EPA 625/1-81-013
(COE EM1110-1-501)
                             PROCESS DESIGN MANUAL
                                      FOR
                               LAND TREATMENT OF
                             MUNICIPAL WASTEWATER
                     U. S. ENVIRONMENTAL PROTECTION AGENCY

                         U. S. ARMY CORPS OF ENGINEERS

                         U. S. DEPARTMENT OF INTERIOR

                        U. S. DEPARTMENT OF AGRICULTURE
                                 October 1981
                                 Published by

                     U. S. Environmental Protection Agency
                 Center for Environmental Research Information
                            Cincinnati, Ohio 45268

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                       ACKNOWLEDGMENTS
This manual presents the state-of-the-art on process design
for land treatment systems.; It replaces the process design
manual  with  the  same  title,  published in October 1977.
Preparation  of  this  manual  was  sponsored  by  the U.S.
Environmental Protection Agency  (EPA),   Office of Research
and Development, and Office of Water; the U.S. Army Corps of
Engineers; the U.S. Department of the Interior (USDI), Office
of Water Research and Technology;   and the U.S. Department,
Of Agriculture  (USDA),  Office of  Environmental Quality and
Farmers Home Administration.    An interagency,coordinating
committee representing these sponsors was established; this
committee then selected a team of contract authors.  Contract
administration was provided' by EPA CERI, Cincinnati, Ohio.

PROJECT OFFICER;  Dr. James;E.  Smith  Jr., EPA, CERI.

Dr. Smith was also chairman'of the interagency coordinating
committee.    Assistance  in  contract  administration  was
provided  by  Enviro Control, Inc., under the direction  of
Mr. Torsten Rothman.        j

CONTRACTOR;  Metcalf & Eddyi, Inc. , Sacramento, California.

Supervision and Principal Authors;
  Ronald W. Crites, Project!Manager,
  E.L. Meyer and R.G. Smith!

Staff Authors;              »
  M. Walker, K. Alston, M. Alpert, C. Stein

Editing and Review;         |   .-.   ,         ,
  F. Burton, J. Miller, C. Pound

Consultant Authors;         '       .-••..               • •. •.
  Dr. A. Wallace, University of Idaho;  Dr. W. Nutter,
  University of Georgia; Mr^. D. Hinrichs, Culp/Wesner/
  Gulp; Mr. B. Whitson, Mr. ; D. Deemer, Dr. Q-. Aly, arid
  Mr. L. Gilde, Campbell SoUp Company; Dr. E. Myers,
  Williams & Works, Inc.; Mr. D. Hirschbrunner and
  Ms. D. Parkes, Bruce Gilmore  & Associates, Inc.

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                      ACKNOWLEDGMENTS

                            II
A  technical  workgroup  composed of members  from  the  spon-
soring agencies,   as well as  other invited  experts,   was
formed.  In addition, a rnultidisciplinary group of  engineers
and scientists also furnished technical review.    Under the
direction of its chairman,  the workgroup defined  the  scope
of the effort, supervised the work of the contractor,   re-
viewed the manual, and provided technical editing  and  input
to the manual.

CHAIRMAN;  Sherwood C. Reed, USA CRREL           '
WORKGROUP;

  EPA:
  U.S. Army:
  US DA:



  USDI:

  USDOE:

  NSF:
Mr.
Dr.
Mr.
Dr.
Dr.
Mr.
Mr.
Mr.
Dr.
Mr.
Mr.
Dr.
Mr.
Dr.
Mr.
Mr.
Ms.
Dr.
R
C
R
N
C
W
N
W
I
J
M
S
P
H
R
.R
B
E
E. Thomas, Dr. J.E. Smith Jr.,
 Harlin, Mr. W. Whittington,
 Bastian, Dr. H. Thacker,
 Kowal, Mr. R. Dean, Mr. J. Ariail,
 Enfield, Mr. J. Roesler,
 Huang, Mr. J. Smith

 Urban, Mr. D. Lament,
 Medding, Mr. P. Carmichael,
 Iskandar, Mr. J. Martel,
 Bouzoun, Dr. R. Lee,
 Cullinane, Mr. J. Bauer,
 Schaub, Dr. H. McKim

 Smith, Mr. C. Rose, Mr. G. Deal,
 Bouwer, Mr. W. Opfer, Dr. D. Urie,
 Phillips, Dr. D. Clapp

 Madancy

 Broomfield

 Bryan
Academic Institutions and Stalbe Agencies:

  Dr. M. Kirkham, Dr. E., Lennette, Dr. W.  Sopper,
  Dr. R. Smith, Dr. A. Overman, Dr. R. Abernathy,
  Dr. M. Overcash, Dr. A. Erickson, Mr. D.  Kendrick

Invited Technical Reviewers;

  Mr. B. Seabrook, Mr. T. Jenkins, Mr. J.  Kreissl,
  Mr. A. Palazzo, Dr. E.. Smith, Ms. H. Farquhar,
  Dr. R. Lewis, Dr. T. Asano, Mr. T. Rothman,
  Mr. R. Sletten, Mr. G, Abele
                             111

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                          ABSTRACT
This  manual presents a rational procedure for the design of
land  treatment systems.  Slow rate, rapid infiltration, and
overland  flow  processes  for  the  treatment  of municipal
wastewaters are discussed in detail, and the design concepts
and  criteria are presented;,  A two-phased planning approach
to site investigation and selection is also presented.

The  manual  includes  examples  of  each  process   design.
Information  on field investigations is presented along with
special  considerations  for small scale systems.  Equations
and  procedures are included to allow calculations of energy
requirements  for  land treatment systems.  Potential health
and   environmental  effects  and  corresponding  mitigation
measures are discussed.
                             IV

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                            CONTENTS
Chapter
          ACKNOWLEDGMENTS I
          ACKNOWLEDGMENTS II                        .
          ABSTRACT       ,                           •
          CONTENTS          ,  . .,.
          FIGURES
          TABLES

          INTRODUCTION AND PROCESS CAPABILITIES
          1.1   Purpose                      ....,.*.•.•,
          1.2   Scope
          1. 3   Treatment Processes
          1.4   Slow Rate Process
                1.4.1  Process Objectives
                1.4.2  Treatment Performance
          1.5   Rapid Infiltration
                1.5.1  Process Objectives
                1.5.2  Treatment Performance
          1.6   Overland Flow
                1.6.1  Process Objectives
                1.6.2  Treatment Performance
          1.7   Combination Systems
          1.8   Guide to Intended Use of the Manual
          1.9   References

          PLANNING AND TECHNICAL ASSESSMENT

          2.1   Planning Procedure
          2.2   Phase 1 Planning
                2.2.1  Preliminary Data
                2.2.2  Land Treatment System Suitability
                2.2.3  Land Area Requirements
                2.2.4  Site Identification
                2.2.5  Site Screening
          2.3   Phase 2 Planning
                2.3.1  Field Investigations
                2.3.2  Selection of Preliminary
                       Design Criteria
                2.3.3  Evaluation of Alternatives
                2.3.4  Plan Selection
          2.4   Water Rights and Potential Water
                Rights Conflicts
                2.4.1  Natural Watercourses
                2.4.2  Surface Waters
                2.4.3  Percolating Waters (Ground Waters)
                2.4.4  Sources of Information
          2.5   References
 Page

   ii
  iii
   iv
    v
   xv
xviii
  1-1
  1-1
  1-2
  1-4
  1-4
  1-8
  1-8
  1-9
  1-11
  1-11
  1-13
  1-13
  1-14
  1-14
  1-17
  2-1
  2-1
  2-1
  2-9
  2-16
  2-16
  2-22
  2-27
  2-27

  2-27
  2-29
  2-34

  2-34
  2-35
  2-37
  2-37
  2-38
  2-38

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                        CONTENTS (Continued)

Chapter                                   ,                 Page

   3      FIELD INVESTIGATIONS                             3-1
          3.1   Introduction                               3-1
          3.2   Physical Properties                        3-1
                3.2.1  Shallow Profile Evaluation          3-3
                3.2.2  Profile Evaluation to
                       Greater Depths                      3-4
          3.3   Hydraulic Properties                       3-4
                3.3.1  Saturated Hydraulic Conductivity    3-5
                3.3.2  Infiltration Capacity               3-6
                3.3.3  Specific Yield                      3-8
                3.3.4  Unsaturated Hydraulic Conductivity  3-8
                3.3.5  Profile Drainage                    3-10
          3.4   Infiltration Rate Measurements             3-10
                3.4.1  Flooding Basin Techniques           3-13
                3.4.2  Cylinder Infiltrometers             3-17
                3.4.3  Sprinkler Infiltrometers            3-20
          3.5   Measurement qf Vertical Hydraulic
                Conductivity (                              3-22
                3.5.1  Double-Tube Method                  3-24
                3.5.2  Air Entry Permeameter               3-24
          3.6   Ground Water                               3-27
                3.6.1  Depth/Hydrostatic Head              3-28
                3.6.2 , Flow                                3-30
                3.6.3  Ground Water Quality                3-36
          3.7   Soil Chemical Properties                   3-36
                3.7.1  Interpretation of Soil
                       Chemical Tests                      3-37
                3.7.2  Phosphorus Adsorption Test  •        3-38
          3.8   References   i                              3-39
                             i
                             t
   4      SLOW RATE PROCESS bESIGN

          4.1   Introduction                               4-1
          4.2   Process Perfqrinance                        4-1
                4.2.1  BOD and Suspended Solids Removal    4-1
                4.2.2  Nitrogen                            4-3
                4.2.3  Phosphorus                          4-5
                4.2.4  Trace ;Elements                      4-7
                4.2.5  Microorganisms                      4-7
                4.2.6  Trace Organics                      4-10
          4.3   Crop Selection                             4-11
                4.3.1  Guidelines for Crop Selection       4-11
                4.3.2  Crop Characteristics                4-15
          4.4   Preapplication Treatment                   4-24
                4.4.1  Preapplication Treatment for
                       Storage and During Storage          4-25
                4.4.2  Preapplication Treatment to
                       Protect Distribution Systems        4-27
                               VI

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                      CONTENTS (Continued)

Chapter                                                    Page

                4.4.3  Industrial Pretreatment             4-28
          4.5   Loading Rates and Land Area Requirements   4-28
                4.5.1  Hydraulic Loading Rate Based
                       on Soil Permeability                4-28
                4.5.2  Hydraulic Loading Rate Based
                       on Nitrogen Limits                  4-30
                4.5.3  Hydraulic Loading Rate Based
                       on Irrigation Requirements          4-34
                4.5.4  Land Area Requirements              4-35
          4.6   Storage Requirements                       4-37
                4.6.1  Estimation of Volume Requirements
                       Using Storage Water Balance
                       Calculations                        4-37
                4.6.2  Estimated Storage Volume
                       Requirements Using Computer
                       Programs                            4-39
                4.6.3  Final Design Storage Volume
                       Calculations '                       4-41
                4.6.4  Storage Pond Design Considerations  4-43
          4.7   Distribution System                        4-44
                4.7.1  Surface Distribution Systems        4-44
                4.7.2  Sprinkler Distribution Systems      4-45
                4.7.3  Service Life of.Distribution
                       System Components                   4-53
          4.8   Drainage and Runoff Control                4-53
                4,. 8.1  Subsurface Drainage Systems         4-53
                4.8.2  Surface Drainage and Runoff Control 4-56
          4.9   System Management                          4-58
                4.9.1  Soil Management                     4-58
                4.9.2  Crop Management                     4-61
          4.10  System Monitoring          •                4-64
                4.10.1 Water Quality Monitoring            4-65
                4.10.2 Soils Monitoring                    4-65
                4.10.3 Vegetation Monitoring               4-66
          4.11  Facilities Design Guidance              ',   4-66
          4.12  References                                 4-68

   5      RAPID INFILTRATION PROCESS DESIGN
          5.1   Introduction                               5-1
                5.1.1  RI Hydraulic Pathway                5-1
                5.1.2  Site Work       '    .  '              5-1
          5.2   Process Performance                        5-3
                5.2.1  BOD and Suspended Solids            5-3
                5.2.2  Nitrogen            .'                5-3
                5.2.3  Phosphorus                          5-5
                5.2.4  Trace Elements                      5-6
                5.2.5  Microorganisms                      5-8
                5,2.6  Trace Organics                      5-9
                              VII

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                        CONTENTS  (Continued)
Chapter
          5.3   Determination of Preapplication
                Treatment Level
                5.3.1   EPA Guidance
                5.3.2   Water! Quality Requirements
                        and Treatment Goals
          5.4   Determination; of Hydraulic
                Loading Rate j
                5.4.1   Measured Hydraulic Capacity
                5.4.2   Selection of Hydraulic Loading
                        Cycle and Application Rate
                5.4.3   Other;Considerations
          5.5   Land Requirements
                5.5.1   Infiltration Basin Area
                5.5.2   Preapplication Treatment
                        Facilities
                5.5.3   Other:Land Requirements
          5.6   Infiltration System Design
                5.6.1   Distribution and Basin Layout
                5.6.2   Storage and Flow Equalization
                5.6.3  • Cold Weather Modifications
          5.7   Drainage     i   ,   .
                5.7.1   Subsurface Drainage to
                        Surface Waters
               , 5.7.2   Ground Water Mounding
                5.7.3   Underdrains
                5.7.4   Wells1
          5.8   Monitoring and Maintenance Requirements
                5.8.1   Monitoring
                5.8.2   Maintenance
          5.9   Design and Construction Guidance
          5.10  References   i               .        .
                             [
          OVERLAND FLOW PROCESS DESIGN
          6.1   Introduction !
                6.1.1   Site Characteristics and
                        Evaluation"
                6.1.2   Water Quality Requirements
                6.1.3   Design and Operating Parameters
          6.2   Process Performance
                6.2.1   BOD Removal
                6.2.2   Suspended Solids Removal
                6.2.3   Nitrogen Removal
                6.2.4   Phosphorus Removal
                6.2.5   Trace Element Removal
                6.2.6   Mircroorganism Removal
                6.2.7   Trace Organics Removal
                6.2.8   Effect of Rainfall
Page


5-10
5-10

5-10

5-12
5-12

5-14
5-17
5-22
5-22

5-22
5-22
5-23
5-23
5-27
5-27
5-28

5-28
5-30
5-38
5-42
5-42
5-42
5-44
5-45
5-46
6-1

6-1
6-1
6-3
6-3
6-3
6-6
6-6
6-8
6-8
6-8
6-9
6-9
                              Vlll

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                       CONTENTS (Continued)

Chapter                                                    Page

                6.2.9   Effect of Slope Grade              6-10
                6.2.10  Performance During Startup         6-10
          6.3   Preapplication Treatment,                   6-10
          6.4   Design Criteria Selection    .              6-11
                6.4.1   Hydraulic, Loading Rate             6-12
                6.4.2   Application Rate                   6-12
                6.4.3   Application Period                 6-13
                6.4.4   Application Frequency              6-14
                6.4.5   Constituent Loading Rates          6-14
                6.4.6   Slope Length                       6-14
                6.4.7   Slope Grade                        6-15
                6.4.8   Land Requirements                  6-15
          6.5   Storage Requirements                       6-18
                6.5.1   Storage Requirements for
                        Cold Weather                       6-18
                6.5.2   Storage for Stormwater Runoff      6-19
                6.5.3   Storage for Equalization           6-21
          6.6   Distribution                               6-22
                6.6.1   Surface Methods                    6-22
                6.6.2   Low Pressure Sprays                6-24
                6.6.3   High Pressure Sprinklers           6-25
                6.6.4   Buried Versus Aboveground Systems  6-27
                6.6.5   Automation     .        •            6-27
          6.7   Vegetative Cover                           6-27
                6.7.1   Vegetative Cover Function          6-27
                6.7.2   Vegetative Cover Selection         6-28
          6.8   Slope Construction                         6-28
                6.8.1   System Layout                      6-28
                6.8.2  , Grading Operations                 6-29
                6.8.3   Seeding and Crop.Establishment     6-29
          6.9   Runoff Collection                          6-31
          6.10  System Monitoring and Management           6-32
                6.10.1  Monitoring                         6-32
                6.10.2  System Management     . :  :/  ,        6-32
          6.11  Alternative Design Methods                 6-34
                6.11.1  CRREL Method                       6-34
                6.11.2  University of California,
                        Davis, (UCD) Method    '            6-36
                6.11.3  Comparison of Alternative Methods  6-38
          6.12  References                                 6-39

   7      SMALL SYSTEMS
          7.1   Introduction    .                           7-1
          7.2   Facility Planning                          7-1
                7.2.1   Process Considerations             7-1
                7.2.2   Site Selection                     7-5
                7.2.3   Site Investigations                7-8

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                     CONTENTS!  (Continued)
                             i •
Chapter                      j                              Page
                             i
          7.3   Facility Design                            7-9
                7.3.1   Preapplication Treatment
                        and Storage                        7-9
                7.3.2   Hydraulic Loading Rates            7-10
                7.3.3   Land Area Requirements             7-15
                7.3.4   Distribution Systems               7-16
          7.4   Typical Small Community Systems            7-17
                7.4.1   Slow Rate Forage System            7-17
                7.4.2   Slow Rate Forest System            7-22
                7.4.3   Rapid; Infiltration                 7-26
                7.4.4   Overland Flow                      7-30
          7.5   References                                 7-31

   8      ENERGY REQUIREMENTS! AND CONSERVATION
          8.1   Introduction                               8-1
          8.2   Transmission Pumping                       8-2
          8.3   General Process Energy Requirements        8-4
                8.3.1   Slow Rate                          8-4
                8.3.2   Rapid; Infiltration                 8-4
                8.3.3   Overland Flow                      8-5
          8.4   Energy Conseryation                        8-6
               - 8.4.1   Areas of Potential Energy Savings  8-6
                8.4.2   Example:  Energy Savings in
                        Slow Rate Design                   8-8
                8.4.3   Summary                            8-10
          8.5   Procedures for Energy Evaluations          8-10
                8.5.1   Slow Rate                          8-11
                8.5.2   Rapid Infiltration                 8-12
                8.5.3   Overland Flow                      8-13
                8.5.4   Examples                           8-13
          8.6   Equations for Energy Requirements          8-16
                8.6.1   Preapplication Treatment           8-17
                8.6.2   Land Treatment Processes           8-18
          8.7   References   \                              8-18
          HEALTH AND ENVIRONMENTAL EFFECTS
          9.1   Introduction
          9.2   Nitrogen
                9.2.1   Crops!
                9.2.2   Ground Water
                9.2.3   Surface Water
          9.3   Phosphorus
                9.3.1   Soils
                9.3.2   Crops;
                9.3.3   Ground Water
                9.3.4   Surface Water
9-1
9-3
9-4
9-4
9-4
9-5
9-5
9-5
9-5
9-5
                               x

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                    CONTENTS (Continued)
Chapter
Appendix
    B
          9.4   Dissolved Solids
                9.4.1   Soils
                9.4.2   Crops
                9.4.3   Ground Water
          9.5   Trace Elements
                9.5.1   Soils
                9.5.2   .Crops
                9.5.3   Ground Water
          9.6   Microorganisms
                9.6.1   Soils
                9.6.2   Crops
                9.6.3   Ground Water
                9.6.4   Surface Water
                9.6.5   Aerosols
          9.7   Trace Organics
                9.7.1   Soils,
                9.7.2   Crops
                9.7.3   Ground Water
                9.7.4   Surface Water
          9.8   References
SLOW RATE DESIGN EXAMPLE
A.I   Introduction
A.2   Statement of Problem
      A. 2.1   Background
      A.2.2   Population and Wastewater
              Characteristics
      A.2.3   Discharge Requirements
      A.2.4   Site Characteristics
      A.2.5   Climate
A.3   Slow Rate System Selection
      A.3.1   Preapplication Treatment
      A.3.2   Crop Selection
A.4   System Design
      A.4.1   Forage Crop Alternative
      A.4.2   Deciduous Forest Crop Alternative
      A.4.3   Selected SR Design
      A.4.4   Energy Requirements

RAPID INFILTRATION DESIGN EXAMPLE
B.I   Introduction
B.2   Design Considerations
      B.2.1   Design Community
      B.2.2   Wastewater Quality and Quantity
      B.2.3   Existing Wastewater
              Treatment Facilities
                                                 Page

                                                 9-5
                                                 9-5
                                                 9-6
                                                 9-6
                                                 9-8
                                                 9-8
                                                 9-9
                                                 9-11
                                                 9-12
                                                 9-13
                                                 9-14
                                                 9-16
                                                 9-16
                                                 9-17
                                                 9-21
                                                 9-21
                                                 9-22
                                                 9-22
                                                 9-23
                                                 9-24
                                                            A-l
                                                            A-l
                                                            A-l

                                                            A-l
                                                            A-l
                                                            A-2
                                                            A-2
                                                            A-4
                                                            A-4
                                                            A-5
                                                            A-5
                                                            A-5
                                                            A-22
                                                            A-28
                                                            A-28
                                                            B-l
                                                            B-l
                                                            B-l
                                                            B-l

                                                            B-2

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                     CONTENTS  (Continued)

Appendix                                                   Page

                B.2.4   Climate                            B-2
          B.3   Site and Process Selection                 B-3
          B.4   Site Investigations                        B-6
                B.4.1   Soil I Characteristics               B-6
                B.4.2   Ground Water Characteristics       B-8
                B.4.3   Hydraulic Capacity                 B-8
          B.5   Determination of Wastewater Loading Rate   B-10
                B.5.1   Preapplication Treatment Level     B-10
                B.5.2   Hydraulic Loading Rate             B-10
                B.5.3   Hydraulic Loading Cycle            B-ll
                B.5.4   Effect of Precipitation on
                        Wastewater Loading Rate    •        B-ll
                B.5.5   Underdrainage                      B-ll
                B.5.6   Nitrification                      B-13
          B.6   Land Requirements                          B-13
                B.6.1   Preapplication Treatment -     '
                        Facilities                    i     B-13
                B.6.2   Infiltration Basins           !     B-14
          B.7   System Design                              B-14
                B.7.1   General Requirements               B-14
                B.7.2   Underdrainage                      B-18
          B.8   Maintenance and Monitoring                 B-18
                B.8.1   Maintenance                ,   '     B-18
                B.8.2   Monitoring                         B-20
          B.9   System Costs :    •                          B-20
          B.10  Energy Budget                              B-20
          B.ll  References               .                  B-22

   C      OVERLAND FLOW DESIGN EXAMPLE
          C.I   Introduction                               C-l
          C.2   Statement of ,the Problem                   C-l
          C.3   Design Considerations                      C-l
                C.3.1   Wastewater Characteristics
                        and Discharge Requirements         C-l
                C.3.2   Climate                            C-2
          C.4   Site Evaluation and Process Selection      C-2
                C.4.1   General Site Characteristics       C-2
                C.4.2   Soil Characteristics               C-4
                C.4.3   Process Selection             :     C-4
          C.5   Distribution^Method                        C-4
          C.6   Preapplication Treatment                   C-4
          C.7   Wastewater Storage                         C-5
                C.7.1   Storage Requirement                C-5
                C.7.2   Storage Facility Description       C-5
          C.8   Selection of Design Parameters             C-6
                C.8.1   Hydraulic Loading Rate             C-6
                C.8.2   Application Period and Frequency   C-6
                             Xll

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Appendix
   D
   E
              CONTENTS (Continued)

                                              ;   Page

      C.8.3   Slope Length and Grade             C-6
      C.8.4   Application Rate                   C-7
      C.8.5   Land Requirements                  C-7
C.9   Distribution System                        C-7
C.10  Preliminary System Layout                  C-9
C.ll  System Design                              C-9
      C.ll.l  Treatment Slopes                   C-9
      C.ll.2  Runoff Channel Design           ,   C-9
      C.ll.3  Collection Waterways               C-12
      C.ll.4  Pumping System                     C-12
      C.ll.5  Monitoring and Collection System   C-13
C.12  Land Requirements                          C-13
C.13  Cover Crop Selection                       C-14
C.14  System Costs                               C-14
C.15  Energy Budget                              C-15
C.16  Alternative Design Methods -
      Design Example                             C-15
      C.16.1  CRREL Method                       C-15
      C.16.2  University of California,
              Davis, Method                      C-17
      C.16.3  Comparison of Methods              C-19
C.17  References                              ,   C-19

LOCATION OF LAND TREATMENT SYSTEMS
D.I   Slow Rate Systems                          D-l
D.2   Rapid Infiltration Systems  '               D-5
D.3   Overland Flow Systems                      D-7

DISTRIBUTION SYSTEM DESIGN FOR SLOW RATE
E.I   Introduction                               E-l
E.2   General Design Considerations              E-l
      E.2.1   Depth of Water Applied             E-l
      E.2.2   Application Frequency              E-l
      E.2.3   Application Rate                   E-2
      E.2.4   Application Period                 E-2
      E.2.5   Application Zone                   E-2
      E.2.6   System Capacity                    E-3
E.3   Surface Distribution System1                E-4
      E.3.1   Ridge and Furrow Distribution      E-4
      E.3.2   Graded Border Distribution         E-10
E.4   Sprinkler Distribution Systems             E-15
      E.4.1   Application Rates                  E-15
      E.4.2   Solid Set Sprinkler Systems        E-15
      E.4.3   Move-Stop Sprinkler Systems        E-20
      E.4.4   Continuous Move Systems            E-24
E.5   References                                 E-31
                              Xlll

-------
Appendix
                       CONTENTS  (Concluded)
          ESTIMATED STORAGE DAYS FOR LAND TREATMENT
          USING  EPA COMPUTER |PROGRAMS
          GLOSSARY  OF TERMS
          CONVERSION FACTORS
Page

F-l

G-l
G-3
                               xiv,

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                            FIGURES


No.                                                        Page

1-1    Slow Rate Hydraulic Pathways                 ,     :  1-5
1-2    Rapid Infiltration Hydraulic Pathways               1-10
1-3    Overland Flow                                       .1-12
1-4    Examples of Combined Systems                        1-15
2-1    Two-Phase Planning Process                          2-2
2-2    Potential Evapotranspiration Versus Mean
        Annual Precipitation                               2-11
2-3    Estimated Design Percolation Rate as a
        Function of Soil Permeability for SR and
        RI Land Treatment                                  2-12
2-4    Winter Operation of Rapid Infiltration
        at Lake George, New York                           2-14
2-5    Estimated Wastewater Storage Days Based
        only on Climatic Factors                           2-15
2-6    Total Land Required (Includes Land for
        Application, Roads, Storage, and Buildings)        2-17
2-7    Example Area of Soil .Map to be Evaluated            2-25
2-8    Example Suitability Map for Soils
        in Figure 2-7                                      2-26
2-9    Staffing Requirements for Land Treatment
        Components  (not Including Sewer System or
        Preapplication Treatment) for Municipally
        Owned and Operated Systems                         2-33
2-10   Dominant Water Rights Doctrines and Areas
        of Water Surplus or Deficiency                     2-36
3-1    Flow Chart of Field Investigations                  3-2
3-2    Infiltration Rate as a Function of
        Time for Several Soils                             3-7
3-3    Porosity, Specific Retention, and Specific
        Yield Variations with Grain Size,
        South Coastal Basin,  California                    3-9
3-4    General Relationship Between Specific Yield
        and Hydraulic Conductivity                         3-9
3-5    Typical Pattern of the Changing Moisture
        Profile During Drying and Drainage                 3-11
3-6    Flooding Basin Used for Measuring Infiltration      3-13
3-7    Groove Preparation for Flashing (Berm)              3-14
3-8    Schematic of Finished Installation                  3-14
3-9    Infiltration Rate and Cumulative Intake Data Plot   3-16
3-10   Cylinder Infiltrometer in Use                       3-18
3-11   Layout of Sprinkler Infiltrometer                   3-21
3-12   Schematic of Double-Tube Apparatus                  3-25
3-13   Schematic of Air-Entry Permeameter                  3-25
3-14   Well and Piezometer Installation                    3-29
3-15   Vertical Flows Indicated by Piezometers             3-30
3-16   Definition Sketch for Auger-Hole Technique          3-33
                               xv

-------
                      FIGURES ! (Continued)
 No.

 3-17
 4-1
 4-2

 4-3

 4-4
 4-5

 4-6

 5-1
 5-2
 5-3
 5-4

 5-5

 5-6
 5-7
 5-8

 5-9
5-10

5-11
5-12
5-13

5-14
5-15
6-1
6-2
6-3

6-4

6-5
7-1
7-2
 Experimental Setup for! Auger-Hole Technique
 Slow Rate Design Procedure
 Nitrogen Uptake Versus! Growing Days for
  Annual and Perennial Crops
 Determination of Storage by EPA Computer
  Programs According to! Climatic Constraints
 Surface Distribution Methods
 Fan Nozzle Used for Spray Application at
  West Dover,  Vermont  !
 Solid Set Sprinklers with Surface Pipe
  in a Forest System   [
 Rapid Infiltration Design Procedure
 Effect of Infiltration'Rate on Nitrogen Removal
 Infiltration Basin Outlet and Splash Pad
 Interbasin Transfer Structure with
  Adjustable Weir      j
 Natural Drainage of Renovated Water
  Into Surface Water   i
 Example Design for Subsurface Flow to Surface Water
 Schematic of  Ground Water Mound
 Mounding Curve for Center of a Square
  Recharge Area        |
 Mounding Curve for Center of a Rectangular
  Recharge Area at Different Ratios of
  Length (L)  to Width (W)
 Rise  and Horizontal Spread of Mound Below a
  Square Recharge Area  |
 Rise  and Horizontal Spread of Mound Below a
  Rectangular  Recharge Area Whose  Length
  is Twice its  Width   j
 Centrally Located Undeirdrain
 Underdrain System Using Alternating            ;
  Infiltration  and Drying  Strips
 Parameters  Used  in  Drain  Design
 Well  Configurations
 Overland  Flow  Design Procedure
 Surface Distribution Using  Gated  Pipe for OF
 Distribution for  OF Using  Low Pressure
 Fan  Spray Nozzles     |
Alternative Sprinkler Configurations  for
 Overland Flow Distribution
 Land Plane Used for Final Grading
Land Area Estimates for Preliminary Planning
 Process  (Including Land for Preapplication
 Treatment)
Typical Annual Hydraulic Loading Rate of
 Small SR and OF Systems
 Page

 3-33
 4-2

 4-17

 4-40
 4-46

 4-51

 4-52
 5-2
 5-19
 5-24

 5-24

 5-29
 5-31
 5-32

 5-34
5-34

5-36
5-37
5-39

5-40
5-41
5-43
6-2
6-23

6-24

6-26
6-30
7-7

7-12
                               xvi

-------
                      FIGURES  (Concluded)
No.

7-3

7-4

7-5

7-6
8-1
8-2
A-l
A-2
A-3
B-l
B-2
B-3
B-4
B-5
B-6
C-l
C-2
C-3

C-4
E-l
E-2

E-3
E-4
E-5
E-6
E-7
E-8
E-9
E-10
Typical Annual Hydraulic Loading Rate  of
 Small SR Systems
Overflow Control Structure  for Pond Discharge
 to SR System
Treatment Facility Layout - Kennett Square,
 Pennsylvania, SR System
SR Facilities at Kennett Square, Pennsylvania
Center Pivot System
Automatic Surface Irrigation System
Soils Map
System Layout:  Forage Crop Alternative
System Layout:  Forest Crop Alternative
Soils Map, Sites 1 and 2
Ground Water Contours
Intake Curves - Infiltration Basin 1
Community B Rapid Infiltration System Flowsheet
Community B Site Layout
Underdrain Location
Proposed Overland Flow Treatment Site
Typical Overland Flow Slope
Contour Map of Proposed Overland Flow
 Treatment System
Overland Flow System Layout
Surface Distribution Methods
Aluminum Hydrant and Gated Pipe at
 Sweetwater, Texas
Outlet Valve for Border Strip Application
Solid Set Sprinkler System
Move-Stop Sprinkler Systems
Side Wheel Roll Sprinkler System
Continuous Move Sprinkler Systems
Hose-Drag Traveling Gun Sprinkler
Center Pivot Rig
Center Pivot Irrigation System
                                                    Page
 7-13

 7-21

 7-23
 7-24
 8-7
 8-8
 A-3
 A-18
 A-26
 B-4
 B-7
 B-9
 B-15
 B-l 6
 B-19
 C-3
 C-8

 C-10
 C-ll
 E-5

 E_ Q
  O
 E-13
 E-16
 E-22
 E-23
 E-25
E-26
E-30
E-30
                             ixvii

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                           TABLES
                             i
No.                          [                             Page

1-1    Comparison of Typical Design Features for
        Land Treatment Processes                          1-3
1-2    Comparison of Site Characteristics for
        Land Treatment Processes                          1-3
1-3    Expected Quality of Treated Water from
        Land Treatment Processes                          1-4
2-1    Important Constituents; in Typical
        Domestic Wastewater                               2-3
2-2    Comparison of Trace Elements in Water
        and Wastewaters      j                             2-4
2-3    Typical BOD Loading Rates                          2-4
2-4    National Interim Primary Drinking
        Water Standards, 197?!                             2-6
2-5    Summary of Climatic Analyses                       2-8
2-6    Land Use Suitability Factors for
        Identifying Land Treatment Sites                  2-19
2-7    Grade Suitability Factors for
        Identifying Land Treatment Sites                  2-19
2-8    Soil Textural Classes and General
        Terminology Used in Soil Descriptions             2-21
2-9    Typical Soil Permeabilities and Textural
        Classes for Land Treatment Processes              2-22
2-10   Site Selection Guidelines                          2-23
2-11   Rating Factors for Site Selection                  2-24
2-12   Characteristics of Soil Series
        Mapped in Figure 2-7 j                             2-25
2-13   Example Use of Rating Factors for Site Selection   2-26
2-14   Applicability of Recovery Systems for
        Renovated Water                                   2-29
2-15   Lease/Easement Requirements for Construction
        Grants Program Funding                            2-31
2-16   Potential Water Rights'Problems for
        Land Treatment Alternatives                       2-37
3-1    Summary of Field Tests ifor Land
        Treatment Processes                               3-3
3-2    Comparison of Infiltration -Measurement Techniques  3-12
3-3    Sample Comparison of Infiltration
        Measurement Using Flooding and
        Sprinkling Techniques                             3-12
3-4    Suggested Vertical Placement of
        Tensiometers in BasiniInfiltrometer Tests         3-15
3-5    Measured Ratios of Horizontal to
        Vertical Conductivity!                             3-32
3-6    Interpretation of SoiliChemical Tests              3-39
4-1    BOD Removal Data for Selected SR Systems           4-3
4-2    Nitrogen Removal Data for Selected SR Systems      4-4
                             xvan

-------
                       TABLES  (Continued)

No.                                                       Page

4-3    Phosphorus Removal Data for Typical SR Systems     4-6
4-4    Trace Element Behavior During SR Land Treatment    4-8
4-5    Suggested Maximum Applications of
        Trace Elements to Soils Without
        Further Investigations                            4-9
4-6    Coliform Data for Several SR Systems               4-10
4-7    Benzene, Chloroform, and Trichloroethylene
        in Muskegon Wastewater Treatment System           4-11
4-8    Relative Comparison of Crop Characteristics        4-13
4-9    Summary of Operational Forest Land Treatment
        Systems in the United States Receiving
        Municipal Wastewater                              4-15
4-10   Height Growth Response of Selected Tree Species    4-15
4-11   Nutrient Uptake Rates for Selected Crops           4-16
4-12   Estimated Net Annual Nitrogen Uptake in the
        Overstory and Understory Vegetation of Fully
        Stocked and Vigorously Growing Forest
        Ecosystems in Selected Regions of the
       . United States                                     4-19
4-13   Biomass and Nitrogen Distribution by Tree
        Component for Stands in Temperate Regions         4-20
4-14   Examples of Estimated Monthly Potential
        Evapotranspiration for Humid and
        Subhumid Climates                                 4-21
4-15   Consumptive Water Use and Irrigation Requirements
        for Selected Crops at San Joaquin Valley,
        California                                        4-22
4-16   Summary of Wastewater Constituents Having
        Potential Adverse Effects                         4-24
4-17   Water Balance to Determine Hydraulic Loading
        Rates Based on Soil Permeability                  4-31
4-18   Estimating of Storage Volume Requirements
        Using Water Balance Calculations                  4-38
4-19   Summary of Computer Programs for Determining
        Storage from Climatic Variables                   4-39
4-20   Final Storage Volume Requirement Calculations      4-42
4-21   Surface Distribution Methods' and
        Conditions of Use                                 4-47
4-22   Advantages and Disadvantages of Sprinkler
        Distribution Systems Relative to
        Surface Distribution Systems                      4-49
4-23   Sprinkler System Characteristics                   4-49
4-24   Suggested Service Life for Components of
        Distribution System                             .  4-54
4-25   Recommended Design Factors for
        Tailwater Return Systems                          4-57
                              xxx

-------
                        TABLES  (Continued)

No.                                                       Page

4-26   Approximate Critical!Levels of Nutrients
         in Soils  for Selected  Crops  in California    ,     4-59
4-27   Grazing Rotation Cycles for Different
         Numbers of Pasture  Areas                          4-62
4-28   Recommended Soil Contact Pressure                  4-67
5-1    BOD Removal for  Selected RI Systems                5-4
5-2    Nitrogen Removal Data for Selected RI Systems      5-5
5-3    Phosphorus Removal Data for Selected RI Systems    5-6
5-4    Comparison of Trace  Element Levels to
         Irrigation and  Drinking Water Limits              5-7
5-5    Heavy Metal Retention in an Infiltration Basin     5-7
5-6    Fecal Coliform Removal  Data for Selected
         RI Systems                                        5-8
5-7    Reported Isolations  of  Virus  at RI Sites           5-9
5-8  '  Recorded Trace Organic  Concentrations at
         Selected RI Sites   (                              5-10
5-9    Suggested Preapplication Treatment Levels          5-11
5-10   Typical Hydraulic Loading Rates for RI Systems     5-13
5-11   Suggested Annual Hydraulic Loading Rates           5-14
5-12   Typical Hydraulic Loading Cycles                   5-16
5-13   Suggested Loading Cycles                           5-17
5-14   Minimum Number of Basins Required for
         Continuous Wastewater  Application                 5-25
6-1    OF Design and Operating Parameters                 6-3
6-2    Summary of Process Operating  Parameters,
         BOD and SS Performance at OF Systems              6-4
6-3    Summary of Nitrogen  and Phosphorus
         Performance at  OF Systems                         6-5
6-4    Removal Efficiencies^  Heavy Metals at
         Different Hydraulic Rates at Utica, Mississippi   6-9
6-5    Overland Flow Design Guidelines                    6-12
7-1    Types and Sources of Data Required for Design
         of Small Land Treatment Systems                   7-2
7-2    General Characteristics  of Small
        Land Treatment  Systems                            7-3
7-3    Typical Staffing Requirements at Small Systems     7-6
7-4    Recommended Level of ; Preapplication Treatment      7-9
7-5    Typical Design Parameters for Several
        Types of Ponds                              ,7-10
7-6    Nitrogen Uptake Rates for Selected Crops           7-14
7-7    Design Information for  SR System                   7-19
7-8    Design Information for Chapman RI System           7-27
7-9    Wastewater Flows to Chapman RI System              7-29
7-10   Treatment Performance of Carbondale OF System      7-31
8-1    Energy Requirements for Crop Production            8-4
8-2    Most Common Unit Energy Requirements for
        Land Treatment of Municipal Wastewater            8-5
                              xx

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                      TABLES  (Continued)

No.                                                       Page

8-3    Example System Characteristics                     8-8
8-4    Comparison of Conventional and Automated Ridge
        and Furrow Systems for 38,000 m3/d                8-9
8-5    Comparison of Impact and Drop-Type Center Pivot
        System Nozzle Designs on Energy Requirements      8-10
8-6    Total Annual Energy for Typical 3,785 m3/d System  8-11
9-1    Land Treatment Methods and Concerns                9-2
9-2    Relationship of Pollutants to Health Effects       9-2
9-3    EPA Long-Term Effects Studies                      9-3
9-4    Tolerance of Selected Crops to Salinity in
        Irrigation Water                               •   9-7
9-5    Mass Balance of Trace Elements in OF System
        at Utica, Mississippi                             9-9
9-6    Trace Element Content of Forage Grasses at
        Selected SR Systems                               9-11
9-7    Trace Element Drinking and Irrigation
        Water Standards                                   9-12
9-8    Virus Transmission Through Soil at RI Systems      9-15
9-9    Aerosol Bacteria at Land Treatment Sites           9-18
9-10   Aerosol Enteroviruses at Land Treatment Sites      9-19
9-11   Comparison of Coliform Levels in Aerosols at
        Activated Sludge and Slow Rate Land
        Treatment Facilities                              9-20
9-12   Trace Organics Removals During Sand Filtration     9-21
9-13   Trace Organics Removals at Selected SR Sites       9-23
9-14   Removal of Refractory Volatile Organics by
        Class at Phoenix RI Site                          9-23
9-15   Chloroform and Toluene Removal During OF           9-24
A-l    Population and Wastewater Characteristics          A-2
A-2    Climatic Data for the Worst Year in 5              A-4
A-3    Hydraulic Loading Rates .Based on Soil
        Permeability:  Forage Crop Alternative            A-7
A-4    Design Hydraulic Loading Rate                      A-9
A-5    Storage Volume Determination:  Forage
        Crop Alternative                                  A-11
A-6    Final Determination of Storage Volume           '   A-14
A-7    Design Criteria for Storage Lagoons:
        Forage Crop Alternative                           A-15
A-8    Slow Rate System Design Data:  Forage
        Crop Alternative                                  A-19
A-9    Cost Estimate Criteria:  Forage Crop Alternative   A-19
A-10   Cost Estimate Calculations:
        Forage Crop Alternative                           A-20
A-ll   Summary of Costs:  Forage Crop Alternative         A-21
A-12   Initial Determination of Storage Volume:
        Forage Crop Alternative                           A-23
                              xxi

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                        TABLES  (Concluded)
                            i
No.                                                       Page
                            I
A-13   Design Data for Storage Pond:  Forest
        Crop Alternative                                  A-24
A-14   Design Data:  Forest JGrop Alternative              A-25
A-15   Summary of Cost:  Deciduous Forests                A-27
B-l    Projected Wastewater [Characteristics               B-l
B-2    Surface Water Discharge Requirements               B-2
B-3    Average Meteorological Conditions                  B-3
B-4    General Soil Characteristics:  Sites 1 and 2       B-5
B-5    Typical Log of Test Hole                           B-6
B-6    Ground Water Quality                               B-8
B-7    Cost of Community B R± System                      B-21
C-l    Raw Wastewater Characteristics                     C-l
C-2    Average Meteorological Conditions                  C-2
C-3    Storage Requirements ;                              C-5
C-4    Land Requirements    |                              C-13
C-5    Cost of Community C OF System                      C-l4
E-l    Optimum Furrow Spacing                             E-6
E-2    Suggested Maximum Lengths of Cultivated Furrows
        for Different Soils,; Grades, and Depths of
        Water to be Applied                               E-6
E-3    Design Guidelines for Graded Border Distribution,
        Deep Ro'oted Crops                                 E-ll
E-4    Design Guidelines for Graded Border Distribution,
        Shallow Rooted Crops                              E-ll
E-5    Recommended Reductions in Application Rates
        Due to Grade                                      E-l5
E-6    Recommended Spacing o|f Sprinklers                  E-18
E-7    Factor (F) by Which Pipe Friction Loss is
        Multiplied to Obtain Actual Loss in a Line
        with Multiple Outlets                             E-l9
E-8    Recommended Maximum Lane Spacing for
        Traveling Gun Sprinklers                          E-28
F-l    Storage Days Using EPA-1 for 20 Year (5%)
        and 10 Year (10%) Return Intervals                F-l
F-2    Storage Days Using EPA-2 for 20 Year (5%)
        and 10 Year (10%) Return Intervals                F-2
F-3    Storage Days Using EPA-3 for 20 Year (5%)
        and 10 Year (10%) Return Intervals                F-3
                             xxiz

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                          CHAPTER 1

            INTRODUCTION  AND PROCESS  CAPABILITIES
1.1  Purpose

The  purpose  of  this  manual  is  to  provide  criteria  and
supporting  information  for  planning  and process  design of
land treatment systems.   Recommended procedures for planning
and  design   are  presented   along   with  state-of-the-art
information on treatment performance, energy  considerations,
and health and environmental effects.

Cost curves  are not included  in  this manual, although  some
cost  information  is . included in  Chapter   2.    Costs  for
planning may  be  obtained  from cost curves in  references [1,
2] , or  through  the CAPDET computer  system  developed by the
Corps of  Engineers for  EPA.   CAPDET computer terminals are
available in EPA regional offices.

This document is a  revision of the  Process  Design Manual
for Land  Treatment  of Municipal Wastewater sponsored by the
U.S.  Environmental protection Agency,  U.S.   Army  Corps of
Engineers, and U.S. Department of Agriculture, and published
in  1977.    The  revision is  necessary because  of  the large
amount  of research  data,  criteria, and operating  experience,
that has  become available  in  recent  years.   As a result of
PL  92-500  and  PL  95-217,  the  interest  in and  use  of  land
treatment   concepts  has   increased   significantly  and  is
expected to continue to increase.

1.2  Scope

Land treatment  is defined as  the  controlled  application of
wastewater  onto the land surface  to  achieve  a designed de-
gree  of treatment  through  natural physical, chemical,  and
biological processes within  the plant-soil-water matrix.

The scope of  this  manual  is limited  to the three major  land
treatment processes:

    •    Slow rate  (SR)

    •    Rapid  infiltration  (RI)

    •    Overland  flow  (OF)

These processes are defined later in this chapter and  dis-
cussed  in detail  in the  design chapters.   The titles  were
adopted  for the original  1977 manual to reflect the rate of
                             1-1

-------
wastewater   application  a'nd   the   flow  path  within   the
process.   Prior to  the 19j?7 manual,  the term  "irrigation"
was often  used  to  describe the slow rate process.  The  pre-
sent term was chosen to focus attention  on wastewater  treat-
ment rather  than on  irrigation  of crops.

Subsurface systems, wetlands, and aquaculture  were discussed
briefly  in  the  1977 manual  but are deleted here since  they
are now  covered in detail in other documents  [3, 4].   Land
application  of  sludge, injection wells, evaporation  ponds,
and other  forms of  treatment  or disposal  that  involve  the
soil matrix  are also excluded.
                           I
Most  of  the information  in this  manual  is  applicable  to
medium-to-large   systems.  |    For   small   systems,   up   to
1,000 m^/d  (250,000 .gal/d) , many  of  the design procedures
can be  simplified.   Special considerations  for  these small
systems  and  a number  of  typical examples  are discussed  in
Chapter 7.    Case studies for larger  systems are  available  in
other  publications  [5-9].     This  manual  addresses   land
treatment  of municipal  wastewater, not industrial  wastes.
Under controlled conditions, however,  land treatment of  many
types of industrial wastewaters and  even hazardous materials
can be both  technically and economically feasible.

Although the principal focus in the manual  is on the three
basic processes  (SR, RI, OF),  the  possibility of combining
two or  more of the  concepts in a  continuous  system  should
not be overlooked.   Overland flow could be a  preapplication
step  for either SR  or RI, or  different processes  could  be
used in cold and warm weather.

1.3  Treatment Processes   ;

Typical  design  features   for   the   three  land  treatment
processes are compared in Table 1-1.   The major  site charac-
teristics are compared for each process  in Table 1-2.  These
are desirable characteristics  and not  limits  to be adhered
to rigorously, as discussed in  Chapter 2.

The expected quality of treated water  for biochemical oxygen
demand  (BOD),  suspended solids  (SS),  nitrogen,  phosphorus,
and  fecal   coliforms  is  presented   for  each  process   in
Table 1-3.    The average and  expected upper range values are
valid  fpr  the  travel  distances  and  applied  wastewater  as
indicated.     The   fate  off  these   materials   (plus  metals,
viruses, and trace  organics)  is discussed  in the  chapters
that follow.
                             1-2

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                                 TABLE 1-1
            COMPARISON  OF TYPICAL DESIGN  FEATURES
                   FOR LAND  TREATMENT  PROCESSES
     Feature
                         Slow rate
                                             Rapid  infiltration  Overland flow
Application techniques
Annual loading
rate, m
Field area
required, hab
Typical weekly
Sprinkler
or surfacea
0.5-6
23-280
1.3-10
Usually surface
6-125
3-23
10-240
Sprinkler or
surface
3-20
6.5-44
6-40°
 loading rate,  cm
 Minimum preapplication
 treatment provided in
 the United States

 Disposition of
 applied wastewater
 Need for vegetation
           Primary
           sedimentation0
                              Primary
                              sedimentation6
           Evapotranspiration  Mainly
           and percolation     percolation
           Required
                              Optional
  Grit removal and
  comminution6


  Surface runoff and.
  evapotranspiration
  with some
  percolation
  Required
  a. . Includes ridge-and-furrow and border strip.
  b.  Field area in hectares not including buffer area,  roads, or ditches for
     3,785 m3/d (1 Mgal/d) flow.
  c.  Range includes raw wastewater to secondary effluent, higher rates for higher
     level of preapplication  treatment.
  d.  With restricted public access; crops not for direct human consumption.
  e.  With restricted .public access.

  Note:  See Appendix G for metric conversions.



                                  TABLE  1-2

               COMPARISON  OF  SITE  CHARACTERISTICS
                    FOR  LAND  TREATMENT  PROCESSES
              Slow rate
                   Rapid infiltration
                                                              Overland  flow
Grade
Soil
permeability


Depth to
ground water

Climatic
restrictions
                   Not critical;  excessive
                   grades require much
                   earthwork
Less than  20% on-
cultivated land;
less than  40% on  '
noncultivated land
Moderately slow to  Rapid (sands,  sandy loams)
moderately rapid


0.6-1 m (minimum)13  .1 m during flood cycleb;
                   1.5-3 m during drying cycle
Storage often
needed for cold
weather and during
heavy precipitation
                   None  (possibly modify
                   operation in cold weather)
                                                              Finish  slopes 2-8%°
                                               Slow (clays,  silts,
                                               and soils with
                                               impermeable barriers)
                                               Not critical0
Storage usually needed
for cold weather
a.  Steeper grades might be feasible at reduced hydraulic loadings.
b.  Underdrains can be  used to maintain this level  at  sites with high ground
    water table.
c.  Impact on ground water should be considered for more permeable soils.
                                         1-3

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                             TABLE 1-3
                EXPECTED  QUALITY  OF TREATED WATER
                 FROM LAND  TREATMENT PROCESSES3
                   mg/L Unless Otherwise  Noted


Constituent
BOD
Suspended solids
Ammonia nitrogen as N
Total nitrogen as N
Total phosphorus as P
Fecal coliforms, No./lOO mL
Slow rateb
Upper
Average ; range
<2 <5
<1 l<5
<0. 5 <2
3e !<8e
<0.1 K0.3
0 ^10
Rapid infiltration0 Overland

Average
5
2
0.5
10
1
10
Upper
range
' <10
<5
<2
<20
<5
<200

Average
10
10
<4
5f
4
200
flowd
Upper
range
<15
<20
<8
<10f
<6
<2,000
   a.  Quality expected with loading rates at the mid to low end of the range
      shown in Table 1-1.            |
   b.  Percolation of primary or secondary effluent through 1.5 m (5 ft) of
      unsaturated soil.             |
   c.  Percolation of primary or secondary effluent through 4.5 m (15 ft) of
      unsaturated soil; phosphorus and fecal coliform removals increase with
      distance (see Tables 5-3 and 5-6).
   d.  Treating comminuted, screened wastewater using a slope length of  30-36 m
      (100-120 ft).                |
   e.  Concentration depends on loading rate and crop.
   f.  Higher values expected when operating through a moderately cold winter or when
      using secondary effluent at high rates.
1.4   Slow Rate Process

Slow rate land treatment  is| the application  of wastewater  to
a  vegetated land surface with  the applied  wastewater being
treated  as  it  flows   through  the   plant-soil  matrix.     A
portion of  the  flow percolates  to the  ground  water  and some
is  used  by  the  vegetation.,   Offsite surface  runoff  of the
applied  water  is  generally  avoided  in  design.    Schematic
views of the typical  hydraulic pathways for  SR treatment, are
shown  in Figure  l-l(a)(b)(c).     Surface  application  tech-
niques  include  ridge-and-furrow and  border strip  flooding.
Application by  sprinklers  can  be  from  fixed  risers  or from
moving systems, such  as cen;ter pivots.

     1.4.1      Process Objectives

Slow rate  processes  can  bej operated  to  achieve  a  number  of
objectives  including:        [
                               i
     1.   Treatment  of applied wastewater

     2.   Economic return  from use of water  and nutrients  to
          produce marketable crops  (irrigation)

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                                 EVAPOTRANSPIRATION
               PERCOLATION


                 (a) APPLICATION PATHWAY
UNOERDRAINS
                  (b)  RECOVERY  PATHWAYS
                                               WELLS
                 (c) SUBSURFACE  PATHWAY

                       FIGURE  1-1
           SLOW  RATE  HYDRAULIC  PATHWAYS
                        1-5

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    3.   Water conservation, by replacing potable water with
         treated effluent, for irrigation

    4.   Preservation and enlargement of greenbelts and open
         space

When   requirements   are   very   stringent   for   nitrogen,
phosphorus, BOD, SS,  pathogiens,  metals, and trace organics,
they  can be  met usually  w|ith SR  treatment.    Nitrogen is
often  the  limiting  factor  for  SR design  because  of  EPA
drinking  water  limits  on ground water  quality.    In arid
regions, however,  maintaining  chlorides and total dissolved
salts  at  acceptable  levels  for  crop  production   may  be
limiting.   Management  apprpaches to meet  these  objectives
within  the  SR  process  are  discussed  under  the   topics
(1) wastewater treatment,  (2) agricultural systems, (3) turf
systems, and  (4) forest systems.
         1.4.1.1
Wastewater Treatment
When the  primary objective of  the  SR process is treatment,
the hydraulic  loading is usually limited  either by the hy-
draulic  capacity  of  the  !soil  or  the  nitrogen  removal
capacity  of the  soil-vegetation matrix.    Underdrains are
sometimes  needed  for development of  sites  with  high ground
water tables,  or where perched water tables or impermeable
layers  prevent  deep  percolation.    Perennial  grasses are
often  chosen  for  the  vegetation   because  of  their  high
nitrogen uptake, a longer wastewater  application season, and
the avoidance  of  annual  planting  and cultivation.   Corn and
other  crops with  higher  market  values  are also  grown on
systems where  treatment  is the major objective.   Muskegon,
Michigan  [10]  is a noted  example in the United States with
over 2,000 hectares  (5,000 acres) of  corn under cultivation.
                            i
                            i
         1.4.1.2   Agricultural Systems

In the more  arid  western portions of the United States, the
water itself (not the  nutrient  content)  is the most valuable
component  of  the wastewater.    Crops  are selected  for  their
maximum market potential  and  the least  possible  amount of
wastewater needed for  irrigation.  Application rates between
2 to 8 cm/wk (0.8 to  3.1 in./wk) are  common.  This is enough
water to  satisfy  crop needs,  plus a  leaching requirement to
maintain a desired salt balance in the root  zone.

In the more  humid  east,  the water component may be critical
at  certain times  of  the  year  and   during  extended drought
periods,  but  the nutrients j in  the  wastewater are  the most
valuable  component.    Systems   are  designed  to  promote the
                             1-6

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 nutrient   uptake   by   the  crop  and  increase  yields.    At
 Muskegon,  Michigan,  for  example,  corn  yields in  1977  were
 6.5 m3/ha  (75 bushels  per acre)  compared to  5.2  m3/ha  (60
 bushels  per  acre) for the nonwastewater  farming  in the  same
 area  [10].  Regardless of geographical  location,  wastewater
 irrigation  can   benefit   crop   production   by   providing
 nutrients  and  moisture.

         1.4.1.3   Turf Systems

 Golf  courses,  parks,  and other turfed areas are used in  many
 parts  of  the  United  States  for  SR systems,  thus  conserving
 potable  water supplies.    These  areas  have  considerable
 public access  and  this requires  strict control of  pathogenic
 organisms.   This  control  can be achieved  by  disinfection  or
 by  natural  processes  in  biological   treatment   ponds   or
 storage ponds.

         1.4.1.4   Forest Systems

 Slow  rate forest systems  exist  in  many  states  including
 Oregon,  Washington,  Michigan,  Maryland,  Florida,  Georgia,
 Vermont,   and  New  Hampshire.    In  addition,   experimental
 systems  in   a  variety   of  locations  are   being  studied
 extensively    to   determine   permissible  loading   rates,
 responses  of various  tree species, and environmental effects
 (see Chapter 4).

 Forests  offer several advantages  that  make  them  desirable
 sites for  land treatment:

    1.   Forest  soils  often  exhibit  higher   infiltration
         rates than agricultural soils.

    2.   Site  acquisition  costs  for forestland are  usually
         lower than  site  acquisition costs  for prime agri-
         cultural land.

    3.   During cold  weather, soil  temperatures  are often
         higher in forestlands than in agricultural  lands.

    4.   Systems can  be developed  on steeper grades in the
         forest as compared to agricultural sites.

The  principal limitations  to  the  use   of   wastewater  for
 forested SR systems are:

    1.   Water needs  and  tolerances of  some  existing trees
         may  be low.
                             1-7

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    2.   Nitrogen removals  are  relatively low unless young,
         developing forests are used or conditions conducive
         to denitrif ication are present.

    3.   Fixed sprinklers,  vj/hich  are expensive,  are usually
         necessary.         I
                            i
    4.   Forest soils may be; rocky or very shallow.
1.4.2
              Treatment Performance
The SR process is capable of producing the highest degree of
wastewater treatment of all the land treatment systems.  The
quality values  shown in Table 1-3  can  be expected for most
well-designed and well-opera|ted systems.
                            i
Organics  are  reduced   substantially  by  SR  land  treatment
within  the  top  1   to  2  cm  (0.4  to  0.8   in.)  of  soil.
Filtration  and  adsorption are  the  initial  steps   in  BOD
removal, but  biological oxidation  is the ultimate treatment
mechanism.   Filtration is  the major  removal mechanism for
suspended  solids.    Residues  remaining after oxidation and
the inert solids become part of the soil  matrix.
                            i
Nitrogen  is  removed primarily by  crop  uptake,  which varies
with the  type of crop grown and the  crop yield.   To remove
the  nitrogen  effectively, i the  crop  must  be  harvested.
Denitrif ication can  also be significant,  even if the soil is
in an  aerobic condition mo?t  of the  time.   Other nitrogen
removal   mechanisms  include  ammonia   volatilization  and
storage in the soil.        i

Phosphorus is removed from solution by fixation processes in
the  soil,  such  as  adsorption and  chemical precipitation.
Removal efficiencies are  generally very high for SR systems
and are  more dependent on the soil  properties  than on the
concentration  of the  phosphorus  applied.    Residual phos-
phorus  concentrations  in  the, percolate  will  generally be
less than 0.1 mg/L  [11].  AjSinall but significant portion of
the  phosphorus  applied is j taken  up  and removed  with the
crop.                       i

1.5  Rapid Infiltration Process

In RI  land treatment,  most  of the  applied  wastewater per-
colates  through the  soil,  and the  treated  effluent drains
naturally  to  surface waters  or joins the ground water.  The
wastewater  is  applied  to moderately and  highly permeable
soils  (such  as sands  and i loamy   sands),  by  spreading  in'
basins  or  by  sprinkling, 'and  is  treated  as  it   travels
                             1-E

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 through the soil matrix.  Vegetation is not usually planned,
 but there  are some  exceptions,  and emergence  of  weeds and
 grasses usually does not cause problems.

 The  schematic  view  in  Figure  1-2(a)   shows  the  typical
 hydraulic  pathway  for  rapid  infiltration.   A  much greater
 portion of  the  applied wastewater  percolates  to  the ground
 water than  with  SR  land  treatment.  There is  little  or no
 consumptive use  by  plants.   Evaporation ranges  from  about
 0.6 m/yr (2 ft/yr)  for  cool  regions to  2  m/yr  (6  ft/yr) for
 hot arid regions.  This is usually a small percentage of the
 hydraulic loading rates.

 In many  cases,  recovery of  renovated  water is an integral
 part of the system.   This can  be  accomplished  using under-
 drains or wells, as  shown  in  Figure l-2(b).   In some cases,
 the water  drains  naturally  to an  adjacent  surface  water
 (Figure  l-2(c)).   Such systems can provide a,higher level of
 treatment  than  most mechanical  systems  discharging: to  the
 same surface water.
     1.5.1
     Process Objectives
 The  objective of  RI  is wastewater treatment.
 treated  water can include:
                                       Uses for the
     1.

     2.


     3.
Ground water recharge
Recovery of renovated water by wells or underdrains
with subsequent reuse or discharge
Recharge  of
ground water
surface  streams  by  interception  of
     4.   Temporary  storage  of  renovated water  in  the  aquifer

If .ground  water  quality  is  being  degraded  by  saltwater.
intrusion,  ground  water recharge by RI can help  to create  a
barrier  and protect  the existing  fresh  ground  water.   In
many  cases,  the  major  treatment  goal   is   conversion of
ammonia  nitrogen to nitrate nitrogen  prior to discharge to
surface  waters.   The  RI  process  offers  a   cost-effective
method for  achieving  this goal with recovery or  recharge as
described  in  items 2 and 3  above.   Return of the  renovated
water to the  surface  by wells, underdrains, or ground water
interception may be necessary  or advantageous when,  discharge
to. a particular surface  water body is controlled  by water
rights, or when existing  ground water quality  is  not  compat-
ible  with  expected  renovated  water  quality.    At  Phoenix,
Arizona, for example,  renovated  water is  being withdrawn by
wells to allow reuse of the water for irrigation.
                             1-9

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                   APPLIED
                   WASTEWATER
                                   EVAPORATION
                                   PERCOLATION


               (a) HYDRAULIC  PATHWAY
           FLOODING BASINS
                                               RECOVERED WATER
                                PERCOLATION
                             (UNSATURATED ZONE)
                                               WELL
UNDERDRAINS                                HELLS


                (b)  RECOVERY  PATHWAYS
                                             FLOODING BASIN
     (c) NATURAL  DRAINAGE  INTO  SURFACE WATERS

                FIGURE  1-2
RAPID  INFILTRATION HYDRAULIC  PATHWAYS
                       1-10

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    1.5.2
Treatment Performance
Removals  of  wastewater  constituents  by the  filtering and
straining  action  of   the  soil  are  excellent.    Suspended
solids,  BOD,  and  fecal  coliforms  are almost  completely
removed.

Nitrification of  the  applied  wastewater is essentially com-
plete  when  appropriate  hydraulic  loading  cycles  are  used.
Thus,  for  communities that have ammonia standards  in  their
discharge requirements,  RI can provide  an  effective  way to
meet such standards.

Generally,  nitrogen  removal  averages  50%  unless  specific
operating procedures  are established to maximize denitrifi-
cation.  These procedures  include optimizing the application
cycle,  recycling  the  portions  of   the  renovated  water that
contain   high    nitrate   concentrations,    reducing   the
infiltration  rate,   and  supplying  an  additional  carbon
source.   Using  these  procedures   in soil  column  studies,
average  nitrogen   removals   of  80%  have  been  achieved.
Nitrogen  removal  by  denitrification can be  significant if
the hydraulic loading  rate is at  the mid range or below the
values  in  Table  1-1 and  the  BOD  to  nitrogen  ratio  is 3 or
more.

Phosphorus removals  can range  from  70  to 99%, depending on
the physical  and  chemical characteristics  of  the  soil.  As
with SR systems, the primary  removal  mechanism is adsorption
with some chemical  precipitation,  so the long-term capacity
is  limited  by the  mass  and  the characteristics  of  soil in
contact with  the  wastewater.    Removals  are related also to
the residence time of  the  wastewater  in  the soil, the travel
distance, and other climatic  and operating  conditions.

1.6  Overland Flow Process

In  OF  land  treatment, wastewater  is applied at  the  upper
reaches of grass covered slopes and  allowed to flow over the
vegetated  surface  to runoff  collection ditches.    The OF
process  is  best  suited to  sites   having  relatively  imper-
meable  soils.    However,  the  process   has  been used  with
success  on   moderately   permeable   soils  with  relatively
impermeable  subsoils.     The  wastewater   is  renovated  by
physical,  chemical,  and biological  means  as  it  flows  in  a
thin film down the length  of  the slope.  A  schematic view of
OF treatment is shown  in Figure 1-3(a),  and a pictorial view
of a typical  system  is shown  in Figure 1-3(b).  As shown in
Figure  1-3(a),   there  is  relatively  little  percolation
involved  either   because   of  an  impermeable  soil   or   a
subsurface barrier to  percolation.
                             1-11

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       1ASTEWATER
SLOPE 2-8«
                    r
GRASS AND
VEGETATIVE LITTER
                                              EVAPOTRANSPIRATION
                                                              RUNOFF
                                                              COLLECTION
                              PERCOLATION


                    (a)  HYDRAULIC PATHWAY
                                          SPRINKLER CIRCLES
                                   RUNOFF
                                   COLLECTION
                                   DITCH
            (b)  PICTORIAL VIEW  OF  SPRINKLER APPLICATION
                          FtCURE  1-3
                         OVERLAND FLOW
                                1-12

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Interest by municipalities  and  design engineers has spurred
research and  demonstration projects  in  South  Carolina, New
Hampshire,     Mississippi,    Oklahoma,     Illinois,    and
California.   Cold-weather  operation  has  been demonstrated
through several winters at Hanover, New Hampshire.   Rational
design  equations  have been  developed based on  research at
Hanover and at Davis, California.
    1.6.1
              Process Objectives
The
     objectives  of  OF  are  wastewater  treatment and,  to a
minor extent, crop  production.   Treatment objectives may be
either:
    1.
    2.
         To achieve secondary effluent quality
         screened  raw   wastewater,   primary
         treatment pond effluent.
when applying
effluent,  or
         To  achieve  high  levels  of  nitrogen,  BOD,  and SS
         removals.
Treated water  is collected at the  toe  of  the OF slopes and
can be  either  reused  or discharged to surface water.  Over-
land  flow   can   also  be  used  for  the  preservation  of
greenbelts.
    1.6.2
              Treatment Performance
Biological oxidation,  sedimentation,  and filtration are the
primary   removal   mechanisms   for  organics  and   suspended
solids.

Nitrogen   removals   are   a  combination  of  plant  uptake,
denitrification,  and  volatilization  of  ammonia   nitrogen.
The dominant mechanism in  a particular  situation will depend
on  the forms  of  nitrogen present  in  the  wastewater, the
amount  of carbon available, the  temperature,  and  the  rates
and schedules of wastewater application.  Permanent  nitrogen
removal by the  plants is  only  possible if  the crop is  har-
vested  and removed from the field.   Ammonia volatilization
can be  significant if the pH of  the  wastewater is  above  7.
Nitrogen  removals usually  range from  75 to  90% with  the  form
of   runoff  nitrogen   dependent   on   temperature   and   on
application rates and  schedule.   Less  removal of nitrate and
ammonium  may  occur  during cold weather  as  a  result  of
reduced biological activity and limited plant uptake.

Phosphorus  is  removed by  adsorption  and  precipitation  in
essentially the same manner as with  the SR and RI  methods.
Treatment efficiencies are somewhat  limited  because of the
limited  contact between  the  wastewater  and  the adsorption
                             1-13

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sites within  the  soil.   Pho'sphorus  removals  usually range
from 50 to  70%  on a mass basis.   Increased removals may be
obtained by adding alum or fe'rric chloride  to the wastewater
just prior to application on the slope.

1.7 Combination Systems      ;

In areas where  effluent  quality must be very good, or where
a high  degree  of treatment  Reliability must be maintained,
combinations of  land treatment  processes  may  be desirable.
For  example,  either an  SR,  RI,  or  a wetlands  treatment
system could follow  an OF system and would result in better
overall treatment  than  the QF  alone.   In particular, these
combinations could be used tb improve BOD,  suspended solids,
nitrogen,  and phosphorus removals.

Similarly, OF  could  be used prior  to RI to reduce nitrogen
levels  to   acceptable   levels.     This   combination  was
demonstrated successfully in  a pilot  scale study  at. Ada,
Oklahoma,  using  screened  raw! wastewater  for the OF portion
[12].                        :

Rapid infiltration may  also precede  SR land treatment.   In
this  combination,  renovated |water  quality  following  RI  is
expected  to  be  high enough  that even  the most restrictive
requirements regarding  the  use  of renovated water  on food
crops can be met.   Also,  the  ground  water aquifer  can be
used  to  store  renovated  water  to  correspond with  crop
irrigation schedules.  Some  of  these combinations are shown
schematically in Figure 1-4.

1.8  Guide to Intended Use of the Manual

This  manual is  organized  similarly  to the original  1977
edition except  that the  design examples are  included  as
appendixes.   Completely  nev^  features  in this  manual  are
chapters on energy,  and health and environmental effects.

Chapters  2  through  6  follow,  in  sequence, a  logical pro-
cedure  for  planning and  design of  land treatment systems.
The  procedure  commences  (Chapter  2) with  screening  of the
entire  study  area  to  identify  potential land  treatment
sites.   The Phase  1 planning  is  based  on existing infor-
mation  and  data  on land  use,  water  rights,  topography,
soils,  and  geohydrology.    If  potentially suitable  sites
exist,  the Phase  2  planninjg  then   involves detailed site
investigations  (Chapter  3)  to determine process suitability
and preliminary design criteria  (Chapters  4, 5,  and 6).

Process selection  for a  particular  situation  is' influenced
by health and environmental  issues  (Chapter 9) and by energy
                             1-1H

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1-15

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 needs (Chapter 8).  Thus,  Phase  2  planning requires the use
 of all the technical chapters in the manual.
                            i
 Small communities  (up to  13,500  population) do  not usually
 need  the  same  level of  planning  and investigation  that  is
 essential for  large  systems.   Nor do they always  need the
 level of sophistication  that  is  normally provided,  in terms
 of equipment and  management procedures,  for  large  systems.
 Procedures  and  shortcuts  ;that  are  unique to  small  land
 treatment systems  are  described  in Chapter  7.    Typical
 examples  are  included  to | illustrate  the  level of  effort
 needed in field work and  de'sign.

 The  final design  of  a land  treatment system needs  only  to
 draw  on the  pertinent chapter  (4,  5,  or  6)  for  the  intended
 process.   Some  additional| field  investigation  (Chapter  3)
 may  be  necessary  to  optimize hydraulic  loading rates  and
 ensure  proper  subsurface • flow   conditions.     The  design
 chapters do  not   present  complete  detail  on  the  hardware
 (i.e.,   pumps,   pipe   materials,   sprinkler   rigs,   etc.)
 involved.    Other  sources  will be  needed  for these  design
 details.   The  cost  information in  reference  [1] or  in  the
 CAPDET  program  is  suitable   for  planning,  comparison  of
 alternatives,   and  preliminary  design   only.     The  final
 construction  cost  estimate   should  be  derived  ,in   the
 conventional way (by material take-off,  etc.)  from the final
 plans.

 Appendixes A,  B,   and  C provide  design  examples  of  SR,  RI,
 and   OF  and   are  intended   to   demonstrate   the   design
 procedure.   Energy budgets  knd  costs are  provided along  with
 the  process  design.   Apperidix D  contains a representative
 list   of  currently   operating  municipal   (also   federal
 government and  selected  industrial)  land treatment  systems
 in the United States.

 Appendix  E  provides  information  on designing   irrigation
 systems  for  SR  facilities.   The  level  of detail  in  this
 appendix  is  sufficient  to develop  preliminary  layouts and
 sizing  for distribution system components.  Appendix  F  con-
 tains  a  list of communities for which the EPA programs  that
 determine    storage    requirements   based    on    climate
 (Section 4.6.2)  have  been , run.    The  final   appendix,  G,
 provides  a  glossary  of  terms  and   conversion  factors  from
metric to U.S. customary  units  for  all figures and tables.

The design approach  for land treatment has been  essentially
empirical,   i.e.,   observation  of   successful   performance
 followed   by  derivation   of  criteria   and   mathematical
expressions  that describe overall performance.    Essentially
the same  approach  was  used; to develop  design  criteria for
                            1-16

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activated  sludge  and other  biological  treatment processes.
The  physical,   chemical,   and   biological   reactions  and
interactions occurring  in  all treatment processes are quite
complex  and  are difficult  to define mathematically.   Such
definition is still evolving  for activated sludge as well as
land  treatment.     As   a   result,  the  design  procedures
presented  in  this  manual  are  still  conservative  and  are
based on successful operating experience.

More  rational  design   procedures  however,  are  becoming
available  (see  Section  6.11).     In   addition,  there  are
mathematical models  available that may  be  used  to evaluate
the  response   to   a   particular   constituent   (nitrogen,
phosphorus,  etc.)  or  used  in  combination   to describe  the
entire system  performance.   A brief  summary of  models, that
are  currently  available is  included  in reference  [13] .   A
more  detailed  discussion   of   specific  models  for  land
treatment can be found  in reference  [14].
1.9  References

 1. Reed,  S.C. ,  et  al.    Cost  of  Land  Treatment Systems.
    U.S. Environmental Protection Agency.  EPA-430/9-75-003,
    MCD 10.  September 1979.
    Culp/Wesner/Culp.   Water Reuse and Recycling.
    U.S.D.I.  OWRT/RU-79/2.  1979.
Vol. 2.
 3. U.S.  Environmental   Protection  Agency.     Aquaculture
    Systems  for  Wastewater Treatment:   Seminar Proceedings
    and  Engineering  Assessment.    Office  of  Water Program
    Operations.    EPA-430/9-80-006,   MCD   67.    September
    1979.

 4. U.S. Environmental Protection Agency.  Design Manual for
    Onsite   Wastewater   Treatmept  and   Disposal   Systems.
    Center  of  Environmental   Research  Information.    EPA-
    645/1-80-012.  October 1980.

 5. U.S.  Environmental  Protection  Agency.   Slow  Rate Land
    Treatment:   A  Recycle Technology.   Office  of Water Pro-
    gram  Operations.   EPA-430/9-80-011a,  MCD   70.   October
    1980.

 6. U.S.  Environmental  Protection Agency.    Rapid  Infiltra-
    tion  Land  Treatment:   A Recycle  Technology.   Office of
    Water Program  Operations.    EPA-430/9-80-011b,  MCD 71.
    (In Press) 1981.
                             1-17

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 7. Proceedings  of  the  International  Symposium  on  Land
    Treatment of Wastewater.  Volumes 1 and  2.  Hanover, New
    Hampshire.  August 20-25, 1978.
                           I
 8. Hinrichs, D.J.,  et al.j   Assessment  of Current Informa-
    tion  on Overland  Flow,  Treatment.    U.S.  Environmental
    Protection   Agency.   '    Office   of   Water   Program
    Operations.   EPA-430/9^80-002, MCD 66.   September 1980.

 9. Leach,  L.E., C.G.  Enfi<=ld,  and C.C.  Harlin, jr. Summary
    of  Long-Term  Rapid  Infiltration System Studies.   U.S.
    Environmental Protection Agency.  Office of Research and
    Development.   Ada,  Oklahoma.    EPA-600/2-80-165.   July
    1980.

10. Walker, J.M.  Wastewater;  Is Muskegon County's Solution
    Your  Solution?   U.S.  Environmental  Protection Agency.
    EPA-905/2-76-004, MCD-3'4.  August 1979.

11. Jenkins, T.F.  and A.J. Palazzo.  Wastewater Treatment by
    a Slow  Rate  Land Treatment System.   U.S.  Army Corps of
    Engineers,  Cold  Regions   Research   and   Engineering
    Laboratory.      CRREL   Report   81-14.      Hanover,   New
    Hampshire.  August 1981.

12. Thomas, R.E.,  et al.   feasibility of Overland Flow for
    Treatment of Raw Domestic Wastewater.  U.S.
    Environmental  Protection Agency.  EPA-66/2-74-087.
    1974.                  '

13. Iskandar, I.K.   Overview on Modeling Wastewater
    Renovation by  Land Treatment.   USACRREL, Special Report.
    USACRREL, Hanover,  New Hampshire.  1981.

14. Iskandar, I.K.  (ed.).  iModeling Wastewater Renovation:
    Land Treatment.   Wiley Unterscience,  New York.  1981.
                            1-18

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                          CHAPTER 2

              PLANNING  AND TECHNICAL  ASSESSMENT
2.1  Planning Procedure

Adequate  planning  must  precede   any  wastewater  treatment
system design to ensure selection of the most cost-effective
process that  is  feasible for  the  situation under consider-
ation.  In  many  cases,  guidelines or specifications for the
planning  procedure  are  provided  by the  agency responsible
for the project.  The  purpose  of  this  chapter is to present
those  aspects of  the  planning  procedure  that  are either
unique  or   require   special   emphasis  because   of  land
treatment.

Process selection for  land  treatment systems is more depen-
dent on site conditions  than are mechanical treatment alter-
natives.   This  can  mean  that  there  is  a need for extensive
and,  in  some cases, expensive  site  investigation and  field
testing programs.   To  avoid unnecessary effort and  expense,
a two-phase planning approach  has  been developed and  adopted
by most agencies concerned.  As shown in Figure 2-1,  Phase  1
involves  identification of  potential sites via screening of
available  information   and  experience.    If potential  sites
for any of  the  land treatment processes are  identified, the
study  moves  into Phase 2.  This phase includes field inves-
tigations and an evaluation of  the alternatives.

2.2   Phase  1  Planning

Early  during Phase  1,  basic  data  that  are common to all
wastewater  treatment  alternatives  must  be collected and
analyzed  along  with  land treatment system requirements  to
determine whether  land treatment is a feasible concept.   If
no  limiting  factors are identified that would eliminate land
treatment  from  further consideration,  the  next steps are  to
identify  potential  land treatment sites and  to evaluate  the
feasibility  of each site.

      2.2.1   Preliminary Data

Service  area definition, population  forecasts,  wastewater
quality and  quantity projections,  and water quality  require-
ments are   usually  either  specified  or  determined  using
procedures  established  by  the responsible authority.   With
the exception of  water  quality  requirements,  the  dati=>  are
generally the same  for all  forms  of  wastewater  treatmeuc.   A
few aspects are  specific to  land  treatment and  are discussed
in  this section.
                              2-1

-------
                                 WASTE
                           CHARACTERIZATION
                            LAND TREATMENT
                          SYSTEM SUITABILITY
                           ESTIMATION OF LAND
                             REQUIREMENTS
PHASE 1
                          SITE IDENTIFICATION
                            SITE   SGREENIN6
                          -   SELECTION OF
                           POTENTIAL  SITES
 LAND  TREATMENT
.NOT FEASIBLE BECAUSE
 OF LIMITING FACTORS OR
 PROJECT  REOUIREMENTS
      LAND  APPLICATION
      NOT  FEASIBLE  IF
      THERE ARE NO
      POTENTIAL SITES
                         FIELD INVESTIGATIONS
PHASE  2
                            DEVELOPMENT OF
                          PRELIMINARY  DESIGN
                          CRITERIA AND COSTS
                            EVALUATION OF
                            ALTERNATIVES
                            PLAN SELECTION
LAND APPLICATION
NOT FEASIBLE FOR
OTHEfl REASONS OR OTHER
ALTERNATIVES MORI-
COST EFFECTIVE
                          INITIATION OF LAND
                           TREATMENT DESIGN
                            FIGURE 2-1
                TWO-PHASE  PLANNING  PROCESS
                                    2-2

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         2.2.1.1  Wastewater Quality and Loadings

Major constituents  in domestic wastewater  are presented  in
Table 2-1.   Trace element concentration ranges are shown  in
Table 2-2.  The values in these tables may  be  used  for  plan-
ning purposes when  a community's  water quality has not been
determined.   Other  important  parameters  in  land  treatment
design  can include  total dissolved solids,  pH, potassium,
sodium, calcium,  magnesium,  boron,  barium, selenium,  fluor-
ide, and silver.

                          TABLE 2-1
              IMPORTANT CONSTITUENTS IN TYPICAL
                   DOMESTIC WASTEWATER [1]
                            mg/L
                                 Type of wastewater
Constituent
BOD
Suspended solids
Nitrogen (total as N)
Organic
Ammonia
Nitrate
Phosphorus (total as P)
Organic
Inorganic
Total organic carbon
Strong
400
350
85
35
50
0
15
5
10
290
Medium
220
220
40
15
25
0
8
3
5
160
Weak
110
100
20
8
12
0
4
1
3
80
For  municipal  land  treatment  systems,  BOD  and  suspended
solids  loadings seldom limit  system capacity.   Typical  BOD
loading  rates at municipal  systems are  shown in Table  2-3
and  are  much lower  than rates used  successfully in  land
treatment  of  food processing wastewaters.   Suspended  solids
loadings  at these industrial  systems would  be  similar  to the
BOD loadings  shown  in  Table  2-3.

In contrast,  if  nitrogen  removal is required,  nitrogen load-
ing  may   limit   the   system   capacity.     Nitrogen  removal
capacity  depends on  the  crop grown,  if  any,  and  on  system
management practices.   The engineer should consult Sections
4.5 and 5.4.3.1 to determine whether nitrogen  loading  will
govern    system  capacity   and,    therefore,   land    area
requirements.
                              2-3

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                           TABLE 2-2
               COMPARISON OF1TRACE ELEMENTS  IN
                     WATER AND WASTEWATERS
                            I  mg/L
Maximum recommended
Untreated
Element wastewater3
Arsenic 0.003
Boron 0.3-1.8
Cadmium 0.004-0.14
Chromium 0.02-0.700
Copper 0.02-3.36
Iron 0.9-3.54
Lead 0:05-1.27
Manganese 0.11-0.14
Mercury 0.002-0.044
Nickel 0.002-0.105
Zinc 0.030-8.31
concentrations for
irrigation water"
0.1
0.5-2.0
0.01
0.1
0.2
5.0
5.0
0.2
No standard
0.2
2.0
a. The concentrations presented encompass the
reported in references
[2-6] .
b. Based on unlimited irrigation .at 1.0 m/yr(3
c. Reference [7] :

EPA recommended
drinking
water standards'3
0.05
No standard
0.01
0.05
1.0
0.3
0.05
0.05
0.002
No standard
5.0
range of values

f t/yr) .

                           TABLE  2-3
                   TYPICAL BOD LOADING RATES
                            kg/ha-yr


                      Slow rate  Rapid infiltration  Overland" flow
             Range for
             municipal
             wastewater  370-1/830  8,000-46,000
2,000-7,500
             Note:  See Appendix Gifor metric conversions.
In  some cases,  other wastewater constituents such  as phos-
phorus  or trace  elements  may control  design.   For example,
if  wastewater trace  element  concentrations  exceed the maxi-
mum recommended  concentrations  for  irrigation  water  (Table
2-2),  SR systems may  be  infeasible or  may  require special
precautions.    This  is  rare,  however,  and most municipal
systems will  be  limited  either  by hydraulic   capacity  or
nitrogen loading.

          2.2.1.2  Water  Quality Requirements

Land   treatment   systems  ;have   somewhat   unique  discharge
requirements   because  many  of  these  systems   do  not  have
                               2-4

-------
conventional point  discharges to receiving  surface waters.
In the past, the ability of the soil to treat wastewater was
not well recognized.   As  a result,  discharge standards were
often imposed  on a wastewater  prior to  its  application on
land, thereby increasing treatment costs and energy require-
ments  without  significantly  improving  overall  treatment
performance.  More  recently,  land has been recognized as an
important  component  in  the  treatment process.    For this
reason,  discharge  requirements  now  apply to  water quality
following land treatment.

For  systems  that discharge to receiving  waters,  such as OF
systems  and  some underdrained or naturally  draining  SR and
RI systems,  renovated water  quality  must  meet surface dis-
charge requirements.   For systems where the renovated water
remains  underground,  EPA  has  established guidance for three
categories  of  ground  water discharge that meet the criteria
for   best   practicable   waste   treatment.     These   three
categories are as follows:

Case 1 - The ground water  can potentially be used for
         drinking water supply.

         The  chemical  and pesticide  levels  in  Table  2-4
         should  not be exceeded  in the  ground water.   If the
         existing  concentration  in  the ground water  of an
         individual  parameter exceeds  the  standards, there
         should  be  no further increase in the concentration
         of  that parameter resulting  from land application
         of wastewater.

Case 2 - The ground water  is  used for  drinking water supply.

         The same criteria as Case 1  apply and the  bacterio-
         logical quality   criterion   from  Table   2-4   also
         applies in  cases where the  ground water  is  used
         without disinfection.

Case 3 T Uses  other than  drinking water supply.
•E
         Ground  water criteria should  be established  by the
         Regional  Administrator  in  conjunction  with  appro-
         priate  .state  agencies  based  on  the   present or
         potential  use  of  the ground  water.

For  each ground water category,  discharge requirements  must
be met at  the  boundary  of  the land treatment project.
                             2-5

-------
                              TABLE  2-4
                     NATIONAL  INTERIM PRIMARY
              DRINKING WATER  STANDARDS, 1977 [7,8]
Constituent
or characteristic
Physical
Turbidity, units
Chemical, mg/L
Arsenic
Barium
Cadmium
Chromium
Fluoride
Lead
Mercury
Nitrates as N
Selenium
Silver
Sodium"
Value3

lb

1 0.05
1.0
0.01
0.05
i 1.4-2.4
0.05
0.002
10
0.01
0.05

Reason
for standard

Aesthetic

Health
Health
Health
Health
Health
Health
Health
Health
Health
Cosmetic
Health
                 Bacteriological
                  Total coliforms,
                  MPN/100 mL

                 Pesticides, mg/L
                  Endrin
                  Lindane
                  Methoxychlor
                  Toxaphene
                  2,4-D
                  2,4,5-TP
0.0002
0.004
0.1
0.005
0.1
0.01
       Disease
Health
Health
Health
Health
Health
Health
                 a.  The latest revisions to the constituents
                    and concentrations should be used.
                 b.  Five mg/L of suspended solids may be
                    substituted if it can be demonstrated
                    that it does not, interfere with
                    disinfection.

                 c.  Dependent on ambient air temperature;
                    higher limits for lower temperatures.
                 d.  Ground water drinking supplies must be
                    monitored at least once every 3 years;
                    surface water supplies must be monitored
                    at least annually.
For  SR  systems,   individual  states  often  have  additional,
crop-specific  preapplication treatment  requirements.    These
requirements are  usually  based  on  the  method  of  wastewater
application, the  degree  of public contact with  the site,  and
the  disposition of  the  crop.   For  example,  crops  for  human
consumption  generally  require  higher  levels   of  preappli-
cation treatment  than  forage  crops.
                                i
Local  and  state water  quality requirements  may  also apply to
site  runoff.   Generally,  all wastewater runoff must be  con-
tained onsite  and  reapplied  or treated.    Stormwater runoff
requirements will vary from site  to  site and will  depend on
                                 2-6

-------
the expected quality  of  the  runoff and the quality of local
surface  waters.    State  and local  water  quality agencies
should be contacted for more specific requirements.

         2.2.1.3  Regional Characteristics

Critical regional parameters  include  climate, surface water
hydrology and quality, and ground water quality.

Climate

Local climate may affect (1) the water balance  (and thus the
acceptable  wastewater  hydraulic  loading  rate),  (2)  the
length  of  the growing  season,   (3)  the  number  of days per
year  that  a  land   treatment  system cannot  be  operated,
(4) the storage  capacity  requirement, (5)  the loading cycle
of RI systems, and (6) the amount of  stormwater  runoff.  For
this   reason,    local  precipitation,   evapotranspiration,
temperature,  and  wind  values   must   be  determined  before
design  criteria  can  be established.   Whenever possible, at
least  10  years  of  data  should  be  used  to  obtain  these
values.

Three publications  of The National  Oceanic and Atmospheric
Administration (NOAA)  provide sufficient  data for most com-
munities.   The  Monthly  Summary  of   Climatic  Data provides
basic   information,   includingtotalprecipitation,  tem-
perature maxima  and  minima,  and relative  humidity, for each
day  of  the  month  and  every  weather  station  in a  given
area.   Whenever available,  evaporation data are included.
An annual  summary of  climatic data,  entitled Local Climato-
logical  Data,  is  published  for  a   small  number of  major
weatherstations.     Included  in  this  publication are  the
normals, means,  and   extremes of all the data  on record to
date  for  each station.   The Climate ' Summary of the United
States  provides  10  year  summariesolthemonthlyclimatic
data.Other data included are:

     •   Total precipitation  for each month  of  the  10 year
         period.

     •   Mean  number  of  days  that  precipitation exceeded
         0.25  and  1.3  cm (0.10  and  0.50  in.)  during each
         month

     •   Total snowfall for each month of the period

     •   Mean temperature for each month of the  period

     •   Mean  daily  temperature maxima and  minima for each
         month                                           —
                             2-7

-------
     •   Mean  number  of  days per month that the  temperature
         was  less  than or equal to  0  °C  (32 °F) or greater
         than  or equal to 32.5  °C  (90  °F)

A  fourth  reference that can be helpful  is EPA's Annual and
Seasonal Precipitation Probabilities [9].   This  publication
includes   precipitation  probabilities   for   93  stations
throughout the United States.

Data  requirements  for planning purposes  are  summarized  in
Table 2-5.   The amount  of  water lost by evapotranspiration
should  also  be estimated,  either by  using  pan  evaporation
data  supplied  by  NOAA  or  by  using theoretical  methods
(Section  4.3.2.3).   The length  of  the growing  season for
perennial crops is usually  assumed to be the number of  con-
tinuous days  per year that  the maximum daily temperature  is
above freezing.  Specific information on growing  seasons can
also be obtained from the local county agent.         ,

                          TABLE 2-5
                SUMMARY  OF QLIMAT1C  ANALYSES
Factor
Precipitation
Rainfall storm
Temperature
Wind
Evapotran-
spiration
Data required
Annual average,
maximum, minimum
Intensity, duration
Days with average
below freezing
Velocity, direction
Annual, monthly
average
Analysis
Frequency
Frequency
Frost free
period
--
Annual
dis tr ibution
Use
Water balance
Runoff estimate
Storage, treatment efficiency,
crop growing season
Cessation of sprinkling
Water balance
Surface Water Hydrology

For SR  systems  (see Chapter  4  for details)  best management
practices for control of stormwater should be used.  Contour
planting  (instead  of  straight-row  planting)   and  incorpo-
rating  plant residues  into the  soil  to  increase  the soil
organic  content  will  also minimize  sediment  and  nutrient
losses.  When designing  drainage and runoff collection sys-
tems, a  10  year return  event  should be the minimum interval
considered.

Ground Water Hydrology

Information  that  should be obtained  includes  soil surveys,
geologic and  ground water  resources  surveys,  well drilling
logs, ground water  level measurements, and chemical analyses
of the ground water.  Numerous federal, state, county,,   and
city agencies have  this  type  of  information as well as uni-
versities, professional and technical societies, and private
                             2-8

-------
 concerns with ground water  related  interests.  Particularly
 good sources  are the  U.S.  Geological Survey (USGS),  state
 water resources  departments,  and county  water conservation
 and flood control districts.   Much of  the information col-
 lected  from these agencies  and  entities  will also be useful
 during  the site  identification step.   (Figure 2-1).

      2.2.2  Land Treatment System Suitability

 Factors  that should  be  considered in  determining suitability
 of  a particular  land treatment process are:

      •    Process  ability  to   meet   treatment  requirements
          (refer  to Chapter 1)
          Study  area  characteristics  that  may  dictate
          eliminate  certain land  treatment processes
or
      •    Secondary project objectives, such as  a  desire for
          increased water supplies for  irrigation  or  recrea-
          tion

Once  a  preliminary decision  regarding process  suitability
has been made,  typical hydraulic and  nutrient  loading  rates
can be  used to estimate  land area.   Minimum preapplication
treatment,  storage, and  other requirements are then deter-
mined,  and the feasibility  of each  type  of land  treatment
process  is  evaluated.

          2.2.2.1   Process Loading Rates

Slow  Rate  Process

The amount of  wastewater  that can  be  applied  to a given  SR
site  per unit  area and per  unit  time is the wastewater hy-
draulic  loading  rate, which  can  be estimated  by using the
following water balance equation:

      Precipitation  + applied wastewater                (2-1)
                    = evapotranspiration + percolation

Runoff  is not  included  in the equation since  SR design  is
based on having no  runoff  of applied wastewater.  The perco-
lation rate  is  the volume of water that must travel through
the soil,  per  unit application  area  and unit  time,  and  is
established during  system design.   To ensure  that there  is
no runoff,  the  design percolation  rate should  never exceed
the saturated  hydraulic  conductivity, or  permeability,  of
the most restrictive  layer  in the  soil profile (i.e., the
minimum  soil  permeability).   Potential  evapotranspiration
values have been  calculated  for various  locations  in the
                             2-9

-------
United  States.    These  evapotranspiration  values  have been
used  along with  local  precipitation  records  to  plot the
difference between potential! evapotranspiration and precipi-
tation as  a function  of location [10].   This plot, included
as Figure  2-2,  can be  used jto  determine rough estimates of
the difference  between  evapotranspiration and precipitation
at any site in the mainland United States.

Experience  has  shown  that  the  maximum  design percolation
rate  should  equal no  more than  a fraction  of  the minimum
soil  permeability or  hydraulic conductivity  measured with
clear water  and  using  typical field and  laboratory  proce-
dures (Sections  3.4  and  3.5).   For  planning purposes, the
fraction ranges from about 4| to 10% of  the minimum (hydraulic
conductivity depending on the uniformity of the soil and the
degree  of  conservativeness (Sections 4.5.1,  5.4.1).    Based
on this  relationship,  the recommended  maximum percolation
rate  is plotted in Figure 2-3  as a function of minimum soil
permeability as measured  with  clear  water.   To use the plot
during  Phase  1,  soil permeability  must be  estimated from
soil  survey  information.   Then,  the  range  of recommended
maximum  percolation   rates  is  read   from   the  graph.    The
recommended  range of  annual  wastewater  hydraulic  loading
rates is estimated using  Equation 2-1,  by adding the-differ-
ence  between  evapotranspiration  and  precipitation   (taken
from  Figure  2-2)  to  the  range  of  percolation rates identi-
fied  in Figure  2-3.   During Phase 2, hydraulic conductivity
measurements should be  conducted at  selected sites and used
to estimate maximum percolation rates.

The range  of percolation  rates that  have been used in  prac-
tice  is broader than  the  maximum recommended range shown in
Figure  2-3.   The. range is  greater because parameters  other
than  soil  hydraulic capacity, such as nitrogen loading, crop
requirements, and  climate,  often limit the allowable  perco-
lation  rate  of  SR  systems.    For   preliminary  planning
purposes,  loading  rates and!land requirements are estimated
by assuming  that  corn or  sorghum  or  forage grasses will be
grown.  Nitrogen  requirements  for these crops are discussed
in Section 4.3.

Rapid Infiltration Process

Wastewater hydraulic  loading  rates for RI systems are  based
on the  hydraulic  capacity of the soil and on the  underlying
soil  geology.   During Phase 1,  hydraulic capacity is  esti-
mated from soil  survey  data  and  other  published sources.
Then, the  range of percolation  rates to use during prelim-'
inary planning  is read from Figure  2-3.   This figure  (2-3)
should not be used for desigjn.
                             2-10

-------

                                      o
                                      LU
                                      DC
                                      0.
                                    CM LU
                                     1 3E
                                    CM
                                      CO
                                    C9LU
                        •*«»   2°      —
                        S^   ^^      Q.
                        *••«   !t*      CO
                         Ul_l  U<-J
                                       o
                                       a.
                         >.<»-«      ~«-
                         o ui  o u<      —
2-11

-------
200   —
           I  I	


       TYPICAL'SR

UNITS
In./h
cn/h
CLEAR RATER PEIWEARILITY, MIL CWMRWIM SERVICE »E»C»lfTI»E TEWS
VERT SLM
< 0.01
•* 0.15
JL»I
t.M-t.2*
0.1 5-1. J1
•MERftTE-
LY SLItf
0.20-D.fO
0.51-1.5
MIERATE
l.lt-2.t
1.5-5.1
MIERATE-
LY RAPID
2 «-f .»
5.I-1S.2
»*f 1*
8.1-M.I
1S.2-M.8
VERY »»Clll
» It.t
> 51.1
      PERMEABILITY OF MOST RESTRICTIVE LAYER IN SOIL PROFILE
                        FIGURE  2-3
   ESTIMATED DESIGN  PERCOLATION RATE  AS A FUNCTION
 OF  SOIL PERMEABILITY  FOR SR AND  Rl  LAND  TREATMENT
                         2-12

-------
During Phase  2,  design percolation  rates  are determined  by
measuring at least one of the following parameters:

     •   Infiltration  rate  using appropriate tests  (Section
         3.4)

     *   Hydraulic conductivity  (permeability)  of the  soil,
         usually in vertical direction

As described  in  Section 5.4.1,  the  design percolation  rate
will always  be  a fraction  of  the  test results.   Considera-
tions  of  nutrient removal  and  cold weather  operation may
require adjustments in the  design percolation rate.

Overland Flow Process
During  Phase  1  and  Phase  2 planning, the  engineer can as-
sume  a hydraulic   loading   rate of 6.3 to 20 cm/wk (2.5 to
8 in./wk)  for  screened  raw wastewater  and a rate of 10 to
25  cm/wk  (4  to 10  in./wk)  for primary  effluent (Section
6.4).  Often,  OF is used to polish wastewater effluent from
biological  treatment  processes.   In  such  cases,  assumed
wastewater loading rates may be  as high as  20 to 40 cm/wk (8
to 16 in./wk).

         2.2.2.2  Storage Needs

For  SR  and  OF systems, adequate  storage  must  be provided
when climatic  conditions halt  operations or require reduced
hydraulic loading rates.   Most RI basins are operated year-
round, even  in  areas  that  experience cold  winter weather
(Figure 2-4).   Rapid infiltration  systems  may  require cold
weather storage  during  periods  when  the  temperature  of the
wastewater to  be applied  is  near freezing  and  the ambient
air  temperature  at  the  site is  below freezing.   Generally,
the  problem  occurs  only when ponds are used for preapplica-
tion  treatment.    Land  treatment  systems  also  may  need
storage   for   flow   equalization,   system   backup   and
reliability,  and system  management,  including crop harvest-
ing  (SR  and  OF)   and  spreading   basin  maintenance  (RI).
Reserve application areas can be used  instead of storage for
these system management  requirements.

During the planning process, Figure  2-5 may  be  used  to ob-
tain a preliminary  estimate of  storage  needs  for  SR and OF
systems.   This figure  was  developed from data collected and
analyzed by the National Climatic Center in Asheville, North
Carolina.   The data were  used  to  develop computer programs
that estimate  site  specific wastewater storage requirements
based on  climate  [11] ,  which,  in  turn,  were used  to plot
Figure 2-5.   The map is  based on the number of freezing days
                             2-13

-------
per  year  corresponding to  a  20  year  return  period.    If
application   rates   are   reduced   during   cold   weather,
additional storage  may be  required.   Should there be a need
for more detailed data, the engineer should contact:

               Director     j
               National Climatic Center
               Federal  Building
               Asheville, North Carolina   28801
               (704)  258-2850

Any communications  should  refer to computer programs EPA-1,
2,  and 3  (Section 4.6.2  and Appendix  F).   Each  of these
programs  costs $225  for  an  initial computer  run  (January
1981).

                          FIGURE 2-4
           WINTER OPERATION OF RAPID INFILTRATION
                  AT LAKE GEORGE,  NEW YORK
Alternatively, for  OF  and SR systems, -4  °C  (25  °F)  can be
assumed as  the minimum  temperature  at which  a  system will
successfully  operate.    Readily available  temperature data
                             2-14

-------
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-------
 may  be   used  by assuming'  that systems do not  operate below
 -4  °C.   Then, the required |Storage  volume  is estimated from
 the  average  cold  weather  flow and  the number  of days  in
 which the  mean  temperature  is  less than -4  °C.
                            i
     2.2.3  Land Area  Requirements

 The  amount  of   land  required  for a  land  treatment  system
 includes   the area  needed  for  buffer  zones,  preapplication
 treatment, storage,  access  roads,  pumping  stations,  and
 maintenance  and  administration buildings, in  addition  to the
 land actually required for ; treatment.    Depending  on  growth
 patterns  in  the study area, and on  the accessibility  of the
 land  treatment  site,  additional  land  may  be required  for
 future expansion or  for plant  emergencies.

 During planning, the total jamount of  land  required, exclud-
 ing any buffer  zones that may  be  required by  state  agencies,
 can  be  roughly  approximate^ from  Figure 2-6.   To use  the
 nomograph  shown in this  figure,  the design  wastewater flow
 must be known.   First, the  wastewater hydraulic  loading rate
 is estimated  (Section  2.2.2).   Then,  the  wastewater flow and
 hydraulic  loading  rate are  located  on the appropriate axes
 and  a  line   is drawn  passing  through  them to  the   pivot
 line.   Next, the  number  of weeks per  year  that the  system
will not  operate,  due  to weather, crop harvesting,  or other
 reasons,  is   estimated.   A: second  line  is  drawn  from  the
 pivot point  to  the number of no.noperating weeks.   The point
 at which  this second  line  crosses  the axis  labeled  "total
 area" corresponds to the estimated required area.

     2.2.4  Site Identification

 Potential  land treatment sites  are identified using existing
 soils,  topography, hydrogeology, and  land use data,  shown  by
parameter  on  individual  study area  maps.    Eventually,  the
data  are  combined  into  composite  study   area maps  that
 indicate  areas   of  high,  moderate,  and  low  land  treatment
suitability.

Potential  land treatment sites  are identified using  a  deduc-
tive approach [13].  First, 'any constraints that might limit
site suitability are identified.   In most  study areas,  all
land within   the area  should  be  evaluated  for each  land
treatment  process.   The next step  is  to classify broad areas
of  land   near   the   area  where  wastewater  is   generated
according  to  their land treatment  suitability.   Factors that
should  be  considered include current  and planned  land  use,
topography, and  soils.
                             2-16

-------
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-------
          2.2.4.1  Land Use!

Land  use in most communities  is  regulated  by local,  county,
and  regional  zoning  laws'.     Land  treatment  systems  must
comply with the appropriate  zoning  regulations.   For  this
reason,  the  planner  should be  fully  aware of the actual  land
uses  and proposed land uses in the study area.   The  planner
should attempt  to develop land treatment  alternatives  that
conform  to  local land  use  goals and  objectives.

Land  treatment  systems can  conform  with the  following  land
use objectives:

     •   Protection  of  open  space  that  is  used  for  land
          treatment

     *   Production  of agricultural  or forest products using
          renovated water on  the land  treatment site

     *   Reclamation of  land   by  using  renovated  water  to
          establish vegetation  on  scarred land

     *   Augmentation  of  parklands by  irrigating such lands
          with  renovated water

     «   Management  of  flood   plains  by using  flood plain
          areas   for  land  treatment,  thus   precluding  land
          development on such sites

     <»   Formation   of  buffer areas   around major   public
          facilities, such  as airports

To evaluate  present  and planned land uses,  city, county,  and
regional  land  use plans should be  consulted.   Because  such
plans  often do  not  reflect  actual  current  land  use,  site
visits  are  recommended  tp  determine  existing  land  use.
Aerial photographic  maps  may be obtained from the  Soil  Con-
servation  Service  (SCS)   or  the  local  assessor's  office.
Other  useful information  may be available from  the USGS  and
the  EPA,  including  true   color,  false  color infrared,   and
color  infrared aerial photos of the study area.

Once the  current and planned land uses  have  been determined,
they should  be plotted  on  a  study area map.  Then, land  use
suitability  may  be  plotted  using  the  factors   shown  in
Table  2-6.

Both land acquisition procedures and treatment system opera-
tion are  simplified  when  few  land  parcels  are involved  and
contiguous parcels are used.   Therefore,  parcel size is  an
important parameter.   Usually,  information  on  parcel  size
                            2-18

-------
can  be  obtained  from  county  assessor or  county  recorder
maps.   Again, the information should be plotted  on  a map of
the study  area.

                           TABLE 2-6
               LAND USE SUITABILITY FACTORS  FOR
            IDENTIFYING  LAND TREATMENT SITES [14]
Type of system
Agricultural Forest Overland
Land use factor slow rate slow 'rate flow
Open or cropland High
Partially forested Moderate
Heavily forested Low
Built upon Low
(residential,
commercial, or
industrial)
Moderate High
Moderately Moderate
high
High Low
Very low Very low
Rapid
infiltration
High
Moderate
Low
Very low
          2.2.4.2   Topography

Steep  grades limit a  site's  potential because  the  amount of
runoff and  erosion that will occur is  increased,  crop culti-
vation is made "more difficult, if not  impossible, and satur-
ation   of   steep   slopes   may  lead  to   unstable   soil
conditions.   The  maximum  acceptable  grade  depends  on  soil
characteristics   and   the   land   treatment   process   used
(Table 1-2).

Grade  and  elevation  information  can  be  obtained  from  USGS
topographic maps,  which  usually  have  scales  of  1:24,000
(7.5 minute series) or  1:62,500 (15 minute  series).   Grade
suitability may  be  plotted  using   the  criteria  listed  in
Table  2-7.

                          TABLE  2-7
          GRADE SUITABILITY FACTORS  FOR IDENTIFYING
                  LAND TREATMENT SITES  [14]
                     Slow rate systems

          Grade factor  Agricultural  Forest
Overland  Rapid
flow    infiltration
0 to 12%
12 to 20%
>20%
High
Low
Very low
High
High
Moderate
High
Moderate
Eliminate
High
Low
Eliminate
                             2-19

-------
Relief  is  another important itopographical consideration  and
is  the  difference in  elevation between  one  part of a  land
treatment  system and another.   The primary impact of  relief
is  its  effect  on the  cost ;of conveying  wastewater to  the
land  application  site.   Often,  the economics  of pumping
wastewater  to  a nearby sites must  be  compared with  the  cost
of constructing  gravity conveyance  to more distant sites.

A  site's  susceptibility  to,  flooding  also  can  affect  its
desirability.   The  flooding  hazard  of  each  potential  site
should  be  evaluated  in termjs  of  both the possible  severity
and  frequency  of  flooding  as  well as   the  areal extent  of
flooding.   In  some  areas, lit may be   preferable  to  allow
flooding of the  application |site provided offsite storage  is
available.   Further, crops ban be  grown in flood plains  if
flooding is infrequent  enough  to make farming economical.

Overland flow  sites  can be located in flood plains  provided
they  are protected  from  direct flooding  which  could  erode
the  slopes.   Backwater from  flooding,   if  it  does  not  last
more  than  a few  days,  should  not be  a problem.   Flood  plain
sites for  RI basins  should be  protected  from flooding by  the
use of  levees.

