^ in a BSP air classifier. During the course of
the Concord tests  it was initially felt that the dust collected  in the bag filter (see
Fig. 8-10) should be wasted from  the process; this was done because initial
batch testing showed the dust to be  high in phosphates.  However, when tested
at the ATTF  with wet classification  blowing  down phosphorus, the dust did not
contain  excessive amounts of phosphorus.  Table 8-5 compares the phosphorus
and other constituent levels in  the accepts to those in the  dust during a period
in the ATTF operation when the process was believed  to be  close to steady state.
Due to the small effect of phosphorus,  dust was returned  to the process along
with the other accepts .

Dry classification performance is expressed similarly  to wet classification per-
formance; for good classification,  high recovery of calcium oxide to the accepts
and dust is desired with low recovery of all other constituents.  As shown in
Table 8-6, essentially no classification of calcium oxide from the other constit-
uents occurred, except for silica and iron.   The period of July 27 to August 30
represented production operation  of the classifier during  the lime recycle project.
The runs on September 20 represented an attempt to operate the classifier closer
to design conditions. During the production runs, the classifier was not loaded
                                      153

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                                                          INLET HOPPER
                                                                   CLASSIFER UNIT
                                                                               ACCEPTS
  EXHAUST
  DUCT THRO
  ROOF
TYPICAL
BLOWER
REJECT BIN
FOR ASH
HAULING
                                                     ASH
                                                     DISCHARGE
                                                     FROM
                                                     FURNACE
                        TYPICAL
                        ROTARY FEEDER
                                                                                      ACCEPTS
                                                                                      TO LIME
                                                                                      STORAGE
    Figure 8-10  Dry classification of recalcined lime (courtesy of Envirotech Systems, Inc.)

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   Table 8-5.   COMPARISON OF ACCEPTS AND DUST COMPOSITION
               DURING ATTF TEST WORK
Date
August 6, 1973

August 10, 1973

August 12, 1973

Sample
Accepts
Dust
Accepts
Dust
Accepts
Dust
Calculated composition, percent dry weight
CaO
61.9
58.3
60.4
61.4
61.1
64.6
MgO
4.3
6.9
4.5
8.2
4.0
5.7
CaCO3
7.4
13.5
7.4
10.1
3.5
5.8
Ca3(P04)2
7.0
10.1
7.2
10.2
7.1
9.7
Fe203
1.6
1.4
1.5
1.4
1.7
1.6
Si02
11.1
1.2
10.7
0.6
15.5
3.0
Other
0.9
0.3
2.3
1.6
1.1
1.3
  Table 8-6.   COMPONENT RECOVERIES IN CLASSIFICATION TESTS
              DURING ATTF TEST WORK
Date
(1973)
July 27
July 31
Aug. 6
Aug. 12
Aug. 14
Aug. 16
Aug. 18
Aug. 20
Aug. 22
Aug. 24
Aug. 26
Aug. 28
Aug. 30
Mass
average
Sept. 20-1
Sept. 20-2
Sept. 20-3
Mass
c
average
Classifier load
kg/hr Ib/hr
—
—
729 1,607
670 1,477
592 1,305
562 1,240
718 1,583
622 1,382
702 1,548
730 1,609
848 1,870
776 1,710
789 1,740
703b l,551b
227 500
227 500
454 1,000
303 667
Recovery to accepts and dust of stated constituent, percent
CaO
99.2
99.2
93.8
95.5
98.5
96.3
97.6
94.8
97.5
97.6
98.2
98.8
96.7
97.3
98.2
97.6
98.5
98.1
Si02
84.6
80.6
88.6
92.2
95.1
93.9
92.7
89.4
94.8
92.0
92.6
94.7
90.3
91.8
79.0
67.6
78.8
76.1
MgO
98.2
98.1
93.1
95.3
98.6
95.4
95.8
93.4
98.2
97.1
97.9
98.8
95.7
96.8
95.5
96.1
97.3
96.6
CaCOg
98.2
99.0
93.1
95.8
97. 8
95.5
96.1
96.5
96.3
97.5
97.1
93.8
98.4
97.7
97.9
98.5
98.6
98.4
Ca3(P04)2
98.0
97.8
93.1
95.0
98.2
96.0
97.1
94.0
97.2
97.0
97. 3
98.1
95.7
96.6
94.6
95.2
96.6
95.7
Fe203
91.4
92.2
92.0
94.3
97.1
94.7
94.9
92.3
96.1
95.4
95.8
96.7
93.6
94. 5
88. 0
84.1
84. 7
86.4
Other
96.8
96.3
85.7
94.8
97.4
94.9
94.3
98.3
81.0
75.9
100.0
100.0
99.1
95.4
84.2
93.3
97.3
92.9
Total
recovery,
percent
98.1
97.8
93.0
94.9
97.9
95.5
96.8
94.1
97.1
96.4
97.0
98.0
95.1
96.5
94.5
93.8
96.0
94.4
 July 27 to Aug. 30
bExcluding July 27 and 31
cSept. 20 only
                                155

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on a steady set basis.  Furnace product, that had been stored in the thermal disc
cooler (see Case History) and a water jacket conveyor, was loaded into the classi-
fier on an intermittent basis.  This resulted in surges in operation which adversely
affected process efficiency.  Constant rate operation on September 20,  1974 pro-
duced performance consistent with Envirotech's previous experience.

Even under the best conditions, the rejection of silica and iron is not high as
compared to the rejections obtained for most constituents in wet classification.
Nonetheless, silica is not classified well in the wet classification process;  there-
fore, dry classification provides a means to blow down additional amounts of a
difficult to reject constituent.  As will be shown in Section X,  dry  classification
is a more efficient means of blowing down silica than direct wasting of  the furnace
product.

Handling  of Lime from the FBR

As described earlier, lime recovered in a pellet bed reactor is discharged from
it in pelletized form. Recalcination of water softening sludges and pulp and
paper mill sludge shows that the product obtained in these  applications is  a
dense, dust free lime pellet which can be handled without difficulty in  mechani-
cal or pneumatic conveyors (see Section V) .  A typical size distribution for this
material is given in Table 8-7.30
        Table 8-7.  TYPICAL SIZE DISTRIBUTION FOR PELLETS FROM A
                   FLUIDIZED BED CALCINER
Accumulative weight
retained, percent
1.5
13.5
24.6
50.1
81.5
19. 5a
U.S. Sieve
series
6
8
10
14
20
< 20
 Weight with particle size smaller than 20 mesh


A distinctive feature of the sand bed FBR used in wastewater sludge applications
(see Fig . 8-6)  is the handling of reclaimed lime in  slurry form.  The problems
associated with lime slurry handling were described in Section VI under Lime
Addition.  The National Lime Association lists several corrective measures to
minimize scaling problems.31  Engineers considering a sand bed FBR to  recover
lime from wastewater sludges should give careful attention to these  types of
problems and provisions  to either correct or alleviate them should be incorporated
into the design.
                                     156

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Handling of Lime from  the RKC

As shown in Fig. 8-7, reclaimed lime discharged from a RKC (rotary kiln calciner)
is transported to storage via mechanical conveyors.  Since the nodulized pro-
duct from a kiln occasionally includes large lumps, up to 15-20 cm (6-8 inch) in
size,32 the recalcined lime is normally screened so only 1.9-2.5 cm (3/4 - 1 inch)
particles are discharged to the screw conveyor.  In the lime reclamation plant at
Miami, Florida,  lumps retained in the screen are put through a crusher and then
fed to the same screw conveyor.32  Reclaimed lime, discharged at approximately
316 C (600 F) from the RKC, is not usually cooled prior to storage; mechanical
conveyors must therefore be designed to handle the hot product.

RELATED PROCESSES

Incineration is not the ultimate means to dispose of wastewater sludges. All com-
bustion processes yield two end products:  a solid residue or ash and a gaseous
product, usually called exhaust or off-gases.  Both have important effects on the
environment and must therefore be subjected to further treatment before final
disposal. Furthermore, off-gases are a source of heat that can be recovered.
Methods used to handle  ash are covered in detail in Section XI.  Handling of
exhaust gases is described in  the following paragraphs.   A third environmental
concern, noise, is often associated with incineration systems.   Since noise and
its  control in areas where operators  are present is receiving increasing attention
by  federal and state authorities, methods to reduce noise levels around incinera-
tion installations will also be briefly reviewed.

Off Gases Scrubbing

It has been stated^S that uncontrolled gases emitted from the MHF and the sand
bed FBR contain approximately 0.9 and 8.0 grains per dry standard cubic foot
 (gr/dscf) of particulate matter respectively. Since the air quality standards
 (see Section IX) limit particulate  emissions to the atmosphere to 0.03 gr/dscf
maximum, high efficiency scrubbers are required to reduce incinerator emissions
to acceptable levels.

Particle collection equipment has  been classified34 as follows:

     "1. High-efficiency, high-cost collectors:
        a.   Electrostatic precipitators.
        b.   Sonic agglomerators.

     2. High-efficiency, moderate-cost collectors:
        a.   Fabric or fibrous filters .
        b.   Wet collectors , packed towers , scrubbers, and centrifugals .

     3. Low-cost, lower efficiency designs:
        a.   Cyclones and  dry centrifugals.
        b.   Dry dynamic.
        c.   Inertial."
                                      157

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To control the emission of participate matter, multiple hearth furnaces are
usually equipped with inertial wet scrubbers of the impingement baffle or
Venturi designs. In fluidized bed reactors, due to their operational features
which result in higher emission of particulates, the wet scrubber is often
preceeded by dry cyclones which reduce the dust load of the secondary (wet)
collector.

The MHF used to recalcine lime from wastewater sludge can be expected to have
higher particulate emissions than units burning organic sludges. This is due
not only to the characteristics of the feed material but also to the fact that classi-
fied lime sludge cakes, at 50-60 percent solids concentration, would tend to dry
in the top hearth (feed hearth) where the off-gases are removed from the
furnace. Dried particles could then be carried by the outgoing gases.  In one
testing and two full-scale installations, the dust load from multiple hearth
furnaces recalcining lime has been found to average approximately 30 Ib per
1000 Ib of exhaust gases.  The dust  loading would  sometimes justify the use  of
a cyclonic precleaner ahead of the wet collector. Cyclones are highly efficient
in removing medium and  coarse dust particles.  Particulate matter collected  in
the dry cyclone, containing an appreciable percentage of calcium carbonate, can
be returned to one of the  furnace's burning hearths for recalcination. To
minimize carry over of small  lime particles (passing a 200 mesh) , the gas
velocity inside  a MHF should  be maintained below 10 fps. 14

Fig.  8-11 shows the arrangement of the scrubbing  equipment for the lime recal-
cination furnaces at the CCCSD water reclamation plant. The wet scrubber is a
three stage venturi-spray unit designed for low head loss  operation.  Besides
removing particulate matter,  wet scrubbers also cool the off-gases to avoid the
formation of a steam plume.  A temperature of approximately 43 C (110 F) is
required to suppress a stack  plume. 12

A more detailed review of gas cleaning techniques is beyond the scope of this
report. The  reader is referred to a series of reports published by the American
Petroleum Institute on the Removal of Particulate Matter from Gaseous Wastes for
a comprehensive coverage of this subject.  (Reference 34 is  part of this series) .
Selection of scrubbing equipment should be made in consultation with the manu-
facturers of incineration  systems or even left entirely to them if a performance
specification, warranting compliance with the applicable air pollution standards,
is used to select the incineration equipment.

Waste Heat Recovery

Incineration of wastewater sludges requires that sufficient heat be generated:
1) to evaporate the remaining moisture from dewatered cakes, and 2) to ignite
and burn the dried  sludge. Furthermore, when lime is to be recovered,  addi-
tional heat is required to  convert calcium carbonate in the sludge to calcium
oxide.  Heat is  derived from combustion of volatile matter in the sludge and
from auxiliary fuel supplied through the incinerator burners. Heat generated
by combustion leaves the incinerator in the exhaust gases, in the hot ash
product, and, in the case of the MHF, in the air used to cool the central shaft.
                                    158

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                    /50 PS/6 STEAM
                                                           TO ATMOSPHERE
TO ATMOSPHERE
SCRUBBER
STACK
^
ffrr
1
SHAFT COOLING
k
:^- WASTE HE
RECOVERY Bl
BOILER FEED
AIR BYPASS
*~\
AFTER 1
BURNER-^ f
? \ ^
	 L CIIO*
Ji^
Kt
t A r* c
                                                                  CYCLONIC
                                                                    DRY  I
                                                                  SCRUBBER
             WET
           SCRUBBER
                                                CENTRI-
                                                FUGED
                                               SLUDGE
                                                FEED
+-SHAFT
COOL ING
AIR RETURN
INDUCED DRAFT
FAN
                AUXILIARY
                AIR SUPPLY
                DUCT
  DUST RETURN
   SCREW
   CONVEYOR
   THICKENED SCUM  FEED
                              	I	J-
                                                       . FUEL OIL  TO BURNER
                              _	|	-2-
                                                           N AT URAL GAS TO
                                                                     BURNER
   AUXILIARY SHAFT
   COOLING AIR  FAN
                                                          SLUDGE GAS TO
                                                          FURNACE
                                              SHAFT
                                              COOLING
                                              AIR FAN
                                                                   FLAME TRAP
                            ASH
                           TO GRINDER
     COMBUSTION
     AIR FAN
                                        CENTER  SHAFT DRIVE
 Figure 8-11  Auxiliary equipment for a MHF at the CCCSD water reclamation
              plant
                                     159

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The heat loss in the hot ash product cannot be recovered economically but is
normally a small fraction of the total heat generated.  Heat losses by radiation
to the surroundings are minimized by the use of thermal insulation. The other
two ways in which heat may leave the incinerator,  and heat recovery methods
applicable to them, are discussed below.

In multiple hearth furnaces, the heat contained in the warmed shaft cooling air,
at a temperature of 149-260 C  (300-500 F) , would normally be recovered by using
it as part of the combustion air, thus reducing fuel requirements.  As mentioned
earlier, in the pellet bed calciner (see Fig. 8-4) , the reactor off-gases are used
to dry the lime sludge before it is fed to the FBR, thereby practically eliminating
the need for auxiliary fuel to evaporate water in the reactor. In the sand bed
units (see Fig.  8-6) , the drying step has been eliminated so no heat recovery
step is inherent.

Apart from the heat recovery features included in multiple hearth and fluidized
bed incineration systems, heat can be recovered from  incinerator off-gases by
using them to generate steam in a waste heat boiler. A waste heat boiler is
essentially a heat exchanger in which heat is extracted from hot gases and
transferred to water to generate steam.  A water-tube  type  (water inside the
boiler tubes, hot gases outside the tubes) is generally to be preferred over a
fire-tube type boiler (gas inside, the tubes, water outside) .36  A basic water-
tube boiler would consist of two steel boiler drums  placed one above the other,
with a multiplicity of small diameter boiler tubes connecting the two drums.
Drums and tubes are enclosed in a refractory lined housing having an inlet and
an outlet for the gases from which heat is being reclaimed.  The heat recovered
with a typical waste heat boiler  is approximately 75 percent of that contained in
the hot gases at a reference temperature of 15.6 C (60  F) .  This value is an
assumed average ambient temperature which is customarily used in combustion
calculations. Heat losses to the surroundings from the casing would be about
two percent of the heat transferred from hot gases to steam.

For the CCCSD water reclamation plant, each multiple hearth furnace has been
provided with a  waste heat boiler.  Each boiler is capable of generating 15,870
kg/hr (35,000 Ib/hr) of steam at a pressure of 10.5 kg/sq  cm (150 psig) and a
temperature of 185 C (365 F) .37  Heat is obtained from 52,200 kg/hr (115,000
Ib/hr) of exhaust gases leaving the furnace at 760 C (1400 F) .  In passing
through the boiler and generating steam, the gases are cooled to approximately
232 C (450 F) .  The high pressure steam produced is used to power turbine-
driven aeration blowers and boiler feed water pumps and to  supply heat to the
plant's air conditioning  and heating systems.

In Fig. 8-11, a waste heat recovery boiler in  a typical MHF at the  CCCSD plant
has been shown.  Worth noticing is the location of the  dry cyclone precleaner
provided ahead of the wet scrubber,  which also reduces the load of fly ash
going to the boiler.  In  the design of the boiler, particular attention should be
given to  the dust load and the size of the particles entering the boiler.
                                    160

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Heat recovery can be expressed as a percentage of the heat input to the incinerator
by making a complete heat balance for the incinerator and the waste heat boiler.
To make this balance the following parameters must be known:  feed rate and com-
position of the sludge; heat of combustion of the sludge volatile solids;  amount of
excess air and furnace temperature required for complete combustion; and physical
dimensions and thermal characteristics of the incinerator.  In addition to the
parameters just listed, the properties and heating value of the fuel must also be
known. The heating value of fuels is expressed in two ways,  (1) as the high
heat value (HHV) also known as "gross" heat value and (2) as the low heat value
(LHV) , also called the "net" heat value. The essential difference between the
HHV and the LHV is the heat of condensation  of water equivalent to the hydrogen
contained in the fuel.  Because the water formed in combustion  always leaves the
furnace as water vapor (uncondensed) , the heat of condensation of the water is
unavailable for  use.  Therefore, in combustion calculations, the LHV is the one
normally used.

The heating value of gaseous fuels is usually expressed as the HHV of 0.028  cu m
(one cubic foot) of the gas measured at 15.6 C (60 F)  and a pressure of 76 cm
(30 inches) of mercury.  Thus, a  stated heating value of 9,450 kcal/cu m
(1,050 Btu/cu ft) for natural gas normally means the HHV for the conditions
stated. The LHV for such a gas would be about 8,550 kcal/cu m (950 Btu/cu
ft) , the exact difference between the HHV and the LHV depending upon the gas
composition.  For liquid and solid fuels, the  heating values are normally
expressed in kcal/kg (Btu/lb) .  Approximate heat values for common petroleum
fuel oils are given  in Table 8-8.
                Table 8-8.  TYPICAL HEAT VALUES OF FUEL OILS

Type

No. 6 - Heavy
No. 6 - Light
No. 2 (Diesel)
Weight

kg/cu m
17.85
16.67
14.72

Ib/gal
8.34
7.79
6.88
Heat values, kcal/kg (Btu/lb)

HHV
10,290(19,540)
10,560(19,020)
10,960(19,750)

LHV
9,730(17,540)
9,950(17,930)
10,270(18,510)
Noise Control

Noise can be defined as undesired sound.  The intensity of sound is usually
measured in decibels (dBA) , a term that expresses the relative magnitude of a
particular sound when compared to a reference sound  pressure level. One
decibel is equal to a force of 0.002 dyne per square centimeter.  It is important
to keep in mind that decibels are measured not on an arithmetic but on  a loga-
                                     161

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rithmic scale.  Thus a reduction of 3 dBA is almost a 50 percent reduction of
noise energy.  Typical sound levels are given in Table 8-9. ^

                  Table 8-9.   TYPICAL SOUND LEVELS
Class
Very faint
(threshold of audibility)
Faint
Moderate
Loud
Very loud
Deafening
Threshold of feeling
Found in
Sound proof room
Whisper
Quiet conversation
Private office
Average conversation
Average office
Average factory
Average street noise
Noisy office
Noisy factory
Unmuffled truck
Loud street
Boiler factory
Nearby riveter

Sound level,
dBA
10
20
30
40
50
50
60
70
80
90
90
100
100
110
120
 The Occupational Safety and Health Act of 1970 (OSHA) considers noise above
 certain established levels as occupational hazards, i.e., possible loss of
 hearing, and has established limits of exposure for workers subjected to noisy
 environments.  Table 8-10 shows permissible noise exposure set forth by OSHA
 Federal and state industrial safety orders have also limited the degree of noise
 exposure that employees may endure without ear protection devices.

 Due to the auxiliary equipment normally associated with sludge incineration
 systems, a large number of noise sources are located near incinerators.  Gen-
 erally speaking, the sound produced by a machine is directly related to the
 horsepower input to it.  Also, high speed machines are noisier than low speed
 units. As an example, Table 8-11 gives estimated  sound pressure levels for
 one of the multiple hearth furnaces at the CCCSD water reclamation  plant.38
 The values given are for the equipment operated alone without background
 noise.  As seen in Table 8-11,  the noise level is  controlled by fan and blower
 noise. Since several pieces of equipment operate  simultaneously, the overall
 sound pressure level will be higher than  shown in the table.   For example, if
 the maximum noise level allowed in the incineration area is set at 95 dBA, the
 noise produced by the shaft cooling fan has to be lowered to meet the combined
 noise level.
                                   162

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    Table 8-10.  PERMISSIBLE NOISE EXPOSURES
Sound Level,
dBA
Duration per
day, hours
       90
       92
       95
       97
      100
      102
      105
      110
      115
    6
    4
    3
    2
    1
   1/2
1/4 or less
Table 8-11. SOUND PRESSURE LEVEL OF MHF EQUIPMENT

Furnace
Center shaft drive
Center shaft cooling air fan
Combustion air fan
Induced draft fan
Lump breaker (intermittent)
Lump breaker (continuous)
Ash cooler
Screw conveyor
Pneumatic conveyor air lock valve
Pneumatic conveyor air blower
Air classification system
Feed bin vibrator (full bin)
Feed bin vibrator (empty bin)
Rotary feeder
Air classifier
Air filter (intermittent)
Pneumatic conveyor air blower
Ash bin discharge screw conveyor
Motor
HP

15
20
40
50
1 1/2

10
2
1/2
10



1/2
25

15
3
dBA @ 3 ft
distance

70
95
85
85
90
80
65
60
50
90

30
70
50
86
90
90
60
                         163

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Several techniques can be applied to control noise.  The level of sound generation
of the source can be reduced.  Examples of this approach are the installation of
acoustic enclosures around the entire fan or blower assembly,  the addition of
inlet and discharge silencers, and the use of low noise electric motors.  Equipment
enclosures have resulted in average reductions of 4 dBA.39  intake silencers can
reduce inlet noise levels by 10-15 dBA,38,40 while discharge mufflers have
resulted in an additional  reduction of 6 dBA.39  Reductions of 4 dBA in the sound
pressure level have been reported for blowers enclosed in acoustic shields. 39
When the incineration equipment is housed in a building,  further reduction  can
be obtained by adding absorbing material to the walls to reduce the reverberant
sound level.  Dobbs40 has reported that a noise reduction of approximately  8-10
dBA could be accomplished with the use of 3-inch thick glass fiber boards for
acoustical absorption.

Vibration isolation is another method of noise control.  Large fans  and blowers
should be mounted on a heavy inertia base and attached to it  with vibration isola-
tors of the combined spring and rubber type.40  Since piping can transmit the
sound generated by machinery, the junction between equipment and ducts should
be through a flexible connector.  The flexible connectors  should have sufficient
mass to be at least equal to that of the duct walls.40 Lead loaded vinyl or rubber
are thus better insulators than the canvas fabric found in standard connectors.

SUMMARY OF LIME RECOVERY CASE HISTORIES

Several wastewater treatment plants have practiced lime recovery  either on  an
experimental or full-scale basis. Information is available from two tertiary
treatment plants (South Tahoe and Piscataway) and two plants practicing
primary lime addition (Blue Plains and Central Contra Costa) .   A  brief descrip-
tion of the lime recovery operations in each of these four plants is  given below.

South Tahoe  Water Reclamation Plant

The water reclamation experiences  at the South Tahoe plant have been extensively
documented and  reported. Reference 2 of this section is a report covering three
years operation of the 7.5 mgd advanced wastewater treatment plant.  The
summary that follows highlights the thickening, dewatering and recalcination
processes only .41

At South Tahoe,  secondary effluent from the activated sludge process is treated
with lime, clarified, passed through an air  scrubber to remove ammonia, recar-
bonated, and finally treated by filtration and carbon adsorption. Sludges from
the  lime clarifier and recarbonation basin are first gravity thickened and then
dewatered in  a solid bowl centrifuge.  The sludge cake is calcined and recycled
for  reuse along with makeup lime in the lime clarifier.  A second centrifuge
dewaters the  centrate from the first unit and its cake is conveyed to an organic
sludge MHF.  The first centrifuge is a concurrent type one and is  operated in a
wet classification mode (see Section VII) . The centrate is sent  to the second
centrifuge of the same type where the remaining solids are removed.  The
centrifuges can be  operated at 2200,  1800, or 1600 rpm.  Initial tests were
                                     164

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                                                                         2
carried out on the lime mud feed stream to determine optimum operating speed.
Data showed approximately the same percent solids in the cake and the same
recovery of solids at all three speeds.  The lowest speed was selected to reduce
wear and maintenance.

At South Tahoe it has been found that the percent capture or recovery of lime
into the first stage cake decreases linearly with increasing feed rate of lime
sludge. At approximately 8 percent solids in the feed, 93 percent capture was
achieved at a feed rate of 10 gpm. When the feed rate  was increased to 20 gpm,
solids capture dropped to 79 percent.41

The  South Tahoe report^ states that at a flow of 7.5 mgd through the water recla-
mation plant, the total blowdown of waste solids from the lime clarification opera-
tion  would  be about 17 tons per day of lime mud  (dry CaO basis) if there were
no lime recovery.  With lime recovery, this quantity is reduced to about 1.5 tons
per day. The cost of recalcined lime at Tahoe ($31.61/ton CaO) is  slightly
higher than that of make up lime. This figure however, does not take into
account the savings in sludge disposal realized through reduction of the solids
volume achieved by incineration and the on-site production of CC>2  for recar-
bonation.

The  centrifuged cake is fed by a belt conveyor to a 4.1 m (14.3  ft)  diameter, six
hearth MHF.  The recalcined lime is discharged by gravity through a crusher
to a  thermal disc cooler where lime  temperatures are lowered from  371 C to
38-66 C (700 F to 100-150 F) . Cooled lime drops into a rotary air lock and is
pneumatically conveyed to a 35 ton capacity recalcined lime storage bin for
reuse. Stack gases are scrubbed in a multiple tray scrubber before being
exhausted to the atmosphere. A portion of the gases are recycled to the recar-
bonation system. Solids are continuously wasted to prevent a buildup of inerts
in the recycled product.

Since 1968  the South Tahoe plant has successfully recalcined lime sludge from the
lime chemical treatment process. Over this period makeup lime has accounted
for only 28 percent of the  calcium oxide used.  Monthly CaO values in the
recalcined  lime have averaged 66.0 percent over the entire period.2  A  reduc-
tion of approximately 40 percent in fuel requirements  was achieved when
centrifugal classification was used rather than whole sludge recovery. 2

The  influence on lime activity of recalcined temperature, rabble arm speed and
feed rate were investigated at South Tahoe.  Of the three parameters, temperature
had  the most effect on recalcined lime activity.  The CaO content in the  recalcined
lime was increased 15 percent by raising the temperatures from 871 to 1038  C
(1600 to 1900 F) .  At nine tons of solids to the MHF per day,  the optimum recal-
cining conditions were 1038 C  (1900 F) on hearths numbers 4 and 5 with a 1.5-
2.0 rpm rabble arm speed.

Fig. 8-12 is a schematic diagram of the lime sludge handling facilities at South
Tahoe.2
                                     165

-------
                        CENTRATE
                        TO PRIMARY
                        CLARIFIER
                        INFLUENT
                        CHANNEL
                                                               SPENT
                                                               LIME
                                                               PUMP-
                              CENTRIFUGE
                              FOR LIME
                              SLUDGE
MAIN
STACK
  INDUCED
  DRAFT
  FAN
    X

BYPASS-
DAMPER
WET	-\  /
SCRUBBERy



        Y
       DRAIN
LIME
RECALCINING
FURNACE	•
                               CENTRIFUGE
                               FOR LI ME OR
                             /SEWAGE
                             'SLUDGE
FURNACE
RABBLE
ARM DRIVE
REVERSIBLE
BELT CONVEYOR -
            BYPASS    \f /
            DEWATERED/Y
            LIME SLUDGE  *
            STORAGE BIN
                       SHAFT COOLING
                       AIR RETURN
                                                          TO
                                                          SEWAGE
                                                          SLUDGE
                                                          FURNACE

                                              LOADING
                               #•
1


1 — 1
J
r
^



i
THERMAL
rDISC.
COOLER

^ /ROIARY
'Am LUOK .








* i
fa<
s
_l
Q
Ul
2
y
<
o
\ LU /




±

/BIN\






                                                   Q.

                                                   LL)
                                                               FROM
                                                               CHEMICAL
                                                               CLARIFIER
                                                               SLUDGE
                                                               PUMP
                                                              FROM LIME
                                                              DELIVERY
                                                              TRUCK
                                                              PNEUMATtC \
                                                              UNLOADING
                                                              AND
                                                              CONVEYING EQUIP
                                                        -TYP LIME FEEDER

                                                        -TYR LIME SLAKER
    COMBUSTION
    AIR BLOWER
            SHAFT
            COOLING
            AIR BLOWER

               RECALCINED
               LIME BLOWER
             RECALCINED
             LIME TO
             SPLITTER
             BOX
FRESH
LIME TO
SPLITTER
BOX
  Figure 8-12 Lime recovery at the South Tahoe water reclamation plant
                                    166

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Piscataway Advanced Wastewater Treatment Plant

The EPA is supervising the operation of a 0.22 cu m/sec  (5 mgd) tertiary facility
at Piscataway, Maryland.  The system employs two-stage lime treatment, effluent
filtration and activated carbon adsorption  (Fig. 8-13) .  A single sludge  dewater-
ing stage (centrifugation)  is employed.  Because the centrifuge is  operated at
high recovery, the inerts  are retained in the recalcined lime.42

The recalcined product has an available lime index of 60 percent.  The calcium
oxide content might even be lower if it were not for the fact that the secondary
effluent is low  in  phosphorus concentration  (3.1 mg/1  as P) .  During a  36-day
operating period when 26 percent of the furnace produce was blown down,  68
percent of the total dose of 271 mg/1 CaO was recalcined lime.  The  resulting pH
for this operation was 11.45.  Secondary effluent alkalinity is approximately
100 mg/1 as CaCO3.42

Blue Plains  Advanced Wastewater Treatment Plant

A two and one-half month  test of lime recovery from combined sludges has been
conducted at the EPA-DC Blue Plains Pilot Plant.43  The system consisted of an
Independent Physical Chemical treatment (IPC) pilot plant with two stage lime
precipitation,  dual media filtration and granular carbon adsorbtion treating
District of Columbia raw wastewater at 189,000 Ipd (50,000 gpd) . The first stage
of clarification with lime addition was operated at approximately pH 11.5 while
the second stage with CC^ recarbonation was operated  at pH 10.0-20.5 with an
Fe+++ dosage of 5 mg/1 as  added flocculant.  Solids from the clarification system
were gravity thickened to 9-13 percent solids and classified in a Sharpies model
P600, 6-in.  diameter solid bowl centrifuge to separate carbonate and noncar-
bonate solids.  The centrifuge cake at 51 percent solids was calcined in  a multiple
hearth furnace, mixed with make-up lime and recycled to the clarification system.
The centrate was wasted from the lime recycle system and dewatered by alternate
centrifugation, vacuum filtration and pressure filtration systems.

The classification centrifuge operated at approximately 74 percent solids recovery.
At this solids recovery the constituent recovery of CaCO3 averaged 93.0 percent
while that of Ca3 (PO4) 2,  Mg(OH)2 and volatile solids averaged 37.3, 46.0 and
41.3 percent, respectively.  The classification centrifuge prevented a buildup of
inert materials  in the recalcined product;  during the test period, the fraction of
calcium oxide hovered between 70 and 80 percent.  During  the test period, the
fraction of reclaimed lime  of the total dose was 72.5 percent.

Comparing the use of virgin lime or recalcined lime, effluent qualities of the
IPC system  were  equivalent  during periods when  the plant was  run under
computer control.  The  comprehensive investigations of the Blue Plains investi-
gators in the area  of dewatering second stage centrate has been summarized in
Section VII.

Central Contra Costa Sanitary District Water Reclamation Plant

In connection with the design of the CCCSD's Water Reclamation Plant, test work
has been conducted at its Advanced Treatment Test Facility on the  reclamation
                                     167

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 SECONDARY EFFLUENT
      FIRST STAGE
    LIME TREATMENT
RECARBONATION
 SECOND STAGE
LIME TREATMENT
      THICKENING
           I
                      FILTER  INLET
                          WELL
    CENTRIFUGATION
           I
                                                 F ILTRATION
    RECALCINAT ION
VIRGIN LIME
                                              NEUTRAL IZATION
       TO  PROCESS
                          REGENERATION
                   MAKE-UP
                   CARBON
                         CARBON
                      ADSORPT ION
                            1
                                                  TO POND
                              RETURN
         Figure 8-13 Piscataway tertiary treatment plant
                               168

-------
and reuse of lime from lime sludges. ^  The test involved the setup of the follow-
ing experimental components of the system:  (1) centrifuge (Sharpies P3000) for,
wet classification, (2) a screw conveyor positioned for loading a truck bed,
(3) a truck unloading hopper at the site of a nearby municipal MHF,  (4) a tem-
porary belt conveying system for loading the MHF,  (5) a thermal disc cooler and
water jacketed screw conveyor for cooling and conveying the furnace product,
(6) an air classification system for the purpose of separating silica from the
furnace product, (7) a hopper for storage of recalcined lime and (8) a slaker for
reclaimed lime hydration.

The experimental procedure involved wet classification by centrifuge of all of the
sludge produced at the ATTF in the chemical primary.  The centrifuge cake was
trucked twice daily to another treatment plant  (the City of Concord's plant) where
an existing MHF was available.  The cake was  unloaded from the trucks into a
receiving hopper, and sludge was conveyed from  the hopper to the furnace at a
uniform rate by  a temporary belt conveyor.  Centrifuge cake was recalcined in
the MHF, and then the furnace product was cooled and fed to a dry classification
system.  In the classification system the furnace product was separated into
three fractions—an accepts fraction, a coarse rejects fraction and a fine dust
fraction.  Each fraction was stored in 55 gallon drums, labeled and weighed.
The accepts and fine dust drums were then trucked  back to the CCCSD's ATTF
where the drums were  unloaded into an accepts hopper.  From the accepts
hopper lime was fed via a rotary valve to the slaker, and the slaked  lime was
then directed back to the chemical clarifier.

Actual recycling of lime was carried out from July 17, 1973 to August 30,  1973, a
period of 5 weeks. Only a portion of this period can be considered representative
of design conditions.  The late July period was characterized by erratic furnace
production caused by filling the space between the rabble arms and the hearth
bottom ("bedding down") , and certain  operational difficulties with the centri-
fuge and the furnace which affected furnace production adversely.  After
August 10, 1973, the centrifuge performance deteriorated markedly due to
centrifuge wear. The rented centrifuge did not have hardened surfaces and
therefore the scroll suffered considerable wear.  The end result was that  after
August 10, calcium carbonate recovery decreased significantly.  Therefore,
the period of August 1 to 10 best represents design conditions.  During this
period, 7,110 kg (15,660 Ib) of new lime  (Ca(OH)2) was used, while 10,199 kg
(22,465 Ib) of reclaimed lime was returned to the  process.  Thus, 17,309  kg
(38,125 Ib) of total lime was used,  resulting in a dose of 332 mg/1 of calcium
hydroxide since the total flow for the 10-day period was 52,235 cu m (13.8 mil
gal) .  This dose corresponded with an operational pH of 11.0.

One artifact was imposed on the experiment that will not be presented in the
CCCSD design.  The Concord MHF had only wet scrubbing of the stack gasses,
whereas the CCCSD design incorporates a dry  cyclone prior to the wet
scrubber.  The solids captured in the cyclone  are returned to the MHF for
recalcination and reuse in the process. During the  tests at Concord, approxi-
mately 21 percent of the calcium carbonate fed  to the furnace were exhausted
with the stack gases.  Analysis of the particle  size of this material indicates
                                     169

-------
that 59 percent of this material will be captured in a cyclone of CCCSD design.
Assuming that a dry cyclone could have been installed during the Concord tests,
a total of 12,165 kg (26,823 Ib) of lime could have been returned to the process.
Under this condition, a total of 70.4 percent of the total dose would derive from
reclaimed lime. This value is in excellent agreement with the predicted recycle
level of 69 percent.7-44 Calcium oxide content of the reclaimed lime during the
10-day period averaged 64 percent;  the predicted content was 63 percent.' The
lime slaked readily and  the average temperature rise in the AWWA slaking rate
test was 36.2 C (range 33.7 to 39.5 C) .  The temperature rise is lower than the
40 C minimum stipulated for new lime in the AWWA test;  however, this merely
indicates that the reclaimed lime has a lower CaO content than new lime.

Chemical primary treatment performance during  the lime recycling period was
superior to a period preceding the lime recycling (Table 8-12) .  Organic re-
movals improved, as indicated by the BOD5, SS, TOC and soluble organic
carbon measurements.  Phosphorus  removal markedly improved, and this
eliminated the need for supplemental coagulant addition that had previously been
necessary for obtaining high phosphorus removals at pH 11.0 or less (see
Tables 6-4 and 6-5)  .  The data in Table 8-12 also indicates that the calcium
reaction was  more complete during lime recycling than prior to  it.
   Table 8-12.  COMPARISON OF PRIMARY SEDIMENTATION PERFORMANCE
               WITH AND WITHOUT LIME RECYCLE


Constituent
(mean value)

BOD
SS
TOC
Soluble organic carbon (SOC)
Total phosphorus as P
Orthophosphate as P
Calcium hardness
d
Magnesium hardness
Hardness increase
With lime recycle
pH 11.0 operation
Ca(OH) -335 mg/1
Raw
sewage,
mg/1
177
230
145
27
10.9
10.4
101

106

Chemical
primary,
mg/1
50
25
34
23
0.60
0.40
127

23
45
Percent
removed
72
89
77
14
95
96



+28
Without lime recycle
pH 11.0 operation0
Ca(OH) -332 mg/1
z
Raw
sewage ,
mg/1
207
205
126
24
11.0
10.4
67

100

Chemical
primary,
mg/1
75
38
44
29
1.45
1.04
144

25
+2
Percent
removed
64
81
65
-19
87
90
_


-1
   July 27 to August 30, 1973, at an average flow of 5,300 cu m/day (1 .40 mgd)

   July 1 to July 25, 1973, at an average flow of 5 ,030 cu m/day (1.33 mgd)
   No ferric chloride addition

   As CaCCX
                                    170

-------
WASTE SLUDGE INCINERATION

As stated in Section VII, when wet classification is employed to separate the
calcium carbonate portion from the other constituents of the lime sludge, one
method to  dispose of the waste solids in the centrifuge centrate is to thicken and
dewater it prior to incineration (Fig.  7-9) .   Incineration of first-stage centrate
cake is similar to incineration of municipal sludge (the purpose is obviously the
same, i.e.,  the destruction of volatile matter to produce an inert ash residue for
final disposal) .  The calorific value of the dewatered centrate cake has been
estimated  at 5,000 to 5,550 kg-cal per kg of volatile solids (9,000 to 10,000 Btu/lb
VS) ,37 which is close to that of biological sludges. ^  Wet classification does  not
normally achieve. 100 percent capture of calcium carbonate (Section VII); there-
fore the centrate from the  first stage centrifuge will contain some CaCOs as well
as other inorganic chemicals  such  as magnesium, phosphorus  and iron com-
pounds.  Since these compounds are inert, their presence tends to reduce the
thermal value of the centrate cake. Moreover, the endothermic decomposition  of
CaCC>3 to CaO further increases the thermal load on the incinerator.  A similar
situation occurs when conditioning chemicals are added to organic sludges to
improve their dewatering  characteristics .

As it was  shown in Figs. 7-6 and 7-7 and in Table 7-10, the moisture content of
the dewatered cake, i.e., the weight of water which must be evaporated prior to
combustion, has a decisive influence on both performance and economics of
waste sludge incineration. Centrifuge centrate, as biological sludges, is also
difficult to dewater. This is  indicated in Table 7-11,  which shows solids con-
centrations ranging from only 17 percent TS for centrifugal (second stage)
dewatering to 25 percent TS for a filter press operated at  100 psi.

Due to the similarities between centrate from centrifugal classification and bio-
logical sludges, it can be  assumed that the same incineration  systems can be
applied to burn both types of dewatered sludges.  Sludge incineration practices
have been reviewed in Reference 4.  Rotary kilns, which  are not covered in
that report, cannot be used to incinerate municipal sludges due to the relatively
high moisture content of the sludge cake.

The presence of lime in the incinerator off-gases might prove troublesome,
particularly in fluidized bed  reactors. Since the normal operating temperature
of the reactor is 760-816 C (1400-1500 F) , some of the CaCC>3 particles carried
with the exhaust gases will be converted to the oxide form. In the sand bed
FBR,  which is normally used for sludge incineration, exhaust gases  are
scrubbed  in a wet scrubber  before being discharged to the atmosphere.  It is
possible for the CaO to slake in the scrubber thereby causing scaling deposits
in this unit  (see Section V) .