Summaries  of  notable  floods  and descriptions of  severe
floods  are published  each year  as  the USGS  Water Supply
Papers.  Maps  of certain areas inundated in past floods  are
published  as  Hydrologic Investigation  Atlases  by the  USGS.
The  USGS  also  has produced more  recent maps of  flood  prone
areas for  many  regions  of  the  county  as part of  the Uniform
National Program for Managing  Flood  Losses.  These-  maps  are
based on  standard 7.5  minute   (1:24,000) topographic sheets
and  identify  areas   that   lie within   the  100  year   flood
plain.  Additional information  on flooding susceptibility  is
available  from local offices of the U.S. Army Corps  of  Engi-
neers and  local  flood control  districts.

         2.2.4.3  Soils

Common  soil-texture  terms  and   their  relationship to the  SCS
textural class names are listed in  Table 2-8.         ":

Fine-textured  soils  do not drain well  and retain water  for
long periods of time.   Thus, infiltration is slower  and  crop
management  is  more difficult   than  for  freely drained  soils
such  as loamy soils.   Fine-textured  soils  are  best suited
for  the OF  process.   Loamy  or medium-textured soils  are
desirable  for  the SR  process,  although sandy  soils may  be
used  with  certain crops that  grow  well in rapidly  draining
soils.   Soil  structure and soil texture are important  char-
acteristics  that relate  to j permeability  and   acceptability
                            '2-20

-------
for  land  treatment.   Structure refers  to  the degree of  soil
particle  aggregation,  .ft well  structured  soil  is generally
more  permeable  than  unstructured   material  of  the   same
type.  The  RI  process is suited  for  sandy or loamy soils.

                           TABLE 2-8
        SOIL TEXTURAL  CLASSES AND GENERAL TERMINOLOGY
                  USED IN SOIL DESCRIPTIONS
                  General terms
            Common name  Texture
                                     Basic soil textural
                                       class names
            Sandy soils  Coarse


                      Moderately coarse


            Loamy soils  Medium




                      Moderately fine



            Clayey soils  Fine
Sand
Loamy sand

Sandy loam
Fine sandy loam

Very fine sandy loam
Loam
Silt loam
Silt

Clay loam
Sandy clay loam
Silty clay loam

Sandy clay
Silty clay
Clay'
Soil  surveys are usually  available from  the  SCS.   Soil  sur-
veys  normally  contain maps  showing  soil  series  boundaries
and textures to a depth of about  1.5  m (5 ft).  The scale  of
these maps  ranges from 1:31,680 to  1:15,840 and even 1:7,920
in  some  locations.    In  a  survey,  limited   information  on
chemical  properties,   grades,  drainage,  erosion  potential,
general  suitability  for  locally  grown crops,  and interpre-
tive and  management information is  provided.   In some areas,
published   surveys   are  not  available   or  exist  only  as
detailed  reports with  maps ranging  in scale  from 1:100,000
to  1:250,000.    Additional  information  on  soil  character-
istics  and  on soil survey availability can be obtained  from
the SCS,  through the  local county agent.

Although  soil depth,  permeability,  and  chemical  character-
istics  significantly affect  site  suitability,  data on these
parameters  are often not  available before  the site investi-
gation  phase.   If  these data are available,  they should  be
plotted  on   a  study  area  map along with  soil texture.    In
identifying potential sites, the planner  should keep in  mind
that  adequate soil depth  is  needed for root  development and
for  thorough  wastewater  treatment.   Further,  permeability
requirements   vary   among   the  land treatment  processes.
Desirable permeability ranges .are shown  by process in Table
2-9 together with desired  soil  texture.  The SCS  permeabil-
ity class definitions are presented in Figure 2-3.
                              2-21

-------
 Certain  geological   formations   are  of   interest   during
 Phase 1.  Discontinuities and  fractures  in bedrock may cause
 shortcircuiting  or   other   unexpected  ground   water  flow
 patterns.    Impermeable  or semipermeable  layers  of  rock,
 clay,  or  hardpan   can  result   in  perched   ground  water
 tables.   The  USGS  and  many state  geological surveys  have
 maps  indicating  the  presence  and  effects  of   geological
 formations.   These  maps and other USGS  studies  may  be  used
 to plot  locations within^  the  study area where  geological
 formations may limit the suitability  for  land  treatment.

                           TABLE 2-9
           TYPICAL SOIL PERMEABILITIES AND  TEXTURAL
             CLASSES FOR LAND TREATMENT PROCESSES
                                 Principal processes
                      Slow rate
               Rapid
               infiltration
Overland
flow
     Soil permeability
     range, cm/h
>0.15
                >5.0
                           <0.5
Permeability
class range
Textural
class range
Unified Soil
Classification
Moderately slow to
moderately rapid
Clay loams to
sandy loams
GM-d, s'M-d, ML,
OL, MH, PT
i
Rapid
Sand and
sandy loams
GW, GP, SW,
SP
Slow
Clays and
clay loams
GM-u, GC,
SM-u, SC,
CL, OL, CH, OH
Once each of  the  parameters discussed in the preceding para-
graphs  have   been   mapped,  the  maps  are  merged  into  a
composite map that indicates  areas  with high, moderate, and
low  suitability.    Map  overlays may  be useful  during this
process.

     2.2.5  Site  Screening                          '

During  the  latter  half  of Phase  lf  each part  of  the study
area that appears to be suitable  for  land  treatment must be
evaluated and rated  in terms  of  technical  suitability and
feasibility.   Rating  is  often accomplished by weighting each
of  the  site  selection   factors   and   using  a  numerical
system.   The  resulting  ratings are  used to  identify sites
that have high overall  suitability and that should be inves-
tigated  more  thoroughly.     If  suitable   sites  are  not
available,  no further  consideration   is   given  to  land
treatment.
                             2-22

-------
Site   selection  factors   and  weightings   should  vary  to  suit
the  needs  and   characteristics   of  the   community.    Several
factors that should   be   considered  are  listed  in  Table 2-10.
A  sample  rating  system  is  shown  in Table  2-11.    This  system
may    be    varied   by   the    planner   to    reflect    available
information.
                                   TABLE 2-10
                        SITE SELECTION  GUIDELINES
  Characteris tic
                     Process
                                       Remarks
  Soil permeability
  Potential  ground
  water pollution
  Ground water storage
  and recovery
  Existing land uses


  Future land use


  Size of site



  Flooding hazard

  Slope
  Water rights
Overland flow


Rapid infiltration
and slow rate

Rapid infiltration
and slow rate
Rapid infiltration






All processes


Al 1 procpssi=>s


All processes



All processes

All processes


Rapid infiltration


Overland flow




All processes
High permeability soils are more suitable
to other processes.

Hydraulic loading rates increase with
permeability.

Affected by the  (1) proximity of the site to
a potential potable aquifer, (2) presence of
an aquiclude,  (3) direction of ground water
flow, and (4)  degree of ground water recovery
bv wells or underdrains.

Capability for storing percolated water and
recovery by wells or underdrains is based
on aquifer depth, permeability, aquiclude
continuity, effective treatment depth, and
ability to contain the recharge mound within
the defined area.

Involves the occurrence and nature of con-
flicting land  use.

Future urban develooment may affect the ability
to expand the  system.

If there are a number of small parcels, it is
often difficult  to purchase or lease the
needed area.

May exclude or limit site use.

Steep grades may (1) increase capital expen-
ditures for earthwork, and  (2)  increase the
erosion hazard during wet weather.

Steep grades often affect ground water
flow pattern.
Steep grades reduce the travel time over the
treatment area and treatment efficiency. • Flat
land requires  extensive earthwork to create
grades.
May require disposal of renovated water in a
particular watershed within a particular
stretch of surface water.
                                       2-23

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       RATING  FACTORS
 TABLE  2-11
FOR  SITE  SELECTION  [14,  15]
Slow rate systems
Characteristic
Soil depth, ma
0.3-0.6
0.6-1.5
1.5-3.0
>3.0
Minimum depth to
ground water, m
<1. 2
1.2-3.0
>3.0
Permeability, cm/h°
<0.15
0.15-0.5
0.5-1.5
1.5-5.0
>5.0
Grade, %
0-5
5-10
10-15
15-20
20-30
30-35
>35
Existing or planned land use
Industrial
High density residential/urban
Low density residential/urban
Forested
Agricultural or open space
Overall suitability rating3
Low
Moderate
High
Agricultural

: Eb
3
8
9


0
4
6

1
: ' 3
5
8
8


6
4
' 0
Q
E
E

0
0
1
1
4

•
15-25
25-35
Forest

E
3
8
9


0
4
6

1
3
5
8
8


8
g


2
0

o
0
1
4
3


15-25
25-35
Overland
flow

o
4
7
7


2
4
6

10
g
g

E


8
2

E
E
g
E


0
1
4


16-25
25-35
Rapid
infiltration

£'

4
8



2
6

E
E

9


8

1
E
E
E
E

i
0 '
0
1
1
4


16-25
25-35
       The higher the maximum number in each  characteristic, the more  important
       the characteristic; the higher!the ranking, the greater the suitability.
a.  Depth of the profile to bedrock.
b.  Excluded; rated as poor.

c.  Permeability of most restrictive layer in soil profile.
d.  Sum of values.
                                   2-24  .

-------
EXAMPLE  2-1:
USE OF RATING FACTORS  TO  DETERMINE
SITE  SUITABILITY
An example of the use of rating factors is presented in the following two
figures and tables.  Example soil types are shown in Figure 2-7 as presented
in a portion of a county SCS soil survey.  Characteristics of the three soil
types and existing land uses are presented in Table 2-12.  The characteristics
are then compared to the rating factors in Table 2-11 to obtain the numerical
values in Table 2-13.  For example, the Bibb silt loam in Table 2-12 has'a
depth of soil above bedrock of 1.5 to 3 m (5 to 10 ft).  From Table 2-11,
this would correspond to values of 8 for SR, 7 for OF, and 4 for RI.  These
values are entered into Table 2-13.
When all factors are evaluated, the numerical values are added together to
obtain a total and to determine the suitability rating.  The high suitability
areas are presented in the soils map in Figure 2-8.  By applying this procedure
to all soils within a given radius of the community, the most suitable sites
(generally 3 to 5) are identified for further field investigation and cost-
effectiveness evaluation.
                                       FIGURE 2-7
                       EXAMPLE AREA OF SOIL MAP TO BE EVALUATED
                                   TABLE 2-12
               CHARACTERISTICS OF SOIL SERIES MAPPED IN FIGURE 2-7

Map symbol
Soil depth, m
Depth to ground water, m
Permeability, cm/h
Grade, %
Land use
Bibb silt loam
Bm
1.5-3.0
<1.2
<0.15
0-5
Agricultural
Sassafras fine
sandy loam
SaB
0.6-1.5
1.2-3.0
1. 5-5.0
0-5
Forested
Evesboro
loamy sand
EoB
>3.0
1.2-3
>5.0
0-5
Industrial
                                      2-25

-------
                                TABLE  2-13
             EXAMPLE USE OF RATING1FACTORS FOR  SITE  SELECTION
            System         Ground  ;Perme-          Land
Spil type    type   Depth  water   .ability  Grade  use   Total  Suitability
Bibb
silt loam
(Em)
Sassafras
fine sandy
loam (SaB)
Evesboro
loamy sand
(EoB)
SR
OF
RI
SR
OF
RI
SR
OF
RI
8
7
4
2
4
E
9
7
8
0
2
E
4
4
2
4
4
2
1
10
1 E
8
1
6
8
E
9
8
8
8
8
8
8
8
8
8
4
4
4
1
1
1
0
0
0
21
31
— a
24
18
__a
29
__a
27
Moderate
High
Eliminate
Moderate
Moderate
Eliminate
High
Eliminate
High
a.  Total not determined because site was clearly eliminated  (E) for this
    type of land treatment based on one or more site factors.
                        [7j  SR or RI HIGH SUITABILITY

                        [V|  OF HIGH SUITABILITY
                        ^  SR MODERATE SUITABILITY
                            SR or OF MODERATE SUITABILITY
                                   FIGURE  2-8
                EXAMPLE  SUITABILITY MAP  FOR  SOILS  IN  FIGURE  2-7
                                   2-26

-------
2.3  Phase 2 Planning

Phase 2,  the  site  investigation phase, occurs only if sites
with  potential  have  been  identified  in  Phase  1.   During
Phase 2,  field  investigations are conducted at the selected
sites  to  determine  whether  land  treatment  is  technically
feasible.   When sufficient data have been collected, prelim-
inary  design criteria are  calculated  for  each  potential
site.  Using these criteria, capital and operation and main-
tenance costs are estimated.  These cost estimates and other
nonmonetary  factors  are  used to evaluate the sites selected
during Phase 1 for cost effectiveness.  On  the basis of this
evaluation,  a land  treatment  alternative  is  selected   for
design.

     2.3.1  Field Investigations

Field investigations that should be performed during Phase  2
include:

     •    Characterization of  the soil  profile to an approxi-
         mate depth  of 1.5  m (5 ft)  for SR, 3 m (10 ft)  for
          RI, and 1m (3 ft)  for OF

     •    Measurements  of  ground  water  depth,   flow,   and
          quality

     •    Infiltration  rate  and  soil  hydraulic conductivity
         measurements

     •    Determination of soil  chemical properties

Methods for these analyses are  detailed in  Chapter 3.

     2.3.2   Selection  of Preliminary Design Criteria

From  information  collected  during the field  investigations,
the  engineer can confirm  the suitability  of  the  sites  for
the  identified  land  treatment process(es).  Using the load-
ing  rates described  previously (Figure 2-3,  Section 2.2.2),
the  engineer should  then select  the  appropriate hydraulic
loading rate for each land  treatment  process that is suit-
able  for  each  site  under  consideration.    Based on   the
loading rate estimates, land  area, preapplication  treatment,
storage,  and other  system  requirements  can  be  estimated.
Reuse/recovery options should  also be  outlined at  this time.
                             2-27

-------
          2.3.2.1   Preapplication Treatment

 Some  degree of wastewater  treatment prior to  land  applica-
 tion  is usually necessary, for  one  or more of  the following
 reasons:                    ;
                            I             •             ,.'
      •    To  avoid  unnecessary  wear  on  the   distribution
          system,  and in  particular,  pumps in  the system
                            I

      •    To allow wastewater  storage prior to land treatment
          without  creating  nuisance conditions

      •    To minimize potential  public health  risks
                            I
      •    To reduce soil  clogging in  RI  land treatment

      •    To obtain  a  higher  overall  level  of  wastewater
          treatment    .     >               •        ,
                                                      i

 Industrial  pretreatment  should  be considered  when industrial
 waste contains materials that (1) could hinder  the treatment
 processes;  (2)  could accumulate in  quantities  that  would  be
 detrimental  to  the  soil-plant system;  or   (3)  could  pass
 through  a land  treatment system and  restrict the beneficial
 uses  of  the renovated  water  or  the native  ground  water.
 Industrial  contaminants  of  concern  include  trace  organics
 and trace elements.  General guidelines  and  time  schedules
 for implementation of industrial waste pretreatment  programs
 can be obtained from the EPA  regional offices.

          2.3.2.2   Recovery of Renovated Water

 The collection of  renovated iwastewater following  land  treat-
ment may  be  either necessary  or desirable.  If  the renovated
wastewater  can  be  reclaimed  for beneficial  uses,  recovery
may even  be  profitable.  In many locations, water rights may
 necessitate  recovery of renovated  water  for  disposal  at  a
 specific  location  in a  given watershed.    In  some locations,
 underdrainage may  be needed  to  control  ground  water  eleva-
 tions and allow site development.

Methods  used  to  recover  renovated wastewater include  under-
drains, recovery wells, surface  runoff collection, and  tail-
water  return.    Wastewater  can  also be  recovered  through
springs  and seeps that result from land treatment  or  by
subsurface  flow  from the land treatment site  to  the  surface
water.  These methods and their  applicability to  each  of the
three  major  types  of   land  treatment   are  summarised  in
Table 2-14.  Design  of recovery  systems is discussed  in  more
detail in Chapters  4,5, and1  6.
                            12-28

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                           TABLE  2-14
    APPLICABILITY OF RECOVERY SYSTEMS  FOR RENOVATED WATER
Recovery system
                   Slow rate
                Rapid infiltration
                                                   Overland flow
Springs, seeps, or
natural drainage


Underdrains


Recovery wells
Often used to
maintain water
rights

Ground water control
and effluent reuse

Usually NA
Often used to       NA
maintain water rights


Ground water control  NA
and effluent reuse
Ground water control  NA
and effluent reuse
Surface runoff
Effluent
Stormwater
Tailwater
Sprinkler application
Surface application
NA
Sediment control

NA
25-50% of applied
flow
NA
NA

NA
NA
Collect,
Collect,

NA
NA
discharge3
discharge3



NA - not applicable.
a.  Disinfect if required before discharge; provide for short-term recycling of waste-
   water after extended periods of shutdown if effluent requirements are stringent.
      2.3.3   Evaluation of  Alternatives

Land treatment  alternatives should be  evaluated  on the basis
of  capital costs,  operation and maintenance costs  (including
energy consumption),  and other  nonmonetary factors,  such  as
public acceptability,  ease  of  implementation, environmental
impact, water  rights, and treatment consistency  and  relia-
bility.

          2.3.3.1  Costs

For cost analyses,  the EPA cost-effectiveness analysis pro-
cedures described  in 40CFR 35, Appendix A,  must  be  used  in
selecting  any  municipal  wastewater management  system that
will be  funded  under  PL  92-500  [16].   For  nongrant  funded
projects,  the   EPA  analysis  may   be  modified  to  fit   a
community's  specific objectives.    The most cost-effective
alternative  is  defined as  follows  [16]:

      The most cost-effective alternative  shall  be the waste
      treatment  management  system which the  analysis  deter-
      mines  to  have  the  lowest  present worth  or  equivalent
      annual  value  unless  nonmonetary  costs  are overriding.
      The most cost-effective alternative  must also, meet the
      minimum    requirements    of     applicable    effluent
      limitations,     groundwater   protection,    or    other
      applicable standards  established  under the  Act.
                               2-29

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Curves  for estimating capital and operation  and  maintenance
costs  may be found  in  reference [17] ,  or' the CAPDET  system
can be  used  for a  preliminary  estimate.

Cost  comparisons  should  include the cost of  preapplication
treatment  and  sludge  handling  as  well  as  land  treatment
process  components,   including  transmission,  storage,  field
preparation,  renovated  water recovery,  and land.   The  costs
of  resolving  any  water  rights  problems  also  raust   be
included.    The  EPA  cost-effectiveness  guidelines require
that grant-funded  projects  use the following  general service
lives:
         Land
         Structures

         Process equipment

         Auxiliary equipment
Permanent
30 to 50 years

15 to 30 years

10 to 15 years
Capital  costs  for land will  vary from site  to site.   Land
treatment systems must have adequate land  for preapplication
treatment facilities,  storage reservoirs, wastewater appli-
cation,  buffer  zones,  administrative  and laboratory build-
ings,  transmission  pipe   easement,  and   other facilities.
Costs of relocating residences and other  buildings depend on
the  location but  also should be included  in  capital  cost
estimates.   The  local offices  of the  U.S.  Army  Corps of
Engineers,  U.S.   Bureau  of Reclamation,  and  state  highway
departments  can  provide  information  on  relocation   cost
estimates.

Several options are  available for acquisition or control of
the land used for wastewater application, including:

     •   Outright purchase (fee-simple acquisition)

     •   Long-term lease or easement

     •   Purchase and  leaseback  of land  (usually  to farmer
         for irrigation)  with no  direct  municipal involve-
         ment i'n land management.
                            2-30

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For  larger  projects,  fee-simple  land  acquisition  is favored
by most federal  agencies,  states, and  communities.   Further,
outright  purchase  provides  the  highest  degree  of  control
over  the  land   application  site  and  ensures  uninterrupted
land  availability.   Estimates indicate that land  leasing  has
been    cost   effective    for   several    hundred    projects
nationwide.   Generally,  these  projects  are in  arid or semi-
arid  areas where renovated water has a high value  and land  a
relatively low value.  Leasing or easement arrangements also
can be  very attractive for smaller  communities.

Capital costs of land for both land treatment  processes  and
storage prior to land application  are  eligible for federal
Construction  Grants   Program  funding   as  specified   in1  EPA
guidance  [18].   During the  cost effectiveness  analyses,  the
engineer must keep  in mind that, unlike  many  other treatment
components, land has  a salvage  value.   In addition,  current
EPA  guidance  allows  the  land  value  to  appreciate  3%   per
year.   Thus,  the salvage value after 20  years is:

               9 n
    (1  + 0.03)zu x present price  = (1.806)(present  price)

The present worth of  this salvage value is calculated using
the   prevailing   interest   rate,  not   the  3%  appreciation
rate.   Long-term easements or leases of  land  for land appli-
cation  processes also are eligible for  Construction Grants
Program funding, provided  that  the conditions  summarized in
Table  2-15 are met.

                           TABLE 2-15
         LEASE/EASEMENT REQUIREMENTS FOR  CONSTRUCTION
                  GRANTS PROGRAM  FUNDING  [18]
     •  Limit the purpose of the lease or easement to land application and activities
       incident to land application.
     •  Describe explicitly the property use desired.

     •  Waive the landowner's right to restoration of the property at the termination'
       of the lease/easement.

     •  Recognizing the serious risk of premature lease termination, provide for full
       recovery of damages by the grantee in such an event.  The grantee must insure
       the capability to operate and meet permit requirements for the useful life of
       the project.

     •  Provide for payment of the lease/easement in a lump sum for the full value of
       the entire term.

     •  Provide for leases/easements for the useful life of the treatment plant,
       with an option of renewal for additional terms,  as deemed appropriate.
Operation  and maintenance  costs  include  labor,  materials,
and  supplies  (including  chemicals),  and  power  costs.   For
cost  comparison  purposes,  they  are assumed  to  be  constant
                               2-31

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during  the  planning  period.   However, if average wastewater
flows  are  expected   to  increase  significantly  during  the
planning  period,  operation and  maintenance costs should  be
developed for  each  year  of the planning process.  Operation
and  maintenance  cost curves  may  be  found  in references
[17, 19].                  '-

To  estimate  labor   costs,  staffing  requirements  for  both
preapplication  treatment and land  treatment must be  deter-
mined.   Staffing requirements  for  preapplication treatment
can  be  found in  reference  [19].   Staffing requirements  at
municipally  owned and operated  land  treatment  systems  have
been  plotted as  a   function  of  flow  in Figure 2-9.    Land
treatment systems that  are !owned and/or operated by  farmers
will have lower municipal staffing requirements.

Annual  costs should  include  the cost of  leasing  land  for
wastewater application, when appropriate.   Annual cost esti-
mates also should take into consideration revenues from crop
sales,  sale  of renovated  water,  sale of  effluent  for  land
application, or  leaseback  of purchased  land for farming  or
other purposes.   Because  of the uncertainty in estimating
these revenues, they  should be used to offset  only a  portion
of the operating  costs in the cost-effectiveness analysis.

Prevailing market values for crops usually can be obtained
from state  university cooperative  extension services.   Pre-
liminary  yield estimates  should be  based  on the  proposed
application  conditions  and on  typical yields in the  local
area.

Another  source  of revenue  may be the  sale  of  recovered  ren-
ovated   water,   particularly   runoff   from  OF   systems   or
renovated water  from RI  system recovery wells.   Markets  for
renovated water  must be  investigated  on a  community  by  com-
munity  basis.   Methods  of  assessing   the  relative  value  of
renovated wastewater for  various  uses and potential  reuse
categories are discussed in reference  [20].

         2.3.3.2  Energy

Basic energy requirements  for unit  processes  and operations
have been described  and  quantified in reference [21].   The
data  in  the report  were  used  to  compare  land treatment
energy requirements  with mechanical system  requirements  and
to develop equations  for calculating the energy  requirements
of each  unit process  [22] .   Equations  in  Chapter  8   can  be
used to generate  accurate power cost estimates for the cost-
effectiveness analysis.
                             2-32

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          2.3.3.3   Nonmonetary  Considerations
                            l
According   to  the  EPA  guidelines,  a   cost-effectiveness
analysis  must  also  consider   nonmonetary factors  such  as
environmental  impacts   [23,   24],   ease   of   implementation
(magnitude   of  potential   water   rights   conflicts,   public
acceptability),  and treatment  consistency and  reliability.
Potential  water rights  conflicts are  discussed briefly  in
Section  2.4.   Public acceptability will be greatly aided  by
an  effective public participation  program,  particularly  if
there  is  any chance that  local farmers will be involved  in
an  SR  system.     Public  participation  regulations  in the
federal  Construction  Grants  Program  are  given in  40 CFR
Part 35.   These regulations implement the public participa-
tion requirements  of 40 CFR Part  25.

Changing discharge  requirements,  wastewater characteristics,
growth  rates, and   land uses for  areas surrounding and  con-
tributing  to the  treatment system  require  treatment  flex-
ibility.    The  ability  of each alternative  to  adapt  to
changes should  be  evaluated.

     2.3.4   Plan Selection

To  select  an alternative,  each  of the  factors considered
during  the  evaluation process  should  be  compared   on  an
equivalent  basis.   Monetary factors should  be expressed  in
terms  of  total present  worth or  equivalent  annual  cost.
Nonmonetary  factors should' be weighted according  to  their
local  importance,  and  reasons  cited  for  abandoning any
alternative  for nonmonetary reasons.  If there are no  over-
riding nonmonetary factors, the alternative selected  should
be  the  plan  with  the  lowest  total  present  worth or  equiv-
alent annual  cost.

Actual  alternative selection  should involve  the wastewater
management  agency,  the  planner/engineer,   advisory  groups,
citizen  and  special  interest  groups,   and  other interested
governmental  agencies.   Once  an  alternative  is tentatively
selected, and before  design; begins, mitigation measures for
minimizing   any   identified   adverse   impacts   should   be
outlined.

2.4  Water Rights and Potential Water Rights Conflicts

Land application of wastewaters may cause several changes  in
drainage and  flow patterns  [25]:

     1.  Site drainage may  be  affected by land preparation,
         soil characteristics,  slope,  method  of wastewater
         application,  cover crops,  climate,   buffer   zones,
         and  spacing of irrigation equipment.
                            2-34

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     2.  Land application  may alter the  pattern  of flow in
         the  body  of  water  that would  have  received  the
         wastewater  discharge.   Although  this  may diminish
         the flow in the body of water, it also may increase
         the  quality.    The  change  may  be continuous  or
         seasonal.

     3.  Land application, may cause surface water diversion,
         because wastewaters that previously would have been
         carried  away  by surface waters  are  now  applied to
         land and often diverted to a different watershed.

Two  basic  types  of  water rights  laws  exist  in  the United
States:    riparian  laws,  which  emphasize  the  right  of
riparian landowners along a watercourse to use of the water,
and  appropriative  laws,  which emphasize  the  right  of prior
users  of  the water  [25] ,,   Most  riparian or land ownership
rights are  in effect east of the Mississippi River, whereas
most   appropriative  rights   are  in  effect  west  of  the
Mississippi River.  Specific areas where  these two doctrines
dominate are shown in Figure 2-10.

Most states  divide  their water  laws  into three categories:
(1)  waters  in  well-defined  channels  or  basins  (natural
watercourses),  (2)   superficial  waters not  in  channels  or
basins  (surface  waters),  and (3) underground waters  not in
well-defined  channels  or  basins  (percolating  waters  or
ground waters).   Potential water  rights  problems involving
each type  of water  and  each of the three primary  types of
land treatment  are  summarized  in Table  2-16.  This table is
intended to aid during planning and preliminary screening of
alternatives, but  is not to be  used as  the  basis for elim-
inating any alternatives.

     2.4.1  Natural Watercourses

Most legal  problems regarding  natural  watercourses involve
the  diversion of a discharge with  the  subsequent reduction
in flow through the watercourse.  In riparian states, diver-
sion of discharges that were not originally part of a stream
should  not be  cause  for  legal  action.    In appropriative
states,  if  the  diversion  would threaten the quantity  or
quality of  a downstream appropriation,  the  downstream user
has  cause  for  legal action.   Legal  action may  be  either
injunctive,  preventing  the  diverter  from  affecting  the
diversion, or monetary, requiring the diverter to compensate
for  the damages.  If the  area  is not water-short  and if the
watercourse  is  not  already  overappropriated,  damages would
be difficult if not impossible to prove.
                            2-35

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2-36

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                            TABLE 2-16
           POTENTIAL  WATER  RIGHTS PROBLEMS  FOR LAND
                     TREATMENT ALTERNATIVES3
                                 Land treatment process
     Water definition and
     water rights theory
Slow rate
        Rapid
        infiltration
                  Overland flow
     Natural watercourses

       Riparian

       Appropriative


       Combination
Unlikely

Likelyb
Unlikely
Likelyb
Likelyb   Likelyb
Unlikely

Depends on location of
discharge from collection ditch

Depends on location of
discharge from collection ditch
Surface waters
Riparian
Appropriative
Combination
Percolating or
ground waters
Riparian
Appropriative
Combination

Unlikely
Unlikely
Unlikely

Unlikely
Likely
Likely

Unlikely
Unlikely
Unlikely

Possible
Likely
Likely

Likely
Likely0
Likely0

Unlikely
Unlikely
Unlikely
     a.  For existing conditions and alternative formulation stage of the planning
        process only.  It is also assumed that the appropriative situations are
        water-short or overappropriated.

     b.  If effluent was formerly discharged to stream.

     c.  If collection/discharge ditch crosses other properties to the
        natural watercourse.
      2.4.2   Surface  Waters

For  surface  waters,  riparian  and  appropriative  rights  are
very  similar.    If  renovated  water  from  a  land  treatment
system crosses private property,  a  drainage or utility  ease-
ment  will be necessary.

      2.4.3   Percolating Waters  (Ground Waters)

Water rights conflicts may  be caused either by a  rise in  the
ground   water  table  that  damages   lands   adjoining  a  land
treatment system  or by the  appearance of  trace contaminants
in  nearby  wells.    In  riparian  states,  the  landowner must
prove  that   his  ground water  is  continuous with and   down-
gradient  from ground  water underlying   the  land  treatment
site.    If  the alleged damages  are  not  the  result  of negli-
gent  treatment  site  operation, cause for  legal   action will
be difficult to show.   In appropriative states, increases in
ground   water table  elevations would  not  usually  threaten
anyone's appropriative right.  Thus, there would  be no  cause
for  legal action.
                                2-37

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     2.4.4  Sources of Information

For larger  systems  and  in problem areas, the state or local
water master  or water rights  engineer should be consulted.
Other  references   to   consider  are  the  publications,  _A
Summary-Digest  of  State  Water  Laws,  available  from   the
National  Water  Commission  [25] ,  and  Land  Application of
Wastewater  and  State  Water Law, Volumes  I  and II  [26,  27].
If problems develop or are likely with  any of the feasible
alternatives, a water rights attorney  should  be consulted.

2.5  References                                     ;
1.
2.
3.
4.
6.
7.
8.
Metcalf & Eddy Inc.  Wastewater Engineering, Treatment,
Disposal,  Reuse.    Second Edition.   McGraw  Hill Book
Company.  New York, N.Y.  1979.

Thomas,  R.E.  and  J.P.  Law.    Properties  of  Waste
Waters.   In:  Soils  for Management  of  Organic Wastes
and  Waste  Waters.    American  Society  of  Agronomy,
Madison, Wisconsin.  1977.  p.47-72.
Davis,  J.A. ,  III,  and  J.  Jacknow.
Wastewater  in   Three   Urban  Areas.
47:2292-2297.  September 1975.
Heavy Metals  in
  journal  WPCF,
Pound,  C.E.,  R.W. Crites,  and J.V.  Olson.   Long-Term
Effects  of Land  Application  of  Domestic  Wastewater:
Hollister, California,  Rapid  Infiltration Site.  Envi-
ronmental  Protection Agency,  Office  of Resecirch  and
Development.  EPA-600/2-78-084.  April 1978.

Ketchum,  B.H.  and  R.F.  Vaccaro.    The  Removal  of
Nutrients and Trace Metals by Spray Irrigation  and in a
Sand  Filter  Bed.    In:   Land  as  a  Waste  Management
Alternative.   Loehr,  R.C. (ed.)   Ann Arbor,  Ann Arbor
Science.  1977.  pp. 413-434.

Chen,  K.Y.,   et   al.     Trace  Metals   in  Wastewater
Effluents.    journal  WPCF,    46:2663-2675.     December
1975.

National  Interim Primary Drinking Water Regulations.
U.S.  Environmental Protection  Agency.   EPA-570/9-76-
003.  1976.

Interim    Primary   .Drinking    Water    Regulations;
Amendments.    Federal  Register.   45(168):57332-57357.
August 27, 1980.     j
                            2-38

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9.   Thomas,  R. E.  and  D.M.  Whiting.   Annual  and Seasonal
     Precipitation   Probabilities.     U.S.   Environmental
     Protection Agency.  EPA-600/2-77-182.  August 1977.

10.  Flach, K.W.   Land Resources.   In:  Recycling Municipal
     Sludges  and  Effluents on  Land.   Champaign, University
     of Illinois.  July 1973.

11.  Whiting,  D.M.    Use  of  Climatic  Data  in Estimating
     Storage Days  for Soil Treatment Systems.  Environmental
     Protection    Agency,     Office    of    Research    and
     Development.  EPA-600/2-76-250.  November 1976.

12.  Thomas,  R.E., et  al.   Feasibility of Overland Flow for
     Treatment  of  Raw  Domestic Wastewater.   U.S.  Environ-
     mental Protection Agency.  EPA-66/2-74-087.  1974.

13.  Sills,  M.A. ,  et  al.    Two  Phase  Evaluation of  Land
     Treatment  as  a  Wastewater Treatment  Alternative  -  A
     Rational  Approach to  Federal and  State  Planning and
     Design  Requirements.   Proceedings of  the Symposium on
     Land  Treatment  of Wastewater, Hanover,  New Hampshire.
     August 20-25,  1978.

14.  Moser,  M.A.   A Method  for  Preliminary  Evaluation  of
     Soil  Series Characteristics to Determine the Potential
     for  Land  Treatment  Processes.    Proceedings  of  the
     Symposium on  Land Treatment  of  Wastewater.   Hanover,
     New Hampshire.  August 20-25,  1978.

15.  Taylor, G.L.  A Preliminary Site Evaluation Method for
     Treatment of  Municipal  Wastewater by  Spray Irrigation
     of  Forest  Land.    Proceedings  of  the   Conference  of
     Applied   Research  and   Practice  on   Municipal   and
     Industrial Waste.   Madison,  Wisconsin.   September 10-
     12, 1980.

16.  U.S.   Environmental Protection  Agency.     40  CFR  35,
   ,  Appendix A,  Cost-Effectiveness Analysis.  September 27,
     1978.

17.  Reed,  S.C.,  et al.   Cost of Land  Treatment  Systems.
     U.S.   Environmental  Protection Agency.    EPA 430/9-75-
     003.   September 1979.
18. ,U.  S.   Environmental
     Planning,    1982.
     September 1981.
Protection  Agency.
  EPA-430/9-81-012.
Facilities
   FRD-25.
                            2-39

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19
20
21
22
23
24
25
26
27
     Patterson,  W.L. and R.'F.  Banker.   Estimating Costs and
     Manpower  Requirements   for  Conventional   Wastewater
     Treatment Facilities.   EPA 17090 DAN.  October 1971.

     Schmidt, C.J.  and  E.V.  Clements,  III.    Demonstrated
     Technology and  Research Needs  for Reuse of Municipal
     Wastewater.   U.S.  Environmental Protection Agency.  EPA
     670/2-75-038.  May 1975.

     Wesner, E.M., et  al.   Energy Conservation in Municipal
     Wastewater Treatment.    U.S. Environmental  Protection
     Agency.  EPA-430/9-77-011.  March 1978.

     Middlebrooks,  E.J.  and  C.H.  Middlebrooks.    Energy
     Requirements    for  Small  Flow   Wastewater   Treatment
     Systems.   U.S. Army  Corps  of  Engineers, Cold Regions
     Research and  Engineering Laboratory.  May 1979.
     Canter, L.   Environmental Impact  Assessment.
     Hill Book Co.  New York, New York.  1977.
                                                     McGraw-
     U.S.  Environmental  Protection Agency.  Regulations  for
     Preparation of Environmental  Impact  Statements «   40  CFR
     Part  6, Section 6.512.

     Dewsnup,  R. L.  and D.W, Jensen,  eds.  A Summary  Digest
     of  State  Water  Laws.    National   Water   Commission.
     Washington, D.C.  May  1973.

     Large,  D.W.   Land Application  of Wastewater and  State
     Water Law:  An Overview  (Volume  I).   U.S.  Environmental
     Protection Agency.   EPA-600/2-77-232.  November  1977.

     Large,  D.W.   Land Application  of Wastewater and  State
     Water Law:   State Analyses (Volume  II).  U.S. Environ-
     mental  Protection Agency.    EPA-600/2-78-175 .    August
     1978.
                             2-40

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                           Chapter 3

                    FIELD INVESTIGATIONS
3.1  Introduction

In contrast  to conventional  technologies,  the analysis and
design of  land  treatment  systems requires specific informa-
tion on  the  properties of the proposed  site  or sites.  Too
little field  data may  lead  to  erroneous  conclusions while
too much will result in unnecessarily high costs with  little
refinement in the design concept.  Experience  indicates that
where  uncertainty   exists,   it  is  prudent   to  adopt  a
conservative    posture    relative    to    data   gathering
requirements.

Figure 3-1 is a flow chart which presents a logical sequence
of field  testing  for a land  treatment  project.  At several
points,   available   data  are   used   for  calculations   or
decisions  that  may  then   necessitate  additional  field
tests.   These additional  tests  are  usually directed  toward
estimation  of  new  parameters,  required for  extending the
analysis.   However,  in  some cases,  additional field tests
may also be required simply to refine preliminary estimates.

Guidance  on   testing  for  wastewater  constituents  and soil
properties  is provided  for  each land  treatment process  in
Table  3-1.    Normally,  relatively  modest programs  of field
testing  and  data  analysis will be satisfactory.  In certain
instances, however, more complex investigations and analyses
are required  with higher levels  of expertise in soil testing
and  evaluation  procedures.   Firms  specializing  in these
areas  are . available  for  assistance  if  expertise  does not
exist  within  the  firm  having  general  design responsibility.

3.2  Physical Properties

Preliminary   screening,  as  described  in  Chapter  2,  of  a
potential  site  (or sites)  will ordinarily be based on  exist-
ing  field data available  from  a SCS  county soil survey and
other  sources.    The  next   step  involves   some  physical
exploration on  the site.   This preliminary  exploration is  of
critical  importance  to  subsequent  phases  of the project.
Its two  purposes  are:   (1)  verification  of  existing data and
(2) identification  of probable,  or  possible, site  limita-
tions; and it should  be performed with  reasonable care.  For
example,   the  presence  of  wet  areas,   water-loving  plant
species,  or  surficial salt crusts should alert the designer
to the need  for detailed  field  studies directed  toward  the
problem   of   drainage.    The  presence  of rock  outcroppings
                             3-1

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would  signify   the   need   for   more   detailed   subsurface
investigations than  might normally  b,e required.  If  a stream
were   located  near  the  site,   there   would   need   to  be
additional  study  of the  surface  and  near-surface  hydrology;
wells would  create  a  concern about  details  of  the  ground
water  flow,  and  so on.    These  points  may   seem  obvious.
However,   there  are  examples   of  systems  that  have  failed
because of  just  such  obvious  conditions:    limitations  that
were  not recognized  until after design and construction were
complete.

                             TABLE 3-1
                   SUMMARY OF  FIELD TESTS FOR
                    LAND TREATMENT PROCESSES
                                  Processes
    Properties
  Slow rate (SR)
    Rapid
 infiltration (RI)
                                                 Overland flow (OF)
   Wastewater
   constituents
   Soil physical
   properties

   Soil hydraulic
   properties
   Soil chemical
   properties
Nitrogen, phosphorus,
SARa, ECa, boron

Depth of profile

Texture and structure
Infiltration rate

Subsurface
permeability
pH, CEC, exchangeable
cations (% of CEC),
ECa, metalsb, phos-
phorus adsorption
(optional)
BOD, SS, nitrogen,
phosphorus
Depth of profile
Texture and structure
Infiltration rate

Subsurface
permeability
pH, CEC, phosphorus
adsorption
BOD, SS, nitrogen,
phosphorus
Depth of profile
Texture and structure
Infiltration rate
(optional)
pH, CEC,  exchangeable
cations (% of CEC)
   a. May be more significant for arid and semiarid areas.
   b. Background levels of metals such as cadmium, copper, or zinc in the soil should
      be determined if food chain crops are planned.

     3.2.1      Shallow Profile  Evaluation

Following  the  initial  field reconnaissance,  some  subsurface
exploration  will be needed.   In the preliminary stages, this
consists of  digging pits, usually with a backhoe,  at  several
carefully  selected  locations.    Besides  exposing  the  soil
profile  for   inspection  and  sampling,  the  purpose  is   to
identify  subsurface  features  that   could develop  into  site
limitations,   or that  point to  potential  adverse  features.
Conditions  such  as  fractured,   near-surface  rock,  hardpan
layers, evidence of mottling in the profile,  lenses of open-
work gravel  and other anomalies  should  be  carefully  noted.
For   OF   site   evaluations,   the   depth   of   soil   profile
evaluation can  be  the  top 1m  (3  ft)  or so.   The  evaluation
should extend to 1.5  m  (5 ft)  for SR and 3m  (10 ft)  or more
for  RI systems.
                                 3-3

-------
    3.2.2
Profile Evaluation to Greater Depths
In  some site  evaluations,  the  2.5  to 3.7  m  (about  8  to
12 ft) deep pits that can  be excavated  by a backhoe will not
yield sufficient information on the profile to allow all the
desired  analyses  to  be  made.    For  example,  it may  be
necessary  to locate  both  the  ground  water  table  and the
depth  to  the  closest  impermeable  layer.    These  depths
together  with  horizontal  conductivity values  and certain
other  data are  required to make  mounding  analyses,; design
drainage   facilities,   and  for   contaminant   mass  balance
calculations.

Auger  holes  or  bore holes  are  frequently used to explore
soil  deposits  below the  limits  of pit excavation.   Augers
are  useful to  relatively  shallow depths compared  to  other
boring  techniques.    Depth  limitation  for  augering varies
with soil  type and conditions, as well  as hole diameter.   In
unconsolidated materials above water tables,  12.7 cm (5  in.)
diameter  holes  have  been  augered  beyond  35  m  (115   ft).
Cuttings that are continuously brought  to the surface during
augering  are  not suitable for logging the  soil materials.
Withdrawal of  the  auger flights  for removal of  the cuttings
near  the  tip   represents  an  improvement  as  a  logging
technique.   The best method is  to withdraw  the flights and
obtain a sample with a Shelby tube or split-spoon1sampler.

Boring  methods, which   can  be  used  to  probe  deeper   than
augering,  include   churn   drilling,    jetting,  and  rotary
drilling.  When using  any of these methods  it is preferable
to clean out the hole and  secure a sample from the  bottom  of
the hole with a Shelby tube or split-spoon sampler.  ,

3.3  Hydraulic Properties

The  planning  and  design  work  relative  to  land   treatment
systems cannot  be  accomplished  without estimates of several
hydraulic  properties of  the  site.   The capacity of the  soil
to accept  and  transmit  water is  crucial to  the  design  of  RI
systems and may be limiting  in the design of  some SR systems
as well.   In  addition,  tracking  the movement  and impacts  of
the wastewater  and its  constituents  after  application will
always be  an important part of design.

For  purposes  of this  manual,  hydraulic properties of  soil
are  considered  to   be   those  properties whose  measurement
involves  the flow  or  retention  of  water  within  the  soil
profile.
                             3-4

-------
    3.3.1
Saturated Hydraulic Conductivity
A material  is  considered permeable if it contains  intercon-
nected  pores,   cracks,  or  other passageways  through  which
water or  gas can flow.   Hydraulic conductivity  (synonymous
with  the  term  permeability  in  this  manual)  is a measure  of
the  ease  with  which liquids  and  gases  pass  through  soil.
The  term  is more easily  understood  if a few basic  concepts
of water flow in soils are  introduced  first.

In  general, water  moves through  soils  or  porous  media  in
accordance  with Darcy's equation:
                                                       (3-1)
where q     =  flux of water, the flow, Q per unit cross
               sectional area, A, cm/h  (in./h)

      K     =  hydraulic conductivity (permeability), cm/h
               (in./h)

      dH/dl =  hydraulic gradient, m/m  (ft/ft)

The total head (H) can be assumed to be the sum of the soil-
water pressure head (h), and the head due to gravity  (Z), or
H =  h  + Z.   The  hydraulic gradient  is  the change in total
head (dH) over the path length (dl).

The hydraulic conductivity is defined as the proportionality
constant,  K.   The conductivity  (K)  is not a true constant
but  a  rapidly  changing function  of water content.   Even
under conditions  of constant  water content, such as  satura-
tion, K may vary over time due to increased swelling  of clay
particles,   change   in  pore   size  distribution   due   to
classification  of particles,  and  change  in  the  chemical
nature of soil-water.   However, for most purposes, saturated
conductivity  (K)  can  be  considered  constant  for  a given
soil.   The K value  for flow  in  the  vertical direction will
not necessarily be  equal  to K  in  the horizontal direction.'
ThisconditionTsknownasanisotropic.ItTsespecially
apparent  in  layered  soils  and those with  large structural
units.

The  conductivity  of  soils  at saturation  is  an important
parameter because it is used in Darcy's equation  to estimate
ground water flow patterns (see Section 3.6.2) and is useful
in  estimating  soil  infiltration  rates.   Conductivity  is
frequently estimated from other physical properties but much
experience  is  required  and  results are   not  sufficiently
                             3-5

-------
 accurate  for design purposes  [1-5].   For  example,  hydraulic
 conductivity is  largely controlled  by soil texture:   coarser
 materials  having  higher conductivities.   However,   in  some
 cases  the  soil  structure  may  be   equally important:  well
 structured   fine   soils  having  higher  conductivities  than
 coarser unstructured  soils.

 In  addition, hydraulic conductivity  for a specific  soil may
 be  affected  by variables other than  those relating  to grain
 size,  structure,  and pore distribution.   Temperature, ionic
 composition  of the water, and the  presence  of  entrapped air
 can alter conductivity values  [1].
     3.3.2
Infiltration Capacity
The  infiltration rate  of  a soil is  defined  as the rate  at
which water enters  the  soil  from the  surface.   When  the  soil
profile   is  saturated  with  negligible  ponding  above   the
surface,  the  infiltration  rate  is  equal  to  the effective
saturated conductivity  of  the  soil profile.

When  the soil  profile  is  relatively dry, the  infiltration
rate  is  higher  because water  is entering  large  pores  and
cracks.    With  time,  these   large   pores  fill  and   clay
particles  swell  reducing  the  infiltration   rate  rather
rapidly  until  a  near steady-state value  is approached.   This
change  in infiltration  rate with time  is  shown  in  Figure 3-2
for several different soils.  The effect  of both texture and
structure on  infiltration  rate  is illustrated  by  the curves
in  Figure 3-2.   The  Aikeri clay  loam has  good  structural
stability and  actually  has I a higher  final  infiltration  rate
than the sandy loam soil.   The  Houston black clay,  however,
has very poor  structure and  infiltration  drops  to  near zero.

For  a   given  soil,  initial  infiltration  rates  may   vary
considerably,   depending   on   the   initial  soil   moisture
level.   Dry  soil  has a higher initial  rate  than wet  soil
because  there  is more empty pore  space  for water to enter.
The  short term  decrease  in infiltration  rate   is primarily
due to the change in soil structure and the filling  of large
pores  as clay  particles  absorb water   and  swell.    Thus,
adequate  time  must be  allowed  when  running  field tests  to
achieve  a steady intake ratja.

Infiltration rates  are  affected by the ionic composition  of
the soil-water,  the type o£ vegetation,  and  tillage of  the
soil  surface.    Factors   that   have  a  tendency  to reduce
infiltration  rates  include clogging  by  suspended  solids  in
wastewater, classification  of  fine  soil particles,  clogging
due to  biological  growths,  gases produced by soil microbes,
swelling  of  soil  colloids,  and  air  entrapped  during  a
                             3-6

-------
 wetting event [6, 7].  These influences are all  likely  to  be
 experienced when  a  site is developed  into a land treatment
 system.    The  net   result  is  to  restrict  the  hydraulic
 loadings of  land treatment systems  to values substantially
 less than those predicted from the steady state  intake  rates
 (see  Figure   3-2),   requiring  reliance  on  field-developed
 correlations   between  clean water  infiltration  rates and
 satisfactory   operating  rates  for full-scale  systems.    It
 should be recognized that good soil management practices can
 maintain or   even   increase  operating  rates,  whereas
 practices can lead to substantial decreases.
                               poor
                   0. 50


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 CROWN SANOY LOAM
          SILT

HOUSTON BLACK CLAY
                        20  40 60  80 1001 20 140

                             TIME, min
                            FIGURE 3-2
                  INFILTRATION RATE AS A FUNCTION
                   OF TIME FOR SEVERAL SOILS  [3]


Although  the measured  infiltration  rate  on the  particular
site may decrease  in time due  to  surface clogging  phenomena,
the  subsurface  vertical  permeability  at  saturation  will
generally remain  constant.   That is, clogging  in  depth  does
not  generally occur.   Thus,  the  short-term measurement  of
infiltration  serves  reasonably well as an  estimate of  the
long-term saturated vertical permeability  if  infiltration is
measured over  a  large area.   Once the infiltration  surface
begins to clog, however, the flow beneath  the clogged layers
tends to be unsaturated and at unit  hydraulic gradient.
                             3-7

-------
The  short-term  change  in infiltration rate as a  function  of
time  is  of  interest  in  the  design and  operation  of  SR
systems.   A knowledge  of how cumulative water intake  varies
with time  is necessary to determine the time of  application
necessary  to  infiltrate the  design  hydraulic   load.   The
design  application  rate  [of  sprinkler  systems   should  be
selected  on the basis of the  infiltration rate  expected  at
the end of  the  application iperiod.
    3.3.3
Specific Yield
The  term specific  yield is  most often  used  in  connection
with  unconfined  aquifers  and  has  also  been  called   the
storage  coefficient  and drainable  voids.   It  is  usually
understood  to  be the  volume  of  water  released from a  unit
volume of unsaturated aquifer material drained by  a  falling
water table.   Although the  term  fillable porosity  has occa-
sionally been  used  as a  synonym  for the above three terms,
it  is  actually a somewhat  smaller  quantity  because  of  the
effect of entrapped  air.   The primary use of specific yield
values is  in computing aquifer properties,  for example,  to
perform ground  water mound  height analysesTFor  relatively
coarse-grained  soils and deep  water tables,  it  is  usually
satisfactory  to  consider  the  specific  yield  a constant
value.  As computations are not extremely sensitive to small
changes in the value of specific  yield,  it  is usually satis-
factory  to  estimate  it  from  knowledge  of  other   soil
properties,  either  physical  as in   Figure   3-3   [8],   or
hydraulic as in  Figure   3-4  [9].   To  clarify  Figure  3-3,
specific  retention  is  equal  to  the  porosity  . minus   the
specific yield.

A note of caution,  however.   For fine-textured soils, espe-
cially as the  water table ^oves  higher in the profile,  the
specific  yield may  not  have a  constant value  because  of
capillarity.   Discussion of  this complication  may be found
in  references  [10,  11].   The effect of decreasing specific
yield with increasing water table height can lead  to  serious
difficulties with mound height analysis  (Section 5.7.2).
    3.3.4
Unsaturated Hydraulic Conductivity
The  conductivity  of  soil  varies  dramatically  as  water
content is reduced below saturation.  As an air phase is now
present,  the  flow channel  is  changed  radically  and  now
consists  of  an  irregular  solid boundary  and  the air-water
interface.   The  flow path  becomes  more  and  more  tortuous
with decreasing water content as  the larger pores empty and
                             3-8

-------
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                    FIGURE 3-3
       POROSITY,  SPECIFIC RETENTION,  AND
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\ 2 34 6810 20 30 40 60 80 100
2.5 5 8 10 152025 50 80 100 1 50 200250
                 HYDRAULIC CONDUCTIVITY
                     FIGURE 3-4
  GENERAL RELATIONSHIP BETWEEN SPECIFIC  YIELD
           AND HYDRAULIC  CONDUCTIVITY  [9]
                        3-9

-------
 flow becomes confined to ^he smaller pores.  Compounding the
 effect of decreasing  cross-sectional area for   flow is the
 effect of added  friction as  the  flow takes place closer and
 closer  to  solid  particle  surfaces.    The  conductivity  of
 sandy soils, although  much higher at  saturation than loamy
 soils,  decreases more  rapidly  as  the  soil  becomes  less
 saturated.  In most cases,  the  conductivities of  sandy soils
 eventually  become lower than finer soils.  This relationship
 explains why  a  wetting  front  moves  more  slowly  in sandy
 soils than  medium or  fine soils after irrigation  has stopped
 and why there is  little  horizontal  spreading of  moisture  in
 sandy soils  after irrigation.

 Estimating  water movement under unsaturated conditions using
 Darcy's  equation  and  unsaturated  K values  is  complex.   A
 discussion  of  such calculations is outside the scope of this
 manual.   The user is referred  to  references  [1,  10, 12, 13]
 for further  details and solution of special cases.
     3.3.5
Profile Drainage
For  SR  systems   that  are  operated  at  application  rates
considerably  in excess of  crop irrigation  requirements,  it
is often desirable to  know  how rapidly the soil profile will
drain  and/or  dry after application has  stopped.   This  know-
ledge, together with knowledge of  the  limiting   infiltration
rate of  the soil and the ground water movement and  buildup,
allows  the designer  to make  a reasonable  estimate of  the
maximum  volume of  water  that can be  applied  to a  site  and
still  produce  adequate  crops.  A typical moisture  profile
and  its  change with time  following  an  irrigation is  illus-
trated  in  Figure  3-5  for  an  initially saturated  profile.
Moisture profile changes may  be determined  in the  field with
tensiometers  [4].

3.4  Infiltration  Rate Measurements

The  value  that is  required  in land  treatment design is  the
long-term  acceptance rate  of the entire soil surface on  the
proposed  site  for the  actual  wastewater  effluent  to  be
applied.   The  value that  can be  measured  is  only  a short-
term equilibrium acceptance rate  for a  number  of  particular
areas within  the overall site.

There are  many potential  techniques for measuring infiltra-
tion  including  flooding  basin,  cylinder  infiltrometers,
sprinkler  infiltrometers  and  air-entry  permeameters.   A
comparison  of  these   four   techniques  is  presented   in
Table 3-2.    In  general,  the  test area  and the  volume  of
water used  should  be  as  large as practical.   The two main
categories  of  measurement  techniques  are  those  involving
                            3-10

-------
flooding  (ponding  over  the   soil   surface)   and   rainfall
simulators  (sprinkling infiltrometer). .^The  flooding type  of
infiltrometer  supplies water   to  the soil  without  impact,
whereas  the  sprinkler   inf iltrometer   provides  an ••"* impact
similar  to  that  of  natural rain.   Flooding  infiltrometers
are  easier  to  operate than sprinkling  infiltrometers, but
they  almost  always  give  higher  equilibrium  infiltration
rates.   In  some  cases, the difference  is very  significant,
as   shown   in   Table 3-3.      Nevertheless,   the   flooding
measurement  techniques are  generally preferred  because  of
their simplicity.   Relationships between  infiltration  rates
as obtained by various flooding  techniques  and the loading
rates of RI systems are discussed  in  Section  5.4.1.   The air
entry permeameter is  described  in  Section  3.5.2.
                      0 ->-WER CONTENTS   SATURATION
                           FIGURE 3-5
                     TYPICAL PATTERN OF THE
      CHANGING MOISTURE PROFILE DURING DRYING AND DRAINAGE
If  a sprinkler  or  flood  application  is  planned, the  test
should  be  conducted  in  surficial  materials.    If  RI  is
planned,  pits must  be  excavated  to  expose lower  horizons
that  will constitute the  bottoms  of  the basins.  If  a  more
restrictive   layer  is present   below the  intended plane  of
infiltration  and  this layer is close  enough to  the  intended
plane  to  interfere,  the  test  should  be  conducted  at  this
layer to  ensure a  conservative  estimate.
                             3-11

-------
                             TABLE 3-2
                    COMPARISON,OF INFILTRATION
                      MEASUREMENT TECHNIQUES
Measurement
technique
Flooding
basin
Cylinder
infiltrometer

Sprinkler
infiltrometer


Air entry
perraeameter
(AEP)



Water Time
use per per test,
test, L h
2,000-10,000 4-12

400-700 1-6

1,000-1,200 1.5-3


10 0.5-1



Equipment
needed
Backhoe
or blade
Cylinder
or earthen
berm
Pump, pres-
sure tank,
sprinkler.
cans
AEP
apparatus,
standpipe
with resevoir


Comments
Tensiometers
may be used
Should use large diameter
cylinders (1 m diameter)

For sprinkler applications,
soil should be at field
capacity before test

Measures vertical hydraulic
conductivity. If used to
measure rates of several
different soil layers, rate
is harmonic mean of conducti-
vities from all soil layers.
   Note:  See Appendix G for metric conversions.
                             TABLE 3-3
         SAMPLE COMPARISON OF( INFILTRATION MEASUREMENT
         USING  FLOODING AND SPRINKLING TECHNIQUES [14]
                  Measurement
                   technique
  Equilibrium infiltration
       rate, cm/h

Overgrazed  Pasture, grazed but
 ', pasture   having good cover
             Double-cylinder        ;
             infiltroraeter (flooding)    2.82

             Type F rainfall
             simulator (sprinkling)      2.90
            5.97


            2.87
Infiltration  test results are typically plotted as  shown in
Figures 3-2  and B-3.    The derivation  of design values  from
these  test results is presented  in Appendix  B.

Before discussing  the  infiltration  measurement techniques,
it should be  pointed out  that the  U.S. Public Health Service
(USPHS)  percolation  test  used for establishing  the  size of
septic tank  drain fields  [15]  is  definitely  not recommended
as a method for estimating infiltration.
                               3-12

-------
    3.4.1
Flooding Basin Techniques
Pilot-scale infiltration basins represent an excelle-nt tech-
nique  for  determining  vertical  infiltration  rates.   The
larger the  test area  is,  the  less the relative error due to
lateral  moisture  movement  will  be  and  the  better  the
estimate.   Where  such basins  have been used,  the plots have
generally  ranged   from  about  0.9  m   (10  ft  )  to  0.1  ha
(0.25 acre).   In  some cases,  pilot  basins of  large scale (2
to  3.2  ha  or  5  to  8  acres)  have  been used  to  determine
infiltration  rates  and  demonstrate  feasibility  with  the
thought  of  incorporating  the test basins  into a subsequent
full-scale  system [16].   Figure 3-6  is a photograph  of a
pilot basin.
        FLOODING BAS
             FIGURE  3-6
         USED FOR MEASURING INFILTRATION
The  Corps of  Engineers  has  used  flooding basin  tests to
determine   infiltration  rates   on  thr'ee   existing   land
treatment  sites   [17].   Basins  of 6.1  m  (20  ft)  and  3 m
(10 ft) diameter were used and it was concluded that  the  3 m
(10 ft) diameter  basin  was  large enough to provide reliable
infiltration  data.   About  4 man-hours  were  required   for
completing an  installation  and  less  than  1,000 L (265  gal)
of water  would probably be  adequate to  complete a test.  As
this  testing  procedure  will  undoubtedly  become more widely
adopted,  Figures  3-7  and  3-8  are  included  to  show   the
details of installation  [18].
                             3-13

-------
                 GROOVE CUTTING TOOL-
CENTER ROD
                                           HANDLE
                                          METAL PIPE-
                                          FOOT STOP
                                          STEEL PLATE
                                                   7
                                                            15cm
t
                       FIGURE 3-7
     GROOVE  PREPARATION FOR  FLASHING (BERM)  [18]
                                                 20c« ABOVt SURFACE
                                                  15 cm BEL ill (f SURFACE
                                         ALUMINUM FLASHING
                        FIGURE 3-8
       SCHEMATIC  OF FINISHED  INSTALLATION  [18]
                             3-14

-------
An  important assumption  in  any  flooding  type  infiltration
test  is  a saturated  (or  nearly  so)  condition in the upper
soil profile.  Thus, an essential part of this method  is  the
installation  of  a  number of  tensiometers  within  the test
area  at  various  depths  to  verify  saturation  by  their
approach  to  a  zero value of  the  matric  potential,  before
obtaining any  head  drop (water level) measurements.   In  the
Corps of  Engineers  studies,  six tensiometers were installed
in a 1 m  (3.3 ft) diameter circle concentric with the  center
of  the  3m  (10  ft)   diameter  test   basin   as  shown   in
Figure 3-8.    Table  3-4  gives  their  suggested- depths   of
placement in a soil of well-developed horizons;  however,  any
reasonable  spacing  above  strata of  lower  conductivity,   if
such  exist,  should  be  adequate.    In   soils  lacking well-
developed  horizons,  a uniform  spacing  down to  about 60  cm
(24 in.) should suffice.  A seventh tensiometer  installed  at
a depth  of  about 150 cm  (60 in.)  is  also suggested,  but  is
not critical.

                          TABLE 3-4
               SUGGESTED VERTICAL PLACEMENT  OF
       TENSIOMETERS IN BASIN INFILTROMETER TESTS [18]
No.
1
2
3
4
5
6
Soil
horizon
A
B
B
B
B
C
Placement
Midpoint of A
1/5
2/5
3/5
4/5
15
distance
distance
distance
distance
cm below
between
between
between
between
A/B
A/B
A/B
A/B
and
and
and
and
B/C
B/C
B/C
B/C
interfaces
interfaces
interfaces
interfaces
B/C interface
Following  installation  and  calibration of the  tensiometers,
a  few preliminary  flooding  events are  executed to  achieve
saturation.    Evidence  of  saturation  is the  reduction of
tensiometer  readings to  near zero  through  the  upper  soil
profile.   Then a final  flooding event  is  monitored  to derive
a  cumulative  intake versus  time  curve.   A  best fit  to  the
data  plotted  on  log-log  paper  allows   calculation  of  the
infiltration parameters, as shown  in Figure  3-9.  Subsequent
observation of tensiometers can then provide  data on  profile
drainage.
                             3-15

-------
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             3-16

-------
    3.4.2
Cylinder Infiltrometers
The equipment  and basic  methodology for  this  popular mea-
surement technique are  described  in references [9, 19, 20].
The equipment setup for a test is shown in Figure 3-10.

To  run a  test,  a  metal  cylinder  is  carefully  driven  or
pushed into  the  soil  to a depth of  about  10 to 15 cm (4 to
6 in.).   Measurement cylinders  of  from 15  to 35  cm (6 to
14 in.) diameter  have generally  been used  in practice, with
lengths of  about 25  to 30.5  cm  (10 to 12  in.).    Divergent
flow,   partially  obstructed by  the  portion  of  the cylinder
beneath the soil  surface, is  further minimized by means of a
"buffer zone" surrounding the central ring.  The buffer zone
is commonly  provided by another  cylinder  40 to 70  cm  (16 to
30  in.)  diameter, driven  to a  depth  of  5  to 10  cm (2 to
4 in.) and  kept  partially full of  water during the  time of
infiltration.   This  particular mode of making measurements
has come  to be known as  the  double-cylinder or double-ring
infiltrometer method.   Care  must  be taken  to  maintain the
water  levels  in  the  inner  and outer cylinders  at the same
level  during the measurements.    Alternately,  buffer zones
are provided  by diking  the area  around the intake cylinder
with low (7.5 to  10 cm or 3 to 4 in.) earthen dikes.

If the cylinder  is installed  properly and  the test  carefully
performed,  the  technique  should produce data  that at least
approximate  the  vertical  component of  flow.  In most soils,
as the wetting  front advances downward through the profile,
the infiltration  rate will decrease  with time and approach a
steady-state  value  asymptotically.   This  may  require  as
little as  20 to 30 minutes in some soils  and  many hours in
others.  Certainly, one could not  terminate  a test  until the
steady-state  condition  was  attained or the  results would be
totally meaningless  (see Figure 3-2).

Anyone  contemplating  the use  of  this  measurement  technique
because of  its apparent simplicity should also be aware of
its limitations.   Discussions dealing specifically with the
problem  of separating  the  desired  vertical component from
the total  moisture flux, which  may include a large  lateral
component,  can be found in references  [21,  22].

A more promising  direction is suggested in reference  [19] in
which  the main conclusion is  applicable:   to minimize errors
in the use  of  the cylinder infiltrometer technique; use only
large-diameter    cylinders
                 and
careful
installation
 techniques.Thespecificrecommendation
 diameterTs  a minimum  of  1  m  (3.3  ft).
                               as  to  cylinder
                             3-17

-------
BUFFER POND
   LEVEL —j
GROUND LEVEL
                         GAGE  INDEX
                         ENGINEER'S SCALE
                         WELDING ROD
                         HOOK
                                               WATER SURFACE
                                  — INTAKE CYLINDER —
                             FIGURE  3-10
                   CYLINDER INFILTROMETER  IN  USE
                                 3-18

-------
Installation should  disturb  the soil as little as possible.
This   generally   requires    thin-walled  cylinders  with a
beveled edge  and  very careful  driving  techniques.   In soft
soils, cylinders  may  be pushed  or jacked  in.    In harder
soils, they must  be  driven in.   The cylinders must be kept
straight   during   this   process,   especially   avoiding   a
"rocking"  or  tilting motion  to advance them  downward.   In
cohesionless coarse  sands and  gravels,  a  poor bond between
the  soil   and  the metal cylinder  often  results,  allowing
seepage around  the edge  of  the  cylinder.   Such conditions
may call for special methods  to be devised.  One such method
is  to construct  the  test  area  by  forming  low  dikes   and
covering  the   inside  walls  with plastic  sheet  to  prevent
lateral  seepage   [19].   This  begins to approach  the basin
flooding method described in  Section 3.4.1.

Measurements  of  infiltration  capacity  of soils  often show
wide  variations  within  a relatively small  area.   Hundred-
fold  differences  are  common  on  some sites.    Assessing
hydraulic  capacity   for  a   project   site   is  especially
difficult because test plots  may  have adequate capacity when
tested  as   isolated  portions,  but   may   prove   to  have
inadequate capacity after water is applied to the total area
for  prolonged  periods.   Problem  areas can  be  anticipated
more  readily  by  field  study  following  spring  thaws  or
extended  periods  of  heavy   rainfall   and  recharge  [23].
Runoff,  ponding,  and  near   saturation conditions  may  be
observed for brief periods  at sites where drainage problems
are likely to occur after extensive  application begins.

Although  far   too few  extensive  tests have  been  made  to
gather meaningful statistical  data on the cylinder infiltro-
meter  technique,  one very comprehensive study is available
from which tentative conclusions  can be  drawn.

Test results from three plots  (357 individual tests) located
on  the same  homogeneous  field  were  compared.   In addition,
test  results   from  single-cylinder  infiltrometers  with  no
buffer zone  were compared  with  those  from  double-cylinder
inf iltrometers.   The inside  cylinders  had a  15  cm  (6 in.)
diameter;  the  outside  cylinders, where used,  had  a  30  cm
(12 in.)  diameter.   For  this  particular soil,  the presence
of  a  buffer  zone did  not have a significant  effect on  the
measured rates.   These data,  although very carefully taken,
overestimate the field average  by about  40%, indicating that
small diameter cylinders  will consistently overestimate  the
true vertical infiltration rate  [14].
                            3-19

-------
    3.4.3
Sprinkler Infiltrometers
Sprinkler  infiltrometers  ar£  used  primarily  to  determine  the
limiting application rate for systems using  sprinklers.   To
measure  the  soil intake rate for  sprinkler  application/  the
method presented in reference [24] can be used.   The  equip-
ment  needed  includes a  trailer-mounted  water  recirculating
unit,  a  sprinkler  head  operating  inside  a  circular  shield
with a small side opening, and approximately 50 rain gages.

A  schematic  diagram of  a typical  sprinkler  infiltrometer is
presented  in  Figure 3-11.    A  1,814  kg  (2 ton) capacity
trailer  houses a 1,135 L  (300 gal)  water supply  tank and  2
self-priming centrifugal  pumps.    The sprinkler pump  should
have  sufficient capacity  to  deliver   at   least 6.3   L/s
(100 gal/min)  at 34.5 N/cm2  (50  lb/in.2)  to  the  sprinkler
nozzle,  and  the  return  flow pump  should  be  capable   of
recycling  all  excess  water  from  the shield  to  the  supply
tank.  The circular  sprinkler shield  is designed to permit a
revolving  head  sprinkler  to operate  normally  inside   the
shield.  The opening in the side of the shield  restricts  the
wetted  area to  about  one-eighth   of a  circle.   Prior   to
testing, the soil  in the  wetted  area is brought up to field
capacity.   Rain gages  are  then  set out in  rows of three
spaced at  1.5  m  (5  ft)  intervals outward from  the sprinkler
in  the center  of the area  to be  wetted.   The  sprinkler  is
operated for about  1 hour.   The  intake of water in the soil
at  various places  between gages  is observed  to  determine
whether  the  application  rate  is  less than, greater than,  or
equal to the infiltration rate.

The area selected for measurement  of  the  application rate is
where  the  applied  water  .just   disappears  from  the  soil
surface  as the  sprinkler  jet returns to the spot.  At  the
end of the test (after 1 hour), the  amount of  water caught
in  the  gages  is  measured  and  the  intake  rate  is calcu-
lated.   The  calculated  rate  of infiltration  is  equal to  the
limiting application rate that  the  soil  system  can accept
without runoff.

Disadvantages  of the  technique  are  the time  and expense
involved  in  determining  intake  rates   using   a   sprinkler
infiltrometer.    There  is, in fact,  little  reason  to try  to
measure maximum  intake  rates on soils that  are going to  be
loaded far below these  maximum rates,  as  is  the case  for
most  SR  system  designs.   However,  where economics dictate
the   use   of  application : rates   far   in  excess  of   the
consumptive use  (CU) of  the  proposed crop on soils of known
or suspected hydraulic limitation, a  test such  as   described
                             3-20

-------
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-------
above  should  be  given  careful  consideration.    Local SCS
field   personnel   or   irrigation  specialists   should  be
consulted  for opinions  on  ithe advisability  of  making such
tests.

3.5  Measurement of Vertical Hydraulic Conductivity

The rate  at  which  water percolates through the soil profile
during  application   depends   on  the  "average"  saturated
conductivity  (K ) of the prbfile.  If the soil is  uniform, K
is  assumed  to Be  constant  ;with depth.   Any differences in
measured  values  of K  are  linen due to  normal variations in
the measurement technique.  ' Thus, average K may be computed
as the arithmetic mean of n samples:
                  K
                                       K
                               (3-2)

where K
       am
       arithmetic mean vertical conductivity
Many  soil  profiles, approximate a  layered  series of uniform
soils  with  distinctly  different  K  values,  generally de-
creasing with  depth.   For such cases,  it  can be shown that
average  K  is  represented  by the  harmonic  mean  of  the  K
values from each layer  [25] ;
                   K
                    hm
                         K.
                       D
                    K.
               + d

                 K~
                                          n
                                          n
                                                        (3-3)
where
D =   soil profile depth
         n
        K
         hm
      depth of nth layer

      harmonic mean conductivity
If  a  bias or  preference  ; for  a  certain  K  value  is not
indicated  by  statistical analysis  of  field  test results, a
random distribution  of  K for a certain layer or soil region
must be assumed.   In. such qases, it has been shown that the
geometric mean provides  the;best  estimate of the true K  [25,
26, 27]:
K
where K
           gm
K
                   K
                                        Kn)
                                           1/n
                                             (3-4)
       gm
       geometric mean conductivity
                             3-22

-------
The  relationships  between  vertical  hydraulic conductivity
and  the  loading  rates  for  RI  systems  are  discussed   in
Section 5.4.1.

There are many in situ methods available to measure vertical
saturated  conductivity.    For  convenience,   these   may   be
divided  into  methods in the presence  of  and  in the  absence
of a water table.   In addition, there  are several  laboratory
techniques which are used to estimate  saturated conductivity
in  soil  samples  taken  from pits  or  bore  holes.   Either
constant-head or  falling-head  permeameters can be used  for
these estimates.   Detailed test  procedures may be found  in
any  good  soil mechanics  text.   The  main  criticisms of  the
use  of   laboratory  techniques  are  the disturbance  of  the
sample  during collection  by pushing  or driving  a   sampler
into  it  and  the  small  size  of  sample  tested.     These
criticisms are entirely valid.   Nonetheless,  when estimates
of  conductivity  are needed  from  deep  lying strata  that
physically  cannot  be examined in  situ,  then  sampling  and
laboratory measurement may be the only feasible technique.

The only  important  test used below a water table is the pipe
cavity,    or   piezometer  tube   method  [28],   described   in
practical terms  in  reference [29].  This test  is  especially
helpful when  the -soils  below  the water  table are layered,
with substantially  different vertical  conductivities  in each
strata.    In  such  cases, a  separate  test should  be  run  in
each  of   the  layers   of   interest   in  order   to   apply
Equation  3-3.   The  most  important application  occurs when
there is  evidence of vertical gradients that could transport
percolate downward  to lower lying aquifers.

Methods available to measure vertical  saturated conductivity
in a soil region  above,  or  in  the absence of  a water table,
include  the  ring permeameter  [9, 30],  the  gradient-intake
[1,  31],   the   double-tube   [1,  30]   and   the  air-entry
permeameter  [1,  32, 33].   With the development of the  newer
techniques,  the  ring permeameter  method, which requires  an
elaborate  setup  and  uses a  lot  of  water  per test,  is  no
longer  in widespread  use.   The gradient-intake technique  is
primarily used as a site screening  method,  for ranking  the
relative  conductivities of  different  soils.    Conductivity
values  obtained  by this  method  are  considered conservative
as they often prove to be lower than those produced by  other
methods.

In practice, the double-tube and air-entry permeameters have
found favor  and  are used  more  frequently  than  the  other
techniques.   Therefore,  only  these  two methods will   be
discussed.   Enough  information will  be given  here to enable
the  user  to  understand  the   basic   measurement  concepts.
                            3-23

-------
Procedural details  are  covered more  completely  in the  refer-
ences supplied.
    3.5.1
Double-Tube Method
The test  is  run in a hole  augered  to the depth  of  the  soil
layer  whose   vertical  conductivity  is desired.    Certainly
that of  the  most restrictive  layer  is needed as a  minimum.
Additional layers  in the profile  should  be  investigated  to
ensure  proper  characterization.   The  value of  K  which  is
computed  from   double-tube   includes  a  small  horizontal
component but primarily reflects vertical flow.   The  appara-
tus (commercially  available*)  is shown  in Figure 3-12.   To
perform a test, it  is  first necessary to create  a  saturated
zone   of   soil   beneath  the   embedded   tubes.     This   is
accomplished  by  applying  water  through   both  tubes   for
several hours.  Then two sets  of measurements are required:

    1.    Water  level versus time readings for the inner  tube
         with   the   supply  to   this  tube  stopped   while
         maintaining the supply to the outer tube.

    2.    Water  level versus time readings for the inner  tube
         with the supply  to this  tube and to the outer  tube
         stopped.   The  level  in  this  outer tube  is  held
         (closely) the same as that  in the  inner  tube  during
         this second set of readings  by manipulating  a valve
         (C in  Figure 3-12).

The curves  of  water  level , decreases versus time  are  then
plotted to the  same scale and K  is  calculated.   Details  of
the calculation and  curves  needed to obtain  a dimensionless
factor for the  calculation are to be  found  in references  [1,
30] and are supplied by the[manufacturer  of  the equipment.
    3.5.2
Air-Entry Permeameter
The  air-entry permeameter  was  devised to  investigctte  the
significance of flows in the capillary  zone  [32].  Using  the
device as  shown  in Figure  3-13,  the soil-water pressure  at
which  air  entered the  saturated  voids  was approximated.
*Soiltest,Inc.,Evanston, Illinois 60202.  Mention of prop-
rietary  equipment does  not  constitute  endorsement  by  the
U.S. Government.
                            3-2M-

-------
      VALVE (TYPICAL)-

WATER SUPPLY
                 =£
]
                     FIGURE  3-12
      SCHEMATIC OF  DOUBLE-TUBE APPARATUS [l]
                               RESERVOIR
                               SUPPLY VALVE
                               DISK
                                   AIR ESCAPE
                                   VALVE
                         WET FRONT
                     FIGURE  3-13
     SCHEMATIC  OF THE AIR-ENTRY  PERMEAMETER [1,32]
                        3-25

-------
Assuming a  relationship between this value and the pressure
just  above  the  advancing  front  of  a  wetted   zone,   the
conductivity of  a  mass of soil absorbing water to the point
of   saturation  can   be  calculated.     Because   of   the
availability of  research data to indicate that this conduc-
tivity  value  is closely  equal  to  one-half  the saturated
hydraulic conductivity,  a new method of  determining vertical
hydraulic conductivity  at saturation became available.

Although  the method  may appear  to  have  the  limitation of
requiring  several  assumptions,  it compares  favorably with
other  accepted  methods and  has some  distinct  advantages.
The  equipment  is relatively simple;  the test does not. take
much  time;  and, perhaps  most important,  not  much water is
required.   A few liters of water will generally  suffice  for
a single test.

In operation,  water  is  added  through  the supply valve with
the  air  valve  open until the embedded cylinder becomes full
(the  function  of the  disk is to act as  a  splash  plate).  On
filling  the  cylinder,  the|air  valve  is  closed and water is
allowed  to  infiltrate  downward,  the  reservoir  being kept
full.

When  the  wet  front,  Lf,  has   reached  the  desired   depth,
dependent  on  soil texture  and  structure  (see   subsequent
remarks), no more water is added  to the  reservoir.  The drop
in water  level with  time  is measured  in order to calculate
an  intake  rate.   Now  the  supply  valve  is  closed  and  the
pressure on  the  vacuum gage is noted periodically. ! At some
point  it will reach  a maximum  (minimum pressure)  and then
begin  to decrease  again.  This minimum  pressure  corresponds
closely  to  the  air-entry pressure,  Pa, of  the wetted zone
when  corrected  for   gage -height,  G,  and  depth  of   wetted
zone, Lf.

When  the  air-entry   permeameter  is  employed  at  the soil
surface,  it  is  essentially an  infiltrometer and  as such
could  readily be  listed with  the  method  of  Section  3.4.2.
Several  investigators  [32,   33]  have   used  the   method  to
develop  vertical  conductivity  profiles.     It  has  been
suggested  that  digging a trench  with  an inclined bottom,
then  moving  the air-entry  permeameter to  selected  points
along  the  trench bottom  is  a  good  method of  accomplishing
this.

A criticism  of the original technique [32] was based  on  the
suggested  methods  of  defining  the  depth of the  wetted zone
beneath  the  cylinder.   These  called  for digging around  the
bottom of  the  cylinder after completion of the measurements
to locate  the wet front  qr  using a metal rod to probe  the
soil,  attempting to  detect  the  depth  at which  penetration
                             3-26

-------
resistance  increases.   However,  the air-entry  permeameter
was  modified  by adding a fine tensiometer  probe  through the
lid  of  the device.   By setting  the probe to  correspond  to
the  desired  depth of wetted  zone,  Lf (about 15 cm or  6 in.
in sand  and  5 cm or 2 in. in massive  clay) ,  it was possible
to  detect the  arrival of  the wetted  front during,  rather
than  after  operation of the  permeameter.   This modification
also  allows  the method to  be used  in somewhat  wetter  soils
than  those previously  required.

Referring   to    Figure   3-13,    the   vertical    hydraulic
conductivity  of  the  "rewet" zone,  i.e.,  the  zone  being
saturated, is calculated  from Equation 3-5.
         K _ Q
         K ~ A TIT
                                                      (3-5)
where:
Q =  volumetric intake rate through area, A, of
     the permeameter
          H-, =
          lr ~» ~~
         •mm
           G =
          Lf =
     the matric potential of the soil just below
     the wetting zone, assumed to be 0.5 Pa.  It
     is less than atmospheric pressure and there-
     fore a negative quantity in Equation 3-5

     air-entry value, calculated as Pm^n + Lf
     + G; also a negative pressure

     minimum pressure (maximum vacuum) read from
     the vacuum gage after stopping the water
     supply

     height of the vacuum gage above the soil
     surface

     depth of the wetted zone
          Hr =  height of the water level  in  the  reservoir
                above the soil surface

Then, as  stated previously,  the  vertical hydraulic  conduc-
tivity at saturation is assumed to be two  times the value oT
K as calculated from Equation 3-5.

3.6  Ground Water

In  most  land   treatment  systems,  and  especially  for the
higher  rate  systems, .interaction  with the  ground water is
important   and  must   be   considered   carefully   in  the
                            3-27

-------
preliminary  analysis   phase,.      Problems   with  mounding,
drainage, offsite  travel and  ultimate  fate of contaminants
in the  percolate  will have to  be  addressed during both the
analysis and design  phases.   Early recognition of potential
problems and  analysis of mitigating  measures are necessary
for  successful  operation  of  the  system.   This  cannot be
accomplished without competent  field investigation.    Some
key questions to be answered are:

    1.   How deep  beneath the  surface  is the  (undisturbed)
         water table?

    2.   How does  the  natural water table  depth fluctuate
         seasonally?         .                         ;

    3.   How will the  ground  water table  respond  to the
         proposed wastewater loadings?

    4.   In what direction  and how fast will the mixture of
         percolate and  groui-id  water  move  from beneath the
         area of  application?    Is  there  any possibility of
         transport   of    contaminants  to   deeper  potable
         aquifers?

    5.   What will  be  the  quality  of  this mixture  as it
         flows away  from the site boundaries?

    6.   If  any  of   the  conditions  measured  or predicted
         above are found  to ;be unacceptable, what steps can
         be taken to correct;the situation?

    3.6.1     Depth/Hydrostatic  Head

A ground water  table is defined as the contact zone between
the  free ground water  and the  capillary zone.   It is the
level  assumed   by the  water  in  a  hole  extended  a   short
distance below  the  capillary zone.   Ground water  conditions
are regular when  there  is only one ground water  surface and
when  the   hydrostatic   pressure  increases  linearly   with
depth.  Under this condition^  the piezometric pressure  level
is the same as the free ground water  level  regardless of the
depth   below  the  ground  ^ater   table   at  which  it  is
measured.   Referring to Figure 3-14,  the water level in the
"piezometer" would stand at the same level as  the "well" in
this condition.

In contrast to a well,  a piezometer is a  small  diameter open
pipe  driven into  the  soil such  that (theoretically)  there
can be no leakage around  the pipe.  As the  piezometer is not
slotted  or  perforated,   it   can   respond   only  to  the
hydrostatic head  at the  point where its  lower open end is
                             3-28

-------
located.   The basic difference  between  water level measure-
ment  with a  well  and  hydrostatic  head measurement  with a
piezometer is  shown in  Figure  3-14.
              WELL
                                          PIEZOMETER
                          GROUND SURFACE
                    .'.'•..'••'. ' GROUND WATER TABLE

                         FIGURE 3-14
              WELL AND PIEZOMETER INSTALLATIONS
Occasionally  there may  be  one  or more  isolated  bodies  of
water "perched" above  the  main water  table because of lenses
of  impervious strata  that  inhibit or even  prevent  seepage
past  them to  the  main  body of ground  water below.   Other
"irregular" conditions are described  by Figure 3-15.

Reliable  determination  of  either ground water   levels  or
pressures  requires  that  the  hydrostatic  pressures   in  the
bore hole and  the  surrounding soil be equalized.   Attainment
of   stable   levels   may   require   considerable   time   in
impermeable materials.   This is called  hydrostatic time-lag
and  may be  froni  hours  to  days   in  materials of  practical
interest  (K >  107  cm/s).

Two or more piezometers  located together,  but terminating at
different  depths,  can indicate  the presence, direction  and
magnitude  (gradient)  of  components of vertical  flow  if such
exists.   Their use  is indicated  whenever there  is  concern
about-  movement  of  contaminants  downward  to  lower  lying
aquifers.   Figure  3-15,  taken  from  reference  [34],  shows
several observable patterns with explanations.  Descriptions
of  the  proper methods of  installation  of both  observation
wells and piezometers  may  be found in references  [9,  34].
                             ,3-29

-------
     I
 .'i> ' f
         i
       '.v .•
       "A  v '. A
    • :
 THE PIEZOMETERS IN-
 DICATE THAT THE
 GROUND WATER IS GO-
 ING DOWN AND THAT
 THERE IS SOME NATU-
 RAL DRAINAGE.
      I
   ". A /\ - V •

   ^>.'!VA:*.
   • -i •. j> • A • v •  •
   '.••.V . v . . . A .
THE PIEZOMETERS IN-
DICATE A HYDROSTATIC
PRESSURE OR THAT
THERE  IS WATER COM-
ING UP FROM A DEEP-
ER STRATA.
THE PIEZOMETERS IN-
DICATE A HYDROSTATIC
PRESSURE IN A STRAT-
UM AND THAT WATER  IS
BEING FORCED BOTH  UP
AND DOWN FROM THE
STRATUM
                                                           '.'• I- •
                                  THE PIEZOMETERS IN -
                                  DICATE THAT GROUND
                                  WATER IS MOVING INTO
                                  A STRATUM AND GOING
                                  OUT OF THE AREA.
                         FIGURE  3-15
          VERTICAL FLOWS  INDICATED BY PIEZOMETERS [34]
    3.6.2
Flow
Exact  mathematical  description  of  flows  in  the saturated
zones  beneath  and  adjacent  to  (usually downgradient)  land
treatment systems  is  a practical  impossibility.   However,
for the  majority of  cases  the possession of sufficient  field
data   will   allow   an  application   of   Darcy's  equation
(Equation 3-1).    Answers  can  thus  be  obtained  which  are
satisfactory for  making  design  decisions.    In particular,
there  are questions which  recur  for each  proposed project,
and which may be approachedi in the  manner suggested.

    1.    What  volume  of  native  ground  water  flows  beneath
          the proposed  site for dilution  of  percolate?   This
          is  a direct application of  Equation 3-1.  The  width
          of   the  site  measured normal  to  the  ground  water
          flow  lines times  the aquifer thickness equals  the
          cross-sectional   area  used  to  compute  the  total
          flow.

    2.    What  is   the   mean  travel  time  between  points  of
          entry of percolate into the  ground water and poten-
          tial  points  of   discharge  or  withdrawal?   Again,
          Equation   3-1  is  ;used   to  compute   the   flux,   q.
          Dividing   the   flux   by   the   aquifer   porosity
          (Figure 3-3)   gives   an   average    ground    water
          velocity.   Travel time  is computed  as the distance
          between  the two points  of interest  (they must both
          lie on the same  flow line)  divided  by the  average
          velocity.
                              3-30

-------
    3.   What   changes   in   hydraulic   gradient    (mound
         configuration)  will  be  required  to  convey  the
         proposed  quantity  of  percolate away  from beneath
         the area of application?  Methods of answering this
         question are presented in Section 5.7.2.

The '  field  data  and  hydrogeologic   estimates   required  to
answer these questions include:

    1.   Geometry  of  the   flow  system,  including  but  not
         limited to

         a.   Depth to ground water

         b.   Depth  to  impermeable  barrier;  generally taken
              to   be  .any  layer  which   has   a  hydraulic
              conductivity  less  than  10%  of  that of  the
              overlying deposits [35].

         c.   Geometry of the recharge  (application) area.

    2.   Hydraulic gradient -  computed  from water levels in
         several observation wells (assuming only horizontal
         flow), knowing distances between wells.

    3.   Specific  yield  (see  Section 3.3.3).   In some areas
         of the United  States,  the  SCS has investigated the
         soil profiles  sufficiently  to  provide  an estimate
         of specific yield for a particular site [5].

    4.   Hydraulic    conductivity    in   the    horizontal
         direction.  Field  measurement  of this parameter by
         the auger-hole  method is covered  in  the following
         section.

         3.6.2.1   Horizontal Hydraulic Conductivity

Horizontal  conductivity  cannot be assumed  from a knowledge
of vertical conductivity  (Section   3.5).   In  field soils,
isotropic  conditions  are rarely encountered,  although they
are   frequently   assumed  for  the   sake  of   convenience.
"Apparent"   anisotropic   conductivity   often   occurs   in
unconsolidated media because of interbedding of fine-grained
and  coarse-grained  materials  within  the  profile.    Such
interbedding restricts vertical  flow much more than it does
lateral  flow   [25].   Although  the  interbedding represents
nonhomogeneity, rather  than anisotropy,  its effects on the
conductivity of a large sample  of   aquifer material  may be
approximated by  treating the  "aquifer"  as  homogeneous  but
anisotropic.  A considerable  amount  of data is available on
the  calculated  or measured  relationships  between vertical
                             3-31

-------
and   horizontal  permeability   for   specific  sites.     The
possible  spread of  ratios  is indicated  in Table 3-5, which
is  based  on  field  measurement^ in  glacial outwash deposits
(Sites  1-5)  [36]  and in a ' river bed  (Site 6)'  [37],,   Both
authors  claim,  with  justification,  that the reported values
would  not  likely  be observed  in  any  laboratory tests with
small quantities of disturbed aquifer material.

                          TABLE  3-5
              MEASURED RATIOS OF HORIZONTAL TO
                VERTICAL CONDUCTIVITY [36,  37]
                 Effective
                 horizontal
                permeability,
           Site     Kh, m/d    Kh/Kv
Remarks
1
2
3
4
5
6



42
75
56
100
72
72,



2.0
2.0
4. 4
7.0
20.0
10.0



Silty
—
—
Gravelly
Near terminal moraine
Irregular succession of
sand and gravel layers ,
(from K measurements in
field)
                     86      16.0   (From analysis of
                                  recharge flow system)
It  is  apparent that  if  accurate  information regarding hori-
zontal  conductivity   is required   for  an  analysis,  field
measurements  will be necessary.  Of the many field measure-
ment techniques  available,  the most useful is the auger hole
technique  [38] .   Details  of the test technique  may also be
found  in  [1,  9,  30,  34].   Although auger hole measurements
are certainly influenced by  the  vertical  component of flow,
studies  have  demonstrated  that  the  technique  primarily
measures the  horizontal  component [39].   A definition sketch
of  the measurement  system  is  shown in  Figure 3-16  and the
experimental  setup  is shown  in Figure  3-17.   The technique
is  based  on  the fact  that  if the  hole  extends  below the
water  table  and water  is  quickly removed  from the hole (by
bailing  or   pumping),   the;  hole  will   refill  at  a  rate
determined by the conductivity of   the  soil,  the dimensions
of the hole,  and the height, of water  in the hole.  With the
aid of either formulas or graphs,  the conductivity is calcu-
lated  from  measured  rates  of  rise  in the hole.    The total
inflow into the  hole  should !be sufficiently small during the
period of  measurement to permit  calculation  of  the conduc-
tivity  based  on  an  "average"  hydraulic  head.   This  is
usually the case.
                             3-32

-------
                                   SOIL SURFACE
                          2a
                                   WATER TABU
                                 Ay in
                    FIGURE 3-16
   DEFINITION  SKETCH  FOR AUGER-HOLE TECHNIQUE
            DOUBLE-ACTING
           DIAPHRAGM PUMP
EXHAUST HOSE
                                      MEASURING POINT
                                        -STANDARD
///////////////////// ^
/
>
SUC-TION HOSE 	 _/f
^Tn »
/
/
TAPE AND /
5cm FLOAT 	 ^
/:
y
/"
/
/
\






^.



"S





i



r1
,
\
^v
\
\
\
V
r
\
*-
\
\
\
\h-\\\\\\\

II
V
^^ — STATIC

^
^ 	 FINISH

^ 	 START T



                     FIGURE 3-17
   EXPERIMENTAL SETUP  FOR AUGER-HOLE  TECHNIQUE
                         3-33

-------
 In  the  formulas and graphs that have been  derived,  the  soil
 is  assumed  to be  homogeneous and  isotropic.   However,  a
 modification    of    the   basic   technique    [39]    allows
 determination  of  the horizontal and vertical  components  (Kh
 and KV  in  anisotropic  soils  by combining  auger hole  measure-
 ments with piezometer  measurements  at  the  same  depth.    If
 the auger  hole terminates at  (or in)  an impermeable;layer,
 the  following  equation applies  (refer  to'  Figure  3-16  for
 symbols):
= 523,000a2
                                    At
                                                    (3-6)
where      a = auger  hole  radius, m

          At = time for water  to  rise  y,  s

          K^ = horizontal  conductivity, m/d

       y0/yj_ = depths defined  in  Figure 3-16,  any  units,
               usually cm   l
If  an  impermeable  layer  is encountered  at  a  great,  depth
below the bottom of the auger hole, the  equation  becomes:
            _/i,o45,ooo da2
            -    (2d + a)
                                  (3-7)
where  d  =  depth of auger hole, m

Charts  for  both cases  are  available  in  references   [29,
34],   An alternative  formula,  claimed to  be slightly  more
accurate, has  been  developed  [40].   This equation employs a
table of coefficients to account for depth of  impermeable or
of very permeable material below the bottom  of the hole.

There are several other techniques for evaluating horizontal
conductivity in  the  presence  of a  water table.  Slug tests,
such as described in reference  [41] can be used to calculate
Ktj from  the  Thiem equation after observing the rate of  rise
or water  in  a well  following an instantaneous removal  of a
volume  of  water  to  create a  hydraulic gradient.   Pumping
tests, which  are already  familiar to  many engineers, would
certainly provide a meaningful  estimate.    A comprehensive
discussion of  pumping  tests>  as well  as  other ground water
problems  is  presented in  reference  [42] ;  example  problems
                             3-34.

-------
and  tables  of  the mathematical functions needed  to  evaluate
conductivity from drawdown measurements  are  also  presented.

There are some  limitations to  full-scale pumping  tests.   The
first is the expense  involved  in drilling  and  installation.
Thus,  if a  well is  not already  located  on  the site,  the
•pumping test technique would probably  not be considered.   If
an  existing production well  fulfills  the conditions  needed
for  the technique to  be valid,  it  should probably be used to
obtain  an  estimate.    However,  this  estimate  may  still
require  modification  through  the  use  of   supplementary
"point" determinations, especially if  the site  is very large
or  if the soils  are quite heterogeneous.

Measurement  of  horizontal conductivity  may  occasionally  be
necessary in  the absence of a  water table.   A typical  case
might  involve  the  presence  of  a  caliche  layer  or  other
hardpan  formation . near  the  surface.    If  the  layer  was
restrictive  enough  to vertical flow,  a  perched water  table
would result upon application  of wastewater.   In  such  cases,
the  mound height analysis described in  Section 5.7.2  should
be  used  to  determine whether  perching  would  be a  problem.
Although  mounding calculations  are p'resented  in Chapter  5
(dealing with  RI),  it  is quite possible  that mounding  may
occur beneath  SR systems as well.   The  user of  this  manual
should be aware of  this possibility.  The analysis  requires
an   estimate  of  the  horizontal  conductivity.    Either  a
modified version of  the  double-tube technique described  in
Section  3.5.1  [31]  or the shallow well  pump-in test  [1,  9,
30]  can  be  used  to  estimate  K^.   The  latter  of these  two
testing methods  is,  in principle, the reverse of  the  auger-
hole test.

         3.6.2.2   Percolate/Ground  Water Mixing

An  analysis of  the mixing  of  percolate with native  ground
water  is needed for  SR or  RI  systems that  discharge  to
ground water if  the quality of  this  mixture  as  it  flows  away
from the   site  boundaries   is  to  be  determined.     The
concentration  of any constituent  in this  mixture  can  be
calculated  as follows:
                                                      (3-8)
where  Cmix = concentration of constituent  in mixture

         CD = concentration of constituent  in percolate
                             3-35

-------
          Q  = flow of percolate
           tr                >

         Cgw = concentration of constituent in ground water

         QqW = flow of ground  water


 The  flow of ground water can  be  calculated  from Darcy's Law
 (Equation  3-1)  if  the  gradient  and  horizontal  hydraulic
 conductivity are known.   Thi^s is  not the entire ground water
 flow,   but   only  the   flow  within   the   mixing   depth.
 Relationships of  the percolate  flow  and concentrations  of
 constituents are discussed  in Chapters  4 and 5. Equation 3-8
 is  valid if  there  is complete mixing  between  the  percolate
 and  the _ native  ground  water.    This  is  usually  not  the
 case.   Mixing in the  vertical direction may  be  substantially
 less than mixing in the  horizontal direction.

 An  alternative  approach  to estimating  the  initial  dilution
 is  to  relate the  diameter of the mound developed by  the
 percolate to  the  diameter ;of the  application area.    This
 ratio  has been  estimated to  be 2.5 to 3.0   [43, 44].   This
 ratio  indicates  the relative1  spread of  the percolate and can
 be  used  to  relate  the mixing   of  percolate  with  ground
 water.   Thus,  an upper  limit  of 3  for the dilution  ratio can
 be  used when  ground  water If low   is substantially  (5  to  10
 times)  more than  the percolate flow.   If the  ground  water
 flow  is  less  than 3  times the percolate flow, the  actual
 ground water flow  should  be used  in Equation 3-8.
    3.6.3
Ground Water Quality
It is recommended that where  a water  table  is  known  to  exist
that  could  possibly  be   impacted   by   the   project,   that
baseline  ground  water  quality  data  be  collected.    The
details  of  number,  location, depth,  etc. of  sampling  wells
are best  left  until after a  preliminary  hydrogeologic  study
of the  site has been  completed.   Then following  reasonably
well established guidelines  [23, 45,  46,  47],  sampling  wells
may be designed in  something  approaching  an optimum  manner.

The parameters that should be measured in samples  taken from
the ground  water  are  those  specified under  the "National
Interim  Primary  Drinking  Water  Regulations"   [48] .,    An
exception  is  made  for  nondrinking water aquifers or  where
more stringent state regulations apply.

3.7  Soil Chemical  Properties

The chemical  composition  of the  soil  is  the major factor
affecting plant growth  and a significant determining factor
                             3-36

-------
in the  capacity  of the soil  to  renovate wastewater.  There
are  16  elements  known  to be  essential  for  crop  growth.
Three  of   these—nitrogen, phosphorus,   and  potassium—are
deficient  in  many  soils.    Secondary  and  micronutrient
deficiencies  are  found  less  often  with sulfur,  zinc,  and
boron being the most common.  Soil pH and salinity can limit
crop  growth   and   sodium  can  reduce  soil  permeability.
Chemical properties should be determined prior to design to
evaluate the  capacity of  the soil to support  plant growth
and  to  renovate  wastewater.    Soils should  be  monitored
during  operation  to  avoid  detrimental  changes   in  soil
chemistry.
    3.7.1
Interpretation of Soil Chemical Tests
Several  chemical  properties,  having  nothing  directly to do
with  nutrient  status, are  nonetheless important.   Soil pH
has  a significant  influence  on  the solubility  of various
compounds, the activities of various microorganisms, and the
bonding  of  ions to  exchange  sites.   Relative  to this last
phenomenon,   soil   clays   and    organic   matter    (known
collectively   as    the   soil   colloids),   are   'negatively
charged.   Thus, they  are able  to adsorb  cations  from the
soil  solution.    Cations adsorbed in  this way  are  called
exchangeable cations.  They can be  replaced by other cations
from  the  soil  solution  without  appreciably  altering  the
structure   of   the   soil  colloids.     The   quantity  of
exchangeable cations that a  particular  soil  can adsorb is
known  as cation exchange capacity  (CEC)  and is measured in
terms  of  milliequivalents  per  100  grams  (meq/100  g)  of
soil.    The  percentage  of  the  CEC  that  is occupied  by a
particular cation  is called  the percent saturation for that
cation.    The  sum  of the  exchangeable  Na,  K,  Ca  and  Mg
expressed as a  percentage of  the CEC is called percent base
saturation.

There  are optimum  ranges for  percent base  saturation for
various  crop and  soil  type  combinations.   Also,  for a given
percent  base  saturation,  it is desirable  that Ca and Mg be
the  dominant cations  rather  than  K and  (especially)  Na.
High  percentages  of  the alkali  metals,  in  particular Na,
will  create severe problems in many fine-texture  soils.  The
exchangeable  sodium percentage  (ESP) should  be  kept below
15%  (Section 4.9.1.4).    It  is  important to  realize that
regardless of the  cation distribution in a natural soil, it
can   be   altered   readily  as   a   result  of  agricultural
practices.  Both the quality of the irrigation water and the
use  of soil  amendments,  such as  lime or gypsum,  can  change
the distribution of  exchangeable cations.
                             3-37

-------
 Another  chemical   property  affecting   plant  growth   is
 salinity/  the concentration pf soluble ionic substances.   It
 is salinity in the soil solution in the root zone that is of
 primary  interest.     Unfortunately,   there   is  no  simple
 relation between this quantity and the salinity of the irri-
 gation  water, the salt balance being complicated by moisture
 transfers  through  evapotranspiration and  deep percolation.
 The  diagnostic tool usually employed is a check on the elec-
 trical  conductivity  (EC)  of  the  irrigation  water and  the
 soil solution.  Guidelines exist  for various  types of crops
 according  to their salt tolerance.  Procedures for computing
 the   deep  percolation  (leaching   requirement)   needed   to
 control root zone salinity are given in references  [9, 29].

 Because of  the  variable  nature  of  the  soil,  few  standard
 procedures   for   chemical  analysis   of   soil  have   been
 developed.    Several  references  that  describe  analytical
 methods are available  [49,  50,  51].  A  complete  discussion
 of  analytical methods and interpretation  of results  for  the
 purpose of  evaluating the soil nutrient  status is  presented
 in  reference  [52].   The  significance of  the  major chemical
 properties  is summarized  in Table  3-6.
    3.7.2
Phosphorus Adsorption Test
Adsorption  isotherms  for  phosphorus  can  be  developed  to
predict  the  removal of phosphorus  by the soil.  Samples  of
soil  are  taken   into  the   laboratory  and   are   added   to
solutions  containing  known  concentrations  of phosphorus.
Concentrations  normally  range from 1 to 30 mg/L.   After  the
soil  is  mixed  into  the  solutions  and  allowed to  come  into
equilibrium  for a period of'time  (up to several days),  the
solution  is   filtered   and  the  filtrate  is  tested   for
phosphorus.   The  difference1 between the  initial   and  final
solution concentrations  is  the amount  adsorbed for a  given
time.  Details  of  the test are available  in reference  [53].

A procedure  for using adsorption  isotherm  data to estimate
phosphorus  retention  by soils  is  suggested  in   reference
[47] .     An   important   consideration   discussed   is   the
possibility of  slow reactions between phosphorus and cations
present  in  the  soil which  |may  "free  'up"  previously used
adsorption sites  for  additional  phosphorus retention.  Cal-
culations involving  adsorption isotherm  data,  which  ignore
these reactions, greatly underestimate  phosphorus retention.
                             3-38

-------
                                TABLE 3-6
               INTERPRETATION OF  SOIL  CHEMICAL  TESTS
            Test result
                                     Interpretation
       pH of saturated soil paste
         <4.2
         5.2-5.5
         5.5-8.4
         >8.4

       CEC, meq/100 g
         1-10
         12-20
         >20
       Exchangeable cations,
       % of CEC
         Sodium
         Calcium
         Potassium
       ESP, % of CEC
         <5
         >10
         >20
       EC, mmhos/cm at 25°
       of saturation extract
         <2
         2-4
         4-8
         8-16
Too acid for most crops to do well
Suitable for acid-tolerant crops
Suitable for most crops
Too alkaline for most crops, indicates ai
possible sodium problem

Sandy soils (limited adsorption)
Silt loam (moderate adsorption)
Clay and organic soils (high adsorption)

Desirable range
±5
60-70
5-10

Satisfactory
Reduced permeability in fine-textured soils
Reduced permeability in coarse-textured soils
No salinity problems
Restricts growth of very salt-sensitive crops
Restricts growth of many crops
Restricts growth of all but salt-tolerant crops
Only a few very salt-tolerant crops make
satisfactory yields .
3.8   References
 1.  Bouwer,  H.     Groundwater  Hydrology.    McGraw-Hill  Book
     Co.   New  York.   1978.
 2.  Freeze,  R.A., and  J.A.  Cherry.   Groundwater.    Prentice-
     Hall.   Englewood  Cliffs, N.J.   1979.
 3.  Taylor,  S.A.   and   Q.L.  Ashcroft.    Physical  Edaphology.
     W.H.  Freeman  & Co.   San Francisco.   1972.
 4.  Richards,   L.A.    Physical  Condition  of  Water  in   Soil.
     In:    Methods of  Soil  Analysis.     Part  1,  Agronomy  9.
     Black,  C.A.   (ed.).     Madison,  Wisconsin.      American
     Society of Agronomy,  Inc.   1965.  pp. 131-136.
                                   3-39

-------
  5.  O'Neal,  A.M.   A Key  fop  Evaluating  Soil  Permeability by
     Means  of  Certain  Field  Clues.    In:   Proceedings  Soil
     Science  Society  of  America.   16:312-315.   1952.

  6.  Jarrett,  A.R. and  D.Di,  Fritton.    Effect of  Entrapped
     Soil  Air  on  Infiltration.    Transcripts  of  American
     Society  of Agricultural Engineers.   21:901-906.   1978.

  7.  Parr, J.F. and A.R.  Be'rtrand.   Water  Infiltration  into
     Soils.   In:  Advances  in  Agronomy.  Norman,  A.G.,  (ed.).
     New York,  Academic  Press.   1960.   pp.  311-363.

  8.  Todd,  O.K.    Groundwater.    In:    Handbook  of  Applied
     Hydrology.  Chow, V.T.  (ed.).  McGraw-Hill Book  Co.   New
     York.  1964.

  9.  Drainage   Manual.    U.S.  Department  of   the  Interior,
     Bureau of  Reclamation.  1st  Edition.   1978.

10.  Childs,  E.G.   An Introduction  to  the Physical  Basis of
     Soil  Water  Phenomena.;   John  Wiley  and   Sons,   Ltd.
     London.  1969.

11.  Duke, H.R.   Capillary Properties of  Soils - Influence
     upon  Specific  Yield.    Transcripts   of   the   American
     Society of Agricultural Engineers.   15:688-691.   1972.

12.  Klute, A.  Soil Water  Flow Theory  and  its  Application in
     Field Situations.   In:  Field Soil Water Regime.   Special
     Publication, Series No. 5.  Madison, Wise., Soil Science
     Society of America.   1973.  pp. 9-35.