ENERGY CONSIDERATIONS

The Energy Crisis has affected practically every field of activity in the U.S. and
in wastewater treatment, its impact has been acutely felt in plants where solids
disposal by  incineration is practiced. In some instances,  the scarcity of fuels
                                     171

-------
has forced the shut down of sludge incinerators and alternate means of sludge
disposal had to be found and implemented within a short period of time.  Where
possible, dewatered cake can be trucked to sanitary dumps.  As both the size of
the plant and the distance to the dump increases, the amount of fuel consumed •
in trucking could become an energy consideration on its own and should be
compared with the fuel requirements for incineration.

In lime recovery from wastewater sludges, the energy considerations are
different than for direct sludge incineration.  Since new lime is obtained by
calcining of limestone, its production is also a process of high energy consump-
tion.  Thus, to evaluate properly the merits of recovering lime from wastewater
sludges from an energy standpoint, a comparison in terms of energy requirements
should be made between reclaiming spent lime at the wastewater treatment plant
and producing new lime from limestone. For a true comparison, the energy used
in transporting new lime to  the treatment plant should be added to the energy of
production  to arrive at the overall energy requirements of makeup lime.

Before introducing numerical calculations, it should be pointed out that what
follows is not a typical economic comparison.  No capital, operating or annual
costs are presented in this section, since  no attempt has been made to assign a
dollar value to the processes examined.  Rather, the following paragraphs will
try to bring the practice of lime sludge recalcination into a balanced perspective.
Incineration processes are highly visible and  therefore, an easy target for those
concerned with fuel consumption.  Costs will be presented in Section XII.  To
illustrate the energy comparison, materials and heat balances for both a MHF and
a FBR will be developed based on the design loadings for the CCCSD's water
reclamation plant.37   Since cake moisture plays a decisive role in the economics
of sludge incineration, heat balances have been made at different percentages of
solids in the second stage cake (see Fig. 7-9)  .

Energy  Requirements of  the MHF

The following conditions have been assumed:

    1.   Sludge flow rate and composition, as  shown in the materials balance,
        Table 8-13.

    2.   Excess air for volatiles combustion to be 100 percent of theoretical
        requirement.

    3.   Temperature of exhaust gases, 760 C  (1400 F) , required for after-
        burning.

    4.   Fraction of calcined solids  passing through the dry cyclone and
        entering the wet scrubber, 7 percent of the total calcined solids. The
        remaining portion is discharged from the bottom hearth.

The materials balance, Table 8-13, requires an explanation of the  chemical re-
actions assumed to take place in the furnace.  The volatile solids were assumed
to be burned completely to carbon dioxide, water, and elemental nitrogen.  The
                                    172

-------
conversion of calcium carbonate to calcium oxide was taken as 90 percent com-
plete.  Magnesium and ferric hydroxides were assumed to be converted completely
to the respective oxides.  The combustion products of the auxiliary fuel  (natural
gas) were assumed to be carbon dioxide and water.
      Table 8-13.  MATERIALS BALANCE FOR MHF IN RECALCINE MODE
Inputs
Water
Sludge solids:
Volatile s
CaCOs
Mg(OH)2
Fe(OH)2
SiO2, etc.

Natural gas ,
J3
Combustion air
Total of Inputs
Outputs
Q
Gases :
H2O
co2
°2
N2

Calcined solids
Q
From bottom hearth
CaO
CaCOa
Others
With off gasesfc
CaO
CaC03
Others

Total of Outputs
kg/hr


596
1,873
66
15
288






4,228
3,053
1,244
2,886



878
175
321

6&
13
24


2,838






2,838
406
16,806
22,888






21,411





1,374



103
22,888
Ib/hr


1,312
4,125
145
34
634






9,313
6,724
2,739
28,384



1,934
384
706

146
29
53


6,250






6,250
894
37,018
50,412






47,160





3,024



228
50,412
     Notes:
     a
      All figures taken at 15.6 C (60 F).
      Includes excess air.
      Taken at 760 C (1400 F).
      93 percent of the total.
      7 percent of the total.
Calculation of the amount of auxiliary fuel required is described in the explana-
tion of Table 8-14,  which shows the heat balance.  Combustion air requirement
was calculated by stoichiometry, using specified excess air of 100 to 10 percent,
respectively, for the volatiles and the auxiliary fuel, together with analyses for
                                      173

-------
the volatiles and the fuel.  Atmospheric moisture in air was taken as 0.0055 Ib of
water per Ib of dry air.   The heat balance shown in Table 8-14 is based on a
customary reference temperature of 15.6 C  (60 F) and all materials entering the
furnace are assumed to enter at that temperature.  The term "sensible heat",
which is used in Table 8-14, means the heat content above 15.6 C  (60 F) in the
process stream named.  The itimized explanations of Table 8-14, given below,
include essential basic data and assumptions used in making the heat and
materials balance calculations.

       Table 8-14. HEAT BALANCE FOR MHF IN RECALCINE MODE
Item
1
2
3
4
5
6

7

8
9
10
11
12

13
14
15
Heat Requirements:
To evaporate moisture in sludge
Heat loss in calcined solids
For heat loss by radiation
For net heat loss in shaft cooling air
Heats of reaction, CaCO3 & Mg(OH)2 decompositions
Sensible heat at 1 ,400 F in gases from incineration
and calcination
Total Heat Requirements
Heat Inputs:
From volatiles, using low heat value (LHV)
From auxiliary fuel (net available at 1,400 F)
Total Heat Inputs
Gross heat input from auxiliary fuel, based on LHV
Sensible heat in auxiliary fuel combustion gases
@ 1,400 F
Sensible heat at 1 ,400 F in evaporated water
Total sensible heat in furnace off -gases
Heat recoverable with waste heat boiler
kcal/hr
2,704,900
214,100
114,700
66,200
759,000
2,171 .100

6,030,000

3,050,500
2,979.500
6,030,000
4,634,400

1,654,900
1,035,600
4,861,600
3,548,900
Btu/hr
10,734,000
849,600
455,000
262,600
3,011,900
8,615.400

23,928,500

12,105,200
11 .823.300
23,928,500
18,390,400

6,567,100
4,109,400
19,291,900
14,083,000
Item 1, is the heat required to convert 2,838 kg  (6,250 Ib) of liquid water at
15.6 C (60 F) into water vapor at 760 C (1,400 F) .  From steam tables this heat
requirement per kg of water is 954.3 kcal (1,717.4 Btu/lb) .

Item 2, the heat loss in the calcined solids,  is for 1,374 kg/hr (3,024 Ib/hr)
leaving the bottom hearth at 649 C (1,200 F) and 103 kg/hr (228 Ib/hr) leaving
the off-gases at 760  C  (1,400 F) .  The average specific heat used was 0 2264
Btu/lb/F.

Item 3 is  an average of the figures supplied  by two manufacturers of the MHF
who provided heat balances for a furnace of the size to be used based on their
experience.

Item 4 is  also an  average of the figures supplied by the same  two MHF manu-
facturers .  A large  amount of air is required to cool the rotating central shaft
and rabble arms  in a MHF, but 85-90 percent of the heat in this warmed air can
be recovered directly  by returning it to the furnace as combustion air.  Item  4
                                    174

-------
is the 10-15 percent of the heat in this air stream which is lost by radiation and
air leakage.

Item  5 is the heat required for the endothermic chemical reactions:

    CaC03	>CaO  + CO2

    Mg (OH) 2	>MgO + H2O (gas)

The heat of reaction for  calcium carbonate decomposition is 436.7 kcal/kg  (786.8
Btu/lb) of CaCC>3;  for magnesium hydroxide conversion to the oxide, 347.9 kcal/
kg (626.8 Btu/lb) of Mg  (OH) 2.  The heat of conversion of ferric hydroxide to
the oxide is negligible because of the small amount present.

Item  6 is the difference in heat content between  15.6 and 760 C (60 and 1,400 F)
for the sum of:   (1) the  gaseous combustion products of the volatile solids,
including  the 100 percent excess air which was specified to insure complete com-
bustion of the volatiles;   (2) the carbon dioxide  evolved in calcium carbonate
decomposition;  and (3)  the water vapor evolved in converting magnesium  and
ferric hydroxides to the respective oxides.

Item  7 is the sum of Items 1 through 6.

Item  8 is the heat generated by combustion  of the volatile  solids based on a low
heat value (LHV) of 5119 kcal/kg (9,223 Btu/lb) .  This was calculated from a
stated high heat value (HHV)  for the volatiles of 5550 kcal/kg  (10,000 Btu/lb)
and the hydrogen content of the volatiles.  Composition of the volatiles was
taken as:

    Carbon 55.8 percent, Hydrogen 8.2 percent, Oxygen 31.0 percent,
    Nitrogen 5.0 percent.

Item  9 is the heat required for the sum of the heat inputs to equal the sum of the
heat requirements .  Numerically, it is equal to  Item 7 minus Item 8.  The fuel
requirement shown in Table 8-13 is obtained by dividing Item 9 by 7,338 kcal/kg
 (13,221 Btu/lb)  which is the calculated net, or  effective,  heating value per
kilogram  (pound) of auxiliary fuel at 1,400 F.

Item  10 shows that the sum of the heat inputs equals the total heat requirements.

Item 11, the gross  heat input from the auxiliary fuel, is obtained by multiplying
the kilograms (pounds)  per hour of auxiliary fuel required, as calculated  from
Item  9, by the LHV for the fuel in kcal/kg (Btu/lb) .  The definition of heating
value of a fuel is the heat evolved per unit weight when the fuel is burned and
the combustion products cooled to 15.6 C (60 F) .  This is exactly equivalent to
assuming  the fuel to be burned and the heat to be evolved at this temperature.
Therefore, in order to obtain the effective heating value of a fuel at a tempera-
ture above 15.6 C  (60 F) , in this case 760 C (1,400 F) , the heat required to
raise the combustion products to the higher temperature must be subtracted
from the published heating value.  Published heating values are given in two
                                     175

-------
ways, as the high heat value  (HHV) , and the low heat value (LHV) .  The essential
difference between HHV and LHV is the heat of condensation at 15.6 C (60 F) of
the water formed by combustion of hydrogen in the fuel.  The LHV has been used
in these combustion calculations because the heat of condensation of water formed
in combustion is unavailable in ordinary combustion processes and excluding it
allows a  clearer presentation  of the heat balance.  In this case, the fuel was
assumed to be natural gas having a LHV of 11,413 kcal/kg (20,564 Btu/lb) and
the following analysis:

    Carbon 73.48 percent, hydrogen 23.20 percent, Oxygen 1.10 percent,
    Nitrogen 2.22 percent.

The calculated net or effective heating value of the gas at 760 C  (1,400 F) , when
burned with a specified 10 percent excess combustion air, is 7338 kcal/kg (13,221
Btu/lb)  of gas. Details of this calculation can  be found in books  dealing with
combustion  stoichiometry.

Item 12 is the difference in heat content, between 760 C (1,400 F) and 15.6 C
 (60 F) of the auxiliary fuel combustion products, including the 10 percent of
excess combustion air assumed to be used with the fuel.  Item 12 is the arithmetic
difference between Item 11 and Item 9.

Item 13 is the difference in heat content between 760 and 15.6 C (1,400 F and
60 F)  of the water vapor evaporated from the sludge.  From steam tables the
difference in heat content of water vapor between these two temperatures is
364.9 kcal/kg  (657.5 Btu/lb)  .

Item 14 is the sum of Items 6,  12,  and 13.  It is the difference in heat content
between 760 and 15.6 C (1,400 F and 60 F)  of all gases leaving the furnace.

Item 15,  the heat potentially recoverable from the furnace off-gases by generating
steam in a waste heat boiler,  is taken as 73 percent of Item 14. In addition to
generating steam,  the waste heat boiler  will have the useful function of cooling
the furnace gases to about 219 C  (425 F) , thereby greatly reducing the cooling
load on  the  wet scrubber.

Table 8-15 is a summary presentation of the heat balance which may be more
readily  understood by readers who are unfamiliar with heat balance calculations.

Discussion  -

From the heat balance in Table 8-14, it can be  seen that of the total heat  gener-
ated in the furnace, approximately 40 percent  is from  combustion of sludge
volatiles and 60 percent from  the auxiliary fuel.  In other words, Item 8  is
approximately 40 percent of the sum of Items 8 and 11. To evaluate the thermal
energy requirement to reburn lime in this way, in comparison with the thermal
energy requirement to produce fresh calcium oxide from limestone in a conven-
tional plant, the heat recoverable in a waste heat boiler should be taken  into
account where a use for steam exists, as in the case of the CCCSD's water
reclamation plant.  To account for the energy requirement to transport calcium
                                     176

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oxide from the producer to the user, the energy requirements of transportation
are as follows4°:

    Rail transport - 98 kcal per ton-km (624 Btu per ton-mile)

    Truck transport - 542 kcal per ton-km (3,462  Btu per ton-mile) .

 Table 8-15  SUMMARY OF  HEAT BALANCES FOR  MHF IN RECALCINE MODE
Gross Heat Inputs
Combustion of volatile solids
From auxiliary fuel
Total of Inputs
Heat Accounted for
To evaporate water at 60 F
Loss by radiation
Loss in shaft cooling air
Chemical reaction heats , CaCC>3 & Mg(OH>2
Heat loss in calcined solids
Heat content above 60 F in off-gases
Total Accounted for
kc«i/V
3,050,500
4,634,400
7,684,900
1,669,300
114,700
66,200
759,000
214,100
4,861,600
7,685,900
Btu/hr
12,105,200
18,390,400
30,495,600
6,624,600
455,000
262,600
3,011,900
849,600
19,291,900
30,495,600
 The materials balance  (Table 8-13)  shows 878 kg  (1934 Ib) of CaO, equivalent
 to 0.967 ton, to be recovered with a gross thermal energy input (Item 11, Table
 8-14) of 4.6 x 106 kcal (18.4 x 106 Btu) .  Heat recoverable with a waste heat
 boiler from the furnace off-gases amounts to 3.5 x 10^ kcal (14.1 x 10^ Btu) .
 The difference between these two heat quantities may be taken as the energy
 requirement to reburn 0.967 ton of CaO, which is equivalent to 1.1 x 10^ kcal
 per ton (4.5 x 106 Btu/ton) of reburned CaO.

 The thermal energy requirement to  produce CaO from  limestone, in modern rotary
 kilns equipped with efficient heat recovery devices, is approximately 1.5 x 106 kcal
 (6 x 10° Btu)  per ton of CaO. 4?-48  -phe rail line distance from a competitive
 supplier's plant to Martinez, California,  where the CCCSD plant is located, is
 approximately 550 miles.  Using .98 kcal per ton-km (624 Btu per ton-mile) for
 rail transport, the energy requirement for transport is approximately 86,000
 kcal (343,000 Btu) per ton of CaO.  Thus, the total thermal energy requirement
 for a ton of fresh CaO delivered  to the CCCSD's water  reclamation plant is  1.6 x
 106 kcal  (6.3 x 106 Btu) compared with 1.1 x 106 kcal (4.5 x 106 Btu) for in-
 plant recalcination.

 Incineration of Second Stage Cake -

 To illustrate the thermal effect of cake moisture in the incineration of dewatered
 sludges, materials and heat balances for three different levels of cake moisture
 are developed in the following paragraphs.  Source of sludge in these cases is
 the thickened centrate from a classification centrifuge (see Fig. 7-9) .  Since
 the purpose of this calculation is to show the relationships between cake moisture
                                      177

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and heat demand, the example only covers incineration in a MHF.  Incineration
in a FBR would show similar increases in heat requirements with increased
percentages of moisture in the cake.

The heat and materials  balances were calculated by the same methods used for
dewatered primary sludge, described earlier in this section, taking into account
the differences in sludge solids  composition.  Calculated results are presented
for sludge moisture levels  of 88, 81 and 70 percent by weight.  The two higher
values represent moisture  contents obtainable in centrifuged cakes;  while the
lowest value might represent moisture content of a cake produced by a filter press,
Compostion of sludge solids, in  weight percent, was taken as:

        Organics (volatiles)                44.6 percent
        CaC03                            15.3
        Ca5(P04)3(OH)                    17.7
        Mg(OH)2                           7.4
        MgO                               3.4
        Fe(OH)3                            2.1
        Fe2O3                              0.9
        SiO2 and others                     8.6
                 Total                   100.0 percent

The fuel value (HHV) of the volatiles was taken as 5,550 kcal/kg (10,000 Btu/lb)
and the calculated low heat value (LHV) was taken as 5,119 kcal/kg  (9,223 Btu/
Ib) , the same as for the volatiles in the primary sludge. The conservative
assumption was made that calcium carbonate, magnesium hydroxide  and ferric
hydroxide were converted to the respective oxides.  The specified gas exit
temperature from  the furnace  was 760 C (1,400 F) .  The basis for calculating
the heat loss in the ash was 93 percent by weight leaving the bottom  hearth at
649 C (1,200 F) and 7 percent leaving in the effluent gases at 760 C  (1,400 F) .
This high exit temperature is  required to destroy odorous organic compounds.
The auxiliary fuel was  assumed to be natural gas with a low heating  value (LHV)
of 11,413 kcal/kg  (20,564 Btu/lb) .  A customary reference temperature of 15.6 C
(60 F) , was used, with all inputs to the furnace assumed to be at that temperature

The effect of reducing the sludge moisture content on auxiliary fuel requirement
can be seen in the materials balance, Table 8-16.  Reducing sludge moisture
from 88 to 70 percent reduces the auxiliary fuel requirement by  74.9 percent.
For a reduction in moisture from 88 to 81 percent,  the  reduction in auxiliary
fuel is 46 percent.

Heat recoverable in a waste heat boiler attached to the MHF is shown for each of
the three moisture levels as Item 10 in Table 8-17, the heat balance tabulation.
Item 10 is taken as 73 percent of Item 8.

For situations where by-product steam can be used, examining the net auxiliary
fuel requirement to incinerate the sludge may be of interest. If the heat recover-
able with the waste heat boiler (Item 10,  Table 8-17) ,  is deducted from the gross
auxiliary fuel input,  (Item 2,  Table 8-17) , the difference may be taken as the net
                                     178

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Table 8-16.  MATERIALS BALANCE FOR MHF AT THREE MOISTURE LEVELS
           OF SECOND STAGE CAKE
Materials
Inputs:
Water in sludge cake
Volatile solids in sludge cake
Inorganic solids in sludge cake
Natural gas
Combustion air, total weight
Total of Inputs
Outputs:
Gases3
H20
C02
02
N2
Total for gases
Ash
Total of Outputs
Cake moisture, % weight
88
kgAr
9,712
590
734
1,149
28,991
41,176
12,722
4,381
1,244
22,212
40,559
617
41,176
Ib/hr
21,391
1,300
1,617
2,531
63,856
90,695
28,022
9,649
2,740
48,926
89,337
1,358
90,695
81
kgAr
5,646
590
734
621
19,428
27,091
7,509
2,958
1,044
14,891
26,402
617
27,019
Ib/hr
12,436
1,300
1,617
1,367
42,793
59,513
16,539
6,515
2,299
32,802
58,155
1,358
59,513
70
kg/hr
3,090
590
734
289
13,423
18,126
4,232
2,064
918
10,295
17,509
617
18,126
Ib/hr
6,806
1,300
1,617
636
29,566
39,925
9,321
4,547
2,023
22,676
38,567
1,358
39,925
  At 760 C (1400 F).
 Table 8-17. SUMMARY HEAT BALANCE FOR MHF AT THREE MOISTURE
            LEVELS OF SECOND STAGE CAKE

Item
No.


1
2


3

4
5
6
7
8

9
10





Gross Heat Inputs
Volatile solids combustion
Natural gas auxiliary fuel
Total of Inputs
Heat Accounted For:
To evaporate water at 15. 6 C
(60 F)
Loss by radiation
Net loss in shaft cooling air
Chemical reaction heats
Heat loss in calcined solids
Heat content above 15.6 C (60 F)
in furnace off gases
Total Heat Accounted For
Heat recoverable with waste heat
boiler:
Cake moisture, % weight
88
1000
kcal/hr

3,021
13,116
16,137


5,713
115
66
114
95

10,034
16,137

7,325
1000
Btu/hr

11 ,990
52,047
64,037


22,672
455
263
451
375

39,821
64,037

29,069
81
1000
kcal/hr

3,021
7,084
10,105


3,321
115
66
114
95

6,394
10,105

4,668
1000
Btu/hr

11,990
28,111
40,101


13,181
455
263
451
375

25,376
40,101

18,524
70
1000
kcal/hr

3 ,021
3,296
6,317


1,818
115
66
114
95

4,109
6,317

3,000
1000
Btu/hr

11,990
13,079
25,069


7,214
455
263
451
375

16,311
25,069

11,907
 Based on LHV.
                              179

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fuel requirement to incinerate the sludge.  The values for the three sludge
moisture levels are presented in Table 8-18.  Table 8-18 shows in another way
the fuel saving benefit to be derived from reducing sludge moisture content to
the lowest feasible level; at 30 percent moisture, the  net heat required to incin-
erate the sludge cake after heat recovery is negligible.


    Table 8-18. AUXILIARY FUEL REQUIREMENTS OF MHF AFTER HEAT
                RECOVERY
Item
Gross auxiliary fuel input
Recovery in waste heat boiler
Net heat required to incinerate
sludge cake
Cake moisture, % weight
88
1000
kcal/hr
13,116
7,325
5,790
1000
Btu/hr
52,047
29,069
22,978
81
1000
kcal/hr
7,084
4,668
2,416
1000
Btu/hr
28,111
18,524
9,587
70
1000
kcal/hr
3,296
3,001
295
1000
Btu/hr
13,079
11,907
1,172
In the design of CCCSD water reclamation plant, steam generated by the waste
heat boilers on the two multiple hearth furnaces is sufficient to supply 94 per-
cent of the average steam requirements of the aeration blowers. ^° Each of three
blowers, driven by a 2,750 hp steam turbine, is capable of supplying 1680 cu m/
min  (60,000 scfm) to the oxidation-nitrification system.  Package steam boilers
are provided to meet peak steam requirements.

Energy Requirements of the FBR

Materials and heat balances are presented below for the same composition and
hourly input rate of dewatered primary lime sludge as was used in calculating
the heat and materials balances for the MHF.

As stated earlier in this  section, the pellet bed FBR is in use to recover lime
from water softening and pulp and paper mill lime sludges. A feature of this
flow sheet is the use of the hot gases from the calcining reactor to evaporate
water from the incoming sludge, whereby the feed to the calciner is moisture-
free.  This use of the hot gases from the calciner,  therefore, is an important
heat recovery feature which is of interest with respect to energy  conservation.

Up to now, the pellet bed reactor has not been used on sewage plant sludges.
The drying of the sludge takes place at a relatively low temperature, with the
gases leaving the dryer  at a temperature of 163 C  (325 F) .  Because of this low
temperature, there is the possibility that some volatile odorous compounds
might not be destroyed and might escape through the final scrubber to the
atmosphere.
                                    180

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Calculation of the materials and heat balances for the pellet bed calciner is rela-
tively complex and requires the use of data which were supplied by Dorr-Oliver,
Inc.^0 The data supplied by Dorr-Oliver are:

    1.  15 percent of dry solids feed to the dryer is  lost by carry-over to the
        scrubber.

    2.  15 percent of the calcined product returns to the dryer by carry-over.

    3.  CaO and MgO in the calcined product carry-over to dryer recombine to
        form CaCO3  and Mg (OH) 2.

    4.  Radiation heat losses from calciner and dryer are about 5 percent of the
        heat input to each.

    5.  Air in-leakage to the dryer (which is under  suction) is 60 mole percent
        of the calciner stack gas  flow.

    6.  Gas temperature leaving  calciner 899 C (1650 F) .

    7.  Gas temperature leaving  dryer 163 C (325 F) .

    8.  Water is injected into the hot gases  leaving  the calciner to  reduce the
        temperature to 760 C (1,400 F) , to  protect the dryer system from too
        high a temperature.

    Other pertinent data  are:

        1.  Heating  value  (LHV) of sludge volatiles was taken as 5119 kcal/kg
            (9,223,  Btu/lb).

        2.  Auxiliary fuel was assumed to  be natural gas  having a LHV of 11,413
            kcal/kg (20,564 Btu/lb) .

        3.  Temperatures  of streams entering the system  was  taken as 15.6 C
            (60 F) except for the combustion and fluidizing air,  supplied by
            blower, which was taken as 54 C (130 F) .

        4.  Recalcination in a pellet bed FBR requires the addition of a small
            amount, less than 0.3 percent, of soda ash  (Na2 003)  to  cause
            pellet formation.  This small addition was considered negligible
            in the materials balance.

The calculations for materials and heat balances are shown in Tables  8-19 and
8-20, respectively.  It will be apparent that separate but interrelated materials
and heat balances must be made for the dryer, the calciner, and gas cooler
(water quench to reduce  calciner gas temperature from 899 to 760 C (1,650 to
1,400 F)) , in order to obtain the overall balances .
                                     181

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Table 8-19.  OVERALL MATERIALS BALANCE FOR FLUIDIZED BED CALCINER

Item

Inputs
Volatile solids
CaCO3
Mg(OH)2
Fe(OH)3
Inerts
Water in sludge
Water to gas cooler
Natural gas
Theoretical combustion air
Excess combustion air
Air in-leakage to dryer
Subtotals
Total


Outputs
N2
H20
C02
°2
Volatile solids
CaCO3
Mg(OH)2
Fe(OH)3
Inerts
CaO
MgO
Fe203
Subtotals
Total
To dryer

kg/hr

596
1,873
66
15
288
2,838
-
122
6,021
4,914
7,348
24,081

Ib/hr

1,313
4,125
145
34
634
6,250

268
13,263
10,823
16,187
53,042
To gas cooler

kg/hr





555




555

Ib/hr

-
-


1,223




1,223
To calciner3

kg/hr

507
1,873
66
15
288
-

-
-
-
-
2,749

Ib/hr

1,117
4,125
145
34
634





-
6,055
24,636 kg/hr (54,265 Ib/hr)
To scrubber
kg/hr

14,003
4,136
2,063
2,823
89
281
10
2
43



23,450
Ib/hr

30,843
9,111
4,544
6,219
197
619
22
5
95
-
-
-
51,655
As product from calciner
kg/hr


-
-
-
_
-
-

245
892
39
10
1,186
Ib/hr


-






539
1,965
85
21
2,610
24,636 kg/hr (54,265 Ib/hr)
  Input to calciner is not additive to dryer input but comes from dryer.


The heat input from auxiliary fuel (LHV) is shown in Table 8-20 as 1,389,000
kcal/hr (5,511,000 Btu/hr) .  Table 8-19 shows the reburned lime (CaO) pro-
duced as 892 kcal/hr  (1,965 Ib/hr) ,  equivalent to 0.982 ton/hr.  The auxiliary
fuel requirement per ton of CaO therefore is 1,414,000 kcal/ton (5,612,000
Btu/ton) .
                                   182

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  Table 8-20.  OVERALL HEAT BALANCE FOR FLUIDIZED BED CALCINER

Gross Heat Inputs:
Volatile Solids
Natural Gas
Combustion and excess air @ 54 C (130 F)
Heats of recarbonation and rehydration
Total of Inputs
Heat Accounted For:
Heat of evaporation of 2,838 kg (6,250 Ib) water in sludge
Heat of evaporation of 555 kg (1 ,223 Ib) water in gas cooler
Heat of reaction, CaCOs— vCaO + CO2
Heat of reaction, hydroxides — > oxides
Radiation loss from calciner
Radiation loss from dryer
Sensible heat loss in product
Sensible heat loss, solids to scrubber
Sensible heat loss, gases to scrubber
Total
Btu/hr

10,289,200
5,511,200
376,000
500,600
16,677,000

6,624,400
1,295,800
3,245,600
90,900
800,000
600,000
174,500
60,900
3,784,900
16,677,000
kcal/hr

2,592,800
1,388,800
94,800
126,200
4,202,600

1, 669,400
326,500
817,900
22,900
201,600
151,200
44,000
15,300
953,800
4,202,600
Comparison may be made with the thermal energy requirements given before for
one ton of CaO. These were:

    1.   Reburning in a MHF with credit taken for heat recovery by means of
        waste heat boiler:   1,122,000 kcal/ton  (4,454,000 Btu/ton) .

    2.   Fresh CaO produced in a modern limestone plant in Nevada and trans-
        ported to Martinez, California:   1,598,000 kcal/ton (6,343,000 Btu/ton) .

If the emission of odors is a problem with the pellet bed calciner operating on
sewage sludge, reheating the off-gases to 760 C (1,400 F) in an afterburner
might be considered a possible solution to the problem.  While this could be
done physically, the thermal energy requirement would be so large that this
approach seems impractical.

In the sand bed FBR installed in Elkhart, Indiana17, the wet sludge is fed directly
to the calciner and all of the recalcined product leaves the  reactor in the  gas
stream.   About 85 percent of the calcined lime  is separated from the gas  stream
in a cyclone and the remainder is removed in a wet scrubber.  If a waste heat
boiler could be successfully operated on gas with this high content of solids, or
if the solids content of the gas could be substantially reduced,  the same  waste
heat recovery process might be applied as  in the case of the MHF.  However, as
the Dorr-Oliver Fluo-Solids process now stands, major  alterations to it would be
required to allow  energy recovery by means of a waste heat boiler.
                                     183

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                         REFERENCES - SECTION VIII


 1.  Disposal of Wastes from Water Treatment Plants .  American Water Works
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 7.  Parker, D.S., K.E.  Train, andF.J. Zadick.  Sludge Processing for Com-
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                                   184

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11.  Unterberg, W., R.J. Sherwood andG.R. Schneider.  Computerized Design
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                                                              \
14.  Carpenter, J.H.  Personal Communication to J.A. Cotteral and E. de la Fuente
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                                     185

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28.  Hinkley, P. Personal Communication to D.S . Parker. S .D. Warren Co.,
    Muskegon, Michigan.  October 5, 1973.

29.  Lewis, C.  Personal Communication to D .S . Parker.  Consultant to the U .S .
    Lime Division of the Flintkote, Co.  November 26, 1973.

30.  Munn, Harry.  Personal Communication to D .S . Parker.  S .D .  Warren Co.,
    Muskegon, Michigan.  October 5, 1973.

31.  Lime Handling, Application,  and Storage in Treatment Processes. National
    Lime Association. Washington, D .C .  Bulletin 213.  May 1971. pl-2 .

32.  Hall,  J.L.  Personal Communication to E. de la Fuente.  Miami  -  Dade Water
    and Sewer  Authority, Hialeah, Florida. January 31, 1974.

33.  Background Information for Proposed New Source Performance Standards.
    U.S. Environmental Protection Agency.  Technical Report No.  13 - Sewage
    Treatment Plants . Tune 1973.  p. 57-61.

34.  Removal of Particulate Matter from Gaseous Wastes  - Filtration.  Department
    of Chemical Engineering, University of Cincinnati.  New York.  American
    Petroleum Institute,  1961.  56 p .

35.  Simonds , S.R.  Personal Communication to W . Henry. Envirotech Corpora-
    tion, SanMateo, California.  May 30,  1972.

36.  Baumeister-Marks.  Standard Handbook for Mechanical Engineers , Seventh
    Edition.  New York, McGraw-Hill Book Company, 1969.  Sections 7,  9, and
    12.

37.  Brown and Caldwell. Plans and Specifications for Water Reclamation Plant,
    Stage 5A - Phase 1.  Central Contra Costa Sanitary District. California.
    April 1973.

38.  Foy,H.E.  Personal Communication to D .L . Eisenhauer. Envirotech Corp-
    oration, Brisbane, California.  May 19, 1972.

39.  Testing for Determination of Blower Produced Sound Levels and Blower
    Adaptation for Sound Control.  Butler Manufacturing Company-Salina
    Division.  Salina, Kansas . October 1, 1972 .  5 p.
                                    186

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40.  Dobbs.B.D. Personal Communication to D.L. Eisenhauer. Fitzroy & Dobbs,
    Acoustical Consultants, San Rafael, California.  November 20, 1972.

41.  Farrell,J.B.  Sludge Information Summary No.  2.  (Presented at the EPA
    Technology  Transfer Design Seminar on Sludge  Handling and Disposal) .
    Anaheim, California.  November 13-23, 1972.

42.  O'Farrell, T.P.  Letter Communication to D.S . Parker.  U.S .  Environmental
    Protection Agency - Blue Plains Pilot Plant, May 17, 1974.

43.-  Bennett, S.M.  Letter Communication to D.S . Parker. U.S . Environmental
    Protection Agency - Blue Plains Pilot Plant.  May 1974.

44.  Parker, D.S., D.G. Niles,  andF.J. Zadick. Processing of Combined
    Physical-Chemical-Biological Sludge. Brown and Caldwell and the Central
    Contra Costa Sanitary District.   (Presented at 46th Annual Conference  of the
    Water Pollution Control Federation.  Cleveland.  October 1, 1973) .  23 p.

45.  Schmid, L.A.,  andR.E.  McKinney.  Phosphate  Removal by a Lime-
    Biological Treatment Scheme.  Journal of the Water Pollution Control
    Federation.   41:  1259-1276, July 1969.

46.  Commoner,  Barry.  The Environmental Cost of Economic Growth.  Commission
    on Population Growth and the American Future.  Research Reports, Vol. III.

47.  Huges ,  H.H. Personal Communication to M .L . Spealman .  U.S. Lime
    Division of the Flintkote Company, Oakland, California. March 1974.

48.  Meier, Morris. Personal Communication to M .L. Spealman.  Allis-Chalmers
    Manufacturing Co., San Francisco, California.   March 1974.

49.  Brown and Caldwell, Consulting Engineers.  Report on Energy Requirements
    for Alternative Modes of Operation of Water Reclamation  Plant. Prepared for
    the Central  Contra Costa  Sanitary District, Walnut Creek,  California.  1974.

50.  Lamb, D.R.  Personal Communication to M .L . Spealman. Dorr-Oliver
    Incorporated, Oakland, California.  March 1974.
                                    187

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                                  SECTION IX

                        AIR QUALITY CONSIDERATIONS


An important problem connected to the operation of sludge incinerators is air pol-
lution .  The air pollutants emitted from incinerators that must in general be con-
trolled include:

    Particulate matter

    Nitrogen oxides  (NO  )
                      X

    Sulfur oxides (SO )
                    yC

    Odorous substances

    Trace quantities of metals, pesticides, polychlorinated biphenyls (PCB) and
    other organic compounds.

The particulate matter released by incinerators burning lime treated sludges
includes small amounts of calcium carbonate  (CaCO3) ,  calcium oxide (CaO) ,
tricalcium phosphate (Cag (P04) 2) ,  magnesium oxide (MgO) and inert solids.
Representative proportions of these constituents which might be expected in the
furnace off-gases are given in Table 9-1,  where predicted  compositions^ are
compared to actual measurements during the  CCCSD's Lime Sludge Recycling
Study.2

A modern sludge incinerator, provided with an adequate scrubbing system and
properly operated, is capable of producing acceptable  stack emissions of parti-
culate matter,  nitrogen oxides, sulfur oxides and odors.3  The  Task Force on
sewage sludge incinerators found however, that while  the gas emissions are
below pollutant levels, most installations did not efficiently control the discharge
of particulate matter.

Under the provisions of the Clean Air Act of 1970, the U .S . Environmental Pro-
tection Agency  (EPA) has implemented standards of performance for municipal
sewage treatment plants which would limit the emission of particulate matter
from new incinerators burning process sludges.4   There are also state and
local codes covering  sludge incinerator emissions and  under the Clean Air Act
of 1970, state and local codes may not be more lenient but can be more stringent.
Typical of these is the regulations of the Bay Area Air  Pollution Control  District
(BAAPCD) .  The BAAPCD has jurisdiction over nine counties in the San Francisco
Bay Area in California. Regulation 2 of the BAAPCD covers particulate  emissions
in terms of capacity and maximum emission by weight per dry standard  cubic
foot (DSCF) .  The weight is corrected for auxiliary fuel consumed in the com-
bustion of sludge.^
                                   188

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      Table 9-1.  SOLIDS COMPOSITION OF LIME FURNACE OFF - CASES,
                 PERCENT
Constituent
CaCOs
CaO
Ca3(PO4)2
MgO
Inerts
S1O2
Other
Total
Unaccounted for
Design
condition
62.5
20.5
5.5
3.5
8.0
0
Measurements during lime Sludge Recycling Study
August 16, 1972
Test 1
68.0
10.4
4.4
4.8
4.9
0.8
0.0
5.7
6.7
Test 2
59.3
20.6
4.5
4.6
4.4
0.7
0.0
5.1
5.9
September 11, 1972
Test 1
64.6
19.8
3.7
3.4
6.6
0.6
0.0
7.2
1.3
Test 2
67.7
16.5
3.1
3.2
6.6
0.5
0.0
7.1
2.4
     Reference 1.

     Reference 2.
In view of the state of flux in which air pollution control regulations seemed to be at
the time this report was written, it would appear to be in the best interest of  each
project to design for  the most rigid control regulations whether they be federal,
state, or local.

Under the present EPA standards, dated March  8, 1970,  particulate emissions to
the atmosphere would be limited to: 4

  11 1.  No more than 70 miligrams per normal cubic meter  (mg/Nm^)  undiluted,
        or 0.031 grains per dry standard cubic foot (gr/dscf) .

    2.   No more than 10 percent opacity."

These same standards do not mention gas pollutant control since the
exhaust concentrations of SOX, NO,,, and CO emitted by  a sludge incinerator
are below serious pollutant levels .°  However it is advisable to check state and
local regulations for  compliance of the gaseous emissions.

In the proposed standards, particulate matter is defined as  "any material, other
than uncombined water, which exists in a finely divided form as a liquid or solid
at standard conditions."  Opacity is defined as "the degree  to which emissions
reduce the transmission of light and obscure the view of an object in the back-
ground."
                                     189

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                                                     4
The following paragraphs are included in the standards:

    "Available data indicate that, on the average, uncontrolled multiple-hearth
    incinerator gases contain about 0.9 gr/dscf of particulate matter. Uncontrolled
    fluid bed reactor gases contain about 8.0 gr/dscf.  For average municipal
    sewage sludge, these values correspond to about 23 Ib/hr in a multiple-hearth
    unit and about 205 Ib/hr in a fluid  bed unit. Particulate collection efficiencies
    of 96.6 to 99.6 percent will be required  to meet the standard, based on the
    above uncontrolled emission rate.  Emissions will be on the order of 1.0
    Ib/hr."

    "Existing state or local regulations tend to regulate sludge incinerator emis-
    sions through incinerator codes or process weight regulations.  The most
    stringent state or local limit, 0.03  gr/dscf, is based on a test method that is
    different from the reference methods  in that it includes impingers.  Many
    state and local standards are corrected to a reference base of 12  percent
    carbon dioxide or 6 percent oxygen.  Corrections to carbon dioxide or
    oxygen baselines are not directly related to the sludge incinerator rate
    because of the high percentage of auxiliary fuel required.  In some regula-
    tions, the carbon dioxide from fuel burning is subtracted from the total in
    determinations of compliance."

    "For a typical incinerator with a rated dry solids charging rate of 0.5 ton/hr
    at a gas flow rate of 3,000  dscfm, the proposed  standard would allow the
    incinerator to emit 0..8  Ib/hr of particulate matter.  The reference process
    weight regulation would limit emissions  to 6.3 Ib/hr, based on a charging
    rate of wet sludge  (80 percent water) of 5,000 Ib/hr.  Dry solids charging
    rates for new incinerators will range from 0.5 to 4.0 tons/hr, with gas flow
    rates of 1,000 to 20,000 dscfm."

The production of odors and their control is  also a consideration in the operation
of sludge incinerators.  It has been indicated that the range of temperatures for
effective control is 649-816 C (1200-1500 F) .7  Since the MHF operates at 760-
982 C (1400-1800 F) in the burning hearths8 and the FBR operates at a minimum
of 760 C (1400 F) 7, both types  of incinerators reach operating temperatures that
are considered effective in the destruction of odorous substances. Nevertheless,
due to certain features of these  incineration  systems, both may require an after-
burner  to ensure off-gases  deodorization, particularly in those cases where
odorous volatile  organics are present in the  sludge.  In the case of a MHF, since
raw sludge is introduced to the upper hearth where, the drying of sludge occurs
before combustion, the temperature of  the exit gas from the upper hearth varies
from 260 to 593 C (500 to 1100 F) 8 which is below the temperature range for
effective odor control.  In the pellet bed FBR, the exhaust gases are  normally
cooled and mixed with the sludge cake  (see Section VIII) .  The preheated
mixture then passes through a two-stage  cyclonic separator before the off-gases
are discharged to atmosphere.  Due to  the intimate mixing of gas and cake solids,
some volatiles may be picked up from the latter and carried over with the
exhaust gas.  These volatiles are a potential source of odors.
                                      190

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Another important area of concern has been the destruction of pesticides and
polychlorinated biphenols (PCB) .  Both multiple-hearth furnaces with after-
burners and fluidized bed reactors will reduce these pollutants to an acceptable
level.  Research^ has shown that 99.9 percent of the PCB contained in sewage
sludges is destroyed in a multiple-hearth furnace operated at an exit gas tempera-
ture of 593 C  (1100 F) .