13.  Kirkham,  D.  and W.L.  Powers.   Advanced  Soil  Physics.
     New York, Wiley-Interscience.  1972.   534  p.

14.  Burgy, R.H. and J.N. Luthin.  A Test of the Single - and
     Double -  Ring  Types of1 Infiltrometers.   Transcripts of
    American Geophysical Union.  37:189-191. 1956.

15. Manual  of  Septic  Tank! Practice.    U.S.   Public Health
    Service.  Publication No. 526.  U.S. Government  Printing
    Office.   1969. 85 p.

16. Wallace, A.T.,  et   al.   Rapid Infiltration  Disposal of
    Kraft Mill Effluent.  In: Proceedings of the 30th Indus-
    trial  Waste  Conference,  Purdue  University,   Indiana.
    1975.
                             3-40

-------
17. Abele, G., et al.  Infiltration Characteristics of Soils
    at Apple  Valley, Minn.;  Clarence Cannon  Dam,  Mo.;  and
    Deer  Creek  Lake, Ohio,  Land Treatment  Sites.   Special
    Report 80-36.  U.S.  Army Cold Regions Research and Engi-
    neering Laboratory,  Hanover, N.H.  1980.   52 p.

18. U.S.   Army   Corps  of  Engineers.     Simplified  Field
    Procedures for Determining  Vertical  Moisture Flow Rates
    in Medium  to Fine  Textured Soils.   Engineer Technical
    Letter.  1980.  21 p.

19. Bouwer, H.   Cylinder Infiltrometers.   In: Monograph on
    Methods of Soil Analysis.  American Society of Agronomy.
    (In press).   1981.

20. Haise, H.R.,  et  al.   The Use of Cylinder  Infiltrometers
    to  Determine the  Intake  Characteristics  of  Irrigated
    Soils.    U.S.  Dept.   of  Agriculture,   Agric.  Research
    Service.   Public No. 41-7.  1956.

21. Hills,    R.C.       Lateral    Flow    Under    Cylinder
    Infiltrometers.      A  Graphical  Correction  Procedure.
    journal of Hydrology.  13:153-162.  1971.

22. Youngs,  E.G.   Two-   and  Three-Dimensional  Infiltration:
    Seepage  from   Irrigation   Channels  and   Infiltrometer
    Rings.  Journal of Hydrology.  15:301-315.  1972.

23. Parizek,   R.R.    Site  Selection Criteria for Wastewater
    Disposal   -   Soils   and   Hydrogeologic  Considerations.
    In:   Recycling  Treated Municipal  Wastewater and Sludge
    Through  Forest   and  Cropland.    Sopper,  W.E.  and  L.T.
    Kardo  (eds.).    Pennsylvania  State  University  press.
    1973.  pp. 95-147.

24. Tovey, R. and C.H.  Pair.   A Method  for Measuring Water
    Intake  Rate  Into  Soil  for  Sprinkler   Design.    in:
    Proceedings  of   the  Sprinkler  Irrigation  Assoc.   Open
    Technical Conference.  1963.  pp. 109-118.

25. Bouwer, H.   Planning  and Interpreting Soil Permeability
    Measurements.    In:    Proceedings  American  Society  of
    Civil Engineers.  Journal of the Irrigation and Drainage
    Division.  28:IRS:391-402.  1969.

26. Rogowski,  A.S.    Watershed  Physics:   Soil  Variability
    Criteria.    Water  Resources  Research.    8:1015-1023.
    1972.

27. Nielson,  D.R., J.W.  Biggar and K.T. Erb.   Spatial Varia-
    bility   of   Field-Measured   Soil-Water   Properties.
    Hilgardia.  42:215-259.  1973.

-------
 28. Frevert,  R.K.  and  D.  Kirkham.    A  Field  Method  for
     Measuring   the   Permeability  of  Soil  Below  a   Water
     Table.    In:  Proceedings  of  Highway  Research   Board.
     48:433-422.  1948.

 29. Luthin,  J.N.    Drainage  Engineering,  Huntington,  New
     York,  R.E. Krieger Publ. Co.  First edition - reprinted
     with corrections.  1973.  250 p.

 30. Boersma, L.  Field Measurement of Hydraulic Conductivity
     Above a Water Table. In: Methods of Soil Analysis.  Part
     1, Agronomy  9.   Black,  C.A.  (ed).   Madison, Wisconsin.
     American Society of Agronomy, Inc. 1965.  pp. 234-252.

 31. Bouwer, H.  and  R.C.  Rice.   Modified  Tube  Diameters  for
     the  Double-Tube  Apparatus.    in:    Proceedings  Soil
     Science Society of America.  31:437-439.  1967

 32. Bouwer, H.   Rapid Field Measurement of  Air Entry Value
     and Hydraulic Conductivity  of  Soil  as  Significant Para-
     meters   in  Flow  System  Analysis.     Water  Resources
     Research.   2:729-738.   1966.

 33. Topp,   G.C.   and   M.R.   Binns.    Field  Measurements  of
     Hydraulic  Conductivity  with a Modified  Air-Entry Permea-
     meter.    Canadian  Journal  Soil   Science.    56:139-147
     1976.

 34.  Drainage   of   Agricultural   Land.      U.S.   Dept.   of
     Agriculture   -   Soil    Conservation   Service   National
     Engineering  Handbook.   Section 16.   May 1971.

 35.  Van  Beers,  W.F.J.   The  Auger Hole  Method -  A  Field
     Measurement  of  the Hydraulic Conductivity of Soil  Below
     a   Water    Table.       ;Wageningen,   The   Netherlands.
     International    Inst.     for   Land   Reclamation   and
     Improvement, Bulletin 1.   1958.

 36.  Weeks,  E.P.   Determining   the  Ratio   of  Horizontal  to
     Vertical Permeability  by Aquifer-Test  Analysis.    Water
     Resources Research.  5:196-214.  1969.

37.  Bouwer, H.   Ground Water Recharge Design for Renovating
    Waste Water.   in:   Proceedings of  American Society  of
    Civil  Engineers,   journal of  the  Sanitary  Engineering
    Division.  96:SA 1:59-73.  1970.

38. Van Bavel, C.H.M.  and D. Kirkham.   Field Measurement  of
    Soil Permeability  Using Auger Holes.   In:   Proceedings
    Soil Science Society of America.  13:90-96.   1948.
                            3-42

-------
39. Maasland,  M.   Measurement  of  Hydraulic Conductivity by
    the  Auger   Hole   Method  in  Anisotropic  Soil.    In:
    Proceedings  Soil  Science  Society  of  America.    19:379-
    388.  1955.

40. Boast,   C.W.   and   D.   Kirkham.    Auger  Hole   Seepage
    Theory.    In:    Proceedings  Soil  Science   Society  of
    America.  35:365-373.  1971.

41. Bouwer,  H.  and R.C. Rice.   A  Slug Test for  Determining
    Hydraulic Conductivity of  Unconfined Aquifers with Com-
    pletely or Partially Penetrating Wells.  Water Resources
    Research.  12:423-428.   1976.

42. Glover,  R.E.    Ground-Water Movement.   U.S.  Bureau  of
    Reclamation,  Water  Resources.    Technical   Publication
    Engineering Monograph No. 31.   1964.

43. Singh,  R.   Prediction of Mound Geometry Under Recharge
    Basins.  Water Resources Research.  12:775-780.   1976.

44. Marino,  M.A.    Artificial  Groundwater  Recharge,  I.
    Circular-Recharging   Area.      journal   of   Hydrology.
    25:201-208.  1975.

45. Smith,  J.L.  et  al.   Mass  Balance Monitoring  of Land
    Application Sites  for Wastewater Residuals.   Transcript
    of American  Society of  Agricultural Engineers.   20:309-
    312.  1977.

46. Blakeslee, P.   Monitoring  Considerations  for Municipal
    Wastewater  Effluent  and   Sludge   Application   to  the
    Land.    In:   Proceedings  of  the   joint Conference  on
    Recycling  Municipal  Sludges  and  Effluents  on  Land.
    Champaign, Illinois.  1973.  pp. 183-198.

47. Loehr, R.C., et al.  Land Application of Wastes,  Vols. I
    & II.  New York.  Van Nostrand Reinhold  Co.   1979.

48. National  Interim  Primary  Drinking Water  Regulations.
    U.S.  Environmental  Protection  Agency,   Office  of Water
    Supply.  EPA-570/9-76-003.  1976.  159 p.

49. Black,  C.A.  (ed.).   Methods  of Soil  Analysis,  Part  2:
    Chemical  and  Microbiological  Properties.    Agronomy  9,
    American Society of Agronomy.  Madison.  1965.

50. Richards,  L.A.  (ed.).    Diagnosis  and  Improvement  of
    Saline and Alkali Soil.   Agricultural Handbook 60.  U.S.
    Department of Agriculture.  1954.
                             3-143

-------
51. Jackson,  M.L.    Soil  Chemical  Analysis
    Cliffs, N.J. Prentice-Hall, Inc.  1958.
                                                   Englewood
52. Walsh, L.M.  and. J.D. Beaton,  (eds.).   Soil Testing and
    Plant  Analysis.    Madison,  Soil  Science  Society  of
    America.   1973.

53. Fox,  R. L.   and   E.J.   Kamprath.     Phosphate  Sorption
    Isotherms for  Evaluating the Phosphate  Requirements of
    Soil.       in:   Proceedings  Soil  Science  Society  of
    America.   34:902-906.  1970.

-------
                           CHAPTER 4

                  SLOW RATE PROCESS DESIGN
4.1  Introduction

The key elements in the design of slow rate (SR) systems are
indicated in  Figure  4-1.   Important  features  are:   (1) the
iterative  nature  of  the  procedure,  and  (2)  the   input
information that must be obtained for detailed design.

Determining  the  design hydraulic  loading rate  is  the most
important step  in  process design because  this parameter is
used  to  determine  the  land  area  required   for  the  SR
system.  The  design  hydraulic loading rate is controlled by
either  soil  permeability or nitrogen  limits  for  typical
municipal wastewater.   Crop  selection  is  usually the  first
design step  because  preapplication  treatment,  hydraulic and
nitrogen loading rates, and storage depend to  some extent on
the  crop.     preapplication   treatment  selection  usually
precedes determination  of hydraulic loading rate 'because it
can  affect   the   wastewater   nitrogen  concentration, and,
therefore, the nitrogen loading.

4.2  Process Performance

The  mechanisms  responsible   for  treatment  and  removal  of
wastewater constituents such  as BOD, suspended  solids  (SS),
nitrogen,  phosphorus,  trace  elements,  microorganisms, and
trace  organics are  discussed briefly.   Levels  of removal
achieved  at  various  SR   sites  are  included  to  show how
removals  are  affected by  loading  rates,  crop,  and soil
characteristics.    Chapter   9  contains  discussion  on the
health and environmental  effects of  these constituents.
    4.2.1
BOD and Suspended Solids Removal
BOD and SS are removed by  filtration  and  bacterial  action  as
the applied wastewater percolates  through the  soil.   BOD and
SS  are normally  reduced  to  concentrations of  less than  2
mg/L  and  less  than  1 mg/L,  respectively,  following 1.5  m
(5 ft)  of  percolation.   Typical loading  rates of BOD and  SS
for  municipal  wastewater  SR  systems,  regardless  of  the
degree  of  preapplication  treatment,  are  far below  the
loading  rates  at   which   performance  is  affected   (see
Section  2.2.1.1).    Thus,  loading rates  for BOD and SS are
normally  not  a  concerninthedesignof  SR   systems^
 RemovalsolBODachieved
 presented  in  Table  4-1.
                at  five  selected  sites  a/re

-------
WASTEWATER
CHAHACTERISTICS
(Section  2.2.1 ,1)
                        SITE  CHARACTERISTICS
                        (Sections 2.2.1.3,
                        2.3.1. t Chapttr 3)
WATER  OUALITY
REQUIBEiENTS
(Section 2.2.1.2)
                             PROCESS
                             PERFORMANCE
                             (Suction  4.2)
PREAPPL I CATION
TREATMENT
(Section 4.4)
                            CROP SELECTION
                            (Sic.tion  4.3)
                         LOADING RATES
                          •SOIL; PERMEABILITY
                          •NITROGEN LIMITS
                         (Section 4.3)
STORAGE
(Section 4.B)
                             FIELD AREA
                             (Section 4.5)
                                 1
'


DRAINAGE AND
RUNOFF CONTROL

DISTRIBUTION
(Section 4.7)
f

4 	 1 DISCHARGE
                                 I
1 SURFACE WATER M 	 1 SUBSURFACE

h.
w-
I
SYSTEM MONITORING
, (Section 4.10)



CROP MANAGEMENT
(Section 4.9)


                            FIGURE  4-1
                SLOW RATE  DESIGN  PROCEDURE
                                 4-2

-------
                          TABLE 4-1
                      BOD REMOVAL  DATA
                FOR SELECTED SR SYSTEMS [1-5]



Location
Dickinson,
North Dakota

Hanover,
New Hampshire


Muskegon,
Michigan
Ro swell,
New Mexico
San Angelo,
Texas
Annual
waste-
water
loading
rate ,
cm/yr
140


130-780


130-260

80

290

BOD
Concentration Concentration
in applied in treated Sampling
Surface wastewater, water, Removal, depth,
soil mg/L mg/L % m
Sandy loams 42 <1 >98 <5
and loamy
sands
Sandy loam 40-92 0.9-1.7 96-98 • 1.5
and silt
loam
Sands and 24 1.3 94 4
loamy sands
Silty clay 42 <1 >98 <30
loams
Clay and 89 0.7 99 2.1
clay loam
  Note: See Appendix G for metric conversions.
    4.2.2
Nitrogen
For  SR  systems  located  above  potable  aquifers,  nitrogen
concentration  in percolate  must be  low  enough that  ground
water  quality  at the  project  boundary * can  meet  drinking
water nitrate  standards.   Nitrogen removal mechanisms  at SR
systems  include crop uptake,  nitrification-denitrification,
ammonia  volatilization,  and storage  in the soil.   Percolate
nitrogen  concentrations less  than 10  mg/L  can be  achieved
with SR  systems if  the  nitrogen loading  rate  is  maintained
within the  combined  removal rates of these mechanisms.   The
nitrogen  removal  rates and  loading  rate  are,  therefore,
important  design  parameters.    Percolate  nitrogen  levels
achieved at selected SR sites  are  given in Table 4-2.

Crop  uptake   is  normally  the   primary  nitrogen  removal
mechanism  operating  in SR  systems.   The  amount of nitrogen
removed  by crop harvest depends on  the nitrogen  content of
the  crop and  the crop  yield.   Annual  nitrogen  uptake  rates
for  specific  crops  are  given in  Section  4.3.2.1.   Maximum
nitrogen removal can be achieved by  selecting  crops or crop
combinations with the highest  nitrogen  uptake  potential.

-------
                           TABLE  4-2
              NITROGEN  REMOVAL DATA FOR  SELECTED
                      SR SYSTEMS  [1, 3-8]
                          Total nitrogen
               Total nitrogen concentration
               concentration   in percolate
                in applied    or;affected
                                                  Total nitrogen
                                                  concentration
                                            Sampling in background
Location
Dickinson,
North Dakota
Hanover,
New Hampshire
Helen,
Georgia3
Roswell,
New Mexico
San Angelo,
Texas
wastewater,
mg/L as N
11.8
27-28
18.0
66.2
35.4
ground water, Removal,
mg/L as N %
3.
7.
3.
10.
6.
9
3
5
7
1
67
72
80
84
83
depth, ground water,
m mg/L as N
11 . 1.9
1.5 —
1.2 . 0..17
30 2.2 ' "
10 —
    a. Forest system.  All others are agricultural systems.
Nitrogen   loss   by   denitrification   depends   on   several
environmental  factors  including  the  oxygen  level  in  the
soil.   Assuming  that most of the  applied nitrogen  is in the
organic or ammonium  form, increased  nitrogen removal due to
denitrification   can  be   expected   under   the   following
conditions:

    •     High levels of  organic  matter in  the soil and/or
          wastewater,  such  as  the concentrations  found  in
          primary effluent

    •     High  soil  cation exchange  capacity—a  character-
          istic of f ine-text|ured and  organic soils.

    •     Neutral to  slightly  alkaline soil pH

    •     Alternating saturated  and unsaturated soil moisture
          conditions

    •     Warm temperatures

Denitrification losses  typically  are  in the  range of  15 to
25% of  the applied, nitrogen,  although measured losses  have
ranged  from 3 to 70%  [4,  9].    The range  of 15 to  25% should
be  used   for conservative;  design.Whenconditions  are
                                     be
favorable,  the  maximum  ra^e  may  be  used.    Lower
should be  used  when conditibns  are  less favorable.
values
Ammonia volatilization lossfes  can  be significant  (about 10%)
if the soil  pH is above 7.8'and  the cation exchange  capacity

-------
                                                For  design.
is   low   (sandy,   low   organic   soils).
volatilization losses  may be considered  included  in the 15
to 25% used for denitrification.
Storage  of  nitrogen  in  the  soil  through plant  uptake and
subsequent conversion of roots and unharvested residues into
spil  humus  'can  account  for  nitrogen  retention  rates  up
to 225  kg/ha'yr  (200 Ib/acre-yr)  in soils  of  arid regions
initially  low  in  organic  matter  (less   than  2%).    In
contrast, nitrogen  storage  will  be near zero for soils rich
in  organic   matter.   In  either  case,  if   nitrogen   input
remains constant, the rate of nitrogen  storage will decrease
with time because  the rate  of decay and release of nitrogen
increases with  the concentration  of  soil organic  nitrogen.
Eventually,  an equilibrium  level of organic nitrogen may be
obtained and net storage then ceases.   Therefore, for design
purposes, the  most conservative approach is  to  assume net
storage will be zero.
    4.2.3
              Phosphorus
Phosphorus  is  removed  primarily  by  adsorption  and  pre-
cipitation  (together  referred to  as  sorption)  reactions in
the soil.   Crop uptake  can  account for phosphorus removals
in  the  range  of 20  to 60 kg/ha-yr  (18   to 53 Ib/acre-yr),
depending   on   the    crop  and   yield  (Section  4.3.2.1).
Percolate phosphorus  concentrations  at several Sk  sites are
presented in Table 4-3.

The phosphorus  sorption capacity  of  a soil profile depends
on  the   amounts   of   clay,   aluminum,  iron,  and  calcium
compounds  present  and  the  soi'l  pH.    In general,  fine
textured  mineral soils have  the highest phosphorus sorption
capacities  and  coarse textured acidic or organic soils have
the lowest.

For  systems with  coarse textured  soils  and limits  on the
concentration   of   percolate   phosphorus,  a   phosphorus
adsorption  test should be  conducted  using soil  from the
selected  site.    This  test,   described   in Section 3.7.2,
determines  the  amount  of phosphorus that the soil can remove
during   short   application  periods.     Actual  phosphorus
retention  at  an operating  system will  be  at least  2  to ~5~
times   the  value   obtained   during   a  5~day  adsorption
test  [13].
                             4-5

-------


























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For purposes  of  design and operation,  the soil profile can
be considered  to  have  a finite phosphorus sorption capacity
associated  with  each  layer.    Eventually,   the  sorption
capacity of the entire soil profile may reach saturation and
soluble phosphorus  will appear in  the  percolate.   In cases
where .effluent quality requirements limit the  concentration
of phosphorus  in the  percolate,  the useful  life  of  the SR
system may be limited  by the phosphorus sorption capacity of
the soil profile.   An  empirical model to predict the useful
life of an SR system has been developed  [9].
    4.2.4
Trace Elements
Trace  element  removal  in  the  soil   is  a  complex  process
involving  the  mechanisms  of  adsorption,  precipitation,  ion
exchange,  and  complexation.    Because  adsorption  of  most
trace  elements  occurs  on  the  surfaces  of  clay minerals,
metal oxides,  and  organic matter, fine textured  and organic
soils have  a  greater adsorption capacity for trace elements
than sandy  soils.

Removal  of  trace elements from  solution  is nearly complete
in  soils  suitable  for  SR  systems.    Consequently,   trace
element  removal is  not a concern in  the  design procedureT
Performance data from selected SR systems  are  presented  in
Table 4-4.

Although  some  trace elements  can  be  toxic to  plants  and
consumers of plants, no universally accepted toxic threshold
values  for  trace element concentrations  in the soil or  for
mass additions  to the soil have  been established.   Maximum
loadings  over   the  life  of   a  system  for several   trace
elements  have  been  suggested  for soils  having  low   trace
element retention  capacities and  are presented  in Table 4-5.

Toxicity hazards can be minimized by maintaining  the soil  pH
above 6.5.   Most trace elements are retained as  unavailable
insoluble  compounds  above  pH 6.5.    Methods  for adjusting
soil pH are discussed in Section  4.9.1.3.
    4.2.5
Microorganisms
Removal of  microorganisms,  including bacteria, viruses, and
parasitic protozoa and helminths  (worms),  is accomplished  by
filtration,  adsorption,  desiccation,  radiation,  predation,
and exposure  to  other adverse conditions.  Because of  their
large  size,  protozoa and helminths are removed primarily  by
filtration  at the soil  surface.   Bacteria also are removed
by  filtration at the soil  surface,  although adsorption may
be  important.    Viruses  are  removed  almost entirely   by
adsorption.
                             4-7

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-------
                              TABLE  4-5
                SUGGESTED MAXIMUM  APPLICATIONS OF
                 TRACE  ELEMENTS TO SOILS WITHOUT
                      FURTHER INVESTIGATION21
Element
Aluminum
Arsenic
Berylium
Boron
Cadmium
Chromium
Cobalt
Copper
Fluoride
Iron
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
Zinc
Mass application
to soil, kg/ha
4,570
92
92
680
9
92
46
184
920
4,570
4,570
184
9
184
18
1,840
Typical .
concentration, mg/L
10
0.2
0.2
1.4C
0.02
0.2
0.1
0.4
1.8
10
10
2.5d
0.4
0.02
0.4
0.04
4
                  Values were based on the tolerances of
                  sensitive crops, mostly fruits and vegetables,
                  grown on soils with low capacities for
                  retaining elements in unavailable forms
                  [15, 16].                       .
                  Based on reaching maximum mass application in
                  20 years at an annual application rate of
                  2.4 m/yr  (8 ft/yr).
                  Boron exhibits toxicity to sensitive plants at
                  values of 0.75 to 1.0 mg/L.
                  Lithium toxicity limit is suggested at 2.5 mg/L
                  concentration for all crops, except citrus which
                  uses a 0.075 mg/L limit.  Soil retention is
                  extremely limited.
As  noted  in  Table  1-3,  fecal coliforms  are  normally absent
after wastewater percolates  through  1.5  m  (5  ft)  of  soil.
Coliform  removals at  several operating  SR systems  are  shown
in  Table  4-6.    Coliform   removal  in  the  soil  profile  is
approximately    the    same    when   primary    or    secondary
preapplication  treatment  is  provided  [4] .    Virus  removals
are   not  as  well  documented.    State  agencies  may  require
secondary treatment  if  edible  crops  are  grown or  if public
contact   is  unlimited.     Microorganism   removal  is  not  a
limiting  factor  jn the  SR design procedure.
                                 4-9

-------
                          TABLE  4-6
                  COLIFORM  DATA  FOR  SEVERAL
                   SR SYSTEMS  [1,4,5,8,12]

Location
Camarillo,
California


Dickinson,
North Dakota

Preapplication
treatment
Activated
sludge and
disinfection


Aerated ponds
and disin-

Coliforms
Total
Fecal

Total
Fecal
Concentration
in applied
wastewater ,
MPN/100 mL
57 x 103
220

TNTCa
TNTC
Concentration
in percolate
or ground water,
MPN/100 mL
7
29
<2
<2
12
0
Distance
of
travel,
m
0.5
1.0
0.5
1.0
30-150
30-150
Concentration
in background
ground waiter,
MPN/100 mL
4
27
<2
4
1
0
           fection
Hanover,
New Hampshire
Mesa,
Arizona


Roswell,
New Mexico

Primary
Trickling
filters


Trickling
filters and
disinfection
Fecal
Total
Fecal

Total
Fecal

1.2 X 104-
3.1 x 105
3.09 x lb6
1.05 x 105

TNTC3
TNTCa

0-1
<2
9
<2
9
TNTCa
52

1.5
0.5
1.0
0.5
1.0
<6
<6

—
20
60
<2
25
~

a. At least one sample too numerous to count.
    4.2.6
Trace Organics
Trace  organics  are removed by  several  mechanisms,  including
sorption,  degradation,  and volatilization.    One  study  at
Muskegon,  Michigan,  evaluated  the effectiveness  of  trace
organics  removal  during preapplication  treatment  (aerated
ponds)  and SR  treatment.   Although  59  organic  pollutants
were  identified  in the raw wastewater, renovated water from
drainage tiles underlying the  irrigation  site contained only
low levels  of 10 organic compounds, including  two  from non-
wastewater  sources.    Benzene,  chloroform,  and  trichloro-
ethylene were monitored for several days;  results  are shown
in Table 4-7.                                         ;

Results  from pilot  SR  studies  at  Hanover,  New  Hampshire,
indicate that significant levels of volatile trace organics
are removed  during sprinkler application  [4].   Measurements
of  chloroform,   toluene,  methylene  chloride, 1,1  dichloro-
ethane, bromodichloromethane,  and  tetrachloroethylene showed
that   an   average   of  65%  of  these  six   compounds  were
volatilized  during the  sprinkling  process,  with  individual
removals ranging from 57%  for  toluene  to 70%  for  methylene
chloride.
                             4-10

-------
                            TABLE 4-7
          BENZENE,  CHLOROFORM, AND TRICHLOROETHYLENE
         IN MUSKEGON WASTEWATER TREATMENT  SYSTEM [17]
Pollutant
Benzene



Chloroform



Trichloroethylene



Sampling
point*3
1
2
3
4
1
2
3
4
1
2
3
4
Concentration, jig/La
8/10/76
6
7
<1
<1
425
105
12
3
13
16 •
7
6
8/11/76
53
2
<1
<1
440
61
9
3
6
3
4
3
8/12/76
6
<1
<1
<1
480
81
4
1
10
5
1
2
9/7/76
41
8
3,
<1
360
365
100 ,
13 .
110
35
11
10
9/8/76
32
5
2
8
2,645
610
75
10
120
33
6
8
        a.  Average for duplicate samples.

        b.  Sampling Point 1 - influent
           Sampling Point 2 - aerated lagoon effluent
           Sampling Point 3 - storage lagoon effluent
           Sampling Point 4 - renovated water from drainage tiles
 Based on these  results,  it appears  that a typical SR  system
 is  quite effective  in removing trace  organics.  However,  if
 a  community's  wastewater  contains  large  concentrations  of
 trace  organics  from  industrial  contributions,  industrial
 pretreatment should be considered.   If hazardous chlorinated
 trace  organics  result  from  wastewater  chlorination,   the
 engineer  must   decide  in   consultation   with  regulatory
 authorities  whether it is more  important to remove pathogens
 or  to  reduce  trace  organic  levels.   This  decision  should
 take  into consideration  the  type  of crop and  the  method  of
 distribution.

 4.3   Crop Selection

 The  crop  is a  critical component  in the  SR process.    It
 removes  nutrients, reduces erosion,  maintains  or  increases
 infiltration rates,  and can  produce  revenue  where  markets
 exist.
    4.3.1
Guidelines for  Crop Selection
Important  characteristics or properties  of  crops that should
be   considered  when   selecting  a   crop  for   SR  systems
include:    (1) nutrient  uptake  capacity,  (2) tolerance  to
high, soil  moisture conditions,  (3)  consumptive  use of water
and  irrigation requirements,  and (4)  revenue potential.   A
relative  comparison  of  these  characteristics  for  several
types of crops is presented in  Table 4-8 as  a  general guide

-------
to  selection.    Characteristics   of   secondary   importance
include  (1) effect  on  soil  infiltration  rate,   (2)   crop
water  quality   requirements  and  toxicity  concerns,   and
(3) management requirements;.

Most SR  systems  are designed to minimize  land area by  using
maximum  hydraulic  loading rates.  Crops that are  compatible
with  high  hydraulic  loading  rates  are  those  having  high
nitrogen  uptake  capacity,  high consumptive  water use,  and
high  tolerance  to  moist soil  conditions.   Other  desirable
crop characteristics for this situation are  low sensitivity
to   wastewater   constituents,    and    minimum    management
requirements.   Crops  grown for  revenue must have a  ready
local  market and  be  compatible with  wastewater  treatment
objectives.

         4.3.1.1   Agricultural  Crops

Agricultural  crops  most compatible  with  the  objective  of
maximum  hydraulic  loading are  the  forage  and turf grasses.
Forage crops that have been  used successfully includes   Reed
canarygrass,   tall   fescue,   perennial  ryegrass,   Italian
ryegrass,   orchardgrass,  and   bermudagrass.     If   forage
utilization   and   value  are   not  a   consideration,   Reed
canarygrass   is  often  a  first  choice  in  its  area   of
adaptation   because  of  high nitrogen   uptake  rate, winter
hardiness,  and  persistence.   However,  Reed  canarygrass  is
slow  to  establish  and  should  be  planted  initially  with  a
companion grass  (ryegrass,  orchardgrass, or tall  fescue)  to
provide good initial cover.

Of  the  perennial grasses grown for  forage  utilization  and
revenue under high wastewater  loading rates, orchardgrass  is
generally  considered to  be  more  acceptable  as  animal  feed
than tall fescue or  Reed  canarygrass.   However, orchardgrass
is  prone  to  leaf   diseases  in  the  southern   and  eastern
states.   Tall fescue  is  generally preferred  as  a  feed  over
Reed canarygrass but is  not!  suitable for use  in the northern
tier  of  states  due  to   lapk  of winter-hardiness.   Again,
other crops may  be  more suitable  for  local  conditions  and
advice of  local  farm advisers or extension specialists will
be helpful  in making the  crop  selection.

Corn will grow satisfactorily where the  water table depth  is
about 1.5 to 2 m, (5 to  7 ft)  but  alfalfa  requires  neiiturally
well-drained  soils  and water  table depths of at  least  3  m
(10 ft)  for  persistence.   The  alfalfa  cultivar selected
should  be   high  yielding with resistance  to root  rot  and
bacterial wilt in  the growing  region,  especially, when  high
hydraulic loading rates  (>?!.5  cm/wk or  3 in./wk) are  used.
                             4-12

-------
                          TABLE  4-8
            RELATIVE  COMPARISON  OF CROP
        CHARACTERISTICS   [Adapted  from  18]
                     Potential
                     as  revenue
                     producer3
      Potential
      as water
        userb
 Potential
as nitrogen
   user0
 Moisture
tolerance^
Field crops
Barley                Marg
Corn, grain           Exc
Corn, silage          Exc
Cotton (lint)          Good
Grain, sorghum        Good
Oats                  Marg
Rice                  -Exc
Safflower             Exc
Soybeans              JGood
Wheat                 Good

Forage crops
Kentucky bluegrass     Good
Reed canarygrass      Poor
Alfalfa               Exc
Bromegrass            Poor
Clover                Exc
Orchardgrass          Good
Sorghum-sudan         Good
Timothy               Marg
Vetch                 Marg
Tall fescue           Good

Turf crops

Bentgrass             Exc
Bermudagrass          Good

Forest crops

Hardwoods             Exc
Pine     -             Exc
Douglas-fir           Exc
        Mod
        Mod
        Mod
        Mod
        Low
        Mod
        High
        Mod
        Mod
        Mod
        High
        High
        High
        High
        High
        High
        High
        High
        High
        High
        High
        High
        High
        High
        High
   Marg
   Good
   Exc
   Marg
   Marg
   Poor
   Poor
   Exc
   Good-exce
   Good
   Exc
   Exc
   Good-exce
   Good
   Good-exce
   Good-exce
   Exc
   Good
   Exc
   Good-exc
   Exc
   Exc
   Good-exc1
   Goodf
  Low
  Mod
  Mod
  Low
  Mod
  Low
  High
  Mod
  Mod
  Low
  Mod
  High
  Low
  High
  Mod-high
  Mod
  Mod
  High
  High
  High
  High
  High
  Highg
  Mod-low9
  Mod
    Potential as revenue  producers is a judgmental estimate based on
    nationwide demand.  Local market differences may be substantial
    enough to change a  marginal  revenue producer to a good or
    excellent revenue producer and vice versa.  Some of the forages
    are extremely difficult  to market due to their coarse nature
    and poor feed values.
    Water user definitions expressed as a fraction of alfalfa
    consumptive-use.
          High           0.8-1.0
          Moderate (Mod)  0.6-0.79
          Low          -< 0. 6

    Nitrogen user ratings  (kg/ha):
          Excellent (Exc}
          Good
          Marginal (Marg}
          Poor
2>200
 150-200
 100-150
<100
    Moisture tolerance ratings:

          High     - withstands  prolonged soil saturation >3 days.
          Moderate - withstands  soil saturation 2-3 days.
          Low      - withstands  no soil saturation.
    Legumes will also take  nitrogen from the atmosphere.
    Higher nitrogen uptake  during juvenile growth stage after crowning.

    Species dependent, check with the State Extension Forester.
                                  4-13

-------
A mixture  of  alfalfa and a persistent forage grass, such  as
orchardgrass,  can  be used  on soils that  are not naturally
well drained.   At  high hydraulic loading rates, the alfalfa
may not persist over 2 years, but the forage  grass will fill
in the areas in the  thinned alfalfa stand.

The most  common agricultural crops grown  for revenue using
wastewater  are  corn  (silage),  alfalfa  (silage,   hay,   or
pasture),  forage"  grass   (silage,  hay,  or  pasture),  grain
sorghum,  cotton,  and  grains  [18]..    However,  any  crop,
including food crops, may b^  grown with  reclaimed wastewater
after suitable preapplicatipn treatment.

In  areas  with  a  long growing  season,   such  as California,
selection  of  a  double  crop  is  an   excellent  means   of
increasing  the  revenue   potential  as  well  as  the annual
consumptive  water  use  and  nitrogen  uptake  of  the  crop
system.   Double crop  combinations  that are  commonly used
include (1) short season varieties of soybeans, silage corn,
or  sorghum  as a summer  crop; and  (2)  barley,  oats, wheat,
vetch, or annual forage grass as a winter crop.

A growing  practice  in the East and"Midwest is  to provide a
continuous vegetative  cover  with  grass  and corn.  This "no-
till" corn management consists of planting  grass in  the fall
and then  applying  a herbicide in the spring  before  planting
the corn.   When the corn  completes  its  growth cycle, grass
is  reseeded.    Thus, cultivation  is  reduced;  water use   is
maximized;   nutrient  uptake   is   enhanced;   and   revenue
potential is increased.

         4.3.1.2   Forest Crops

The most  common forest  croups used in SR  systems have been
mixed  hardwoods and pines.   A  summary  of  representative
operational  systems  and  types  of  forest  crops   used   is
presented in Table 4-9.

The growth responses of  a number  of tree species to a range
of wastewater  loadings are  identified  in  Table  4-10.   The
high growth  response column is most suitable for wastewater
application  because of  nitrogen  uptake  and  productivity.
The growth response will vary in accordance with a number  of
factors;  one  of the most  important is  the adaptability   of
the selected  species to  the local  climate.   Local foresters
should  be consulted  for specific  judgments  on  the likely
response of selected species.                              .
                             4-14

-------
                                TABLE  4-9
           SUMMARY  OF OPERATIONAL FOREST  LAND TREATMENT
               SYSTEMS IN THE UNITED  STATES RECEIVING
                          MUNICIPAL WASTEWATER
Location
Clayton County,
Georgia
Flow,
m3/d
73,800
Forest type
Loblolly pine
plantation and
natural hardwood
Date
started
1981
Hydraulic
loading,
cm/wk
6.3
Other conditions
Ground water to be
recycled as drinking
water
 Helen, Georgia

 Kings Bay
 Submarine Support
 Base, St. Marys,
 Georgia

 Mackinaw City,
 Michigan

 Mt. Sunapee State
 Park, Newbury,
 New Hampshire
 State College,
 Pennsylvania
 (Penn State
 University)

 West Dover,
 Vermont
   76 Mixed hardwood
      and pine
 1,250 Slash pine
      plantation
  760 Aspen, white
      pine birch

   26 Mixed hardwood
11,350  Mixed hardwood;
      red pine plantation;
      spruce, old field


 2,080  Northern hardwoods;
      balsam, hemlock,
      spruce in understory
1973

1981




1976


1971



1963




1976
 7.6


 1.3




11.3


 5.0
 2.0-
 7.5
        <6.3
Site drainage with
open ditches
Frost free, seasonal
application

Water stored and
applied in June and
July only

Ground water to be
recycled as drinking
water


Operates at air
temperatures above
-18 °C
     4.3.2
                               TABLE  4-10
                 HEIGHT GROWTH  RESPONSE  OF  SELECTED
                   TREE SPECIES [Adapted from 19]

                           Height growth response class
                    Low
                                 Intermediate
                                                 High
Slash pine
Cherry-laurel
Arizona cypress
Live oak
Holly
Hawthorne
Northern white cedar
Red pine




Tulip poplar
Bald cypress
Saw-tooth oak
Red cedar
Laurel oak
Magnolia
Nuttall oak
Cherry bark oak
Loblolly pine
Shortleaf pine
Virginia pine
Douglas- fir
Cottonwood
Sycamore
Green ash
Black cherry
Sweetgum
Black locust
Red bud
Catalpa
Chinese elm
White pine


 Crop  Characteristics
Reference  data and  information  on  the  crop  characteristics
of   (1)  nutrient   uptake,   water  quality  requirements,  and
toxicity   concerns;    (2) water   tolerance;    (3)  consumptive
water  use;  and  (4) effect  on  soil  hydraulic properties are
presented  in  this  section  for  both  agricultural  crops and
forest  crops.
                                   4-15

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         4.3.2.1    Nutrient Uptake

Agricultural Crops

In  general,  the  largest nutrient removals can  be achieved
with  perennial  grasses and  legumes that are  cut frequently
at  early stages  of growth.   it  should be recognized that
legumes  can  fix -nitrogen  from the air, but they are active
scavengers for  nitrate if it  is present.   The potential for
harvesting  nutrients  with  annual crops  is   generally less
than  with  perennials  because  annuals  use  only  part  of the
available  growing  season   for  growth  and  active  uptake.
Typical  annual  uptake rates of  the major  plant  nutrients—
nitrogen,   phosphorus,    and    potassium—are   listed   in
Table 4-11 for  several commonly  selected crops.

The  nutrient removal capacity  of  a  crop is not a  fixed
characteristic  but-  depends  on  the  crop  yield  and  the
nutrient  content  of  the  plant  at  the   time  of  harvest.
Design  estimates  of   harvest  removals  should be based  on
yield goals  and nutrient compositions  that local experience
indicates  can  be  achieved with good management  on  similar
soils.                                               :
                         TABLE  4-11
                  NUTRIENT UPTAKE RATES FOR
                       SELECTED CROPS
                          kg/ha-yr

Forage crops
Alfalfa3
Bromegrass
Coastal bermudagrass
Kentucky bluegrass
Quackgrass
Reed canarygrass
Ryegrass
Sweet clovera
Tall fescue
Orchardgrass
Field crops
Barley
Corn
Cotton
Grain sorghum
Potatoes
Soybeans2
Wheat
Nitrogen

225-540
130-225
400-675
200-270
235-280
335-450
200-280
175
150-325
250-350

125
175-200
75-110
135
230
250
160
Phosphorus

22-35
40-55
35-45
45
30-45
40-45
60-85
20
30
20-50

15
20-30
15
15
20
10-20
15
Potassium

175-225
245
225
200
275
315
270-325
100
300
225-315

20
110
40
70
245-325
30-55
20-45
             a.  Legumes will also take nitrogen from the atmosphere.
                            4-16

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The  rate  of  nitrogen  uptake  by crops  changes during  the
growing  season  and is a  function of the rate  of  dry matter
accumulation   and  the   nitrogen  content  of   the   plant.
Consequently,  the pattern of  nitrogen uptake  is  subject to
many  environmental  and  management  variables  and   is  crop
specific.  Examples of measured nitrogen uptake rates versus
time  are  shown  in Figure 4-2  for  annual  crops and perennial
forage'grasses receiving  wastewater.

The amounts of phosphorus in  applied wastewaters are  usually
much  higher  than  plant   requirements.    Fortunately,  most
soils  have  a  high sorption capacity  for  phosphorus  and very
little    of  the   excess passes  through    the soil   (see
Section 4.2.3).
Potassium  is  used  in  large  amounts   by  many  crops,
but
typical  wastewater  is  relatively  deficient  in  this  ele-
ment.   In  most cases, fertilizer potassium may be  needed to
provide  for  optimal plant growth, depending  on the  soil and
crop  grown  (see  Section  4.9.1.2).    Other  macronutrients
taken  up by  crops  include  magnesium,  calcium and  sulfur;
deficiencies of  these  nutrients  are  possible  in some areas.
s
  400 i-
  300 -
  200 -
  100 -
        REED CANARY6RASS
        AND CORN
          APR
                         FIGURE 4-2
            NITROGEN UPTAKE VERSUS GROWING DAYS
           FOR  ANNUAL AND  PERENNIAL CROPS [20,21]
                             4-17

-------
 The  micronutrients important to  plant  growth (in descending
 order)  are:  iron, manganese,  zinc,  boron,  copper,  molyb-
 denum,  and,  occasionally,  sodium,   silicon,  chloride,  and
 cobalt.   Most wastewaters  contain an ample  supply  of these
 elements;    in    some   cases,    phytotoxicity   may   be   a
 consideration.

 Forest  Crops

 Vegetative  uptake  and  storage  of nutrients  depend  on  the
 species  and forest stand density, structure,  age,  length  of
 season,  and temperature.   In addition to the  trees,  there  is
 also  nutrient uptake and storage  by  the  understory  tree  and
 herbaceous   vegetation.     -The   role   of   the   understory
 vegetation  is particularly important in  the  early  stages  of
 tree  establishment.

 Forests  take up and store nutrients  and  return  a portion  of
 those  nutrients back to  the soil in  the form of leaf  fall
 and  other debris  such  as dead  trees.    Upon  decomposition,
 the  nutrients  are released  and  the trees  take  them  back
 up.   During  the  initial  stages  of   growth  (1  to 2  years),
 tree  seedlings  are  establishing  a  root  system;   biomass
 production  and  nutrient  uptake   are  relatively slow.    To
 prevent  leaching  of  nitrogen  to ground  water  during  this
 period,  nitrogen  loading  must  be   limited   or understory
 vegetation  must  be established  that  will take up and  store
 applied  nitrogen that is  in  excess  of the tree crop  needs.
 Management    of   understory   vegetation   is   discussed   in
 Section 4.9.

 Following the initial  growth stage,  the  rates of growth and
 nutrient  uptake  increase  and   remain  relatively   constant
 until maturity  is approached and  the rates decrease.  When
 growth  rates and  nutrient  uptake rates  begin to decrease,
 the  stand  should  be  harvested  or  the  nutrient   loading
 decreased.   Maturity may  be  reached at  20  to  25 years for
 southern pines,  50 to 60 years  for  hardwoods,  and  60 to  80
 years  for  some  of  the  western  conifers  such  as   Douglas-
 fir.   Of course, harvesting may be practiced  well in  advance
 of maturity  as   with  short-term  rotation management  (see
 Section 4.9.2.5).

 Estimates of  the net annual nitrogen  storage  for a number  of
 fully   stocked    forest   ecosystems   are   presented    in
Table 4-12.     These  estimates  are   maximum  rates   of  net
nitrogen  uptake  considering   both  the   understory  and
overstory  vegetation  during  the  period  of  active  tree
growth.
                             4-18

-------
                             TABLE 4-12
          ESTIMATED NET  ANNUAL  NITROGEN UPTAKE  IN THE
         OVERSTORY  AND UNDERSTORY  VEGETATION OF  FULLY
             STOCKED AND VIGOROUSLY GROWING  FOREST
   ECOSYSTEMS  IN SELECTED  REGIONS  OF THE  UNITED  STATES  [22]
                                        Average annual
                                 Tree    nitrogen uptake,
                                 age, yr    kg/ha-yr
                 Eastern forests
                 Mixed hardwoods       40-60
                 Red pine         ,  25
                 Old field with white   15
                 spruce plantation
                 Pioneer succession

                 Southern forests
                 Mixed hardwoods       40-60
                 Southern pine with    20
                 no understory
                 Southern pine        20
                 with understory

                 Lake states forests
                 Mixed hardwoods       50
                 Hybrid poplar'3       5

                 Western forests
                 Hybrid poplarb       4-5
                 Douglas-fir         15-25
                 plantation
270
110
280
280
340
220a

320
110
155
300-400
150-250
                 a.  Principal southern pine included in these
                    estimates is loblolly pine.
                 b.  Short-term rotation with harvesting at 4-5 yr;
                    represents first growth cycle from planted
                    seedlings (see Section 4.9.2.4).

Because  nitrogen stored within the biomass  of trees is  not
uniformly  distributed  among  the tree components,  the amount
of  nitrogen that can  actually  be removed with a  forest  crop
system will be substantially less  than the  storage estimates
given  in Table 4-12  unless 100%  of  the aboveground biomass
is   harvested    (whole-tree  harvesting).       If   only   the
merchantable  stems  are  removed  from  the  system,   the  ne~t
amount of   nitrogen  removed by  the system will be  less  than
30%  of the amount stored in  the biomass.The distributions
"51biomassandnitrogenfornaturally  growing hardwood  and
conifer  (pines,   Douglas-fir,  fir,   larch,  etc.)  stands  in
temperate  regions are  shown in Table 4-13.'   For  deciduous
species, whole-tree  harvesting must take place in the summer
when the leaves  are  on  the  trees  if maximum nitrogen removal
is  to be achieved.
                                4-19

-------
                         TABLE  4-13
         BIOMASS AND NITROGEN DISTRIBUTIONS  BY TREE
       COMPONENT FOR STANDS  IN  TEMPERATE  REGIONS  [23]
                           Percent
                          Conifers
                                         Hardwoods
         Tree component   Biomass  Nitrogen  Biomass  Nitrogen
Roots
Stems
Branches
Leaves
10
80
8
2
17
50
12
20
12
65
22
1
18
32
42
8
The  assimilative  capacity  for  both  phosphorus  and  trace
metals  is  controlled  more  by  soil properties  than  plant
uptake.   The relatively low pH (4.2 to 5.5) of most  forest
soils  is  favorable to  the retention of  phosphorus but  not
trace metals.   However,  the high level of organic  matter in
forest soil  improves the metal  removal  capacity.   The  amount
of phosphorus  in trees  is small, usually less  than 30 kg/ha
(27  Ib/acre);    therefore, the  amount  of annual  phosphorus
accumulation is  quite small.
         4.3.2.2
Moisture Tolerance
Crops that  can  be exposed to prolonged periods  of  high soil
moisture  without  suffering  damage  or yield  reduction  are
said  to  have  a  high moisture  or  water  tolerance.    This
characteristic   is   desirable   in   situations   (1)   where
hydraulic  loading rates  must be  maximized,  (2)  where  the
root  zone  contains a slowly permeable soil, or  (3)  in humid
areas where sufficient  moisture  already  exists  for  plant
growth.     Refer  to  Table  4-8  for  a  comparison  of  crop
moisture  tolerances.   Alfalfa  and  red  pine,   for  example,
have  low moisture  tolerances.

         4.3.2.3   Consumptive Water Use

Consumptive   water    use    by   plants    is   also   termed
evapotranspiration  (ET).   Consumptive water use varies with
the  physical characteristics  and the growth  stage of  the
crop, the  soil moisture  level,  and  the  local  climate.   In
some  states, estimates of maximum monthly consumptive water
use  for  many crops  can  be obtained  from  local  agricultural
extension  offices or  research  stations or  the  SCS.   Where
this  information  is not  available,  it will be  necessary to
make  estimates  of evapotranspiration using temperature  and
                             4-20

-------
other  climatic   data.      Several   methods  qf  estimating
evapotranspiration  are   available  and   are   detailed   in
publications  by  the  American  Society  of  Civil  Engineers
(ASCE) [24] ,  the  Food  and Agriculture Organization  (FAO)  of
the United Nations [25], and the SCS [26].

Agricultural Crops

In humid  regions  estimates'of  potential evapotranspiration
(PET)  are  usually  sufficient  for  perennial,  full-cover'
crops.ExamplesofestimatedPETfor  humidandsubhumid
climates  are  shown  in  Table  4-14'.    Examples .  of  monthly
consumptive use in arid  regions are shown in Table  4-15  for
several California crops.   These  table  values  are  specific
for  the  location  given  and  are  intended to  illustrate
variation  in  ET  due  to crop  and  climate.    The   designer
should obtain or estimate ET values  that  are specific  to  the
site under design.

                         TABLE 4-14
           EXAMPLES OF  ESTIMATED MONTHLY POTENTIAL
     EVAPOTRANSPIRATION FOR HUMID AND SUBHUMID CLIMATES
                             cm
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Paris,
Texas
1.5
1.5
3.6
6.8
9.9
14.7
16.0
16.2
9.7
6.4
2.7
1.4
90.4
Central
Missouri
0.7
1.3
3.0
6.6
10.8
14.5
16.9
15.2
10.3
6.3
2.6
1.1
89.3
Brevard ,
North Carolina
0.2
0.3
2.1
4.6
7.6
10'. 2
11.4
10.4
7.4
4.6
1.6
0.3 ,
60.7
Jonesboro,
Georgia
1.3
1.3
3.0
5.8
10.9
14.7
15.7
15.0
10.9
5.8
2.5
1.3
88.2
Hanover,
New Hampshire
0.0
,0.0
0.1
2.9
8.2
12.9
13..7
11.9
7.4
4.0
0.3
0.0 •
61.4
Seabrook,
New Jersey
0.2
0.3
2.0
4.0
7.4
11.4
13.9
13.6
9.9
4.9
2.1
0.3
70.0
In arid or  semiarid  regions,  water in excess of consumptive
use  must  be  applied  to  (1)  ensure  proper  soil  moisture
conditions  for  seed  germination,  plant  emergence,  and root
development;  (2)  flush  salts  from  the  root, zone;  and
(3) account  for nonuniformity of  water  application  by the
distribution system  (see  Section1 4.7).  This requirement  is
the  irrigation  requirement   and   examples  are  shown   in
Table 4-15.      Local   irrigation   specialists   should   be
consulted for specific values.
                             4-2-1

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                               TABLE  4-15
     CONSUMPTIVE WATER USE AND IRRIGATION REQUIREMENTS  FOR
  SELECTED  CROPS  AT SAN JOAQUIN  VALLEY,  CALIFORNIAa  [27,  28]
                         Depth  of Water  in cm
         Pastures or alfalfa*5
    Double crop
barley and grain (sorghumc
                                                          Sugar beets e
Month
Jan
Fob
Mar
Apr
•Hay
Jun
Jul
Aug
Sop
Oct
Nov
Dae
Total
Consumptive
use
2.3
S.I
9.7
13.2
17.8
21.8
23.9
22.1
14.7
10.9
S.I
2.5
149.1
Irrigation
requirements
3.0
6.9
13.0
17.8
23.9
29.2
32.0
29.7
19.8
14.7
6.9
3.3
200.2
Consumptive
use
2.5
5.1
9.7
13.2
6.6
—
11.4
20.3
15.2
7.6
~
2.5
94.1
Irrigation
requirements
__
-'-
15.2
15.2
—
125.49
17.8
,30.1
'22.9
—
—
25.4
152.0
Consumptive
use
„
—
—
1.5
3.0
9.1
18.3
21.3
15.2
6.4
—
	
74.8
Irrigation
requirements
„
38.1£
~
—
—
12.7
30.5
30.5
—
—
—
	
111.8
Consumptive
use

—
—
2.5
6.4
12.7
17.8
20.3
—
—
—
	
59.7
Irrigation
requirements

—
12.7
22.9
12.7
22.9
19.1
"' 11.4
1
—
15.29
__
116.9
   «. Other cropa having similar growing seasons and ground cover will have similar consumptive use.

   b. Estimated maximum consumptive use (evapotranspiration) of water by mature crops with nearly complete ground
     cover throughout the year.

   o. Barley planted in November-December, harvested in June.  Grain sorghum planted June 20-July 10, harvested
     in November-December.

   d. Rooting depth of mature cotton: 1.8 m. Planting dates! March 15 to April 20. Harvest:  October, November,
     and December.

   o. Rooting depth:  1.5 to 1.8 m. Planting date:  January.  Harvest:  July 15 to September 10.

   f. Preirrigation should wet soil to 1.5 to 1.8 m depth prior to planting.

   9, Preirrigation is used to ensure germination and emergence. First crop irrigations are heavy in order to
     provide deep moisture.
Forest  Crops

The  consumptive  water  use  of  forest  crops  under  high  soil
moisture conditions  may  exceed  that  of  forage  crops  in  the
same  area  by as  much as  30%.   For design  purposes,  however,
the potential ET  is  used because there is  little information
on   water   use  of  different  forest  species.     The  seasonal
pattern of water  use  for  conifers  is more  uniform  than  for
deciduous  trees.

           4.3.2.4    Effect  on Soil Hydraulic Properties

In   general,  plants  tend  to  increase  both  the  infiltration
rate  of   the  soil   surface  and  the  effective  hydraulic
conductivity  of  the  soil  in  the root  zone as  a  result  of
root  penetration   and   addition   of  organic  matter.     The
magnitude   of  this  effect  varies   among   different  crops.
Thus,  the   crop  selected  can  affect  the  design application
rate  of  sprinkler distribution   systems,   which  is  based  on

-------
the  steady state  infiltration  rate of  the  soil  surface.
Steady  state   infiltration  rate   is   equivalent   to  the
saturated  permeability  of  surface  soil.   Design sprinkler
application  rates   can   be  increased   by   50%  over  the
permeability value for most full-cover crops and by 100% for
mature  (>4 years  old), well-managed permanent pastures (see
Appendix E).    The design  application rate  (cm/h  or in./h)
should not be confused with hydraulic loading rate (cm/wk or
cm/mo)  which  is  based  on  the  permeability  of  the  most
restrictive layer  in the  soil  profile.   This layer,  in many
cases, is below the  root zone and is unaffected  by the crop.

Forest  surface  soils  are  generally characterized  by high
infiltration  capacities  and  high  porosities  due  to  the
presence of high levels of organic matter.  The  infiltration
rates of  most  forest surface soils  exceed  all but the most
extreme    rainfall    intensities.       Therefore,   surface
infiltration  rate   is  not  usually  a   limiting factor  in
establishing  the  design  application  rate  for  sprinkler
distribution in forest systems.

In  addition,   the permeability  of  subsurface  forest  soil
horizons  is  generally improved over  that found under other
vegetation  systems   because   there  is:  (1)   no  tillage,
(2) minimum compaction  from vehicular traffic,  (3) decompo-
sition  of  deep pentrating  roots,  and  (4)  a well-developed
structure  due  to  the  increased organic  matter content and
microbial  activity.    Where   subfreezing temperatures  are
encountered, the forest floor serves to  insulate the soil so
that soil  freezing,  if it does occur, occurs slowly and does
not penetrate deeply.   Consequently, wastewater application
can often  continue through the winter at  forest  systems.

         4.3.2.5   Crop Water Quality Requirements and
                   Toxicity Concerns

Wastewaters may  have constituents  that:  (1)  are harmful to
plants  (phytotoxic), (2)  reduce the quality of  the crop for
marketing, or  (3)  can be  taken up by plants and result in  a
toxic  concern  in the  food  chain.   Thus,  the  effect  of
wastewater constituents on the crop  itself and  the potential
for  toxicity  to  plant  consumers must  be considered during
the  crop  selection   process.    Agricultural  crops  are  of
primary concern.

A   summary  of   common   wastewater  constituents  that  can
adversely  affect certain crops either through a  direct toxic
effect  or through degradation  of  crop  quality  is  given in
Table 4-16.  Also  indicated in the  table  are the constituent
concentrations  at which  problems  occur.   These effect are
discussed  in further detail in Chapter 9.
                             4-23

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                             TABLE 4-16
                SUMMARY OF  WASTEWATER CONSTITUENTS
                 HAVING POTENTIAL ADVERSE EFFECTS
                           ON CROPS  [29]
                           Constituent level
       Problem and
     related constituent
              No    Increasing  Severe
            problem  problems  problems
                                            Crops affected
     Salinity (ECW) ,        <0.75   0.75-3.0   >3.0
     nunho/cm

     Specific ion toxicity
     from root absorption

      Boron, mg/L         <0.5    0.5-2'   2.0-10.0
                                  Crops in arid climates only
                                  (see Table 9-4)
                                            Fruit and citrus trees -
                                            0.5-1.0 mg/L; field crops
                                            1.0-2.0 mg/L; grasses -
                                            2.0-10.0 mg/L
Sodium, adj-SARa
Chloride, mg/L
Specific ion toxicity
from foliar absorption
Sodium, mg/L
Chloride, mg/L
Miscellaneous
NH4-N + N03-N, mg/L
HC03 , mg/L
pH, units
<3
<142

<69
<106

<5
<90
6.5-8.4
3.0-9.0
142-355

>69
>106

5-30
90-520
4.2-5.5
>9.0
>355

	

30
>520
<4.2 and
>8.5
Tree crops
Tree crops

Field and vegetable
crops under sprinkler
application

Sugarbeets, potatoes,
cotton, grains
Fruit
Most crops
    a.  Adjusted sodium adsorption ratio.
Trace elements, particularly zinc,  copper,  and nickel  are of
concern  for  phytotoxicity.   However,  the  concentration of
these elements in  wastewaters,is well below  the toxic level
of  all crops  and phytotoxicity   could only  occur as a  result
of  long-term  accumulation of these  elements in the soil.

4.4  Preapplication Treatment

Preapplication treatment is provided for three reasons:

     1.   Protection of  public  health  as it relates to human
          consumption  of  crops  or  crop  byproducts   or  to
          direct exposure to applied  wastewater
     2.

     3.
Prevention of nuisance conditions during storage

Prevention  of  operating  problems  in  distribution
systems
Preapplication  treatment  is not necessary for  the SR process
to  achieve maximum  treatment,  except  in the case of harmful
                               4-24

-------
or '  toxic   constituents   from   industrial   sources    (see
Section 4.4.3).  The  SR process is capable of removing  high
levels   of   most   constituents   present    in   municipal
wastewaters,  and  maximum   use  should  be  made  of   this
renovative   capacity    in   a  complete   treatment  system.
Therefore,  the  level  of  preapplication  treatment provided
should be  the  minimum necessary to achieve the three stated
objectives.    In  general,  any  additional   preapplication
treatment will result in higher costs and energy use.

The  EPA  has  issued  general guidelines  for  assessing  the
level of  preapplication treatment  necessary  for  SR systems
[30] .    The guidelines are  intended  to  provide  adequate
protection  for public health:

    A.   Primary   treatment  -   acceptable   for   isolated
         locations with restricted  public access  and   when
         limited to crops not for direct human consumption.

    B.   Biological treatment by  ponds  or inplant processes
         plus control  of  fecal  coliform  count to  less  than
         1,000  MPN/100  mL   -   acceptable  for  controlled
         agricultural irrigation except for human food crops
         to be eaten raw.

    C.   Biological treatment by  ponds  or inplant processes
         with  additional  BOD or  SS  control   as needed  for
         aesthetics plus disinfection to log mean of 200/100
         mL (EPA fecal  coliform criteria for bathing waters)
         - acceptable for application in public access areas
         such as parks  and golf courses.

In most cases, state or local public health or water quality
control   agencies   regulate   the   quality   of   municipal
wastewater  that  can  be used  for  SR.   The appropriate state
and local  agencies  should be contacted  early in  the design
process to determine specific restrictions on  the quality of
applied wastewater.

    4.4.1     Preapplication Treatment for Storage and
              During Storage

Objectionable  odors  and  nuisance  conditions  can  occur if
anaerobic  conditions  develop near  the surface in  a storage
pond.  Two preapplication treatment options are available to
prevent odors:

    1.   Reduce the oxygen demand of the wastewater prior to
         storage.                                         	
                             4-25

-------
     2.    Design the storage pond as a deep facultative pond,
          using appropriate•BOD loading.

 Complete   biological   treatment   and    disinfection   are
 unnecessary  prior  to  storage.    The  level  of  treatment
 provided  should  not   exceed   that   necessary  to  control
 odors.   For  storage  ponds with short detention  times (less
 than 10  to   15   days),   a  reduction  in  the  BOD  of  the
 wastewater to a range of  40 to  75  mg/L  should  be sufficient
 to prevent odors.  An aerated cell is are  normally used  for
 BOD reduction in such cases.  For  storage  ponds  with longer
 detention  times,  BOD reduction before  storage  is  normally
 not required because   the  storage  pond   is   serving  as  a
 stabilization pond.

 Wastewater undergoes  treatment  during  storage.    Suspended
 solids,  oxygen  demand,   nitrogen,  and   microorganisms  are
 reduced.   In  general, the  extent of reduction depends on  the
 length  of  the storage  period.    In  the  case  of  nitrogen,
 removal  during storage  can  affect  the design  and  operation
 of the   SR process because  the  allowable  hydraulic  loading
 rate may  be  governed by  the  nitrogen  concentration  of  the
 applied  wastewater.   Nitrogen removal in  storage  reservoirs
 can be  substantial and  depends on  several  factors  including
 detention   time,   temperature,  pH,  and   pond  depth.     A
 preliminary  model  to estimate  nitrogen  removals  in  ponds
 during ice-free periods  has  been developed  [31]:
where  Nt =
       No -
        Nt = N0 e-

nitrogen concentration in pond effluent
(total N), mg/L

nitrogen concentration entering pond
(total N), mg/L
                                                        (4-1)
        t =  detention time, d
A  more   precise   model  for  predicting  ammonia  nitrogen
removals  in  ponds  is presented in the Process Design Manual
on Wastewater Treatment Ponds  [32].

Nitrogen  in pond effluent is predominantly in the ammonia or
organic  form.    In  most  cases,  it  is  desirable  to apply
nitrogen  in  these  forms to  SR systems because they are held
at least  temporarily in the  soil  profile and are available
for plant uptake  for longer  periods  than nitrate,  which is
mobile  in the  soil  profile.   Ammonia and  organic  nitrogen
which is  converted to ammonia, are particularly desirable in
                             4-26

-------
forest  systems because  many  tree  species  do not  take up
nitrate as efficiently as ammonia.

A model  describing the  removal  of fecal  coliforms  in  pond
systems has also been developed  [33]:
                   Cf =
                            ,-Kte
(4-2)
where  Cf =  effluent fecal coliform concentration,
             No./lOO mL

       C- =  entering fecal coliform concentration,
        1    No./lOO mL

        K =  0.5 warm months;
             0.03 cold months

        t =  "actual" detention time, d

        9 =  1.072

        T =  liquid temperature,  °C.
Based on this model, actual detention  times  of  about  17  days
and  21  days would be  necessary at 20  °C  (68 °F) to  reduce
the  coliform  level   of  a  typical  domestic  wastewater  to
1,000/100  mL and 200/100 mL,  respectively.   Thus, effluent
from  storage reservoirs,  in many  cases,  may  meet  the  EPA
coliform    recommendations    for   SR   systems    without
disinfection.

Removal  of  viruses  in  ponds  is  also quite  rapid  at  warm
temperatures.  Essentially complete removal  of  Coxsackie and
polio viruses was observed after  20 days at  20  °C [34].

     4.4.2     Preapplication Treatment to  Protect
              Distribution Systems

Deposition of settleable  solids  and  grease  in  distribution
laterals or ditches  can  cause  reduction in the  flow capacity
of   the  distribution  network  and odors  at the  point  of
application.     Coarse  solids   can   cause  severe clogging
problems   in  sprinkler  distribution   systems.    Removal  of
settleable  solids   and   oil   and  grease   (i.e.,   primary
sedimentation or equivalent)  is  therefore recommended  as  a
minimum level of  preapplication  treatment.Forsprinkler
systems,   It  has  been  recommended  that  the  size  of  the
largest particle in  the  applied wastewater be less than one-
                             4-27

-------
 third  the   diameter  of  the  sprinkler  nozzle,  to  avoid
 plugging.
     4.4.3
  Industrial Pretreatment
 Pollutants that  are compatible with  conventional secondary
 treatment  systems  would generally  be compatible  with land
 treatment  systems.    As  with  conventional  systems,  pre-
 treatment  requirements  will be necessary  for such constit-
 uents  as   fats,  grease  and  oils,  and  sulfides  to  protect
 collection systems  and treatment components.   Pretreatment
 requirements for conventional biological treatment will also
 be sufficient for land treatment processes.

 4.5  Loading Rates  and Land Area Requirements

 The  hydraulic  loading  rate  is  the  volume  of  wastewater
 applied per  unit area  of  , land  over at  least one  loading
 cycle.    Hydraulic  loading  rate  is  commonly expressed  in
 cm/wk or m/yr  (in./wk  or ft/yr) and is used  to  compute the
 land  area  required  for  the  SR process.    The  hydraulic
 loading  rate  used   for  design   is  based  on   the   more
 restrictive of  two limiting  conditions—the  capacity  of the
 soil  profile to  transmit water  (soil permeability) or the
 nitrogen concentration in water percolating  beyond the root
 zone.

 A  separate  case  is  considered for those  systems in  arid
 regions where crop revenue  is  important and  the  wastewater
 is  used as  a valuable source of irrigation water.   For such
 systems,  the  design hydraulic loading rate  is usually  based
 on  the  irrigation requirements of  the  crop.
     4.5.1
 Hydraulic Loading  Rate  Based on  Soil
 Permeability
The  general water  balance equation  with rates  based on  a
monthly  time period  is  the  basis  of this  procedure*.  The
equation, with  runoff of  applied water  assumed to be  zero,
is:
                             - Pr + P
                                     w
                                           (4-3)
where
       ET =

       Pr =
       pw =
wastewater hydraulic loading rate

evapotranspiration rate

precipitation rate

percolation rate
                             4-28

-------
The basic  steps in the  procedure are:

    1.   Determine  the  design precipitation  for each  month
         based on  a  5 year  return period frequency analysis
         for monthly  precipitation.   Alternatively, use a 10
         year  return  period  for  annual precipitation  and
         distribute it  monthly based  on the ratio  of average
         monthly to average  annual precipitation.

    2.   Estimate  the monthly ET rate  of the selected crop
         (see Section 4.3.2.3).

    3.   Determine  by  field  test  the  minimum  clear  water
         permeability of the  soil profile.    If the minimum
         soil  permeability   is   variable   over  the   site,
         determine an average  minimum  permeability based on
         areas of different  soil types.

    4.   Establish a  maximum  daily  design  percolation rate
         that  does not  exceed  4  to  10%  of  minimum  soil
         permeability (see Figure  2-3).   Percentages  on the
         lower end of the scale are recommended  for variable
         or poorly defined soil  conditions.   The percentage
         to use  is a judgment decision to  be  made 'by  the
         designer.  The  daily percolation rate is determined
         as follows:

         pw(daily) =  Permeability, cm/h (24  h/d)(4  to  10%)

    5.   Calculate   the   monthly   percolation   rate   with
         adjustments  for those   months  having  periods  of
         nonoperation.   Nonoperation  may.be  due  to:

          •  Crop management. Downtime must be  allowed for harvesting,
             planting,  and  cultivation as applicable.

          •  Precipitation.   Downtime  for  precipitation  is already
             factored into  the water balance  computation.   No adjust-
             ments are necessary.
          •  Freezing temperatures.   Subfreezing  temperatures  cause
             soil frost  that reduces surface  infiltration rate.  Oper-
             ation is usually stopped when this occurs.  The most con-
             servative approach to adjusting  the  monthly percolation
             rate for freezing conditions is  to allow no operation for
             days during the month when  the  mean temperature is less
             than 0 °C  (32  °F).   A less conservative approach is to use
             a lower minimum temperature.  The  recommended  lowest mean
             temperature for operation is -4  °C (25 °F).  Data sources
             and procedures  for determining  the number  of  subfreezing
             days  during  a month are presented in  Sections 2.2.1.3,
                              4-29

-------
              2.2.2.2, and 4.6.  Nonoperating days due to freezing con-
              ditions may also be estimated using the  EPA-1 computer
              program without  precipitation  constraints  .(see Section
              4.6.2).   For forest crops,  operation can often  continue
              during subfreezing^ conditions.

              Seasonal crops.    When single  annual crops  are grown,
              wastewater is not  normally  applied  during  the   winter
              season, although applications may  occur  after   harvest
              and before the next planting.    The design monthly per-
              colation rate may be calculated as follows:

                pw(monthly) = [Pw(daily)]  x (No. of operating d/mo)
6.
          Calculate the monthly hydraulic  loading rate  using
          Equation 4-3.   The  monthly hydraulic  loadings  are
          summed   to   yield  the  allowable  annual  hydraulic
          loading  rate  based  on soil  permeability  [L w/p\].
          The  computation  procedure  is  illustrated by  an
          example   for  both   arid   and   humid  climates   in
          Table 4-17.     The  example   is   based  on  systems
          growing  permanent pasture and  having similar winter
          weather  and soil conditions.   Downtime  is allowed
          for  freezing  conditions,  but  pasture  management
          does not require harvesting downtime.

 The  allowable    hydraulic  .loading   rate   based   on    soil
 permeability calculated by  the above procedure  L^/pN is  the
 maximum rate for  a particular site and  operating conditions,
 and this rate will be used  for design if there  are no other
 constraints  or  limitations.    If  other  limitations exist,
 such as percolate  nitrogen concentration,  it  is  necessary  to
 calculate  the  allowable  hydraulic  loading   rate  based   on
 these limitations  and compare that rate with  the L ,m.   The
 lower of the two  rates  is  used for design.          ( '•

     4.5.2     Hydraulic Loading Rate Based on
               Nitrogen  Limits

 In  municipal wastewaters  applied to  SR systems,  nitrogen  is
 usually the limiting  constituent when protection  of potable
 ground  water aquifers  is  a  concern.    If  percolating water
 from an SR  system will enter 'a potable ground  water aquifer,
 then  the   system   should   be  designed   such  that   the
 concentration of  nitrate  nitrogen  in the  receiving  ground
water at the project boundary does  not exceed  10 mg/L.
                              4-30

-------
                           TABLE  4-17
         WATER BALANCE TO DETERMINE HYDRAULIC  LOADING
               RATES  BASED ON SOIL PERMEABILITY
                               cm
,-Ionth
Arid
(2) (3)
ET, Pr,
Evapotrans- precip-
piration itation


(4) = (2)-(3)
Net ET

(5)
PW a
Percolation

(6) = (4) + (5)
Lw(p) '
wastewater
hydraulic loading

climates
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
2.3
5.1
9.7
13.2
17.7
21.8
23.9
22.1
14.7
10.9
5.1
2.5
149.0
3.0
2.8
2.8
2.0
0.5
0.3
—
—
0.3
0.8
1.3
2.5
16.3
-0.7
2.3
6.9
11.2
17.2
21.5
23.9
22.1
14.4
10.1
3.8
0.0
132.7
5.1
12.6
16.3
18.0
18.0
18.0
18.0
18.0
18.0
18.0
17.0
14.1
191.1
4.4
14.9
23.2
29.2
35.2
39.5
41.9
40.2
32.4
28.1
20.8
14.1
323.8
Humid
climates
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual


1.3
1.3
3.0
5.8
10.9
14.7
15.7
15.0
10.9
5.8
2.5
1.3
88.2


13.5
13.0
15.5
11.3
11.1
11.7
13.3
11.1
9.1
8.0
8.0
12.8
138.4


-12.2
-11.7
-12.5
- 5.5
- 0.2
3.0
2.4
3.9
1.8
- 2.2
- 5.5
-11.5
-50.2


5.1
12.6
16.3
18.0
18.0
18.0
18.0
18.0
18.0
18.0
17.0
14.1
191.1


0.0b
0.9
3.8
12.5
17.8
21.0
20.4
21.9
19.8
15.8
11.5
2.6
148.0
      a. Based on a soil profile with a moderately slow permeability
         (0.5 to 1.5 cm/h) ,  Pw(inax) = (0.5 cm/h)  (24 h/d)  (30 d/mo) (0.05) = 18.0

      b. 1  cannot be less than zero.
The  approach  to  meeting  this  requirement  involves  first
estimating an  allowable  hydraulic  loading  rate based  on an
annual  nitrogen  balance  (Lw/n\)f and  comparing that  to the
previously   calculated   Lw(p)    to   determine  which   value
controls.   The detailed  stepis in this  procedure are:

    1.    Calculate  the  allowable   annual hydraulic  loading
          rate  based  on  nitrogen  limits  using the  following
          equation:
                T  ,  x  _ (C )(Pr - ET)
                •Lw(n)  -- &
(4-4)
                                       -  C
                              4-31

-------
where  Lw(n) =
          CP =

          Pr =

          ET =

           u =


          cn =
allowable annual hydraulic loading rate
based on nitrogen limits, cm/yr

nitrogen concentration in percolating water,
mg/L

precipitation rate, cm/yr

evapotranspiration rate, cm/yr

nitrogen uptake by crop, kg/ha•yr
(Tables 4-2, 4-11, 4-12)

nitrogen concentration in applied
wastewater, mg/L (after losses in
preapplication treatment)

fraction of applied nitrogen removed by
denitrification and volatilization (4.2.2).
         Compare the value  of.  Lw/n)  with the value of
         calculated previously (Section 4.5.1).  If L
         greater than  L ,  x,i do not  continue  the procedure
                       for design.  If
                             is less than or
                          e'based  on
and use
equal  to "£J/p\ >  design  should uc  uaocu un  u  ,  *.
The value  or i^(n) calculated  in Step 1 above may
be used  to estimate land requirements  for purposes
of  Phase  2  planning,   but  for  final  design  the
procedure  outlined  in Steps 3 and 4 should be used.

Calculate  an  allowable  monthly  hydraulic   loading
rate  based on  nitrogen  limits using  Equation 4-4
with  monthly values  for Pr,  ET, and  U.    Monthly
values  for  Pr  and  ET  will  have  been determined
previously  for   the  water   balance   table   (see
Section 4.5.1).  Monthly values for crop uptake (U)
can  be  estimated  by  assuming  that   annual  crop
uptake is  distributed monthly according  to the same
ratio as monthly to total growing season ET.

If data  on  nitrogen  uptake  versus time,  such as
that  shown  in  Figure 4-2, are available  for  the
crops and  climatic region specific  to the  project
under design,  then  such  information may be  used to
develop  a  more   accurate   estimate   of   monthly
nitrogen uptake values.

Compare  each  monthly  value  of  I\,(n)  with  the
corresponding  monthly  value   of  LW/P)  calculated
previously  (Section 4.5.1).   The lower  of  the two
                            4-32

-------
            values   should   be   used   for   design.     The   design
            monthly hydraulic  loading  rates  are  summed  to yield
            the  design annual  hydraulic loading  rate.

            The  above  procedure  is   illustrated  in  Example  4-1
            for  an  arid   climate  and  a  humid  climate using  the
            climatic    and    operating    conditions    given    in
            Table  4-17.
EXAMPLE   4-1:
LOADING  RATE
        CALCULATION  TO   ESTIMATE   DESIGN   HYDRAULIC
    Conditions
        Applied wastewater nitrogen concentration (Cn)» mg/L
        Crop nitrogen uptake  (U),  kg/ha-yr
        Denitrification + volatilization
                        (as a fraction of applied nitrogen)
        Limiting percolate nitrogen concentration (Cp), mg/L
        Precipitation (Pr)  and evapotranspiration (ET) (see
        Table 4-17).
                                               Humid
                                              climate
                                                25

                                               336


                                                 0.2

                                                10
                                         Arid
                                        climate

                                          25

                                         336


                                          0.2

                                          10
    Calculations
    1.
        Calculate allowable annual 1^ (nj  using Equation 4-4.
                   (Cp) (Pr - ET) + (U) (10)
                      (1 - f) (Cn) - Cp
                     Humid climate
                                                       Arid climate
         Lw(n)
 (10)(138.4 - 88.2) + (336)(10)
      (1 - 0.2) (25) - 10
 386.2 cm/yr
                                             Lw(n)
    2.  Compare LW (n) with
                 Humid climate
         Lw(n) = 386.2 cm/yr
         Lw(p) = 148.0 cm/yr
         .•.Lw(p)  controls.  Use Lytpi for
          design (see Table 4-17)
                      (10)(16.3 - 149) + (336)(10)
                            (1 - 0.2) (25)  - 10

                      203.3  cm/yr


                      Arid climate
                             Lw(n)  = 203.3 cm/yr
                             Lw(p)  = 323.8 cm/yr
                                     controls.
                               Step'3.
                                              Continue to
    3.
        Compute allowable monthly Lw(n)  using Equation 4-4 and estimated monthly nitrogen
        uptake and monthly  (Pr - ET) values.  Compare with monthly LW(P)  and use lower
        value for design.  Tabulate results.  (Arid climate only)
        Month
        Jan
        Feb
        Mar
        Apr
        May
        Jun
        Jul
        Aug
        Sep
        Oct
        Nov
        Dec
        Annual
(Pr - ET), cm  (U), kg/ha  Lw(nl> cm  Lw(p), cm  Design
  0.
 -2.
 -6.
-11.
-17,
-21
-23.
-22,
-14
-10,
 -3,
     0.0
                 -132.7
  5.2
 11.5
 21.9
 29.8
 39.9
 49.2
 53.9
 49.8
 33.1
 24.6
 11.5
  5.6
336
  5.
  9.
 15.
 18.
 22.
 27.
 30.
 27.
 18.
 14.
  7.7
  5.6
203.3
                                     4.4
                                    17.5
                                    23.
                                    29.
                                    35.
                                    39.
                                    41.
                                    40.
                                    32.4
                                    28.
                                    20.
  4.
  9.
 15.
 18.
 22.
 27.
 30.
 27.
 18.
 14.
  7.
                                    14.1
                                   323.8
  5.6
201.8
                                      4-33

-------
 The  above   procedure   for  calculating  allowable  hydraulic
 loading  rate   based  on, nitrogen  limits  is  based  on  the
 following assumptions:
 1

 2

 3
          All percolate nitrogen is in the nitrate form.

          No storage of -nitrogen occurs in the soil profile.

          No mixing  and  dilution  of  the  percolate with  in
          situ ground water occurs.
 Use  of  these  assumptions results  in  a very  conservative
 estimate   of  percolate  nitrogen.    This  procedure  should
 ensure  that the nitrogen  concentration in the  ground  water
 at  the  project  boundaries will be  less than  the  specified
 value of  Cp.

 As indicated  by the  example,  nitrogen  loading is more likely
 to govern the design  hydraulic loading rate  for  systems  in
 arid  climates than  in humid  climates.   The  reason  for this
 is that  the net positive ET rate in arid climates  Cciuses  an
 increase  in the concentration  of  the  nitrogen  level  in  the
 percolating water.

 For systems in  arid  climates,  it  is  possible  that the design
 monthly  hydraulic loading rates  based  on  nitrogen  limits
 will  be  less than  the irrigation requirements (IR) of  the
 crop.   The designer should compare the design Lw  with  the
 irrigation  requirement   to  determine   if   this   situation
 exists.   If  it  does exist,  the  designer has  three  options
 available  to  increase LWn sufficiently to meet the IR.
    1.
    2.
     Reduce  the  concentration of  applied  nitrogen  (Cn)
     through preapplication treatment.      '  '   ,

     Demonstrate  that  sufficient  mixing   and  dilution
     (see  Section 3.6.2) will  occur with  the existing
     ground  water to permit  higher  values  of percolate
     nitrogen   concentration   (C^)   to   be   used   in
     Equation 4-4.
3.
         Select  a  different  crop  with  a  higher nitrogen
         uptake  (U).

    4.5.3     Hydraulic Loading Rate Based on
              Irrigation Requirements

For SR systems in arid regions that have crop production  for
revenue as  the objective,  the design hydraulic loading rate
can  be  determined  on the  basis  of  the  crop   irrigation

-------
requirement  (see  Section  4.3.2.1)
balance equation:
                       using  a  modified water
                      Lw =  IR -  Pr
                                         (4-5)
where  LW =  hydraulic loading rate

       IR =  crop irrigation requirement

       Pr =  precipitation
The annual  hydraulic loading rate  is  determined by  summing
the   monthly   hydraulic   loading   rates   computed   using
Equation 4-5.   The  computational  procedure  is  similar  to
that outlined in Section 4.5.1.

The monthly hydraulic  loading  rate  based on  IR should  be
checked against the  allowable rate based on nitrogen  limits
(Lw/n\) as discussed in Section 4.5.2.
    4.5.4
Land Area Requirements
The  land  area  to which  wastewater is  actually  applied  is
termed  a  field.   In  addition to the  field  area, the  total
land  area  required  for  an  SR  system  includes  land  for
preapplication   treatment  facilities,  administration   and
maintenance  buildings,  service  roads,   buffer  zones,   and
storage reservoir.   Field area requirements and  buffer  zone
requirements  are discussed in  this section.   Storage  area
requirements   are  discussed   in  Section  4.6   and   area
requirements   for   preapplication   treatment    facilities,
buildings,  and  service   roads  are  determined by standard
engineering practice not  included in this manual.

         4.5.4.1   Field Area Requirements

The  required  field  area  is  determined  from  the  design
hydraulic loading rate according  to the  following  equation:
                   (Q)(365)(d/yr) + AV
              Aw =
                                                        (4-6)
where  Aw =  field area, ha (acre)

       Q  =  average daily community wastewater flow
             (annual basis), m3/d (ft3/d)
                            4-35

-------
      AVS =
        C =
 net loss or gain in stored wastewater volume
 due to precipitation, evaporation and seepage
 at storage pond, m3/yr (ft3/yr)

constant, 100 (3,630)

design hydraulic loading rate, cm/yr (in./yr)
The  first calculation  of field  area  must  be  made without
considering  net  gain or  los?  from storage.   After storage
pond area is computed, the value  of AV  can  be computed  from
precipitation and evaporation data.  Field area then must be
recalculated to account for AV_.
                              o                   -     ,

Using the design hydraulic loading rate for  the arid climate
in  Example  4-1,  the field area  for  a  daily wastewater  f.low
of 1,000 m3/d, neglecting AV^f is:
                     (1,000)(365)
                  (104)(201.8)(0.01)
                           = 18.1 ha
         4.5.4.2   Buffer Zone Requirements

The objectives  of buffer zones  around  land treatment sites
are  to control  public access,  and  in  some  cases,  improve
project  aesthetics.    There  are no   universally  accepted
criteria for determining the width of buffer zones  around SR
treatment systems.   In practice, the widths of buffer -zones
range  from zero  for  remote  systems  to  60 m (200 ft) or more
for systems  using sprinklers near populated areas.    In many
states,  the  width  of  buffer  zones  is  prescribed  by
regulatory  agencies, and  the  designer   should  determine if
such requirements exist.

The  requirements  for  buffer  zones in forest  systems  are
generally  less   than  those  of  other  vegetation  systems
because  forests  reduce  wind  speeds   and,  therefore,  the
potential  movement  of aerosols.    Forests  also provide  a
visual screen  for the publip.   A minimum buffer zone width
of  15  m (50  ft) that  is  managed as a multistoried forest
canopy  will be   sufficient  ,to  meet all  objectives.   The
multistoried effect  is achieved  by  maintaining mature trees
on  the inside edge  of  the  buffer next  to the irrigated area
and filling  beneath the canopy  and  out to the outside edge
of  the buffer with  trees  that grow  to  a moderate height and
have full,  dense canopies.    Evergreen  species are  the best
selection if year-round operation is planned.   If existing
natural forests  are  used  for the buffer, a minimum width of
                             4-36

-------
15 m may  be  sufficient to meet  the  objectives,  if there  is
an adequate vegetation density.

4.6  Storage Requirements

In  almost all  cases,  SR  systems  require  some  storage for
periods when the amount of available wastewater flow exceeds
the  design hydraulic  loading  rate.   The  approach  used  to
determine  storage  requirements  is  to  first  estimate  a
storage volume requirement using a water balance computation
or  computer  programs  developed to  estimate  storage   needs
based on  observed  climatic variations throughout the United
States.    The  final  design volume  then  is  determined  by
adjusting  the  estimated  volume  for  net  gain or  loss due  to
precipitation  and  evaporation  using  a monthly water balance
on  the  storage  pond.    These estimating  and  adjustment
procedures are described in the  following sections.

Some  states  prescribe a  minimum  storage  volume  (e.g.,  10
days  storage).    The  designer  should   determine   if   such
storage requirements exist.

All  applied  wastewater does  not  need  to  pass  through the
storage  reservoir.    In  cases  where  primary effluent  is
suitable  for application, only  the water  that must be stored
need  receive   prestorage   treatment.     Stored  and   fresh
wastewater is  then blended for  application.

    4.6.1      Estimation of Volume Requirements Using
               Storage Water Balance  Calculations

An  initial  estimate  of the storage  volume requirements may
be  determined  using  a water  balance calculation procedure.
The  basic steps in the procedure  are illustrated using the
arid climate example from Example 4-1:

    1.    Tabulate  the  design  monthly hydraulic loading  rate
          as indicated  in Table  4-17.

     2.    Convert  the  actual volume  of  wastewater available
          each  month   to   units  of  depth   (cm)  using the
          following relationship.
                     W  =  (Qm)dO"2)
(4-7)
         where  Wa -  depth of  available wastewater,  cm1

                Q_ =  volume of  available  wastewater  for  the
                      month, m^
                             4-37

-------
        Aw =  field area,  ha
Insert  the  results  for  each  month  into  a water
balance table,  as  illustrated  by  the  example  in
Table   4-18.      In   some   communities,.   influent
wastewater flow varies  significantly  with the  time
of  year.   The  values  used for  Qm should  reflect
monthly   flow   variation   based   on   historical
records.     In   this   example,   no   monthly   flow
variation  is  assumed.

                 TABLE 4-18
 ESTIMATION OF STORAGE  VOLUME REQUIREMENTS
     USING WATER BALANCE CALCULATIONS
                     cm
(1)


Month
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
(2)
wastewater
hydraulic
loading
14.5
7.7
5.6
4.4
9.2
15.0
18.6
22.6
27.6
30.0
27.9
18.7
(3)
Wa,
available
wastewater3
16.8
16.8
16.8
: 16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
(4)
Change
in
storage
2.3
9.1
11.2
12.4
7.6
1.8
- 1.8
- 5.8
-10.8
-13.2
-11.1
- 1.9
(5)

Cumulative
storage
-0.2b
2.3
11.4
22.6
35.0
42.6
44.4°
42.6
36.8
26.0
12.8
1.7
    Annual
            201.8
                    201.6
    a.  Based on a field area of 18.1 ha and 30,438 m^/mo
       of wastewater.
    b.  Rounding error. Assume zero.
    c.  Maximum storage month.


Compute  the  net change  in  storage  each month  by
subtracting the monthly  hydraulic loading  from the
available wastewater in the same  month.

Compute  the cumulative  storage at the end  of each
month  by adding the  change in  storage  during one
month  to the  accumulated quantity from the previous
month.    The  computation  should  begin  with  the
reservoir  empty  at  the   beginning  of the  largest
storage  period.   This month is  usually  October  or
November,   but   in   some  humid   areas  it  may  be
February or March.
                    M--38

-------
    5.   Compute  the   required   storage   volume  using  the
         maximum  cumulative storage  and  the  field area  as
         indicated below.

         Required storage  volume         '
         =  (44.4 cm)(18,1  ha)(10~2  m/cm)(104 m2/ha)
         =  8.04 x 104 m3

The  advantage  of   using   this  water  balance  procedure  to
estimate  storage volume   requirements  is  that  all  factors
that  affect  storage,  including   (1)  seasonal  changes  in
precipitation,  evapotranspiration,  and wastewater  flow;  and
(2) downtime  for   precipitation  or  crop   management  are
accounted  for  in  the  design  hydraulic loading  rate.   The
disadvantage  of this  procedure  is that  downtime  for  cold
weather  has  to be  determined separately and  added   in  by
reducing allowed monthly percolation.

    4.6.2     Estimated Storage Volume  Requirements
              Using  Computer Programs

The National  Climatic  Center  in  Asheville,  North  Carolina,
has  conducted  an   extensive   study of  climatic  variations
throughout  the  United States   and   the   effect   of   these
variations  on   storage  requirements  for   soil   treatment
systems  [35].   Based on this study,  three  computer  programs,
as presented  in Table  4-19, have been developed to estimate
the storage days  required when inclement  weather  conditions
preclude land treatment system operation.

                         TABLE 4-19
        SUMMARY OF COMPUTER PROGRAMS  FOR DETERMINING
            STORAGE  FROM CLIMATIC VARIABLES  [36]
        EPA
       program  Applicability
Variables
                Remarks
EPA-1
EPA- 2
EPA- 3
Cold climates
Wet climates
Moderate climates
Mean temperature,
rainfall , snow depth
Rainfall
Maximum and minimum
temperature, rainfall,
'snow depth
Uses freeze index
Storage to avoid
surface runoff
Variation of EPA-1
for more temperate
regions
Depending on  the dominant climatic  conditions of a  region,
one  of  the three  computer programs will  be most  suitable.
The  program  best suited to  a  particular region  is shown  in
Figure 4-3.   The storage days are calculated  for recurrence
intervals of  2,  4, 10, and 20  years.    A  list   of  stations
                             4-39

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-------
with  storage  days  for  10 and  20  year  recurrence  intervals
from  EPA  computer  programs  is  presented  in Appendix  F.   A
list   of  244   stations   for  which  EPA-1   has  been  run  is
included  in reference  [35].  To use  these  programs,  contact
the  National  Climatic  Center  of, the  National  Oceanic  and
Atmospheric  Administration   in  Asheville,  North   Carolina
28801;  a  fee is required.

Storage   days   required   for   crop   management   activities
(harvesting,  planting,  etc.) must  be added  to the  computer
estimated  storage days  due  to  weather  to  obtain the   total
storage days required in  each month.   The  estimated  required
storage   volume   is   then   calculated   by   multiplying   the
estimated  number   of  storage  days  in  each month times  the
average daily flow  for the  corresponding month.

    4.6.3      Final  Design  Storage  Volume  Calculations

The  estimated  storage volume requirement   obtained by  water
balance calculation  or computer programs must be  adjusted  to
account for net gain  or loss in volume  due to precipitation
or  evaporation.   The  mass  balance procedure  is  Illustrated
by  Example  4-2 using  arid climate data  from  Example  4-1  and
the  estimated  storage volume from Table  4-18.   .An  example
for a  system in a  more humid climate  is given in  Appendix  E.

EXAMPLE 4-2:   CALCULATIONS TO DETERMINE FINAL STORAGE VOLUME
REQUIREMENTS

   1.  Using the initial estimated storage volume and an assumed storage pond depth
      compatible with local conditions, calculate a required surface area  for the
      storage pond:
                           AS = Vs^St)                    (4-8)
      where As  = area of  storage pond, m2
      vs{est)  = estimated storage volume, m3
          ds  = assumed  pond depth, m
      For the example, assume ds = 4 m  ,
                           .    (8.02 x 104 m3)
                           AS	j-j;	
                              = 2 x 104 m2
   2.  Calculate the monthly net volume of water gained or lost from storage due  to
      precipitation, evaporation, and seepage:   '
               AVS =  (Pr  - E - seepage) (As) (10~2 m/cm)             (4-9)
     where AVS = net gain or loss in storage volume, m3
           Pr = design  monthly precipitation, cm
           E = monthly evaporation, cm
           As = storage pond area
      Estimated lake evaporation in the local area should be used for E, if available.
      Potential ET values may be used if no other data are available.  Tabulate monthly
     values and sum to determine the net annual AVS.
     For example, assume:
                         E = ET
                     Seepage = 0
     Results are tabulated in Column (2)  of Table 4-20.

-------
                                          TABLE  4-20
                         FINAL STORAGE VOLUME REQUIREMENT CALCULATIONS
                                          m3 x 103


Month
Oot
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
(2)
AVS
Net
gain/loss
-2.0
-0.7
0.0
0.1
-0.5
-1.4
-2.2
-3.4
-4.3
-4.8
-4.4
-2.9
(3)
Available
wastewater
30.4
30.4
30.4
30.4
30.4
30.4
30.4
30.4
30.4
30.4
30.4
30.4
(4)
Vw
Applied
wastewater
24.3
12.9
9.4
7.4
15.4
25.2
31.2
37.9
46.3
50.3
46.8
31.4
(5) = (2) + (3) - (4)
AVs
Change in storage
4.1
16.8
21.0
23.1
14.5
3.8
-3.0
-10.9
-20.2
-24.7
-20.8
-3.9

Cumulative
storage
-0.2a
4.1
20.9'
41.9
65.0
79.5
83. Jb
' 80.3
69.4
49.2
24. 5
3.7
          Annual
                    -26.5
                               365
                                           338.5
          a.   Rounding error (assume zero).

          b.   Maximum design storage volume.

    Tabulate  the  volume of wastewater available each month (Qm)  accounting for any
    expected  monthly flow variations.   For the example,  monthly  flow is constant.
                              (1,000 m3/d)(365 d/yr)
                                     12 mo/yr
                              30.4 x 1Q3 m3/mo                                  :
                     Qm
    Calculate an adjusted field area to account for annual net gain/loss in storage
    volume.
                        Aw1  =
                                                   m/cm)
                               (1CP mVha) U<>-
where  AW' » adjusted field area, ha
     EAVs  = annual net storage gain/loss, m3
      £Qm  = annual available wastewater, m3

       Ly,  - design annual hydraulic loading rate, cm

For the example:

                    AW- =
                                                                            (4-1.0)
                              365 X 103 - 26.5 x 103
                                (201.8) (10.4) (io-
                            = 16.8 ha
    Mote:
        The  final  design calculation reduced the field area
        from 18.1  ha to 16.8 ha.
5.
    Calculate the monthly volume of applied wastewater  using  the  design  monthly
    hydraulic loading rate and adjusted  field  area:
(Lw>
                                               ™2/ha) (10~2 m/cm)
                                                                          (4-111
    where Vw = monthly volume of applied wastewater, m3

          LW z design monthly hydraulic loading rate, cm
         Aw' = adjusted field area, ha
    Results are tabulated in Column  (4) of Table 4-20.

6.  Calculate the net change in storage each month by subtracting  the monthly
    applied wastewater (Vw) from the sura of available wastewater  (Qra) and  net
    storage gain/loss (AVS) in the same month.  Results are  tabulated in
    Column  (5) of Table 4-20.

7.  Calculate the cumulative storage volume at the end of each month by adding  '
    the change in storage during one month to the accumulated total from the
    previous month.  The computation should begin with the cumulative storage
    equal to zero at the beginning of the largest storage period.  The maximum
    monthly cumulative volume is the storage volume requirement used for design.
    Results are tabulated in Column  (6) of Table 4-20.

                          Design Vs = 83.3 x 103 ra3

-------
     8.  Adjust the assumed value of storage pond depth (ds) to yield the required
        design storage volume using Equation 4-12.
        For the example
                                                       (4-12;
                              83.3 x 103 m3
                                2 x 10« mi

                             = 4. 16 m
        If the pone depth cannot be adjusted due to subsurface constraints, then the
        surface area must be adjusted to obtain the required design volume.  However,
        if the surface area is changed, another iteration of the above procedure will
        be necessary because the value of net storage gain/loss 'iVs)will be different
        for a new pone area.
     4.6.4
Storage  Pond  Design Considerations
 Most   agricultural   storage    ponds   are   constructed   of
 homogeneous earth embankments,  the  design of which  conforms
 to the  principles  of  small dam  design.    Depending  on  the
 magnitude of  the project,  state  regulations  may govern  the
 design.   In  California,  for  example,  any  reservoir  with
 embankments  higher  than  1.8  m  (6  ft)  and  a  capacity  in
 excess  of  61,800  mj   (50  acre-ft)   is  subject  to  state
 regulations on  design  and  construction  of  dams, and  plans
 must   be  reviewed  and  approved  by  the appropriate  agency.
 Design criteria  and information sources are included  in  the
 U.S.  Bureau of Reclamation publication, Des i gn of Small Dams
 [37].   In many  cases,  it will  be necessary  that  a competent
 soils  engineer  be  consulted  for proper soils  analyses  and
 structural design of  foundations and embankments.

 In   addition   to   storage  volume,   the  principal   design
 parameters are  depth and area.   The  design  depth  and  area
 depend on the function  of the pond and  the topography  at  the
 pond   site.    If  the  storage  pond   is  to  also  serve  as  a
 facultative  pond, then  a  minimum water  depth of at least  0.5
 to  1  m (1.5  to  3 ft) should be  maintained  in the pond when
 the  stored volume is at  a minimum.   The  area must  also  be
 sufficient to  meet  the  BOD pond  loading  criteria  for  the
 local   climate.     The  use  of  aerators   can  reduce  area
 requirements.    The  maximum depth   depends   on .whether  the
 reservoir is constructed  with  dikes or embankments on  level
 ground or is  constructed  by damming a natural  water  course
or  ravine.   Maximum  depths of  diked  ponds  typically  range
 from  3 to  6  m  (9 to 18  ft).   Other  design  considerations
 include  wind  fetch,  and  the  need  for riprap and  lining.
These  aspects of  design are covered in standard  engineering
references and assistance  is  also available  from local  SCS
offices.
                              4-43

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4.7  Distribution System

Design  of  the  distribution  system  involves  two  steps:
(1) selection  of  the  type  of  distribution  system,  and
(2) detailed design  of  system components.  Emphasis in this
section is  placed  on criteria for  selection  of the type of
distribution system.   Design  procedures for SR distribution
systems are presented  in  Appendix E.   Only  basic  design
principles  for each  type of  distribution  system  are  pre-
sented  in  the  manual,   and  the  designer  is referred  to
several  standard  agricultural  engineering  references  for
further  design  details.    Certain  design  requirements  of
distribution systems  for  forest  crop systems do not conform
to  standard agricultural  irrigation practice  and  are  dis-
cussed under a separate heading.
    4.7.1
Surface Distribution Systems
With surface  distribution systems, water  is  applied to  the
ground surface  at one end of  a  field  and allowed to spread
over  the   field   by  gravity.    Conditions  favoring   the
selection  of  a  surface  distribution  system  include   the
following:

    1.   Capital  is  not  available  for  the  initial  investment
         required for more sophisticated  systems.

    2.   Skilled  labor  is available  at reasonable rates  to
         operate  a surface system.

    3.   Surface   topography   of   land   requires   little
         additional  preparation  to make  uniform grades  for
         surface  distribution.
The  principal   limitations  or
systems include  the  following:
                    disadvantages  of  surface
         Land  leveling  costs
         terrain.
                 may  be  excessive  on uneven
         Uniform distribution  cannot  be  achieved  with  highly
         permeable  soils.

         Runoff control  and  a  return  system must  be  provided
         when  applying wastewater.

         Skilled labor is  usually  required  to achieve  proper
         performance.

         Periodic maintenance  of leveled surface  is  required
         to maintain  uniform grades.
                             4-44

-------
Surface  distribution  systems  may be  classified  into  two
general  types:  ridge  and  furrow  and  graded  border  (also
termed  bermed  cell).  The  distinguishing physical  features
of  these  methods are  illustrated  in  Figure  4-4.  A  summary
of  variations  of  the  basic  surface  methods and  conditions
for  their  use  is   presented  in  Table  4-21.    Details  of
preliminary design are presented  in Appendix  E.
    4.7.2
Sprinkler Distribution Systems
Sprinkler distribution systems simulate rainfall by  creating
a rotating  jet of water  that  breaks  up into small  droplets
that  fall  to  the  field  surface.    The  advantages   and
disadvantages  of  sprinkler  distribution systems relative  to
surface distribution systems are summarized  in Table 4-22.

         4.7.2.1   Types  of Sprinkler Systems

In  this  manual,  sprinkler  systems  are  classified according
to  their  movement  during and between  applications  because
this  characteristic determines  the  procedure  for   design.
There are three major  categories of sprinkler systems based
on   movement:    (1)   solid   set,   (2)    move-stop,    and
(3) continuous  move.    A summary  of  the  various  types  of
sprinkler systems under each category is given in Table  4-23
along with respective operating characteristics.

         4.7.2.2   Sprinkler Distribution Systems for Forest

The  requirements  of  distribution  systems   for  forests   are
somewhat  different  from those  for  agricultural  and   turf
crops.

Solid-set  irrigation  systems  are  the  most  commonly   used
systems in  forests.   Buried systems are less susceptible  to
damage from  ice and snow and  do not  interfere  with forest
management    activities    (thinning,    harvesting,     and
regeneration).   A  center pivot  irrigation  system  has   been
used  in Michigan  for irrigation of Christmas  trees because
their growth height would not exceed the height of the pivot
arms.  Traveling guns have also been used to irrigate short-
term rotation hardwood plantations.

As  discussed   in  Section  4.3.2.4,  the  design  sprinkler
application rate  is  usually not  limited by  the infiltration
capacity of most forest soils..   Steep grades (up to  35%),  in
general,  do not limit  the design hydraulic loading  rate  per
application for forest systems.  In fact, hydraulic  loadings
per application may be increased up to 10% on grades greater
than  15% because  of the  higher  drainage  rate.   Precautions
must  be taken to make sure that water  draining  through  the
surface soil  does  not  appear  as  runoff  further  down   the
slope.

                            4--U5

-------
                                     -?*+•&&»
     y -^tS^^,^^^:^S^*^50P"^
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(a)   RIDGE AND  FURROW  METHOD
      USING GATED  PIPE
   ^SS-^^&S^^

   (b)   GRADED BORDER  METHOD

             FIGURE 4-4
 SURFACE DISTRIBUTION METHODS

             4-4-6

-------











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-------
                                     TABLE  4-22
          ADVANTAGES  AND  DISADVANTAGES  OF   SPRINKLER
           DISTRIBUTION  SYSTEMS  RELATIVE  TO  SURFACE
                             DISTRIBUTION   SYSTEMS
                Advantages
                                                             Disadvantages
 1.  Can be used on porous  and variable soils.
 2.  Can be used on shallow soil profiles.L-
 3.  Can be used on rolling terrain.
 4.  Can be used on easily  eroded soils.
 5.  Can be used with small flows.
 6.  Skilled labor not required.
 7.  Can be used where high water tables exist.
 8.  Can be used for light,  frequent
     applications.
 9.  Control and measurement of applied water
     is easier.
10.  Interference with cultivation is minimized.
11.  Higher application efficiencies are
     usually possible.
12.  Tailwater control and  reapplication
     not usually required.
 1.   Initial capital cost  can be high.
• 2.   Energy costs are higher than for surface
     systems.
 3.   Higher humidity levels can increase
     disease potential,  for some crops.
 4.   Sprinkler application of high salinity
     water can cause leaf  burn.
 5.   Water droplets can  cause blossom damage to
     fruit crops or reduce the quality of some
     fruit and vegetable crops.
 6.   Portable or moving  systems can get stuck
     in  some clay soils.
 7.   Higher levels of preapplication treatment
     generally are required for sprinkler systems
     than for surface systems to prevent operating
     problems (clogging).
 8.   Distribution is subject to wind distortion.
 9.   Wind drift of sprays  increases,the potential
     for public exposure to wastewater.
SPRINKLER
Typical
application
rate , cm/h
Solid set
Permanent
Portable
Move- stop
Hand move
End tow
Side wheel roll
Stationary gun
Continuous move
Traveling gun
Center pivot
Linear move

0
0

0
0
0
0

0
0
0

.13-5.
.13-5.

.O3-5.
.03-5.
.25-5.
.64-5.

.64-2.
.51-2.
.51-2.

08
08

08
08
08
08

54
54
54
TABLE 4-23
SYSTEM CHARACTERISTICS
Labor
required
per
application,
h/ha

0.
0.

0
0.
0.
0.

0.
0.
0.

02-0.
08-0.

.2-0.
O8-0.
04-0.
08-0.

04-0.
02-0.
02-0.

04
10

6
16
12
16

12
06
06
Nozzle Size of
pressure single
range, system,
N/cm2 ha

21-69
21-41

21-41
21-41
21-41
35-69

35-69
10-41
10-41

Unlimited
Unlimited

8-16
8-32
8-16

16-41
16-65
16-130
Maximum
crop
Shape of Maximum height,
field grade, % m

Any shape ~-
Any shape — —

Any shape 20 —
Rectangular 5-10 —
Rectangular 5-10 1-1.2
Any shape 20 —

Any shape
Circular3 5-15 2.4-3
Rectangular 5-15 2.4-3
  a.   Travelers are available to allow irrigation of any shape  field.

-------
Solid  set  sprinkler  systems   for  forest  crops  have   some
special  design requirements.    Spacing of  sprinkler heads
must be closer and operating pressures  lower  in  forests  than
other  vegetation  systems  because  of the  interference  from
tree trunks and leaves and possible damage to bark.   An  18 m
(60  ft)  spacing  between,  sprinklers  and  a  24  m  (80   ft)
spacing  between  laterals  has  proven  to  be  an  acceptable
spacing  for  forested  areas   [39].    This  spacing,   with
sprinkler overlap, provides  good wastewater distribution at
a reasonable cost.  Operating pressures at the nozzle should
not exceed  38  N/cm2  (55 lb/in.2),  although pressures up to
59  N/cm2  (85  lb/in.)  may  be   used  with mature  or thick-
barked  hardwood  species.   The  sprinkler risers  should be
high  enough  to  raise  the  sprinkler   above  most   of   the
understory  vegetation,  but  generally  not  exceeding  1.5 m
(5 ft).   Low-trajectory sprinklers  should be  used  so  that
water  is  not  thrown  into the tree canopies, particularly in
the winter  when  ice buildup on pines and  other evergreen
trees can cause the trees to be  broken  or uprooted.

A number  of  different methods of applying wastewater during
subfreezing   temperatures   in   the   winter   have    been
attempted.    These  range  from  various  modifications  of
rotating   and   nonrotating   sprinklers    to   furrow    and
subterranean applications.   General practice  is to use  low-
trajectory,  single   nozzle  impact-type  sprinklers,   or   low
trajectory,  double  nozzle  hydraulic  driven  sprinklers.   A
spray  nozzle  used   at West  Dover,  Vermont,  is shown in
Figure 4-5.