The use of a high energy scrubber, such as venturi or impingement type, that is
required to achieve the maximum particulate removal from the exit gas stream,
will also further reduce the pollutant gases.  The total energy required by either
of the above types of scrubbers is approximately the same (see Section VIII) .
                                      191

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                                 SECTION IX

                                REFERENCES
1.   Simonds, S.R. Personal Communication to W. Henry.  Envirotech Corpora-
    tion. San Mateo,  California.  May 30,  1972.

2.   Brown and Caldwell, Consulting Engineers.  Final Report, Lime Sludge
    Recycling Study.  Prepared for the Central Contra Costa Sanitary District,
    Walnut Creek, California.  1974.

3.   EPA Task Force Report, "Sewage Sludge Incineration", U .S . Environmental
    Protection Agency, Office of Research and Monitoring,  EPA-R2-72-040,
    August 1972 (NTIS PB211323)  .

4.   Environmental Protection Agency.  Air Programs, Standards of Performance
    for New Stationary Sources, Additions and Miscellaneous Amendments.
    Federal Register, Vol. 39, No. 47,  March  8, 1974.

5.   Bay Area Air Pollution Control District Regulation 2. San Francisco.
    Novembers, 1971.  54 p.

6.   Goldberg, Morris. Personal Communication to L.O . Britt. U.S. Environ-
    mental Protection  Agency,  9th Regional Office.  San Francisco, California.
    November 19, 1973.

7.   Millward, R.S ., and W.A. Darby.  Fluidized Bed Combustion.  (Presented
    at the Thirteenth  Annual Waste Engineering Conference, University of
    Minnesota).  Minneapolis.  December 10, 1966.  17 p.

8.   Sebastian, F .P . Advances in Incineration and Thermal Processes .  Short
    Course on the Theory and  Design of Advanced Waste Treatment Processes.
    California, Berkeley.  September 30 - October 1, 1973.

9.   Miller,  W. News  Release.  Envirotech Corporation, Menlo Park. October 10,
    1972.
                                   192

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                                  SECTION X

             MASS EQUILIBRIUM BALANCES OF SOLIDS PROCESSING

                      SYSTEMS BY DIGITAL COMPUTATION
The design and operation of a chemical sludge solids processing system requires
the computation of theoretical mass equilibrium values for each component in all
process streams of importance.  For the solids processing systems such as those
shown in Fig.  7-8 and 7-9, manual computation of mass equilibrium values for
each component in every process stream is a tedious and time consuming process.
Furthermore, new mass equilibrium values for each component need to be calcu-
lated each time a change in an operational parameter is made. The importance of
having a theoretical model capable of predicting accurate mass equilibrium values
for all components in such a complex process can not be overstressed. Rapid
calculation of component equilibrium values for various operational modes is
important in monitoring the operation of a solids processing system of this type.
Also, in the design of this type of system, many different modes of operation
must be evaluated before final design decisions are made.  A computer program
is  then needed that can model the system and calculate mass equilibrium values
for differing modes of operation.

A computer program, SOLIDS 1A, has been developed  to solve (by direct nonit-
erative equations) for the equilibrium mass values of all components in the
solids processing sequence shown in Fig. 7-8 and 7-9. The solids processing
sequence employs wet classification of primary sludge with recalcination of the
recovered sludge solids;  with options for second stage dewatering of the centrate
from the wet classification step, and incineration of the recovered  solids from
the dewatering step. Also optional in the solids processing sequence  are blow-
down of  a portion of the recalcination furnace product, dry classification of the
recalcination furnace product to selectively purge inert materials from the
process, and the ability to recycle furnace wet scrubber water back to the
primary-   By appropriate adjustment of input data, the program is readily
adapted to substitution of vacuum filters  or filter presses for the second stage
dewatering step; or a Plural Purpose Furnace flow sheet (Fig. 7-8) can be run
by inputting high recoveries in the first stage dewatering step. In this event,
centrifuges, vacuum filters, or filter presses could be assumed.

In the program, a simplifying assumption is made that solids in the thickener
overflows are not returned to the primary stage.  In terms of the first stage
thickener,  such overflows have no impact on any process stream except the
primary sludge stream.  In terms of the second stage thickener, it is assumed
that the "thickener" is more-or-less a holding tank with little or no thickening
action taking place so that no stream would return to the primary.
                                     193

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This program was compared to the full-scale test data generated during test work
on lime recalcining and recycle at the CCCSD's ATTF.  Agreement between pro-
totype and computer output was found to be reasonably good.l  The program was
developed in Fortran IV language for use on the time sharing service of General
Electric Information Services, Business Division.  It can be easily modified for
use on other time share or batch processing services.  A listing of the program
is given in Section XV. A; symbols used in the program are given in Tables 10-1
through 10-3.  If for some reason the design engineer does not have convenient
access to a computer, the equations presented in this section and in the program
listing in Section XV. B can be used for manual calculations.
        Table 10-1.  COMMON PREFIXES USED IN PROGRAM "SOLIDS 1A"
      Prefix
          Meaning
   CA
   CAC
   CAP
   CAO
   CAH
   FE
   FEOH
   FEO
   FECL3
   XMG
   XMGH
   XMGO
   ORG
   P
   SI
   All

   XLB
   RE
   TOTLB
   FR
Calcium as Ca
Ca CO_, Calcium carbonate
Ca« (POJ2/ Tri calcium phosphate
Ca O, calcium oxide
Ca (OH)2/ calcium hydroxide
Iron as Fe
Fe (OH) -, Ferric Hydroxide
Fe2 O3, Ferric oxide
Fe CL3, Ferric chloride
Magnesium as Mg
Mg (OH)?, Magnesium Hydroxide
Mg O, Magnesium oxide
Organics, Volatile Matter
Phosphorus as P
Si O2, Silicon dioxide
Acid insoluble inerts
 (Other than silica)
Pounds of
Recovery of
Total pounds  of
Fraction of
                                   194

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    Table 10-2. COMMON SUFFIXES USED IN PROGRAM "SOLIDS 1A"
  Suffix
               Meaning
-MGL
-IN,-INF
-OUT,  -EFF,  -EF

-SLG
-CAK1
-CNT1
-CAK2
-CNT 2
-1
-2
-WAS

-SSI, -SSIN
-SSO,  -SSOUT

-FP
-FPI
-F
-FI
-CL

-CR
-RS

-BD

-SE1

-SE2

-IP

-IND
-EFD,  EFFD
In units of mg/1
Into the primary flocculation basin
Out of the primary sedimentation basin
 (primary effluent)
In the primary sludge
In the first  stage centrifuge cake
In the first  stage centrifuge centrate
In the second stage centrifuge cake
In the second stage centrifuge centrate
(Recovery) In the first stage centrifuge
(Recovery) In the second stage centrifuge
Waste activated (secondary)  sludge added
to the primary
Suspended  solids into the primary
Suspended  solids out of the primary (in
the effluent)
In the recalcination furnace  (product stream)
In the incineration furnace  (product stream)
(Recovery) In the recalcination furnace
(Recovery) In the incineration furnace
(Recovery) In the classifier for recalcined
product
In the classifier reject stream
In the recycled solids accepts stream back
to the primary
In the blowdown stream from the
 recalcination furnace
In recalcination furnace wet scrubber
effluent stream
In incineration furnace wet scrubber
effluent stream
In the first pass precipitation (sludge) in
the primary
Dissolved in the primary influent raw sewage
Dissolved in the primary effluent
                                 195

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      Table 10-3.  OTHER SYMBOLS USED IN PROGRAM "SOLIDS  1A"
  Symbol
            Meaning
XMGD
FECL3MGL
CAHTODOS

FRBD

RECALEFF

XMGEFMGL
FRAIISSO

FRAIISSI

FRSIWAS

FRAIIWAS

FRVWASIN

FRVSSIN

FRVSSOUT

FRSISSI

FRSISSO

FRSINEW
FRAIINEW
FRMGONEW
FRCAONEW
CAOTOMGL
CAONEW
TOTLBNEW

CAONMGL
CAORMGL

CAORSFRA
Flow into the primary, mgd
Dose of Fe CL3 to the primary, mg/1
Total dose of calcium hydroxide to the
 primary in units of mg/1
Fraction of recalcination furnace stream
 to blowdown
Recalcining efficiency of converting
 Ca CO3 to Ca O
Magnesium as Mg in primary effluent, mg/1
Wt. Fraction of acid insoluble inerts in
 suspended solids out (effluent)
Wt. fraction of acid insoluble inerts in
 suspended solids into the primary
Wt. fraction silicon dioxide in waste
 activated sludge
Wt. fraction acid insoluble inerts in waste
  activated sludge
Wt, fraction volatile solids in waste
 activated sludge to the primary
Wt. fraction volatile solids in influent
 suspended solids
Wt. fraction volatile solids in effluent
 suspended solids
Wt. fraction silicon dioxide in influent
 suspended solids
Wt. fraction silicon dioxide in effluent
 suspended solids
Wt. fraction of stated component in the
new (makeup) dry  lime solids added to
the primary

Total dose to primary of CAO, in mg/1
Makeup CAO  (lime) added to primary
Total new makeup lime added,
 including impurities, Ib
CAO makeup added to primary, as mg/1
CAO in recycled  solids (RS) stream, as
 mg/1
CAO in recycled  solids stream, fraction
 of total CAO dose
                                196

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        Table 10-3. OTHER SYMBOLS USED IN PROGRAM "SOLIDS 1A"
                    (CONTINUED)
    Symbol
              Meaning
  TOTRE 1

  TOTRE2

  TOTRECL



  SEREC

  CLASSIF

  FURNACE
Total solids recovery in the first stage
 centrifuge (wet classification)
Total solids recovery in the second stage
 centrifuge (dewatering)
Total solids recovery in dry classification
 of recalcined furnace product (recovery
 in accepts stream)
Option code for return or nonreturn of furnace
 scrubber water to the primary
Option code for including or excluding dry
 classification of furnace product
Option code for including or excluding second
 stage dewatering and incineration of cake in
 the processing sequence
DESCRIPTION OF PROGRAM

For a given set of operating conditions and unit performances,  the equilibrium
mass values for the following components are calculated for each process stream:
        Organics
        Calcium carbonate
        Calcium phosphate
        Magnesium hydroxide
        Magnesium oxide
        Ferric hydroxide
        Ferric oxide
        Silicon dioxide
        Acid insoluble inerts
        Calcium oxide
           (volatile matter)
           (CaCO3)
           (Ca3(P04)2)
           (Mg(OH)2)
           (MgO)
           (Fe(OH)3)
           (Fe203)
           (Si02)
           (other than
           (CaO)
The program also calculates the fraction of the total lime dose (as CaO) to the
primary contributed by the recycled CaO from the recalcining furnace.

Description of Input

Inputs are required to specify the type of operation desired as described under 1
and 2 below:

    1.   The type of processing sequence  (either Plural Purpose Furnace or
        ATTF  system cases, i.e. , dewatering alone or wet classification
                                   197

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    followed by dewatering) to be specified is inputted by using the appro-
    priate code for "FURNACE".  For ATTF system cases, "FURNACE" = 2.0,
    while for Plural Purpose Furnace cases, "FURNACE" = 1.0. Also, if a
    dry classifier is included in the processing sequence, "CLASSIF" = 1.0,
    while if no dry classifier is wanted,  "CLASSIF" = 0.0. If a blowdown
    stream from the recalcination furnace product is desired (with or without
    the dry classifier)  the appropriate fraction of the furnace product stream
    to be the blowdown is inputted for "FRBD".  If no blowdown is wanted,
    set "FRBD" = 0.0.  The blowdown stream is located ahead of dry classi-
    fication in  the processing sequence.  If furnace scrubber effluent water
    is to be returned to the primary, then set "SEREC" = 1.0.  If not, then
    set "SEREC" = 0.0.

2.   The order  of process and performance parameters to be inputted is:

    a.   Flow rate in MGD as "XMGD".

    b.   Waste activated sludge solids added to the primary,  in Ib/day as
        "XLBWAS".

    c.   Ferric chloride dose to the primary, mg/1 as "FECL3MGL".

    d.   Total lime dose as Ca (OH) 2, in mg/1 as "CAHTODOS" .

    e.   Fraction blowdown as "FRBD".

    f.   Recalcining efficiency of converting CaCC>3  to CaO, fraction, as
        "RECALEFF" (as measured on the furnace product) .

    g.   "FURNACE" as 2.0  or 1.0, and "CLASSIF" as 1.0 or  0.0 as explained
        previously.

    h.   Primary pH as  "PH"

    i.   "SEREC"  as 1.0 or  0.0, as explained previously-

    j.   Iron as Fe in the  primary influent raw sewage, mg/1, as "FEINFMGL".

    k.   Silica dissolved in the primary influent raw sewage, in mg/1 of
        SiOo, and silica dissolved in the primary effluent in mg/1 of SiOo,
        as lfSIINDMGL", and "SIEFMGL", respectively.

    1.   Suspended solids in the primary influent in mg/1 as  "SSINMGL",
        and suspended solids in the primary effluent in mg/1 as "SSOUTMGL".

    m.  Magnesium as Mg in primary influent, mg/1, as "XMGINMGL",  and
       in the effluent  (mg/1) as  "XMGEFMGL".

    n.  Calcium (dissolved and suspended) as Ca in the primary influent,
       mg/1, as CAINFMGL,  and calcium (dissolved and suspended)  as
       Ca in the primary effluent as "CAEFFMGL".
                                 198

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o.  Total phosphorus as P, mg/1, in the primary influent as "PINFMGL",
    and in the effluent as "PEFFMGL".

p.  Iron as Fe in the primary effluent,  mg/1 as "FEEFFMGL".

q.  Weight fraction of acid insoluble inerts (inerts other than SiC^)
    present in the suspended solids in the effluent as "FRAIISSO", and
    in the primary influent as "FRAIISI".

r.  Weight fraction SiO2 in waste activated sludge solids as "FRSIWAS",
    and the weight fraction acid insoluble inerts in the waste activated
    sludge solids as "FRAIIWAS".

s.  The weight fraction of volatile matter in the waste activated sludge
    solids as "FRVWASIN", in the suspended solids in the influent
    "FRVSSIN" and in the suspended solids in the effluent as "FRVSSOUT".

t.  The weight fraction SiOo in the suspended solids in influent as
    "FRSISSI", and in the effluent as "FRSISSO".

u.  The weight fraction of SiC>2, acid insoluble inerts, MgO and CaO in
    the new makeup lime solids as "FRSINEW", "FRAIINEW", "FRMGONEW",
    and "FRCAONEW", respectively.

v.  Recoveries of all components in the first stage (wet classification)
    centrifuge cake as fraction recovered:

        RECAP1 is recovery of Ca3(PC>4) 2)
        RECAC1 is recovery of CaCO3
        RESI1 is recovery of SiC>2
        REAII1 is recovery of acid insoluble inerts
        REXMGH1 is recovery of Mg (OH) 2
        REXMGO1 is recovery of MgO
        REFEOH1 is recovery of Fe (OH) 3
        REFEO1 is recovery of Fe2O3
        REORG1 is recovery of organics  (volatile matter)

w.  Similarly, fractional  recoveries for all components in the second
    stage (dewatering) centrifuge cake are inputted as in "v" above,
    with the suffix being "2" instead of "1":

        RECAP2, RECAC2, RESI2,  REAII2, REFEOH2, REFEO2,
        REORG2, REXMGH2, REXMGO2 are inputted.

x.  Fractional recoveries of all components in the recalcination furnace
    are inputted (suffix is "F"  for  these components) . Furnace
    recovery means what is recovered as furnace product.  Whatever is
    lost to the furnace dry cyclone  is presumed to be recovered in a
    wet scrubber and the scrubber water returned to the primary.
                               199

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    Recalcination furnace recovery inputs are:

        RECAPF, RECACF, RESIF, REAIIF, REFEOHF,  REFEOF, REORGF,
        REXMGHF, REXMGOF.

    The recovery of organics and metal hydroxides in the furnaces are
    intrinsically zero in the program, because all organics  are assumed
    to be combusted, and all metal hydroxides (Fe (OH) 3 and Mg (OH) 2)
    are assumed to be converted to metal oxides  (Fe2O3 and MgO)  .
    Hence, the recoveries of the metal oxides in the furnaces will  be
    used for the  metal hydroxides because they will exit the furnaces as
    metal oxides. Also, CaCO3 is converted to CaO in the furnace, and
    the program uses the  CaCO3 recovery and recalcine efficiency to
    determine the CaO in  the furnace product.

y.   The fractional recoveries of all components in the incineration
    furnace are inputted,  similar to those for the recalcination furnace.
    The inputs are given  the suffix "FI" for the incineration furnace.
    Recovery inputs are:

        RECAPFI, RECACFI, RESIFI, REAIIFI, REFEOHFI, REFEOFI,
        REORGFI, REXMGHFI, REXMGOFI.

    Again,  recoveries are defined as in the case discussed  above for the
    recalcination furnace, and inputs for recoveries of organics and
    metal hydroxides will be zero.

z.   The fractional recoveries of compounds in the dry classifier for
    recalcined product are inputted last. The fractional recovery is
    defined as the mass of material accepted and recycled back to the
    primary divided by the total mass of material classified. Classifier
    rejects are assumed to be discarded. Again, recoveries of organics,
    and metal hydroxides are inputted as zero because none of these
    appear in the recalcined product to be classified.

    Inputs are given the suffix "CL", as:

        RECAPCL, RECACCL, RESICL, REAIICL, REFEOHCL, RECAOCL,
        REFEOCL,  REORGCL, REXMGHCL,  REXMGOCL.

    The recovery of CaO is inputted here because it is present in the
    recalcination furnace  product, as a separate compound, along with
    the remaining CaCO3  that was not recalcined.  If no dry classifier  is
    to be used, input the  recoveries of all components (except organics,
    Mg(OH)2 and Fe(OH)3, which are zero)  in the classifier as 1.0
    (total recovery) .
                             200

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Input Data Format
The input data is arranged into three data files (e.g., three separate magnetic
cards, three sets of punch cards, etc.) .  The first input file, which is called
"DAT1" simply lists a line number followed by the input terms.  There are two
lines on the first (DAT1) file. Line numbers have been  assigned arbitrarily.
The first input file is shown in Table 10-4.

              Table 10-4.  FORMAT FOR DATA FILE  "DAT!"
     Input parameters in computer code
                                        Description
                                                               Sample file list
  L,XMGD,XLBWASIN,FECL3MGL,CAHTODOS,
  FRBD.RECALEFF
  L , FURNACE , CLASSIF , PH , SEREC , FEINFM GL ,
  SIINDMGL.SIEFDMGL
File list no. , primary flow, Ib/day waste
 activated sludge added; FeCL dose,
 total dose of lime as mg/1 of Ca(OH),
 fraction blowdown,
 recalcination efficiency
                                                     '2'
File list no. , furnace option code, classifier
 option code, primary pH , furnace scrubber
 water return option, Iron as rng/1 Fe
 in raw sewage, dissolved silica as
 mg/1 SiO in raw sewage and primary
 effluent
110,30.0,9746.0,14.0,400.0,
0.0,0.95
115,2.0,0.0,11.0,1.0,0.0,
0.0,0.0
A sample of the numbers which might be used for a two stage centrifuge-furnace
case with dry classification of the recalcined product is shown  (case 100,
Section XV. B) .  The format is in the "variable specification", so that any
floating point format can be used for any of the input numbers.  The first number
on each line is the line number required to construct a data file list by the time
share service.

The second group  and third groups of input data,  which the program recognizes
as files "DAT2" and "DATS" are shown in  Tables 10-5 and 10-6.

It is important to input recovery values  for all components, even those that are
intrinsically zero  (as recovery of organics or  metal hydroxides  in the furnaces
or classifier - in these cases, the input values would be 0.0) .   Also,  in the
case that any  component will not be present in the primary influent or in any
stream added to the primary (hence, this  component will not be in any of the
process  streams printed out) , it is important to input hypothetical recovery
values for that component in either the first stage or second stage centrifuge to
prevent  division by zero in certain equations.  In  fact, if ever the recoveries in
both the first and second stage centrifuge are inputted as zero for a particular
component, division by zero results, causing the calculated amount of that com-
ponent present in the primary sludge to be infinite.

Outputs

The program prints out calculated equilibrium values as well as some specified
recoveries, performance parameters, and operational conditions.  Output for the
cases evaluated for this report are shown  in Section XV. B .
                                      201

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                                                                   Table  10-5.    FORMAT  FOR DATA  FILE  "DAT2"
                                               Input parameters in computer code
                                                                                                                      Description
                                                                                                                                                                  Sample file list
                              L,SSINM(.;L, SSOUTMGLrXMCINMGL,XMGEFMGL,CAINFMGL,CAEFrMGL
                              L, PINFM! ;L, PErrMGL,FCErFMGL,FARIISSO,FRAlISSI
                              L, FRSIVVAS , FRAIIWAS , FRVWASIN , FRVSSIN , FRVSSOUT
                             L, FRSISSI ,FRSISSO, FRSINEW , FRAIINEW , FRMGONEW, FRCAONEW
   File list no. ,  influent primary suspended solids (mg/1);
   effluent primary suspended solids (mg/1); magnesium as
   Mg in the primary influent (mg/1); primary effluent total
   Mg as Mg  (mg/1); primary influent calcium as Ca (mg/1);
   Primary effluent total calcium as Ca (mg/1)

   Tile list no. ,  influent total P as P (mg/1), primary
   effluent total P (mg/1); primary effluent total Fe as
   Fe (mg/1);  weight fractions of:  acid insoluble inerts
   in effluent suspended solids, acid insoluble inerts in
   Influent suspended solids

   File list no. ,  weight fractions of:  SiO  in waste
   activated sludge, acid insoluble inerts in waste
   activated sludge, volatile matter in waste activated
   sludge,  volatile matter in Influent suspended solids,
   volatile matter in effluent suspended solids

   File list no.,  weight fractions of:  SiO- In influent
   suspended solids, SiO. in effluent suspended solids,

   makeup lime,  MgO in makeup lime, CaO In makeup lime
                                                                                                                                                      131,240.0,26.0,22.3,8.74,30.0,60.0
                                                                                                                                                      132,10.0,0.66,0.0,0.0024,0.0024
                                                                                                                                                      141,0.035,0.0024,0.80,0.80,0.80
                                                                                                                                                      151,0.035,0.035,0.027,0.0096,0.07,0.89
                                                                 Table  10-6.    FORMAT FOR  DATA  FILE  "DAT3"
to
o

                                 L, RECAP! ,RECAC1 , RESI1 ,REAII1


                                 L , REXMGH 1 , REXMGO1, REFEOH 1, REFEO1, REORG1
                                 L, RECAP2, RECAC2 ,RESI2 ,REAII2, REFEOH2


                                 L, REFEO2, REORG2, REXMGH 2 , REXMGO2
                                 L , RECAPF . RECACF , RESIF , REAIIF , REFEOHF


                                 I., REFEOF, REORGF, REXMGHF , REXMGOF
                                 L, RECAPFI, RECACFI, RESIFI, REAIIFI, REFEOHFI


                                 L , REFEOFI, REORGFI, REXM GHF1. REXMGOFI
                                L, RECAPCL , RECACCL , RESICL, REAIICL, REFEOH CL, RECAOCL


                                L, REFEOCL , REORGCL, REXMGHCL . REXM GOCL
                                                                                                              Description
Recoveries in the first stage centrifuge of:

   File list no., Ca  (PO )   CaCO   SiO
    Acid Insol. Inerts

   File list no., Mg(OH)    MgO, Fe(OH)  ,
    FB203, Organics

Recoveries in the second  stage centrifuge  of:

   File list no., Ca  (PO )  , CaCO   SIO  ,
    Acid Insol. Inerts, FefOH) 3

   File list no., Fe O   Organics, Mg(OH)
    MgO          2  3                  2

Recoveries in the recalcination furnace of:

   File list no., Ca  (PO )   CaCO   SiO
    Acid Insol. Inerts, FefOH)

   File list no., Fe O   Organics, Mg(OH)
    MqO          2  3                  2
Recoveries in the incineration furnace of:

   File list no. , Ca  (PO )  , CaCO ,  SiO  ,
    Acid Insol. Inerts, FefOH) 3

   File list no., Fe,O   Organios, Mg(OH)
    MgO

Recoveries in the dry classifier of:

   File list no., Ca  (PO )   CaCO ,  SiO  ,
    Acid Insol. Inerts, FefOH)  ,  CaO

   File list no., Fe O   Organics, Mg(OH)
    MgO          2  J                  2
                                                                                                                                                           Sample file list
161,0.20,0.825,0.90,0.77


171,0.27,0.27,0.30,0.30,0.40
181,0.90,0.99,0.97,0.81,0.90


182,0.90,0.78,0.90,0.90
191,0.94,0.93,0.98,0.87,0.0


192,0.95,0.0,0.0,0.92
201,0.94,0.93,0.98,0.87,0.0


202,0.95,0.0,0.0,0.92
211,0.957,0.984,0.761,0.929.0.0,0.981


212,0.864,0.0,0.0,0.966

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The first output line is for primary operating pH,  primary flow (MGD) , and lime
use as calcium oxide.  The total lime dose required for primary operation at pH
11.0 is printed (this was an input value) .  Calculated values for the doses (mg/1)
of required makeup lime and recovered recalcined lime are printed also on the
first line ,  as well as the fraction of the total dose contributed by the recovered
lime (CaO) .
The second output line simply prints out the inputted values for the dose of
(mg/1) used in the primary and the amount of waste biological sludge added to
the primary.

The third output line prints out the specified fraction of recalcination furnace
product to be blown down and the specified efficiency of recalcination  (fractional
conversion)  of CaCC>3 to CaO, as measured in the furnace product.

The fourth output lists the weight fractions of SiC>2, acid insoluble inerts, MgO
and CaO specified in the new  (makeup) lime solids added to the primary.

The fifth output line lists the primary influent compositon (mg/1)  of suspended
solids, magnesium, calcium,  phosphorus, SiOo, acid insoluble inerts, and iron.
The suspended solids composition in the raw sewage does not include the  waste
activated sludge solids added to the primary.  The SiO2 composition, however,
for program calculation reasons, does include the SiO2 present in the raw sewage
suspended solids, the waste activated sludge solids, and the makeup lime.
Similarly, the acid insoluble inerts includes what is present in the raw sewage
suspended solids , the added waste activated sludge solids ,  and the new added
makeup lime. The magnesium,  calcium and phosphorus  composition values are
based on total magnesium, calcium and phosphorus  (as the elements) in the raw
sewage.

The sixth output line lists the primary effluent composition values (mg/1)  speci-
fied for total calcium, magnesium,  phosphorus and iron  (Fe) as the elements, as
well as composition values for suspended solids, Si02 and acid insoluble inerts.
The SiO2 and acid insoluble inerts values  are calculated from the inputted weight
fraction of each component present in the effluent suspended solids.

The next several outputs are for the amount of each component present in  each
process stream.  The "First Pass Precipitation"  stream is the amount of each com-
ponent that would precipitate in the primary sludge if the primary was isolated
and received only raw sewage and chemical addition streams;  that is, there are
no return streams to the primary sedimentation  tank from solids processing
operations.  For the purpose of this calculation, the fraction of lime that comes
from the recalcined product is assumed to be 100 percent CaO.  Note that CaO
and Fe2O3 will always be zero in this stream , because CaO added reacts to form
CaCO3 and FeCl3 added precipitates as Fe(OH) 3 and not  Fe2O3_

The "Primary Sludge" component output includes the materials in the first pass
precipitation stream plus all materials recycled  to the primary from the
following streams: recycled  (recalcined)  solids,  centrate recycle  (second stage
                                     203

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or first stage, depending on what mode of operation is desired) to the primary,
and furnace wet scrubber water returned to the primary.  Note again it is
assumed that there will never be any CaO present in the primary sludge  (it all
precipitates as
The "First Stage Cake" stream is calculated by using the recoveries inputted for
each component in the first stage centrifuge  (wet classification) step .  Note that
any separation process (centrifuge, filter press, vacuum filter, etc.)  could be
used for the first stage dewatering step .

The "First Stage Centrate" stream is the portion of the primary sludge not
recovered in the first stage dewatering step .

The "Recalcination Furnace Product" stream is the mass of each component
recovered from the recalcination of the first stage cake stream . The recovered
furnace product is calculated by subtracting from the furnace feed the portion
of material not recovered in the furnace.  This portion is calculated from the
inputted recoveries  for each component.

The "Recalcination Furnace Wet Scrubber" stream is, as explained before, the
unrecovered portion of material in the recalcination furnace which is returned to
the primary via wet scrubber water.

The "Recycled Solids Accepts" stream is the portion of recalcination furnace pro-
duct,  minus any blowdown  (if specified) , which has been accepted by the dry
classification step.  If no dry classification step is specified, the recycled solids
stream is the recalcination furnace product stream, less any blowdown.

The "Second Stage Cake" component stream is calculated from inputted component
recoveries for the second stage centrifuge (dewatering step) .  The second stage
cake is that  portion of the first stage centrate solids (from wet classification)
which is recovered by dewatering .

The "Second Stage Centrate" is the portion of the first stage centrate not
recovered in the dewatering step, and therefore recycled back to  the primary.

The "Incineration Furnace Waste Ash" stream is the portion of  the second stage
cake which is recovered (not lost to the incineration furnace wet scrubber) in
the incineration furnace product.  This ash product is disposed to waste.  Note
that the incineration  furnace is run at a lower temperature than the recalcination
furnace, so  it is assumed that no CaCOg is recalcined to CaO; however, metal
hydroxides are assumed to be converted to the oxides .

The "Incineration Furnace Wet Scrubber" stream is the portion of  unrecovered
material in the incineration furnace, which is captured by a final  wet scrubber
and returned to the primary.

The "Recalcination Furnace Blowdown" stream is the portion of the furnace pro-
duct that is to be wasted (or "blown down") to purge the system of inerts.  This
stream is printed out only if there is a blowdown fraction specified.
                                     204

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The "Classifier Rejects Stream" is the material rejected by the dry classifier and
disposed of as waste.  This stream is shown only if there is a dry classifier for
recalcined furnace product.

The final output group lists the inputted recoveries for each component in the first
stage (wet classification)  centrifuge, recalcination furnace,  second stage (de-
watering) centrifuge, incineration furnace and dry classifier. The calculated
total recovery of solids in the wet classification, dewatering, and dry classification
steps is shown also.

DERIVATION OF EQUATIONS  AND PROGRAM MECHANICS

The equations used to  solve for the equilibrium mass values of each component
present in the primary sludge are the key equations.  Once the total composition
of the primary sludge is known, the composition of every other process stream
can be  easily obtained by using the component recovery values inputted for the
first and second stage centrifuges (wet classification and dewatering steps) , the
recalcination and incineration furnaces, and the dry classifier.  The chemical
reactions producing sludge precipitates have been described in Section VI.

Metal Hydroxides and Organics

Basically, the amount of a component precipitated in the primary sludge is the
summation of the amounts of that  component present in all the streams, or
chemicals returned or fed to  the primary;  less the amount of that component
leaving in the primary effluent.   The ferric hydroxide (Fe(OH)3) precipitated in
the primary sludge from the  chemical addition of ferric chloride, plus the ferric
hydroxide returned to the primary from the recycled centrate, plus the Fe in the
raw sewage (taken as Fe(OH) 3) , minus the ferric hydroxide leaving in the
effluent; equals the equilibrium amount of Fe(OH) 3 present in the primary sludge
for a given mode of operation.  Recall, FEOHSLG is the symbol for the equilibrium
mass value of Fe(OH) 3 in the primary sludge.   In terms of the program symbols
(Tables 10-1 to 10-3) and Fortran algebra the equation would be:

    FEOHSLG =  (FECL3) * (107./162.5) + FEOHCNT2
             -  (FEEFF) * (107./56.) + (FEINFMGL)
            *   (XMGD)  * (8.33) * (107./56.)                        (1)

The conversion factors of FECL3  and FEEFF in equation (1) convert ferric chloride
and elemental iron (Fe) to equivalent Fe (OH) 3 .

There are two unknowns in equation (1); FEOHSLG and FEOHCNT2.  Therefore,
in order to solve the equation, the number of unknowns must be reduced to one.
To accomplish this, the FEOHCNT2 (Fe(OH)3 in  the recycled centrate) can be
related to FEOHSLG (the Fe(OH) 3 in the primary sludge at equilibrium)  by apply-
ing the recovery factors for Fe(OH) 3 in the first and second stage centrifuge
operations. Thus:

    FEOHCNT2 =  (1.-REFEOH1)  * (1.-REFEOH2) *  (FEOHSLG)          (2)
                                     205

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                                      3
Recall, REFEOH1 is  the recovery of Fe(OH)3 in the first stage centrifuge, so
(1.-REFEOH1)  is the fraction of the Fe(OH) 3 in the primary sludge that appears
in the first stage centrate.  Likewise, (1 .-REFEOH2)  is the fraction of the Fe(OH)
in the first stage centrate that is not recovered in the second stage centrifuge
(dewatering step) and appears in the second stage centrate.   Hence, solving
the original equation for the equilibrium value of Fe (OH) 3 in the primary sludge
gives:

    FEOHSLG -  ((FECL3)  *  (107./162.5)  +  (FEINFMGL) * (107./56.)
             *  (XMGD) * (8.33)  -  (FEEFF) * (107./56))
             /  (l.-(l.-REFEOH2) * (1.-REFEOH1))                     (3)

All the terms on the  right hand side of the equation are known, allowing a simple
algebraic solution for FEOHSLG.

Once the value of FEOHSLG is obtained, the amount of Fe (OH) 3 in the first stage
cake (FEOHCAK1) can be obtained by multiplying FEOHSLG by the recovery of
Fe(OH) 3 in the first stage centrifuge (REFEOH1)  as follows:

    FEOHCAK1 = (FEOHSLG)  * (REFEOH1)                                (4)

Similarly the Fe(OH) 3 in the first stage centrate would be:

        FEOHCNT1 = FEOHSLG * (1.-REFEOH1)                           (5)

The Fe(OH) ~ in the second stage cake is found from:

        FEOHCAK2 - (FEOHCNT1) * (REFEOH2)                           (6)

As mentioned before, there is no Fe(OH)3 in either of the furnace products,  or  in
the furnace wet scrubber water streams which are returned to the primary.

A similar set of equations can be used to solve for Mg (OH) 2 and organics in the
various process streams (see Section XV. A) .  Recall, there is no Mg (OH) 2 or
organics in either of the furnace products, or in the  furnace scrubber water
streams. Magnesium hydroxide  entering the primary is composed of that Mg (OH) 2
present in the recycle centrate stream plus that precipitated from reactions of
magnesium ions present in the raw sewage.  The organics coming into the primary
are from the volatile portion of the influent suspended solids  and added waste
activated sludge solids, plus the organics in the  recycled centrate stream.

Metal  Oxides

The solution for  the equilibrium values of metal oxides (Fe2O3 or MgO) in the
primary sludge uses basically the same approach as that for the  metal hydrox-
ides except that more streams are involved in the balance. For instance,  the
MgO present in the primary sludge at equilibrium is composed of MgO from the
following sources:   (1) Recycled recalcined solids stream;  (2) Trace amount
(as impurity) in new makeup CaO added;  (3) Wet scrubber water stream from
recalcining furnace;  (4) Wet scrubber water stream from incineration furnace;
206

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and  (5) Recycled centrate stream.   The metal hydroxides that are converted to
metal oxides in each furnace must be included as part of the recycled metal oxide
streams.  Hence, there is more metal oxide in the furnace product than in the
feed because of the metal hydroxide converted to oxide in the furnace.   A mate-
rial  balance for the MgO  in the primary sludge (XMGOSLG) , is shown in Table
10-7.  The sources contributing to the equilibrium value  of MgO in the primary
sludge are listed, with the corresponding equations used in the program to
describe the MgO source.
   Table 10-7.  MATERIAL BALANCE DESCRIPTION FOR MAGNESIUM OXIDE
                IN THE  PRIMARY SLUDGE
          Sources contributing to
       primary sludge equilibrium MgO
    Program equation for MgO source
  MgO in recycled solids from conversion of
   Mg(OH)7 to MgO in the recalcining furnace

  MgO in recalcining furnace scrubber water due to
   Mg(OH)  conversion to MgO and captured by the
   wet scrubber
  MgO in incineration furnace scrubber water due to
   Mg(OH)  conversion to MgO in the furnace and
   captured by the wet scrubber
  MgO as impurities in new lime

  MgO from second stage centrate recycle

  MgO from recycled solids stream that was present
   in the first stage cake as MgO

  MgO from the recalcination furnace wet scrubber
   (this is MgO that was present as MgO in the
   first stage cake but not recovered in the
   furnace)

  MgO from the incineration furnace wet scrubber
   (this is MgO that was present as MgO in the
   second stage cake  but not recovered in the
   furnace)
XMGOSLG = the sum of the following terms:

(XMGHCAK1) * (REXMGOF) * (l.-FRBD)
 * (REXMGOCL) * (40./58.3)

(1.-REXMGOF) * (XMGHCAK1) * (40./58.3)
(l.-REXMGOFI) * (XMGHCAK2) * (40./58.3)



XMGO NEW

XMGOSLG * (1.-REXMGO1) * (1.-REXMGO2)

XMGOSLG * (REXMGO1) * (REXMGOF)
 * (REXMGOCL) * (l.-FRBD)

(XMGOSLG) * (1.-REXMGOF) * (REXMGO1)
(XMGOSLG) * (1.-REXMGO1) * (REXMGO2)
 * (1 .-REXMGOFI)
The equations in the right hand side of Table 10-7 can be summed up, and
solved for XMGOSLG, the equilibrium value for MgO in the primary sludge.
This results in:

     XMGOSLG =  ((XMGHCAK1) *  (REXMGOF) * (l.-FRBD)
                *  (REXMGOCL) * (40.758.3)  + (1.-REXMGOF)
                *  (XMGHCAK1) * (40.758.3)  + (XMGONEW)
                +  (l.-REXMGOFI)  * (XMGHCAK2)  * (40.758.3))
                /  (1.-REXMG01)  * (1.-REXMGO2)  *  (l.-FRBD)
               -  (1.-REXMGOF)  * (REXMGO1) -  (1.-REXMGOF)
                *  (REXMGO1)  - (1.-REXMGO1) *  (REXMGO2)
                *  (l.-REXMGOFI)
                                   (7)
                                        207

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This is the approach used to solve for the equilibrium mass values for all quan-
tities in the primary sludge.  The equations can be examined in the program
listing in Section XV. A.  The equation for MgO was used as an example because
it illustrates most of the concepts employed in solving for the mass equilibrium
values of each component.

Inert Materials

The inert components represented in the program are silicon dioxide  (SiC^) and
acid insoluble inerts (inerts other than SiO2) .  The inerts come into the primary
as part of the suspended solids and waste activated sludge solids,  as  impurities
in new (makeup) lime added to the primary,  and in the case of silica, as dis-
solved material in the raw sewage.   The method of solving for the equilibrium
values of SiC>2 and acid insoluble inerts in the primary sludge is similar to that
for MgO.  However, neither of the two inert components have hydroxide forms,
and it has been assumed that they behave as inerts in the furnace.

Tri Calcium Phosphate

Tri calcium phosphate  (Ca3 (PO^) 2) is assumed to behave as an inert material
during recalcination or incineration, and its  equilibrium value in the  primary
sludge is calculated by a similar approach as for the inerts and metal oxides.

Calcium Carbonate and Calcium Oxide

The calcium carbonate that precipitates in the primary sludge is calculated by
adding the calcium (as  calcium carbonate) in the raw influent sewage, the calcium
oxide (as calcium carbonate) in the total lime  (makeup plus recycle) ,  the calcium
carbonate from the centrate recycle, the calcium carbonate from the recycled
solids from the recalcine-classification operation, and the calcium  carbonate
returned to the primary in the wet scrubber water streams from both furnaces;
minus the amount of calcium precipitated by the phosphorus (as 033^04) 2)
which is removed in the primary, and minus the calcium (as calcium carbonate)
leaving in the primary  effluent.  In the recalcining furnace, if the recalcination
efficiency  is less than one, then some CaCOg will appear in the furnace product.
The recovery of calcium oxide in the recalcining furnace is assumed to be equal
to the recovery of CaC03, since CaCO3 is converted to CaO in the recalcining
furnace. Recalcine efficiency as a fraction is defined in terms of the split
between CaO and CaCO3 in the furnace products as follows:

    RECALEFF = CAOFP * (100./56.) / (CAOFP * (100./56.)  + (CACFP))

The CaO picked up by the wet scrubber is assumed to react to form CaCO3.
Hence the  CaC03 not recalcined in the furnace but lost out the stack, and the
CaO lost out the stack,  are both treated as CaCO3 in computing the loss of non-
phosphorus calcium to the furnace wet scrubber water.

It is assumed that there is no recalcination of CaC03 to CaO in the incinerator
furnace since this furnace is operated at a temperature lower than  the conver-
sion temperature (see Section VIII) .
                                    208

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The total lime dose required for a certain mode of operation is inputted to the pro-
gram as Ca(OH) 2, mg/1.  The program converts this dose to equivalent CaO for
computations.

The amount of each component that would precipitate in a once through primary
operation is calculated by the program.  In the case of CaCO3, the total lime dose
(recycled plus makeup)  would be considered as a chemical addition stream to the
primary in order to determine the amount of CaCC>3 that would precipitate in a
first pass situation.  The amount of calcium (as calcium carbonate) in the raw
sewage plus the calcium carbonate precipitated from total lime additions, minus
the calcium (as  CaCC^) lost to the effluent and to the precipitated Ca3(PC>4)2,
gives the calcium carbonate in the first pass precipitation.

MATERIAL BALANCES FOR SEVERAL CASES

Several cases were run on the computer, simulating various process modes of
operation.  The cases were  constructed using data on unit processes presented
in earlier sections of this report as well as other reports on the ATTF test work
(1, 2) .  Table 10-8 summarizes the process description for each case.  Most runs
were made simulating pH 11.0 operation,  with a primary flow rate of 1.31  cu m/
sec (30 mgd) , 400 mg/1 of Ca (OH) 2 as a total lime dose, and 14 mg/1 of FeCls
added to the primary. The  processing sequence was varied to simulate both
Plural Purpose Furnace and ATTF System cases,  employing one stage  (high
recovery)  or two stage (wet classification and dewatering) processing of
primary sludge. Other process options included or excluded in the cases were
dry classification and/or blowdown of recalcined furnace product.

Table 10-9 lists some of the important solids balance comparisons for various
solids processing cases.  At pH 11.0, with both wet classification and dewater-
ing of primary sludge solids,  comparisons were made using a solid bowl centri-
fuge for wet classification and either a solid bowl centrifuge, vacuum filter, or
filter press for the second stage dewatering step.  The solids processing
sequence employed for each case is described in Table 10-8 (100, 101 and 102) .

The use of pressure filtration for the second stage dewatering step has an advan-
tage over a solid bowl centrifuge or vacuum filter in that the amount of sludge
produced in the primary is  slightly less, because less solids are recycled back
to the primary from the dewatering step.  The amount of makeup lime  required
for each case is not significantly different.  Pressure filtration results in a
significantly drier second stage cake than either vacuum filtration or centrifu-
gation. This property results in less moisture to be evaporated (Table 7-11)
and less energy requirement for the second stage MHF (Table 8-18) .

In Plural Purpose Furnace cases 106, 114 and 116, dry classification as well as
a 20 percent blowdown of furnace product was  included.  The blowdown was
included to keep the amount of silica  produced in the primary  as low as possible
without wasting too much CaO.  Fig.  10-1 shows the effect of blowdown for a
Plural Purpose Furnace  case upon recovery of CaO.  The optimum operating
blowdown will depend on the economics for each situation. Fig.  10-2 shows the
effect of furnace blowdown on primary sludge production.  The amount of sludge
                                     209

-------
                       Table 1Q-8.  SOLIDS PROCESSING SEQUENCE OPTIONS FOR VARIOUS CASES
Case
a
no.
ioob

ioib

102b

106°

114°
116°
117b

120b

121b

122b

113°
112°

pH
11:0

11.0

11.0

11.0

11.0
11 .0
11.0

11.0

10.2

11.5

11.0
11.0

Ca(OH)2
dose,
mg/1
400

400

400

400

400
400
400

400

289

500

400
400

FeC13
dose,
mg/1
14.0

14.0

14.0

14.0

14.0
14.0
14.0

14.0

24.0

0.0

14.0
14.0

Processing options
Wet
classification
of
primary sludge
Solid bowl
centrifuge
Solid bowl
centrifuge
Solid bowl
centrifuge
Solid bowl
centrifuge
Vacuum filter
Filter press
Solid bowl
centrifuge
Solid bowl
centrifuge
Solid bowl
centrifuge
Solid bowl
centrifuge
Vacuum filter
Solid bowl
centrifuge
Recalcination
MHF

MHF

MHF

MHF

MHF
MHF
MHF

MHF

MHF

MHF

MHF
MHF

Dry
classification
of
recalcined ash
Yes

Yes

Yes

Yes

Yes
Yes
No

No

Yes

Yes

Yes
Yes

Slowdown ,
percent
0

0

0

20

20
20
0

28

0

0

0
100

Dewatering of
first stage
centrate
Solid bowl
centrifuge
Vacuum filter

Pressure filter
press
No

No
No
Solid bowl
centrifuge
Solid bowl
centrifuge
Solid bowl
centrifuge
Solid bowl
centrifuge
No
No

Incineration of
second stage
cake
MHF

MHF

MHF

None

None
None
MHF

MHF

MHF

MHF

None
None

NJ
M
O
             All plant flows at 1.31 cu m/sec (30 mgd)


             ATTF System Case - two-stage dewatering
             Plural Purpose Furnace Case - single stage dewatering

-------
              Table  10-9.  MATERIAL BALANCE COMPARISONS FOR VARIOUS SOLIDS PROCESSES CASES
Case
no.
100
101
102
106
114
116
117
120
121
122
113
112
pH '
11.0
11.0
11.0
11.0
11.0
11 .0
11.0
11.0
10.2
11.5
11.0
11.0
Primary
sludge
production,
kg per day
(Ib per day)
100,940
(224,312)
98,043
(217,875)
96,036
(213,414)
132,036
(293,415)
131 ,817
(292,928)
125,856
(279,680)
111,327
(247,394)
99,788
(221,752)
82,539
(183,421)
111,780
(248,401)
338,620
(752,489)
93,482
(207,738)
First stage cake to
recalclning
kg per day
(Ib per day)
62,977
(139,950)
62,104
(138,011)
61 ,653
(135,945)
126,204
(278,281)
126,204
(278,281)
126,204
(278,281)
72,162
(160,360)
62,283
(138,407)
42,803
( 95,119)
76,079
(169,066)
321,689
(714,865)
89,610
(199,134)
Percent
TS
58
58
58
24
28
44
58
58
42
58
28
24
Recycled
solids from
recalcinlng,
kg per day
(Ib per day)
29,962
( 66,583)
29,986
( 66,636)
29,579
( 65,733)
56,290
(125,089)
56,290
(125,089)
56,290
(125,089)
40,527
( 90,062)
22,406
( 49,792)
19,705
( 43,789)
37,161
( 82,580)
245,329
(545,177)
0
(0)
Recycled
solids from
dewatering
step ,
kg per day
(Ib per day)
4,837
(10,749)
2,156
( 4,792)
348
( 775)
6,810
(15,134)
6,590
(14,646)
629
( 1,398)
4,892
(10,873)
4,795
(10,657)
7,088
(15,752)
4,517
(10,039)
16,930
(37,624)
3,871
( 8,604)
Recycled
solids from
furnace wet
scrubbers ,
kg per day
(Ib per day)
4,844
(10,766)
4,805
(10,679)
4,793
(10,650)
6,828
(15,174)
6,828
(15,174)
6,828
(15,174)
5,069
(11,265)
4,741
(10,537)
3,259
( 7,243)
5,703
(12,675)
20,301
(45,115)
4,491
( 9,981)
Second stage cake to
incineration
kg per day
(Ib per day)
33,126
(73,614)
33,782
(75,073)
34,782
(76,694)
Q
(0)
0
(0)
0
(0)
34,272
(76,161)
32,709
(72,688)
32,647
(72,550)
31,182
(69,295)
0
(0)
0
(0)
Percent
TS
17
20
25
-
-
-
17
17
18
13
28
-
Furnace
ash to
disposal
kg per day
(Ib per day)
19,433
(43,186)
19,071
(42,382)
19,486
(43,302)
0
(0)
0
(0)
0
(0)
20,546
(45,658)
19,043
(42,318)
17,264
(38,365)
18,220
(40,491)
0
(0)
0
(0)
Makeup CaO
b
CaO,
kg per day
(Ib per day)
12, .786
(28,413)
12,583
(27,963)
12,786
(28,413)
13,494
(29,988)
13,494
(29,988)
13,494
(29,988)
12,359
(27,464)
18,611
(41,358)
12,729
(28,288)
15,001
(33,336)
8,085
(17,967)
34,039
(75,644)
Percent
of total
CaO dose
38.0
37.0
38.0
40.0
40.0
40.0
36.0
55.0
52.0
35.0
24.0
100.0
Dry
classifier
rejects,
kg per day
(Ib per day)
1,602
( 3,560)
1,598
( 3,553)
1,575
( 3,500)
17,364
(38,587)
17,364
(38,587)
17,364
(38,587)
0
(0)
0
(0)
1,484
( 3,299)
1,760
( 3,913)
11,101
(24,669)
0
(0)
Recalcination
furnace
blowdown
stream ,
kg per day
(Ib per day)
0
(0)
0
(0)
0
(0)
14,730
(32,735)
14,730
(32,735)
14,730
(32,735)
0
(0)
8,713
(19,363)
0
(0)
0
(0)
0
(0)
41,184
(91,521)
I\J
        Includes CaO.
        Basis 89 percent CaO.

-------
generated in the primary increases sharply as percent blowdown is decreased
from about 20 percent to zero percent.  Figs. 10-1 and 10-2 are based on cases

103-112, presented in Section XV. B.
     1-0
UJ
t/>
o
Q

Q
o
O
     0-8
  fe  0-6

  z
  o
  o

  o:  0 .4
  u_

  o
  o
  O

  Q
  6
  UJ
  cr
                  0.2         0.4        0.6

                         BLOWDOWN  FRACTION
                                                   0-8
1-0
            Figure 10-1 Effect of blowdown on recovered CaO
For the Plural Purpose Furnace cases 106, 114, and 116 in which there is a high

recovery step for dewatering primary sludge, followed by furnaces for both

combined recalcination and incineration of cake solids, there is more sludge

production in the primary than for any of the three ATTF System cases (100,

101, and 102) when the makeup lime requirement is comparable. The mass of
                                  212

-------
  800,000
   700,000
   600,000
CD
   400,000
   200,000
   100,000
360,000
315,000
270,000
                                                                225,000
180,000
                                                               135,000
                                                               90,000
                                                               45,000
         0         0.2        0.4        0.6       0.8        10

                          SLOWDOWN  FRACTION
    Figure 10-2  Effect of blowdown on primary sludge production for
                 cases  103-112
                                   213

-------
cake solids to be fed to the Plural Purpose Furnace is greater than the combined
amount of first and second stage cake fed to the two furnaces for the ATTF
System cases.  Further, considering the dryness of the cakes produced,  there is
more water to be eliminated for the Plural Purpose Furnace cases than the ATTF
System cases (Table 7-11) .

A basis for judging  the effectiveness of wet classification is presented by the
computer output listed in Section XV. B .  For case  117, the solids that would be
produced on a single pass through the primary are 82,527 kg/day (183,395
Ib/day) .   Recycle streams increase primary sludge  production to 111,327 kg/day
(247,394 Ib/day) .  Thus, 28,799 kg (63,998 Ib) of unwanted solids are returned
to the primary sedimentation tank amounting to 26 percent of the solids appear-
ing in the underflow.   Insertion of dry classification improves the picture consi-
derably (Case 100,  Section XV. B) .  Single pass precipitation for this case is
82,579 kg/day (183,509 Ib/day) with recycle streams increasing primary sludge
production to 100,940  kg/day (224,312 Ib/day) .  In  this  case unwanted solids
appearing in the primary underflow is 18,361 kg/ day (40,803 Ib/day) , amount-
ing to 18 percent of  the underflow solids.  The improvement over case 117 is
primarily  due to increased silica blowdown attributable to the dry classifier.

The beneficial effect of the dry classification step is portrayed in Table 10-10.
Case 100 is an ATTF System  case with dry classification  whereas, in case 117,
the dry classification step has been omitted.  As can be deduced from the table,
silica builds up to quite high levels (31 percent as SiC^)  in the  recalcined pro-
duct without dry classification;  when dry classification is employed the silica
is reduced to only 10 percent (as SiC^) of the recalcined product.  Silica in the
recalcined product can also be reduced by blowing down directly from the
furnace product, instead  of by dry classification (case 120, Table 10-10) . By
using 28 percent blowdown,  the silica content can be reduced to 13 percent.
However,  this  is accomplished at the expense of lime consumption. The per-
centage recycled lime  decreases from 62 to 45 percent.

Two other cases were  included in Table 10-10, employing pH values of 10.2 and
11.5 in the primary.  In Case 121, (pH 10.2) because of  increased difficulty of
classifying and dewatering the sludge, the percentage of makeup lime is signi-
ficantly higher than for a similar processing sequence at pH 11.0 (Case 100) .
At pH 11.5 in the primary (case 122) , sludge wet classification and dewatering
are slightly improved  over the pH 11.0 operation, and the percent of makeup
lime required is slightly lower than for the similar operation at pH 11.0 (case
100) .  The actual mass of makeup lime at pH 11.5 is  greater than that required
for  pH 11.0 operation because of the higher total lime dose needed to reach pH
11.5.

Comparisons between  operation at pH 10.2, 11.0 and 11.5 are interesting (Cases
121, 100 and 122 respectively in Table 10-10) .  Twenty-two percent more solids
are generated in the primary at pH 11 than 10.2, while 35 percent more are
generated at pH 11.5 than 10.2.  The effect of increased  sludge production is
primarily felt in the recalcination furnace; increased doses of lime increase the
quantity of calcium carbonate to be recalcined.  It is noticeable that the second
stage cake to be incinerated stays fairly constant, despite changes in pH levels
between cases.
                                    214

-------
 Table  10-10. CALCULATED SOLIDS BALANCES FOR CASES 100, 117,
              120, 121 and 122
Parameter
pH
Ca(OH) dose, mg/1
FeOlj, mg/1
Recycled lime , percent
Recalcined product blowdown , percent
Ash classification
Primary sludge , kg/day
(Ib/day)
Organics
CaCO3
sio2
Ca3(P°4'2
OtherC
Total
First stage cake, kg/day
(Ib/day)
Organics
CaCO
sio2
Ca3(P04,2
OtherC
Total
Recycled solids , kg/day
(Ib/day)
CaO
CaCOj
S102
Ca3(P04)2
Other1"
Total
Second stage cake, kg/day
(Ib/day)
Organics
CaCO3
sio2
Ca3(P04>2
OtherC
Total
Solids processing case no.
iooa
11.0
400
14
62
0
Yes
26,222
( 58,272)
53,087
(117,972)
4,523
( 10,053)
7,651
( 17,003)
9,455
( 21,012)
100,938
(224,312)
10,489
( 23,309)
43,797
( 97,327)
4,071
( 9,047)
1,530
( 3,401)
3,089
( 6,866)
62,976
(139,950)
21,257
( 47,239)
2,003
( 4,453)
3,036
'( 6,747)
1,376
( 3,059)
2,288
( 5,085)
29,960
( 66,583)

12,271
( 27,271)
9,197
( 20,439)
438
( 975)
5,508
( 12,242)
5,709
( 12,687)
33,123
( 73,614)
117b
11.0
400
14
64
0
No
26,222
( 58,272)
53,124
(118,054)
14,418
( 32,042)
7,742
( 17,206)
9,819
( 21,821)
111,325
(247,394)
10,489
( 23,309)
43,827
( 97,394)
12,976
( 28,837)
1,548
( 3,441)
3,320
( 7,379)
72,160
(160,360)
21,684
( 48,187)
2,038
( 4,529)
12,717
( 28,261)
1,455
( 3,235)
2,632
( 5,851)
40,526
( 90,062)

12,271
( 27,271)
9,203
( 20,453)
1,398
( 3,108)
5,575
( 12,389)
5,823
( 12,941)
34,270
( 76,161)
120b
11.0
400
14
45
28
No
26,222
( 58,272)
52,490
(116,646)
4,562
( 10,139)
7,184
( 15,965)
9,337
( 20,750)
99,795
(221,752)
10,489
( 23,309)
43,304
( 96,233)
4,106
( 9,125)
1,436
( 3,193)
2,946
( 6,547)
62,281
(138,407)
15,426
( 34,281)
1,449
( 3,222)
2,897
( 6,439)
972
( 2,161)
1,660
( 3,689)
22,404
( 49,792)

12,271
( 27,271)
9,094
( 20,209)
442
( 983)
5,172
( 11,495)
5,728
( 12,730)
32,707
( 72,688)
121a
10.2
289
24
48
0
Yes
27,923
( 62,052)
33,948
( 75,441)
4,938
( 10,975)
7,971
( 17,714)
7,757
( 17,239)
82,537
(183,421)
9,773
( 21,718)
24,443
( 54,318)
4,445
( 9,878)
2,072
( 4,606)
2,069
( 4,599)
42,802
( 95,119)
11,863
( 26,364)
1,118
I 2,485)
3,315
( 7,367)
1,864
( 4,143)
1,543
( 3,430)
19,703
( 43,789)

14,157
( 31,461)
7,889
( 17,532)
400
( 889)
5,485
( 12,191)
4,715
( 10,478)
32,646
( 72,550)
122a
11.5
500
0
65
0
Yes
25,225
( 56,057)
65,996
(146,659)
4,738
( 10,531)
7,693
( 17,096)
8,126
( 18,058)
111,778
(248,401)
10,342
( 22,983)
56,757
(126,127)
4,312
( 9,583)
1,769
( 3,932)
2,898
( 6,440)
76,078
(169,066)
27,547
( 61,217)
2,596
( 5,771)
3,216
( 7,147)
1,591
( 3,537)
2,208
( 4,908)
37,158
( 82,580)

11,608
( 25,797)
9,147
( 20,327)
413
( 919)
5,331
( 11,847)
4,681
( 10,404)
31,180
( 69,295)
a Dry classifier in operation.

 No dry classifier in operation.
                                  215

-------
                          REFERENCES - SECTION X
1.   Brown and Caldwell, Consulting Engineers.  Lime Sludge Recycling Study.
    Prepared for the Central Contra Costa Sanitary District, Walnut Creek,
    California, June 1974.

2.   Parker, D.S., K.E. Train and F.J. Zadick.  Sludge Processing for Combined
    Physical-Chemical-Biological Sludges.  U.S. Environmental Protection Agency,
    Washington, D.C.  Report Number EPA-R2-73-250, July 1973. 141 p.
                                  216

-------
                                  SECTION XI

                          ULTIMATE DISPOSAL OF ASH
Although incineration of wastewater sludges greatly reduces the volume of waste
material, it produces an end product, ash,  for which a final place must be found
before the solids disposal problem can be considered solved.

ASH CHARACTERISTICS

The term "ash" is somewhat loosely applied to various waste products of inciner-
ation and related processes.  Apart from the most common use of the name  (the
solid product of combustion discharged at the bottom of multiple hearth  furnaces)
dust particles,  carried with the off-gases and captured in dry cyclones or re-
moved in a wet scrubber, are sometimes referred to as ash.  Finally, the  rejects
from the dry classification process described in Section VIII, can also be consi-
dered as ash, although they contain reactive lime. Each of  these ash-like pro-
ducts  is handled in a different way but all would eventually converge in a
common waste stream to be  carried to the point of ultimate disposal.

Gerlich and Rockwell^ have characterized the physical properties of wastewater
sludge ash discharged from a MHF .  The data are shown in  Table  11-1. The
physical and chemical properties  of the ash are likely  to vary from plant to
plant.  These differences are due to sludge characteristics, use of chemical
conditioners, type of incinerator and combustion temperature.  This variation
is illustrated in Table 11-2, which shows particle size distribution of ash from
three  wastewater treatment plants.2  Gerlich and Rockwell^ have also reported
the results of particle size analyses of sludge ash. These results  are shown in
Fig. 11-1.

As was mentioned before, combustion ash from a FBR is removed in a wet
scrubber.  Ash is then separated  from the scrubbing water  in a hydrocyclone.
A particle size analysis of the dried cyclone underflow is given in Table 11-3.3

USES  OF SLUDGE ASH

Since  in wastewater treatment plants practicing sludge incineration there is a
continuous supply of the waste product of combustion, attempts have been made
from time to time to find a use for  it. So far these efforts have been mostly
directed towards using ash as a sludge conditioner prior to mechanical  dewater-
ing,l,2 although ash from the organic sludge furnace was experimentally used at
South Tahoe to  condition flotation  thickened mixtures of primary,  waste activated
and lime sludges prior to incineration. 4  Sludge ash has also been tried as raw
material for the phosphate industry5 and as a construction material.6
                                    217

-------
       Table 11-1. PHYSICAL PROPERTIES OF SLUDGE ASH
       Specific gravity
       Bulk density, kg/cu m (Ib/cu ft)
       Color
       Mean particle size,  mm
       Range of particle size, mm
2.63-2.78
 800 (50)
 Yellow
   29
 22-40
Table 11-2. CLASSIFICATION OF ASH PARTICLES BY "BAHCO" MICRO
           PARTICLE SIZE ANALYZER
                                Percent of given size
Effective particle
size (10~3 mm)
0.00 0.92
0.92 1.60
1.60 2.97
2.97 - 7. 71
7.71 - 12.19
12.19 - 20.75
20.75 24.72
24.72 27.30
>28.38
<420.
Kansas City
1.49
2.95
5.70
9.05
14.56
22.41
9.21
8. 83
25. 80

Lake Tahoe
1.38
2.71
7.53
9. 83
10.95
16.20
10.13
4.28
36.99

Millcreek
2.22
3.70
7.81
21.86
26.52
22.46
6.83
8.60
CO 0

           Table 11-3. PARTICLE SIZE OF "FBR" ASH
Mesh
48
65
100
150
200
325
-325
Microns
295
208
147
104
74
43
-43
Retained
%
2.07
9.7
37.0
43.6
46.6
61.8
38.2
                             218

-------
          100
       LU

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    50


    40


    30


z   20
LL)
CJ

S   10
Q.
                  4  5 6  7 8   10        20    30  40 50
                         MICRON  DIAMETER  (yu)
                                                       100
       Figure 11-1 Particle size analysis of wastewater sludge ash
Although ash conditioning of wastewater sludges has experienced limited
success, the results so far are inconclusive and even conflicting . 1 /2 Moreover,
this application cannot be  considered a method of disposal.  The portion of ash
added to the sludge is recycled through the dewatering-incineration process
while the remaining still has to be disposed of.  Also worth noting is the fact
that ash acts as an inert filler, thereby lowering the heat content of the sludge
cake. This will tend to  offset some of the benefits of improved solids dewatering
on the cost of sludge incineration.

Obferkuch, et al.^ prepared an economic analysis of the commercial uses of ash
and sludges  generated in wastewater treatment plants using lime treatment.  In
the evaluation of sludge (or ash) for agricultural uses, it was concluded that
the product had no economic value in comparison to commercial  products
(aglime, agrock,  and  fertilizers) , but that it could be given away to farmers.
In fact,  uses of sludge for agricultural purposes is a common practice in the
U.S. and abroad and is, in many cases, an economically feasible method of
sludge disposal.
                                    219

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In their evaluation of sludge (or ash) as a product for the phosphate industry,
Obferkuch, et aL concluded that the cost of processing the sludge far exceeded
the value of the product.

Since the physical and chemical composition of sludge ash is not greatly different
than the composition of coal fly  ash, Gray and Penessis6 conducted a study to de-
termine if the former could be used as a construction material.  Fly  ash has long
been successfully used in road  subbases, lightweight back-fills and load-
bearing fills.  Other uses of fly ash  include building block material, concrete
additive and soil stabilizer.  Physical, chemical and engineering properties
determined by Gray and Penessis  included "grain size distribution, chemical
and mineralogic composition, specific gravity, leachate composition, compaction-
strength characteristics, frost heave behavior, and  response to Portland cement
stabilization".  Ash samples  were obtained from eight wastewater treatment plants.
The tests conducted on compacted ash samples showed the suitability of sludge
ash as a load-bearing fill, however, ash would have to be stabilized with Portland
cement before  use in subbases  and structural fills.  Cement addition requirements
ranged from 3 to 7 percent.6 Significantly, it was concluded that ash from treat-
ment plants using lime for flocculation and sludge conditioning, would have
improved  strength and durability after wetting and compaction.

Although the potential use of sludge ash appears  encouraging, actual use of this
product has been limited. Local market conditions and acceptability of ash as a
suitable construction and building material are two of the factors more likely to
influence its useful application. In the  great majority of installations, sludge
ash remains a  waste product to be disposed of.

ASH HANDLING PRIOR TO DISPOSAL

Ash produced  during sludge incineration can be  handled in dry or in wet form.
Dry ash is discharged from a MHF, from dry cyclones and as  rejects from the
air classification process (see Section VIII) .  Wet ash is discharged  from wet
scrubbers.

Dry Ash Handling

Ash from the MHF, often after grinding and cooling, can be handled in pneu-
matic or mechanical conveyors. The same devices can be used to convey ash
collected in dry cyclones and rejected by air classifiers.  The conveyors
normally transport the waste product to storage bins,  from which it  is loaded
into trucks and carried to the disposal site.  To avoid dusting, the dry ash is
normally wetted before being loaded. The screw conveyor transferring  the
product from storage to truck is often used for the wetting operation, since
spray nozzles  can be easily installed on the conveyor.

Wet Ash Handling

The handling of wet ash usually follows an elaborate path. In the fluidized bed
calciner shown in Fig.  8-6, the underflow of the  ash thickener, which contains
most of the inert product, is  pumped to a vacuum filter for dewatering.  The
                                     220

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ash cake is then ready for final disposal.  In the FBR used for sludge incinera-
tion, ash removed in the wet scrubber is separated from the scrubbing water in
a hydrocyclone. The cyclone underflow is then dewatered in  a rake type classi-
fier from which it is  discharged to a storage hopper or to a truck parked under-
neath .

Dry ash discharged at the bottom of a MHF can also be handled in wet form.  The
hot product discharges into a quench tank where cooling water is added.  The ash
slurry thus formed is subsequently pumped to the disposal site.  Abrasion-
resistant pumps, of the type used to handle grit slurries, are recommended for
this application.

When wet scrubbing  is the last step in the dust collection train,  the amount of ash
removed in the scrubber can be expected to be small and the scrubbing water can
be discharged to the drainage system and returned to the influent end of the
plant.  This is often  the case in a MHF installation (see Fig. 8-11) .

FINAL  DISPOSAL SITES

When a beneficial use is not found, sludge ash is normally disposed of in land-
fills or in lagoons.  The former is generally  associated with dry transport while
the latter is used when ash is handled as a slurry.  Dry ash deposited in a
landfill should be covered before the water added during loading evaporates and
the dried ash causes a serious dusting problem.  Ash lagoons are similar to
conventional sludge  lagoons,  although the potential odor problem associated with
the latter does not exist in ash lagoons.  As shown in Table 11-1, sludge ash has
a high specific gravity and will settle rapidly in the lagoon. As long as a layer
of water is kept over the settled ash, the possibility of drying and dusting is
eliminated.
                                     221

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                         REFERENCES - SECTION XI
1.   Gerlich, J.W.,  and M.D. Rockwell.  Pressure Filtration of Wastewater Sludge
    with Ash Filter Aid. U.S. Environmental Protection Agency, Washington, D.C.
    Report No. EPA-R2-73-231. June 1973. 153 p.

2.   Smith, I.E., S.W. Hathaway,  J.B. Farrell and R.B. Dean. Sludge Condi-
    tioning  with Incinerator Ash.  (Presented at the 27th Purdue Industrial
    Waste Conference, May 2-4, 1972) .

3.   Albertson, O.E.  Low Cost Combustion of Sewage Sludges.  (Presented at
    the 35th Annual Conference of the Water Pollution Control  Federation.
    October 8, 1963) .

4.   Gulp, R.S ., and G.L. Gulp.  Advanced Wastewater Treatment. First
    Edition. New York, Van Nostrand Reinhold Company,  1971.  310 p.

5.   Obferkuch, R.E., T. Ctvrtnicek, and S.M. Mehta. Study of Utilization
    and Disposal of Lime  Sludges Containing Phosphates. U.S . Environmental
    Protection Agency, Washington, D.C.  Project #17070FBE. March 1972.
    78 p.

6.   Gray, D.H., and C. Penessis.  Engineering Properties  of Sludge Ash.
    Journal of the Water Pollution Control Federation.  44: 847-858, May 1972.
                                    222

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                                  SECTION XII

                       DEVELOPMENT OF COST ESTIMATES
GENERAL CONSIDERATIONS

It has been customary practice to present cost data in the form of cost curves
relating a given design parameter, such as flow,  organic loading,  etc., to a
certain type of cost, such as construction, capital, annual, etc.  The curves are
generally adjusted to a common base year through a cost index.  Among these,
the Engineering News Record (ENR)  Construction Cost Index is the most widely
used. Although useful for preliminary cost estimates to compare engineering
alternatives, there are practical limitations to the use of cost curves.  The curves
normally reflect average  conditions and therefore do not reflect the influence of
several important factors .  These factors include  soil conditions , architectural
and landscaping treatment, allowances for future  expansion, local  labor condi-
tions, degree of automation, process sophistication, etc.  With regards to new
treatment processes, another important drawback of cost curves is the limited
availability of actual construction and operation and maintenance cost data from
which the curves  may be constructed,  since many of these plants are still in the
planning and design stages.

In view of the factors considered above, a Case Example format has been deter-
mined to be a more suitable approach for this report.  Since the water reclama-
tion plant for the Central Contra Costa  Sanitary District (CCCSD) ,  California,
was bid in  June 1973, actual construction costs for many of the main processes
described in the preceeding sections are now available and can be  readily
adjusted to reflect present economic conditions.  Construction costs are broken
down in this section by unit operations, i.e.,  chemical addition, flocculation
and sedimentation; centrifugation; etc.  To present variations in the basic flow
sheet, alternate units are substituted for the original ones; for example,  centri-
fuges have  been replaced by vacuum filters and filter presses.

Detailed engineering cost estimates were also available for another advanced
treatment plant, the Lower Molonglo Water Quality Control Centre in Australia.
Estimates from this facility have been used to illustrate the cost difference
between solids-contact lime reactors and rectangular flocculation and sedimen-
tation tanks.

Operating costs are based on chemical  use, installed horsepower,  and fuel con-
sumption where applicable.  Fuel use has been based on materials  and heat
balances similar to those developed in Section VIII and presented in an engineer-
ing report.1 With the exception of calcination and incineration processes, where
the continuous presence of an operator is normally required by codes, it is difficult
to assign a  cost value to operator attendance since this is a direct function of the
degree of automation provided,  which varies  widely from plant to plant.  As an
example, the CCCSD water  reclamation plant is entirely controlled  by a computer-
                                      223

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                                                                          o
based system and most processes are continuously monitored by the computer >
The presence of an operator for control purposes is therefore not required.  This
is certainly not the case in smaller or less sophisticated facilities where conven-
tional analog instruments are used or manually controlled units have been
provided.

Wherever possible,  maintenance costs have been based on the equipment manu-
facturer's recommendations for preventive maintenance frequency and procedures.
It should be pointed out that, with the possible exception of the largest treatment
plants, equipment maintenance is performed by the plant operators;  consequently,
for smaller plants a portion of the manpower requirements for preventive main-
tenance is included  under operation attendance.

THE LOWER MOLONGLO WATER QUALITY CONTROL CENTRE

The Lower Molonglo Water Quality Control Centre is an advanced treatment facility
for the Australian Capital territory. Initial dry weather flow capacity of the  plant
is 109,000 cu m/day (28.8 mgd) , practically equal to the capacity of the CCCSD
water reclamation plant. The treatment processes include lime coagulation for
phosphorous and  solids removal; nitrogen removal by a modified nitrification-
denitrification system; dual  media filtration for removal of virus and residual
suspended solids; effluent disinfection;  wet classification and solids dewatering
by centrifugation; lime reclamation; and solids disposal by incineration.

Originally, design of the plant included solids-contact clarifiers and ammonia
stripping towers for nitrogen removal.3  Subsequently, limitations of the
ammonia stripping process led to its replacement by a modified nitrification-
denitrification process.4 Also, the dry  classification of recalcined lime initially
considered, was replaced by a combination of wet and dry classification, based
on the experimental worked  conduct at the CCCSD's ATTF (see Sections VII and
VIII) .  The solids-contact lime reactors were substituted with rectangular sedi-
mentation tanks.  This change was also based on results obtained at the ATTF.5
Design parameters for both types of flocculation-sedimentation tanks are given
in Table 12-1.

The two design reports on the Lower Molonglo WQCC included detailed  engineer's
estimates of construction costs of the proposed facilities. Costs were based on
bidding conditions prevailing in Australia in June 1970.  Table 12-2 shows costs
in Australian dollars for both types of flocculation-settling basins.  Since the
purpose is to compare these  two  alternatives, the  figures given in Table 12-2
have not been converted to American dollars nor adjusted to reflect present
construction costs.  However, it can be  seen that  rectangular tanks  are consi-
derably less costly than solids-contact clarifiers.  Although the original Lower
Molonglo WQCC design contemplated solids dewatering by vacuum filtration
following gravity  thickening; and therefore, the proposed processes did not
include grit removal;  grit removal chambers ahead of the primaries  have been
added to the cost of  the solids-contact clarifiers alternative in Table 12-2, to put
the comparison on an equal treatment basis .
                                      224

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 Table  12-1 .   DESIGN  DATA FOR FLOCCULATION
                AT THE  LOWER  MOLONGLO WQCC
                    SEDIMENTATION BASINS
                     Parameter
         Solids-contact
           clarifier
Rectangular flocculatlon
  sedimentation tanks
  Lime dosage, mg/1 as CaO

  Solids - contact clarifiers
    Number
    Diameter, m (ft)
    Depth,  m (ft)
    Effective surface area each, sq m (sq ft)
    Overflow rate at ADWF,  cu m/day sq m (gpd/sq ft)
    Detention time in flocculation zone at ADWF,  min
    Detention time at ADWF,b hr
    Hydraulic capacity each, 1, 000 cu m/day (mgd)

  Preaeration-grit removal tanks
    Number
    Width,  m (ft)
    Length, m (ft)
    Average depth, m (ft)
    Detention time at ADWF,b min

  Primary sedimentation tanks
    Number
    Width,  m (ft)
    Length, m (ft)
    Average depth, m (ft)  ,
    Overflow rate at ADWF,  cu m/day sq m (gpd/sq ft)
    Detention time at ADWF,b hr
    Hydraulic capacity each, 1,000 cu m/day (mgd)
             250
          42.7   (140)
           6.1    (20)
         1,208 (13,000)
          24. 9   (610)
             20
             5.8
           125    (33)
                                   250
                                 9.1 (30)
                                24.1 (79)
                                 4.0 (13)
                                   24
                                11.9 (39)
                                67.1 (220)
                                 2.9 (9.5)
                                28.8 (705)
                                   2.1
                                 151 (40)
  , Preaeration and grit removal tanks used for flocculation.
   Average dry weather flow.
Table 12-2.  COST COMPARISON  BETWEEN SOLIDS-CONTACT CLARIFIERS
               AND RECTANGULAR FLOCCULATION-SEDIMENTATION TANKS
         Cost item
Solids-contact
   clarifiers
  Rectangular
      tanks
     Solids separation

     Preaeration -
          grit removal

          Total, A.$
   1,035,000


     602,000

   1,637,000
       753,000


       602,000

    1,355,000
                                            225

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THE CCCSD WATER RECLAMATION PLANT

The water reclamation plant is a 114,000 cu m/day  (30 mgd) facility scheduled
for completion in 1976. Once in operation, the plant will produce water for
industries located along the southern shore of Suisun Bay, in the Sacramento
River estuary.  In  1972 the CCCSD completed contract negotiations with the
Contra Costa County Water District (CCCWD) for the purchase of an  estimated
72,000 cu m/day (19 mgd) increasing by 1980 to an average of 91,000 cu m/day
(24 mgd) with a peak daily use of 121,000 cu m/day (32 mgd) . Industries will
use about 75 percent of the reclaimed water for cooling and the remainder for
process purposes.   Reclaimed water that is produced in excess of industry's
needs will be discharged  directly to Suisun Bay.  A flow diagram of the CCCSD
water reclamation plant is shown in Fig. 12-1.  As stated in Section VI, lime is
added ahead of the preaeration and grit removal tanks. A brief description of
the plant units associated with lime treatment,  recovery and reuse is given below.

Liquid Processing

After bar screening and influent pumping, combined preaeration and grit removal
will be obtained in two reinforced concrete tanks designed to provide a detention
time of 20 minutes at average  dry weather flow. Air at the rate of 0.08 to 0.16 cu
m/min (3 to 6 cfm)  per foot of tank length will be introduced along the  side of
each tank through header pipes fitted with air diffusion units.  Grit will be
removed as a result of the currents set up by the rising column of air and
deposited in hoppers under the air piping.  Material in the hoppers  will  be
pumped directly to cyclonic separators located in the  solids conditioning
building.  After dewatering, grit will be conveyed to the sludge incineration
furnace. Lime will be added to the wastewater flow in the distribution channel
feeding the preaeration and grit removal tanks. Lime  coagulation of the waste-
water will be performed in the air-stirred preaeration tanks.

Primary sedimentation will take place in four rectangular reinforced concrete
tanks.  Each tank is designed for a detention period of 2.2 hours  and an over-
flow rate of 31.8 cu m/day/sq m (780 gpd/sq ft) at average dry weather flow
conditions.  Each sedimentation tank will be equipped  with two longitudinal
sludge collection mechanisms  and a cross collector.  After collection at the
influent end of the tanks,  the  lime sludge will be removed by positive displace-
ment pumps and pumped first to the sludge thickening tanks.  From  there, it
will be discharged  at a constant rate to the solids dewatering and incineration
processes.   Scum collected on the water surfaces in the sedimentation tanks will
be moved to the inlet ends by water jets and removed from the tanks by skimming
mechanisms which will drop the accumulated material to a receiving  sump.  From
here,  primary scum will be pumped to a scum concentrator at the solids condi-
tioning building .  Thickened  scum will then be incinerated .

Solids  Processing

The solids processing systems consist of processes for classification and dewa-
tering of the primary sedimentation tank underflow; scum and grit dewatering;
recalcining of the calcium carbonate-rich solids discharged from  the centrifuge
                                    226

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to
                          Figure 12-1 .  Flow diagram of the CCCSD water reclamation plant.

-------
classification stage; and incineration of the solids discharged from the dewater-
ing stage, together with the dewatered scum and grit.  Two of the existing sludge
digestion tanks will be used as storage and thickening tanks for the sludge under-
flow from the primary sedimentation tanks. The modified tanks consist of circular
reinforced concrete tanks  18.9 m  (62 ft) in diameter and side water depths of 7.2
m (23.5 ft)  and 9.9 m (32.5 ft) .

The solid-bowl centrifuges will operate in series.  The first stage centrifuges
will classify or separate the phosphorus and organic solids from the calcium
solids, and the second stage centrifuges will dewater the centrate discharged
from the first stage centrifuge.  The calcium solids discharged in the cake from
the first stage centrifuges will be recalcined in multiple hearth furnaces,  and the
undesirable chemical precipitates and organic  solids will be discharged in the
centrate.  The second stage dewatering centrifuges will produce a centrate of
high clarity, and the cake will be discharged to the sludge, scum, and grit
incinerating furnace.

The multiple-hearth furnaces will be equipped with sufficient drying, combustion
and cooling hearths to provide odor-free operation and complete combustion of
all organic material. The  temperature in the combustion zone will be automati-
cally controlled to ensure  efficient combustion, and each incinerator will be
equipped with a full complement of safety controls.  The furnaces are  designed
for recalcining of lime sludge as well as for combustion of organic material.  All
gases of combustion will be afterburned at 760 C (1400 F) and scrubbed in dry
scrubbers.  Waste heat boilers will be used to  recover heat in the form of steam.
The exit gas from the boilers will be cooled in  wet scrubbers and, when
necessary, reheated prior to release to the atmosphere to prevent the formation
of a vapor plume on cold days .

Recalcined lime from the furnaces will be conveyed pneumatically to lime storage
bins located in the chemical storage area.  Sufficient storage volume will be pro-
vided for a full week's  supply of lime, and makeup lime  may be added to the
storage bins through a pneumatic  delivery system from bulk delivery trucks or
rail cars.  Lime will also be conveyed pneumatically from storage to the lime
feeders and slakers. The  slakers and the automatically  controlled gravimetric-
type feeders will be located just above the distribution channel feeding the
preaeration and grit removal tanks.

Table 12-3 shows the design data for the processes described in the preceeding
paragraphs.  Some differences will be noted in the solids loads as indicated in
Table 12-3 and the current solids  balance for the system (Case 100, Section XV) .
These reflect the estimates prevailing  at the time of design vs. the post design
estimates prevailing currently.  Design values are shown in Table 12-3, since
they were the basis of design.