Installation  of  a   buried  solid-set  irrigation  system in
existing  forests  must be done  with  care  to avoid excessive
damage  to  the  trees  or  soil.    Alternatively,  solid-set
systems  can  be   placed  on  the  surface  if  adequate   line
drainage  is provided  (see  Figure 4-6).   For buried systems,
sufficient vegetation must be removed during construction to
ensure   ease   of   installation   while   minimizing    site
disturbance  so  that  site  productivity  is not  decreased or
erosion hazard  increased.   A 3  m wide  (10  ft)  path cleared
for  each   lateral   meets  these   objectives.     Following
construction, the disturbed  area must  be  mulched or seeded
to  restore  infiltration   and   prevent-  erosion.    During
operation  of the  land  treatment  system,  a  1.5  mi (3   ft)
radius  should  be kept  clear around  each sprinkler,,   This
practice  allows  better  distribution  and  more   convenient
observation  of  sprinkler   operation.    Spray  distribution
patterns  will  still  not meet  agricultural  standards,   but
this is  not as important  in forests because  the roots  are
quite extensive.
                             4-50

-------
              a .
                  SPRAYING
             b.  DRAINING
 BRASS TUBE  IN LEFT HALF DRAINS QUICKLY,
 UNTIL LIQUID LEVEL IS  BELOW ITS TOP.
 THEN ONLY RIGHT HALF  CONTINUES TO  DRAIN.
             c.  LINE DRAINED

  SMALL AMOUNT OF ICE HAS FORMED  TO BLOCK
  RIGHT HALF OF NOZZLE.  BRASS  TUBE LEFT
  HALF  IS OPEN AND  READY FOR NEXT SPRAY
  CYCLE.
         d.   NEXT SPRAY CYCLE

•WATER INITIALLY SPRAYS THROUGH THE BRASS
 TUBE ON THE  LEFT SIDE.  THE  HEAT FROM
 THE LIQUID MELTS THE  ICE PLUG BLOCKING
 THE RIGHT HALF OF THE NOZZLE AND SPRAY-
 ING RESUMES  IN THE NORMAL MANNER AS
 SHOWN IN a .
                                  FIGURE  4-5
FAN NOZZLE USED  FOR SPRAY APPLICATION AT WEST  DOVER,  VERMONT
                                      4-51

-------
           FIGURE 4-6
   SOLID SET SPRINKLERS WITH
SURFACE PIPE IN A FOREST SYSTEM
              14-52

-------
    4.7.3     Service Life of Distribution System
              Components

The  expected   service   life   of  the  distribution  system
components  is  a  design  consideration  and  'must be  used to
develop  detailed  cost  comparison.   The  suggested  service
lives of common distribution system components are listed in
Table 4-24.

4.8  Drainage and Runoff Control

Provisions  to   improve  or  control subsurface  drainage are
sometimes  necessary  with SR systems  to remove excess water
from  the  root  zone  or  to  remove  salts from  the  root  zone
when these conditions adversely  affect  crop growth.  Control
of surface  runoff  is necessary for^SR  systems"using surface
distribution  methods.    In humid  areas with  intense  rain-
falls,  control  of surface drainage  is  necessary to prevent
erosion  and  may be  helpful in  reducing the amount of water
entering  the soil profile  and  thereby reducing or elimin-
ating   the   need   for   subsurface   drainage.     Design
considerations  for  drainage  and  runoff  control 'provisions
are discussed in the following sections.
    4.8.1 •-
Subsurface Drainage Systems
Subsurface drainage systems are used  in .situations where  the
natural   rate   of   subsurface  drainage  is  restricted   by
relatively  impermeable  layers in  the' soil  profile near  the
surface  or  by  high  ground  water.    As  a  result  of  the
restrictive  layer, shallow ground  water tables  can form that
extend into  the  root  zone and even to  the soil  surface.

The  major  consideration  for wastewater  treatment  is  the
maintenance  of an aerobic  zone  in the  upper  soil profile.
Many of the  wastewater  removal mechanisms require  an  aerobic
environment  to  function most  effectively.  A  travel distance
of 0.6 to 1m  (2 to 3 ft) through  aerobic soil  is  considered
the  minimum  distance   to  achieve   treatment  by   the   SR
process.   Therefore,  a  water  table depth of 1 m (3 ft)  or
more is desirable  from  a wastewater treatment standpoint.
                             4-53

-------
                      TABLE 4-24
SUGGESTED SERVICE  LIFE FOR  COMPONENTS  OF
            DISTRIBUTION SYSTEM  [40]
Service life3

Well and casing
Puir.p plane housing
Pump, turbine
Bowl (about 50* of cost of pump unit)
Column, etc.
Pump, centrifugal
Power transmission
Gear head
V-belt
Flat belt, rubber and fabric
Flat belt, leather
Power units
Electric motor
Diesel engine
Gasoline or distillate
Air cooled
Water cooled
Propane engine
Open farm ditches (permanent)
Concrete structures
Concrete pipe systems
Wood flumes
Pipe, surface, gated
Pipe, water works class ,
Pipe, steel, coated, underground
Pipe, aluminum, sprinkler use
Pipe, steel, coated, surface use only
Pipe, steel galvanized, surface only
Pipe, wood buried
Sprinkler heads
Solid set sprinkler system
Center pivot sprinkler system
Side roll traveling system
Traveling gun sprinkler system
Traveling gun hose system
Land grading0
Reservoirsd
Hoursb
	
--

16,000
32,000
32,000

30,000
6,000
10,000
20,000

50,000
28,000
8,000
18,000
28,000
—
—
—
	
—
--
—

—
—
--
__
—
—
—
—
—
—
years
20
20

s
16
16

15
3
5
10

25
14
4
9
14
20
20
20
8
10
40
20
15
10
15
20
8
20
10-14
15-20
10
4
None
None
  a.  Certain  irrigation equipment may have a shorter life
      when used in a wastewater treatment  system.
  b.
  d.
These hours may be used  for year-round operation.
The comparable period in years was based on a
seasonal  use of 2,000 h/yr.

Some sources depreciate  land leveling in 1 to 15
years.  However, if proper annual maintenance is
practiced, figure only interest on the leveling
costs.  Use interest on  capital invested in water
right purchase.

Except where silting'from watershed above will fill
reservoir in an estimated period of years.

-------
For  SR  systems  where  wastewater  treatment  and  maximum
hydraulic  loading  rate  are  the  design  objectives,  the
presence of  excess  moisture in the  root  zone is of limited
concern for crops because water tolerant crops are generally
selected for  such  systems.   However, restrictive subsurface
layers and  resulting  high water  tables  limit the allowable
percolation   rate   and,   therefore,   the  design  hydraulic
loading   rate.      Subsurface  drains   placed   above  the
restrictive  layer  eliminate  the  effect of  that  layer on
percolation  and  allow  the  design  percolation  rate  to be
based on more permeable overlying soil horizons.  The  design
hydraulic loading rate is thereby increased.

In arid  regions,  the  additional problem of salinity control
is encountered.   With such systems,  excess water is applied
to   remove   salts  that   concentrate  in   the   root   zone
(Section 4.3.2.3).    Where  the  natural  drainage   rate is
insufficient  to remove salty  leaching water  from  the  root
zone  within 2  to  3 days,  crop damage due  to salinity may
occur  depending  on  the  tolerance  of  the  crop   and  the
salinity  of  the  applied  water  (see Section  4.3.2.5).   In
such  cases,  the objectives of  a  subsurface drainage  system
are to (1) prevent  the persistence of high water tables  when
leaching  is  practiced,  and  (2)   to keep  the  water  table
sufficiently  low between growing  seasons to minimize evapor-
ation  from  the  water table  and  resulting salt  accumulation
in  the root  zone.    As  a  rule  of  thumb,  the  water table
should not be permitted to  come closer than about 125  cm (49
in.)  from  the  surface to  prevent salt  accumulation.    This
minimum  depth is  greater than those generally used  in humid
areas.  Any drainage water  from crop revenue  systems that is
discharged  to surface waters must meet applicable discharge
requirements.

The  decision  to use  subsurface drains  must be based  on the
economic benefit  to be gained from their use.  For  example,
the  cost of  installing  and maintaining  a  subsurface drain
system  should  be  compared  to  the  value  of  developing an
otherwise  unsuitable  site  or  to  the cost  of a larger  land
area  that  will be  required if  subsurface  drains  are not
used.

Buried plastic, concrete,  and  clay  tile  lines are  normally
used  for underdrains.  The  choice  usually depends on price
and  availability  of materials.   Where  sulfates are present
in  the  ground  water,  it  is  necessary  to  use  a   sulfate-
resistant  cement,  if  concrete- pipe  is  chosen,  to prevent
excess  internal stress  from crystal formation.   Most  tile
drains are  mechanically laid in  a  machine  dug trench or by
direct plowing.  Open  trenches can be  used for subsurface
drainage,  but  if  closely  spaced,  they  can  interfere  with
farming  operations  and consume  usable land.
                             4-55

-------
 Underdrains  are normally  buried  1.8  to  2.4 m  (6  to 8  ft)
 deep but  can  be as  deep as 3 m (10 ft) or as shallow  as  1 m
 (3 ft).    Drains are  normally 10 to  15 cm  (4 to 6 in.)  in
 diameter.   Spacings as small  as  15  to 30 m (50 to 100  ft)
 may  be  required for  clayey  soils.   For  sandy  soils,  120 m
 (400. ft)  is typical with  the  range  being from  60  to 300 m
 (200 to 1,000 ft).

 Procedures  for  determining the proper  depth and spacing of
 drain  lines  to  maintain  the  water  table   below  a minimum
 depth  are discussed  in Section  5.7.    Additional  detailed
 design  procedures  and  engineering  aspects of  subsurface
 drainage systems are described in references  [41, 42,  43].
     4.8.2
Surface Drainage and Runoff Control
 Drainage  and   control   of  surface  runoff   is   a  design
 consideration for SR systems as it relates to tailwater from
 surface distribution systems and  stormwater runoff from all
 systems.
          4.8.2.1   Tailwater Return Systems
 Most surface distribution systems
 which is referred  to  as tailwater
 wastewater  is  applied,  tailwater
 the  treatment site  and  reapplied.
 system is  an  integral  part  of an
 distribution methods.   A  typical
 consists  of  a  sump or reservoir
 pipeline.
                    will  produce  some
                       When  partially
                    must  be contained
                      Thus a  tailwater
                      SR  system using
                      tailwater return
                    ,   a  pump(s),  and
runoff,
treated
 within
 return
surface
 system
 return
The  simplest and most  flexible  type of system  is  a  storage
reservoir  system in which all or a  portion  of  the  tailwater
flow   from  a  given   application   is  stored  and   either
transferred  to a main  reservoir  for later  reapplication  or
reapplied  from the tailwater reservoir to other portions  of
the  field.   Tailwater  return  systems should be designed  to
distribute  collected water  to  all   parts  of the field, not
consistently  to the  same area.    If  all the  tailwater  is
stored,  pumping can be  continuous   and can  commence  at the
convenience  of the  operator.   Pumps  can  be any convenient
size,  but  a  minimum  capacity of  25% of  the  distribution
system  capacity is  recommended  [44].   If a portion  of the
tailwater  flow  is   stored,  the  reservoir  capacity  can  be
reduced but pumping must begin during  tailwater  collection.

Cycling pump  systems and continuous pumping systems  can  be
designed  to minimize  the  storage  volume  requirements, but
these systems  are  much less flexible  than storage -systems.
The  designer  is  directed  to  reference   [44]  for  design
procedures.
                             4-56

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The principal  design variables  for  tailwater return systems
are the  volume  of  tailwater and  the duration  of tailwater
flow.    The expected  values of these parameters for a well-
operated  system  depend  on  the  infiltration  rate  of   the
soil.      Guidelines  for  estimating  tailwater  volume,   the
duration  of tailwater   flow,  and  suggested  maximum design
tailwater volume  are  presented in Table 4-25.

                          TABLE 4-25
                  RECOMMENDED DESIGN FACTORS
              FOR TAILWATER RETURN SYSTEMS  [44]
    Permeability
Maximum'duration    Estimated    Suggested maximum
 of tailwater   tailwater volume, design tailwater
            % of application  volume, % of appli-
Class
Very slow
to slow
Slow to
moderate
Moderate to
moderately
rapid
Rate, cm/h Texture range application time volume
0.15-0.5 Clay to clay 33 15
loam
0.5-1.5 Clay loam to 33 25
silt loam
1.5-15 Silt loams to 75 35
sandy loams

cation volume
30

50

70 '


Runoff  of  applied  wastewater  from  sites  with   sprinkler
distribution  systems  should  not occur  because  the  design
application  rate of  the sprinkler  system is  less than  the
infiltration  rate of the  soil-vegetation surface.  However,
some  runoff  from systems on  steep  (10 to  30%)   hillsides
should  be  anticipated.    In  these  cases,  runoff  can  be
temporarily   stored   behind  small   check  dams  located  in
natural   drainage  courses.     The   stored  runoff   can  be
reapplied with  portable sprinkling equipment.

          4.8.2.2   Stormwater Runoff Provisions

For  SR  systems,  control  of  stormwater runoff  to  prevent
erosion  is  necessary.   Terracing of steep  slopes  is  a  well
known  agricultural  practice  to prevent  excessive erosion.
Sediment  control basins   and   other  nonstructural  control
measures, such  as  contour  plowing,  no-till  farming,  grass
border  strips,   and  stream buffer zones  can be used.   Since
wastewater  application will  usually be stopped during storm
runoff  conditions,  recirculation of  storm runoff for  further
treatment is  usually  unnecessary.     Channels  or  waterways
that  carry stormwater  runoff . to discharge  points  should  be
designed  with a capacity to carry  runoff  from a  storm  of a
specified return frequency (10 year  minimum).

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4.9  System Management
    4.9.1
Soil Management
Management  of  the  soil  involves  tillage  operations  and
maintenance of  the proper  so,!!  chemical  properties  including
plant  nutrient levels,  pH,  sodium  levels,  and   salinity
levels.   Much  of what  is discussed  under soil management
refers to  agricultural crop systems, since most  forest crop
systems require very little soil  management.

         4.9.1.1   Tillage Operations

One  of the  principal objectives of tillage operations  is  to
maintain  or enhance  the infiltration capacity of  the  soil
surface and the permeability of the entire  soil profile.   In
general, tillage  operations  that expose bare soil  should  be
kept  to  a  minimum.    Minimum  tillage  and  no-till  methods
conserve  fuel,  reduce labor' costs,  and  minimize compaction
of soils by heavy equipment.  Conventional  plowing  (20  to  25
cm  or  8 to  10 in.)  arid preparation  of a  seedbed free  of
weeds and  trash are necessary  for most  vegetables and  root
crops.   Many field crops, however,  can  be planted directly
in  sod  or residues  from  a  previous crop  or after  partial
incorporation of residues  by shallow disking.   Crop residues
left on  the  surface  or partially incorporated  to a depth  of
8 or 10  cm  (3  or 4 in.)  provide protection against runoff
and   erosion   during    intervals  between   crops.     The
decomposition of  residues  on  or near the soil  surface  helps
to  maintain a  friable,  open  condition conducive  to   good
aeration  and   rapid  infiltration  of   water.    Actively
decomposing  organic   matter  also  helps   to  reduce  the
concentration of other soluble pollutants and can hasten the
conversion of toxic organics, like pesticides,  to less  toxic
products.

At  sites  where  clay  pans  have  formed  and  reduce  the
effective  permeability  of  the  soil  profile,  it  may  be
necessary to plow very deeply (60  to 180 cm or  2 to 6 ft)  to
mix  impermeable subsoil strata with more permeable  surface
materials.   Impermeable  pans  formed  by  vehicular  traffic
(plow pans) or  by cementation  of fine  particles (hard  pans)
can  be  broken  up by  subsoiling  equipment that  leaves the
surface  protected   by  vegetation  or   stubble.     To   be
effective, however, the subsoiling equipment must completely
break through the pan  layers.   This  is difficult if the pan
layers  are  more  than  30  cm  (1 ft)   thick.    Local   soil
conservation   district   personnel  should  be    consulted
regarding tillage practices appropriate  for specific crops,
soils,  and terrain.
                             4-58

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          4.9.1.2
     Nutrient Status
During  design, it is recommended that  the  nutrient status  of
the  soil be  evaluated.   Periodic  evaluation  is recommended
as part of  the system monitoring program  (Section 4.10).

Sufficient  nitrogen,  phosphorus,  and most other  essential
nutrients  for  plant  growth  are generally supplied  by most
wastewaters.    Potassium  is the  nutrient  most  likely to  be
deficient  since  it  is usually  present in  low  concentrations
in  wastewater.    For  soils  having   low   levels of   natural
potassium,  the following relationship has  been developed  to
estimate potassium fertilizer requirements?
where    Kf =

          U =


        Kww =
        Kf  = 0.9U - Kww                   (4-1.3)

annual  fertilizer potassium needed, kg/ha

estimated annual crop uptake of nitrogen,
kg/ha

amount  of potassium applied in wastewater,
kg/ha
On  the  basis  of  commonly used  test  methods  for available
nutrients,    the  University   of   California   Agricultural
Extension  Service  has   developed  a   summary  of  adequate
available levels  in the soil  of  the nutrients most commonly
deficient  for  some   selected   crops.     This  summary   is
presented in Table  4-26.   Critical  values for nitrogen  are
not  included because  there are  no well accepted methods  for
determining available nitrogen.

                           Table 4-26
           APPROXIMATE CRITICAL LEVELS  OF  NUTRIENTS
          IN  SOILS FOR SELECTED CROPS  IN CALIFORNIA
          Nutrient
              Approximate
           critical range, ppm
                                           Test method
        Phosphorus
         Range and pasture

         Field crops and warm
         season vegetables
         Cool season vegetables

        Potassium
         Grain and alfalfa
         Cotton
         Potatoes
                10

                 5-9


                12-20



                45-55

                55-65

                90-110
                         0.5 M NaHCC>3 extraction
                         at pH 8.5
1.0 N ammonium acetate
extraction at pH 7.0
        Zinc
                              0.4-0.6
                                        DPTA extraction

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          4.9.1.3   Soil pH Adjustment

 In general,  a pH less  than  4.2 is  too  acid for most  crops
 and  above  8.4 is too alkaline  for  most  crops.   The optimum
 PH  range  for crop  growth  depends  on   the  type  of   crop.
 Extremes in  the  soil pH  also  can  affect the performance of
 an SR  system or  indicate  problem conditions.  Below pH 6.5,
 the capacity of the soil  to retain metal  is  reduced.  A soil
 PH above 8.5 generally indicates a  high sodium content and
 possible permeability problems.

 The pH  of  soils can be  adjusted by the  addition  of liming
 materials or acidulating chemicals.  A pH adjustment program
 should  be  based on  the  recommendations  of  a  professional
 agricultural consultant or county or state farm adviser.

          4.9.1.4   Exchangeable Sodium Control

 Soils containing  excessive exchangeable  sodium are  termed
 "sodic"   soils.     A  soil  is  considered  sodic  when  the
 percentage   of  the   total cation  exchange  capacity  (CEC)
 occupied by  sodium,   the  exchangeable   sodium  percentage
 (ESP),  exceeds 15%.   High levels  of sodium  cause  low  soil
 permeability, poor  soil  aeration, and difficulty in seedling
 emergence.    Fine-textured soil  may be  affected  at an  ESP
 above  10%,  but coarse-textured soil  may not be damaged  until
 the ESP reaches about 20%.  The  ESP  should  be determined  by
 laboratory  analysis before design  if sodic  soils  are  known
 to  exist in the  area  of  the  site.  Sodic  soil conditions may
 be  corrected  by  adding  soluble  calcium  to the  soil  to
 displace the  sodium  on   the  exchange   and  removing   the
 displaced  sodium by  leaching.   Advice  on correcting"sodic
 soils  should  be  obtained  from  agricultural consultants  or
 farm  advisers.

         4.9.1.5   Salinity Control

 Salinity control may  be  necessary  in arid  climates where
 natural  rainfall is  insufficient to flush  salts  from the
 root zone.  The salinity leve^L  of a  soil  is  usually measured
 on  the  basis  of  the  electrical  conductivity of an extract
 solution  from a  saturated  soil (ECe).   Saline  soils are
 defined  as  those yielding  an  EC  value  greater than 4,000
 micromhos/cm at 25 °C (77  °F).

 Soils  that  are   initially  saline  may  be  reclaimed  by
 leaching;  however,  management  of  the   leachate   is  often
 required  to   protect  ground   water  quality.    The  U.S.
 Department  of  Agriculture's  Handbook 60 [45] deals with the
diagnosis and improvement of   such   soils  for agricultural
purposes.   This  reference  can  be used  as a practical guide

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for managing saline and saline-sodic soil conditions in arid
and semiarid regions.
      4.9.2
Crop Management
Because of  their substantially  different  requirements, the
management  of  agricultural  crops  and  forest  crops  are
discussed separately.

         4.9.2.1   Agricultural Crop Planting and Harvesting

Local  extension  services  or  similar  experts  should  be
consulted regarding planting techniques and schedules.  Most
crops  require a  period  of  dry  weather  before  harvest to
mature  and   reach  a   moisture   content  compatible  with
harvesting equipment.   Soil  moisture at harvest time should
be   low   enough   to   minimize   compaction   by  harvesting
equipment.  For these reasons, application should be discon-
tinued well  in advance  of  harvest.   The  time required for
drying will depend  on  the soil drainage and the weather.  A
drying time  of 1 to 2 weeks  is  usually sufficient if  there
is  no precipitation.    However,  advice  on this  should be
obtained from  local agricultural  experts.

Harvesting  of  grass  crops  and  alfalfa  involves  regular
cuttings,  and a  decision  regarding  the  trade-off between
yield and quality must be made.   Advice can be  obtained  from
local  agricultural  experts.    In  the northeast  and  north
central   states,   three  cuttings   per  season  have   been
successful with grass crops.

         4.9.2.2    Grazing

Grazing  of  pasture by  beef  cattle  or sheep  can provide an
economic  return  for SR  systems.   No health hazard has  been
associated   with   the   sale   of   the  animals  for   human
consumption.

Grazing  animals  return  nutrients   to  the ground  in  their
waste  products.    The chemical  state  (organic and  ammonia
nitrogen)  and rate of  release of  the nitrogen reduces  the
threat  of nitrate  pollution  of  the  ground water.   Much of
the  ammonia-nitrogen volatilizes and the  organic  nitrogen  is
held in  the soil where  it is  slowly mineralized  to  ammonium
and   nitrate   forms.     Steer  and  sheep  manure   contain
approximately 20% nitrogen after volatile losses, of  which
about  40%  is mineralized  in  the   first  year,  25%  in  the
second, and  6% in  successive  years  [41].

In  terms  of pasture management,  cattle or sheep  must  not  be
allowed  on wet  fields  to avoid  severe soil  compaction  and
                             4-61

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 reduced soil  infiltration  rates.   Wet grazing conditions can
 also lead  to  animal hoof diseases.   Pasture  rotation should
 be practiced  so that wastewater  can be  applied  immediately
 after the livestock are  remdved.   In general, a pasture area
 should not  be grazed longer  than 7 days.  Typical  regrowth
 periods  between   grazings  range   from  14   to  35  days.
 Depending on  the  period of  regrowth provided, one  to three
 water applications  can  be made  during the regrowth  period.
 Rotation grazing  cycles for  3  to 8 pasture  areas are given
 in Table 4-27.  At least 3  to  4  days drying  time  following
 an  application  should  be  allowed  before   livestock  are
 returned to the pasture.

                          Table 4-27
                 GRAZING ROTATION CYCLES FOR
              DIFFERENT NUMBERS OF  PASTURE AREAS
               No. of     Rotation    Regrowth    Grazing
             pasture areas cycle, days period, days period, days
3
4
5
6
7
8
21
28
35
36
35
32
14
21
28
30
28
28
7
7
7
6
7
4
          4.9.2.3   Agricultural Pest Control

Problems   with  weeds,  insects,   and   plant  diseases  are
aggravated under conditions  of frequent  water application,
particularly  when a single crop is  grown  year after year or
when   no-till  practices  are  used.    Most  pests  can  be
controlled by selecting resistant  or tolerant crop varieties
and  by  using  pesticides  in  combination with  appropriate
cultural   practices.    State  and   local  experts  should  be
consulted  in  developing an overall  pest control program for
a given situation.

         4.9.2.4    Forest  Crops

The  type  of   forest  crop  management  practice selected  is
determined  by the species  mix grown,  the  age  and structure
of the stand, the method of  reproduction  best  suited and/or
desired  for  the  favored  species,  terrain,  and  type  of
equipment  and technique used by local  harvesters.   The most
typical  forest  management situations   encountered  in  land
treatment   are  management   of   existing  forest   stands,
reforestation,  and short-term rotation.

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Existing Forest Ecosystems

The general objective of the forest management program  is  to
maximize biomass  production.    The  compromise between  fully
attaining  a  forest's  growth  potential  and  the  need   to
operate  equipment efficiently  (distribution  and  harvesting
equipment)   requires  fewer  trees  per  unit  area.     These
operations  will  assure  maintenance  of  a  high  nutrient
uptake, particularly nitrogen,  by the  forest.

For  uneven-aged  forests,  the  desired  forest  composition,
structure,  and  vigor can be best  achieved through  thinning
and selective harvest.  However, excessive thinning  can make
trees  susceptible to wind  throw and  caution  is   advised  in
windy  areas.   The objective of these operations would  be  to
maintain an  age  class  distribution in  accordance with the
concept  of optimum nutrient storage (see Section  4.3).  The
maintenance of  fewer trees than normal would permit  adequate
sunlight to reach the understory to promote reproduction and
growth of the understory.  Thinning should be done initially
prior  to construction  of  the  distribution  system and only
once every 10 years or  so to minimize  soil and site  damage.

In  even-aged  forests,  trees will  all reach  harvest age  at
the  same time.   The usual  practice  is  to  clear-cut  these
forests  at harvest  age  and  regenerate  a stand  by either
planting seedlings,  natural seeding,  sprouting  from stumps
(called  coppice),  or  a  combination  of  several   of the
methods.   Even-aged  stands may require  a  thinning at  an
intermediate  age  to maintain  maximum  biomass  production.
Coniferous  forests,  in general, must  be replanted,  whereas
hardwood forests can  be  reproduced  by coppice  or  natural
seeding.

The  concept of  "whole-tree  harvesting" should be  considered
for  all  harvesting  operations,  whether  it be  thinning,
selection   harvest,   or  clear-cut   harvest.      Whole-tree
harvesting  removes   the  entire   standing   tree:     stem,
branches,   and   leaves.     Thus,  100%   of   the   nitrogen
accumulated in  the aboveground  biomass would  be removed (see
Section  4.3.2.1).

Prescribed  fire  is  a  common  management practice   in many
forests  to reduce the  debris  or  slash  left  on the site
during   conventional   harvesting   methods.      During  the
operation,  a  portion  of  the  forest   floor  is  burned and
nitrogen   is  volatilized.    Although  this  represents   an
immediate  benefit  in  terms  of  nitrogen removal from the
site,  the buffering  capacity that the  forest  floor offers  is
reduced  and  the  likelihood  of a  nitrate leaching to the
ground  water  is increased when application of wastewater  is
resumed.

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 Reforestation

 Wastewater  nutrients  often  stimulate   the  growth  of  the
 herbaceous vegetation  to such  an  extent that  they  compete
 with and shade out the desirable forest species.  Herbaceous
 vegetation is necessary  to  act  as  a  nitrogen  sink while the
 trees  are becoming  established,  and  therefore,  cultural
 practices must be designed  to control  but  not eliminate the
 herbaceous vegetation.   As  the  tree crowns begin to close,
 the  herbaceous vegetation will be  shaded and  its role in the
 renovation cycle  reduced.  Another alternative to control of
 the  herbaceous vegetation is  to eliminate  it  completely and
 reduce   the  hydraulic   and   nutrient   loading   during  the
 establishment period.

 Short-Term Rotation

 Short-term  rotation   forests   are   plantations   of  closely
 spaced   hardwood   trees   that  are  harvested  repeatedly  on
 cycles  of less than 10  years^   The  key  to rapid  growth  rates
 and  biomass development is the rootstock that  remains in the
 soil  after harvest and then resprouts.   Short-term rotation
 harvesting systems are  readily  mechanized because the  crop
 is uniform and relatively small.

 Using conventional tree  spacings of 2,5  to  4 m (8 to  12 ft),
 research on  systems  where  wastewater  has been applied  to
 short-term rotation  plantations has  shown that  high growth
 rates and high nitrogen removal are possible  [16].   Planted
 stock will produce only  50% to  70% of the biomass produced
 following  cutting  and resprouting  [47,  48].  If  nitrogen and
 other nutrient uptake is proportional to biomass,  the  first
 rotation from  planted   stock  will  not  remove   as  much  as
 subsequent  rotations  from coppice.   Therefore,   the  initial
 rotation must  receive  a reduced  nutrient  load  or  other
 herbaceous   vegetation   must   be   employed   for  nutrient
 storage.   Alternatively,  closer  tree  spacings may be  used  to
 achieve   desired   nutrient  uptake   rates   during   initial'
 rotation.

 4.10  System Monitoring

 The  broad  objectives of  a monitoring   program', for  an  SR
 system are  to  determine if the effluent quality  requirements
 are  being  met,  to determine  if  any corrective action  is
necessary   to   protect   the   environment  or  maintain  the
 renovative  capacity   of  the system,  and  to  aid in system
operation.   The components of the  environment that need  to
be  observed   include   water quality,  the  soils  receiving
wastewater, and in some  cases,  vegetation  growing in:  soils
 that are receiving wastewater.
                             4-64

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    4.10.1
Water Quality Monitoring
Monitoring of water quality for land application systems can
be  more  complex  than  for  conventional  treatment systems
because   nonpoint  discharges   of   system   effluent  are
involved.   Monitoring  of  applied wastewater  and   renovated
water  quality  is  useful  for  process  control.    For  SR
systems,  renovated water would  only be  monitored  in. cases
where underdrains  are used.  Monitoring of receiving waters,
surface  or  ground water,  may  be  required  by  regulatory
authorities.

In most cases, a water  quality monitoring program,  including
constituents  to  be analyzed  and frequency of analysis, will
be  prescribed by local  regulatory  agencies.    It may  be
desired to monitor additional constituents or parameters for
purposes of crop and soil management.

Ground  water  monitoring  data  are  difficult  to   interpret
unless  sampling  wells  are   located properly and correct
sampling  procedures are followed.   In  addition to quality,
the depth to  ground water should be measured at the sampling
wells to  determine if  the hydraulic response of the aquifer
is consistent with what was  anticipated.   For SR systems, a
rise  in   water   table  levels   to   the   root  zone  would
necessitate   corrective  action  such as  reduced   hydraulic
loading or adding  underdrainage.  The appearance of seeps or
perched ground water tables might also  indicate the need for
corrective action.
    4.10.2
Soils Monitoring
In  some  cases, application  of  wastewater to  the land will
result  in  changes  in  soil  properties.    Results  of soil
sampling  and  testing will  serve  as the  basis for deciding
whether  or not  soil  properties  should  be  adjusted  by the
application  of chemical  amendments.   Annual  monitoring of
the soil properties described in Section 4.9.1 is sufficient
for most systems.

It  is  recommended  that  the level  of  trace  elements  of
concern  (see  Chapter 9)  in  the soil  be  monitored every few
years  so  that the rate  of  accumulation  can  be observed and
toxic  levels  avoided.    Total  metal  analysis by  hot acid
digestion   is  recommended   for  monitoring  and  comparison
purposes.
                             4-65

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    4.10.3
Vegetation Monitoring
Plant  tissue  analysis is more  revealing than soil  analysis
with  regard  to deficient  or toxic  levels  of elements.   If
visual  symptoms  of  nutrient  deficiencies  or   toxicities
appear, plant  tissue testing can  be used for confirmation,
and corrective  action can be taken.  A  regular plant,  tissue
monitoring program can often detect  deficiencies or  toxicity
before visual symptoms and damage  to the plant occurs.

Nitrate should  be  determined in forages  or leafy  vegetables
if there  is  reason to suspect concentrations which  might  be
toxic  to  livestock.   Detailed information on plant  sampling
and testing may be  found in references  [49,  50].  Extension
specialists  or  local  farm  advisers   should be  consulted
regarding plant tissue testing.

4.11  Facilities Design Guidance

The  purpose  of  this section  is   to  provide  guidance   on
aspects of facilities design that may be unfamiliar to some
environmental engineers.

    •    Standard surface  irrigation practice is  to produce
         longitudinal slopes of  0.1 to  0.2% with  transverse
         slopes not exceeding 0.3%.

         Step 1.  Rough grade to 5 cm  (0.15 ft) at
                   30 m  (100 ft) grid stations.

         Step 2.   Finish grade to ±3 cm (0.10 ft) at
                   30  m  (100  ft)  grid  stations  with   no
                   reversals in slope between stations.
         Step 3.   Land plane with a 18 m (60 ft) minimum
                   wheel  base,   land  plane
                   perfect" finished grade.
                                 to
'near
         Access to sprinklers  or  distribution piping should
         be provided  every  390 m  (1,300  ft)  for convenient
         maintenance.

         Both  asbestos-cement  and  PVC  irrigation  pipe' are
         rather  fragile  and  require care  in  handling and
         installation.

         Diaphragm-operated globe valves are recommended for
         controlling flow to laterals.

         All   electric   equipment   should   be   grounded,
         expecially  when   associated  with   center  pivot
         systems.
                             4-66

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Automatic     controls    can     be    electrically,
hydraulically,  or pneumatically  operated.  Solenoid
actuated,     hydraulically    operated     (by    the
wastewater)  valves  with  small  orifices  will clog
from the solids.

Valve boxes,  1  m (36 in.) or  larger,  should be made
of corrugated metal, concrete, fiber  glass, or pipe
material.   Valve boxes should extend  15 cm (6 in.)
above grade  to  exclude stormwater.

Low pressure  shutoff valves should be used to avoid
continuous  draining  of the  lowest sprinkler on the
lateral.

Automatic  operation  can  be  controlled  by  timer
clocks.   It is important that when the timer shuts
the  system  down  for  any  reason that  the  field
valves  close automatically  and  that  the sprinkling
cycles   resume  as   scheduled   when   sprinkling
commences.   The clock  should  not reset to time zero
when an interruption occurs.

High  flotation  tires  are   recommended  for  land
treatment   system   vehicles.      Recommended   soil
contact pressures   for center   pivot  machines  are
presented  in  Table  4-28.

                 TABLE  4-28
     RECOMMEDED SOIL CONTACT  PRESSURE
     % fines
       20
       40
       50
17

11

 8
25

16

12
     Note: To illustrate the use of this table,
     if 20% of the soil fines pass through a
     200-mesh screen, the contact pressure of the
     supporting structure to the ground should be
     no more than 17 N/cm2 (25 lb/in.^).  If this
     is exceeded, one can expect wheel tracking
     problems to occur.
                     4-67

-------
4.12  References

 1.  Benham-Blair  and   Affiliates,   Inc.   and  Engineering
    Enterprises, Inc.  Long-term Effects of Land Application
    of Domestic  Wastewater:   Dickinson,  North Dakota, Slow
    Rate  Irrigation  Site.    U.S.    Environmental  Protection
    Agency.   EPA-600/2-79-144.  August 1979.

 2.  Demirjian,  Y.A.   et al.    Muskegon  County  Wastewater
    Management  •System.     U.S.   Environmental  Protection
    Agency.   EPA-905/2-80-004.  February 1980.

 3.  Hossner, L.R., et  al.   Sewage  Disposal  on Agricultural
    Soils:   Chemical and Microbiological  Implications (San
    Angelo,  Texas).   U.S.  Environmental  Protection Agency.
    EPA-600/2-78-131a,b.  June 1978.

 4.  Jenkins, T.F. and A.J.  Palazzo.  Wastewater Treatment by
    a Slow  Rate Land Treatment System.  U.S.  Army  Corps  of
    Engineers,   Cold  Regions  Research  and  Engineering
    Laboratory.      CRREL  Report   81-14.      Hanover,,   New
    Hampshire.  August 1981.

 5.  Koerner, E.L. and D.A. Haws.   Long-Term  Effects of Land
    Application   of  Domestic  Wastewater:     Roswell,  New
    Mexico,  Slow Rate  Irrigation  Site.   U.S.  Environmental
    Protection Agency.   EPA-600/2-79-647.  February 1979.

 6.  Iskandar,   I.K.,  R.P.   Murrmann,  and   D.C.   Leggett.
    Evaluation  of  Existing ISystems  for  Land  Treatment  of
    Wastewater   at   Manteca,   California    and    Quincy,
    Washington.     U.S.  Army  Cold  Regions  Research  and
    Engineering  Laboratory.   CRREL Report 77-24.  September
    1977.

 7.  Nutter,  W.L.,  R.C.  Schultz,   and G.H.  Bristeir.    Land
    Treatment of Municipal  Wastewater on Steep Forest Slopes
    in the Humid Southeastern United States.   Proceedings  of
    Symposium on Land Treatment  of  Wastewater.   Hanover,  New
    Hampshire.   August 20-25,  1978.

 8.  Stone, R. and J. Rowlands.    Long-Term Effects of  Land
    Application   of   Domestic  Wastewater:    Mesa,   Arizona,
    Irrigation   Site.      U.S.    Environmental   protection
    Agency.   EPA-600/2-80-061.   April 1980.

 9.  Enfield,   C.G.  and  B.E.   Bledsoe.   Kinetic  Model  for
    Orthophosphate  Reactions  in Mineral Soils.   EPA-S60/2-
    75-002.   U.S. Government  Printing Office.   June 1975.
                             4-68

-------
10.  Land  as  a Waste  Management  Alternative.    R.C.  Loehr,
    ed.  Ann Arbor Science.  Ann Arbor, Michigan.  1977.

11.  Overman,  A.R.    Wastewater  Irrigation  at  Tallahassee,
    Florida.   U.S. Environmental  Protection Agency.   EPA-
    600/2-79-151.  August 1979.

12.  Stone, R.  and  J.  Rowlands.   Long-Term  Effects  of Land
    Application   of   Domestic   Wastewater:     Camarillo,
    California,   Irrigation   Site.      U.S.  Environmental
    Protection Agency.  EPA-600/2-80-080.  May 1980.

13.  Tofflemire,  T.J.  and  M.  Chen.    Phosphate  Removal  by
    Sands  and Soils.    In:    Land  as  a Waste  Management
    Alternative.    Loehr,  R.C.  (ed).   Ann Arbor,  Ann Arbor
    Science.  1977.

14.  Uiga,  A.  and  R.W.  Crites.    Relative  Health  Risks  of
    Activated   Sludge   Treatment   and    Slow   Rate   Land
    Treatment.   Journal  WPCF, 52(12):2865-2874.   December
    1980.

15.  Pratt,  P.F.   Quality  Criteria  for   Trace   Elements  in
    Irrigation Waters.  University of  California, Riverside,
    Department    of    Soil    Science    and   Agricultural
    Engineering.    1972.

16.  National  Academy  of  Science.   Water  Quality Criteria
    1972.   Ecological Research Series.   U.S. Environmental
    Protection Agency.  Report No. R3-73-033.  March 1973.

17.  U.S.   Environmental   Protection   Agency.    Preliminary
    Survey  of Toxic  pollutants at  the  Muskegon Wastewater
    Management   System.     Robert   S.  Kerr  Environmental
    Research  Laboratory,  Groundwater Research Branch.  Ada,
    Oklahoma.  1977.

18.  Hinrichs,  D.J.     Design  of   Irrigation  Systems   for
    Agricultural Utilization  of Effluent.   Presented at  the
    California  Water Pollution Control  Association Annual
    Conference,' Monterey, Calif.  May  1,  1980.

19.  Smith,  W.H.  and J.O. Evans.   Special Opportunities  and
    Problems   in   Using  Forest  Soils   for Organic  Waste
    Application.    In:    Soils  for  Management  of  Organic
    Wastes  and  Waste Waters..    ASA,  CSSA,  SSSA, Madison,
    Wisconsin.  pp. 429-451.   1977.

20.' Palazzo,  A. J. , and  J.M.   Graham.    Seasonal  Growth  and
    Uptake  of  Nutrients   by  Orchardgrass   irrigated  with
    Wastewater.     U.S.   Army  Cold   Regions  Research   and
    Engineering Laboratory.   CRREL Report 81-8.   June  1981.
                             4-69

-------
21. Duscha,   L.A.     Dual,  Cropping   Procedure   for   Slow
    Infiltration    of    Land    Treatment    of   Municipal
    Wastewater.     Department  of   the  Army,   Engineering
    Technical Letter No.  1110-2-260.  March  12, 1981.

22. McKim,  H.L.,  et  al.   Wastewater .Application in  Forest
    Ecosystems.   CRREL Report 119, Corps of Engineers,  U.S.
    Army.  May 1980.

23. USDA  Forest Service.   Impact of Intensive Harvesting on
    Forest  Nutrient Cycling.   Northeast  Forest  Experiment
    Station.  Broomall, Pa.  1979.

24. Jensen,  M.E.    (ed.).    Consumptive Use  of  Water and
    Irrigation Water Requirements.  ASCE.  ASCE Committee on
    Irrigation Water Requirements.  1973.            :

25. Doorenbos,  J.   and   W.O.   Pruitt.     Guidelines  for
    Predicting  Crop  Water  Requirements.    Irrigation and
    Drainage Paper  24.  Presented at United  Nations  Food and
    Agriculture Organization.  Rome.  1975.

26. Irrigation Water   Requirements.   Technical  Release No.
    21,  U.S.  Department  of  Agriculture,  Soil Conservation
    Service.  September 1970.

27. Vegetative Water  Use  in  California, 1974.   Bulletin No.
    113-3,   State  of   California   Department  of   Water
    Resources.  April  1975.

28. Booher, L.J.  and  G.V. Ferry.   Estimated Consumptive Use
    and    Irrigation  •  Requirements    of   Various    Crops.
    University of California Agricultural Extension  Service,
    Bakersfield,  Calif.   March 10, 1970.

29. Ayers, R.S.   Quality of Water  for  Irrigation,  Jour, of
    the  Irrigation  and Drainage  Division,   ASCE,  Vol.  1O3,
    No. IR2.  June  1977.  pp. 135-154.

30. U.S.   Environmental   Protection  Agency.     Facilities
    Planning,  1982. EPA-430/9-81-012.   FRD-25.   September
    1981.

31. Reed, S.C. Treatment/Storage  Ponds  for  Land Application
    Systems. CRREL Special Report.  December 1981.

32. Environmental  Protection Agency.   Process  Design  Manual
    for Wastewater Treatment Ponds (In Preparation),

33. Bowles,  D.S.,   et  al.   Coliform Decay  Rates  in  Waste
    Stabilization Ponds,  Journal  WPCF,  51(l):87-99, January
    1979.
                            4-70

-------
34.  Sagik,  B.P.   et   al.    The  Survival  of  Human  Enteric
    Viruses in Holding Ponds.  Contract Report DAMD 17-75-C-
    5062.    U.S.  Army  Medical  Research  and  Development
    Command.  1978.

35.  Whiting,  D.M.    Use  of  Climatic   Data  in  Estimating
    Storage Days  for  Soil  Treatment Systems.   Environmental
    Protection Agency,  Office of Research  and  Development.
    EPA-600/2-76-250.   November 1976.

36.  Whiting,  D.M.   Use  of  Climatic Data  in  Design  of Soil
    Treatment  Systems.    EPA-660/2-75-018.    Environmental
    Protection Agency,  Office of Research  and  Development.
    July 1975.

37.  U.S.    Department   of   the    Interior,    Bureau   of
    Reclamationo    Design  of Small  Dams.   Second  Edition.
    U.S. Government Printing Office.  1973.

38.  Booher,  L.J.   Surface  Irrigation.    FAO  Agricultural
    Development   Paper   No.   95.     Food  and  Agricultural
    Organization  of the United Nations.  Rome.  1974.
                                                         t •
39.  Myers,  E.A.   Design  and Operational Criteria for Forest
    Irrigation  Systems.    In:    Utilization  of  Municipal
    Sewage  Effluent  and  Sludge on  Forest  and  Disturbed
    Land.     The  Pennsylvania  State   University   Press,
    University Park,   Pa.  p. 265-272.  1979.
                                           Systems.      U.S.
                                           EPA-430/9-75-001.
40. Evaluation   of   Land  Application
    Environmental  Protection   Agency.
    March 1975.
41. Luthin,  J.N.   (ed.).   Drainage  of  Agricultural  Lands
    Madison, American Society of Agronomy.  1957.
42. Van  Schilfgaarde,  J,   ed.    Drainage  for Agriculture.
    American Society of Agronomy, Madison, Wisconsin.   1974.

43. Drainage of Agricultural Land.  A Practical Handbook for
    the  Planning,  Design,   Construction,  and Maintenance of
    Agricultural  Drainage  Systems.    U.S.   Department  of
    Agriculture, Soil Conservation Service.  October  1972,

44. Hart,  W.E.   Irrigation  System  Design,  Colorado  State
    University,  Department  of  Agricultural  Engineering,.
    Fort Collins, Colorado.  November 10, 1975.

45. Richards,  L.A.  (ed.).    Diagnosis  and  Improvement of
    Saline and Alkali Soil.  Agricultural Handbook  60.   U.S.
    Department of Agriculture.   1954.
                             4-71

-------
46. California Fertilizer Assn.  Western Fertilizer Handbook
    Sixth  Ed.    The  Interstate  Printers  and  Publishers.
    1980.

47. Saucier,  J.R.    Estimation  of  Biomass  Production  and
    Removal.   In:   Impact of Intensive Harvesting on Forest
    Nutrient Cycling.   College  of Environmental Science and
    Forestry,  State University  of New York,  Syracuse,  New
    York, p. 172-189.  1979.

48. Steinbeck, K.  and  C.L.  Brown.   Yield and Utilization of
    Hardwood  Fiber  Grown  on  Short  Rotations.    Applied
    Polymer Symposium 28:  393-401.  1976.

49. Walsh, L.M.  and J.D. Beaton,  (eds.).   Soil Testing and
    Plant  Analysis.    Madison,   Soil  Science  Society  of
    America.  1973.

50. Melsted, S.W.   Soil-Plant  Relationships (Some Practical
    Considerations  in  Waste Management).   In:   Proceedings
    of the  Joint Conference on  Recycling  Municipal Sludges
    and   Effluents   on   Land,   Champaign,   University   of
    Illinois.  July 1973.  pp.  121-128.
                            4-72

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                          CHAPTER 5

              RAPID INFILTRATION PROCESS DESIGN

5.1  Introduction

The  design   procedure  for   rapid   infiltration  (RI)   is
diagrammed  in Figure  5-1.   As  indicated by  this figure,
there are  several  major elements  in  the design process  and
the design approach is somewhat  iterative.  For example,  the
amount of  land required  for  an RI system  is  a function  of
the loading rate, which is affected by  the  loading  cycle  and
the  level  of  preapplication  treatment.   If  the engineer
initially assumes  a  level of preapplication treatment and  a
loading cycle  that result in  a loading rate requiring more
land than  is  available at the  selected  site,  the level  of
preapplication   treatment   and   loading   cycle   can    be
reevaluated to reduce the  land  area required.

     5.1.1  RI Hydraulic Pathway

The engineer  and  the community  must  decide which  hydraulic
pathway   (see   Figure 1-2)    is   appropriate   for   their
situation.    This  decision  is  based  on  the   hydrogeologic
characteristics of the selected  site  and  regulatory  agency
decisions.

     5.1.2  Site Work

For  RI design,  the  results  of  the  field   investigations
(Chapter 3) must be  analyzed and interpreted.   Backhoe pits
and  drill  holes  are  needed   to  establish  the  depth   and
hydraulic  conductivity of the  permeable  material  and  the
depth  to  ground water.    Sufficient  subsurface  information
must be obtained in the Phase ,2  planning  process  (Chapter 2)
to allow the engineer to calculate:

     1.     Infiltration rate  (Section  5.4)

     2.     Subsurface flow  (Section 5.7)

            •      Potential  for  mounding
            •      Drainage (if  needed)
            •      Natural  seepage  (if adequate)

     3.     Mixing  of  percolate  with  ground  water   (if
            critical  to meet performance  requirements)
                             5-1

-------
WASTEWATER
CHARACTERISTICS
(SECTION  2.2.1)
WATER QUALITY
REQUIREMENTS
(SECTION  2.2.1)
                      SITE
                 CHARACTERISTICS
                 (SECTIONS 2.2.1,
                  2.3.1 )
                        RI
                 HYDRAULIC PATHWAY
                  (SECTION 5.1.1)
                  PREAPPLICATION
                  TREATMENT LEVEL
                  (SECTION 5.3)
                  LOADING  RATE
                  (SECTION 5.4.)
                  LOADING  CYCLE
                  (SECTION 5.4.2)
                      LAND
                   REQUIREMENTS
                   (SECTION 5.5)
                   BASIN DESI6N
                   AND  LAYOUT
                   (SECTION 5.6)
                 DRAINA6E AND/OR
                 RECOVERY
                 (SECTION 5.7)
                  MONITORING AND
                  MAINTENANCE
                  REQUIREMENTS
                  (SECTION 5.8)
                 FIGURE  5-1
  RAPID  INFILTRATION  DESIGN PROCEDURE
                       5-2

-------
 5.2   Process Performance                      ;

 The  RI  mechanisms ' for  removal  of wastewater  constituents
 such  as BOD,  suspended  solids, nitrogen,  phosphorus,  trace
 elements,  microorganisms, and  trace organics are  discussed
 briefly along  with typical  results from  various  operating
 systems.   Chapter  9 contains  discussions of  the health  and
 environmental effects  of these constituents.

      5.2.1   BOD and Suspended Solids

 Particulate   BOD   and   suspended   solids  are  removed   by
 filtration  at or near the soil surface.   Soluble BOD may be
 adsorbed by  the soil or may be removed  from  the percolating
 wastewater   by  soil  bacteria.   Eventually,  most  BOD  and
 suspended  solids  that  are removed  initially by filtration
 are  degraded   and   consumed  by  soil  bacteria.    BOD  and
 suspended  solids removals are generally  not  affected by  the
 level  of preapplication treatment.   However,  high  hydraulic
 loadings of  wastewaters with high concentrations of  BOD  and
 suspended  solids can  cause  clogging of  the  soil.    Typical
 BOD   loadings   (Table 2-3)    are    less   than  130  kg/ha«d
 (115 lb/acre-d)   for   municipal   wastewaters^Removals
 achievedatselectedRIsystemsarepresented   in
 Table  5-1.   Some systems have been  operated  successfully at
 higher  loadings.

     5.2.2   Nitrogen

 The  primary  nitrogen  removal  mechanism  in   RI  systems   is
 nitrification-denitrification.   This mechanism involves  two
 separate  steps:     the  oxidation  of   ammonia  nitrogen   to
 nitrate  (nitrification)   and   the  subsequent  conversion   of
 nitrate to nitrogen gas  (denitrification).  Ammonium  adsorp-
 tion  also  plays an  important  intermediate role  in nitrogen
 removal.

 Both  nitrification and  denitrification  are accomplished   by
 soil bacteria.  The  optimum temperature  for nitrogen  removal
 is 30  °C to  35  °C (86  °F to 95 °F).  Both  processes  proceed
 slowly between  2  °C  and  5 °C  (36 °F  and  41  °F) and stop near
 the freezing point  of/water.  Nitrification rates  decline
 sharply  in  acid  conditions  and reach  a  limiting  value   at
 approximately pH  4.5.   The denitrification reaction rate  is
reduced substantially  at pH  values  below  5.5.   Thus,  both
 soil  temperature  and  pH  must  be   considered  if  nitrogen
removal  is   important   (Section   5.4.3.1).    Furthermore,
alternating   aerobic  and  anaerobic   conditions   must   be
provided for  significant nitrogen  removal  (Section  5.4.2).
Because aerobic bacteria deplete soil oxygen during flooding
periods, resting  and flooding  periods  must be alternated   to
result in alternating aerobic and anaerobic soil conditions.
                             5-3

-------
                            TABLE 5-1
                      BOD REMOVAL  DATA FOR
                   SELECTED RI SYSTEMS  [1-6]
Location
Calumet,
Michigan
Fort Devens,
Massachusetts
Hollister,
California
Lake George,
New York
Milton,
Wisconsin
Phoenix,
Arizona
Vineland,
New Jersey
Preapplication
treatment
Untreated

Primary

Primary

Trickling
filters '
Activated
sludge
Activated
sludge
Primary

Sampling
depth, m
3.3

20

8

3

8-29

6-9

2-14


Average
loading
rate,
kg/ha -da
80

87

177

53

155

45

48

BOD
Treated
water concen- Removal,
tration, mg/L %
llb 86

12 86

8C 95

1.2 98

1.0-19.0 88-99

0-1 98-100

6.5° 86
•
      a. Total kg/ha-yr applied divided by the number of days in the operating
        season (365 days for these cases).
      b. Soluble total organic carbon.
      c. Average value from several wells.

      Note: See Appendix G for metric conversions.
Organic  carbon is needed in the applied  wastewater  to 'supply
energy   for  the   denitrification   reaction.    Approximately
2 mg/L  of  total  organic carbon (TOG)  is  needed to  denitrify
1 mg/L  of nitrogen.   Because the BOD concentration  decreases
as   the   level   of   preapplication  treatment  increases,
preapplication treatment must  be  limited  if denitrification
is  to  occur  in  the  soil.    Thus,  if   the goal   of  RI  is
nitrogen   removal,    primary   preapplication   treatment   is
preferred.

Nitrogen  removal   efficiencies   at  various   operating   RI
systems  are  shown  in Table 5-2.    As shown in  this table,
nitrogen removals of  approximately  50% are typical"!  Greater
amounts  can  Be  removed  using  special management proced ure s
(Section 5.4.3.1).
                               5-4

-------
                           TABLE 5-2
            NITROGEN  REMOVAL DATA FOR SELECTED RI
                      SYSTEMS [1,2,4,6-9]
           Concentration                     Concentration in
            in applied   Loading       Flooding  renovated water, mg/L Removal,
            wastewater:   rate,  BOD:N  to drying  	  % of
  Location   total N, mg/L  m/yr   ratio  time ratio  NO-.-N    Total N  total N
N03-N
Boulder,
Colorado
Brookings,
South Dakota
Calumet,
Michigan
Disney World,
Florida
Fort Devens,
Massachusetts
Hollister,
California
Lake George,
New York
Phoenix,
Arizona
16.5

10.9

24.4

—

50

40.2

11.5
12.0
27.4

48

12

17

54

30

15

58
58
61

.8

.2

.1

.9

.5

.2

.0
.0
.0

2.3:

2:

3.6:

0.3:

2.4:

5.5:

2:
2:
1:

1

1

1

1

1

1

1
1
1

1:

1:

1:

150:

2:

1:

1:
1:
9:

3 6-16

2 5.3

2 3.4

14

12 13.6

14 0.9

4
4
12 6.2

9-16 10-20

6.2 43

7.1 71

12

19.6 61

2.8 93

7.70 33
7.50 38
9.6. 65

At some  sites the goal  of  RI may be  only nitrification  (for
example,   Boulder,  Colorado).     Generally,  nitrification
occurs  if wastewater application periods are  short enough
that the  upper soil layers remain aerobic.  For this reason,
if nitrification  is  the objective  of RI ,  short application
periods   followed  by  somewhat  longer  drying  periods   are
used.     Because   the  nitrification  rate  decreases  during
winter months, reduced loading rates  may be required in  cold
climates.      Under   favorable    temperature   and   moisture
conditions,  up to 50  ppm ammonia nitrogen (as nitrogen)  per
day  (soil basis)  may be converted to  nitrate  [10].  Assuming
that nitrification only occurs  TH  the  top  10 cm (4 in. )  of
soil,  this  corresponds to  nitrification  rates of  up  to
67 kg/ha-d  (60 Ib/acre -d) .    At  the  Boulder,  Colorado,  RI
system,  the  percolate ammonia  concentration  remained below
1 mg/L on a  year-round basis.

     5.2.3   Phosphorus

The  primary  phosphorus  removal  mechanisms in RI systems  are
the  same  as  described in Section 4.2.3  for  SR.   Phosphorus
removals  achieved  at  typical  RI  systems  are  provided  in
Table 5-3.
                              5-5

-------
                           TABLE 5-3
             PHOSPHORUS REMOVAL  DATA FOR SELECTED
                    RI SYSTEMS  [1,  2,  4-9]
Average
concentration
in applied
wastewater ,
Location mg/L
Boulder,
Colorado
Brookings, .
South Dakota
Calumet,
Michigan
Fort Devens, .
Massachusetts
Hollister,
California13
Lake George,
New Yorkb
Phoenix,
Arizona3
Vineland, .
New Jersey
6.2

3.0

3.5
3.5
9.0

10.5

2.1
2.1
8-11
7.9
4.8
4.8
c
Distance of travel, m
Vertical
2.4-3.0

0.8

3-9
	 c
15

6.8

3
	 c
9.1
6
2-18
4-16
Horizontal
0

0

0-125
1,700C
30

0

0
600C
0
30
0
26O-530
Average
oncentration
in renovated
wastewater,
mg/L
0.2-4.5

0.45

0.1-0.4
0.03
0.1

7.4

<1
0.014
2-5
0.51
1 . 54
0.27
Removal,
%
40-97

85

89-97
99
99

29

>52
' 99
40-80
94
68
94
      a.  Total phosphate measured.

      b.  Soluble phosphate measured.

      c.  Seepage.
      5.2.4   Trace Elements

Trace   element   removal   involves  essentially  the   same
mechanisms  discussed  in  Section 4.2.4  for  SR systems.   The
results   presented  in   Table   5-4  compare   trace   element
concentrations  in  wastewater  at  Hollister,  California, to
drinking  water  and irrigation requirements.

At  RI sites,  trace  elements accumulate in  the upper  soil
layers.   Data  from  Cape  Cod,  Massachusetts,  reflect  this
phenomenon  and  are presented in  Table 5-5.   As  indicated in
this  table, the  percent  retention of  most  of the metals is
quite  high.   For example, 85%  of the  copper applied  over
33 years  was  retained  in  the   top  0.52 m  (1.7 ft).    The
distribution of   the  retained  metals  is  also  shown  in
Table  5-5.
                              5r-6

-------
                  TABLE 5-4
  COMPARISON OF TRACE ELEMENT LEVELS TO
 IRRIGATION AND DRINKING WATER LIMITS [6]
                     mg/L
Maximum
Recommended maximum concentration
in irrigation in drinking
Element waters waters
Ag
As
Ba
Cd
Co
Cr
Cu
Fe
Hg
Mn
Ni
Pb
Se
Zn
(silver)
(arsenic)
(barium)
(cadmium)
(cobalt)
(chromium)
(copper)
( iron )
(mercury)
(manganese)
(nickel)
(lead)
(selenium)
(zinc)
~«
0.1
— a
0.01
0.1
0.05
0.2
5.0
	 a
0.2
0.2
5.0
0.02
2.0
0.05
0.05
1.0
0.010
	 a
0.05
	 a
— a
0.002
	 a
	 a
0.05
0.01
	 a
Hollister,
California,
average
wastewater
concentration
<0.008
<0.01
<0.13
<0.004
<0.008
<0.014
0.034
0.39
<0.001
0.070
0.051
0.054
<0.001
0.048
a.  None set.
                  TABLE 5-5
       HEAVY METAL RETENTION  IN AN
          INFILTRATION BASIN a

                  Percent
Depth, m
0-0.04
0.04-0.06
0.14-0.16
0.24-0.26
0.29-0. 31
0.44-0.46
0.50-0.52
Total .
Percent
retention
of 33 year
loads
0-0.52
Cadmium
84
12
1
1
1
0.5
0.5
100




113
Chromium Copper
87
10
0
2
0
1
0
100




62
76
23
0.4
0.4
0.1
0.1
0.0
100




85
Lead
88
12
0
0
0
0
0
100




129
Zinc
82
13
1
2
0.8
1.2
0
100




49
    a.  Adapted from reference [11].
                       5-7

-------
      5.2.5  Microorganisms

 Removal   mechanisms  for  microorganisms  are  discussed   in
 Section  4.2.5.

 Fecal  coliform removal  efficiencies obtained at selected  RI
 sites  are  given  in Table t  5-6.    As  shown  in  this table,
 effective removal  of fecal  coliforms  can be  achieved with
 adequate travel distance.

                           TABLE 5-6
                FECAL COLIFORM REMOVAL DATA  FOR
               SELECTED RI SYSTEMS  [1,  3-6,  12]
                           Fecal coliforms, MPN/100 mL
                                                 Distance; of
         Location   Soil type Applied wastewater Renovated water  travel, ra
Hercet ,
California
Hoi lister,
California
Lake George,
New York
Landis,
New Jersey
Milton,
Wisconsin
Phoenix,
Arizona
Santee,
California
Vineland,
New Jersey
Sand
Sandy
loam
Sand
Sand and
gravel
Gravelly
sands
Sand
Gravelly
sands
Sand and
gravel
60,000
12,400,000
359,000
359,000
TNTC3
TNTCa
244,071
244,071
130,000
130,000
TNTC3
11
171,000
72
0
16
0
104
0
580
<2
0
2
7 ,
2
7
1-2
8-17
30
90
61
762
. 6-7
      a. At least one sample too numerous to count.
The  primary  removal  mechanism  for  viruses  is  adsorption.
Because  of  their  small,  size,  viruses  are  not removed  by
filtration  at the soil surface, but  instead, travel into the
soil  profile.   Only a  limited number  of studies  have been
conducted  to determine  the  efficiency of  virus  removal.  At
Phoenix,  Arizona,  results  indicate  that  90  to 99%  of the
applied virus is removed within 10 cm (4  in.)  of travel when
either primary or secondary effluent  is applied  [13, 14] and
that  99.99%  removal  is achieved  during  travel  through 9  m
(30  ft)  of  soil  following  the  application  of  secondary
effluent  [15].

The  only  RI  sites  at  which  viruses have been detected  in
ground water, and  the  distances traveled  by the virus  prior
to  detection  are  listed   in  Table  5-7.    As noted  in the
                              5-8

-------
table,  all four  of  these  sites  are located  on coarse sand
and  gravel type  soils.    Infiltration  rates  on these soils
are  relatively  high,  allowing  constituents  in the applied
wastewater  to   travel   greater  distances   than  normally
expected.   Thus,  the coarser  the  soil  is,  the  higher  the
loading  rate, and  the higher  the  virus  concentration,   the
greater  the risk of  virus migration.

                          TABLE 5-7
        REPORTED ISOLATIONS OF VIRUS AT RI  SITES [16]
             Location
Soil type
                                Distance of migration, m

                                  Vertical  Horizontal
East Meadows,
New York
Fort Devens,
Massachusetts
Holbrook,
New York
Vineland,
New Jersey
Sands and
gravel
Sands and
gravel
Sands and
gravel
Sands and
gravel
11
18
6
16
.3
.3
.1
.8
3
183
45.7
250
          a. Application of unchlorinated primary effluent.
     5.2.6  Trace  Organics

Trace  organics can  be  removed by  volatilization, sorption,
and  degradation.    Degradation may  be  either  chemical  or
biological; trace  organic removal  from the soil is primarily
the result of  biological degradation.

Studies  to  determine  trace  organic  removal  efficiencies
during  RI  were conducted  at  the  Vineland and  Milton sites
[3, 5].   At these two  systems, applied  effluent and ground
water  were  analyzed  for  six  pesticides  and the  results  of
the studies are summarized  in Table 5-8.   At both locations,
the concentrations  of  2,4-D,  2,4,5-TP  silvex,  and  lindane
were  well  below  the  maximum concentrations   for  domestic
water  supplies established  in  the  National  Primary Drinking
Water  Regulations.

If  local  industries   contribute   large   concentrations  of
synthetic  organic  chemicals  and  the  RI  system  overlies  a
potable   aquifer,    industrial   pretreatment   should   be
considered.    Further,  since  chlorination  prior  to  land
application causes  formation  of  chlorinated  trace  organics
that may be more  difficult  to remove,  chlorination before
application should be avoided whenever possible.
                             5-9

-------
                           TABLE 5-8
            RECORDED TRACE ORGANIC CONCENTRATIONS
                  AT  SELECTED RI SITES  [3,5]
                              ng/L
Vineland, New Jersey3
Pesticide
Endrin
Lindane
Methoxychlor
Toxaphene
2,4-D
2,4,5-TP
ailvex
Applied
<0.03
2,830-
1,227
<0.01
<0.1
9.5-
10.5
72
Shallow
ground
water
<0.03
453-
1,172
<0.01
<0.1
16.4-
13.0
26.8-
120
Control
ground
water
<0.03
21.3
<0.01
<0.1
10.4
185
Applied
<0.03
41
<0.01
<0.1
53.8
16.2
Milton,
Shallow
ground
water"
<0.03
157.6
<0.01
<0.1
92.4
41.2
Wisconsin
Down-
gradient0
<0.03
3.9
<0.01
<0.1
23.6
38.7
1
Control
ground
water
<0.03
7.4
<0.01
<0. 1
31.0
76.8
     b.
     c.
If two values are listed, the first is for the Vineland site and the second
is for the Landis site (see reference [5]). If one value is listed, results
were the same at both sites.
Shallow ground water was sampled directly below infiltration basins.
Ground water sampled approximately 45 m (148 ft) downgradient from the infil-
tration basins.
5.3  Determination of  Preapplication Treatment  Level

The first step in designing an RI  system is to  determine the
appropriate level of preapplication  treatment.  This section
describes the  factors  that should be considered as  well as
the levels of  preapplication treatment  that  should  be  used
to meet  various treatment objectives.

     5.3.1  EPA Guidance

EPA has  issued guidelines suggesting the following  levels of
preapplication treatment for RI systems  [17]:

     •       Primary  treatment  in   isolated   locations  that
             have restricted public access

     •       Biological  treatment  by  lagoons  or   in-plant
             processes  at  urban  sites  that  have controlled
             public access

     5.3.2  Water Quality Requirements and Treatment Goals

Preapplication treatment is used to  reduce soil clogging and
to   reduce    the    potential    for   nuisance   conditions
(particularly odors)  developing  during  temporary storage at
the application  site.    If  surface discharge  is required and
ammonia  discharge  requirements  are  stringent, the  treatment
                               5-10

-------
objective should  be  to maximize nitrification.   In  all other
cases,  system  design  is  based  on  achieving  the  maximum,
cost-effective  loading rate that provides the  required level
of overall treatment.

For all  systems,  the  equivalent  of primary treatment  is the
minimum recommended  preapplication treatment.   This level of
treatment reduces wear on  the  distribution system,  prevents
unmanageable  soils   clogging,   reduces  the   potential  for
nuisance  conditions,  and allows  the potential for  maximum
nitrogen removal.

Nitrification   may   be  achieved  using  either primary  or
secondary  preapplication  treatment.   For  this reason,  the
selection  of a preapplication  treatment level to  maximize
nitrification   at  a   specific  site  is  based  on  the  same
factors  that  influence  the selection  of  a  preapplication
treatment level for  maximizing infiltration rates.

In mild  climates, ponds can  be  used if  land  is  relatively
plentiful and  not expensive,.   In areas  that experience cold
winter weather, it may not be possible to operate  RI systems
that use ponds  for preapplication treatment.   Also,  if ponds
are used prior  to infiltration, algae carryover may increase
the potential  for soil clogging.   Ponds  can also be used to
reduce the nitrogen  loading (Section 4.4.1).

Recommended   levels   of   preapplication   treatment   are
summarized  in  Table  5-9.  This  table should t be  used only as
a guide; the designer should select preapplication  treatment
facilities  that  reflect local  conditions,  including  local
preapplication    treatment    requirements    and    existing
wastewater treatment facilities.

                          TABLE  5-9
          SUGGESTED PREAPPLICATION  TREATMENT LEVELS
               RI system objective
Preapplication
treatment level
               Maximize infiltration
               rates or nitrification
                General case

                Limited land

                High quality effluent
                polishing

               Maximize nitrogen
               removal

                General case
 Primary
 Secondary
 Secondary or
 higher
 Primary
                              5-11

-------
5.4  Determination of Hydraulic Loading Rate

Selection of  a  hydraulic  loading  rate is the most important
and, at the same time, the most difficult step in the design
procedure.   The  loading  rate  is a  function of  the site-
specific hydraulic  capacity,  the  loading cycle, the quality
of the applied wastewater, and the treatment  requirements.

     5.4.1  Measured Hydraulic Capacity

Hydraulic  capacity  varies  from  site  to  site  and  is  a
difficult  parameter  to  measure.    For  design  purposes,
infiltration  tests  are usually  used to  estimate hydraulic
capacity.   The  most commonly  employed measurement  for RI
design   is   the    basin   infiltration   test;   cylinder
inf iltrometers   are  used   when   basin   testing   is   not
feasible.  Both methods are described in Section 3.4»

Saturated  vertical   hydraulic  conductivity  (also  called
permeability)  is sometimes  measured.    However,  saturated
vertical  hydraulic   conductivity  is  a  constant  with time,
whereas  infiltration rates  decrease  as wastewater  solids
clog   the   soil  surface.     Thus,   vertical ,  conductivity
measurements  overestimate the wastewater infiltration rates
that can be  maintained  over  long  periods of  time.  For  this
reason,  and  to  allow adequate time  for  drying  periods and
for proper basin  management,  annual hydraulic loading rates
should be limited to between 4 and 10% of the measured clear
water permeability of the most restrictive soil  layer.

Although  basin  infiltration  tests  are  more accurate   than
soil   hydraulic  conductivity  measurements   and   are  the
preferred  method,  the  small  areas  usually  used allow  a
larger  fraction  of  the  wastewater  to   flow   horizontally
through  the  soil  from the test site than from an operating
basin.   The   result  is  that infiltration  rates  at the  test
sites  are   higher   than  rates  . operating  systems  would
achieve.  Thus, design annual  hydraulic loading  rates should
be no  greater than  10 to 15% of measured basin  infiltration
rates.

Cylinder   infiltrometers   greatly   overestimate  operating
infiltration  rates.   When cylinder  infiltrometer measure-
ments  are  used, annual  hydraulic  loading rates should be no
greater  than 2  to  4% of the  minimum measured  infiltration
rates.   Annual  hydraulic  loading rates based  on air entry
permeameter   test  results ! should  be  in  the   same  range.
Annual  loading  rates  and corresponding  infiltration rates
                           RI   systems   are   presented  in
                          loading  rates  are  summarized in
for   several
Table 5-10.
Table 5-11.
operating
Suggested
                             5-12

-------













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                          TABLE  5-11
           SUGGESTED ANNUAL  HYDRAULIC LOADING RATES
            Field measurement
                                  Annual loading rate
         Basin infiltration test

         Cylinder infiltrometer •
         and air entry permeameter
         measurements
         Vertical hydraulic
         conductivity measurements
10-15% of minimum measured
infiltration rate

2-4% of minimum measured
infiltration rate

4-10% of conductivity of most
restricting soil layer
The  total  hydraulic  load  includes  both  precipitation  and
wastewater.     If  the  local  precipitation  is  significant,
wastewater loading rates should  be adjusted accordingly.

Once  the hydraulic  capacity has been measured, the engineer
must  calculate an annual hydraulic loading rate.  Experience
in  the  United  States  with  treatment  systems  using  RI  has
been  limited to annual loading rates of about 120 m (400  ft)
or less.

For example, if the basin test infiltration rate is 3.6 cm/h
(1.4  in./h)f the annual hydraulic  loading rate  is calculated
to equal:


  3.6 cm/h x  24  h/d  x  365  d/yr x 1 m/100  cm x  (0.1  to  0.15)
           =  31.5  to 47.3  m/yr (103  to  155  ft/yr)
It  is  necessary to  ensure that BOD and  suspended solids  are
within  typical  ranges  (Sections  2.2.1.1  and  5.2.1)  at  the
calculated  annual loading rate.   If the  applied wastewater
contains  150 mg/L  BOD  and  100 mg/L  suspended  solids „  at  a
loading rate of 31 m/yr (102 ft/yr),  the BOD and SS loadings
would  average  127 kg/ha-d  (114  lb/acre-d)  and  85 kg/ha-d
(76 lb/acre-d), respectively.   These quantities  are within
the typical BOD range given in Table 2-3  and  the suspended
solids range discussed in Section 2.2.1.1.

     5.4.2   Selection of  Hydraulic  Loading Cycle
             and Application Rate

Wastewater  application  is  not  continuous in  RI ,   instead,
application  periods  are  alternated  with drying   periods.
This   improves   wastewater  treatment  efficiency,  maximizes
long-term infiltration  rates,  and  allows  for periodic  basin
maintenance.

-------
Loading  cycles  are  selected  to maximize  either the  infil-
tration  rate,  nitrogen  removal,  or  nitrification.    To
maximize  infiltration  rates,   the  engineer  should  include
drying periods  that  are long  enough for soil reaeration and
for drying and oxidation of filtered solids.

Loading  cycles  used  to maximize nitrogen  removal vary with
the level  of  preapplication treatment  and with the  climate
and season.   In  general,  application  periods , must be long
enough for  soil bacteria to deplete  soil  oxygen,  resulting
in anaerobic conditions.

Nitrification requires  short application periods  followed by
longer drying periods.   Thus,  hydraulic loading cycles used
to  achieve  nitrification  are   essentially the  same  as the
cycles used to maximize infiltration rates.

Hydraulic loading  cycles  at selected RI sites  are  presented
in  Table  5-12.     Recommended  cycles  are  summarized  in
Table 5-13.   Generally, the shorter drying periods shown in
Table 5-13 should  be used  only in mild climates; RI  systems
in cooler climates should use  the longer drying  periods.  In
areas  that  experience  extremely cold  weather,  even  longer
drying  periods  than those  presented  in  Table  5-13  may be
necessary.  The cycles  suggested in Table  5-13  are  presented
only  as  guidelines; the  actual cycle selected  should be
suitable  and  flexible  enough   for  the  community's climate,
flow, and treatment  site characteristics.

Application rates  can be  calculated from  the annual  loading
rate and  the loading cycle.  For example,  the annual  loading
rate is  31 m/yr (102 ft/yr) and the loading cycle  is  3 days
of application  followed by  11  days of drying.

     •      Total cycle time =  3 + 11 = 14 d

     •      Number of cycles per year = 365/14  = 26

     •      Loading  per cycle  = 31/26 = 1.19 m/cycle

     •      Application rate =  (1.19 m/cycle)/(3  d)
            =0.4 m/d

The  application  rate  can  then  be  used  to  calculate the
maximum  depth  of applied  wastewater.   For  example,   if 'the
basin  infiltration  test  rate  of  3.6  cm/h  (1.4 in./h)  is
maintained  over  the 3 day application period,  the  appli-
cation  rate  of  0.4 m/d   (1.3  ft/d)  should not  result in
standing  water  at the end of 3  days:

       (0.4 m/d  x  100 cm/m)  - (3.6 cm/h  x 24  h/d)
                            = -46.4 cm  (-18.3  in.)
                             5-15

-------
                                     TABLE  5-12
              TYPICAL  HYDRAULIC LOADING  CYCLES  [6,  9,  18,  19]
Location
Boulder,
Colorado

Calumet,
Michigan
Flushing Meadows,
Arizona
Year-round

Stunner

Winter

Year-round

Fort Devens,
Massachusetts
year-round

Year-round

Hollister,
California
Summer

Winter

Lake George,
New York
Summer

Winter

Tel Aviv,
Israel

Vineland,
New Jersey

Westby,
Wisconsin
Whittier Narrows,
California
Preapplication
treatment
Trickling filters

Untreated
Activated sludge









Primary





Primary





Trickling filters





Ponds, lime preci-
pitation, and
ammonia stripping
Primary

Trickling filters
Activated sludge
with filtration d
Cycle objective
Maximize nitrifi-
cation and infil-
tration rates
Maximize infil-
tration rates


Maximize nitrifi-
cation
Maximize infil-
tration rates
Maximize infil-
tration rates
Maximize nitrogen
removal


Maximize infil-
tration rates
Maximize nitrogen
removal


Maximize infil-
tration rates
Maximize infil-
tration rates


Maximize infil-
tration rates
Maximize infil-
tration rates
Maximize
polishing

Maximize infil-
tration rates

Maximize infil-
tration rates
Maximize infil-
tration rates
Application Resting
period period
<1 d <3 1/2 d

1-2 d 7-14 d-


2 d 5 d

2 wk 10 d

2 wk 20 d

9 d 12 d



2 d 14 d

7 db 14 d



1 d 14-21 d

1 d 10-16 d



9 h 4-5 d

9 h 5-10 d

5-6 d 10-12 d

1-2 d 7-10 d

2 wk 2 wk
9 h 15 h •
Bed surface
Sand (disked) ,
solids turned
into soil
Sard (not
cleaned)


Sand (cleaned)3

Sand (cleaned)3

Sand (cleaned)3

Sand (cleaned)3



Weeds (not
cleaned)
Weeds (not
cleaned)


Sand

Sand



Sand (cleaned)3

Sand • (cleaned) a

Sand c

Sand (disked)
solids turned
into soil
Grassed
Pea gravel
a.   Cleaning usually involved physical removal of surface solids.
b.   Caused clogging and reduced long-term hydraulic capacity.
c.   Maintenance of sand cover is unknown.
d.   Treated wnstewater blended with surface waters before application..
                                           5-16

-------
                          TABLE  5-13
                   SUGGESTED LOADING CYCLES
         Loading cycle
           objective
  Applied         Application  Drying
wastewater  Season   period, da period, d
Maximize
infiltration
rates
Maximize
nitrogen
removal
Maximize
nitrification

Primary
Secondary
Primary
Secondary
Primary
Secondary
Summer
Winter
Summer
Winter
Summer
Winter
Summer
Winter
Summer
Winter
Summer
Winter
1-2
1-2
1-3
1-3
1-2
1-2
7-9
9-12
1-2
1-2
1-3
1-3
5-7
7-12
4-5
5-10
10-14
12-16
10-15
12-16
5-7
7-12
4-5
5-10
         a.  Regardless of season or cycle objective, application
            periods for primary effluent should be limited to
            1-2 days to prevent excessive soil clogging.


If  the  calculated depth  is  a positive number,  the maximum
design  wastewater depth  should not exceed  46 cm (18 in.);  a
maximum  depth of  30 cm  (12  in.)  is preferable because  soil
clogging  and  algae  growth decrease as  the  loading depth  and
detention  time  decrease.  If the calculated depth exceeds 46
cm  (18  in.) either the application  period  must be lengthened
or  the  loading  rate  decreased.    From  this example,  it  is
clear   that  infiltration  rates   must  be   determined   as
accurately as possible.   If  the  infiltration  rate is over-
estimated,  basin  depth  will  be  underestimated  and  diffi-
culties will  arise when system operation begins.

     5.4.3  Other Considerations

The following three  subsections  describe  other factors  that
can affect the  loading  cycle  and  loading rate  and must  be
considered by the designer.
             5.4.3.1
   Nitrogen Removal
The  amount  of nitrogen  that  theoretically  (under optimal
conditions)   can  be   removed   by  denitrification  can   be
described by  the  equation [19].
                        AN - TOC -  K
                                  (5-1)
                              5-17

-------
 where   AN =

       TOC =


         K =
change in total nitrogen concentration, mg/L

total organic carbon concentration in the
applied wastewater, mg/L (see Table 2-1)

TOC remaining in percolate, assumed to
equal 5 mg/L
The  equation  is  based on  experimental data  that  indicated
2 grams  of wastewater carbon are needed  to  denitrify  1  gram
of wastewater  nitrogen [19] .

Equation 5-1 can be  used  tp determine whether  a  wastewater
contains enough  carbon  to  remove  the  desired  amount  of
nitrogen.   For example,  if the applied  wastewater  contains
42  mg/L TOC  and  25.8  mg/L  total  nitrogen,  it  is  only
possible to remove  (42-5)/3> mg/L or  18.5  mg/L of  nitrogen
and   to   reduce  the   total  nitrogen   concentration   from
25.8 mg/L   to   7.3  mg/L.     Thus,  using  this  wastewater,
complete nitrogen  removal  could not  be achieved.   If  the
applied  wastewater  contains,248  mg/L TOC  and 40.2  mg/L total
nitrogen,  there is  sufficient  carbon  to remove 121 :mg/L  of
nitrogen.    This means  that,   theoretically,  under  proper
management,  all of  the nitrogen could  be removed during  RI
(although   total   removal   might  never   be  achieved   in
practice).   If nitrogen removal is  important, the  engineer
should   use  Equation   5-1   to   determine whether   nitrogen
removal  is  feasible using RI.   If so, a loading  cycle  should
be selected  that maximizes  nitrogen removal.

Nitrogen removal  from  secondary effluent is more difficult
than nitrogen  removal from  a wastewater  that contains  high
concentrations  of  organic  carbon.     Nitrogen  removal  is
especially  difficult  when  infiltration rates   are  high,
because  nitrates tend to   pass  through  the  soil  profile
before they can  be converted  to nitrogen  gas.   In  fact,
nitrogen   removal   from    secondary   effluent   increases
exponentially as the infiltration rate  decreases [20].   This
relationship is shown  in Figure  5-2.                 ;

Although  Figure  5-2  is  based  on  data  from  soil  column
studies  using   loamy  sand,  data  from   operating  systems  in
warm climates indicate that  the  figure  can be  used to obtain
conservative estimates  of a similar soil's nitrogen removal
potential.    Thus,  if  secondary  effluent infiltrates  at a
rate  of  30  cm/d (12  in./d),  using  a loading cycle  that
promotes nitrogen removal,  it should be  possible  to remove
at  least  30%  of the  applied  nitrogen.   To  achieve 80%
                             5-18

-------
nitrogen removal,  the soil column  studies  indicated maximum
infiltration rates are:

     •      20  cm/d  (8  in./d)  for  primary  preapplication
            treatment

     •      15  cm/d   (6  in./d)  for secondary  preapplication
            treatment

If nitrogen  removal  is  important  and these  suggested rates
are exceeded, soil column studies  or  pilot  testing should be
conducted  to determine  how  much  nitrogen  can  be  removed.
Also,   infiltration   rates   can   be  reduced   somewhat  by
decreasing  the  depth   of  the  applied  wastewater,  or  by
compacting the  soil  surface.
                 90
                 80
                 70

                 60

                 50
              ^

              i  40
              o
              X -
              UJ
              <>=  30
                 20
                 1 0
                  10        20     30   40  50 60

                         INFILTRATION RATE, cm/d
                           FIGURE  5-2
     EFFECT OF  INFILTRATION RATE  ON NITROGEN REMOVAL  [20j
                             5-19

-------
             5.4.3.2
Phosphorus Removal
 The  amount  of  phosphorus  that   is  removed  during  Ri  at
 neutral pH can be estimated  from the  following equation  [19,
 e,J. J J
                       CX ~ G06
                               -kt
                               (5-2)
 where  Cx = total phosphorus concentration at a distance  ,
             x along the percolate flow path, mg/L

        C0 = total phosphorus concentration in the applied
             .wastewater, mg/L

         k = instantaneous rate constant and equals
             0.002 h ••• at neutral pH

         t = detention time = X0/I, h

         where  x = distance along the flow path, cm

                9 = volumetric water content,  cm3/cm3,
                     use 0.4

                I = infiltration rate during system
                    operation, cm/h (use basin test results,
                    20%  of  cylinder infiltration results,  or
                    horizontal conductivity for horizontal
                    flow)


Because  the minimum phosphorus precipitation  rate  occurs at
neutral  pH,  this  equation  can  be  used  to  conservatively
estimate  phosphorus removal.   if the  calculated  phosphorus
concentration   is  an  acceptable  value,  phosphorus  con-
centrations  from  an  operating  Ri   system  should  'be well
within  limits.     However,   if  the   calculated   phosphorus
concentration  at a distance  x  exceeds acceptable values, a
phosphorus  adsorption test should  be performed.   This test
measures  the ability  of a  specific  soil  to  remove  phosphorus
and is described  in Section 3.7.2.

For  example,  consider  a  site  where  wastewater  percolates
through the  soil  to  the  ground water  table,  which  is 15 m
(49  ft)   below the  soil   surface.    The  initial phosphorus
concentration  is  10  mg/L  and  the basin  infiltration test
rate  is 40 cm/d  (16 in./d).    By the  time  the water reaches
                            5-20

-------
the ground water  table,  the phosphorus concentration should
be less than:
           Q Q02h-
(10  mg/L)e-°-002h  \ 0.4
                          15
                               m/d
                                            - 4.9 mg/L
If the  movement  is then predominantly  horizontal,  with the
renovated water seeping into a creek 200 m  (650 ft) from the
infiltration site, and the horizontal hydraulic conductivity
is 120  cm/d  (47  in./d),  the phosphorus concentration in the
seepage should be less than:
                 -200
                 Q 002h-
     (4.9 mg/L)e-°-002h  V 1.2 m/d
                                                0.2 mg/L
            5.4.3.3
                  Climate
In  regions  that  experience  cold  weather,  longer  loading
cycles    may    be   necess'ary    during    winter    months
(Section 5.4.2).   Nitrification, denitrification,  ox-idation
(of  accumulated  organics),  and  drying rates  all  decrease
during  cold  weather,  particularly as the temperature  of  the
applied  wastewater decreases.    Longer application  periods
are  needed  for denitrification so that the  application  rate
can  be  reduced  as  the  rate of  nitrogen removal  decreases.
Similarly,  longer resting periods  are  needed to  compensate
for  reduced  nitrification  and drying  rates.

Combined  with  the reduced  hydraulic  capacity  experienced
during  cold  weather,  the need  for longer loading  cycles
changes  the  allowable wastewater loading rate.   Cold weather
loading  rates  are  somewhat  lower  than warm weather  rates;
therefore, more land  is required during cold weather as  long
as winter and  summer  wastewater  flows are  equal.   If loading
rates  must  be  reduced  during  cold weather,  either the  cold
weather  loading  rate   should  be  used  to  determine  land
requirements or. cold  weather  storage  should be  included.

In  communities  that  use  ponds  as preapplication  treatment
and  experience  cold  winter weather, winter storage  may be
required.  This is because the  temperature  of the wastewater
becomes  quite  low prior  to  land  treatment  and  makes  the
applied  wastewater susceptible to  long-term freezing in the
basin.    Alternatively,  RI  may  be  continued  through  cold
weather if warmer wastewater  from the first cell of the  pond
system  (if possible) is applied.  In  such  communities,  the
engineer must  keep  in mind  that  the  annual  loading  rate
                              5-21

-------
 actually applies only to the portion  of  the  year when RI is
 used.
 5.5
Land Requirements
 An RI site must have  adequate  land  for infiltration basins,
 buffer zones, and  access roads.   At some systems,  land  is
 also  needed   for   preapplication   treatment   facilities,
 storage,  or future  expansion.

      5.5.1  Infiltration Basin  Area

 If  wastewater  flow  equalization  is   provided  (including
 treatment ponds),  the land area  required for  infiltration
 only (ignoring land  required between and around  basins)  is
 simply the  average annual  wastewater  flow  divided by  the
 annual wastewater loading rate.   For example,  if  the annual
 average   daily  flow  is  0.3   mj/s   (6.8  Mgal/d )  and  the
 wastewater loading  rate  is  25 m/yr  (82  ft/yr),  the  area
 required  for infiltration is:
   (0.3 m3/s) (86,400  s/d ) (365 d/yr )  =
         (25 m/yr) (101 mVha)
If the wastewater  flow  varies with  season  and  seasonal  flows
are  not  equalized, the highest average  seasonal  flow should
be used.   An RI site must either have enough  basins so  that
at  least  one  basin can  be  dosed  at  all   times  or   have
adequate   storage    for   equalization   between   application
periods.

     5.5.2   Preapplication Treatment  Facilities

The  communities that already have preapplication  treatment
facilities   will,  in general,  only need additional land  for
facilities   to  convey  wastewater  to   the  RI   site.     In
communities  that are  constructing a completely 'new  treatment
facility,  land  requirements  for  preapplication  trecitment
will  vary  with  the  level  and method  of   preapplication
treatment.

     5.5.3   Other Land Requirements

Additional  land may be  needed  for  buffer   zones,  access
roads,  storage or  flow  equalization (when  provided),   and
future expansion.    Buffer  zones can  be used  to screen  RI
sites  from public  view.   Preapplication  treatment facili-
ties, access  roads,  and storage or  flow  equalization may  be
included in  the buffer area.
                             5-22

-------
Access roads  must be  provided  so that  equipment  and labor
can  reach  the  infiltration  basins.    Maintenance  equipment
must  be  able  to  enter  each  basin  (for  scarification or
surface maintenance).

Typically/ access  roads  should  be 3 to  3.7  m (10  to 12 ft)
wide.  In  any case, access roads  should be wide enough for
the  selected  maintenance  equipment  and  curves  should  have
large  enough  radii  to allow  maintenance  equipment  to  turn
safely.

Land requirements  for  flow equalization  or  storage vary  with
the  type  and  amount  of  storage provided.   This subject is
discussed in greater detail in Section 5.6.2.

5.6  Infiltration  System Design

Items  that must be addressed during RI system design  include
wastewater distribution,  basin  layout  and dimensions, basin
surfaces, and  flow equalization or storage.   In areas  that
experience  cold   winter   weather,   cold   weather  system
modifications should also  be considered.

     5.6.1  Distribution and Basin Layout

Although sprinklers  may  be used, wastewater  distribution is
usually by  surface  spreading.   This  distribution technique
employs gravity flow from  piping systems or ditches to flood
the  application area.   To ensure uniform basin  application,
basin  surfaces should  be reasonably flat.

Overflow weirs  may  be  used  to regulate basin  water depth.
Water  that flows  over  the  weirs  is  either collected and
conveyed  to  holding ponds  for  recirculation or distributed
to  other  infiltration basins.   If  each  basin is to  receive
equal  flow, the distribution piping channels  should be sized
so  that  hydraulic  losses between  outlets  to basins  are
insignificant.   Design  standards for  distribution  systems
and   for   flow  control   and   measurement   techniques  are
published by  the  American Society of Agricultural Engineers
(ASAE).  Outlets used  at currently operating  systems  include
valved  risers  for underground  piping   systems  and  turnout
gates  from distribution  ditches.    An  infiltration basin
outlet  and  splash  pad   are  shown  in Figure 5-3.    An
adjustable weir used as an interbasin transfer  structure is
shown  in Figure 5-4.

Basin  layout  and  dimensions  are  controlled  by topography,
distribution  system   hydraulics,  and  loading   rate.   The
number of  basins   is  also affected by  the selected  loading
cycle.  As a minimum,  the  system  should have enough  basins
                             5-23

-------
                            FIGURE  5-3
                  INFILTRATION BASIN OUTLET AND
                            SPLASH  PAD
                150 cm
CONCRETE FILL
                                          REMOVABLE RINGS

                                          (WOOD.  PLASTIC. OR NCNCORRODING

                                          METAL ALL SUITABLE)

                                          (15 cm  INCREMENTS)
                            FIGURE  5-4
     INTERBASIN  TRANSFER STRUCTURE WITH  ADJUSTABLE WEIR
                               S-24

-------
so  that  at  least one  basin  can be  loaded at  all times,
unless storage  is provided.   The minimum  number of basins
required for continuous  wastewater application is presented
as a function of  loading cycle in Table 5-14.  The  engineer
should keep  in  mind  that if the minimum number of basins  is
used,  the  resulting  loading  cycle  may  not be  exactly  as
planned.   For  example,  if  the selected  loading  cycle  is 2
application  days  followed by  6 days  of drying and  4 basins
are  constructed,  the  resulting  loading  cycle will be the
same as the  selected  loading cycle.   However, if a  cycle  of
2  days of   application   followed  by  9 days  of  drying  is
selected  initially   and  6  basins  are  constructed,  the
resulting   loading   cycle   wll  actually   be   2  days   of
application  followed by  10 days of drying.

                          TABLE  5-14
            MINIMUM NUMBER OF BASINS REQUIRED FOR
             CONTINUOUS  WASTEWATER APPLICATION
Loading Cycle Minimum
application drying number of
period, period, infiltration
d d basins
1
2
1
2
1
2
3
1
2
3
1
2
1
2
7
8
9
7
8
9
5-7
5-7
7-12
7-12
4-5
4-5
4-5
5-10
5-10
5-10
10-14
10-14
12-16
12-16
10-15
10-15
•10-15
12-16
12-16
12-16
6-8
4-5
8-13
5-7
5-6
3-4
3
6-11
4-6
3-5
11-15
6-8
13-17
7-9
3-4
3
3
3-4
3
3
The number of basins also depends on  the  total  area  required
for infiltration.   Optimum basin size can range from  0.2  to
2 ha  (0.5 to 5 acres)  for small  to medium sized systems  to 2
to  8  ha (5  to  20  acres)  for large  systems.    For  a 25  ha
(62 acre) system,  if  the selected loading cycle is  1  day  of
wastewater application alternated with 10 days  of drying,  a
                             5-25

-------
typical  design  would  include  22  basins  of  1.14  ha  (2.8
acres)  each.   Using 22 basins, 2 basins would be  flooded  at
a  time and there  would be ample time for  basin  maintenance
before each flooding  period.

At   many   sites,   topography   makes   equal-sized   basins
impractical.   Instead,  basin  size is  limited  to what  will
fit  into  areas having  suitable slope and soil type  (Section
2.3.1).   Relatively uniform  loading rates and loading  cycles
can  be   maintained  if  multiple  basins   are   constructed.
However,  some  sites  will  require  that  loading  rates  or
cycles vary with individual  basins.

In  flat  areas,  basins  should be  adjoining and  should  be
square  or rectangular to maximize land use.  In areas where
ground  water  mounding  is  a  potential   problem  (Section
5.7.2),  less  mounding  occurs when  long,  narrow basins  with
their  length  normal to the prevailing ground water  flow are
used  than  when square  or  round  basins  are   constructed.
Basins  should be  at  least  30  cm (12 in.)  deeper than the
maximum   design    wastewater   depth,    in  case  initial
infiltration  is slower than expected and  for  emergencies.
Basin walls are  normally compacted soil with slopes ranging
from   1:1   to  Is 2    (vertical   distance   to    horizontal
distance).   In areas  that experience  severe winds or heavy
rains,  basin  walls should be  planted  with grass  or covered
with riprap to prevent  erosion.

If  basin  maintenance  will  be  conducted  from  within  the
basins,  entry ramps  should  be  provided.    These  ramps are
formed of compacted soil  atj  grades of 10 to 20% and cire  from
3.0  to  3.7 m  (10  to  12  ft) wide.  Basin  surface area for
these ramps and  for wall slopes should not be considered  as
part of the necessary  infiltration area.

The  basin surface   may  be bare or covered  with vegetation.
Vegetative covers  tend  to remove suspended  solids  by filtra-
tion and  maintain   infiltration rates.   However,  vegetation
also  limits  the application depth to  a value  that avoids
drowning  of  vegetation,  increases basin  maintenance needs,
requires  an  increased   application  frequency  to  promote
growth, and reduces the  soil drying rate.   At Lake George,
New York,  allowing grass to  grow  in the basins improved the
infiltration rate when  flooding depths exceeded 0.3 m  (1 ft)
but decreased  the  rate at shallower wastewater  depths  [1] .
Gravel  covered  basins  are  not recommended.   The long-term
infiltration capacity of gravel covered basins is  lower  than
the  capacity  of  sand  covered  basins,  because  sluclge-like
solids  collect  in  the voids  between  gravel  particles  and
because gravel prevents the  underlying soil from drying  [4].
                             5-26

-------
     5.6.2  Storage and Flow Equalization

Although RI systems  usually are capable of operating during
adverse  climatic  conditions,  storage  may  be  needed  to
regulate wastewater  application  rates or  for  emergencies.
Flow equalization  may be  required if  significant  daily or
seasonal  flow  peaking  occurs.    Equalization  also  may be
necessary  to  store wastewater  between application periods,
particularly  when  only one  or two  infiltration  basins are
used and  drying  periods  are  much longer  than application
periods.

One example of  flow equalization at an RI site occurs at the
Milton,  Wisconsin,  system.    Milton  discharges  secondary
effluent to three  lagoons.   One of these lagoons is used as
an  infiltration basin;  the  other  two lagoons  are  used for
storage.    In  this   way,   Milton  is   able , to maintain  a
continuous flow into the infiltration  basin  [3].

In  contrast,  the  City of Hollister  formerly equalized  flow
with an  earthen reservoir  that was ahead  of the treatment
plant  headworks.   In  addition, one  infiltration  basin was
kept in  reserve  for primary  effluent during  periods  when
wastewater flows were excessive  [6].

Winter storage  may be  needed if the soil permeability is on
the low end for RI.   In  such cases,  the water may not drain
from the profile fast enough to avoid  freezing.

     5.6.3  Cold Weather Modifications

Rapid  infiltration systems  that operate successfully during
cold winter  weather  without any  cold  weather modifications
can be found  in Victor, Montana; Calumet, Michigan; and Fort
Devens,  Massachusetts.    However,  a   few   different  basin
modifications   have  been   used  to   improve  cold  weather
treatment  in  other communities.  First, basin surfaces that
are  covered   with  grass  or weeds should  be  mowed  during
fall.   Mowing  followed by  disking should  prevent  ice from
freezing to vegetation near the soil surface.  Floating ice
helps  insulate  the  applied  wastewater,  whereas  ice  that
freezes at the  soil surface prevents infiltration.  Problems
with   ice  freezing  to  vegetation  have  been  reported  at
Brookings, South   Dakota, where basins  were not  mowed  and
ponds  are used  for preapplication  treatment  [7].

Another cold  weather modification involves  digging  a ridge
and  furrow   system   in   the   basin   surface.     Following
wastewater  application,  ice  forms  on  the  surface  of  the
water  and  forms  bridges between  the  ridges as  the water
level  drops.    Subsequent  loadings are  applied  beneath the
                             5-27

-------
 surface of  the  ice,  which insulates  the  wastewater and the
 soil surface.   For  bridging  to occur, a  thick  layer of ice
 must form before  the wastewater  surface  drops below the top
 of the ridges.   This modification has been used successfully
 in Boulder,  Colorado, and Westby, Wisconsin.

 The third  type  df  basin modification  involves the  use  of
 snow fencing or other  materials  to  keep a  snow  cover over
 the infiltration  basins.   The  snow  insulates  both applied
 wastewater and  soil.

 5.7  Drainage

 Rapid   infiltration   systems  require  adequate  drainage  to
 maintain  infiltration rates and  treatment efficiencies.  The
 infiltration rate  may be  limited  by the horizontal hydraulic
 conductivity of  the  underlying  aquifer.   Also, if  there  is
 insufficient drainage,  the soil  will remain  saturated with
 water  and reaeration will be  inadequate  for  oxidation  of
 ammonia nitrogen to  occur.

 Renovated  water may  be  isolated  to  protect either  or both
 the ground  water  or the  renovated water.   In both  cases,
 there  must  be  some  method  of engineered  drainage  to keep
 renovated  water  from  mixing with  native ground water,,

 Natural drainage often involves  subsurface flow  to ,surface
 waters.   If  water  rights are  important,  the engineer must
 determine   whether  the   renovated  water  will  drain   to
 the  correct  watershed or  whether  wells or  underdrains will
 be  needed  to convey  the renovated  water  to  the  required
 surface  water.    In  all  cases,  the  engineer   needs   to
 determine  the direction of subsurface flow due to  drainage
 from RI basins'!  ~~

     5.7.1   Subsurface Drainage to  Surface Waters

 If  natural  subsurface drainage to  surface water is  planned,
 soil  characteristics can  be  analyzed to determine if the
 renovated  water  will  flow from   the  recharge  site to the
 surface water.   For  subsurface discharge to a surface  water
 to occur,  the width of the infiltration area must  be limited
 to  values  equal  to or less than the width calculated  in the
 following equation [22] :
                         W = KDH/dL
(5-3)
where  W = total width of infiltration area in direction of
           ground water flow, m  (ft)
                             5-28

-------
       K = permeability of aquifer in direction of
           groundwater flow, m/d  (ft/d)

       D = average thickness of aquifer below the water
           table and perpendicular to the direction of
           flow, m (ft)

       H = elevation difference between the water level
           of the water course and the maximum allowable
           water table below the  spreading area, m  (ft)

       d = lateral flow distance  from infiltration area
           to surface water, m (ft)

       L = annual hydraulic loading rate  (expressed as
           daily rate), m/d (ft/d)
Examples of these parameters are shown in Figure  5-5.
                                         IMPERMEABLE LAYER
                        FIGURE 5-5
            NATURAL DRAINAGE OF RENOVATED WATER
                    INTO SURFACE WATER  [22]
                             5-29

-------
 As an example,  consider an infiltration  site  located above
 an aquifer  whose  permeability is  1.1 m/d  (3.6  ft/d)  and
 whose  average  thickness  is   9   m   (30   ft).    The  annual
 hydraulic loading rate  is  30  m/yr or 0.082 m/d (98 ft/yr or
 0.27  ft/d).    The  surface  water  elevation is  6 'm  (20  ft)
 below the  infiltration  site, and   the  water  table  should
 remain at least  1.5  m  (5  ft)  below the  soil  surface.   The
 infiltration  site  is  25 m  (82 ft)   from  the  surface water.
 Thus,
W -
W ~
m/d)(9 m)(6 m - 1.5 m)
(25 m)(0.082 m/d)
                                        ^
                                          22 m (72 ftj
Under  these conditions, either  a single basin  22 m  (72 ft)
wide  or  multiple basins  having  a  combined  width  of  22 m
could  be constructed.  If more  infiltration  area  is  needed,
additional  basins  could  be  built  in  the  two  directions
perpendicular  to the direction  of ground water flow.   Four
basins   oriented   in  this   manner  are    illustrated   in
Figure  5-6.

If  the  calculated width is quite small  (less  than  about  10 m
or  33  ft) ,  natural  subsurface drainage  to surface waters  is
not feasible and  engineered  drainage should be  provided.

     5.7.2  Ground Water Mounding

During  RI ,  the applied  wastewater travels  initially downward
to  the  ground  water, resulting  in a temporary  ground water
mound  beneath  the   infiltration  site.   This  condition  is
shown  schematically  in  Figure 5-7.  Mounds continue to  rise
during   the  flooding  period  and  only  recede during  the
resting  period.

Excessive mounding  will inhibit  infiltration and reduce the
effectiveness of  treatment.   For  this reason,  the capillary
fringe  above  the ground water  mound  should  never be closer
than 0.6 m (2 ft)  to the bottom of  the infiltration basin
[23] .   This distance corresponds to a  water  table depth  of
about 1  to  2 m (3 to 7  ft),  depending  on the  soil texture.
The distance  to  ground water  should  be  1.5 to  3 m  (5  to
10 ft)  below the  soil surface within 2 to 3 days following  a
wastewater  application.   The  following  paragraphs describe
an  analysis that can be  used to estimate  the mound height
that will occur  at  various  loading conditions.  This method
can be  used to estimate whether a site has adequate natural
drainage  or whether  mounding  will  exceed  the recommended
values without constructed drainage.
                             5-3Q

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                                    SURFACE WATER
  LENGTH  BASED ON NECESSARY
  INFILTRATION AREA
                                      DIRECTION OF
                                   GROUND HATER FLOW
                       FIGURE 5-6
EXAMPLE DESIGN  FOR SUBSURFACE FLOt TO  SURFACE WATER
                            5-31

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SOIL SURFACE
 WASTEWATER APPLICATION

llllillll
                   FIGURE 5-7
           SCHEMATIC OF GROUND WATER MOUND
                         5-32

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Ground water mounding can be estimated by applying heat-flow
theory and  the Dupuit-Forchheimer  assumptions  [24].   These
assumptions are as follows:

     1.     Flow within ground water occurs along horizontal
            flow  lines  whose  velocity  is   independent  of
            depth.

     2.     The velocity  along these horizontal streamlines
            is proportional  to the slope of  the free water
            surface.

Using   these  assumptions,   heat-flow   theory   has  been
successfully  compared  to  actual  ground water depths  at
several existing RI sites.

To  compute  the height  at  the center  of the  ground water
mound, one must calculate the values of W//4at and Rt,

where   W = width of the recharge basin, m (ft)

        ct = KD/V,  m2/d (ft2/d)

        where  K = aquifer  (horizontal) hydraulic
                   conductivity, m/d  (ft/d)

               D = saturated thickness,of the
                   aquifer, m  (ft)      ,

               V = specific yield or fillable pore space
                   of the soil, m3/m3  (ft3/ft3)
                    (Figures 3-5 and 3-6)

        t = length of wastewater application, d

        R = I/V, m/d (ft/d)

        where  I = infiltration rate or volume of water per
                   unit area of soil surface, m EUO/m -d
                   (ft3H20/ft2-d)


The parameters that can be shown schematically are illustra-
ted in Figure 5-5.

Once the value of  W//4at is obtained, one can use dimension-
less plots of W//4at versus ho/Rt,   provided as Figures 5-8
(for square recharge areas) and 5-9  (for rectangular recharge
areas), to obtain  the value of ho/Rt, where ho is the rise at
the center of the  mound.   Using the calculated value of  Rt,
one can solve for  ho.
                             5-33

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        1.0
        0.8
        0.6
       0.4
        0.2
1 . 0
                                     2. 0
                           3.0
   1 .0 r-
   0.8
    0.6
    0.4
    0.2
   0.0
                         FIGURE 5-8
           MOUNDING  CURVE FOR CENTER OF A  SQUARE
                      RECHARGE AREA  L24J
1.0
                                         2.0
                                                           3.0
                         FIGURE  5-9
MOUNDING CURVE  FOR CENTER OF A  RECTANGULAR RECHARGE AREA  AT
      DIFFERENT RATIOS OF  LENGTH (L) TO WIDTH (W) [241
                            5-34

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For example, an RI  system  is  planned  above an aquifer that is
4 m  (13 ft) thick..  Auger hole  measurements  (Section 3 . 6 . 2 .1)
have indicated that the hydraulic  conductivity is   (5 m3/d)/
4 m or 1.25 m/d  (4.1  ft/d).   Using Figure 3-6 with this   hy-
raulic conductivity,  the  specific  yield is 15%. ;.   The basins
are to be  12 m  (39 ft) wide  and square;  the  basin   infiltra-
tion rate  is 0.20  m/d (7.9 in./d); and the application  per-
iod  will  be 1 day long.     Using  these data,  the following
calculations are performed.
                     a
= (1.25 m/d)(4m)
        0.15

= 33.3 m2/d (360 ft2/d)
                    R =
  0.20 m/d
    0.15
=1.3 m/d (4.3 ft/d)
                   Rt =  (1.3 m/d)(Id)
                      =1.3 m  (4.3 ft)
                                  12 m
                         [4(33.3 m2/d)(l d) ] V2
                      =  1.0

Using Figure 5-8, hQ/Rt  equals 0.53.

Thus, h0  equals  (0.53)(1.3  m)  or 0.7  m  (2.3  ft).   If  the
initial ground water depth is 6.0 m  (20  ft), the depth after
wastewater application is still 5.3 m  (17  ft) and  engineered
drainage  is  unnecessary.  Should  the  calculations  indicate
that the  ground  water  table  will  rise  to within less than  1
to 2m  (3.3  to  6.6  ft)  below the basin, additional  drainage
will be needed.                           '

Figures  5-10  (for   square   recharge  areas)  and  5-11   (for
recharge  areas that  are  twice  as  long  as they are wide)  can
be  used  to  estimate  the  depth  to  the  mound  at  various
distances  from   the  center  of  the  recharge basin.   Again
the values of W//4at and Rt  must be determined  first..  Then,
for  a  given value  of  x/W,  where  x  equals  the  horizontal
distance  from  the  center of  the  recharge basin,  one   can
obtain   the   value   of   hQ/Rt   from    the   correct  plot.
Multiplying  this  number  by  the  calculated   value of  Rt
results in the  rise  of the  mound, h ,  at  a distance x from
the  center  of  the  recharge  site.   The depth  to  the mound
from the  soil  surface is simply  the difference between  the
distance  to  the  ground  water  before  recharge  and the rise
due to the mound.
                             5-35

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      1. 0
     0. 0
                             EDGE OF PLOT
                                        1. 0
                FIGURE 5-10
RISE AND HORIZONTAL SPREAD OF MOUND BELOW
        A SQUARE RECHARGE  AREA [24]
                    5-36

-------
          1.0 r-
                •3. 0
          0.3  -
          0.2 -
          0.1 1
          0.0
                                   EDGE OF  PLOT
                                            1. 0
                           (f)
                  FIGURE 5-11
RISE AND HORIZONTAL SPREAD OF  MOUND BELOW A
   RECTANGULAR RECHARGE AREA WHOSE  LENGTH
             IS  TWICE  ITS WIDTH [24]
                        5-37

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To evaluate -mounding beneath  adjacent  basins,  Figures 5-10
and 5-11 should be used to plot ground water table mounds as
functions of  distance from the center  of  the  pldt and time
elapsed  since  initiation of wastewater  application.   Then,
critical mounding  times  should be  determined,  such  as when
adjacent or relatively  close  basins  are  being  flooded,, and
the mounding  curves  of  each basin  at these times should be
superimposed.    At  sites where drainage  is critical because
of severe  land limitations, or extremely  high  ground water
tables,  the  engineer should  use the  approach  described in
reference [25] to evaluate mounding.

In areas where  both the  water  table and  the  impermeable
layer  underneath  the aquifer  are  relatively  close  to the
soil  surface,  it  may be  possible  to  avoid the  complicated
mounding analysis by  using the following procedure:

     1.     Assume underdrains are  needed and  calculate the
            underdrain spacing (Section 5.7.3).

     2.     If   the   calculated   underdrain   spacing   is
            relatively  narrow, between 15  and  50 m (50 and
            160 ft),  underdrains  will be required and there
            is  no  need  to verify that the mound will reach
            the soil  surface.

     3.     if  the  calculated spacing  is less  than about
            10 m  (30 ft),  the loading rate may  have  to be
            reduced   for  the  project  to  be  economically
            feasible.

     4.     If  the  calculated  spacing is greater than about
            50 m  (160 ft),  mounding  should  be  evaluated to
            determine if any underdrains will be  necessary.

This   procedure  is  not   appropriate  for  unconfined  or
relatively  deep  aquifers.    For  such  aquifers, mounding
should always be evaluated.

     5.7.3  Underdrains

For  RI  systems located  in  areas  where both the  water  table
and   the  impermeable  layer  underneath   the  aquifer' are
relatively close to  the  soil surface,  renovated water  can be
collected  by  open  or closed  drains.   In  such  areas, when
drains  can  be  installed  at depths  of  5  m (16 ft) or  less,
underdrains are more effective  and  less  costly  than wells
for  removing  renovated  water  from  the aquifer.   Horizontal
drains have been  used to collect renovated river water  from
RI systems in western Holland, where polluted Rhine water is
treated, and  at Dortmund, Germany,  where water  from the  Ruhr
                             5-38

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River  is  pretreated for a municipal  water supply  [23].   At
Santee,  California,  an  open  ditch  was  used  to  intercept
reclaimed water  [23].

Rapid  infiltration  systems  using underdrains may consist  of
two parallel infiltration strips with a drain midway  between
the  strips  or  a series  of  strips  and  drains.   These two
types  of  configurations  are  shown  in  Figures  5-12  and
5-13.  In the  first system,  the drains are left open  at all
times  during  the loading  cycle.   If the  second system  is
used,  the drains below the  strips  receiving wastewater are
closed and  renovated water  is collected from drains  beneath
the resting strips.  When infiltration beds are rotated, the
drains  that were  closed  before  are  opened and  those that
were  open  are  closed.    This  procedure  allows   maximum
underground detention times and  travel distance.

To  determine  drain  placement,  the  following  equation   is
useful [27]:
                  S =
 f4KH
•^
-(2d + H)
                                      1/2
                          (5-4)
where S = drain spacing, m  (ft)

      K = horizontal hydraulic conductivity of the  soil,
          m/d  (ft/d)

      H = height of the ground water mound above  the drains,
          m  (ft)

     1^ = annual wastewater loading rate, expressed as  a
          daily rate, m/d (ft/d)

      P = average annual precipitation rate, expressed  as  a
          daily rate, m/d (ft/d)

      d = distance from drains to underlying impermeable
          layer, m (ft)
                           INPERNEAIIE
                       FIGURE  5-12
             CENTRALLY LOCATED UNDERDRAIN [260
                            5-39

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                           IMPERMEABLE
                           IMPERMEABLE
     O DRAIN OPEN

     & DRAIN CLOSED
                          FIGURE  5-13
              UNDERDRAW SYSTEM USING ALTERNATING
               INFILTRATION AND DRYING STRIPS  [26]
For   clarification,    these   parameters   are    shown   in
Figure 5-14.  When L,  P,  K, and the maximum acceptable  value
of H are known,  this  equation can be used to determine  S  for
various  values  of  d.   For  example,  consider  an RI system
loaded at  an average rate  of 44 m/yr or 0.12 m/d  (144  ft/yr
or 0.40 ft/d).   Using Equation 5-4, the drain spacing can be
calculated using the  following data:

      K = 12 m/d (39  ft/d)

      H = 1 m  (3.28 ft)

      d = 0.6 m  (2  ft)
                             5-JtO

-------
                       HYDRAULIC LOADING RATE LW + P

             I    I    1    i   I    1    1    1   1   1    1
                                           SOIL SURFACE
                                         WATER TABLE
                            IMPERMEABLE LAYER
                         FIGURE  5-14
             PARAMETERS USED IN DRAIN DESIGN [26]
The  application rate must  include precipitation  as well  as
wastewater.     Therefore,   a   design  storm   of   0.03  m/d
(0.10 ft/d)  is  added to the 0.12  m/d (0.40 f t/d ) wastewater
load for a total  of  0.15  m/d (0.50 ft/d).  The drain spacing
is calculated as:
S2 =
                    +  P)] (2d + H)
   =    4(12 m/d) (1 m)
     0.12 m/d +0.03 m/d

   = 704 m2
                              [2(0.6 m) + 1 m]
      S = 26 m  (85  ft)

Generally,  drains  are spaced 15 m  (50  ft)  or more apart and
are at  depths  of 2.5 to  5.0 m (8 to 16  ft).  In soils with
high  lateral   permeability,  spacing  may  approach  150  m
(500 ft).  Although  closer drain  spacing allows more control
over the  depth of  the  ground water table,  as drain spacing
decreases the cost  of providing underdrains increases.  When
designing a drainage system, different  values of d should be

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selected  and  used  to  calculate  S,  so  that  the  optimum
combination  of d,  H, and  S can be determined.    Detailed
information  on drainage  may be  found in the U.S.   Bureau  of
Reclamation  Drainage  Manual  [28]  and  in  the American Society
of Agronomy  manual, Drainage  for  Agriculture  [29].

Once  the drain  spacing  has  been  calculated,  drain  sizing
should be determined.  Usually, 15  or 20 cm  (6  in.  or 8  in.)
drainage  laterals  are  used.    The  laterals  connect  to  a
collector  main that  must be sized to  convey  the  expected
drainage flows.   Drainage laterals should be placed  so  that
they  will   be  free   flowing;  the  engineer   should check
drainage hydraulics to determine  necessary drain  slopes.

     5.7.4   Wells

Rapid  infiltration   systems  that  utilize  unconfirmed  and
relatively   deep   aquifers   should  use  wells   to   improve
drainage or  to remove renovated  water.  Wells are  used  to
collect  renovated  water  directly  from  the  RI  sites  at  both
Phoenix, Arizona,  and Fresno,  California.   Wells are  also
involved in  the reuse of recharged  wastewater at  Whittier
Narrows, California;  however,  the wells pump  ground water
that happens to contain  reclaimed water, rather than  pumping
specifically for renovated water.

The  arrangement of wells  and recharge  areas  varies; wells
may  be  located  midway  between  two recharge areas,  may  be
placed on  either  side of a  single recharge strip, or may
surround   a   central  infiltration  area.      These  three
configurations  are  illustrated  in Figure 5-15.   Well  design
is  beyond  the scope  of this  manual  but  is  described  in
detail in reference [30]  .

5.8  Monitoring and Maintenance Requirements

The  purpose  of  discussing  monitoring   and   maintenance
requirements  is to enable  the  engineer  to  determine labor
and equipment  needs.   The engineer must know these needs  to
complete a  thorough  cost estimate  and  to ensure  that the
necessary labor and equipment are available.

     5.8.1   Monitoring

There are two distinct reasons for  monitoring RI  systems:

     1.       To   document   that   the   system    meets  any
             requirements    established    by     appropriate
             regulatory  agencies  and  to confirm  that  the
            design provides adequate treatment
                             5-42

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IMPERMEABLE
  LAYER
                                 WASTEWATER

                                 APPLICATION
                                   WATER TABLE
                 (a)
  a.  VELLS MIDWAY  BETWEEN TWO  APPLICATION  STRIPS
          1
          (b)
 •

(c)
  b.  and c. WELLS  (DOTS) SURROUNDIN6 APPLICATION AREAS

                      (HATCHED AREAS)
                      FIGURE 5-15

              WELL  CONFIGURATIONS [26]
                      5-43

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      2.      To  provide  data  needed   to  make  management
             decisions

 A  monitoring  program  may  include  measurements  of  ground
 water quality,  soil  characteristics applied  water  quality,
 and,  when appropriate,  the quality of water removed  from the
 aquifer   for  reuse.   Representative measurements of  ground
 water quality are difficult  to obtain.   Because constituent
 movement is  slower  than  in  surface water,  a  ground  water
 sample  can  contain  contributions   from  several years  past
 that  do  not  accurately  reflect treatment occurring  at the RI
 site.    For  this reason,  it  is  important  to  place  sampling
 wells  in  positions   that  minimize   the  time  period  between
 wastewater   application   and   appearance   of  wastewater
 constituents   in  the observation  wells.    Techniques  for
 monitoring well design and sampling procedures  are  included
 in  references  [31,  32].    Guidance  in  determining  what
 parameters  and  site  conditions to  monitor can be  obtained
 from  federal,  state,  and  local agencies.

 Although soil monitoring  is  not  required at  many sites,  it
 is  periodically desirable.  Below pH 6.5,  soil  retention of
 metals decreases substantially and  the  possiblity of  ground
 water  contamination  by  heavy metals  increases.  Potential
 soil permeability  problems may be  indicated by either  a high
 pH  (above 8.5)  or  a high  percent  of  sodium  on  the  soil
 exchange complex  (over  10  to  15%).     High soil  pH  can
 indicate a  high  sodium  content.    This  condition  may  be
 corrected by  displacing the sodium with  soluble  calcium.

 Both  applied  wastewater  and  any  renovated water collected
 from   the  aquifer   for   reuse  or  discharge  should   be
 monitored.   Applied  wastewater  analyses  are  necessary  for
 process  control  to ensure that the  design  hydraulic  loading
 is  maintained.  Renovated water  that is  recovered  for  any
 purpose  must  meet  whatever water quality  criteria have  been
 established for  those purposes.

     5.8.2  Maintenance

 Basic  maintenance requirements are as follows:

     •      Periodic  scarification  or scraping  of  RI  basin
            surfaces                                     .

     •      Periodic  mowing of vegetated surfaces

As  a  result  of  bacterial  activity  and  solids deposition, a
mat forms on  the surfaces of  infiltration areas and reduces
 infiltration  rates.    Furthermore,  wastewater applications
may cause classification of  the  underlying soils,  allowing
                             5-44

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the  fines  to  migrate  to  the  top  and  to  seal  the  soil
surface.    Periodically,  basin  surfaces  must  be  scarified
(raked, harrowed,  or  disked)  to break up the mat and  loosen
the  soil  surface.   Alternatively,  the  mat  may  be scraped
from  the  soil  surface with   a  front-end  loader  [4]   and
landfilled  or  buried.   These operations should be  performed
whenever  regular  drying fails  to restore infiltration rates
to  acceptable  levels.   If  scraping  alone  does not restore
the  initial infiltration rate,  the  soi.l  surface  should  be
loosened  by disking  or harrowing.   Basin  surfaces  may  be
scarified  following  each drying period  if  time,  labor,  and
equipment  are  available;  basin  scarification  or scraping
should be done at  least once every  6  months  to  1  year.

If .grasses  or  other vegetation are .grown on  basin  surfaces,
the  vegetation  can  be  allowed to  grow  and  die without
maintenance.   Heavy mechanical equipment that  would compact
the  soil  surface  should not be operated on  the infiltration
basins.   For aesthetic  reasons,  periodic mowing of  the grass
or  harrowing  of  the soil surface may be desirable.  In  cold
weather  climates,  vegetation   should  be  mowed during  late
October   or early November   to  prevent   ice   chunks  from
freezing  to the vegetation and thereby cooling  the applied
wastewater.

5.9  Design and Construction Guidance

Some  specific  items   that  are  unique  to  RI  design   and
construction  should be  considered:

     •      Underdrains  will   operate  only   in  saturated
            soil.   If  the water table  does not  rise, or is
            not already at  the elevation of  the drains,  they
            will  not  recover any water.

     •      A  filter  sock can .be  used  in place  of a  gravel
            envelope  around   plastic  drain  pipe  in   sandy
            soil.   The•filter  sock will clog,  however,  with
            fines if  used alone in  silty  clay soils.

     •      RI  basins,  when  constructed,, should be ripped to
            alleviate  traffic  compaction.    After ripping,
            the  surface should be  smoothed  and leveled, but
            never compacted.

     •      If  soils  at   the  RI  site   contain  varying
            percentages of clay  or silt,  the  heavier soils
            should be segregated and used  for  berms.   Berms
            should be  compacted,  but  infiltration surfaces
            should not  be  compacted.
                             5-45

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 5.10   References

  1.   Aulenbach,  D.B.   Long Term Recharge of Trickling Filter
      Effluent  into  Sand.    U.S.  Environmental  Protection
      Agency.   EPA-600/2-79-068.   March 1979.

  2.   Baillod,  C. R. , et  al.   Preliminary  Evaluation of  88
      Years  of  Rapid Infiltration of  Raw  Municipal  Sewage  at
      Calumet,  Michigan.    In:   Land  as  a Waste  Management
      Alternative.   Ann Arbor Science.   1977.

  3.   Benham-Blair   &  Affiliates,   Inc.,  and   Engineering
      Enterprises,   Inc.      Long-term   Effects   of   Land
      Application of Domestic Wastewater:   Milton,  Wisconsin,
      Rapid  Infiltration  Site.   U.S.  Environmental  Protection
      Agency.   EPA-600/2-79-145.   August  1979.

  4.   Bouwer,  H.,  et  al.    Rapid-Infiltration  Research  at
      Flushing  Meadows  Project,  Arizona.     Journal Water
      Pollution Control Federation.   52(10 ):2457-2470. 1980.

  5.   Koerner,  E.T., and D.A. Haws.    Long-Term Effects  of
      Land Application  of Domestic Wastewater:   Vineland, New
      Jersey  Rapid  Infiltration  Site.    U.S.   Environmental
      Protection  Agency.  EPA-600/2-79-072.  March  1979.

  6.   Pound,  C.E.,  R.W.  Crites,  and J.V.  Olson.   Long-Term
      Effects  of  Land  Application of  Domestic Wastewater  -
      Hollister,  California, Rapid Infiltration  Site.  U.S.
      Environmental  Protection  Agency.     EPA-600/2-78-084.
      April 1978.

  7.   Dornbush,   J.N.      Infiltration   Land   Treatment    of
      Stabilization   Pond   Effluent.     Technical  Progress
      Report 3.   South Dakota State  University,  Brookings,
      South Dakota.  April  1978.

  8.   Satterwhite,  M.B.,  B.J.  Condike,   and   G.L.  Stewart.
      Treatment   of  Primary  Sewage   Effluent   by   Rapid
      Infiltration.     U.S.   Army  Corps  of Engineers,  Cold
      Regions Research-and  Engineering Laboratory.   December
      1976.

  9.   Smith,   D.G.,  K.D.    Linstedt,   and   E.R.   Bennett.
     Treatment   of  Secondary  Effluent   by  Infiltration-
     Percolation.    U.S.  Environmental   Protection  Agency.
      EPA-600/2-79-174.   August 1979.

10.  Broadbent,   F.E.,   K.B.   Tyler,   and    G.N.  : Hill.
     Nitrification   of  Ammonical    Fertilizers   in  Some
     California Soils.   Hilgardia.  27:247-267.  1957.
                            . 5-46

-------
11.   Vaccaro,  R.F.,  et  al.    Wastewater  Renovation  and
     Retrieval at  Cape  Cod.   U.S.  Environmental Protection
     Agency.  EPA-600/2-79-176.  August 1979.

12.   Merrell,  J.C.,  Jr.,  et  al.    The  Santee  Recreation
     Project:    Santee,  California   (Final  Report).    U.S.
     Department  of the  Interior,  Federal   Water  Pollution
     Control   Administration,   Water   Pollution   Control
     Research Series Publication No. WP-20-7.  1967.

13.   Lance,  J.C. ,   C.P.  Gerba,  and  J.L.   Melnick.    Virus
     Movement in Soil Columns  Flooded with Secondary Sewage
     Effluent.    Applied  and  Environmental  Microbiology.
     32:520-526.   1976.

14.   Gerba,  C.P.  and J.C.  Lance.   Poliovirus  Removal from
     Primary   and   Secondary   Sewage   Effluent   by   Soil
     Filtration.    Applied  and  Environmental  Microbiology.
     36:247-251.   1978.

15.   Gilbert, R.G., et  al.   Virus and Bacteria Removal from
     Wastewater    by    Land    Treatment.       Applied   and
     Environmental Microbiology.  32(3):333.  1976.

16.   Gerba,  C.P.  and  J.C.  Lance.    Pathogen  Removal from
     Wastewater    During    Groundwater   Recharge.      In:
     Proceedings   of  Symposium   on  Wastewater  Reuse  for
     Groundwater Recharge, Pomona, California.  September 6-
     7, 1979.

17.   U.S.   Environmental   protection  Agency.      Facilities
     Planning,  1982.  EPA-430/9-81-012.   FRD-25.  September
     1981.

18.   Pound,  C.E.,  and R.W. Crites.   Wastewater Treatment and
     Reuse   by  Land   Application.      U.S.  Environmental
     Protection  Agency.    EPA-660/2-73-006a and b.    August
     1973.

19.   Leach,  E.,  C.G.  Enfield,  and C.C« Harlin, Jr.  Summary
     •of  Long-Term  Rapid Infiltration System Studies.   U.S.
     Environmental  protection Agency.     EPA-600/2-80-165.
     July  1980.

20.   Lance,  J.C. ,  F.D.  Whisler,  and R.C.  Rice.    Maximizing
     Denitrification  During  Soil   Filtration   of   Sewage
     Water.    journal  of  Environmental  Quality.    5:102.
     1976.
                             5-47

-------
 21.   Clapp,  R.B.  and  G.M. Hornberger.   Empirical  Equations
      for Some  Soil Hydraulic  Properties.   Water  Resources
      Research.   14(4):601-604.   1978.
                                                      'i '•
 22.   Bouwer,  H.   Infiltration  -  Percolation Systems.   In:
      Land Application  of Wastewater.    Proceedings  of  a
      Research  Symposium Sponsored by  the  USEPA,  Region III,
      Newark, Delaware.  pp.  85-92.   November,  1974.

 23.   Bouwer, H.   Zoning  Aquifers  for Tertiary Treatment  of
      Wastewater.     Ground Water.    14(6):386.   .November-
      December  1976.

 24.   Bianchi,  W.C.  and C.  Muckel.    Ground-Water  Recharge
      Hydrology.        U.S.    Department   of   Agriculture,
      Agricultural  Research Service.   ARS  41161.   December
      1970.

 25.   Hantush,  M.S.  Growth  and Decay of  Groundwater-Mounds
      in  Response  to Uniform Percolation.   Water Resources
      Research.   3(1):227-234.   1967.

 26.   Bouwer,   H.      Renovating   Secondary   Effluent   by
      Groundwater  Recharge with Infiltration  Basins.    In:
      Conference  on  Recycling  Treated  Municipal  Wastewater
      Through  Forest  and  Cropland.    U.S.   Environmental
      Protection Agency.   EPA-660/2-74-003.  1974.

 27.   Kirkham, D.,  S. Toksoz, and R.R.  van der Ploeg.  Steady
      Flow  to   Drains   and  Wells.     In:     Drainage   for
     Agriculture.  J.  van  Schifgaarde, ed.  American  Society
      of Agronomy Series on Agronomy, No. 17.  1974.

28.   Drainage  Manual.     U.S.  Department  of  the Interior,
     Bureau of Reclamation.  1978.

29.   Drainage  for  Agriculture.    J.  van  Schifgaarde, ed.
     American  Society  of Agronomy  Series  on  Agronomy,
     No. 17.   1974.

30.  Campbell,  M.D.  and J.H.  Lehr.  Water Well Technology.
     McGraw-Hill, Inc.   New York.  1973.

31.  Blakeslee,   P.A.      Monitoring   Considerations   for
     Municipal  Wastewater Effluent and Sludge Application to
     Land.   In:   Proceedings  of  the   Joint  Conference  on
     Recycling   Municipal  Sludges  and Effluents  on  Land,
     Champaign, Illinois.  July 9-13, 1973.
                             5-48

-------
32.   Dunlap, W.J.,  et al.   Sampling  for  Organic Chemicals
     and   Microorganisms   in   the   Subsurface.      U.S.
     Environmental  Protection  Agency.    EPA-600/2-77-176.
     August 1977.
                             5-49

-------

-------
                          CHAPTER 6

                OVERLAND FLOW PROCESS DESIGN
6.1  Introduction

The design procedure  for overland flow  (OF) is presented  in
Figure  6-1.    Application rate  and  hydraulic  loading rate
determinations  are  the most  important  design  steps because
these values  plus  the storage requirement fix the land area
requirements.   Preapplication treatment can be increased  if
inadequate land area  is available.

    6.1.1      Site Characteristics and  Evaluation

Overland flow  is best suited  for  use at  sites having surface
soils that  are slowly permeable or have a restrictive  layer
such  as a claypan  at depths of  0.3  to 0.6 m  (1  to 2 ft).
Overland flow  can also be used  on moderately permeable  soils
using higher  loading  rates than would be possible with  an  SR
system.   It   is  possible to  design an OF system  on very
permeable  soils  by  constructing  an  artificial  barrier  to
prevent downward  water movement  through the soil,  although
the  capital  costs  of such  construction may be prohibitive
for all but the smallest  systems.

Overland  flow may be used at sites with gently sloping ter-
rain  with grades in  the  range  of 1 to 12%.   Slopes  can  be
constructed  on nearly level terrain  and terraced  construc-
tion  can be used when the natural slope grade exceeds  about
10%.   Topographic maps of  proposed  sites with 0.3 m  (1  ft)
contour  intervals   should   be   used   in   detailed   site
evaluation.
     6.1.2
Water Quality Requirements
 Most  of the treated water leaving an OF  site  occurs  as sur-
 face  runoff, and discharge requirements  to receiving waters
 must  be met.  Protection of  ground water quality at OF sites
 is generally ensured by  the  fact  that  little  water (usually
 less  than  20%)  percolates and  the  heavy clay  soils  remove
 most  of the pollutants.   Based on limited experience with OF
 on moderately permeable  soils,  a long-term decrease -in the
 percolation rate  can be  expected due  to clogging  of soil
 pores  and   a  relatively  small  percentage of  the  applied
 wastewater will percolate.   If OF is  considered  for use on
 moderately permeable soils,  however,  it  is recommended that
 consideration be given  to ground  water impacts as discussed
 for SR systems in Chapters 4 and 9.
                              6-1

-------
WASTEWATER
CHARACTERISTICS
(Section 2.2. 1)


SITE CHARACTERISTICS
(SECTIONS 2.2.1, 6.t)

1

WATER QUALITY
REQUIREMENTS
(Sections 2.2. 1 , 8. 1)

p

STORA6E  REQUIREMENTS
(Section 6.5)
                              PROCESS PERFORMANCE
                              (Section 6.2)
                            PREAPPLlCATION TREATMENT
                            (Section 6.3)
LOADING DESIGN
CRITERIA AND RATES
(Section 6.4.1)
                               LAMO REQUIREMENTS
                               (Section 6.4.8)
                              DISTRIBUTION  SYSTEM
                              (Section  6.6)
                               VEGETATIVE  COVER
                               (Section  6.7)
                               SLOPE CONSTRUCTION
                               (Section 6.8)
                               RUNOFF  COLLECTION
                               (Section 6.9)

r
SYSTEM MONITORING
AND MANAGEMENT
(Section 6.10)
                                FIGURE  6-1
               OVERLAND FLOW DESIGN  PROCEDURE
                                    6-2

-------
    6.1.3
Design and Operating Parameters
The  basic  design  and operating  parameters  are defined  in
Table 6-1.

                          TABLE 6-1
             OF DESIGN AND  OPERATING  PARAMETERS
        Parameter
                          Definition
                             Range of values
                              in practice
Hydraulic
loading rate
Application
rate
Application
period
Application
frequency
Average flowrate divided
by the wetted slope area
Flowrate applied to the
slope per unit width of slope
Length of time per day of
wastewater application
Number of days per week
that wastewater is applied
to the slope
0.6-6.7 cm/d
6.3-40 cm/wk
0.03-0.24 m3/m-h
5-24 h/d
5-7 d/wk
       Note:  See Appendix G for metric conversions.
6.2  Process Performance

Knowledge  of  the relationship  of  process  performance  and
design criteria  for  OF  systems is necessary before the design
can  be  accomplished.   The  removal mechanisms  discussed in
this section  relate to operating  parameters, slope lengths,
and  levels of  preapplication treatment.  A summary of design
and  operating  characteristics  for  existing  municipal  OF
systems  is presented  in  Tables  6-2  and  6-3.    Health  and
environmental  effects o'f  trace  elements  and trace organics
are  discussed  in  Chapter  9.
     6.2.1
BOD Removal
Biological  oxidation is the  principal  mechanism responsible
for   the   removal  of   soluble   organic  materials  in  the
wastewater.   The diverse  microbial populations  in the soil
and  the  surface organic layer  sorb and subsequently oxidize
these  substances  into  stable  end products  much  like the
biological  slimes on trickling  filter  media.   Suspended and
colloidal  organic materials,  which contribute  about 50% of
the   BOD   load   in   raw  domestic  sewage,  are  removed  by
sedimentation and filtration through  the  surface  grass and
organic  layers.    Subsequent  breakdown  of  the   degradable
settled particulate  materials is also achieved by  the micro-
organisms   on  the   slope.    Typical   removals   of  BOD are
presented  in Table  6-2.
                              6-3

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 The performance of OF systems treating primary and secondary
 effluent  in  cold  regions  was  evaluated  in  Hanover,  New
 Hampshire  [4] .    For primary  effluent,  it was  found  that
 runoff BOD  concentration was not  substantially  affected by
 temperature  until  the   soil  temperature  dropped to  about
 10 °C (50  °F).   Below 10 °C, effluent  BOD levels increased
 with  decreasing  temperatures.    At soil  temperatures  below
 4 °C  (39  °P)  effluent   BOD  levels exceeded  30 mg/L.    For
 secondary  effluent,  OF   effluent  BOD  values remained  below
 15 mg/L  at  soil  temperatures  of  4  °C.    Storage  may  be
 required during cold  weather to meet stringent  BOD discharge
 requirements.

 Relationships between BOD removal  and  the process operating
 parameters are not  well  defined.   However, results of recent
 studies conducted to develop rational design methods for OF
 indicate that, for primary effluent, BOD removal  is  largely
 a function of application rate  and slope length and is  inde-
 pendent of hydraulic loading rate  within the ranges  used at
 existing  systems  [5,  8]  (see  Section 6.11).                !
     6.2.2
Suspended Solids Removal
 Suspended  and  colloidal  solids  are  removed  by sedimentation,
 filtration through the grass and  litter, and adsorption  on
 the  biological   slime  layer.    Because  of  the  low  flow
 velocities and shallow flow  depths  on  the OF slopes,  most  SS
 are   removed  within  a   few   meters   from   the  point   of
 application.

 Removal  of  algae  from  stabilization  pond  effluent  by  OF
 systems  is somewhat variable  and  depends  on the nature  of
 the  algae.   If  OF  is  not  being  used in  the locality for
 treatment  of  pond effluent,  pilot studies may be advised  to
 ascertain  treatability.

 Removal  of SS requires that a  thick stand  of vegetation  be
 maintained  and  that gullies or other  short-circuiting down
 the  slopes  be   avoided.    Removal   of  SS   is  relatively
 unaffected  by cold  weather  or  changes  in  process  loading
 parameters  compared to BOD removal.~~~~
    6.2.3
Nitrogen Removal
Important   mechanisms  responsible   for   nitrogen  removal
by _ OF  _include  crop  uptake,   biological  nitrification-
denitrification,  and  ammonia  volatilization.    Removal  of
nitrogen by crop  harvest  depends on the nitrogen content of
the crop  and  the  dry matter yield  of  the crop as discussed
in Section 4.3.2.1.   The  water tolerant forage grasses used
for  OF  generally  have  high  nitrogen  uptake  capacities.
                             6-6

-------
Annual nitrogen  uptake measured at  the Utica, Mississippi,
system for a  grass  mixture  of Reed canary, Kentucky 31 tall
fescue,  perennial   ryegrass,   and  common  Bermuda  ranged
between  222   and  179 kg/ha  (198  and   160  Ib/acre).    Crop
uptake at  the Utica  system accounted  for approximately 11
and 33% percent of  the applied  nitrogen at the high and low
hydraulic loading rates, respectively  (see Table 6-3)  [7].

Ammonia  volatilization  is  known  to  occur  during  OF.
Researchers  at  the  Utica  site  estimated   volatilization
losses  to  be   about  9%   of  the  applied   pond  effluent
nitrogen [7].

Nitrification-denitrification  is usually  the  major removal
mechanism.   At Utica, the  losses attributable to denitrifi-
cation ranged from 34  to 42% of  the applied nitrogen  [7].

Nitrification takes  place  in the aerobic environment at the
soil  surface.    The   nitrates  then   diffuse through  the
organic-rich  surface  materials  where  anaerobic  conditions
necessary  for   denitrification   exist.     Denitrification
requires   the   presence  of  a   readily  available  carbon
source.  Consequently,  the  best nitrogen removals are found
using  raw  wastewater  or  primary effluent  that  have high
carbon to  nitrogen  ratios  (>3).  Lesser nitrogen removals
are found  using  secondary or pond  effluent when the carbon
to nitrogen ratios are  about one.

Typical effluent values for the  different  nitrogen forms are
indicated in Table 6-3.  The effects of operating parameters
on  nitrogen   removal  are  not  well  understood.    Specific
design and  operating  criteria  to  optimize nitrogen removal
or ammonia conversion have not  been  established.   However,
some general relationships can be  stated:

    1.   Total  nitrogen and  ammonia   removal  is  inversely
         related to  application  rate and  directly related to
         slope length.

    2.   The  rate  of nitrification is  reduced if wastewater
         is applied  continuously.

    3.   The overall  nitrogen removal  and  ammonia conversion
         efficiency  is  reduced as  the  soil temperature drops
         below  13  to  14   °C  (55  to  57  °F).    With pond
         effluent  at  the  Utica  system,  nitrogen  removal
         efficiency  decreased  from  90%  in the  spring and
         summer  to  less  than  80%  during the  winter  [2] .
         Results obtained at  the Hanover  system with primary
         and  secondary  effluents,   showed   that  nitrogen
         removal efficiency dropped  to about  30% during the
                             6-7

-------
          winter  [5].    The  reduced  efficiency  in  colder
          temperatures-is attributed  to the decreased rate of
          the  biological nitrification-denitrification  pro-
          cess as well as reduced plant uptake.

     6.2.4     Phosphorus Removal

 The major  mechanisms  responsible for  phosphorus removal by
 OF include sorption on  soil clay colloids and precipitation
 as insoluble complexes of calcium, iron, and aluminum.  When
 low permeability surface  soils are  present,  as  is the case
 for most  OF  systems,  much  of the applied  wastewater flows
 over the  surface  and does  not contact the  soil matrix and
 phosphorus adsorption sites.   As a  result  of  this  limited
 soil contact,  phosphorus removals  achieved  at  exisftljig  oF
 systems generally  range from 40 to  60%.Phosphorus  data
 from some OF systems are shown in Table 6-3.

 Improved  phosphorus  removal  efficiency can  be  achieved  by
 the addition of aluminum sulfate  to  the wastewater prior to
 application to the  land.   Applications of  aluminum  sulfate
 to raw  sewage at  a  concentration   of  20 mg/L  reduced  the
 phosphorus concentration  from 8.8 mg/L to  1.5 mg/L or  85%
 removal  efficiency  in  experiments  at Ada,  Oklahoma  [9].
 Addition  of aluminum sulfate  to  stabilization pond effluent
 in amounts equal to 1:1, aluminum  to phosphorus, prior  to
 application resulted in significant  reduction  of phosphorus
 in the  runoff to about  1 mg/L or removal efficiency  better
 than  80%  at the Utica  system [10].
    6.2.5
Trace Element Removal
The  major mechanisms  responsible  for trace element  removal
include  sorption  on clay colloids and organic matter  at  the
soil  surface  layer,  precipitation   as   insoluble   hydroxy
complexes,  and formation  of organometallic  complexes with
the  organic  matter  at  the slope  surface.    The   largest
proportion  of  the heavy metals  accumulate in the biomass on
the  soil   surface  and  close  to  the   point   of  effluent
application.   Trace  metal  removal  data  reported  from  the
Utica system are  presented  in Table  6-4  to  illustrate  the
removal levels that can be achieved with  OF.
    6.2.6
Microorganism Removal
The major mechanisms  responsible for removal of microorgan-
isms in OF systems include sedimentation, filtration through
surface organic  layer  and  vegetation,  sorption to soil par-
ticles, predation, irradiation,  and  desiccation during dry-
ing periods.
                             6-8

-------
                          TABLE 6-4
             REMOVAL EFFICIENCY OF HEAVY METALS
               AT  DIFFERENT  HYDRAULIC RATES AT
                   UTICA, MISSISSIPPI  [7]
Hydraulic
loading
rate , cm/d
1.27
2.54
3.81
5.08
Runoff concentration, mg/L
Cadmium
0.0046
0.0036
0.0079
0.0142
Nickel
0.0131
0.0217
0.0302
0.0486
Copper
0.0129
0.0293
0.0382
0.0524
Zinc
0.0558
0.0525
0.0757
0.0853
Removal efficiency, %
Cadmium
85.4
90.9
77.7
63.2
Nickel
92.1
87.6
79.6
66.0
Copper
93.1
82.4
73.5
64.4
Zinc
88.4
87.4
78.8
75.4
Generally,   the   removal  efficiency   of   OF  systems   for
pathogenic organisms such as viruses and indicator organisms
is  comparable to  that  which  is  achieved  in conventional
secondary treatment systems without chlorination.  Disinfec-
tion may be required by the regulatory  agency.
    6.2.7
Trace Organics Removal
Removal of  trace  organics in OF  systems  is achieved by the
mechanisms  of  sorption  on  soil  clay  colloids  or organic
matter, biodegradation,  photodecomposition, and volatiliza-
tion.   The  importance  of one  or  a  combination  of   these
mechanisms will  depend on the  nature of  the  trace organic
substance.
    6.2.8
Effect of Rainfall
The effect of rainfall on OF process performance was studied
at  Paris,  Texas;   Utica,  Mississippi;  Ada,  Oklahoma;  and
Hanover, New Hampshire [11, 7, 4].  In all of  these studies,
it was  observed that precipitation  events occurring during
application  did  not significantly affect the concentration
of the  major constituents  in  the runoff.  However, the mass
discharges of constituents did increase  due  to the increased
water  volume from  the  storm  events.    In  situations where
discharge  permits  are based on  mass  discharge, discussions
with  regulatory officials  should be  held  to determine  if
permits  can  be  written  to  reflect   background  loadings
occurring  as a  result of rainfall runoff from OF fiel-ds  or
to allow  higher  mass discharges during periods of high flow
in receiving waters.   In some cases,  collection and recycle
of stormwater may be necessary.
                             6-9

-------
     6.2.9
Effect of Slope Grade
The  effect of slope grade on treatment performance  has  been
evaluated  at  several  systems  [2,  7,  8].   The  conclusion  from
all  studies was  that  slope grade  in  the range  of  2 to  8%
does  not  significantly  affect   treatment  performance  when
systems  are operated within  the  range of application rates
reported in Table 6-2.
     6.2.10
Performance During Startup
A period of  slope  aging  or  acclimation  is  required  following
initial startup  before process  performance approaches  satis-
factory   levels.     During  this   period,  the   microbial
population on  the  slopes is increasing and slime layers  are
forming.  The  initial acclimation period may  be  as  long as  3
to  4  months.  If  a  variance  to allow discharge during this
period  can  not  be  obtained,  provisions   should  be made to
store  and/or  recycle  the  effluent  until effluent quality
improves to  the  required  level.

An  acclimation  period   also  should  be  provided  following
winter  storage periods  for those  systems  in cold  climates.
Acclimation  following winter  shutdown should  require less
than  1  month.   Acclimation is not  necessary  following shut-
down  for  harvest  unless  the  harvest period  is  extended to
more than 2  or 3 weeks due  to inclement weather.

6.3  Preapplication  Treatment

Preapplication  treatment   before   OF   is   provided   to
(1) prevent  operating  problems  with  distribution systems
and,   (2)  prevent   nuisance   conditions   during   storage.
Preapplication treatment to  protect  public  health  is   not
usually  a   consideration  with  OF   systems  because public
contact with the treatment  site  is  usually controlled and no
crops are grown  for  human consumption.

Except  in  the  case  of  harmful or  toxic substances  from
industrial   sources   (see  Section  4.4.3),  preapplication
treatment of municipal  wastewater  is not  necessary for  the
OF process to  achieve maximum treatment.   The OF process is
capable of removing  higher levels  of  constituents  than  are
normally present  in municipal  wastewater and  maximum   use
should be made of this  renovating  capacity.   Consequently,
the level of preapplication treatment provided should be  the
minimum necessary  to achieve the two stated objectives.  Any
additional  treatment,  in  most  cases, will  only   increase
costs and  energy  use,  and,  in some  cases,  can  impair  or
reduce the consistency-of process performance.  Algal solids
have proven  difficult to remove  from some  stabilization pond
                             6-10

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effluents and  reduced nitrogen removals  have  been observed
with  secondary effluents.   These  statements  do  not imply
that existing  treatment  facilities  should not be considered
for use in preapplication treatment.

The  EPA has  issued  guidelines for assessing the  level of
preapplication  treatment  necessary  for  OF  systems.   The
guidelines are as follows:

    1.   Screening  or comminution—acceptable  for isolated
         sites with no public access.

    2.   Screening  or comminution  plus  aeration to  control
         odors during storage or application—acceptable for
         urban locations with no public access.

Municipal wastewater  contains rags,  paper,  hair,  and other
large  articles that can blind and  clog orifices and valves
in surface  and sprinkler distribution systems.  Comminution
is   generally   not   sufficient    to   eliminate   clogging
problems.    Fine screening  or  primary  sedimentation   with
surface skimming is necessary to prevent  operating difficul-
ties.    For  sprinkler   distribution  systems,  screen sizes
should  be less than one-third the diameter of the sprinkler
nozzle.   Static inclined  screens  with  1.5  mm  (0.06  in.)
openings  have  been  used  successfully   for  raw wastewater
screening.

Grit  removal  is  advisable  for wastewaters  containing  high
grit  loads.   Grit reduces pump life'and can deposit in low
velocity distribution pipelines.

6.4  Design  Criteria  Selection

The principal  OF design  and operating parameters are  defined
in Section  6.1 and values used at existing systems are given
in  Table  6-1.   Traditionally,  OF  design and operation has
been an empirical procedure based on  a  set of  general guide-
lines  established through successive  trials with the  various
process parameters at different OF  systems.  The guidelines,
as presented here, reflect successful construction and oper-
ation  of  full-scale systems,  but the degree of  conservation
inherent  in the guidelines  has  not  been established.   The
design criteria  shown in Table 6-5 have  been  used at exist-
ing  OF systems  during  spring,  summer,  and  fall to  achieve
effluent  BOD  and suspended  solids  concentrations less  than
20 mg/L,  total nitrogen less than  10 mg/L, ammonia nitrogen
less  than 5  mg/L, and total phosphorus  less  than 6 mg/L.
                            , 6-11

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                          TABLE 6-5
               OVERLAND FLOW DESIGN GUIDELINES
Hydraulic
Preapplication loading rate,
treatment cm/d
Screening
Primary sedimentation
Stabilization pond
Complete secondary
biological
0.9-3
1.4-4
1.3-3.3
2.8-6.7
Application Application
rate, period,
m3/m-h h/d
0.07-0.12 8-12
0.08-0.12 8-12
0.03-0.10 8-18
0.10-0.20 8-12
Application Slope
frequency, , length,
d/wk m
5-7
5-7
5-7
5-7
36-45
30-36
45
30-36
     6.4.1
Hydraulic Loading Rate
Traditionally,  hydraulic loading rate  has  been used as  the
principal  OF  design parameter.  Current guidelines  call  for
hydraulic  loadings  rates  to  be  varied with  the  degree  of
preapplication  treatment as  indicated  in  Table  6-5.    For
systems  operating  year-round,  the  hydraulic  loading  rates
generally  have  been reduced during  the winter  to  compensate
for  the reduction  in  BOD  and nitrogen  removal  efficiency
when  soil  temperatures  drop below 10 to 15 °C  (50 to 59  °F)
(see  Sections 6.2.1  and 6.2.3).    Reductions  in hydraulic
loading rates during  the winter have been somewhat arbitrary
and  guidelines  are  not well established.   A 30% reduction
from  summer rates  has  been used at  the  Ada  system while  a
50% reduction has been  recommended at the Utica  system.

The performance  of  OF systems is dependent on  the detention
time  of the wastewater  on the slope.  The detention time  is
in   turn    directly  related   to   the   application   rate.
Therefore,  it is  possible   to  compensate for  lower winter
temperatures by decreasing  the application rate  and  increas-
ing  the  application  period  while  maintaining the hydraulic
loading  rate  constant.   It  is  also  possible  to  increase
hydraulic  loading  rates for  short  periods,  such  as when  a
portion of  the  system is shutdown for harvesting or repair,
without affecting performance, by increasing the application
period and maintaining  the  application  rate constant.
    6.4.2
Application Rate
Design  guidelines for  application rates  based  on existing
systems are  presented  in Table 6-5.   Values at the high end
of  the  range may  be  used during  spring,  summer, and fall,
while values at the low  end should be used when soil temper-
atures  drop  below  about  10  °C  or   if  maximum  removal
efficiency for  any constituent is desired.  These rates are
based on  slope lengths  in  the range of 30 to 40  m (98 to
                             6-12

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131 ft).   Application  rates less  than the  minimum values
shown in Table  6-5 may be difficult to distribute  uniformly
with surface distribution systems.

Hydraulic  loading  rate  is  related  to   application   rate/
period, and the slope  length as shown  in Equation 6-1.
     Lw = (Ra)
                                (100 cm/m)
(6-1)
where  LW =
hydraulic loading rate, cm/d

application rate, m3/h*m

application period, h/d

slope length, m
The calculation  can  be  started  in  one  of  two  ways:

    1.    Select  application rate,  period,  and slope  length
          and  calculate  hydraulic  loading  rate,  or

    2.    Select   application   period,   slope  length,   and
          hydraulic   loading  rate   and  calculate  application
          rate.

    6.4.3     Application Period

A  wide range  of  application periods has been  used  success-
fully,  ranging from just  a  ,few hours  to as  high as  24  h/d.
The application  periods that have  been used  most frequently
in existing  OF projects range  between  6  and 12 h/d.

Use  of design application periods of  12 h/d or  less allows
more  operating flexibility  during  periods  when parts of the
system  must  be  shutdown  for  harvest   or   repair.    For
instance, if the design application period is  .8-h/d, waste-
water normally would  be applied  to one-third of the  total
land  area at any given time assuming a 24-hour system opera-
tion.  If one-third  of the system were shutdown for  harvest,
the  application period  could  be  increased to  12 h/d on the
remaining two portions  of  the system,  and  the  entire  flow
could be applied without increasing the  application  rate.

Systems generally are  designed to operate on  a 24 hour basis
to minimize  land requirements.   For small systems,  it may be
more  convenient  or cost effective to operate  only during one
                             6-13

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 working  shift.   In this  case, the  entire land  area  would
 receive  the  full  design  daily wastewater  flow  during  the
 8  hour application  period*,    Storage  facilities would  be
 required  to hold wastewater flow during the 16 hour nonoper-
 ating  period.
     6.4.4
Application Frequency
A  design application  frequency  of  7 d/wk  is  generally  used
to minimize land area  requirements  and eliminate or  reduce
storage  requirements.    There  does  not  appear to  be  any
advantage   in  terms  of  process  performance  to using  less
frequent applications.    For  small  systems  with   storage
facilities, it may be more convenient  to  use  an application
frequency of  5 d/wk and shut  down on weekends.
     6.4.5
Constituent Loading Rates
Historically,  OF design and operation has not been  based  on
mass  loading rates of  wastewater  constituents such as  BOD,
suspended  solids,  and nitrogen.  The rates used  at  existing
systems  apparently are  well below  those  that might  affect
process  performance,  since  no  correlations  between process
performance  and  constituent  loading  have been  found.
     6.4.6
Slope Length
In  general,  OF  process  performance has  been  shown  to  be
directly  related to  slope  length and  inversely related  to
application  rate  (see  Section  6.11).   Thus,  longer  slope
lengths  should  be  used with  higher application  rates or,
conversely,  shorter  slope  lengths should be used with  lower
application  rates  to achieve an equivalent degree of treat-
ment.   The  combinations of  slope  lengths  and application
rates  that   are  suggested  for   design  are   indicated   in
Table 6-5.

The  minimum  slope   lengths  indicated  have  been  used  with
surface  distribution systems or  low-pressure  spray systems
that  distribute  the  wastewater  across  the   top  of  the
slope.   Traditionally,  longer  slope  lengths  (45 to 60 m  or
150  to  200  ft)  have  been  used  with  full-circle,,   high-
pressure  impact  sprinklers.    However,  nearly all  of the
experience with  impact sprinkler OF  distribution systems has
been with  high strength food processing  wastewater„   There
are  no  data  to  indicate  the need  for  longer  slope lengths
when using  sprinklers  to apply municipal wastewater.   With-
out  such  information,  the recommended  minimum slope length
for sprinkler distribution systems is 45 m (150 ft) for part
circle   sprinklers.     For  full   circle  sprinklers,   the
recommended  minimum  slope length  is the  sprinkler diameter
plus about 20 m  (65  ft).
                            6-14

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From a  process  control standpoint,  it  is desirable to have
all slopes approximately the same length.  However, this may
not always  be  possible due to the  shape  of  the site bound-
aries  or site  topography.    If  slope  length  must  differ
substantially  (>10  m or 33 ft)  from the  design value, then
the application  rate  used  on these  slopes  may  need  to be
adjusted.  For design, a first approximation to  the adjusted
rate may be made by equalizing the hydraulic loading rate on
all slopes.  Equation  6-1 may be used to  estimate  the neces-
sary application rate.  Adjustment in the field  during oper-
ation may be necessary to achieve equivalent treatment.
    6.4.7
Slope Grade
Although slope grades ranging from less than 1%  to  10 or  12%
have been  used  effectively for OF,  experience has  shown  the
optimum  range  to  be  between 2  and  8%.   Slope  grades less
than  2%  increase  the  potential for  ponding,  while  those
greater  than  8% increase the risk of  erosion.   It has been
shown through several studies that slope grades  in  the  range
of  2  to 8% do  not affect  process  performance.   Therefore,
there is  no need to  adjust slope length or application rate
for changes in  slope  grade within-this range.   Slope grades
greater  than  about  8%  also  increase  the  risk  of  short
circuiting and  channeling and  may require lower application
rates or longer  slope lengths to achieve adequate treatment,
although there are no performance data  to  confirm this.

Although there exist some  circumstances where natural ground
contours can provide the  slope grade necessary for  effective
treatment, few sites offer  conditions that are ideal  for  the
smooth  sheet  flow of water along  the ground surface,  which
is  important  to  the  OF  concept.   Therefore,  it  is almost
always  necessary  to  reshape  the  site into  a  network   of
slopes  that  conform to  the  length  and   grade guidelines
outlined previously.  The  grade  of each slope  is established
by  the  existing site conditions.   For example,  if the site
has  a  general  slope  grade of  4%, the  slope  should also  be
shaped  to 4%  grades.   If the  site is  very flat,  2% grades
should  be used.    If  the  site is  quite   steep,   the  slope
grades  should  be reduced  to 8%.   This procedure will  mini-
mize the cost required  to  reshape  the site.   Since  natural
grades   can  vary  considerably  within  the  confines  of  a
specific  site,  the individual  OF  slopes  can  vary in  grade
although each should be within the 2 to 8%  range.
     6.4.8
Land Requirements
The  area  of land to which wastewater is actually  applied  is
termed  slope  area.   In  addition  to  the  slope  area,  the  total
                             6-15

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 land area required  for an OF system  includes  land for pre-
 application    treatment,   administration   and   maintenance
 buildings,   service   roads,  buffer   zones   (see  Section
 4.5.4.2),  and storage  facilities.    At  existing  systems,
 other  area   requirements   (not   including  buffer  zones  or
 storage facilities) have ranged  from  15 to  40% of  the slope
 area.

 For  systems   where  storage  is  provided,  the  slope  area
 requirement may be calculated using the following equations.
                       Q(365 d/yr) + AVe
    (Da) (Lw)
                              m2/ha) (10-2 m/cm)
                                                        (6-2)
where   A,,  =   slope  area,  ha
        Q  =
        Da  =
net loss or gain  in  storage  volume  due  to
precipitation,  evaporation,  and  seepage, m^/yr

average daily  flow,  m3/d

number of operating  days/yr

design hydraulic  loading  rate, cm/d
The  value  of   AV   depends  on   the  area  of  the  storage
reservoir.  Thus,  €he  final  design slope  area  must be deter-
mined after the  storage  reservoir  dimensions are  determined.

Combining  equations  6-1 and  6-2  allows  calculation of  A
based on  application rate and slope length.    Equations 6-2
and  6-3  can also  be  used  for systems with no  storage  since
the  term AVS will  then be  equal to zero.
                      Q(365  d/yr)  +
                     (Da) (Ra) (P)
                                (104
                                                        (6-3)
where  A_ =
        0
        Q =
      AV,
       Da =
slope area, ha

average daily flow, m3/d

net storage gain or loss, m3/yr

number of operating days per year
                            6-16

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       Ra =  design application rate, mj/h-m

        P =  design application period, h/d

        S =  .slope length, m
Equations 6-2 and 6-3 may also be used for systems  in warmer
climates that operate  year-round without reducing  hydraulic
loading  rates during the winter.   As stated previously,  it
is  possible  to  compensate  for  lower  removal  efficiency  at
low  soil temperatures,  without  reducing  hydraulic loading
rates, by decreasing the application rate and increasing  the
application  period.    This  winter  operating  procedure will
minimize slope  area  requirements and eliminate the need  for
any winter storage.

If lower hydraulic loading rates are used during the winter,
for  a  system  operating  year-round,  the  designer  has  two
alternative  approaches that  may be  used  to  determine  the
slope area requirements.  Under  the  first alternative,  slope
area requirement is  based only on the winter hydraulic  load-
ing  rate,   in   which  case   no  winter  storage  will   be
required.  Under the second alternative, slope area would  be
based on the higher  hydraulic loading rates used during  the
rest of the year, in which case  a portion of the winter flow
would have to be stored.  The first  approach would  result  in
maximum  land area   requirements  and  conservative  loadings
during  the warmer  periods of  the  year,  but would  eliminate
storage  requirements.    The  second  approach  would minimize
land area requirement  but may require preapplication .treat-
ment facilities  for  storage.  An economic analysis  should  be
performed to determine which alternative is most cost-effec-
tive.   If  storage facilities  are going to  be  provided  for
other reasons (see Section 6.5), then the second alternative
will probably prove most cost effective.

Slope area requirements using the  first  alternative  may  be
computed using   the  following  equation,  assuming  a  7 d/wk
application frequency:
             As -
                              Q,.,
                   (Lww)(104 m2/ha)(10 2 m/cm)
(6-4)
where  AS =  slope area, ha

       Qw =  average daily flow during winter, m3/d

      LWW =  winter hydraulic loading rate, cm/d
                            6-17

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Slope  area  requirements using the second  alternative  may  be
compluted using  the  following  equation:
       As -
where
        Q =
      AVS =
      D
       aw
      D
                         (QH365 d/yr)  +  AVS
       as
(Lww)(Daw) +  (Lws)(Das)(104 m2/na)(10-2 m/cm)


slope area, ha

annual average daily flow, m /d

net gain or loss of water from storage, m^/yr

winter hydraulic loading rate, cm/d

number of operating days at winter rate

non-winter hydraulic loading rate, cm/d

number of operating days at non-winter rates
6.5  Storage Requirements

Storage  facilities  may be required  at  an OF system for  any
of the following three reasons:

    1.   Storage of  water during the winter due to reduced
         hydraulic loading rates or  complete shutdown.

    2.   Storage of  stormwater runoff to  meet mass discharge
         limitations.

    3.   Equalization  of  incoming flows  to permit constant
         application rates.

Estimating storage volume requirements  for  the above reasons
is  discussed  in  this  section.    Storage  reservoir  design
considerations are discussed in Section 4.6.3.
    6.5.1
 Storage Requirements for Cold Weather
Due to the limited operating experience with OF in different
parts of  the  country,  cold weather storage requirements are
not well  defined.   In  general,  OF systems must be shut down
for the winter  when effluent quality requirements cannot be
met due   to  cold  temperatures  even at  reduced application
rates or when ice begins to form on the slope.  The duration
of the shutdown period and, consequently, the required stor-
age period will,  of  course,  vary with the local climate and
the required effluent quality.
                             6-18

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In  studies at the  Hanover system,  a  storage period of  112
days including acclimation was estimated  to  be  required when
treating primary effluent  to  BOD  and suspended  solids  limits
of  30  mg/L [4] .   This  estimate was reasonably close to  the
130  storage  days predicted by the EPA-1  program using 0  °C
(32  °F)  mean temperature  (see  Section 4.6.2).   For design
purposes,  the EPA-1 or  EPA-3  programs may be used to conser-
vatively estimate winter storage  requirements for OF.  A  map
showing  estimated  storage  days   from  the EPA-1  program  is
shown  in  Figure  2-5  and  tabulated  data are  presented  in
Appendix  F.    In  areas of   the  country  below the  40   day
storage  contour, OF  systems  generally can be operated year-
round.   However, winter temperature data at the proposed  OF
site should  be  compared with those at existing systems that
operate  year-round  to  determine   if  all   year  operation  is
feasible.

Storage  is required at  OF systems  that  are operated year-
round  but at  reduced  hydraulic   loading rates  during   the
winter.  The required storage volume for  such systems can  be
estimated  using the following equation:
where
    Vs = (QW)(DW) - (As)(Lww)(Daw)(10-2 m/cm)

       storage volume, m3

       average daily flow during winter, m3/d

       number of days in winter period

       slope area, m2

LWW =  hydraulic loading rate during winter, cm/d
                                                        (6-6)
Vs =
       Qw =
       Dw -
       As =
      D
       aw
    =  number of operating days in winter period
The  duration  of  the  reduced  loading  period  at  existing
systems generally has been about 90 days.

Unless  the  winter storage reservoir  is  an integral part of
the  preapplication  treatment  system,   the  winter  storage
reservoir should be  bypassed during  the warm season opera-
tion to minimize algae  production in the applied wastewater
and  to  minimize  energy  costs  for  prestorage  treatment.
Stored  water should be  blended with  fresh  incoming waste-
water before application on the OF slopes.
    6.5.2
        Storage for Stormwater Runoff
In  some  cases,  discharge  permits may  allow  discharge of
Stormwater  runoff  from  the OF  system but  require monthly
                             6-19

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mass  discharges  for  certain  constituents  to  be  within
specified limits.  In such cases, stormwater runoff may need
to  be  stored  and  discharged  at  a  later  time when  mass
discharge  limits would  not  be exceeded.   A  procedure for
estimating  storage  requirements  for  stormwater runoff  is
outlined below.

     1.  Determine  the   maximum   monthly   mass  discharge
         allowed   by   the   permit   for   each   regulated
         constituent.

     2.  Determine expected  runoff concentrations  of regu-
         lated   constituents   under  normal  operation  (no
         precipitation).

     3.  Estimate monthly runoff  volumes  from  the  system
         under  normal  operation   by  subtracting  estimated
         monthly  ET  and  percolation  losses  from,  design
         hydraulic loading.

     4.  Estimate the  monthly  mass discharge  under  normal
         operation by  multiplying  the  values  from  Steps  2
         and 3.

     5.  Calculate the allowable mass discharge of regulated
         constituents   resulting    from   storm   runoff   by
         subtracting the estimated monthly mass discharge in
         Step 5 from the permit value in Step 1.

     6.  Assuming  that   storm  runoff   contains  the  same
         concentration  of  constituents  as  runoff  during
         normal  operation, calculate  the  volume of  storm
         runoff  required  to  produce a  mass discharge equal
         to the value in Step 5.

     7.  Estimate runoff  as  a fraction of  rainfall  for the
         particular site soil conditions.  Consult the local
         SCS office  for guidance.

     8.  Calculate the total  rainfall  required  to produce SL
         mass  discharge  equal  to  the  value  in  Step  5  by
         dividing  the  value   in  Step  6  by  the value  in
         Step 7.

     9.  Determine for each month a probability distribution
         for rainfall  amounts and  the  probability  that the
         rainfall amount in Step 8 will be exceeded,

    10.  In consultation  with regulatory  officials,  deter-
         mine what probability  is  an  acceptable risk before
         storm runoff  storage is required and use this value
         (Pd)  for design.
                             6-20

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    11.  Storage must  be  provided for those months  in which
         total rainfall probability exceeds the design value
         (PCJ) determined  in Step  10.

    12.  Determine  the change in  storage  volume  each month
         by  subtracting  the  allowable  runoff  volume   in
         Step 6  from  the runoff  volume  expected  from rain-
         fall having  an  occurrence  probability of  Pd.    In
         months  when  the expected storm  runoff exceeds the
         allowable  storm  runoff,  the difference   will   be
         added to  storage.   In months when allowable runoff
         exceeds expected runoff, water  is  discharged from
         storage.

    13.  Determine  cumulative storage  at  the  end  of each
         month by  adding the  change in  storage  during one
         month to the accumulated quantity from the  previous
         month.   The  computation should begin  at  the start
         of  the  wettest  period.   Cumulative  storage cannot
         be less than zero.

    14.  The required storage volume is the largest  value  of
         cumulative  storage.    The  storage  volume  must   be
         adjusted  for  net gain or loss due to precipitation
         and evaporation  (see Section 4.6.3).

If stored  storm  runoff does  not meet  the  discharge permit
concentration limits  for regulated  constituents,  then the
stored water must be reapplied to the OF system.  The amount
of stored  storm  runoff is expected  to  be  small relative  to
the  total  volume   of   wastewater applied,  and  therefore,
increases  in slope  area should not be necessary.   The addi-
tional water volume can  be  accommodated by  increasing the
application period as necessary.
    6.5.3
Storage for Equalization
From a process control standpoint it is desirable to operate
an OF system  at  a constant application rate and application
period.   For systems that do not have storage facilities for
other reasons, small  equalizing basins can  be  used to even
out  flow  variations  that  occur   in  municipal  wastewater
systems.  A storage  capacity of 1  day flow should be suffi-
cient to  equalize flow in most cases.  The  surface area of
basins should be  minimized to reduce intercepted precipita-
tion.   However,   an  additional half  day  of  storage  can be
considered  to   hold   intercepted   precipitation   in   wet
climates.

For  systems providing only  screening  or  primary sedimenta-
tion  as   preapplication  treatment,  aeration   should  be
                             6-21

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provided  to  keep  the  basin  contents  mixed   and  prevent
anaerobic odors.  The added cost of aeration, in most cases,
will be  offset  by savings resulting from reduced pump sizes
and  peak power  demands.    The  designer  should  analyze the
cost  effectiveness  of  this  approach  for  the system   in
question.

6.6  Distribution

Wastewater  distribution onto OF  slopes can be  accomplished
by  surface  methods,  low pressure  sprays,  and high pressure
impact sprinklers.   The choice  of system should be based  on
the following factors:

    1.   Minimization of operational difficulties, such as

         •    Uneven wastewater distribution onto the slopes
              and  the   creation  of   short-circuiting  and
              channeling

         •    Solids    accumulation   at   the   point    of
              application

         •    Physical  damage due to maintenance activities
              and freezing                          ;

    2.   Capital, operating,  and energy costs
    6.6.1
Surface Methods
Surface  distribution  methods   include  gated  aluminum pipe
commonly  used  for  agricultural irrigation  (Section 4.7.2),
and slotted or perforated plastic pipe.  Commercially  avail-
able gated pipe can have gate spaces ranging  from  0„6  to  1.2
m  (2  to  4 ft)  and gates can be placed on one or  both  sides
of  the  pipe (see  Figure  6-2).    A  0.6 m  (2 ft)  spacing  is
recommended  to  provide operating flexibility.   Slide  gates
rather  than screw  adjustable  orifices are  recommended  for
wastewater  distribution.   Gates can be adjusted manually to
achieve  reasonably  uniform  distribution  along  the   pipe.
However, the pipe  should be operated under low pressure,  1.5
to  3.5 N/cm2 (2 to 5 lb/in. ),  to achieve good uniformity at
the application  rates recommended  in  Table 6-5,  especially
with long pipe lengths.  Pipe lengths  up to  520  m  (1,700  ft)
have  been used,  but  shorter  lengths  are  recommended.   For
pipe  lengths greater  than 100 m  (300 ft),  inline  valves
should be  provided along the pipe  to allow additional flow
control   and   isolation  of  pipe   segments  for  separate
operation.
                             6-22

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                         FIGURE 6-2
       SURFACE DISTRIBUTION USING GATED  PIPE FOR OF
Slotted  or  perforated plastic  pipe have  fixed  openings at
intervals ranging  from 0.3  to 1.2  m  (1  to  4  ft).   These
systems  operate  under gravity or very  low pressure and the
pipe must be  level  to achieve uniform distribution.  Conse-
quently,  such methods should  be  considered  only  for small
systems  having  relatively  short  pipe  lengths  that  can be
easily leveled.

The principal advantages  of  surface systems are low capital
cost and  low  energy consumption and power costs.  The major
disadvantage  with   surface   systems  is  the   tendency  of
discharge orifices to accumulate debris and become partially
plugged;  Consequently, orifices must be inspected regularly
and cleaned  as  necessary to maintain  proper distribution.
Another disadvantage of surface systems is the potential for
deposition  of  solids  at  the point   of  application  when
treating  wastewaters  with high concentrations of' suspended
solids.   Deposition  problems have  not been  reported  with
surface  distribution  systems applying  municipal wastewater,
either  screened  raw  or  primary  effluent,  at  conventional
                            6-23

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'hydraulic  loading  rates and  application  rates.    However,
 solids  buildup  has  occurred when  applying food  processing
 wastewater with  solids  concentrations >500 mg/L.
     6.6.2
Low Pressure Sprays
                             o                   9
 Low  pressure,  10 to  15  N/cm  (15 to 20 Ib/in.  ),  fan  spray
 nozzles  mounted on  fixed  risers that  distribute  was.tewater
 across the  top  of  the slope  have been used successfully with
 stabilization  pond  effluent   (see  Figure  6-3).    However,
 experience  using this method for screened  raw wastewater has
 been  mixed.  Preapplication treatment  with  fine  screens  is
 essential  for  this method to be  used with raw wastewater  or.
 primary  effluent.
                           FIGURE 6-3
   DISTRIBUTION FOR OF USING  LOW PRESSURE  FAN SPRAY NOZZLES
                             6-24

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Low pressure fan nozzles mounted on rotating  booms were  used
previously  but  found to require  too  much maintenance to  be
practical.
    6.6.3
High Pressure Sprinklers'
High  pressure,  35  to  55 N/cm   (50 to  80 Ib/in.),  impact
sprinklers have  been  used successfully with food processing
wastewa.ters   containing  suspended   solids  concentrations
>500 mg/L.    The  position  of  the  impact  sprinkler ,on  the
slope  depends on  whether the  sprinkler  rotation  is   full-
circle  or  half-circle  and  on  the  configuration of  the
slopes.   Several  possible sprinkler location configurations
are   illustrated   in   Figure   6-4.     With  configuration
(a), slope  lengths in  the  range  of  45  to 60  m  (150  to
200 ft)   are  required   to   prevent  spraying  into   runoff
channels  and  to  provide some downslope  distance  beyond  the
spray  pattern.    Use  of  half-circle  sprinklers,  configura-
tions  (c)  and (d),  or full-circle  sprinkler  in configura-
tion (b)  allows   the  use of  slope  lengths less  than  45 m
(Section 6.4.6).

The spacing of the sprinkler  along the slope depends  on  the
design   application  rate   and   must   be   determined   in
conjunction with the  sprinkler  discharge  capacity and  the
spray  diameter.    The  relationship between  OF  application
rate and  sprinkler spacing  and discharge  capacity  is  given
by the following equation:             "
                q  =
                            3  m3/L)(3,600 s/h)
                                                       (6-7)
where  q =  OF application rate, m /h-m

      Q_ =  sprinkler discharge rate," L/s
       5                      "

      Ss =  sprinkler spacing, m
The sprinkler spacing should allow for some .overlap of spray
diameters.   A  spacing  of about  80% of  the  spray diameter
should be  adequate  for  OF.   Using the design OF application
rate and  the  above  criteria  for spray diameter, a sprinkler
can  be  selected  from  a manufacturer's  catalog.   Sprinkler
selection  is  discussed  in Appendix E.  Application rate can
be adjusted by regulating the sprinkler operating pressure.
                             6-25

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                                       1—0
                                       '
                                       C3 CD

                                       U-QC

                                       O c/0
                                       CD —
                                    tO
                                    CD '^
                                        LLl
                                        0=0
6-26

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Sprinkler  distribution  systems  are  capable of  providing a
uniform  distribution across  the  slope  and  distributing a
high solids  load over  a  large area  to  avoid accumulation.
Operator attention requirements are expected to be less with
sprinkler  systems than  with surface systems.  Disadvantages
associated  with sprinkler  distribution  include  relatively
high capital  costs,  high  energy requirements, and potential
short-circuiting due  to wind drift of  sprays.   :>Preapplica-
tion treatment must be sufficient  to prevent nozzle clogging
(Section 6.3 ).
    6.6.4
Buried Versus Aboveground System
Low  pressure  sprays and  sprinkler systems  may have either
aboveground or  buried  piping.   Surface piping  generally has
a  lower  capital cost,  but buried  pipe  has a longer service
life- and  is not  as  susceptible to damage from freezing or
harvesting equipment.
    6.6.5
Automation
Both  gravity  and  pressure  distribution  systems   can  be
automated  to  any  degree  that  is  desired.,   The  value  of
automation  increases with the 'size  of  the  system.   The
components required to effectively automate an OF system are
relatively   simple   and   trouble-free.     Care   should  be
exercised  to  avoid  over-designing  an  automatic   control
system.   The primary objective is  to allow the operator to
program any portion of the system to  operate at any time for
any length of  time.  Pneumatically or hydraulically operated
diaphragm  valves,   tied  into  a  centrally  located   control
station,  are  commonly  used.  > A  clock-timer  system  coupled
with  a liquid  level  controller  for the pumping  system is
usually adequate to provide a satisfactory  control system.

6.7  Vegetative Cover
    6.7.1
Vegetative Cover Function
A close  growing  grass cover crop is essential  for  efficient
performance  of  OF  systems.    The  cover  crop  serves  the
following functions in the process.

    1.   Erosion   protection   -   crop   provides    surface
         roughness which  acts  to spread the water  flow  over
         the  surface  and  reduces  the velocity  of  surface
         flow thus helping to prevent  channeling.

    2.   Support  media for microorganisms  -,the biological
         slime  layer  that develops on the slope surface  is
         supported  by  the   grass  shoots  and  vegetative
         litter.
                             6-27

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    3.   Nutrient   uptake   -   crop   takes   up   nitrogen   and
         phosphorus which  can  be removed by harvesting.

    6.7.2     Vegetative Cover Selection

An  OF  cover crop should have  the following  characteristics:
perennial  grasses;  high   moisture  tolerance;  long  growing
season;  high  nutrient uptake;  and  suited  for  the local
climate and soil conditions.

A mixture  of grasses  is  generally  preferred  over a  single
species.   The  mixture should contain  grasses whose  growth
characteristics  compliment each other,  such as sod  formers
and bunch  grasses  and species that are dormant at  different
times  of the  year.   Another advantage of using a mixture  is
that,  due   to  natural  selection,  one  or   two  grasses will
often  predominate.    One  particular mixture  which has been
found  to  be  quite successful  is  Reed  canarygrass, tall
fescue,  redtop,  dallisgrass,  and   ryegrass.    in northern
climates,  substitution of  orchardgrass for  the  redtop  and
dallisgrass is  suggested.   Although this mixture has  proven
effective  in  a  variety of climates,  it is  always best  to
consult with  a  local  agricultural  advisor  when selecting a
seed mix to meet the criteria  given  above.

Salt  sensitive  plants,  such   as  most  varieties  of  clover,
should  be   avoided.    Pure stands  of  grasses  whose   growth
characteristics are dominated  by a single seed  stalk  such  as
Johnson grass, yellow  foxtail, and most of  the  grains  should
be  avoided.   In  the  early stages  of  growth,  these  grasses
provide a  quick and effective cover.  However, as  the plant
matures,  the  bottom  leaves  wither and disappear,  leaving
only  the  primary  seed stalk  which  eventually produces  the
grain  crop.   When  this happens,  the value  of these crops  as
OF  cover  vegetation is greatly  reduced.   Of  course, crops
having  low moisture .tolerance, such  as alfalfa,  should  not
be used.

6.8  Slope Construction
6.8.1
              System Layout
The general  arrangement  of individual slopes should be such
that gravity flow from the  slopes  to the runoff collection
channels and finally to the main collection channels will be
possible.  A grading plan  should be prepared that will mini-
mize earthwork  costs.   Criteria for  selecting  slope grades
are given in Section 6.4.7.  From an operational standpoint,
it is preferable  to have the grading plan result in a single
final  discharge  point.   Occasionally,  however,  existing
                             6-28

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terrain features will  make a single point discharge  imprac-
tical.  In  such  cases,  it is usually more cost effective  to
create multiple  discharge points  (and  monitoring  stations)
rather than attempt to overcome the terrain constraints with
extensive earthwork.
    6.8.2
Grading Operations
Since the  principle  of smooth sheet  flow down the slope  is
of critical importance to consistent OF process performance,
appropriate   emphasis  must   be   placed  ,on   the  proper
construction  of the  slopes.    Naturally  occurring  slopes,
even if they are within the required length and grade range,
seldom  have  the  uniform  overall  smoothness required   to
prevent    channeling,   short-circuiting,  .  and    ponding.
Therefore,  it  is necessary to completely clear the site  of
all vegetation  and to regrade  it into a series of  OF slopes
and  runoff collection  channels.   The  first phase  of  the
grading operation  is  commonly referred  to as rough  grading
and should  be  accomplished  within a grade tolerance of 3  cm
(0.1 ft).   If  a buried distribution  system  is being  used,
the  rough  grading  phase  is  generally  followed   by   the
installation of  the distribution piping and appurtenances.

After  the  slopes  have  been  formed   in  the  rough  grading
operation, a farm disk should be used  to  break up  the clods,
and the soil  should  then  be smoothed with a land  plane (see
Figure 6-5).   Usually, a grade  tolerance of  plus or minus
1.5 cm  (0.05  ft)  can be  achieved  with three  passes  of  the
land plane.  Surface distribution  piping may be installed  at
this stage.

Soil  samples  of  the  regraded  site  should  be   taken  and
analyzed  by  an agricultural  laboratory  to  determine  the
amounts  of  lime  and  fertilizer  that  are  needed.     The
appropriate  quantities   should   then  be  added   prior   to
seeding.  A light disk should be used  to  eliminate any wheel
tracks on the slopes as final preparation  for  seeding.
    6.8.3
Seeding and Crop Establishment
It has been found that a Brillion seeder  is capable of doing
an excellent job of seeding the slopes.   The Brillion seeder
carries   a   precision  device   to   drop   seeds  between
cultipacker-typer rollers  so  that the seeds are firmed  into
shallow  depressions,  allowing  for  quick germination  and
protection against  erosion.   Hydroseeding may also be  used
if  the  range  of  the  distributor is  sufficient  to provide
coverage of the slopes so  that the vehicle does no.t have  to
travel on the slopes.  When seeding is completed,  regardless
of the means, there should be no wheel tracks  on the slopes.
                             6-29

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                          FIGURE 6-5
              LAND  PLANE USED FOR FINAL GRADING
It  is  important to establish  a good vegetative cover  prior
to  applying  wastewater  to  the slopes.   Good planning  will
minimize  the  effort and cost required to achieve  this.   The
construction  scheduling  should  be  organized  so  that  the
seeding operation  is accomplished during  the  optimum  periods
for planting grass  in  the particular  project  locality,   This
is  generally sometime during  the  fall  or  spring  of  each
year.   During  these  periods, sufficient  natural precipi-
tation  is often available  to  develop growth.   In arid  and
semiarid  climates  or whenever  seed  is planted during  a  dry
period, it may  be  necessary to irrigate  the  site  with  fresh
water,  if wastewater  is unavailable, to  establish the  grass
crop.    In   these   cases,  a  portable  sprinkler   irrigation
system  should be  used  to provided  irrigation water coverage
over the  entire slope  area,  since use  of  the  OF distribution
system  would  cause erosion  of the  bare  slopes.   It may  be
necessary to  sow  additional seed or  to repair erosion  that
may occur as a  result of heavy rains prior to the stabili-
zation of the slopes.

As  a  general  rule,  wastewater  should   not  be  applied  at
design  rates  until the crop has grown enough to receive  one
cutting.   Cut grass from  the  first  cutting  may  be  left  on
the  slope to  help  build  an  organic  mat  as  long  as  the
                             6-30

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clippings are  short  (0.3 m  or 1 ft);  long clippings tend to
remain on top  of  the  cut grass thus shading the surface and
retarding regrowth.

6.9  Runoff Collection

The  purpose   of   the  runoff  collection  channels  is  to
transport  the  treated  runoff and  storm  runoff to  a final
discharge  point   and  allow  runoff  to  flow freely  off  the
slopes.  The collection channels are usually vegetated with
the same species of grasses growing on the slopes and should
be  graded  to   prevent  erosion.    There  are   some  cases,
however, where additional  construction is necessary.  Sharp
bends  or  steep grades  along runoff  channels  will increase
the  potential   for  erosion,   and   it  may  be   necessary  to
provide  additional   protection  in  the  form  of  riprap,
concrete,  or  other  stabilizing   agent  at  these  points.
Runoff channels  should  be  graded to  no  greater than 25% of
the slope grade to prevent cross flow on  the slope.

In humid regions, particularly where the  topography is quite
flat  and  the   runoff  channels  have  small  grades,  grass
covered  channels  may  not  dry  out  entirely.   This  may
increase channel maintenance  problems and encourage mosquito
populations.   In  these cases,  concrete  or asphalt  can be
used  or  a more  elaborate  system  involving  porous drainage
pipe lying in the channel beneath a gravel cover.  It should
be emphasized, however,  that it is usually not  necessary to
go  to these  lengths  to obtain free-flowing  yet erosion-
protected runoff  channels.    Small  channels  are normally V-
shaped,  while  major  conveyance  channels  have trapezoidal
cross-sections.

In  addition  to  transporting  treated effluent  to  the final
discharge point,  the  runoff channels must also  be capable of
transporting all stormwater  runoff from  the   slopes.   The
channels should  be designed, as a  minimum,  to  carry runoff
from  a  storm  with  a  25 year  return  frequency.    Both
intensity and  duration of  the  storm  must be  considered.   A
frequency  analysis of rainfall  intensity must  be performed
and a rainfall-runoff relationship  developed to estimate the
flowrate  due  to  storm  runoff  that must be carried  in the
channels.   The local  SCS  office can  provide  assistance in
performing  this   design.   References  [12,  13]   can  also be
consulted.  In some  cases,  it may be desirable  to provide a
perimeter  drainage channel  around the  OF site to exclude
offsite stormwater from entering the OF drainage channels.
                             6-31

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6.10  System Monitoring and Management

The  primary objective  of  the OF  system  is  to  produce  a
treated  effluent  that  is  within the  permit requirements.
Therefore, a monitoring program and a preventive maintenance
program  are necessary  to ensure continued  compliance with
discharge requirements.

    6.10.1    Monitoring

         6.10.1.1  Influent and Effluent

The  influent  and  effluent  monitoring  requirements  will
usually  be  dictated  by the discharge permit established  for
the system  by  the regulatory  authorities.   An open channel
flow measuring device  (Parshall  flume,  weir, etc.) equipped
with  a  continuous  flow recorder is  generally satisfactory
for monitoring the treated effluent.  Most types of portable
or permanent automatic  samplers can be used  for sampling.

         6.10.1.2  Ground Water

The  need  to  install  ground  water  monitoring  wells  will
generally be determined by the regulatory  authorities.   In
certain  cases,  the  authorities  will   also establish   the
number and location of monitoring wells.  If those decisions
are  left  to   the designer,  however,  it  is advisable  to
consider a minimum of two ground water monitoring wells,  one
located  upstream  of  ground  water  movement  through   the
treatment site  which will  serve  as a background  well,   and
the second  immediately  downstream from  the site to show  any
impacts from the treatment operation.

         6.10.1.3  Soils and Vegetation

Suggested monitoring programs for soils and vegetation given
in Sections 4.10.2 and 4.10.3 for SR systems are also appli-
cable to OF systems.   If  the vegetation on  the  treatment
site is  harvested  and  used for fodder,  samples may be taken
at  each  harvest  and  analyzed  for  various  nutritive  para-
meters  such as  percent  protein,  fiber,  total  digestible
nutrients, phosphorus, and dry matter.
    6.10.2
System Management
         6.10.2.1  Operation and Maintenance

Process control  involves  regulating the distribution system
to provide design application rates and application periods,
and adding water to and releasing water from storage at the
                             6-32

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appropriate  times  (see  Section  6.4 and  6.5).   A  routine
operation  and   maintenance   schedule  should  be   followed
including  a  daily  inspection of  system  components  (pumps,
valves,  sprinklers,  distribution  orifices on  surface  sys-
tems,  flowmeters).   Application rates and periods should  be
checked and maintained within design  limits.

         6.10.2.2  Crop Management

After  the  cover crop has  been  established,  the slopes  will
need little, if  any, maintenance work.  It will, however,  be
necessary to mow the grass periodically.  A few systems  have
been operated  without  cutting, but  the  tall  grass  tends  to
interfere with  maintenance operations.   Normal practice has
been  to cut  the  grass  two  or  three  times   a  year.    As
mentioned previously,  the first cutting may  be left on the
slopes.  After  that, however, it is desirable to remove the
cut grass.   The advantages of  doing so  are that additional
nutrient  removal  is  achieved,  channeling  problems  may  be
more readily observed,  and revenue can sometimes be  produced
by  the sale  of  hay.   Depending on  the  local  market  condi-
tions,  the cost of  harvesting can at least be offset by the
sale of hay.

Slopes  must be  allowed  to dry sufficiently such that mowing
equipment  can   be  operated without  leaving  ruts  or  tracks
that  will  later result  in  channeling  of the flow.   The
drying  time required before mowing varies with the  soil and
climatic conditions  and  can range from a  few  days  to a few
weeks.  The downtime required for harvesting  can be reduced
by  a   week  or  more  if  green-chop  harvesting  is  practiced
instead  of mowing,  raking,  and  baling.    However,  local
markets  for  green-chop  must  exist   for  this  method  to  be
feasible.

It  is  common  for certain  native  grasses  and  weeds  to begin
growing on  the  slopes.   Their presence usually  has  little
impact  on treatment  efficiency  and  it  is   generally  not
necessary to eliminate  them.   However,  there  are exceptions
and  the local  extension  services  should  be  consulted  for
advice.

Proper management of the slopes and  the application  schedule
will  prevent   conditions  conducive   to  mosquito  breeding.
Other  insects  are  usually no  cause for concern, although  an
invasion of certain pests  such  as army worms  may be harmful
to  the  vegetation  and   may   require periodic  insecticide
application.
                             6-33

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 6.11   Alternative  Design Methods

 Recently,   two  rational  methods  have  been  developed  for
 determining OF design  criteria.   One,  based on  detention
 time  on  the slope,  was  developed  at  the U.S.  Army  Cold
 Regions  Research  and  Engineering Laboratory  (CRREL)  [14] .
 The other,  based  on slope distance and  application  rate  was
 developed at the University  of  California,  Davis  [15].   Both
 approaches   have   been  validated  with  results   from  other
 studies  and have  been  used  for  preliminary or  pilot  scale
 design  of   OF  systems.   A design  example  comparing  the
 traditional empirical approach  with these  two  methods can be
 found  in Appendix  C.
    6.11.1
CRREL Method
         6.11.1.1  Method  Description

The  basis  of  the  CRREL method  is a  relationship,  between
detention time and mass  BOD reduction using  performance  data
from  the CRREL  system,  and  validated  with data  from  the
Utica  and  University  of California, Davis,  systems,,   With
this  relationship,  the   required   detention   time   can be
calculated  for  a  specified  mass  BOD  reduction.     This
detention  time is  then used  in an equation  which  relates
detention time, slope  length, and slope grade to application
rate.  Thus, for  an  OF slope  with a given length and grade,
the  required  application  rate  can  be   determined  for a
specified detention time or, indirectly,  for a  specified BOD
reduction.   The  application rate is then used to calculate
the required land area.

         6.11.1.2  Design Procedure

1.  Calculate detention  time.

The relationship  between detention  time and mass BOD reduc-
tion is expressed as:
                    E = (1 - Ae~Kt)100

where  E =  percent mass BOD removal

       A =  nonsettleable fraction of BOD in applied
            wastewater (constant = 0.52)

       K =  average kinetic rate constant (0.03 min"-'-)

       t =  detention time, min
                                        (6-8)
                             6-34

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2.  Calculate average OF rate.

The average OF rate needed to obtain this required detention
time is calculated using the following equation:

                    q = (0.078S)/(G1/3t)                (6-9)

where  q =  average OF flowrate (qappiied + qrunoff)/2'
            m3/h-m of slope width

       S =  length of section, m

       G =  slope of section, m/m

       t =  detention time, min


To  use  Equation 6-9,  section length  (s)  and section  slope
(G)  must  first  be  determined  by  an  investigation  of  the
proposed  site.   This  investigation should  yield a  section
with length and width dimensions and with a specific  section
slope   which   will   be   used   when   determining   area
requirements.   Actually,  more than  one section size can  be
selected  if the  topography  of the  site is  such that  less
land forming would be required if the  site were  not composed
of  uniform sections.  Equation 6-9  would then  be used  with
the parameters  from  each section to  determine the  average OF
rate for each section.

3.  Calculate application  rate.

The  following  equation is used to determine  the application
rate for each section:
                         Q = qw/r

where  Q =  application rate, m^/h per section

       q =  average^OF flowrate  [qapplied +
                                                       (6-10)
                             «m

        w =   width of  section,  m

        r =   (1.0  + runoff fraction)/2


 The runoff  fraction  is the fraction of the  applied  waste-
 water  which  reaches  the  runoff  collection  ditches.    The
 runoff   fraction  must   be   assumed   in   order  to   use
 Equation 6-10.    The  runoff fraction ranges  from  0.6  to 0.9
                             6-35

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 depending on  the permeability  of the  soil  and evaporation
 losses.

 4.   Calculate annual loading rate.

 The annual loading  rate  (m3/yr)  must  be determined for each
 section.   To do  this,  the  number of days of application per
 year must be  calculated  and the  application  period  must be
 selected.   Given these  values  and the loading  rates,  the
 annual loading rates for  each section  can be calculated.

 5.   Calculate total  annual  water volume.

 An  estimate  of the volume of precipitation minus evapotrans-
 piration  that will  collect  in  the storage  or preapplication
 treatment basin must be made and  added  to  the annual waste-
 water volume  to obtain the  total annual  water volume.,

 6.   Calculate  land area requirements.

 The number of  sections are  calculated  using the total annual
 water volume  and  annual  application  rate  to  each  section.
 However,  the  number  of sections  of a  particular size may be
 determined by physical constraints at  the  site.   The  land
 requirement  is now  calculated  by multiplying  the  number of
 sections  of each  particular size by its  area.

     6.11.2    University  of California,  Davis, (UCD)  Method

          6.11.2.1  Method Description

 The  basis for the UCD method is  a model  which describes  BOD
 removal as a  function of  slope  length and  application  rate,
 where  the application  rate  has  the  units  m^/h-m of  slope
 width.  This model was  developed  using performance  data  from
 the  UCD  system  and  was  substantiated  using  data from  the
 CRREL  system.   By  knowing the influent BOD  requirements,  the
 model  can  predict  either  the  required  slope  length   or
 application rate,  once the  other parameter has been  fixed.
 Once  both parameters are  known  and a  design  daily flowrate
 is given,  the area requirements  can be determined.

          6.11.2.2  Design Procedure

 1.  Determine slope  length or application rate.

 Either  slope  length  or application  rate can  be calculated,
once the other parameter has been  fixed,  using the  following
equation:
                  CS/C0 =
(6-11)
                             6-36

-------
where
       co =

        A =

        K =

        S =

        q =

        n =
concentration BOD at point S, mg/L

initial BOD concentration, mg/L

constant = 0.72

rate coefficient (constant = 0.01975 m/h)

distance downslope, m

application rate, m /h-m slope width

exponent (constant = 0.5)
Site conditions  may dictate the  allowable  slope length,  in
which case  slope length would  be the independent parameter
and  application  rate would  be  the computed  parameter.    If
slope length is  not restricted, then  application rate should
be used  as  the independent parameter.  Currently, the model
is valid in the range of  0.08  to  0.24  m3/h-m and  so  the
application rate selected for a design should be within  this
range.

The  effect  of  water loss  due to  evaporation and percolation
is incorporated  into  the  rate coefficient (K).  Significant
changes  in  the value of K  are  not expected  as  a result  of
changes  in  water   losses  normally  experienced  with   OF
systems.   Additional  field  testing  is  necessary to confirm
this.

2.   Select an  application period.

See  Section  6.4.4  for a discus.sion on selecting an applica-
tion period.

3.   Compute the  average daily flow to OF  system.

To  compute  the  average   daily  flowrate,   the  application
season  (days  of application per year) must be calculated.
Also, the  volume of  precipitation  minus evapotranspiration
that  will  collect  in  the  storage  basin or preapplication
treatment  basin  must  be  estimated.   With  this information
and  the  average  daily wastewater  flowrate, the average daily
flow to  the OF system can be calculated.

4.   Compute the  required wetted area.

The  wetted area  is  computed  using the following  equation:

                         Area = QS/qP                 (6-12)
                             6-37

-------
 where  Q =

        S =

        q =

        p =


     6.11.3
average daily flow to the OF system, m3/d

slope length, m                          ;

application rate, m3/h-m

application period, h/d


  Comparison of Alternative Methods
Although  the CRREL and  UCD equations appear  different,  the
basic  approach  and calculation  method  are  quite  similar.
Combining  and  rearranging  Equations  6-8 and  6-9  from  the
CRREL method produces:
where  M0 =
         o

       M0 =

         S =

         /•^ —


         q =
 Mc/Mrt = 0.52e(~0-0°234S)/(G1/3q)
  O  \J


 mass of BOD at point S,  kg

 mass of BOD at top of slope,  kg

 slope length,  m

 slope grade, m/m

 average overland flow, m3/h-m
                                                       (6-13)
This is quite similar to  the UCD Equation  6-11:
  C  /C   =  0.72e(-°-01975S/q0-5)
  s o
                                                       (6-14)
All terms are defined previously.

The major differences in these two rational approaches are:

    1.   Use of  slope  grade as a variable in CRREL equation
         and not in UCD equation.

    2.   Use of  mass  units in  CRREL equation  and concen-
         tration units in UCD equation.

    3.   Value of exponents and coefficients.
                            6-38

-------
6.12  References

 1.  Bledsoe, B.E.   Developmental  Research for Overland Flow
    Technology.  In:  Proceedings of the National Seminar on
    Overland   Flow  Technology,   Dallas,   Texas.      U.S.
    Environmental   Protection   Agency.     EPA-600/9-81-022.
    September 1980.

 2.  Hall,  D.H.,  et al.   Municipal Wastewater  Treatment by
    the   Overland   Flow   Method   of    Land   Application.
    Environmental   Protection   Agency.     EPA-600/2-79-178.
    August 1979.

 3.  pollock,  T.E.    Design  and  Operation of  Overland Flow
    Systems   -   The   Easley   Overland   Flow   Facility.
    Proceedings  of  Workshop on Overland  Flow for Treatment
    of Municipal Wastewater.   Clemson University.  Clemson,
    South Carolina.  June 1980.

 4.  Martel,  C.J.,  et  al.    Wastewater  Treatment   in Cold
    Regions by Overland Flow.  CRREL Report 80-7.  U.S. Army
    Corps of Engineers.  Hanover, New Hampshire.  1980.

 5.  Martel, C.J.,  et al.   Development  of a Rational  Design
    Procedure  for  Overland  Flow Systems.   CRREL, U.S. Army
    Corp   of   Engineers,  Hanover,  New   Hampshire.      (In
    preparation).   December 1981.

 6.  Scott,  T.M.  and D.M. Fulton.   Removal of Pollutants in
    the  Overland Flow (Grass  Filtration)  System.  Progress
    in Water  Technology, Vol.  11, Nos.  4 and 5.   pp 301-
    313.   1979.

 7.  Peters,   R.E.,   C.R.   Lee,  and  D.J.  Bates.      Field
    Investigations  of  Overland Flow  Treatment  of Municipal
    Lagoon  Effluent.   U.S. Army  Engineer Waterways Experi-
    ment    Station,   Vicksburg,   Massachusetts.        (In
    preparation).

 8.  Smith,  R.G.   Development of  a Rational Basis  for  the
    Design of  Overland Flow Systems.  In:  Proceeding  of  the
    National  Seminar on Overland  Flow  Technology.   Dallas,
    Texas.     U.S.  Environmental  Protection Agency.   EPA-
    600/9-81-022.   September 1980.

 9.  Thomas,  R.E.,  et  al.    Overland  Flow Treatment  of  Raw
    Wastewater  with  Enhanced  phosphorus  Removal.     USEPA,
    Office  of Research and  Development.   EPA-660/2-76-131.
    1976.
                              6-39

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10. Peters,  R.E.,  et al.   Field  Investigations of Advanced
    Treatment  of  Municipal  Wastewater  by  Overland   Flow.
    Volume 2.  Proceedings  of the  International  Symposium on
    Land  Treatment of Wastewater.   Hanover, New Hampshire.
    August 1978.

11. Law,  J.P., et  al.   Nutrient Removal from Cannery Wastes
    by Spray  Irrigation  of Grassland.  Water Pollution Con-
    trol  Research  Series,  16080-11/69.   U.S. Department of
    the Interior.  Washington, D.C.  November 1969.

12. U.S. Dept. of Commerce.  Rainfall Frequency  Atlas of the
    United States  for  Durations  from 30 minutes to 24 hours
    and Return  Periods  from  1-100 Years.   Technical Paper
    40.  1961.

13. Water  Resources  Council.    A  Uniform  Technique  for
    Determing  Flood  Flow  Frequencies.    Bulletin No.  15.
    1967.

14. Martel,  C.J.  et al.   Rational Design  of Overland Flow
    Systems.   Proceedings of the ASCE National Conference of
    Environmental Engineering.  July 1980.

15. Smith,  R.G.     Development  of  a  Predictive  Model  to
    Describe the Removal  of Organic Material with the Over-
    land Flow Treatment  Process.   Ph.D. Thesis.  University
    of California, Davis.   1980.
                            6-40

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                          CHAPTER 7

                        SMALL SYSTEMS
7.1  Introduction

The procedures  in this  chapter are  intended  primarily  for
systems with wastewater flows of 950 m3/d  (250,000 gal/d) or
less,  but,  in  some situations, may be  used  for flows up to
3,785 m3/d  (1  Mgal/d).   The objectives  for  land treatment
systems  are the   same  regardless  of  the community size.
However, the design  of  small systems should include  special
emphasis  on  the  ease   of  operation  and  on  minimizing
construction and operating  costs.   Most communities  in this
size range  cannot  hire  full-time treatment plant operators,
and  the  treatment  system  must  be   capable   of  providing
consistent,  reliable treatment  in  the absence of frequent
attention.   In general,  most  treatment   systems  that meet
these objectives are nonmechanical  and have no discharge to
surface waters.

The procedures  described  in  this  chapter  can be  used  to
streamline  Phase 1 of the planning process.   Limited field
work should be conducted  during Phase 2  to  verify  Phase 1
assumptions  and  to  optimize design  criteria,  particularly
when designing RI  systems.   When  more detailed planning or
design  procedures  are needed,  the engineer  should refer to
Chapters 4, 5,  and 6.

7.2  Facility planning

The procedures for planning and design of small systems  are
similar  to, but  less detailed  than,   the  requirements   for
large  facilities.    Maximum  use  is made  of  local expertise
and  existing   published   information.     The  area  Soil
Conservation  Service  (SCS)  staff,  the  county  agent,   and
local  farmers  can all provide  assistance and  advice.    The
types  of  information that  should be  obtained  from these
local or published sources are summarized  in Table 7-1.   The
level  of detail  and the period  over which  data have been
recorded will vary with the  community.
    7.2.1
Process Considerations
Any of the three major land treatment processes  (SR,  RI, and
OF)  or  combinations  of  these  processes  are  suitable for
small  communities.    Seepage  ponds have  been used success-
fully  in many  small  communities  and  are similar  to RI  in
that  relatively high  hydraulic  loading rates  are used and
treatment  occurs   as  wastewater  percolates   through  the
                              7-1

-------
 soil.    The  primary  difference  is  that  seepage  ponds  are
 loaded  continuously,  whereas RI  systems  use a  loading  cycle
 that includes  both application  and drying periods, resulting
 in  improved   treatment  and  maximum  long-term  infiltration
 rates.    Other  processes,  including  complete   retention  and
 controlled discharge  pond  systems,  also  have  potential  for
 small communities.  information on these  pond  systems  can be
 found   in  the  EPA  Process  Design   Manual   for  Wastewater
 Treatment Ponds  [1].

                             TABLE 7-1
         TYPES  AND  SOURCES OF DATA  REQUIRED FOR DESIGN
                 OF  SMALL LAND TREATMENT SYSTEMS
              Type of data
                                         Principal sources
      Wastewater quantity and quality
      Soil type and permeability
      Temperature (mean monthly and
      growing season)
      Precipitation (mean monthly/
      maximum monthly)
      Evapotranspiration and
      evaporation (mean monthly)
      Land use
      Zoning


      Agricultural practices


      Surface and ground water
      discharge requirements

      Ground water (depth and quality)
            NOAA, local airports,


            NOAA, local airports.
Local Wastewater authorities

SCS soil survey

SCS soil survey,
newspapers

SCS soil survey,
newspapers

SCS soil survey, NOAA, local airports,
newspapers, agricultural extension service

SCS soil survey, aerial photographs from
the Agricultural Stabilization and
Conservation Service, and county assessors'
plats
Community planning agency, city or county
zoning maps

SCS soil survey, agricultural extension
service, county agents

State or EPA
State water agency,
of nearby wells
               USGS, drillers' logs
Design  features,  site  characteristics,  and  renovated water
quality  of  the   three  major  land  treatment  processes   are
summarized  in  Tables  1-1,  1-2,  and  1-3.    General  charac-
teristics  of small land  treatment  systems  are summarized  in
Table 7-2.   This  table should  be used  as a  guide  to process
selection.     Final   criteria  should   be  determined  during
facilities  design.

          7.2.1.1    Operation and  Ownership  Alternatives

Small systems  may  be•owned  and operated  by  a municipality  or
wastewater   authority,   although  municipal   ownership   and
operation  are not always  necessary.    In all cases,  overall
system management should be  under  the  control of  the muni-
cipal  agency   held   responsible  for   performance.    Oppor-
tunities often exist,  and should be  sought,  for contractual
                                 7-2

-------
agreements  with  local  farmers   to  take  and  use  partially
treated  wastewater  for  irrigation  and other  purposes.   By
taking  advantage of  such  agreements,   a  community  can avoid
investments  in  equipment  and  land,  and  can  eliminate  the
need to  hire  and train new employees.

                           TABLE 7-2
               GENERAL CHARACTERISTICS  OF SMALL
    «950 m3/d  OR  <250,000 gal/d) LAND TREATMENT SYSTEMS

Process
Slow rate
Surface
application
Sprinkler
application



Minimum
preappl ication
treatment Crops

Primary
Ponds
Annuals
Perennials
or double
cropping




Application season
Growing season
(3-5 months)
Year-round with
exception of down-
time for planting,
harvesting.
maintenance, and
cold-weather
storage if necessary

Application
schedule
8 h, 1 d/wk
8 h, 1 d/wk




Storage
requirements
See Figure 2-5
See Figure 2-5



Rapid
infiltration

Overland
flow
Primary
Screening and
comminution
Not
applicable

Perennial
grasses
                             Year-round
Year-round with
exception of down-
time for planting,
harvesting,
maintenance, and
cold-weather
storage if necessary
               2 d application, 7-30 d for
               10-18 d drying   emergencies
8-12 h/d,
5-7 d/wk
                                              See Figure 2-5
Arrangements  between   local  farmers   and   communities   can
involve  any  of  several  alternatives.    For  example,   the
community  can  provide  partially  treated   wastewater  to  a
farmer, who  is then  responsible  for  all  components  of  the
land  treatment process.    Alternatively,  the  community  may
provide and maintain irrigation  equipment that is used by  a
farmer  who  is  responsible  for  all  farming  operations.    In
either   case,   the  farmer  agrees  to  take  a  predetermined
amount  of water each year to use  on his own  land.  A third
alternative is  for the  community  to purchase  or lease land
and  equipment  for  land  treatment and assume  responsiblity
for  all aspects of the  system except  planting, cultivating,
and  harvesting.  These  three tasks  are accomplished by  the
local  farmer on a contractual or crop  sharing basis.

Land  used for wastewater application either  can be purchased
outright  (fee-simple acquisition)  or  leased on  a long-term
basis.   Long-term leases should include the  items  summarized
in Table  2-15.   Grant  eligible costs of a long-term lease
are  paid  to the community  in a  lump sum at  the beginning of
the  leasing term.
                               7-3

-------
 Contractual   arrangements  between  local  farmers  and  com-
 munities  should  specify  the  following:

    •     The  duration  of the agreement.

    •     Projected  quality  of  water  that will be  delivered
          to farmers.

    •     Any  limits on  application  rates, buffer  zones,  or
          runoff  control.

    •     Any  limitations on  crop  types due to  local or state,
          requirements.

    •     Cost to local farmer and/or  community.

    •     Method  and timing of payments (generally annual).

    •     Method  of  transferring contract.

 Arrangements  between  local farmers and communities  are  most
 practical  when   forage   grasses   or  grazing  animals   are
 involved,  since  there is  less  constraint on application  of
 wastewater  in years  of  high  rainfall.   Other agricultural
 crops with  shorter growing  seasons or  which are less water
 tolerant  than forage  grasses may require  additional  storage
 or other  considerations.  Most arrangements have involved  SR
 systems.   Overland flow systems  normally  are  owned by  the
 community to  ensure control  over  system operation.   However,
 contract  harvest  of   OF grasses  is  advantageous   in  com-
munities  that  lack  the necessary  equipment  and expertise.

 Rapid infiltration  systems also tend  to be municipally owned
 and operated  to  ensure control over the wastewater  treatment
process.   No   crops are  involved; thus,  the  only  potential
 agreements  between   farmer   and   community  are   for   land
 leasing, property easements,  or use of recovered water.

         7.2.1.2   Water Rights Considerations

 In  the  western  states,  water rights  must  be  considered.
Return of renovated water, including  OF runoff and  SR and  RI
percolate, to  the  original point  of community discharge may
be necessary.   Sometimes, RI  basins  can  be located so  that
seepage and subflow proceed  directly  to  the stream or water
body  (Figure   l-2c; Section  5.7.1) that  received   discharge
from the  previous  system.   The local  water rights  situation
should be checked with the state agency in charge.
                             7-4

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         7.2.1.3    Preapplication  Treatment

Most   land   treatment   systems   include  a   preapplication
treatment  step.    In small  communities, wastewater  storage
often  is  provided  in  the preapplication treatment  process.
The  use  of  existing  treatment  facilities  may  reduce  the
capital cost  of  a land treatment  system but may  necessitate
construction of  separate  storage  facilities.

Preapplication  treatment  facilities  should  be  as close  to
the  application  site as  the topography, land  availability,
and  system  objectives   allow.     Most  existing  treatment
facilities  serving  small  communities  are   located  at  a
relatively  low elevation  to allow a  gravity sewer  system.
Thus,  if  existing facilities are  used,  it probably  will  not
be   possible   to  locate  the  application  site  near  the
preapplication   treatment  system.    Instead,  it  is  often
necessary  to  pump  the  partially  treated  wastewater to  the
application site.

         7.2.1.4    Staffing  Requirements

Staffing requirements  depend on the types of  preapplication
treatment  and  land  treatment,  the size of  the  system,  and
whether   the   community  or  a  farmer  operates  the   land
treatment portion of the  system.   Staffing requirements  for
municipally  owned  and  operated '  systems  are  presented  in
Figure  2-9.   Staffing requirements at  a variety  of  smaller
systems are shown  in Table 7-3.
    7.2.2
Site Selection
Before  a  community can begin the site  selection  process,  it
must  be  able  to  estimate  the  amount  of • land  that a  land
treatment  system   will   require.     Approximate   land   area
requirements  have  been  plotted as  a  function  of  average
design  flow  for  each  of  the  three  major types  of  land
treatment in  Figure 7-1.   Although land area estimates  are
.shown  only for  flows  of 950 m3/d  (250,000  gal/d)  or  less,
land  requirements  for flows  of  up  to 3,785 m3/d  (1 Mgal/d)
can be  extrapolated  from the  curves.

In  addition,   for  SR  application  periods between 6 a.nd  12
months  per year, land area requirements  can be  interpolated
from  the  two  SR curves.  For OF application periods greater
than  or  less  than 10.5 months  per year and RI  application
periods less  than  12 months per  year,  land area  requirements
can   be   extrapolated   from   the  OF   and   RI   curves,
respectively.   Figure  7-1 can be used  to determine what size
site  to  search  for  during  the  site  selection process,  but
should . not  be  used   for  design  purposes.     Final   land
                             7-5

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requirements  will  vary  with  the  crop  grown,  site  char-
acteristics,  and   whether  the   site  is  operated  by  the
community or a  local  farmer.

                           TABLE 7-3
                 TYPICAL STAFFING REQUIREMENTS
                        AT SMALL  SYSTEMS


                                            Municipal staff requirements
            1980 flow
 Location
n3/d
                gal/d   Site use
            Pre-      Land
          application  treatment   Annual
          components, components,  total,
Site control  man-days/yr man-days/yr man-days
Chapman ,
Nebraska
Falkner,
Mississippi
Kennett
Square,
Pennsylvania
Ravenna,
Michigan
Santa Anna,
Texas
Way land,
Michigan
Winters,
Texas
66
106
190
275
285
950
1,130
17,400
28,000
50,000
72,000
75,000
250,000
297,000
Grass (RI)
Grasses (OF)
Forest
Open, un-
cultivated
fields
Alfalfa,
grass,
pasture
Hay , corn
Hay
City
City <89
City 130
City 68
Farmer owns, 54
city operates
equipment
City owns, 104
farmer
harvests
Farmer owned 52
<165a
<93 <182
68 198
7 75
46 100
68 172
0 52
Note:  Preapplication treatment by ponds.

a.  Includes labor spent maintaining three pumping stations in collection system.
The  site selection process  can be divided  into parts:   site
identification   and   site   screening   (Sections   2.2.4  and
2.2.5).   In small  communities, the  first step  in  identifying
potential land  treatment  sites  is  to determine whether any
of  the  local  farmers  are  willing  to participate in  a land
treatment project or  are  interested  in selling  or  leasing
property for  a  land  treatment  site.   Questionnaires  and
meetings with local  groups  can be particularly helpful when
making   this  determination.    If  one  or  more  farmers  are
interested  in participating and  have  enough land  to  take and
use  the  wastewater,  or are  interested  in selling  or  leasing
enough    property   for    a    land   treatment   site,   site
investigation  can  begin.    If  the  local   farmers  are  not
interested  or  if the  interested  farmers do  not have  enough
suitable land,  it will  be necessary to  identify  and  screen
potential  sites   using   existing   soils,    topographical,
hydrogeological,  and land use data.    The identif icaition and
                              7-6

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(ha)
 (30).
        acres
  (25)—
  (20)-
  (15)—
  (10)—
   (5)—
     gil/d
50.008
190.000
150.000      2 00.000	250.000
    (»3/d)  (100)   (200)  (300)   (400)  (500)   (600)  (700)   (800)  (900)(1.000)
                     AVERAGE DESIGN tASTEBATER FLO I! OF COMMUNITY
   It
    NUNIER «F MONTHS PER YEAR THAT MSTEIATER IS APPLIED TO LAND.
                                FIGURE 7-1
    LAND  AREA  ESTIMATES  FOR PRELIMINARY  PLANNING  PURPOSES
          (INCLUDING LAND FOR PREAPPL I CAT I ON  TREATMENT)
                                    7-7

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screening  processes  are detailed  in  Chapter 2;  only  the
highlights are presented in this  chapter.