COST ESTIMATES FOR THE CCCSD WATER RECLAMATION PLANT

    Detailed cost estimates will be presented for the following processes:

    1.   Lime addition, flocculation and sedimentation.
                                     228

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Table 12-3.   DESIGN DATA FOR;CCCSD WATER RECLAMATION  PLANT


       Design Loadings - Stage 5A

       Population served, thousands                                       310
       Flow contribution, 1 pcd (gpcd) (industrial flow not included)            303        (80)
       Flow
          Average dry weather cu in/day (mgd)                          113,550        (30)
          Maximum dry weather cu m/day (mgd)                        181,680        (48)
          Peak wet weather cu m/day (mgd)                             529,900       (140)
       Loadings
          BOD,  1,000 kg/day (1,000 Ib/day)                               24.5        (54)
          BOD,  including recycle 1,000 kg/day  (1,000 Ib/day)               27.2        (60)
          Suspended solids, 1,000 kg/day (1,000 Ib/day)                    27.2        (60)
          Suspended solids, including recylcle,  1, 000 kg/day (1, 000 Ib/day)   32.7        (72)
          Total nitrogen as N, mg/1                                      30
          Total phosphorus as P, mg/1                                    11
        Preaeration, Flocculation,  Grit Removal

       Tanks
          Number, one existing                                             2
          Width, m (ft)                                                   9.1        (30)
          Length,  m  (ft)                                                 18.8      (61.5)
          Average  water depth, m (ft)                                      4.6        (15)
          Design capacity,  cu m/day (mgd)                             113,550        (30)
          Detention time, ADWF, hr                                     0.33
          Max hydraulic capacity,  cum/day (mgd)                      283,875        (75)
          Air supplied, cu  m/m (cu ft/gal)                                 0.74      (0.10)
        Grit pumps
          Number                                                          6
          Capacity, each unit,  I/sec (gpm)                                 12.6       (200)

        Primary Chemical Feed Equipment
        Lime slaker hopper
          Number                                                          3
          Capacity, each unit,  cum (cu ft)                                  2.1        (75)
        Lime feeder
          Number                                                          3
          Type                                                      gravimetric
          Capacity, each unit,  kg (Ib) CaO per hour                       3.630     (8,000)
        Lime slaker
          Number                                                          3
          Type                                                         paste
          Capacity, each unit,  kg (Ib) CaO per hour                       3,630     (8,000)

        Primary Sedimentation

        Tanks
          Number, two existing                                             4
          Width, (ft)                                                      H-6        (38)
          Length,  (ft)                                                    77.4       (254)
          Average water depth, (ft)                                        2.9       (9.5)
          Detention time, ADWF, hr                                      2.2
          Overflow rate, ADWF, cu m/day/sq m (gpd/sq ft)                 31.8       (780)
          Mean forward velocity, m/min (ft/min)                           0.58       (1.9)
          Design capacity,  each tank, cu m/day (mgd)                     37,850        (10)
          Max hydraulic capacity, each tank, cu m/day (mgd)            141,938       (37.5)
          Effluent  collection pipes
             Number per tank                                               4
             Diameter,  cm (inch)                                          50-8        (2°)
        Primary sludge pumps
          Number                                                          4
          Capacity, each unit,  l/sec(gpm)                                  12.6       (200)
        Primary sludge recirculation pumps
          Number                                                          2
          Capacity, each unit,  I/sec (gpm)                                  3-8        (6°)
        Primary scum pumps
 	Capacity,  each unit. I/sec (gpm)   	3. 8	(6.0J	


                                           (continued)
                                                229

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Table  12-3.   DESIGN  DATA  FOR THE CCCSD  WATER RECLAMATION

       	PLANT  (CONTINUED)	

     Primary Treatment Performance

     BOD removal
       Percent                                                         70
       1,000 kg/day (1,000 Ib/day)                                      19-1         (42)
     Suspended solids removal
       Percent                                                         70
       1,000 kg/day (1,000 Ib/day)                                      22.7         (50)

     Primary Effluent
       BOD, 1,000 kg'/day (1,000 Ib/day)                                 8.2         (18)
       Suspended solids, 1,000 kg/day (1,000 Ib/day)                       10         (22)

     Sludge Thickening

     Primary sludge thickener (existing digester)
       Tanks
           Number                                                       1
           Diameter,  m (ft)                                             18.9         (62)
           Side water depth,  m (ft)                                       5.84      (19.17)
           Surface area, sq m (sq ft)                                     280      (3,020)
           Volume, each tank, 1,000 cu m(1,000 cu ft)                      1.7         (62)
           Detention time, hr                                             23
           Sludge to thickener, 1,000 kg/day (1,000 Ib/day)               110.3        (243)
           Surface loading, kg/day/sq m (Ib/day/sq ft)                      390         (80)
           Solids  recovery, percent                                        90
           Average sludge solids cone, percent                              6
           Average thickened  sludge solids cone, percent                     8
       First stage centrifuge feed pumps
           Number                                                       3
           Capacity,  each unit,  I/sec (gpm)                              20.8        (330)
     Air mixing blower
       Number                                                          2
       Capacity, each unit,  at discharge pressure, cu m/min (cfm)          35      (1,250)
       Discharge pressure, kg/sq cm (psig)                              1.3        .(18)
     Centrate thickener, (existing digester)
       Tanks
           Number                                                       1
           Diameter,  m (ft)                                             18.9         (62)
           Side water depth,  m (ft)                                      10.11      (33.17)
           Surface area, sq m (sq ft)                                     280      (3,020)
           Volume, 1,000 cum (l.OOOcuft)                               2.7         (95)
           Detention time, hr                                             22
           Sludge to thickener, 1,000 kg/day (1,000 Ib/day)                  58        (128)
           Surface loading, kg/day/sq m (Ib/day/sq ft)  DS                  205         (42)
           Solids  recovery, percent                                        90
           Average centrate solids cone, percent                          1.5
           Average thickened  centrate solids cone, percent                   3
     Second stage centrifuge feed pumps
       Number                                                          3
       Capacity, each pump, I/sec  (gpm)                                26.5        (420)

     Centrifagation

     First stage centrifuge
       Number                                                          2
       Type                                                      solid bowl
       Max feed  rate, I/sec (gpm)                                      16.1        (255)
       Feed solids cone, percent                                          8
       Max G force,  G                                               3,100
       Cake solids cone, percent                                         55
       Centrate solids cone,  percent                                      2
       Horsepower                                                     250
     Second stage centrifuge
       Number                                                          2
       Type                                                      solid bowl
       Max feed  rate, I/sec (gpm)                                      16.4        (260)
       Feed solids cone, percent                                          4
       Max polymer dosage,  kg/ton  (Ib/ton) DS                           0.9          (2)
       Max G force,  G                                               3,100
       Cake solids cone, percent (minimum)                               14
       Centrate solids cone,  percent                                    0,5
       Horsepower                                                     250

                                         (continued)
                                             230

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Table 12-3.  DESIGN  DATA  FOR THE CCCSD WATER RECLAMATION

	PLANT  (CONTINUED)	___

       Furnaces

       Sludge incineration
         Number                                                         1
         Type                                                        MHF
         Outside diameter,  m (ft)                                       6.78     (22.25)
         Hearths                                                        11
         Off gas temperature C (F)                                        760     (1,400)
         Ash, kg/hr (Ib/hr)                                              817     (1,800)
         Loading, 1,000 kg/day (1,000 Ib/day) DS                        31.8        (70)
         Feed solids cone, percent                                      12-18
         Volatile solids, percent                                         43
       Lime recalcination
         Number                                                         1
         Type                                                        MHF
         Outside diameter,  (ft)                                         6.78     (22.25)
         Hearths                                                        11
         Off gas temperature C (F)                                        760     (1,400)
         Ash, kg/hr (Ib/hr)                                            1,589     (3,500)
         Loadings, 1,000 kg/day (1,000 Ib/day) DS                         68        (150)
         Feed solids cone  percent                                      50-60
         Volatile solids, percent                                         21
         CaCOs feed,  1,000 kg/day (1,000 Ib/day)                        44.5         (98)

       Furnace Auxiliary Equipment

       Lump breaker
         Number                                                          2
         Capacity, each unit, kg (Ib) per hour                           2,270     (5,000)
       Ash cooler
         Number                                                          2
         Outlet ash temperature, C (F)                                   93        (200)
       Exhaust gas equipment
         Dry scrubber
             Number                                                       2
             Max entering gas temperature, C (F)                           760     (1,400)
             Efficiency, percent                                          70
         Waste heat boiler
             Number                                                       2
             Capacity,  each unit, mil kg-cal/hr (mil Btu/hr)                 8.8         (35)
             Max entering gas temperature, C (F)                           760     (1,400)
             Exiting gas temperature,  C (F)                                232        (450)
         Wet scrubber
             Number                                                       2
             Max entering gas temperature, C (F)                           288        (550)
             Exiting gas temperature,  C (F)                                49        (120)
             Scrubber water pumps
               Number                                                  12
               Capacity, each pump,  I/sec (gpm)                          54.3        (860)
       Ash hoppers
         Number                                                          4
         Capacity, each hopper, cum (cu ft)                               35     (I.250)

       Sludge, Scum and  Grit Reduction

       Loadings
         Scum, kg/day (Ib/day) DS                                        636     (1,400)
          Grit, kg/day (Ib/day)  DS                                       1,272     (2,800)
         Sludge 1,000 kg/day (1,000 Ib/day)                              31.8         (70)
             Volatile solids, percent                                      43
             Feed solids  cone, percent                                  12-18
       Scum  dewatering equipment
         Thickener
             Number                                                       1
             Surface loading kg/day/sq m (Ib/day/sq ft) DS                  68.3         (14)
         Thickened scum pumps
             Number                                                       2
             Capacity,  each  pump,  I/sec (gpm)                            °-°9        (1-5)
       Grit dewatering equipment
         Separator
             Number                                                       4
             Capacity,  each  unit, I/sec (gpm)                               6.3        (100)
         Dewaterer
             Number                                                       2
             Capacity,  each  unit, i/sec (gpm)                               7.9        (125)
                                              231

-------
    2.   Gravity sludge thickening.

    3.   Sludge classification and dewatering.

    4.   Lime recalcination and sludge incineration.

    5.   Related processes, i.e.,  heat recovery and pneumatic conveying.

The basic cost will be developed for the type of units included in the CCCSD plant
As previously stated, these units  will be replaced for illustration purposes by
other units capable of comparable performance. The alternates considered are:

    1.   Dewatering of first stage  centrate by pressure filtration prior to sludge
        incineration.

    2.   Primary sludge dewatering by vacuum filtration prior to lime recalcina-
        tion in Plural Purpose furnaces .

Capital  Costs

Capital costs of the units associated with the lime treatment and recovery at the
CCCSD's plant are presented in Table 12-4.  Construction costs given in the
table are representative of bidding conditions in the San Francisco Bay Area
during June 1973, representing an ENR Construction Cost Index of 2000.  These
costs are based on a combination of the engineer's estimate and bidding informa-
tion submitted by the general contractor.   Engineering includes field surveying
and soil investigations,  design, preparation of plans and specifications, office
engineering during construction,  resident engineering, inspection, materials
testing and construction surveying.  Engineering costs depend on  factors  such
as the size and complexity of the work, required construction period, owner
facilities,  etc.  Engineering  charges are computed by several methods, or
combination of two or more of these methods .6  in the table a value of 12 percent
has been used for illustration purposes.   Contingencies cover such factors as
removal of unknown structures and alterations and changes during construction.
Contingency charges for construction are usually set at 5 to 10 percent of the
total construction cost of the project. A contingency allowance of 5 percent has
been used in Table 12-4 to arrive at a total capital cost.

In Section VII, a comparison of dewatering techniques was made for a 1.31 cu
m/sec (30 mgd) plant.  The  results of this comparison are shown in Table 7-10.
The data presented in Table 7-10  have been used in the evaluation  of the impact
of alternate dewatering equipment on lime treatment costs as if this equipment
had been applied to the CCCSD water reclamation plant.   Table 12-5 presents
capital cost data for the substitution of vacuum filters for two-stage centrifugal
dewatering, converting  the CCCSD design from an  ATTF  processing  system
(Fig. 7-9) to a Plural Purpose Furnace flow sheet (Fig.  7-8) .  Another estimate
is presented in Table 12-6 which involves the  substitution of filter  presses for
the second stage centrifugal dewatering of the  CCCSD design.   The two alterna-
tives evaluated produce differing quantities of wet  sludge to be incinerated.
This has a significant impact on MHF sizing and cost. To account for this  effect,
                                     232

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                      Table 12-4. CAPITAL COST FOR LIME TREATMENT AND RECOVERY

                                 AT THE CCCSD WATER RECLAMATION PLANT
Item
I



II
III
IV
V
VI
VII

Process
Flocculation, grit removal and primary sedimentation. Includes one
covered preaeration tank and two sedimentation tanks; distribution
and effluent channels; preaeration, sludge collection and scum re-
mova.1 equipment; lime feed building and equipment; equipment gal-
lery; grit, sludge and scum pumps; piping; electrical switchgear;
controls and instrumentation.
1. Lime feeders and slakers (three units).
2. Flocculation and grit removal tank.
3. Primary sedimentation tanks.
Subtotal
Gravity sludge thickening. Includes conversion of two existing
digesters to thickeners; sludge thickening equipment; piping; con-
trols and instrumentation.
Wet classification. Includes two vertical centrifuges; piping; con-
trols and instrumentation.
Sludge dewatering. Includes two vertical centrifuges; polymer feed
equipment; piping; controls and instrumentation.
Lime recalcination. Includes one complete multiple hearth furnace;
material conveyors; dry classification equipment; piping; switchgear;
controls and instrumentation.
Sludge incineration. Includes one complete multiple hearth furnace;
material conveyors; grit and scum handling equipment; piping;
switchgear; controls and instrumentation.
Belated process.
1. Heat recovery equipment. Includes two waste heat recovery
boilers and two package steam boilers; boiler feed water
system; piping; controls and instrumentation.
Struct.
& bldg. a

81,000
163,000
408,000
36,000
e
5,000f
463,000
467,000

e
Mechanical
equip, b

110,000
33,000
301,000
93,000
439,000
464,000
2,194,000
2,291,000

446, 000
Piping

2,000
66,000
31,000
9,000
209,000
217,000
26,000
55,000

213,000
Elect. &
ins trum entation0

17,000
61,000
174,000
12,000
85,000
91,000
396,000
418,000

88,000
Total cost,
dollars'3

210,000
323,000
914,000
1,447,000
150,000
733,000
777,000
3,079,000
3,231,000

747,000
U)
U)

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                               Table  12-4.  CAPITAL COST FOR  LIME  TREATMENT AND  RECOVERY AT
                                                THE CCCSD WATER RECLAMATION PLANT (CONTINUED)
Item
VII










Process
2. Pneumatic conveying and storage. Includes penumatic con-
veying equipment to (a) unload make up lime, (b) transport
reclaimed lime from furnace to storage bins, (c) transfer
process lime from storage to slaker day hoppers, (d) trans-
port ash to storage; lime storage bins; blowers and auxiliary
equipment; screw conveyors; rotary air locks; air filters;
piping; controls and instrumentation.
3. Auxiliary facilities. Includes the percentage allpcated to
solids processing of administration and maintenance buildings;
piping tunnels; outside piping; fuel storage; electrical sub-
stations and general site development.
Struct.
& bldg. a






g



g
Mechanical
equip. "






g



g
Piping






g



g
Elect. &
instrumentation0






g



g
Total cost,
dollars^






593,000



3,091,000
IV)
OJ
         Total construction cost
         Engineering, 12 percent of construction cost

         Contingencies, 5 percent of construction cost

         Total capital cost
13,848,000

 1,662,000

   692,000
16,202,000
               facilities are housed in multipurpose structures and buildings, cost were obtained in proportion to floor space occupied.
          Includes installation cost.
         .Does not include computer cost.
         gBased on June 1973 prices (ENE Index:  2,000).
         „ Equipment housed in the furnace building.
         Cost of housing polymer feed equipment only.

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                    Table 12-5.  CAPITAL COST OF ALTERNATE  DEWATERINC PROCESS AT THE CCCSD
                                    PLANT - VACUUM FILTERS IN A PLURAL PURPOSE FURNACE FLOW  SHEET
Item


VIII
IX
X
Process
From total construction cost in Tabie 12-4, delete items III, IV, V
and VI.
Vacuum filters.6 Includes three belt-type vacuum filters complete
with base; vacuum, sludge and filtrate pumps; cake conveyor;
chemical conditioning equipment; piping; controls and instrumen-
tation.
Lime and sludge furnaces. £ Includes two complete multiple hearth
furnaces; material conveyors; dry classification equipment; grit and
scum handling equipment; piping; switchgear; controls and instrumen-
tation.
Add allowance on Items IX for larger furnaces. %
Struct.
& bldg. a

-
212,000
930,000
-
Mechancial
equip, b

-
430,000
4,485,000
-
Piping

-
321,000
81,000
-
Elect. &
instrumentation0

-
74,000
814,000
-
Total cost,
dollars^

6,028,000
1,037,000
6,310,000
701,000
NJ
UJ
         Total construction cost

         Engineering, 12 percent of construction costs

         Contingencies,  5 percent of construction cost

         Total capital cost
14,076,000

 1,689,000

   704,000
16,469,000
         rwhen facilities are housed in multipurpose structures and buildings, cost were obtained in proportion to floor space occupied.
          Includes installation cost.
         .Does not include computer cost.
          Based on June 1973 prices (ENR Index: 2,000).
         .Vacuum filters to be housed in enlarged furnace building; see Table 7-11 for equipment sizing.
          Furnaces operated in Plural Purpose mode (20% blowdown).
         gMaximum solids load is 39 kg/sq m/hr (8 Ib/sq ft/hr) vs. 35.1 kg/sq m/hr (7.2 Ib/sq ft/hr) for the CCCSD plant design (See Table 12-10).

-------
           Table  12-6.  CAPITAL  COST  OF ALTERNATE DEWATERING PROCESS AT THE  CCCSD  PLANT -
                            FILTER PRESSES SUBSTITUTED FOR CENTRIFUGAL DEWATERING  IN THE SECOND PHASE
Item
-
XI
XII
Process
From total construction cost in Table 12-4, delete Item IV.
Filter presses. e Includes four 7. 4 kg/sq cm (105 psi) filter presses
complete with drip flaps, safety curtains, cloths, feed pump, piping,
controls and instrumentation,
Less allowance on Items VI and VI for smaller furnaces.
Struct.
& bldg. a
-
254,000
-
Mechanical
equip
-
880,000
-
Piping
-
428,000
-
Elect. &
ins trumentationc
-
203,000
-
Total cost,
dollarsd
13,071,000
1,165,000
2,103,000
NJ
OJ
         Total construction cost
         Engineering,  12 percent of construction

         Contingencies, 5 percent of construction cost

         Total capital cost
12,733,000

 1,528,000

   637,000
14,898,000
               facilities are housed in multipurpose structures and buildings, cost were obtained in proportion to flow space occupied.
          Includes installation cost.
         ,Does not include computer cost.
         eBased on June 1973 prices (ENB Index: 2, 000).
         ..Filter presses to be housed in enlarged furnace building, see Table 7-11 for equipment sizing.
         Maximum solids load is 23.4 kg/sq m/hr  (4. 8 Ib/sq ft/hr) vs. 35.1 kg/sq m/hr (7.2 Ib/sq ft/hr) for the CCCSD plant design (See Table 12-10).

-------
the cost of the multiple hearth furnaces in the two alternates were adjusted up-
wards or downwards proportionate to the wet sludge load on the MHF.

The capital cost of the Plural Purpose Furnace flow sheet is 2 percent more costly
than the CCCSD design, while the substitution of filter presses yields costs 14
percent less costly than the CCCSD design.

Operation and Maintenance  Costs

Predicted operation and maintenance (O&M) costs of the lime treatment and
recovery processes at the CCCSD water reclamation plant are given in Table
12-7.  The  cost of operating labor shown in the table reflect the computer control
features of  the CCCSD plant.  Labor charges include a proportional share of the
cost of administration,  supervisory and laboratory staff recommended for the
water reclamation plant. In computing operating outlays, the following unit costs
were used:

    Power:            1.283 £/kw-hr
    Natural gas:       6.148 £71000,000 Btu (1 Therm)
    Lime (92% CaO) :   $30.55/ton
    Ferric  Chloride (dry basis)  $100/ton as FeCl3
    Anionic polymer:  $1.25/lb
    Labor cost (including fringe benefits) $9.00/man-hr.

The O&M costs for the alternate dewatering  processes  described in Tables 12-5
and 12-6, are given in Tables 12-8 and  12-9, respectively.  Fuel costs in Tables
12-7,  12-8  and 12-9 are based on material balances calculated using the computer
program described  in Section X. A summary of fuel requirements of the cases
studied is given  in Table 12-10.  Comparing O&M costs,  it can  be seen that the
Plural Purpose flow sheet (Table 12-8) is 7 percent more costly than the CCCSD
design, while the filter press alternate is 9 percent less  costly than the CCCSD
design.

Total  Annual Costs

Total  annual costs are compared  in Table 12-11.  The  CCCSD design is 3.5 per-
cent less costly than the Plural Purpose flow sheet.  Substitution of filter presses
for the centrifuges in the second stage dewatering step at the CCCSD design
would allow savings of nine percent of the annual cost of the CCCSD design.  (It
should be noted that the filter press information became available after the design
of the CCCSD plant  was completed.  Solids processing using filter presses will
be considered as an alternative in future plant expansions)  .

Cost of Reclaimed Lime  Production vs. Purchased Lime

It is not an easy  matter to separate the cost of lime recovery from the cost of
solids disposal in the ATTF solids processing system. It could be argued that
the thickening, dewatering and incineration steps are all required for sludge
disposal and that the incremental cost of lime recovery is only  the capital and
O&M costs of the  extra energy required to convert calcium carbonate to calcium
                                     237

-------
                    Table 12-7.  OPERATION AND MAINTENANCE COST FOR LIME TREATMENT AND

                                 RECOVERY AT THE CCCSD WATER RECLAMATION PLANT


Item
I
II
III
IV
V
VI
VII
VIII
DC




Process
Chemical addition
Preaeration and grit removal
Primary sedimentation
Sludge thickening
Wet classification
Sludge dewateringb
Lime recalcination
Sludge incineration
Related processes
a. Heat recovery
b. Pneumatic conveying
Cost item, dollar/year
Energy
Power
500
8,500
2,600
200
23,400
25,700
38,300
36,500

11,500
11,000
Fuel
-
-
-
-
-
-
12,100
53,200

-
-
Chemicals
Lime
173,400
-
-
-
-
-
-
-

-
-
Polymer & other
-
-
-
-
-
38,300a
-
-

3,000
-

Operating
labor
3,900
6,000
16,700
2,800
23,600
23,800
25,500
26,200

19,600
10,900

Maintenance, repairs
& supplies
5,500
3,100
3,700
1,900
11,000
11,600
43,900
45,800

44,900
35,600
Total O&M cost

Total O&-AI
cost
183,300
17,600
23, 000
4,900
58,000
99,400
119,800
161,700

79,000
57,500
804,200
U)
00
       ,At 0. 9 kg (2 Ib) per ton DS
        Case 100, Section X

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                   Table 12-8.  OPERATION AND MAINTENANCE COST FOR ALTERNATE DEWATERINC
                                 PROCESS AT THE CCCSD PLANT  - VACUUM FILTERS


Item
I
II
III
IV
V
VI
VII




Process
Chemical addition
Preaeration and grit removal
Primary sedimentation
Sludge thickening
Sludge dewateringa
Lime recalcination
Related processes
a. Heat recovery
b. Pneumatic conveying
Cost item, dollar/ vear
Energy
Power
500
8,500
2,600
200
24,100
74,800

11,500
11,000
Fuel
-
-
-
-
-
122,700

-
-
Chemicals
Lime
183,100
-
-
-
-
-

-
-
Polymer & other
-
-
-
-
66,800b
-

3,000
-

Operating
labor
3,900
6,000
16,700
2,800
45,500
51,700

19,600
10, 900

Maintenance, repairs
& supplies
5,500
3,100
3,700
1,900
11,500
87,800

44, 900
35,600
Total O&M cost

Total O&M
cost
193,000
17,600
23,000
4, 900
147,900
337, 000

79,000
57,500
859, 900
NJ
CO
       ,Case 114, Section X,  Plural Purpose flow sheet.
        At 0. 45 kg (1 Ib) ton of DS.
       CTwo furnaces operating on Plural Purpose mode - 20 percent blowdown.

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            Table 12-9.  OPERATION AND MAINTENANCE COST FOR ALTERNATE DEWATERING
                          PROCESS AT THE CCCSD  PLANT  - FILTER PRESSES


Item
I
II
III
IV
V
IV
VII
VIII
rx




Process
Chemical addition
Preaeration and grit removal
Primary sedimentation
Sludge thickening
Wet classificationa
Sludge dewateringa
Lime recalcination
Sludge incineration
Related processes
a. Heat recovery
b. Pneumatic conveying
Cost item, dollar/year
Energy
Power
500
8,500
2,600
200
23,400
5,100
38,300
36,500

11,500
11,000
Fuel
-
-
-
-
-
-
11,800
21,300

-
-
Chemicals
Lime
173,400
-
-
-
-
-
-
-

-
-
Polymer & other
-
-
-
-
-
-
-
-

3,000
-

Operating
labor
3,900
6,000
16,700
2,800
23,600
28,100
25,500
26,200

19,600
10,900

Maintenance, repairs
& supplies
5,500
3,100
3,700
1,900
11,000
26,400
43,900
45,800

44, 900
35,600
Total O&M cost

Total O&M
cost
183,300
17,600
23,000
4,900
58,000
59,600
119,500
129,800

79,000
57, 500
732,200
Case 102, Section X, ATTF Solids Processing System with pressure filtration in the second stage.

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                                       Table  12-10.  FUEL  REQUIREMENTS FOR ALTERNATIVE CASES


Wet cake rate, kg/day
(Ib/day)
Furnace loading rate,
kg/sq m/hr(lb/sq ft/hi)
Gross heat inputs
Combustion of vola-
tiles
Net-auxiliary fuel
Total
Heat accounted for
Usesa
Total sensible heat in
stack gases
Heat recoverable in
waste heat boilerb
Gross heat-auxiliary
fuelc
Total gas required
Gas assigned to recal-
cination or incinera
tion
Total gas assigned
to recalcination and
incineration
ATTF system case with
(Case 1
Eecalcine
furnace
109,400 (241,000)
19 (3.9)
kg-cal/hr BTU/hr
2,453,918 9,737,770
2,105,992 8,357,113
4,559,910 18,094,883
1,275,546 5,061,691
3,284,364 13,033,192
4,559,910 18,094,883
2,397,609 9,514,320
3,275,669 12,998,688
kg/hr Ib/hr
287 632
77 169
kg/hr
416
2nd stage centrifuge
00)
Waste sludge
furnace
204,600 (450,700)
35.1 (7.2)
kg-cal/hr BTU/hr
2,857,172 11,337,984
5,839,287 23,171,773
8,696,459 34,509,757
1,559,117 6,186,973
7,137,342 28,322,784
8,696,459 34,509,757
5,210,259 20,675,632
9,082,451 36,041,473
kg/hr Ib/hr
795 1,752
339 746
Ib/hr
915
ATTF system case wit]
(Case 1(
Recalcine
furnace
106,400 (234,400)
18.3 (3.75)
kg-cal/hr BTU/hr
2,383,920 9,460,000
2,045,736 8,118,000
4,429,656 17,578,000
1,239,336 4,918,000
3,190,320 12,660,000
4,429,656 17,578,000
2,328,984 9,242,000
3,182,004 12,627,000
kg/hr Ib/hr
279 614
75 165
kg/hr
211
i 2nd stage filter press
12)
Waste sludge
furnace
137,100 (302,000)
23.4 (4.8)
kg-cal/hr BTU/hr
3,172,252 12,588,300
3,404,362 13,509,372
6,576,614 26,097,672
1,447,469 5,743,923
5,129,145 20,353,749
6,576,614 26,097,672
3,744,275 14,858,236
5,295,158 21,012,533
kg/hr Ib/hr
464 1,021
136 299
Ib/hr
464
Plural purpose with
vacuum filter
per furnace basis
(2 furnaces required)
451,200 (993,880)
39 (8)
kg-cal/hr BTU/hr
2,644,356 10,493,475
6,310,310 25,040,912
8,954,666 35,534,387
1,633,057 6,480,383
7,321,609 29,054,004
8,954,666 35,534,387
5,344,787 21,209,472
9,815,083 38,948,739
kg/hr Ib/hr
859 1,893
391 861
kg/hr Ib/hr
782 1,722
KJ
          ^Evaporation of water, radiation losses, shaft heating air,  heat of reaction, heat loss in calcine product.
           Taken as 73 percent of total sensible heat of furnace off gases.
          °Batio to net heating value:  20, 564/13, 221 = 1. 555402 (cf Section VIII).
           Calculated as the difference between the gross heat from auxiliary full less that recovered in the waste heat boiler,  divided by the gross heat-input
           times the total gas required; e.g., for the recalcine furnace in Case 100: 632 (12,998,688 - 9, 514, 320)/(12, 998,688) =169.

-------
oxide plus the cost of operation of the dry classification step.  On this basis,  the
cost of reclaimed lime would be low.   Investigators at South Tahoe reasoned  that
the reclaimed lime cost was the total cost of the recalcining step, since lime sludge
thickening and dewatering would be common to any lime coagulation process.7
Costs for the example in this report are calculated on the same basis as for South
Tahoe, and include only the recalcination step. The O&M and annual cost estimate
for recalcination totals  $388,200/yr.  Since it was found that recalcined lime
eliminated the need for the use of ferric chloride as a supplemental coagulant
(Table 8-12) ,  a savings of $63,800 can be credited to recalcination, leaving a
balance of $324,400/yr. For this case, 8620 tons/yr of CaO are returned to the
process . The unit cost of recalcination is $37.63 per ton of CaO.   While  it appears
that recalcined lime costs 13 percent more than new lime, several other factors
must be considered.  First, the recent quotation of $33.20 per ton  (100% CaO)  has
been made by the manufacturer with the cautionary  statement that a significant
increase in cost is expected in the near future. Second, a portion of the  cost of
recalcination could be attributed to ultimate disposal of the large quantity of
calcium carbonate sludge generated by the process.  On this basis, the cost of
reclaimed lime is considered competitive  with the  cost of new lime for this case.
        Table 12-11 .  COMPARISON OF TOTAL ANNUAL COSTS FOR
                     LIME TREATMENT AND SOLIDS PROCESSING
System
CCCSDdesigna
1st: centrifuge
2nd: centrifuge
Plural Purpose^3
(vacuum filters)
Modified design0
1st: centrifuge
2nd: filter press
Cost category, dollar/year
O&M
804,200
859,400
732,200
Annual cost
of capital
1,412,600
1,435,800
1,298,900
Total
annual cost
2,216,800
2,295,200
2,031,100
        bCase 100, Section X
         Case 114, Section X
        dCase 102, Section X
         CEF at 20 years and 6 percent = 0. 08718456
                                     242

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Cost of  Sludge Processing

The entire sequence of operations in the CCCSD Water Reclamation Plant, begin-
ning with thickening and ending with the production of ash for ultimate disposal
and reclaimed lime for reuse, can be considered the sludge processing system.
The unit cost of operation for the total system expressed per ton of DS processed
is of interest.  The annual cost of capital for the system is $l,265,000/yr, exclu-
sive of Item I in Table 12-4. O&M cost totals $580,300, exclusive of Items I, II and
III in Table 12-7. Total annual cost is $l,845,300/yr. A total of 33,490 tons/yr of
new sludge is precipitated  in the system, exclusive of recycled solids. Therefore
the unit cost of sludge processing is $55,10/ton of DS .  This cost is competitive
with the cost of other  sludge disposal systems.  The cost can also be  expressed
per unit of wastewater treated; on this basis the cost is $167/mil gal based on an
average dry weather flow of 30 mgd.
                                    243

-------
                                 SECTION XII

                                 REFERENCES

1.   Brown and Caldwell, Consulting Engineers. Report on Energy Requirements
    for Alternative Modes of Operation of Water Reclamation Plant. Prepared for
    the Central Contra Costa Sanitary District, Walnut Creek, California.  1974.

2.   Flanagan, M.J .  Direct Digital Control of Central Contra Costa Sanitary
    District Water Reclamation Plant.  (Presented at IAWPR Specialized Con-
    ference, London). September, 1973.  12 p.

3.   Caldwell Connell Engineers.  Design Report - Lower Molonglo Water Quality
    Control Centre.  Prepared for the National Capital Development Commission,
    Canberra, Australia.  April,  1971.

4.   Caldwell Connell Engineers.  Revisions to Design Report - Lower Molonglo
    Water Quality Control Centre.  Prepared for the National Capital Development
    Commission,  Canberra,  Australia.  May, 1972.

5.   Parker, D.S., K.E. Train, andF.J. Zadick.  Sludge Processing for Com-
    bined Physical-Chemical-Biological Sludges.  U.S. Environmental Protection
    Agency, Washington, D.C. Report No. EPAR2-73-250, July, 1973.  141 p.

6.   Consulting Engineering  -  A Guide for the Engagement of Engineering
    Services. American Society of Civil Engineers, New York.  ASCE Manual
    on Engineering Practice Number 45. July, 1972. 96 p.

7.   Advanced Wastewater Treatment as  practiced at South Tahoe. South Tahoe
    Public Utility District.  Washington, D.C. Project 17010 ELQ. U.S.  Environ-
    mental Protection Agency.   August 1971.  436 p .
                                   244

-------
                                 SECTION XIII

                    LIST OF INVENTIONS AND PUBLICATIONS
No inventions have resulted from this work, nor have any patent applications
been made as a result of this work. All processes described in this work were
state-of-the-art prior to inception of this project.  To date (May, 1974) no
publications have resulted from this work.
                                  245

-------
                                 SECTION XIV

                                  GLOSSARY
This glossary explains the various abbreviations used throughout the report;  see
Tables 10-1, 10-2, and 10-3 for symbols used in the computer program.

Btu                                    British thermal units
C                                      degrees Celsius
cfm                                    cubic feet per minute
cfs                                     cubic feet per second
cu ft                                   cubic foot (feet)
cu m                                   cubic meter
DS                                     dry solids
F                                      degree Farenheit
FBR                                   fluidized bed reactor
ft                                      foot (feet)
G                                      gravitational force per pound mass,
                                         feet per (second) 2
gal                                    gallon (s)
gpd                                   gallons per  day
gpm                                   gallons per  minute
HHV                                   high heat value
in.                                     inch(es)
kg                                     kilogram (s)
kcal                                   kilocalories
L                                      bowl length, cm
1                                      liter (s)
lb                                      pound (s)
LHV                                   Low heat value
I/sec                                   liters per second
m                                      meter
mgd                                   million gallons per  day
mg/1                                   milligram (s) per liter
MHF                                   multiple hearth furnace
PPm                                   part(s) per million
                                       pound (s)  per square inch
                                       radius of the liquid surface, cm
                                       radius of the inner wall of the bowl, cm
                                       rotary kiln calciner
                                       difference in revolutions per minute
                                         for  centrifuge, A RPM is bowl speed
E                                         minus conveyor speed
                                       " sigma" factor
s<3 ft                                   square foot  (feet)
sqin.                                  square inch (es)
sc! m                                   square meter
                                    246

-------
SS                                        suspended solids
TS                                        total solids
VS                                        Volatile solids  (or volatile matter)
w                                         rate of rotation, rad/sec
wt                                        weight
                                     247

-------
                                 SECTION XV

                                 APPENDICES
The attached appendix is in two parts.  Appendix A contains a listing of the
solids balance computer program, SOLIDS IA, which has been described in detail
in Section X.  Appendix  B  contains copies of the output from this program for
23 cases that were run for this project. Table B-l is an index for these cases.
                                   248

-------
    APPENDIX A




LISTING OF SOLIDS 1A
        249

-------
 SOLIDS1A    11:50PDT

 100C  THIS  IS A  PROGRAM TO  CALCULATE THE  EQUILIBRIUM MASS BALANCES FOR
 HOC  SEVERAL COMPONENTS IN A LIME SLIDGE PROCESSING SEQUENCE EMPLOYINB
 I20C  WET CLASSIFICATION,RECALCIUATION,DRY CLASSIFICATION OF RECALCIN-
 150C  ED  PRODUCT,DEWATERING AND INCINERATION OF CENTRATE SOLIDS FROM WET
 140C  CLASSIFICAT!ON,WITH OPTIONS FOR SLOWDOWN OF RECALCINED PRODUCT,
 150C  OR  SINGLE  FURNACE CASE WITH NO DEWATER ING AND INCINERATION STEPS.
 160C  IF  FURNACE STACK  LOSSESCRECOVERED  IN THE WET SCRUBBER) ARE TO BE
 I70C  RETURNED TO THE PRIMARY,  THEN INPUT "SEREC" AS 1.0.  IF THE WET
 18DC  SCRUBBER EFFLUENT IS  NOT TO BE RETURNED TO THE PRIMARY,  THEN
 190C  INPUT "SEREC" AS  0.0
 200C  IF  NO SLOWDOWN  IS WANTED,  THEN "FRBD" =0.0.
 210C  IF  NO CLASSIFIER  FOR  RECALCINED PRODUCT IS WANTED,"CLASSIF"=0.0.
 220C  IF  CLASSIFIER IS  EMPLOYED,  LET "CLASSIF" =1.0.
 230C  IF  NO SECOND STAGE CENTRIFUGE AND  INCINERATION FURNACE ARE USED,
 240C  LET "FURNACE" EQUAL 1.0;  IF THEY ARE INCLUDED, LET "FURNACE"=2.0.
 250C  IF  NO CLASSIFIER  EMPLOYED,  INPUT ALL COMPONENT CLASSIFIER RECOVERY
 260C  FRACTIONS  AS 1.0, CTOTAL RECOVERY),  EXCEPT ORGANICS,  FECOHJ3,  AND MGOXJ2
 270C  WHICH ARE  ALL ZERO.
 280C  INPUT THE  RECOVERIES  OF ORGANICS, FE(OH)3,  MG(OH)2 IN FURNACES
 290C  AND CLASSIFIER  AS 0.0 FOR ALL CASES.
 300C  IF  NO SECOND STAGE CEt^TRIFUGE OR INCINERATION FURNACE USED,  LET THE
 310C  RECOVERY OF ALL COMPOUNDS  IN THESE  EQUAL ZERO.
 320C  PROGRAMMER: F.J.  ZADICK,BROWN 6  CALDWELL,  SAN FRANCISCO,  CALIF.,FEB., 197"t
 330   FILELIST  "DAT1","DAT2","DAT3"
 3"tO   110  FORMATCV)
 3<»5
 350C  STATEMENT  224 is  USED TO SUPRESS DIAGNOSTICS  DURING  COMPILING
 360   224  L=123+L
 365
 370C  READ  FROM  FILES DAT1,   DAT2,  DAT3
 380   225  READCl,110)L,XMGD,XLBWASIN,FECL3MGL,CAHTODOS,FRBD,RECALEFF
 390   227  READC1,110)L,FURNACE,CLASSIF,PH,SEREC,FEINFMGL,SIINDMGL,SIEFDM6L
 1)00   2.9  READ(2,110X,SSINlMGL,SSCnjTMGL,XMG^riGL,XMGEFMGL,CAINFMGL,CAEFFMGL
 410   231  READC2, 110X,PINFMGL,PEFFMGL,FEEFFMGL,FRAIISSO,FRAIISSI
 1(20   233  READC2, 110X,FRSIWAS,FRAIIWAS,FRVWASIN,FRVSSIN,FRVSSOUT
 430   235  READC2,110)L,FRSISSI,FRSISSO,FRSINEW,FRAIINEW,FRMGONEW,FRCAONEW
 440   237  READC3, 110X,RECAP1,RECAC1,RESI1,REAII1
 450   239  READ(3,110X,REXMGH1,REXMG01,REFEOH1,REFE01,REORG1
 460   241  READC3, 110X,RECAP2,RECAC2,RESI2,REAII2,REFEOH2
 470   243  READC3, 110X,PEFEO2,REORG2,REXMGH2,REXMGO2
 480   245  READ(3,110X,RECAPF,RECACF,RESIF,REAIIF,REFEOHF
 490   247  READC3,110X,REFEOF,REORGF,REXMGHF,REXMGOF
 500   249 READC3, 110)L,RECAPFI,RECACFI,RESIFI,REAIIFI,REFEOHFI
 510   251  READ(3,110X,REFEOF],REORGFI,REXM6HFI,REXMGOFI
 520   253  READC3,110)L,RECAPCL,RECACCL,RESICL,REAIICL,REFEOHCL,RECAOa.
 530   255 READC3,110X,REFECCL,REORGCL,REXMGHCL,REXMGOCL
 540   800  XLBSSII^XMGD-S.SS-SSir-MGL
 550   803 XLBSSOUT=XMGO"8.33"SSOUTMGL
 560   805 XMGINF=XMGD-"8.33::XMGnM;L
 570   807 XMGEFF=XMGD"8.33::XMGEFMGL
 580   810 CAINF=XMGD"8.33"-CAINFMGL
 590   814 CAEFF:XMGD=:8.33::CAEFFM&L
 600   816 PIN^XMGD-S^^INFMGL
 610   818 PEFF=XMGD=:8.33::PEFFMG1.
 620   822 AIIEFFiXLBSSOUT^CFRAIISSO)
 630   828 FEEFF=XMGD::8.33"FEEFFMGL
 640       SIlrO=SIINDMGL"8.33:rXMGD
 650       SIEFFD^SIEFDMGL-S.SS^XMGD
 660   826 SIEFF=XLBSSOUT::CFRSISSO)+SIEFFO
 670   830 FECL3=XMGD:;8.33::FECL3MGL
 680   834 CAHTOTLB^CAHTODOS-XMGD1^.33
690   836 CAOTOTLB=CAHTOTLB"C56./74.)
 700   837 CAOTOMGL=CAHTODOS"56./74.
 705
 710C CALCULATE FECOH)3   IN PRIMARY SLUDGE
 720   840 FEOHSLG=((FECL3)::C107./l62.5)+(FEINFMGL)"C107./56.)"CXMGD)»C
 730      S8.33)-(FEEFF)KC107./56.))/(!.-O.-REFEOH2)«O.-REFEOH1)>