As discussed  in  Section 2.2.4, existing data  can be used  to
classify broad areas  of  land near the community according  to
their  land  treatment  suitability.   Factors  that should  be
considered  include  current and  planned  land  use,  parcel
size,  topography,  present  vegetative  cover,  susceptibility
to flooding,  soil  texture, geology, distance  from the area
where  wastewater  is  generated,  and need  for underdrainage
(based  on  recommendations  of  local   SCS  representative).
Generally, the characteristics of the closest suitable site
will greatly  influence the selection of  the  land treatment
system  type   to  be  designed.    The detailed  rating  factor
approach  in   Chapter  2  is  usually  unnecessary  because
economics  will  limit  the  number  of   sites  that  can   be
considered.
    7.2.3
Site Investigations
As in larger communities, field investigations are conducted
to  verify  any  data  used  to  select sites  and-  to verify
overall  land  treatment  suitability.   However,  the level of
effort  needed  to  conduct  site  investigations  in  smaller
communities  is much lower.   In smaller  communities,  it is
more  practical to  conduct minimal  field investigations and
assume  relatively  conservative  design  criteria   than  to
complete  the  extensive  and expensive investigations needed
to pinpoint optimal design criteria.

Generally,  soils  information  available  from the  area SCS
office and  limited  field  observations will yield  sufficient
information  for most SR  and  OF system  designs.   The  first
step  in  the  site investigation procedure should be  to  visit
the  potential   site  with  a local  SCS representative.   The
primary purpose of  these  site  visits is to confirm  the data
used  to identify and select suitable  sites.   A few,  shallow,
hand-auger  borings  to  identify  the  soil  profile  should be
conducted to confirm  the  SCS  data and check  for impermeable
layers  or  shallow  ground  water.     Infiltraton  tests   (see
Section 3.4.1)  are  usually only needed for RI sites.  For RI
sites, a  few backhoe pits to  3m  (10 ft)  or more are also
recommended,  but  drill  holes  are  usually  deferred   until
preliminary design.

If crops  will  be grown,  a site visit with the county  agent
or  local  agricultural  or forestry  advisor  is recommended.
The  purpose  of  this site visit is  to obtain advice on the
type  of crops  to use and  on crop management practices.,
                             7-8

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7.3   Facility Design

Because only  limited  field  investigations  are  conducted  in
small .communities,   it  is  important   to   use  conservative
design  criteria.     The  application  schedules   and  storage
requirements   presented   in   Table   7-2   are   examples   of
conservative  criteria.   Other design criteria  that  must  be
identified  include  the   level  and   type  of  preapplication
treatment  and  storage,  the land  area  required, wastewater
loading rates  and  schedules,  and  pumping  needs  and  other
mechanical  details.    Land area  requirements are  estimated
during the  planning process and are  refined  as the  hydraulic
loading  rate,  method   of  preapplication   treatment,  and
storage requirements  are defined more precisely.  ,
     7.3.1
Preapplication Treatment and  Storage
EPA  guidance on minimum  levels  of preapplication  treatment
is summarized in Table 7-4.

                             TABLE  7-4
                       RECOMMENDED LEVEL OF
                    PREAPPLICATION TREATMENT
 Type of land
   treatment
     Situation
    Recommended
preapplication treatment
 Slow rate    Isolated location; restricted public
            access; crops not for human consumption.
            Controlled agricultural irrigation;
            crops not to be eaten raw by humans.

            Public access areas such as parks,
            golf courses.
 Rapid       Isolated location; restricted public
 infiltration  access.
            Urban location; controlled public
            access.

 Overland flow Isolated site; no public access.
            Urban location; no public access.
                           Primary.


                           Biological (ponds or in-plant
                           processes) with control of fecal
                           coliforms to <1,000 MPN/100 mL.

                           Biological (ponds or in-plant
                           processes) with disinfection to
                           log mean fecal coliforms of
                           -200 MPN/100 mL.

                           Prim'ary.


                           Biological (ponds or.in-plant
                           processes).

                           Screening or comminution.

                           Screening or comminution with
                           aeration to control odors during
                           storage or application.
In  small  communities,  ponds  are  usually  the  most  practical
form  of  preapplication   treatment  and  storage.    They  are
relatively  easy to  operate,  require  minimal  maintenance, are
less expensive  than  many  types  of  treatment,  and  eliminate
the  need  for  separate  storage  facilities.    Although  some
communities  will  want  to  use  or  upgrade  other  existing
                                 7-9

-------
 facilities  for use  as preapplication  treatment facilities,
 many  small  communities will1 find  it advantageous to convert
 to  pond systems  because of  their  consistency, reliability,
 flexibility,  ease of operation and maintenance, and cost.

 Generally,  ponds  are constructed  with one  to three cells.
 In  a  three-cell system, the  first  cell is usually small and
 may  be  aerated  to   control   odors.     Alternatively,   if
 sufficient  land is available, the  first cell may be designed
 as   a  facultative   cell   with  a   BOD   loading  of  about
 120 kg/ha-d  (107 Ib/acre-d).   The water  level in this cell
 is  usually  constant and can be controlled with an adjustable
 overflow  weir  or  a gated manhole.   The  final  cells  can be
 used  for storage  and flow  equalization.    For this reason,
 these  two  cells  are made  as  deep as  possible.   Typical
 design  parameters for  several  types of ponds  are presented
 in  Table 7-5.

                          TABLE  7-5
            TYPICAL DESIGN PARAMETERS FOR  SEVERAL
                      TYPES  OF PONDS [2]


                           Aerobic  Facultative  Anaerobic
Pond size (individual
cells) , ha
Detention time, d
Depth , m
BOD5 loading, kg/ha-d
BOD 5 removed, %
Effluent suspended
solids , mg/L
<4
10-40
1-1.5
40-120
80-95
80-140
1-4
7-30
1-2.5
15-200
80-95
40-100
0.2-1
20-50
2.5-5
200-500
50-85
80-160
         1 ha = 2.47 acres
         1 m = 3.28 ft
         1 kg/ha-d = 0.893 Ib/acre-d
An  additional  benefit  of.  using  ponds  is   that  the  long
detention  times  (30 days  or  more) promote nitrogen  removal
and pathogen inactivation.   Preliminary models  to  estimate
nitrogen  and  bacterial   removals  in  ponds  are  given  in
Section 4.4.1.
    7.3.2
Hydraulic Loading Rates
The  first  step in  designing the  land  treatment  portion  of
the  system is  to  select  a  hydraulic loading  rate.    As  an
initial assumption, the  hydraulic  loading  rate  for SR and  RI
                             7-10

-------
systems  is  based  on  the  most  limiting  SCS  permeability
classification of the soils at the selected site.  Hydraulic
loading rates  that may be  used  in each  of the three major
types  of   land  treatment  systems have   been  plotted  as a
function of  SCS permeability  classification  in Figures  7-2
and 7-3.   Both figures represent  average hydraulic  loading
rates.  In Figures 7-2  and  7-3,  whenever a range of  loading
rates  is given, the lower  end of the range  should be used
for primary  effluents,  the  mid zone  for pond effluents,  and'
the  upper  portion of  the  range  for  secondary  effluent.
Lower loading rates than shown in Figures 7-2 and 7-3 can be
used  but will  require  more land.   If OF  is  used  to polish
trickling filter or activated  sludge effluent,  loading rates
of 30 to 40 cm/wk (12 to 16 in./wk) can be  used.

Loading rates  at SR and  RI systems  that overlie  potential
drinking water  aquifers  may be  limited  by nitrogen  loading
rather than soil permeability.  At these  systems, the ground
water  concentration  of  nitrate  is  limited  to 10  mg/L as'
nitrogen at  the  project  boundary (or the background  nitrate
concentration,  if  it   is   greater  than  10  mg/L).    Rapid
infiltration  systems  should  not be  located  above drinking
water aquifers unless thorough field testing  is conducted to
verify that  the nitrate standard  can be met or unl'ess  the
renovated  water  will  be   recovered   (Sections   5.4.3.1
and 5.7).
    7.3.2.1
Slow Rate
For  SR systems .located  above drinking  water aquifers,  the
following equation  should  be used  to  calculate the maximum
allowable nitrogen loading rate based on nitrogen limits:
where  L.
        'w(n)
          Pr

          ET

           U
                         Cp(Pr - ET) + 10U
                 Lw(n) =  (1 - f)(Cn - Cp)
                                         (7-1)
   wastewater hydraulic loading rate based
   on nitrogen limits, cm/yr (in./yr)

   percolate nitrogen concentration,
   mg/L = 10 mg/L

   precipitation rate, cm/yr (in./yr)

   evapotranspiration rate, cm/yr (in./yr)

   crop nitrogen uptake rate, kg/ha-yr
   (Ib/acre-yr)
                             7-11

-------
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           CLEAR WATER PERMEABILITY OF MOST  LIMITING SOIL LAYER
i n./h
cm/h
< 2.0
< 5.1
2-6
5.1-15
6-20
15-51
>20
>51
                        FIGURE 7-3
TYPICAL  ANNUAL HYDRAULIC LOADING RITE OF SMALL Rl SYSTEMS
                            7-13

-------
            f  =  fraction of applied  nitrogen removed
                  by volatilizaton, denitrification, and
                  storage =0.15

           :n  =  nitrogen concentration  in applied
                  wastewater, mg/L
Conservative values should be  assumed  for  nitrogen  losses
and  crop uptake  rates  to ensure  adequate  nitrogen removal.
For  this reason, nitrogen storage and  ammonia volatilization
are  ignored in  Equation  7-1 and the denitrification rate  is
assumed  to  equal 15% of the nitrogen loading rate.  Nitrogen
losses during preapplication treatment depend on the type  of
treatment.   For conventional primary or  secondary treatment,
nitrogen loss is negligible.   As discussed  in Section  4.4.1,
the   nitrogen   loss  in   a  pond   can  be   estimated   from
Equation 4-1.

Conservative  nitrogen   uptake   values  are  -presented   for
typical  crops in Table  7-6.

                           TABLE  7-6
          NITROGEN  UPTAKE RATES  FOR  SELECTED  CROPSa
                     Crop
Nitrogen uptake
rate, kg/ha-yr
                Forage

                 Alfalfa                300
                 Bromegrass              130
                 Coastal bermudagrass      400
                 Kentucky bluegrass       200
                 Quackgrass              240
                 Reed canarygrass         340
                 Ryegrass               200
                 Sweet clover            180
                 Tall fescue             160
Field
Barley
Corn
Cotton
Milomaize (sorghum)
Potatoes
Soybeans
Wheat

70
180
80
90
230
110
60
               a.  Values represent lower end of ranges
                   presented in Table 4-12 and are
                   intended for use in Equation 7-1.
               1 kg/ha-d = 0-. 893 lb/acre-d
                              7-m

-------
The  calculated value  from  Equation 7-1  of  Lw(n)  ^-s  tnen
divided  by  the  number  of  weeks  per  year  or   expected
operation  and  compared  with  the  hydraulic  loading  rate
obtained from Figure 7-2. At this  point, the  engineer  should
check  with  the  local  agricultural  or forestry  adviser  to
verify  that  the selected  crop  is tolerant  of the  lower  of
the  two  calculated  loading rates.   If  so,  the lower  of  the
two  loading  rates should  be used for  design purposes.   If
the selected crop cannot tolerate  the design  loading rate,  a
crop  with  higher  moisture  tolerance or   nitrogen  uptake
should be selected.

In small communities, the application schedules presented  in
Table  7-2  are  recommended.   Again,  if a  farmer agrees  to
take and use the wastewater on his own  land,  he may  continue
to use any application schedule that has resulted  in a well-
managed agricultural system.

         7.3.2.2   Rapid Infiltration

Hydraulic  loading   rates   for   small  RI  systems  can   be
estimated using Figure 7-3.   The permeability  of  the  most
restricting soil  layer in the  soil  profile can be  measured
using  techniques  described in Section  3.4.   In  Figure 7-3,
the lower curve should be used when primary or pond  effluent
is  to  be  applied,   and  the  upper curve  can be  used  when
secondary effluent is to be applied.
         7.3.2.3
          Overland Flow
The  hydraulic loading  rates for  small OF  systems  are  the
same  as  recommended  in  Chapter 6,  Table 6-5.   Because  of
operational  considerations,  it  is recommended  that  either
8 or 12 h/d  application  periods be  used,  whichever is most
convenient.    Simple  automation  using  time  switches   and
solenoid valves  allows  flexibility in  selecting application
periods.
    7.3.3
     Land Area Requirements
Once  the hydraulic  loading rate  has been  determined,  the
amount   of   land   required  for  land   treatment  can   be
calculated.   For systems that  operate  year-round, the  land
required  is  simply  the   design  average  wastewater   flow
divided  by  the  annual hydraulic  loading  rate.  For systems
that  are  not  operated  year-round,  the  area  required  is
calculated as follows:
    A =
   Q(365)(100)
(Lw)(t)(10,000)
(Metric units)
(7-2)
                             7-15

-------
    A =
               Q(365)(100)
         (Lw)(t)(7.48)(43,560)
                        (U.S. customary units)
where  A =

       Q =


      Lw "


       t =
area required, ha (acres)

design average wastewater flow, m^/d
 (gal/d)

hydraulic loading rate, cm/wk (in./wk)
(see Section 7.3.2)

number of weeks per year during which
wastewater is applied
For  example,  if  a  system is  operated  43 weeks  out of the
year,  the  acceptable  hydraulic loading  rate is  5»8 cm/wk
(2.3  in./wk),  and  the  design  average  wastewater  flow  is
900 m3/d (240,000   gal/d),   the  area   required   for   land
treatment is:
                    A =
             (Q)(365)(100)
             Lw)(t)(10,000)

          =     (900)(365)
            (5,8)(43)(10,000)

          = 13.2 ha (32.5 acres)
Additional  land is  required for  preapplication treatment,
storage,  access roads, and  in  some cases  buffer  zones.   A
preliminary  allowance of  15 to  20% of  the field  area  is
often made  for  roads, buffer zones, and small unusable land
areas.   Land requirements  for  preapplication treatment and
storage  are determined in  the  preliminary  design  of these
components.
    7.3.4
  Distribution Systems
Detailed information on SR distribution systems is presented
in  Section  4.7 and  Appendix E.   Additional considerations
for small communities are presented in this section.

Distribution methods  are  selected on  the  basis of terrain,
type of land treatment system, and local practice.  In small
communities, it  is  prudent to choose  a  distribution method
that  is  used locally or  that will result  in  a system that
requires only part-time operational attention.  If a locally
                             7-16

-------
used  distribution  method   is  selected,  any  specialized
equipment  and  necessary  expertise  will  be  more  readily
available.

Traveling guns  require  relatively high amounts of labor and
are  more adaptable   to  systems  where  several,  odd-shaped
fields are  irrigated  each  season, so they are usually owned
and operated  by a local farmer.   Both solid  set and center
pivot  irrigation  systems  can  be  adapted  to  either  muni-
cipally  owned  or farmer  owned  small  irrigation  systems.
Center  pivots  will  generally  not  be applicable  for  very
small SR systems  (below 16 ha or  40  acres).

Distribution  systems  for Rl  and OF  facilities are described
in Sections 5.6.1 and 6.6,  respectively.

7.4  Typical Small Community Systems

To  illustrate  some  of  the   features of  small  scale  land
treatment systems,  four cases are  described  in  this  sec-
tion.   These  include two SR options,  one RI, and  one OF
system.   It is not intended  that the site  specific criteria
for these four systems be applied  for process design else-
where.   The concepts  will  be valid,  but specific criteria
will depend on  individual site characteristics.

    7.4.1      Slow Rate Forage System

         7.4.1.1   Introduction

A  pond  system  using  SR application  of  wastewater  onto
several grassed plots is often a  workable design for a small
community that does  not generate sufficient wastewater flow
to be economically beneficial  for irrigating a cash crop.

         7.4.1.2   Population

The  community, located  in  eastern  Nebraska,  has  a present
population  of  approximately  300.   The design population for
the treatment  facility is 310.
         7.4.1.3
Flow
The  flow  to  the  treatment  facility  is  strictly domestic
wastewater,   because  there   are   no   industries  in  the
community.   The system is  designed  to treat an average per
capita  flow of  0.25 m3/d  (65 gal/d),  or a  total  flow of
76 m3/d  (20,000  gal/d).    Low  per  capita  flows  are very
common  for  small communities  having no  industries and very
minimal  commercial  development.   Actual flows to  the  system
have  gradually   increased  as  residents  switched  from  their
                             7-17

-------
old   septic  tank   systems   to  the  municipal   collection
system.   Flows  are  commonly in the 57 to 95 m3/d  (15,000  to
25,000 gal/d) range.
         7.4.1.4
Climate
The  normal  annual precipitation is 84 cm/yr  (33  in./yr)  and
the  average  annual  gross  lake  evaporation  is  109  cm/yr
(43  in./yr).   The mean  number  of  days in which  the  maximum
daily  temperature exceeds 32 °C (90 °F) is 40, and the mean
number  of  days in which the minimum daily temperature  falls
below  0 °C  (32 °F)  is  130.   In an  average  year, there  are
232  days between  the  last killing  frost  in  the spring  and
the  first frost in  the  fall.
         7.4.1.5
Site Characteristics
The silt loam soils at the proposed  treatment  site  are  deep,
nearly level, and well drained.   Surface  soils are  silt loam
and  the  subsoils  are  silty  clay  loam.    Permeability  is
moderately  slow in the  1.0  to 1.5  cm/h  (0.4  to 0.6 in./h)
range. • The  site  is  relatively level and does not  overlie  a
potable aquifer.

         7.4.1.6   Treatment Facility Design

The treatment  facility consists  of  a  single  cell  unaerated
pond  followed  by  a  series   of  four  grassed  plots   which
receive  wastewater   from  the   pond.     Effluent  is  not
disinfected.   The pond  provides  both  wastewater  treatment
and storage.   The  degree of treatment  in the  pond is  not  a
significant  factor in design,  other than providing at  least
the necessary primary treatment for removal of heavy solids
and rags  that  could   plug distribution  piping.  The storage
volume facilitates operation  of the system, since  it is not
necessary  to  have  an  overflow  during  periods   of   heavy
precipitation  or  other  unfavorable   conditions,  and the
grassed plots can  be  allowed  to dry between applications  to
allow mowing and  maintenance.   The design  information  is
summarized in-  Table  7-7.   ;

The single cell pond  is sized  similarly to  the  first cell  of
a  conventional  facultative  pond  system.   The  design BOD
loading is  34  kg/ha:d (31 lb/acre:d),  a generally accepted
loading rate in Nebraska, and  results  in minimal  septicity
or  blue-green  algae  problems.    Higher  loadings may  be
allowed  by  other  states where  ponds  do  not become ice
covered  in  the winter.   By   having  a  1.8  m   (6  ft)   water
depth, 1.2 m (4 ft)  of storage volume is provided  above the
0.6 m (2 ft) water level.   The storage  volume  in the 0.7  ha
(1.7  acre)  pond  is   7,378 m3   (1.95 Mgal)  above  the  0.6  m
                             7-18

-------
(2 ft)  depth.    This  capacity  provides  adequate  storage
during  the  approximately  133  days  (19  weeks)  each  winter
that  the  plots are  not irrigated,  based on the  design flow
and seepage  losses  of 0.3 cm (0.125 in.)  per day.

                           TABLE  7-7
              .        DESIGN INFORMATION
                        FOR SR SYSTEM
                Design flow,  rfr/d

                BOD loading,  kg/d
                Design population
                Treatment pond

                  Size, ha
                  Depth, m
                  Capacity above 0.6m level,

                Bermed grassed plots
                  Number
                  Size (each), ha
                       m-
76

24

310


0.7

1.8

7,378


4

0.35
The  total  size  of  the  grassed  plots  was  determined  as
follows.   Calculated design  losses from  the  pond,  including
seepage   and   net  evapotranspiration,   totaled   142  cm/yr
(56 in./yr).   Using this value, the design  overflow from the
pond (Q0) was  calculated:          •   ,   •.
Q0 = (76 m3/d x  365  d/yr)
   - (142 cm/yr  x  1  m/100  cm x 7,000 m2

   =-17,800 m3/yr  (4.7,Mgal/yr)
                                                         (7-3)
Using   the   limiting   soil   permeability   of   l.Q   cm/h
(0.4 in./h) ,   a   hydraulic   loading  rate   of   3.8   cm/wk
(1.5 in-./wk)  was obtained  from Figure  7-2.   Next,  the area
required  for  SR was calculated (Equation  7-4):


            A  =  [(17,800 m3)/(3.8 cm/wk  x  33 wk)]        (7-4)

              x  (100 cm/m)  x (ha/10,000 m2)

              =  1.4 ha (3.5 acres)

Four grassed  plots, each 0.35 ha (0.88  acre) were designed.
     t
Multiple  small  plots  were  selected  for  several  reasons.
Each  plot  is small  enough to  facilitate  uniform flooding.
                              7-19

-------
 Also,  the use  of multiple plots  makes it possible  for the
 operator  to  mow or  make repairs  on a dry  plot while the
 other  plots  are being used for wastewater  application.

 Any  one plot does not receive more  water  than  can percolate
 within 12 hours.   This  helps prevent  damage  to the  grass
 cover  and  also  provides  some  leeway in case precipitation is
 received  after  a cell  has  been  flooded.    Ignoring  evapo-
 transpiration,  the  limiting  soil  permeability rate of 1.0
 cm/h (0.4  in./h)  dictates that not more than  12 cm (4»7 in.)
 can  be applied  per  each  1 day application  period.   To obtain
 an average hydraulic  loading  rate  ,of 3.8 cm/wk  (1.5  in./wk),
 each  application  period  must be  followed  by 21  days  of
 drying.   in  practice, one plot is flooded  on each of  4 con-
 secutive  days.   After   an  additional  18  days  of  drying,
 flooding  is  resumed.  This  sequence continues  for  approxi-
 mately 232  days.    During   the  winter  (approximately  133
 days), all wastewater is  stored•in the pond.

 The  overflow  control  structure  designed  for  this  system
 requires minimal  operator attention.   The  structure  uses an
 overflow pipe that  can be raised or  lowered in  increments to
 release the  necessary volume  of  effluent.   A  cross-sectional
 detail of the structure  is included  in Figure 7-4.

 The  grassed  plots  are   quite  shallow, having only  0.6 m
 (2 ft)  high  dikes.    The  slopes are  4:1,  making  the  basins
 readily accessible  to mowing equipment.  This  design  helped
 minimize  the   amount  of  earthwork  necessary   during   con-
 struction and also maximized  the amount of  usable  area  since
 less dike  area was required.   Local SCS offices  and publi-
 cations were consulted  to obtain  the  necessary information
 for  selecting a seeding mixture, which  needed to be  suitable
 for  periodic  flooding.    A  mixture  of  Reed   canarygrass,
 switchgrass,   redtop,   and    intermediate   wheatgrass   was
 planted.                           •

 Effluent distribution to the grassed plots is  by  gated  pipe
 along  the  toe  of the inner slope  of  one side.   This allows
more uniform flooding of  the  basin  as compared to a single
 inlet  structure ^    The   area  under   the  pipe  and  in  the
direction  of flow  from  the  pipe  has  a  layer of  rock  to
minimize erosion and  channelization of  the  flow.
                            7-2Q

-------
     TWIST LINK
    MACHINE CHAIN
     REINFORCED
     CONCRETE PIPE
   CONCRETE FILLET
                                                SHEAR GATES
                                                CAST IRON
                                                PIPE RISER
                         FIGURE  7-4
               OVERFLOW  CONTROL  STRUCTURE FOR
                 POND DISCHARGE  TO SR  SYSTEM
         7.4.1.7
Performance
When the facility  was first started up, flows were quite  low
until  all  of  the  residences  were  connected.   The pond
provided  complete  retention of  all flows  during the  first
2 years  of  operation,   with  no  overflow  to   the   grassed
plots.  In  the  third year, only two application  periods were
used:    one in the spring and one  in  the fall.  The number
of  applications per year  has  been gradually increasing  as
flows  have approached  the  anticipated design  loadings.    A
good  stand of grass has been  maintained  in  the  application
plots.   This  grass  cover enhances infiltration  and  provides
maximum evapotranspiration of the wastewater  applied.

         7.4.1.8    Staffing

The  system requires  only one part-time operator.  Duties at
the  pond  include mowing,  valve operation, weed  control,  and
maintenance of  fences, access road, valves,  and  distribution
piping.
                              7-21

-------
     7.4.2      Slow Rate Forest System

          7.4.2.1   Introduction

 This forested  SR  system  is  located at  Kennett Square  in
 southeastern  Pennsylvania.    The  system, consisting  of  a
 series  of  treatment ponds  followed  by sprinkler application,
 has  been  operated since  1973.    The  system  serves  two
 retirement communities  and  is  operated  by  the  wastewater
 authority.

          7.4.2.2   Population and Flow

 The  population  of  the  two  communities totals  725.  The  flow,
 which is  entirely  domestic  wastewater,  is  currently  189 mP/d
 (50,000 gal/d).  The design flow  is 265  m3/d  (70,000 gal/d).
          7.4.2.3
Climate
Precipitation  and evaporation are nearly equal with  average
annual  precipitation at 110  cm  (43  in.) and average  annual
pan  evaporation estimated  to be 120  cm (47 in.).   Average
annual  temperature  is  11.9  °C (53.4  °F).

         7.4.2.4    Site  Characteristics

The  application  area  is  covered  with  a  native  stand  of
beech,  maple,  poplar,  and  oak trees.   The soils are  basi-
cally  silt  loams with predominant  slopes  between 3 and  8%.
Soils are moderately deep and permeable  with  slightly  acidic
pH values.  The soil permeability of  1.5 to  5 cm/h (0.6  to 2
in./h)  would support a loading rate of 5 cm/wk  (2  in./wk)  or
more on a hydraulic  loading basis (Figure 7-2).

         7.4.2.5    Treatment  Facility  Design

The   layout  of   treatment  facilities  is   presented   in
Figure  7-5; photographs  of  the treatment pond and sprinkler
application are  shown  in Figure  7-6.   Wastewater  is treated
in  three  treatment  ponds,  disinfected,   and  applied   via
sprinklers  onto  3.24  ha   (8  acres).   The  first  pond  is
aerated, covers  a surface area  of 0.128 ha (0..3  acre),  and
is  4  m  (13 ft)  deep.    Aeration  is  provided  by a  7.5  kW
(10 hp) floating  surface aerator.   Wastewater then flows  by
gravity through  two nonaerated ponds  that  are  2.1 m  (7  ft)
and 2.4 m   (8  ft)  deep  and cover  0.68 ha  (1.69  acres)  and
0.30 ha (0.75  acre), respectively.    Total  detention  in  the
three ponds is 80 d  at current flows.
                            7-22

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          -ICrt  0,3
                                          LU

                                          I—

                                          CO
                                          ce
                                          oo
7-23

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                  TREATMENT POND
  SPRINKLER APPLICATION IN EXISTING HARDWOOD FOREST

                     FIGURE 7-6
SR FACILITIES AT  KENNETT SQUARE, PENNSYLVANIA
                      7-24

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The design  hydraulic loading rate  is  5.1 cm/wk (2  in./wk),
which is  the  State  of Pennsylvania guideline.  The  nitrogen
loading is 279 kg/ha-yr  (248 lb/acre-yr)  for  the design  flow
which  is  somewhat  high  for  application  to an   existing
hardwood  forest.    Because  of the  relatively mild  climate,
year-round application was planned.

The application  area is  divided  into 14  separate  areas or
plots.  Wastewater  is applied for  24  hours  on 4  to 6 plots
each day, 5 days  per week.   On this schedule, an individual
plot  receives  effluent  every  fourth  day.   Storage   for
weekends  and  cold   weather  is  possible  in  the   treatment
ponds.   The main lines  and laterals  are buried  with drain
valves to drain the  lines after applications  are complete.

A buffer  zone of approximately 46  to 61 m  (150 to 200  ft) is
maintained  between  the   application   site  and  the nearest
residence.  This  area is covered  with grass  and trees.   All
stormwater  runoff  from  the  community  is diverted around  the
site.   Stormwater  generated onsite  is  allowed  to run  off
onto adjacent  land.   Site access is controlled by  signs  and
fencing;  however,  there  are some  nature  trails in  the  area
to which  access is permitted.

          7.4.2.6   Operation and Performance

The system  has operated  satisfactorily for 8 years.   During
winter   operation,    sprinkling   is   practiced   until   the
temperature drops  to -6.7 °C (20 °F).  Frost heave problems
have  affected  valve boxes placed  in  the forest.    Screening
of the applied water is  needed to  avoid nozzle clogging  from
debris that falls into the ponds.

Treatment performance of  the system  can be measured  using
the  ground water  monitoring  wells.    The  depth   to  ground
water  varies  from  3.6  to  9.1 m   (12 to  30  ft)  in  the 11
monitoring  wells.   The   range  of  nitrate  nitrogen concen-
trations  is from 0  to 4.8 mg/L  and   indicates satisfactory
performance,   in  spite   of   the   relatively  high   nitrogen
loading  (Section  7.4.2.5).

          7.4.2.7    Staffing  and Budget

One  operator  spends  approximately 6  h/d,  5 d/wk  operating
and  maintaining the  wastewater  treatment  system.   Of  this
total,  2  h/d  is  associated with the  SR  land  treatment
system.

A  total  of $15,000/yr  is budgeted  for  operation  and  main-
tenance  of  the system.   Of  this  total,  37%  or $4,070/yr is
associated  with  land treatment.
                             7-25

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     7.4.3      Rapid Infiltration

          7.4.3.1    Introduction

 An RI system for a small community  need  not  be  designed for
 intensive  wastewater  applications at maximum  RI  rates,  which
 could involve  the  need for  recovery of renovated water  and a
 relatively high level of operation and management.   Instead,
 the  design  can be  simplified  to  meet  the  objectives  of
 wastewater treatment  and still maintain ease of  operation.
 The  following example  illustrates  an adaptation  of an  RI
 system that normally  operates  at very low application rates,
 but  has the  capability of  treating the  exceptionally  high
 flows  that occur occasionally.

         7.4.3.2    Population

 The  facility serves the small,  rural community of  Chapman  in
 east central Nebraska..  The  community  is  primarily  resi-
 dential, with  a small  commercial  district,  but with no in-
 dustries.   The present population  is estimated to  be  400.
         7.4.3.3
                    Flow
The  treatment pond  was designed  to serve  a population  of
500.  When the treatment facility was designed,  there  was  no
past  history  of  wastewater  flows  and  an average per  capita
contribution  of  0.26 m3/d  (70  gal/d), or  total  flow  of
132.5 mj/d  (35,000  gal/d),  was assumed.  Actual dry-weather
flows  have  averaged  approximately 66  m3/d  (17,400 gal/d).
This   flow  amounts  to  less  than  0.19  m-3 /capita* d   (50
gal/capita-d), but  is typical for this  type of small, rural
community where average water  use is low.  The fact  that  the
town  does not  have  a municipal  water system  is  another
reason that water use and wastewater flows are very  low.

In contrast to  the low average  dry-weather  flows,  however,
are very  high peak  flows  during periods when  parts of  the
collection  system  are  subject  to  infiltration  from high
ground wate.r  elevations.   Peak flows have ranged to as high
                                                         The
as  1,341 m-Vd  (354,400  gal/d)  on  a monthly  average.
peak  flows  are sustained, and  have  in  the past stayed  high
for as  long as 6  months  at a  time.   This is a significant
factor  affecting  a treatment facility since the pond system
must  handle,  at times,  flows ranging from 2 to 10 times  the
design  average flow.

         7.4.3.4   Climate

The normal  annual precipitation is 63.5  cm/yr  (25 in./yr)
and the average annual gross lake evaporation  is 114.3 cm/yr
                            7-26

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(45 in./yr).   There  are 45 days per year when maximum  daily
temperatures  exceed  32  °C  (90  °F)  and  150 days  when  the
minimum temperature  is  below 0 °C (32 °F).  The mean length
of the frost-free period in  the area is 160  days.

         7.4.3.5   Site Characteristics

Soils  in  the  area formed in alluvium on river bottom lands,
and  the  topography  is  relatively flat.   At the pond  site,
the  predominant  soil  type   is  a  moderately  deep, nearly
level,  somewhat  poorly drained  loam  formed  in  calcareous
loamy  alluvium.   The  depth  to the  water table ranges from
0.6  to 1.2  m  (2 to  4 ft).   The  loam  surface  layer  and
subsoil have  moderate permeability  of  1.5  to 5.1 cm/h (0.6
to 2.0 in./h).  The  underlying gravelly sand, which  is  found
51 to 102 cm  (20  to 40 in.)  below  the ground  surface,  has
very  rapid permeability of over 51 cm/h (20  in./h).

          7.4.3.6   Treatment Facility  Design and
                   Performance

The  treatment  facility  includes a  pond  and   a  single  RI
basin;  design criteria  for  these facilities are  summarized
in Table  7-8.   The pond consists of two  cells,  one  having a
suface area  of  0.7 ha  (1.8  acres)  and  the  other  having
0.4  ha (1.0  acre).   The maximum water  depth of  the  cells is
1.5 m (5.0  ft).     Dikes  around  the  pond  have an  overall
height of  2.4  m (8  ft).  The soils  at the bottom of  the pond
were  medium  and fine sands.   Bentonite was added at  the rate
of  4.5 kg/m2  (20 tons/acre)  to  the  bottom of the pond to
limit seepage  to  less than 0.64 cm/d (0.25 in./d).

                           TABLE 7-8
           DESIGN  INFORMATION FOR CHAPMAN  RI SYSTEM
Design flow, m /d
BOD loading, kg/d
Year built
Design population
Pond cell No. 1
Surface area, ha
Depth, m 3
Capacity above drawoff level, m
Pond cell No. 2
Surface area, ha
Depth, m 3
Capacity above drawoff level, m
Total detention time above drawoff
level at design flow, d
Infiltration basin size, ha
Hydraulic loading rate at design flow, m/yr
132.5
45
1965
500

0.7
1.5
6,190

0.4
1.5
3,160

70
0.6
5
                              7-27

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 The design  of  the pond  is  such that  the two cells  can be
 operated either in series or parallel.   The overflow control
 box can be adjusted so that the water level in either of the
 cells  can  be  drawn down  or set for constant  overflow from
 one or both cells.   Water  is  drawn from the  pond  cells at
 the 0.6 m (2 ft)  depth.

 The normal operating  sequence for the system has been series
 flow through the  two  cells when the pond is not ice covered,
 with a constant  overflow from the  second cell  in  series to
 the infiltration  basin.    During the  winter  when  the  pond
 cells  are ice  covered, operation is switched  to  parallel to
 spread  the  incoming  load  over  the maximum  surface  area.
 This results in a shorter recovery  period in the spring when
 the ice cover melts  and  the cells  go  from  the  anaerobic to
 the aerobic state.   There is normally  some overflow  to the
 infiltration basin during the  winter.   At  the  design flow,
 the net ..yearly overflow  to  the infiltration basin  v/ould be
 29,300  m^ (7,444,000  gal).

 The two pond cells are  followed by  a  single  RI basin.   To
 take advantage  of the higher permeability of  the-underlying
 soil materials,  the  top  0.9 m  (3 ft)  of RI basin  soil was
 stripped  during  basin construction.    However,  the  design
 hydraulic  loading rate was  limited  to  5.0 m/yr  (16.4  ft/yr)
 to  simplify  basin  operation.   A  basin  area  of  0.6  ha
 (1.4 acres)  was necessary to  allow  the design loading  rate
 at  the  design  pond overflow rate.    Following  construction,
 the basin was  seeded  with a mixture  of  Reed canarygrciss and
 bromegrass.    A  grass  cover  has been maintained  to  help
 preserve  the soil's permeability.

 Currently,  the  average influent  flow is  approximately  half
 the  design  flow  (Table  7-9)  and  the  net  overflow to  the
 infiltration   basin   averages   5,150    m3/yr    (1,360,000
 gal/yr).   The  resulting  hydraulic  loading rate is  0.9  m/yr
 (2.9 ft/yr).   However, during periods  of  heavy  infiltration
 into the collection system,  the  average  daily  flow  to  the RI
 basin  is  1,375 m3/d   (350,000  gal/d).    This   results   in  a
 periodic hydraulic loading rate  of 22.6  cm/d (8.9  in./d),  or
 82.5 m/yr  (271 ft/yr) expressed  as an annual rate.   Although
 this temporary  rate  is well below the measured soil permea-
 bility of  at least 51 cm/h (20  in./h),  it  exceeds the  recom-
mended loading shown  in Figure  7-2 somewhat.
                             7-28

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                          TABLE 7-9
            WASTEWATER FLOWS TO CHAPMAN  RI  SYSTEM
                             m3/d

                                     Monthly  flows
Year
1974
Jan-Jun
Jul-Dec
1976
1977
1979a
Avg daily flow

870.6
63.0
65.5
65.9
8.6.3
Minimum

292
55.1
58.7
60.2
71.9
Maximum

1,341
79.0
82.1
78.3
132.1
              a.  During the months of May, June, and July,
                 flows were above normal and were in the
                 122-132 m-Vd range.  This corresponded to
                 a period of high ground water elevations.
Although  the  design  and  actual  average  hydraulic  loading
rates are considerably lower than the range  of  50  to 60 m/yr
(165  to  200 ft/yr)  recommended in Figure  7-2,  the  use  of  a
lower rate  was  advantageous for several reasons,  including:

    •    A  grass cover  can be  maintained  in  the bottom  of
         the basin  to help preserve soil permeabiity.

    •    The   treatment  facility  is  able  to  treat  peak
         wastewater flows that greatly exceed design average
         flows.

         7.4.3.7   Ground Water Quality

Since  high  ground  water levels  are typical of the  area  in
which  the  treatment  facility  is located,  the performance  of
the facility in terms of possible ground water  contamination
is  an  important  consideration.     The  pond  has  been  in
operation  for  15 years,  so  there  has been adequate  time for
possible  water  quality  changes caused  by pond operation  to
have  been detected.  The data indicate that  the facility has
not  caused  increased  ground  water  levels of nitrates  or
chlorides   that  could   be   associated   with   wast.ewater
discharges.

         7.4.3.8   Costs and Staffing

The  total  cost for  constructing the  collection  system and
treatment   ponds  in  1965  was  $110,958.    The  treatment
facility portion of the total amounted to  $40,520.
                              7-29

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 The  entire  system  has  been  operated  by  one  part-time
 operator whose  duties  include maintenance  of three pumping
 stations   in   the  collection  system   and  operation  and
 maintenance  at  the  pond  site.     Work at  the  treatment
 facilities  consists  of  operating   valves,   mowing,  weed
 control around  the  edge  of  the water in  the  pond cells and
 in  the  RI  basin,  and  maintenance  of  access  road  and
 fences.   Since  there  is no  surface discharge  of  effluent
 from the facility,  laboratory testing of water  quality has
 not been required.
     7.4.4
Overland Flow
          7.4.4.1
     Introduction
 A smal^L,  full-scale  OF  system  is operating  at  Carbondale,
 Illinois,   treating  pond  effluent.     The  wastewater  is
 domestic in nature and  generated at the 54  unit Cedar Lane
 Trailer  Court.   The  population  of  135 has  been relatively
 stable  since construction in  the  1950s.  Wastewater flow is
 38 mj/d  (10,000  gal/d).

 Prior  to 1976,  wastewater was  treated  using a  septic tank
 followed by  a  0.28  ha  (0.7  acre)  stabilization  pond  and
 surface  water discharge.    Effluent  from  the pond did  not
 meet   Illinois   intermittent   stream  requirements,   which
 include  a  1.5  mg/L  ammonia  nitrogen  limit on  the  dis-
 charge.    An  upgrading  of  the  treatment,  therefore,  was
 required.

         7.4.4.2   Site  Characteristics

 The terrain is rolling and the grass covered  site,  which is
 near the pond, has slopes ranging  from 7 to  12%.   The soil
 is fine  granular  glaciated  material  with  low permeability.
 A section  of the slope"  10 m  (30 ft)  wide  and 60 m  (200  ft)
 long (downslope)  was used.

         7.4.4.3    Treatment Facility Design

 The hydraulic  loading  rate is 44 cm/wk (17.3  in./wk),  which
 is higher  than  recommended  in Figure 7-2.    The  first. 30 m
 (100 ft)  of slope  is  at  7% grade and  the  last  30  m  is  at
 12%.    The  pond  effluent  is  pumped to  the  top of the  slope
 and applied  uniformly  across the  top of  the slope via a  10
 cm (4  in.)  perforated  pipe.   The  predominant grass on  the
 slope  is  tall  fescue.    The  system   was  constructed   by
 Southern Illinois University and  used for several years as a
research facility.   No  storage  is provided  other than  the
existing stabilization pond  [3].
                             7-30

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         7.4.4.4   Operation

During 1976 and  1977,  application rates varied from  0.29  to
0.57  m3/m-h  (24  to  42  gal/ft-.h).    The  application  period
varied from 4  to 24 h/d.   A typical. application period was
9 h/d.  Runoff from the  slopes accounted for over 80% of the
applied wastewater.  Erosion was  not  a problem.
         7.4.4.5
Performance
The  treatment performance  of the  OF  system  was monitored
relatively  intensely  in the  fall of  1976.   The results  are
presented in Table 7-10.

                         TABLE 7-10
      TREATMENT PERFORMANCE OF CARBONDALE OF SYSTEM [4]
                    mg/L except as noted
Constituent Applied wastewater
BOD
SS
Phosphorus , total
Ammonia nitrogen
Fecal coliforms,
30-110
20-60
3-4
20-40

Treated runoff
4-7
4-7
0.2-0.
0.1-1.



5
5

         colonies/100 mL
          35,000
600-2,500
In 1977 when application rates and  daily  application periods
were  increased,  the  treatment  performance  declined.    For
example, when application  times  of  24  h/d were  used, removal
of ammonia dropped off  significantly.   The runoff after 60 m
(200  ft),  however,  contained less  than  1 mg/L  ammonia when
application periods were 12  h/d  or  less.

7.5   References

 1. Environmental Protection Agency.   Process  Design Manual
    for Wastewater Treatment Ponds.   (In  Preparation).
 2. Metcalf   &   Eddy,   Inc.
    Treatment,  Disposal, Reuse,
    New York, N.Y.   1979.
                Wastewater    Engineering:
                McGraw Hill  Book Company.
    Hinrichs,  D.J.  et  al.   Assessment of Current information
    on  Overland  Flow  Treatment  of  Municipal  Wastewater.
    Environmental   protection   Agency,   Office  of   Water
    Programs.   EPA  430/9-80-002.   MCD-66.   May 1980.
                             7-31

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4. Muchmore,  C.B.   Overland  Flow as  a  Tertiary Treatment
   Procedure Applied to a Secondary Effluent.  Presented at
   Illinois Workshop  on Land Application  of Sewage Sludge
   and Wastewater.   Champaign,  Illinois.    October 18-20,
   1976.
                            7-3:

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                          CHAPTER 8

            ENERGY REQUIREMENTS AND CONSERVATION
8.1  Introduction

Land  treatment systems  energy  needs  consist  of preappli-
cation  treatment,  transmission  to the  application  site,
distribution pumping  (if  necessary),  and tailwater recovery
or pumped  drainage  (if required).   The  energy required for
preapplication  treatment varies  considerably  depending on
the degree  of  treatment  planned.   The  degree  of treatment
depends on  type  of  system,  local conditions, and regulatory
requirements.  Determining  energy requirements for all  pre-
application  treatment systems  is  beyond the  scope  of  this
manual; however, equations for estimating energy  consumption
of minimum preapplication  unit  processes  are  presented in
Section 8.6.   Energy  required for construction is too site-
specific to be included in this manual.

Energy  for transmission  from the  preapplication treatment
site  to  the land treatment  site depends on topography and
distance.   This  is  especially  important  when  considering
alternative  sites.    The energy required  for transmission
pumping can range anywhere  from  zero  to nearly 100% of the
energy requirements  for a land  treatment  system.  This may
often  justify  a  higher priced parcel  of land closer to the
application  site.   Transmission  pumping   is  sometimes de-
signed  to  also provide  pressure  for sprinkler application.
For sites  located below preapplication treatment facilities
with  surface  application systems,  pumping  usually will not
be required.

Slow  rate  systems vary  in  terms  of distribution energy and
possible  tailwater  control.    Distribution  systems  may be
surface or  sprinkler.  Tailwater control requirements depend
on  the  type  of  distribution  system  and   discharge  stan-
dards.    Sprinkler  systems  can  be controlled  so  that no
tailwater  is produced.   Surface systems will  usually  have
tailwater  that must be contained and reapplied.

Rapid  infiltration  systems  are usually designed  for surface
distribution  and  application  and   so  require  minimal en-
ergy.   There  is  no  tailwater pumping,  but pumped drainage
may be necessary to  control  ground water levels or recover
treated percolate.

Overland  flow  systems can use surface distribution with low
head  requirements  (Section 6.6.1).    Sprinkler  systems can
also   be    used   so   energy   will   be   required   for
                             8-1

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 pressurization.   There is no significant subsurface drainage
 with OF so this  potential energy requirement is avoided.

 8.2   Transmission Pumping

 Under  conditions  with   favorable   topography,   a  gravity
 transmission  system  may  be  possible  and   pumping   not
 required.    If pumping  is required,  the  energy  needs  vary
 substantially depending  on the  required  head  and how  the
 transmission system is  designed.   The effect  of  topography
 on pumping costs and energy use  should  be  thoroughly  evalu-
 ated during the  planning process.

 Energy  efficient  design involves coordination  of all  ele-
 ments of  the  system including  sizing of pumps,  pipelines,
 and  storage facilities,  as  well  as system  operating  strat-
 egy.   The  system  operating strategy  involves  placement  and
 sizing  of storage  facilities.   Wet wells are  typically  not
 designed  for  significant ;flow  equalization.    Transmission
 pumping  systems  are  sized  to  handle  the  peak  community
 flows.  This  can  be accomplished  by  multiple pumps, one  pump
 with a variable  speed drive, or  some combination.   Each  sys-
 tem  has differing  constraints that  alter  decisions on  its
 design.   Ideally,  all  flow is  equalized  to provide  nearly
 constant  flow  pumping.   This allows  selection of a pump  at a
 maximum efficiency.

 Variable  speed drives,  which  are not as  efficient as  con-
 stant speed drives, would  not be required.   Unfortunately,
 flow equalization  is  not always  feasible.    in  some   in-
 stances,  equalization  costs may not be  recovered  by energy
 savings.    The choice  of  pumping   and  equalization  system
 design  is  site-specific.   Regardless  of  the pumping  system
 used, pipeline size  can  be  optimized.  Optimization of pipe-
 line size will provide the  optimum transmission  system.

 The  following pipe size  optimization procedure  was  taken
 from reference  [1].   Obviously,  larger pipe sizes  result  in
 lower pumping  energy;  however,  excessively  large  pipes  are
not economical.
where
        Jopt

          A

          Q

          C
 Dopt = AQ°-486C-°-316(KT/PE)°-17

optimum pipeline diameter, m (ft)

constant, 3.53 (2.92)

average flow, m3/s (ft3/s)

Hazen-Williams coefficient
                                                        (8-1)
                             3-2

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          K = average price of electricity, $/kWh

          T = design life, yr

          p = unit cost of pipe, $/linear m-iran dia.
              ($/linear ft-in. dia.)

          E = overall pumping system efficiency,
              decimal

For example,  at a flow of 0.219 m3/s  (7.7 ft3/s), a Hazen-
Williams coefficient of 100, a pipeline cost of $0.26/linear
ra-mm diameter,  an overall pumping  system efficiency of 75%,
electricity  at  $0.045/kWh,  and  a  design  life  of 20 years,
the optimum pipe diameter  is 0.50 m  (20 in.) [2].

With the line size determined and a pumping system selected,
the actual  energy requirement can  be determined .by the fol-
lowing equation.

              Energy, kwh/yr  =
where  Q = flow, L/min  (gal/min)

     TDK = total dynamic head, m  (ft)

       t = pumping time, h/yr

       F = constant,  6,123  (3,960)

       E = overall pumping  system efficiency,  decimal

The overall  efficiency  varies not only with  design  specifics
but  also  with the  quality of   liquid  being pumped.    Raw
wastewater  pumping requires  pumps  that  pass larger  solids
than  treated  effluent.   These  pumps  are  less efficient.
When  a specific  design is  being contemplated,  the overall
efficiency   should  be  determined  using  pump,   motor,   and
driver  efficiencies  determined  for  the  equipment  to  be
used.  For initial planning or preliminary work  such as  site
selection,   overall   system efficiencies  can be assumed as
follows.

     Raw wastewater                               40%

     Primary effluent                            65%

     Secondary or  better effluent,  tailwater,
     recovered ground water, or  stormwater       75%
                             8-3

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 8.3   General Process Energy Requirements

      8.3.1   Slow Rate

 Energy  consumption   for   SR  consists,  of   transmission,
 distribution,   possible  tailwater  reapplication,  and  crop
 management.     A   wide  range  of   surface  and   sprinkler
 distribution  techniques  is   possible.     Surface   systems
 require  energy for distribution  and tailwater  reapplication
 to  the  site.    Sprinkler systems  are highly  variable  w.ith
 possible pressure  requirements ranging  from 10 to 70 m (30
 to  230 ft).   Generally,  pressures will be in the  15  to  30  m
 (50 to 100  ft)  range.

 Crop  production energy varies substantially between the  type
 of  crops grown.    Table 8-1  shows  energy  requirements  for
 corn  and forage crops.

                          TABLE 8-1
                    ENERGY REQUIREMENTS  FOR
                      CROP PRODUCTION [3]
                                  Requirement, MJ/ha
Operation
Tillage and seeding
Cultivation
Herbicide/ insecticide
Harvest
Drying
Transportation
Total
Corn
1.41
0.37
0.37
0.37
4.69b
1.04
8.25
Alfalfa
0.22
NA
0.37
1.51a
NAC
1.53
3.63
               a.  Hay.
               b.  Mechanically dried; may in some cases
                  be field dried.
               c.  Not applicable,  field dried.

     8.3.2   Rapid  Infiltration

Rapid  infiltration system energy  requirements are primarily
thpse  needed  for  transmission.     Surface  distribution  is
normally  used.   There  are  no crops  grown  so no  fuel  is
consumed   for  that   purpose.    Occasionally,   there  are
situations  where recovery  wells  and  pumps are  used.    Fuel
will be  needed for basin scarification,  but the quantity  is
not significant  because  the operation is infrequent.
                              8-4

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     8.3.3  Overland  Flow

Overland  flow  treatment  can  use  either surface  distribution
or  sprinkler  distribution.    Surface  distribution  requires
minimal    energy   (see   Section 8.6),   while    sprinkler
distribution requires pressurization e'nergy.

To  prevent  nozzle  clogging,  raw  wastewater   or  primary
effluent   should   be   screened   prior   to  distribution.
Mechanically  cleaned  screens  are  preferred  over  comminution
since  shredded  material  returned to  the stream can  still
cause clogging.   The  amount of energy  required for screening
is  insignificant  compared to  the pumping energy  required.
Equation  8-2 applies  for the pumping energy  computation.

Overland  flow  systems  require  a  cover crop  that  is  often
harvested and  removed  from  the  site.   Energy  is  required in
the   form   of   diesel   fuel   for   operating    harvesting
equipment.     Fuel  required   is   the   same  as  presented  in
Table 8-1 for  alfalfa harvest.

A   summary  of   energy   requirements   for  land  treatment
processes is  shown on Table 8-2.   The values presented are
typical of actual practice.

                           TABLE  8-2
        MOST COMMON UNIT ENERGY  REQUIREMENTS FOR  LAND
               TREATMENT OF MUNICIPAL WASTEWATER
Treatment
system
Slow rate

Total
Component
Pumping for distribution
Crop planting, cultivation,
harvest, drying, transport
Energy credit for fertilizer
value of wastewater
Electricity,
kWh/1,000 m3
0.14
—

0.14
Fuel,
MJ/1,000 mj
--
0.68
(0.50)
0.18
Total equivalent,
kWh/1,000 m3
0.14
0.20
(0.14)
0.20

Total
Rapid
infiltration
Total
Overland flow

Total
value of wastewater

Distribution (gravity)
Recovery wells

Tr ansraiss ion
Forage harvest

—
0.14
—
0.05
0.05
0.10
—
0.10
(0.50)
0.18
--

—
--
0.22
0.22
(0.14)
0.20
—
0.05
0.05
0.10
0.06
0.06
 Note:  See Appendix G for metric conversions; kWh are used for electricity and total
      equivalent energy, MJ used for fuel.
                               J-5

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 8.4   Energy  Conservation

      8.4.1   Areas  of  Potential  Energy Savings

 With  respect  to  energy  conservation,  there  are  two  main
 areas  to  review.    First  is  transmission  to  the  site.
 Location  of  the  facility should,  if possible,  provide  for
 adequate   drop  in  elevation  between  the   preapplication
 treatment  and  the land  treatment  sites.   This  layout  is
 sometimes  possible with  RI  systems  and certain SR  systems.
 It  is more  difficult to design  OF  systems  in this  manner
 since sloping  land is necessary as part of  the process.   For
 OF  systems,  site  grading   is  usually required  to  obtain
 desired   slope   so  distribution   pumping   is  typically
 necessary.

 The  second  area  of  potential  energy  savings  is  with  the
 distribution method.   For  domestic  wastewater with  minimal
 preapplication   treatment,  surface  systems are preferred,
 since  surface  systems  are  not  as subject  to clogging  and
 usually require  less  energy.

 Distribution for SR systems is a function of  topography  and
 the  crop.    Surface  systems  can be  used on level or  graded
 sites  (see  Section 4.7.1).   In  the past,  surface   systems
were preferred  by  the agricultural industry; however,  due  to
 increased labor  costs and poor  irrigation efficiencies,  some
 existing  surface  systems have  been  converted  to sprinkler
 irrigation.  For municipal authorities  where labor wages  are
 higher than  farm worker wages,  the increased labor costs  are
 important.

 Sprinkler  distribution  systems  are relatively high-pressure
 devices.  Recent advances have  been made in sprinkler  nozzle
design to  lower headloss without  sacrificing  uniformity  of
 application.   Figure 8-1 illustrates  a center pivot  system
with  two types  of  sprinklers.   The impact sprinklers  have a
 typical pressure loss of approximately 60 to  65 m  (200  to
 215 ft); whereas,  drop nozzles  have a headloss of 15  to  20 m
 (50 to 65 ft).   This difference represents an energy  savings
of  about  95 kWh/1000 m-*, without  sacrificing distribution
efficiency.

Surface systems may  not  require pumping  energy except  for
tailwater  recycling.     In  this  case,  automated   surface
systems (Figure  8-2) can be introduced  to minimize tailwater
recycling requirements.
                             8-6

-------
   DROP NOZZLE SYSTEM
 IMPACT SPRINKLER SYSTEM

      FIGURE 8-1
CENTER  PIVOT SYSTEM
         8-7

-------
              Reuse pump
                             Tailwater Collection
                                FIGURE  8-2
               AUTOMATIC SURFACE IRRIGATION  SYSTEM  [4]
      8.4.2   Example:   Energy Savings in Slow Rate  Design
The  following example illustrates  how effective planning and
design  can  result  in  energy  conservation.    A  summary  of
assumed  system  characteristics   used  for   this  example   is
presented in Table  8-3.
                             TABLE  8-3
                 EXAMPLE SYSTEM CHARACTERISTICS
           Average flow,
           System
           Preapplication treatment
           Application season
           Hydraulic loading, m/yr
           Net land area, ha
           Crop
           Topography

           Tailwater control
38,000
Slow rate
Pond
May to October (5 months)
1.2
1,130
Corn
Nearly level, suitable for
all types of irrigation
No surface discharge of
applied wastewater allowed
                                8-8

-------
Three  systems will  be considered:    surface distribution by
ridge  and  furrow,  and  two  examples of  center-pivot  appli-
cation.   Since transmission  of  wastewater  is essentially the
same with all alternatives,  it will  not be included  in this
discussion.

Ridge  and furrow  distribution  does  not  require  pumping for
distribution;   but  due   to   a   no  discharge   of  tailwater
requirement,  energy  is  required  to return  tailwater  back to
the application point (assumed head:  3 meters).   Depending
on  the  system  design,the  maximum  tailwater  recycle  will
range  from 30  to 70% of  that  applied.   Conventional ridge
and  furrow  designs   result   in  lower  efficiency,  with the
higher  recycle  pumping  requirement.    Alternatively,  ridge
and  furrow  systems   with   automated   recycle   cutback  or
automated valves can  improve efficiency by lowering  pumping
requirements.   The  potential savings from  system automation
is summarized  in Table 8-4.

                           TABLE  8-4.
        COMPARISON OF  CONVENTIONAL AND AUTOMATED RIDGE
             AND FURROW SYSTEMS FOR 38,000 m3/da
      System
               Tail-
               water   Electric-        Labor
              pumping,   ity,    Labor,   cost,
               kWh/yr   $/yr    h/yr   $/yr
              Total
       Amortized annual
Capital  capital,  cost,
cost, $   $/yr    $/yr
Conventional
Automated
Difference
89,300
33,500
55,800
2,950
1,100
1,850
2,800
1,400
1,400
30,800
15,400
15,400
16,000
45,000
-29,000
1,520
4,300.
-2,780
35,270
20,800
. 14,470
    a.  Electricity at $0.036/kWh.  Labor at 1.2 h/ha-d for automated systems;
       2.5 h/ha/d for conventional systems.  Labor cost at $11.00/h. Capital costs
       for pipeline, distribution system, reuse system meters (January 1980) .
       Capital amortized at 7-1/8% for 20 years.
The potential savings using  automated irrigation systems are
significant;  both energy  consumption and cost  can be reduced
substantially.   In  this example,  energy  requirements  were
reduced  by about  two-thirds,  at an  overall cost savings of
over  50%.

If  a  center  pivot  irrigation  system  is  used,  tailwater
recovery is not needed.   However, pumping  energy is required
to provide nozzle pressure.   In this case  the  main factor in
energy  conservation  is  nozzle  design.   The general  goal is
to  achieve  uniform  distribution   at  the  lowest  possible
pressure  loss.    A  conventional center   pivot   rig  employs
impact   sprinklers  on   top   of   the  pivot  pipeline.    These
devices  require  a  pumping  pressure  of  approximately  65 m
(21 ft).   Alternatively,  drop  nozzles  are  used  in  modern
                               8-9

-------
 rigs  which develop a headloss of  about  15  m (150 ft).   Drop
 nozzles  have  an additional advantage of  producing less aero-
 sol  than impact  systems.   Capital  costs,  and  operation and
 maintenance   requirements   (except   for   electricity)   are
 comparable  between these  two systems.   The impact on energy
 savings  is  shown on Table 8-5.   In this  instance, costs were
 reduced  and aerosols were decreased  by designing to conserve
 energy.

                           TABLE 8-5
              COMPARISON OF IMPACT  AND DROP-TYPE
              CENTER PIVOT SYSTEM NOZZLE  DESIGNS
                   ON ENERGY REQUIREMENTS,
                        38,000 m3/day
Nozzle type
Impact
Drop
Difference
Electricity,
kWh/yr
2,230,000
1,030,000
1,200,000
Energy
cost, $/yr
73,600
34,000
39,600
     8.4.3  Summary

For  purposes  of  comparison  the  total  energy  (electricity
plus  fuel)  for typical  3,785 m3/d  (1  Mgal/d)  systems  is
listed  in  Table 8-6 in order  of increasing energy  require-
ments.   It is quite apparent from Table 8-6 that  increasing
energy  expenditures do  not necessarily  produce  increasing
water quality benefits.   The four systems at the  top of  the
list,  requiring the  least  energy,  produce  effluents  com-
parable to the bottom four  that  require the most.

8.5  Procedures for Energy  Evaluations

The  following section provides  step-by-step  procedures  for
computing  energy  use for  each  of the  three  land treatment
systems.   Examples  are  also  provided.   The  energy compu-
tation  requires site  selection  and  a  decision  concerning
location of  preapplication  and  storage  facilities  because
elevation differences for pumping are critical.  The distri-
bution method must also be determined.
                             8-10

-------
                 TABLE 8-6
TOTAL ANNUAL ENERGY FOR TYPICAL  3,785 m3/d
 (1 Mgal/d) SYSTEM (ELECTRICAL PLUS  FUEL,
      EXPRESSED AS 1,000  kWh/yr)  [5]

Treatment system
Rapid infiltration (facultative pond)
Slow rate, ridge + furrow (facultative pond)
Overland flow (facultative pond)
Facultative pond + intermittent filter
Facultative pond + microscreens
Aerated pond + intermittent filter
Extended aeration + sludge drying
Extended aeration + intermittent filter
Trickling filter + anaerobic digestion
RBC + anaerobic digestion
Trickling filter + gravity filtration
Trickling filter + N removal + filter
Activated sludge + anaerobic digestion
Activated sludge + anaerobic digestion + filter
Activated sludge + nitrification + filter
Activated sludge + sludge incineration
Activated sludge + AWT
Physical chemical advanced secondary
NOTE: RBC = rotating biological contactor.
8.5.1 Slow Rate
Step 1: Transmission Pumping
1. Elevation at site m
2. Elevation at source m
3. Elevation difference m
4 . Average annual f lowrate
5. Pumping system efficiency
6. Pipeline diameter cm
7. Pipeline length m
8. Pipeline headless m
9. Total dynamic head m
Effluent quality, mg/L Energy,
i nnn

BOD
5
1
5
15
30
15
20
15
30
30
20
20
20
15
15
20
<10
10







SS P
1 2
1 0.1
5 5
15
30
15
20
15
30
30
10
10
20
10
10
20
5 <1
10 1







N kWh/yr
10 150
3 181
3 226
10 241
15 281
20 506
683
708
783
794
805
5 838
889
911
1,051
1,440
<1 3,809
4,464






L/min
%









10. Energy requirement kWh/yr





(Eq. 8-2)
                     8-11

-------
Step 2:  Distribution Energy
     1
     2
     3
     4
     5
     6
     7
     1.
     2.
     3.
     4.
     5.
     6 .
     1,
     2,
     3,
     4,
     5,
     6,
     7.
     8,

Step 5:
     Flowrate
                        L/min
     Pressure head required 	
     System efficiency	 %
     Operating time 	 h/yr
     Pipeline headloss	  m
     Total dynamic head	
     Energy requirement 	
                                      m
                                  m
                                  kWh/yr
(Eq.  8-2)
Step 3:  Tailwater Pumping (if required)
     Flowrate
     Lift required
     Headloss
                        L/min
                             m
                        m
                     ^
         Assumed pumping system efficiency
         Operating time _ h/yr
         Energy requirement _ kWh/yr
                                               (Eq. 8-2)
Step 4:  Crop Production (Table 8-1)
     Tillage and seeding  _ MJ/ha-yr
     Cultivation _ MJ/ha-yr
     Insecticides and herbicides
     Harvest _ MJ/ha-yr
     Drying _ MJ/ha-yr
     Transportation __ MJ/ha-yr
                                           MJ/ha-yr
     Crop area
                         ha
         Total fuel requirement 	 Mj/yr

         Combine Steps 1 through 4, expressed as kWh/yr
     8.5.2  Rapid Infiltration

Step 1:  Transmission Pumping
                                 m
                                   m
                                    m
 1.   Elevation at site _
 2.   Elevation at source
 3.   Elevation difference ^_^___
 4.   Average flow _ L/min
 5.   Assumed pumping system efficiency
 6.   Pipeline diameter _ cm
 7.   Pipeline length _
 8.   Pipeline headloss _
 9.   Total dynamic head _ m
10.   Energy requirement _ kWh/yr
                               m
                                 m
                                                    (Eq. 8-2)
                             3-12

-------
Step 2:  Drainage Water Control (if necessary)
     1,
     2,
     3,
     4,
     5,
     6,
     7.
Elevation of water source
Elevation of discharge	
Difference in elevations 	
Pumping system efficiency
Operating hours 	 h/yr~
Pumped flow	L/min
                                m
                             m
                               m
Energy requirement
                         kWh/yr
Step 3:  Combine Steps 1 and 2

     8.5.3  Overland Flow

Step 1:  Transmission Pumping
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
Elevation at site 	
Elevation at source
Elevation difference
Average annual flow
                        m
                          m
                           m
                          L/min
                      m
Assumed pumping system efficiency
Pipeline diameter 	 cm
Pipeline length   ~
Pipeline headloss _
Total dynamic head
Energy requirement
                        m
                         m
                         kWh/yr
Step 2:  Distribution System
     1,
     2.
     3
     4,
     5
     6,
     7
Type of system
Flowrate	 L/min
Pressure head required 	 m
Assumed pumping efficiency 	
Operating time       h/yr
Total dynamic head
Energy requirement
                         m
                         kWh/yr
Step 3:  Grass Removal (Table 8-1)
     1,
     2,
     3,
     4,
(Eq.  8-2)
(Eq.  8-2)
Maintenance requirements, fuel use
Grass removal frequency 	 harvest/yr
Fuel for harvest
(Eq.  8-2)
                                         MJ/harvest
Total fuel required
                       MJ/ha
                          Mj/year
Step 4:  Combine Steps 1 through 3/ express as kWh/yr

     8.5.4  Examples

Using the previously  presented step-by-step procedures, the
following example problems were developed.
                             8-13

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            8.5.4.1  Slow Rate

The  slow  rate system is designed  to treat pond effluent as
follows:
     Average flow
     Season
     Applied flow
     Crop grown
     Distance to site
     Tailwater pumping
     Area

Step 1:  Transmission Pumping
                                  15,000 L/min
                                  5 months
                                  36,000 L/min
                                  Corn
                                  100 m
                                  Not required
                                  650 ha
     1.  Elevation at site  50 m
     2.  Elevation at source  48 m
     3.  Elevation difference  2 m
     4.  Average annual flowrate  15,000 L/min
     5.  Pumping system efficiency  40%
     6.  Pipeline diameter  76 cm
     7.  Pipeline length  100 m
     8.  Pipeline headloss  3.4 m
     9.  Total dynamic head  5.4 m
    10.  Energy requirement  289,711 kWh/yr

Step 2:  Distribution Energy

     1.  Flowrate  36,000 L/min
     2.  Pressure required  10 m
     3.  System efficiency  75%
     4.  Operating time  3,600 h/yr
     5.  Pipeline headloss  2 m
     6.  Total dynamic head  12 m
     7.  Energy requirement  338,658 kWh/yr

Step 3:  Tailwater Pumping (if required) (not required with
         sprinklers)

     1 .  Flowrate       L/min
     2.  Lift required       m
     3.  Assumed pumping efficiency _ _ %
     4.  Operating time _____ h/yr
                   ___
5.  Energy requirement
                                  kWh/yr
                             8-14

-------
Step 4:  Crop Production (full)

     1.  Tillage and seeding  1.41 MJ/ha-yr
     2.  Cultivation  0.37 MJ/ha-yr
     3.  Insecticides and herbicides  0.37 Mj/ha*yr
     4.  Harvest  0.37 MJ/ha«yr
     5.  Drying  4.69 MJ/ha-yr
     6.  Transportation  1.04 MJ/ha-yr
     7.  Crop area  650 ha
     8.  Total fuel requirement  5,120 MJ/yr = 1,422 kWh/yr

Step 5:  Total energy use = 629,791 kWh/yr

            8.5.4.2  Rapid Infiltration

The rapid  infiltration  system is designed  to  treat primary
effluent as follows:
     Flowrate
     Distance to site
     Drainage

Step 1:  Transmission Pumping
15,000 L/min
5,000 m
pumped wells
     1.  Elevation at site  1,115 m
     2.  Elevation at source  1,105 m
     3.  Elevation difference  10 m
     4.  Average flow  15,000 L/min
     5.  Assumed pumping system efficiency  65%
     6.  Pipeline diameter  50 cm
     7.  Pipeline length  5,000 m
     8.  Pipeline headloss  20 m
     9.  Total dynamic head  30 m, operating 8,760 h/yr
    10.  Energy requirement  990,465 kWh/yr

Step 2:  Drainage Water Control (if necessary)

     1.  Elevation of water source  1,105 m
     2.  Elevation of discharge  1,115 m
     3.  Difference in elevations  10 m
     4.  Pumping system efficiency  75%
     5.  Operating hours  2,920 h/yr
     6.  Pumped flow  10,000 L/min
     7.  Energy requirement  63,585 kWh/yr

Step 3:  Total energy use = 1,054,050 kWh/yr
                            8-15

-------
             8.5.4.3   Overland  Flow

An  overland flow  system  is planned  for  a small  community,
The  system will be  used  to treat  screened raw  wastewater,
Design parameters  are as  follows:
     Design  flow
     Distribution method
     Distance  from source  to  site
     Hydraulic loading
     Land area

Step 1:  Transmission Pumping
137 m/d
Gated pipe
100 m
4.5 m/yr
1 ha
     1.  Elevation at site  125 m
     2.  Elevation at source of  120 m
     3.  Elevation difference  5m
     4.  Average annual flow  95 L/min
     5.  Assumed pumping system efficiency   40%
     6.  Pipeline diameter  10 cm
     7.  Pipeline length  100 m
     8.  Pipeline headloss  1.22 m
     9.  Total dynamic head  6.22 m
    10.  Energy requirement  2f113 kWh/yr

Step 2:  Distribution System

     1.  Type of system - gated pipe
     2.  Flowrate  95 L/min
     3.  Pressure head required  3 m
     4.  Assumed pumping efficiency  40%
     5.  Operating time  8,760 h/yr
     6.  Total dynamic head  3.3 m
     7.  Energy required  1,121 kWh/yr

Step 3:  Grass Removal

     1.  Maintenance requirements, fuel use  0.59 MJ/harvest
     2.  Grass removal frequency  3 harvest/yr
     3.  Fuel for harvest (including transportation)
         3.04 MJ/ha ,
     4.  Total fuel required  3.63 Mj/yr = 1.0 kWh

Step 4:  Total energy use = 3,235 kWh/yr

8.6  Equations for Energy Requirements

In  addition  to  Equation  8-1, a  large number  of equations
have been developed from the curves in reference  [6] and are
presented  in reference  [5] .   Selected  equations  are pre-
sented  in  this  section  to allow  the engineer  to estimate
                             8-16

-------
energy requirements for minimum preapplication treatment and
for the  three  land treatment processes.   In all equations,
Y is the energy requirement in kWh/yr.

     8.6.1  Preapplication Treatment

Mechanically Cleaned Screens
            log Y = 3.0803 + 0.1838(log X)
                  - 0.0467 (log X)2
                  + 0.0428 (log X)J

where Y = electrical energy required, kWh/yr

      X = flow, m3/d (Mgal/d)

Assumptions = normal run times are 10 min/h,
              bar spacing 1.9 cm  (0.75 in.),
              worm gear drive is  50% efficient
(8-3)
Comminutors
            log Y = 3.6704 + 0.3493(log X)
                  + 0.04.37(log X)2
                  + 0.0267 (log X)J
(8-4)
Grit Removal
                  ,0.24
            Y = AX
            A = 73.3  (530)
            X = flow, m3/d  (Mgal/d)

Assumptions = nonaerated, square tank, 2 h/d operation

Aerated Ponds

            Y = AX1'00
            A = 68.7  (260,000)
            X = flow, m3/d   (Mgal/d)
(8-5)
(8-6)
Assumptions = low speed mechanical aerators,  30 d detention,
              1.1 kg 02/kWh

Other  preapplication treatment processes  will involve many
potential  sludge  treatment  and  disposal  options  and  are
included in reference  [5].
                             8-17

-------
     8.6.2  Land Treatment Processes
For sprinkler application  in each  land  treatment process and
OF  and  RI  distribution,   use  the  previous  checklist and
Equation 8-2.  Equations are presented  for  ridge and  furrow,
and graded border SR application along  with the assumptions.

Ridge and Furrow

            Application =  250 d/yr,  tailwater  return  at
                           25% annual leveling  and ridge
                           and furrow replacement
                      Y = AX1'00 - electrical
                      A = 3.17 (12,000)
                      X = flow, m3/d (Mgal/d)

                      Y = AX**00 - fuel
                      Y = MJ/yr (106 Btu/yr)
                      A = 1.55 (20)
                                                       (8-7)
                                                        (8-8)
                      X = flow,
                                      (Mgal/d)
Graded border
            Application = 250 d/yr, tailwater return at 25%

                                                       (8-9)
                      Y = AX1.00
                      A = 4.2 (16,000)
                      X = flow, m3/d  (Mgal/d)
8.7

1.
     References
     Culp/Wesner/Culp.   Energy Considerations in Wastewater
     Treatment.   CWC,  Cameron Park, California.  September,
     1980.
     Patton,   J.L.,   and
     Distribution   Energy
     No. 6.  June 1980.
                            M.B.   Horsley.
                            Appe t i te.   AWWA
 Curbing
Journal,
the
72,
4.
5.
     Stout, B.A.   Energy Use  in Agriculture.   Council  for
     Agricultural  Science  and  Technology.    Ames,  Iowa.
     Report Number 68.  August 1977.

     Eisenhauer,  D.E.  and  P. E.  Fischbach.   Automation  of
     Surface  Irrigation.     Proceedings  of  the  Irrigation
     Association Annual Conference.  February 1978.

     Middlebrooks,  E.J.  and  C.J.  Middlebrooks.    Energy
     Requirements  for   Small   Flow   Wastewater  Treatment
     Systems.    Reprint  of   CRREL  SR  79-7.   MCD-60,  OWPO,
     USEPA.  April 1979.
                            8-18

-------
6.   Wesner,  G.M.,   et  al.     Energy   Considerations  in
     Municipal Wastewater Treatment,  MCD-32.   USEPA, Office
     of Water Program Operations.  March 1977.
                             8-19

-------

-------
                          Chapter 9

              HEALTH AND ENVIRONMENTAL EFFECTS
9.1  Introduction

Wastewater constituents that are of major concern for. health
or environmental reasons are:

     •   Nitrogen

     •   Phosphorus

     •   Dissolved solids

     •   Trace elements

     •   Microorganisms

     •   Trace organics

Potential effects of these constituents vary among the  three
major  types  of land treatment, as shown  in Table 9-1.   The
relationship of wastewater constituents to  health effects  is
presented in Table 9-2.

In  general,   constituent   removals   are   greatest  for   SR
systems.   Health  and  environmental  effects of  RI  systems
depend  on   site   selection  and  design   factors  such   as
hydraulic loading rate and length of application and resting
cycles.   Overland  flow has  the  fewest potential impacts  on
ground water because  very  little water penetrates below the
soil  surface.   However, renovated water  from OF systems  is
normally  discharged  to local  surface  waters  as a   point
source, and, therefore, can  affect surface  water quality.

Recently,  the  EPA  has  funded extensive  studies  at several
operating land treatment systems to evaluate potential  long-
term  health  and  environmental effects.  The ten study  sites
are presented  in Table  9-3.  Results  from these and  other
studies are included in this chapter.
                             9-1

-------
                           TABLE  9-1
      LAND TREATMENT METHODS AND  CONCERNS  [1]
Potential Concerns
Nitrogen
Health: drinking water aquifers
Environment: eutrophioation
crops
Phosphorus
Environment: eutrophication
Dissolved solids
Health: drinking water aquifers
Environment: soils
crops
ground water
Trace elements
Health: drinking water aquifers
crops
Environment: crops
animals
Microorganisms
Health: drinking water aquifers
crops
aerosols
Environment: animals
Trace organics
Health: drinking water aquifers
crops
SR

X
X
X

X

X
X
X
X

X
X
X
X

X
X
X
X

X
X
RI

X
X
—

X

X
X
__
X

X
—
__
—

X
	
—
--

X
"
OF

. __
X
—

X

—
X
X


__
X
__
X

__
X
X
X

__
""~
      Note:  An X in the matrix indicates the possibility for
            concern. The magnitude of the impact is not considered.
                         TABLE  9-2
RELATIONSHIP OF  POLLUTANTS  TO HEALTH EFFECTS3
      Pollutant  (agent)
                                   Principal health effect
    Nitrate nitrogen
    Sodium
    Trace elements
    Microorganisms
       Bacteria
       Virus
       Protozoa
       Helminths
    Trace organics
Methemoglobinemia
Cardiovascular
Toxicity
Infection, disease
                                   Toxicity, carcinogenesis
    a.  Adapted from reference [2J,
                             9-2

-------
                             TABLE 9-3
                 EPA LONG-TERM EFFECTS STUDIES
Date
operation
Location started
Slow rate
systems
Camarillo, 1966
California [3]


Dickinson, 1959
North Dakota [4]


Mesa, 1950
Arizona [5]

Roswell, 1944
New Mexico [6]




San Angelo, 1959
Texas [ 7 ]
Tooele, 1967
Utah [8]


Flow
during
study ,
raVs


0.130



0.044



0.208


0.175





0.241

0.061



Level of
preapplioation
treatment


Secondary
(activated
sludge) with
disinfection
Secondary
(aerated
ponds ) with
disinfection
Secondary
(trickling
filters)
Secondary
(trickling
filters followed
by oxidation
ditch) with
disinfection
Primary

Secondary
(trickling
filters) with
disinfection
Crops


Tomatoes ,
broccoli


Forage
grasses


Grain, .corn,
barley

Corn, alfalfa,
sorghum




Forage grasses.
pasture
Forage grasses.
alfalfa. Test
plots of beans.
carrots, lettuce.
Hydraulic
loading
rate , m/yr


1.6



1.4



4-8.6


0.8





2.9

0.6



                                           peas, radishes,
                                           sweet corn, wheat
  Rapid
  infiltration
  systems	
  Hollister,         1945    0.044
  California  [9]
  Lake George,       1939    0.058
  New York 110]

  Milton,           1957    0.013
  Wisconsin til]

  Vineland,         1926    0.215
  New Jersey  [12]
Primary

Secondary
(trickling
filters)
Secondary
(activated
sludge)
Primary
 15


 43


224


 19
  Note: See Appendix G for metric conversions.

9.2   Nitrogen

Both  nitrates  and ammonia  are of  concern in  land  treatment
systems.   Other  nitrogen  compounds  either  are  harmless  or
are degraded  during  land treatment.

Storage ponds can be used  in conjunction with land  treatment
to achieve high nitrogen removals.   Although such ponds work
well  for  SR  and OF  systems, the  resulting  algal growth may
cause soil clogging  at RI  systems.   The use  of storage ponds
for   nitrogen  removal  is   described  in  greater  detail   in
Section 4.4.1.
                                 9-3

-------
      9.2.1  Crops

 In  the  general  case,  nitrogen  is  beneficial  for  crops,
 increasing yields  and quality.   However, uptake  of  excess
 nitrogen  in  some  crops  can  increase  succulence  beyond
 desirable  levels causing lodging  in  grain crops  and reduced
 sugar content in  beets  and cane, for example.   High  levels
 of nitrogen or application beyond seasonal  needs may  induce
 more  vegetative   than  fruit  growth,   and   also   delay
 ripening.   High-nitrate content  in forages  can be  a concern
 if these are the  principal  ration for livestock.   Cattle can
 also suffer  from  grass  tetany, which  is   related  to  an
 imbalance  of nitrogen,  potassium,  and magnesium  in pasture
 grasses.   These potential  nitrogen related  crop  effects are
 not expected with  typical  municipal  wastewaters applied  to
 properly designed  and  well  managed land  treatment systems.

      9.2.2  Ground Water

 As indicated in previous chapters,  EPA guidance requires  a
 maximum  contaminant   level  (MCL)  of   10 mg/L   nitrate  as
 nitrogen at the land  treatment boundary.   This  is  to  avoid
 the  potential  of methemoglobinemia  in  very  young  infants
 using the  water supply.   AS a  result, nitrogen is  often the
 limiting parameter for  land  treatment  design.   Methods  to
 satisfy  this  requirement   are  described  in   the design
 chapters (Sections  4.5.2 and  5.4.3.1).

      9.2.3   Surface Water

 Un-ionized  ammonia  is  toxic   to  several   species  of  young
 freshwater  fish.    The oxygen  carrying  capacity  of certain
 fish  can be  impaired  at concentrations as  low  as  0.3  mg/L
 un-ionized  ammonia  (approximately 2.5  mg/L  total ammonia
 nitrogen at normal pH values)  [13].   For this reason,  many
 land  treatment  systems that discharge to  surface waters are
 designed to provide nitrification.  using  normal  application
 rates,   OF  and   SR   systems  produce   a  well    nitrified
 effluent.   Renovated  water  from  Ri  systems  contains   very
 little  ammonia  nitrogen  if   relatively  short   application
periods  are alternated  with  somewhat longer drying periods
 (Table 5-13).

Land  treatment  systems that discharge  to  surface waters  in
which nitrogen  is  the  limiting  nutrient are designed to
achieve nitrogen removal to avoid algal blooms and  increased
rates of  eutrophication.   Methods   for  achieving   nitrogen
removal are described  in Sections 4.5.2, 5.4.3.1, and 6.5.2.
                             9-4

-------
9.3  Phosphorus

Phosphorus  is  not  known  to  cause  adverse  health effects.
Like  nitrogen,  it  is  an   important  nutrient   for  crops.
Because there are no drinking or irrigation water  standards,
the principal concern is that phosphorus can be the limiting
nutrient that controls eutrophication of surface waters.

     9.3.1  Soils

The  principal  phosphorus removal  mechanisms  at   SR  and RI
systems  are soil  adsorption and  precipitation.    Removals
achieved at operating  SR  and RI systems are shown in Tables
4-3 and 5-3.

     9.3.2  Crops

Normal  crop uptake of phosphorus  occurs in both  SR and OF
systems  with   loadings  far  in  excess  of  crop  needs.   No
adverse effects on crops from phosphorus have been reported.

     9.3.3  Ground Water

Phosphorus concentrations found in percolates from SR and RI
systems  are  presented in Tables  4-3  and 5-3.  As shown in
these  two  tables,  percolate phosphorus  concentrations are
reduced   substantially  within  relatively   short   travel
distances.

     9.3.4  Surface Water

Because  phosphorus concentrations  in SR and  RI   percolates
generally  are  quite  low   (less  than  1  mg/L),  adequate
phosphorus  removal  usually  occurs  before  any  percolate
intercepts  surface  water.   At  OF  systems,  where phosphorus
removal  averages  50  to  60%,  additional  treatment  may be
necessary if phosphorus is limited by the discharge permit.

9.4  Dissolved Solids

Salt  concentrations  in  domestic   wastewater  vary  widely,
according to the  salinity of the local water source and the
chemicals  added  during  preapplication  treatment  (if  any).
Depending on  the  salinity  of  the  applied  wastewater,  soil
properties,  crops,   and  water  for  livestock   and   human
consumption may be affected.

     9.4.1  Soils

High  concentrations  of   sodium in  applied wastewater can
cause  substitution  of sodium ions  for  other cations in the
                             9-5

-------
 soil.   This  substitution tends  to  disperse clay particles
 within the  soil,  leading to decreased permeability,  lowered
 shear   strength,   and   increased   compressibility   [14]
 Wastewater  with an  SAR of less than 4 has caused no  changes
 xn  these  properties  [8].    No  adverse  soil  impacts are
 expected unless the SAR exceeds 9.

      9.4.2  Crops

 Salinity, as  measured  by the electrical conductivity of the
 water, can  cause  yield  reductions  in  crops.    Crops  vary
 widely in  tolerance to  salinity.   The  salinity tolerances
 and leaching  requirements of several field and forage crops
 are given in Table 9-4.  Salinity effects are generally only
 of concern  in arid  regions  where  accumulated  salts  are not
 flushed from  the  soil  profile  by  natural precipitation.  No
 salinity  problems have  been reported at  the systems listed
 in Table  9-3.

 Boron toxicity can  occur because  this  element tends  to  be
 unaffected   by  most   preapplication  treatment  processes.
 Fruit and  citrus trees  are affected  at  0.5  to 1.0  mg/L-
 field crops can  be  affected at 1.0  to  2.0 mg/L; and  most
 grasses are  relatively  tolerant at 2.0 to 10.0  mg/L.

 Sodium and  chloride ions  are  usually  present together  in
 wastewaters.  Most  tree crops are  sensitive to  sodium and
 chloride  taken up by the roots.   Leaves of many crops may
 show   leaf-burn   due  to   excessive  sodium  or   chloride
 adsorption   or bicarbonate   deposition  under  low-humidity,
 high-evaporation   conditions.     Irrigating  at  night  or
 increasing  the rotation  speed  of  sprinkler heads can  help
 avoid  these  problems.

      9.4.3   Ground Water

 The  salinity of percolate  from some  systems may limit  the
 potential for  reuse  of  renovated  water.   National drinking
 water   standards   recommend   that  finished  potable  water
 contains  less  than  500 mg/L total  dissolved solids  (TDS),
 but more  saline waters have  been  used without ill effects.
 Excessive TDS  can cause  poor taste  in  drinking  water, may
 have   laxative  effects  on  consumers,   and  may   corrode
 equipment   in   water  distribution   systems.      Salinity
 restrictions   on   water  for  livestock  uses  are   not  as
 stringent  as  for  drinking  water.   in  general,  a  TDS of
 10,000 mg/L  is the  upper limit for  healthy larger  animals
 such as cows and sheep;  a limit of 5,000 mg/L TDS should be
 used  for   smaller animals  (including  poultry),  lactating
animals, and young animals [13].
                             9-6

-------
                                TABLE  9-4
                 TOLERANCE  OF  SELECTED  CROPS  TO
               SALINITY  IN IRRIGATION WATER  [15]

Field crops
Barley
Sugarbeets
Cotton
Saf flower
Wheat
Sorghum
Soybean
Rice (paddy)
Corn
Sesbania
Broadbean
Flax
Beans (field)
Forage crops
Bermudagrass
Tall wheatgrass
Crested wheatgrass
Tall fescue
Barley (hay)
Perennial rye
Harding grass
Birdsfoot trefoil
Beardless wild rye
Alfalfa
Orchardgrass
Meadow foxtail
Clover
Notes :
ECe = electrical
ECW = electrical
Yield decrement
salinity of
0%
EC-, ECy,
mmho/cm mmho/cm
8 5.3
6.7a 4.5
6.7 4.5
5.3 3.5
4.7a 3.1
4 2.7
3.7 2.5
3.3 2.2
3.3 2.2
2.7 1.8
2.3 1.5
2 1.3
1 0.7

8.7 5.8
7.3 4.9
4 2.7
4.7 3.1
5.3 3.5
5.3 3.5
5.3 3.5
4 2.7
2.7 1.8
2 1,3
1.7 1.1
1.3 0.9
1.3 0.9

conductivity of saturation
conductivity of irrigation
to be expected due to
irrigation water

LR,
%
12
11
11
12.5
8
7.4
10
9
12
7
8
7
6

13
11
6
8
10
10
10
10
6
5
4
4
6


ECe,
mmho/cm
18
16
16
14
14
12
9
8
7
9
6.5
6.5
3.5

18
18
18
14.5
13.5
13
13
10
11
8
8
6.5
4

50%
ECW,
mmho/cm
12
10.7
10.7
8
9.3
8
6
5.3
4.7
6
4.3
4.3
2.3

12
12
12
9.7
9
8.7
8.7
6.7
7.3
5.3
5.3
4.3
2.7

]
LR,
% mi
27
26
26
28.5
23
22
23
22
26
23
24
24
19

27
27
27
24
25
24
24
24
26
19
20
18
19

Maximum
ECdwr
mho/cm
24
42
42
28
40
36
26
24
18
26
18
18
12

44
44
44
40
36
36
36
28
28
28
26
24
14

extract.
water
.



LR = leaching requirement: that fraction of the irrigation water that must
be leached through the active root zone to control soil salinity at the
tolerance level. This is in addition to the irrigation water taken up by
the plants. LR = EC, x 100/EC
-------
 If the salinity of a community's wastewater is significantly
•higher than the salinity of the ground water,  land treatment
 may be limited to processes that discharge to  surface waters
 or  renovated  water  recovery  may  be required  to  protect
 ground water quality.   This condition occurs most frequently
 in the arid western states where water resources are limited
 and protection of ground water from increasing salinity is a
 major  concern.

 9.5 Trace  Elements

 Trace  elements  (heavy  metals)  in municipal wastewaters  are
 contributed by  both domestic  and  industrial  dischargers;
 contributions  vary widely with  industry.   Frequently,,  trace
 element concentrations  in municipal  wastewaters are  lower
 than the limits established for  drinking  water.   Therefore,
 in most  communities,  land  treatment is  unlikely  to  cause
 direct adverse  health or environmental effects [16].

 The fate   of  trace  elements   during land  treatment  is  a
 concern primarily for two reasons:
         Trace    elements,    particularly
         accumulate  in  the food  chain.
cadmium,    can
     •   Trace  elements  can  move  through  soil  and  enter
         ground water.

     9.5.1  Soils

Movement  of  trace  elements  into  and through  the soil  may
occur during  wastewater application or after land  treatment
operations  have ceased.   For  this  reason,  it  is  important to
understand  removal   mechanisms  and  the  conditions   that
influence  retention  in and transport  through the  soil  -(see
Sections 4.2.4 and 5.2.4).

Concentrations  of  trace   elements   retained   in   the   soil
profile at  SR and RI sites  are  highest near the  soil  surface
and  decrease  with  depth  [17].    Removal efficiencies  at
selected systems are presented  in  Tables 4-4 and 5-4.   Soils
can retain  a  finite amount of  trace elements;  the capacity
or design life for metals removal  is at least the  same  order
of magnitude as for phosphorus.  For example, in typical  New
England soils, the  design life for copper and cadmium  based
only on ion exchange capacity could be several hundred  years
using an SR system and seasonal wastewater application  [1].

At  OF   systems,  trace  elements are  adsorbed  at  the   soil
surface in the organic-layer of decomposing organic material
and plant  roots.   Because  adsorption  occurs  as the  applied
                             9-8

-------
wastewater  flows  across  the  soil  surface,  metals  tend to
accumulate  near  the  point  of  wastewater application.   In
pilot studies  near  Utica,  Mississippi, approximately 50% of
the monitored  trace elements  (cadmium,  copper,  nickel, and
zinc) was  removed on  the upper third of the treatment  slope
[18].  Data  from  the  same pilot studies, presented in  Table
9-5, indicate  that  most of  the trace elements entering  this
system are  retained near the  soil  surface.   The system has
not approached its  full  capacity for trace element removal.

                          TABLE 9-5
            MASS BALANCE OF TRACE ELEMENTS IN OF
              SYSTEM AT UTICA,  MISSISSIPPI [18]
Metal
Cadmium



Copper



Nickel



Zinc



Component
Applied
Grass
Runoff
Soil
Applied
Grass
Runoff
Soil
Applied
Grass
Runoff
Soil
Applied
Grass
Runoff
Soil
Grams
46.21
0.54
3.50
42 . 14
90.39
3.59
13.13
73.67
110.11
1.50
5.20
103.39
264.05
20.03
32.06
212.03
Percent
of applied

1.2
7.6
91.2

4.0
14.5
81.5

1.4
4.7
93.9

7.6
12.1
80.3
The  results  of  one  study  on  an  abandoned  RI  basin  are
reported  in  Table 5-5.  These data,  collected  approximately
1  year  after the last wastewater  application,  indicate  that
relatively little leaching occurred  both  during  the  33  years
of operation and in the year following operation.   Leaching
should  not  be a problem provided  a  soil  pH of at least  6.5
is  maintained.     At   this  pH,   most trace   elements   are
precipitated  as insoluble  compounds.  Methods  for adjusting
soil pH are  discussed  in Section  4.9.1.3.

     9.5.2   Crops

Bioconcentration of trace  elements in the food  chain is  most
likely  to  occur during  the  operational  years  of  a  land
treatment system.   Plant uptake  of  trace elements  occurs
when  the elements  are present  in  soluble or  exchangeable
                              9-9

-------
 form in the root zone.   Generally, this occurs in increasing
 amounts as  more adsorption  sites are  occupied  and  as  the
 soil pH decreases.   To minimize  the plant  uptake  of trace
 elements,   the   soil  pH   should   be  maintained  at  6.5.  or
 above,.   The trace elements that are  of  greatest  concern  are
 cadmium, copper, molybdenum,  nickel,  and zinc.

 With regard to health effects, nickel and  zinc are  of least
 concern because  they  cause visible adverse  effects in plants
 before  plant concentrations are high  enough to be of concern
 to  animals or man.   Cadmium, copper, and molybdenum all  may
 be  harmful to animals at  concentrations that are too low to
 visibly affect plants.   Copper  is  not a  health hazard to  man
 or  monogastric  animals,  but can be toxic to  ruminants (cows
 and  sheep).  These animals'  tolerance   for copper  increases
 as  available molybdenum  increases.  Molybdenum  itself  may
 cause  adverse effects in  animals  at  10  to 20 ppm  in forage
 that is low  in  copper  [13] .    Cadmium  is  toxic  to  both  man
 and  animals in  doses  as  low as 15 ppm,  but ruminants absorb
 very small  proportions  of the cadmium they ingest.  Once
 absorbed,  however,  this  metal  is  stored in  the  kidneys  and
 liver   [19] ,  so   that  most  meat  and milk  products  remain
 unaffected   by   high   cadmium  concentrations  ingested   by
 livestock  [13] .

 With regard  to  effects  on crops, trace elements have  not
 caused  any adverse  effects on any of the crops grown at  the
 SR  systems  listed  in Table  9-3.    Similarly,  analyses  of
 forage  crops  grown  at  the  Melbourne.,  Australia,   system,
 which   has   operated  since 1896,  show relatively  little
 increase in  trace element  uptake over forage  crops  irrigated
 with    potable   water   [20].      Typical    trace    element
 concentrations in forage  grasses are presented in Table  9-6
 with  concentrations in  forage  crops grown  at  selected   SR
 sites.

At  the  OF  site near  utica,  trace  elements have  had   no
 adverse  effects  on  the grasses grown.   As  with the  soil  in
 this system, grass uptake  of trace elements is greatest near
 the  point  of  wastewater  application   and   decreases with
distance down  the treatment slope.   Grass  uptake accounted
 for  only 1.2, 1.4,  4.0,   and  7.6% of  the  applied  cadmium,
nickel,  copper,   and  zinc, respectively  [18].    If. trace
element  uptake  is a concern, the  use of Festuca  rubi'a (red
fescue)  at  OF systems is  recommended because trace  element
uptake  by   this  plant is   approximately  a  third  the trace
element uptake of most grasses  [18].
                             9-10

-------
                          TABLE 9-6
         TRACE ELEMENT CONTENT OF  FORAGE. GRASSES  AT
               SELECTED SR SYSTEMS  [4,  7,  21]
                             ppm
Melbourne,
Australia
Trace
element
Boron
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Molybdenum
Nickel
Zinc
Typical
range
1.0-80
0.2-0.8
0.1-0.5
0.05-0.5
2.0-15
250-600
0.1-10
15-200
0.1-4.0
0.1-3.5
8.0-60
Control
site
NTa
0.77
6.9
<0.64
6.5
970
<2.5
149
NT
2.7
50
Wastewater
irrigated
forage
NT
0.64-1.28
6.9-28
<0. 64-1. 28
11-19
361-987
<2.5
44-54
NT
2.7-9.1
58-150
Dickinson,
North Dakota
Control
site
14.1
<5
2
<1
7.4
NT
<5
53
<0.05
<0.5
22
Wastewater
irrigated
forage
19.6
<5
<5
<1
6.8
NT
<5
78
<0.05
<0.5
37
San Angelo,
Texas
Wastewater
irrigated
forage
NT
0.2-0.5
<0.5-1.5
NT
3.8-9.1
NT
NT
NT
NT
1.2-4.0
10-61
      a.  Not tested.
     9.5.3  Ground Water

Trace  elements  in  ground  water  can  limit  its  use  for
drinking  or  irrigation  purposes.    For  this  reason,  the
potential for trace element contamination of  ground  water is
a concern at SR and RI  systems overlying potable  aquifers or
aquifers  that  can  be  used  as  irrigation  water supplies.
Drinking  and  irrigation  water  standards  are  presented  in
Table 9-7.

The most  toxic  metals  to  man--cadmium,  lead, and mercury—
were demonstratably  absent in the  percolate  at five of  the
six  SR  sites  listed   in  Table  9-3;  the  sixth  site   gave
inconclusive  data  because   fallout  from  nearby   smelters
contaminated  the  soils.   Concentrations of  the metals  have
not  approached  toxic  levels  in any  of the  sites  studied
after up to 50 years of operation.

Cadmium, lead,  and mercury concentrations  in shallow ground
water were  comparable  to  concentrations in control  wells at
two of  the  three  RI  sites where trace metals were monitored
[17] .   At Hollister,  shallow ground water concentrations of
cadmium and lead were only slightly higher than control  well
concentrations   and    were   well   within    drinking   water
standards.    At  the   sites  studied,  trace  element   con-
tamination  of ground water has  not  been a  problem.  As  long
as  the  soil pH  is maintained  at 6.5 or higher, ground  water
contamination is likely to remain nonexistent.
                             9-11

-------
                           TABLE 9-7

             TRACE ELEMENT DRINKING AND IRRIGATION
                WATER STANDARDS  [8, 13, 22-27]

                             mg/L
Irrigation water


Drinking

Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Barium (Ba)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Chromium (Cr+6)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Selenium (Se)
Silver (Ag)
Thallium (Tl)
Vanadium (V)
Zinc (Zn)
a. Normal irrigation
b. Normal irrigation
c. Recommended Water
on Water Quality
water
—
0.145d
0.05^
1.0e
—
—
0.01e
0.05e
—
1.0*
0.3f
0.05e
0.05f
0.002e
—
—
0.016
0.05e
0.004d
—
5f
practice
practice
Quality
Criteria.
For fine
textured
soils3
20C
—
2°
—
0.5C
0.75°
0.05C
1.0C
5C
5C
20°
10C
10. Oc
—
0.05°
2.0°
0.02C
4-89
—
1.0C
10C
for 20 years.
, no time limit
Standards, 1972

d. EPA Toxic Pollutants Standards for Human

For
any soil
—
—
0.1°
__
O.lc
2c
0.01C
O.lc
0.5°
0.2C
5C
5.0C
0.02C
—
0.01C
0.2°
0.02°
	
—
0.1°
2c

.
Report to

Health.

For
livestock
5°
— «
0.2C
__
--
5.0p
0.05C
1.0C
1.0C
0.5C
— «.
O.lc
— «_
0.016
_._
_..
0.05C
_„
— .-
0.1<"
25C


EPA


e. EPA Primary Drinking Water Standards.
f. EPA Secondary Drinking Water Standards.
g. EPA Recommended Irrigation
Water Standards.
9.6  Microorganisms


Three classes of microorganisms can  be  pathogenic  to man and
animals:


     a   Bacteria


     ©   Viruses


     ©   Parasitic protozoa and helminths
                             9-12

-------
Several approaches have  been used at land treatment systems
to minimize the public health impacts of pathogens.  Many SR
and  RI  systems  use  primary  sedimentation  prior  to  land
treatment, thereby  removing most helminths.   Holding ponds
also can  be . used before  land treatment  to  inactivate most
pathogens.  Generally, a long detention time  (about 30 days)
and  moderate   temperatures  are   required   for  effective
pathogen removal (Section  4.4.1).     Many SR and RI systems
rely  on  the  filtering  capacity  of  the  soil  to  remove
bacteria,  helminths,  and  protozoa,  and on  soil adsorption
for virus removal.

There  are five  potential  pathways  for  pathogen transport
from land treatment systems:

     •   Soils

     •   Crops

     •   Ground water

     •   Surface waters

     •   Aerosols

     9.6.1  Soils

Straining  and  microbiological  activity  are   the  primary
mechanisms  for  bacterial  removal  as  wastewater  passes
through  soil.   Finer soils,  of  course,  tend to have higher
capacity  for pathogen  removal.   Depending on the particular
system  design,  there will  be either a mat  on  top  of  or  a
zone within  the  soil where intense microbiological activity
occurs.   Here,  bacteria,  protozoa,  and  helminths and their
eggs are  removed by  straining  and the predations of other
organisms, which consume the dead  organisms along with the
BOD  in  the applied  wastewater and convert them  primarily to
carbon  dioxide  and  ammonia.  No lasting  adverse effects to
soil have been noted that  result from these  organisms.

Bacteria  removal  in  the   finer  textured   soils  commonly
encountered at SR systems  is  usually quite high  (as shown in
Table  4-6).    Research  has  shown  that   complete bacteria
removal  generally occurs  within  the top 1.5 m (5 ft) of the
soil profile [28].   Similar  research has indicated that die-
off  occurs  in  two   phases:     during  the  first  48  hours
following wastewater  application,  90% of the bacteria died;
the  remainder  of  the  bacteria died  during  the following
2 weeks  [29].
                             9-13

-------
 Removal efficiencies at selected Rl systems are presented in
 Table 5-6.   As indicated by  this  table,  effective bacteria
 removals are achieved  at  RI  sites  when adequate soil travel
 distance is provided.

 At OP sites,  bacteria are removed near the  soil  surface by
 filtration,  biological  predation,  and  ultraviolet  radia-
 tion.   Fecal  coliform removals  in  excess  of  95%  can  be
 obtained by maximizing the OF residence time (increasing the
 removal  of  suspended solids)  and  applying wastewater  at  a
 slow and  relatively  continuous rate [30].   For  example,
 daily application of wastewater  for extended  periods (12 to
 18 hours)  results in  better  removal efficiency than shorter
 application  periods   (6  hours)   alternated   With  weekend
 drying.

 Adsorption is  the primary  mechanism   for  virus removal  at
 land treatment  systems.    Virus removal  at  SR systems  is
 quite effective.    Virus  removal  at  Rl   sites  depends  on
 initial  concentration,  hydraulic loading  rate,  soil  type,
 and  distance  traveled through the soil.   Virus transmission
 through  soil   at  RI   systems  is  presented  in  Table  9-8.
 Removal  at OF  sites  is generally the same  order of  magnitude
 as virus removal during conventional secondary treatment.

 It  is   possible  for  parasite  eggs,   such  as  Ascaris  and
 helminths,  to  survive for  months  to years  in  soil.   Although
 no conclusive  evidence has  been  found to  link  transmission
 of parasitic  infections  to operating land  treatment systems,
 vegetables  that will be consumed raw  should not be  grown  at
 land  treatment sites  for  at least 1  to  2 years after  land
 treatment  operations  are  terminated.

      9.6.2  Crops

 In the  United States,  the use of wastewater  for  irrigation
 of  crops  that  are eaten  raw  is not   common.   At  present,
 crops  usually   grown  include  fiber,  feed,  fodder,   and
 processed grains.   No  incidents  of infection  resulting  from
 crops  receiving  wastewater  have  been  identified  in   the
 United States.   Sewage farms  in  Paris apply raw wastewater
 to  fruit  and  vegetable  crops  (not   eaten  raw)  which   are
 approved for  public  consumption  by the Ministry of  Health,
with no  reported health problems.

Systemic   uptake   of   pathogens  by   crops  and  subsequent
 transmission through  the  food chain is not a problem.   When
extremely  high concentrations  of  viruses  were  applied to
damaged  roots and leaves,  plants did take up organisms along
with  water and nutrients  [31].  Several  studies performed
using  typical  wastewaters   on  undamaged  crops   show no
pathogen uptake [4, 6],
                            9-14

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                         TABLE 9-8
             VIRUS TRANSMISSION THROUGH SOIL AT
                       RI SYSTEMS [1]
Sampling Virus concentration, PFU/L
Location
Phoenix,
Arizona
(Jan- Dec
1974)


Gainesville,
Florida
(Apr-Sep
1974)




Santee,
California
(1966)
Ft. Devens,
Massachusetts
(1974)
Medford,
New York
(Nov 1976-
Oct 1977)



Vineland,
New Jersey
(Aug 1976-
May 1977)
aj-snance, 	 	 	
m At source
3-9 8
27
24
2
75
11
7 0.14 (avg over study period)
0.14 (avg over study period)
0.14 (avg over study period)
0.14 (avg over study period)
0.14 (avg over study period)
0.14 (avg over study period)
0.14 (avg over study period)
0.14 (avg over study period)
61 Concentrated type 3 polio


17 Indigenous virus, 276 (avg)
f2 bacteriophage seed,
2.2 x 105
0.75-8.34 Indigenous virus, 1.1-81.0

0.75 Polio virus seed, 7 x 104
(6 cm/h infiltration rate)
0.75 1-84 x 105 {100 cm/h
infiltration rate)
0.6-16.8 13 (avg over study period)
13 (avg over study period)
13 (avg over study period)
13 (avg over study period)
At sample point
0
0
0
0
0
0
0.005
0
0
0
0
0
0
0
0


8.3 (avg)
1.3 x 105

17 samples negative;
6 positive, at 0.47
(avg); range 0.14-0.66
Range 0-25.5

Range 0.03 x 104 to
97.5 x 104
9 of 10 positive, 1.62 avg
7 of 10 positive
2 of 10 positive, 1.95 avg
0 of 10 positive, 0.48 avg
When  wastewater  is applied  by  sprinklers,  the potential
exists for  pathogens to survive on  the  surface of a plant.
Sunlight is  an  effective disinfectant, killing pathogens  in
a few  hours to a  few  days;  but any  place  that stays warm,
dark,  and  moist  could harbor  bacteria.    For  this reason,
wastewater  is not  used to  irrigate crops that are eaten raw
unless a very  high degree  of  preapplication  treatment  is
provided.    To  protect  livestock,  grazing  should not  be
allowed  on  pasture   irrigated  with  disinfected  pond   or
secondary  effluent  for  3  to  4  days  following  wastewater
application.   At  least 1  week  should be  allowed between
applications  of   primary  effluent   and  grazing.    Longer
resting periods are  recommended for cold, northern climates,
particularly  when  forage  crops  such as  Reed canarygrass,
orchardgrass, and  bromegrass are irrigated  [29, 32].

The  National Technical Advisory Committee  on Water Quality
advises a standard  of-1,000 fecal  coliforms/100 mL  for water
used   in  agriculture   [20].    'Even   lower   fecal  coliform
                             9-15

-------
 concentrations  can  be  achieved,  without  disinfection,  by
 settling   and  storing   the  effluent  before   application
 (Section  4.4.1).

      9.6.3   Ground Water

 Because  viruses  can  survive  outside an  animal  host  for
 longer  periods of  time than  bacteria and other  pathogens,
 and   because  ingestion  of  only  a   few  viruses  may  cause
 disease,  virus  transmission  is  the , primary  concern  when
 evaluating  the ground  water pathway.   Other pathogens  are
 removed largely by filtration  or natural die-off  before they
 have  an  opportunity  to migrate  into  ground water.   Although
 no viral  standards  have been established, SR and  RI  systems
 that  discharge  to potable aquifers are designed  to meet  the
 bacterial  standard  listed in Table 2-4.  The intent,  of this
 standard  is  to  ensure that  renovated water is  essentially
 bacteria- and virus-free.

 As indicated in Section  9.6.1,  virus removal at  SR  systems
 is quite effective, mainly due  to  the adsorptive  capacity of
 soils  used  for  SR  systems.   Thus,   most  research on  virus
 transmission  has been  focused  on  RI systems  and  coarser
 textured   soils,  such  as   the   studies   summarized   in
 Table 9-8.   As indicated  in this table,  viruses can  enter
 ground water, particularly  when large virus concentrations
 are applied at high loading, rates to very permeable  soils.
 However,  the number  of viruses  that  are transmitted  is low,
 and  the   risk to  potential  consumers is  minimal provided
 adequate distance between the treatment site and  any  ground
 water wells  is maintained.

 Coliform  levels  found  in ground water underlying SR  and  RI
 systems  are  shown  in  Tables  4-6 and  5-6.    These  tables
 indicate  that over  99% of  the applied coliforms  is  removed
 within short travel  distances.   Provided  adequate distance
 is allowed,  it is possible  for any  well-operated SR  or  RI
 system to meet the coliform  standard  for drinking  waters.

     9.6.4   Surface Water

 Land treatment systems  that  discharge  to surface waters used
 for  drinking,  irrigation,   or  recreation  must  meet  local
 discharge   standards   for  microorganisms.     As  mentioned
 previously,   SR  and  RI  systems  should   have  no problems
meeting discharge standards.  The  microbiological  quality  of
 renovated water  from  OF systems generally  is comparable  to
 effluent   from   conventional  secondary  treatment   systems
without  chlorination.    Bacteria  removals  of 90  to  95%  or
 higher and  virus removals  of 70  to  90% are typical at  OF
 systems (Section 6.2.6).
                             9-16

-------
     9.6.5  Aerosols

Aerosols  are  very  small  airborne  droplets,  less  than  20
microns in diameter, that may be carried beyond the range  of
discernible  droplets  from sprinklers.   Sprinkler generated
aerosols  are slightly  smaller  than  ambient  aerosols;  two-
thirds to  three-fourths of  the 'sprinkler generated aerosols
are  in the  potentially  respirable  size  range  of  1  to  5
microns [33].   Aerosols may carry bacteria and viruses,  but
do not normally contain pathogenic protozoa or helminths  and
their  eggs.    Aerosols  may  come  from  sources  other  than
wastewater  treatment  sites,  such  as  cooling   towers   and
public  facilities.    As  a  result  of these  other sources,
ambient bacterial  concentrations in  the air  of some  cities
are  comparable   to  the  concentrations  found  near   land
treatment sprinkler zones.

As aerosols are generated, they  are  immediately subjected  to
an  "impact  factor"  that  may  reduce bacteria concentrations
by  90%  and virus concentrations by  70%  within seconds  [2] .
Further reduction may be  caused  by desiccation, temperature,
deposition,  and   solar  radiation.     Aerosol  dispersion,
influenced   by  wind   speed,   air   turbulence,   and  local
topography, occurs  concurrently.

The  concentration  of bacteria and  viruses  in aerosols  is  a
function  of  their  concentration in  the  applied wastewater
and  the aerosolization  efficiency of  the spray process.   The
latter  of these  factors  depends on  nozzle  size, pressure,
angle  of  spray  trajectory,  angle  of spray  entry  into  the
wind,  and impact  devices  [34].   Studies have  shown  that
approximately  0.32%  of  the  liquid  leaving  the  nozzle  is
aerosolized  [35].

Bacteria  cannot be  detected in aerosols at distances of  even
10 m   (33 ft)  from  sprinklers  unless  the  bacteria   con-
centrations  in the applied  wastewater are at  least  10^  to
104/mL,  [36].   When undisinfected  wastewater  is sprinkler
applied,  aerosol  bacteria  have  been  found  to  travel  a
maximum distance  of 400  m  (1,312  ft) from a sprinkler  line
[37].   Under some conditions, viruses have been-detected  at
distances  of up to  100 m (328  ft)  [2].   Concentrations  of
bacteria  and  enteroviruses  that  have  been  detected  near
various SR land  treatment sites are shown in Tables 9-9  and
9-10.
                             9-17

-------
                                    TABLE  9-9
                         AEROSOL  BACTERIA AT  LAND
                             TREATMENT SITES  [2]
Kastewater type
Raw or primary














Ponded,
chlorinated


Secondary/
nondisinfected






















Distance
downwind
Location from site, m
Germany 90-160'-'
Germany 63-400b»°
California 32&
Kibbutz Tzora, 10
Israel 10
20
60
70
100
150
200
250
300
350
400
Deer Creek, Control value
Ohio 21-30
41-50
200
Ft. Huachuca, Control value
Arizona Control value
45-49°


120-152°

Pleasanton, Control value
California 30-50







100-200







Bacteria
Coliforms
Col i forms
Coliforms
Coliforms
Fecal coliforms
Coliforms
Coliforms
Salmonella
Coliforms
Coliforms
Coliforms
Coliforms
Coliforms
Colifonrs
Coliforms
Standard plate count
Standard plate count
Standard plate count
Standard plate count
Standard plate count
Coliforms
Standard plate count

Klebsiella
Standard plate count

Standard plate count
Standard plate count
Total coliforms
Fecal coliforms
Fecal streptococci
Pseudomonas
Klebsiella
Clostridium perfringens
Mycobacterium
Standard plate count
Total coliforms
Fecal coliforms
Fecal streptococci
Pseudomonas
Klebsiella
Clostridium perfringens
Mycobacterium
Density
range3. No.
— „
—
—
11-496
35-86
0-480
0-501

30-102
0-88
4-32
0-17
0-21
0-7
0-4
23-403
46-1, 582^
0-1,429<3
<0-223
-------
                         TABLE  9-10
                AEROSOL ENTEROVIRUSES AT LAND
                     TREATMENT SITES [2]
Wastewater
type
Nondisinf acted
Location
Pleasanton,
Distance
downwind
from
sprinkler, m
50
Wastewater entero-
viruses, PFU/L
Range
45-330
Mean
188
Aerosol entero-
viruses, PFU/m
Range
0.011-0.017
Mean
0.014
  secondary    California
  effluent
Raw
wastewater


Kibbutz
Tzora,
Israel

36-42
50
70
100
0-650
—
170-13,000
0-82,000
125
650
6,585
16,466
0-0.82
—
0-0.026
0-0.10
0.015
Q.14
0.013
0.038
The  data in  Tables 9-9  and 9-10  can be  used to  estimate
human exposure  to aerosol bacteria  and enteroviruses.   For
example, a reasonable estimate may be  obtained  by  using  data
from Pleasanton, California.  At a distance  of  50  m  (164 ft)
downwind  from a sprinkler,  an  adult  male  engaged  in  light
work and  breathing at  a  rate of 1.2  m-^/h  (42 ft^/h) would
inhale  an   average  of  1  plaque-forming  unit   (PFU)   of
enterovirus  after  59 hours  of  exposure.    Although  this
represents   an   extremely   low   rate   of  potential  viral
exposure, methods  for recovering enteric viruses  currently
are not  entirely efficient and  actual viral exposure  may be
somewhat higher  [38] .

As shown  by  the data in  Table  9-11, aerosol fecal  coliform
concentrations  are lower  at SR  systems than  at  activated
sludge facilities.   Thus, the risk of disease  transfer  from
SR sites  should  be no greater  than  from  activated  sludge
facilities.  For this reason, epidemiological studies  of the
health effects  of  aerosols from activated sludge  plants may
be used  to conservatively estimate  the health  effects of SR
facility aerosols.

Epidemiological  studies of activated sludge plants  indicate
that  there  is   no  significant  disease  rate  increase   for
nearby populations  [39-44].  Based on  these  studies,  it  does
not  appear  that land  treatment system  employees  or  people
living near  sprinkler irrigation sites should anticipate  a
risk of disease due to aerosols.
                             9-19

-------
                           TABLE 9-11
                 COMPARISON OF  COLIFORM LEVELS
              IN AEROSOLS AT ACTIVATED SLUDGE AND
         SLOW RATE LAND TREATMENT FACILITIES [37,  45]
                             Maximum
                                         Median
                                                  Minimum
          Activated sludge
          Aerosols, No./m
           Upwind              28          0         0
           Over basins          146          14        0
           Downwinda            141          7         0
          Wastewater, No./lOO mL    8 x 107       1.6 x 106   1.1 x 104
          Aerated pond
          Aerosols, No./m
           Downwind
             30 m              452          ~        4
             100 m             5           --        1
             150 m             4  —        —
             200 m             5           —        0
             250 m             4           —-        0
          Wastewater, No./lOO mL    105          --        104
          Slow rate land treatmenta
          Aerosols, No./m3
           Upwind              1.0          BDC       BD
           Downwindd            12.2         1.0       BD
          Wastewater, No./lOQ mL    1.86 x 105     8.1 x 104   2.4 x 104

          a.  Fecal coliform levels reported.
          b.  Total coliform levels reported.
          c.  Below detection.
          d.  Up to 30 m (98 ft) downwind.
If necessary, several measures can be used to further reduce
bacterial  and  viral  exposure   through  aerosols.     First,
operating  sprinklers during  daylight  hours  increases  the
number  of   microorganisms  killed   by   ultraviolet   radia-
tion  [2] .  Sprinkling during  early  morning  hours is  prefer-
able   in   arid  or   semiarid   areas   for  water  conservation
purposes.     Second,  the  use   of   downward-directed„   low
pressure  sprinklers  results  in  fewer  aerosols than  upward-
directed  high pressure  sprinklers.    Ridge-and-furrow irri-
gation  or   surface  flooding   are  recommended  when  these
application  techniques are  feasible  [2].   Third, when public
residences are  near  the  sprinkler  system,  buffer  zones may
be  used   to  separate  the  spray  source   and  the  general
public.    In  general, public  access to  the  irrigation  site
should be  limited.    Finally,  planting vegetation around the
site  can reduce the  aerosol concentrations  leaving  the  site
[46] .   Coniferous  or deciduous  vegetation  have achieved up
                               9-20

-------
to 50% aerosol  removal by filtration.   Planted as a barrier,
these  types  of vegetation should  be able  to  reduce aerosol
concentrations  several orders  of magnitude  through vertical
dispersion and  dilution.

9.7  Trace Organics

Concern   over   trace   organics   arose   when   chlorinated
hydrocarbons  and  other trace organics  were  found in potable
water  supplies.    At  land  treatment sites,  the  concern  is
that trace  organics may  travel through the  soil profile  and
enter  drinking  water  aquifers  or  accumulate  in  the  soil
profile and be  taken up by plants.

     9.7.1  Soils

Many  trace  organics are  adsorbed as  they move  through  the
soil profile  at SR and RI  systems.   Chloroform is one  such
compound,  as   indicated   in  Table  4-7;   other  chlorinated
hydrocarbons  behave  similarly.    Although  the  adsorptive
capacity of a  soil is limited, once  trace organics have  been
adsorbed they may  be biodegraded  or  volatilized and released
to  the  atmosphere.    In  either  case,  the. adsorption  site
becomes  available  for  adsorption   of  additional  organic
molecules.

The  amount of  trace   organics  that can  be  removed   during
movement  through   the  soil  is  not  well  understood.    Some
research  has  been  conducted in  West Germany  using natural
sand  beds  to  filter  contaminated  river  water.   The river
water   contains  high  concentrations  of  trace  organics,
particularly  chlorinated hydrocarbons.  The observed removal
efficiencies  are  presented  in Table 9-12.   As shown in  this
table,  trace  organics  removal can be highly effective,  even
in coarser  soils.                                   ,

                          TABLE  9-12          .
                TRACE ORGANICS  REMOVALS  DURING
                     SAND FILTRATION  [47]
                        Constituent
                                          % removal
                Chlorobenzene                    96

                Dichlorobenzene                  45

                Trichlorobenzene                  12

                Chlorotoluene                    94

                Dichlorbtoluene                  62

                Dissolved organic chlorides          38

                Dissolved nonpolar organic chlorides    73

                Dissolved organic.carbon            68

                Benzene                        80

                Toluene                        95
                              9-21

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      9.7.2   Crops

 Plants   can   absorb  many   organic   pesticides   and   some
 organophosphate   insecticides  through   their   roots,   with
 subsequent  translocation to plant  foliage.   Uptake of  these
 organics  is  affected by the solubility,  size, concentration,
 and  polarity of  the  organic  molecules;  the  organic content,
 pH,  and  microbial  activity  of  the  soil;  and the  climate
 [48] .   However,  a recent  study  on health  risks  associated
 with  land application of sludge has found that the level  of
 pesticide  and herbicide  absorption is  quite  low;  not  more
 than  3% of the molecules  that were in the  soil passed  into
 plant  foliage [48].   Most trace  organics  are too  large  to
 pass  through  the  semipermeable   membrane   of  plant  roots.
 Thus,  it  is  unlikely  that  crop  uptake of trace  organics
 during  land  treatment is  significant enough  to  be 'harmful  to
 man or  animals.

     9.7.3   Ground  Water

 As  mentioned  in  Section   9.7.1,  soil  adsorption  of  trace
 organics  at  SR  and  RI  sites  can be an effective  removal
 mechanism.     For  this  reason, only  low  levels  of  trace
 organics  would be expected  to migrate to underlying ground
 water.     The  results   of   studies  at  two  SR   systems
 (Table  9-13)  and  two RI  systems  (Table 5-8)  indicate  that
 significant  removals  do  occur at  these systems  with the
 exception  of  the  Milton  RI  site  which  was  operated  at
 continuous  (no drying) extremely  high wastewater  loadings.
 At the  Milton site,  high  removals are achieved by  the  time
 ground  water  travels  a   distance   of  45  m   (160  ft)
 downgradient.   Endrin,  methoxychlor,  and toxaphene  were not
 detectable   in   the   wastewaters  of   any  of   the   four
 communities,  and  the concentrations of  lindane, 2,4-D, and
 2,4,5-TP silvex were  all well  below drinking  water  limits  in
 the  ground  waters   underlying the   land   treatment  sites
 (Table  2-4).

 Recent  research  at   the  phoenix   RI  site has  examined the
 removal  of  refractory volatile   organics  during  RI using
 secondary  effluent   [54].     The  results  are  presented  in
 Table 9-14.    As  shown by  this table,  fairly  high  removal
 efficiencies were obtained  (70  to  100%).

 Similar  research  conducted  at  the   Fort   Devens   RI   site
 indicated that 80 to  100% of  the applied  refractory  organics
 is removed during RI; average removal  of trace organics was
 96%  [50].   Based  on the  results  of these  studies, it does
not appear  that  normal concentrations of trace organics  in
 applied wastewaters  would  cause  problem levels  in ground
waters  underlying  SR and  RI sites.  Detailed studies on the
                             9-22

-------
fate  of trace  organics  during  land treatment are  underway  at
the   Muskegon   SR   site;   these   studies   should   provide
additional  insight  into  the potential  risk  of ground water
contamination.
                            TABLE 9-13
     TRACE  ORGANICS  REMOVALS AT SELECTED SR  SITES  [4,  6]
                               ng/L

Endrin
Lindane
Methoxychlor
Toxaphene
2,4-D
2,4, 5-TP
silvex
Roswell ,
Wastewater
<0.03
560
<0.01
<0.1
29.0
28.0
New Mexico
Ground water
<0.03
74.3
<0.01
<0.1
10.4
25.8
Dickinson,
Wastewater
<0.03
397
<0.01
<0.1
17.0
93
North Dakota
Ground water
<0.03
53.6
<0.01
<0.1
6.2
47.1
                            TABLE  9-14
            REMOVAL  OF REFRACTORY VOLATILE ORGANICS
                BY CLASS  AT PHOENIX RI SITE [49]
               Class (typical example)
Removal,  %
           Chloroalkanes (tetrachloroethylene)          70
           Chloroaromatics  (p-dichlorobenzene)          94
           Alkyabenzenes (o-xylene)                   98
           Alkyaphenols (p-isopropylphenol)             85
           Alkylnaphthalenes (2-methylnapthalene)      100
           Alkanes  (hexatriacontane)                  71
           Alcohols  (2,4-diraethl-3-hexanol)             95
           Ketones  (2,6-d-t-butyl-p-benzoquinone)       98
           Indoles,  Indenes (IH-indole)                96
           Amides (N-[3-methylphenyl]  acetamide)        74
           Alkoxyaromatics  (butoxymethylbenzene)        91
            Weighted average                        92
      9.7.4   Surface  Water
Discharge  from  the  OF  process will  directly impact  surface
water  in  most  cases.    The  effectiveness  of trace organics
removal  during  OF  has  been  studied  at  a  pilot  system  in
Hanover,  New  Hampshire.   Chlorinated  primary  effluent  was
used in  these  studies;  this effluent contained  6.7  to  17.8
                                9-23

-------
ug/L  chloroform,  10.2  to  33.1   ug/L  toluene,  and  lesser
amounts   of   bromodichloromethane,   1,1,1-trichloroethane,
tetrachloroethylene,  and  carbon tetrachloride [51].  Using a
30.5 m  (100 ft) long  slope  with a 5%  grade,  chloroform and
toluene  removals were as presented  in  Table 9-15.   These
efficient   removal    rates   are   thought  to  result   from
volatilization  as  the wastewater  flows  over the  slope  or
sorption near  the soil surface followed  by either microbial
degradation  or volatilization.   Based  on  these  results,  it
appears  that   volatile  trace  organics  contamination  of
surface waters  by renovated  water from  OF systems should not
be  a  problem  unless  initial  concentrations  are  excessive.
Studies  are  underway  on  the removal  of  nonvolatile organic
compounds.

                          TABLE 9-15
                CHLOROFORM AND TOLUENE REMOVAL
                        DURING OF  [51]
Application
rate,
cm/h
Chloroform
0.40
0.60
0.80
1.05
1.32
Toluene
0.40
0.60
0.80
1.05
1.32
Concentration at various travel distances.
Waste-
water
17.8
6.7
13.2
6.7
9.0

33.1
10.2
28.7
21.5
18.8
3.8 m
12.4
5.7
6.4
—
7.8

20.7
6.2
10.0
—
9.9
7.6 m
6.9
3.8
5.9
5.9
6.8

4.9
2.4
7.8
9.8
7.7
15.7 m
3.1
2.1
3.7
4.1
6.1

BDa
0.5
3.9
7.4
6.3
22.9 m

0.9
1.5
—
1.4

— •
BD
BD
--
1.4
ug/L
Runoff
0.3
0.5
0.8
1.1
1.9

BD
BD
BD
0.7
0.8
Total
removal ,
%
98.3
92.5
93.9
83.6
78.9

100.0
100.0
100.0
96.7
95.7
9.8
   a.  BD - concentration was below a detection limit estimated at
         0.01 pg/L.

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                             9-24

-------
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10.   Aulenbach, D.B.  Long-Term Recharge of Trickling Filter
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11.   Benham-Blair   &   Affiliates,  Inc.,   and  Engineering
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12.   Koerner,  E.L. and D.A. Haws.  Long-Term Effects of Land
     Application  of  Domestic  Wastewater:    Vineland,  New
     Jersey Rapid  Infiltration Site.    U.S.  Environmental
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                             9-25

-------
13.



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Uiga,  A.,  R.C.  Fehrmann, and  R.W.   Crites.   Relative
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Leach, L.E., C.G. Enfield, and C.C. Harlin.  Summary of
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Peters,  R.E.,   C.R.   Lee,  and  D.J.  Bates.    Field
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Seabrook,  B.L.    Land   Application   of  Wastewater in
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430/9-75-017.  May 1975.
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1979.  pp. 15926-15970.
                                              March 15,
Federal  Register.   Water  Quality Criteria.   July 25,
1979.  pp. 43660-43697.
Federal Register.   Water  Quality Criteria.
1979.  pp. 56628-56657.
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29,
25.   Metcalf   &   Eddy,   Inc.     Wastewater   Engineering:
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26.   Manual of Treatment  Techniques  for Meeting the Interim
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27.   McKee,  J.E.  and  H.W.  Wolf.   Water  Quality Criteria.
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     1963.

28.   Jenkins,  T.F.  and A.J.  Palazzo.   Wastewater Treatment
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     Bell,  R.G.   and  J.B.   Bole.    Elimination  of  Fecal
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30.   Hoeppel,  R.E.,  R.G.  Rhett,  and  C.R.  Lee.    Fate  and
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31.   Shuval, H.I.   Land Treatment of  Wastewater in Israel.
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32.   Popp,  L.     Irrigation   with  Sewage  from  the  Hygenic
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33.   Bausum, H.T.,  et'al.   Microbiological  Aerosols from  a
     Field   Source   During    Sprinkler   Irrigation   with
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     August  20-25,' 1978.

34.  Schaub,  S.A.,   et al.    Monitoring  of Microbiological
     Aerosols  at  Wastewater  Sprinkler   Irrigation  Sites.
     Proceedings  of  the  Symposium  on  Land   Treatment  of
     Wastewater,  HanoVer,  New  Hampshire.    August  20-25,
     1978.
                             9-27

-------
35.  Sorber,  C.A.,  et al.  A Study of  Bacterial  Aerosols  at
     a  Wastewater  Irrigation Site.   journal WPCF.   48(10):
     2367-2379.  1976.

36.  Johnson,    p.E. ,    et   al.        The    Evaluation    of
     Microbiological    Aerosols    Associated    with   the
     Application   of   Wastewater   to   Land:     Pleasanton,
     California.    U.S.   Environmental  Protection   Agency.
     EPA-600/1-80-015.   1980.

37.  Katzenelson,  E.  and  B.  Teltch,  Dispersion  of  lEnteric
     Bacteria by Spray Irrigation.  journal  WPCF.  48(4)710-
     716.  1976.

38.  Teltsch,  B. ,  et al.   Isolation  and Identification  of
     Pathogenic   Microorganisms    at   Wastewater-Irrigated
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     39:1183-1190.  1980.

39.  Uiga,  A.  and  R.W.  Crites.   Relative  Health Risks  of
     Activated   Sludge    Treatment  and   Slow   Rate   Land
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40.  Clark,  C.S.,   et al.    A  Seroepidemiologic Study  of
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     August 20-25, 1978.

41.  Pahren,   H.R.     Wastewater  Aerosols  and  Disease.
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     September 28 to October 3, 1980.

42.  Carnow, B. , et  al.   Health Effects of  Aerosols  Emitted
     from  an  Activated  Sludge Plant.    U.S.  Environmental
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43.  Crites, R.W.  and A.  Uiga.   An Approach for Comparing
     Health Risks  of  Wastewater  Treatment  Alternatives  - A
     Limited  Comparison  of Health Risks Between Slow  Rate
     Land  Treatment  and  Activated  Sludge  Treatment  and
     Discharge.    U.S.   Environmental  Protection   Agency.
     EPA-430/9-79-009, MCD-41.  1979.

44.  Pahren,  H.R.   and  W.  Jakubouski,  eds.    Wastewater
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     Agency.  EPA-600/9-80-028.  December 1980.
                             9-28

-------
45.   Sorber, C. et. al.  Bacterial Aerosols Created by Spray
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46.   Spendlove,  J.C.,  et  al.    Supression  of  Microbial
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47.   Sontheimer, H.   Experience with River Bank Filtration
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49.   Tomson,  M.B.,  et  al.    Ground  Water  Contamination by
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50.   Tomson,  M.B.,  et al.   Trace Organic  Contamination of
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51.   Jenkins,  T.F., D.C.  Leggett,  and C.J.  Martel.   Removal
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                             9-29

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                         APPENDIX A

                  SLOW RATE DESIGN EXAMPLE
A.I  Introduction

This  design example  is  presented  to  .illustrate  the pro-
cedures described in Chapter 4 for the preliminary design of
slow rate  (SR)  systems.   The  example  is detailed enough to
allow cost comparison with other alternatives.  The focus of
this example is on determining the major design variables in
land treatment  systems including  crop  selection, hydraulic
loading rate, land  area  requirements,  storage requirements,
and  application method.    Supplemental  components  such as
pumping and headworks requirements are discussed  briefly and
listed for cost comparison purposes.

A. 2  Statement of Problem
    A.2.1
Background
City  A is  located  in central  Missouri in  an area  charac-
terized by  fertile soils -and intensive  farming.  Rainfall  is
more plentiful than is needed for most  crops,  but  is  distri-
buted  unevenly during  the year,  Supplemental irrigation  is
beneficial  to most crops  in summer.

The  existing wastewater  treatment  facility  consists  of  a
single  stage trickling filter  with anaerobic digestion  and
sludge  drying, beds.   The  facility  is in  poor  structural
condition   and   unable   to  meet   present   NPDES  permit
requirements.
    A.2.2
Population and Wastewater Characteristics
Population  and  wastewater characteristics  are presented  in
Table A-l.  Industrial flows  are expected to  be nontoxic  and
biodegradable.
    A.2.3
Discharge Requirements
Surface discharge of wastewater  is  prohibited  for  streams  in
the area, and  the ground water aquifer  is  used as  a  drinking
water  source  so drinking water  quality will  be expected  at
the project boundary.
                             A-l

-------
                           TABLE A-l
           POPULATION AND WASTEWATER CHARACTERISTICS
              Design year

              Population

              Average annual flow, m /d

               Industrial
               Municipal

                 Total

              Maximum monthly avg flow, m3/d

              Infiltration into sewers


              Wastewater strength, mg/L

               BOD 5
               SS

              Total nitrogen, mg/L (as N)

              Total phosphorus, mg/L (as P)
                             2005

                             18,900
                               416
                             7,154

                             7,570

                             9,085

                              None
                          (nonexcessive)
                               200
                               200

                               38

                                8
    A.2.4
Site Characteristics
The  proposed  site  for  the  treatment  facility  is  shown in
Figure  A-l.    The site  was chosen because  of its  isolation
from  population  centers,  its  location  downwind   from  the
city,  and  the  availability of  flat,  well-drained  soils in
the area.   According to  an old SCS map, shown in Figure A-l,
Bosket  fine   sandy  loam dominates   the  treatment   site  and
Cooter  silty  clay dominates  the  treatment  pond  site.   Both
areas have 0  to 1% slope.
    A.2.5
Climate
The  area is  subject to  frequent changes  in weather  with no
prolonged  periods  of  very cold  or  very  hot  weather.   The
last  freeze is usually5 in  late March and the first freeze in
early November.        •

Climatic data,   obtained   from  the  National   Oceanic  and
Atmospheric  Administration's   Climatography  of  the  United
States,  are shown in Table A-2 for the nearest  United States
No. 20  recording station to City A.   The  data  represent the
worst year  in   5   for  monthly  average  precipitation  and
temperature.
                              A-2

-------
                                    PROPOSED
                                        POND
TREATMENT
SITE
PROPOSED SR SITE

Predominant
soil series
Bosket '


Broseley

Canalou


Cooter

Crevasse

Gideon

Lilbourn
Sikeston

Map
symbol
BtA,
BtB

ByA,
ByC

Cd


Co

CsB

Gd,
Ge
Lb
St
Depth to
seasonal high Depth from
water table, m surface, cm
>1.5 0-64
64-147
147-198
>1.5 0-94
94-160
160-190
0.6-0.9 0-51
51-122
122-160
0.6-0.9 0-38
38-152
>1.0 0-25
25-152
0-0.3 0-114
114-173
0-0.5 0-94
0-0.3 0-30


Permeability,
Dominant USDA texture
Fine sandy loam
Clay loam and sandy clay loam
Fine sandy loam and sand
Loamy fine -and
Fine sandy loam
Loamy fine sand
Loamy sand
Sandy loam
Sand
Silty clay
Loamy sand and sand
Loamy sand
Sand
Loam
Clay loam
Fine sandy loam
Sandy clay loam ,
cm/n
• 5-15
1.5-5
5-15
15-51
5-15
15-51
15-51
15-51
15-51
0.15-0.5
15-51
15-51
15-51
1.5-5
1.5-5
5-15
1.5-5
          FIGURE  A-1
           SOILS  MAP
                 A-3

-------
                          TABLE A-2
            CLIMATIC DATA FOR THE WORST YEAR IN 5
Temperature °C
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Mean daily,
Mean minimum
-0.7
-0.9
1.3
12.7
16.7
21.1
24.1
24.4
19.8
11.9
4.6
-0.1
-6.6
-8.1
-5.6
4.6
8.3
13.9
16.7
15.9
9.6
0.2
-3.1
-6.6
Days with
mean
temperature,
<.-4 °C
20
15
12
0
0
0
0
0
0
4
12
17
80
Total
precipitation ,
cm
10.1
10.4
15.1
15.8
17.4
14.2
14.0
12.2
14.7
9.9
14.8
13.0
162
A.3  Slow Rate System Selection

The  selection  of the type of land treatment process  is  dic-
tated  by site conditions,  climate,  and regulatory require-
ments.   In the  case of  City A,  the prohibition of  surface
discharge eliminated overland  flow from consideration.   The
limit  of 10 mg/L nitrate  in the  ground water, coupled  with
the  high ground water  table,  eliminated rapid infiltration
as an  alternative.   The  SR process appeared  feasible based
on land  availability, soil  permeability, and climate.
    A.3.1
Preapplication Treatment
The  existing  treatment  facilities  cannot be  used for  pre-
application   treatment   without  extensive  rehabilitation.
Consequently, treatment  prior to land  application is to be
provided by  a series of  treatment/storage  ponds.  The  pri-
mary  cell  is designed  according  to  state  standards:;   BOD
loading equals 38.1 kg/ha-d  (34 lb/acre-d) with an operating
depth of 1.0 m.   The secondary cell is designed for storage.
                             A-4

-------
    A.3.2
  Crop Selection
As discussed  in Section 4.3,  the  crop selected  for the SR
process depends on  whether the objective is crop production
for  revenue  or minimization  of  land  area  by  maximizing
hydraulic  loading  rates.    For City A, the  objective is to
minimize  land  area.    Based  on  the  selection  criteria in
Chapter 4  and  conversations  with  the local  farm  advisor,
City A chose  to evaluate water  tolerant  forage grasses  and
deciduous  forest as two possible crops in an SR system.   The
proposed  site shown in Figure A-l  would  be used for either
crop.

A.4  System Design

    A.4.1     Forage Crop Alternative

Minimizing  land area  requires  the use of the maximum allow-
able hydraulic  loading rate which  is governed  either by  soil
permeability  or  nitrogen  loading.    Once   the   hydraulic
loading rate  is determined, field area and storage  require-
ment are obtained.

         A.4.1.1    Hydraulic Loading Based  on  Soil
                    Permeability

The  general water  balance equation is used to determine  the
allowable   hydraulic  loading  based   on  soil  permeability
(Section  4.5.1) and is shown as:
where  LW =

       ET =
       Pr

       pw
         Lw = ET - Pr + Pw                (4-3)

wastewater hydraulic loading rate, cm/unit time

evapotranspiration rate, cm/unit time

precipitation rate, cm/unit time

percolation rate, cm/unit time
The  computation is performed on a monthly basis  in  the' form
of a water balance table shown in Table A-3.   The  procedure
follows  that  presented  in  Section  4.5.1  and  is  outlined
below:

     1.   Design precipitation for each month is based  on  a
         5_vear return period and is obtained  from  climatic
         data  (Table A-2).    The  frequency analysis  is per-
         formed according  to  standard  procedures  available
                             A-5

-------
     in  most hydrology  texts  or reference  books.    The
     precipitation values are entered  in Column  (1).

2.   Estimated  monthly  evapotranspiration  (ET)  values
     for  the forage grass  are obtained  from the local
     Cooperative  Extension  Service  and are  entered  in
     Column  (2).

3.   The  net ET  for each  month  is determined  by  sub-
     traction of Column  (1)  from Column (2).

4.   The maximum design  percolation rate  is based on  4%
     of  the  minimum permeability in  the  soil profile—
     1.5 cm/h  (0.6  in./h).   A  value  of  4%   is   used
     because  it  is  necessary  to  be   conservative   for
     preliminary design.   Further  optimization  will  be
     possible during final  design.   The limiting perme-
     ability is 1.5 cm/h in the clay loam layer at 64  cm
     (25  in.)  in  the  Bosket  soils (Figure A-l)»   The
     maximum  daily  percolation  rate  is  computed   as
     follows:

        Pw (daily)  = 0.04 (1.5 cm/h)(24 h/d)
                   = 1.44 cm/d

     The monthly rate  is then  determined  by multiplying
     the  daily  rate  by  the  number  of operating  days
     during  the  month.     Some  months  may  have  non-
     operating days  due to  farming operations  or  cold
     weather.

     Green chop  harvesting  is planned for  this  system
     such  that   downtime for  harvesting  will  not  be
     necessary.    Operation  will stop  on  days when  the
     mean temperature is less than  -4 °C (25 °F).   Based
     on  the  climatic  data   in  Table A-2,  nonoperating
     days due to  cold weather  are  expected  during  the
     months of October through March.

     For  example,  in  January,  the  design  percolation
     rate is:

          Operating days  = 31 - 20  = 11 d

                Pw  (Jan)  = (1.44  cm/d)(11  d/mo)

                         = 15.8 cm/mo

     The  design  percolation  rate  for  each  month  is
     entered  in  Column  (4).
                         A-6

-------
    5.    The allowable hydraulic loading rate for each month
         is computed  by adding  Column (3)  and  Column  (4).
         The annual  hydraulic  loading  rate  is  computed by
         summing  the   monthly  rates  and   equals  326 cm
         (128 in.).

                         TABLE A-3
            HYDRAULIC  LOADING  RATES  BASED  ON SOIL
           PERMEABILITY:  FORAGE CROP ALTERNATIVE
                             cm
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
(1)
Precipitation
Pr
10.1
10.4
15.1
15.8
17.4
14.3
14.1
12.3
14.7
9.9
14.8
13.0
162
(2)
Evapo-
transpiration
ET
0.3
0.7
2.1
5.6
9.7
13.4
15.7
13.9
8.9
5.0
1.8
0.6
78
(3)
ET - Pr
(2)-(l)
-9.8
-9.7
-13.0
-10.2
-7.7
-0.9
1.6
1.6
-5.8
-4.9
-13.0
-12.4
-84
(4)
Percolation
PW
15.8
18.7
27.4
43.2
44.6
43.2
44.6
44.6
43.2
38.9
25.9
20.2
410
(5)
Hydraulic Loading
Lw(P)
(3) + (4)
6.0
9.0
14.4
33.0
36.9
42.3
46.2
46.2
37.4
34.0
12.9
7.8
326
         A. 4.1.2   Hydraulic Loading Based on Nitrogen
                   Loading

The  annual  hydraulic   loading  rate  based  on  nitrogen  is
determined by using equation 4-4, shown below:
               Jw(n)
= (Cp)(Pr - ET) + (U)(10)
      (1 - f)(Cn) - Cp
                                                       (4-4)
where  LW(n) = allowable annual hydraulic loading rate
                 based on nitrogen limits, cm
                             A-7

-------
cp
Pr

ET

U

f


cn
              = percolate  nitrogen  concentration,  mg/L

              = design precipitation,  cm/yr

              = evapotranspiration  rate,  cm/yr

              = crop nitrogen uptake,  kg/ha' yr

              = fraction of applied nitrogen removed  by
                volatilization, denitrification, and  storage

              = applied wastewater  nitrogen  concentration,
                mg/L
The  computation  was performed  using  annual rates  according
to the  procedure  presented in Section 4.5.2 and  is outlined
,as follows:

    1.   Determine parameter values for Equation  4-4.

         a.   Crop uptake  (U)

              U = 224 kg/ha'yr  (from Table  4-11)

         b.   Volatilization  +  denitrification  +
              (V + D + S)
    2.
                                             storage
      f = 0.2 (estimated, Section 4.2.2)

 c.    Applied nitrogen concentration (C )

      Compute  reduction  in  nitrogen  concentration
      during  storage  based   on  a  53  day  storage
      period which is  the  minimum detention time in
      the treatment/storage ponds (Table A-7 ) .

      Cn = (38 mg/L)e-°-0075(53>

         = 26 mg/L

 d.    Percolate nitrogen concentration (C,-.)
                                         P
      C  = 10 mg/L  (required)

 Solve Equation 4-4.

              =  10(84) + 224(10)
                      = 285 cm/yr  (112 in./yr)
                             A-8

-------
         A.4.1.3   Design Hydraulic Loading Rate

As  shown  in  Sections A.4.1.1  and  A.4.1.2,  the  allowable
annual hydraulic  loading  rate based on soil permeability  is
326 cm  (128  in.)  and the  rate  based on  nitrogen limits  is
285 cm (112  in.).  Since nitrogen loading  limits  the  hydrau-
lic  loading  rate  in this example,  the  allowable  hydraulic
loading  rate is  determined  by comparing  monthly Lw^p^ and

Lw(n)'

Monthly hydraulic  loading rates based on  nitrogen limits are
determined using  Equation 4-4 with monthly values for Pr and
ET  obtained  from Table  A-3.   Sufficient data  on nitrogen
uptake versus  time for forage crops were  not  available, re-
quiring monthly  values for U to be estimated  from the ratio
of  monthly ET to  the  total  growing  season ET multiplied  by
the annual crop  uptake value  (Table A-4,  Column  2).

                          TABLE A-4
                DESIGN HYDRAULIC LOADING RATE
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
(1)
Pr-ET,
cm
9.8
9.7
13.0
10.2
7.7
0.9
-1.6
-1.6
5.8
4.9
13.0
12.4
(2)
u,
kg/ha
0.9
2.0
6.1
16.1
28.0
38.5
45.3
40.1
25.7
14.4
5.2
1.7
(3)
Lw(n) »
cm
9.9
10.8
17.7
24.4
33.0
36.5
40.5
35.6
29.2
17.9
16.9
13.1
(4)
LW(P) '
cm
6.0
9.0
14.4
33.0
36.9
42.3
46.2
46.2
37.4
34.0
12.9
7.8
(5)
Design Lw,
cm
6.0
9.0
14.4
24.4
33.0
36.5
40.5
35.6
29.2
17.9
12.9
7.8
267
                             A-9

-------
 The monthly values of  Lw,n)  and  Lv(r))  are compared with the
 lower  value  used  for  the  monthly design  hydraulic  rate
 (Table A-4, Column 5).   Summing the design monthly hydraulic
 loading rate  gives the  design annual hydraulic loading rate,
 267 cm (105 in.).

          A.4.1.4   Field Area Requirements

 The design annual  hydraulic  loading rate  is  used  to deter-
 mine the field  area requirement:
                                                        (4-6)
where
 Aw =

  Q =

AV,, =
       A  = Q(365) + AVg
              104  (Lw)

field area, ha

average daily flow, m3/d

net gain or loss in stored wastewater volume
due to precipitation, evaporation, and
seepage at storage pond, m3/yr
         Lw = design  annual  hydraulic  loading  rate,-m/yr


For the first calculation  of field  area,  AVS  is  assumed  zero
(see Section A. 4. 1.6) and  the field area  is calculated ass
                   (365  d/yr)  =
           Aw = 7,570 m
                (104mVha)(2,67 m/yr)
         A.4.1.5   Storage Requirements

Storage of wastewater is required for periods when available
wastewater exceeds  design  hydraulic loading  rate.   A water
balance  computation   is  used   to   estimate  the  storage
requirement.   The procedure is outlined as follows:

    1.   Enter   the   design  monthly :loading   rates  from
         Table A-4 (Column 5) into Table A-5, Column 1.

    2.   Determine available wastewater for each month.

                           w  = Q(D)(O.OD
                           "a   	
         where
        W.
                     Aw

       = monthly  available  wastewater,  cm/mo
                            A-10

-------
         Q  = average  daily flow, m3/d

         D  = days  per month
         w
            = field  area,  ha
The  average daily  flow  is  assumed constant.   For
example   the  monthly   wastewater   available  for
June is:
  ,
a June
          = (7,570 m yd) (30  d/mo) (0.01)
                       103.4  ha
          =  22.0  cm/mo

The  monthly  values  of  available  wastewater  are
entered  in Column (2)  of Table A-5.

                 TABLE A-5
       STORAGE VOLUME DETERMINATION:
          FORAGE CROP ALTERNATIVE
                     cm
Month
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
(1)
Hydraulic
load ing j
Lw
29.2
17.9
12.9
7.8
6.0
9.0
14.4
24.4
33.0
36.5
40.5
35.6
(2)
Wastewater
available,
"a
22.0
22.7
22.0
22.7
22.7
20.5
22.7
22.0
22.7
22.0
22.7
22.7
(3)
Change in
storage,
(2)-(l)
-7.2
4.8
9.1
14.9
16.7
11.5
8.3
-2.4
-10.3
-14.5
-17.8
-12.9
(4)
Cumulative
storage,
Sc
0.2a
4.8
13.9
28.8
45.5
57.0
65.3
62.9
52.6
38.1
20.3
7.4
     a.  Rounding error, assume zero.
                    A-ll

-------
     3.
4.
5.
     Compute  the  change  in  storage each  month by  sub-
     tracting hydraulic loading  [Column  (1)]  from  avail-
     able wastewater  [Column  (2)].  Enter  the  results
     Column (3).
                                                            in
          Compute  the cumulative  change  in  storage  in the end
          of  each  month by  adding the  change  in storage  in
          Column (3)  to  the  accumulated  quantity  from  the
          previous month in  Column (4).

          Compute  the required  total  storage  volume  using the
          maximum  cumulative  storage  in Column  (4)  and  the
          estimated field area:
                  =  (65.3  cm)(103.4  ha)(102  m3/cm-ha)

                  =  675,200 m3

          A.4.1.6    Final  Storage  and Pond Design

The facultative  pond for preapplication treatment, serves  as
the storage  reservoir.  A two-cell  pond system  is  selected
with  the  design criteria  of  the  primary  cell based on  the
state's   BOD    loading    criteria  of    38.1 kg   BOD/ha'd
(34 lb/acre*d) and an  operating depth of 1.0 m.
     Ap = area  (primary)
        _ (7570  m3/d)(200  mg/L)(10"6 kg/mg)(103 L/m3)
                            38.1 kg/ha-d
        = 39.7   use  40 ha
     Vp = volume (primary)
        - (40 ha)(lO* m2/ha)(1.0 m)

        = 400,000 m3

The  storage  volume  in  the second  cell  is the  difference
between  the  required  total storage  and  the  volume of  the
primary cell.

                     vsec  = Vs - Vp
                           = 675,200 - 400,000

                           = 275,200 m3

The actual  volume of  the  secondary  pond will change due  to
evaporation, precipitation and seepage in the  two cell  pond
                             A-12

-------
area.   To  obtain  the  final  storage  volume  the following
steps are used.

    1.   Calculate the storage area of the second cell using
         a volume  of 275,200  m3  and an  operating  depth of
         1.5 m.
         Asec ~  fec
                                                   (4-8)
              _ 275,200
                ~T75
              = 183,500 m'
                         use 18 ha
         Determine  the  monthly net gain  or  loss in storage
         volume due to precipitation, evaporation, and seep-
         age (Table A-6, Column 3).  Annual lake evaporation
         equals 89 cm (33 in.) and is distributed monthly  in
         the  same ratios  of monthly  ET to  annual  ET.   A
         maximum  seepage rate  of 0.15  cm/d  is  allowed  by
         state  standard.    As an  example,  the  net  gain  or
         loss for July is:
            july
             = (Precipitation - evaporation - seepage)

             x (surface area)

             = (14.1 - 18.0 - 4.6H58 ha)

             x  [(102 m/cm) (104 m2/ha)]

             = -49,300 m3

3.   Tabulate  the  volume  of  wastewater  available  each
     month,  Qm.    In  this  example,  the daily  flow  is
     assumed  constant  and  monthly  flows vary according
     to  the   number   of   days  per  month   (Table A-6,
     Column 4).

             Qm     =  (7,570  m3/d)(31 d)
              mjuly
                    = 234.7 x 103 m3/mo


4.   Determine  the adjusted  field  area  accounting for
     the net gain  from storage.
                          £AV
                                                   (4-10)
                      (Lw)(10  m/ha)
                             A-13

-------
                    = (108.0  +  2,763.3)(103 m3)

                           2.67 m  (104)
                    = 107.5 ha  (266  acres)
                           TABLE
            FINAL DETERMINATION
                              A-6
                              OF STORAGE VOLUME
Month
Sep
Got
Nov
Dec
Jan
Feb
Mar
Apr
May
(Tun
Jul
Aug
Annual
(1)
Evaporation ,
cm
10.2
5.7
2.1
0.7
0.3
0.8
2.4
6.4
11.1
15.3
18.0
15.9
(2)
Seepage,
cm
4.5
4.6
4.5
4.6
4.6
4.2
4.6
4.5
4.6
4.5
,4.6
4.6
(3)
Net gain/loss
AVB
m3 x 103
0
-2.3
47.6
44.7
30.2
31.3
47.0
28.4
9.9
-31.9
-49.3
-47.6
108.0
(4)
Available
wastewater
,Qnu ,
m3 x 10J
227.1
234.7
227.1
234.7
234.7
212.0
234.7
227.1
234.7
227.1
234.7
234.7
2,763.3
(5)
Applied
wastewater
m^x'lO3
313.9
192.4
138.7
83.8
64.5
96.8
154.8
262.3
354.7
392.4
435.4
382.7
2,872.4
(6)
Change in
storage*3
m3 x 103
-86.8
40.0
136.0
195.6
200.4
146.5
126.9
-6.8
-110.0
-197.2
-250.0
-195.6
(7)
Cumulative
storage
Sc,
m3 x 103
85.7
-l.la
40.0
176.0
371.6
572.0
718.5
845. 4b
838.6
728.5
531.3
281.3
a.  Rounding error, assume zero.
b.  Design storage volume
5.   Calculate  the monthly  volume of  applied wastewater
     (Table  A-6,   Column 5)  using  the  design  monthly
     hydraulic  loading   rate  and  adjusted   field
     For example:
                                                        area.
        V
         w
          July      "July   w

               =  (40.5 cm)(107.5 ha)(102)

               =  435.4 x 103 m3
(10~2 m/cm)
                                                     (4-11)
                              A-14

-------
    6.   Determine  the  net  change  "in  storage  each  month
         (Table   A-6,   Column 6)  based  on  monthly  applied
         wastewater, Vw,  available  wastewater,  Q ,  and  net
                       .w
         storage  gain/loss,  AVS.

               Change in storage  =  Q  + AV_ - V,
                                                'w
    7.   Calculate the cumulative  storage volume  for the end
         of  each  month (Column  7)  to determine  the maximum
         design storage volume.
               Vs = 845,400 nr
    8.   Adjust the depth  of the  second cell to  accommodate
         the  increased storage  volume.
                 s
                    = 845,400  -  400,000 = 445,400
                    = vsec _  445,400 m3
                                       2
(4-12)
                              180,000 m
                    = 2.47m,  use 2.5m.
The depth  of  ground water prevents lowering  the  depth of the
pond more  than 1.5 m  (5 ft) below  the ground surface.   Con-
sequently,  most  of  the storage  pond  volume will be  above
ground surface and require  embankments.  The  design criteria
for the  storage lagoons are shown in Table A-7.

                           TABLE A-7
             DESIGN CRITERIA FOR STORAGE LAGOONS:
                    FORAGE CROP ALTERNATIVE
              Primary cell
                Surface area, ha              40.0
                Total depth, m                 1.5
                Operating depth, m             1.0
                Total storage, d              79
                Storage above 0.5 m, d         53
              Secondary cell
                Surface area, ha              18.0
                Total depth, m                 3.0
                Operating depth, m             2.5
                Total storage at 2.5 m, d       59

              Total storage at operating depth
                Days                        112
                m3                         850,000
                              A-15

-------
          A.4.1.7   Distribution and Application

When  selecting  the type  of distribution system,  the designer
must  consider  the  terrain,   crop,  soils,  and  capital  and
operation/maintenance  costs.   Based on a cost comparison not
included  in the example,  the designer  recommended  a  center
pivot irrigation  system as  the  most  cost-effective  system
for the forage  crop alternative.

The design of the distribution system  is  based  on  the  maxi-
mum hydraulic loading rate per application.  In this  case,
the  maximum  monthly  loading  equals  40.5 cm (15.9 in.)  in
July.   An application frequency  of four  times  per  month  is
selected  to  allow adequate drying  between applications (see
Appendix  E for  guidelines on making  this  determination).
The   hydraulic  loading  rate  per  application  then  equals
10.1  cm (4.0  in.) .

In  consultation with  manufacturers of  center  pivot  equip-
ment,  it  was  determined  that  two  center pivot systems  could
be used  for distribution each  irrigating  an  area of 53.8  ha
and using a  revolution period of  170 hours.  The unit  capa-
city  is then determined  as  follows (Section E.2.6):

                       Q =  CAD/t

                         ='28.1 (53.8)(10.1)
                                   170

                         =89.8 L/s

where  Q  = discharge capacity,  L/s (gal/min)

       C  = constant, 28.1  (453)

       A  = field area  for one  center pivot,  ha (acre)

       D  = hydraulic loading/application depth,  cm  (in.)

       t  = number  of operating  hours per application

Using  the unit  capacity,   the design  of  the  center   pivot
system is completed. ,  In order to determine the nozzle and
pipeline  size,  the  design  must consider  headlosses in the
line and  the pressure  required  to  ensure proper  operation of
the nozzles.

Unit  capacity  also is used  to develop  design  criteria for
the pumps.  Pumps  are  required to deliver wastewater to the
site   and  at  a   pressure   sufficient   to  allow  proper
                             A-16

-------
distribution  of  the  wastewater.    Assuming  the  two pivots
operate simultaneously, the pumps are sized  for a  total  flow
of 179.6 L/s.  The designer chose four pumps and one  standby
rated  at  45 L/s.   The  force  main  is sized using a  maximum
velocity of 1.7 m/s and the following formula;
                         A =

where  A = area of pipe

      Qt = total flow

       V = maximum velocity

For circular pipes:

                          D =


where  D = pipe diameter

Applying the equation gives:
         D  =
              (180.L/s) (10~3 m3/L)   (_4_)
   = 0.37 m, use 0.38 m
                     1.7  m/s
ir
A  final  consideration  in  the  design  of ' the center  pivot
system  is the disruption  of  the tracking system due  to wet
soil  conditions.   Because  of  the pivot  rotational speed, the
application  rate  at  the  unit  capacity equals 1.0  cm/h during
the   9  to  10 h  period  it  takes  to  pass  a given  point.
Although  this rate  is less than  the permeability  or  basic
infiltration rate of  the  surface soil, precautions  need to
be  taken.  These precautions  include preparing  the tracking
route by  either  soil compaction or gravel installation.

A  summary of design data for  the  treatment  site  is given in
Table A-8.     Figure A-2 shows  the  pond  and  distribution
system  layout.

          A.4.1.8   Cost Estimates

Cost  estimates  of  the  forage  crop  irrigation  system are
determined   from  EPA  publication  "Cost  of  Land  Treatment
Systems"   EPA-430/9-75-003,   using  the  criteria  shown  in
Table A-9.   Cost  estimate  calculations and  total  costs are
presented in Tables  A-10 and  A-ll, respectively.
                             A-17

-------
                                         LJJ
                                         Ul
                                         in
A-18

-------
                     TABLE A-8
      SLOW RATE  SYSTEM  DESIGN  DATA:
          FORAGE  CROP  ALTERNATIVE
Irrigation system
  Annual hydraulic loading rate, cm
  Fiel<3 area, ha
  Buffer, m
  Application frequency,  No./mo
  Maximum hydraulic loading per application,  cm
  Application equipment,  No. of center pivots
  Lateral length, m
  Operating pressure,  N/cm*
  Field dimensions with buffer zone, m x m
  Total area, ha

Pumping station
  Duty pumps, No. at m3/min
  Standby pumps. No. at m3/min
  Pumping time  (peak flow)
    h/d
    d/wk
    h/wk

Force main
  Velocity, m/s
    Average
    Maximum
  Pipe diameter, m
  Maximum headloss, m/1,000  m
267
107.5
15
4
10.1
2
408
34.5
1,662 x
140.6
846
4 at 2.7
1 at 2.7

24
7
168
1.1
1.7
0.38
6   '
                     TABLE  A-9
           COST  ESTIMATE CRITERIA:
          FORAGE CROP  ALTERNATIVE3
 Circulation date
 Sewage treatment plant index update,  370.1/177.5
 Sewer index update,  397.2/194.2

 Operation and maintenance update,  2.13/1.00
 Construction cost locality factor
 Operation and maintenance/labor cost  factor
 Power cost locality  factor
 Interest rate, i

 Interest period, n
 Present worth factor, PWF
 Capital recovery factor, CKF
                                                 October 1980
    085
    045
  2.13
   .0

   .0

   .0

   .125%

  20

  0.2525

  0.0953
 a.  Based on "Cost  of Land Treatment  Systems,1
    EPA-430/9-75-003.
                            A-19

-------
                           TABLE  A-10
              COST  ESTIMATE CALCULATIONS:
                 FORAGE  CROP ALTERNATIVE
 1.  Preliminary treatment
      Capital ($48,000 x 2.085)                                $100,100
      Operation and maintenance ($9,400 x  2.13)                  20,000

 2.  Treatment

      Capital
        Primary cell ($150,000 x 1.7  x 2.085)                  $531,700
        Asphalt liner ($352,000 x 2.085)                        733,900
      Operation and maintenance ($10,000 x 2.13)                 21,300

 3.  Pumping to application site

      Peak flow =180 L/s
      Avg flow = 135 L/s
      Capital ($210,000 x 2.085 x 0.80)                        5350,300
      Operation and maintenance ($26,100 x 2.13)                 55,600

 4.  Force main (2.6 km:  0.38 m)
      Capital ($162,100 x 2.045)                               $331,500
      Operation and maintenance ($400 x 2.13)                      900

 5.  Storage (D = 59d, depth = 3.0 m)
      Capital ($447,000 x 2.045)                               $914,100
      Operation and maintenance ($2,400 x  2.13)                   5,100

 6.  Field preparation
      Pond area (58 ha x 1.25 = 72.5  ha, brushes and trees)
        Capital ($80,000 x 2.045)                              $163,600
      Application site (53.8 ha x 2 = 107.6 ha, pasture)
        Capital ($1,700 x 2.045)                                  3,500

 7.  Distribution, center pivots (107.6 ha)

      Capital {$135,000 x 2.045)                               $276,100
      Operation and maintenance ($18,400 x 2.13)                 39,200

 8.  Administrative and laboratory
      Capital ($64,000 x 2.045)                               $130,900
      Operation and maintenance ($10,200 x 2.13)                 21,700
 9.   Monitoring wells  (six wells at 12 m depth)

       Capital  ($4,800 x 2.045)
       Operation and maintenance ($600 x 2.13)

10.   Roads  and  fences  (application site, 140.6  ha)

       Capital  ($102,000 x 2.045)
       Operation and maintenance ($2,700 x 2.13)

11.   Planting and harvesting
       Operation and maintenance
         Variable costs ($319/ha x 107.5 ha)
         Fixed  costs  ($247/ha x 107.5 ha)

12.   Annual crop revenue
       107.5 ha x 15.6 tons/ha x $42/ton

13.   Land costs
       Pond area  (72.5 ha x $2,000/ha)
       Application  area (140.6 ha x $3,700/ha)
$  9,800
   1,300
$208,600
   5,800
$ 34,300
  26,600
$ 70,400
$145,000
 520,200
                                 A-20

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                          TABLE  A-11
      SUMMARY  OF  COSTS:   FORAGE CROP  ALTERNATIVE
         Component
 Capital
Salvage0
Operation and
 maintenance
Preliminary treatment
Treatment/storage ponds
Pumping
Force main
Site clearing
Distribution
Administration building
Monitoring
Roads and fences
Planting and harvesting
Crop revenue
Total construction
$ 100,100
2,179,700
350,300
331,500
167,100
276,100
130,900
9,800
208,600
—
—
$3,754,100
$ 20,000
1,089,800
42,000
165, ,800
0
0
26,200
0
68,200
—
—
$1,412,000
$ 20,000
26,400
55,600
900
0
39,200
21,700
1,300
5,800
60,900
-70,400
$ 161,400
Engineering,  contingencies,
overhead, etc.

Land

  Total project

Present worth

  Total present worth

Equivalent annual  cost
   938,500           0            0

   665,200   1,201,400    	0

$5,357,800  $2,613,400   $  161,400

      .        -659,000    1,693,600

$6,392,400

$  609,200
a.  Salvage values  are determined by straight line depreciation
    over the useful life of the components,  e.g.,  useful  life of
    ponds N = 40  yr; planning period P = 20  yr;  salvage value
    F = (1 - P/N)  (initial cost) = 0.5(2,179,700)  = 1,089,800.

b.  Equivalent annual cost = present worth x 0.0953.
                                A-21

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    A. 4. 2
Deciduous Forest Crop Alternative
As  in  the forage crop  design,  the selection of the maximum
allowable hydraulic  loading  for the forest  crop alternative
minimizes  the required land  area.    In  the  City A region,
deciduous  trees,  in  particular  poplar,  grow  well.     The
poplar is a fast-growing tree and  a pulp wood market exists.

    A.4.2.1   Hydraulic Loading  Based on Soil
                   Permeability

The monthly water balance  calculations are  determined as  in
the forage  crop  water  balance.   The  growing season for  the
deciduous tree  selected lasts 214 days  based  on an average
mean  temperature of  10 °C  (50  °F).    Evaporation  from  the
forest during the growing  season is assumed  to equal  that
from a  full  cover pastureland.    No  evaporation is assumed
for  the  nongrowing  season;  wastewater  applied  during  this
time is  limited  by precipitation  and  percolation.   Because
the site is the  same for both forage and forest  alternative,
the  design  percolation rate is  the  same.   Applying  these
assumptions to  the  water balance  Equation 4-3  results  in  a
maximum hydraulic loading  of 321 cm (126 in.) and a maximum
monthly loading  of 46.2 cm (18.2  in.).

         A. 4.2.2   Hydraulic Loading Based on Nitrogen
                   Loading

Equation 4-4  is   used   to  determine  the  hydraulic loadings
based on  nitrogen loading  as in the forage  crop alternative
(Section A.4.1.2).   No  crop  growth or  nitrogen uptake  was
assumed for  the  months of December  through  March.   using  a
whole-tree  harvest  approach, the  total  annual nitrogen  up-
take  is  assumed  to   equal  200 kg/ha (178 Ib/acre)    (see
Section 4.3.2.1).   Based  on  these assumptions,  the annual
hydraulic loading equals 268 cm  (105.5 in.).

         A. 4.2.3   Design Hydraulic Loading  Rate

As  in  the forage crop  alternative,  nitrogen loading limits
the  hydraulic   loading  rate.     Design  monthly  hydraulic
loading  rates   are  determined  by  comparing   the  monthly
hydraulic  loading  rates  based  on  soil  permeability   and
nitrogen  loading and using the  lower value.  Based on  this
comparison  the  design  annual  hydraulic   loading  rate  is
254 cm (100 in.).
                             A-22

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         A.4.2.4   Field Area  Requirements

Applying  Equation 4-6 and  assuming  the  net gain/loss  from
storage, AVS,  is  zero, the  initial  field  area is:


         A  =  (7,570 m3/d)(365 d/yr)   =108.8ha
                (104 ra2/ha)(2.54  m)
         A. 4.2.5   Storage  Requirements

As  in  the  case  with  forage, storage  of wastewater  during
nonoperating time  depends on monthly hydraulic  loadings and
available   wastewater.      Applying   the   water   balance
Equation 4-3  and  following  steps  1-4  of  Section A.4.1.5
results  in  Table  A-12.   The net storage  volume  required for
year-round application  is shown  below:

         Vst = (64.6 cm)(108.8 ha)(102) = 702,800 m3

                          TABLE A-12
          INITIAL  DETERMINATION  OF STORAGE VOLUME:
                   FOREST CROP ALTERNATIVE
                              cm
Month
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Annual
P
, 9.9 .
14.8
13.0
10.1
10.4
15.1
15.8
17.4
14 . 2
14.0
12.2
14.7
162
ET
5.0
0
0
0
0
0
5.6
9.7
13.4
15.7
13.9
8.9
72 "
ET-P
-4.9
-14.8
-13.0
-10.1
-10.4
-15.1
-10.2
-7»7
-0.9
1.6
1.6
-5.8
-90
PW
38.9
25.9
20.2
15.8
18.7
27.4
43.2
44.6
43.2
44.6
44.6
43.2
410
Lw(P)
34.0
11.1
7.2
5.7
8.3
12.3
33.0
36.9
42.3
46.2
46.2
37.4
321
Lw(n)
17.3
13.7
12.0
9.4
9.6
14.0
23.8
32.0
35.1
38.7
34.1
28.2
268
Available
wastewater
Lw Wa
17.3
11.1
7.2
5.7
8.3
12.3
23.8
32.0
35.1
38.7
34.1
28.2
254
21.5
20.9
21.5
21.5
19.5
21.6
20.9
21.6
20.9
21.6
21.6
20.9
Change in
storage
4.
9.
14.
15.
11.
9.
-2.
-10.
-14.
-17.
-12.
-7.
2
8
3
8
2
3
9
4
2
1
5
3
Cumulative
storage
sc
, 0.2a
• 4.2
14.0
28.3
44.1 .
55.3
64.6
61.7
51.3
37.1
20.0
.7.5
  a.  Rounding error, assume zero.
                             A-23

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          A. 4.2.6  Final Storage and Pond  Design

 The  steps outlined in Section A.4.1.6 are  followed  to deter-
 mine the final  storage and pond  design.   The design  of  the
 primary cell remains  the  same with the secondary cell being
 used to incorporate the net gain/loss from the pond area  due
 to  precipitation, evaporation,  and  seepage.  As before,  the
 initial depth  of  the secondary  cell  is  assumed  at  1.5 m
 (5 ft)   resulting   in  a   storage   pond  area   of   20 ha
 (50  acres).    The adjusted  field area  is  calculated to  be
 113.2 ha (280 acres).  The  results  of secondary cell  design
 are  shown in Table A-13.

                          TABLE A-13
                DESIGN DATA  FOR STORAGE  POND:
                   FOREST CROP ALTERNATIVE
Secondary cell

  Surface area, ha
  Total depth, m

  Operating depth, m

  Storage at operating depth,  d

Total storage at operating depth

  Days
                                              20

                                             2.9

                                             2.4

                                              63
                                             116

                                          880,000
         A.4.2.7   Distribution and Application

Solid  set sprinkler  systems,  both surface  and  buried, are
the  most  common  methods  used in  forest crops  for distri-
buting  wastewater.   in  the  case  of  City  A,  the proposed
treatment  site  is  under pasture and the subsoils are uniform
without  much  debris,   consequently   either  system  would
work.   The installation cost  for  the  surface system is less
than the buried system, but the cost for operation and main-
tenance  is  less   for  the  buried   system.    After  comparing
total  cost and discussing  with City A  their desire for low
operation  and maintenance  cost,  the  designer  selected the
buried solid  set sprinkler  system.

The design of the  sprinkler system is  based on the maximum
hydraulic  load per application. An application frequency of
4  times  per  month is  chosen  to  allow  adequate  aeration of
the tree  root system.  Based  on a  maximum monthly hydraulic
loading of 38.7 cm (15.2  in.), the maximum hydraulic loading
per application of 9.7  cm  (3.8 in.)  is obtained.   Referring
to  manufacturers   literature  for  solid   set  irrigation
                             A-24

-------
systems,    design   data   are    obtained   and   presented   in
Table A-14.   The pond  and  irrigation system  layout  is shown
in  Figure A-3.

                               TABLE  A-14
                             DESIGN  DATA:
                       FOREST  CROP ALTERNATIVE
  Irrigation system
    Annual hydraulic loading rate, cm
    Field area, ha
    Buffer,  m
    Application frequency,  No./mo
    Total area, ha
    Maximum hydraulic loading per application, cm
    Distribution system

    Spacing,  m x m
    Sprinkler flow, L/s at  N/cm
    Lateral length, m
    Sprinklers per line, No.
    Application period, h
    Settings per day. No.
    Operating time, h/d
    Laterals per setting, No.
    Pumping rate, 9 x 24 x  0.85, L/s
  Pumping station
    Duty pumps. No. at m /min
    Standby pumps, N.o. at m /min
    Pumping  time
      h/d
      d/wk
      h/wk
  Force main
    Velocity, m/s
      Average
      Maximum
    Pipe diameter, m
    Maximum headless, m/1,000 m
                   254
                   113
                    15
                     4
                 123.5
                   9.7
          Buried solid
        set sprinklers
               18 x 21
0.85  @  36, 0.63 cm diam
                   432
                    24
                    12
                     2
                    24
                     9
                   184
             4 at 2.76
             1 at 2.76
                    24
                     6
                   144
                   1.1
                   1.7
                  0.38
                   6.4
                                   A-25

-------
I— >-
a. i—
zee
                                                                           C9
                                                                              CO
                                                                              >-
                                                                              CO
                                  A-26

-------
          A. 4.2.8    Cost Estimates

Cost  estimates  are  determined  by  the same method  used  for
the  forage  crop  alternative  (Table A-9)  and  are summarized
in  Table A-15.   Crop  revenue  is based on a harvest of  one-
fourth  of the  area every  year beginning  the  fourth year, an
annual  growth  rate of  25  tons/ha,  a dry  weight of 0.4   ton/
cord, and a stumpage  price of  $4/cord used  for pulpwood.

                           TABLE  A-15
              SUMMARY OF  COSTs   DECIDUOUS  FORESTS
Component
Preliminary treatment
Treatment/storage ponds
Pumping
Force main
Site clearing
Distribution
Administration building
Monitoring
Roads
Planting and harvesting
Crop revenue
Total construction
Capital
$ 100,100
2,206,300
325,300
314,000
167,500
1,295,700
130,900
9,800
112,500
14,000
—
$4,676,100
Salvage
$ 20,000
1,103,100
39,000
157,000
0
0
26,200
0
75,000
—
—
$1,420,300
Operation and
maintenance
$ 20,000
26,800
55,600 .
900
0
54,200
21,700
1,300
4,900
2,800
-28,000
$ 160,200
    Engineering, contingencies,
    overhead,  etc.

    Land

      Total project

    Present worth

      Total present worth

    Annual equivalent cost
 1,169,000

   606,900   1,096,100
$6,452,000  $2,516,400   $  160,200

 	—    -635,400   1,681,000

$7,497,600

$  714,500
                                A-27

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    A. 4. 3
Selected SR Design
Comparing  annual  equivalent  costs,  the  forage  crop alter-
native  is  the  most  cost-effective  alternative,   with  an
annual equivalent cost of $609,200/yr, and is selected.

Management  of  the  selected  alternative  consists  of  an
initial    seedbed    preparation,    seeding,    cultivating,
irrigating, and  harvesting four  times per year.   Prior to
harvesting, the  field requires  a drying  period  of  2  to 3
weeks.    The  harvested  forage  grass  is  then chopped  and
hauled away for  use.  The  harvesting  may be  handled either
by  City  A  personnel  or  contracted  outside.    Assuming
contract harvesting, the estimated staff requirement  for all
of the remaining operation  is 1.5 man-years per year.
    A.4.4
Energy Requirements
The  two  areas  of  operation  that  contribute  most  to  the
system    energy   requirements    are    pumping   and   crop
production.   Assuming  3,900 hours of  operating  time,  75%
overall  system  efficiency,  and  20%  headloss  through  the
distribution  system,  the energy  required  for  pumping  is
shown below:

    TDK = pipe losses + operating pressure + losses through
                        at sprinkler         distribution
                                             system

        = 2,600 m (5.5 m) +35+7
                1,000 m

        = 56.3 m

Energy  = (Q)(TDH)(t)
    yy    (6,123)(E)

        = 515,200 kWh/yr

Energy required for forage crop production is computed using
the energy requirement factor given in Table 8-1.

Energy  = 107.5 ha x (3.63 Mj/ha)
               3.6 MJ/kWh

        = 110 kWh/yr

Therefore,  the  total  annual   energy  budget   for  this  SR
example is:

          110 + 515,200 = 515,310 kWh/yr
                            A-28

-------
The total  energy budget for  an  activated sludge and anaer-
obic  digestion  treatment   system  of  equal  size  would  be
680,000 kWh/yr electrical energy and 3,100 x 106  BTU/yr fuel
energy or a total of 967,000 kWh/yr.
                             A-29

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                          APPENDIX B

              RAPID INFILTRATION  DESIGN  EXAMPLE
B.I  Introduction

The design example  described in this appendix is  intended  to
demonstrate  only   the  RI  design  procedures  described   in
Chapter 5;  therefore,  components  that are  common  to most
wastewater  treatment systems,  such as  transmission  systems
and  pumping  stations,   are  described  but  not  designed   in
detail.   However,   a  cost estimate and an  energy budget are
developed for  the entire  system.

B.2  Design Considerations
     B.2.1
Design Community
Community  B  is located in  the  southeastern United States  on
the Coastal  Plain.   The area in  which  the community is  loc-
ated is characterized  by  relatively flat areas lying between
numerous creeks and  swamps  that drain into North Creek.  One
of these  creeks,  South Creek,  borders  the northeast edge  of
the community.   The elevation  of Community B is 45.7 m  (150
ft);  near  the  community,   elevations  range  from  42.7  to
54.9 m (140  to 180  ft).
     B.2.2
Wastewater Quality  and  Quantity
The design average daily  flow is 6,060 m3/d (1.6 Mgal/d) and
the design peak  flow  is 9,090 m3/d (2.4 Mgal/d).

Expected  wastewater  characteristics  under design  flow con-
ditions are  presented in Table  B-l.   Wastewater is essenti-
ally  domestic in  character  and expected  concentrations of
trace elements and organics are low.

                          TABLE  B-l
            PROJECTED WASTEWATER CHARACTERISTICS
                        Parameter
                                         Value
                   c, mg/L

                Total suspended solids, mg/L

                Total nitrogen, mg/L

                Ammonia nitrogen (as N), mg/L

                Total phosphorus (as- P), mg/L

                pH, units
                            175

                            150

                             50

                             20

                             10

                            6.9
                              B-l

-------
      B.2.3
Existing Wastewater  Treatment Facilities
The  existing  treatment facilities provide primary treatment,
and   treated   wastewater  fails   to  meet  present  discharge
requirements.    The  facilities  are old  and  would  require
significant  repairs  and additions  to  produce treated water
that would meet all discharge requirements.
      B.2.4
Discharge Requirements
Discharge  requirements  for  surface waters  are presented in
Table B-2.   The ammonia  nitrogen limit during summer months
is  intended  to prevent ammonia  toxicity to fish.  The inhi-
bited test for carbonaceous  BOD does not measure nitrogenous
BOD.   The test  is  often specified  for  systems that nitrify
wastewater,  because  such systems  tend  to  have  higher BODc
concentrations although the  water quality is equivalent.

                          TABLE  B-2
             SURFACE WATER DISCHARGE REQUIREMENTS
                      Parameter
                            North  South
                            Creek  Creek
           BOD5/ mg/L
           (inhibited test for carbonaceous BOD)
                              30
                                   20
Dissolved oxygen, mg/L
PH
Total suspended solids, mg/L
Fecal coliforms, MPN/100 mL
Ammonia nitrogen (as N) , mg/L
(May-October only)
5
6-9
30
200
2
5
6-9
20
200
2
     B.2.5
Climate
Average  temperature and  precipitation  in Community  B were
obtained  from local  climatological  data and  are  shown  by
month  in  Table   B~3.    A  rainfall  frequency  distribution
curve, developed  from 26 years  of recorded  data,  indicates
that the wettest  year  in 10  yields 137  cm (54 in-)  of preci-
pitation in  Community B.   The average  total  annual precipi-
tation (rain plus snow) is  111 cm (43.7 in.).
                             B-2

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                          TABLE  B-3
             AVERAGE METEOROLOGICAL  CONDITIONS
Temper a tui
Month °C
Jan
Feb
Mar
Apr
May
Jun
Jul
, Aug
Sep
Oct
Nov
Dec
Year
8.6
9.3
12.6
17.5
22.2
26.0
27.0
26.6
23.8
18.3
12.6
8.4
17.8
Precipitation, cm
Rain
6.71
8.05
9.24
9.17
7.34
10.87
15.85
11.61
10.41
5,54
5.87
7.77
108.43
Snpwa
0.25
0.51
1.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Trace
0.76
2.54
               a.  Water equivalent.

B.3  Site and Process Selection

Community  B  contacted  landowners  within  a  4 km  (2.5 mile)
radius  of  the  existing  treatment facilities  to determine
their interest in leasing or selling their property  for  land
treatment.     Five  potential  sites  were  identified during
Phase 1  of the planning  process  and  screened in  accordance
with  the procedure  in Chapter 2.   Two  of  the  sites  were
available  for  purchase  and  had  soils  suitable   for  RI
(Sites 1 and 2  on  Figure  B-l).   One  of  these  two sites
(Site 2) and the three  remaining sites had enough  land to  be
suitable for  SR.   None of the soils  in  the area  were suit-
able  for OF  (Table  B-4).   Therefore,  OF was  eliminated  from
consideration as a viable alternative.

During phase 2 of the planning process,  field investigations
were  conducted  at  each  of  the  five  sites.  Based on  the
field investigations,  preliminary design  criteria  and  cost
estimates  were  developed.  This analysis  indicated  that the
two RI alternatives  were  more cost effective than  any of the
SR  alternatives  and lower  in  total present worth  than  the
best   conventional   secondary   treatment   and  discharge
alternative.   The preliminary analysis  also  indicated  that
an  RI facility at Site 1 would be slightly  less  expensive
than  an  RI system  at Site 2.   For these reasons,  the alter-
native selected by Community B was RI  at Site 1.
                             B-3

-------
    LEGEND

Cx   COXVIUE SERIES
HcB   HUCKABEE SERIES
LaB.LaD.LkA  LAKELAND  SERIES
NoA.NoB.NsB  NORFOLK SERIES
OK   OKENEE SERIES
Pm   PLUMMER SERIES
Sw   SWAMP
e   2(0
'
SCALE
410   600
          811  HOC
           ^mmmmi
           METERS
                              FIGURE B-1
                     SOILS  MAP, SITES  1  AND  2
                                   B-4

-------












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                                                          5

     B-5

-------
 B.4  Site Investigations
 The  selected site  for  Ri  is  2.4 km  (1.5 miles)  from  the
 existing wastewater treatment facilities.   The site contains
 48 ha  (120  acres)  of  land  and  was  covered with  brush  and
 trees.    Near North Creek, the  ground  surface  drops verti-
 cally about 6 m (20 ft),  forming  a relatively steep bluff as
 indicated  in Figure  B-2.    West  of the  bluff,  elevation
 varies  less than'0.6 m  (2  ft).

      B.4.1    Soil Characteristics

 As indicated  by  Figure  B-l and  Table  B-4,  the soils  at
 Site  1  that  are  best suited for  RI  are the  Lakeland  sands
 (LaB  and  LaD in  Figure  B-l).    These  permeable  soils  are
 found at Site 1 only near  the center of the  site.   Thus,  RI
 is potentially  feasible  only   in   a   limited  portion  of
 Site  1.   Because  it would have cost  Community B  as  much  to
 buy only the land needed  for the treatment  system as to buy
 the entire site  (the unused portion of the  site being mostly
 swamp  and  therefore   undevelopable),   acquisition  of  the
 entire  site  was  necessary.

 To verify that Site 1  has adequate  soil depth and depth  to
 ground  water  for   RI,   and   to   ascertain  the  absence  of
 shallow,   impermeable   soil  layers,  nine   test  holes  were
 drilled  as shown in Figure B-2.    A typical boring log  from
 the investigation  is presented in Table B-5.   At  this parti-
 cular test hole,  the presence of  ground  water at  a depth  of
 3.2 to  3.5 m (10 to 11  ft) and an impermeable clay layer  at
 6.5 m (21 ft)  means that  percolation could  occur only  to a
depth of  about  3.2 to  3.5 m  (10  to 11 ft)  and that the  flow
of  water  below  this depth  is  primarily  horizontal rather
than vertical.

                          TABLE B-5
                  TYPICAL LOG OF  TEST HOLE
             Depth, m   USDA texture
                Remarks
               0-1

               1-2

               2-2.2

             2.2-3.2

             3.2-3.5

             3.5-6.5

               >6.5
Loamy sand
Sandy loam
Loamy sand
Sand
Sand
Sand
Clay
With thin silt lenses


Ground water table
Saturated

Impermeable
                             B-6

-------
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-------
      B.4.2
Ground Water Characteristics
 At the  selected  site,  the depth to ground  water ranges from
 1.5 to 4.6 m  (5  to 15  ft)  and  is  typically 3 m (10 ft).  The
 ground water  aquifer  is 1.5 to 4.6 m  (5  to 15 ft)  thick and
 is underlain  by  impermeable clay.   The  clay  layer prevents
 deep  vertical percolation and causes the  ground water  to
 flow  laterally  toward  North   Creek,  as  indicated  by  the
 approximated  ground  water  contours   shown in  Figure  B-2.
 Because of the shallow ground  water table,  there is a poten-
 tial  for  mounding  of the  percolate  and  underdrains  must  be
 considered.    Horizontal   hydraulic   conductivity  in  the
 aquifer   was   measured  using  the   auger  hole   technique
 (Section 3.6.2.1) and averaged  3.4 m/d (11  ft/d).

 Furthermore,  although  ground  water quality is  adequate  for
 water  supply  purposes,  the aquifer   is  too  thin to  allow
 production wells to extract ground water economically.   The
 closest domestic water  supply  well to the  Ri  site  is 1.6  km
 (1 mile)  southwest  and upgradient of  the  site.    This  well
 and others in the area  pump water from depths of  90  to over
 150 m  (300  to  over  500 ft).    Thus,  the  shallow  aquifer
 underlying the area to  be used  for  RI  and  between the  Ri
 area and  North Creek  will not be  used  as a  potable  water
 source.   Current ground  water  quality data are  presented  in
 Table B-6.

                          TABLE B-6
                     GROUND WATER QUALITY
                      Parameter
                                       Concentration
               pH,  units

               Specific conductance, ymhos

               Nitrate nitrogen, mg/L

               Fecal coliforms, MPN/100 mL
                           6.8

                           120

                           8.4

                             0
     B.4.3    Hydraulic Capacity

Basin infiltration  tests at the selected site were performed
with  clear water  using  3.6  by 3.6  by 0.5m  (12 by  12 by
1.5 ft)  basins  filled  to a  depth  of 22  to  30 cm  (9 to
12 in.).   Because  the  soil and  ground  water characteristics
were generally  uniform  throughout  the  site, only two basin
infiltration  tests  were performed.   If  the  results of these
two tests  had conflicted,  additional tests would have been
conducted.   Results from  one  of the two  infiltration tests
are plotted  in  Figure B-3.   As shown  in this  figure,  the
resulting   limiting  infiltration  rate  at  this  basin  was
                             B-8

-------
3XV1NI 110 >3 '3XV1NI  031VinMn99V
              B-9

-------
 2.5 cra/h (1 in./h).   This  was the minimum infiltration rate
 from the two tests and was used as the basis for design.

 B.5  Determination of Wastewater Loading Rate

      B.5.1     Preapplication Treatment Level

 The  existing  treatment  facilities  are  old  and  necessary
 repair work  would nof be  cost  effective.   Therefore,  new
 preapplication treatment facilities are needed.   To consoli-
 date the treatment facilities, Community B decided to locate
 the preapplication treatment  facilities adjacent  to  the  RI
 facilities   at Site  1.    Because  Site 1  is  close  to  the
 community,  biological treatment prior  to  land  treatment was
 appropriate   (Section 5.3.1).    The  area  experiences  mild
 winter weather, making ponds  the most cost-effective form of
 preapplication treatment.

 The land  available for preapplication treatment  was somewhat
 limited;  to  minimize the  pond  area,  an  average depth  of
 3.6 m (12 ft)  was  selected.   The pond design included  sur-
 face aerators to  be  used  periodically for odor control  and
 to  keep the  pond  from becoming entirely anaerobic.   The  pond
 was divided  into  three aeration  cells for flexibility  and
 reliability.   A design detention time of  3  days  was selected
 and adjustable weirs were included  in each cell to allow
 wastewater withdrawal after 1  to  2 days if treatment effi-
 ciency  is high or if the BOD:N ratio  must be  increased  to
 promote  denitrification during  RI.   The  expected  effluent
 quality   from  the aerated  lagoons  is  75 mg/L   BOD,-  and
 99  mg/L SS.    Because  of  the  short  detention  time^   the
 nitrogen  content  will remain at  50 mg/L  and  the ammonia
 nitrogen  content will  be approximately  20 mg/L.

     B.5.2    Hydraulic Loading  Rate

The  annual hydraulic  loading  rate was designed  to  be within
10   to  15%    of   the  limiting   basin  infiltration  rate
 (Table 5-11  and  Section 5.4).   A  median  value  of   12.5% was
selected  and  the  wastewater loading  rate  was  calculated as
follows:

               12.5% x 2.5 cm/h x 0.01 m/cm
                     x 365 d/yr
                     =27.4 m/yr (90  ft/yr)
                            B-1Q

-------
     B.5.3    Hydraulic Loading Cycle

Because  the  renovated  water  will  flow  laterally or  be
drained into North Creek, nitrification or  ammonium  nitrogen
removal  is  necessary  during  the  months  of  May  through
October.    To  maximize  nitrification, a  loading  cycle  of
2 days  of  flooding  alternated with  12  days of  drying was
selected (Section  5.4.2).   Using  this loading cycle and the
assumed  loading  rate,  the  volume  of water  applied during
each loading cycle is:
(2d + 12d)/cycle
    365 d/yr
m/
                                      100 cm
                                         m
                        = 105 cm/cycle  (41.4  in. /cycle)
     B.5.4    Effect of Precipitation on Wastewater  Loading
              Rate

As shown in Table B-3, precipitation  in Community  B  averages
111 cm/yr  (3.6  ft/yr)  and  varies  throughout  the  year  from
5.5 to  15.9 cm/mo  (2.2  to  6.2 in./mo).    As  mentioned  in
Section  B.2.5,  the  wettest year  in 10 would  yield  137  cm
(54 in.) of  precipitation.   This amount roughly corresponds
to    a    maximum   monthly    precipitation   of    20 cm/mo
(8.0  in./mo).   Adding  maximum monthly  precipitation  to  the
average  wastewater  loading  rate  of  2.3  m/mo   (7.5  ft/mo)
resulted  in  a  maximum  monthly  hydraulic  loading  rate  of
2.5 m/mo  (8.2 ft/mo).   This combined loading rate is  13%  of
the test  basin  infiltration rate and, therefore,  was  accep-
table (Section  5.4.1).

For land requirement calculations,  the previously  calculated
wastewater  loading  rate  (27.4 m/yr  or 90 ft/yr)  was  used
because  precipitation  is  relatively insignificant  most  of
the time.

      B..5.5    Underdrainage

As  discussed in  Section  5.7.2, at  RI  sites where  both  the
ground  water table and 'the  impermeable layer  underneath  the
aquifer  are relatively close  to the  soil surface,  it  may be
possible  to avoid  lengthy mounding  equations  by using  the
following  procedure:

      1.   Assume underdrairis  are needed.

      2.   Use Equation  5-4  to calculate  drain  spacing.

      3.   If  the   calculated  drain  spacing   is  reasonable
          (between 10 m and  50 m or 33 ft  and  160 ft),  drains
          should be used.
                             B-ll

-------
      4.  If  the  calculated  spacing  is  less  than  10  m,  no
          mounding  calculations  are needed  but the  cost  of
          the underdrains may cause the system not to be cost
          effective  and  may  necessitate reconsideration  of
          other sites identified during phase 1.

      5.  If the calculated  spacing  is  greater  than 50 m,  an
          evaluation of ground water mounding is necessary.

 Because Site 1  is  underlain by a  relatively  shallow imper-
 meable layer, underdrains would be  the appropriate drainage
 method.   A  drain  depth  of  3m  (10 ft)  and  an  allowable
 ground water mound  height  above the drains of  0.6 m (2 ft)
 were   assumed.     Using  Equation  5-4,   drain   spacing  was
 calculated:
                          4KH
                         Lw
where   S  =  drain spacing,  m
                               •(2d + H)
1/2
        K  =  horizontal  hydraulic  conductivity,  m/d
          =  3.4 m/d  (Section B.4.2)

        H  =  allowable height of  the  ground  water mound
            above  the drains, m
          =  0.6 m

        d  =  distance from  drains  to  underlying  impermeable
            layer, m
          =  3 m

      LW  =  annual wastewater loading  rate, m/d

          =  2365 d/yr =  0'°75 m/d

        P  =  average precipitation rate, m/d
          =  i'll m/vr =  0.003 m/d
            365 d/yr

        S  =  / 4 x 3.4 m/d  x  0.6 m [(,  x 3 m) +  0<6 m]Vl/2
            \0.075 m/d + 0.003 m/d          '    u  °   J/
          =  26 m (85 ft)

Because this  spacing  is  reasonable and  will  keep  the mound
from  becoming  a  problem,  additional  mounding  calculations
were not  necessary.   Because the percolate collected in the
underdrains  will  be  discharged  into North  Creek,  it  was
necessary to design the remainder  of  the system to meet the
discharge requirements summarized in Table B-2.
                             B-12

-------
     B.5.6    Nitrification

To  determine whether  the  proposed  system  could  meet the
summer ammonia nitrogen discharge requirements, the nitrifi-
cation potential  of the  system  was  evaluated.   First, the
nitrogen loading rate was calculated  as follows:

                             10CnLw
                        Ln ~   365

where  Ln = nitrogen loading rate, kg/ha«d

       Cn = applied total nitrogen concentration, mg/L

       L,7 = annual loading rate, m/yr
        W

       Ln = 10 x 50 mg/L  x 27.4 m/yr
                        365
          = 37.5 kg/ha-d  (33.5 lb/acre-d)

This loading  rate  is  well within the range of  nitrification
rates  reported  under  favorable  temperature  and  moisture
conditions   (Section   5.2.2).     Because  nitrification   is
required  only during  summer  months  when  temperatures are
fairly high,  temperatures at the RI system will be  favorable
for the required nitrification.  Furthermore,  the relatively
short  application  periods and longer drying  periods of the
selected loading cycle will ensure  favorable  moisture condi-
tions  and  should  allow  virtually  complete  nitrification
within    a    relatively   short    soil   travel   distance
(Section 5.4.2).

B.6  Land Requirements

     B.6.1    preapplication Treatment  Facilities

The average  liquid  depth  of the  aerated pond  was designed  to
be  3.6 m  (12 ft),  based  on an  average detention period  of
3 days.   An  additional  1m (3.3  ft) of  freeboard was  pro-
vided  to  allow the  liquid depth  to  vary during peak  flows
and emergency conditions.  Each pond cell berm was designed
to  have  a 1:3 slope  (verticalhorizontal)  on  both  interior
and  exterior  sides and  to be  1.2  m  (4 ft)  wide  on  top.
Thus,  the  total  area required for  the  pond  is approximately
1.7 ha (4.2  acres).
                             B-13

-------
      B.6.2    Infiltration Basins

 The area needed for infiltration was calculated as follows:

                     A = (365 Q)/(104 Lw)

 where  A = area required,  ha

        Q = average wastewater flow, m3/d

       Lw = annual loading  rate, m

        A = (365 x 6,060 m3/d)/(104 x 27.4 m/yr)
          = 8.1 ha (19.9 acres)

      B.6.3    Other Land Requirements

 Additional land was required for  berms  around  the infiltra-
 tion basins and  for  access roads.   Preliminary  system lay-
 outs indicated that a  total of  about 14 ha (35 acres)  would
 be   required.   This  number was  used  for preliminary  cost
 estimates; actual  land requirements  were developed  during
 final  system design.

 B.7   System Design

      B.7.1    General  Requirements

 A   schematic  of  Community  B's  Ri  system   is   shown   in
 Figure  B-4.  The  existing  screening  and  grit  removal  facili-
 ties will  be retained  and  used  because they are necessary to
 protect  the new pumping station.

 A  pumping  station  will be  constructed  at the site  of  the
 abandoned  treatment facilities  to pump  the screened waste-
 water  through  a 30 cm  (12  in.)  force main to  the  treatment
 ponds.   Three  3.14 mj/min (830 gal/min)  pumps will  be  in-
 cluded.   Two pumps operated together will  be able  to handle
 a peak  flow of 9,090 m*/d  (2.4 Mgal/d).   The  third  pump will
 be a standby.   Standby power at the pumping station will  be
 provided  by a  diesel  generator.  Distribution  to  the infil-
 tration basins will be  by gravity  flow from the ponds.

 Infiltration basins were located on  the  area having the most
 suitable  soils.   Because this  area is relatively  flat, very
 little  grading was required  and  nearly equal-sized  basins
could  be  located  adjacent  to  one  another.    The selected
 14 day  loading cycle  required  that at  least  7  basins   be
constructed  to enable  dosing  of  at least one basin  every
2 days.  For this reason, the area having  suitable  soils  was
divided  as shown  in  Figure B-5,  with  7  basins  ranging   in
size from 0.98  to 1.3 ha (2.4 to 3.2 acres).
                             B-14

-------
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           B-15

-------
B-16

-------
To control the basin loading rate, adjustable overflow weirs
were designed  for  each pond cell.  During normal operation,
the overflow weirs are to be set  at the 3.65 m  (12  ft) .level
of the pond  (the  average  water depth).  This means that  the
instantaneous  wastewater  flow  to a basin at any time 'during
a 2  day  loading period will equal the wastewater  flow just
pumped into  the pond.   In  other words,  although the design
average wastewater flowrate is  6,060 m^/d  (1.6 Mgal/d),  up
to  9,090  m3/d  (2.4 Mgal/d) may  be delivered  to each basin
during  peak  flows  (Section B.2.2).    The  peak wastewater
application rate was calculated  as follows:
                     Qmax x 100  cm/m
  A
               mn
                     10,000 m2/ha x 24 h/d
where
       Q
        max
= peak application rate, cm/h

= peak wastewater flow, m3/d
       A  .  = basin area of  smallest  basin, ha


                   9,090 m3/d  x  100 cm/in
                                               =  3.86  cm/h
              0.98 ha x  10,000 m2/ha  x  24  h/d

In contrast,  the average wastewater loading  rate  is:

                R _ 	Q  x  100  cm/m  x  N    	
                  AT x 10,000 m2/ha x 24 h/d

where   R  = average application  rate, cm/h

        Q  = average wastewater  flow,  m3/d

        N  = number of infiltration basins

       Am  = total area covered  by basins,  ha
              R =
                     6,060  m3/d  x  100  cm/m 7
                 8.1  ha x  10,000  m2/ha x 24 h/d

               =  2.18 cm/h

 Comparing  the  peak  and  average  application  rates  to  the
 lowest  measured  basin  infiltration  rate  of  2.54  cm/h  or
 1.0  in./h  (Section B.4.3],  it can be seen that during  appli-
 cation,  infiltration would exceed application at least half
 the  time.    Also, all  of the water applied during a  1 day
 period would  infiltrate during the same period.
                             B-17

-------
 Therefore, the basin depth necessary to allow up to 12 hours
 of flooding at the peak application rate:
                    D "
                                      12  h
 where
           D  = maximum  depth  for  wastewater,  cm

             = basin  area  of  largest  basin,  ha

           I  = limiting  infiltration  rate, cm/h

             D = (3.86  cm/h - 2.54 cm/h) x 12 h
              = 16 cm  (6.2 in.)

The  required total  depth was  found by  rounding  off  D  to
15 cm  (6.0 in.)  and by adding  30 cm  (12 in.) of  freeboard
(Section 5.6.1).  The  resulting  design  basin depth  was  45  cm
(18 in.).    This  depth  should  provide more  than adequate
freeboard  during normal operations and  will  provide a margin
of safety  for unexpected conditions  and emergencies.

A  typical  slope, of  1:2 was  selected  for the  sides  of the
berms, on  both interior and exterior sides,  and the width  of
each berm  was set at 122  cm  (48  in.).   A single road around
the outer  edge  of the basins was included  with  ramps into
each  basin  for  access.   With  these  additions,  the  area
covered by the  infiltration  basins was approximately 8.3  ha
(20.5 acres),  including  8.1  ha  (19.9 acres)  available for
infiltration.
     B.7.2
              Underdrainage
Drain  laterals  and a  collector  drain were located  as  shown
in  Figure B-6.    Drain lateral  sizing  will vary between  15
and  20 cm (6 and 8 in.),  as  recommended  in  Section  5.7.3.
The  collector drain  will be  20 cm  (8  in.)  in diameter  to
ensure  free  flowing conditions.   To meet the  dissolved  oxy-
gen requirements  for discharge to North  Creek,  the  renovated
water will be routed through a cascade aerator placed  at the
bluff west of North Creek.

B.8  Maintenance  and Monitoring

     B.8.1    Maintenance

Occasional cleaning  and  ripping  of  the basins  will be  re-
quired    to     maintain     design    infiltration    rates
(Section 5.8.2).   Also,  periodic maintenance  of the ponds,
pumping   station,  screens,   and  grit  chamber   will   be
necessary.   A  staff  of  two  full-time  employees  should  be
able to  handle  all the operation and maintenance  needs  of
Community B's system (Section 2.3.3.1).
                             B-18

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                                                 o
                                              Q   30  60  90

                                              SCALE       m
                                                OUTFALL
LATERALS
COLLECTOR DRAIN
                  FIGURE B-6
             UNDERDRAIN LOCATIONS
                       B-19

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     B.8.2    Monitoring
The renovated water will be monitored  at  the outfall  for  the
parameters  listed, in Table B-2.   Three monitoring wells  to
monitor ground  water  concentrations of ammonia nitrogen  and
total  dissolved  solids  will  be   installed  as  shown   in
Figure B-5.  An observation well will  be  installed between
the bluff and  Basin  4 to  monitor  ground  water  levels  and
evaluate  underdrain performance.

B.9  System Costs

Total  costs of  Community  B's  RI  system  are  presented  in
Table B-7.    Capital   costs  were  estimated  using  the  EPA
report on Cost of  Land  Treatment Systems  [1] .   Costs were
updated to October 1980 using the EPA  Sewage Treatment  Plant
Construction Cost index  value  of 397.2.  Contractor's  over-
head and  profit are  included   in  the  cost  estimates.    The
land was  assumed to cost $4,900/ha ($2,000/acre).  Operation
and maintenance  costs were estimated  using the  cost curves
and current local prices for power and labor.  Present  worth
was  determined  using   an  interest  rate  of  7-1/8%   for
20 years.

B.10  Energy Budget

In Community  B,  energy required for land treatment will  be
used primarily  to  convey  screened  wastewater to  the  land
treatment site.   The amount of energy needed  for this pur-
pose  can  be   estimated   using  the  format  presented   in
Section 8.6.2, as follows:
     Elevation at treatment site

     Elevation at pump station

     Elevation difference

     Average flow


     Assumed pumping system
     efficiency

     Pipeline diameter

     Pipeline length

     Pipeline headless

     Total dynamic head
44 m (145 ft)

32 m (105 ft)

12 m (40 ft)

4,208 L/min
(1,111 gal/min)


40%

30 cm (12 in.)

2,680 m (8,000 ft)

12 m (40 ft)

24 m (80 ft)
                            B-20

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                   TABLE  B-7
      COST  OF  COMMUNITY B  RI  SYSTEM
   Thousands  of  Dollars,  October 1980
Capital costs
  Transmission  pumping
  Transmission  main
  Aerated lagoons
  Field preparation
  Infiltration  basins
  Underdrains
  Cascade aerator
  Outfall pipe
  Monitoring wells
  Service roads and fencing
  Standby power
  Laboratory equipment
  Sewer rehabilitation
  Land acquisition
  Legal, administrative, engineering,
  interest,  contingencies
    Total capital costs
Operation and maintenance costs
  Annual labor
  Annual materials
  Annual power
    Total operation and maintenance costs
Total project costs
  Total capital costs
  Present worth of operation and
  maintenance
    Total present worth of costs
  Salvage value of land
    Net present worth
  290
  289
  153
   94
  153
   65
   17
   18
   10
   52
   48
   24
  113
  273
  332
1,931

   15
    7
   IT.
   39

1,931
  409
                         B-21

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     Energy requirement (using
     Equation 8-2)
361,000 kWh/yr
The energy required for scarification is within the range of
error of the  estimated  energy required to convey wastewater
to the treatment site.  For this reason, energy requirements
for scarification are neglected.  The energy required by the
three cell pond  would be  approximately 395,000 kWh/yr.  The
total energy requirement of the system is 756,000 kWh/yr.

B.ll  References

1.   Reed, S.C.,  et  al.    Cost of Land  Treatment Systems.
     U.S.  Environmental Protection  Agency.   EPA-430/9-75-
     003.  September 1979.
                             B-22

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                         Appendix  C

                OVERLAND FLOW  DESIGN EXAMPLE
C.I  Introduction

The  purpose  of  this  design example is to demonstrate the
design  procedures  described   in Section 6.4.   This example
represents a preliminary  design suitable for Step 1 facility
planning.   It  does  not go  into the details of system com-
ponents such as specific  equipment and hardware.

C.2  Statement of the Problem

Community  C,  a  small   rural community in the mid-Atlantic
United States, has  a 30 year  old wastewater treatment system
that  is not meeting its  discharge permit.  The community is
totally  residential  with no industry discharging into'the
sewer  system  and  has ~a 20  year  design wastewater flow
projection  of  1,890  m  /d   (0.5 Mgal/d).  The objective of
this  project  is to provide  the community with a wastewater
treatment   system   capable    of   meeting   the  discharge
requirements.

C.3   Design Considerations

     C.3.1  Wastewater Characteristics and Discharge
            Requirements

The  raw  wastewater  characteristics are presented in Table
C-l.   Although  not listed  in Table C-l, the concentrations
of trace elements are within  the typical range for municipal
wastewater,  and  are  therefore amenable to land treatment.
The  state regulatory agency  has imposed the following limi-
tations for  any  point   source discharge;   BOD,-/  20 mg/L;
suspended solids, 20 mg/L; fecal coliforms, 200 HPN/100 mL.

                           TABLE C-l
               RAW  WASTEWATER CHARACTERISTICS
                      Parameter
                                        Value
                  BOD,-, mg/L

                  Suspended solids, mg/L

                  Total nitrogen, as N, mg/L

                   Ammonia as N

                   Organic as N

                  Total phosphorus, as P, mg/L
200

200

 40

 25

 15

 10
                              C-l

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      C.3.2  Climate

 Average  monthly  temperature  and  precipitation  data  for
 Community C  were  obtained  from  the  U.S.   Department  of
 Commerce,  National  Oceanic  and Atmospheric Administration
 (NOAA), Asheville,  North Carolina, and are shown in Table C-
 2.   A 25 year,  1 hour storm for the community was determined
 using  the  Rainfall  Frequency  Atlas of the United States,
 U.S.   Department  of  Commerce,  Technical Paper 40, and was
 found to yield  8.1  cm (3.2  in.).

                            TABLE  C-2
              AVERAGE METEOROLOGICAL CONDITIONS
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Year
Temperature,
°C
5.2
6.2
10.0
14.7
19.6
24.3
25.8
25.1
22.1
16.2
10.2
5.8
14.2
Precipitation
(Pr) , cm
8.7
9.3
10.2
8.8
.9.2
9.1
11.2
11.3
8.2
8.5
7.0
9.3
110.8
Potential evapo-
transpiration,
(ET) , cm
0.3
0.2
1.9
4.3
9.3
13.1
15.6
13.8
9.7
5.2
2.0
0.2
75.6
Net
precipitation
(Pr-ET) , cm
8.4
9.1
8.3
4.5
-0.1
-4.0
-4.4
-2.5
-1.5
3.3
5.0
9.1
35.2
C.4  Site Evaluation and Process Selection

     C.4.1  General Site Characteristics

A  preliminary  site  investigation determined that approxi-
mately 35 ha  (86 acres) of land near the, existing wastewater
treatment  system  is  available   (Figure  C-l).  A USGS- map
showed  the  site  to  have  a moderate to gentle slope that
drains  naturally  into Crooked Creek, the small stream that
receives  the  treated  effluent from the existing treatment
system.   A  large portion of the site is wooded with pines,
hardwoods, and thick undergrowth.
                             C-2

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o
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                                                                                       CO
                                                                                       CD
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      C.4.2  Soil Characteristics

 As  shown  in  Figure C-l,  the proposed site is  dominated  by
 soil of the Enon series.   These soils have a fine  sandy loam
 top  soil  underlain  with  clays having a slow permeability.
 Also  present  is Colfax  sandy loam,  which is underlain with
 clay loam and mixed  alluvial  land along the stream.   Both  of
 these  soils  have  permeabilities ranging from  slow  to very
 slow.

      C.4.3  Process  Selection

 The  slow  permeability   of the Enon  soils will  prohibit the
 use  of  RI and will severely limit the use of this site for
 SR  treatment.    Preliminary   estimates  indicated  that  OF
 treatment  was  more  cost  effective than an SR system  on this
 site  and  was   lower in  total present worth than the best
 conventional  secondary   treament and discharge  alternative.
 Therefore,   OF   treatment  was  the  alternative selected  by
 Community C.

 C.5  Distribution Method

 High  pressure  sprinklers are used in this example to illus-
 trate the  procedure.   Gravity distribution is  usually more
 cost  effective  and energy efficient.   For high solids con-
 tent wastewaters,    such    as   food    processing  effluent,
 sprinklers   can  offer  the advantage of greater solids dis-
 persion over  the  application  area.

 C.6   Preapplication  Treatment

 Continued   operation of  the  existing  treatment facilities
would  not   be  cost  effective because  of the  need for sludge
 treatment   and  disposal.   A  new  system consisting of the
minimum recommended  treatment,  that is,  two-stage screening,
was   selected.   An   economic  analysis   indicated  the  cost
savings   from   using  less  land   (higher   hydraulic  loading
rates)  did  not offset the cost  of preapplication treatment
 (Section  6.3) beyond  screening.

The  two-stage screening system includes  a  coarse screen  (bar
rack)  and  a   fine  screen.   Since sprinkler  application was
selected as the distribution  method,  the fine screen must be
capable  of removing particles  that could  clog the sprinkler
nozzles.   The  screen  mesh  will  be 1.5 mm  (0.06 in.), as
recommended  in  Section  6.3.    The new two-stage screening
system  will  be  located  at  the headworks of the abandoned
existing plant.
                             C-4 •

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C.7  Wastewater Storage

     C.7.1  Storage Requirement

The  required  storage for this project was calculated using
historical  air  temperature  data obtained from the NOAA in
Asheville,  North  Carolina, and the design method described
in  Section 6.4 for moderate climate zones.  Twenty years of
data  were  reviewed  for  the  air  temperature limitations
specified  by  the  design  method to determine the critical
year, or the year that would have required the most storage.
The required storage days for the critical year are given on
a monthly basis in Table C-3.  The total storage requirement
is  44 days, or 83,160- m    (22.0 Mgal) of wastewater at the
design flow of 1,890 m /d (0.5 Mgal/d).

                          TABLE C-3
                    STORAGE REQUIREMENTS
Month
Nov
Dec
Jan
Feb
Mar
Total
Storage,
days
0
15.5
14.5
14.0
0
44.0
Potential
application,
days
30
15.5
16.5
14.0
31
The  storage  pond  will  be filled only during cold weather
when  temperatures  fall below -4 °C (25 °F).  The procedure
for  applying  the  stored  wastewater  on  the  OF  site is
described in Section 6.5.

     C.7.2  Storage Facility Description

Storage consists of a facultative pond.  The design depth is
2  m  (6.6  ft) and the surface area is 4.2 ha (10.4 acres).
Wastewater will be diverted to storage in December, January,
and  February  and  will  be  drawn  out of storage over the
period from March through May.  The daily BOD loading on the
storage pond during the days of storage will be 89 kg/ha (80
Ib/acre)  and  odors  should  not  be  a  problem.   The net
precipitation  falling  on  the storage pond will add 18,600
m  (5 Mgal) so that a total of 101,760  m   (26.9 Mgal) will
have  to  be  removed  from  the  storage  pond each spring.
Seepage from the pond is neglected for the storage period.
                             C-5

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The  pond  berm has interior and exterior side slopes of 3:1
(horizontal:vertical),  a  height  above grade of 2.6 m (8.5
ft),  and a crest width of 3.7 m (12 ft) which will serve as
a  service  road.   The  interior  berm has a 30 cm (12 in.)
layer  of  riprap  for  embankment  protection.  The pond is
lined  with  compacted  local  clay to meet applicable state
requirements.   The  exterior  berm  slopes -are  planted to
grass.   The total area required for the storage pond is 5.4
ha (13.3 acres).

C.8  Selection of Design Parameters

     C.8.1  Hydraulic Loading Rate

From  Table  6-5,  the  range of hydraulic loading rates for
screened  wastewater  application  is 0.9 to 3 cm/d (0.35 to
1.2 in./d).  The selected hydraulic loading rate is 1.4 cm/d
(0.57  in./d).   This  rate  has been used successfully with
screened  raw  wastewater in a similar climate (Sections 6.4
and  6.2).   A more conservative loading rate is unnecessary
because  prolonged  subfreezing temperatures are not common.
A  higher  loading  rate  during  periods  of  near freezing
temperatures would be inappropriate.

     C.8.2  Application Period and Frequency

The  application  period selected is 8 h/d.  This period can
be  increased  to  12  h/d  during drawdown from storage and
during  harvest  periods  (Table 6-5).  The application fre-
quency is 7 d/wk.

     C.8.3  Slope Length and Grade

As  recommended  in  Section 6.4.6, the minimum slope length
for  OF  using  full circle sprinklers is 30 m (100 ft) plus
one  sprinkler  radius.   The  sprinklers  chosen  for  this
project (Section C.9) have a spray radius of 21.4 m (70 ft).
Thus,  the  minimum  slope length is 51.4 m (168 ft).   To be
more conservative, the design slope length is 61 m (200 ft).
The  grade  will  range  from  2 to 4% depending on existing
grades that are within this range.
                             C-6

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     C.8.4  Application Rate

Using  the  selected  hydraulic  loading  rate,  application
period and frequency, and slope length, the application rate
is calculated:
where
        w
        S =
        P =
           ^a   p(ioo cm/m)

application rate, m^/m-h
hydraulic loading rate, 1.4 cm/d
slope length, 61 m
application period, 8 h

           0  _ 1.4(61)
                         a    8(100)

                           = 0.071 m3/m°h

This is within the acceptable range from Table 6-5.