740C CALCULATE FE(OH)3   IN OTHER LIQUID STREAMS
750   842 FEOHlP=CFECL3)::C107./162.5)-(FEEFF)"C107./56.>i.CFEINFMGL)K<
 760      6XMT,D):=C8.33D"C107./56.)
770    844 FEOHCAK1=CREFEOH1)"CFEOHSLG)
780    850 FEOHCNT1=CFEOHSLG)-CFEOHCAK1)
790    853 FEOHCAK2=(FEOHCNT1)"(REFEOH2)
800    856 FEOHCNT2=(FEOHCNT1)::(1.-REFEOH2)
805
                                    250

-------
8IOC NO FE(OH)3  IN ASH STREAMS  OR SCRUBBER WATER
820   859 FEOHFP=0.0
8JO   862 FEOHFPI=0.0
81)0   861* FEOHRS=0.0
850   867 FEOH8D=0.0
860   870 FEOHCR=0.0
865
870C FE(OH)3 MOT PRESCNT  IK  EITHER FURNACE 'PRODUCT OR CLASSIFIER ACCEPTS
880   873 REFEOHF=0.0
890   876 REFEOHCL=0.0
900   879 REFFOHFI=0.0
910   880 FEOHSE1=0.0
°20   881 FEOHSE2=0.0
U30       IFCSEREC.EQ.0.0) GO TO 885
935
94CC CALCULATE FE203  IN PRIMARY SLUDGE
950   883 FEOSLG=CCFEOHCAKn::CREFEOF)"C 160./21CFEOH
960      ECAKl)::Cl.-REFEOF)"C160./21't.>CFEOHCAK23::Cl.-REFEOFO"C160./21l*.)
970      S)/Cl.-Cl.-REFE01)"(l.-REFE023-fREFE01)"(PEFEOF)"Cl.-FRBD)"(REFEOCL
9£(J      E3-CREFE01)"Cl.-REFEOF3-Cl.-REFEOn::CREFE02)"Cl.-REFEOFO)
990       IF(SEREC.EQ.l.O) GO TO 895
1000   885 FEOSLG=CCFEOHCAK13"CREFFCF)"C160./211».)"Cl.-FRBD)KCREFEOCL))/
1010      C(l.-Cl.-REFE01)::Cl.-REFt02)-(REFE01)"CREFEOF)::Cl.-FRBD):!(REF
1020      SEOCL))
1025

1030C CALCUALTE  FE203  IN  CTJ-ER  STREAMS
1040   B95 FEOCAK1=FEOSLG:H'PEFE01)
1050   898 FEOCHT1=FEOSLG"C1.-PEFE01)
1060   901 FEOCAK2=FEOCNT1::(REFE02)
1070   905 FEOCNT2=FEOCNT1"(1.-REFE02)
1080   908 FEOFP=FEOCAKl-CP.EFEOF>|.FEOHCAKl"CREFEOF5«Cl60./21lt.)
1090   910 FEOBD=FEOFP:;(FRBD)
1100   911 FE01P=0.0
1110   912 FEORS=FEOFP::(1.-FRBD)"(REFEOCL)
1120   911* FEOCR=FEOFP;:C1.-FRBD):;C1.-REFEOCL)
1130   916 FEOFPI = FEOCAK2"CREFECFI>(FEOHCAK2)::CREFEOFO
1140   917 FEOSEl=FEOCAKl"Cl.-REFEOF>CFEOHCAKl)"(l.-REFEOF);5C160./21't.)
1150       IF(SEREC.EQ.O.O)  GO  TO 919
1155
1160C CALCULATE  CA3CTO14)2 IN PRIMARY SLUDGE
1170   918 CAPSLG=CCPINF-PEFF)"(310./62.)VC1.-C1.-RECAP13"C1.-RECAP2)-CRECA
1180      GP1)::CRECAPF)::(1.-FRBD)::CRECAPCL)-CRECAP1)::C1.-RECAPF)-C1.-RECAP1)
1190      5::Cl-.-RECAPFI)::CRECAP2))
1200       IFCSEREC.EQ.1.0)  GO  TO 921
1210   919 CAPSLG=CCPn^F-PEFF)"C310./62.))/Cl.-Cl.-RECAPl)::(l.-RECAP2)-CRECA
1220      6P1)::CRECAPF)::C1.-FRBD)"CRECAPCL)5
1225
1230C CALCULATE  CA3CP0452 IN OTHER STREAMS
1240   921 CAPlP:(PlNF-PEFF}"(31G./62.:>
1250   922 CAPCAK1=CAPSLG::CRECAP1)
1260   923 CAPFP=CAPCAK1;:CRECAPF)
1270   925 CAPCrm=CAPSLG::Cl.-RECAPl)
1280   927 CAPCAK2=CAPCNT1::CRECAP2)
1290   929 CAPCNT2=CAPCNT1::O.-RECAP2)
1300   931 CAPFPI=CAPCAK2::CRECAPFO
1310   933 CAPBD=CAPFP;:(FRBD)
1320   935 CAPRS=CAPFP::C1.-FP.BD)"(RECAPCL)
1330   937 CAPCR=CAPFP;:Cl.-FRBD)::Cl.-RECAPCO
13"tO   939 CAPSE1=CAPCAK1:!O.-RECAPF)
1350   940 CAPSE2=CAPCAK2::C1.-RECAPFO
1355
1360C CALCULATE  MGCOH52  IN PRIMARY SLUDGE
137C   941 XMSHSLG=C(XMGINF-XMGEFF);:C58.3/2'*.3))/Cl.-Cl.-REXMGH13::(l.-REXMGH2
1380      £))
1385
1390C CALCULATE  MGCOH)2  IN OTHER STREAMS
mOO   942 XNGHlP=C>T-lGINF-X/'GEFF)::C58.4/2'*.3!)
1410   943 XMGHCAK1=W1GHSLG::CREXMGH1)
1420   945 X)-1SHCNT1=XMGHSLG::C1.-REXM5H1)
1430   947 X)-T,HCAK2=CXMGHCNTiy:(REXMG-H2)
11)1*0   949 X/-1GHCNT2=CXt-1GHCNTl)::(l.-REXMGH2)
1445
1450C NO MG(OH)2 IN ASH STREAMS
1460   951 XMSHFP=0.0
1470   953 >MGHRS=0.0
1480   955 XMGHED=0.0
1490   957 XMGHFPI=0.0
1500   959 X)«HCR=0.0
1505
                                     251

-------
-1510C NO MGCOH)2 PRESENT  IN EITHER FURNACE  PRODUCT OR CLASSIFIER ACCEPTS
1520   961 REXMGHF=0.0
1530   963 REXMGHFI=0.0
15W   965 REXMGHCL=0.0
IS'tS
1550C NO MG(OH)2 IN SCRUBBER WATER
1560   966 XMGHSE1=0.0
1570   967 XM6HSE2=0.0
1575
1580C CALCULATE ORGANICS  IN PRIMARY  SLUDGE
1590   969 OR6SLG=CCXLBSSIN)::(FRVSSIN>CXLBWASIN)"CFRVWASIN)-CXLBSSOUT>(FRVS
1600      £50UT))/C1.-C1.-REORGO"C1.-REORG2))
1605
1610C CALCULATE ORGANICS  IN OTHER LIQUID  STREAMS
1620   972 ORG1P=(XLBSSIN)"CFRVSSINMXLBWASIN)"CFRVWASIN)-XLBSSOUT"FRVSSOUT
1630   973 ORGCAK1=ORGSLG"(REORG1)
^O   975 ORGCNT1=ORGSLG"C1.-REORG1)
1650   977 ORGCAK2=ORGCNT1"(REORG2)
1660   979 ORGCNT2=ORGCNT1::(1.-REORG2)
1665
1670C NO ORGANICS  IN ASH  STREAMS
1680   981 ORGFP=0.0
1690   983 ORGFPI=0.0
1700   985 ORGCR=0.0
1710   987 ORGBD=0.0
1720   989 ORGRS=0.0
1725
1730C NO ORGANICS  IN SCRUBBER  WATER
17itO   990 ORGSE1=0.0
1750   991 ORGSE2=0.0
1760   992 REORGF=0.0
1765
1770C ORGANICS NOT PRESENT  IN  EITHER FURNACE PRODUCT OR SCRUBBER WATER
1780   993 RFORGFI=0.0
1790   995 REORGCL=0.0

1800       IFCSEREC.EQ.0.0) GO TO 998
1805
1810C CALCULATE CAC03 IN  PRIMARY SLUDGE
1820   997 CACSLG=CCCAINF-CAEFF)"C100.AO.)+(CAOTOTLB)"(100./56.)-CPINF-PEFF)
1830      S'!C120./62.0)::(100./1tO.))/Cl.--CRECACl)"(RECACf->"Cl.-FRBD):;CREMCCL)
1840      6::Cl.-RECALEFF)-(l.-RECACl)"(;i.-RECAC2)-CRECACl)"(l.-RECACF)-Cl.-RE
1850      6CACO"CRECAC2)::C1.-RECACFI))
1860       IFCSEREC.EQ.1.0) GO TO 1000
1870   998 CACSLG=((CAINF-CAEFF)"C100./'tOO+CCAOTOTLB)::C100./56.)-CPIMF-PEFF)
1880      S::C120./62.0)"C 100./<*0. ))/(!.-CRECACn::CRECACF)"Cl.-FRBD)"CRECACCL)
1890      E::C1.-RECALEFF)-C1.-RECAC1)::C1.-RECAC2))
1895
1900C CALCULATE CAC03 IN OTHER STREAMS
1910  1000 CAClPiCCAINF-CAEFFJ-ClOO./^OO+CAOTOTLB-ClOO./se.J-CPIMF-PEFF^'Cl
1920      C20./62.)::(100./I)0.)
1930  1001 CACCAK1=CACSLG"CRECACO
ig'tO  1002 CACFP=CRECACF)::CCACCAK1)::C1.-RECALEFF)
1950  lOOll CACCNT1=CACSLG::C1.-RECAC1)
1960  1007 CACCAK.2=CACCNT1"CRECAC2)
1970  1009 CACCNT2=CACCNT1"(1.-RECAC2)
1980  1011 CACFPI=CACCAK2"CRECACFO
1990  1012 CACSE1 = (CACCAK1)"G.-RECACF)
2000  1013 CACSE2=CACCAK2"(1.-RECACFO
2010  1015 CACBD=CACFP"(FRBD)
2020  1017 CACRS=CACFP"C1.-FRBD)"CRECACCL)
2030  1018 CACCR=CACFP"C1.-FRBD)"C1.-RECACCL)
2035
20"*OC CALCULATE CAO IN RECALCIMATION FURNACE PRODUCT
2050  1019 CAOFP=CACCAK1::(R£CACF>:CRECALEFF)"C56./100.)
2055
2060C CALCULATE CAO IN THE SLOWDOWN AND CLASSIFIER STREAMS
2070  1021 CAOBD=(CAOFP3::(FRBD)
2080  1023 CAORS=CAOFP"a.-FRBD)"CRECAOCL)
2090  1025 CAOCR=CAOFP"C1.-FRBD)"C1.-RECAOCL)
2095
2100C CALCULATE NEW LIME REQUIRED
2110  1027 CAONEW=CAOTOTLB-CAORS
2115
2120C NO CAO  IN RECALCINE FURNACE SCRUBBER WATER
2130  1028 CAOSE1=0.0
2135
21<*OC NO CAO  IN INCINERATION FURNACE WASTE ASH
2150  1029 RECAOFI=0.0
2160  1031 TOTLBNEW=CAONEW/FRCAONEW
2165
2170C NO CAO  IN SECOND STAGE DEWATERING STREAMS
2180  1033 RECA02=0.0
2190  1035 CAOM"GL=CCAOMEW)/C8.33KXMGD)
2195
                                       252

-------
2200C NO CAO IN FIRST STAGE DEV/ATERING  STREAMS
2210  1037 RECA01=0.0
2220  1039 CAORM6L=CCAORSVC8.33::XMGD)
2225
2230C NO CAO IN SECOND STAGE CENTRATE
221)0  1041 CAOCNT2=0.0
2250  1042 SLMDOS^CAONMGL+CAORMGL
2260  1044 CAORSFRA=CAORMGL/SUMDOS
2265
2270C NO CAO IN LIQUID STREAMS
2280  1047 CAOCAK2=0.0
2290  1048 CA01P=0.0
2300  1049 CAOSLG=0.0
2310  1051 CAOCAK1=0.0
2320  1055 CAOCNT1=0.0
2330  1056 CAOSE2=0.0
2335
2340C NO CAO IN INCINERATION FURNACE WASTE ASH
2350  1057 CAOFPI=0.0
2355
2360C SUM THE SOURCES OF ACID INSOL.INERTSCEXCEPT SILICA  INTO  THE  PRIMARY  ON FIRST PASS
2370  1061 AIIIN=      (TOTLBNEW)"CFRAIINnO+CXLBSSIN)::CFRAIISSO+(XLBWASIN)«
2380      ECFRAIIWAS)
2385
2390C CALCULATE ACID INSOL.INERTS PRECIPITATED ON FIRST PASS
2400       AII1P=AIIIN-AIIEFF
2410  1062 AIIINMGL=AIIIN/C8.J3!!XMGD)
2420       IF(SEREC.EQ.O.O) GO TO 1064
2425
2430C CALCULATE ACID INSOL.INERTS IN PRIMARY SLUDGE
2440  1063 AI ISLG=C(AinN)-CAIIEFF5)/(l.-Cl.-REAIIl)::Cl.-REAII2>CREAIIl):!CRE
2450      £AIIF)"C1.-FRB03::(REAIICL)-(1.-REAII1)::(REAII2)::(1.-REAIIFO-(REAII
2460      C13-C1.-REAIIF))
2470       IF(SEREC.EQ.l.O) GO TO 1065
2480  1064 AIISLG=CCAlIIN-AIIEFF3)/Cl.-Cl.-REAin)"Cl.-REAII2>CREAII13«CRE
2490      CAII F)::(l. -FRBD)"(REAI ICD)
2495
2500C CALCULATE ACID INSOL.INERTS IN OTHER STREAMS
2510  1065 AnFP=CAIISLrO"(REAin)xCREA1IF)
2520  1067 AIICAKl=CAIISLC,):;CREAnl)
2530  1071 Al 1CNT1 = (A11SLG)::(1.-REAII1)
2540  1073 A1ICAK2=(AI1CNT1)"CREA112)
2550  1075 A1ICNT2=(AIICNT1)"(1.-REAI12)
2560  1077 AIIBn=(A!IFP)"(rRBD)
2570  1079 AIIRS=CAIirFO::(l.-FRBD)"CREA!ICL)
2580  1081 AI]FP1 = (AI ICAIO)"(RCA1IF1)
2590  1083 AIICR=(AIirr)::(].-FRBn):!Cl.-REAnCL)
2f,oo
2610  103
2615
2620C SUM THE SOURCES OF  SI02 INTO  THE  PRIMARY  ON THE FIRST PASS
2630  1085 SIIN=     (XLBSSIN)::(FRSISSD+(XLBWASIN;)"(FRSIWAS>4-CTOTLBNEVO"(FRS
2640      SINEW>+CSIIND)
2645
2650C CALCULATE SI02 PRECIPITATED ON THE FIRST  PASS
2660       S1021P=SIH1-SIEFF
2670  1086 SIIMMGL=SIIN/C8.33::XMGD:)
2680       IF(SEREC.EQ.O.O) GO  TO  1088
2685
2690C CALCULATE SI02 IN THE PRIMARY SLUDGE
2700  1087 SISLG:CCSIIN5-CSIEFF))/C1.-C1.-RESI1)"C1.-RESI2)-CPESIO"CRESIF)::(
2710      Sl.-FRBO>:CRESICL>Cl.-RESIl)"CRESI2)"Cl.-RESIFO-CRESIir"Cl.-RESIF
2720      6)5
2730       IF(SEREC.EQ.l.O) GO  TO  1089
2740  1038 SISLG=CCSIIN)-(SIEFF))/C1.-C1.-RESI1)::C1.-RESI2)-CRESI13"CRESIF)::(
2750      £1.-FRBD)::CRESICL))
2760  1089 SIEFFMGL=S[trF/(8.33"XMGD)
2765
2770C CALCULATE SI02 IN OTHER STREAMS
2780  1090 S!FD-CS!SLG}"CP.E5I1)::CP.ES!F)
2790  1091 SICAK1=CSISLG)"(RESI1)
2800  1093 SICNT1=(SISLG)"C1.-RESI1)
2810  1095 SICAK2=CSICNT1)::CRESI2)
2820  1097 SICNT2=(SICNT1)"O.-RESI2)
2830  1099 SIBD=CSIFP);:(FRED)
2840  1101 SIRS=CSIFP)"(1.-FRED)"CRESICL)
2850  1103 SIFPI = (SICAK2)"(PESIFD
2860  1105 SICR=CSIFP)"(1.-FRBD5"C1.-RESICL)
2870  1106 SISE1=SICAK1;:C1.-RESIF)
2875
5880C CALCULATE MGO INPUT  FROM NEW  LIME
2890  1107 XMGONEW=(FP>'GCt\EW):;(TOTLBNEVO
2900  1108 XMG01P=XMT,ONEW
                                          253

-------
2910       IF(SEREC.EQ.O.O) GO TO 1110
2915
2920C CALCULATE MGO IN PRIMARY SLUDGE
2930  1109 XMGOSLG=CCXMGHCAKn::CREXWOF)"(l.-FRED)"CREXMGOCL)::C'tO./58.3>Cl.
29M      S-REXMGOF)"CXMGHCAKl5:;CttO./58.3>CXMGONEV,0+Cl.-REXMGOFO"CXNGHCAX2
2950      £)"CitO./58.3))/(l.-Cl.-REXMGOO"Cl.-REXMG02)-CREXMGOn!!CREXMGOF)»CR
2960      £EXW»CL>Xl.-FRBD)-a.-REXMGOF):KREXMG01)-(l.-REXMG01)"(REXMG02)"(
2970      El.-REXMGOFI))
2980       IFCSEREC.EQ.1.0) GO TO 1111
2990  1110 XMGOSLG=((XN1GHCAia)"(REXMGOF)"a.-FRBD)"(REXMGOCL)"(40./58.3)
3000      6+CXMGONEW))/a.-Cl.^EXMG01)"a.-REXMG02)-(REXMG01)"(REXMGOF)"(R
3010      SEXMGOCL)"(1.-FRBD))
3015
3020C CALCULATE MGO IN OTHER STREAMS
3030  1111 XMGOCAK1=XMGOSLG::CREXMG01)
3040  1113 XMGOCNT1=XMGOSLG"C1.-REXMGO1)
3050  1115 XMGOCAK2=XMGOCNT1::CREXMG02)
3060  1117 XMGOCNT2=XMGOCNT1::O.-REXMG02)
3070  1119 XMGOFP=XMGOCAKl"CRE»COF)+XMGHCAKl::CREXMGOF)::C'tO./58.3)
3080  1121 XMGOBD=XMGOFP"(FRBD)
3090  1123 XMC-OP.S=XMGOFP"(1.-FRBD)::(REXMSOCL)
3100  1125 XMGOCR= XMGOFP"(1.-FR£D);:(1.-REXMGOCL)
3110  1127 XMGOFPI=XMGOMK2"CREXMGOFI)4.(XMGHCAK2)"(REXMGOFI)
3120  1129 XMWSEl = (XMTOCAKl)"(l.-REXMGOF)4XMC-HCAK2"Cl.-REXMGOFI)"C1*0./58.3)
311(0  1132 FEOSE2=FEOCAK2"a.-REFEOFI)+(FEOHCAK2)"a.-REFEOFl)::a60./210
3530   367 FOF^WT(8X,F5.2,1GX,F5.2)
3540   415 FORMO,T(1H-,35H "PRIhWRY SLUDGE COMPONENTS,LB/DAY")
3550   420 FGRKAT(lH-,/9H ORGANICS,16X,F9.0,1H ,/4H CAO,21X,F9.0,1M ,/6M CACO
3560      83,19X,F9.0,1H ,/4H MGO,21X,F9.0,1H ,/8H MG(OH)2,17X,F9.0,1H ,/6H F
3570      SE203,19X,F9.0,1H ,/8H FECOH)3, 17X..F9 . 0,1H ,/5H SI02, 20X, F9 .0,1H ,
3580      S/19H ACID If.,SOL. INERTS,6X, F9.0, 1H ,/10H CA3CP04)2,15X,F9. 0.//6H T
3590      EOTAL,17X,FU.O)
3600   400 FORMATO-H-, //f.4H :                PRIMARY EFFLUENT COMPOSITION MG/L
3610      6             ")
3620   410 FORMATCeW "SUSP.SOLIDS"WGNESIUH"CALCIUM"PHOSPHORUS"SI02"A. I INE
3630      CRTS::IROM::)
3640   411' FORMAT(5X,F5.1,6X, FJ. l,"tX,F5. 1,4X,F6.2, 3X,F5 . 1, 2X,F5. 1, 2X,F6.2)
3650   430 FORMAT(lH-,//37H -FIRST STAGE CAKE COMPONENTS,LB/DAY")
3660   440 FORMAT(lH-,//50H "RECALCINATION FURNACE PRODUCT COMPONENTS,LB/DAY"
3670      E)
3680   450 FORMATClH-,//41H "FIRST STAGE CENTRATE COMPONENTS,LB/DAY")
3690   460 FORMATClH-,//38H "SECOND STAGE CAKE COMPONENTS,LB/DAY")
3700   470 FORMAT(lH-,//50H "SECOND STAGE CENTRATE RECYCLE COMPONENTS,LB/DAY"
3710      5)
                                    254

-------
3720   "480 FORMAT(lH-,//51H "INCItERATION  FURNACE  WASTE ASH COMPONENTS,LB/DAY
3730      e:0
3740   490 FORMAT OH-,//51H ::RECALCINATION FURMACE SLOWDOWN COMPONENTS, LB/DAY
3750      6")
3760   495 FORMAT(lH-,//4J*H "RECYCLED  SOLIDS ACCEPTS COMPONENTS, LB/DAY")
3770   500 FORMATClH-,//3SH -CLASSIFIER  REJECTS  COMPONENTS, LB/DAY")
3780   505 FORMAT(lH-,//55H -RECOVERIES  OF COMPONENTS IN PROCESS  STREAMS,FRAC
3790      ETION")
3800   508 FORMATC55H            FIRST  "  RECALCINE  "SECOND"INCINEFATION"  DRY)
3810   510 FORMATC55H            STAGE                STAGE                   )
3820   515 FORMATC60H            CAKE     FURNACE    CAKE    FURNACE     CLASS!
3830      EFIER)
3840   518 FORMAT(1H1,/9H ORGANICS, 3X.F4.2, 7X, F4.1, 5X, F4 . 2, 6X, F4 . 2, 7X, F4. 2)
3850   520 FO,VWT(im,/4H CAO, 8X,F4.2, 7X, F4. 2, 5X, F4 . 2, 6X, F4. 2, 7X,F4. 2)
3860   522 FORMAT(1H1,/6H CAC03,6X,F4.2,7X, F4. 2, 5X,F4.2,6X,F4.2,7X,F4.2)
3870   525 FORMAT(1H1,/4H MGO, 8X,F4. 2, 7X, F4. 2, 5X, F4. 2, 6X, F4 . 2, 7X, F4. 2)
3880   530 FOPMATC1H1,/8H MG(OH)2,4X, F4. 1, 7X, F4. 2, 5X,F4 . 2, 6X, F4 . 2, 7X,F4 . 2)
3890   535 FORMAT(1H1,/6H FE203,6X,F't.2/7X,Flt.2,5X,Fl|.2,6X,Fl(.2,7X,F'*.2)
3900   540 FOPMATCIHI^/SH FECOH^,1)/, F4. 2, 7X,F4 . 2, 5X, F4. 2, 6X, F4. 2, 7X,F<*.2)
3910   545 FOPJ^TC1H1,/5H SI02,7X,F4.2, 7X,F4.2, 5X, F4. 2, 6X,F4. 2, 7X,F4.2)
3920   550 FOPJ-'ATClHl,/?^! IKERTS, 5X, F4. 2, 7X, F4 . 2, 5X, F4. 2, 6X,F4.2, 7X, F4. 2)
3930   551 FORMATC1H1,/10H  CA3(P04)2,2X, F4.2, 7X, F4.2,5X, F4.2,6X, F4.2, 7X,F4.2)
3940   553 FORMAT(1H1,/6H TOTAL,6X, F4. 2, 16X, F4. 2, 17X, F4. 2)
3950   560 FORMATClHl,44H::r.'BV MAKEUP LIME  ADDED, FRACTION COMPOSITIONK)
3960   570 FORMATC1H1,44H;'-  SI02   :; ACID INSOL.  INERTS   :: MGO  "CAO  ")
3970   573 FORMATC2X,F5.2,9X,F5.2,11X,F5.2, 2X,F5.2)
3980   620 FORMAT(lH-,//6'*H "              PRIMARY  INFLUENT COMPOSITION,MG/L
3990      S             ")
4000   630 FORMATC64H "SUSP.SOLIDS"MAGNESIUM::CALCIUM"PHOSPHORUS"SI02"A. I . INE
4010      CRTS::IRON::)
4020   633 FORMATC5X,F5.1,6X,F5.1,4X,F5.1,4X,F6.2,3X,F5.1,2X,F5.1,2X,F6.2)
4030  1199 PRINT 301
4040  1200 PRINT 300
4050  1201 PRINT 301
4060  1205 PRINT 310
4070  1210 PRINT 315
4080  1215 PRINT 320
4090  1220 PRINT 321,PH,XMGD,CAOTOMGL/CAONMGL,CAORMGL,CAORSFRA
4100  1221 PRINT 301
4110  1225 PRINT 340
4120  1240 PRINT 350
4130  1250 PRINT  353,FECL3M;L,X1_BWASIN
4140  1251 PRINT 301
4150  1260 PRINT 360
4160  1270 PRINT 365
4170  1280 PRINT 367,FRBO,RECALEFF
4180  1281 PRINT 301
4190  1290 PRINT 560
4200  1300 PRINT 570
4210  1310 PRINT 573,FRSINEW,-FRAIINEW,FRMGONEW,FRCAONEW
4220  1311 PRINT 301
4230  1390 PRINT 620
4240  1400 PRINT 630
4250  1410 PRINT 633,SSINM£L,XMGINMGL,CAINFMGL,PINFMGL,SI INMGL,AI IINMGL, FE1NFMGL
4260  1420 PRINT 400
4270  1430 PRINT 410
4280  1432 PRINT 411, SSOUT>GL,XMGEFMGL,CAEFFMGL,PEFFMGL, SIEFFMGL.AI IEFMGL,
4290      EFEEFFMGL
4300  1433 PRINT 301
4310  1434 PRINT 354
4320  1435 PRINT 420,ORG1P,CA01P,CAC1P,XMG01P,XMGH1P/FE01P,FEOH1P,SI021P,
4330      £AII1P,CAP1P,TOT13
4340  1436 PRINT 301
4350  1440 PRINT 415
4360  1450 PRINT 420,ORGSLG,CAOSLG,CACSLG,XMGOSLG,XMGHSLG,FEOSLG,FEOHSLG,SISI_
4370      CG,AIISLG,CAPSLG,TOT1
4380  1453 PRINT 301
4390  1460 PRINT 430
4400  1470 PRINT 1)20,ORGCAK1,CAOCAK1,CACCAK1,XMSOCAK1,XM6HCAK1,FEOCAK1,FEOHCA
4410      SK1,SICAK1,AIICAIU,CAPCAK1,TOT2
4420  1473 PRINT 301
4430  1475 PRINT 450
4440  1476 PRINT 420,ORGOrTl,WOCrrrl,CACCOTl,XMSOChn-l,X>WHCNTl,FECOJT:,FEOHCN
4450      CTl,SICNTl,AnCNTl,CAPCMTl,TOT3
4460  1477 PRINT 301
4470  1480 PRINT 440
4480  1490 PRINT 4:0,ORGFP,CAOFP,CACFP,XMGOFP/XMGHFP, FEOFP, FEOHFP,SIFP-, AIIFF
4490      CCAPFP, TOT4
4500  1492 PRINT 301
4510  1493 PRINT 355
4520  1494 PRINT 420,ORGSEl,C/>OSEl,CACSEl,XMr.OSEl,XMf.HSEl,FEOSEl,FEOHSEl,SISE
                                       255

-------
1(530      n,AIISrl,CAPSEl,TOT5
WO  1495 PRINT 501
WO  11(06 PRINT 1(95
1(560  1497 PRINT 1(20,ORGRS.CAORS^CRS.XMTORSjXWHRS^ORS^EOI-RS,SIRS,AI IRS,
1(570      try\fR5,TOT6
1(580  1418 PPIW 301
man  lU'iu irmjt:i*\rr..f:o.j.o} co TO  jn»-
1(600  1500 PRINT i(60
1(610  1510 PRINT M20,ORGCAK2,CWD«2/CACCAK2,X^^XAK2/»KHCAK2,FEOCAK2,FEaHCA
1(620      CK2,SICAK2,AIICAK2,CAPCAK2,TOT7
1(630  1511 CONTINUE
i(6i(0  1513 PRINT 301
1(650  1560 PRINT 1(70
1(660  1570 PRINT i(20,ORG<>rn/aMX^2,CACCNT2,XMGOChlT2,XMGHCNT2,FEOCNT2/FEOHCN
1(670      ET2,SICNT2,AIICNT2,CAPCNT2,TOT8
1(680  1575 PRINT 301
"(690  1580 PRINT 1(80
1(700  1590 PRINT lt20,ORGFPI,CAOFPI,CACFPI/XMGOFPI,XNGHFPI,FEOFPI,FEOHFPI,SIFP
1(710      SI,AIIFPI,CAPFPI,TOT9
1(720  1595 PRINT 301
1(730  1596 PRINT 356
1(71(0  1597 PRINT 420,ORGSE2,U\OSE2,CACSE2,XMGOSE2,XMGHSE2,FEOSE2,FEOHSE2,SISE
"(750      62,AIISE2,CAPSE2,TOT10
1(760  1598 PRINT 301
1(770  1599 CONTINUE
1(780  1600 IF(FRBD.EQ.O.O) GO TO  1617
1(790  1601 PRINT 1(90
1(800  1603 PRINT 420,ORGBD,CAOBD,CACBD,XMGOBD,XMGHBD,FEOBD,FEOHBD,SIBD,AIIBD,
"(810      &CAPBD,TOT11
1(820  1617 CONTINUE
"(830  1620 IFCCLASSIF.EQ.O.O) GO TO  1650
1(840  1630 PRINT 500
1(850  161(0 PRINT l+20,ORGCR,CAOCR,CACCR,XMGOCR,XMGHCR,FEOCR,FEOHCR,SICR,AIICR/
1(860      ECAPCR,TOT12
1*870  161(3 PRINT 301
1(880  1650 PRINT 505
1(890  1652 PRINT 301
1(900  1660 PRINT 508
1(910  1670 PRINT 510
1(920  1680 PRINT 515
1(930  1690 PRINT 518/REORG1,REORGF,REORG2,REORGFI,REORGCL
1(940  1695 PRINT 520,RECA01,RECACF,RECA02,RECAOFI,RECAOCL
4950  1700 PRINT 522,RECAC1,RECACF,RECAC2,RECACFI,RECACCL
4960  1710 PRINT 525,REXMGG1,REXMGOF,REXM»2,REXMSOFI,REXMGOCL
4970  1720 PRINT 530,REXMGH1,REXMGHF, REXMGH2,REXMGHFI ,REXMGHCL
4980  1730 PRINT 535,REFE01,REFEOF,REFE02,REFEOFI,REFEOCL
4990  1740 PRINT 540,REFEOH1,REFEOHF,REFEOH2,REFEOHFI,REFEOHCL
5000  1750 PRINT 545,RESI1,RESIF,RESI2,RESIFI,RESICL
5010  1760 PRINT 550,REAII1,REAIIF,REAII2,REAIIFI,REAIICL
5020  1761 PRINT 551,RECAP1,RECAPF,RECAP2,RECAPFI,RECAPCL
5030  1762 PRINT 553,TOTRE1,TOTRE2,TOTRECL
5040  1763 CONTINUE
5050  1800 STOP;END
                                        256

-------
   APPENDIX B




OUTPUT FOR CASES
      257

-------
                        Table B-1 .  CASE DESCRIPTIONS
a
Case no.
100b
lolh
102b
103°
104°
105°
106°
107 =
108
109°
iioc
111°
112°
113C
114C
115C
116°
117b
118b
119
!2°H,
b d
121K
h e
122 '
First stage wet
classification
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Vacuum filter
Vacuum filter
Pressure filter
Pressure filter
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Second stage
dewatering
Centrifuge
Vacuum filter
Pressure filter
None
None
None
None
None
None
None
None
None
None
None
None
None
None
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Centrifuge
Incineration of
second stage cake
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Classifier for
recalcined
product
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
Yes
Yes
Slowdown of
recalcination
furnace product,
percent
0
0
0
0
10
15
20
24
28
31
35
45
100
0
20
0
20
0
20
24
28
0
0
All cases are for the following conditions (unless noted):
pH:  11.0
Primary flow:  1.31 cu m/sec
Fed, dose to primary:  14.0mg/l
Ca(OH)2dose:  400.0mg/l

ATTF System case

Plural Purpose Furnace case

pH 10.2,  289 mg/1 Ca(OH)    24.0 rng/1 Fed.
                       £               3
pH 11.5,  500 mg/1 Ca(OH)    0.0 mg/1 Fed,
                       L,              O
                                         258

-------
 CASE 100
                                                                      "FIRST PASS PRECIPITATION COMPONENTS,LB/DAY:1
DAT1

110,30.0,97%.0, lit.0,400.0,0.0,0.95
115,2.0,1.0, 11.0,1.0,0.0,0.0,0.0
DAT2
 131,2:PH - MGD-TOTAL DOSE-NEW LIf-€>!  RECYCLED    LIME"
              MG/L      MG/L     MG/L    FRACTION
 11.0  30.00  302.7     113.7     189.0      0.62
 "FECL3 DOSE:=WASTE BIOLOGICAL SLUDGE"
 "    MG/L  "     ADDED, LB/DAY      K
      14.0              9746.0
ORGAN ICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID INSOL.
CA3(P04)2

TOTAL
                                                                                  INERTS
               23309.
                   0.
               97327.
                1817.
                2368.
                 255.
                 743.
                9047.
                1683.
                3401.

              139950.
                                                                     "FIRST STAGE CENTRATE COMPONENTS, LB/DAYI!
 ^FURNACE BLOVOCH*JKRECALCINING EFFICIENCY"
 *    FRACTION    »       FRACTION       x
         0.                   0.95
 "NEW MAKEUP LIME ADDED,FRACTION OPPOSITION"
 " SI02   " ACID INSOL. INERTS  K MGO   "CAO  "
   0.03          0.01            0.07    0.89
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID  INSOL.
CA3(P04)2

TOTAL
                                                                                   INERTS
               34963.
                   0.
               20645.
                4912.
                6402.
                 596.
                1734.
                1005.
                 503.
               13603.

               84363.
 >'•               PRIMARY  INFLUENT COMPOSITION,MG/L             «
 >:SUSP.SOLIDSItMAGNESIUM"-CALCIUM:IPHOSPHORUS::SI02'1A. I. INERTS11! RON"
     240.0       22.3      30.0      10.00     13.2     1.9    0.
 K               PRIMARY EFFLUENT  COMPOSITION,MG/L             «
 XSUSP.SOLIDS1!MAGNESIUM!;CALCIUM"PHOSPHORUSI!SI02':A. I . INERTS"IRON"
      26.0        8.7      60.0       0.68      0.9    0.1    0.
                                                                     "RECALCINATION  FURNACE  PRODUCT COMPONENTS, LB/DAY*
ORGAN ICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL.
CA3(P04)2

TOTAL
                                                                                  INERTS
                   0.
               48154.
                4526.
                3166.
                   0.
                 770.
                   0.
                8866.
                1464.
                3197.

               70143.
                                                           259

-------
"RECALCINATION FURNACE WET SCRUBBER WATER COMPONENTS,LB/DAY"
                                                           "INCINERATION FURNACE WET SCRUBBER WATER  COMPONENTS,LB/DAY*
ORGAN I CS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CP04)2
TOTAL
0.
0.
6813!
275.
0.
41.
0.
181.
219.
201*.
7733.
ilNV, ll^lUVt 1 1 Win I i^ruinvt m^ I

ORGANICS
CAO
CAC03
MGC
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CPO"O2
1 J^f\ULJU[_l\

0.
0.
11(31.
670.
0.
85.
0.
20.
53.
735.
                                                             TOTAL
                                                                                         2993.
"RECYCLED SOLIDS ACCEPTS- COMPONENTS, LB/DAY«
 TOTAL
                           66583.
                                                           ''-CLASSIFIER REJECTS COMPONENTS, LB/DAY«
ORGANICS
CAO
CAC03
MOO
MG(OH)2
•FE203
FECOH03
SI02
ACID INSOL. INERTS
CA3CP04)2
0.
"47239.
4453.
3059.
0.
666.
0.
6747.
1360.
3059.
ORGANICS
CAO
CAC03
MSO
MGCOH)2
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3CP04)2
0.
915.
72.
108.
0.
105.
0.
2119.
104,
137.
                                                           TOTAL
                                                                                       3560.
"SECOND STAGE CAKE COMPONENTS, LB/DAY«
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3(P04)2
27271.
0.
20439.
4421.
5762.
536.
1561.
975.
407.
12242.
                                                          "RECOVERIES OF COMPONENTS  IN PROCESS  STREAMS,FRACTION"
 TOTAL
                           7361"(.
                                                                    FIRST " RECALCINE 1!SECOND«INCINERATION!!  DRY



STAGE

CAKE FURNACE
"SECOND STAGE CENTRATE
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3(P04)2

TOTAL

-INCINERATION FURMACE
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CP04)2
RECYCLE COMPONENTS, LB/DAY"
7692.
0.
206.
1(91.
61(0.
60.
173.
30.
96.
1360.

1071(9.

WASTE ASH COMPONENTS, LB/DAYK
0.
0.
19008.
9369.
0.
1992.
0.
956.
354.
11508.
ORGANICS
CAO

CAC03

MGO

MG(OH)2

FE203
FECOH33

SI02
INERTS
CA3CPQ1O2
TOTAL

0.40
0.

0.83

0.27

0.27

0.30
0.30

0.90
0.77
0.20
0.62

0.
0.93

0.93

0.92

0.

0.95
0.

0.98
0.87
0.9"(


STAGE

CAKE FURNACE
0.78
0.

0.99

0.90

0.90

0.90
0.90

0.97
0.81
0.90
0.87

0.
0.

0.93

0.92

0.

0.95
0.

0.98
0.87
0.9"(



CLASSIFIER
0.
0.98

0.98

0.97

0.

0.86
0.

0.76
0.93
0.96
0.95

PROGRAM STOP AT 3250

USED




.91 UNITS























 TOTAL
                           43186.
                                                         260

-------
CASE 101
DAT1
110,30. 0,9746.0,14. 0,1*00.0,0.0,0.95
115,2.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2
 131,240. 0,26.0,22.3,8.7"*, 30.0,60.0
 132,10.0,0.68,0.0,0.0024,0.002'*
 141,0.035,0.0024,0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
 DAT3
 161,0.20,0.825,0.90,0.77
 171,0.27,0.27,0.30,0.30,0.40
 181,0.94,0.94,0.94,0.94,0.9"»
 182,0.94,0.94,0.94,0.94
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.94,0.93,0.98,0.87,0.0
 202,0.95,0.0,0.0,0.92
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.864,0.0,0.0,0.966
LIME SOLIDS PROCESSING MASS BALANCE
"   "FLOW-           LIME USE AS CAO            «
::PH - MGD'H'OTAL C«SE"NEW LIME"  RECYCLED    LIME"
             MG/L      MS/L     MG/L    FRACTION
11.0  30.00  302.7     111.9     190.8     0.63
                                                                  "FIRST PASS PRECIPITATION COMPONENTS,LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOH)2
 FE203
 FE(OH)3
 SI02
 ACID  INSOL.
 CA3(P04)2

 TOTAL
                                                                               INERTS
               50580.
                   0.
              105069.
                2200.
                8144.
                   0.
                2304.
                3061.
                 453.
               1.1645.

              183456.
 "PRIMARY SLUDGE  COMPONENTS,LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOO2
 FE203
 FECOH53
 SI02
 ACID INSOL.
 CA3CP04)2

 TOTAL
INERTS
 52469.
     0.
119060,
  6324.
  8502.
   797.
  2405.
 10106.
  1924.
 16288.

217875.
                                                                  "FIRST STAGE CAKE  COMPONENTS. LB/DAY"
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOH)3
SI02
ACID  INSOL.
CA3(P04)2

TOTAL
INERTS
 20987.
     0.
 98225.
  1708.
  2296.
   239.
   721.
  9096.
  1482.
  3258.

138011.
"FECL3 DOSE^ASTE BIOLOGICAL SLUDGE-
•"    MG/L  "     ADDED, LB/DAY      *
     14.0              9746.0
"FURNACE BLOWDOWN-RECALCINING EFFICIENCY*
"    FRACTION    "       FRACTION       K
        0.                   0.95
:=NEW MAKEUP LIME ADDED, FRACTION COMPOSITION"
" SI02   :: ACID INSOL. INERTS  " MGO  "-CAO "
  0.03          0.01            0.07   0.89
«FIRST STAGE CENTRATE COMPONENTS,LB/DAY"
 ORGAfUCS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FECOH03
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
                                                                               INERTS
               31481.
                   0.
               20836.
                4617.
                6207.
                 558.
                1683.
                1011.
                 443.
               13030.

               79865.
                                                                  "RECALCULATION FURNACE PRODUCT COMPONENTS,LB/DAY-
"               PRIMARY INFLUENT COMPOS IT ION,MG/L             "
"SUSP.SOLIDS"MAGNESIUM::CALCIUM::PHOSPHORUS"SI02"A. I . INERTS"IRONK
    240.0       22.3     30.0     10.00    13.2     1.9    0.
K               PRIMARY EFFLUENT COMPOSITIO^MG/L             a
«SUSP.SOLIDS::MAGNESIUM::CALC!UM"PHOSPHORUS!;SI02!cA.I.INERTS!tIRON![
     26.0        8.7     60.0      0.68     0.9    0.1     0.
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOH)2
 FE203
 FECOH53
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
 INERTS
     0.
 48598.
   4567.
   3020.
     0.
    7J9.
     0.
   8914.
   1289.
   3062.

 70190.
                                                          261

-------
"RECALCINATION FURNACE WET SCRUBBER WATER COMPONENTS,LB/CWY*
 ORGAN ICS
 CAO
 CAC03
 MGO
 M6(OH)2
 FE203
 FECOt-03
 SI02
 ACID INSOL. INERTS
 CA3(P04)2

 TOTAL
                   0.
                   0.
                6876.
                 263.
                   0.
                  39.
                   0.
                 182.
                 193.
                 195.

                7747.
"RECYCLED SOLIDS ACCEPTS COMPONENTS,LB/DAY!1
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FECOH33
 SI02
 ACID INSOL.  INERTS
 CA3(P04)2

 TOTAL
                   0.
               47674.
               4494.
               2917.
                   0.
                 639.
                   0.
               6783.
               1197.
               2930.

               66636.
 "SECOND  STAGE CAKE COMPONENTS,LB/DAY*
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
INERTS
29592.
    0.
19585.
 4340.
 5834.
  524.
 1582.
  950.
  416.
12249.

75073.
                                                           "INCINERATION FURNACE WET SCRUBBER WATER COMPONENTS, LB/DAY*
                               ORGAN I CS
                               CAO
                               CAC03
                               MGO
                               MG(OH)2
                               FE203
                               FE(OH)3
                               SI02
                               ACID INSOL.
                               CA3(P04)2

                               TOTAL
                                                                       INERTS
    0.
    0.
 1371.
 667.
    0.
   85.
    0.
   19.
   54.
 735.

 2932.
                               "CLASSIFIER REJECTS COMPONENTS, LB/DAY"
                                              ORGAN I CS
                                              CAO
                                              CAC03
                                              MGO
                                              MG(OH)2
                                              FE203
                                              FE(OH)3
                                              SI02
                                              ACID  INSOL.  INERTS
                                              CA3(P04)2

                                              TOTAL
   0.
 923.
  73.
 103.
   0.
 101.
   0.
2130.
  92.
 132.

3553.
                                                           RECOVERIES OF  COMPONENTS IN PROCESS STREAMS,FRACTION"
"SECOND STAGE CENTRATE RECYCLE COMPONENTS,LB/DAY"
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3(P04)2
TOTAL


"INCINERATION FURNACE WASTE
ORGAN I CS
CAO
CAC03
MGO
MGCOH52
FE203
FE(OK)3
SI02
ACID INSOL. INERTS
CA3CP01O2
TrvrAi
1889.
0.
1250.
277.
372.
33.
101.
61.
27.
782.
4792.


ASH COMPONENTS, LB/DAY!!
0.
0.
18214.
9360.
0.
2001.
0.
931.
362.
11514.

FIRST !1 RECALCINE

STAGE

CAKE FURNACE
ORGANICS

CAO

CAC03
MGO
MGCOH52
FE203
FECOH)3
SI02

INERTS
CA3CP04)2
TOTAL
0.40

0.

0.83
0.27
0.27
0.30
0.30
0.90

0.77
0.20
0.63
0.

0.93

0.93
0.92
0.
0.95
0.
0.98

0.87
0.94

!ISECOND!!INCINERATION1! DRY
STAGE
CAKE
0.94

0.

0.94
0.94
0.94
0.94
0.94
0.94

0.94
0.94
0.94

FURNACE
0.

0.

0.93
0.92
0.
0.95
0.
0.98

0.87
0.94


CLASSIFIER
0.

0.98

0.98
0.97
0.
0.86
0.
0.76

0.93
0.96
0.95
PROGRAM STOP AT 3250
USED
.90 UNITS




                                                         262

-------
CASE 102
DAT1
110,30.0,97%.0,14.0,400.0,0.0,0.95
115,2.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2
 131,21(0.0,26.0,22.3,8.74,30.0,60.0
 132,10.0,0.68,0.0,0.0024,0.002'*
 141,0.035,0.0024,0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
 DAT3
 161,0.20,0.825,0.90,0.77
 171,0.27,0.27,0.30, 0.30,0.40
 181,0.99,0.99,0.99,0.99,0.99
 182,0.99,0.99,0.99,0.99
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.94,0.93,0.98,0.87,0.0
 202,0.95,0.0,0.0,0.92
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.864,0.0,0.0,0.966
 LIME SOLIDS PROCESSING  MASS  BALANCE
 •"   "FLOW*           LIME  USE AS  CAD             «
 "PH - MGD'TOTAL DOSE-NEW LIME" RECYCLED    LIME*
              MG/L      MG/L     MG/L    FRACTION
 II.0  30.00   302.7     113.7      189.0      0.62
                                                                  "FIRST PASS PRECIPITATION COMPONENTS, LB/DAY"
 ORGANICS
 CfO
 CAC03
 MGO
 MGCOH)2
 FE203
 FECOH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
                                                                               INERTS
               50580.
                   0.
              105069.
                2234.
                8144.
                   0.
                2304.
                3075.
                 458.
               11645.

              183509.
"PRIMARY SLUDGE COMPONENTS,LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOH)2
 FE203
 FECOH53
 SI02
 ACID INSOL.
 CA3CP04)2

 TOTAL
INERTS
 50885.
     0.
117972.
  5983.
  8190.
   736.
  2320.
  9988.
  1865.
 15474.

213414.
-FIRST STAGE CAKE COMPONENTS,LB/DAY"
  ORGANICS
  CAO
  CAC03
  MGO
  MGCOH)2
  FE203
  FECOH)3
  SI02
  ACID INSOL.
  CA3
-------
::RECALCINATION FURNACE WET SCRUBBER WATER COMPONENTS, LB/DAY*
ORGAN I CS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH33
SI02
ACID INSOL.
CA3CP04)2
TOTAL



0.
0.

6813.
251.
0.
37.
0.
180.
INERTS 187.
186.
7653.



x INCINERATION FURNACE WET



ORGANICS
CAO
CACO3
MGO
MGCOH)2
FE203
FECOH33
SI02
ACID INSOL. INERTS
CA3CPO
-------
CASE 103
                                                                   KFIRST PASS PRECIPITATION COMPONENTS,LB/DAY«
DATl
110, 30.0,9746.0,14.0,400.0,0.0,0.95
115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2
 131,240.0,26.0,22.3,8.74,30.0,60.0
 132,10.0,0.68,0.0,0.0024,0.0024
 141,0.035,0.0021*, o.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
                                                             ORGAN ICS
                                                             CAO
                                                             CAC03
                                                             MGO
                                                             MGCOH)2
                                                             FE203
                                                             FE(OH)3
                                                             SI02
                                                             ACID INSOL.
                                                             CA3CP04)2

                                                             TOTAL
                           50580.
                               0.
                          105069.
                            mm.
                            8144.
                               0.
                            2304.
                            2758.
                             346.
                           11645.

                          182259.
DAT3
 161,0.
 171,0.
 181,0.
 182,0.
 191,0.
 192,0.
 201,0.
 202,0.
 211,0.
 212,0.
89,0.99,0.99,0.95
97,0.97,0.87,0.87,0.91
0,0.0,0.0,0.0,0.0
0,0.0,0.0,0.0
94,0.93,0.98,0.87,0.0
95,0.0,0.0,0.92
0,0.0,0.0,0.0,0.0
0,0.0,0.0,0.0
957,0.981*, 0.761,0.929,0.0,0.981
864,0.0,0.0,0.966
ORGAN i cs
CAO
CAC03
MSO
FE203
FE(OH)3
SI02
ACID INSOL.
CA3CPO'*)2

TOTAL
                                                                             SLUDGE COMPONENTS, LB/DA Y1-'
               55582.
                   0.
              120024.
              224681.
                8381.
               13343.
                2648.
               11895.
INERTS          5890.
              323717.
                                                                                              766161.
LIME SOLIDS PROCESSING MASS BALANCE
*   KFLOW*           LINE USE AS CAO            -
KPH " MGD;rTOTAL DOSE^EW LINE"  RECYCLED    LINE"
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7      71.9     230.8     0.76
                                                             =FTRST STAGE  CAKE  COMPONENTS,LB/DAY^
KFECL3 DOSE::WASTE BIOLOGICAL SLUDGE*
"    MG/L  ~     ADDED, LB/DAY      »
     14.0              9746.0
 "FURNACE BLOWDOWN-RECALCINING EFFICIENCY15
 x    FRACTION    "       FRACTION       *
        0.                   0.95
 ::NEW MAKEUP LIME ADDED,FRACTION COMPOSITION"
 " SI02   " ACID INSOL. INERTS  :: MGO  "CAO *
  0.03          0.01            0.07   0.89
                                                             ORGANICS
                                                             CAO
                                                             CAC03
                                                             MGO
                                                             MG(OH)2
                                                             FE203
                                                             FECOH)3
                                                             SI02
                                                             ACID  INSOL.
                                                             CA3CP04)2

                                                             TOTAL
             INERTS
               50580.
                   0.
               118823.
               217940.
                8130.
               11609.
                2304.
               11776.
                5595.
               288108.

               714865.
                                                                    TIRST STAGE CENTRATE COfPONENTS,LB/DAY::
*               PRIMARY INFLUENT COMPOSITION,MG/L              K
"SUSP SOLIDS::MAGNESIUM::CALC1UM:IPHOSPHORUS::SI02"A.I . INERTS^IRON"
    240.0       22.3     30.0      10.00     "  "     '  '•
                                     11.9    1.4
                                                    0.
X               PRIMARY EFFLUENT COMPOSITION,MG/L             *
"SUSP SOL!DS"MAGNESIUM::CALC:UM::PHOSPI-ORUS"SI02::A. I . INERTS^IRON*
     26 0        8.7     60.0
                             0.68
                                      0.9
                                             0.1
                                                    0.
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3CPO4)2

 TOTAL
                                                                          UJERTS
                 5002.
                    0.
                 1200.
                 6740.
                  251.
                 1735.
                  344.
                  119.
                  294.
                35609.

                51296.
                                                          265

-------
                             „ „„„,  „.,  , D,^v»              "RECOVERIES OF COMPONENTS  IN PROCESS  STREAMS,FRACTION"
 "RECALCINATION FURNACE PRODUCT COMPONENTS, LB/DAYK





                                                                        FIRST « RECALCINE  "SEGONDXINCINERATION*   DRY
r irvs i n.L.>-^tv. J (^L.
ORGANICS 0. STAGE
CAO 58789. ru.F RRMArp
CAC03 5525. CAKE RJRNftCE
M60 205637. ORGANICS 0.91 0.
MGCOH)2 0.
FE203 12665. CAO 0 0 93
ACID INSOL. INERTS "*868.
CA3(PO
-------
CASE 104
                                                            "FIRST PASS PRECIPITATION COMPONENTS,LB/DAY"
DAT1

110,30.0,9746.0,14.0,400.0,0.1,0.95
115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2
131,240.0,26.0,22.3,8.74, 30.0,60.0
13.2., 10.0,0.68,0.0,0.0024,0.0024
141,0.035,0.0024,0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MGCC+O2
FE203
FE(OH)3
SI02
ACID  INSOL.
CA3CP04)2

TOTAL
INERTS
 50580.
     0.
105069.
  1888.
  8144.
     0.
  2304.
  2941.
   mi.
 11645.

182982.
DAT3

161,0.89,0.99,0.99,0.95
171,0.97,0.97,0.87,0.87,0.91
181,0.0,0.0,0.0,0.0,0.0
182,0.0,0.0,0.0,0.0
191,0.94,0.93,0.98,0.87,0.0
192,0.95,0.0,0.0,0.92
201,0.0,0.0,0.0,0.0,0.0
202,0.0,0.0,0.0,0.0
211,0.957,0.984,0.761,0.929,0.0,0.981
212,0.864,0.0,0.0,0.966
LIME SOLIDS PROCESSING MASS BALANCE
 KPRIMARY SLUDGE  COMPONENTS,LB/DAYX
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL.
CA3(P04)2

TOTAL
                                                                        INERTS
               55582.
                   0.
              119406.
               58311.
                8381.
                7391.
                2648.
                9621.
                3032.
              100359.

              364731.
K   -FLOW5-"           LIME USE AS CAO             «
KPH K MOD-TOTAL DOSE1!NEW LIME11  RECYCLED    LIME"
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7      96.1     206.6      0.68
"FECL3 DOSE'WSTE BIOLOGICAL SLUDGE*
*    MG/L  »     ADDED, LB/DAY      :1
     14.0              9746.0
"FURNACE BLOWDOWN-RECALCINING EFFICIENCY"
K    FRACTIC*1    !t       FRACTION       "
        0.1IJ                 0.95
"NEW MAKEUP Ll^€ ADDED,FRACTION COMPOSITION11
!l SI02   K ACID INSOL. INERTS  !! MGO   !1CAO "
  0.03          0.01            0.07    0.89
x               PRIMARY  INFLUENT  COMPOS IT ION, MG/L             »
!!SUSP. SOLIDS!1MAGNESIUMI:CALCIUM:tPHOSPHORUS!:S I02:!A. I . INERTS"IRON:1
    240.0       22.3      30.0      10.00    12.7    1.7    0.
«               PRIMARY  EFFLUENT COMPOSITION,MG/L             «
"SUSP SOLIDS::MAGNESIUM>:CALCIUM::PHOSPHORUS:;SI0211A.I.INERTSI1IRON«
     26 0        8.7      60.0       0.68     0.9    0.1    0.
                                                           267

-------
CASE 105
                                                                KFIRST PASS PRECIPITATION COWONENTS,LB/OAY*
DAT1
110,30.0,9746.0,14.0,400.0,0.15,0.95
115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2

131,21*0.0,26.0,22.3,8.74,30.0,60.0
132,10.0,0.68,0.0,0.002if, 0.0024
1"» 1,0.035,0.0024,0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MGOO2
FE203
FECC+O3
SI02
ACID  INSOL.
CA3CP04)2

TOTAL
                                                                            INERTS
              50580.
                   0.
             105069.
                212l».
                8Wt.
                   0.
                2301*.
                3032.
                 W.
              1161*5.
DAT 3
                                                                 "PRIMARY SLUDGE COMPONENTS,LB/DAY*
161,0.89,0.99,0.99,0.95
171,0.97,0.97,0.87,0.87,0.91
181,0.0,0.0,0.0,0.0,0.0
182,0.0,0.0,0.0,0.0
191,0.94,0.93,0.98,0.87,0.0
192,0.95,0.0,0.0,0.92
201,0.0,0.0,0.0,0.0,0.0
202,0.0,0.0,0.0,0.0
211,0.957,0.984,0.761,0.929,0.0,0.981
212,0.864,0.0,0.0,0.966
LINE SOLIDS PROCESSING MUSS BALANCE
"   "FLOW"           LIME L-SE AS CAO            x
"PH ••• MGO::TOTAL DOSE::NEW Ll'TE-  RECYCLED    LIME*
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     108.1     194.7     0.64
"FECL3 DOSE::WASTE BIOLOGICAL SLUDGE"
-    MG/L  -     ADDED, LB/QAY      K
     14.0              9746.0
"FURM^CE BLOWDOWN-RECALCININ6 EFFICIENCY1'
'•'•    FRACTION    "       FRACTION       x
        0.15                 0.95
::NEW K4KEUP LIME ADDED,FRACTION COMPOSITION"
" 5102   :: ACID INSOL. INERTS  -' MSO  "CAO *
  0.03          0.01            0.07   0.89
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FECOH53
 SI02
 ACID INSOL.
 CA3CP0452

 TOTAL
               55582.
                   0.
              119099.
INERTS
  8381.
  5866.
  2648.
  8849.
  2548.
 74617.

320082.
"               PRIMARY INFLUENT COMPOSITION,MG/L              K
"SUSP. SOLIDS::MAWJESILW::CALCILW::PHOSPHORUS"SI02::A. I . INERTS"IRON"
    240.0       22.3     30.0     10.00     13.0     1.8     0.
=•               PRIMARY EFFLUENT COMPOSITION,MG/L              !:
"SUSP. 5OLIDS::MAGNESHM::CALCIUM::PHOSPHORUS::SI02"A. I. INERTS"IRON"
     26.0        8.7     60.0      0.68      0.9     0.1     0.
                                                            268

-------
CASE  106
                                                                "FIRST PASS  PRECIPITATION COMPONENTS,IB/DAY"
DAT1
110,30.0,97%.0,14.0,1*00.0.0.20,0 95
"5,1.0,1.0,11.0,1.0,0.0,o'o,0.0
DAT2
131,21(0.0,26.0,22.3,8.74,30.0,60.0
132,10.0,0.68,0.0,0.0024,0.0021*
lit 1,0.035,0.0024,0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FEO>03
SI02
ACID INSOL.
CA3CP04)2

TOTAL
                                                                            INERTS
                         50580.
                              0.
                         105069.
                           2358.
                           8144.
                              0.
                           2304.
                           3122.
                            475.
                          11645.

                         183697.
DAT3
                                                                 "PRIMARY SLUDGE COMPONENTS,LB/DAY"
 161,0.89,0.99,0.99,0.95
 171,0.97,0.97,0.87,0.87,0.91
 181,0.0,0.0,0.0,0.0,0.0
 182,0.0,0.0,0.0,0.0
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201-,0.0,0.0,0.0,0.0,0.0
 202,0.0,0.0,0.0,0.0
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.864,0.0,0.0,0.966
LIME SOLIDS PROCESSING MASS BALANCE
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOH)3
SI02
ACID  INSOL.
CA3CP04)2

TOTAL
           INERTS
 55582.
     0.
118794.
 33391.
  8381.
  4769.
  2648.
  8227.
  2239.
 59385.

293415.
K   "FLOW*           LIME USE AS CAO            «
:W " MGO-TOTAL DOSE::NEW LIME"  RECYCLED    LIME"
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     120.0     182.7     0.60
 "FIRST  STAGE  CAKE  COMPONENTS, LB/DAY"
"FECL3 DOSE::WASTE  BIOLOGICAL SLUDGED
K    MG/L  ••'•    ADDED, LB/DAY      x
     14.0             974S.O
"FURNACE BLOWDOW:!RECALCINING EFFICIENCY*
"    FRACTION     «       FRACTION       *
        0.20                0.95
KNEW MAKEUP LIME ADDED, FRACTION COMPOSITION"
" SI02   :: ACID  INSOL. INERTS  " MGO  "CAO x
  0.03          0.01            0.07    0.89
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOI-02
 FE203
 FECOH)3
 SI02
 ACID INSOL.
 CA3CP0452

 TOTAL
            INERTS
 50580.
     0.
117606.
 32389.
  8130.
  4149.
  2304.
  8144.
  2127.
 52853.

278281.
                                                                 "FIRST STAGE CENTRATE COMPONENTS, LB/DAY"
K               PRIMARY  INFLUENT COMPOSITION,MG/L             "
!!SUSP.SOL1DS"MAGNESIUM"CALCIUM::PHOSPHORUS"SI02::A. I . INERTS"IRON"
    240.0       22.3      30.0      10.00     13.4     2.0    0.
»               PRIMARY  EFFLUENT COMPOSITION,MG/L             «
«SUSP.SOLIDS"MAGNESIUM"CALCIUM"PHOSPHORUS"SI02"A. I . INERTS:IIRON:!
     26.0        8.7     60.0      0.68      0.9     0.1    0.
ORGANICS
CAO
CAC03
MGO
MGCOt-02
FE203
FE(OH)3
SI02
ACID INSOL.
CA3CP04)2

TOTAL
                             5002.
                                0.
                             1188.
                             1002.
                              251.
                              620.
                              344.
                               82.
                              112.
                             6532.

                            15134.
                                                         269

-------
>:RECALCIUATION FURNACE PRODUCT  COMPONENTS, LB/DAY"
                                                             "CLASSIFIER  REJECTS COMPONENTS, LB/DAY"
ORGAN 1CS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH03
SI02
ACID INSOL. INERTS
CA3(P04)2
TOTAL
"RE CALCINATION FURNACE
ORGAN I CS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOHJ3
SI02
ACID INSOL. INERTS
CA3(P04)2
TOTAL


0.
58187.
5469.
34930.
0.
5578.
0.
7982.
1850.
1*9681.
163676.
WET SCRUBBER WATER COMPONENTS, LB/DAY*
0.
0.
8232.
3037.
0.
291!.
0.
163.
276.
3171.
ism.


"RECYCLED SOLIDS ACCEPTS OPPONENTS, LB/DAY*

ORGAN I CS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3(P04)2
TOTAL
"RECALCINATION FURNACE
ORGAN I CS
CAO
CAC03
MGO
MGCOH32
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3(PO
-------
CASE 107
                                                                 "FIRST PASS  PRECIPITATION COfPONENTS,LB/DAY*
DAT1
110,30.0,9746.0, lit.0,1*00.0,0.24,0.95
115,1.0,1.0,11.0,1. 0, 0.0,0.0,0.0
DAT2
 131,2'tO. 0,26.0,22.3,8. 71*, 30. 0,60.0
 132,10. 0,0.68, 0.0,0.002i»,0.0021*
 1"*1,0.035,0.002"*, 0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID INSOL.
CA3CPOIO2

TOTAL
                                                                              INERTS
 50580.
     0.
105069.
  251*5.
  8m.
     0.
  2301*.
  319i».
   501.
 1161*5.

183981.
DAT3
 161,0.89,0.99,0.99,0.95
 171,0.97,0.97,0.87,0.87,0.91
 181,0.0,0.0,0.0,0.0,0.0
 182,0.0,0.0,0.0,0.0
 191,0.91*,0.93,0,98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.0,0.0,0.0,0.0,0.0
 202,0.0,0.0,0.0,0.0
 211,0.957,0.98"*, 0.761,0.929,0.0,0.981
 212,0.86i*,0.0,0.0,0.966
     SOLIDS PROCESSING  MASS BALANCE
                                                                   "PRIMARY SLUDGE COMPONENTS, LB/MY*
ORGANICS
CAO
CAC03
MGO
MGCOH32
FE20J
FECC+03
SI02
ACID INSOL.
CA3CPCHO2

TOTAL
                                                                              INERTS
 55582.
     0.
118551.
 28^88.
  8381.
  1*090.
  261*8.
  7809.
  2061.
 5101*8.

278658.
1!   "FLOW-1            Llf-E USE AS  CAO            «
«PH " MGO'TOTAL DOSE::NEW LIME= RECYCLED    LIME*
             MG/L       MG/L    MC-/L    FRACTION
11.0  30.00  302.7      129.5     173.2     0.57
"FIRST  STAGE CAKE COMPONENTS,L8/DAY"
"FECL3 DOSE::WASTE BIOLOGICAL SLUDGE"
K    MG/L  ::     ADDED, LB/DAY      K
     1<*.0              971*6.0
ORGANICS

USED      .60 UNITS
"FURNACE BLOWDOVM::RECALCINING EFFICIENCY*
•'•    FRACTION    '•'•        FRACTION       *
        0.21*                  0.95
:!NDV MAKEUP LIME .ADDED, FRACTION COMPOS ITION*
!! SI02   « ACID INSOL.  INERTS  :; MGO  KCAO *
  0.03          0.01             0.07   0.89
 110, 30.0,97'+6.0,11*. o,i*00.0,0.28,0.95
 115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
 NEW  DAT1

 READY
 110,30.0,971*6.0,11*.0,400.0,0.28, 0.95
 115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
 OLD  CSOLIDS1
*               PRIMARY INFLUENT COMPOSITION,MG/L              *
«SUSP.SOLIDS:WGNESIUM-~KLALCIl*li:PHOSPHORUS"SI02"A. I. INERTS:tIRON=«
    21*0.0       22.3      30.0     10.00    13.7     2.1     0.
-               PRIMARY EFFLUENT COMPOSITION,MG/L              a
"SUSP.SOLIDS::MAGNESIUM:'-CALCIUM----PHOSPHORUS"SI02::A.I.INERTS«IRCt«(«
     26.0         8.7      60.0      0.68     0.9     0.1     0.
                                                           271

-------
CASE  108
                                                               KFIRST PASS PRECIPITATION COMPONENTS,LB/DAY"
OATl

110,30.0,9746.0,14.0,400.0,0.28,0.95
115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
 DAT2
 131,240.0,26.0,22.3,8.74,30.0,60.0
 132,10.0,0.68,0.0,0.0024,0.0024
 141,0.035,0.0024,0.80,0.80,0.80
 151,0.035,0.035,0,027,0.0096,0.07,0.89
ORGANICS
CAO
CACO3
MGO
MG(OH)2
FE203
FEC003
SI02
ACID INSOL.
CA3(P04)2

TOTAL
                                                                            INERTS
 50580.
     0.
105069.
  2730.
  8144.
     0.
  2304.
  3266.
   526.
 11645.

184264.
 OAT3
 161,0.89,0.99,0.99,0.95
 171,0.97,0.97,0.87,0.87,0.91
 181,0.0,0.0,0.0,0.0,0.0
 132,0.0,0.0,0.0,0.0
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.0,0.0,0.0,0.0,0.0
 202,0.0,0.0,0.0,0.0
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.864,0.0,0.0,0.966
LIME SOLIDS PROCESSING MASS BALANCE
                                                                 "PRIMARY SLUDGE COMPONENTS, LB/DAY*
ORGANICS
CAO
CAC03
MGO
MS(OH)2
FE203
FE(OH)3
SI02
ACID INSOL.
CA3(P04)2

TOTAL
                                                                            INERTS
 55582.
     0.
118309.
 24827.
  8381.
  3535.
  2648.
  7446.
  1923.
 44764.

267415.
"   "FLOW*           LIME USE AS CAO            "
"PH " MGD-TOTAL DOSE::NEW LIME"  RECYCLED    LIMEK
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     138.9     163.8     0.54
"FECL3 DOSE::WASTE BIOLOGICAL SLUDGE*
"    MG/L  »     ADDED, LB/DAY      K
     14.0              9746.0
"FURNACE BLOWDOW-RECALCINING EFFICIENCY*
'•'•    FRACTION    K       FRACTION       x
        0.28                 0.95
::NEW MAKEUP LIME ADDED, FRACTION COMPOSITION*
" SI02   :: ACID INSOL. INERTS  '" MGO  "-CPO K
  0.03          0.01            0.07   0.89
*               PRIMARY INFLUENT COMPOSITION,MG/L             *
"SUSP.SOLIDS::MAGNESIUM::CALCIUM::PHOSPHORUS"SI02::A.I.INERTS*IRONS
    240.0       22.3     30.0     10.00    14.0    2.2    0.
*               PRIMARY EFFLUENT COMPOSITION,MG/L             K
=SUSP.SOLIDS::MAGNESIUM"CALCIUM::PHOSPHORUS"SI02"A. I. INERTS::IRON*
     26.0        8.7     60.0      0.68     0.9    0.1    0.
                                                          272

-------
CASE 109
                                                                "FIRST PASS PRECIPITATION COMPONENTS,LB/CAY*
DAT1
110,30.0,9746.0,1<». 0,
-------
 CASE 110
                                                                KFIRST PASS PRECIPITATION COMPONENTS,UB/OW*
 DAT1
 110,30.0,9746.0,14.0,400.0,0.35,0.95
 115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
 DAT2
 131,240.0,26.0,22.3,8,7"*, 30.0,60.0
 132,10.0,0.68,0.0,0.0024,0.0024
 I1*!, 0.035,0.002"*, 0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MGCOHD2
FE203
FECOH)3
SI02
ACID INSOL.
CA3(P04)2

TOTAL
                                                                             INERTS
 50580.
     0.
105069.
  JOS'*.
  81V*.
     0.
  230
-------
 CASE 111
                                                                   "FIRST PASS PRECIPITATION COMPONENTS, LB/DAY"
 DAT1
 110, 30.0,9746. 0, l
-------
 XRECALCINATION FURNACE PRODUCT COMPONENTS, LB/DAY;:
"CLASSIFIER REJECTS COMPONENTS,LB/DAY*
ORGAN! CS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
AC 10 INSOL. INERTS
CA3CPCCO2
TOTAL
!:RECALCINATION FURNACE
0.
57
-------
CASE 112
                                                                 "FIRST PASS PRECIPITATION COMPONENTS,LB/DAY"
DAT1
110,30.0,9746.0,14.0,400.0,1.0,0.95
115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2
131,240.0,26.0,22.3,8.74, 30.0,60.0
132,10.0,0.68,0. .0,0.0024, 0.0024
Ml, 0.035,0.0024,0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH53
SI02
ACID INSOL.
CA3CPOJt)2

TOTAL
                                                                             INERTS
               50580.
                   0.
              105069.
                5950.
                8144.
                   0.
                230
-------
::RECALC1UATION  FURNACE  PRODUCT COMPONENTS,LB/DAY"
                                              "CLASSIFIER REJECTS COMPONENTS,LB/DAY"
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH53
SI02
ACID  INSOL.
CA3CPO'*)2

TOTAL
INERTS
    0.
55897.
 5253.
11528.
    0.
 1722.
    0.
 "*508.
  968.
new.

91521.
ORGAN1CS
CAO
CAC03
MGO
MG(OH)2
FE203
FFC003
5102
ACID INSOL.
CA3CFXTO2

TOTAL
                                                           INERTS
"RECALCINATION FURNACE WET SCRUBBER WATER  COMPONENTS,LB/DAY"
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL.
CA3CP0432

TOTAL
                   0.
                   0.
                7908.
                1002.
                   0.
                  91.
                   0.
                  92.
                 1<*5.
                 7"*3.

                9981.
"RECYCLED SOLIDS ACCEPTS COMPONENTS,LB/DAY*
ORGANICS
CAO
CAC03
MGO
MGCOH02
FE203
FECOH53
SI02
ACID INSOL.
CA3(PO
-------
CASE  113


DAT1
"FIRST PASS PRECIPITATION  COMPONENTS,LB/DAY"
110,30.0,97^6.0,14.0,1(00.0,0.0,0.95
115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
DAT2
131,240.0,26.0,22.3,8. 74, 30.0,60.0
132,10.0,0.68,0.0,0.0024,0.0024
mi, 0.035,0.002i», 0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
ORGAN ICS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOH)3
SI02
ACID INSOL.
CA3CP04)2

TOTAL
                                                                            INERTS
              50580.
                  0.
             105069.
               I'm.
               am1*.
                  o.
               2304.
               2758.
                346.
              1161*5.

             182259.
DAT3
                                                                 "PRIMARY SLUDGE COMPONENTS, LB/DAY"
161,0.95,0.95,0.95,0.95
171,0.95,0.95,0.95,0.95,0.95
181,0.0,0.0,0.0,0.0,0.0
182,0.0,0.0,0.0,0.0
191,0.94,0. 93,0.98,0.87,0.0
192,0.95,0.0,0.0,0.92
201,0.0,0.0,0.0,0.0,0.0
202,0.0,0.0,0.0,0.0
211,0.957,0.984,0.761,0.929,0.0,0.981
212,0.864,0.0,0.0,0.966
LIME SOLIDS PROCESSING MASS BALANCE
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FE(OH)3
SI02
ACID INSOL.
CA3CP01O2

TOTAL
INERTS
                          53242.
                              0.
                         125077.
                         229411.
                           8558.
                          12220.
                           2425.
                          12396.
                           5890.
                         303272.

                         752489.
*   "FLOW11           LIME USE AS CAO           "
«PH :: MGD-TOTAL DOSE-NEW LIME"  RECYCLED     LIME"
             MG/L      MG/L     MG/L   FRACTION
11.0  30.00  302.7      71.9     230.8      0.76
 "FIRST STAGE CAKE COMPONENTS,LB/DAY"
KFECL3 DOSE"WASTE BIOLOGICAL SLUDGE"
x    MG/L  J!     ADDED, LB/DAY      «
     14.0              9746.0
"FURNACE BLOWDOWN"RECALCINING EFFICIENCY"
«    FRACTION    !!       FRACTION       "
        0.                   0.95
KNEW MAKEUP LIME ADDED,FRACTION COMPOSITION"
* SI02   « ACID INSOL.  INERTS   « MGO  "CAO  *
  0.03          0.01            0.07   0.89
 ORGANICS
 CAO
 CAC03
 MGO
FE203
FECOH)3
SI02
ACID INSOL.
CA3CP0452

TOTAL
             INERTS
               50580.
                   0.
              118823.
              217940.
                8130.
               11609.
                2304.
               11776.
                5595.
              288108.

              714865.
                                                                 "FIRST STAGE CENTRATE  COMPONENTS,LB/DAY"
K               PRIMARY INFLUENT COMPOSITION,MG/L             "
KSUSP.SOLIDS!=WGNESIUM"CALCIUMI;PHOSPHORUS"SI02!:A. I. INERTS:!IRON"
    240.0       22.3     30.0     10.00     11.9     1.4    0.
K               PRIMARY EFFLUENT COMPOSITION,MG/L             "
KSUSP.SOLIDS!!MAGNESIUM!!CALCIUM!CPHOSPHORUSI!SI02"A. I. INERTS5CIRONM
     26.0        8.7     60.0      0.68      0.9     0.1    0.
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
 INERTS
                            2662.
                               0.
                            6254.
                           11471.
                             428.
                             611.
                             121.
                             620.
                             294.
                           15164.

                           37624.
                                                         279

-------
    "RECALCI NATION FURNACE PROPUCT COMPONENTS, LB/DAY"
''RECOVERIES OF COMPONENTS  IN PROCESS  STREAMS,FRACTION"
ORGANICS
CAO
CAC03
M30
MGCOH)2
FE203
FECOH53
SI02
ACID INSOL. INERTS
CA3CPCXO2

TOTAL



-'RECALCINWION FURNACE

ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CPCJt)2
TOTAL
"RECYCLED SOLIDS ACCEPTS
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CPOW2
TOTAL
0.
58789.
5525.
205637.
0.
12665.
0.
115:SECOND"INCINERATION>; DRY
STAGE STAGE
CAKE FURNACE CAKE FURNACE CLASSIFIER

ORGANICS 0.95 0. 0. 0. 0.

CAO 0. 0.93 0. 0. 0.98

CAC03 0.95 0.93 0. 0. 0.98
MGO 0.95 0.92 0. 0. 0.97

MGCOH)2 0.95 0. 0. 0. 0.
FE203 0.95 0.95 0. 0. 0.86
FECOH53 0.95 0. 0. 0. 0.
SI02 0.95 0.98 0. 0. 0.76
INERTS 0.95 0.87 0. 0. 0.93
CA3CPO
-------
 CASE
                                                                 "FIRST PASS PRECIPITATION COMPONENTS,LB/DAY"
 DAT1
 110,30.0,9746,0,14.0,400.0,0.20,0.95
 115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
 OAT2
 131,240.0,26.0,22.J,8.74,30.0,60.0
 132, 10.0,0.68,0.0,0.0021*, 0.0024
 1<*1,0.035,0.0021*, 0.80,0.80,0.80
 151,0.055,0.035,0.027,0.0096,0.07,0.89
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOt-03
SI02
ACID INSOL.
CA3CP04;>2

TOTAL
                                                                             INERTS
               50580.
                   0.
              105069.
                2358.
                8144.
                   0.
                2304.
                3122.
                 475.
               11645.

              183697.
 DAT3

 161,0.95,0.95,0.95,0.95
 171,0.95,0.95,0.95,0.95,0.95
 181,0.0,0.0,0.0,0.0,0.0
 182,0.0,0.0,0.0,0.0
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.0,0.0,0.0,0.0,0.0
 202,0.0,0.0,0.0,0.0
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.864,0.0,0.0,0.966
LIME SOLIDS PROCESSING MUSS BALANCE
 "PRIMARY SLUDGE COMPONENTS,LB/DAY"
ORGANICS
CAO
CAC03
MGO
MG(Ot-02
FE203
FECOH53
SI02
ACID INSOL.
CA3CP04)2

TOTAL
                                                                             INERTS
               53242.
                   0.
              123796.
               34094.
                8558.
                4367.
                2425.
                8573.
                2239.
               55634.

              292928.
*   "FLOW"           LIME USE AS CAO            «
«PH * MGD'TOTAL DOSEJCNEW LIMEI:  RECYCLED    LIME1!
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     120.0     182.7     0.60
"FIRST STAGE CAKE COMPONENTS,LB/DAY"
"FECL3 DOSE!:WASTE BIOLOGICAL SLUDGE"
J:    MG/L  :t     ADDED, LB/DAY      :t
     14.0              9746.0
"FURNACE BLOWDOWN"RECALCINING EFFICIENCY"
-    FRACTION    "       FRACTION       K
        0.20                 0.95
:tNEW MAKEUP LIME ADDED, FRACTION COMPOSITION"
" SI02   » ACID INSOL. INERTS  " MGO  "CAO *
  0.03          0.01            0.07   0.89
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FECOH)3
SI02
ACID INSOL.
CA3CP04)2

TOTAL
INERTS
 50580.
     0.
117606.
 32389.
  8130.
  4149.
  2304.
  8144.
  2127.
 52853.

278281.
                                                                 "FIRST STAGE CENTRATE COMPONENTS, LB/DAY"
*               PRIMARY INFLUENT COMPOS IT ION,MG/L            *
"SUSP.SOLIDS"MAGNESIUM!:CALCIUM"PHOSPHORUS"S I02«A. I. INERTS"IRON"
    240.0       22.3     30.0     10.00    13.4    2.0    0.
«               PRIMARY EFFLUENT COMPOS ITION,MG/L            "
"SUSP. SOL 1 DS::MAGNES I UM"CALC IUM-PHOSPHORUS "S102"A. I. INERTS" I RON"
     26.0        8.7      60.0      0.68    0.9     0.1    0.
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FE(OH)3
SI02
ACID INSOL.
CA3(PO>O2

TOTAL
INERTS
  2662.
     0.
  6190.
  1705.
   428.
   218.
   121.
   429.
   112.
  2782.

 14646.
                                                         281

-------
 *RECALCINATION FURNACE PRODUCT COMPONENTS, LB/DAY*
                                                          CLASSIFIES REJECTS COMPONENTS, LS/DAY"
ORGAN IC5
CAO
CAC03
MGO
HG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CPO
-------
CASE  115

tWTl
"FIRST PASS PRECIPITATION COMPONENTS, LB/DAY"
 110,JO.O,97't6.0,m.O/3
SI02
ACID INSOL.
CA3CP01*)2

TOTAL
INERTS
 50580.
     0.
105069.
  mi*.
  81V*.
     0.
  230
-------
  ::RECALC I NATION FURNACE  PRODUCT  COMPONENTS, LB/OAY«
                                                                 "RECOVERIES  OF OPPONENTS IN PROCESS  STREWS,FRACTION"
                                                                           FIRST  « RECALCINE KSECOND«INCINERATION!t  DRY
  ORGANICS
  CAO
  CAC03
  MGO
  MG(OH)2
  FE203
  FECOH)3
  SI02
  ACID INSOL. INERTS
  CA3CPQ102
      0.
  58789.
   5525.
 205637.
      0.
  12665.
      0.
  1151*0.
   1*868.
 270822.
                                                               ORGAN ICS

                                                               CAO

                                                               CAC03

                                                               MGO

TOTAL                     56981*5.                              MG(OH)2

                                                               FE203

                                                               FECOH)3

                                                               SI02

"RECALCIN1ATION FURNACE WET SCRUBBER WATER COMPONENTS, LB/DAY"  INERTS

                                                               CA3(PO'O2

                                                               TOTAL

                                                              PROGRAM STOP AT 3250

                                                              USED     .80 UNITS
  ORGANICS
  CAO
  CAC03
  MGO
  MG(OH)2
  FE203
  FEC003
  SI02
  ACID INSOL. INERTS
  CA3CPCC02

  TOTAL
      0.
      0.
   8318.
  17881.
      0.
    667.
      0.
    236.
    Til.
  17287.