     C.8.5  Land Requirements

The slope area can be calculated  from Equation 6-2.
                 AVg]/(DaLw(100)]
               As =  [Q(365)

where A  = slope area, ha
       s                        3
       Q = average daily flow, m /d

     AVS = net change in storage = 18,600 m /yr  (C.7.2)

      Da = number of operating days per year

      iv^ = hydraulic loading rate, cm/d


      Ac = [1,890(365) + 18,600]/[(365 - 44 ) ( 1 .4 ) ( 100 )
       o
         = 15.8 ha (39 acres)

C.9  Distribution System

Impact  sprinklers  with 2^*1 mm (9/32 in.) diameter nozzles
'operating  at  41.4  N/cm    (60  Ib/in. )  are  selected  to
apply  the  wastewater.   The  OF  slope  and  the sprinkler
positions are shown in Figure C-2.  the sprinkler spacing of
24 m (80 ft) provides adequate overlap of the spray diameter
which is 42.7 m (140 ft).
                             C-7

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C.10 Preliminary System Layout

The  field  area and slope lengths have now been determined.
Given  these,  a  preliminary layout of the treatment system
was  made  on  a  USGS map using the guidelines from Section
6.6.   The  dimensions for storage have also been determined
and  were  added  to  the  overall  layout.   Using this and
remembering  that area is required for collection waterways,
service  roads,  buffer  zones, etc., the size of the survey
area  was  determined.   It can not be overemphasized that a
sufficient  amount  of  land greater than the apparent needs
must  be  surveyed so that changes in the system layout that
may  occur  do not require that additional land be surveyed.
This  not  only adds a greater cost to the project, but also
takes additional time that delays the design.

For  this  project, the entire site was surveyed so that any
future  expansions  to the system could be performed without
another  survey.   From  this  survey,  a  contour  map with
contour intervals of 0.3 m (1.0 ft) was developed (Figure C-
3); however, due to the scale of Figure C-3, only the 3.05 m
(10.0 ft) contours are used.

C.ll System Design

     C.ll.l  Treatment Slopes

Given  the slope area requirements and the slope length, the
contour   map  developed  from  the  survey,  and  the  site
development  guidelines in Section 6.6, the treatment slopes
were  laid out (see Figure C-4).  This layout has the slopes
all  graded  in  -the  same  direction  (southeast) while the
runoff  collection channels convey the effluent northeast to
a  collection  waterway.   With this layout, all effluent is
discharged  from  the site at a single point as indicated on
the figure.

     C.ll.2  Runoff Channel Design

The   runoff   collection   channels   are   formed  by  the
intersection  of  the  foot  of one treatment slope with the
backslope  of  the next treatment slope (Figure C-2).  These
channels  will be graded to no greater than 25% of the slope
grade  of  the  treatment slope to prevent cross-flow on the
treatment  slope.   This  slight grade will be sufficient to
cause flow to the collection waterways and will preclude the
need  for any type of erosion protection other than planting
the  channels  with  the  same  grasses  as  are used on the
treatment slopes.
                             C-9

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     C.11.3  Collection Waterways

The  collection  waterways  transport  the effluent from the
runoff  collection  channels to the receiving stream  (Figure
C-4).   These  waterways  were  designed  to handle both the
design  runoff from the system plus precipitation that falls
on the site during a 25 year storm.

The  Rational  Method,  which  can  be found in any soil and
water  engineering  text,  was  used  to determine the storm
runoff  from the treatment slopes.  The 25 year storm runoff
for  each  slope was determined and the flows accumulated as
each  runoff" collection  channel  contributed  flow  to the
collection  waterway.   The flow increases in quantity as it
comes  downgrade  until  all runoff collection channels have
fed  it.   Therefore,  the  collectipn  waterway  must  also
increase  in size as it comes downgrade to prevent high flow
velocities that cause erosion.

Working  from the treatment slope with the highest elevation
down  (northeast corner of spray field to southeast corner),
the  waterway  was designed for the expected effluent runoff
and  the  25  year  stormwater flow for each section between
runoff  collection  channels.   The  procedure for designing
grassed  waterways,  which can be obtained from the SCS, was
used to size each section.  Since the topography of the site
is such that the collection waterway will have a slope of 4%
or  less/  there  was  no  need for embankment protection at
bends; the grass is sufficient to prevent erosion.

     C.11.4  Pumping System

The  pumping  system  includes  three  pumps,  each  with  a
capacity  of  1,325  L/min  (350 gal/min) at a total head of
72.5 m (238 ft).  The headless was determined by summing all
the  headlosses,  from the farthermost sprinkler back to the
pump, of the critical piping path or that path that produces
the greatest headless.

The  pumps work in parallel and feed a 20.3 cm (8 in.) force
main that runs to the spray field.  The combined capacity of
the  three  pumps is three times the average design .flowrate
so  there  is  an  adequate safety factor for peak flows and
diurnal fluctuations.

The  pumping  station  is  located immediately after the two
stage  screening  unit on the existing treatment plant site.
As  shown  in  Figure  C-4, the storage basin is at a higher
elevation,  which means wastewater must be pumped to storage
and then flow back to the pumping station through a separate
pipeline  by  gravity.  Sufficient land was not available to
                             C-12

-------
locate  the  storage basin between the screening  unit and the
pumping  station  to allow gravity flow  intq  storage and out
         pumping  station.   During  favorable   days  in the
         a   valve  is opened on the return  pipeline from the
                    the  pumping  station and wastewater is
to  the
spring/
storage
applied
flowrate.
pond  to
to  the  slopes   at  1.5  times  the  average  daily
     C.11.5   Monitoring and Collection  Systems

A  monitoring  station  is  located on  the  site, as shown in
Figure   C-4.   This station consists of  a  Parshall flume with
a  continuous  flow metering device and a composite sampler.
The  Parshall flume was designed to handle  the 25 year storm
flow  without  sustaining  significant  damage.   A  standby
chlorination  system was installed at  this location and three
ground   water  monitoring  wells  were  installed as shown in
Figure  C-4  to satisfy state regulatory  requirements.

C.I2  Land  Requirements

The final  land area requirement was determined after all the
components  of  the  OF system had been sized and located on
the  site   plan.   A  15  m   (50  ft) buffer zone around the
application  site  was recommended by the state agency since
residential  developments are close to  the  site.  The buffer
zone  will  remain wooded and will require 2.3 ha (5.7 acres)
of  land.   All  of  the land requirements  of the system are
listed  in  Table C-4.  Although the total  land requirement is
29.3  ha  (72.3  acres), the entire 35  ha (85 acre) site was
purchased   since the owner refused to sell  only a portion of
the property.

                           TABLE C-4
                       LAND REQUIREMENTS
                                              Area
                         Item
                                            ha
                                                acres
             Field area with collection channels   15.8  39.0
             Storage pond

             Buffer zone

             Miscellaneous
               Roads, collection waterways,
               monitoring station

             Surplus landa

               Total
                                            5.4  13.3

                                            2.3   5.7
                                            29.3 72.3
              a.  Surplus land is that land which does not fit
                 economically into the grading plan.
                              C-13

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C.13   Cover Crop Selection

Based  on   experiences with  varieties of grasses at  other OF
systems,   it was decided to  use the  mixture  given in Section
6.7   which  includes  Reed canarygrass, tall fescue> redtop,
dallisgrass,  and   ryegrass.    The   local agricultural agent
concurred   and  also  suggested orchardgrass be added to the
mix  since  this grass flourished in the area.

C.14   System Costs

Total  costs for the OF system for Community C are presented
in  Table   C-5.   Capital costs were estimated using the EPA
technical   report   on  Cost   of  Land Treatment Systems [1].
Costs " were  updated  to September 1980 using the EPA Sewage
Treatment  Plant Construction Cost Index value of 362 and the
EPA   Sewer  Construction  Cost  Index  of 387. . Contractor's
overhead and profit are included in  the cost estimates,.  The
land  was assumed to cost $4,.900/ha ($2,000/acre) .  Operation
and   maintenance  costs were  estimated using the cost curves
and current local prices for  power and labor.  Present worth
was   determined  using  an   interest  rate   of 7-1/8% for 20
years.

                             TABLE C-5
                  COST OF COMMUNITY C  OF SYSTEM
              Thousands of Dollars, September  1980
              Capital costs
                Preapplication treatment                   42
                Pumping                              271
                Force main                             29
                Piping to and from storage                  20
                Storage pond                           316
                Site'clearing                           70
                Slope construction                       60
                Runoff collection ,     ,                  14
                Distribution (sprinklers, laterals, controls)    72
                Agriculture (preparation and seeding)          20
                Service roads                           24
                Chlorination and flow monitoring             56
                Monitoring wells                          5
                Contingencies (30%)                      300
                Land                                172
                 Total capital costs       •            1,471

              Operation and maintenance costs
                Annual labor                            27
                Annual materials                          7
                Annual power                             8
                 Total operation and maintenance costs        42

              Total-project costs
                Total capital costs                     1,471
                Present worth of operation and maintenance     441
                 Total present worth of costs             1,912
                Present worth of salvage value of land        (78)
                 Net present worth                     1,834

-------
C.15  Energy Budget

Pumping,  crop  production, and chlorination require quanti-
fiable primary  energy.   For pumping raw wastewater, stored
wastewater,  and accumulated precipitation at a head of 72.5
m  (238  ft), 222,000 kWh/yr is required.  Crop harvest will
require  20,000  kWh/yr  and  disinfection,  if  used,  will
required  5,000  kWh/yr.  The total primary energy budget is
247,000  kWh/yr.   If a gravity distribution system had been
possible,  the  pumping requirements would have been reduced
to  about  58,000  kWh/yr  due  to  the  lower  pumping head
requirement of approximately 20 m (66 ft).

C.16  Alternative Design Methods - Design Example

The  data  used  to  design  the  OF  system in the previous
example  will  be  used  with  the alternative CRREL and UCD
design  methods.   These two methods determine the land area
and  loading  requirements  for  a system and thus would not
alter   the  other  parts  of the design procedure just used.
These   methods represent a rational OF design procedure, but
have  been' used  to   a  limited  extent  for  design  as of
September  1981.

     C.16.1   CRREL Method

Given:

     Daily flowrate =  1,890 m3/d
     Influent BOD = 200 mg/L
     Effluent BOD = 20 mg/L
     Storage  requirement =  44  days                 3
     Volume of  precipitation  in  storage  =  18,600  m /yr
     Runoff fraction,  r =  60%

 Constants  for the design equation  are  (see  Section  6.11.1):

     A = 0.52     ,
      K = 0.03 min"

 The necessary calculations are:

      1.   Calculate detention time on the slope:
                           (1.0)(200)  - 0.6(20)
           % BOD removal =  •*	(i.Q)(200)	

                         x  100 = 94%
                              C-15

-------
 Using Equation 6-8 (Section 6.11.1.2)

      E  = (1 - Ae~Kt)100

      94 = (1 - 0.52e~°*03t)100
      t  = 72 min

 Calculate  average  overland  flowrate.    The site
 investigation revealed the site had a gentle slope
 of  4  to  6%.   For  design purposes, the natural
 slope  of 5% will be used and a section  size of 40
 m  long and 30 m wide (131 by 98 ft)  will  be used,
 based   on  site   characteristics.   The   average
 overland flowrate is calculated using Equation 6-9
 from Section 6.11.1.2.

      q = (0.078S)/(G1/3t)

        = [0.078(40 m)]/[(0.05)1/3(72)]
        =0.12 m3/m-h

 Calculate  application   rate.   Using  Equation 6-10
 from   Section   6.11.1.2,    the   application  is
 calculated.
Q = qw/r

  = [(0.12 m3/m-h)(30 m)]
  = 4.5 m /h per section
                                      0.6)/2]
Calculate  annual  loading  rate.   An application
period  of 8 h/d and an application frequency of 7
d/wk  will  be  used   in  this example.  Since the
storage requirement is 44 days and the application
frequency  is  7  d/wk,  the  number  of  days  of
application  is 321 d/yr.  The annual loading rate
per section is therefore:
Annual loading
              = (321 d/yr)(8 h/d)
                      3
              x (4.5 m /h per section)
Rate per section   = 11,556 m /yr

Calculate  total  annual  water  volume.   Given a
daily  flowrate  of  1,890  m   and  a  volume  of
precipitation  that  ends  up  in  the  storage as
18,600  m /yr,  the  total  annual water volume is
708,450
                  C-16

-------
     6.    Calculate   land   area requirements.   The  number of
          sections required is:

          No.  sections  = (708,450  m /yr)
                       4 (11,556 m /yr per section)

                       = 62 sections

          The  total  area requirement is

          Area = [(62 sections)(30 m x 40 m/section)

               4 10,000 m2/ha

               = 7.4 ha (18.3 acres)

          For  comparison to the previous example, the weekly
          hydraulic  loading rate can be calculated  as:

          4.5  m3/h x 8  h/d x 7 d/wk = 252 m3/wk

          252  m3/wk  x (1/1,200)(section/m2)
                    x 100 cm/m
                    =21 cm/wk

     C.16.2  University of California, Davis, Method

Given:

     Daily flowrate  = 1,890 m3/d
     Influent BOD =  200 mg/L
     Effluent BOD = 20 mg/L
     Storage requirement = 44  days                 3
     Volume of precipitation in storage = 18,600 m /yr

Constants for the design equation are  (see Section 6.11.2):

     A = 0.72
     n = 0.5
     K = 0.01975 m/h

The necessary design calculations are:

     1.   Compute the required removal ratio CS/CQ.

          C /C  = 20/200 = 0.10
           s  o
                            C-17

-------
The   length   of   slope  is  not  restricted  by
topography,  so select a value for the application
rate  (q)  in  the  valid  range of the model  (see
Section 6.11.2)

Select q = 0.16 m3/m-h

Compute  the  required  value  of slope length (S)
using Equation 6-11 from Section 6.11.2.


Cs/Co = Ae'
  0.1 = 0.72e

    S = 40 m
                  -0.04938S
4.   Select an application period  (P)

     P = 8 h/d

5.   Compute  the  average  daily  flow to the OF system
     using  44  days  of  storage, a 7 d/wk application
     frequency,  and 18,600  nT/yr  additional water in
     storage from precipitation.

     Q = [(365 d)(l,890 m3/d)

       + 18,600 m3)]/(365 - 44)

       = 2,207 m3/d

6.   Compute  the  required  wetted area using Equation
     6-5 from Section 6.11.2.

     Area = QS/qP

          = ['(2,207 m3/d)(40)]/[(0.16 m3/m-h)

          x (8 h)(10,000 m2/ha)]

          = 6.9 ha (17.0 acres)

     For  comparison  to the other examples, the weekly
     hydraulic loading rate can be calculated  as:

     (2,207 m3/d)(7 d/wk)  = 15,449 m3/wk

     (15,449 m3/wk)(1/68,500 m2)(100 cm/m)  = 22.6 cm/wk
                       C-18

-------
     C.16.3  Comparison of Methods

Although  the  CRREL and UCD equations appear different', the
basic  approach  and  calculation  method are quite similar.
Combining  and  rearranging  Equations  6-8 and 6-9 from the
CRREL method produce:
     Ms/Mo
           = 0.52e(~°-00234S)/(Gl/3q)
                         (6-13)
where
       M  = mass of BOD at point S, kg
       M  = mass of BOD at top of slope, kg
        § = slope length, m             _
        q = average overland flowrate, m /m-h
        G = slope grade, m/m

This is quite similar to the UCD Equation 6-11:

     Cs/C0 = o.72e(-0-01975S)/^°'5)

All terms as defined previously.

The  major  difference  in these two rational approaches are
the use of slope as a variable in the CRREL equation and the
value  of the coefficients and exponents.  Comparison of the
results from all three methods are tabulated below:
   Method
Traditional
CRREL
UCD
                 Land
               area, ha

                 15.8
                  7.4
                  6.9
  Slope
length, m

   60
   40
   40
  Hydraulic
loading, cm/wk

     10
     21
     22.6
The  major difference between the three methods is the slope
length  required.   The hydraulic loadings are similar since
the traditional method would permit at least 15 cm/wk during
the  warm  months.   The  CRREL and UCD methods are based on
assumed gravity distribution, so a shorter slope can be used
since   there   is  no  need  to  provide  space  above  the
application  point  for  full  circle  sprinkler impact.  If
gravity  application had been used in the traditional design,
the  gated  pipe  could  have  been  placed at the sprinkler
nozzle location shown in Figure C-2.  This would result in a
40  m  (130  ft)  slope  length  which  is identical to that
determined by the rational methods.

C.17  References

1.   Reed,  S.C.  et  al.   Cost  of Land Treatment Systems.
     U.S.  Environmental  Protection  Agency.  EPA-430/9-75-
     003.  September 1979.
                             C-19

-------

-------
                                APPENDIX D

                LOCATION  OF LAND  TREATMENT  SYSTEMS

This  appendix  contains  lists   of  publicly  owned   treatment
facilities   and  selected  industrial   facilities  that  employ
land  treatment.    The  lists  were  derived  from  a  variety  of
sources including  the  EPA  Needs  Surveys,  the  literature,  and
individual  states'  lists  and  the  Corps of Engineers.

The number  of  land treatment  systems  increased steadily  from
about  300  in 1940  to  about 700  in 1976.   It  is probable  that
there   are  more  industrial  and  more  private  land  treatment
systems   than    there  are   publicly   owned   land   treatment
systems.   The  present  count of  publicly  owned land  treatment
systems  is  839  SR,  323  RI,  and 18  OF  systems that  are  oper-
ating  or  are  under construction in 1981.
D.I
Slow
Rate
Systems
 REGION  I

 Maine
 Greenville

 Massachusetts
 Franklin
 New Hampshire
 Mt. Sunappee
 Wolfeboro

 Vermont
 West Dover

 REGION II

 New Jersey
 East Windsor
 Neptune

 REGION III

 Maryland
 Caroline Acres
 Deep Creek Lake
 Highlands
 Rossmoor
 St. Charles
 Snowden's Mill
 Swanton
 Tuckahoe
Village Center
Village Inn at Wisp
White

Virginia
John Kerr Lake

Pennsylvania
Benner Twp (Bureau of Corr.)
Gettysburg
Hamilton Twps
Kennett Square
State College

REGION IV

Florida
Apopka
Bay County
Brevard County
Coco Beach
East Point
Elgin AFB
Fort Walton Beach
Billiard
Jennings
Largo
L. Buena Vista  (Disneyworld)
Lynn Haven
MacDill AFB
Marco  Island
Newsberry
Okaloosa County
Pensacola  (Scenic Hills)
St. Petersburg
Tallahassee
Tyndall AFB
Venice
Winter Haven
Zephyr Hills

Georgia
Braselton
Camp Oliver  (Ft.  Stewart)
Clayton Co.  (R.L. Jackson)
Holiday Trav-L-Park (Lowndes Co.)
Jonesboro  (Clayton Co.)
Kings  Bay  (Navy)
Skidaway Island
Stonewall  Courthouse (Fulton Co.)
Mississippi
Arkabutla Lake

North Carolina
Pine Hurst
Seaboard
Woodland

South Carolina
Hilton Head Isl. (Bread Crk)
Hilton Head Isl. (Forest Beach)
Hilton Head Isl. (Plantation)
Sea Pines

REGION V

Illinois
                                                 Camp Point
                                                 Rend Lake, Big Muddy River
                                                 Michigan
                                                 Allegan
                                                 Belding
                                                 Bellaire
                                                 Beulah
                                                 Bloomingdale
                                                 Bowne Township
                                                 Caledonia
                                                 Cassopolis
                                                 Chatham
                                                 Clarence Township
                                                 Clark Township
                                                 Colon
                                                 Columbiaville
                                                 Crystal Township
                                                 Denton Township
                                                 East Jordan
                                                 Farwell
                                                 Fremont
                                                 Grayling
                                                 Harbor Springs
                                                 Harrison
                                                 Hart
                                                 Honor
                                                 Houghton Co. BPW
                                                 Kalkaska
                                                 Kingsley
                                                 Lake Odessa
                                      D-l

-------
 Lawton
 Leoni Township
 Livingston Co.
 Mackinaw
 Hanton
 Marion
 Harkey-Houghton
 McBain
 Hiddleville
 Huskegon
 Paw Paw
 Pinckney
 Quincy
 Ravenna
 Roscomraon
 Springport
 Sunfield
 Union City
 Verroontville
 Wayland
 Wixon
 Whitehall
 Webberville

 Minnesota
 Annandale
 Battle Lake
 Beardsley
 Belgrade
 Belle Plalne
 Blackduck
 Breezy Point
 Caas Lake
 Detroit Lakes
 Eden Valley
 Elysian
 Frazee
 Hayward
 Henning
 Kensington
 Kiraball
 Lake Henry
 New Auburn
 New York Mills
 Ortonville
 Paynesville
 Pequot Lakes
 Walker
 Watkins
 Wyoming
 Ohio
  ear Creek
 Wisconsin
 Arena
 Avoca
 Sauk City
 Stone Lake

 REGION VI

 Arkansas
 Amity Landing,
 Caddo River

 New Mexico
 Alaroogordo
 Cimarron
 Clayton
 Clovis
 Doming
 Dexter
 Eunice
 Gallup
Jal
Lordaburg
Los Alamos
DeGray Lake
 Loving
 Lovington
 New  Mexico Dept of Corr.
    (Santa Fe Co.)
 Portales
 Raton
 Roswell
 San Jon
 Silver City
 Tularosa

 Oklahoma
 Amber
 Apache
 Bixby
 Boise City
 Byng
 Calumet
 Carter
 Clinton
 Cordell
 Crescent
 Davidson
 Devol
 Dill City
 Duncan
 Edmond
 El Reno
 Erick
 Fairview
 Frederick
 Gage
 Garber
 Geary
 Granite
 Helena
 Hobart
 Hydro
 Kingfisher
 Lahoma
 Laverne
 Lone  Wolf
 Moore
 Noble
 Ochelata
 Oklahoma  City  (Willow Ck)
 Pauls Valley
 Pond  Creek
 Sentinel
 Shattack
 Spencer
 Sportsmans Acres
 Stillwater
 Terral
 Tupelo
 Velma

 Texas
 Abernathy
 Abilene
 Albany
 Amarillo
 Amherst
 Andrews
 Anson
 Anton
 Aspermont
 Austin (Williamson)
 Benjamin
 Bexar County
Big Lake
Blanco
Bonham
Booker
Bovina
  Brady
  Brownfield
  Burnett
  Castroville
  Chillicothe
  Claude
  Clyde
  Coahoma
  Coleman
  Colorado City
  Comfort
  Crane
  Crockett County
  Crosbyton
  Cross Plains
  Crystal City
  Dalhart
  Darrouzett
  Del Rio
  Denver City
  Devine,
  Dimmitt
  Dublin
  Dumas
  Earth
  Eldorado
 El Paso (Ascarte)
 El Paso (Fabens)
 El Paso (Socorro)
 Estelline
 Fabens
 Falfurias
 Falls City
 Farwell
 Florence
 Floydada
 Ft. Stockton
 Fredericksburg
 Freer
 Friona
 Fritch
 Georgetown
 Goldsmith
 Goldthwaite
 Gorman           -
 Graford
 Grandfalls
 Granger Lake
 Greenfield
 Groom
 Gustine
 Hale Center
 Happy
 Hart
 Hedley
 Hereford
 Holliday
 Hondo (East)
 Hondo
 Houston  (CIWA)
 Idalou
 Ingleside
 Johnson City
 Karnes City
 Kermit
 Kerrville
 Kilgore
 Kingsville
 Kress
 Lames a
 Levelland
 Littlefield
 Llano
 Lockney
 Loraine
Lorenzo
Lubbock
Lubbock (NW)
                                            D-2

-------
Lubbock (Yellowhouse)
McCaraey
McLean
Mason
Matador
Mathis
Meadow
Memphis
Midland
Miles
Monahans
Morton
Muleshoe
Munday
New Home
Nordheim
North Fork Lake
Odonnell
Olton
Orange Grove
Ozona
Paducah
Pearsall
Pecos
Perryton
Petersburg
Plains
Poteet
Poth
Fremont
Quitaque
Rails
Rankin
Richland Springs
Rio Grande City
Roaring Springs
Robinson (North)
Robinson (South)
Roby
Ropesville
Roscoe
Rot an
Runge
Sabinal
San Angelo
San Angelo  (Airport)
San Antonio  (partial)
San Suba
Santa Anna
Seagraves
Seminole
Shallowater
Shamrock
Silverton
Slaton
Snyder
Somerville Lake
Sonora
Stanton
Stinnett
Stockdale
Stratford
Sudan
Sundown
Sunray
Sweetwater
Tahoka
Texline
Tolar
Troy
Tulia
Turkey
Uvalde
Van  Horn
Vega
Weinert
Wellington
Wheeler
White Deer
Wilson
Winters
Wolfford
Youth Center

REGION VII

Iowa
New Hampton
Storm Lake

Kansas
Belleville
Bucklin
Chanute
Cheney
Colby
Elkhart
Elsmore
Enterprise
Formosa
Glen Elder
Goodland
Great Bend
Hays
 Hugoton
 luka
Kinsley
 Leoti
 Madison
 Minneola
 Montez.uma
 Park Meadows
 Parker
 Plains
 Plainville
 Quinter
 Ransom
 Rolla
 Russell
 St. Francis
 St. John
 Scott City
 Stockton
 Sublette
 Sylvia
 Syracuse
 Treece
 Odall
 Ulysses
 West  Plains

 Missouri
 Bennet  Spring
 Brunswick
 Clarence Cannon Dam,  Salt River
 Clearmont
 Crowder St.  Park
 Lockwood
  Mark  Twain National Forest
  Montauk
 Vandalia
 Wright  City

 Nebraska
  Clay  Center
  Davenport
  David City
  Gordon
  Humphrey
  Morrill
Oak
Phillips
Schuyler
SpaIding
Upland

REGION VIII

Colorado
Air Force Academy
Aurora
Burlington
Colo. Springs
Donala Development
Fitzsimmons AMC
Ft. Carson
Greeley
Holyoke
Inverness Development
Lake of  the Pines
Northglenn
Snowmass
Steamboat  Springs
Tammeron Development
Taylor  Park
Wray

 Montana
 Aerial  Fire  Depot
Big Sky Development
 Eureka
 Rexford
 Richey
 Roberts
 Rocky Boy
 Roy

 North Dakota
 Alexander
 Bowman
 Dickinson
 Sheyenne
 Valley City
 Watford

 South Dakota
 Eagle Butte
 Gettysburg
 Huron
 Lake Andes
 Mitchell

 Utah
 Bear River Central Disposal
 Heber
 Provo River Cental Disposal
 Roosevelt
 Spanish Fork
 Tooele
 Vernal

 Wyoming
 Cowley
 Snowy  Range Central Disposal
 Thayne

 REGION  IX
  Arizona
  Alpine
  Arizona City
  Benson
  C'asa Grande
  Catalina
  Coolidge
  Ft. Huachuca
  Gilbert
  Joseph City
                                             D-3

-------
  Lake  Havasu (South WWTF)
  Lake  Havasu (Island WWTF)
  Hesa
  Page
  Prescott
  Safford
  St. Johns
  Taylor
  Tucson
  Tucson  (Airport)
  Williams AFB
  Winslow

  California
  Apple Valley
  Angels
  Antelope Valley
  Armona CSD
  Arvin
 Atascadero
 Avenal
 Bakersfield (No. 1 and 2)
 Bakersfield (No. 3)
 Bass Lake
 Beale AFB
 Bear Creek Estates
 Bear Valley
 Bodega Bay
 Bolinas
 Brentwood
 Buena Vista
 Butte Community College
 Buttonwillow
 Boulder Creek
 Calif. Inst. for Hen (Chino)
 Calif. Hed. Facility
   (Vacaville)
 Calif. Hens Colony (SLO)
 Calipatria
 Calistoga
 Cnraarillo
 Cnraarillo  St.  Hospital
 Cambria
 Camp Pendleton
 Caittpo
 Castle AFB
 Chico
 China  Carap  (Harin)
 China  Lake
 Chowchilla
 Clearlake Oaks
 Coachella
 Coachella Valley
 Coalinga
 Colt Ranches (Hendota)
 Colfax
 Corning
 County Estates (Ramona)
 Cutler-Orosi
 Delano
 Dinuba
 Douglas Flat
 Earlimart
 Edgemont
 El Dorado Hills
 El Toro
 Exeter
 Fairfield
 Fnllbrook
 Fed. Corr. Inst.
  (Santa Barbara)
 Fernbridge
 Ferndale
Fontana
 Forestville
Ft.  Hunter-Liggett
Furnace Creek
 George AFB
 Golden Gate Park (SF)
 Goldside Estates
 Gonzales
 Graton
 Groveland
 Guadalupe
 Gustine
 Half Moon Bay
 Hanford
 Healdsburg
 Hemet
 Houston Creek (Crestline)
 Indian Mills
 Indio
 lone
 Ivanhoe
 Kerman
 Kern Co.  Ind.  Farm
 King City
 La Canada
 La Crescenta
 Lag una
 Laguna Hills
 La Honda
 Lake Arrowhead
 Lake Berryessa
 Lake Berryessa (Napa Co.)
 Lake Cachuma
 Lake Co.  (Clearlake Highlands)
 Lake Elsinore
 Lake Elsinore  (Canyon Lake)
 Lake Hughes
 Lakeport
 La Hont
 Las Virgines
 Le Grande
 Lemon Cove
 Lemoore
 Limoneira Ranch
 Lincoln
 Lindsay
 Livermore
 Lodi
 Los Alisos
 Los Angeles Co.
   (Acton  Rehab.  Center)
 Los Angeles Co.
    (Lancaster)
 Los Angeles Co.
    (Palmdale)
 Los Angeles Co.
    (Warm  Springs)
 Los Banos
 Loyalton
 McFarland
 Hadera  Co.  (North Fork)
 Halibu  (Probation Camp)
 Hanteca
 March AFB
 Headowood
 Hendocino City
 Merced
 Michelson (Irvine Ranch)
 Moccasin
 Hodesto
 Mokelumne  Hill
 Moulton-Niguel No. 1A
 Houlton-Niguel No. 3
 Mt. Vernon
 tfurphys
Newcastle
North Fork
North Lakeport
North River No. 1
North Shore
 Novato
 Oakshores
 Occidental
 Ocotillo
 Orange Cove
 Pacific Union College (Angwin)
 Palmdale
 Palm Springs
 Parlier
 Ferris
 Petaluma
 Pixley
 Plymouth
 Pomona
 Prado Regional Park
 Quincy
 Ramona
 Rancho California
 Richardson Bay
 Richardson Springs
 Ridgecrest
 Riverdale
 Rohnert Park
 Rosamond
 Sacramento (Metro Airport)
 San Bernardino
 San Bernardino Co. No.  70
 San Buenaventura
 San Clemente
 San Joaquin Co.  Gen.  Hospital
 San Juan Bautista
 San Luis Obispo
 San Luis Rey (Oceanside)
 San Pasqual Acad.
   (Escondido)
 Santa Maria  ,
 Santa Nella
 Santa Paula
 Santa Rosa (Laguna)
 Santa Rosa (Oakmont)
 Santa Rosa (West College)
 Scotts Valley
 Seeley Creek (Crestline)
 Sea Ranch
 Shady Glen
 Shafter
 Shasta Dam
 Shastina
 Sheridan
 Smith River
 Snelling
 Sonoma Valley
 South  Tahoe
 Spanish Flat
 Strathmore
 Sun  City
 Sunnymead
 Sunol  Valley
 Susanville
   (Dept of' Corrections)
 Sutter Creek
 Taft
 Tehachapi
 Terra  Bella
 Thousand Oaks
 Toraales
 Tulare
 Tulare  Correction Center
 Twentynine Palims
 U.S. Vet. Admin,, Hosp.
   (Livermore)
Veteran Home (Yountville)
Wasco
Weed
Western Hi HE  (Chino)
                                            D-4

-------
Westport
Willits
Wilseyville
Windsor
Windsor (Sonoma Co. Airport)
Winton
Woodlake
Woodland
Woodville
Woodward Bluff
Yountville

Hawaii
Hanalei
Kailua Kona
Kaunakakai
Keauhou
Lahaina
Schofield Barracks
Wai me a

Nevada
Carson City
Dayton
Douglas Co.
Elko
Gerlach
Glen Meadows
Incline Village
Las Vegas (partial)
Las Vegas (Clark Co.)
   (partial)
Lemmon Valley
Owyhee
Winnemucca

REGION X
Idaho
Albion
Ashton
Boise (Gowen Field)
Bottle Bay
Bruneau
Donnelly
Enunett
Garfield Bay
Hazelton
Melba
Menan
Mt. Home
New Plymouth
Plummer
Rupert
Santa
St. Anthony
Wendell

Oregon
Adrian
Arch Cape
Ely
Boardman
Brownsville  (North)
Brownsville  (South)
Burns
Butte Falls
Corvallis  (Airport)
Cottage Grove Lake
Cove
Creswell
Culver
Dexter Lake
Eagle Point
Echo
Eugene  (Airport)
Forest Grove
Freeman Creek, Dworshak Dam
Gaston
Grouse Creek, Applegate Lake
Haines
Hillsboro, West Side
Hines
Jordan Valley
Junction City
Lakeside
Lakeview
Long Creek
Lowell
Madras
Metolius
Milton Freewater
Moro
Paisley
Prairie City
Richardson Point Park
  Fernridge Reservoir
Richland
St. Paul
Seneca
Sherwood
Siletz
Somerset West
Stewart Lake, Lost Creek
Sutherlin
Ukiah
Unity
Wasco
Yamhill

Washington
Camp Booneville
Cusick
Ephrata
Grandview
Naches
Prosser
Quincy
Soap Lake
Walla Walla  (Industrial)
Warden
Waterville
iTakiraa  (industrial)

D.2   Rapid
        Infiltration

        Systems

REGION I

Massachusetts
Barnstabie
Chatham
Concord
Edgartown
Fort Devens
Nantucket (2 )
Wareham

REGION  II

New Jersey
Cranbury
Seabrook Farms  (industrial)
Vineland

New  York
Birchwood-North  Shore
    (Holbrook)
Cedar  Creek  (Wantagh)
College Park (Farmingdale)
County Sewer District
    (Central  Islip)
 County Sewer  District
    (Holbrook)
 County Sewer  District
    (Holtsville)
 County Sewer  District #5
   (Huntington)
 County Sewer  District #11
    (Ronkonkoma)
 County Sewer  District 112
    (Holtsville)
 Heatherwood  (Calverton)
 Huntington Sewer District
 Lake George
 Riverhead
 Strathmore Ridge (Brookhaven)

 REGION III
 Maryland
 Calhoun Marine
   Engineering School
 Fort  Smallwood
 Jensen's  Inc. - Hyde Park

 Quality Inn of Pecomore, Inc.
 South Dorchester K-8 Center

 REGION IV
 Florida
Avon Park
Lehigh Acres
Sandlake (Orlando)
Tavares
Williston

Kentucky
Horse Cave

REGION V

Illinois
Meredosia
Sangaman Valley

Michigan
Alpha
Bangor
Baraga
Bates Township
Calumet
Chatham
Crystal Falls
Decatur
Dimondale
Edmore
Forsythe Township
Gaastra
Cedar Springs (Grand Rapids)
Grayling
Hopkins
Howard
Marcellus
Olivet
Onekama
Ottawa County Road Commission
Pentwater
Shelby
Stockbridge
Tekonsha

Minnesota
Medina
                                            D-5

-------
  Wisconsin
  Almond
  Baldwin
  Balsam Lake
  Bacron
  Birchwood
  Boyceville
  Coloma
  Deer Park
  Penwood
  Fifield
  Fontana
  North Moraine (Glenbeulah)
  Glenwood City
  Grantsburg
  Hammond
  Haugen
  Iron River
  Kellnersville
  King Veterans Home
  Knapp
  Lone Rock
  Lyndon Station
  Haribel
  Hattoon
  Merrimac
  Hilton
  Hinong
  Mount Calvary
  Neshkoro
  Plainfield
  Roberts
  Rosholt
  Sand  Creek
  Scandinavia
  Sextonville
  Spooner
  Spring Green
  Stetsonville
 Stone Lake
 Rozellville (Stratford)
 Kelly Lake (Suring)
 Unity
 Warrens
 Wautoma
 Wheeler
 White Lake
 Wild Rose
 Williams Bay
 Winter
 Wittenberg
 Wyocena

 REGION VI
 Plains
 Stevensville
 Victor

 North Dakota
 Parshall
 Reeder
 Louisiana
 Ft.  Polk
New  Mexico
Hobbs
Springer
Vaughn

REGION VII

Nebraska
Chapman
Elwood

REGION VIII

Colorado
Sterling

Montana
Bazin
Bozeman
Corvallis
 South Dakota
 Madison
 REGION IX

 Arizona
 Arcosanti (Cordes Junction)
 Lo Lo Mai Springs
 Mammoth
 Phoenix (23rd Avenue)
 Papago Tribal Wastewater
   Treatment System (Sells)
 St. David
 Thatcher
 Marana (Tucson)
 Green Valley (Tucson)
 Arizona Correctional Training
   Facility (Tucson)
 Corona de Tucson (Tucson)
 Sunrise Resort (White  River)
 Wickenburg
 Willcox

 California
 Applegate
 Arbuckle
 Baker
 Banning
 Barstow
 Bieber
 Pfeiffer  Big  Sur State Park
 Biola College  (Los Angeles)
 Bishop
 Placer County  (Blue Canyon)
 Blue  Lake
 Blythe
 Bombay Beach
 Desert Lake  (Boron)
 Bridgeport
 Buellton
 Burney
 Byron
 California City
 Calpella
 Camino Heights
 Caruthers
 Cascade Shores
Warm  Springs Rehabilitation
  Facility (Castaic)
 Ceres
Chester
 Chualar
Coalinga
Corcoran
Corona
Courtland
Glen Helen Rehabilitation
  Center (Crestline)
Del Rey
Delhi
Desert Crest
 Desert Hot  Springs
 Desert Shores
 Discovery Bay
 Whittier Narrows  (Los
   Angeles County,  El Monte)
 Escalon
 Etna
 Farmersville
 Fillmore
 Firebaugh
 Floriston
 Fontana
 Franklin
 Fresno   i
 Gait
 Garberville
 Gilroy
 Gorman
 Grass  Valley
 Grayson
 Greenfield
 Gridley
 Hamilton City
 Silver Lake (Helendale)
 Pleasant Ridge  School
   (Higgins  Corner)
 Hilmar
 Hollister
 Hopland
 Huron
 Idyllwild
 Inyokern
 Isleton
 Julian
 June Lake
 Selma  Community (Kingsburg)
 Knights Landing
 La Selva Beach
 Laguna Niguel
 Lake of the Pines
 Copper Cove (Lake Tulloch)
 Laton
 Lechuza
 Linda
 Linden
 L'innell
 Livingston
 Lompoc
 Lone Pine
 Lopez  Lake
 Madera
 Madison
 Malaga
 Mammoth  Lakes
 Maricopa  '
 Mariposa
 McCloud
 McKittrick
 Mineral
 Mojave
 Montague
 Montalvo
 Moorpark
 Mt.  Shasta
Newell
Oakdale
Orland
Victor Valley (Oro Grande)
Palm Desert
California Youth Authority
   (Paso Robles)
Pauma Valley
Pine Valley
Pinecrest
                                            D-6

-------
Poplar (Woodville Farm)
Porterville
Portola
Rancho Ponderosa
Rancho Santa Fe
Redlands
Reedley
Rialto
Richvale
Ripon
Riverbank
Running Springs
Salida
Salton City
San Ardo
Hemet San Jacinto
San Miguel
San Onofre State Beach
Sanger
Santee
Seeley
Shelter Cove
Smith Flat
Donner Summit (Soda Springs)
Soledad
Springville
St. Helena
Stirling City
Stratford
Tipton
Tranquillity
Tres Pinos
Tahoe-Truckee
Valley Center
Weaverville
Westley
Westwood
Wheatland
Whispering Palms
Whitter (Los Angeles County/
  San Jose Creek)
Willow Creek
Woodbridge
Yreka
Yuba City
Yucaipa
Nevada
Alamo
Beatty
Blue Diamond
Boulder City
Empire
Eureka
Gabbs
Goldfield
Hawthorne
Henderson
Jackpot
McDermitt
McGill
Montello
Overton
Panaca
Paradise Spa
Paradise Valley
Pioche
Stead
Tonopah
Wendover
Yerington

REGION X
Washington
Ritzville

D.3   Overland

        Flow Systems

 REGION  I

 REGION  II

 New York
 Harriraan (pilot  scale)

 REGION  III

 Maryland
 Beltsville
 Chestertown (industrial)

 Virginia
 Gretna

 REGION  IV

 Georgia
 Woodburry

 Mississippi
 Cleveland
 Falkner
 South Carolina
 Easley (R&o)
 REGION V

 Illinois
 Carbondale
 Fillmore

 Indiana
 Middleburry (industrial)

 Michigan
 Glenn  (industrial)

 Ohio
 Alum Creek Lake
 Napoleon (industrial)

 REGION VI

 Louisiana
 Vinton
Idaho
Dent Acres
 Oklahoma
 Ada  (R&D)
 Heavener

 Texas
 El Paso  (industrial)
 Paris  (industrial)
 Rocky  Point, Sulphur River
 Sherman

 REGION VII

 REGION VIII

 REGION IX

 California
 Davis
 Davis  (industrial)
 Newman
 Sebastopol  (industrial)

 Nevada
 Minden-Gardnerville
                                            D-7

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-------
                         APPENDIX E

          DISTRIBUTION SYSTEM DESIGN FOR SLOW RATE

E.I  introduction

Details of distribution system design for the SR process are
presented  in  this appendix  for both surface  and sprinkler
distribution  methods.   Some  aspects covered here are also
applicable to  RI or OF distribution techniques.   The  level
of  detail  presented  in  this  appendix  is sufficient   to
develop  preliminary  layouts  and   sizing   of  distribution
system components.   References are  cited  that  provide more
complete design  information.

E.2  General Design Considerations

Several  design  parameters  are  common   to  all  distribution
systems and are  defined in the  following.
    E.2.1
Depth of Water Applied
The  depth  of  water  applied  is  the  hydraulic  loading  per
application  expressed  in  cm   (in.)  and  can  be  determined
using  the  relationship:
where   D  =
      Lw  -

        F  =
            D = LW/F                   (E-D

depth of water applied, cm  (in.)

monthly hydraulic loading,  cm  (in.)

application frequency, number  of applications
per month
 The  monthly hydraulic loadings will have been established as
 a result  of  the water  balance  calculations developed  in
 Section 4.5.
     E.2 .2
Application Frequency
 The  application  frequency  is  defined   as  the  number  of
 applications  per  month  or  per  week.     The  application
 frequency to  use for  design is  a  judgment decision  to be
 made by the designer considering:  (1) the objectives of the
 system,  (2 ) the  water  needs  or tolerance   of  the  crop,
 (3) the moisture  retention properties of  the  soil, (4) the
 labor  requirements  of  the distribution  system,  and (5) the
 capital  cost  of  the  distribution  system.    Some general
                              E-l

-------
 guidelines   for   determining  an   appropriate  application
 frequency are presented  here,  but  consultation with a local
 farm adviser is recommended.

 Except for  the water  tolerant forage  grasses,' most crops,
 including  forest   crops,  require  a  drying period  between
 applications to allow  aeration of the  root zone to achieve
 optimum  growth  and  nutrient  uptake.   Thus,  more  frequent
 applications are  appropriate  as  the ET  rate   and  the  soil
 permeability increase.   In practice,  application frequencies
 range from once every  3  or  4 days for  sandy soils  to about
 once every  2  weeks  for  heavy clay  soils.  An application
 frequency of once  per week is commonly used.

 The operating and  capital costs  of  distribution systems can
 affect  the  selection  of   application  frequency,,     With
 distribution systems that must be moved between applications
 (move-stop  systems),  it  is usually  desirable  to  minimize
 labor and operating  costs by minimizing the number  of moves
 and therefore the  frequency of  application.    On the  other
 hand,  capital costs  of the  distribution system are  directly
 related  to  the flow capacity  of  the  system.   Thus,  the
 capital cost may  be reduced  by  increasing  the application
 frequency to reduce system capacity.
     E.2.3
Application Rate
Application, rate is  the  rate at  which water is  applied  to
the  field  by  the  distribution  system.    In  general,  the
application  rate should be matched  to  the  infiltration rate
of the  soil  or  vegetated  surface  to  prevent excessive runoff
and  tailwater  return  requirements.    Specific  guidelines
relating  application  rates  to infiltration properties  are
discussed  under the different  types  of  distribution systems.
    E.2.4
Application Period
The  application period  is  the time  necessary  to apply  the
desired  depth  of  water  (D).    Application  periods  vary
according  to   the  type  of  distribution  system,  but,   in
general  are  selected to  be  convenient  to  the  operator  and
compatible   with   regular   working   hours.      For   most
distribution  systems,  application  periods  are  less  than
24 hours.
    E.2 .5
Application Zone
In  most systems,  wastewater is  not applied  to  the  entire
field area during the application period.  Rather, the  field
area  is   divided  into  application  plots   or  zones  and
wastewater   is   applied  to  only   one   zone  at  a   time.
                             E-2

-------
Application is  rotated  among  the zones such that the entire
field  area receives  wastewater within  the  time   interval
specified  by  the  application  frequency.   Application  zone
area can be computed with the following:
where Aa =

      Aw -
          Aa = Aw/Na                    (E-2)

application zone area, ha (acres)

field area, ha (acres) (see Section 4.5.4.1)

No. of application zones
The  number of  applicati9n  zones is  equal  to the  number  of
applications  that  can  be  made  during  the  time  interval
between   successive  applications .  on  the  same   zone   as
specified  by  the  application  frequency.     ,.      .

For   example,  if  the  application   period   is   11  hours,
effectively  2 applications can  be  made each operating  day.
If the application  frequency  is  once per week and the system
is operated  7 days  per  week,  then there are 7 operating  days
between  successive  applications on  the same  zone  and  the
number of  application zones is:

           N = (2  applications/day)(7 operating  days)
             a = 14

If the field area is 100 ha (40  acres), then the  application
zone is:
                       A_ = 100 ha/14
                        d

                          = 7.14 ha
     E.2.6
 System Capacity
 Whatever  type  of  distribution  system  is  selected,  the
 maximum flow  capacity of  the  system must  be  determined so
 that components, such as pipelines and pumping stations, can
 be properly sized.   For systems with a constant application
 rate throughout the application period, the flow capacity of
 the system can be computed using the following formula:
                         Q = CAaD/ta
                                         (E-3)
                              E-3

-------
 where  Q =

        C =
       Aa =

        D =
discharge capacity, L/s  (gal/min)

constant, 28.1 (453)

application area, ha  (acres)

depth of water applied, cm (in.)

application period, h
Other   methods  of   computing  system  flow   capacity   are
illustrated  for each  of  the  distribution systems.
E.3   Surface  Distribution Systems
    E.3.1
Ridge and Furrow Distribution
The  design   procedure   for   ridge   and   furrow  systems  is
empirical   and   is  based  on  past   experience   with   good
irrigation   systems  and  field   evaluation   of   operating
systems.   For more detailed  design procedures,  the designer
is referred  to references  [1]  and  [2].

The  design  variables  for  furrow  systems  include  furrow
grade,   spacing,   length,   and   stream   size   (flowrate)
(Figure E-la).   The  furrow  grade  will  depend  on  the  site
topography.   A  grade  of 2%  is  the  recommended maximum  for
straight furrows.   Furrows can be oriented  diagonally  across
fields  to  reduce  grades.   Contour  furrows or  corrugations
can be used  with grades  in the range of  2 to  10%.

The   furrow  spacing   depends   on    the   water   intake
characteristics  of the  soil.   The principal  objective  in
selecting  furrow spacing  is  to  make  sure  that the lateral
movement of  the  water between adjacent  furrows will wet  the
entire  root  zone  before  it  percolates  beyond  the   root
zone.  Suggested furrow spacings based on different soil  and
subsoil conditions  are given  in Table  E-l.

The length  of the  furrow  should  be as  long  as will permit
reasonable   uniformity   of    application,    because  labor
requirements  and capital  costs  increase as  furrows become
shorter.   Suggested  maximum  furrow   lengths  for  different
grades,  soils,   and depths of  water  applied  are  given  in
Table E-2.
                             E-4-

-------
         FURROW SPACIN6
                    - FURROW STREAM SIZE q
    (a)  RIDGE  AND  FURROW
             BORDER
     (b)  GRADED  BORDER
           FIGURE E-1
SURFACE  DISTRIBUTION METHODS
             E-5

-------
                             TABLE  E-l
                   OPTIMUM FURROW SPACING  [3]
                      Soil condition
  Optimum
spacing,  cm
            Coarse sands - uniform profile            30
            Coarse sands - over compact subsoils       46
            Fine sands to sandy loams - uniform        61
            Fine sands to sandy loams - over
            more compact subsoils                    76
            Medium sandy-silt loam - uniform          91
            Medium sandy-silt loam - over
            more compact subsoils                   102
            Silty clay loam - uniform               122
            Very heavy clay soils - uniform           91
                             TABLE E-2
            SUGGESTED MAXIMUM LENGTHS OF CULTIVATED
           FURROWS FOR DIFFERENT SOILS,  GRADES,  AND
               DEPTHS OF WATER TO BE  APPLIED [1]
                                m
Avg depth
Furrow
grade, %
0.05
0.1
0.2
0.3
0.5
1.0
1.5
2.0
Clays
7.5
300
340
370
400
400
280
250
220
15
400
440
470
500
500
400
340
270
22.5
400
470
530
620
560
500
430
340
30
400
500
620
800
750
600
500
400
5
120
180
220
280
280
250
220
180
of water applied2, cm
Loams
10
270
340
370
400
370
300
280
250
15
400
440
470
500
470
370
340
300
20
400
470
530
600
530
470
400
340
5
60
90
120
150
120
90
80
60
Sands
7.5
90
120
190
220
190
150
120
90
10
150
190
250
280
250
220
190
150
12.5
190
220
300
400
300
250
220
190
       From Equation E-l.
The  furrow stream size or application  rate is  expressed  as a
flowrate  per  furrow.    The  optimum stream  size  is usually
determined  by  trial  and  adjustment in  the  field  after  the
system   has   been   installed   [2].      The   most   uniform
distribution  (highest application  efficiency) generally  can
                                E-6

-------
be  achieved  by  starting  the  application with  the  largest
stream size that  can  be safely carried in the furrow.  Once
the  stream   has   reached  the   end   of  the  furrow,   the
application rate  can be  reduced  or cut  back to reduce  the
quantity of runoff that must be handled.  As  a general  rule,
it  is  desirable  to  have  the  stream  size  large  enough  to
reach  the  end of  the  furrow within one-fifth  of the  total
application  period.    This  practice  will  result   in   an
application efficiency of greater than 90% for most soils if
tailwater is returned (see Section  4.8.2.1).

The application  period  is the  time needed to infiltrate  the
desired depth of water plus the time required for  the stream
to  advance to the  end  of  the furrow.   The time required  for
infiltration depends  on  the  water  intake characteristics of
the furrow.   There is no  standard method for estimating  the
furrow  intake   rate.     The  recommended  approach   is   to
determine  furrow  intake   rates   and  infiltration  times  by
field trials as described in reference  [2].

Design  of  supply  pumps  and transmission systems^ should  be
based on providing the maximum allowable stream  size,  which
is  generally  limited by  erosion  considerations when grades
are greater  than 0.3%.   The  maximum nonerosive  stream size
can be estimated  from the equation:
                        qe = C/G

where  qe = maximum unit stream size, L/s  (gal/min)

        C = constant, 0.6 (10)

        G = grade, %
                                                       (E-4)
For grades  less  than  0.3%,  the  maximum allowable stream size
is governed by the  flow  capacity  of  the furrow,  estimated as
follows:
where   qc

         C
                        qc = CFa
            furrow flow capacity,  L/s  (gal/min)

            constant,  50  (74)
                                              2     2
            cross-sectional area of  furrow, m''  (ft )
                                                       (E-5)
                              E-7

-------
Various  conveyance  systems and  devices are  used to  apply
water  to   the  head  of  the   furrows.     The  most   common
conveyance  systems  are open  ditches or  canals  (lined  and
unlined),   surface   pipelines,   and  buried   low-pressure
pipelines.     For  wastewater   distribution,   pipelines  are
generally  used.    If  buried  pipelines  are  used to  convey
water,  vertical riser  pipes with valves are  usually  spaced
at   frequent   intervals  to release  water  into  temporary
ditches   equipped   with   siphon  tubes  or   into hydrants
connected to  portable  gated surface  pipe (Figure E-2 ).
                          FIGURE E-2
                ALUMINUM HYDRANT AND GATED PIPE
                     AT SWEETWATER,  TEXAS
The spacing of the risers is governed either by the headless
in the gated pipe  or by widths of border strips when graded
border and  furrow  methods  are  alternated on the same field.
The  valves  used  in  risers  usually  are  alfalfa  valves
(mounted  on top of  the riser)  or orchard  valves (mounted
inside the  riser).   Valves must be  sized to  deliver the
design flowrate.
                             E-£

-------
Gated  surface  pipe  may  be  aluminum,  plastic,  or  rubber.
Outlets   along   the  pipe   are  spaced   to  match   furrow
spacings.    The pipe and  hydrants  are portable so  that  they
may  be moved  for each  irrigation.   The  hydrants  are mounted
on valved  risers,  which are spaced along the buried pipeline
that   supplies  the  wastewater.    Operating  handles  extend
through  the  hydrants   to  control  the   alfalfa  or  orchard
valves located in  the  risers.    Control of  flow  into  each
furrow is accomplished  with  slide gates or  screw adjustable
orifices  at  each  outlet.   Slide gates   are  recommended  for
use  with wastewater.   Gated  outlet capacities vary with  the
available  head  at the gate, the velocity of  flow  passing  the
gate,  and   the gate  opening.    Gate openings  are  usually
adjusted  in the field to  achieve the  desired stream size.
 EXAMPLE E-l:
            DETERMINATION OF  PRELIMINARY  DESIGN CRITERIA
            FOR A  RIDGE AND FURROW DISTRIBUTION SYSTEM
               sandy loam over clay
 Design Conditions

 1.  Soil conditions:

 2.  Final grade:  0.5%

 3.  Maximum monthly hydraulic loading  (1^) :  40 cm

 4.  Application frequency  (FJ :  4 times per month (1/wk)

 5.  Total field area  (Aw) : 100 ha

 6.  Crop:  corn

 Design Calculations

 1.  Determine depth of water to be applied during application.

         D = LW/F
      ^    = 40/4
           = 10 cm

 2.  Determine the application zone area with Equation E-2.

     Assume four applications per day will be performed,
     7 d/wk.
                                                            (E-l)
Application zone area (A_) =
                    a
                             -^-5 - =-= - •r-.
                             28 application zones
                             100 ha
                                                                 (E-2)
                               28
                           = 3.6 ha

     Select furrow spacing from Table E-l.

         Sf = 76 cm

     Select furrow length from Table E-2.

         L  = 370 m
                                E-9

-------
5.  Estimate maximum furrow stream size  (application rate) from Equation E-4.
       ge
                                                               (E-4)
          -1.2 L/S
   This  flow is used until the stream reaches the end of the furrow, at which
   time  the flow is reduced.
   Calculate the number of furrows used per application zone.
                        (Aa) (104 m2/ha)
       No. of furrows =
                      (Lf)(Sf)(0.01 m/cm)
                           (3.6 ha)(104 m2/ha)
                      (370 m)(76 cm/furrow)(0.01 m/cm)

                    =127 furrows
   Calculate the maximum flow that must be delivered to each application area
    (distribution system capacity).

        Q = (No. of furrows)(qe)
         = (127)(1.2 L/s)
         = 152 L/s (2,417  gal/min)
     E.3.2
Graded  Border Distribution
Preliminary   design   considerations   for   straight",   graded
border  distribution  systems  are  discussed  here.    Quasi-
rational design  procedures  have  been  developed  by the  SCS
for  all  variations  of  border  distribution systems and  are
given  in  Chapter  4,  Section  15,  of  the  SCS   Engineering
Handbook [5] .

The  design variables for graded border  distribution are:

     1.   Grade  of the border strip

     2.   Width  of the border strip

     3.   Length of the border strip

     4.   Unit stream size

Graded border distribution can be used  on grades  up to about
7%.    Terracing  of graded  borders can be used for  grades up
to 20%.

The   widths   of   border   strips  are  often   selected  for
compatibility with  farm implements,   but  they also  depend to
a  certain  extent  upon grade  and soil type,  which affect the
uniformity  of  distribution  across  the strip.   A  guide  for
estimating strip widths  is presented  in Tables E-3  and E-4.
                               E-10

-------
                           TABLE E-3
             DESIGN GUIDELINES FOR GRADED BORDER
             DISTRIBUTION,  DEEP ROOTED CROPS  [1]
.Soil type
and
infiltration
rate
Sandy ,
^2.5 cm/h
Loamy sand ,
1.8-2.5 cm/h
Sandy loam
1.2-1.8 cm/h
Clay loam,
0.6-0.8 cm/h
Clay,
0.3-0.6 cm/h
Grade, %
0.2-0.4
0.4-0.6
0.6-1.0
0.2-0.4
0.4-0.6
0.6-1.0
0.2-0.4
0.4-0.6
0.6-1.0
0.2-0.4
0.4-0.6
0.6-1.0
0.2-0.3
Unit flow
per 1 m of
strip width,
L/s
10-15
8-10
5-8
7-10
5-8
3-6
5-7
4-6
2-4
3-4
2-3
1-2
2-4
Avg depth3
of water
applied, cm
7-10
7-10
7-10
10-13
10-13
10-13
10-15
10-15
10-15
15-18
. 15-18
15-18
15-20
Border
Width
12-30
9-12
6-9
12-30
8-12
8
12-30
6-12
6
12-30
6-12
6
12-30
strip, m
Length
60-90
60-90
75
75-150
75-150
75
90-250
90-180
90
180-300
90-180
90
350+
     a.  From Equation E-l.
                           TABLE  E-4
             DESIGN GUIDELINES FOR GRADED BORDER
            DISTRIBUTION, SHALLOW ROOTED  CROPS [1



Soil profile
Clay loam, 60 cm
deep over per-
meable subsoil
Clay, 60 cm deep
over permeable
subsoil
Loam, 15-45 cm
deep over hardpan



Grade , %
0.15-0.6
0.6-1.5
1.5-4.0
0.15-0.6
0.6-1.5
1.5-4.0
1.0-4.0

Unit flow
per 1 m of
strip width.
L/s
6-8
4-6
2-4
3-4
2-3
1-2
1-4


Avg depth
of water
applied, cm
5-10
5-10
5-10
10-15
10-15
10-15
3-8


Border


Width
5-18
5-6
5-6
5-18
5-6
5-6
5-6


strip, m


Length
90-180
90-180
90
180-300
180-300
180
90-300

  a. From Equation E-l.
The  length  of border  strips should  be  as long  as  practical
to minimize capital  and operating costs.  However,  extremely
long  runs are  not  practical due  to time  requirements  for
patrolling  and   difficulties  in  determining   stream  size
adjustments.   Lengths in excess  of  400  m (1,300  ft)  are not
recommended.  In  general,  border  strips  should  not  be  laid
                              E-ll

-------
out  across  two  or  more soil  types with  different  intake
characteristics  or  water  holding  capacities,  :and  border
strips  should not  extend across  slope grades  that  differ
substantially.    The appropriate  length  for a  given  site
depends  on the grade, the allowable stream size, the  depth
of  water applied,  the  intake characteristics  of the  soil,
and   the  configuration  of  the   site  boundaries.     For
preliminary   design,   the  length  of  the  border  may  be
estimated  using Tables E-3 and E-4.

The  application  rate or  unit stream size  for graded  border
irrigation  is expressed  as  a  flowrate  per unit  width  of
border  strip, L/s-m  (ft^/s-ft).    The  stream  size  must  be
such  that the  desired volume  of water  is  applied to  the
strip  in a  time  equal  to,  or slightly less than,   the  time
necessary  for  the  water to infiltrate  the  soil   surface.
When the desired volume of water has  been delivered  onto the
strip,  the stream  is  turned  off.   Shutoff normally  occurs
when  the stream  has advanced  about 75% of the length  of the
strip.   The  objective is to have sufficient water remaining
on the border after shutoff to apply  the desired  water  depth
to the remaining length of border with  very  little runoff.

Use  of  a proper  stream size  is  necessary to achieve uniform
and  efficient application.    Too  rapid a  stream results  in
inadequate application  at the upper  end of the strip or  in
excessive  surface runoff  at the lower end.   If  the stream  is
too  small,  the lower  end of the  strip receives inadequate
water  or  the upper end has  excessive  deep  percolation.
Actually achieving  uniform  distribution with minimal  runoff
requires  a good  deal of  skill and experience on  the part  of
the operator.  The optimum stream size  is best determined  by
field  trials as described  in reference [2] .   The   range  of
stream  sizes given in Tables E-3 and  E-4  for  various  soil
and  crop  conditions may be used  for  preliminary design.
Procedures given  in reference  [5]  may be  used  to  obtain  a
more accurate estimate of stream size.

The  application  period  necessary  to  apply the desired  depth
of water may be determined from the  following equation:
where  ta =

       L  =

       D  =

       C  =
          ta = LD/Cq

application period, h

border strip length, m (ft)

depth of applied water, cm (in.)

constant, 360 (96.3)
                                                       (•E-6)
                             E-12

-------
       q  =   unit stream size, L/s-m of width  (gal/min-
              ft of width

The  conveyance  and  application  devices   used  for border
distribution are  basically  the same as  described for  ridge
and furrow distribution  (Section E.3.1).  Open ditches with
several evenly  spaced  siphon tubes are often used to supply
the required  stream size  to  a  border strip.   When buried
pipe is used for conveyance, vertical risers with valves are
usually spaced at intervals equal  to the width  of the border
strip and are located midway in the border strip.  With this
arrangement,  one  valve  supplies  each  strip.   Water   is
discharged from the valve directly to the ground surface,  as
indicated in Figure E-3, and is distributed across the width
of  the strip  by gravity  flow.   For  border  strip widths
greater than 9 m (30 ft), at least two outlets  per strip are
necessary  to  achieve  good   distribution  across  the strip.
Hydrants  and  gated  pipe can  be  used  with  border  systems.
Use of gated pipe provides much more uniform distribution  at
the head  of  border strips  and  allows  the  flexibility   of
easily  changing  to  ridge  and  furrow  distribution  if  crop
changes are desired.
                           FIGURE E-3
           OUTLET  VALVE  FOR BORDER STRIP APPLICATION
                             E-13

-------
 EXAMPLE E-2:
               DETERMINATION  OF PRELIMINARY  DESIGN  CRITERIA
               FOR  GRADED  BORDER  DISTRIBUTION  SYSTEM
Design Conditions
1.  Soil conditions:  deep clay
2.  Final grade:  0.5%
3.  Maximum monthly hydraulic loading (1^):  40  cm
4.  Application frequency (F):   4  times/month
5.  Total field area (Aw):  100 ha
6.  Crop:  pasture
Design Calculations
1.  Determine depth of water to be applied (D).
         D = 10 cm (see Example E-l)
2.  Select strip width and length  from Table E-4 based on design conditions.
         W - 12 m
         L = 180 m
3.  Select unit stream size (q) from Table E-4.
         q = 4 L/s-m
4.  Estimate period of application (ta)  using  Equation E-6.

         ta - §                                                            <*-
               (180 m)(10 cm)
                (360)(4 L/s)
            = 1.25 h
5.  Determine number of applications per day.   Assume a  12 h/d operating period.
         No. of applications = (12 h/d)(1.25 h/application) .
                             = 15
6.  Determine application zone area (Aa).   Assume application  7 d/wk.
            _ 	Aw	
         Aa   (7 d)(15 applications/d)
            _ 100 ha
            ~   105
            = 0.95 ha
7.  Determine number of border strips per application  zone.
         No. of strips = ^s
                         (0.95 ha)(104 m2/ha)
                          (180 m)(12 m/strip)
8.
                   = 4.4
                   = 5
Determine system flow capacity (Q)
     Q = (5 strips)  (W)  (q)
       = (5)  (12 m)  (4 L/s-m)
       * 240  L/s (3,803 gal/min)
                                     E-14

-------
E.4  Sprinkler Distribution Systems
    E.4.1
Application Rates
The principal  design variable for  all sprinkler systems  is
the application  rate,  cm/h (in./h).   The design  application
rate  should  be   less  than  the  saturated  permeability  or
infiltration  rate of  the surface  soil (see  Chapter 3)  to
prevent  runoff and  uneven distribution.   Application  rates
can be  increased  when a  full cover  crop  is present  (see
Section  4.3.2.4).    The  increase  should not exceed  100%  of
the bare  soil application rate.   Recommended reductions  in
application   rate   for   sloping   terrain   are   given   in
Table E-5.   A practical minimum  design application  rate  is
0.5 cm/h (0.2  in./h).   For  final  design,  the  application
rate should  be based on field infiltration  rates determined
on  the  basis of previous  experience with similar  soils  and
crops or from  direct field measurements.

                          TABLE E-5
           RECOMMENDED REDUCTIONS IN APPLICATION
                   RATES  DUE TO GRADE  [6]
                           Percent
Grade
0-5
6-8
9-12
13-20
over 20
Application
rate reduction
0
20
40
60
75
    E.4.2
                    a.  Percent of level ground
                       application rate.
Solid Set Sprinkler  Systems
Solid  set sprinkler  systems remain  in one  position  during
the  application season.   The system  consists of a grid of
mainline   and   lateral  pipes  covering   the  field   to  be
irrigated.   Impact  sprinklers are mounted  on riser  pipes
extending  vertically frorii  the  laterals.   Riser heights are
determined by  crop heights and spray  angle.   Sprinklers are
spaced  at  prescribed  equal  intervals along  each  lateral
pipe,  usually  12  to  27 m (40 to 90 f t).   A schematic  layout
of  a solid set sprinkler  system  is shown in Figure E-4.  A
system  is  called fully permanent  or  stationary when  all
                             E-15

-------
lines  and  sprinklers  are  permanently  located.    Permanent
systems   usually  have  buried  main  and  lateral  lines  to
minimize  interference  with  farming operations.    Solid set
systems are  called fully portable when  portable surface pipe
is  used  for main  and  lateral lines.    Portable  solid set
systems  can  be used  in  situations where  the surface pipe
will  not  interfere  with  farming  operations  and  when  it is
desirable to remove  the pipe  from  the  field  during  periods
of winter storage.  When the mainline  is permanently -located
and the  lateral lines  are portable surface pipe,  the system
is called semipermanent or alternatively semiportable.
             SURFACE OR
             BURIED LATERALS
             WITH MULTIPLE
             SPRINKLER
LATERAL
SPACIN6
                                               WETTED DIAMETER
                                               OF SPRINKLER
                                            SURFACE OR
                                            BURIED MAIN
                                              PREVIOUSLY IRRIGATED
                                                  AREA
                                    SPRINKLER
                                    SPACING
                             FIGURE E-4
                   SOLID SET SPRINKLER SYSTEM
The  primary advantages  of solid  set  systems  are  low labor
requirements  and maintenance  costs,  and adaptability to all
types  of  terrain,  field shapes,  and  crops.   They  are also
the    most    adaptable    systems    for   climate    control
requirements.   The  major disadvantages  are high  installation
costs and obstruction of farming equipment by  fixed risers.

         E.4.2.1 Application Rate

For  solid set systems,  the application rate is  expressed as
a function  of the  sprinkler  discharge  capacity,  the spacing
                             E-16

-------
of the sprinklers  along  the  lateral,  and the spacing of the
laterals along the main according to the following equation:
                        I = qsC/SsSL

where   I  =  application rate, cm/h (in./h)

        qs =  sprinkler discharge rate, L/s,  (gal/min)

        C  =  constant = 360 (96.3)

        S_ =  sprinkler spacing along lateral, m  (ft)
         s

        ST =  lateral spacing along main, m  (ft)
                                                        (E-7)
Detailed  procedures  for  sprinkler  selection  and   spacing
determination  to achieve  the desired  application  rate  are
given in references  [6, 7, 8].

         E.4.2.2   Sprinkler  Selection  and  Spacing
                   Determination

Sprinkler  selection and  spacing determination  involves  an
iterative  process.   The  usual  procedure  is to  select  a
sprinkler  and  lateral  spacing; then determine the sprinkler
discharge   capacity   required   to   provide   the    design
application  rate  at the  selected  spacing.   The  required
sprinkler   discharge  capacity   may   be   calculated   using
Equation E-7.

Manufacturers'  sprinkler  performance data  are then  reviewed
to  determine  the  nozzle sizes,  operating  pressures,  and
wetted  diameters  of  sprinklers operating  at  the  desired
discharge  rate.   The wetted  diameters  are  then  checked with
the   assumed   spacings   for   conformance   with   spacing
criteria.  Recommended  spacings  are  based  on a percentage of
the  wetted  diameter  and vary  with   the  .wind   conditions.
Recommended spacing  criteria  are  given  in  Table  E-6.

The  sprinkler and nozzle size should be selected  to operate
within  the pressure range  recommended by  the manufacturer.
Operating  pressures  that  are  too low cause large drops which
are  concentrated in a ring a  certain distance away  from the
sprinkler, whereas high pressures result in fine drops which
fall  near the  sprinkler.     Sprinklers   with   low  design
operating   pressures    are    desirable   from   an    energy
conservation  standpoint.
                             E-17

-------
                          TABLE E-6
            RECOMMENDED SPACING OF SPRINKLERS  [6]
Average wind speed
km/h
0-11
11-16
>16
(mi/h) Spacing, % of wetted diameter
(0-7) 40
65
(7-10) 40
60
(>10) 30
50
(between
(between
(between
(between
(between
(between
sprinklers)
laterals)
sprinklers)
laterals)
sprinklers)
laterals)
         E.4.2.3   Lateral Design

Lateral  design  consists  of   selecting   lateral   sizes   to
deliver  the  total  flow requirement  of  the  lateral with
friction  losses  limited  to  a  predetermined  amount.    A
general  practice  is  to  limit  all  hydraulic losses  (static
and dynamic)  in a lateral to  20%  of the operating pressure
of the sprinklers.   This will result in sprinkler  discharge
variations  of  about 10%  along the  lateral.   Since flow  is
being discharged  from a  number of sprinklers, the  effect  of
multiple  outlets  on  friction  loss  in  the  lateral must  be
considered.    A  simplified  approach  is   to multiply  the
friction loss  in  the entire  lateral at full  flow  (discharge
at  the   distal end)  by   a  factor  based  on the  number  of
outlets.    The factors for  selected numbers  of  outlets are
presented  in  Table  E-7.   For long lateral lines, capital
costs may be reduced by using  two or more  lateral sizes that
will satisfy the headloss requirements.

The  following  guidelines  should  be used  when  laying  out
lateral lines:

    1.   Where  possible,  run  the  lateral   lines  across  the
         predominant  land  slope  and provide  equal lateral
         lengths on both sides of the mainline.

    2.   Avoid  running laterals uphill where possible.    If
         this  cannot  be  avoided,  the lateral length must  be
         shortened to allow for the loss in static head.

    3.   Lateral  lines  may  be  run  down   slopes  from  a
         mainline  on  a  ridge,  provided   the   slope    is
         relatively  uniform  and not  too steep.   With this
         arrangement,  static  head  is  gained  with  distance
                            E-18

-------
        downhill,  allowing  longer  or smaller  lateral  lines
        to be  used compared  to  level ground  systems.

   4.    Lateral  lines  should run  as nearly as  possible  at
        right  angles  to  the  prevailing  wind  direction.
        This  arrangement  allows the  sprinklers rather than
        laterals  to  be  spaced more   closely  together  to
        account  for  wind distortion and  reduces the  amount
        of pipe  required.

                          TABLE E-7
          FACTOR (F) BY WHICH PIPE FRICTION  LOSS
          IS  MULTIPLIED TO OBTAIN ACTUAL  LOSS IN
              A LINE WITH  MULTIPLE OUTLETS [3]
No. of outlets
1
2
3
4
5
6
7
8
9
10
15
20
25
30
40
50
100
Value of F
1.000
0.634
0.528
0.480
0.451
0.433
0.419
0.410
0.402
0.396
0.379
0.370
0.365
0.362
0.357
0.355
0.350
EXAMPLE  E-3 :
DETERMINATION OF PRELIMINARY DESIGN  CRITERIA
FOR SOLID SET SPRINKLER SYSTEM
Design Conditions

1.  Soil conditions:  loam, permeability - 0.75 cm/h
2.  Crop: forage grass
3.  Depth of water applied (D):  7.5 cm
4.  Application zone  area (Aa):  10 ha
5.  Average wind speed:  8 km/h
                              E-19

-------
                                   Assume 50% greater than bare soil
 Design Calculations

 1.  Determine design application rate (I) .
    permeability rate due to cover crop.

        Use I - 1.13 cm/h  (0.45 in./h)

 2.  Select sprinkler and lateral spacings.
        Use Ss = 12.2 m  (40 ft)
            SL = 18.3 m  (60 ft)

 3.  Calculate required sprinkler discharge using Equation E-7.

           = (I) (Ss) (SL)
             (1.13 cm/h) (12.2 m) (18.3 m)
                       360
           =0.7 L/s (11.1 gal/rain)

    Select sprinkler pressure and nozzle size from manufacturer's
    performance data to provide qs.

       Use 0.56 cm (7/32 in.) nozzle at 48 N/cm2 (70 lb/in.2).
       Wetted diameter = 38.1 m (125 ft)

    Check selected spacing against spacing criteria in Table E-6.

                             (100%)
       Sprinkler spacing = ^t''

                       = 32%

       Lateral spacing   = , ''
                          <40%

                          (100%)
                   = 48%  <65%

Determine system flow capacity  (Q)
    Q = (Aa) (I)

      = (10 ha)(1.13 cm/h)(10* m2/ha)(10~2 m/cm)(0.28

      = 314 L/s (4,975 gal/min)
Determine application period.

    ta - D/I
       _  7.5 cm
         1.13 cm/h
       = 6.6 h
                                                    m3/h'
     E.4.3
            Move-Stop  Sprinkler Systems
With move-stop  systems,  sprinklers  (or a  single  sprinkler)
are   operated  at   a  fixed   position  in  the   field  during
application.    After  the  desired  amount  of water  has"  been
applied,  the  system  is  turned  off  and  the  sprinklers  (or
sprinkler)  are  moved  to  another position  in  the  field  for
the  next  application.   Multiple sprinkler move-stop systems
include  portable  hand-move  systems,  end  tow  systems,  and
side-wheel  roll systems.   Single sprinkler move-stop systems
include   stationary   gun   systems.       The    operational
characteristics of  these systems and a discussion of design
procedures  are described  in the  following  paragraphs.
                                E-20

-------
         E.4.3.1   Portable Hand-Moved Systems

portable hand-moved  systems  consist of a network of  surface
aluminum lateral pipes connected to a main  line which may  be
portable or  permanent.   Lateral  lines are  constructed  of
aluminum pipe   in  9  or  12  m  (30  or  40   ft)  lengths  with
sprinklers mounted  on  vertical  risers extending  from the
lateral  at  equal  intervals.   There are  not enough  lateral
lines to cover  the entire field; thus,  lateral  lines  must  be
hand-moved between applications  to  different  positions  along
the main to apply water to the entire  field.  A schematic  of
a  portable  hand moved system is  shown in Figure E-5a.  The
major  advantages  of portable  systems include  low  capital
costs   and   adaptability  to   most  field   conditions  and
climates.  They may  also be  removed from  the  fields  to  avoid
interference    with    farm   machinery.       The   principal
disadvantage  is the  high  labor requirement  to operate the
system.

         E.4.3.2    End Tow Systems

End  tow systems are multiple-sprinkler laterals mounted  on
skids  or wheel assemblies   to  allow  a  tractor to pull  the
lateral  intact  from  one  position  along  the  main  to  the
next.   As  indicated  in Figure E-5b, the lateral is  guided  by
capstans to  control  its alignment.   The pipe  and  sprinkler
design  considerations^ are  identical  to  those for  portable
pipe   systems   with  the  exception  that  pipe  joints  are
stronger than  hand moved systems  to  accommodate  the pulling
requirements.

The  primary advantages of an end  tow  system are  lower labor
requirements  than hand moved systems,  relatively low system
costs,   and  the capability  to  be  readily  removed  from the
field  to  allow farm  implements to operate.   Disadvantages
 include  crop   restrictions   to  movement  of  laterals  and
cautious operation to avoid  crop and  equipment damage.

          E.4.3.3   Side Wheel Roll

 Side wheel roll or  wheel move  systems are  basically lateral
 lines  of  sprinklers suspended   on  a  series  of wheels.   The
 lateral line is aluminum pipe,  typically 10.2  to 12.7 cm  (4
 to 5 in.)  in diameter and up to 403  m (1,320 ft) long.  The
 wheels  are  aluminum and are 1.5  to  2.1  m  (5 to  7 ft)   in
 diameter  (see   Figure  E-6).    The end  of  the lateral   is
 connected by   flexible hose to  hydrants  located  along  the
 main line.  The unit is stationary during  application and  is
 moved  between  applications  by an integral  engine powered
 drive  unit  located  at  the  center  of  the  lateral  (see
 Figure E-5c).   The drive unit is controlled  by an operator.
                              E-21

-------
PREVIOUSLY
APPLIED
AREA
LATERAL WITH MULTIPLE
SPRINKLERS
                                MAIN
LATERAL WITH MULTIPLE
SPRINKLERS
    (a) -PORTABLE HAND MOVED
                                                PREVIOUSLY
                                                APPLIED
                                                AREA
DISASSEMBLED
MAIN  LENGTHS
                                                 (b)  END TOW
            •HEEL-SUPPORTED LATERAL
    MAIN,    VITH MULTIPLE SPRINKLER
                      PREVIOUSLY
                      APPLIED
                      AREA
                 LATERAL BI1IH SPRINKLER
                      CONNECTIONS
                                                                       MAIN
     (c)  SIDE IHEEL  IOLL
                                                                      6UN-TYPE
                                                                      SPRINKLER
                            (d)  STATIONARY  GUN
                               FieURE E-5
                     MOVE-STOP SPRINKLER SYSTEMS
                                   E-22

-------
                         FIGURE E-6
             SIDE WHEEL ROLL SPRINKLER SYSTEM
The sprinklers  are mounted on  swivel  connections to  ensure
upright  positions  at , all  times.   Sprinkler  spacings  are
typically 9.2 to 12.5 m  (30 or 40 ft) and wheel  spacings  may
range  from  9.2  to  30.5  m  (30  to  10O ft).    Side  wheel
laterals may be equipped with trail  lines up  to  27 m  (90  ft)
in  length  located at  each  sprinkler connection on the axle
lateral.   Each  trail  line  has  sprinklers mounted on  risers
spaced  typically  at 9 to 12 m  (30  to 40 ft).   Use of  trail
lines  allows  a  larger area to  be  covered by a  single  unit,
which  reduces  either  the  number of moves  or the number  of
•units required to  cover  a  given  field.

The  principal  advantages   of  side  wheel roll  systems  are
relatively  low  labor requirements  and  overall costs,  and
freedom    from    interference    with    farm    implements.
Disadvantages include restrictions to crop height and  field
shape,  and  misalignment  of  the  lateral caused  by  uneven
terrain.
                             E-23

-------
          E.4.3.4   Stationary Gun Systems

 Stationary  gun  systems  are  wheel-mounted  or skid-mounted
 single  sprinkler units,  which  are  moved  manually between
 hydrants  located  along  the  laterals  (see  Figure  E-5d).
 Since  the  sprinkler  operates  at  greater   pressures  and
 flowrates  than multiple  sprinkler  systems,  the  irrigation
 time  is  usually  shorter.    After an  application  has  been
 completed  for  the lateral,  the  entire lateral is  moved to
 the next point along  the main.   In some  cases,  a number of
 laterals and sprinklers may be provided to minimize movement
 of laterals.

 The advantages  of a  stationary gun are  similar  to  those of
 portable pipe   systems  with  respect   to  capital  costs  and
 versatility.  In addition,  the larger nozzle of the gun-type
 sprinkler is relatively  free from clogging.   The drawbacks
 to  this  system are  similar  to those   for  portable  pipe
 systems in that labor requirements are high due  to  frequent
 sprinkler moves.  Power requirements  are  relatively  high due
 to  high  pressures  at   the  nozzle,   and  windy  conditions
 adversely affect distribution  of the  fine  droplets created
 by the higher pressures.

          E.4.3.5  Design Procedures

 The  design  procedures  regarding application  rate, sprinkler
 selection,  sprinkler and  lateral  spacing,  and lateral  design
 for  move-stop   systems   are  basically the  same  as  those
 described for  solid  set  sprinkler systems.    An  additional
 design variable for move-stop systems is  the number  of units
 required  to  cover  a given area.   The minimum required  number
 of units  is  a function of the area covered  by each unit,  the
 application  frequency,  and the period  of application.   More
 than the  minimum number  of  units  can  be  provided to reduce
 the  number  of  moves  required to  cover a  given  area.,    The
 decision  to provide  additional  units  must  be  based on  the
 relative  costs  of equipment and labor.
    E.4.4
Continuous Move Systems
Continuous  move  sprinkler systems  are  self-propelled  and
move continuously  during  the  application period.  The three
types  of  continuous  move  systems  are   (1)  traveling gun,
(2) center pivot,  and (3)  linear  move.    Schematics  of  the
systems are shown in Figure E-7.
                            E-24-

-------
ANCHOR
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                                                        HOSE
                                                                   TAKE-UP
                                                                   REEL
       SELF-PROPELLED
       DRIVE UNIT WITH
       BUN-TYPE  SPRINKLER
                                                                     PREVIOUSLY
                                                                     APPLIED
                                                                     AREA
    (a) TRAVELING  GUN (HOSE DRAG)
                                        (b) TRAVELING GUN (REEL-TYPE)
POWE
DRIVE
SUPPORTS
                                           SUPPLY MAIN~V
                                                                FLEXIBLE  HOSE
                                                                {OPTION)
                                LATERAL
                                WITH
                                .MULTIPLE
                                SPRINKLER
                                PREVIOUSLY
                                APPLIED
                                AREA
                           LATERAL WITK
                           MULTIPLE SPRINKLERS
                                      PREVIOUSLY
                                      APPLIED
                                      AREA
          (c)  CENTER PIVOT
                                 (d)  LINEAR MOVE
                                  FIGURE E-7
                  CONTINUOUS  MOVE SPRINKLER  SYSTEMS
                                     E-25

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         E.4.4.1   Traveling Gun  Systems

Traveling  gun  systems are  self-propelled,  single large gun
sprinkler units that are connected to  the supply  source  by a
hose 6.4 to  12.7  cm (2.5 to  5  in.)  in diameter.  Two types
of travelers are available, the hose drag-type  and the reel-
type.   The hose drag  traveler  is driven by  a hydraulic or
gas-driven winch  located within  the  unit, or a gas-driven
winch located  at  the end of  the  run  (see  Figure E-8).   In
both cases,  a cable anchored  at  the  end of  the run guides
the  unit  in a  straight path  during  the application.   The
flexible rubber hose  is  dragged behind the  unit.  The reel-
type traveler consists of a sprinkler  gun cart  attached  to a
take-up reel  by  a semirigid polyethylene hose.  The gun is
pulled toward  the  take-up reel as the hose is slowly wound
around the  hydraulic powered  reel.    Variable speed drives
are  used to  control travel speeds.   Typical  lengths of run
range between 201 and 403 m (660  and 1,320  ft), and  spacings
between travel  lanes range  between  50  and 100  m   (i.65 and
330 ft).   After application on  a  lane is complete,   the  unit
shuts off automatically.  Some units also shut  off the water
supply automatically.  The  unit must be moved  by tractor to
the beginning of the next lane.
                         FIGURE E-8
            HOSE-DRAG TRAVELING GUN SPRINKLER
                            E-26

-------
The more  important  advantages  of  a traveling gun system are
low  labor requirements  and  relatively  clog-free  nozzles.
They may  also  be  adapted  to  fields of  somewhat irregular
shape  and   topography.     Disadvantages  are  high  power
requirements, hose travel lanes required  for hose drag units
for most crops, and drifting of sprays in windy conditions.

In   addition  to   the   application   rate   and   depth  of
application,  the  principal design  parameters  for traveling
guns  are   the  sprinkler  capacity,  spacing between travel
lanes, and the travel speed.

The   minimum  application  rate   of  most  traveling  gun
sprinklers  is about 0.6 cm/h  (O.23 in./h), which is higher
than  the   infiltration  rate  of  the  less  permeable soils.
Therefore,  the  use  of  traveling  guns  on  soils   of  low
permeability   without   a   mature   cover  crop   is   not
recommended.   The relationship between sprinkler capacity,
lane  spacing,  travel  speed,  and  depth of  application  is
given by  the  following equation:
                       D =
(E-8)
                            (St)(Sp)

where  D    = depth of water  applied,  cm  (in.)

       qs   = sprinkler  capacity,  L/s  (gal/min)

       St   = space between travel lanes,  m  (ft)

       S    = travel  speed, m/min  (ft/min)

       C    = conversion constant, 6.01  (1.60)
 The  usual  design  procedure  is  as  follows:

     1.   Select   a  convenient  application  period  (usually
         about 11 or 23 hours) to allow time  (about 1 hour)
         for  moves  between  applications.

     2.   Measure  the  longest  travel  lane  length (403 m  or
         1,320 ft maximum  for  hose  drag;  360 m  or  1,180  ft
         maximum  for reel-type)  based on site boundaries.

     3.   Calculate  the travel speed  necessary  to travel  the
         longest  travel  lane  in  the  desired  application
         period.
                             E--27

-------
7.
8.
      Select a sprinkler and sprinkler operating  pressure
      from manufacturers'  performance tables with  wetted
      diameters compatible with  site boundaries  and  with
      application  rates  suitable  for  soil  conditions.
      Sprinkler  operating   pressures  should  be   above
      55  N/cm2 (80 lb/in.z).

      Compute  the  required  lane  spacing  to  provide  the
      desired   depth    of    water   application    using
      Equation E-8.

      Check  lane   spacing  against  spacing  criteria  in
      Table E-8.

                      TABLE  E-8
           RECOMMENDED MAXIMUM LANE SPACING
             FOR TRAVELING GUN SPRINKLERS
          Wind speed
         km/h  (mi/h)  Lane spacing, % of wetted diameter
          0    (0)
          0-8   (0-5)
          0-16  (0-10)
                            80

                            70-75

                            60-65

                            50-55
Adjust  sprinkler  selection  and  lane
necessary to meet  spacing  criteria.
                                               spacing   as
Select a  hose  size for the  unit  such that friction
loss of the design  sprinkler flow capacity does not
exceed 28 N/cm2  (40 lb/in.2).
9.   Determine  the  total area covered by a single unit


     Unit area, m2  =  (St)(avg travel distance per day)
                    x  (days between application)


10.  Determine  total  number of units required

     Units required = (field area, m2)
                    x (unit area,  m2)

11.  Determine  the  system supply capacity (Q)

                Q =  (qt,)(No.  of units)
                      o
                         E~28

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         E.4.4.2   Center Pivot Systems

Center  pivot  systems  consist  of  a  lateral  with multiple
sprinklers  or  spray  nozzles  that  is  mounted  on  self-
propelled, continuously  moving  tower units  (see Figure E-9)
rotating  about a  fixed  pivot in  the center  of  the  field.
Sprinklers  on  the  lateral  may  be  high   pressure   impact
sprinklers; however, the trend is toward use of low pressure
spray  nozzles  to  reduce  energy  requirements.   Water   is
supplied  by  a  well or  a  buried  main  to  the  pivot, where
power is also  furnished.  The lateral is usually constructed
of 15 to  20  cm (6 to  8  in.)  steel pipe 61 to 793 m  (200  to
2,600 ft)  in  length.   A typical  system  with a 393 m  (1,288
ft)  lateral   covers   a  64  ha   (160   acre)   parcel  (see
Figure E-10).    The circular pattern  reduces  coverage   to
about 52 ha (13O acres), although systems with traveling end
sprinklers are available to irrigate  the corners.

The tower units are driven electrically or  hydraulically and
may  be  spaced from 24 to 76 m  (80 to 250  ft)  apart.  The
lateral  is  supported   between   the  towers  by   cables   or
trusses.  Control  of the travel speed is achieved  by  varying
the running time of the  tower motors.

An  important  limitation of  the  center pivot  system  is the
required  variation in  sprinkler application rates along the
length of the  pivot lateral.  Because the area circumscribed
by  a  given length of  pivot  lateral increases with distance
from the pivot point (as does the  ground speed of  the  unit),
the  application rate  provided  by  the  sprinklers  along the
lateral  must  increase  with  distance  from  the  center   to
provide  a  uniform depth  of application.    Increasing the
application  rates  can  be  accomplished  by  decreasing the
spacing of  the sprinklers along  the lateral and  increasing
the sprinkler  discharge  capacity.   The resulting application
rates  at  the  outer  end  of  the   pivot   lateral   can   be
unacceptable for many  soils.

Application  rates approaching 2.5 cm/h  (1.0  in./h)   may  be
necessary  at  a distance of 400 m (1,300 ft).   The designer
should  be particularly  aware of  this  limitation at  sites
where  soil  permeabilities  vary   within, the  pivot  circle.
Areas  of  slower  permeability can  be  flooded,  causing crop
damage  and traction  problems for  the drive  wheels.   This
particular  problem  has  been encountered  at  the Muskegon
project.  Determination  of the proper sprinkler  spacings and
capacities  for a  center pivot  rig is  beyond  the scope  of
this manual.   The  designer  should consult  the manufacturer
for design details.
                             E-29

-------
1 **•
                  FIGURE  E-9
               CENTER  PIVOT RIG
                FIGURE  E-10
      CENTER  PIVOT  IRRIGATION  SYSTEM
                   E-30

-------
Another  limitation  of  center  pivots  is  mobility  under
certain  soil  conditions.    Some  clay soils  can  build up on
wheels and eventually  cause-the  unit to stop.   Drive wheels
can lose  traction on slick  (silty)  soils  and  can sink  into
soft soils and become stuck.

         E.4.4.3   Linear Move Systems

Linear move  systems  are constructed and driven in a_similar
manner to  center pivot systems, except that the unit moves
continuously  in  a linear path rather than, a circular path.
Complete coverage of rectangular fields can  thus  be  achieved
while  retaining  all the  advantages  of  a  continuous  move
system.    Water  can  be  supplied   to  the  unit  through  a
flexible  hose that is pulled along  with  the unit or it  can
be  pumped from  an open  center  ditch  constructed  down  the
length of  the linear path.   Slopes  greater,  than  5%  restrict
the  use   of  center  ditches.     Manufacturers  should  be
consulted  for design details.
E.5  References

 1. Booher,  L.J.    Surface  Irrigation.    FAO  Agricultural
    Development   Paper  No.  94.    Food   and   Agricultural
    Organization  of  the  United Nations.   Rome.   1974.

 2. Merriam,   J.L.   and   J.   Keller.   Irrigation   System
    Evaluation:    A  Guide  for  Management.     Utah   State
    University, Logan, Utah.  1978.

 3. McCulloch,   A.W.  et   al.     Lockwood-Ames   Irrigation
    Handbook.  W.R.  Ames Company,  Gering,  Nebraska., 1973.

 4. Hart,  W.E.   Irrigation System  Design.  Colorado  State
    University,   Department  of   Agricultural   Engineering.
    Fort Collins, Colorado.  November  10,  1975.

  5. Border Irrigation.   Irrigation,  Chapter 4.   SCS National
    Engineering   Handbook,  Section 15.   U.S.  Department  of
    Agriculture,  Soil Conservation Service.  August 1974.

  6. Fry,  A.W.   and  A.S.  Gray.    Sprinkler   Irrigation
    Handbook.        Rain   Bird   Sprinkler   Manufacturing
    Corporation,  Glendora, California.  10th edition.   1971.

  7.  Sprinkler  Irrigation.    Irrigation,  Chapter  11.    SCS
    National  Engineering   Handbook,   Section  15.     U.S.
     Department of  Agriculture,  Soil  Conservation  Service.
    July 1968.
                              E-31

-------
8. Pair,  C.H.  et  al.f  eds.   Sprinkler Irrigation, Fourth
   Edition.    Sprinkler  Irrigation Association.    Silver
   Spring, Maryland.  1975.
                            E-32

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                         APPENDIX F

          ESTIMATED STORAGE DAYS FOR LAND TREATMENT
                  USING EPA COMPUTER PROGRAMS
Computer  programs  have  been developed to estimate storage
days for land treatment systems based on climatic conditions
(Section  4.6.2).   Selected  locations  for which the EPA-1
program  have  been  used  are  presented  in  Table F-l for
recurrence  intervals of 10 and 20 years.  The EPA-2 program
(for  SR  systems) uses soil information as well as rainfall
(see  reference  35  in  Chapter  4 for details).  The EPA-3
program  (for SR or OF systems  ) uses temperature, rainfall,
and snow depth.  Storage days for communities for which EPA-
2 has  been  run  are  listed   in  Table  F-2 for recurrence
intervals  of 10 and 20 years.  Storage days for communities
for  which EPA-3  has  been  run are listed in Table F-3 for
recurrence intervals of 10 and  20 years.

                          TABLE F-l
          STORAGE DAYS USING EPA-1 FOR  20 YEAR  (5%)
             AND 10 YEAR  (10%)  RETURN INTERVALS
Percentiles
Station Name
Bridgeport
Boise
Pocatello
Des Moines
Hampton
Logan
Shenandoah
Greenville
Muskegon
International Falls
Minneapolis
Park Rapids
Billings
Bozeman
Great Palls
Missoula

Buffalo
Rochester
Water town

State
CT
ID
ID
IA
IA
IA
IA
ME
MI
MN
MN
MN
MT
MT
MT
MT

NY'
NY
NY

0.05
68
87
125
111
136
107
95
172
119
172
143
159
102
152
102
128

108
121
128

0.10
64
77
109
106
126
105
77
169
116
168
143
155
100
144
91
121

103
115
126

Station Name
Bismarck
Devils Lake

Burns
Aberdeen
Brookings
Pierre
Rapid City
Burlington
Spokane
Ashland
Eau Claire
Green Bay
Lacrosse
Madison
Rhinelander
Weyerhauser
Afton
Casper
Gillette
Ruck Springs
Wheatland
State
ND
ND

OR
SD
SD
SD
SD
VT
WA
WI
WI
WI
WI
WI
WI
WI
WY
WY
WY
WY
WY
Percentiles
0.05
144
168

119
142
136
136
100
136
106
149
147
139
134
125
156
148
156
101
113
142
66
0.10
140
156

102
138
131
126
99
.134
100
148
141
135
127
119
149
145
144
95
108
136
58
                              F-l

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                        TABLE  F-2
    STORAGE DAYS USING  EPA-2 FOR 20 YEAR jf5%)
        AND  10 YEAR  (10%) RETURN INTERVALS*
Percentiles
Station name
Bay Minette
Brewton
Clanton
Mobile
Selma
Thomasville
Dumas
Little Rock
Avon Park
Belle Glade
Bradenton
Clermont
Daytona Beach
Orlando
Punta Gorda
Tampa

Augusta
Ma con
Newnan
Savannah

Alexandria
Franklinton
Houma
Lafayette
Lake Providence
Leesville
Monroe
New Orleans
Schriever
Shreveport
St Joseph
Winnfield
Aberdeen
Biloxi
Canton
Clarksdale
Columbia
Greenwood
Jackson
Meridian
Pontotoc
Poplarville
Stoneville
Vicksburg
Charlotte
Pinehurst
Raleigh
Weldon
State
AL
AL
AL
AL
AL
AL
AR
AR
FL
FL
FL
FL
FL
FL
FL
FL

GA
GA
GA
GA

LA
LA
LA
LA
LA
LA
LA
LA
LA
LA
LA
LA
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
NC
NC
NC
NC
0.05
13
16
20
14
18
23
19
12
12
10
13
11
8
11
16
30

10
11
15
16

19
16
16
12
18
31
12
16
15
10
11
15
23
13
15
16
27
15
12
13
19
22
17
27
12
12
13
11
0.10
13
11
11
11
11
13
14
12
9
8
12
7
8
9
11
17

9
9
10
11

14
15
11
10
14
16
12
9
13
8
11
14
13
10
11
11
16
12
10
11
14
13
15
23
11
9
12
10
Station name
Wilmington
Wilson

Eugene
Forest Grove
Headworks
Hillsboro
Medford
Portland
Salem
Arecibo
Coloso
Guayama
Humacao
San Juan

Columbia
Conway
Darlington
Hampton
Summerville

Bristol
Crossville

Brownsville
Corpus Christi
Dallas
Houston
Luling
Mexia
Paris
Port Isabel
Sealy
Sugar Land
Blackstone
Buchanan
Chatham
Columbia
Diamond Springs
Leesville
Lynchburg
Norfolk
Richmond
Washington DC
Aberdeen
Longview
Olympia
Seattle
Vancouver

State
NC
NC

OR
OR
OR
OR
OR
OR
OR
PR
PR
PR
PR
PR

SC
SC
SC
SC
SC

TN
TN

TX
TX
TX
TX
TX
TX
TX
TX
TX
TX
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
WA
WA
WA
WA
WA

Percentiles
0.05
10
12

34
134
150
119
19
126
34
11
17
24
25
7

13
9
11
10
16

23
24

11
11
15
36
40
42
16
10
32
77
21
31
21
23
15
31
23
17
15
22
213
53
58
40
28

0.10
9
11

31
129
144
111
11
110
25
10
13
16
19
6

8
9
9
8
8

19
22

6
5
12
26
36
35
11
9
26
51
16
19
19
21
11
3L6
18
14
14
19
181
35
38
24
19

Available water capacity range from 15 to 30 cm (6 to 12 in.) in top 1.5 m
(5 ft) of soil profile. ' Depletion rate usually set at 1.9 cm/d (0.75 in./d)
                            F-2

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                      TABLE  F-3
STORAGE DAYS USING  EPA-3 FOR  20  YEAR  (5%)
    AND  10  YEAR  (10%) RETURN INTERVALS
Percen tiles
Station Name
Sterling
Belle Plaine
Des Moines
Grinnell
Indianola
Keosauqua
Logan
Newton
Osceola
Oskaloosa
Shenandoah
Winterset

Ashton
Ottawa
Plymouth
Baltimore
Beltsvilleb
Blackwater Refuge

State
CO
IA
IA
IA
IA
IA
IA
IA
IA
IA
IA
IA

ID
IL
MA
MD
MD
MD

a. Temperature thresholds
0.05
118
133
135
139
122
111
126
134
122
130
114
134

151
115
95
77
76
35

: mean
0.01
110
128
128
133
113
91
114
126
118
121
101
127

148
89
91
57
58
29

0 °C
Station Name
Chestertown
Westminster
Freehold
Pemberton
Santa Fe
Minden0
Reno
Rochester
Coatesville
George School
Lancaster
Philadelphia
York
Corsicana"
Alta
Diversion Dam
Lander
Pavillion
Riverton
(32 °F) ; minimum
State
MD
MD
NJ '
NJ
NM
NV
NV ,
NY
PA
PA
PA .
PA
PA
TX
WY
WY
WY
WY
WY
-4 °C
Percen tiles
0.05
73
86
88
80
98
69
61
123
89
87
86
80
85
8
172
140
146
140
150
(25 °F) ;
0.10
46
82
77
72
88
63
57
122
85 '
83
84
66
80
6
160
137
139
137
144
maximum
                       snow 2.54 cm (1  in.); Precipitation 1.27 cm
          (40  °F)
    Precipitation thresholds:
    (0.5 in.).
    Drawdown rate:  ratio of flow output from storage on favorable days to
    average daily wastewater flow =0.5.
b.  Temperature thresholds;  minimum -5.5 °C (22 °F); maximum"!.7 °C (35 °F).
c.  Temperature thresholds:  minimum -6.7 °C (20 °F); maximum 1.7 °C (35 °F).
d.  Temperature thresholds;  minimum -2.2 °C (28 °F); maximum 2.2 °C (36 °F).
                              F-3

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-------
                         APPENDIX G

                      GLOSSARY OF TERMS
                     CONVERSION FACTORS
                      GLOSSARY OF TERMS
acre-foot—A  liquid measure of a volume equal to covering a
1 acre area to 1 foot of depth.

aerosol—A suspension of colloidal solid or liquid particles
TnaTr  or gas, having small diameters ranging from 0.01 to
50 microns.

aquiclude—A  geologic  formation which, although porous and
capableof  absorbing  water  slowly,  will not transmit it
rapidly  enough  to furnish an appreciable supply for a well
or spring.
available
can  be  taken  up
growth;  the  moisture
ultimate wilting point
moisture—The  part of the water in the soil that
         by  plants at rates significant to their
             content of the soil in excess of the
coppice—sprouting from tree stumps.

cultivar—A cultural variety of a plant species.

evapotranspiration—The  combined loss of water from a given
areaandduring a specified period of time, by evaporation
from   the  soil surface, snow, or intercepted precipitation,
and by the transpiration and building of tissue by plants.

field  area—The  "wetted   area" where treatment occurs  in  a
land application system.

field  capacity—(field   moisture  capacity)—The  moisture
contentofsoil in the field 2 or 3 days  after having  been
saturated  and  after  free drainage has practically ceased;
the  quantity  of  water  held in a soil by capillary action
after  the  gravitational   or free water has been allowed  to
drain; expressed as moisture percentage, -dry weight basics.

 fragipan—A loamy, dense, brittle subsurface horizon that  is
very  low  in organic  matter and clay but  is rich in silt  or
very  fine sand.  The  layer is seemingly cemented and slowly
or very slowly permeable.

 horizon (soil)—A  layer  of soil,  approximately parallel  to
 thesoil surface, with distinct characteristics produced  by
 soil-formltvq processes.
                             G-l

-------
 infiltrometer—A  device  by  which  the  rate and  amount  of
 water  infiltration  into  the soil is determined  (cylinder,
 sprinkler,  or basin flooding).

 matric  potential—Attractive  forces  of  soil particles for
 water and water molecules for each other.

 micronutrient—A  chemical  element  necessary in only  small
 trace  amounts  (less  than  1  mg/L)  for  microorganisms and
 plant growth.  Essential micronutrients are  boron,  chloride,
 copper,  iron, manganese, molybdenum,  and zinc.

 mineralization—The conversion of  a compound from an organic
 form   to  an  inorganic  form  as  a  result  of   microbial
 decomposition.

 sodic  soil—A  soil  that  contains   sufficient  sodium   to
 interfere  with the growth of most crop plants, and in  which
 the  exchangeable sodium'percentage is  15 or  more.

 soil  water—That  water  present   in   the  soil pores  in  an
 unsaturated  (aeration)   zone  above  the ground water table.
 Such  water  may  either  be  lost by evapotranspiration  or
 percolation to the ground water table.

 tensiometer—A  device  used to measure  the negative pressure
 (or  tension)  with which water is held  in the soilj  a porous,
 permeable   ceramic  cup  connected  through  a  tube   to  a
 manometer or vacuum gage.

 till—Deposits   of  glacial  drift laid  down in place as the
 glacier   melts,   consisting  of a  heterogeneous mass of rock
 flour,    clay,    sand,    pebbles,   cobbles,   and  boulders
 intermingled  in any proportion;  the agricultural cultivation
 of fields.

 tilth—The   physical condition of a  soil as  related to its
 ease  of  cultivation.    Good  tilth  is  associated  with high
 noncapillary  porosity   and  stable, granular  structure, and
 low  impedance  to seedling  emergence and  root penetration.

 transpiration—The   net   quantity   of water  absorbed through
 plant  roots  that is  used  directly in building plant tissue,
 or   given  off   to  the  atmosphere  as a vapor from the leaves
 and  stems of  living  plants.

 volatilization—The   evaporation   or changing of a  substance
 from liquid  to vapor.

wilting point—The minimum quantity of water in a given soil.
 necessary  to  maintain  plant  growth.  When the quantity of
moisture  falls   below   this,   the  leaves begin to drop and
 shrivel up.
                             G-2

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    CONVERSION FACTORS   .
Metric .to" U.S. Customary
* ; . '..'.• Metric . .
Name
qentimeter (s) '
centimeter (.s) per hour
f . • ' .
cubic meter

cubic meters per day

cubic meters per hectare

cubic meters per second

degrees Celsius
gram ( s )
hectare
Joule
"kilogramCs)
kilograms per hectare
kilograms per hectare
• per day
kilograms 'per square
centimeter. •
kilometer
kilowatt
liter

liters per hectare per day
liters per second


megagram (metric tonne)
megagrams per hectare
.mega joule
megaiiters (liters x 106)
meters (s)
meters per second
micrograms per liter
milligrams per liter
nanograms per liter
Newtons per square
centimeter
square centimeter
square kilometer
square meter

Symbol
cm
cm/h
m3

m3/d

m3/ha

m3/s

°C
g
ha
J
kg
kg/ha
kg/ha -d

kg/cm2

km
kW
L

L/ha-d
L/s


Mgfor t)
mg/ha
MJ
ML
m
m/s
pg/L
mg/L
ng/L
N/cm2

cm
km2
m2
Multiplier
0.3937
0.3937
8.1071 x 10~4
35.3147
264.25
2.6417 x 10~4

1,069 x 10~4

22.82

1.8(°C) + 32
0.0022
2.4711
0.004
9.48 x 10"4
2.205
0,0004
0.893

14.49

0.6214
1.34
0.0353
0.264
o.ii
0.035
22.826
15.85
0.023
1.10
0.446
0.278
0.264
3.2808
2.237
1.0
1.0
1.0
1.45

0.155-
0.386
10.76
U.S.
customary
Abbreviation
in.
in./h
acre-f t
ft3
' Mgal
Mgal/d

Mgal/acre

Mgal/d

•F
Ib
acre
mi2
Btu
Ib
tons/acre
Ib/acre-d

Ib/in . 2

mi
hp
ft3 ;
gal .
gal/acre -d
ft3/S
gal/d
gal/rain
Mgal/d
ton (short)
tons/acre
kWh
Mgal
ft
mi/h
ppb
ppm
ppt
Ib/in.2

in.2
mi2
ft2
unit .. '
Name - ,
inches
inches per hour
acre-foot
cubic foot
million gallons
million gallons
per day
million gallons
per acre
million gallons
per day
degrees Fahrenheit
pound (.s)
acre
square miles
British thermal unit
pound (s)
tons per acre
pounds per acre per day

pounds per square inch

mile •
horsepower
cubic foot
gallon (s)
gallons per acre per day
cubic feet per second
gallons per day
gallons per minute
million gallons per day
ton (short)
tons per acre
kilowatt hour
million gallons
foot (feet)
miles per hour
parts per billion
parts per million
parts per trillion
pounds per square inch

square inch
square .mile
square foot
                       •U.S.COVBWMENIPRINTINCOmCE:l993 -750.002, 60170
              G-3

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