  "(5115.
STAGE
CAKE
0.99
0.
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
FURNACE
0.
0.93
0.93
0.92
0.
0.95
0.
0.98
0.87
0.91*

STAGE.
CAKE
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
FURNACE
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.

CLASSIFIER
0.
0.98
0.98
0.97
0.
0.86
0.
0.76
0.93
0.96
0.96
  "RECYCLED SOLIDS ACCEPTS CCMPONENfTS, LB/DAY*
 ORGANICS                        0.
 CAO                         57672!
 CAC03                        51437.
 MGO                        19861*5.
 MG(OH)2                         0.
 FE203                       10942.
 FE(OH)3                         0.
 SI02                         8782.
 ACID INSOL. INERTS           
-------
 CASE 116
                                                                 "FIRST  PASS  PRECIPITATION COMPONENTS,LB/DAY*
 DAT1
 110,30.0,9746.0,14.0,400.0,0.20,0.95
 115,1.0,1.0,11.0,1.0,0.0,0.0,0.0
BAT2
 131,240.0,26.0,22.3,8.74,30.0,60.0
 132,10.0,0.68,0.0,0.0024,0.0024
 141,0.035,0.0024,0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
                                                         ORGANICS
                                                         CAO
                                                         CAC03
                                                         MGO
                                                         MGCOH)2
                                                         FE203
                                                         FECOH)3
                                                         SI02
                                                         ACID  INSOL.
                                                         CA3CP04)2

                                                         TOTAL
                                                                             INERTS
                           50580.
                               0.
                          105069.
                            2358.
                            8144.
                               0.
                            2304.
                            3122.
                             475.
                           11645.

                          183697.
 DAT3
 161,0.
 171,0.
 181,0.
 182,0.
 191,0.
 192,0.
 201,0.
 202,0.
 211,0.
 212,0.
995,0.995,0.995,0.995
995,0.995,0.995,0.995,0.995
0,0.0,0.0,0.0,0.0
0,0.0,0.0,0.0
94,0.93,0.98,0.87,0.0
95,0.0,0.0,0.92
0,0.0,0.0,0.0,0.0
0,0.0,0.0,0.0
957,0.984,0.761,0.929,0.0,0.981
864,0.0,0.0,0.966
                                                                  "PRIMARY  SLUDGE  COMPONENTS, LB/DAY*
     SOLIDS PROCESSING MASS  BALANCE
ORGANICS
CAO
CAC03
MGO
MGCOt-02
FE203
FECOH)3
SI02
ACID INSOL.
CA3CP04)2

TOTAL
                                                                             INERTS
 50834.
     0.
118197.
 32552.
  8171.
  4170.
  2315.
  8185.
  2137.
 53118.

279680.
:t   "FLOW*           LIME  USE AS CAO             Jt
«PH :t MGO-TOTAL DOSE!:NEW LIMEK  RECYCLED    LIME"
             MG/L      MG/L     MG/L     FRACTION
11.0  30.00  302.7      120.0      182.7      0.60
                                                                 "FIRST STAGE  CAKE COMPONENTS, LB/DAY*
"FECL3 DOSE!!WASTE BIOLOGICAL  SLUDGE"
x    MG/L  !!     ADDED, LB/DAY      !t
     14.0               9746.0
"FURNACE BLOWDOWN-RECALCINING  EFFICIENCY"
K    FRACTION     K        FRACTION       "
        0.20                 0.95
"NEW MAKEUP LIME ADDED,FRACTION COf-POSITION"
» SI02   » ACID INSOL.  INERTS   !t MGO   J:CAO !t
  0.03          0.01             0.07    0.89
                                                          ORGANICS
                                                          CAO
                                                          CAC03
                                                          MSO
                                                          MGCOH32
                                                          FE203
                                                         ' FECOI-03
                                                          SI02
                                                          ACID  INSOL.
                                                          CA3CP0452

                                                          TOTAL
                                                                             INERTS
                           50580.
                               0.
                           117606.
                           32389.
                            8130.
                            4149.
                            2304.
                            8144.
                            2127.
                           52853.

                           278281.
                                                                 !:FIRST STAGE CENTRATE COMPONENTS, LB/DAY*
Jt               PRIMARY  INFLUENT COMPOSITION,MG/L              "
KSUSP.SOLIDSKMAGNESIUM:!CALCIUM!tPHOSPHORUS"SI02"A.I.INERTS:!lRON)l
    240.0       22.3      30.0      10.00     13.4     2.0     0.
x               PRIMARY EFFLUENT COMPOSITION,MG/L              "
»SUSP SOLIDS)!MAGNESIUM1!CALCIUM!!PHOSPHORUS1:SI02!IA.I. INERTS" I RON"
     26.0        8.7     60.0       0.68      0.9  '   0.1     0.
                                                          ORGANICS
                                                          CAO
                                                          CAC03
                                                          MGO
                                                          MGCOt-02
                                                          FE203
                                                          FECOH53
                                                          SI02
                                                          ACID  INSOL.
                                                          CA3(P04)2

                                                          TOTAL
                                                                             INERTS
                              254.
                                0.
                              591.
                              163.
                               41.
                               21.
                               12.
                               41.
                               11.
                              266.

                             1398.
                                                          285

-------
  ::RECALClrWTION FURNACE PRODUCT COMPONENTS, LB/DAY*
 ORGANIC5                       0.
 CAO                         58187.
 CACOI                        S469.
 MGO                         Jl.930.
 M6(OH)2                        0.
 FE203                        5578.
 FECOH53                        0.
 SI02                         7982.
 ACID  INSOL.  INERTS          1850.
 CA3CP01O2                   1*9681.

 TOTAL                      163676.
                                                             '^CLASSIFIER REJECTS COMPONENTS,LB/DAY*
                                                 ORGAN ICS
                                                 CAO
                                                 CAC03
                                                 MGO
                                                 MG(OH)2
                                                 FE203
                                                 FE(OH)3
                                                 SI02
                                                 ACID INSOL.
                                                 CA3CPO
-------
OASE 117
                                                                  •"FIRST PASS PRECIPITATION COMPONENTS,LB/DAY*
DAT1

110,30.0,9746.0,14.0,400.0,0.0,0.95
115,2.0,0.0,11.0,1.0, 0.0,0.0,0.0
DAT2
131,240.0,26.0,22.3,8.74, 30.0,60.0
132,10.0,0.68,0.0,0.0021*, 0.0024
141, 0.035,0.0024,0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
                                                                 ORGAN ICS
                                                                 CAO
                                                                 CAC03
                                                                 MGO
                                                                 MG(OH)2
                                                                 FE203
                                                                 FECOHJ3
                                                                 SI02
                                                                 ACID INSOL.
                                                                 CA3(P04)2

                                                                 TOTAL
                                                                              INERTS
                           50580.
                               0.
                          105069.
                            2160.
                            8144.
                               0.
                            2304.
                            3046.
                             448.
                           11645.

                          183395.
DAT3
161,0.20,0.825,0.90,0.77
171,0.27,0.27,0.30,0.30,0.1*0
181,0.90,0.99,0.97,0.81,0.90
182,0.90,0.78,0.90,0.90
191,0.94,0.93,0.98,0.87,0.0
192,0.95,0.0,0.0,0.92
201,0.94,0.93,0.98,0.87,0.0
202,0.95,0.0,0.0,0.92
211,1.0,1.0,1.0,1.0,1.0,1.0
212,1.0,1.0,1.0,1.0
LIME SOLIDS PROCESSING MASS BALANCE
                                                                   "PRIMARY SLUDGE COMPONENTS,LB/DAY*
                                                                 ORGANICS
                                                                 CAO
                                                                 CAC03
                                                                 MGO
                                                                 MGCOH32
                                                                 FE203
                                                                 FE(OH)3
                                                                 SI02
                                                                 ACID INSOL.
                                                                 CA3CP04)2

                                                                 TOTAL
                                                                             INERTS
                           58272.
                               0.
                          118054.
                            6784.
                            8770.
                            1026.
                            2477.
                           32042.
                            2764.
                           17206.

                          247394.
K   "FLOW"           LIME USE AS CAO            x
"PH " MGD'TOTAL DOSE:=NEW LIMEJ:  RECYCLED    LIME"
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     109.9     192.8     0.64
                                                                  "FIRST STAGE CAKE COMPONENTS,LB/DAY*
«FECL3 DOSE:VASTE BIOLOGICAL SLUDGE"
);    MG/L  J!     ADDED, LB/DAY      :t
     14.0              9746.0
"FURNACE BLOWX)WN:(RECALCINING EFFICIENCY"
«    FRACTION    K       FRACTION       *
        0.                   0.95
>:NEW MAKEUP LIME ADDED, FRACTION COMPOSITION"
K SI02   '•'• ACID INSOL. INERTS  " MGO  "CAO "
  0.03          0.01            0.07   0.89
                                                                 ORGANICS
                                                                 CAO
                                                                 CAC03
                                                                 MGO
                                                                 MGCOH)2
                                                                 FE203
                                                                 FECOH)3
                                                                 SI02
                                                                 ACID INSOL.
                                                                 CA3CP0452

                                                                 TOTAL
                                                                              INERTS
                           23309.
                               0.
                           97394.
                            1832.
                            2368.
                             308.
                             743.
                           28837.
                            2128.
                            3441.

                          160360.
                                                                  :!FIRST  STAGE CENTRATE COMPONENTS,LB/DAYK
«               PRIMARY INFLUENT COMPOSITION,MG/L             «
KSUSP.SOLIDS!=MAGNESIUM!:CALCIUM:tPHOSPHORUS"SI02"A. I. INERTS111 RON"
    240.0       22.3     30.0     10.00    13.1
                                                   1.9
                                                         0.
"               PRIMARY EFFLUENT  COMPOSITION,MG/L
"SUSP.SOLIDS!:MAGNESIUM"CALCIUM::PHOSPHORUS::SI02"A. I
     26.0        8.7     60.0       0.68     0.9
                                                  . INERTS:!IRONX
                                                   0.1    0.
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
S102
ACID INSOL.
CA3(P04)2

TOTAL
                                                                              INERTS
34963.
    0.
20659.
 4952.
 6402.
  718.
 1734.
 3204.
  636.
13765.

87034.
                                                        287

-------
  "RECALCINATION FURNACE PRODUCT OPPONENTS, LB/DAY*
                                                             "INCINERATION FLRNACE WASTE ASH COMPONENTS, LB/DAY*
ORGANICS
CAO
CAC03
MGO
FE203
FECC+03
SI02
ACID INSOL. INERTS
CA3CPCJO2

TOTAL
                                  0.
                              it8187.
                               1(529.
                               3180.
                                  0.
                                820.
                                  0.
                              28261.
                               1851.
                               3235.

                              90062.
ORGANICS
CAO
CAC03
MGO
MGCOH32
FE203
FE(OH)3
SI02
ACID INSOL.
CA3CP01O2

TOTAL
INERTS
    0.
    0.
19021.
 91*02.
    0.
 2096.
    0.
 30
-------
CASE  118
DAT1
                                                                 "FIRST PASS PRECIPITATION COMPONENTS,LB/DAY"
 110,30.0,9746.0,14.0,400.0,0.20,0.95
 115,2.0,0.0,11.0,1.0,0.0,0.0,0.0
 DAT2
 i3i,24o.o,2&.o,22.3,8.74,3o.o,6o.o
 132, 10.0,0.68,0.0,0.0024,0.0024
 I'd, 0.035,0.0024,0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0,89
 DAT 3
 161,0.20,0.825,0.90,0.77
 171,0.27,0.27,0.30,0.30,0.40
 181,0.90,0.99,0.97,0.81,0.90
 182,0.90,0.78,0.90,0.90
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.94,0.93,0.98,0.87,0.0
 202,0.95,0.0,0.0,0.92
 211,1.0,1.0,1.0,1.0,1.0,1.0
 212,1.0,1.0,1.0,1.0
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOt-02
 FE203
 FECOH)3
 SI02
 ACID  INSOL.
 CA3CP04)2

 TOTAL
                                                                              INERTS
               50580.
                   0.
              105069.
                2944.
                8144.
                   0.
                2304.
                3348.
                 555.
               11645.

              184589.
"PRIMARY SLUDGE COMPONENTS, LB/DAY"
 ORGAN ICS
 CAO
 CAC03
 MGO
 MGO>02
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3CP0432

 TOTAL
INERTS
                                                                                             58272.
                                                                                                 0.
                                                                                            117045.
                                                                                              7010.
                                                                                              8770.
                                                                                               776.
                                                                                              2477.
                                                                                             12334.
                                                                                              1876.
                                                                                             16301.

                                                                                            224860.
                                                                 -FIRST STAGE CAKE COMPONENTS,LB/DAY"
LIME SOLIDS PROCESSING MASS BALANCE
"   "FLOW51           LIME USE AS CAO             »
"PH " MGO-TOTAL DOSE"NEW LIME"  RECYCLED     LINE"
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     149.8     152.9      0.51
"FECL3 DOSE::WASTE BIOLOGICAL SLUDGE"
::    MG/L  '•'•     ADDED, LB/DAY      »
     14.0              9746.0
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
                                                                              INERTS
               23309.
                   0.
               96562.
                1893.
                2368.
                 233.
                 743.
               11101.
                1445.
                3260.

              140912.
                                                                 "FIRST  STAGE CENTRATE COMPONENTS,LB/DAY"
"FURriACE BLOWDOWN-RF.CALCINING EFFICIENCY'1
••••    FRACTION    '•••        FRACTION        «
        0.20                 0.95
"•NEW MAKEUP LIME ADDED, FRACTION COMPOSITION"
" 5102   " ACID INSOL. INERTS  >: MGO  :CCAO :I
  0.03          0.01            0.07   0.89
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID  INSOL.
CA3CP04)2

TOTAL
                                                                              INERTS
              34963.
                   0.
              20483.
                5118.
                6402.
                 543.
                1734.
                1233.
                 431.
              13041.

              83948.
K               PRIMARY  INFLUENT  COMPOSITION,MG/L
"SUSP. SOL IDS!=MAGNES I Uf^CALC I UM"PHOSPHORUS"S 102"A. I. INERTS" I RON"
    240.0       22.3      30.0      10.00     14.3     2.3     0.
::               PRIMARY EFFLUENT  COMPOSITION,MG/L              !t
!.-SUSP.SOLIDSI«AGNESIUM;tCALCIUM"PHOSPHORUS!:SI02!:A. I. INERTS-IRON"
     26.0         8.7      60.0       0.68      0.9     0.1     0.
                                                                 "RECALCINATION FURNACE PRODUCT COMPONENTS,LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MT, (OH) 2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
INERTS
                                                                                                 0.
                                                                                             47775.
                                                                                              4490.
                                                                                              3236.
                                                                                                 0.
                                                                                               749.
                                                                                                 0.
                                                                                             10879.
                                                                                              1257.
                                                                                              3065.

                                                                                             71450.
                                                         289

-------
'^CALCINATION FURNACE WET SCRUBBER WATER COMPONENTS, LB/DAY"
 ORGAN ICS
 WO
 CAC03
 MGO
 MS(OH)2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.  INERTS
 CA3(P04)2

 TOTAL
                   0.
                   0.
                6759.
                 281.
                   0.
                  39.
                   0.
                 222.
                 188.
                 196.

                7686.
"RECYCLED SOLIDS ACCEPTS COMPONENTS, LB/DAY1'
 ORGANICS
 CAO
 CAC03
 MGO
 MG(OH)2
 FE203
 FE(OH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
INERTS
    0.
38220.
 3592.
 2589.
    0.
  599.
    0.
 8703.
 1005.
 2452.

57160.
 "SECOND  STAGE CAKE COMPONENTS, LB/DAY*
ORGAN I CS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3(P04)2
27271.
0.
20278.
4606.
5762.
489.
1561.
1196.
350.
11737.
                                                           :=INCINERATION  FURNACE WET SCRUBBER WATER COMPONENTS,LB/MY"
                                ORGANICS
                                CAO
                                CAC03
                                MGO
                                MG(OH)2
                                FE203
                                FE(OH)3
                                SI02
                                ACID INSOL. INERTS
                                CA3CP04)2

                                TOTAL
   0.
   0.
1419.
 685.
   0.
  83.
   0.
  24.
  45.
 704.

2961.
                                               "RECALCINATION FURNACE SLOWDOWN COMPONENTS,LB/DAY"
ORGAN I CS
CAO
CAC03
MGO
MG(OH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CP04)2
0.
9555.
898.
61*7.
0.
150.
0.
2176.
251.
613.
                                                            TOTAL
                                                                                        14290.
 TOTAL
                            732149.
                                                            "RECOVERIES OF COMPONENTS IN PROCESS STREAMS,FRACTION-
                                                                      FIRST » RECALCINE "SECOND-ING INERATION5!   DRY
"SECOND STAGE CENTRATE
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3(P04)2
TOTAL

RECYCLE COMPONENTS, LB/DAY"
7692.
0.
205.
512.
6")0.
5"t.
173.
37.
82.
1301*.
10699.

"INCINERATION FURNACE WASTE ASH COMPONENTS, LB/OAY!!
ORGANICS
CAO
CAC03
MGO
MGCOH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3(P04)2
0.
0.
18859.
9538.
0.
m?.
0.
1172.
304.
11032.

ORGANICS

CAO

CAC03

MGO

MG(OH)2
FE203
FECOH53
SI02
INERTS

CA3CP01»)2

TOTAL

STAGE
CAKE
0.40

0.

0.83

0.27

0.27
0.30
0.30
0.90
0.77

0.20

0.63

PROGRAM STOP AT

USED


FURNACE
0.

0.93

0.93

0.92

0.
0.95
0.
0.98
0.87

0.94



3250

STAGE
CAKE
0.78

0.

0.99

0.90

0.90
0.90
0.90
0.97
0.81

0.90

0.87



FURNACE
0.

0.

0.93

0.92

0.
0.95
0.
0.98
0.87

0.94





CLASSIFIER
0.

1.00

1.00

1.00

0.
1.00
0.
1.00
1.00

1.00

0.80



.90 UNITS





TOTAL
                           42853.
                                                         290

-------
 CASE 119
 DAT1
                                                                "FIRST PASS PRECIPITATION COMPONENTS, L8/DAY"
 110,30.0,974G.0, l;    FRACTION    "       FRACTION       )!
        0.24                 0.95
'•MEW MAKEUP LIME ADDED, FRACTION COMPOSITION"
- SI02   " ACID  INSOL. INERTS  :: MGO   "CAO  "
  0.03           0.01            0.07    0.89
                                                                "FIRST STAGE CENTRATE' COMPONENTS,LB/DAY*
ORGANICS
CAO
CACO3
MGO
MGCOH)2
FE203
FECOH33
SI02
ACID INSOL.
CA3CP04)2

TOTAL
                                                                             INERTS
                           34963.
                               0.
                           20448.
                            5146.
                            6402.
                             511.
                            1734.
                            1111.
                             411.
                           12905.

                           83631.
K               PRIMARY  INFLUENT COMPOSITION,MG/L
"'SUSP. SOLIDS-MAGNESIUM-CALCIUM-PHOSPHORUS-S102"A. I. INERTSKIRON" .
    240.0       22.3      30.0      10.00     14.5     2.4     0.
RECALCULATION  FURNACE  PRODUCT COMPONENTS, LB/DAY::
                                                                 ORGANICS
                                                                 CAO
                                                                 CAC03
                                                                 MGO
                PRIMARY EFFLUENT COMPOS IT ION, MG/L              •"  MG(OH)2
!:SUSP.SOLIDS"MAGNESIUM"CALCIUM"PHOSPHORUS"SI02"A.I.INERTS-IRON"  FE203
     26.0       "8.7     60.0      0.68      0.9     0.1     0.     FE(OH)3
                                                                 SI02
                                                                 ACID INSOL.
                                                                 CA3(P04)2

                                                                 TOTAL
             INERTS
                               0.
                           47693.
                            4482.
                            3246.
                               0.
                             736.
                               0.
                            9800.
                            1197.
                            3033.

                           70186.
                                                          291

-------
 "PECALCINATION  FURNACE WET SCRUBBER WATER COMPONENTS,UP/DAY"
 ORGAN1CS
 CAO
 CACOJ
 MGO
 MT, (OH) 2
 FE203
 FECOH)3
 5102
 AC10 INSOL. INERTS
 CA3(P04)2

 TOTAL
   0.
   0.
6748.
 282.
   0.
  39.
   0.
 200.
 179.
 194.

761*1.
                                                            "INCINERATION FURNACE WET SCRUBBER WATER COMPONENTS,IB/DAY"
 "RECYCLED SOLIDS ACCEPTS COMPONENTS,LB/DAY"
ORGAN ICS
CAO
CAC03
MGO
MGCOH)2
FE203
FE(OH)3
SI02
ACID INSOL. INERTS
CA3CPO
-------
 CASE  120


DAT1
                                                            "FIRST PASS  PRECIPITATION  COMPONENTS, LB/DAY"
 110, 30.0,9746.0,11*. 0,1)00.0,0.28,0.95
 115,2.0,0.0,11.0,1.0,0.0,0.0,0.0
DAT 2
131,21*0.0,26.0,22.3,8.74,30.0,60.0
132,10.0,0.68, 0.0,0.00211,0.0024
141,0.035,0.002'), 0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
DAT 3
161,0
171,0
181,0,
182,0
191,0.
192,0.
201,0.
202,0,
211,1.
212,1.
20,0.825,0.90,0.77
27,0.27,0.30,0.30,0.1*0
90,0.99,0.97,0.81,0.90
90,0.78,0.90,0.90
94,0.93,0.98,0.87,0.0
95,0.0,0.0,0.92
94,0.93,0.98,0.87,0.0
95,0.0,0.0,0.92
0,1.0,1.0,1.0,1.0,1.0
0,1.0,1.0,1.0
                                                             ORGANICS
                                                             CAO
                                                             CAC03
                                                             MSO
                                                             MG(OH)2
                                                             FE203
                                                             FE(OH)3
                                                             SI02
                                                             ACID INSOL.
                                                             CA3CP0452

                                                             TOTAL
                                                                               INERTS
                           50580.
                               0.
                          105069.
                            3253.
                            8144.
                               0.
                            2304.
                            3468.
                             598.
                           11645.

                          185061.
                                                                  "PRIMA.RY SLUDGE COMPONENTS, LB/DAY51
ORGANICS
CAO
CAC03
MGO
MGCOI-02
FE203
FECOH03
SI02
ACID INSOL.
CA3(P04)2

TOTAL
INERTS
 58272.
     0.
116646.
  7086.
  8770.
   687.
  2477.
 10139.
  1710.
 15965.

221752.
LIME SOLIDS PROCESSING MASS BALANCE
"   "FLOW71           LIME USE AS CAO             *
"PH " MGD-TOTAL DOSE"NEW LIME-"  RECYCLED    LIMEI:
             MG/L      MG/L     MG/L    FRACTION
11.0  30.00  302.7     165.5      137.2      0.45
"FECL3 DOSE::WASTE  BIOLOGICAL  SLUDGE"
"    MG/L  "     ADDED, LB/DAY      "
     14.0              9746.0
                                                                  "FIRST STAGE CAKE COMPONENTS, LB/DAY"
                                                             ORGANICS
                                                             CAO
                                                             CAC03
                                                             MGO
                                                             MGCOH)2
                                                             FE203
                                                             FECOH)3
                                                             SI02
                                                             ACID INSOL.
                                                             CA3(P04)2

                                                             TOTAL
                                                                               INERTS
                           23309.
                               0.
                           96233.
                            1913.
                            2368.
                             206.
                             743.
                            9125.
                            1317.
                            3193.

                          138407.
"FURNACE BLOWDOWN"RECALCINING  EFFICIENCY"
::    FRACTION     "        FRACTION       J:
        0.28                 0.95
"NEW MAKEUP  LIME ADDED,FRACTION COMPOSITION"
" SI02    :c ACID  INSOL.  INERTS   " MGO  "CAO !'
  0.03           0.01             0.07   0.89
                                                                  "FIRST STAGE CENTRATE COMPONENTS,LB/DAY"
                                                             ORGANICS
                                                             CAO
                                                             CAC03
                                                             MGO
                                                             MGCOH02
                                                             FE203
                                                             FECOH)3
                                                             SI02
                                                             ACID INSOL.
                                                             CA3(P04)2

                                                             TOTAL
                                                                               INERTS
                           34963.
                               0.
                           20413.
                            5173.
                            6402.
                             481.
                            1734.
                            1014.
                             393.
                           12772.

                           83345.
"                PRIMARY INFLUENT COMPOSITION,MG/L             «
"SUSP.SOLIDS"MAGNESIUM"CALCIUM"PHOSPHORUS"SI02"A.I.INERTS"!RON"
     240.0        22.3      30.0      10.00    14.8    2.5    0.
"                PRIMARY EFFLUENT COMPOS IT ION,MG/L             >'
"SUSP. SOL I DS::MAGNES IUM"CALC I UM"PHOSPK1RUS"S 102"A. I . INI[RTS" I RON"
      26.0         8.7      60.0      0.68     0.9    0.1    0.
                                                            "RECALCINATION FURNACE PRODUCT COMPONENTS,LB/DAY"
                                                             ORGANICS
                                                             CAO
                                                             CAC03
                                                             MGO
                                                             MG(OH)2
                                                             FE203
                                                             FECOH)3
                                                             SI02
                                                             ACID INSOL.
                                                             CA3(P04)2

                                                             TOTAL
                                                                               INERTS
                               0.
                           47612.
                            4475.
                            3255.
                               0.
                             724.
                               0.
                            89M.
                            111(6.
                            3001.

                           69155.
                                                          293

-------
 !:RECALCINATION FURNACE WET SCRUBBER WATER COMPONENTS, LB/CAY"
  ORGANICS
  CAO
  CAC03
  MGO
  MG(OH)2
  FE203
  FE(OH)3
  SI02
  ACID  INSOL.  INERTS
  CA3CPQ1O2

  TOTAL
    0.
    0.
 6736.
  283.
    0.
   38.
    0.
  183.
  171.
  192.

 7603.
 "RECYCLED SOLIDS ACCEPTS COMPONENTS,LB/DAY-
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOH52
 FE203
 FE(OH)3
 SI02
 ACID  INSOL.  INERTS
 CA3(PO
-------
CASE  121

DAT1-

110, 30.0,12995.0,21*.0,289.0,0.0,0.95
115,2.0,1.0,10.2,1.0,0.0,0.0,0.0


DAT2
 131,2140.0,26.0,22.3,15.6,30.0,65.2
 132,10.0,0.68,0.0,0.0024,0.0021*
 141, 0.035,0.0024, 0.80,0.80,0.80
 151,0.035,0.035,0.027,0.0096,0.07,0.89
 "FIRST PASS PRECIPITATION COMPONENTS, LB/DAY*
  ORGANICS
  CAO
  CAC03
  MGO
  MGCOH52
  FE203
  FE(OH)3
  SI02
  ACID INSOL.
  CA3(P04)2

  TOTAL
                                                                              INERTS
               531/9.
                   0.
               61*335.
                2225.
                1*024.
                   0.
                3949.
                3185.
                 "*65.
               116<*5.

              143007.
 DAT3
 161,0.26,0.72,0.90,0.61*
 171,0.25,0.25,0.18,0.18,0.35
 181,0.93,0.83,0.81,0.68,0.75
 182,0.75,0.78,0.90,0.90
 191,0.94,0.93,0.93,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.94,0.93,0.98,0.87,0.0
 202,0.95,0.0,0.0,0.92
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.8611,0.0,0.0,0.966
                                                                "PRIMARY SLUDGE COMPONENTS,LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MS(OH)2
 FE203
 FE(OH)3
 S102
 ACID INSOL.
 CA3(P04)2

 TOTAL
INERTS
 62052.
     0.
 75441.
  4942.
  4343.
  1146.
  4968.
 10975.
  1840.
 17714.

183421.
LIME SOLIDS PROCESSING MASS BALANCE
»   "FLOW"           LIME USE AS CAO           »
-PH - MGD-TOTAL DOSE::NEW LIME"  RECYCLED     LIMEJ;
             MG/L      MG/L     MG/L   FRACTION
10.2  30.00  218.7     113.2     105.5      0.48
"FECL3 DOSE"WASTE BIOLOGICAL SLUDGE"
"    MG/L  "     ADDED, LB/DAY      "
     24.0             12995.0
                                                                 "FIRST STAGE CAKE COMPONENTS, LB/DAY*
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOHJ2
 FE203
 FECOH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
                                                                             INERTS
               21718.
                   0.
               54318.
                1235.
                1086.
                 206.
                 894.
                9878.
                1178.
                4606.

               95119.
"FURNACE BLOWDOWN-RECALCINING EFFICIENCY"
«    FRACTION    »       FRACTION       *
        0.                   0.95
"NEW MAKEUP LIME ADDED, FRACTION COMPOS ITI ON"
» SI02   !! ACID INSOL.  INERTS  :c MGO  I!CAO «
  0.03          0.01            0.07   0.89
                                                                "FIRST STAGE  CENTR-VT. rrir'PONENTS LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOH)2
 FE203
 FECOH)3
 SI02
 ACID  INSOL.
 CA3CP04)2

 TOTAL
                                                                             INERTS
              40334.
                  0.
              21123.
               3706.
               3257.
                940.
               4073.
               1098.
                663.
              13108.

              88303.
«               PRIMARY INFLUENT COMPOS IT ION, MG/L             *
»SUSP.SOLIDS!:MAGrESIUM"CALClUM"PHOSPHORUS"SI02!!A. I . INERTS" I RON"
    240.0       22.3     30.0     10.00    13.7     1.9     0.
*               PRIMARY EFFLUENT COMPOSITION,MG/L              ;t
"SUSP.SOLIDS"MAGt,'ESlUM"CALCIUM"PHOSPHORUS"SI02"A. I . INERTS"IRON"
     26.0       15.6     C5.2      0.68     0.9    0.1     0.
"RECALCULATION FURf-WCE  PRODUCT COMPONENTS,LB/DAY"
 ORGANICS
 CAO
 CAC03
 MGO
 MGCOH)2
 FE203
 FECOH)3
 SI02
 ACID INSOL.
 CA3(P04)2

 TOTAL
                                                                             INERTS
                  0.
              26874.
               2526.
               1822.
                  0.
                831.
                  0.
               9680.
               1025.
               4329.

              47087.
                                                         295

-------
  "RECALCULATION  FURNACE  WET SCRUBBER WATER COMPONENTS, LB/DAY11
  ORGANICS
  CAO
  CAC03
  MGO
  MGC002
  FE203
  FECOI-03
  SI02
  ACID  1NSOL.  INERTS
   TOTAL
   0.
   0.
3802.
 158.
   0.
  W*.
   0.
 198.
 153.
 276.

1*631.
 "RECYCLED SOLIDS ACCEPTS COMPONENTS,L8/DAY*
ORGANICS
CAO
CAC03
MGO
MSCOH)2
FE203
FEC003
SI02
ACID INSOL.
CA3(POl*)2
TOTAL
"SECOND STAGE
ORGANICS
CAO
CAC03
MGO
MGCOH52
FE2O3
FE(OH)3
SI02
ACID INSOL.
CA3(POl*)2
0.
26361*.
21*85.
1760.
0.
718.
0.
7367.
INERTS 952.
i)li*3.
1*3789.
CAKE COMPONENTS, LB/DAY"
311*61.
0.
17532.
3336.
2931.
705.
3055.
889.
INERTS 1*51.
1?191.
."INCINERATION FURNACE WET  SCRUBBER WATER COMPONENTS,LB/DAY*
ORGANICS
CAO
CAC03
MGO
M6COH)2
FE203
FE(OK>3
SI02
ACID INSOL.
CA3CP0452

TOTAL
                                                                        INERTS
   0.
   0.
1227.
 1*28.
   0.
 H*9.
   0.
  18.
  59.
 731.

2612.
                                                            CLASSIFIER REJECTS COMPONENTS, LB/DAYK
                                                            ORGANICS
                                                            CAO
                                                            CAC03
                                                            MGO
                                                            MG(OH)2
                                                            FE203
                                                            FE(OH)3
                                                            SI02
                                                            ACID INSOL.  INERTS
                                                            CA3(PO"*)2

                                                            TOTAL
                                                             0.
                                                           511.
                                                            1*0.
                                                            62.
                                                             0.
                                                           113.
                                                             0.
                                                          231t.
                                                            73.
                                                           186.

                                                          3299.
  TOTAL
                             72550.
                                                            ^RECOVERIES OF COMPONENTS IN PROCESS STREAMS, FRACTION"
"SECOND STAGE CENTRATE RECYCLE COMPONENTS,LE/DAYX
                                                                      FIRST :! RECALCINE «SECOND::INCINERATION"  DRY
ORGANICS
CAO
CAC03
MGO
MG(OH)2
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3CP01O2
TOTAL


"INCINERATION FURMACE

ORGANICS
CAO
CAC03
MGO
MGCOH)2.
FE203
FECOH)3
SI02
ACID INSOL. INERTS
CA3CP0102
8873.
0.
3591.
371.
326.
235.
1018.
209.
212.
918.
15752.


WASTE ASH COMPONENTS, LB/DAY"

0.
0.
16305.
5766.
0.
3572.
0.
871.
392.
m59.

STAGE

CAKE FURNACE

ORGANICS

CAO

CAC03

MGO
MGCOH)2
FE203
FECOH)3

SI02

INERTS

CA3CPQ1O2

TOTAL


0.35

0.

0.72

0.25
0.25
0.18
0.18

0.90

0.61*

0.26

0.52


0.

0.93

0.93

0.92
0.
0.95
0.

0.98

0.87

0.91*



STAGE
CAKE

0.78

0.

0.83

0.90
0.90
0.75
0.75

0.81

0.68

0.93

0.82


FURNACE

0.

0.

0.93

0.92
0.
0.95
0.

0.98

0.87

0.91*




CLASSIFIER

0.

0.98

0.98

0.97
0.
0.86
0.

0.76

0.93

0.96

0.93

PROGRAM STOP AT 5050

USED

.90 UNITS








TOTAL
                           38365.
                                                          296

-------
CASE  122
DAT1
110,30.0,9746.0,0.0,500.0,0.0,0.95
115,2.0,1.0,11.5,1.0,0.0,0.0,0.0
DAT 2

131, 2<40.0,35.0,22.3, 9. 72,28.8, 72.8
132,10.0,0.96,0.0,0.0024,0.0024
141,0.035,0.0024,0.80,0.80,0.80
151,0.035,0.035,0.027,0.0096,0.07,0.89
                                                               -FIRST PASS PRECIPITATION COMPONENTS, LB/DAY*
   ORGANICS
   CAO
   CAC03
   MGO
   MGCOH)2
   FE203
   FECOHJ3
   SI02
   ACID INSOL.
   CA3CP04)2

   TOTAL
             INERTS
 1*8780.
     0.
130431.
  2622.
  7555.
     0.
     0.
  3146.
   506.
 11295.

20"*336.
DAT3
 161,0.23,0.86,0.91,0.75
 171,0.30,0.30,0.18,0.18,0.41
 181,0.90,0.99,0.97,0.81,0.75
 182,0.75,0.78,0.90,0.90
 191,0.94,0.93,0.98,0.87,0.0
 192,0.95,0.0,0.0,0.92
 201,0.94,0.93,0.98,0.87,0.0
 202,0.95,0.0,0.0,0.92
 211,0.957,0.984,0.761,0.929,0.0,0.981
 212,0.864,0.0,0.0,0.966
                                                               "PRIMARY SLUDGE COMPONENTS, LB/DAY*
  ORGANICS
  CAO
  CAC03
  MGO
  MGCOH)2
  FE203
  FE(OH)3
  SI02
  ACID  INSOL.
  CA3CP0452

  TOTAL
             INERTS
 56057.
     0.
146659.
  7674.
  8110.
     0.
     0.
 10531.
  2274.
 17096.

248"t01.
LIME SOLIDS PROCESSING MASS BALANCE
    "FLOW11           LIME USE AS CAO            -
"-PH ~ MGD^TOTAL DOSE::NEW LIME"  RECYCLED    LIME*
             MG/L      MG/L     MG/L    FRACTION
11.5  30.00  378.4     133.4     2^5.0     0.65
"FECL3 DOSE::WASTE BIOLOGICAL SLUDGE*
"    MG/L  "     ADDED, LB/DAY      "
      0.               9746.0
"FIRST STAGE CAK

 ORGANICS
 CAO
 CAC03
 MGO
 MGCOI-02
 FE203
 FE(OH)3
 5102
 ACID INSOL.
 CA3CP04)2

 TOTAL
                                                                             INERTS
                              22983.
                                  0.
                             126127.
                               2302.
                               2433.
                                  0.
                                  0.
                               9583.
                               1705.
                               3932.

                             169066.
                                                                "FIRST  STAGE  CENTRATE COMPONENTS,LB/DAYX
"FURNACE BLOWDOWN:!RECALCINING EFFICIENCY*
-:    FRACTION    "       FRACTION       "
        0.                   0.95
"NEW MAKEUP LIME ADDED, FRACTION COMPOSITION*
:: SI02   - ACID INSOL. INERTS  :: MGO  ::CAO "
  0.03          0.01            0.07   0.89
   ORGANICS
   CAO
   CAC03
   MGO
   MGCOH)2
   FE203
   FE
-------
-RECALCULATION FURNACE WET SCRUBBER WATER COMPONENTS,LB/WY»
 ORGANICS
 CAO
 CAC03
 MOO
 MG(OH)2
 FE203
 FECOI-03
 SI02
 ACID INSOL. INERTS
 CA3(PO
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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
1. REPORT NO.
  EPA-600/2-75-038
                                                           3. RECIPIENT'S ACCESSI Ol* NO.
4. TITLE AND SUBTITLE
  LIME USE IN  WASTEWATER TREATMENT:
  DESIGN  AND COST  DATA
                                                           5. REPORT DATE
                                                            October 1975 (Issuing Date)
             6. PERFORMING ORGANIZATION CODE
              Dermy S. Parker,  Emilio de la Fuente,
  Louis 0. Britt, Max L.  Spealman,  Richard J. Stenquist,
  and Fred J. Zadick
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
  Brown and Caldwell
  Consulting Engineers
  1501 N. Broadway
  Walnut Creek, California  94596
             10. PROGRAM ELEMENT NO.

              1BB043; RQAP 21-ASD; Task  18
             11. CONTRACT#55}QSSf NO.
              68-03-0334
 12. SPONSORING AGENCY NAME AND ADDRESS
  Municipal Environmental  Research Laboratory
  Office of Research and Development
  U.S. Environmental Protection Agency
  Cincinnati, Ohio  45268
             13. TYPE OF RE PORT AND PERIOD COVERED
              Final,  6/29/73 - 5/30/74
             14. SPONSORING AGENCY CODE

              EPA-ORD
 15. SUPPLEMENTARY NOTES
 16. ABSTRACT
  This report presents design and cost information on lime use  in wastewater treatment
  applications.  It includes  design and cost information on lime handling,  liquid
  processing, solids generation and dewatering, lime recovery and ultimate  ash disposal
  The report takes a design manual approach so that the information presented has
  maximum usefulness to environmental engineers engaged in both the conceptual and
  detailed design of wastewater treatment plants.

  Design data on alternate sludge thickening and dewatering processes  are presented
  with special emphasis on wet classification of calcium carbonate from unwanted
  materials and on maximizing the dewatering of wasted solids.

  Alternative recalcining techniques are assessed and problem areas identified.   A
  relatively new technique for beneficiation of the recalcined  product is presented.
  Approaches to heat recovery are presented that minimize the net energy requirements
  for recalcination and incineration.

  A computer program for computation of solids balances is included as a design aid and
  two case histories are presented which portray the cost of lime treatment,  sludge
  processing and lime reclamation.	
17.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
 Sludge disposal, Dewatering, Centrifuging
                                              b IDENTIFIERS/OPEN ENDED TERMS
Sludge treatment,  Ulti-
mate disposal, Chemical
precipitation, Solid
wastes, Chemical  sludge
processing, Centrifugal
classification, Centrifu-
gal Dewatering, Recalcina
tion. Chemical treatment
                             COSATl I;icld/Group
                                                                               13B
13. DISTRIBUTION STATEMENT


  RELEASE TO PUBLIC
19 SECURITY CLASS (This Report)
      UNCLASSIFIED
21. NO. OF PAGES
       315
20 SECURITY CLASS (This page)

      UNCLASSIFIED
                           22. PRICE
EPA Form 2220-1 (9-73)
                                            299
                                                   U S GOVfRNMFNI PRINTING (HHU  1975-657-695/5328 Region No. 5-11

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